Although Santamaria and collaborators [51] concluded in their studies with cell lines (HEK293 EBNA expressing ADAMTS-4 and -5) that ADAMTS-5 is a versicanase 18 times more potent than ADAMTS-4 (while the activity of the versicanase ADAMTS-1 is comparatively low), this enzyme may exhibit different behaviors in mammary tumors. This evidence concerns the gene ADAMTS4 and breast cancer.