Toward development of senolytic CAR T cells - PROJECT SUMMARY/ABSTRACT Aberrant accumulation of senescent cells is a major contributor to age-dependent tissue degeneration and its associated pathologies, including fibrosis, neurodegenerative diseases, atherosclerosis, arthritis, and metabolic disorder. Cellular senescence, a stress response program, is characterized by stable cell cycle arrest and a proinflammatory secretory program that mediates tissue damage and regeneration. Senescence has beneficial effects in tumor suppression and wound healing; however, in aging, senescent cell accumulation contributes to tissue decline, and, if not cleared, eventually causes organ dysfunction. Indeed, in model organisms, ‘senolytic’ approaches, i.e. those that ablate senescent cells, ameliorate these disorders and lengthen healthspan. Our goal is to develop senolytics suitable for clinical development to treat age-associated disorders. Rather than pursuing small-molecule senolytics, which to date have had considerable toxicities, we focus on chimeric antigen receptor T (CAR T) cells capable of targeting cell-surface proteins highly expressed on senescent cells. This renewal proposal builds upon our prior success with senolytic CAR T cells that target a senescence-associated protein called uPAR. These uPAR CAR T cells efficiently ablate senescent cells and improve fibrosis and metabolic dysfunction in old mice. We propose further preclinical development of uPAR CAR T cells. This will include testing for safety and for efficacy in multiple disease contexts, including organ function in old mice, as well as extension of these studies to our recently developed human uPAR CAR T cells. We also propose to develop novel senolytic CAR T cells, first identifying candidate targets by comprehensively characterizing cell- surface proteins that are selectively expressed on senescent cells in multiple contexts of age-associated diseases. This work will have the added benefit of yielding novel markers for the challenging tasks of identifying senescent cells in vivo and delineating their roles in disease. For the top candidate targets, we will develop new senolytic CAR T cells. Finally, to improve the specificity and efficacy of the senolytic CAR T cells, we will apply recent technical advances, namely AND-gated CARs and engineered CD3 signaling domains, to develop second-generation senolytic CAR T cells. Our team combines the extensive expertise of the Lowe laboratory in senescence mechanisms and biology with the expertise of the Sadelain Laboratory in CAR T cell innovations. The feasibility of the proposed work is supported by strong preliminary data. We expect our studies to better define senescent states, generate new insights into senescence biology, and produce the next generation of cell-based therapies for treating pathologies associated with senescence and aging.
