Effect of cyclin-dependent kinase 7 silencing on cisplatin sensitivity in endometrial carcinoma cells

The aim of the present study was to determine the effect of cyclin-dependent kinase 7 (CDK7) silencing on the sensitivity of the HEC-1-A endometrial carcinoma cell line to cisplatin [cis-dichlorodiammineplatinum (II), or DDP]. Four CDK7 siRNA fragments were designed and synthesized based on the gene sequence of CDK7 and transfected into HEC-1-A cells. The RNA interference of the fragments was confirmed by semi-quantitative polymerase chain reaction (PCR) and western blot analyses. The CDK7-423 siRNA fragment exhibited the most marked silencing of CDK-7 (>70%), and was chosen for the subsequent experiments in HEC-1-A endometrial carcinoma cells. The sensitivity of the cells to a chemotherapeutic agent (cisplatin) was determined before and after transfection of the siRNA, using a MTT cytotoxicity assay, flow cytometry and Hoechst/propidium iodide (PI) double-staining immunofluorescence microscopy. The results of the MTT cytotoxicity assay showed that the half maximal inhibitory concentration of cisplatin was reduced from 45.12 μg/ml to 3.200 μg/ml following the inhibition of CDK7 expression levels, indicating a significantly increased cytotoxicity in the treated cells (P<0.05). The flow cytometry analysis showed that the mean rate of apoptosis in the CDK7 low-expression group was 37.57%, which was significantly higher than the rate in the parental cells (11.66%) (P<0.05). Hoechst/PI co-immunofluorescence microscopy revealed that the number of apoptotic bodies in the CDK7 low-expression HEC-1-A cells was significantly increased as compared with the parental cells. Downregulation of CDK7 expression levels in HEC-1-A endometrial carcinoma cells via the transfection of CDK7 siRNA may significantly enhance cancer cell sensitivity to cisplatin chemotherapy and increasing apoptosis. CDK7 is a novel promising treatment for endometrial carcinoma that requires further in-depth study.