Tumor necrosis factor-α promotes human papillomavirus (HPV) E6/E7 RNA expression and cyclin-dependent kinase activity in HPV-immortalized keratinocytes by a ras-dependent pathway
✍ Scribed by Darci Gaiotti; Jean Chung; Maite Iglesias; Matthias Nees; Patricia D. Baker; Charles H. Evans; Craig D. Woodworth
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 319 KB
- Volume
- 27
- Category
- Article
- ISSN
- 0899-1987
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✦ Synopsis
Tumor necrosis factor-a (TNF-a) 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-a promoted cell cycle progression by increasing expression of HPV-16 E6/E7 RNAs and enhancing activity of cyclindependent 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-a 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, HPVimmortalized 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-a 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-a. These studies define a pathway by which ras mutations, which occur in a subset of cervical cancers, may contribute to pathogenesis. Mol. Carcinog.