MMP9 and neoplasm: Dox-inducible CD133 expression in BAK-P cells upregulated active MMP2 and MMP-9 secretion, and significantly enhanced invasion, confirming the role of a CD133-MMP axis in tumor progression and explaining the importance of our original finding of a significant correlation between CD133, Breslow thickness, recurrent disease, poor clinical outcomes, and short overall survival [34].