title: Combined effects of human papillomavirus-18 and N-methyl-N'-nitro-N-nitrosoguanidine on the transformation of normal human oral keratinocytes.
abstract: We immortalized oral keratinocytes by transfecting them with recombinant human papillomavirus (HPV) type 18 DNA and established three cell lines. These lines were morphologically different from their normal counterpart, contained integrated entire HPV-18 DNA, and expressed the viral E6/E7 genes. The cells contained less p53 protein and more c-myc mRNA than normal cells. However, they proliferated only in keratinocyte growth medium (KGM) containing low calcium and were not tumorigenic in nude mice. To test the hypothesis that tumors result from the combined effect of a "high-risk" HPV and chemical carcinogens in the human oral cavity, we exposed the immortalized cells to the chemical carcinogen N-methyl-N'-nitro-N-nitrosoguanidine. Three chemically transformed cell colonies were isolated. These cells (a) proliferated well in both KGM and Dulbecco's modified minimum essential medium containing physiological levels of calcium; (b) were capable of proliferating in nude mice; (c) contained intact, integrated HPV-18 sequences; (d) transcribed substantially more HPV-18 E6/E7, transforming growth factor-alpha, and c-myc than the immortalized counterpart; and (e) contained, like the immortalized counterpart, less wild-type p53 protein and DCC message. These data indicate that human oral keratinocytes can be transformed by sequential exposure of normal keratinocytes to a "high-risk" HPV and chemical carcinogens.
authors.affiliation: School of Dentistry, University of California, Los Angeles.
authors.forename: K H
authors.initials: KH
authors.lastname: Shin
authors.forename: B M
authors.initials: BM
authors.lastname: Min
authors.forename: H M
authors.initials: HM
authors.lastname: Cherrick
authors.forename: N H
authors.initials: NH
authors.lastname: Park
mesh_terms: D000818:Animals; D001483:Base Sequence; D002455:Cell Division / Q000502:physiology; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic / Q000187:drug effects; D002472:Cell Transformation, Viral / Q000187:drug effects; D004279:DNA, Viral / Q000032:analysis / Q000235:genetics; D066246:ErbB Receptors / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics; D016259:Genes, myc / Q000235:genetics; D016158:Genes, p53 / Q000235:genetics; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects* / Q000502:physiology / Q000821:virology*; D008769:Methylnitronitrosoguanidine / Q000494:pharmacology*; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009062:Mouth Neoplasms / Q000139:chemically induced* / Q000473:pathology / Q000821:virology*; D027383:Papillomaviridae / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012367:RNA, Viral / Q000032:analysis; D014158:Transcription, Genetic / Q000235:genetics; D014162:Transfection; D016211:Transforming Growth Factor alpha / Q000235:genetics
chemical_list: D004279:DNA, Viral; D012333:RNA, Messenger; D012367:RNA, Viral; D016211:Transforming Growth Factor alpha; D008769:Methylnitronitrosoguanidine; D066246:ErbB Receptors