The inhibition of MARK2 suppresses cisplatin resistance of osteosarcoma stem cells by regulating DNA damage and repair.

ABSTRACT

OBJECTIVE: This study aims to explore the role of MARK2 in chemotherapeutic resistance and potential mechanism within cisplatin resistance models of CD133+ MG-63 and MNNG/HOS cells. METHODS: CD133- and CD133+ MG-63 and MNNG/HOS cells were differentiated and obtained by MACS(Magnetic bead sorting). Cell activity was determined by CCK-8 assay. siRNA was employed to down regulate the Microtubule Affinity Regulated Kinase 2 (MARK2) expression. Immunofluorescence detection and RT-qPCR were used to measure the expressions of MARK2 and DNA-PKcs at both protein and mRNA levels. Western blot was applied to test the levels of MARK2, γH2AX (S139), DNA-PKcs, Phospho-PI3 Kinase p85 (Tyr458), Akt, phospho-Akt (T308) antibodies, mTOR, phospho-mTOR (Ser2448). RESULTS: Compared with CD133- MG-63 cells, CD133+ MG-63 cells showed significantly strong cisplatin resistance, with high levels of MARK2, DNA-PKcs and potent DNA damage repair ability (p<0.05). Down regulation of MARK2 reduced the cisplatin resistance of CD133+ MG-63 cells, with deceasing expression of DNA-PKcs (p<0.05). PI3K/Akt/mTOR pathway was potentially activated in CD133+ MG-63 cells, and involved in the cisplatin resistance of MG-63 cells. The similar results were observed in CD133+ MNNG/HOS cells. The reduction of MARK2 retarded the activity of PI3K/Akt/mTOR pathway and further impeded the cisplatin resistance in CD133+ MG-63 and MNNG/HOS cell. CONCLUSION: Our data suggested that MARK2 was related to cisplatin resistance in CD133+ MG-63 and MNNG/HOS cells. The decrease of MARK2 restricted the cisplatin resistance of CD133+ MG-63 and MNNG/HOS cells by down regulating the expression of DNA dependent protein kinase catalytic subunit (DNA-PKcs) and inhibiting activity of PI3K/Akt/mTOR signaling pathway, which provides new clues for the osteosarcoma chemotherapy strategy.