Investigating the role of apoptosis regulation in cancer therapy-induced vascular toxicities

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PROJECT SUMMARY Cancer treatments have evolved extensively over the past few decades, leading to vast improvements in overall survival and cure rates. However, the collateral damage inflicted upon healthy tissues by both targeted and cytotoxic agents frequently causes life-threatening irreversible toxicities. Some of the most common toxicities include therapy-induced vascular impairments such as atherosclerosis, heart failure, ischemia, acute thrombosis, and venous thromboembolism. Despite their widespread use, it is poorly understood how chemotherapies and ionizing radiation cause vascular toxicities. Most cancer therapies typically induce apoptosis (programmed cell death) by damaging common cellular components such as DNA or by blocking critical signaling pathways. Since vascular cells are also exposed to these agents at high concentrations, they could be vulnerable to therapy-induced apoptosis. However, the vasculature is comprised of several cell types including vascular endothelial and smooth muscle cells; it is unknown which cells are sensitive to anti-cancer agents and how they may contribute to long-term vascular dysfunction in patients. Using human induced pluripotent stem cells (hiPSCs) for in vitro disease modeling, we will investigate vascular toxicities in hiPSC- derived vascular endothelial cells and vascular smooth muscle cells. Utilizing robust differentiation protocols already established in our laboratory, we will rigorously test how the survival and function of these cells are affected by cancer treatments. We will also characterize the regulation of apoptosis in both vascular cell types by measuring apoptotic priming and expression of BCL-2 family proteins. Additionally, we will look at the functional and morphological changes that these cells undergo in response to cancer treatments that may contribute to vascular toxicities. We hypothesize that each vascular cell type possesses differential levels of apoptotic priming, and unique vulnerabilities to our panel of FDA-approved cancer therapies that drive therapy- induced vascular toxicities. Our studies will elucidate potential mechanisms and determine contributions of each cell type to vascular toxicities observed in cancer patients. Further, since aging is known to play a role in both vascular toxicity and regulation of apoptosis, we will investigate how age affects apoptotic priming and therapy sensitivity of vascular cells. We will replicate key experiments in mice at various life stages (neonate, juvenile, adult and advanced age) to validate our in vitro findings and elucidate how age affects the development of vascular toxicities. We will also utilize endothelial cell-specific BAX/BAK double knockout mice to determine the extent to which apoptosis blockade can ameliorate vascular toxicity induced by cancer treatment. Altogether, our work will test how apoptosis regulation affects the sensitivity of vascular cells to chemotherapy and radiation and how this is altered by aging. These results will lay the groundwork for improved therapy regimens in the clinic that may decrease long-term vascular toxicities in cancer patients.