Abstract B104: Characterization and specificity analysis of tumor infiltrating lymphocytes in ovarian carcinoma

Abstract

Abstract Introduction: The great majority of patients suffering from ovarian cancer (OvCa) relapse after initial therapy, making OvCa the most lethal gynecological malignancy. The immunogenic nature of OvCa is highlighted by frequent infiltration with immune cells, which represent an independent prognostic factor in OvCa patients and argues in favor for the development of immunotherapies, including peptide-based cancer vaccines. The phenotype of OvCa infiltrating T cells as well as their specificity and expression of inhibitory receptors is so far unknown. This information is however critically important for the design of novel immunotherapies including the application of checkpoint inhibitor therapy. Materials and Methods: Tumor infiltrating lymphocytes (TILs) were isolated from fresh tumor tissue of OvCa patients obtained during tumor debulking surgery. The phenotype and expression of inhibitory molecules LAG3, CTLA4, PD1 and TIM3 was assessed by flow cytometry. Peptide specificity of infiltrating T cells was analyzed by screening for reactivity against naturally presented HLA ligands employing IFNγ ELISPOT and flow cytometry. These natural presented HLA ligands have been originally identified by mass spectrometry in an extensive HLA ligandome analysis of OvCa samples. Results: TILs from each analyzed OvCa sample demonstrated expression of at least one of the investigated inhibitory receptors. While LAG3 and PD1 were most prominent during this analysis, CTLA4 expression was only weak or absent. Furthermore, high amounts of effector memory, but few naive or central memory T cells were present. Notably, OvCa infiltrating CD4+ T cells and CD8+ T cells shared a similar expression pattern of inhibitory surface markers within each single patient. We further obtained first results in peptide-specificity of OvCa-derived T cells by screening them for reactivity against naturally presented HLA ligands identified on OvCa samples. Conclusion: In summary, we provide first insight into the expression of various inhibitory receptors on OvCa infiltrating T cells and their peptide specificities. Citation Format: Janet Kerstin Peper, Kevin Röhle, Heiko Schuster, Philipp Wagner, Hans-Georg Rammensee, Stefan Stevanovic. Characterization and specificity analysis of tumor infiltrating lymphocytes in ovarian carcinoma. [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 B104.