The Effects Of Bortezomib On Myelodysplastic Syndrome And Its Drug-resistance Investigation

Objective: Our study aims to explore the effects of BTZ(bortezomib) on myelodysplastic syndrome(MDS) cell line SKM-1, and to investigate the mechanism of its drug resistance.Methods:(1) Cell apoptosis and cell cycle were performed by flow cytometry.(2) The mechanism of BTZ on SKM-1 cell apoptosis and cell cycle were assessed by Western blot and immunofluorescence.(3) Treat SKM-1 cells with BTZ intermittently to establish the BTZ-resisitant cell line SKM-1R.(4) Elucidate the mechanism of SKM-1R drug-resistance by Flow cytometry, MTT assay and Western blot.(5) Subcutaneous inoculation of SKM-1 cells in 4-week old Nod/SCID mice to establish mice xenografts in vivo.Results: Our results indicate that BTZ can cause SKM-1 cell cycle arrest at G2/M phase via increasing Wee1 protein expression after treatment with BTZ for 24 hours; BTZ is able to induce cell apoptosis by up-regulation of cleaved caspase-3 and down-regulation of p-ERK protein expression; and an increase of autophagy marker LC3-II is evident.In SKM-1R cells, we observed that cells are resistant to BTZ induced apoptosis and this is consistent with cell viability did not decrease in BTZ treated groups; activation of LC3-II was not observed, but both total and p-ERK1/2 was upregulated by BTZ; further more, we found BTZ resistance could be reversed by MEK/ERK inhibitors U0126 and D98059.In vivo, BTZ can inhibit the growth of tumor apparently, and extend the survival of mice,and this is consistant with our results in vitro.Conclusion: Our present study demonstrates that BTZ can induce cell cycle arrest, apoptosis and autophagy in SKM-1 cells, and in vivo, it can inhibit the tumor growth and promote the survival of mice.The cytotoxic effects of BTZ appeared to depend, at least in part, on the inhibition of the MEK/ERK pathway and BTZ resistance could be reversed by MEK/ERK inhibitors U0126 and D98059.Based on our present observations, a combinational therapy of BTZ and MEK/ERK inhibitors may be an effective complement to current therapeutic approaches for MDS.