Matters of the heart: elucidating the cardiotoxic mechanism of proteasome inhibitors

Drug-induced cardiovascular toxicity is a significant challenge in cancer therapy, as adverse effects can interfere with treatment and compromise long-term patient survival. Proteasome inhibitors, the cornerstone of multiple myeloma treatment, are associated with increased risk of cardiotoxic events, particularly carfilzomib. Despite attempts to identify clinical factors that could predict cardiotoxicity, the underlying molecular mechanisms remain unknown, partly due to the lack of relevant models. Most studies examining molecular mechanisms have been conducted on animal models lacking genetic heterogeneity, which is crucial for reflecting human population diversity. To address this research gap, our study has three objectives. First, we will investigate the involvement of the PP2A-AMPKα signaling axis in the toxicity of proteasome inhibitors on primary human cardiomyocytes. These cells have been chosen as the experimental model due to their ability to accurately reflect the characteristics of cardiomyocytes under in vivo conditions. The cells will be treated with clinically-used proteasome inhibitors and then study their effects on the PP2A-AMPKα signaling axis, which was reported to play a role carfilzomib-induced toxicity in mouse models . Thus, we will demonstrate the possible relevance of this molecular pathway in proteasome inhibitor-induced cardiotoxicity in in vitro human cell models. Second, we will investigate whether proteasome activity can serve as a predictive factor for proteasome-related cardiotoxic adverse events in multiple myeloma patients. Here, we will focus on carfilzomib, because studies suggest that the incidence of cardiovascular adverse events are higher for carfilzomib than other proteasome inhibitors. We will enroll around 60-80 multiple myeloma patients who were either newly diagnosed or are undergoing the first relapse. In blood samples from these patients, proteasome expression and activity levels will be determined (at the beginning and the end of the chemotherapeutic cycle) and correlated to patients' clinical data. With this approach we aim to identify if individual catalytically-active proteasome subunits can be considered as potential predictive biomarkers for cardiotoxicity of carfilzomib. Last, we will generate patient-derived induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM) from patients who have and have not experienced carfilzomib-induced cardiotoxic events (Cfz-CT and Cfz-NCT, respectively). These cells will be treated with carfilzomib, and we will use high-content analyses to determine changes in viability, hypertrophy, and morphology. This will help us determine if the iPSC-CMs from the Cfz-CT group recapitulate their sensitivity to carfilzomib as observed in vivo in patients. In the event of significant differences in cardiotoxicity between the two groups, additional proteome analyses will be conducted. The creation of this iPSC-CM-based experimental platform will allow us to investigate the inter-individual variabilities involved in developing a cardiotoxic response to proteasome inhibitors and identify candidate predictive biomarkers. The significance of our study lies in improving our understanding of the mechanisms underlying proteasome-induced cardiotoxicity and identifying potential predictive biomarkers. Our proposed research could lead to the development of therapeutic intervention strategies to protect patients against cardiotoxicity and improve their long-term survival. The use of primary cardiomyocytes and patient-derived iPSC-CMs is a contemporary approach that has the potential to provide important insights into inter-individual variability and inform personalized treatment strategies.