Abstract 5654: Lymphodepletion induces T cell homeostatic proliferation and augments antitumor effects of PD-1/PD-L1 blockade therapy

Programmed death receptor-1 (PD-1)/programmed death receptor ligand-1 (PD-L1) blockade therapy has demonstrated to enhance antitumor immunity. Recent evidence has shown that anti-PD-1/PD-L1 therapy restores the function of exhausted effector T cells and augments antitumor immune responses. The expression of PD-L1 has been best studied as a biomarker for the anti-PD-1/PD-L1 therapy. Because PD-L1 expression on tumor cells is induced by IFN-γ which is mainly produced by effector T cells, induction of antitumor effector T cells in cancer patients could be an important for the anti-PD-1/PD-L1 therapy. Indeed, previous studies have suggested that the increase of tumor-infiltrating lymphocytes is the predictive biomarker for PD-1/PD-L1 blockade therapy. We and others have demonstrated that lymphodepletive therapies, such as chemotherapy and radiotherapy, induce tumor-specific effector T cells from naive T cells. Naive T cells rapidly proliferate and elicit memory-like functions after lymphodepletion (homeostatic proliferation). These findings indicate that lymphodepletive regimens could augment the antitumor efficacies of the anti-PD-1/PD-L1 therapy. In the current study, we transferred naive T cells into mice after whole-body irradiation or chemotherapy. These mice were inoculated s.c. with PD-L1 + B16F10 melanoma cells or PD-L1 - MCA205 fibrosarcoma and then were treated with anti-PD-1 mAbs. Lymphodepletion by whole body irradiation, but not cytotoxic agents following the transfer of naive T cells significantly enhanced antitumor immunity of anti-PD-1 mAbs. This augmentation required both of CD4 + and CD8 + T cells, but not NK cells. Further experiments revealed that immune cells infiltrating MCA205 expressed PD-L1. Transfer of naive T cells from IFN-γ knockout mice abrogated the enhancement of antitumor effects of anti-PD-1 mAb therapy by lymphodepletion. These results suggest that lymphodepletion induces homeostatic proliferation of T cells and augments antitumor effects of PD-1/PD-L1 blockade therapy. Citation Format: Masashi Arita, Satoshi Watanabe, Takahashi Miho, Miyuki Sato, Aya Ohtsubo, Kosuke Ichikawa, Rie Kondo, Tetsuya Abe, Junta Tanaka, Toshiyuki Koya, Toshiaki Kikuchi. Lymphodepletion induces T cell homeostatic proliferation and augments antitumor effects of PD-1/PD-L1 blockade therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5654. doi:10.1158/1538-7445.AM2017-5654