Effects of lycorine on HL‐60 cells via arresting cell cycle and inducing apoptosis

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Abstract
As a natural anti‐cancer alkaloid extracted from Amaryllidaceae, lycorine shows various biological effects on tumor cells. The survival rate of HL‐60 cells exposed to lycorine was decreased in a dose‐dependent manner with 1 μM as the 50% inhibitory concentration (IC50), cell growth was slowed down by arresting cell cycle at G2/M phase, and cell regeneration potential was inhibited. HL‐60 cells exhibited typical apoptotic morphological changes, apoptotic DNA “ladder” pattern, and sub‐G1 peak in cell phase distribution, showing apoptosis of HL‐60 cells. To further understand the apoptotic molecular mechanism of lycorine on HL‐60 cells, caspase activity was tested by colorimetric assay, and the expression of Bcl‐2 and Bax proteins was examined by Western blotting. The increase of caspase‐8, ‐9, ‐3 activities demonstrated that caspase was a key mediator of apoptotic pathways induced by lycorine. Under‐expression of Bcl‐2 and increase of Bax:Bcl‐2 ratio showed that Bcl‐2 family proteins were involved in apoptosis. Our finding suggests that lycorine can suppress leukemia growth and reduce cell survival via arresting cell cycle and inducing apoptosis of tumor cells.