Phosphatidylinositol 3-kinase (PI3-K) induces mitogenesis, cell growth, and cell transformation. Amplification of the gene encoding the P110alpha subunit likely is an important event in ovarian cancer progression, and PI3-K inhibitors are possible therapeutic agents for this disease. We evaluated effects of LY294002, a potent inhibitor of PI3-K, on growth of ovarian carcinoma in vivo and in vitro, and on ascites formation in vivo. Athymic mice were inoculated i.p. with the ovarian cancer cell line OVCAR-3. Seven days after inoculation, mice were treated with or without LY294002 (100 mg/kg of body weight) for 3 weeks. Body weight and abdominal circumference were measured twice weekly. At the end of the experiment, mice were sacrificed, ascites volume was measured, and tumors were excised. Mean tumor burden in the LY294002-treated group was reduced by approximately 65% versus controls. Virtually no ascites developed in the treatment group; mean volume of ascites in controls was 3.3 +/- 0.38 ml. OVCAR-3 cells also were cultured in vitro without and with LY294002 (1, 5, and 10 microM) for 24 h. The number of cells in 1, 5, and 10 microM LY294002-treated wells was reduced by 27, 56, and 75%, respectively, versus controls. In vivo and in vitro morphological studies demonstrated that LY294002 induced marked nuclear pyknosis and diminished cytoplasmic volume in the tumor cells, confirmed as apoptosis. Thus, LY294002 significantly inhibits growth and ascites formation of ovarian carcinoma in vivo and markedly inhibits ovarian cancer cell proliferation in vitro, suggesting an important role of PI3-K inhibitors as a potentially useful treatment for women with ovarian carcinoma.