CDK4 down-regulation induced by paclitaxel is associated with G(1) arrest in gastric cancer cells

Paclitaxel induces a cell cycle block at G(2)-M phase by preventing the dep olymerization of microtubules and induces p53-independent apoptosis in many cancer cells, We observed that gastric cancer cells treated with paclitaxe l have shown a cyclin-dependent kinase (CDK)4 do down-regulation, This pacl itaxel-induced CDK4 down-regulation resulted in a cell cycle arrest at G(1) -S phase. To confirm this observation,,ve prepared stable transfectants tha t overexpressed CDK4 and analyzed the cell cycle progression. Ectopic expre ssion of CDK4 in SNU cells resulted in a release of paclitaxel-induced G(1) arrest. The release of G(1) arrest by enforced expression of CDK4 seems to make the cells more sensitive to paclitaxel-induced apoptosis. From this f inding, we could then suggest that paclitaxel treatment induces both G(1)-S and G(2)-M blocks in the cell cycle progression of gastric cancer cells.