Novel mechanisms and therapeutics for Tyrosine Kinase Inhibitor-induced Cardiotoxicity

PROJECT ABSTRACT Tyrosine kinase inhibitors (TKIs) have become a cornerstone in treating broad spectrum cancers with remarkable improvement in cancer-related outcomes. However, their use has been limited by significant cardiotoxicity, most notably left ventricular dysfunction. Recently, there have been increasing reports linking cardiac dysfunction to osimertinib, a third generation TKI targeting activating mutation of epidermal growth factor receptor (EGFR) in lung cancer. Yet, the mechanism underlying osimertinib-induced cardiac dysfunction (OICD) remains poorly understood and presently there is no specific therapy to prevent or rescue OICD. Therefore, the overarching goal of this proposal is to investigate the molecular mechanism of OICD and explore potential therapeutic targets. To achieve this goal, we first established a novel mouse model for OICD. Through single nucleus-RNA sequencing of osimertinib-treated mouse hearts, we identified a significant downregulation of myosin light chain kinase 3 (MYLK3), which is responsible for phosphorylation of myosin light chain 2 (MYL2) and promoting the interaction between cardiac myosin and actin to initiate contraction. When human induced pluripotent stem cell- derived cardiomyocytes (iPSC-CM) were subjected to osimertinib, we observed profound contractile dysfunction along with markedly decreased MYLK levels and significantly reduced MYL2 phosphorylation. This formulates our central hypothesis that EGFR TKI osimertinib causes contractile dysfunction by interfering actin- myosin interaction through the suppression of MYLK3 and disrupted MYL2 phosphorylation. To test this hypothesis, we will first examine the association between MYLK3 and OICD using control iPSC-CM lines, performing comprehensive molecular and functional analyses. To establish the causal link between MYLK3 and OICD, we will assess whether overexpressing MYLK3 in osimertinib-treated iPSC-CMs as well as in the OICD mouse model would sufficiently prevent the observed cardiotoxicity (Aim 1). Next, we will investigate whether variation in baseline levels of MYLK3 and MYLK-related pathways contribute to differential susceptibility to OICD by leveraging pooled iPSC lines derived from 20 patients with and without OICD (Aim 2). Finally, we will explore myosin activators as a therapeutic strategy to prevent OICD while preserving anti-cancer activity of osimertinib (Aim 3). This proposal addresses important knowledge gaps in cardiovascular complications of osimertinib. The results of this proposal hold immediate translational potential, ultimately improving the care of lung cancer patients suffering from cardiovascular complications.