Abstract 945: Live attenuated MMR vaccines modulate tumor immune cell infiltration and synergize with standard of care to prolong survival in preclinical HCC models

The global burden of hepatocellular carcinoma (HCC) continues to rise, driven by increasing metabolic risk factors such as nonalcoholic fatty liver disease, obesity, and type II diabetes. Patients with advanced HCC have limited therapeutic options and a dismal prognosis. While recent advancements in combination therapies—including immune checkpoint blockade (ICB) with anti-PD-1/PD-L1 and anti-CTLA-4 agents and anti-angiogenics—have improved survival for some, up to 80% of patients fail to respond, underscoring an unmet need for new strategies. Emerging data indicate a strong association between increased tumor-infiltrating lymphocytes (TILs) and better responses in ICB-treated HCC, suggesting TIL enhancement as a promising approach. However, HCC’s inherent low immunogenicity and immunosuppressive tumor microenvironment (TME) limit the efficacy of current TIL-promoting strategies. Here, we demonstrate that low-dose intratumoral immunotherapy using the trivalent MMR vaccine—composed of live attenuated measles, mumps, and rubella viruses—modulates TME immune infiltration, increases cytotoxic T cell frequency, and delays tumor growth in multiple murine HCC models. Importantly, intratumoral or systemic MMR administration in combination with dual ICB (anti-mPD-1/anti-mCTLA-4) significantly prolongs survival, promoting tumor-specific and memory immune responses in both subcutaneous and orthotopic HCC models. These findings reveal a unique mechanism of vaccine-induced anti-tumor activity, highlighting MMR as a viable, globally accessible option for enhancing immune responses in advanced HCC therapy. Citation Format: Mulu Z. Tesfay,Aleksandra Cios,Khandoker U. Randal S. Shelton,Bahaa Mustafa,Camila C. Simoes,Steven Post,Thomas Kelly,Moaven Moaven,Lewis R. Roberts,Mitesh J. Borad,Martin J. Cannon,Alexei Basnakian,Nagalo Bolni. Live attenuated MMR vaccines modulate tumor immune cell infiltration and synergize with standard of care to prolong survival in preclinical HCC models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 945.