PD-1 Inhibitor Enhanced Radiosensitivity by Reactivating T Cells and Inducing G2/M Phase Arrest in Esophageal Squamous Cell Carcinoma.

Radiotherapy is a main treatment for esophageal squamous cell carcinoma (ESCC), but radioresistance leads to treatment failure ultimately. The combination of radiotherapy and PD-1 inhibitors showed significant antitumor effects. Our study showed that high-immune score, IFNG and CD8A level were associated with a low-radiosensitivity index (RSI) in the TCGA-ESCC cohort. And blocking PD-1 promoted exhausted T cells proliferation and IFN-γ expression. PD-1 inhibitor-reactivated T cells promoted G2/M-phase arrest, apoptosis and impaired DNA damage in radioresistant cells in an IFN-γ-dependent manner. Our study showed PD-1 inhibitors promote radiosensitivity though enhancing exhausted T cells expansion and IFN-γ expression, and highlights that neoadjuvant anti-PD-1 therapy and radiotherapy could offer an optimum strategy for improving cancer patients' outcome.