Tumor Necrosis Factor a as an Autocrine and Paracrine Growth Factor for Ovarian Cancer : Monokine Induction of Tumor Cell Proliferation and Tumor Necrosis Factor a Expression 1

Ovarian tumor cells produce macrophage colony stimulating factor, a potent chemoattractant for monocytes. Monocytes and macrophages pro duce tumor necrosis factor a (TNF-a) and interleukin la or interleukin IÃŸ (II.-l/ii that can stimulate ovarian tumor cell growth. The present study has explored whether paracrine stimulation by monocyte derived cytokines might induce autocrine growth stimulation of normal and malignant ovarian epithelial cells. Endogenous expression of TNF-a niKN \ was detected in ascites ovarian cancer cells isolated directly from patients, but not in established cultures of normal or malignant ovarian epithelial cells. When ascites tumor cells were cultured for 7 days, TNF-a expression ceased but could be reinduced by treatment with TNF-a or IL-1/3. Ascites fluid contained concentrations of the cytokines that could mediate these effects. Similarly, treatment of normal or malignant ovarian epithelial cells with purified recombinant IL-lÃŸor TNF-a induced transcription of TNF-a mRNA within 1 h. TNF-a protein could be detected by enzymelinked immunosorbent assay in conditioned medium from IL-lÃŸtreated ovarian cancer cells. |'l I |th\ niiilinr incorporation by normal or malignant ovarian epithelial cells was stimulated by a 24-h incubation with IL-lÃŸor TNF-a. Stimulation of proliferation by IL-lÃŸcould be partially blocked by an antibody against TNF-a or by soluble TNF-a-receptor. Thus, TNF-a may function as both an autocrine and a paracrine growth factor in ovarian cancer. INTRODUCTION TNF-a' and IL-1 are cytokines produced primarily by monocytes and macrophages. TNF-a and IL-1 share several biological activities, despite the fact that they are structurally unrelated and bind to differ ent cell surface receptors (1,2). Both TNF-a and IL-1 can inhibit the growth of certain tumor cells (3-5), stimulate human fibroblast pro liferation, promote bone reabsorption by osteoclasts. down-regulate lipogenic gene expression, and stimulate the production of collagenase in synovial cells (6). Conversely, TNF-a and IL-1 can also stim ulate the growth of normal cells as well as certain cancer cells in culture (6, 7). Since TNF-a can be constitutively produced by malig nant cells (8), its expression could contribute to tumor progression and spread (9, 10) as well as indicate resistance to the cytotoxicity of exogenous TNF-a (11). Ovarian cancer is the leading cause of death from gynecological malignancy. Over 60% of patients present with disease that has spread beyond the pelvis and into the peritoneal cavity (12). Although metastatic disease can be treated with cytoreductive surgery and combi nation chemotherapy, the survival of these patients is poor. Recent studies have focused on factors that regulate the growth of malignant ovarian epithelium ( 13). with the expectation that a more fundamental Received 9/9/92: accepted 2/8/93. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1Supported in part by Grant ROÃ•CA39930 from the N1H. Department of Health and Human Services. 2 To whom requests for reprints should be addressed, at Box 3843. Department of Medicine. Duke University Medical Center. Durham. NC 27710. 'The abbreviations used are: TNF-a. tumor necrosis factor a; IL-1, interleukin-1; IL-1 a. interleukin-la; IL-lÃŸ. interleukinIÃŸ;FBS. fetal bovine serum: cDNA, comple mentary DNA; HBSS. Hanks' balanced salt solution; SDS. sodium dodecyl sulfate; SSC. standard saline-citrate; ELISA, enzyme linked immunosorbent assay. understanding of these factors might suggest novel and potentially more effective approaches to treatment. Macrophages are found in solid tumor implants of ovarian canceras well as in ascites fluid (14. 15). Previous studies have indicated that ovarian cancer cells produce macrophage colony stimulating factor which is a potent chemoattructant for monocytes (16-18). Monocyte derived cytokines including TNF-a, IL-1. and interleukin 6 can stim ulate proliferation of ovarian cancer cells (7). Other investigators have shown that ovarian and other cancer cells express TNF-a in vitro and in vivo (8, 19, 20). Whether or not endogenous expression of TNF-a is important for growth of ovarian cancer cells remains to be resolved. In this article, we have explored the possibility that endogenous ex pression of TNF-a is maintained in vivo by exogenous TNF-a or IL-1 and that endogenous production of TNF-a may trigger tumor cell