What does matrix metalloproteinase-1 expression in patients with breast cancer really tell us?

Please see related article http://www.biomedcentral.com/1471-2407/11/348 webciteBreast cancer (BC) is the most common cancer in women worldwide, comprising at least 16% of all female cancers. BC results from multiple environmental and hereditary risk factors, even though genetic traits, age and hormones are the main recognized BC-predisposing risk factors [1]. Human female BC encompasses a variety of tumors, which differ in their morphological, biochemical and molecular characteristics, all guiding clinical outcome and patient survival. Although well-documented classic diagnostic/prognostic biomarkers/profiles are reliable (for example, tumor grade and stage, p53, bcl-2, Ki-67, hormone receptor status,: human epidermal growth factor receptor 2 (HER-2) expression), there is the urgent need to differentiate between BC subclasses (for example, non-basal-like luminal A and B, basal-like, triple-negative BC)[2,3], patients with different prognoses and treatment responses to the same therapy [4-6].Examining new BC biomarkers has proven that matrix metalloproteinases (MMP), which are zinc-dependent endopeptidases belonging to the Metzincin superfamily, are involved in several key events of both physiologic processes (for example, tissue remodelling, stem cell differentiation and proliferation, apoptosis) [7-11] and in pathological conditions (for example, inflammation, degeneration and cancer) [12-14]. The MMP family comprises several classes of proteases [15], which cleave almost all extracellular matrix components and a variety of proteins and growth factors crucial for neoplastic initiation and progression; these data suggest MMPs as good targets for tumor biomarker discovery. In humans, there are 24 MMP genes, but only 23 MMP proteins [16], including 17 soluble, secreted enzymes and 6 membrane-associated proteinases. MMPs are built up by a diverse structural domain architecture, and differ in their substrate specificity and in temporal and tissue specific expression pa