CDK4/6 inhibitor ribociclib induces cardiotoxicity in dynamic engineered heart tissues, mitigated by E2F1 overexpression

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Research Council CDK4/6 inhibitor Ribociclib induces cardiotoxicity in dynamic engineered heart tissues, mitigated by E2F1 overexpression Background Ribociclib, a novel chemotherapeutic agent for metastatic breast cancer, functions as a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor1. Its mechanism of action involves the CDK4/6-Rb-E2F1 pathway. Ribociclib use has very recently been associated with development of heart failure (HF)2, yet the causality of its cardiac effects remains to be explored. Aims This study aims to investigate ribociclib's cardiotoxic effects in dynamic human engineered heart tissues (dyn-EHTs), focusing on the CDK4/6-Rb-E2F1 axis. Methods and Results Dyn-EHTs were generated using human induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) and treated with repeated doses of ribociclib (7 µM) to mimic clinical drug administration. Post-treatment, dyn-EHTs exhibited a 17.0% (p<0.001) increase in tissue dilatation, an 8.9% (p<0.001) decrease in systolic force generation, and a 22.1% (p<0.001) increase in systolic stress, indicating significant cardiac dysfunction. Additionally, an increase in phosphorylation levels of Rb protein (Ser249 and Thr252) was observed (FC=0.445, p=0.009). Overexpression of E2F1 in iPSCs resulted in a threefold increase in E2F1 protein expression and successfully mitigated the ribociclib-induced tissue dilatation (p=0.007), decreased systolic force generation (p=0.005), and increase in systolic stress (p=0.004) making their performance comparable to healthy controls, as shown by linear regression analysis. Conclusions Our study demonstrates that ribociclib induces significant cardiotoxic effects in dyn-EHTs and iPSC-CMs through the CDK4/6-Rb-E2F1 pathway. The prevention of these effects by E2F1 overexpression highlights the pathway's involvement in ribociclib's cardiotoxic profile. These findings emphasize the need for careful cardiac monitoring in patients treated with CDK4/6 inhibitors and suggest further research into specific mechanisms of cardiotoxicity in cancer therapeutics.Graphical Abstract