ERRα activates SHMT2 transcription to enhance the resistance of breast cancer to lapatinib via modulating the mitochondrial metabolic adaption

Lapatinib, a tyrosine kinase inhibitor, can initially benefit the patients with breast tumors but fails in later treatment due to the inevitable development of drug resistance. Estrogen-related receptor a (ERR alpha) modulates the metabolic adaptations in lapatinib-resistant cancer cells; however, the underlying mechanism remains unclear. ERR alpha was predicted to bind to the serine hydroxymethyltransferase 2 (SHMT2) transcription initiation site in the ER- and HER2-positive cell line BT-474; thus, we hypothesize that ERR alpha might modulate the resistance of breast cancer to lapatinib via regulating SHMT2. In the present study, we revealed that 2.5 and 5 mu M lapatinib treatment could significantly decrease the expression and protein levels of ERR alpha and SHMT2; ERR alpha and SHMT2 expression and protein levels were significantly up-regulated in breast cancer cells, in particularly in breast cancer cells with resistance to lapatinib. ERR alpha knockdown restored the inhibitory effects of lapatinib on the BT-474R cell viability and migration; in the meantime, ERR alpha knockdown rescued the production of reactive oxygen species (ROS) whereas decreased the ratio of glutathione (GSH)/oxidized glutathione (GSSG) upon lapatinib treatment. Via targeting SHMT2 promoter region, ERR alpha activated the transcription of SHMT2. The effects of ERR alpha knockdown on BT-474R cells under lapatinib treatment could be significantly reversed by SHMT2 overexpression. In conclusion, ERR alpha knockdown suppresses the detoxification and the mitochondrial metabolic adaption in breast cancer resistant to lapatinib; ERR alpha activates SHMT2 transcription via targeting its promoter region, therefore enhancing breast cancer resistance to lapatinib.