In this article, the in vitro effects of seleno-short-chain chitosan (SSCC, molecular weight between 5,000 and 10,000 Da) on the proliferation of human leukemia K562 cells were investigated to illustrate the possible mechanisms involved. 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assays showed that short-chain chitosan significantly suppressed the growth of K562 cells in a dose-dependent and time-dependent manner, although normal mouse embryonic fibroblasts NIH3T3 were viable after the same treatment. Cell growth inhibitory rate could reach 95% after exposure with more than 100 microg/ml SSCC for 72 h. Flow cytometry analysis revealed that treatment of K562 cells with SSCC resulted in the accumulation of cells in the G(2)/M phase. The growth inhibition of K562 cells after treatment with SSCC was subsequently associated with the induction of apoptosis, as evidenced by (1) the typical apoptotic morphologic changes measured by a fluorescence microscope, (2) the internucleosomal DNA fragmentation into a ladder determined by agarose gel electrophoresis and (3) the occurrence of sub-G(0)/G(1) phase cells analyzed by flow cytometry. All these results indicated that SSCC may have therapeutic potential in human leukemia treatment.
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