Virus-induced hepatocellular carcinomas cause antigen-specific local tolerance

Area of Science:

• Immunology
• Oncology
• Virology

Background:

• T cell surveillance is crucial for eliminating virus-associated tumors due to their high immunogenicity.
• The mechanisms underlying immune surveillance failure in virus-associated hepatocellular carcinoma (HCC), such as those linked to hepatitis B and C viruses, remain unclear.

Purpose of the Study:

• To establish a murine model for studying virus-induced HCC and immune evasion.
• To investigate the role of T cell responses and immune suppression in the progression of virus-associated HCC.

Main Methods:

• Development of a transgenic murine model of HCC using adenovirus-induced activation of SV40 large T antigen (TAg) in hepatocytes.
• Analysis of T cell infiltration, antigen-specific cytotoxic T lymphocytes (CTLs), and expression of programmed cell death protein-1 (PD-1) and its ligand PD-L1.

Main Results:

• Adenovirus infection induced CTLs that cleared most infected cells, but some escaped immune clearance and developed HCC.
• HCC cells expressed TAg similarly to non-tumorigenic cells, indicating CTL clearance does not solely select for low immunogenicity.
• Progressive immune suppression was observed, characterized by reduced T cell infiltration in late-stage HCC compared to early-stage.
• Expression of PD-1 on T cells and PD-L1 on HCC cells contributed to local tumor-antigen-specific tolerance.

Conclusions:

• The developed model mimics virus-induced HCC and highlights immune evasion mechanisms.
• Progressive local immune suppression, mediated by PD-1/PD-L1 interactions, plays a significant role in HCC progression.
• Understanding these immune evasion strategies is vital for developing effective therapies for human HCC.