HNSCC is the 6th most common cancer, with around 650,000 new cases yearly. Gain of function mutations in the PI3K pathway are common in HNSCC, and inhibition of the PI3K p110γ subunit has shown promise in HNSCC treatment. However, given that PI3K p110γ plays an important role in myeloid and lymphoid immune cell function, it is essential to understand how PI3K p110γ inhibition affects the anti-tumor immune response independent of tumor cells. To elucidate PI3K p110γ function in HNSCC, we employed an orthotopic mouse model using poorly immunogenic and aggressive cell line MOC2 on Pik3cg-/- mice. We observed that wild-type and Pik3cg-/- mice displayed similar rates of HNSCC tumor growth and metastasis after 20 days post tumor injection. T cell infiltration and intrinsic T cell responses to MOC2 oral tumors were comparable between wild-type and Pik3cg-/- mice. Interestingly, the immune response of tumor-bearing Pik3cg-/- mice was marked by increased anti-tumor cytotoxic molecules (IFN-γ, IL-17, PD-1) by T cells, and immune checkpoint marker (PD-L1) expression by myeloid cells compared to tumor bearing wild type mice. Taken together, our findings demonstrate that inhibition of PI3K p110γ modulates tumor associated immune cells, which likely potentiates HNSCC treatment when used in combination with selective PD-L1 inhibitors.

Citation Format: Kelvin Anderson, Nathan Ryan, Anastasia Alkhimovitch, Arham Siddiqui, Steve Oghumu. Inhibition of host PI3K-gamma modulates anti-tumor immunity in poorly immunogenic HNSCC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1486.