Development of a T Cell Exhaustion Assay for Identification of Novel Immuno-Oncology Targets and In Vitro Drug Screening

Cancer immunotherapy utilizes the body’s own immune system to treat cancer. The key cell type in immunotherapy is T cells. T cells recognize tumor-associated antigens through their T cell receptors (TCRs) and respond to these for destruction of tumor cells. The body’s own capacity to fight malignant growth is limited by a dysfunctional state of T cells, known as T cell exhaustion. The aim of cancer immunotherapy is to reinvigorate exhausted T cells, and hence aid the immune system in the fight against tumor cells. For identifying novel immune-oncology targets and screening of new drug candidates, an in vitro assay for obtaining an exhausted phenotype of T cells is required. In this study, four different assays for T cell exhaustion were developed and evaluated: T cell exhaustion by 1) Mitomycin C treated A375-T cell co-culture, 2) MDA-MB-231 cancer conditioned medium, 3) ImmunoCult CD3/CD28 TCR stimulation and 4) Staphylococcal enterotoxin B (SEB). The methods were evaluated by cell surface marker expression analysis with flow cytometry (FACS) and ELISA cytokine secretion analysis. Out of the methods developed and evaluated, the A375-T cell co-culture proved to be the most beneficial assay for T cell exhaustion and was proposed as a standardized method for novel target identification and in vitro drug screening at Orion Pharma