Abstract: AimTo elucidate the molecular mechanism of cell cycle arrest and apoptosis of MCF-7 cells induced by paclitaxel. MethodsFlow cytometry was used to determine the cell cycle changes of MCF-7 cells upon paclitaxel treatment. Gene expression profiles of MCF-7 cells induced by paclitaxel were obtained by using cDNA microarrays containing 9 984 genes and expressed sequence tags (ESTs). Results Cell cycle analysis showed that 77.8% of cells arrested at G₂/M phase and 1.3% of cells underwent apoptosis upon 100 nmol·L^-1 paclitaxel treatment for 24 hours; cDNA microarray results revealed that 27 and 77 genes were differentially expressed upon 12.5 nmol·L^-1 (IC5₅₀) and 100 nmol·L^-1 paclitaxel treatment, respectively. ConclusionPaclitaxel stabilized microtubules and caused G₂/M cell cycle arrest and apoptotic cell death in a concentration-dependent manner, which is associated with the regulation of selected genes related to microtubule assembly and cytoskeleton, cell cycle regulation, and DNA repair and apoptosis.