Patterns of Gelatinase-B Expression in Leukemic Cell Lines

Gelatinase-B named MMP-9 (matrix metalloproteinase-9), is a protease that degrades collagen type ІV and V of extracellular matrix. MMP-9 production is increased in various types of cancers including leukemia and has an essential role in tumor invasion, metastasis and angiogenesis. In this study, patterns of MMP-9 activity in a number of leukemic cells have been evaluated in-vitro. Human leukemic T cells (Jurkat and Molt-4) and monocyte (U937) were cultured in complete RPMI-1640 medium. Then the cells were seeded at a density of 10 6 cells/ml and were incubated with different concentrations of PMA (1-25ng/ml) or PHA (1-10 μg/ml) for 24 hours. Afterwards, MMP-9 activity and MMP-9 protein level in cell-conditioned media were evaluated by gelatin zymography and ECL Western blotting, respectively. PHA/ PMA significantly induced MMP-9 activity in Molt-4 and Jurkat cells after 24-hour incubation in a dose-dependent manner compared with untreated control cells. Moreover, PHA/ PMA extensively and dose-dependently augmented MMP-9 activity in U937 cells after 24-hour incubation time compared with untreated control cells. Besides, PHA/ PMA increased MMP-9 level in U937 cells after 24-hour incubation time as was detected by western blotting compared with untreated control cells. According to the results of this study, human leukemic Jurkat, Molt-4, and U937 cells could exhibit MMP-9 activity with different extents. Among these cell lines, it seems that Molt-4 and U937 human leukemia cell lines, which greatly show MMP-9 activity after stimulation with PHA or PMA, may provide valuable tools for screening MMP enhancers or inhibitors and for assessment of regulatory mechanisms of MMP activity.