Advanced Search

Publications > Journals > Cancer Screening and Prevention > Article Full Text


DNA Methylation and Anticancer Drug Resistance in Gynecological Tumors

  • Heidi Schwarzenbach1,*  and
  • Peter B. Gahan2
 Author information
Cancer Screening and Prevention   2022;1(1):47-63

doi: 10.14218/CSP.2022.00004


DNA methylation is essential for regulating tissue-specific gene expression, genomic imprinting, X chromosome inactivation and retroviral element silencing. The transformation from normal to cancer cells is accompanied by changes in DNA methylation resulting in the activation of oncogenes and inactivation of tumor suppressor genes. This process is regulated by methylation and contributes to the support and development of tumors. Epigenetic modifications account for the development of resistance in cancer cells treated with anticancer drugs. Dysregulated signaling pathways involved in tumor drug resistance include the Wnt canonical and non-canonical pathways and the PI3K/PTEN/AKT/mTOR pathway. This review considers the mechanisms and specific methylated biomarkers that participate in such resistances and how resistance to individual treatments for breast, ovarian, uterine and cervix tumors are introduced.


Epigenetics, Breast cancer, Ovarian cancer, Endometrial cancer, Cervical cancer, Wnt, PI3K/PTEN/AKT/mTOR, DNA damage repair, DNA methyltransferase, TET


Based on Baldwin’s suggestion at the end of the nineteenth century of the “correct” allele choosing a new environment, which leads to a permanently changed evolutionary development within that environment,1,2 Waddington suggested the term epigenetics. He described a context in which a characteristic acquired within a total population in response to an environmental stimulus might be inherited in the absence of DNA mutations.3,4 This process involved a phenotypic modification occurring through the alteration of gene expression; however, with no modification in the actual gene DNA sequence. Despite initial opposition to the theory, epigenetics has become a central aspect of genetic studies. It plays a role in numerous processes, for example, cell type-specific gene inactivation (Fig. 1). It is important in the initiation and development of cancers and the development of anticancer drug resistance. The epigenetic modification of importance is DNA methylation and its involvement in nucleosome repositioning, histone post-translational modification and post-transcriptional gene regulation by microRNAs (miRNAs).5

DNA methylation and its role in benign and malignant cells.
Fig. 1  DNA methylation and its role in benign and malignant cells.

ELISA was performed to assess the percentage of DNA methylation in leukocytes and MDA-MB-468 cells. Then, the measurements were depicted in a bar chart. The results show DNA methylation in the metastatic adenocarcinoma breast cell line MDA-MB-468 with a 50 % lower DNA methylation than in normal leukocytes. These results highlight a decrease in DNA methylation in cancer cells. The binding of RNA polymerase and transcription factor (TF) to methylated DNA is inhibited by methyl groups (depicted on a DNA strand wrapped around histones), leading to the inhibition of RNA transcription. DNA methylation plays an important role in processes, such as the inactivation of the X chromosome, imprinting genes, testis-specific genes, and cell type-specific genes.

DNA methylation, which was first identified in 1944,6 involves the DNA cytosine residue rather than the adenine residue that is rarely methylated in humans. Cytosine methylation is catalyzed by the DNA methyltransferase (DNMT) family of enzymes that transfer a methyl group from S-adenosyl-methionine to the fifth carbon of a cytosine residue to form 5-methylcytosine (5mC). These enzymes include: (1) DNMT1 which functions in DNA replication by binding to the newly synthesized, unmethylated DNA daughter strand to ensure that it is similarly methylated to the parent strand.7 In addition, DNMT1 can act as a maintenance enzyme due to its ability to repair DNA methylation.8 The recruitment of DNMT1 to cytosine depends upon the binding of URFH1 (ubiquitin-like, containing PHD and RING finger domains 1). Failure to do so means no methylation. In addition, DNA methylation is further regulated by the arginine methyltransferase PRMT6 through its ability to methylate the arginine residue at position 2 of histone 3 (H3R2me2a) in the nucleosome complex. The presence of H3R2me2a blocks the binding of URFH1 and hence cytosine methylation;9 (2) DNMT2 (TRdnmt), which is a DNMT homolog that does not methylate DNA; and (3) DNMT3a and DNMT3b that methylate DNA with approximately 75% of CpG dinucleotides being methylated in somatic cells.10 These enzymes can cooperate with histone-modifying enzymes that act by either adding or removing either of both histone markers to result in repression of the gene region.11 However, DNMT3a is expressed in most differentiated tissues and DNMT3b is poorly expressed,12 and knockout studies on mouse embryos have indicated that DNMT3b is primarily important in embryo development.13 An additional DNMT3 (DNMT3L) does not have a catalytic function but seems to associate with DNMT3a and DNMT3b stimulating their methyltransferase activity. In addition, DNMT3L is needed for maternal and paternal genomic imprinting, X chromosome compaction and retrotransposon methylation (Fig. 2).11

Production of methyl groups and DNA methylation.
Fig. 2  Production of methyl groups and DNA methylation.

Synthesis of the amino acid methionine produces SAM, the main donor for DNA methylation. Two cofactors are necessary: vitamin B12 and folic acid. Varying amounts of these cofactors in food lead to higher or lower cellular DNA methylation. The intake of folic acid and vitamin B12 promotes erythrocyte formation. DNMT3A, DNMT3B, and DNMT3L are responsible for the establishment of the first DNA methylation pattern. This de novo DNA methylation, passed on by the parent to the progeny, establishes key epigenetic modifications that are essential for cellular differentiation and embryonic development. DNMT1 supports DNA methylation by copying the pattern from the old DNA strand by transferring methyl groups to the newly synthesized strand. DNMT, DNA methyltransferase; SAH, S-adenosyl-homocysteine; SAM, S-adenosyl-methionine; THF, tetrahydrofolate.

DNA methylation occurs on cytosines present at the CpG sites of the DNA that are spread throughout the genome. It does occur at those cytosines present in the CpG islands, for instance, stretches of DNA of demethylation 300–3,000 base pairs long have a higher CpG density than the rest of the genome.14–16 Expanses of CpG islands in non-methylated stretches have been termed large valleys or canyons and appear to be present throughout the mammalian genome.17,18 Overall, 70% of promoters present adjacent to transcription start sites of genes appear to contain a CpG island.19,20 Therefore, stable silencing of genes can be achieved by the methylation of the CpG islands associated with the promotor regions.21

In general, DNA methylation is essential for regulating tissue-specific gene expression, genomic imprinting, X chromosome inactivation and, importantly, retroviral element silencing (Fig. 1). Overall, 70% of gene promotors are contained within CpG islands including those of housekeeping genes.22

Although DNA methylation appears to be stabilized in postmitotic cells once an embryo has fully developed, cancer cell initiation will reactivate DNA methylation or demethylation in these cells. DNA activity is modified by methylation and by demethylation, which is a less well-understood process. This activity is initiated by the ten-eleven translocation (TET) enzyme family that includes TET1, TET2 and TET3.23 They are α-ketoglutarate-dependent dioxygenases involved in the TET-mediated oxidation of 5mC and 5-hydroxymethylcytosine (5hmC), the alpha-ketoglutarate being converted into succinate and CO2. The products of this activity, 5mC and 5hmC, are then converted into 5-formylcytosine (5fc) and 5-carboxycytosine (5caC).24,25 The produced 5hmC is a stable epigenetic modification and accounts for 1–10% of the 5mC.24 5mC and 5hmC are then oxidized into other cytosine forms, for example, 5fc and 5caC,26 which are then identified and excised by thymine DNA glycosylase, repaired through the base-excision repair system and subsequently replaced by cytosine (Fig. 3).27 The role of DNMT and TET proteins compose the control of the methylation of the CpG islands associated with the promoter regions;21 therefore, permitting the stable flow of epigenetic information between cell generations including gene expression in embryonic and differentiated tissues.

DNA demethylation pathway.
Fig. 3  DNA demethylation pathway.

Demethylation is performed at the 5′ positions on the pyrimidine ring of cytosine 5′ to guanosine within the DNA (Fig. 2). The TET enzymes catalyze the hydroxylation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), then the oxidation of 5hmC to 5-formylcytosine (5fC), 5fC to 5-carboxycytosine (5caC), and finally 5caC to cytosine. For clarity, only the single modified cytosines are depicted. TET, ten-eleven translocation.

The homeodomain-containing protein NANOG is essential to establish the ground state of pluripotency during somatic cell reprogramming. This protein has a physical association with TET1 and TET2, which leads to an enhanced reprogramming efficiency.28 In addition, Costa et al. determined 27 protein interaction partners of NANOG. Furthermore, they indicated that TET1 was recruited by NANOG and enhanced key reprogramming target gene expression. NANOG is thought to function together with additional proteins, for example, PO5F1 and SOX2 in embryonic stem cells, which is an important factor in tumor cells where it is highly expressed.29 NANOG appears to function as an oncogene leading to carcinogenesis since its high expression can be used as a marker of poor prognosis.29–31 In addition, the expression of the NANOG p8 protein is important in cancer stem cells.32

Recently, an uncharacterized protein (QSER1) was suggested as a TET1 cobinding protein.33 When competing for DNA binding sites in competition with DNMT3A and DNMT3B, they are mutually dependent.

Major signaling pathways involved in tumor development and growth

Major signaling pathways involved in tumor drug resistance include the Wnt canonical and non-canonical pathways and the PI3K/PTEN/AKT/mTOR pathway. These can be regulated by methylation to contribute to the support and development of tumors.

Wnt canonical and non-canonical signaling pathways

The Wnt family contains a variety of secreted cysteine-rich lipoproteins that activate several signaling pathways through their binding to frizzled receptors and coreceptors on the cell membrane.34–37 These derived signals participate in key cellular functions that include proliferation, differentiation, migration, genetic stability and apoptosis. Two Wnt pathways are involved: the canonical pathway that relies on the involvement of B-catenin (Fig. 4) and the non-canonical pathway that does not rely on it. The latter is activated by the Wnt/planar cell polarity and Wnt/Ca2+ pathways.37–41 Van Amerongen et al.42 proposed the possibility of an integrated Wnt pathway in which there was a combination of the canonical and non-canonical pathways that lead to multiple inputs at the Wnt receptor binding and downstream intracellular responses. Consequently, a variety of tumors that include breast and ovarian show a deregulated methylation pattern in the Wnt pathway.43

Three signaling pathways.
Fig. 4  Three signaling pathways.

The activation of the canonical Wnt, PI3K/PTEN/AKT/mTOR, and RAS/RAF/ERK signaling pathways with the essential components. APC, adenomatous polyposis coli; BAD BCL2, associated agonist of cell death; Bcl-2 agonist of cell death; BCL2, anti-apoptotic B cell lymphoma 2; ERK, extracellular-signal regulated kinase; GSK-3, glycogen synthase kinase-3; MEK, mitogen-activated protein kinase; PI3K, phosphatidylinositol-3-kinase; PTEN, phosphatase and tensin homolog; RAF, rapidly accelerated fibrosarcoma; RAS, rat sarcoma; TOR, target of rapamycin.

PI3K/PTEN/AKT/mTOR signaling pathway

Phosphatidylinositol 3-kinase (PI3K) or AKT, a serine/threonine protein kinase that is known as protein kinase B, and the target of rapamycin (mTOR) are major components in this pathway (Fig. 4). They are activated by upstream tyrosine kinases together with, for example, hormones and mitogenic factors. The signaling pathway is important in a range of cellular processes including general cell metabolism, cell proliferation, protein synthesis for cell growth, cell motility and apoptosis.44 PI3K is composed of three classes of which class 1 is important in cancer.45 Class 1 PI3K is activated by either receptor tyrosine kinases or G protein-coupled receptors. They are primarily linked to the conversion of phosphatidylinositol 4,5-bisphosphate (PI4, 5P2) to phosphatidylinositol 3,4,5-trisphosphate (PIP3). The central pathway point (AKT) is activated by PIP3 resulting in its binding to the cell membrane and acting downstream in cellular processes that are linked to cell survival, growth and proliferation.46,47 mTOR is an important protein that can act upstream and downstream of AKT.48 mTOR is active in the targeting of rapamycin complexes (e.g., TORC1 and TORC2) and regulates a number of cellular processes including the synthesis of proteins for cell growth and proliferation.48 DNA methylation, and therefore, modification of this pathway and an imbalance in oncogenes, lead to cancer cell maintenance and development and drug resistance. The PI3K/PTEN/Akt/mTOR signaling pathway is deregulated in numerous cancers leading to altered cellular processes, which makes this axis an attractive target for therapeutic manipulations. Upregulated DNMT induces hypermethylation of components of this oncogenic pathway, for example, the inactivation of the negative regulator and tumor suppressor gene phosphatase tensin homolog (PTEN). Reduced PTEN expression is associated with activation of AKT leading to the aberrant deregulation of the pathway to confer tumor growth and drug resistance.49,50

Other signaling pathways

To date, numerous other signaling pathways involved in tumor drug resistance that are deregulated by DNA methylation have been described. Among others, the MAPK pathway leads to cell proliferation, differentiation, migration, senescence and apoptosis51 whilst DNA damage repair pathways support genomic integrity and DNA replication.52 Cell adhesion/tight junction pathways link key signaling pathways in cell proliferation, transformation and metastasis53 and the NOTCH pathway influences differentiation, proliferation and apoptotic cell fates.54

Major additional signaling pathways involved in DNA methylation

Important signaling pathways involved in DNA methylation have been described in a review by Hegde and Joshi.55 A brief description of these pathways follows.

