[SIRT2-Reverses Drug-Resistance of HL-60/A through Autophagy Mechanism].

OBJECTIVE: To investigate the effect of targeting the silent information regulator 2 hemolog 2 (SIRT2) expression on the apoptosis of drug-resistant AML cell line HL-60/A and its mechanism. METHODS: The expression of SIRT2 and antophagy-related protein LCT, P62 in HL-60/A and HL-60 was detected by Western blot, the effect of cytorabine on the apoptosis of HL-60/A cells was detected by using Annexin V/PI double staining after targeting inhibition of SIRT2 expression resulting from transfecting HL-60/A cells with SiRNA. The Western blot and transmission electray microscopy were used to detect the cell autophagy. To further clarify the role of autophragy in the regulatory effect of SIRT2 on the drug-resistance of HL-60/A cells, the autophagy-specific agonist, repamycin, was added into the cell culture medium after SIRT2-siRNA transfection. Then, the autophagy and apoptosis of HL-60/A were detected, respectively. RESULTS: The SIRT2 protein expression obviously increased in HL-60/A cells than that in HL-60 cells. Moreover, the expression rate of LC3II/I was higher, but P62 expression was lower in HL-60/A cells. After siRNA successfully transfecting into HL-60/A cells, quantitative PCR and Western blot should that the expression of SIRT2 significantly decreased. Meawhile, Western blot showed that the expression of LC3 II/I decreased, but P62 increased. Meanwhile, By TEM found that the number of autophagosome also decreased, suggesting the autophagy was inhibited after down-regulation of SIRT2. In addition, the drug senstivity of HL-60/A cells to cytarabine in siRNA-transfection group increased, and the apoptotic rate detected by Annexin V/PI double staining significantly increased. However, after co-culture with rapamycin, the suppressed autophagy in siRNA-trasfect HL-60/A cells was activated, leading to the reappearance of drug resistance of cells to cytarabine, and more significantly decrease of apoptotic rate. CONCLUSION: The high expression of SIRT2 in HL-60/A cells activates the protective autophagy mechanism, which closely related with drug resistance.