Abstract POSTER-THER-1403: FZD7 drives aggressiveness in stem-A subtype of ovarian cancer via regulation of non-canonical Wnt/PCP pathway

Abstract

Abstract Ovarian cancer (OC) can be classified into five biologically distinct molecular subgroups—Epi-A, Epi-B, Mes, Stem-A and Stem-B. Among them, Stem-A expresses genes relating to stemness and is correlated with poor clinical prognosis. In this study, we show that FZD7, a receptor for Wnt signalling, is overexpressed in the Stem-A subgroup. To elucidate the functional roles of FZD7, we used an RNA interference (RNAi) gene knockdown approach in three Stem-A cell lines: CH1, PA1 and OV-17R. Si-FZD7 OC cells showed reduced cell proliferation with an increase in the G0/G1 subpopulation, with no effect on apoptosis. The cells also displayed a distinctive morphological change by colony compaction to become more epithelial-like and polarised with smaller inter-nuclear distances and increased z-axis height. Immunofluorescence (IF) staining patterns of pan-cadherin and β-catenin suggested an increase in cadherin-based cell-cell adhesion in si-FZD7 cells. We also observed a significant rearrangement in the actin cytoskeleton and an increase in tensile contractility in si-FZD7 OC cells, as evident by the loss of stress fibres and the redistribution of phospho-myosin light chain (pMLC) from the sites of cell-cell contacts to the periphery of cell colonies. Furthermore, there was reciprocal regulation of RhoA and Rac1 activities upon FZD7 knockdown, with a significant reduction in RhoA activity and a concomitant up-regulation in Rac1 activity. These changes in pMLC and RhoA as well as the increased TOPFLASH reporter activities in si-FZD7 cells suggested involvement of the non-canonical Wnt/planar cell polarity (PCP) pathway. Selected PCP pathway genes (CELSR3, PRICKLE4, DAAM1, PFN2, PCDH9, PCDHA1, PCDHB17, PCDHB3, SPRY1, and PTK7) were found to be more highly expressed in Stem-A than non Stem-A subgroup of OC. Taken together, our results suggest that FZD7 might drive aggressiveness in Stem-A OC by regulating cell proliferation, cell cycle progression, maintenance of the mesenchymal phenotype, and cell migration via CK1ϵ-mediated non-canonical Wnt/PCP pathway. Citation Format: Mohammad Asad, Wong Meng Kang, Tan Tuan Zea, Mahesh Choolani, Jeffery Low, Seiichi Mori, Jean Paul Thiery, Ruby Yun-Ju Huang. FZD7 drives aggressiveness in stem-A subtype of ovarian cancer via regulation of non-canonical Wnt/PCP pathway [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-THER-1403.