Ras/AP-1 signaling pathway

The RAS superfamily of GTPases (Fig. 4) regulates cell proliferation, apoptosis and cell migration. Increased expression of RAS plays an important role in the epigenetic silencing of several genes in human tumors. Since the DNMT1 promoter contains several AP1 sites, the RAS signaling pathway regulates DNMT1 via AP1. Aberrant expression of RAS in breast cancer (BC) results in increased DNA methylation as has been well documented.55

JAK1/STAT3 signaling pathway

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor (TF) that, on phosphorylation by JAK1 tyrosine kinase, forms homo or heterodimers to modulate cell proliferation, apoptosis and cell motility. The binding of STAT3 to the DNMT1 promoter in BC cells indicates its crucial role in epigenetic changes during tumorigenesis and metastasis.55

Other signaling pathways

To date, numerous other signaling pathways involved in DNA methylation have been reported. These include retinoblastoma and TP53 signaling that regulate DNMT1-mediated gene promoter methylation.55

Abnormal methylation of apoptosis-related genes in cancer drug resistance

Apoptosis plays a key role in the control of cancer cell growth. It can be triggered either by extrinsic receptor stimulation or intrinsic mitochondria-mediated signaling. The extrinsic pathway involves, for example, cell surface death receptor gene (FAS), tumor necrosis factor (TNF) or TNF-related apoptosis-inducing ligand (TRAIL), which activate caspase-8. Then, activated caspase-8 either directly cleaves or activates caspase-7 and caspase-3, promoting apoptosis. However, the intrinsic pathway leads to the activation of B cell lymphoma-2 (BCL2) associated X (BAX) at the mitochondrial outer membrane leading to the release of different apoptosis-mediating molecules, such as cytochrome c, which activates caspase-9. Then, caspase-9 cleaves and activates caspase-3 and caspase-7 to promote apoptosis. In addition, the tumor suppressor p53, which is a key regulator of apoptosis, has an essential role in apoptosis. At the transcriptional level, p53 either upregulates (e.g., BAX) or reduces the expression of BCL-2, which antagonizes BAX. A high ratio of BCL-2 to BAX protein confers a poor prognosis with decreased rates of complete remission and overall survival.56 Therefore, DNA methylation, which mediates the downregulation of genes involved in apoptosis, is an essential mechanism through which tumor cells avoid apoptosis and survive. As described in the following sections or the detailed review by Hervouet et al.,57 numerous genes implicated in apoptosis may be aberrantly methylated in cancer. This is frequently associated with chemoresistance.

DNA methylation and drug resistance in cancer cells

As mentioned previously, CpG islands are associated with gene promotor regions21 that are stabilized by methylation in postmitotic cells. In such healthy cells, the CpG islands tend to be hypomethylated and the remaining part of the genome tends to be methylated. In cancer cells; however, a reverse process is observed where the CpG islands are hypermethylated. The result of this process is the blocking of key genes by CpG island hypermethylation of promoter regions in cancer cells leading to diminished gene expression relevant to normal cell performance. Cancer types have specific groups of these hypermethylated CpG islands, which are known as CpG island methylator prototype (CIMP) that are specific for a given tumor and are different between cancer types. One of the first CIMP examples was identified in colorectal cancer.56

This could lead to tumor cell resistance to trastuzumab, anti-estrogen, doxorubicin and tamoxifen in BC and radiation in cervical cancer. In addition, ovarian cancer (OC) cells show resistance to cisplatin, carboplatin, gefitinib and paclitaxel.49 Romero-Garcia et al. reviewed the effects of hypomethylation of promoter genes leading to increased gene expression. In this case, resistance is associated with tamoxifen, doxorubicin, paclitaxel, cyclophosphamide, docetaxel, doxorubicin and radiation for BC and carboplatin and cisplatin for OC (Table 1).49,58–81 The course of action of doxorubicin in the different pathways leading to cell death and cell growth arrest is shown in Figure 5.82 Several tumors, such as lung, breast, prostate, colon, gastric, and OCs, among others, exhibit a pattern of deregulated methylation in cancer-associated pathways.35,58,83

Table 1

Hypermethylated and hypomethylated promoters or genes and drug resistance (after49)

TissuePromoter or geneDrugs
Palomeras et al.61BreastTGFB1Trastuzumab
Zhang et al.58BreastERαAnti-estrogen
Ponnusamy et al.62BreastMSH2Doxorubicin
Tuo et al.63BreastMGPDoxorubicin
De Marchi et al.64BreastPSAT1Tamoxifen
Kim et al.65CervixSOCS 1, SOCS 3Radiation
Wu et al.66CervixZNF582Radiation
Jin et al.67OvarianUCHL1Cisplatin
Yang et al.59OvarianOXCT1Cisplatin
Prieske et al.68OvarianBRCA 1Cisplatin
Deng et al.69OvarianmiR-199a-3pCisplatin
Tian et al.60OvarianhMSH2Cisplatin
Gao et al.70OvarianRassF1ACisplatin/Placitaxel
Ha et al.71OvarianNAGACisplatin
Kritsch et al.72OvarianTRIB2Cisplatin
Zhang et al.73BreastID4Tamoxifen
Chen et al.74BreastERp29/MGMTRadiation
Hu et al.75BreastmiR-663Docetaxel
Chekhun et al.76BreastMDR1, GSTpi, MGMT, UpaDoxorubicin
Pan et al.77OvarianSERPINE1Carboplatin
De Leon et al.78OvarianTMEM88Carboplatin
Li et al.79OvarianBCRA1, SIRT1, EGFRCisplatin
Iramaneerat et al.80OvarianHERVCisplatin
Lee et al.81OvarianMALCisplatin
Role of doxorubicin in cellular pathways.
Fig. 5  Role of doxorubicin in cellular pathways.

Doxorubicin initiates the extrinsic pathway of apoptosis by FASL/FAS, activating caspase-8, -3, -6 and -7 and the intrinsic pathway by upregulating AMPK so leading to the upregulation of p53, JNK and mTORC1. The inhibition of anti-apoptotic BCL2 and the increase in pro-apoptotic BAX lead to the activation of caspases-3, -6 and -7. Upregulated p21 inhibits the CDC2/CDK1 ratio leading to cell growth arrest. The necrosis pathway is initiated by the activation of either TNF or TRAIL and the inhibition of caspase-8. RIPK1 activates RIPK3, leading to the activation of MLKL. Upregulated PARP-1 and H2AX decrease glycolysis to induce necrosis. Upregulated AMPK inhibits mTOR in the PI3K/PTEN/AKT/mTOR leading to the inhibition of cancer growth. These pathways are abbreviately shown because of the clarity, but a detailed description is given by Meredith et al.82 Other chemotherapeutic agents, such as carboplatin, act in a similar way. DNA methylation of the upregulated components of the pathway leads to inhibition of cell death and tumor growth so inducing chemoresistance. AMPK, activated protein kinase; BAX, BCL-2-associated X; BCL-2, B cell leukemia/lymphoma 2; CDC2, cell-division cycle 2; CDK, cyclin-dependent kinase; FASL, FAS ligand need to eplain; JNK, c-Jun N-terminal kinase; MLKL, mixed-lineage kinase domain-like protein; mTORC1, mammalian target for rapamycin complex 1; PARP-1, poly (ADP-ribose) polymerase-1; PI3K, phosphatidylinositol 3-kinase; PTEN, phosphatase and tensin homolog; RIPK, receptor-interacting serine/threonine protein kinase; TNF-α, tumor necrosis factor alpha; TRAIL, TNF-related apoptosis-inducing ligand.

Drug transport

Anthracyclines, such as doxorubicin, and taxanes, such as paclitaxel or carpoplatin, are highly effective drugs that are used in the treatment of BC and other cancers, drug transports limit their clinical efficacy. On entering the body, anticancer drugs will pass through a series of complex processes that include drug transport and metabolism. Tumors can either be intrinsically resistant to these agents or acquire resistance upon exposure to chemotherapeutic drugs. Drug resistance, whether intrinsic or acquired, is assumed to cause therapy failure in >90% of patients with metastatic tumors.84

Drug transporters are ubiquitous membrane-bound proteins regulating the movement of drugs and endogenous metabolites into and out of the cell. In mammals, they are expressed primarily in the liver, intestines, blood-brain barrier, blood-testis barrier, placenta and kidneys,85 maintaining homeostasis and mediating processes that are important for pharmacokinetics. They are divided into the ATP binding cassette (ABC) family including P-glycoprotein, BC resistance protein, multidrug resistance proteins (MRPs) and the solute carrier (SLC) family including organic anion and cation transporters.86 ABC drug transporters are closely connected to metabolic pathways and using ATP, actively pump endogenous metabolites and cytotoxic drugs out of tumor cells and SLC transporters mediate the influx of cytotoxic drugs into cells.87 Therefore, they control the influx and efflux of chemotherapeutic drugs, modulating the intracellular drug concentration and therefore, determining the therapeutic efficacy and the success or failure of patient treatment.

Of the ABC transporters, MRP1, 2 and 4 are involved with platin transport, MRP1 transports only oxaliplatin and MRP2 and 4 transport cisplatin and oxaliplatin. Furthermore, doxorubicin and irinotecan affect the expression of MRPs in a promoter methylation-dependent manner.88 In addition, the ATPases (e.g., ATP7A and ATP7B) transport cisplatin, oxiplatin and carboplatin.89

The overexpression of ABC drug transporter may be caused by epigenetic changes that are essential for the acquisition of drug resistance and are associated with resistance to numerous chemotherapeutic agents. Early work on DNA methylation levels and drug resistance dates from the mid-1980s. For example, Nyce90 reported the effects of drug-induced methylation in lung adenocarcinoma and rhabdomyosarcoma cells. Pulse exposure to a range of antitumor agents affecting different aspects of the tumor cells included etoposide, nalidixic acid, doxorubicin, vincristine, vinblastine, colchicine, cisplatin, hydroxyurea, 1-beta-D-arabinofuranosylcytosine, 5-fluorouracil, 5-fluorodeoxyuridine and methotrexate, which all led to drug-induced DNA hypermethylation. That this was not a cell culture-specific event was confirmed by its occurrence in leukemic patients undergoing treatment with high-dose 1-beta-D-arabinofuranosylcytosine and hydroxyurea. Subsequent studies have shown that similar results occur in cancer drug resistance.

Epigenetic regulation of organic cation transporters has been shown for OCT1 (octamer, SLC22A1),91 OCT2 (SLC22A2),92 OCT3 (SLC22A3),93 MATE1 (SLC47A1),94 OCTN1 (SLC22A4)95 and OCTN2 (SLC22A5).96 An example of anticancer drug transport can be observed through studies of platin drugs. Therefore, cisplatin is a substrate for OCT1 and OCT2 and oxiliplatin is a substrate for OCT2 and OCT3.89 Variations in the methylation of these transporters can lead to a drug resistance through the modified availability of the anticancer drug employed. In an early study, Schaeffeler et al.,91 observed a significant downregulation of OCT1 protein expression in hepatocellular carcinoma compared with normal adjacent tissue due to increased OCT1 methylation. Qu et al.96 employed methylation-specific PCR and bisulfite genomic sequencing to demonstrate that the degree of individual methylated CpG sites within OCTN2 was inversely correlated with its levels of activity in different cancer cells; therefore, resulting in the reduced uptake of oxiliplatin. Furthermore, this reduced activity could be reversed by the application of dichloroacetate, which increased OCTN2 expression and enhanced oxiliplatin uptake. Subsequently, Buelow et al.95 determined that an increased basal OCTN1 methylation was linked with a decreased cytarabine uptake in acute myeloid leukemia cell lines. Pre-treatment with hypomethylating agents, such as 5-azacytidine and decitabine led to increased cellular uptake of cytarabine with an associated increase in cellular sensitivity to cytarabine.

