Combined radiation and PD-L1 blockade improved tumor control in mouse head and neck Squamous Cell Carcinoma (HNSCC)

Purpose/Objective(s): Expression of the negative immune regulatory molecule, programmed death-ligand 1 (PD-L1) by tumor cells is associated with T cell dysfunction, attenuated antitumor immune responses, and poor clinical outcomes. Blocking the interaction between PD-L1 and its receptor, programmed death-1 (PD-1), expressed on activated CD8+ cytotoxic T lymphocytes (CTLs) enhances antitumor activity. Radiation induces cell death and is known to result in the release of tumor-associated antigens capable of triggering antitumor responses as well as enhancing antigen presentation. Radiation therapy (RT) is a commonly used treatment for locally advanced or recurrent HNSCC. In the current study, we examined the effect of radiation on major histocompatibility complex class I (MHC-I) and PD-L1 expression on HNSCC cell lines, and whether the combination of RT and PD-L1 blockade will improve tumor control.