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

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.