Loss of MMP-8 in ductal carcinoma in situ (DCIS)-associated myoepithelial cells contributes to tumour promotion through altered adhesive and proteolytic function

Sarper, Muge, Allen, Michael D., Gomm, Jenny, Haywood, Linda, Decock, Julie, Thirkettle, Sally, Ustaoglu, Ahsen, Sarker, Shah-Jalal, Marshall, John, Edwards, Dylan R. and Jones, J. Louise (2017) Loss of MMP-8 in ductal carcinoma in situ (DCIS)-associated myoepithelial cells contributes to tumour promotion through altered adhesive and proteolytic function. Breast Cancer Research, 19. ISSN 1465-5411

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      Abstract

      Background: Normal myoepithelial cells (MECs) play an important tumour-suppressor role in the breast but display an altered phenotype in ductal carcinoma in-situ (DCIS), gaining tumour-promoter functions. Matrix metalloproteinase-8 (MMP-8) is expressed by normal MECs but is lost in DCIS. This study investigated the function of MMP-8 in MECs and the impact of its loss in DCIS. Methods: Primary normal and DCIS-associated MECs, and normal (N-1089) and DCIS-modified myoepithelial (β6-1089) cell lines, were used to assess MMP-8 expression and function. β6-1089 lacking MMP-8 were transfected with MMP-8 WT and catalytically inactive MMP-8 EA, and MMP-8 in N-1089 MEC was knocked down with siRNA. The effect on adhesion and migration to extracellular matrix (ECM), localisation of α6β4 integrin to hemidesmosomes (HD), TGF-β signalling and gelatinase activity was measured. The effect of altering MEC MMP-8 expression on tumour cell invasion was investigated in 2D and 3D organotypic models. Results: Assessment of primary cells and MEC lines confirmed expression of MMP-8 in normal MEC and its loss in DCIS-MEC. Over-expression of MMP-8 WT but not MMP-8 EA in β6-1089 cells increased adhesion to ECM proteins and reduced migration. Conversely, knock-down of MMP-8 in N-1089 reduced adhesion and increased migration. Expression of MMP-8 WT in β6-1089 led to greater localisation of α6β4 to HD and reduced retraction fibre formation, this being reversed by MMP-8 knock-down in N-1089. Over-expression of MMP-8 WT reduced TGF-β signalling and gelatinolytic activity. MMP-8 knock-down enhanced TGF-β signalling and gelatinolytic activity, which was reversed by blocking MMP-9 by knock-down or an inhibitor. MMP-8 WT but not MMP-8 EA over-expression in β6-1089 reduced breast cancer cell invasion in 2D and 3D invasion assays, while MMP-8 knock-down in N-1089 enhanced cancer cell invasion. Staining of breast cancer cases for MMP-8 revealed a statistically significant loss of MMP-8 expression in DCIS with invasion vs. pure DCIS (p=0.001). Conclusions: These data indicate MMP-8 is a vital component of the myoepithelial tumoursuppressor function. It restores MEC interaction with the matrix, opposes TGF-signalling and MMP-9 proteolysis, which contributes to inhibition of tumour cell invasion. Assessment of MMP-8 expression may help to determine risk of DCIS progression.

      Item Type: Article
      Uncontrolled Keywords: ductal carcinoma in-situ,myoepithelial cell,microenvironment,mmp-8,adhesion,hemidesmosomes, organotypic assays,invasion
      Faculty \ School: Faculty of Science > School of Biological Sciences
      Faculty of Medicine and Health Sciences > Norwich Medical School
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      Depositing User: Pure Connector
      Date Deposited: 08 Mar 2017 01:41
      Last Modified: 27 Nov 2018 11:30
      URI: https://ueaeprints.uea.ac.uk/id/eprint/62883
      DOI: 10.1186/s13058-017-0822-9

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