Objective   To study the effect of grape seed procyanidin extract (GSPE) on the cell cycle arrest in human bladder cancer BIU87 cells and investigate the underlying molecular mechanism.    Methods   BIU87 cells were treated with different concentrations of GSPE (50

100 and 200 μg/ml) and cultured for 24 h. The untreated group served as control. Flow cytometry was used to evaluate the cell cycle

and RT-PCR and Western blotting were used to detect the mRNA and protein expressions of CyclinD

1

and cyclin-dependent kinase 4 (CDK

4

).    Results   GSPE inhibited the cell growth through cell cycle arrest at G

1

p

hrase in a dose-dependent manner. Semi-quantitated RT-PCR and Western blot analyses indicated that GSPE decreased CyclinD

1

and CDK

4

expressions in a dose-dependent fashion (

P

<

0.01).    Conclusion   GSPE induces cell cycle arrest in BIU87 cells

and the effect may be related with its down-regulation of CyclinD

1

and CDK

4

.