Abstract POSTER-BIOL-1352: Notch3 promotes anoikis resistance in ovarian cancer

Abstract Epithelial ovarian cancer (EOC) is the most lethal gynecologic cancer. Recently, a number of genome-wide studies in ovarian cancer patient samples have postulated that the course of disease can influenced by the Notch3 signaling pathway. In one study, 11% of human tumor samples showed mutation or amplification of the Notch3 receptor alone. Subsequent papers have correlated Notch3 overexpression in human samples with shorter progression-free survival as well as overall survival. In vitro studies have shown Notch3 to be involved in apoptosis resistance and chemoresistance, as well as cell cycle alterations. Together, these human studies have implicated Notch3 expression and amplification with decreased outcomes in ovarian cancer patients. To test the potential mechanism by which Notch3 over-expression promotes ovarian cancer, we examined several molecular and cellular functions of Notch3 in ovarian cancer cells. Decreasing the levels of Notch3 in ovarian cancer cells increases the susceptibility of these cells to apoptosis, which is consistent with previous studies. Using an effective siRNA-mediated knockdown of Notch3 combined with transfer to ultra-low attachment plates revealed a significant decrease in the ability of Notch3-knockdown IGROV-1 cells to remain viable in anchorage-independent conditions over 24 hours. Our data show that not only does Notch3 prevent apoptosis, but specifically promotes anoikis resistance. Further examining the mechanism underlying this novel finding revealed the positive roles of extracellular matrix proteins and FAK in promoting the anchorage-independent growth of IGROV-1 cells. Strikingly, mRNA and protein levels of col4α2 are reduced when Notch3 levels are decreased and exogenous collagen IV supplementation can largely reverse the anoikis sensitivity. Reduction of col4α2 expression by siRNA induces cell death on its own and high Notch3 expression levels correlate with higher col4α2 expression in human ovarian tumor samples. Together, these studies have revealed that Notch3 promotes anoikis resistance through col4α2 expression and may partly explain its positive correlation with poor survival in ovarian cancer patients. Citation Format: Caitlin W. Brown, Alexander S. Brodsky, Richard N. Freiman. Notch3 promotes anoikis resistance in ovarian cancer [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-BIOL-1352.