Abstract: AIM: To investigate the apoptosis of human leukemia cell line K562 induced by mimics of manganese superoxide dismutase (MnSOD_m) in vitro and the possible molecular mechanisms.METHODS: The apoptosis in K562 cells was examined by MTT colorimetric method, FITC-Annexin V and propidium iodide (PI) double staining and morphological changes method, the expression level of Fas protein was measured with flow cytometry(FCM), and the mRNA expression and the activity of Caspase-3 were detected by RT-PCR and colorimetric assay,respectively.RESULTS: After administration with MnSOD_m, the proliferation of K562 cells was obviously inhibited, the cellular apoptosis was markedly enhanced with Annexin V/PI staining and the cells showed the typical apoptotic morphological changes. The expression of Fas protein in K562 cells up-regulated greatly, which accompanied with the significant increase of both mRNA expression and activity of Caspase-3.CONCLUSION: The apoptosis of leukemia K562 cells induced by MnSOD_m may involved in the Fas death receptor pathway.

Key words: Mimcs of MnSOD, Leukemia, Apoptosis, Fas protein, Caspase-3