HPV-18 confers resistance to TNF-α in organotypic cultures of human keratinocytes

The proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) inhibits normal keratinocytes proliferation. However, many human papillomavirus (HPV)-immortalized or transformed cell lines are resistant to TNF-alpha antiproliferative effect. The present study analyzes the effects of TNF-alpha on organotypic cultures of primary human keratinocytes (PHKs) that express HPV-18 oncogenes. Raft cultures prepared with PHKs acutely transfected with HPV-18 whole genome or infected with recombinant retroviruses containing only E6/E7 or E7 were treated with 2 nM TNF-alpha. While BrdU incorporation into basal/parabasal cells of normal PHKs cultures was markedly inhibited by TNF-alpha cultures transfected with HPV-18 whole genome showed proliferation in all cell strata. Furthermore, BrdU incorporation into cultures expressing E6/E7 or E7 was not significantly reduced, indicating that E7 alone confers partial resistance to TNF-alpha. Besides, TNF-alpha treatment did not alter p16(ink4a), p21(cip1), p27(kip1), or cyclin E levels, but did reduce cyclin A and PCNA levels in sensitive cells. (C) 2004 Elsevier Inc. All rights reserved.