Abstract 4023: Notch3 signal activation promotes tumorigenesis in a mouse model of peritoneal epithelial ovarian cancer

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA This study investigates how Notch3 signal activation affects ovarian cancer metastatic growth in order to provide insight into the mechanisms of ovarian cancer progression. Ovarian cancer is often detected at late stages after peritoneal metastasis, at which point prognosis is poor. TCGA defined the Notch signaling pathway as detectably altered in 22% of high-grade serous ovarian cancers, and NOTCH3 in particular is commonly overexpressed. Patients with NOTCH3-high recurrent tumors exhibit worse prognosis and decreased survival. NOTCH3 expression is correlated with resistance to platinum-based chemotherapy. To investigate the mechanisms by which Notch3 signaling functions to promote ovarian cancer, we performed experiments using the ID8 IP2 luciferase mouse ovarian surface epithelial line. This low-Notch3 expressing line was lentivirally infected with Notch3 intracellular domain (N3IC), an activated form of the Notch3 receptor. Increase in N3IC expression and Notch signal activation were confirmed with a dual luciferase reporter assay and via quantitative PCR for N3IC and downstream HES and HEY family targets. We then compared Notch3 activated ID8 IP2 cells to control cells using in vitro assays to evaluate growth properties of the cells, and in vivo intraperitoneal implants in NCR-nu/nu athymic mice to assess metastatic potential. In vitro N3IC and control cells were found to be morphologically similar, and assessment of N3IC cells demonstrated no significant effect on proliferation rate. Anchorage independent growth was also not significantly altered upon activation of Notch3. In addition, the effect of platinum therapy response was assessed in N3IC and control lines. When tested in a DIMSCAN cytotoxicity assay with cisplatinum doses raging from 2-16 μM, no significant difference in sensitivity to platinum treatment, as measured by IC50, was observed. In vivo, however, preliminary results indicate that activation of Notch3 signaling leads to acceleration of ascites accumulation and tumorigenesis. Ascites derived from mice with Notch3 activated tumors had a notably higher blood content indicating alteration of tumor vasculature. Finally, mice display a significant reduction in overall survival with Notch3 activation. We conclude that Notch3 signal activation in ID8 IP2 cells promotes metastatic growth in the peritoneum and ascites accumulation. Notch3 activation was associated with a decreased overall survival of tumor bearing mice. The growth properties of cultured ID8 IP2 cells were not noticeably altered due to Notch3 activation. We propose that Notch3 activation promotes increased tumorigenesis by influencing interaction between cancer cells and the host environment. Citation Format: Jessica Price, Nathaniel Jones, Jan Kitajewski. Notch3 signal activation promotes tumorigenesis in a mouse model of peritoneal epithelial ovarian cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4023. doi:10.1158/1538-7445.AM2015-4023