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. 2019 Jan 24;15(3):668–679. doi: 10.7150/ijbs.30168

Figure 4.

Figure 4

RA inhibits the STAT3 phosphorylation and reduces MDR1 expression in drug-resistant OS. (A) MDR1, MRP1, STAT3, and p-STAT3Tyr705 levels were determined by immunoblotting in drug-resistant cells compared with drug-sensitive cells (KHOSR and HOS, U2OSR and U2OS). (B) KHOSR and U2OSR cells were treated with vehicle or the indicated concentration of RA for 48 h. MDR1 and MRP1 expression were detected by immunoblotting. (C) MDR1 expression was determined by real-time qPCR in KHOSR and U2OSR after RA treated. (D) U2OSR and MG63 cells were transfected with pCDNA or pGMSTAT3 for 48 h and then treated with puromycin to establish a STAT3-overexpressing cell line (MG63-STAT3 and U2OSR-STAT3). MDR1 expression was detected by immunoblotting. (E) STAT3, p-STAT3Tyr705, and MDR1 levels were determined by immunoblotting in STAT3-overexpressing cell lines treated with series concentrations of RA. (F) U2OSR cells were treated with the indicated concentration of RA with or without STAT3 siRNA transfection for 48 h, and MDR1, STAT3, and p-STAT3Tyr705 expression were determined by immunoblotting. (G) MG63 cells were transfection with NC/STAT3 siRNA or pcDNA3/pGMSTAT3 for 48 h, treated with or without doxorubicin for 48h. The cell viability was detected by CCK8 assay.