Doxorubicin is a chemotherapeutic drug used for the treatment of various malignancies; however, patients can experience cardiotoxic effects and this has limited the use of this potent drug. The mechanisms by which doxorubicin kills cardiomyocytes has been elusive and despite extensive research the exact mechanisms remain unknown. This review focuses on recent advances in our understanding of doxorubicin induced regulated cardiomyocyte death pathways including autophagy, ferroptosis, necroptosis, pyroptosis and apoptosis. Understanding the mechanisms by which doxorubicin leads to cardiomyocyte death may help identify novel therapeutic agents and lead to more targeted approaches to cardiotoxicity testing.

Summary Ibrutinib (IB) is an oral Bruton's tyrosine kinase (BTK) inhibitor that has demonstrated benefit in B cell cancers, but is associated with a dramatic increase in atrial fibrillation (AF). We employed cell-specific differentiation protocols and optical mapping to investigate the effects of IB and other tyrosine kinase inhibitors (TKIs) on the voltage and calcium transients of atrial and ventricular human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs). IB demonstrated direct cell-specific effects on atrial hPSC-CMs that would be predicted to predispose to AF. Second-generation BTK inhibitors did not have the same effect. Furthermore, IB exposure was associated with differential chamber-specific regulation of a number of regulatory pathways including the receptor tyrosine kinase pathway, which may be implicated in the pathogenesis of AF. Our study is the first to demonstrate cell-type-specific toxicity in hPSC-derived atrial and ventricular cardiomyocytes, which reliably reproduces the clinical cardiotoxicity observed.

Doxorubicin is a potent anticancer drug used to treat a variety of cancer types. However, its use is limited by doxorubicin-induced cardiotoxicity (DIC). A missense variant in the RARG gene (S427L; rs2229774) has been implicated in susceptibility to DIC in a genome wide association study. The goal of this study was to investigate the functional role of this RARG variant in Dic. We used induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) from patients treated with doxorubicin. iPSC-CMs from individuals who experienced DIC (cases) showed significantly greater sensitivity to doxorubicin compared to iPSC-CMs from doxorubicin-treated individuals who did not develop DIC (controls) in cell viability and optical mapping experiments. Using CRISPR/Cas9, we generated isogenic cell lines that differed only at the RARG locus. Genetic correction of RARG-S427L to wild type resulted in reduced doxorubicin-induced double stranded DnA breaks, reactive oxygen species production, and cell death. conversely, introduction of RARG-S427L increased susceptibility to doxorubicin. Finally, genetic disruption of the RARG gene resulted in protection from cell death due to doxorubicin treatment. Our findings suggest that the presence of RARG-S427L increases sensitivity to DIC, establishing a direct, causal role for this variant in Dic. Doxorubicin is an anthracycline chemotherapeutic drug used in the treatment of solid organ and hematological malignancies for both adult and pediatric patients 1. Despite its effectiveness as an anti-cancer agent, the use of doxorubicin is limited by cardiotoxicity which affects up to one quarter of patients 2. Doxorubicin-induced cardiotoxicity (DIC) leads to cardiomyopathy with systolic dysfunction, arrhythmia, congestive heart failure, and in some cases death 1,3. Despite extensive investigation, the mechanisms of DIC remain incompletely understood, and we lack the ability to predict this adverse drug reaction in individual patients. Genetic association studies have identified several genetic variants that are associated with DIC 4. However, lack of replication of these findings and the absence of functional validation has precluded their implementation as clinical tests. Among the variants with the strongest genetic evidence is a non-synonymous coding variant (rs2229774, S427L) in the retinoic acid receptor gamma gene, RARG, which was identified in a genome-wide association study (GWAS) of DIC (odds ratio = 4.7, p = 5.9 10 −8) 5. However, the directionality of this effect is controversial 6 , and genetic association studies cannot prove a causal relationship between a genetic locus and the phenotype of interest. As a consequence, direct functional assessment of the role of this variant in DIC is essential.

No abstract

No abstract