Objective: The human papillomavirus type 16 (HPV16) early gene (E5) could stimulate cell proliferation and transformation in different ways, and complement or enhancement the function of E6 and E7. It is closely sodiated with the carcinogens of cervical cancer. This study was to investigate the effects of HPV16 E5 on the human cervical cancer cell line SiHa.
Methods: The sense sequence of HPV16 E5 was cloned into eukaryotic expression vector pEGFP-C1 to prepare recombinant plasmid, which was stable transfected into SiHa cells. The mRNA and protein levels of E5 and p21 gene were detected by Western blot and reverse transcription-polymerase chain reaction (RT-PCR). Cell proliferation after stable transfection was evaluated by MTT assay. The tumorigenesis of SiHa/16E5 cells was assessed both in vitro and in vivo by soft agar clone form test and naked mouse form test.
Results: After stable transfection of HPV16 E5 sense DNA, the mRNA and protein levels of HPV16 E5 in SiHa cells were obviously increased, but that of P21 were decreased. The proliferation activity of SiHa/16E5 cells was significantly higher than that of SiHa/pEGFP-C1 and SiHa cells (P < 0.05). The clone numbers of SiHa/16E5 cells, were significantly more than SiHa/pEGFP-C1 and SiHa cells [(33.4 +/- 1.6) vs (15.1 +/- 3.1), (16.3 +/- 2.5), P < 0.05] in vitro. The growth of tumors on naked mouse was much faster in SiHa /16E5 group than those in the SiHa/pEGFP-C1 and SiHa cells groups (P < 0.05).
Conclusion: HPV16 E5 decreased the expression of P21 in SiHa cells, and enhancement the proliferation of SiHa cells and the ability of tumorigenesis.