Regulator role of HPV E7 protein on miR-21 expression in cervical carcinoma cells and its functional implication

Cervical cancer is the second leading malignant tumor in women. Human papillomavirus 16 (HPV16) is one risk factor for cervical cancer, with its expressed E7 protein can facilitate the transformation of cervical epithelial cells. MicroRNA-21 (miR-21) is one important tumor growth regulatory factor involving in angiogenesis, tumor invasion and metastasis. This study thus aimed to investigate the role of high-risk HPV16 E7 protein in regulating miR-21 expression in cervical carcinoma and its related functions. Hela cells were transfected with pcDNA-HPV16 E7 expressing vectors. The expression level of E7 was determined by Western blotting, while miR-21 level was quantified by real-time PCR. The alternation of tumor cell proliferation is determined by transfecting miR-21 inhibitor into E7-overexpressing Hela cells. Cell apoptosis was studied by caspase-3 assay, while cell invasion was illustrated in Transwell chamber. The overexpression of HPV E7 protein facilitated the expression of miR-21, which potentiated Hela cell proliferation and invasion. The inhibition of miR-21 in E7-overexpressin Hela cells can inhibit both proliferation and invasion, but without significant effects on caspase-3 activity. HPV16 E7 protein can up-regulate host miR-21 expression, thus elevating cervical carcinoma cell growth, proliferation and invasion. Therefore, E7 protein is one critical factor in occurrence and progression of cervical carcinoma.