title: Lack of transforming growth factor-β signaling promotes collective cancer cell invasion through tumor-stromal crosstalk.
abstract: BACKGROUND
  Transforming growth factor beta (TGF-β) has a dual role during tumor progression, initially as a suppressor and then as a promoter. Epithelial TGF-β signaling regulates fibroblast recruitment and activation. Concurrently, TGF-β signaling in stromal fibroblasts suppresses tumorigenesis in adjacent epithelia, while its ablation potentiates tumor formation. Much is known about the contribution of TGF-β signaling to tumorigenesis, yet the role of TGF-β in epithelial-stromal migration during tumor progression is poorly understood. We hypothesize that TGF-β is a critical regulator of tumor-stromal interactions that promote mammary tumor cell migration and invasion.
  
  
  METHODS
  Fluorescently labeled murine mammary carcinoma cells, isolated from either MMTV-PyVmT transforming growth factor-beta receptor II knockout (TβRII KO) or TβRIIfl/fl control mice, were combined with mammary fibroblasts and xenografted onto the chicken embryo chorioallantoic membrane. These combinatorial xenografts were used as a model to study epithelial-stromal crosstalk. Intravital imaging of migration was monitored ex ovo, and metastasis was investigated in ovo. Epithelial RNA from in ovo tumors was isolated by laser capture microdissection and analyzed to identify gene expression changes in response to TGF-β signaling loss.
  
  
  RESULTS
  Intravital microscopy of xenografts revealed that mammary fibroblasts promoted two migratory phenotypes dependent on epithelial TGF-β signaling: single cell/strand migration or collective migration. At epithelial-stromal boundaries, single cell/strand migration of TβRIIfl/fl carcinoma cells was characterized by expression of α-smooth muscle actin and vimentin, while collective migration of TβRII KO carcinoma cells was identified by E-cadherin+/p120+/β-catenin+ clusters. TβRII KO tumors also exhibited a twofold greater metastasis than TβRIIfl/fl tumors, attributed to enhanced extravasation ability. In TβRII KO tumor epithelium compared with TβRIIfl/fl epithelium, Igfbp4 and Tspan13 expression was upregulated while Col1α2, Bmp7, Gng11, Vcan, Tmeff1, and Dsc2 expression was downregulated. Immunoblotting and quantitative PCR analyses on cultured cells validated these targets and correlated Tmeff1 expression with disease progression of TGF-β-insensitive mammary cancer.
  
  
  CONCLUSIONS
  Fibroblast-stimulated carcinoma cells utilize TGF-β signaling to drive single cell/strand migration but migrate collectively in the absence of TGF-β signaling. These migration patterns involve the signaling regulation of several epithelial-to-mesenchymal transition pathways. Our findings concerning TGF-β signaling in epithelial-stromal interactions are important in identifying migratory mechanisms that can be targeted as recourse for breast cancer treatment.
authors: Lauren A
authors: LA
authors: Matise
authors: Trenis D
authors: TD
authors: Palmer
authors: William J
authors: WJ
authors: Ashby
authors: Abudi
authors: A
authors: Nashabi
authors: Anna
authors: A
authors: Chytil
authors: Mary
authors: M
authors: Aakre
authors: Michael W
authors: MW
authors: Pickup
authors: Agnieszka E
authors: AE
authors: Gorska
authors: Andries
authors: A
authors: Zijlstra
authors: Harold L
authors: HL
authors: Moses
mesh_terms: D000818:Animals; D015820:Cadherins / Q000378:metabolism; D002450:Cell Communication; D045744:Cell Line, Tumor; D002465:Cell Movement; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics; D005347:Fibroblasts / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D055786:Gene Knockout Techniques; D006801:Humans; D007365:Intercellular Junctions / Q000378:metabolism; D051379:Mice; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D010641:Phenotype; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021381:Protein Transport; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D015398:Signal Transduction; D017154:Stromal Cells / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism
chemical_list: D015820:Cadherins; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D051176:beta Catenin; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II