Abstract 3806: STAT3/STAT5 blockade by WP1066 inhibits ovarian cancer cell proliferation and induces cell death

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA BACKGROUND: Ovarian cancer is the most deadly gynecologic malignancy with 22,240 new cases and 14,030 deaths estimated in 2013. In order to improve the clinical management of women with ovarian cancer, it is critical to dissect the molecular drivers of ovarian neoplastic transformation and find efficient means of pharmacologic control. Constitutive activation of the signal transducer and activator of transcription 3 and 5 (STAT3 and STAT5) pathways is found in 70% of ovarian cancer patients. Overexpression of STATs is associated with a malignant phenotype and confers resistance to chemotherapy. Our drug discovery and development program has led to the development of a series of unique, small molecule inhibitors of STATs including a promising lead compound WP1066. The aim of this work was to investigate the antiproliferative and proapoptotic effects of WP1066 in selected ovarian cancer cells with constitutively activated or inducible STAT3 and STAT5. EXPERIMENTAL DESIGN: The effects of WP1066 on the levels of p-STAT3 and p-STAT5 were assessed with Western blotting and the MSD assay. Nuclear translocation of p-STAT3 and p-STAT5 was confirmed with confocal microscopy. Cell viability was determined with the MTS assay and dye exclusion test. Apoptosis induction was assessed on the basis of morphological markers using live-cell imaging (cell rounding, membrane blebbing and chromatin condensation) and biochemical markers using the MSD assay and confocal microscopy (cleaved PARP, cleaved caspase 3). SK-OV-3, SK-OV-3 CR (carboplatin resistant) and OVCAR-5 cells were used for in vitro studies. RESULTS: SK-OV-3 and OVCAR-5 cells grown in vitro show constitutive activation of STAT3, but not STAT5. Treatment of ovarian cancer cells with IL-6 or IFN-α and -β results in high levels of p-STAT3 with subsequent p-STAT3 translocation to the nucleus. Treatment with EGF results in low level STAT3 activation. Cells treated with IFN-α and β or EGF exhibit activation of STAT5, while IL-6 treatment does not affect p-STAT5 level. Importantly, cells extracted from disseminated intraperitoneal ovarian tumors express high levels of phosphorylated STAT3 and clearly show nuclear p-STAT3 localization. WP1066 inhibits both p-STAT3 and p-STAT5 but not STAT3 and STAT5 in the panel of tested ovarian cancer cells. Treatment with WP1066 inhibits cell growth, is cytotoxic to SK-OV-3 and OVCAR-5 cells as well as the carboplatin resistant subline, SK-OV-3 CR, all at low micromolar concentrations. We found that WP1066 induces robust apoptosis, starting 4h after its addition to the culture medium. CONCLUSION: Coordinated inhibition of p-STAT3/p-STAT5 by WP1066 results in profound apoptosis in ovarian cancer cells. Inhibition of STATs in ovarian cancer should be further explored as a potential therapeutic strategy for women with ovarian cancer. Citation Format: Rafal Zielinski, Aleksandra Rusin, Anna Priebe, Jayakumar Arumugam, Radjendirane Venugopal, Stanislaw Skora, Izabela Fokt, Waldemar A. Priebe. STAT3/STAT5 blockade by WP1066 inhibits ovarian cancer cell proliferation and induces cell death. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3806. doi:10.1158/1538-7445.AM2014-3806