Submicromolar paclitaxel induces apoptosis in human gastric cancer cells at early G1 phase.

Paclitaxel induced apoptosis has been reported in many cancer cell lines, but the relationship between G2/M phase arrest and apoptosis is not clear. We have reported that low dose (10 nM) paclitaxel induced apoptosis in gastric cancer cells without G2/M phase arrest. In this study, SC-M1 gastric cancer cells were synchronized at early G1, late G1, S and G2/M phases by staurosporine, mimosine, hydroxyurea and berberine, respectively. We have found that paclitaxel could not induce apoptosis of gastric cancer cells in late G1, S and G2/M phases; however, paclitaxel induced apoptosis in the early G1 phase. Our results suggest that cells arrested at G2/M phase by paclitaxel eventually entered the early G1 phase then proceeded to apoptosis.