Papillomavirus type 16 E6/E7 and human telomerase reverse transcriptase in esophageal cell immortalization and early transformation.
Infection with high-risk human papillomavirus (HPV) has been implicated in the pathogenesis of esophageal squamous cell carcinoma, and up-regulation of telomerase in esophageal adenocarcinoma. We immortalized normal esophageal epithelial cells by over-expression of the HPV16 E6/E7 and human telomerase reverse transcriptase (hTERT) genes. HPV16 E6/E7-induced immortalization was accompanied by reduced RB and p53, but increased p16 and p21, protein expression. hTERT-immortalized cells had unaffected RB and p53, but significantly decreased p16 and p21, protein expression. Aurora-A protein was also up-regulated in E6E7 immortalized cells, and to a less extent in hTERT immortalized cells. Fluorescence in situ hybridization showed that the Aurora-A gene locus was amplified in E6E7 immortalized cells, which might account in part for the Aurora-A over-expression. These molecular changes led to an abrogation of the G2 checkpoint. E6E7 and hTERT immortalized esophageal cells recapitulated many of the molecular changes observed in esophageal carcinomas, where RB and p53 are frequently down-regulated. However, down-regulation of p16 and p21 occurred frequently in esophageal cancer, owing to aberrant gene promoter methylation. We showed in the immortalized cells that aberrant methylation had not yet set in, suggesting that promoter methylation might not be necessary for cellular immortalization. In addition to supporting the role of HPV and telomerase in esophageal carcinogenesis, our cell lines may also be useful in vitro models for further studies of esophageal carcinogenesis.
Department of Medicine, University of Hong Kong, Professorial Block, Queen Mary Hospital, Pokfulam Road, Hong Kong, China.
Hao
H
Zhang
Yuesheng
Y
Jin
Xuehua
X
Chen
Charlotte
C
Jin
Simon
S
Law
Sai-Wah
SW
Tsao
Yok-Lam
YL
Kwong
D064127:Aurora Kinases; D015153:Blotting, Western; D015820:Cadherins / Q000235:genetics; D002453:Cell Cycle / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D002478:Cells, Cultured; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D004947:Esophagus / Q000166:cytology / Q000378:metabolism; D005434:Flow Cytometry; D005784:Gene Amplification; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D015739:Nocodazole / Q000494:pharmacology; D009856:Oncogene Proteins, Viral / Q000235:genetics* / Q000378:metabolism; D050725:Papillomavirus E7 Proteins; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D019098:Telomerase / Q000235:genetics* / Q000378:metabolism; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics
D015820:Cadherins; D019941:Cyclin-Dependent Kinase Inhibitor p16; C068651:E6 protein, Human papillomavirus type 16; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; C411762:RASSF1 protein, human; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C059731:oncogene protein E7, Human papillomavirus type 16; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases; C509186:TERT protein, human; D019098:Telomerase; D015739:Nocodazole