Abstract 606: Targeting multiple immune checkpoints and their ligands using a humanized mouse model of ovarian cancer

Abstract

Abstract We have recently reported that multiple immune checkpoints are expressed in the TILs (tumor infiltrating T lymphocytes) and TALs (tumor associated T lymphocytes) from a murine ovarian cancer model and that blockade of one checkpoint pathway induces an upregulation of the other unblocked checkpoints. We hypothesized that resistance to single agent blockade (e.g. anti-PD1) is resulted from the compensatory upregulation of the other pathways (e.g. CTLA4 or LAG-3). To test this hypothesis in human ovarian cancer, we first examined the level of several immune checkpoints and their ligands in TILs or TALs from ovarian cancer patients. In addition to the highly expressed PD-1 and CTLA4, other checkpoint molecules such as TIM3, LAG3, VISTA, and TIGIT are also elevated in TALs as compared with control PBMC. The levels of multiple ligands for the immune receptors in the tumor samples were also analyzed. To translate the results from mice to humans, we developed several aggressive human ovarian cancer cell lines from patient derived xenografts to test the combinatorial checkpoint blockade strategies. Using a humanized mouse model of ovarian cancer we observed that adaptive transfer of autologous T cells in combination with checkpoint blockade of PD1 mildly delays ovarian tumor growth. The effect of blocking PD-1 and CTLA-4 pathways on tumor growth and the upregulation of other checkpoints are currently underway. Citation Format: Ruea-Yea Huang, Kunle Odunsi. Targeting multiple immune checkpoints and their ligands using a humanized mouse model of ovarian cancer [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 606. doi:10.1158/1538-7445.AM2017-606