MMP1 and neoplasm: In TNBC models, tumor cell-derived MMP-9 is required for Matrigel invasion and for formation of pulmonary metastases.37, 38, 39 MMP-1 is crucial for transendothelial migration and vascular intravasation.40 As MLK3 deletion decreases both MMP-1 and MMP-9 levels, we tested whether deletion of MLK3 impacts Matrigel invasion and transendothelial migration in TNBC cells.