Tumor necrosis factor-alpha promotes human papillomavirus (HPV) E6/E7 RNA expression and cyclin-dependent kinase activity in HPV-immortalized keratinocytes by a ras-dependent pathway.
Tumor necrosis factor-alpha (TNF-alpha) inhibits growth of normal cervical keratinocytes but stimulates proliferation of human papillomavirus (HPV)-immortalized and cervical carcinoma-derived cell lines when mitogens such as epidermal growth factor (EGF) or serum are depleted. Current work identifies the mechanism of growth stimulation. TNF-alpha promoted cell cycle progression by increasing expression of HPV-16 E6/E7 RNAs and enhancing activity of cyclin-dependent kinase (cdk)2 and cdc2 after 3 d. Increased kinase activity was mediated by upregulation of cyclins A and B and decreases in cdk inhibitors p21(waf) and p27(kip). TNF-alpha stimulated these changes in part by increasing transcription and stabilization of RNA for amphiregulin, an EGF receptor ligand, and amphiregulin directly increased HPV-16 E6/E7 and cyclin A RNAs. To define which components of the EGF receptor signaling pathway were important, HPV-immortalized cells were transfected with activated or dominant negative mutants of Ha-ras, raf, or MAPKK. Expression of activated Ha-ras maintained HPV-16 and cyclin gene expression and promoted rapid growth in the absence of EGF. Furthermore, ras activation was necessary for TNF-alpha mitogenesis as transfection with a dominant negative ras mutant (Asn-17) strongly inhibited growth. Thus, activation of ras promotes expression of HPV-16 E6/E7 RNAs, induces cyclins A and B, and mediates growth stimulation of immortal keratinocytes by TNF-alpha. These studies define a pathway by which ras mutations, which occur in a subset of cervical cancers, may contribute to pathogenesis. Mol. Carcinog. 27:97-109, 2000. Published by Wiley-Liss, Inc.
Gaiotti
D
D
Laboratory of Biology, National Cancer Institute, Bethesda, MD 20892-4255, USA.
Chung
J
J
Iglesias
M
M
Nees
M
M
Baker
P D
PD
Evans
C H
CH
Woodworth
C D
CD
D002453:Cell Cycle / Q000235:genetics; D002461:Cell Line, Transformed; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D004789:Enzyme Activation / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism / Q000821:virology; D009856:Oncogene Proteins, Viral / Q000235:genetics* / Q000378:metabolism; D027383:Papillomaviridae / Q000235:genetics* / Q000502:physiology; D050725:Papillomavirus E7 Proteins; D012367:RNA, Viral / Q000096:biosynthesis*; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis / Q000378:metabolism; D012097:Repressor Proteins; D015398:Signal Transduction / Q000235:genetics*; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*; D018631:ras Proteins / Q000502:physiology*
C068651:E6 protein, Human papillomavirus type 16; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D012367:RNA, Viral; D018124:Receptors, Tumor Necrosis Factor; D012097:Repressor Proteins; D014409:Tumor Necrosis Factor-alpha; C059731:oncogene protein E7, Human papillomavirus type 16; D018844:Cyclin-Dependent Kinases; D018631:ras Proteins