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.