Human papillomavirus type 16 E7 protein sensitizes cervical keratinocytes to apoptosis and release of interleukin-1alpha.
Interleukin-1alpha (IL-1alpha) is a multifunctional cytokine that promotes inflammation, tissue remodeling and epithelial hyperplasia. Keratinocytes produce and sequester large amounts of biologically active IL-1alpha which can be released after injury or infection. We show that high level expression of human papillomavirus (HPV) type 16 E6 and E7 oncoproteins enhanced release of IL-1alpha from cultures of normal cervical keratinocytes (relative effectiveness E7 > E6/E7 >> E6 > control). The amount of IL-1alpha released was directly related to the ability of E7 or E6/E7 to stimulate apoptosis. E7 proteins that bound the retinoblastoma protein (Rb) strongly (HPV-16 and -18) induced more IL-1alpha release than those that bound poorly (HPV-6 and an HPV-16 E7 24gly mutant). Furthermore, overexpression of the E2F-1 transcription factor, a downstream target of Rb, induced extensive apoptosis and IL-1alpha release. Apoptosis and IL-1alpha release in response to growth factor removal occurred in part through a p53-independent pathway as coexpression of E6 and downregulation of p53 did not prevent either response. Immunohistochemical analyses showed that IL-1alpha was expressed by keratinocytes in normal cervical epithelia, low and high grade dysplasias, and cervical carcinomas. However, HPV-16 E6/E7 RNA expression and apoptosis increased in parallel in proliferating keratinocytes in severe dysplasias and carcinomas suggesting that IL-1alpha release is associated with progression to high grade disease. Thus, high level expression of the HPV-16 E7 protein sensitizes keratinocytes to apoptosis which results in release of IL-1alpha.
Laboratory of Biology, National Cancer Institute, Bethesda, Maryland 20892, USA.
M
M
Iglesias
K
K
Yen
D
D
Gaiotti
A
A
Hildesheim
M H
MH
Stoler
C D
CD
Woodworth
D017209:Apoptosis / Q000235:genetics*; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D002584:Cervix Uteri / Q000166:cytology* / Q000821:virology; D016207:Cytokines / Q000378:metabolism; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D007375:Interleukin-1 / Q000235:genetics / Q000378:metabolism*; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism / Q000821:virology*; D009856:Oncogene Proteins, Viral / Q000235:genetics* / Q000494:pharmacology; D050725:Papillomavirus E7 Proteins; D012097:Repressor Proteins; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000378:metabolism; D002583:Uterine Cervical Neoplasms / Q000378:metabolism / Q000473:pathology / Q000821:virology
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D016207:Cytokines; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C068651:E6 protein, Human papillomavirus type 16; D007375:Interleukin-1; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D012097:Repressor Proteins; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; C059731:oncogene protein E7, Human papillomavirus type 16