Cell growth inhibition, G₂M cell cycle arrest, and apoptosis induced by the novel compound Alternol in human gastric carcinoma cell line MGC803

Alternol is a novel compound purified from fermentation products of a microorganism in the bark of the yew tree. Because it has a similar origin as the anticancer agent paclitaxel, we hypothesized that Alternol may also have an anti-tumor effect. In this report, we chose human gastric carcinoma cell line MGC803 as the model to investigate the effects of Alternol. We evaluated cell viability using the CCK8 kit. The cell cycle distribution was analyzed by flow cytometry. AnnexinV combined with PI was performed to evaluate the apoptosis rate. The mitochondria membrane potential (MMP) was measured by a fluorescence-activated cell sorter using Rhodamin123 staining. We observed the morphological changes by immunofluorescence and Hochest33342 staining. RT-PCR and Western blot analysis were used to evaluate the changes of G₂M-related regulators. Our data show that Alternol inhibited the growth of MGC803 and induced G₂M arrest. Coincident with G₂M arrest, phosphorylation of CDC2 on Tyr-15 was significantly elevated, which could be explained by the increase of Wee1 and decrease of CDC25C. The decreased expression of PLK1 may cause the elevation of Wee1 and CyclinB1 protein levels. Moreover, the apoptosis seemed to be secondary to G₂M arrest because the elevated Caspase3, decreased MMP, and typical apoptotic morphology changes appeared after G₂M arrest. These findings suggested that Alternol could inhibit the growth of MGC803 by inducing G₂M arrest and apoptosis. We expected Alternol may be used as a lead compound one day and our experiments might provide some clues for further research.