title: Plasma levels of the MMP-9:TIMP-1 complex as prognostic biomarker in breast cancer: a retrospective study.
abstract: BACKGROUND
  Worldwide more than one million women are annually diagnosed with breast cancer. A considerable fraction of these women receive systemic adjuvant therapy; however, some are cured by primary surgery and radiotherapy alone. Prognostic biomarkers guide stratification of patients into different risk groups and hence improve management of breast cancer patients. Plasma levels of Matrix Metalloproteinase-9 (MMP-9) and its natural inhibitor Tissue inhibitor of metalloproteinase-1 (TIMP-1) have previously been associated with poor patient outcome and resistance to certain forms of chemotherapy. To pursue additional prognostic information from MMP-9 and TIMP-1, the level of the MMP-9 and TIMP-1 complex (MMP-9:TIMP-1) was investigated in plasma from breast cancer patients.
  
  
  METHODS
  Detection of protein:protein complexes in plasma was performed using a commercially available ELISA kit and, for the first time, the highly sensitive in-solution proximity ligation assay (PLA). We screened plasma from 465 patients with primary breast cancer for prognostic value of the MMP-9:TIMP-1 complex. Both assays were validated and applied for quantification of MMP-9:TIMP-1 concentration. In this retrospective study, we analyzed the association between the concentration of the MMP-9:TIMP-1 complex and clinicopathological data and disease free survival (DFS) in univariate and multivariate survival analyses.
  
  
  RESULTS
  Following successful validation both assays were applied for MMP-9:TIMP-1 measurements. Of the clinicopathological parameters, only menopausal status demonstrated significant association with the MMP-9:TIMP-1 complex; P = 0.03 and P = 0.028 for the ELISA and PLA measurements, respectively. We found no correlation between the MMP-9:TIMP-1 protein complex and DFS neither in univariate nor in multivariate survival analyses.
  
  
  CONCLUSIONS
  Despite earlier reports linking MMP-9 and TIMP-1 with prognosis in breast cancer patients, we here demonstrate that plasma levels of the MMP-9:TIMP-1 protein complex hold no prognostic information in primary breast cancer as a stand-alone marker. We demonstrate that the highly sensitive in-solution PLA can be employed for measurements of protein:protein complexes in plasma.
authors: Stine B
authors: SB
authors: Thorsen
authors: Sarah Lt
authors: SL
authors: Christensen
authors: Sidse O
authors: SO
authors: Würtz
authors: Martin
authors: M
authors: Lundberg
authors: Birgitte S
authors: BS
authors: Nielsen
authors: Lena
authors: L
authors: Vinther
authors: Mick
authors: M
authors: Knowles
authors: Nick
authors: N
authors: Gee
authors: Simon
authors: S
authors: Fredriksson
authors: Susanne
authors: S
authors: Møller
authors: Nils
authors: N
authors: Brünner
authors: Anne-Sofie
authors: AS
authors: Schrohl
authors: Institute of Veterinary Disease Biology and Sino-Danish Breast Cancer Research Centre, Faculty of Health and Medical Sciences, University of Copenhagen, Strandboulevarden 49, DK-2100 Copenhagen, Denmark. stenvang@sund.ku.dk.
authors: Jan
authors: J
authors: Stenvang
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000097:blood*; D001774:Blood Chemical Analysis / Q000592:standards; D001943:Breast Neoplasms / Q000097:blood* / Q000473:pathology; D018270:Carcinoma, Ductal, Breast / Q000097:blood* / Q000473:pathology; D018450:Disease Progression; D018572:Disease-Free Survival; D004797:Enzyme-Linked Immunosorbent Assay / Q000592:standards; D005260:Female; D006801:Humans; D057230:Limit of Detection; D020780:Matrix Metalloproteinase 9 / Q000097:blood*; D008875:Middle Aged; D015999:Multivariate Analysis; D011379:Prognosis; D016016:Proportional Hazards Models; D012015:Reference Standards; D012189:Retrospective Studies; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000097:blood*
chemical_list: D014408:Biomarkers, Tumor; C560822:TIMP1 protein, human; D019715:Tissue Inhibitor of Metalloproteinase-1; C579270:MMP9 protein, human; D020780:Matrix Metalloproteinase 9