The human breast cancer cell lines we examined (MDA-MB-231, MCF7, and SK-BR-3; Fig. 2A and data not shown) did not express MMP-8 at a level that was detectable by Western blot analysis, and only MDA-MB-231 cells expressed a very small amount of endogenous MMP8 that was detectable by TaqMan quantitative real-time RT-PCR (data not shown, see also Fig. 5C). This evidence concerns the gene MMP8 and breast carcinoma.