OBJECTIVETo investigate the change of autophagy level of bone marrow mononuclear cells（BMMNCs）in patients with myelodysplastic syndromes（MDS）.

METHODSThirty- eight patients with MDS and 26 megaloblastic anemia patients were enrolled in this study. The autophagic vacuoles were observed by transmission electron microscopy （TEM） and the quantity of autophagic vacuoles was detected by monodansylcadaverine （MDC） staining. The LC3 protein positive cells were counted by immunofluorescence assays. The expression of Beclin 1, LC3A, mTOR mRNA were measured by real time PCR. The expression of Beclin 1 proteins were detected by Western blotting.

RESULTSThe autophgic vacuoles of double membrane that surrounds lysosomes appeared in MDS patients. The percentage of MDC positive cells was significantly higher in MDS patients［（9.75±2.63）%］than that of controls［（2.90± 0.89）%, P＜0.05）. The percentage of LC3 protein cells was also increased in MDS patients（6.13±1.03）% vs（1.5±0.58）%, P＜0.05）. The expression of Beclin 1 and LC3A mRNA in low-risk and intermediate-1 MDS were higher compared with controls （3.61 ± 3.02 vs 1.55 ± 1.03 and 6.56 ± 3.97 vs 1.21 ± 0.95 respectively, both P＜0.05）. The expression of mTOR mRNA was down- regulated in low- risk and intermediate-1 MDS compared with controls（0.39±0.37 vs 1.50±1.03, P＜0.05）. There were no significant difference in expression of Beclin 1, LC3 and mTOR mRNA among intermediate-2 and high-risk MDS and controls. Beclin 1 protein expression was higher in low- risk and intermediate- 1 MDS patients（1.257 ± 0.197）than that of controls（0.528±0.086）and inermediate-2 and high-risk MDS patients（0.622±0.118）.

CONCLUSIONThe autophagy levels were increased in low- risk and intermediate- 1 MDS, while not enhanced in intermediate-2 MDS. Autophagy might be considered as a cell protective mechanism in MDS. The relatively defective autophagy in intermediate- 2 and high- risk MDS might contribute to disease's progression.