Hepatocellular carcinoma (HCC)
More than 90% of HCCs are correlated to a known etiology,9 and hepatocarcinogenic mechanisms can be classified as etiologically specific and nonspecific mechanisms.10 Specific mechanisms include hepatitis B via viral integration, with the constant cis- and trans-activation of oncogenic factors,11 hepatitis C via the oncogenic effects of the core antigen and NS5A protein,12,13 and aflatoxin via direct genotoxic effects, leading to TP53 codon 249 mutations.14 Nonspecific mechanisms accumulate the abnormalities imposed by chronic liver diseases.15 HCC usually develops from chronic liver disease to a dysplastic nodule, prior to progression into HCC. The molecular markers for high-grade dysplasia include telomere shortening, telomerase reverse transcriptase (TERT) activation, and cell-cycle checkpoint inactivation.16 Early HCC accumulates mutations in CTNNB1, which encodes β-catenin, and progressed HCC further presents with TP53 mutations, DNA amplification, alterations in methylations, and other genetic abnormalities.17 Multiple immunohistochemical markers are used to assist in the HCC diagnosis: polyclonal CEA, CD10, HepPar, arginase-1, and albumin in situ hybridization (ISH) are used as hepatocellular markers, while glypican-3, glutamine synthetase (GS), HSP70, CD34, alpha-fetoprotein (AFP) and clusterin are used to identify hepatocellular malignancy.2 HSP70, glypican-3 and GS have been recommended in international guidelines.18 Molecular testing is used for DNAJB1-PRKACA translocation, in order to diagnose fibrolamellar variant HCCs.3
Serologically, due to the low sensitivity (20%) in early HCC and fluctuating levels in cirrhosis, AFP was removed from the present screening assessment guidelines of the Canadian Association for the Study of the Liver (CASL), and the European Association for the Study of the Liver (EASL).19,20 However, AFP is still presently used with other serological biomarkers, such as Lens culinaris-agglutinin-reactive fraction of AFP, and protein-induced by vitamin K absence or antagonist-II (PIVKA-II), for high risk populations.21 Furthermore, studies have determined the des-gamma-carboxy prothrombin in patients with negative AFP. The results revealed that AFP was positive in 67% of HCCs, while AFP was negative in 66% of small HCCs and 20% of all HCCs.22,23 However, none of the serologic markers were accepted by clinical practice guidelines for HCC screening due to cost-effectiveness, challenges in availability, and study result variations.19
Numerous markers are under investigation. Autophagy-related genes and their regulatory proteins are associated with HCC, including Beclin-1, ATG5 and ATG7, and these control a large number of molecular pathways in HCC oncogenesis, such as phosphatidylinositol-4,5-bisphosphate 3-kinase PI3K/AKT/mTOR, ERK/mitogen-activated protein kinase (MAPK), and apoptosis p53 pathways.24,25 For example, the ATG-4B mRNA expression controlled by autophagy-related genes may contribute to HCC development via the noncoding of miRNA-661, and this has been proven to be clinically useful, with 100% sensitivity, in a clinical validation, especially in early-stage HCC.26 Furthermore, HBV-related HCC is associated with mutated TP53, which involves the genetic integration with host genomes.27 HCV-related HCC overexpress the Kinesin family member 20A, Cyclin B1, Hyaluronan-mediated motility receptor, and other genes. In addition, these markers are linked to lower survival in patients with HCV-associated HCC.28 A study on IL-28 genetic polymorphisms revealed the association of the T allele with higher risk of HCC development.29 Another study revealed that two genotypes of certain single nucleotide polymorphisms (SNPs) of IL-28 were associated with lower risk of HCC development.30 Thus, the role of IL28 in diagnosing and prognosticating HCC appears unclear, if not contradictory.
Molecular factors are also used for the prognosis. Cytokeratin 19 (CK19) positivity is associated with increased recurrence rates, nodal metastasis, and more resistance to trans-arterial chemoembolization and percutaneous radiofrequency ablation.31–33 The expression of miR-1180-3p increases in HCC, and is linked to tumor proliferation and poor survival.34 A study conducted on KEGG pathways revealed that this epigenetic marker is associated with the regulation of the MAPK pathway, cell proliferation, apoptosis, and cell differentiation.34
Immune checkpoint proteins drive signaling pathways that suppress T-cell function,35 including PD-1, PD-L1 and CTLA-4. Nivolumab was the first US Food and Drug Administration (FDA)-approved anti-PD-1 antibody for treating HCC. In addition, in 2020, the FDA granted the accelerated approval to nivolumab, in combination with ipilimumab, which targets CTLA-4 for the treatment of patients with HCC, who were previously treated with sorafenib.36 Furthermore, a study has recommended the anti-PD-1 antibody agent for PD-L1 positive HCC patients.37 Tumor mutation burden and microsatellite instability (MSI)/mismatch repair (MMR) are used to guide the immunotherapy for several cancers. These may play an important role in HCC immunotherapy in the future.2
Hepatoblastoma (HB)
Approximately 80% of HBs exhibit genetic alternations in the Wnt/β-Catenin signaling pathway. These alterations include the deletion of CTNNB1 exon 3, AXIN genes, and the APC gene.38–40 Overexpressed targets for Wnt signaling were also observed, such as cyclin D1, survivin and MYC. In addition, MYC further activates the Wnt signaling as a positive feedback mechanism.41 The genomic profiling of HB can be classified into two subtypes, based on genetic instability (gains of chromosomes 8q and 2p): the overexpression of hepatic progenitor cell markers (AFP, CK19 and EpCAM), and the upregulation of MYC. Tumors with genetic instability are more aggressive, with a higher grade, and are more likely to metastasize.42 Histopathologically, HBs can be classified as epithelial or mixed epithelial, and mesenchymal.43 Epithelial HB may consist of fetal, embryonal, small cell undifferentiated, cholangioblastic and macrotrabecular components. β-catenin and glutamine GS are expressed in mesenchymal and fetal components.44 Furthermore, AFP highlights less-differentiated epithelial components, and HepPar1 can be observed in more differentiated epithelial components. Moreover, glypican-3 is expressed in epithelial fetal and embryonal components.15 In addition, CK7 and CK19 are positive in cholangioblastic components. SMARCB (INI1) highlights all HB components, except for small cell undifferentiated components.15