Abstract A221: Epigenetic therapy restores polyfunctionality of malignant pleural effusion T-cells in patients with non-small cell lung cancer without downregulation of PD-1

Abstract Cytotoxic T-cells in patients with advanced tumors are often dysfunctional due to persistent cancer antigen exposure. These dysfunctional T-cells, known as exhausted T-cells, are characterized by an increased expression of inhibitory receptors and the gradual loss of effector functions, which contribute to immune evasion of cancer cells. Immune checkpoint blockade therapy works by removing the inhibitory signals, reversing the T-cell exhausted state, thereby leading to immune-mediated tumor regression. While immunotherapy has become a front-line treatment for many lung cancer patients for its promising clinical outcome, the durability of this reversal of T-cell exhaustion still remains unsatisfactory, which contributes to eventual treatment failure. Emerging evidence in animal models suggests that exhausted T-cells have a distinct epigenetic landscape that remains unaltered following immune checkpoint blockade therapy. Thus, we hypothesized that epigenetic therapy may reprogram tumor-reactive T-cells to enhance their effector functions. We isolated CD3+ T-cells from malignant pleural effusion or primary tumor tissues of 20 lung cancer patients and examined their immunophenotypes, including surface markers (CD4 and CD8), proliferative index (Ki67), as well as inhibitory receptors (PD-1, TIM3, and CTLA4). T-cells were subject to in vitro daily treatment of decitabine, a DNA methyltransferase inhibitor, for 72 hours. Polyfunctional T-cells that co-express effector functions (i.e., TNF-α, IFN-γ, IL-2 and CD107a) were analyzed by multichromatic flow cytometry. We discovered that T-cells in the malignant pleural effusion or primary lung cancer tissues have higher CD4/CD8 ratios as compared with peripheral blood mononuclear cells from healthy volunteers. The majority of T-cells from lung cancer patients exhibited the exhausted phenotype and expressed at least one inhibitory receptor at higher levels. This indicates that T-cells from malignant pleural effusion could potentially reflect dysfunctional immune states in lung cancer patients when tumor tissues are not available. Moreover, treatment of decitabine at clinically relevant concentrations significantly increased the polyfunctionality of PD-1 positive CD4+ and CD8+ T-cells from selected patients. Interestingly, the reinvigoration of polyfunctional T-cell responses did not associate with the downregulation of PD-1. On the other hand, the effects of decitabine on PD-1 negative CD4+ and CD8+ T-cells were only modest. This suggests that malignant pleural effusion T-cells, which are often PD-1 positive, may respond to epigenetic reprogramming via PD-1-independent mechanisms. Our data shed light on the potential uses of epigenetic therapy in lung cancer treatment by immunomodulation. Citation Format: Hsing-Chen Tsai, Yi-Chieh Wu, Shu-Yung Lin, I-Yu Chen, Jih-Hsiang Lee, Kuang-Hua Cheng, Ping-Huai Wang, Huan-Jang Ko, Wen-Chien Huang, Yi-Jhen Huang, Kai-Lin Wei, Chong-Jen Yu, Yen-Ling Chiu. Epigenetic therapy restores polyfunctionality of malignant pleural effusion T-cells in patients with non-small cell lung cancer without downregulation of PD-1 [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A221.