MMP1 and neoplasm: We propose that interstitial collagenase may be one of the mediators of the tumor- and metastasis-suppressing function of c-Myb in ER-negative breast cancer cells because interstitial collagenase was clearly downregulated in MDA-MB-231MYBup cells (Figure 4), 4T1MYBup cells (Additional file 8) and in the c-myb-overexpressing tumors (Additional file 8).