Human papillomavirus 16/18 E6 oncoprotein is expressed in lung cancer and related with p53 inactivation.
Inactivation of p53 by human papillomavirus 16/18 E6 plays a crucial role in cervical tumorigenesis. To investigate the involvement of HPV16/18 in lung tumorigenesis, the association between HPV16 or HPV18 E6 and p53 protein expression in 122 lung tumors was evaluated by immunohistochemistry, and data showed that HPV16/18 E6 expression correlated inversely with p53 expression, which was further confirmed by tissue in situ immunostaining. Real-time reverse transcription-PCR analysis indicated that E6-positive tumors had lower p21(WAF1/CIP1) and mdm2 mRNA levels than E6-negative tumors. To elucidate the role of E6 in p53 inactivation, we successfully established lung adenocarcinoma cell lines with or without HPV16 infection from patients' pleural effusions. Western blotting showed that E6 protein was indeed expressed in HPV16-infected cells and a lower level of p53 protein was observed in E6-positive cells compared with E6-negative cells. Moreover, the levels of p21(WAF1/CIP1) and mdm2 mRNA in E6-positive cells were lower than in E6-negative cells. The interaction of E6 with p53 protein was revealed by immunoprecipitation assay showing that p53 could be inactivated by E6 protein. Conversely, p53 proteins and p21(WAF1/CIP1) and mdm2 mRNA expressions were restored in E6-knockdown cells by RNA interference compared with control cells. These results reveal that HPV16/18 E6 may be partially involved in p53 inactivation to down-regulate p21(WAF1/CIP1) and mdm2 transcription. In conclusion, HPV16/18 E6 is indeed expressed in HPV DNA-positive lung tumors and is involved in p53 inactivation to contributing to HPV-mediated lung tumorigenesis.
Cheng
Ya-Wen
YW
Institute of Medicine, Lung Cancer Research Center, Chung Shan Medical University, Taichung, Taiwan, ROC.
Wu
Ming-Fang
MF
Wang
John
J
Yeh
Kun-Tu
KT
Goan
Yih-Gang
YG
Chiou
Hui-Ling
HL
Chen
Chih-Yi
CY
Lee
Huei
H
D000230:Adenocarcinoma / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D015967:Gene Expression Regulation, Viral; D052162:Human papillomavirus 16 / Q000378:metabolism*; D052161:Human papillomavirus 18 / Q000378:metabolism*; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism* / Q000821:virology*; D008297:Male; D008954:Models, Biological; D009856:Oncogene Proteins, Viral / Q000096:biosynthesis*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000096:biosynthesis; D012097:Repressor Proteins / Q000096:biosynthesis*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004268:DNA-Binding Proteins; C068651:E6 protein, Human papillomavirus type 16; C052603:E6 protein, Human papillomavirus type 18; D009856:Oncogene Proteins, Viral; D012097:Repressor Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2