To circumvent the action of drug transporters, alternative strategies have been reported, for example, the application of monoclonal antibodies directed against P-glycoprotein and liposome-encapsulated drugs.97


Drug metabolism includes a modification of anticancer drugs through catalysis by drug-metabolizing enzymes (DMEs), such as phase I and II DMEs. The expression of DMEs is epigenetically regulated, for instance, by DNA methylation. Habano et al.98 reported that some DME genes were regulated by DNA methylation, which permitted inter- and intra-individual differences in drug metabolism. An analysis of the DNA methylation landscape facilitated clarification of the role of DNA methylation in the regulation of DME genes leading to potential tumor suppression.

Cytosine DNA methylation of DME genes can lead to their activation, metabolic inactivation and, finally, chemotherapy resistance.99 There are two groups of DMEs, such as phase I (functionalization) and II (conjugation) reactions. Phase I reactions concern the redox or hydrolysis of the drug to either activate or detoxify it. This involves cytochrome P450 enzymes (P450s), flavin-containing monooxygenases, alcohol dehydrogenases and aldehyde dehydrogenases.100 Phase II are transferases, such as UDP-glucuronosyltransferases, sulfoctransferases, glutathione S-transferases (GSTP1) and N-acetyltransferases (NAT1).101 Therefore, the various breakdown components are converted into water-soluble products that can be readily excreted.

GSTP1 participates in the metabolism of drugs, such as oxaliplatin and adriamycin. In particular, in prostate cancer patients, the GSTP1 promoter is usually methylated and the methylation level is a marker for distinguishing either benign prostatic hyperplasia from prostate cancer or to predict the prognosis of prostate cancer or drug resistance.102 In addition, the methylation level of NAT1 was detected to be higher (62%) in BC patients with tamoxifen-resistant tumors than in normal tissues.103 These findings indicate that methylation of DMEs may contribute to drug resistance.

DNA methylation and drug resistance in the female reproductive system

Deregulation of signaling pathways may occur through epigenetic changes being prominent in the onset of chemoresistance.49,104 In the following section, the focus is on studies that analyzed DNA methylation associated with the development of drug-treated resistance. The histogram in Figure 6 shows the number of articles derived from PubMed that were specifically related to the investigation of samples from BC, OC, uterine cancer and cervical cancer patients from 2005 to 2022, which are discussed in the following paragraphs.

Histogram of the number of articles.
Fig. 6  Histogram of the number of articles.

The number of articles specifically related to the investigation of samples from BC, OC, uterine cancer, and cervical cancer patients from 2005 to 2022 was used in this article.

Breast cancer

Estrogen receptor (ER)-positive BC is usually treated with tamoxifen, a drug that inhibits the binding of estrogen to its receptor; however, downregulation of ERα is the dominant mechanism of tamoxifen resistance.105 Since the promoter region of ER is rich in CpG dinucleotides, the loss of expression of ER in tumors may be due to aberrant methylation of CpG islands. Epigenetic factors, such as DNMTs, histone deacetylases (HDACs), miRNAs and ubiquitin ligases are important regulators of ER loss in BC. Restoring the response to endocrine therapy through re-expression of ERα by inhibiting the expression of these regulators is, therefore, an essential component of a therapeutic approach.106 The activation of DNMTs in BC was confirmed by Jahangiri et al.105 For immunohistochemical experiments, they used 72 formalin-fixed paraffin-embedded (FFPE) tumor tissues from anti-estrogen tamoxifen sensitive and resistant BC patients. They demonstrated that DNMTs might be an effective factor in the development of tamoxifen resistance in BC.107 In addition, they studied 107 BC tumors and normal breast tissues and revealed that the low methylation status of DNMT3A promoter and the overexpression of DNMT3B could contribute to disease recurrence in tamoxifen-treated BC patients.105 Performing univariate and multivariate analysis, Xu et al.108 compared cisplatin-resistant with cisplatin non-resistant triple-negative BC (TNBC) patients and demonstrated that cisplatin resistance was associated with ERα methylation. Therefore, ERα methylation might be a surrogate biomarker for outcome prediction and cisplatin resistance in TNBC patients. Not all ER-positive BC patients are responsive to endocrine therapy (de novo resistance). The resistance mechanism of ER-positive BC to neoadjuvant endocrine therapy was investigated by Jia et al.109 A microarray was performed on 109 pairs of samples untreated and post-treated with neoadjuvant aromatase inhibitor therapy. Aromatase inhibitors, such as anastrozole, letrozole and exemestane, are alternatives to tamoxifen.110 A study109 found that the methylation of BRCA2 led to incomplete suppression of RAD51, a key protein of homologous recombination;111 therefore, causing an increased expression of RAD51 and then aromatase inhibitor resistance and poor prognosis in ER-positive BC patients. Selli et al.112 investigated the long-term aromatase inhibitor-induced dormancy and acquired resistance in BC patients. In sequential tumor samples from BC patients receiving extended neoadjuvant aromatase inhibitor therapy, global loss of DNA methylation were observed in their tumors. Epigenetic alterations led to an escape from dormancy and drove acquired resistance in a subset of patients. The exemestane resistance was investigated by Liu et al.113 They recruited 16 patients who received first-line exemestane-based hormone therapy and detected synchronized changes in methylation density and methylation ratio on chromosome 6 in the blood samples during exemestane treatment. They suggested that this DNA methylation may be a predictor of exemestane resistance.

Yu et al.114 demonstrated that the protein levels of DNMTs correlated with the response to decitabine in patient-derived xenograft organoids derived from chemotherapy-sensitive and resistant TNBC patients. Depletion of TNF-associated factor 6, which, as an E3 ubiquitin ligase participates in the interleukin-1 receptor/Toll-like receptor family and TNF receptor superfamily pathways,115 blocked decitabine-induced DNMT degradation to confer resistance to decitabine.114

To date, methylation of the components of the cell cycle has been analyzed in relation to drug resistance.116 In their genome-wide DNA methylation analysis, Klajic et al.117 used paired tumor samples from locally advanced BC patients treated with doxorubicin and 5-fluorouracil-mitomycin C. They identified key cell cycle regulators differentially methylated before and after neoadjuvant chemotherapy, such as cyclin-dependent kinase (CDK) inhibitor 2A and cyclin A1. They suggested that the methylation patterns in these genes might be potential predictive markers of anthracycline or mitomycin sensitivity. The relevance of the CDK10 in the resistance to endocrine therapies was demonstrated by Iorns et al.118 They reported that CDK10 silencing increased ETS2-driven transcription of c-RAF, resulting in activation of the MAPK pathway51 and loss of tumor cell reliance upon ER signaling. Patients with ERα-positive tumors that expressed low levels of CDK10, because of promoter methylation, relapsed early on tamoxifen treatment.118

GSTP1 plays an important regulatory role in the detoxification by glutathione conjugation and anti-oxidative damage.119 GSTP1 expression, along with the resistance to neoadjuvant paclitaxel followed by 5-fluorouracil/epirubicin/cyclophosphamide (P-FEC) in BC patients, was investigated by Miyake et al.120 They detected that GSTP1 expression could predict pathological response to P-FEC in ER-negative tumors but not in ER-positive tumors. However, GSTP1 promoter hypermethylation might be implicated in the pathogenesis of luminal A, luminal B and human epidermal growth factor receptor 2 (HER2)-enriched tumors rather than basal-like tumors. Moreover, Arai et al.121 suggested that GSTP1 protein expression, but not GSTP1 methylation status, may be associated with the response to docetaxel and paclitaxel.121

Ye et al.122 demonstrated that spalt-like transcription factor 2 (SALL2) that participates in growth arrest and pro-apoptotic functions,123 upregulated ERα and PTEN through direct binding to their DNA promoters. However, its expression was significantly reduced during tamoxifen therapy in nine paired primary pretamoxifen-treated and relapsed tamoxifen-resistant BC tissues. Silencing of SALL2 by hypermethylation induced downregulation of ERα and PTEN and activated the AKT/mTOR signaling pathway124 resulting in ER-independent growth and tamoxifen resistance in ERα-positive BC. In vivo experiments showed that DNMT inhibitor-mediated SALL2 restoration resensitized tamoxifen-resistant BC to tamoxifen therapy.125

Deregulation of steroid receptor coactivator (SRC) is especially involved in hormone-dependent tumors. By integrating steroid hormone signaling and growth factor pathways, SRC proteins exert diverse functions in oncogenic regulation in cancer.126 Ward et al.127 found that SRC-1 dependent epigenetic remodeling is a regulator of the poorly differentiated state in ER-positive BC. They revealed an epigenetic reprogramming pathway, where concerted differential DNA methylation was potentiated by SRC-1 in the endocrine-resistant setting. Jahangiri et al.128 assessed SRC-3 in 102 BC tissues and adjacent normal breast specimens. They observed overexpression of SRC-3 combined with aberrant promoter methylation of the TF paired box 2 in tamoxifen-resistant BC patients compared with the sensitive ones.

Using Illumina Human Methylation Bead Chips (San Diego, CA, USA) for analyzing FFPE specimens, Gampenrieder et al.129 performed genome-wide DNA methylation profiling of 36 HER2-negative metastatic BC patients under chemotherapy in combination with bevacizumab as first-line therapy. Significantly differentially methylated CpGs with an important change in methylation levels between responders and non-responders were identified and further analyzed in 80 bevacizumab-treated BC patients and 15 patients treated with chemotherapy alone. A nine-gene methylation signature (e.g., WNT2B, MLH1, POLK, NOX4, PKNOX2, TMBIM6, SNRPN, UNC119, and GNAS) and a three-gene signature (e.g., MLH1, POLK, and TMBIM6) could discriminate between responders and non-responders to a bevacizumab-based therapy in metastatic BC patients.

Using a microarray-based technology, Martens et al.130 examined the promoter methylation status of 117 candidate genes in a cohort of 200 steroid hormone receptor-positive tumors of patients who received tamoxifen as a first-line treatment for recurrent BC. They found that promoter hypermethylation and mRNA expression of phosphoserine aminotransferase (PSAT1) might act as indicators for a response to tamoxifen-based endocrine therapy in steroid hormone receptor-positive patients with recurrent BC.

Cancer patients have an elevated level of DNA in their blood, which is caused by active release (e.g., apoptotic and necrotic cells) and active secretion (i.e., extracellular vesicles).131,132 The analyses of circulating methylated DNA in the blood of BC patients have been performed for drug resistance.133 Measurements of serum DNA methylation were performed by Fiegl et al.134 This laboratory showed that loss of Ras association domain family 1 isoform A (RASSF1A) DNA methylation in serum during treatment with tamoxifen highlighted a response, and the persistence or new appearance indicates resistance to adjuvant tamoxifen treatment.

Ovarian cancer

Studies on pathways that contribute to the onset of chemoresistance in epithelial ovarian cancer (EOC) revealed hypermethylation-mediated repression of cell adhesion and tight junction pathways53 and hypomethylation-mediated activation of the cell growth-promoting pathways135 TGF-beta and cell cycle progression.136,137

Numerous studies reported that patients with platinum-resistant OC experienced poor outcomes.52 In a clinical trial, tumors from primary high-grade serous OC (HGSOC) patients were compared with recurrent platinum-resistant HGSOC patients by Cardenas et al.138 Differences in 452 CpG island-containing gene promoters that acquired DNA methylation in platinum-resistant and primary tumors were described. In primary platinum-resistant EOC patients, reduced representation of bisulfite sequencing was performed by Hua et al.139 to screen for aberrantly methylated genes that might serve as potential epigenetic biomarkers for the prediction of primary platinum resistance. Nineteen differentially methylated regions located in the promoter region, which included TRC-GCA11-1, LOC105370912, ANO7P1, DHX4, MSH2, CDCP2, CCNL1, ARHGAP42P2, PRDM13, LOC101928344, USP29, ZIC5, IL1RAPL1, EVX2, ABR, MGRN1, UBALD1, LINC00261, and ISL2, were detected between eight primary platinum-resistant and eight extremely sensitive EOC patients. Furthermore, Yang et al.59 suggested that 3-oxoacid CoA transferase 1 (OXCT1), a key enzyme in ketone body metabolism,140 which was downregulated and hypermethylated at the promoter CpGs in cisplatin-resistant patients, might provide a potential therapeutic target for cisplatin chemotherapy in patients with recurrent EOC. Epigenetic inactivation of the putative DNA/RNA helicase Schlafen-11 (SLFN11) was identified as a predictor of resistance to platinum drugs in human cancer by Nogales et al.141 EOC patients harboring hypermethylation of SLFN11 had a poor response to cisplatin and carboplatin treatments. The CDK inhibitor p57(Kip)2, a cell cycle inhibitor,142 is epigenetically regulated in carboplatin-resistant EOC patients. Coley et al.143 showed that silencing of p57(Kip)2 decreased the apoptotic response under platinum treatment but produced sensitization to seliciclib. In addition, EOC biopsies indicated an association between high levels of p57(Kip)2 mRNA with complete responses to chemotherapy and improved outcomes.

