Additionally, we analyzed the level of MT1-MMP protein in human 21 T breast cancer cell lines, which represent a progression from atypical ductal hyperplasia (ADH) to invasive mammary carcinoma (IMC), to show that the metastatic cell line produces little MT1-MMP protein, consistent with our conclusions using MCF-7 and MDA-MB 231 breast cancer cells. This evidence concerns the gene MMP14 and invasive breast carcinoma.