In vitro evaluation of cardiotoxicity of tyrosine kinase inhibitor regorafenib with molecular techniques

Regorafenib is a tyrosine kinase inhibitor drug that inhibits many kinases responsible for cancer. It is used in the treatment of colorectal cancer, gastrointestinal stromal tumor and hepatocellular carcinoma. Regorafenib has been reported to cause life-threatening hypertension and ischemia, and its molecular mechanism is not fully known. In the study, it was aimed to elucidate the molecular mechanisms of regorafenib-induced cardiotoxicity using H9c2 cardiomyblastic cell line. Cardiac cells highly need ATP for their functioning. Therefore, regorafenib-induced toxic effects on cardiomyoblasts were investigated by focusing pathways that are related to mitochondrial and cellular stress after 48- and 72-hours exposure of 5, 10 and 20 μM regorafenib. A decrease in intracellular ATP level in all groups in both exposure times and disruption of membrane potential at 20 μM after 72-hours exposure were detected. An increase in expressions of mitochondrial dynamic genes at high doses in both end-points was seen. Mitochondrial complex I and V expressions reduced at 20 μM following 72-hours exposure. No significant change was detected in the expressions of mitochondrial proteins cytochrome c, UCP2 and LONP1 levels. While an increase in HSP70 protein expression was detected at 10 and 20 μM after 72-hours exposure, GRP94 level did not show significant change. A decrease in mtDNA content was detected following 72-hours exposure. In addition, procaspase 3 protein level decreased at 20 μM in both exposures. This study shows that the regorafenib-induced cardiotoxicity can be linked with mitochondrial damage. However, this theory needs to be supported by in vivo and clinical studies.