Quercetin attenuates the cardiotoxicity of doxorubicin–cyclophosphamide regimen and potentiates its chemotherapeutic effect against triple‐negative breast cancer

Doxorubicin combined with cyclophosphamide (AC) is the most commonly used regimen for triple‐negative breast cancer (TNBC) chemotherapy; however, its clinical application is severely limited by its serious adverse effect on cardiomyocytes. The cardiotoxicity of AC is mainly the result of oxidative stress caused by the imbalance between reactive oxygen species (ROS) and antioxidants, and it also involves multiple signaling pathways. Quercetin (Que) has been proven to possess strong antioxidant activity, and therefore we investigated whether it had potential protective effect against AC‐induced cardiotoxicity. Meanwhile, we also evaluated its effect on the antitumor activity of AC. Our in vitro studies showed that Que could attenuate AC‐induced cardiotoxicity by inhibiting ROS accumulation and activating ERK1/2 pathway in cardiomyocytes, but interestingly, Que could enhance the antitumor activity of AC by inhibiting ROS accumulation and ERK1/2 pathway in TNBC cells. In addition, our in vivo studies further confirmed that Que could enhance the chemotherapeutic effect of AC against TNBC while it reduced the injury of cardiotoxicity induced by AC. Therefore, Que could be used as a novel agent for the treatment of cardiotoxicity induced by AC regimen in TNBC chemotherapy.