title: Rspo2/Int7 regulates invasiveness and tumorigenic properties of mammary epithelial cells.
abstract: Rspo2 was identified as a novel common integration site (CIS) for the mouse mammary tumor virus (MMTV) in viral induced mouse mammary tumors. Here we show that Rspo2 modulates Wnt signaling in mouse mammary epithelial cells. Co-expression of both genes resulted in an intermediate growth phenotype on plastic and had minor effects on the growth-promoting properties of Wnt1 in soft agar. However, individual Rspo2 and Wnt1 HC11 transfectants as well as the double transfectant were tumorigenic in athymic nude mice, with tumors from each line having distinctive histological characteristics. Rspo2 and Rspo2/Wnt1 tumors contained many spindle cells, consistent with an epithelial-mesenchymal transformation (EMT) phenotype. When Rspo2 and Rspo2/Wnt1 tumor cells were transferred into naïve mice, they exhibited greater metastatic activity than cells derived from Wnt1 tumors. For comparison, C57MG/Wnt1/Rspo2 co-transfectants exhibited invasive properties in three-dimensional (3D) Matrigel cultures that were not seen with cells transfected only with Wnt1 or Rspo2. Use of Dickkopf-1, a specific antagonist of the Wnt/β-catenin pathway, or short hairpin RNA targeting β-catenin expression demonstrated that the invasive activity was not mediated by β-catenin. Our results indicate that Rspo2 and Wnt1 have mutually distinct effects on mammary epithelial cell growth and these effects are context-dependent. While Rspo2 and Wnt1 act synergistically in the β-catenin pathway, other mechanisms are responsible for the invasive properties of stable double transfectants observed in 3D Matrigel cultures.
authors: Oncogenetics Section, Mammary Biology and Tumorigenesis Laboratory, National Cancer Institute, Bethesda, MD 20892, USA.
authors: Malgorzata
authors: M
authors: Klauzinska
authors: Bolormaa
authors: B
authors: Baljinnyam
authors: Ahmed
authors: A
authors: Raafat
authors: Jaime
authors: J
authors: Rodriguez-Canales
authors: Luigi
authors: L
authors: Strizzi
authors: Yoshimi Endo
authors: YE
authors: Greer
authors: Jeffrey S
authors: JS
authors: Rubin
authors: Robert
authors: R
authors: Callahan
mesh_terms: D000818:Animals; D002460:Cell Line; D004847:Epithelial Cells / Q000166:cytology / Q000473:pathology* / Q000502:physiology*; D005260:Female; D027261:Fusion Regulatory Protein-1 / Q000378:metabolism; D020869:Gene Expression Profiling; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008175:Lung Neoplasms / Q000556:secondary; D008321:Mammary Glands, Animal / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D008325:Mammary Neoplasms, Experimental / Q000378:metabolism* / Q000473:pathology*; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D009361:Neoplasm Invasiveness / Q000473:pathology; D009368:Neoplasm Transplantation; D019699:Thrombospondins / Q000235:genetics / Q000378:metabolism*; D060449:Wnt Signaling Pathway / Q000502:physiology; D051155:Wnt1 Protein / Q000235:genetics / Q000378:metabolism; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism; D000098907:R-Spondins
chemical_list: D027261:Fusion Regulatory Protein-1; D036341:Intercellular Signaling Peptides and Proteins; D019699:Thrombospondins; D051155:Wnt1 Protein; D051176:beta Catenin; C501127:Dkk1 protein, mouse; C518904:RSPO2 protein, mouse; D000098907:R-Spondins; C495246:Wnt1 protein, mouse