Expression of matrix metalloprotease-9 in vascular pericytes in human breast cancer

Lab Invest. 1997 Oct;77(4):345-55.


Matrix metalloprotease-9 (MMP-9; 92-kd type IV collagenase, gelatinase B) is regarded as important for degradation of the basement membrane and extracellular matrix during cancer invasion and other tissue-remodeling events. Expression of MMP-9 was analyzed in 22 cases of human ductal breast cancer by immunohistochemistry and in 8 of these cases also by in situ hybridization. For immunohistochemistry we used affinity-purified polyclonal antibodies as well as a MMP-9-specific monoclonal antibody (clone 6-6B). Three different stromal cell types with a positive MMP-9 immunoreaction were identified morphologically: neutrophils and macrophage-like cells in all cases and vascular cells in 16 of 22 cases. Double immunofluorescence with antibodies to CD68 conclusively demonstrated MMP-9 expression in macrophages. To identify the positive vascular cells, we employed antibodies to von Willebrand factor and PAL-E for identification of endothelial cells, high molecular weight melanoma-associated antigen for pericytes, and alpha-smooth muscle actin for vascular smooth muscle cells. Using conventional and confocal double immunofluorescence microscopy, colocalization of MMP-9 was seen with high molecular weight melanoma-associated antigen, the pericyte marker, whereas little or no coexpression was seen with alpha-smooth muscle actin. Virtually no coexpression was seen with the endothelial cell markers PAL-E and von Willebrand factor. In situ hybridization showed that MMP-9 mRNA colocalized with MMP-9 immunoreactivity in macrophages and vascular structures, whereas no MMP-9 mRNA was detected in neutrophils. No MMP-9 immunostaining or in situ hybridization signal was detected in cancer cells in any of the cases. Based on these results, it is concluded that MMP-9 in human breast cancer is located in tumor-infiltrating stromal cells, including neutrophils, macrophages, and vascular pericytes, and that the latter two cell types also produce this metalloprotease. We suggest that the MMP-9 produced in pericytes may play a role in extracellular matrix degradation during tumor angiogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / analysis
  • Antibodies, Monoclonal
  • Antigens, CD / metabolism
  • Antigens, Differentiation, Myelomonocytic / metabolism
  • Breast Neoplasms / chemistry
  • Breast Neoplasms / metabolism*
  • Carcinoma, Ductal, Breast / chemistry
  • Carcinoma, Ductal, Breast / metabolism
  • Collagenases / metabolism*
  • Connective Tissue Cells / chemistry
  • Connective Tissue Cells / metabolism*
  • Fluorescent Antibody Technique, Indirect
  • Humans
  • Immunohistochemistry
  • In Situ Hybridization
  • Macrophages / chemistry
  • Macrophages / metabolism
  • Matrix Metalloproteinase 9
  • Melanoma / immunology
  • Muscle, Smooth, Vascular / metabolism
  • Platelet Endothelial Cell Adhesion Molecule-1 / metabolism
  • RNA, Messenger / analysis
  • von Willebrand Factor / analysis


  • Actins
  • Antibodies, Monoclonal
  • Antigens, CD
  • Antigens, Differentiation, Myelomonocytic
  • CD68 antigen, human
  • Platelet Endothelial Cell Adhesion Molecule-1
  • RNA, Messenger
  • von Willebrand Factor
  • Collagenases
  • Matrix Metalloproteinase 9