Objective: To investigate the expression of cyclin D1 in cervical intraepithelial neoplasia (CIN) and squamous cell carcinoma and its relationship with human papillomavirus 16 (HPV16) E7 gene expression.
Methods: Both SiHa and Hcc94 cell lines were obtained from cervical epithelial cells of squamous cell carcinoma. E6/E7 gene was silent in Hcc94 cell line.Expression levels of cyclin D1 mRNA and protein in CIN and squamous cell carcinoma were detected by QT-PCR and immunohistochemistry (IHC) respectively. SiRNA was constructed for targeting the promoter of HPV16 E7 and then transfected into SiHa cells to establish cm-16 line with stable silencing of E7. Control cell line B3 was obtained by blank plasmid transfection into SiHa cells. RT-PCR and Western blot were used to detect cyclin D1 mRNA and protein expression in the SiHa, B3, and cm-16 cells, respectively.
Results: Cyclin D1 was expressed in the basal cells of normal cervical squamous epithelia and the expression gradually decreased in the progression from CIN1 to CIN3. Squamous cell carcinoma showed negative or scattered expression of cyclin D1 (P<0.05). Both mRNA and protein of cyclin D1 in E7(+) SiHa cells were lower than those in cm-16 and Hcc94 cells.
Conclusion: Squamous cell carcinoma with high HPV E7 expression shows low level of cyclin D1, suggesting that HPV16 E7 gene inhibits the expression of cyclin D1.