MMP9 and B-cell chronic lymphocytic leukemia: The P6 peptide, FDAIAEIGNQLYLFKDGKYW, is a novel CD44-binding peptide that was identified from studying the interaction of pro matrix metalloproteinase-9 (pro-MMP-9) with CD44 as it relates to the proliferation of chronic lymphocytic leukemia (CLL) cells [46].