Fig 1: miR-9 was involved in oestrogen-related receptors alpha (ERRa) regulated mRNA stability of ABCB1. MG-63/Dox (A) or HOS/Dox (B) were treated with or without 1 µmol/L XCT-790 for 24 h, the expression of miRNAs was measured; (C) MG-63/Dox cells were transfected with RNA scramble control or miR-9 mimics for 12 h and then further treated with Act-D for the indicated times, the mRNA of ABCB1 was measured; MG-63/Dox cells were transfected with si-NC or miR-9 inhibitor for 12 h and then further treated with or without 1 µmol/L XCT-790 for 24 h, the mRNA (D) or protein (E) expression of P-gp was measured and quantitatively analyzed. (F) The schematic of ERRa regulated ABCB1 expression via binding with SP3 and suppressing miR-9 expression in OS cells. Data are presented as means ± SD of three independent experiments. **P < 0.01 compared with control