DNA damage repair pathways play an important role in supporting genomic integrity and DNA replication. Their dysfunction leads to accumulated DNA damage, predisposition to cancer and high sensitivity to chemotherapy and radiotherapy. Clinical studies suggest combining agents that target these pathways, such as poly (ADP-ribose) polymerase (PARP) inhibitors. No chemotherapy activates DNA damaging agents. Some types of chemotherapy cause DNA damage only for some drugs. Here, DNA mismatch repair (MMR) plays a role. Loss of MMR proteins lead to resistance in cancer patients, and there are emerging data that concern MMR deficiency in clinical drug resistance in EOC patients.144 Its loss is accompanied by hypermethylation of the hMLH1 gene promoter that occurs at a high frequency in EOC. Re-expression of MLH1 is associated with a decrease in hMLH1 gene promoter methylation.145,146 Tian et al.60 screened 16 platinum-sensitive or resistant samples from EOC patients with a reduced representation of bisulfite sequencing and detected that the upstream region of the hMSH2 gene was hypermethylated in the platinum-resistant group.

Deregulation of cellular metabolism has been recognized as a key event in tumor growth and development, for example, argininosuccinate synthetase 1 (ASS1), which is a rate-limiting step in the arginine synthesis.147 In EOC patients, ASS1 methylation at diagnosis was associated with significantly reduced overall survival and relapse-free survival. In relapsed patients, ASS1 methylation was significantly more frequent than in non-relapsed patients. These data, generated by Nicholson et al.148 demonstrated the epigenetic inactivation of ASS1 as a factor of response to platinum chemotherapy and imply that transcriptional silencing of ASS1 contributes to treatment failure and clinical relapse in EOC patients.

PLK2 is an acidophilic kinase belonging to the polo-like kinases (PLK), a family with five members with a central role in the cell cycle.149 Syed et al.150 reported that resistance might be conferred by the downregulation of PLK2. Experiments revealed that its downregulation occurred by DNA methylation of the CpG island in the PLK2 gene promoter in primary tumors and serum of EOC patients. PLK2 promoter methylation varied with the degree of drug resistance and transcriptional silencing of the promoter. In tumor tissues and matched sera, DNA methylation of the PLK2 CpG island was associated with a higher risk of relapse in patients treated postoperatively with carboplatin and paclitaxel.

BRCA1 and BRCA2 participate in DNA repair processes and are important markers for BC and EOC. Apart from the hundreds of mutations identified in these genes, they are methylated. Their loss impairs DNA repair and causes irregularities in DNA synthesis.151 In preclinical models and EOC patients, Kondrashova et al.152 demonstrated that quantitative assessment of BRCA1 methylation might provide information on the PARP inhibitor response. Analysis of 21 BRCA1-methylated platinum-sensitive recurrent HGSOC demonstrated that homozygous or hemizygous BRCA1 methylation predicts rucaparib clinical response and that methylation loss can occur after exposure to chemotherapy.152

Homeobox (HOX) genes are developmental genes that code for TFs involved in embryogenesis. Numerous reports have shown that their altered expression can play key roles in the development of tumors.153 Rusan et al.154 revealed that HOXA9 promoter methylation in circulating tumor DNA could serve as a biomarker in patients with platinum-resistant BRCA-mutated EOC undergoing treatment with PARP inhibitors. Bonito et al.155 studied DNA methylation in independent tumor cohorts using Illumina Human Methylation arrays. Hypomethylation of CpG sites within the Msh homeobox 1 (MSX1) gene was associated with resistant HGSOC disease and expression of MSX1, which resulted in platinum drug sensitivity.

High DNA methylation in normal 1 (HIN-1) was detected in paclitaxel-resistant tumor tissues of patients with ovarian clear cell carcinoma (OCCA) by Ho et al.156,157 The demethylating agent 5-aza-2-deoxycytidine (5-aza-2-dC) reversed the methylation of HIN-1, reactivated the expression of HIN-1, to finally suppress the in vivo tumor growth of paclitaxel-resistant OCCC cells.156,157 Li et al.158 showed that methylation-associated miR-9 downregulation might be responsible for paclitaxel resistance in EOC patients. Paclitaxel resistance is mediated by the deficiency of this miRNA that binds to CCNG1, a commonly induced p53 target.159

Chen et al.160 examined the methylation of various genes in OCCA and ovarian endometrioid adenocarcinoma (OEA) and evaluated methylation biomarkers referring to patient chemo response and outcome. The frequencies of gene methylation in RASSF1A (79% versus 59%), a Ras effector that promotes the antiproliferative properties of Ras,161E-cadherin (30% versus 10%), a calcium-dependent, epithelial cell adhesion molecule162 and deleted in lung and esophageal cancer 1 (DLEC1, 71% versus 43%)163 were higher in OCCA patients than in OEA patients. The chemoresistant cohort had a higher percentage of E-cadherin methylation (36.7% versus 16.1%) than the chemosensitive group.160

In EOC, deficiency in human sulfatase-I (hSulf-1) is involved in the metabolic reprograming of glycolysis and the cell cycle.164 EOC patients who expressed higher levels of hSulf-1 displayed a 90% response rate to chemotherapy compared with a response rate of 63% in patients with weak or moderate levels. The findings reported by Staub et al.165 indicated that hSulf-1 was epigenetically silenced in EOC and that epigenetic therapy targeting hSulf-1 might sensitize OC to conventional first-line therapies.165

Methylation controlled DNAJ (MCJ) is in the mitochondria.166 Strathdee et al.167 determined the methylation status of 35 CpG sites of an MCJ CpG island by sequencing sodium bisulfite modified tumor DNA derived from tumor tissues of 41 EOC patients at stage III/IV. The presence of high levels of CpG island methylation correlated significantly with poor response to therapy and poor overall survival.167

Uterine cancer

Phosphoglycerate kinase 1 (PGK1) is a key glycolytic enzyme.168 In endometrial cancer, Zhou et al.169 reported that PGK1 expression was elevated in tumor tissues and its high levels correlated with clinical stages and metastasis. PGK1 mediated DNA repair and methylation through the HSP90/ERK pathway, and eventually enhanced the chemoresistance to cisplatin. PGK1 interacted directly with the heat shock protein HSP9 and modulated the ATPase activity of HSP90, a molecular chaperone that assists in the conformational folding, stabilization and degradation of cellular proteins.170

Cervical cancer

Septin 9 (SEPT9) is a member of the conserved family of cytoskeletal GTPases. It participates in numerous biological processes, such as cytokinesis, polarization, vesicle trafficking, membrane reconstruction, DNA repair, cell migration and apoptosis. For example, SEPT9 might serve as a marker for the early screening of colon cancer since the presence of freely circulating, methylated SEPT9 DNA in blood plasma strongly correlates with the occurrence of colon cancer. The commercial SEPT9 test detects methylated DNA of the SEPT9 gene in blood plasma to predict colon cancer.171 Using methylation-specific PCR, Jiao et al.172 detected methylated SEPT9 in different cervical tissues. SEPT9 promoted tumorigenesis and radioresistance in cervical cancer by targeting the high-mobility group box-1-retinoblastoma axis which participates in antitumor growth.173 SEPT9 was reported to be involved in proliferation, invasion, migration and influenced the cell cycle of cervical cancer.173

In total, 100 cervical cancer patients at FIGO stage IIB/III who underwent chemoradiation treatment were evaluated by Sood et al.174 The methylation frequency of ERα, BRCA1, RASSF1A, MLH1, myogenic determination factor 1 (MYOD1) and human telomerase reverse transcriptase (hTERT) genes were from 40% to 70%. A pattern of unmethylated MYOD1, unmethylated Erα, methylated hTERT promoter, and lower ERα transcript levels predicted chemoradiation resistance.

Finally, Chaopatchayakul et al.175 showed that aberrant DNA methylation of apoptotic signaling genes resulted in acquired resistance to therapy in cervical cancer patients. The methylation frequency of death-associated protein kinase and FAS molecules that play an important role in apoptosis,176 exhibited a statistically significant difference between therapeutic non-responders and responders.175

Epigenetic therapies

The main barrier to the successful treatment of cancer patients is the development of drug resistance. Therefore, the analysis of specific methylated biomarkers could improve cancer treatment and overcome drug resistance and recurrence. It is a high priority to understand these methylation changes that accompany cancer development and progression and therefore, be able to predict the patients that will benefit from specific treatment strategies. Epigenetic modifiers, such as DNMT inhibitors, in combination with HDAC inhibitors, have emerged as promising drug targets for cancer therapy in advanced-stage malignancies.177 However, global genomic hypomethylation and acetylation might cause genomic instability, leading to chromosomal breaks.178

Thirty years ago, Jones and Taylor179 reported that the analogs of cytidine, 5-aza-cytidine (5-aza-C) and 5-aza-2-dC induced differentiation of cultured mouse embryo cells to muscle cells. The ability of both drugs to induce differentiation and cell death provoked their investigation into the treatment of different cancer types. Both agents can be incorporated into DNA; however, 5-aza-C can be incorporated additionally into RNA and therefore, is an inhibitor for DNMT and RNA methyltransferases.180 They have been demonstrated to be potent alternatives to conventional chemotherapy, particularly in the therapy of myelodysplastic syndrome and acute myeloid leukemia. Compared with conventional medical care, therapy of myelodysplastic syndrome with 5-aza-C doubled the 2-year survival rate of these patients.181 The limitations of these components are their instability in aqueous solution, inactivation by cytidine deaminase to 5-azauridine and the potential re-establishment of DNA methylation by the withdrawal of DNMT inhibitors. However, another cytidine analog, zebularine, that lacks the amino group on C-4 of the pyrimidine ring is stable in an aqueous solution and can be administered orally.182

Histone deacetylase inhibitors have several functions. They modulate gene transcription by inhibiting the deacetylation of histones and proteins, including TFs. They inhibit proliferation at the G2 cell cycle checkpoint and upregulate pro-apoptotic molecules. In addition, they induce G1 cell cycle arrest via activation of p21 in tumors with defective p53 function.183 In several cancer types, histone deacetylase inhibitors are efficient in combination therapy, and cutaneous T-cell lymphoma was successfully treated by vorinostat alone that can be administered orally.184 The development of drugs that target the epigenome (epi-drugs) to modulate the sensitivity of tumors to other anticancer drugs and to overcome therapy resistance continues and could provide new approaches to clinical investigations. To date, immunotherapy has emerged as an important strategy to treat cancer, because epigenetic processes are essential in regulating immune cell function and mediating antitumor immunity. A detailed report on these therapies was recently published by Topper et al.185 Therefore, the development of epi-drugs should follow a precision-medicine approach with sequential treatment. A new generation of epi-drugs, which were developed for specific targets, have promising activity in populations with selected biomarkers. These have now entered early phase clinical trials and eventually might display promising efficacy.186


In this review, DNA methylation related to gynecological tumors was discussed to gain a deeper insight into the epigenetic alterations that lead to the inactivation of tumor suppressors and DNA instability.187 Epigenetic modifications can be investigated by numerous different techniques. As detailed in a review by Gouil et al.,188 DNA methylation can be detected by bisulfite sequencing, methylation-specific PCR, multiplex ligation-dependent probe amplification, sequenom mass array technology, or methylation bead chip methodology.

However, to succeed in the detection of specific methylated biomarkers, a more genome-wide approach and screening methods must be applied. To date, investigations of the methylome have revealed important signaling pathways that contribute to therapy resistance, such as the Wnt189 and PI3K/PTEN/AKT/mTOR124 signaling pathways and cell adhesion or tight junction pathways.53 The deregulation of cellular metabolism and DNA damage repair are examples of DNA hypermethylation.144 Some methylation patterns have been established for specific tumors; however, few DNA methylation patterns have the specificity and sensitivity to identify specific cancer types with certainty. Despite these shortcomings, regimens with demethylating agents combined with standard therapies appear to be encouraging. Studies have attempted to change drug resistance-associated DNA methylation patterns using DNMT- and TET-dependent demethylation methods.190 These agents provided an imbalance in the global DNA methylation pattern that caused the activation of tumor suppressor genes and oncogenes, which resulted in undesirable side effects. Therefore, a fine balance between DNA methylation is necessary to establish a correct drug response.

