Berberine reverses lapatinib resistance of HER2-positive breast cancer cells by increasing the level of ROS.

Lapatinib, a novel tyrosine kinase inhibitor of HER2/EGFR, is used to treat HER2-positive breast cancer. However, acquired drug resistance has limited the clinical therapeutic efficacy of lapatinib. Our previous study found that inhibition of autophagy can reduce the proliferation, DNA synthesis, and colony-forming capacity of lapatinib-resistant cells. Berberine has attracted extensive attention due to its wide range of biochemical and pharmacological effects in breast cancer treatment. It has been reported that berberine can induce oxidative stress and the mitochondrial-related apoptotic pathway in human breast cancer cells. In our current study, we found that a new combination therapy of berberine with lapatinib overcame lapatinib resistance. Furthermore, we found that berberine induced apoptosis of lapatinib-resistant cells through upregulating the level of ROS. Specially, lapatinib activated both the c-Myc/pro-Nrf2 pathway and GSK-3β signaling to stabilize Nrf2 and maintain a low level of ROS in resistant cells. However, berberine can upset the ROS balance by downregulating c-Myc to reverse the lapatinib resistance. Our finding provides a novel strategy of using berberine to overcome lapatinib resistance.