title: Cervical keratinocytes containing stably replicating extrachromosomal HPV-16 are refractory to transformation by oncogenic H-Ras.
abstract: Ras expression in human epithelial cells with integrated HPV genomes has been shown to cause tumorigenic transformation. The effects of Ras in cells representing early stage HPV-associated disease (i.e., when HPV is extrachromosomal and the oncogenes are under control of native promoters) have not been examined. Here, we used human cervical keratinocyte cell lines containing stably replicating extrachromosomal HPV-16 and present the novel finding that these cells resist transformation by oncogenic H-Ras. Ras expression consistently diminished anchorage-independent growth (AI), reduced E6 and E7 expression, and caused p53 induction in these cells. Conversely, AI was enhanced or maintained in Ras-transduced cervical cells that were immortalized with a 16E6/E7 retrovirus, and minimal effects on E6 and E7 expression were observed. Ras expression with either episomal HPV-16 or LXSN-E6/E7 was insufficient for tumorigenic growth suggesting that other events are needed for tumorigenic transformation. In conclusion, our results indicate that Ras-mediated transformation depends on the context of HPV oncogene expression and that this is an important point to address when developing HPV tumor models.
authors.affiliation: Department of Microbiology, Holden Comprehensive Cancer Research Center, University of Iowa, 375 Newton Road, 2202 MERF, Iowa City, IA 52242, USA.
authors.forename: Kristi L
authors.initials: KL
authors.lastname: Berger
authors.forename: Felicia
authors.initials: F
authors.lastname: Barriga
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lace
authors.forename: Lubomir P
authors.initials: LP
authors.lastname: Turek
authors.forename: Gideon J
authors.initials: GJ
authors.lastname: Zamba
authors.forename: Frederick E
authors.initials: FE
authors.lastname: Domann
authors.forename: John H
authors.initials: JH
authors.lastname: Lee
authors.forename: Aloysius J
authors.initials: AJ
authors.lastname: Klingelhutz
mesh_terms: D000818:Animals; D002460:Cell Line; D002472:Cell Transformation, Viral; D002584:Cervix Uteri / Q000166:cytology* / Q000821:virology; D005260:Female; D052162:Human papillomavirus 16 / Q000235:genetics* / Q000472:pathogenicity*; D006801:Humans; D015603:Keratinocytes / Q000821:virology*; D051379:Mice; D009856:Oncogene Proteins, Viral / Q000378:metabolism; D050725:Papillomavirus E7 Proteins; D030361:Papillomavirus Infections / Q000503:physiopathology / Q000821:virology; D010957:Plasmids / Q000235:genetics*; D012097:Repressor Proteins / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D002583:Uterine Cervical Neoplasms / Q000503:physiopathology / Q000821:virology; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C068651:E6 protein, Human papillomavirus type 16; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53; C059731:oncogene protein E7, Human papillomavirus type 16; D018631:ras Proteins