title: Less is more: low expression of MT1-MMP is optimal to promote migration and tumourigenesis of breast cancer cells.
abstract: Membrane Type-1 Matrix Metalloproteinase (MT1-MMP) is a multifunctional protease implicated in metastatic progression ostensibly due to its ability to degrade extracellular matrix (ECM) components and allow migration of cells through the basement membrane. Despite in vitro studies demonstrating this principle, this knowledge has not translated into the use of MMP inhibitors (MMPi) as effective cancer therapeutics, or been corroborated by evidence of in vivo ECM degradation mediated by MT1-MMP, suggesting that our understanding of the role of MT1-MMP in cancer progression is incomplete.
  
  
  
  MCF-7 and MDA-MB 231 breast cancer cell lines were created that stably overexpress different levels of MT1-MMP. Using 2D culture, we analyzed proMMP-2 activation (gelatin zymography), ECM degradation (fluorescent gelatin), ERK signaling (immunoblot), cell migration (transwell/scratch closure/time-lapse imaging), and viability (colorimetric substrate) to assess how different MT1-MMP levels affect these cellular parameters. We also utilized Matrigel 3D cell culture and avian embryos to examine how different levels of MT1-MMP expression affect morphological changes in 3D culture, and tumourigenecity and extravasation efficiency in vivo.
  
  
  
  In 2D culture, breast cancer cells expressing high levels of MT1-MMP were capable of widespread ECM degradation and TIMP-2-mediated proMMP-2 activation, but were not the most migratory. Instead, cells expressing low levels of MT1-MMP were the most migratory, and demonstrated increased viability and ERK activation. In 3D culture, MCF-7 breast cancer cells expressing low levels of MT1-MMP demonstrated an invasive protrusive phenotype, whereas cells expressing high levels of MT1-MMP demonstrated loss of colony structure and cell fragment release. Similarly, in vivo analysis demonstrated increased tumourigenecity and metastatic capability for cells expressing low levels of MT1-MMP, whereas cells expressing high levels were devoid of these qualities despite the production of functional MT1-MMP protein.
  
  
  
  This study demonstrates that excessive ECM degradation mediated by high levels of MT1-MMP is not associated with cell migration and tumourigenesis, while low levels of MT1-MMP promote invasion and vascularization in vivo.
authors.affiliation: Department of Biology, Faculty of Science, University of Western Ontario, 1151 Richmond St N., London, Ontario, N6A 5B7, Canada.
authors.forename: Mario A
authors.initials: MA
authors.lastname: Cepeda
authors.affiliation: Department of Biology, Faculty of Science, University of Western Ontario, 1151 Richmond St N., London, Ontario, N6A 5B7, Canada.
authors.forename: Jacob J H
authors.initials: JJ
authors.lastname: Pelling
authors.affiliation: Department of Biology, Faculty of Science, University of Western Ontario, 1151 Richmond St N., London, Ontario, N6A 5B7, Canada.
authors.forename: Caitlin L
authors.initials: CL
authors.lastname: Evered
authors.affiliation: Translational Prostate Cancer Research Laboratory, Lawson Health Research Institute, London, ON, Canada.
authors.forename: Karla C
authors.initials: KC
authors.lastname: Williams
authors.affiliation: Department of Biology, Faculty of Science, University of Western Ontario, 1151 Richmond St N., London, Ontario, N6A 5B7, Canada.
authors.forename: Zoey
authors.initials: Z
authors.lastname: Freedman
authors.affiliation: Department of Biology, Faculty of Science, University of Western Ontario, 1151 Richmond St N., London, Ontario, N6A 5B7, Canada.
authors.forename: Ioana
authors.initials: I
authors.lastname: Stan
authors.affiliation: Department of Biology, Faculty of Science, University of Western Ontario, 1151 Richmond St N., London, Ontario, N6A 5B7, Canada.
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Willson
authors.affiliation: Department of Surgery, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada.|Translational Prostate Cancer Research Laboratory, Lawson Health Research Institute, London, ON, Canada.
authors.forename: Hon S
authors.initials: HS
authors.lastname: Leong
authors.affiliation: Department of Biology, Faculty of Science, University of Western Ontario, 1151 Richmond St N., London, Ontario, N6A 5B7, Canada. sdamjano@uwo.ca.|Lawson Health Research Institute, London, ON, Canada. sdamjano@uwo.ca.
authors.forename: Sashko
authors.initials: S
authors.lastname: Damjanovski
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics*; D002470:Cell Survival / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000235:genetics* / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D006801:Humans; D020935:MAP Kinase Signaling System; D061986:MCF-7 Cells; D053511:Matrix Metalloproteinase 14 / Q000235:genetics* / Q000378:metabolism; D008954:Models, Biological; D010641:Phenotype; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D012333:RNA, Messenger; D019716:Tissue Inhibitor of Metalloproteinase-2; D053511:Matrix Metalloproteinase 14
keywords: 3D culture; Breast cancer; Cell migration; Intravital imaging; MMP-14; MT1-MMP