Objective  To investigate inhibitive effect of lutein on the proliferation of human prostate cancer PC-3M cells and the mechanism of the effect in vitro.

  Methods  Human prostate cancer PC-3M cells were randomly divided into a control group and 4 lutein treatment groups at doses of 5, 10, 20, and 40 μmol/L. The inhibitive rate of PC-3M cells proliferation was measured with methyl thiazolyl tetrazolium (MTT) assay; the cell cycle of PC-3M cells was detected with flow cytometry; the cell morphology was observed with fluorescence development; and the content of caspase-3 in the cell culture supernatant was measured with ultraviolet spectrophotometry.

  Results  Compared with that in the control group, the inhibitive rate of the PC-3M cells′ proliferation was significantly increased in all lutein dose groups in a dose- and time-dependent manner (P < 0.01). The proportion of the cells in G1 phase increased but that in G2M phase decreased significantly for the PC-3M cells treated with lutein at various doses in comparison with that of cells of control group (both P < 0.01). Significantly changed morphologies were observed in lutein-treated PC-3M cells, including rounded cell shape, nucleus fragmentation, condensed nuclear chromatin, and formation of apoptotic bodies, in contrast to those of the control cells; the number of apoptotic cells increased significantly with the increment of lutein doses. The content of caspase-3 in culture supernatant of PC-3M cells treated with various doses of lutein was significantly higher than that of control cells and the increase of caspase-3 was positively correlated with the increment of lutein dose significantly (P < 0.05).

  Conclusion  Lutein can inhibit the proliferation and induce apoptosis of human prostate cancer PC-3M cells in vitro; the mechanism of the effect may be related to the increased expression of caspase-3 in the lutein-treated PC-3M cells.