Improving CAR-T cell therapy in metastatic breast cancers by reprogramming obesity-aggravated tumor microenvironment via physical activity - Improving CAR-T cell therapy in metastatic breast cancers by reprogramming obesity-aggravated tumor microenvironment via physical activity Breast cancer (BC) is the leading cause of cancer-associated death in women worldwide. Metastatic BC (mBC) is the most common cause of death in BC patients. Chimeric antigen receptor (CAR)-T cell immunotherapy has revolutionized hematologic cancer therapy. However, CAR-T cell therapy is largely ineffective in solid tumors, including BCs, due to hostile tumor microenvironment (TME) such as abnormal vasculature, hypoxia, and immunosuppression. We and others have shown that exercise training (ExTr) can normalize tumor vasculature, TME, and anti-tumor immunity in primary tumors. However, the effect of ExTr on neither CAR-T cells nor metastatic tumors is known. Here, we propose to evaluate whether physical activity improves the delivery and function of CAR-T cells via vascular normalization, alleviation of hypoxia and immunosuppression, and improvement of response to CAR-T cells in mBCs. To this end, we will use well-controlled preclinical mBC animal models—spontaneous BC lung metastasis following primary BC removal—and moderate-intensity exercise (60% of maximal incremental exercise, optimal based on our recent studies). We will determine how ExTr affects tumor vasculature and immune TME, immune cell profile, and progression of mBCs. We will also assess the effect of ExTr on transcriptional profiles and protein expression in innate and adaptive immune cells, stromal cells, and tumor cells in BC lung metastases (Aim 1a). Based on previous studies in primary tumors, we expect to find an increase in the number and function of cytotoxic T lymphocytes (CD8+ T cells) in mBCs by moderate ExTr. Then, we will assess the effect of ExTr on CAR-T cell infiltration and function in mBCs. We chose TnMUC1 as an initial target for CAR-T cells as it is highly and selectively expressed in all BC subtypes, and TnMUC1-CAR-T cells are being tested in ongoing clinical trials. We will transduce TnMUC1 in murine BC cells and test the delivery and function of TnMUC1-CAR-T cells in TnMUC1+ mBC models (Aim 1b). Next, we will determine if ExTr potentiates CAR-T cell therapy for mBCs. We will assess how ExTr, in combination with TnMUC1-CAR-T cells, affects lung mBC progression and survival (Aim 1c). Obesity is a significant confounding factor for many types of tumors, including BCs. It aggravates abnormal TME, interferes with immune cell recruitment and function, and promotes tumor progression, metastasis, and treatment resistance. Hence, we will determine if physical activity can alleviate obesity-aggravated immunosuppressive TME and enhance anti-tumor immune cells (Aim 2a). Finally, we will evaluate if ExTr can improve TnMUC1-CAR-T cell delivery and function and the response to CAR-T cell therapy in mBCs under obesity (Aim 2b). In summary, this is a high-impact project with multiple strengths. The proposed approach is conceptually novel and will reshape physical activity in cancer patients from general fitness to supportive therapeutic intervention. Hence, the applicability of the proposed approach would be immense. With the successful accomplishment of this study, we can rapidly transform ExTr-CAR-T cell immunotherapy, making it more effective in mBCs, even in obesity.
