Abstract 4143: Bz-423, a novel benzodiazpine, inhibits PI3 kinase signaling in ovarian cancer cells

Abstract

Abstract Objective: Bz-423 is a 1,4-benzodiazepine with immunomodulatory and cytotoxic properties. The effect of Bz-423 on survival signaling in lymphoid neoplasms predicts activity against similar pathways in ovarian cancer cells. Having previously established the cytotoxic activity of Bz-423 against ovarian cancer, we now characterize the mechanism of action. Methods: Human ovarian cancer cell lines were maintained in culture. Cells were treated with Bz-423 or vehicle control. Cell survival and proliferation were evaluated, along with signaling mechanisms including the PI3-kinase-Akt-mTOR axis. DNA degradation (apoptotic fraction), mitochondrial function and caspase activation were evaluated by flow cytometry. Cytochrome c release and protein kinase activation were analyzed by immunoblotting. Apoptosome complex formation was monitored by gel filtration chromatography. Cellular ultrastructure was determined by electron microscopy (EM). Results: Growth inhibition and apoptosis were observed in all ovarian cell lines following treatment with Bz-423. Caspase-9 and −3 cleavage, along with cytochrome c release were seen, consistent with activation of the intrinsic pathway of apoptosis. Early mitochondrial changes identified by ultrastructural evidence of mitochondrial swelling and the accumulation of superoxide within 1 hr of treatment were seen. Bz-423 induced cell death was associated with inhibition of Akt activation through a oxidant dependent mechanism. Antioxidants blocked Bz-423-induced signaling. Conclusions: Bz-423 is a novel benzodiazepine being developed as a mitochondria targeted therapy, and displays anti-neoplastic activity against ovarian cancer cells in vitro. Results show that by acting on mitochondrial complex V, this compound inhibits PI3-kinase signaling, including the tumor survival factor Akt. PI3-kinase signaling is increasingly recognized as a survival and growth promoting mechanism in ovarian cancer. Since Akt inhibition by Bz-423 is dependent upon cellular bioenergetics and anti-oxidant balance, strategies employing this compound offer a selective new approach to target ovarian cancer cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4143.