ent‐Kaurane‐Type Diterpenes Induce ROS‐Mediated Mitochondrial Dysfunction and Apoptosis by Suppress the Homologous Recombination DNA Repair in Triple‐Negative Breast Cancer Cells

Abstract Six ent ‐kaurane‐type diterpenes were isolated from the roots of Isodon ternifolia . Previous studies have shown that compounds 1 and 2 exhibited cytotoxicity against three human cancer cell lines (MCF‐7, A549, and HCT116), but its molecular mechanism has not been studied yet. In the present study, the inhibited proliferation of compounds 1 and 2 of two triple‐negative breast cancer (TNBC) cell lines (4T1 and MDA‐MB‐231) have been demonstrated by MTT and colony formation assay. Flow cytometry, western blotting, and qPCR were used to further demonstrate the apoptosis process in TNBCs. Importantly, the following mitochondrial membrane potential (MMP) decrease during apoptosis was demonstrated to correlate to reactive oxygen species (ROS) production. In addition, DNA damage induced by compounds 1 and 2 was illustrated by detect of homologous recombination (HR) DNA repair genes and proteins expression, such as RAD51. These results indicated that compounds 1 and 2 could trigger the TNBCs apoptosis mediated by ROS‐induced mitochondrial dysfunction and induce DNA double‐strand breaks (DSBs) by down regulating HR DNA repair. Furthermore, this research reveals that the mechanism between mitochondria dysfunction and DNA damage is deserved to be investigated for elucidating the dynamic signal transduction between the nucleus and the cellular matrix during apoptosis.