Investigating the impact of hyperglycemia on modulating T cell populations in breast cancer

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PROJECT ABSTRACT This grant application is for the F31-Diversity support of Courtney Swain during her MD-PhD training. The research focus of this proposal is to establish a mechanism in which hyperglycemia and Hedgehog (Hh) signaling conspire to modulate CD8+ T cell exhaustion and regulatory T cell (Treg) immunosuppression in triple-negative breast cancer (TNBC). Breast cancer continues to threaten the lives of many women in the U.S. and worldwide as it accounts for more than 30% of all female cancer cases. Additionally, type 2 diabetes mellitus (T2D) is a highly prevalent morbidity and about a quarter of breast cancer patients are diabetic, which can increase treatment complications and limit therapy options. TNBC tumors are immunologically “cold,” characterized by the limited infiltration of cytotoxic populations and increased abundance of immunosuppressive constituents in the primary tumor. Hyperglycemia in T2D pathogenesis has been implicated to impair CD8+ T cells, lymphocytes critical in tumor killing and immunotherapy response, and their exhaustion process. Upon tumor challenge, subsets of immunologically reactive TCF1+ stem-like and TCF1- transitory effector CD8+ T cells are generated. These CD8+ T cell subsets have been found to be highly essential in tumor control despite their phenotype and nomenclature of early exhaustion. Notably, hyperglycemia exacerbates dysregulated Hh signaling in breast cancer. Initial investigations have revealed that hyperglycemia and Hh signaling may be cooperatively driving dysfunctional CD8+ T cell exhaustion in the mammary tumor milieu. Additionally, the presence of Tregs during mammary tumorigenesis correlates with poorer prognoses in TNBC. Supporting evidence in this proposal underscores that both, Hh signaling and hyperglycemia, impair CD8+ T cell exhaustion and promote Treg immunosuppression. However, the mechanisms by which these factors influence these key T cell populations are unknown. Therefore, this proposal will apply unique model systems of Hh signaling and hyperglycemia to delineate their roles in CD8+ T cell and Treg activity in TNBC. Findings will provide more relevance for combination TNBC therapies, especially for the distinct patient population of diabetic breast cancer patients. The proposed training plan for the PI is sponsored by her PhD mentor, Dr. Lalita Shevde-Samant. The goals of the training plan are to provide the PI with: (i) a rigorous research project using distinctive pre-clinical models of diabetes-associated breast cancer, novel genetically engineered mice, and tumor-immune crosstalk; (ii) opportunities in developing immunologic and bioinformatic techniques and in expanding training in responsible conduct of research, rigor, reproducibility, and principles of scientific integrity; and (iii) a scientifically enriching and equipped environment essential for developing a successful career as an oncologist-scientist. Given this project’s focus on the interaction of two major disease challenges of the U.S., breast cancer and diabetes, the PI will have exemplary guidance and a solid foundation to develop into a very competent physician-scientist.