Smad6 determines BMP-regulated invasive behaviour of breast cancer cells in a zebrafish xenograft model.
The transforming growth factor-β (TGF-β) family is known to play critical roles in cancer progression. While the dual role of TGF-β is well described, the function of bone morphogenetic proteins (BMPs) is unclear. In this study, we established the involvement of Smad6, a BMP-specific inhibitory Smad, in breast cancer cell invasion. We show that stable overexpression of Smad6 in breast cancer MCF10A M2 cells inhibits BMP signalling, thereby mitigating BMP6-induced suppression of mesenchymal marker expression. Using a zebrafish xenograft model, we demonstrate that overexpression of Smad6 potentiates invasion of MCF10A M2 cells and enhances the aggressiveness of breast cancer MDA-MB-231 cells in vivo, whereas a reversed phenotype is observed after Smad6 knockdown. Interestingly, BMP6 pre-treatment of MDA-MB-231 cells induced cluster formation at the invasive site in the zebrafish. BMP6 also stimulated cluster formation of MDA-MB-231 cells co-cultured on Human Microvascular Endothelial Cells (HMEC)-1 in vitro. Electron microscopy illustrated an induction of cell-cell contact by BMP6. The clinical relevance of our findings is highlighted by a correlation of high Smad6 expression with poor distant metastasis free survival in ER-negative cancer patients. Collectively, our data strongly indicates the involvement of Smad6 and BMP signalling in breast cancer cell invasion in vivo.
Department of Molecular Cell Biology and Cancer Gemonics Centre Netherlands, Leiden University Medical Centre, 2300 RC Leiden, The Netherlands.
Miriam
M
de Boeck
Department of Molecular Cell Biology and Cancer Gemonics Centre Netherlands, Leiden University Medical Centre, 2300 RC Leiden, The Netherlands.
Chao
C
Cui
Department of Molecular Cell Biology, Electron Microscopy Section, Leiden University Medical Center, 2300 RC Leiden, The Netherlands.
Aat A
AA
Mulder
Department of Molecular Cell Biology, Electron Microscopy Section, Leiden University Medical Center, 2300 RC Leiden, The Netherlands.
Carolina R
CR
Jost
Laboratory of Biochemistry, Showa Pharmaceutical University, Tokyo 194-8543, Japan.
Souichi
S
Ikeno
Department of Molecular Cell Biology and Cancer Gemonics Centre Netherlands, Leiden University Medical Centre, 2300 RC Leiden, The Netherlands.|Ludwig Institute for Cancer Research, Science for Life Laboratory, Uppsala University, Box 595, 75124 Uppsala, Sweden.
Peter
P
Ten Dijke
D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002465:Cell Movement; D018920:Coculture Techniques; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D009361:Neoplasm Invasiveness; D009368:Neoplasm Transplantation; D011960:Receptors, Estrogen / Q000378:metabolism; D015398:Signal Transduction; D051905:Smad6 Protein / Q000235:genetics* / Q000378:metabolism*; D016019:Survival Analysis; D015854:Up-Regulation; D015027:Zebrafish
D019485:Bone Morphogenetic Proteins; D011960:Receptors, Estrogen; C497802:SMAD6 protein, human; D051905:Smad6 Protein