Role of MMP-9 in CCL21/CCR7-driven B-CLL cell migration. B-CLL cells with or without previous incubation with the indicated inhibitors or transfected with siRNAs were added to Transwell filters coated with Matrigel (A) or HUVEC (B). CCL21 (1000 ng/mL) was added to the medium in the bottom chamber, except for the control. After 24 hours, migrated cells were counted by flow cytometry. Values represent the percentage of total cells added. (C) The conditioned media of untreated or CCL21-treated B-CLL cells was added to FITC-gelatin-coated wells in the presence or absence of the indicated inhibitors (TIMP-1, 5 nmol/L; Abs, 10 μg/mL). TIMP-1 or anti-MMP-9 Ab alone were also added to the wells. After 24 hours, the fluorescence was quantitated. Values are the average of 2 different patients with duplicate determinations. *P ≤ .05; **P ≤ .01.