title: FZD7 drives in vitro aggressiveness in Stem-A subtype of ovarian cancer via regulation of non-canonical Wnt/PCP pathway.
abstract: Ovarian cancer (OC) can be classified into five biologically distinct molecular subgroups: epithelial-A (Epi-A), Epi-B, mesenchymal (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 frizzled family receptor 7 (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 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 sub-population, with no effect on apoptosis. The cells also displayed a distinctive morphologic change by colony compaction to become more epithelial-like and polarised with smaller internuclear 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 (Ras homolog family member A) and Rac1 (Ras-related C3 botulinum toxin substrate 1 (Rho family, small GTP-binding protein Rac1)) activities upon FZD7 knockdown, with a significant reduction in RhoA activity and a concomitant upregulation 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 (cadherin EGF LAG seven-pass G-type receptor 3 (CELSR3), prickle homolog 4 (Drosophila) (PRICKLE4), dishevelled-associated activator of morphogenesis 1 (DAAM1), profilin 2 (PFN2), protocadherin 9 (PCDH9), protocadherin α1 (PCDHA1), protocadherin β17 pseudogene (PCDHB17), protocadherin β3 (PCDHB3), sprouty homolog 1 (SPRY1) and protein tyrosine kinase 7 (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 Mes phenotype and cell migration via casein kinase 1ɛ-mediated non-canonical Wnt/PCP pathway.
authors.affiliation: Cancer Science Institute of Singapore, Centre for Translational Medicine NUS Yong Loo Lin School of Medicine, Singapore, Singapore.
authors.forename: M
authors.initials: M
authors.lastname: Asad
authors.affiliation: Cancer Science Institute of Singapore, Centre for Translational Medicine NUS Yong Loo Lin School of Medicine, Singapore, Singapore.
authors.forename: M K
authors.initials: MK
authors.lastname: Wong
authors.affiliation: Cancer Science Institute of Singapore, Centre for Translational Medicine NUS Yong Loo Lin School of Medicine, Singapore, Singapore.
authors.forename: T Z
authors.initials: TZ
authors.lastname: Tan
authors.affiliation: Department of Obstetrics and Gynaecology, National University Hospital of Singapore, Singapore, Singapore.
authors.forename: M
authors.initials: M
authors.lastname: Choolani
authors.affiliation: 1] Department of Obstetrics and Gynaecology, National University Hospital of Singapore, Singapore, Singapore [2] National University Cancer Institute of Singapore, Singapore, Singapore.
authors.forename: J
authors.initials: J
authors.lastname: Low
authors.affiliation: Division of Cancer Genomics, Cancer Institute of Japanese Foundation for Cancer Research, 3-8-31 Ariake, Koto-Ku, Tokyo, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Mori
authors.affiliation: Duke NUS Graduate Medical School, Singapore, Singapore.
authors.forename: D
authors.initials: D
authors.lastname: Virshup
authors.affiliation: 1] Cancer Science Institute of Singapore, Centre for Translational Medicine NUS Yong Loo Lin School of Medicine, Singapore, Singapore [2] National University Cancer Institute of Singapore, Singapore, Singapore [3] Department of Biochemistry, National University of Singapore, Singapore, Singapore [4] Institute of Molecular and Cell Biology, A*STAR, Singapore, Singapore.
authors.forename: J P
authors.initials: JP
authors.lastname: Thiery
authors.affiliation: 1] Cancer Science Institute of Singapore, Centre for Translational Medicine NUS Yong Loo Lin School of Medicine, Singapore, Singapore [2] Department of Obstetrics and Gynaecology, National University Hospital of Singapore, Singapore, Singapore [3] National University Cancer Institute of Singapore, Singapore, Singapore.
authors.forename: R Y-J
authors.initials: RY
authors.lastname: Huang
mesh_terms: D000818:Animals; D002453:Cell Cycle; D045744:Cell Line, Tumor; D002465:Cell Movement; D016764:Cell Polarity; D049109:Cell Proliferation; D004330:Drosophila; D005260:Female; D051157:Frizzled Receptors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D010051:Ovarian Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D060449:Wnt Signaling Pathway; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
chemical_list: C115810:FZD7 protein, human; D051157:Frizzled Receptors; D051176:beta Catenin