Future experiments will determine whether interventions into the methylation patterns will succeed in overcoming drug resistance.



argininosuccinate synthetase 1


B-cell lymphoma-2 associated X


breast cancer


B-cell lymphoma


breast cancer 1




cyclin dependent kinase


drug metabolizing enzymes


DNA methyltransferase


epidermal growth factor receptor


epithelial ovarian cancer


estrogen receptor α


cell surface death receptor gene


glutathione S transferase


histone deacetylases


human epidermal growth factor receptor 2


human endogenous retrovirus


high-grade serous ovarian cancer




human sulfatase-I


DNA-binding inhibitor 4




myelin and lymphocyte


multidrug resistance 1


O6-methylguanine-DNA methyltransferase


matrix gla protein




DNA mismatch repair


multidrug resistance proteins


mismatch protein






ovarian cancer


ovarian clear cell carcinoma




3-Oxoacid CoA transferase 1


poly (ADP-ribose) polymerase


patient-derived xenograft


phosphoglycerate kinase 1




phosphatidylinositol 3-kinase


phosphatidylinositol 3,4,5-trisphosphate


kinase B


polo-like kinases


phosphoserine aminotransferase 1


phosphatase tensin homolog


Ras association domain family 1A


receptor tyrosine kinase


spalt-like transcription factor 2


Septin 9




solute carrier




suppressor of cytokine signaling


steroid receptor coactivator


signal transducer and activator of transcription 3


ten-eleven translocation


transforming growth factor B1


Toll-like receptor


transmembrane protein 88


triple-negative breast cancer


tumor necrosis factor


target of rapamycin


TNF-associated factor 6


TNF-related apoptosis-inducing ligand


tribbles 2


ubiquitin C-terminal hydrolase L1




ubiquitin-like, containing PHD and RING finger domains 1


zing finger 582






Conflict of interest

The authors have no conflicts of interest related to this publication.

Authors’ contributions

HS wrote the paragraph “DNA methylation and drug resistance in the female reproductive system” and “Epigentic therapies”, and created the figures and the table. PBG wrote the introduction and “DNA methylation and drug resistance in cancer cells” and checked the English. HS and PBG wrote together the paragraphs on signaling pathways, drug transport and metabolism, and the conclusion.


