Inhibition of growth, transformation, and expression of human papillomavirus type 16 E7 in human keratinocytes by alpha interferons.
We used a model system of normal human keratinocytes (HKc) and HKc immortalized with human papillomavirus type 16 DNA (HKc/HPV16) to investigate the effects of alpha interferons (IFN-alpha) on the growth of HPV16-immortalized human epithelial cells, on HPV16-mediated immortalization of normal HKc, and on HPV16 gene expression. Normal HKc and HKc/HPV16 were treated with several recombinant human IFN-alpha subtypes (IFN-alpha B, IFN-alpha D, and IFN-alpha B/D). These IFN-alpha subtypes inhibited proliferation of both normal HKc and HKc/HPV16 in a dose-dependent fashion; however, although 1,000 to 10,000 U of IFN-alpha per ml were required to inhibit growth of normal HKc, HKc/HPV16 were substantially growth inhibited by 100 U/ml. In addition, 100 U of IFN-alpha B/D per ml inhibited transformation of normal HKc by HPV16 DNA. Northern (RNA) blot analysis showed no effect of IFN-alpha on the mRNA levels of the HPV16 E6 and E7 open reading frames. However, immunofluorescence studies of the HPV16 E6 and E7 proteins with anti-E6 and anti-E7 monoclonal antibodies showed significant inhibition of E7 protein expression in cells treated with IFN-alpha, whereas E6 protein expression was not altered. The inhibition of E7 protein expression in cells treated with IFN-alpha was further confirmed by Western immunoblot analysis. These results suggest that IFN-alpha may inhibit HPV16-mediated transformation of HKc and proliferation of HKc/HPV16 through an inhibition of HPV16 E7 protein expression.
Khan
M A
MA
Department of Pathology, University of South Carolina School of Medicine, Columbia 29208.
Tolleson
W H
WH
Gangemi
J D
JD
Pirisi
L
L
D002455:Cell Division / Q000187:drug effects; D002472:Cell Transformation, Viral / Q000187:drug effects*; D002478:Cells, Cultured; D004279:DNA, Viral / Q000494:pharmacology; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology*; D015603:Keratinocytes / Q000187:drug effects* / Q000382:microbiology; D009856:Oncogene Proteins, Viral / Q000096:biosynthesis*; D027383:Papillomaviridae; D050725:Papillomavirus E7 Proteins; D012333:RNA, Messenger / Q000096:biosynthesis; D012097:Repressor Proteins
D004279:DNA, Viral; C068651:E6 protein, Human papillomavirus type 16; D016898:Interferon-alpha; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; C059731:oncogene protein E7, Human papillomavirus type 16