2007P Spatio-temporal separation of tumor infiltrating CD8+ T-cells and HER2/neu+ tumor cells in tumor-immune milieu of infiltrating ductal carcinoma of the breast

Abstract Background Designated tumor infiltrating lymphocytes (TIL) within tumor microenvironment (TME) comprised of both regulatory cells and effector cells, and their interaction with tumor cells account for the immune escape and immunosurveillance mechanisms respectively. The number and location of CD8+ tumor infiltrating lymphocytes (TILs) are the measures of immune response and carries prognostic significance and predictive potential in the era of immuno-oncology. The present study was an attempt to find the relation between the treatment response and the spatio-temporal separation of tumor infiltrating CD8+ T-cells and HER2/neu+ tumor cells in breast cancer TME. Methods In this study, a total of 7 breast cancer patients were enrolled and surgically removed fresh tumor tissues were evaluated for the baseline HER2/neu and CD8 expression by immunohistochemistry (IHC) using dual stain (duplex IHC). The tumor tissues were also tested for the response to HER2 blocker in a novel humanized ex vivo platform that preserves tumour microenvironment using tumour explants, maintained in defined tumour grade-matched matrix support and autologous patient serum. Results Tumors responded to HER2 blockade had a majority of the CD8+ T cells (60-80%) concentrated around the HER2/neu+ tumor area (within 50-100µm). While, the non-responding tumors had significantly lesser number of the CD8+T cells (20-40%) proximal to HER2/neu+ zone compared to the responders. The present study indeed delineated a preferential spatial relationship of tumor infiltrating CD8+ cells in HER2/neu+ tumor region especially for the recognition of tumor antigen, cross presentation and tumor cell killing. Conclusions Assessment of distribution pattern of effector cells surrounding tumor area had a correlation on the efficacy of HER2 inhibition. It warrants validation in the larger cohort of patient tumors to underpin its clinical relevance for possible immunotherapies like combination of check point inhibitors with HER2/neu blocker and others. Identification of other co-stimulatory and pathway molecules on the tumors not responded to HER2 blocker is being studied to understand the mechanism of resistance. Legal entity responsible for the study The authors. Funding Mitra RxDx Inc. Disclosure All authors have declared no conflicts of interest.