Wip1 inhibits cell growth. T98G cells were transfected with either pCMV-neo, or pCMV-neo containing p53, waf1, wip1, and wip1-del cDNAs. Following transfection cells were selected in medium containing G418 (800 μg/ml), and two weeks later colonies were scored. Shown are the mean values ± SD of three different experiments.