Background and purpose: Cyclin-dependent kinase 4 (CDK4) is a kind of protein kinases regulating the cell cycle progression

which has been reported to be overexpressed in endometrial carcinoma tissues. But the role of CDK4 in endometrial carcinogenesis and relative mechanisms has not been identified yet. In this study

we used a small interfering RNA targeting CDK4

and explored the effects of

CDK4 on endometrial cancer cells HEC-1B biological function and relative mechanisms. Methods: The chemically synthesized small interfering RNA targeting CDK4 (si-CDK4) was transiently transfected into HEC-1B cells; the quantitative real time-PCR assays and Western blot assays were performed to explore the mRNA and protein expression levels of CDK4 and its downstream genes

Rb and p-Rb

in HEC-1B cells upon transfection; Moreover

the CCK-8

flow cytometry (FCM) and invasion assays were performed to indentify the effects of si-CDK4 on the proliferation

cell cycle distribution

apoptosis and invasion abilities of HEC-1B cells

respectively. Results: The results showed that the mRNA and protein expressions of CDK4 were suppressed in HEC-1B cells upon transfection with si-CDK4 (P0.01); Suppression of CDK4 inhibited cell proliferation and invasion of HEC-1B cells; the number of cells migrating through the transwell membrane in si- CDK4 group was 117±21

which was much fewer than the cells in si-control (269±39) and untreated groups (262±35) (P0.01); the early apoptosis rate of cells treated with si-CDK4 ［(21.7±3.5)%］ was much higher than the untreated ［(12.4±2.1)%］ and si-control groups ［(11.8±1.9)%］ (P0.01); moreover

suppression of CDK4 increased cells in G

1

phase (P0.01) and correspondingly decreased cells in S phase (P0.01); further Western blot results showed that suppression of CDK4 down-regulated the expression of p-Rb in cells

but did not influence the expression of total Rb. Conclusion: CDK4-siRNA specifically and efficiently blocks the constitutively activated CDK4 in human endometrial cancer cells HEC-1B

resulting in tumor suppression.