Epigenetic rewiring and T cell exhaustion in HBV-induced HCC with implications for precision therapies

Globally, third leading cause of cancer-related deaths is contributed by Hepatocellular carcinoma (HCC). Chronic hepatitis B virus infection is one of the seminal etiological drivers of HCC. Hepatitis B viral DNA integration, host genomic instability, persistent inflammatory responses and the oncogenic activity of the viral oncoprotein Hepatitis B virus X (HBx), contribute to the hepatocarcinogenesis. Emerging evidences indicate that epigenetic dysregulation plays a seminal role in linking viral persistence in the liver tissue to its malignant transformation. In HBV-infected hepatocytes, aberrant DNA methylation, histone modifications, and dysregulated non-coding RNAs reprogram transcriptional networks that activate oncogenic pathways, promote proliferative signaling, and sustain cancer stem cell-like phenotypes driving HCC progression. The epigenetic modifications in the infected, malignant hepatic cells can influence the tumor microenvironment, contributing to the infiltration of exhausted cytotoxic T lymphocytes with elevated PD-1 and Tim-3 expression. Further, the T lymphocytes exhibit reduced proliferative capacity, impaired cytokine secretion, and diminished cytotoxic activity. In the clinical perspective, long-term nucleotide analogue therapy causes viral suppression and attenuation of inflammation, thereby reducing HCC progression by 40-80%. Despite the extensive T-cell exhaustion, HBV-associated HCC (HBV-HCC) is responsive to immune checkpoint blockade, as highlighted in the CheckMate-040 trial. Emerging therapeutic strategies combine anti-viral agents with immune checkpoint inhibitors, epi-drugs and HBsAg-directed TCR-engineered T cells. These clinical approaches aim to simultaneously restore antitumor immune responses as well as neutralize the viral oncogenic drivers, offering promising avenues for improved management of HBV-induced HCC.