Mechanism of Ponatinib induced vascular toxicity - PROJECT SUMMARY/ABSTRACT The development of first generation Abl-tyrosine kinase inhibitor (Abl-TKI) imatinib (Im) to treat chronic myelogenous leukemia (CML) in 2001 has changed this previously lethal cancer into a chronic illness. Despite initial success, Im intolerance and resistance necessitates development of newer generation Abl-TKIs. Ponatinib (Po), a newer Abl-TKI that is lifesaving for T315I mutation CML, is associated with a four-fold increased risk of acute arterial occlusive events, including life-threatening heart attack or stroke, compared to Im, which has nullified any cancer survival benefit. With a rapidly growing prevalence of over 100,000 survivors and 10,000 new cases annually in the US alone, there exists an urgent need to determine the mechanism of Abl-TKI toxicity to improve CML outcomes. Previous published studies assessing direct effects of Po on platelets and clotting are inconclusive. Because CML patients present with high prevalence of cardiovascular risk factors and underlying atherosclerotic disease, we introduce the novel hypothesis that Po acts to instead inflame pre-existing atherosclerotic plaques and prime them for rupture and subsequent thrombosis. Endothelial cells (ECs) lining the vasculature are anti-inflammatory but become proinflammatory in the setting of injury, expressing adhesion molecules that induce leukocyte trafficking and subsequent plaque inflammation. As these patients also exhibit elevated serum proinflammatory cytokine TNFa despite remission, this proposal also tests the hypothesis that Po sensitizes ECs to TNFa signaling via increased expression of TNF receptor (TNFR) on cell surface, resulting in increased adhesion molecule expression on human ECs in vitro, increased leukocyte trafficking into vessels in vivo, and thus more inflamed atherosclerotic plaques in vivo. Preliminary data confirms that Po: 1) induces expression of adhesion molecules in ECs in vitro and that this increase is prevented by a TNFR inhibitor, 2) increases leukocyte trafficking by intravital microscopy in vivo, and 3) increases plaque leukocyte content, a marker of plaque inflammation, measured by flow cytometry in atherogenic mice (ApoE-KO). This proposal tests this hypothesis for Im, Po, and asciminib which is recently approved but vascular safety is unknown. Aim 1 explores the mechanism by which Po induces EC adhesion molecule expression and the role of EC TNFR signaling in vitro using genetic and pharmacologic approaches to block TNFR. Aim 2 examines the impact of Po on leukocyte trafficking and plaque inflammation in vivo via intravital microscopy in EC-TNFR1-KO mice and on plaque inflammation in ApoE-KO mice by aortic arch flow cytometry. Successful completion of these aims will test a recently approved Abl-TKI for toxicity and provide novel insight into Po’s mechanism of vascular toxicity, which can lead to support for an EC protective strategy that will prevent arterial thrombosis and improve CML outcomes. The detailed training plan will prepare the PI for a career as an independent academic physician-scientist through rigorous training in molecular and vascular biology and guidance from a translational and transdisciplinary advisory team.
