A Novel CD44-binding Peptide from the Pro-Matrix Metalloproteinase-9 Hemopexin Domain Impairs Adhesion and Migration of Chronic Lymphocytic Leukemia (CLL) Cells

(pro)MMP-9 binds to CLL cells through the PEX9 domain and contributes to CLL progression. To biochemically characterize this interaction and identify potential therapeutic targets, we prepared GST-PEX9 forms containing structural blades B1B2 or B3B4. We recently described a sequence in blade B4 (P3 sequence) that bound α4β1 integrin and partially impaired cell adhesion and migration. We have now studied the possible contribution of the B1B2 region to cell interaction with PEX9. CLL cells bound to GST-B1B2 and CD44 was the primary receptor. GST-B1B2 inhibited CLL cell migration as effectively as GST-B3B4. Overlapping synthetic peptides spanning the B1B2 region identified the sequence FDAIAEIGNQLYLFKDGKYW, present in B1 and contained in peptide P6, as the most effective site. P6 inhibited cell adhesion to PEX9 in a dose-dependent manner and with an IC₅₀ value of 90 μm. P6 also inhibited cell adhesion to hyaluronan but had no effect on adhesion to VCAM-1 (α4β1 integrin ligand), confirming its specific interaction with CD44. Spatial localization analyses mapped P6 to the central cavity of PEX9, in close proximity to the previously identified P3 sequence. Both P6 and P3 equally impaired cell adhesion to (pro)MMP-9. Moreover, P6 synergistically cooperated with P3, resulting in complete inhibition of CLL cell binding to PEX9, chemotaxis, and transendothelial migration. Thus, P6 is a novel sequence in PEX9 involved in cell-PEX9/(pro)MMP-9 binding by interacting with CD44. Targeting both sites, P6 and P3, should efficiently prevent (pro)MMP-9 binding to CLL cells and its pathological consequences.     

The tumor suppressor activity of the transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2) correlates with its ability to modulate sarcosine levels

The type I transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2) is expressed in brain and prostate and overexpressed in prostate cancer, but its role in this disease is unclear. Several studies have suggested that TMEFF2 plays a role in suppressing the growth and invasive potential of human cancer cells, whereas others suggest that the shed portion of TMEFF2, which lacks the cytoplasmic region, has a growth-promoting activity. Here we show that TMEFF2 has a dual mode of action. Ectopic expression of wild-type full-length TMEFF2 inhibits soft agar colony formation, cellular invasion, and migration and increases cellular sensitivity to apoptosis. However, expression of the ectodomain portion of TMEFF2 increases cell proliferation. Using affinity chromatography and mass spectrometry, we identify sarcosine dehydrogenase (SARDH), the enzyme that converts sarcosine to glycine, as a TMEFF2-interacting protein. Co-immunoprecipitation and immunofluorescence analysis confirms the interaction of SARDH with full-length TMEFF2. The ectodomain does not bind to SARDH. Moreover, expression of the full-length TMEFF2 but not the ectodomain results in a decreased level of sarcosine in the cells. These results suggest that the tumor suppressor activity of TMEFF2 requires the cytoplasmic/transmembrane portion of the protein and correlates with its ability to bind to SARDH and to modulate the level of sarcosine.     

Synthesis and X-ray crystal structure analysis of 1:1 and 1:2 complexes of cisplatin with the model nucleobase 9-methyladenine in its protonated form and a unique HNO3 adduct of cis-[(NH3)2Pt(9-MeAH-N7)2]

The 1:1 and 1:2 complexes of cis-(NH₃)₂Pt^II with 9-methyladeninium cations, 9-MeAH⁺, have been prepared and characterized by X-ray crystallography: cis-[(NH₃)₂Pt(9-MeAH-N7)Cl](NO₃)₂ (1) and cis-[(NH₃)₂Pt(9-MeAH-N7)₂](NO₃)₄ · 2HNO₃ · 2H₂O (2). The pK_a values for 9-MeAH⁺ in H₂O are 1.7 in 1 as well as 0.4 (pK_a1) and 1.3 (pK_a2) for 2, as determined by pD dependent ¹H NMR spectroscopy. Compound 2 is special in that it crystallizes with two equivalents of HNO₃ per Pt entity. The HNO₃ molecules are stacked in rectangular channels provided by cis-(NH₃)₂Pt^II units, 9-methyladeninium ligands and nitrate anions, which form a porous network of hydrogen bonds.