Abstract:

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 (P<0.01); 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) (P<0.01); 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)%］ (P<0.01); moreover, suppression of CDK4 increased cells in G₁ phase (P<0.01) and correspondingly decreased cells in S phase (P<0.01); 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.

Key words: Endometrial carcinoma, RNA interference, Cyclin-dependent kinase 4, Retinoblastoma