Proliferative Inhibition and Apoptotic Induction Effects of Crocin on Human Leukemia HL-60 Cells and Their Mechanisms

This study was to investigate the proliferative inhibition and apoptosis of human leukemia HL-60 cells induced by crocin and their possible mechanisms. The cell viability was tested by cell counting.The morphology of HL-60 cells was observed by fluorescence microscopy. The MTT assay was used to evaluate the inhibitory effect of crocin on the growth of HL-60 cells. Flow cytometry was used to measure the cell cycle. RT-PCR was used to detect bcl-2 and bax expression. The results indicated that the growth of HL-60 cells was inhibited remarkably in the dose and time dependent way. When the crocin concentration was higher than 5 mg/ml,the percentage of apoptotic HL-60 cells was not increased,on the contrary this percentage decreased,the cells manifested necrosis. Flow cytometry profiles revealed that cells were blocked in G0/G1 phase,the cell proliferation was inhibited obviously at 5 mg/ml. RT-PCR detection revealed that the expression of bcl-2 was down-regulated strikingly and bax was up-regulated. It is concluded that the crocin can inhibit the proliferation of HL-60 cells effectively,and block cells in G0/G1 phase. The mechanisms by which crocin induced apoptosis in HL-60 cells may be related to the inhibition of bcl-2 and activation of bax.