Matrix metalloproteinases in neoplasm-induced extracellular matrix remodeling in breast carcinomas

Structural changes in the extracellular matrix (ECM) are necessary for cell migration during normal and pathologic tissue remodeling and neoplastic cell invasion. The matrix metalloproteinases (MMPs) and their inhibitors have been identified to be critical modulators of ECM composition and are thus, crucial in neoplastic cell progression, invasion and metastasis. Expression of MMP-2, -3, -9, -10, and -13 was investigated in human breast carcinomas (BCs) employing an indirect, biotin-streptavidin based, alkaline phosphatase conjugated immunocytochemical technique. Evaluation of the results was based on (a) the percent of neoplastically transformed cells/surrounding stroma that reacted positively and (b) a measure of staining intensity [graded from A (highest) to D (negative)]. The two forms of stromelysin, MMP-3 and -10, share 82% sequence homology, but exhibit differences in cellular synthesis and inducibility by cytokines and growth factors in vitro. Strong overall expression of MMP-3 and -10 was found in BCs, especially in the ECM adjacent to blood vessels. Positive immunoreactivity could be seen for these two MMPs in the ECM surrounding over 90% of the neoplastically transformed cells (++++), and the staining intensity was also the strongest possible (A). High intensity immunoreactivity (A,B) but focal was detected employing a MoAB targeted against the MMP-9 enzyme. No presence of MMP-2 or -13 could be established in the BC cases observed by us. Based on these results we propose that MMP-3 and -10 are implicated in the pathogenesis of BC, while MMP-9 is possibly involved in neo-angiogenic events also closely associated with growth and expansion of the neoplastically transformed cell mass, as well as metastasis of individual, extremely aggressive, expressing dedifferentiated cellular immunophenotype (IP) cell clones selected during the microevolution of the BC.