Objective   This study was aimed to investigate the influence of CDK7 siRNA on the sensitivity of endometrial carcinoma cell line HEC-1-A to cisplatin (DDP)-based chemotherapy.

  Methods   Different CDK7 siRNA fragments were synthesized based on the designs of the CDK gene sequence and were transfected into HEC-1-A. Real time reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis were employed to demonstrate the effects of transfection. The best CDK7 siRNA was chosen to specifically silence CDK7 expression in HEC-1-A.The sensitivity of the cells to DDP therapy before and after transfection was determined by methyl thiazol tetrazolium (MTT) cytotoxicity assay, flow cytometry, and Hoechst/PI double-staining fluorescence microscopy.

  Results   A total of four different CDK7 siRNA segments were designed and successfully transfected into HEC-1-A cells. The interference effect in each group was confirmed by real time RT-PCR and Western blot assays. CDK7-423 was determined as the best performing CDK7 siRNA (over 70%) to transfect into HEC-1-A cells. MTT cytotoxicity test showed that IC₅₀ of DDP decreased to a range from 45.122 μg/mL and 3.200 μg/mL after inhibition of CDK7 expression. DDP toxicity to the endometrial carcinoma cells significantly increased (P < 0.05). Flow cytometry revealed that the average cell apoptosis rate significantly increased after the inhibition of CDK7 expression (11.66 % to 37.57%, P < 0.05). Similar results were observed using Hoechst/PI double-staining fluorescence microscopy, and the number of apoptotic corpuscle demonstrated an apparent increase in the low CDK7-expressing group compared with the parental cells.

  Conclusion   After the downregulation of CDK7 expression by CDK7 siRNA transfection, DDP chemotherapy sensitivity and apoptosis of endometrial carcinoma cells significantly increased. Further research is anticipated on the use of CDK7 as a new treatment target for endometrial carcinoma.