Different HPV16 E6/E7 oncogene expression patterns in epithelia reconstructed from HPV16-immortalized human endocervical cells and genital keratinocytes.
Human papillomavirus type 16 (HPV16) E6/E7 oncogenes immortalize two types of human genital epithelial cells in vitro, endocervical cells and ectocervical or foreskin keratinocytes. Epithelia reconstructed in in vivo nude mouse implants or in vitro organotypic raft cultures from immortalized endocervical cells form higher grade dysplasia than those from keratinocytes. Here, we compared viral E6/E7 mRNA expression in immortalized cell lines of the three cell types using implants, rafts and in situ hybridization assays. Endocervical cells expressed E6/E7 throughout their reconstructed epithelia. In contrast, oncogenes were limited to basal cells for keratinocyte lower grade dysplasias. To study the role of the HPV16 promoter/enhancer in this repression in the upper layers of keratinocyte epithelia, new cell lines were established by immortalization with E6/E7 controlled by the SV40 promoter. The oncogenes were shown to be controlled from the SV40 elements after immortalization. Nevertheless, E6/E7 in the two cell types had the same cell-specific expression pattern as that controlled from the homologous HPV16 promoter. In addition, naturally occurring premalignant lesions having integrated HPV16 DNA expressed E6/E7 extensively in the high-grade dysplastic region of undifferentiated metaplasia. On the other hand, oncogene expression was restricted to lower layers in the lower grade dysplastic region of more mature differentiation. Our data suggest that keratinocytes have an inherent HPV16 promoter-nonspecific mechanism of repression. Apparently this mechanism, which can be acquired during maturation, is initially nonfunctional in in vitro and in vivo epithelia derived from metaplastic endocervical cells.
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Division of Basic Medical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St John's, Canada.
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D000818:Animals; D018929:Cell Culture Techniques / Q000379:methods; D002461:Cell Line, Transformed; D002472:Cell Transformation, Viral / Q000235:genetics; D002584:Cervix Uteri / Q000166:cytology*; D004279:DNA, Viral / Q000032:analysis / Q000235:genetics; D004742:Enhancer Elements, Genetic; D004847:Epithelial Cells / Q000378:metabolism / Q000637:transplantation / Q000821:virology*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D015967:Gene Expression Regulation, Viral; D005813:Genes, Synthetic; D005814:Genes, Viral; D006801:Humans; D017403:In Situ Hybridization; D015603:Keratinocytes / Q000378:metabolism / Q000637:transplantation / Q000821:virology*; D008297:Male; D008679:Metaplasia / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009856:Oncogene Proteins, Viral / Q000096:biosynthesis* / Q000235:genetics; D009857:Oncogenes; D009928:Organ Specificity; D027383:Papillomaviridae / Q000235:genetics*; D050725:Papillomavirus E7 Proteins; D010413:Penis / Q000166:cytology*; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics; D012097:Repressor Proteins; D013539:Simian virus 40 / Q000235:genetics; D014158:Transcription, Genetic; D002578:Uterine Cervical Dysplasia / Q000473:pathology; D015678:Viral Structural Proteins / Q000235:genetics*
D004279:DNA, Viral; C068651:E6 protein, Human papillomavirus type 16; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D015678:Viral Structural Proteins; C059731:oncogene protein E7, Human papillomavirus type 16