We have previously shown that P-cadherin overexpression in breast cancer cells promotes an increase in cell migration and invasion due to the secretion of pro-invasive factors, such as MMP1 and MMP2, which then leads to P-cadherin ectodomain cleavage (soluble Pcad, sP-cad) that also has pro-invasive activity by itself [49]. Here, MMP1 is linked to breast cancer.