Further characterization of MMP-9 interaction with B-CLL cells. (A) Schematic domain structure of the recombinant full-length (fl) and proMMP-9 variants used (modified from ³¹ ). Pro indicates prodomain; Act, active site; FN, gelatin-binding fibronectin-like domain; Zn²⁺, Zn²⁺-binding domain; OG, O-glycosylated domain, with vertical lines indicating probable attachment sites for O-linked sugars; and Hem, hemopexin domain. A indicates that the catalytic Glu/E⁴⁰² residue was substituted by alanine. (B) BCECF-AM–labeled B-CLL cells were added to wells coated with the indicated rproMMP-9 variants (110 nM each) and cell adhesion was measured as explained. (C) Binding of soluble rproMMP-9 variants to B-CLL cells, measured by flow cytometry. Values in panels B and C represent the average data from cells of the 4 patients studied. (D) proMMP-9 was treated with 2 mM APMA for 4 hours at 37°C and activation confirmed by gelatin zymography. (E) BCECF-AM–labeled B-CLL cells were added to wells coated with proMMP-9 or active MMP-9 (110 nM each), and cell adhesion was measured as explained. (F) Flow cytometric analysis of the binding of soluble proMMP-9 or active MMP-9 to B-CLL cells. Values in panels E and F represent the averages obtained with cells of 3 patients studied. MFI indicates mean fluorescence intensity. *P ≤ .05; **P ≤ .01; ***P ≤ .001.