Downregulation of DNA-PKcs suppresses P-gp expression via inhibition of the Akt/NF-κB pathway in CD133-positive osteosarcoma MG-63 cells

Abstract

The development of chemoresistance is closely linked to the plateau of the survival rate in osteosarcoma (OS) patients. CD133-positive (CD133+) OS cells are known as cancer stem cells (CSCs) in OS and exhibit the characteristic of chemoresistance. In this study, CD133+ and CD133-negative (CD133-) MG-63 cells were isolated by magnetic activated cell sorting (MACS). We verified that CD133+ MG-63 cells were more resistant to cisplatin (CDDP) than CD133- MG-63 cells. DNA-dependent protein kinase catalytic subunit (DNA-PKcs) and P-glycoprotein (P-gp) were expressed at higher levels in the CD133+ MG-63 cells compared with those levels in the CD133- MG-63 cells, whereas downregulation of DNA-PKcs by small interfering RNA (siRNA) decreased chemoresistance to CDDP and P-gp expression at the mRNA and protein levels in these cells. This indicated that DNA-PKcs was correlated with P-gp expression in the CD133+ MG-63 cells. The Akt/NF-κB pathway was hyperactivated in the CD133+ MG-63 cells, whereas inhibition of the Akt/NF-κB pathway downregulated P-gp expression. In addition, downregulation of DNA-PKcs suppressed the activity of the Akt/NF-κB pathway. These results revealed that downregulation of DNA-PKcs could decrease P-gp expression via suppression of the Akt/NF-κB pathway in CD133+ MG-63 cells. Therefore, inhibition of DNA-PKcs decreases P-gp expression and sensitizes OS CSCs to chemotherapeutic agents in vitro, which needs to be further validated in vivo.