Abstract 3715: Analysis of tumor infiltrating lymphocytes and in vitro exhausted T-cell models to identify unique Immuno-Oncology targets
Authors: James Ackroyd, Joanne Berry, Yaoyao Fu, Jason Allen, Martin Barnes, Alexander Patterson, Angelo Kaplan, Christian Rohlff, Haining Huang, Livija Deban, Robert Boyd
Journal: Cancer Research (2017)

Abstract In cancer, T cells are exposed to persistent antigen stimulation and/or inflammatory signals. Such prolonged stimulation is often associated with deterioration of T cell effector functions resulting in a functional state termed ‘exhaustion’. Exhausted T cells are characterized by expression of multiple inhibitory receptors, loss of cytolytic function and decline in cytokine production capability. T cell exhaustion is likely associated with inefficient control of tumor progression. Identification of cell surface proteins involved in induction and maintenance of the exhausted state could inform novel immunomodulatory cancer therapies. To comprehensively investigate cell surface signature of the exhausted state and identify potential immuno-oncology (I-O) targets, we conducted in-depth expression profiling of membrane proteins from intact tumors (Colorectal, Pancreatic, Lung, Breast and Prostate cancer), different in vitro models of T cell exhaustion and primary tumor-derived lymphocytes (Colorectal, Breast and Lung cancer) by targeted proteomics for known cell type and activation markers. Using proteomic expression analysis and statistical clustering analysis methods, novel I-O targets were identified in both the in vitro models of T cell exhaustion and primary tumor-derived lymphocytes (TILs). The cancer specify of novel I-O targets was then interrogated using the expression profiling of cell membrane proteins from intact tumors. Using this approach we identified most known T cell inhibitory receptors (PD-1, CTLA-4, BTLA, TIM-3, KIRs, LAG-3 and TMIGD2) and their described ligands (B7-H1 to B7-H7). To generate more precise expression data to validate I-O targets emerging from the above discovery approaches and their known interacting partners we analyzed single tumors using an integrated evaluation methodology. Tumors were subject to multiple parallel analysis steps: (i) proteomic analysis of the tumor and TILs; (ii) TILs were subject to flow cytometry analysis for specific proteins; (iii) tumor tissue sections were subject to immuno-histochemical analysis for specific proteins. The multiple analysis platforms were integrated by key cell type and functional markers allowing the different types of information provided by each technique to be placed in an overall 3-D tumor context. We present one example of a potential I-O target identified using our integrated proteomic discovery approach which is further validated at the expression level using multiple whole tumor and TIL analyses. Citation Format: James Ackroyd, Joanne Berry, Yaoyao Fu, Jason Allen, Martin Barnes, Alexander Patterson, Angelo Kaplan, Christian Rohlff, Haining Huang, Livija Deban, Robert Boyd. Analysis of tumor infiltrating lymphocytes and in vitro exhausted T-cell models to identify unique Immuno-Oncology targets [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 3715. doi:10.1158/1538-7445.AM2017-3715