Oestrogen‐related receptor alpha mediates chemotherapy resistance of osteosarcoma cells via regulation of ABCB1

Chemotherapy resistance is one of the major challenges for the treatment of osteosarcoma (OS). The potential roles of oestrogenic signals in the chemoresistance of OS cells were investigated. As compare to the parental cells, the doxorubicin and cisplatin (CDDP) resistant OS cells had greater levels of oestrogen‐related receptors alpha (ERRα). Targeted inhibition of ERRα by its specific siRNAs or inverse agonist XCT‐790 can restore the sensitivity of OS resistant cells to chemotherapy. This might be due to that si‐ERRα can decrease the expression of P‐glycoprotein (P‐gp, encoded by ABCB1), one important ABC membrane transporter for drug efflux. XCT‐790 can decrease the transcription and mRNA stability of ABCB1, while had no effect on protein stability of P‐gp. ERRα can bind to the transcription factor of SP3 to increase the transcription of ABCB1. Furthermore, XCT‐790 treatment decreased the expression of miR‐9, which can bind to the 3′UTR of ABCB1 and trigger its decay. Collectively, we found that ERRα can regulate the chemoresistance of OS cells via regulating the transcription and mRNA stability of ABCB1. Targeted inhibition of ERRα might be a potential approach for OS therapy.