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Metalloproteinase and timp expression by the human breast carcinoma cell line 8701‐BC

It is widely accepted that collagenolytic enzymes are required to facilitate the invasion and spread of tumour cells into host tissues. Immunohistochemical, zymographic and PCR analyses have produced evidence that the recently established human mammary carcinoma cell line, 8701‐BC, expresses several metalloproteinases (MMP‐1, ‐2, ‐9 and ‐10) and their tissue inhibitors (TIMP‐1 and ‐2). Application of these different techniques has led to several observations, both complementary and dissimilar. Whereas PCR analysis showed that mRNA was detected for each of the proteins, the immunolocalization study demonstrated that MMP‐1, MMP‐2, MMP‐9 and TIMP‐1 production was restricted to only a proportion of the tumour cells, with no evidence of MMP‐3 or TIMP‐2 synthesis. Such observations suggested phenotypic heterogeneity within the cell line, which was further examined by use of the tumour cell clones BC‐3A and BC‐61 derived from the parental 8701 ‐BC line. Comparative studies using zymography and PCR analysis demonstrated differences in MMP‐2 and MMP‐10 expression between the 3 cultures. The data indicate that the 8701 ‐BC cell line retains an inherent capacity for metalloproteinase and TIMP expression, with the production of both interstitial collagenase (MMP‐1) and the 2 basement‐membrane‐degrading enzymes (MMP‐2 and MMP‐9) representing an aggressive collagenolytic pheno‐type. The concomitant production of TIMP‐1 by these cell cultures, and the apparent phenotypic heterogeneity displayed by these lines, suggest that metalloproteinase dysregulation may represent an important feature of clonal heterogeneity. Although the 8701‐BC and BC‐61 cells were much more invasive than those of the BC‐3A clone, as judged by the penetration of “Matrigel”, it has not yet been possible to relate this invasive potential to the metalloproteinase and TIMP profiles reported here for each cell line.