RNA interference against HPV16 E7 oncogene leads to viral E6 and E7 suppression in cervical cancer cells and apoptosis via upregulation of Rb and p53.
The simultaneous expression of human papillomavirus type 16 (HPV16) E6 and E7 oncogenes is pivotal for malignant transformation and maintenance of malignant phenotypes. Silencing these oncogenes is considered to be applicable in molecular therapies of human cervical cancer. However, it remains to be determined whether HPV16 E6 and E7 could be both silenced to obtain most efficient antitumor activity by using RNA interference (RNAi) technology. Herein, we designed a small interfering RNA (siRNA) targeting HPV16-E7 region to degrade either E6, or truncated E6 (E6*) and E7 mRNAs and to simultaneously knockdown both E6 and E7 expression. Firstly, the sequence targeting HPV16-E7 region was inserted into the shRNA packing vector pSIREN-DNR, yielding pSIREN-16E7 to stably express corresponding shRNA. HPV16-transformed SiHa and CaSki cells were used as a model system; RT-PCR, Western Blotting, MTT assay, TUNEL staining, Annexin V apoptosis assay and flow cytometry were applied to examine the effects of pSIREN-16E7. Our results indicated that HPV16-E7 specific shRNA (16E7-shRNA) induced selective degradation of E6 and E7 mRNAs and proteins. E6 silencing induced accumulation of cellular p53 and p21. In contrast, E7 silencing induced hypophosphorylation of retinoblastoma (Rb) protein. The loss of E6 and E7 reduced cell growth and ultimately resulted in massive apoptotic cell death selectively in HPV-positive cancer cells, compared with the HPV-negative ones. We demonstrated that 16E7-shRNA can induce simultaneous E6 and E7 suppression and lead to striking apoptosis in HPV16-related cancer cells by activating cellular p53, p21 and Rb. Therefore, RNAi using E7 shRNA may have the gene-specific therapy potential for HPV16-related cancers.
Cancer Biology Research Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1095 Jiefang Ave., Wuhan, Hubei 430030, PR China.
Ni
N
Sima
Wei
W
Wang
Debo
D
Kong
Dongrui
D
Deng
Qian
Q
Xu
Jianfeng
J
Zhou
Gang
G
Xu
Li
L
Meng
Yunping
Y
Lu
Shixuan
S
Wang
Ding
D
Ma
D017209:Apoptosis; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D005260:Female; D005814:Genes, Viral; D052162:Human papillomavirus 16 / Q000235:genetics; D006801:Humans; D009856:Oncogene Proteins, Viral / Q000235:genetics* / Q000378:metabolism; D009857:Oncogenes; D050725:Papillomavirus E7 Proteins; D034622:RNA Interference; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D015854:Up-Regulation; D002583:Uterine Cervical Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000821:virology
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C068651:E6 protein, Human papillomavirus type 16; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D012097:Repressor Proteins; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; C059731:oncogene protein E7, Human papillomavirus type 16