  1. Baldwin JM. A new factor in evolution. The American Naturalist 1896;30(354):441-451 View Article
  2. Noble D. Conrad Waddington and the origin of epigenetics. J Exp Biol 2015;218(Pt 6):816-818 View Article PubMed/NCBI
  3. Waddington CH. Genetic assimilation. Adv Genet 1961;10:257-293 View Article PubMed/NCBI
  4. Waddington CH. The genetic basis of the ‘assimilated bithorax’ stock. J Genet 1957;55:241-245 View Article
  5. Esteller M. Epigenetics in cancer. N Engl J Med 2008;358(11):1148-1159 View Article PubMed/NCBI
  6. Avery OT, Macleod CM, McCarty M. Studies on the chemical nature of the substance inducing transformation of pneumococcal types: induction of transformation by a desoxyribonucleic acid fraction isolated from pneumococcus type Iii. J Exp Med 1944;79(2):137-158 View Article PubMed/NCBI
  7. Leonhardt H, Page AW, Weier HU, Bestor TH. A targeting sequence directs DNA methyltransferase to sites of DNA replication in mammalian nuclei. Cell 1992;71(5):865-873 View Article
  8. Mortusewicz O, Schermelleh L, Walter J, Cardoso MC, Leonhardt H. Recruitment of DNA methyltransferase I to DNA repair sites. Proc Natl Acad Sci U S A 2005;102(25):8905-8909 View Article PubMed/NCBI
  9. Veland N, Hardikar S, Zhong Y, Gayatri S, Dan J, Strahl BD, et al. The arginine methyltransferase PRMT6 regulates DNA methylation and contributes to global DNA hypomethylation in cancer. Cell Rep 2017;21(12):3390-3397 View Article PubMed/NCBI
  10. Tost J. DNA methylation: an introduction to the biology and the disease-associated changes of a promising biomarker. Mol Biotechnol 2010;44(1):71-81 View Article PubMed/NCBI
  11. Moore LD, Le T, Fan G. DNA methylation and its basic function. Neuropsychopharmacology 2013;38(1):23-38 View Article PubMed/NCBI
  12. Xie S, Wang Z, Okano M, Nogami M, Li Y, He WW, et al. Cloning, expression and chromosome locations of the human DNMT3 gene family. Gene 1999;236(1):87-95 View Article PubMed/NCBI
  13. Okano M, Bell DW, Haber DA, Li E. DNA methyltransferases Dnmt3a and Dnmt3b are essential for de novo methylation and mammalian development. Cell 1999;99(3):247-257 View Article PubMed/NCBI
  14. Bird A, Taggart M, Frommer M, Miller OJ, Macleod D. A fraction of the mouse genome that is derived from islands of nonmethylated, CpG-rich DNA. Cell 1985;40(1):91-99 View Article PubMed/NCBI
  15. Fatemi M, Pao MM, Jeong S, Gal-Yam EN, Egger G, Weisenberger DJ, et al. Footprinting of mammalian promoters: use of a CpG DNA methyltransferase revealing nucleosome positions at a single molecule level. Nucleic Acids Res 2005;33(20):e176 View Article PubMed/NCBI
  16. Zeisberg EM, Zeisberg M. The role of promoter hypermethylation in fibroblast activation and fibrogenesis. J Pathol 2013;229(2):264-273 View Article PubMed/NCBI
  17. Jeong M, Sun D, Luo M, Huang Y, Challen GA, Rodriguez B, et al. Large conserved domains of low DNA methylation maintained by Dnmt3a. Nat Genet 2014;46(1):17-23 View Article PubMed/NCBI
  18. Xie T, Zhang J, Yuan X, Yang J, Ding W, Huang X, et al. Is X-linked methyl-CpG binding protein 2 a new target for the treatment of Parkinson’s disease. Neural Regen Res 2013;8(21):1948-1957 View Article PubMed/NCBI
  19. Deaton AM, Webb S, Kerr AR, Illingworth RS, Guy J, Andrews R, et al. Cell type-specific DNA methylation at intragenic CpG islands in the immune system. Genome Res 2011;21(7):1074-1086 View Article PubMed/NCBI
  20. Saxonov S, Berg P, Brutlag DL. A genome-wide analysis of CpG dinucleotides in the human genome distinguishes two distinct classes of promoters. Proc Natl Acad Sci U S A 2006;103(5):1412-1417 View Article PubMed/NCBI
  21. Mohn F, Weber M, Rebhan M, Roloff TC, Richter J, Stadler MB, et al. Lineage-specific polycomb targets and de novo DNA methylation define restriction and potential of neuronal progenitors. Mol Cell 2008;30(6):755-766 View Article PubMed/NCBI
  22. Gardiner-Garden M, Frommer M. CpG islands in vertebrate genomes. J Mol Biol 1987;196(2):261-282 View Article PubMed/NCBI
  23. Wu X, Zhang Y. TET-mediated active DNA demethylation: mechanism, function and beyond. Nat Rev Genet 2017;18(9):517-534 View Article PubMed/NCBI
  24. Lio CJ, Rao A. TET Enzymes and 5hmC in adaptive and innate immune systems. Front Immunol 2019;10:210 View Article PubMed/NCBI
  25. Scourzic L, Mouly E, Bernard OA. TET proteins and the control of cytosine demethylation in cancer. Genome Med 2015;7(1):9 View Article PubMed/NCBI
  26. Ito S, Shen L, Dai Q, Wu SC, Collins LB, Swenberg JA, et al. Tet proteins can convert 5-methylcytosine to 5-formylcytosine and 5-carboxylcytosine. Science 2011;333(6047):1300-1303 View Article PubMed/NCBI
  27. Deaton AM, Bird A. CpG islands and the regulation of transcription. Genes Dev 2011;25(10):1010-1022 View Article PubMed/NCBI
  28. Costa Y, Ding J, Theunissen TW, Faiola F, Hore TA, Shliaha PV, et al. NANOG-dependent function of TET1 and TET2 in establishment of pluripotency. Nature 2013;495(7441):370-374 View Article PubMed/NCBI
  29. Gong S, Li Q, Jeter CR, Fan Q, Tang DG, Liu B. Regulation of NANOG in cancer cells. Mol Carcinog 2015;54(9):679-687 View Article PubMed/NCBI
  30. Jeter CR, Yang T, Wang J, Chao HP, Tang DG. Concise Review: NANOG in cancer stem cells and tumor development: an update and outstanding questions. Stem Cells 2015;33(8):2381-2390 View Article PubMed/NCBI
  31. Gawlik-Rzemieniewska N, Bednarek I. The role of NANOG transcriptional factor in the development of malignant phenotype of cancer cells. Cancer Biol Ther 2016;17(1):1-10 View Article PubMed/NCBI
  32. Zhang W, Sui Y, Ni J, Yang T. Insights into the Nanog gene: A propeller for stemness in primitive stem cells. Int J Biol Sci 2016;12(11):1372-1381 View Article PubMed/NCBI
  33. Dixon G, Pan H, Yang D, Rosen BP, Jashari T, Verma N, et al. QSER1 protects DNA methylation valleys from de novo methylation. Science 2021;372(6538):eabd0875 View Article PubMed/NCBI
  34. Niehrs C. The complex world of WNT receptor signalling. Nat Rev Mol Cell Biol 2012;13(12):767-779 View Article PubMed/NCBI
  35. Komiya Y, Habas R. Wnt signal transduction pathways. Organogenesis 2008;4(2):68-75 View Article PubMed/NCBI
  36. Nusse R, Varmus HE. Many tumors induced by the mouse mammary tumor virus contain a provirus integrated in the same region of the host genome. Cell 1982;31(1):99-109 View Article PubMed/NCBI
  37. Nusse R, Clevers H. Wnt/β-Catenin signaling, disease, and emerging therapeutic modalities. Cell 2017;169(6):985-999 View Article PubMed/NCBI
  38. Wu CI, Hoffman JA, Shy BR, Ford EM, Fuchs E, Nguyen H, et al. Function of Wnt/β-catenin in counteracting Tcf3 repression through the Tcf3-β-catenin interaction. Development 2012;139(12):2118-2129 View Article PubMed/NCBI
  39. MacDonald BT, Tamai K, He X. Wnt/beta-catenin signaling: components, mechanisms, and diseases. Dev Cell 2009;17(1):9-26 View Article PubMed/NCBI
  40. Shi J, Chi S, Xue J, Yang J, Li F, Liu X. Emerging role and therapeutic implication of Wnt signaling pathways in autoimmune diseases. J Immunol Res 2016;2016:9392132 View Article PubMed/NCBI
  41. Lang CMR, Chan CK, Veltri A, Lien WH. Wnt Signaling pathways in keratinocyte carcinomas. Cancers (Basel) 2019;11(9):E1216 View Article PubMed/NCBI
  42. van Amerongen R, Nusse R. Towards an integrated view of Wnt signaling in development. Development 2009;136(19):3205-3214 View Article PubMed/NCBI
  43. Ying Y, Tao Q. Epigenetic disruption of the WNT/beta-catenin signaling pathway in human cancers. Epigenetics 2009;4(5):307-312 PubMed/NCBI
  44. Fruman DA, Chiu H, Hopkins BD, Bagrodia S, Cantley LC, Abraham RT. The PI3K pathway in human disease. Cell 2017;170(4):605-635 View Article PubMed/NCBI
  45. Damelin M, Bestor TH. Biological functions of DNA methyltransferase 1 require its methyltransferase activity. Mol Cell Biol 2007;27(11):3891-3899 View Article PubMed/NCBI
  46. Barrès R, Yan J, Egan B, Treebak JT, Rasmussen M, Fritz T, et al. Acute exercise remodels promoter methylation in human skeletal muscle. Cell Metab 2012;15(3):405-411 View Article PubMed/NCBI
  47. Irizarry RA, Ladd-Acosta C, Wen B, Wu Z, Montano C, Onyango P, et al. The human colon cancer methylome shows similar hypo- and hypermethylation at conserved tissue-specific CpG island shores. Nat Genet 2009;41(2):178-186 View Article PubMed/NCBI
  48. Tsuboi K, Nagatomo T, Gohno T, Higuchi T, Sasaki S, Fujiki N, et al. Single CpG site methylation controls estrogen receptor gene transcription and correlates with hormone therapy resistance. J Steroid Biochem Mol Biol 2017;171:209-217 View Article PubMed/NCBI
  49. Romero-Garcia S, Prado-Garcia H, Carlos-Reyes A. Role of DNA methylation in the resistance to therapy in solid tumors. Front Oncol 2020;10:1152 View Article PubMed/NCBI
  50. Spangle JM, Dreijerink KM, Groner AC, Cheng H, Ohlson CE, Reyes J, et al. PI3K/AKT signaling regulates H3K4 methylation in breast cancer. Cell Rep 2016;15(12):2692-2704 View Article PubMed/NCBI
  51. Cargnello M, Roux PP. Activation and function of the MAPKs and their substrates, the MAPK-activated protein kinases. Microbiol Mol Biol Rev 2011;75(1):50-83 View Article PubMed/NCBI
  52. Damia G, Broggini M. Platinum resistance in ovarian cancer: Role of DNA Repair. Cancers (Basel) 2019;11(1):E119 View Article PubMed/NCBI
  53. Bhat AA, Uppada S, Achkar IW, Hashem S, Yadav SK, Shanmugakonar M, et al. Tight junction proteins and signaling pathways in cancer and inflammation: A Functional Crosstalk. Front Physiol 2018;9:1942 View Article PubMed/NCBI
  54. Brzozowa-Zasada M, Piecuch A, Michalski M, Segiet O, Kurek J, Harabin-Słowińska M, et al. Notch and its oncogenic activity in human malignancies. Eur Surg 2017;49(5):199-209 View Article PubMed/NCBI
  55. Hegde M, Joshi MB. Comprehensive analysis of regulation of DNA methyltransferase isoforms in human breast tumors. J Cancer Res Clin Oncol 2021;147(4):937-971 View Article PubMed/NCBI
  56. Mohammad RM, Muqbil I, Lowe L, Yedjou C, Hsu HY, Lin LT, et al. Broad targeting of resistance to apoptosis in cancer. Semin Cancer Biol 2015;35(Suppl):S78-S103 View Article PubMed/NCBI
  57. Hervouet E, Cheray M, Vallette FM, Cartron PF. DNA methylation and apoptosis resistance in cancer cells. Cells 2013;2(3):545-573 View Article PubMed/NCBI
  58. Zhang J, Zhou C, Jiang H, Liang L, Shi W, Zhang Q, et al. ZEB1 induces ER-α promoter hypermethylation and confers antiestrogen resistance in breast cancer. Cell Death Dis 2017;8(4):e2732 View Article PubMed/NCBI
  59. Yang SD, Ahn SH, Kim JI. 3-Oxoacid CoA transferase 1 as a therapeutic target gene for cisplatin-resistant ovarian cancer. Oncol Lett 2018;15(2):2611-2618 View Article PubMed/NCBI
  60. Tian H, Yan L, Xiao-Fei L, Hai-Yan S, Juan C, Shan K. Hypermethylation of mismatch repair gene hMSH2 associates with platinum-resistant disease in epithelial ovarian cancer. Clin Epigenetics 2019;11(1):153 View Article PubMed/NCBI
  61. Palomeras S, Diaz-Lagares Á, Viñas G, Setien F, Ferreira HJ, Oliveras G, et al. Epigenetic silencing of TGFBI confers resistance to trastuzumab in human breast cancer. Breast Cancer Res 2019;21(1):79 View Article PubMed/NCBI
  62. Ponnusamy L, Mahalingaiah PKS, Chang YW, Singh KP. Reversal of epigenetic aberrations associated with the acquisition of doxorubicin resistance restores drug sensitivity in breast cancer cells. Eur J Pharm Sci 2018;123:56-69 View Article PubMed/NCBI
  63. Tuo YL, Ye YF. MGP is downregulated due to promoter methylation in chemoresistant ER+ breast cancer and high MGP expression predicts better survival outcomes. Eur Rev Med Pharmacol Sci 2017;21(17):3871-3878 PubMed/NCBI
  64. De Marchi T, Timmermans MA, Sieuwerts AM, Smid M, Look MP, Grebenchtchikov N, et al. Phosphoserine aminotransferase 1 is associated to poor outcome on tamoxifen therapy in recurrent breast cancer. Sci Rep 2017;7(1):2099 View Article PubMed/NCBI
  65. Kim MH, Kim MS, Kim W, Kang MA, Cacalano NA, Kang SB, et al. Suppressor of cytokine signaling (SOCS) genes are silenced by DNA hypermethylation and histone deacetylation and regulate response to radiotherapy in cervical cancer cells. PLoS One 2015;10(4):e0123133 View Article PubMed/NCBI
  66. Wu NY, Zhang X, Chu T, Zhu S, Deng Y, Zhou Y, et al. High methylation of ZNF582 in cervical adenocarcinoma affects radiosensitivity and prognosis. Ann Transl Med 2019;7(14):328 View Article PubMed/NCBI
  67. Jin C, Yu W, Lou X, Zhou F, Han X, Zhao N, et al. UCHL1 is a putative tumor suppressor in ovarian cancer cells and contributes to cisplatin resistance. J Cancer 2013;4(8):662-670 View Article PubMed/NCBI
  68. Prieske K, Prieske S, Joosse SA, Trillsch F, Grimm D, Burandt E, et al. Loss of BRCA1 promotor hypermethylation in recurrent high-grade ovarian cancer. Oncotarget 2017;8(47):83063-83074 View Article PubMed/NCBI
  69. Deng Y, Zhao F, Hui L, Li X, Zhang D, Lin W, et al. Suppressing miR-199a-3p by promoter methylation contributes to tumor aggressiveness and cisplatin resistance of ovarian cancer through promoting DDR1 expression. J Ovarian Res 2017;10(1):50 View Article PubMed/NCBI
