The pathogenesis of cervical cancer is associated with multiple sexually transmitted infections, chronic inflammation, and tissue damage. Chronic inflammation results in increased expression of cytokines by cells within the cervical mucosa. Present work involves the biological response of normal, human papillomavirus (HPV)-immortalized, and carcinoma-derived cervical cells to selected cytokines. Three cytokines, interleukin (IL)- 1alpha, tumor necrosis factor (TNF)-alpha, and transforming growth factor (TGF)-beta1, inhibited proliferation of normal ectocervical epithelial cell cultures but significantly stimulated proliferation of HPV- immortalized and carcinoma-derived cell lines. Another cytokine, IL-6, was mitogenic for both normal and transformed cells. For each cytokine, growth stimulation of immortal cells was preceded by increased expression of amphiregulin and TGFalpha, two ligands for the epidermal growth factor (EGF) receptor. TGF-beta1 also stimulated expression of EGF receptor RNA, resulting in increased numbers of cell surface receptors. Growth stimulation was inhibited by a monoclonal antibody that blocked EGF receptor signal transduction or a pool of several monoclonal antibodies that neutralized amphiregulin activity. IL-6 stimulation was also partially inhibited by a neutralizing antibody to TGF-alpha. Studies focused on identifying the signal transduction pathway responsible for TNF-alpha-induced mitogenesis. Agonistic antibodies for the TNF receptors p55 and p75 demonstrated that both mitogenic and inhibitory signals were mediated by the p55 receptor. Exogenous inhibitors or stimulators of specific signal transduction pathways provided evidence that turnover of membrane sphingomyelin and phospholipase A2 activity are important in mitogenic and inhibitory responses, respectively. In summary, these studies indicate that several proinflammatory cytokines stimulate proliferation of immortal and malignant cervical keratinocytes by an EGF receptor-dependent pathway requiring autocrine stimulation by amphiregulin. Furthermore, they suggest that chronic inflammation and release of proinflammatory cytokines may provide a selective growth advantage for abnormal cervical cells in vivo.
