MMP1 and ductal breast carcinoma in situ: MMP1 (collagenase-1)/MMP8 (collagenase-2)/MMP13 (collagenase-3) can break down collagen types I, II, III and V. MMP13 is overexpressed in human BC tissues, in Danish and Taiwanese populations, and imply that in the process of BC turning from ductal carcinoma in situ to invasive ductal carcinoma, MMP13 can break down basement membranes resulting in invasive cancer23, 28.