  70. Gao B, Yang F, Chen W, Li R, Hu X, Liang Y, et al. Multidrug resistance affects the prognosis of primary epithelial ovarian cancer. Oncol Lett 2019;18(4):4262-4269 View Article PubMed/NCBI
  71. Ha YN, Sung HY, Yang SD, Chae YJ, Ju W, Ahn JH. Epigenetic modification of α-N-acetylgalactosaminidase enhances cisplatin resistance in ovarian cancer. Korean J Physiol Pharmacol 2018;22(1):43-51 View Article PubMed/NCBI
  72. Kritsch D, Hoffmann F, Steinbach D, Jansen L, Mary Photini S, Gajda M, et al. Tribbles 2 mediates cisplatin sensitivity and DNA damage response in epithelial ovarian cancer. Int J Cancer 2017;141(8):1600-1614 View Article PubMed/NCBI
  73. Zhang Y, Zhang B, Fang J, Cao X. Hypomethylation of DNA-binding inhibitor 4 serves as a potential biomarker in distinguishing acquired tamoxifen-refractory breast cancer. Int J Clin Exp Pathol 2015;8(8):9500-9505 PubMed/NCBI
  74. Chen S, Zhang Y, Zhang D. Endoplasmic reticulum protein 29 (ERp29) confers radioresistance through the DNA repair gene, O(6)-methylguanine DNA-methyltransferase, in breast cancer cells. Sci Rep 2015;5:14723 View Article PubMed/NCBI
  75. Hu H, Li S, Cui X, Lv X, Jiao Y, Yu F, et al. The overexpression of hypomethylated miR-663 induces chemotherapy resistance in human breast cancer cells by targeting heparin sulfate proteoglycan 2 (HSPG2). J Biol Chem 2013;288(16):10973-10985 View Article PubMed/NCBI
  76. Chekhun VF, Kulik GI, Yurchenko OV, Tryndyak VP, Todor IN, Luniv LS, et al. Role of DNA hypomethylation in the development of the resistance to doxorubicin in human MCF-7 breast adenocarcinoma cells. Cancer Lett 2006;231(1):87-93 View Article PubMed/NCBI
  77. Pan JX, Qu F, Wang FF, Xu J, Mu LS, Ye LY, et al. Aberrant SERPINE1 DNA methylation is involved in carboplatin induced epithelial-mesenchymal transition in epithelial ovarian cancer. Arch Gynecol Obstet 2017;296(6):1145-1152 View Article PubMed/NCBI
  78. de Leon M, Cardenas H, Vieth E, Emerson R, Segar M, Liu Y, et al. Transmembrane protein 88 (TMEM88) promoter hypomethylation is associated with platinum resistance in ovarian cancer. Gynecol Oncol 2016;142(3):539-547 View Article PubMed/NCBI
  79. Li D, Wu QJ, Bi FF, Chen SL, Zhou YM, Zhao Y, et al. Effect of the BRCA1-SIRT1-EGFR axis on cisplatin sensitivity in ovarian cancer. Am J Transl Res 2016;8(3):1601-1608 PubMed/NCBI
  80. Iramaneerat K, Rattanatunyong P, Khemapech N, Triratanachat S, Mutirangura A. HERV-K hypomethylation in ovarian clear cell carcinoma is associated with a poor prognosis and platinum resistance. Int J Gynecol Cancer 2011;21(1):51-57 View Article PubMed/NCBI
  81. Lee PS, Teaberry VS, Bland AE, Huang Z, Whitaker RS, Baba T, et al. Elevated MAL expression is accompanied by promoter hypomethylation and platinum resistance in epithelial ovarian cancer. Int J Cancer 2010;126(6):1378-1389 View Article PubMed/NCBI
  82. Meredith AM, Dass CR. Increasing role of the cancer chemotherapeutic doxorubicin in cellular metabolism. J Pharm Pharmacol 2016;68(6):729-741 View Article PubMed/NCBI
  83. Ghosh J, Schultz B, Coutifaris C, Sapienza C. Highly variant DNA methylation in normal tissues identifies a distinct subclass of cancer patients. Adv Cancer Res 2019;142:1-22 View Article PubMed/NCBI
  84. Longley DB, Johnston PG. Molecular mechanisms of drug resistance. J Pathol 2005;205(2):275-292 View Article PubMed/NCBI
  85. Vasiliou V, Vasiliou K, Nebert DW. Human ATP-binding cassette (ABC) transporter family. Hum Genomics 2009;3(3):281-290 View Article PubMed/NCBI
  86. Nigam SK. What do drug transporters really do?. Nat Rev Drug Discov 2015;14(1):29-44 View Article PubMed/NCBI
  87. Choi YH, Yu AM. ABC transporters in multidrug resistance and pharmacokinetics, and strategies for drug development. Curr Pharm Des 2014;20(5):793-807 View Article PubMed/NCBI
  88. Baker EK, Johnstone RW, Zalcberg JR, El-Osta A. Epigenetic changes to the MDR1 locus in response to chemotherapeutic drugs. Oncogene 2005;24(54):8061-8075 View Article PubMed/NCBI
  89. Zhou J, Kang Y, Chen L, Wang H, Liu J, Zeng S, et al. The Drug-resistance mechanisms of five platinum-based antitumor agents. Front Pharmacol 2020;11:343 View Article PubMed/NCBI
  90. Nyce J. Drug-induced DNA hypermethylation and drug resistance in human tumors. Cancer Res 1989;49(21):5829-5836 PubMed/NCBI
  91. Schaeffeler E, Hellerbrand C, Nies AT, Winter S, Kruck S, Hofmann U, et al. DNA methylation is associated with downregulation of the organic cation transporter OCT1 (SLC22A1) in human hepatocellular carcinoma. Genome Med 2011;3(12):82 View Article PubMed/NCBI
  92. Liu Y, Zheng X, Yu Q, Wang H, Tan F, Zhu Q, et al. Epigenetic activation of the drug transporter OCT2 sensitizes renal cell carcinoma to oxaliplatin. Sci Transl Med 2016;8(348):348ra97 View Article PubMed/NCBI
  93. Chen L, Hong C, Chen EC, Yee SW, Xu L, Almof EU, et al. Genetic and epigenetic regulation of the organic cation transporter 3, SLC22A3. Pharmacogenomics J 2013;13(2):110-120 View Article PubMed/NCBI
  94. Tanaka T, Hirota T, Ieiri I. Relationship between DNA methylation in the 5′ CpG island of the SLC47A1 (multidrug and toxin extrusion protein MATE1) gene and interindividual variability in MATE1 Expression in the human liver. Mol Pharmacol 2018;93(1):1-7 View Article PubMed/NCBI
  95. Buelow DR, Anderson JT, Pounds SB, Shi L, Lamba JK, Hu S, et al. DNA methylation-based epigenetic repression of SLC22A4 promotes resistance to cytarabine in acute myeloid leukemia. Clin Transl Sci 2021;14(1):137-142 View Article PubMed/NCBI
  96. Qu Q, Qu J, Zhan M, Wu LX, Zhang YW, Lou XY, et al. Different involvement of promoter methylation in the expression of organic cation/carnitine transporter 2 (OCTN2) in cancer cell lines. PLoS One 2013;8(10):e76474 View Article PubMed/NCBI
  97. Kong L, Chen Q, Campbell F, Snaar-Jagalska E, Kros A. Light-triggered cancer cell specific targeting and liposomal drug delivery in a zebrafish xenograft model. Adv Healthc Mater 2020;9(6):e1901489 View Article PubMed/NCBI
  98. Habano W, Kawamura K, Iizuka N, Terashima J, Sugai T, Ozawa S. Analysis of DNA methylation landscape reveals the roles of DNA methylation in the regulation of drug metabolizing enzymes. Clin Epigenetics 2015;7:105 View Article PubMed/NCBI
  99. Wang J, Yu L, Jiang H, Zheng X, Zeng S. Epigenetic regulation of differentially expressed drug-metabolizing enzymes in cancer. Drug Metab Dispos 2020;48(9):759-768 View Article PubMed/NCBI
  100. Nebert DW, Dalton TP. The role of cytochrome P450 enzymes in endogenous signalling pathways and environmental carcinogenesis. Nat Rev Cancer 2006;6(12):947-960 View Article PubMed/NCBI
  101. Almazroo OA, Miah MK, Venkataramanan R. Drug metabolism in the liver. Clin Liver Dis 2017;21(1):1-20 View Article PubMed/NCBI
  102. Goering W, Kloth M, Schulz WA. DNA methylation changes in prostate cancer. Methods Mol Biol 2012;863:47-66 View Article PubMed/NCBI
  103. Kim SJ, Kang HS, Jung SY, Min SY, Lee S, Kim SW, et al. Methylation patterns of genes coding for drug-metabolizing enzymes in tamoxifen-resistant breast cancer tissues. J Mol Med (Berl) 2010;88(11):1123-1131 View Article PubMed/NCBI
  104. Cabrera-Licona A, Pérez-Añorve IX, Flores-Fortis M, Moral-Hernández OD, González-de la Rosa CH, Suárez-Sánchez R, et al. Deciphering the epigenetic network in cancer radioresistance. Radiother Oncol 2021;159:48-59 View Article PubMed/NCBI
  105. Jahangiri R, Mosaffa F, Emami Razavi A, Teimoori-Toolabi L, Jamialahmadi K. Altered DNA methyltransferases promoter methylation and mRNA expression are associated with tamoxifen response in breast tumors. J Cell Physiol 2018;233(9):7305-7319 View Article PubMed/NCBI
  106. Gajulapalli VNR, Malisetty VL, Chitta SK, Manavathi B. Oestrogen receptor negativity in breast cancer: a cause or consequence?. Biosci Rep 2016;36(6):e00432 View Article PubMed/NCBI
  107. Jahangiri R, Jamialahmadi K, Gharib M, Emami Razavi A, Mosaffa F. Expression and clinicopathological significance of DNA methyltransferase 1, 3A and 3B in tamoxifen-treated breast cancer patients. Gene 2019;685:24-31 View Article PubMed/NCBI
  108. Xu J, Sun T, Guo X, Wang Y, Jing M. Estrogen receptor-α promoter methylation is a biomarker for outcome prediction of cisplatin resistance in triple-negative breast cancer. Oncol Lett 2018;15(3):2855-2862 View Article PubMed/NCBI
  109. Jia Y, Song Y, Dong G, Hao C, Zhao W, Li S, et al. Aberrant regulation of RAD51 promotes resistance of neoadjuvant endocrine therapy in ER-positive breast cancer. Sci Rep 2019;9(1):12939 View Article PubMed/NCBI
  110. Dutta U, Pant K. Aromatase inhibitors: past, present and future in breast cancer therapy. Med Oncol 2008;25(2):113-124 View Article PubMed/NCBI
  111. Wassing IE, Esashi F. RAD51: Beyond the break. Semin Cell Dev Biol 2021;113:38-46 View Article PubMed/NCBI
  112. Selli C, Turnbull AK, Pearce DA, Li A, Fernando A, Wills J, et al. Molecular changes during extended neoadjuvant letrozole treatment of breast cancer: distinguishing acquired resistance from dormant tumours. Breast Cancer Res 2019;21(1):2 View Article PubMed/NCBI
  113. Liu XR, Zhang RY, Gong H, Rugo HS, Chen LB, Fu Y, et al. Methylome variation predicts exemestane resistance in advanced ER+ breast cancer. Technol Cancer Res Treat 2020;19:1533033819896331 View Article PubMed/NCBI
  114. Yu J, Qin B, Moyer AM, Nowsheen S, Liu T, Qin S, et al. DNA methyltransferase expression in triple-negative breast cancer predicts sensitivity to decitabine. J Clin Invest 2018;128(6):2376-2388 View Article PubMed/NCBI
  115. Wang J, Wu X, Jiang M, Tai G. Mechanism by which TRAF6 Participates in the Immune Regulation of Autoimmune Diseases and Cancer. Biomed Res Int 2020;2020:4607197 View Article PubMed/NCBI
  116. Caldon CE, Daly RJ, Sutherland RL, Musgrove EA. Cell cycle control in breast cancer cells. J Cell Biochem 2006;97(2):261-274 View Article PubMed/NCBI
  117. Klajic J, Busato F, Edvardsen H, Touleimat N, Fleischer T, Bukholm I, et al. DNA methylation status of key cell-cycle regulators such as CDKNA2/p16 and CCNA1 correlates with treatment response to doxorubicin and 5-fluorouracil in locally advanced breast tumors. Clin Cancer Res 2014;20(24):6357-6366 View Article PubMed/NCBI
  118. Iorns E, Turner NC, Elliott R, Syed N, Garrone O, Gasco M, et al. Identification of CDK10 as an important determinant of resistance to endocrine therapy for breast cancer. Cancer Cell 2008;13(2):91-104 View Article PubMed/NCBI
  119. Cui J, Li G, Yin J, Li L, Tan Y, Wei H, et al. GSTP1 and cancer: Expression, methylation, polymorphisms and signaling (Review). Int J Oncol 2020;56(4):867-878 View Article PubMed/NCBI
  120. Miyake T, Nakayama T, Naoi Y, Yamamoto N, Otani Y, Kim SJ, et al. GSTP1 expression predicts poor pathological complete response to neoadjuvant chemotherapy in ER-negative breast cancer. Cancer Sci 2012;103(5):913-920 View Article PubMed/NCBI
  121. Arai T, Miyoshi Y, Kim SJ, Akazawa K, Maruyama N, Taguchi T, et al. Association of GSTP1 expression with resistance to docetaxel and paclitaxel in human breast cancers. Eur J Surg Oncol 2008;34(7):734-738 View Article PubMed/NCBI
  122. Ye L, Lin C, Wang X, Li Q, Li Y, Wang M, et al. Epigenetic silencing of SALL2 confers tamoxifen resistance in breast cancer. EMBO Mol Med 2019;11(12):e10638 View Article PubMed/NCBI
  123. Hermosilla VE, Hepp MI, Escobar D, Farkas C, Riffo EN, Castro AF, et al. Developmental SALL2 transcription factor: a new player in cancer. Carcinogenesis 2017;38(7):680-690 View Article PubMed/NCBI
  124. Carnero A, Blanco-Aparicio C, Renner O, Link W, Leal JF. The PTEN/PI3K/AKT signalling pathway in cancer, therapeutic implications. Curr Cancer Drug Targets 2008;8(3):187-198 View Article PubMed/NCBI
  125. Ye L, Lin C, Wang X, Li Q, Li Y, Wang M, et al. Epigenetic silencing of SALL2 confers tamoxifen resistance in breast cancer. EMBO Mol Med 2022;14(3):e15618 View Article PubMed/NCBI
  126. Wang L, Lonard DM, O’Malley BW. The role of steroid receptor coactivators in hormone dependent cancers and their potential as therapeutic targets. Horm Cancer 2016;7(4):229-235 View Article PubMed/NCBI
  127. Ward E, Varešlija D, Charmsaz S, Fagan A, Browne AL, Cosgrove N, et al. Epigenome-wide SRC-1-Mediated Gene Silencing Represses Cellular Differentiation in Advanced Breast Cancer. Clin Cancer Res 2018;24(15):3692-3703 View Article PubMed/NCBI
  128. Jahangiri R, Mosaffa F, Emami Razavi A, Teimoori-Toolabi L, Jamialahmadi K. PAX2 promoter methylation and AIB1 overexpression promote tamoxifen resistance in breast carcinoma patients. J Oncol Pharm Pract 2022;28(2):310-325 View Article PubMed/NCBI
  129. Gampenrieder SP, Rinnerthaler G, Hackl H, Pulverer W, Weinhaeusel A, Ilic S, et al. DNA Methylation Signatures Predicting Bevacizumab Efficacy in Metastatic Breast Cancer. Theranostics 2018;8(8):2278-2288 View Article PubMed/NCBI
