Progressive suppression of DNA repair genes with persistent p53 target activation in doxorubicin-treated cardiomyocytes.

Doxorubicin (DOX) is an effective anticancer drug; however, it can cause cardiotoxicity by inducing DNA double-strand breaks in cardiomyocytes. Cardiotoxicity can manifest immediately or years following treatment. Most human in vitro models of DOX-induced cardiotoxicity (DIC) focus on the acute effects of DOX treatment. To understand the long-term effects, we profiled the global gene expression response to DOX exposure over time. We treated iPSC-derived cardiomyocytes from six individuals with DOX for 24 h and assayed responses after 0, 24, and 144 h of recovery. DNA damage, determined by γH2AX expression, is induced following DOX treatment and is resolved by the final recovery timepoint. We identified both acute and chronic gene expression response signatures. The chronic signature, representing 501 genes, is enriched for p53 target genes, DNA damage response (DDR) genes, and senescence-associated genes compared to acute response genes. p53 target genes are persistently activated, and DDR genes are progressively downregulated over time. Our results suggest an altered cell state following repair of double-strand breaks that is distinct from preexposed cells. Doxorubicin response genes with persistent changes in expression can be applied to the design of toxicity biomarkers or therapeutic targets.