¹Laboratory of Biology, National Cancer Institute, Bethesda, Maryland 20892, USA

²Laboratory of Environmental Epidemiology Branch, National Cancer Institute, Bethesda, Maryland 20892, USA

³Department of Pathology, University of Virginia Health Sciences Center, Charlottesville, Virginia 22901, USA

^aAuthor for correspondence

^bCurrent address: Laboratorio 1.7, Instituto de Investigaciones Biomedicas, CSIC, Arturo Duperier 4, 28029 Madrid Spain

^cCurrent address: Laboratory of Cellular Carcinogenesis and Tumor Promotion, Building 37/Room 3B25, National Cancer Institute, Bethesda, MD, 20892

Interleukin-1 (IL-1) is a multifunctional cytokine that promotes inflammation, tissue remodeling and epithelial hyperplasia. Keratinocytes produce and sequester large amounts of biologically active IL-1 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-1 from cultures of normal cervical keratinocytes (relative effectiveness E7>E6/E7E6> control). The amount of IL-1 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-1 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-1 release. Apoptosis and IL-1 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-1 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-1 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-1.

apoptosis; cervical carcinoma; human papillomavirus; interleukin-1; keratinocyte