  130. Martens JW, Nimmrich I, Koenig T, Look MP, Harbeck N, Model F, et al. Association of DNA methylation of phosphoserine aminotransferase with response to endocrine therapy in patients with recurrent breast cancer. Cancer Res 2005;65(10):4101-4117 View Article PubMed/NCBI
  131. Schwarzenbach H. The potential of circulating nucleic acids as components of companion diagnostics for predicting and monitoring chemotherapy response. Expert Rev Mol Diagn 2015;15(2):267-275 View Article PubMed/NCBI
  132. Schwarzenbach H. CNAPS and General Medicine In: Gahan P (ed). Nucleic Acids in Early Diagnosis, Prognosis and Treatment Monitoring. 1st ed. Springer. 2015;5:143-163 View Article
  133. Sharma G, Mirza S, Parshad R, Gupta SD, Ralhan R. DNA methylation of circulating DNA: a marker for monitoring efficacy of neoadjuvant chemotherapy in breast cancer patients. Tumour Biol 2012;33(6):1837-1843 View Article PubMed/NCBI
  134. Fiegl H, Millinger S, Mueller-Holzner E, Marth C, Ensinger C, Berger A, et al. Circulating tumor-specific DNA: a marker for monitoring efficacy of adjuvant therapy in cancer patients. Cancer Res 2005;65(4):1141-1145 View Article PubMed/NCBI
  135. Ediriweera MK, Tennekoon KH, Samarakoon SR. Role of the PI3K/AKT/mTOR signaling pathway in ovarian cancer: Biological and therapeutic significance. Semin Cancer Biol 2019;59:147-160 View Article PubMed/NCBI
  136. Kastan MB, Bartek J. Cell-cycle checkpoints and cancer. Nature 2004;432(7015):316-323 View Article PubMed/NCBI
  137. Li M, Balch C, Montgomery JS, Jeong M, Chung JH, Yan P, et al. Integrated analysis of DNA methylation and gene expression reveals specific signaling pathways associated with platinum resistance in ovarian cancer. BMC Med Genomics 2009;2:34 View Article PubMed/NCBI
  138. Cardenas H, Fang F, Jiang G, Perkins SM, Zhang C, Emerson RE, et al. Methylomic signatures of high grade serous ovarian cancer. Epigenetics 2021;16(11):1201-1216 View Article PubMed/NCBI
  139. Hua T, Kang S, Li XF, Tian YJ, Li Y. DNA methylome profiling identifies novel methylated genes in epithelial ovarian cancer patients with platinum resistance. J Obstet Gynaecol Res 2021;47(3):1031-1039 View Article PubMed/NCBI
  140. Zhang S, Xie C. The role of OXCT1 in the pathogenesis of cancer as a rate-limiting enzyme of ketone body metabolism. Life Sci 2017;183:110-115 View Article PubMed/NCBI
  141. Nogales V, Reinhold WC, Varma S, Martinez-Cardus A, Moutinho C, Moran S, et al. Epigenetic inactivation of the putative DNA/RNA helicase SLFN11 in human cancer confers resistance to platinum drugs. Oncotarget 2016;7(3):3084-3097 View Article PubMed/NCBI
  142. Creff J, Besson A. Functional Versatility of the CDK Inhibitor p57Kip2. Front Cell Dev Biol 2020;8:584590 View Article PubMed/NCBI
  143. Coley HM, Safuwan NA, Chivers P, Papacharalbous E, Giannopoulos T, Butler-Manuel S, et al. The cyclin-dependent kinase inhibitor p57(Kip2) is epigenetically regulated in carboplatin resistance and results in collateral sensitivity to the CDK inhibitor seliciclib in ovarian cancer. Br J Cancer 2012;106(3):482-489 View Article PubMed/NCBI
  144. Sun W, Zhang Q, Wang R, Li Y, Sun Y, Yang L. Targeting DNA damage repair for immune checkpoint inhibition: mechanisms and potential clinical applications. Front Oncol 2021;11:648687 View Article PubMed/NCBI
  145. Plumb JA, Strathdee G, Sludden J, Kaye SB, Brown R. Reversal of drug resistance in human tumor xenografts by 2′-deoxy-5-azacytidine-induced demethylation of the hMLH1 gene promoter. Cancer Res 2000;60(21):6039-6044 PubMed/NCBI
  146. Helleman J, van Staveren IL, Dinjens WN, van Kuijk PF, Ritstier K, Ewing PC, et al. Mismatch repair and treatment resistance in ovarian cancer. BMC Cancer 2006;6:201 View Article PubMed/NCBI
  147. Phillips MM, Sheaff MT, Szlosarek PW. Targeting arginine-dependent cancers with arginine-degrading enzymes: opportunities and challenges. Cancer Res Treat 2013;45(4):251-262 View Article PubMed/NCBI
  148. Nicholson LJ, Smith PR, Hiller L, Szlosarek PW, Kimberley C, Sehouli J, et al. Epigenetic silencing of argininosuccinate synthetase confers resistance to platinum-induced cell death but collateral sensitivity to arginine auxotrophy in ovarian cancer. Int J Cancer 2009;125(6):1454-1463 View Article PubMed/NCBI
  149. Cozza G, Salvi M. The acidophilic kinases PLK2 and PLK3: structure, substrate targeting and inhibition. Curr Protein Pept Sci 2018;19(8):728-745 View Article PubMed/NCBI
  150. Syed N, Coley HM, Sehouli J, Koensgen D, Mustea A, Szlosarek P, et al. Polo-like kinase Plk2 is an epigenetic determinant of chemosensitivity and clinical outcomes in ovarian cancer. Cancer Res 2011;71(9):3317-3327 View Article PubMed/NCBI
  151. Varol U, Kucukzeybek Y, Alacacioglu A, Somali I, Altun Z, Aktas S, et al. BRCA genes: BRCA 1 and BRCA 2. J BUON. J BUON 2018;23(4):862-866 PubMed/NCBI
  152. Kondrashova O, Topp M, Nesic K, Lieschke E, Ho GY, Harrell MI, et al. Methylation of all BRCA1 copies predicts response to the PARP inhibitor rucaparib in ovarian carcinoma. Nat Commun 2018;9(1):3970 View Article PubMed/NCBI
  153. Bhatlekar S, Fields JZ, Boman BM. HOX genes and their role in the development of human cancers. J Mol Med (Berl) 2014;92(8):811-823 View Article PubMed/NCBI
  154. Rusan M, Andersen RF, Jakobsen A, Steffensen KD. Circulating HOXA9-methylated tumour DNA: A novel biomarker of response to poly (ADP-ribose) polymerase inhibition in BRCA-mutated epithelial ovarian cancer. Eur J Cancer 2020;125:121-129 View Article PubMed/NCBI
  155. Bonito NA, Borley J, Wilhelm-Benartzi CS, Ghaem-Maghami S, Brown R. Epigenetic regulation of the homeobox Gene MSX1 associates with platinum-resistant disease in high-grade serous epithelial ovarian cancer. Clin Cancer Res 2016;22(12):3097-3104 View Article PubMed/NCBI
  156. Ho CM, Huang CJ, Huang CY, Wu YY, Chang SF, Cheng WF. Promoter methylation status of HIN-1 associated with outcomes of ovarian clear cell adenocarcinoma. Mol Cancer 2012;11:53 View Article PubMed/NCBI
  157. Ho CM, Huang CJ, Huang SH, Chang SF, Cheng WF. Demethylation of HIN-1 reverses paclitaxel-resistance of ovarian clear cell carcinoma through the AKT-mTOR signaling pathway. BMC Cancer 2015;15:789 View Article PubMed/NCBI
  158. Li X, Pan Q, Wan X, Mao Y, Lu W, Xie X, et al. Methylation-associated Has-miR-9 deregulation in paclitaxel- resistant epithelial ovarian carcinoma. BMC Cancer 2015;15:509 View Article PubMed/NCBI
  159. Okamoto K, Li H, Jensen MR, Zhang T, Taya Y, Thorgeirsson SS, et al. Cyclin G recruits PP2A to dephosphorylate Mdm2. Mol Cell 2002;9(4):761-771 View Article PubMed/NCBI
  160. Chen CA, Chiang YC, Chang MC, Hu YH, You SL, Cheng YY, et al. Gene methylation profiles as prognostic markers in ovarian clear cell and endometrioid adenocarcinomas. Am J Transl Res 2015;7(1):139-152 PubMed/NCBI
  161. Donninger H, Harrell-Stewart D, Clark GJ. Detection of endogenous RASSF1A interacting proteins. Methods Mol Biol 2021;2262:303-310 View Article PubMed/NCBI
  162. Rodriguez FJ, Lewis-Tuffin LJ, Anastasiadis PZ. E-cadherin’s dark side: possible role in tumor progression. Biochim Biophys Acta 2012;1826(1):23-31 View Article PubMed/NCBI
  163. Lin HW, Fu CF, Chang MC, Lu TP, Lin HP, Chiang YC, et al. CDH1, DLEC1 and SFRP5 methylation panel as a prognostic marker for advanced epithelial ovarian cancer. Epigenomics 2018;10(11):1397-1413 View Article PubMed/NCBI
  164. Mondal S, Roy D, Camacho-Pereira J, Khurana A, Chini E, Yang L, et al. HSulf-1 deficiency dictates a metabolic reprograming of glycolysis and TCA cycle in ovarian cancer. Oncotarget 2015;6(32):33705-33719 View Article PubMed/NCBI
  165. Staub J, Chien J, Pan Y, Qian X, Narita K, Aletti G, et al. Epigenetic silencing of HSulf-1 in ovarian cancer:implications in chemoresistance. Oncogene 2007;26(34):4969-4978 View Article PubMed/NCBI
  166. Schusdziarra C, Blamowska M, Azem A, Hell K. Methylation-controlled J-protein MCJ acts in the import of proteins into human mitochondria. Hum Mol Genet 2013;22(7):1348-1357 View Article PubMed/NCBI
  167. Strathdee G, Vass JK, Oien KA, Siddiqui N, Curto-Garcia J, Brown R. Demethylation of the MCJ gene in stage III/IV epithelial ovarian cancer and response to chemotherapy. Gynecol Oncol 2005;97(3):898-903 View Article PubMed/NCBI
  168. Bernstein BE, Hol WG. Crystal structures of substrates and products bound to the phosphoglycerate kinase active site reveal the catalytic mechanism. Biochemistry 1998;37(13):4429-4436 View Article PubMed/NCBI
  169. Zhou JW, Tang JJ, Sun W, Wang H. PGK1 facilities cisplatin chemoresistance by triggering HSP90/ERK pathway mediated DNA repair and methylation in endometrial endometrioid adenocarcinoma. Mol Med 2019;25(1):11 View Article PubMed/NCBI
  170. Lacey T, Lacey H. Linking hsp90’s role as an evolutionary capacitator to the development of cancer. Cancer Treat Res Commun 2021;28:100400 View Article PubMed/NCBI
  171. Sun J, Zheng MY, Li YW, Zhang SW. Structure and function of Septin 9 and its role in human malignant tumors. World J Gastrointest Oncol 2020;12(6):619-631 View Article PubMed/NCBI
  172. Jiao X, Zhang S, Jiao J, Zhang T, Qu W, Muloye GM, et al. Promoter methylation of SEPT9 as a potential biomarker for early detection of cervical cancer and its overexpression predicts radioresistance. Clin Epigenetics 2019;11(1):120 View Article PubMed/NCBI
  173. Jiao Y, Wang HC, Fan SJ. Growth suppression and radiosensitivity increase by HMGB1 in breast cancer. Acta Pharmacol Sin 2007;28(12):1957-1967 View Article PubMed/NCBI
  174. Sood S, Patel FD, Ghosh S, Arora A, Dhaliwal LK, Srinivasan R. Epigenetic alteration by DNA methylation of ESR1, MYOD1 and hTERT gene promoters is useful for prediction of response in patients of locally advanced invasive cervical carcinoma treated by chemoradiation. Clin Oncol (R Coll Radiol) 2015;27(12):720-727 View Article PubMed/NCBI
  175. Chaopatchayakul P, Jearanaikoon P, Yuenyao P, Limpaiboon T. Aberrant DNA methylation of apoptotic signaling genes in patients responsive and nonresponsive to therapy for cervical carcinoma. Am J Obstet Gynecol 2010;202(3):281.e1-281.e9 View Article PubMed/NCBI
  176. Nikoletopoulou V, Markaki M, Palikaras K, Tavernarakis N. Crosstalk between apoptosis, necrosis and autophagy. Biochim Biophys Acta 2013;1833(12):3448-3459 View Article PubMed/NCBI
  177. Moufarrij S, Dandapani M, Arthofer E, Gomez S, Srivastava A, Lopez-Acevedo M, et al. Epigenetic therapy for ovarian cancer: promise and progress. Clin Epigenetics 2019;11(1):7 View Article PubMed/NCBI
  178. Ducasse M, Brown MA. Epigenetic aberrations and cancer. Mol Cancer 2006;5:60 View Article PubMed/NCBI
  179. Jones PA, Taylor SM. Cellular differentiation, cytidine analogs and DNA methylation. Cell 1980;20(1):85-93 View Article PubMed/NCBI
  180. Lu LJ, Randerath K. Mechanism of 5-azacytidine-induced transfer RNA cytosine-5-methyltransferase deficiency. Cancer Res 1980;40(8 Pt 1):2701-2705 PubMed/NCBI
  181. Fenaux P, Mufti GJ, Hellstrom-Lindberg E, Santini V, Finelli C, Giagounidis A, et al. Efficacy of azacitidine compared with that of conventional care regimens in the treatment of higher-risk myelodysplastic syndromes: a randomised, open-label, phase III study. Lancet Oncol 2009;10(3):223-232 View Article PubMed/NCBI
  182. Singh V, Sharma P, Capalash N. DNA methyltransferase-1 inhibitors as epigenetic therapy for cancer. Curr Cancer Drug Targets 2013;13(4):379-399 View Article PubMed/NCBI
  183. Bolden JE, Peart MJ, Johnstone RW. Anticancer activities of histone deacetylase inhibitors. Nat Rev Drug Discov 2006;5(9):769-784 View Article PubMed/NCBI
  184. West AC, Mattarollo SR, Shortt J, Cluse LA, Christiansen AJ, Smyth MJ, et al. An intact immune system is required for the anticancer activities of histone deacetylase inhibitors. Cancer Res 2013;73(24):7265-7276 View Article PubMed/NCBI
  185. Topper MJ, Vaz M, Marrone KA, Brahmer JR, Baylin SB. The emerging role of epigenetic therapeutics in immuno-oncology. Nat Rev Clin Oncol 2020;17(2):75-90 View Article PubMed/NCBI
  186. Morel D, Jeffery D, Aspeslagh S, Almouzni G, Postel-Vinay S. Combining epigenetic drugs with other therapies for solid tumours - past lessons and future promise. Nat Rev Clin Oncol 2020;17(2):91-107 View Article PubMed/NCBI
  187. Baylin SB, Ohm JE. Epigenetic gene silencing in cancer - a mechanism for early oncogenic pathway addiction?. Nat Rev Cancer 2006;6(2):107-116 View Article PubMed/NCBI
  188. Gouil Q, Keniry A. Latest techniques to study DNA methylation. Essays Biochem 2019;63(6):639-648 View Article PubMed/NCBI
  189. Braune EB, Seshire A, Lendahl U. Notch and Wnt Dysregulation and its relevance for breast cancer and tumor initiation. Biomedicines 2018;6(4):E101 View Article PubMed/NCBI
  190. Wu YC, Ling ZQ. The role of TET family proteins and 5-hydroxymethylcytosine in human tumors. Histol Histopathol 2014;29(8):991-997 View Article PubMed/NCBI
  • Cancer Screening and Prevention
  • pISSN 2993-6314
  • eISSN 2835-3315
Back to Top

DNA Methylation and Anticancer Drug Resistance in Gynecological Tumors

Heidi Schwarzenbach, Peter B. Gahan
  • Reset Zoom
  • Download TIFF