HBx-Associated Reactivation of the IGF2 Locus in Chronic HBV Infection and HBV-Related Hepatocarcinogenesis: Evidence Boundaries and Biomarker Implications

Chronic hepatitis B virus (HBV) infection remains one of the main causes of hepatocellular carcinoma (HCC), even though vaccination and long-term viral suppression have reduced new infections and circulating viral replication. This residual cancer risk suggests that serum HBV DNA alone does not capture the full biology of HBV-related carcinogenesis. Hepatitis B virus X protein (HBx) is a relevant entry point because it maintains the transcriptional competence of covalently closed circular DNA (cccDNA), engages host chromatin regulators, and may persist in tumors as cccDNA-derived, integration-derived, full-length, truncated, or fusion forms. This review focuses on a specific question: does the available literature support HBx-associated reactivation of the IGF2 locus in chronic HBV infection and HBV-related hepatocarcinogenesis, and, if so, at which regulatory layer is the claim defensible? The most direct evidence remains promoter-proximal. Classic mechanistic work shows acute HBx-dependent activation of IGF2 promoter P4 through Sp1- and PKC/ERK-dependent signaling. Human tissue and cell-based studies also support a broader fetal-promoter compartment, including P3/P4 transcript enrichment, local promoter hypomethylation, MBD2-HBx-CBP/p300 recruitment, and increased histone H3/H4 acetylation. These observations do not, however, establish HBV exclusivity, uniform loss of imprinting, or direct HBx-mediated rewiring of the human IGF2/H19 topological domain. Recent integration-aware and long-read studies further argue against treating tumor-stage HBx as a single biological variable. In the present evidence framework, HBx-associated IGF2 locus reactivation is therefore more appropriately viewed as a stage-aware, promoter-resolved, biomarker-oriented hypothesis than as a universal mechanism or a treatment algorithm for HBV-related HCC.