MMP14 and ductal breast carcinoma in situ: The reversion of MDA-MB 231 cells to a DCIS-like phenotype in 3D culture as a result of MT1-MMP overexpression is consistent with our analysis of MT1-MMP protein levels in the 21 T cell lines whereby DCIS (21NT) cells produce more active MT1-MMP and predominately form acini in 3D culture, and IMC (21MT-1) cells produce less MT1-MMP protein and display invasive 3D behavior [39], similar to our MT1-MMP MDA-MB 231 cells and parental MDA-MB 231 cells, respectively.