Loss of giant obscurins from breast epithelium promotes epithelial-to-mesenchymal transition, tumorigenicity and metastasis.
Obscurins, encoded by the single OBSCN gene, are giant cytoskeletal proteins with structural and regulatory roles. The OBSCN gene is highly mutated in different types of cancers. Loss of giant obscurins from breast epithelial cells confers them with a survival and growth advantage, following exposure to DNA-damaging agents. Here we demonstrate that the expression levels and subcellular distribution of giant obscurins are altered in human breast cancer biopsies compared with matched normal samples. Stable clones of non-tumorigenic MCF10A cells lacking giant obscurins fail to form adhesion junctions, undergo epithelial-to-mesenchymal transition and generate >100-μm mammospheres bearing markers of cancer-initiating cells. Obscurin-knockdown MCF10A cells display markedly increased motility as a sheet in 2-dimensional (2D) substrata and individually in confined spaces and invasion in 3D matrices. In line with these observations, actin filaments redistribute to extending filopodia where they exhibit increased dynamics. MCF10A cells that stably express the K-Ras oncogene and obscurin short hairpin RNA (shRNA), but not scramble control shRNA, exhibit increased primary tumor formation and lung colonization after subcutaneous and tail vein injections, respectively. Collectively, our findings reveal that loss of giant obscurins from breast epithelium results in disruption of the cell-cell contacts and acquisition of a mesenchymal phenotype that leads to enhanced tumorigenesis, migration and invasiveness in vitro and in vivo.
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, USA.
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Shriver
1] Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD, USA [2] Johns Hopkins Institute for NanoBioTechnology, The Johns Hopkins University, Baltimore, MD, USA [3] Johns Hopkins Physical Sciences-Oncology Center, The Johns Hopkins University, Baltimore, MD, USA.
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Stroka
Marlene and Stewart Greenebaum National Cancer Institute Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA.
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Vitolo
Marlene and Stewart Greenebaum National Cancer Institute Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA.
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Martin
Department of Molecular and Comparative Pathobiology, The Johns Hopkins University and The Sidney Kimmel Comprehensive Cancer Center, Baltimore, MD, USA.
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Huso
1] Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD, USA [2] Johns Hopkins Institute for NanoBioTechnology, The Johns Hopkins University, Baltimore, MD, USA [3] Johns Hopkins Physical Sciences-Oncology Center, The Johns Hopkins University, Baltimore, MD, USA.
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Konstantopoulos
1] Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, USA [2] Marlene and Stewart Greenebaum National Cancer Institute Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA.
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Kontrogianni-Konstantopoulos
D001706:Biopsy; D015153:Blotting, Western; D001940:Breast / Q000378:metabolism* / Q000473:pathology; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D002448:Cell Adhesion / Q000235:genetics; D002460:Cell Line; D002465:Cell Movement / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000235:genetics* / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics*; D004848:Epithelium / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007365:Intercellular Junctions / Q000378:metabolism; D018613:Microscopy, Confocal; D009362:Neoplasm Metastasis; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras); D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D064067:Rho Guanine Nucleotide Exchange Factors / Q000235:genetics* / Q000378:metabolism; D014183:Transplantation, Heterologous; D014746:Vimentin / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism
D015820:Cadherins; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D064067:Rho Guanine Nucleotide Exchange Factors; D014746:Vimentin; C578224:OBSCN protein, human; D017346:Protein Serine-Threonine Kinases; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins