Abstract B074: Tumor-reactive CD4+ T cells in metastatic gastrointestinal cancer refractory to chemotherapy

Abstract

Abstract Purpose: To evaluate whether patients with metastatic gastrointestinal adenocarcinomas refractory to chemotherapy harbor tumor-reactive CD4+ T cells. Experimental Design: Expansion of CD4+ tumor-infiltrating lymphocytes (TIL) and cancer cell lines was performed from gastrointestinal cancer metastases in 5 patients for the study of antitumor immune recognition. Retroviral transduction of genes encoding the class II, major histocompatibility complex, transactivator (CIITA) was used to induce the expression of major histocompatibility complex (MHC) class II in tumor cell lines. Recognition of autologous tumor cell lines by TIL was evaluated by up-regulation of 4-1BB and OX40 by flow cytometry, and/or secretion of IFNg by ELISA. Results: TIL were expanded from metastases, and new tumor cell lines were generated in 5 patients. Retroviral transduction of CIITA in tumor cell lines effectively induced expression of MHC class II in >80% of cells. Autologous tumor recognition was found in CD4+ TIL from 2 of these 5 patients. In a patient with gastric cancer liver metastases, tumor-reactive CD4+OX40+ TIL were cell-sorted from a TIL cell line. These cells up-regulated OX40 in the presence of all 4 autologous cancer cell lines albeit at different levels, but they did not produce IFNg. This recognition was specifically abolished by pan-MHC class II blocking antibodies. CD4+ TIL clones have been isolated and are being further characterised. Interestingly, tumor-reactive CD8+ TIL were previously identified and characterized in this patient. In a second patient with colon cancer abdominal wall metastases, tumor-reactive CD4+OX40+ TIL were cell-sorted from a TIL cell line. These cells were reactive to all 4 autologous cancer cell lines as they up-regulated OX40 and secreted IFNg. Recognition was blocked by anti-HLA-DR blocking antibodies. CD4+ TIL clones have been isolated and are being further characterized. In the near future, we expect to identify the TCR and HLA restriction element for both patients. We will also determine if CD4+ TIL clones have cross-reactivity against allogeneic HLA-matched gastrointestinal tumor cell lines. Conclusions: This study provides a basis for the development of immunotherapy for patients with advanced gastrointestinal malignancies by first establishing the presence of naturally occurring tumor-reactive CD4+ TIL at the molecular level. Citation Format: Sandy Pelletier, Simon Turcotte. Tumor-reactive CD4+ T cells in metastatic gastrointestinal cancer refractory to chemotherapy. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B074.