MMP-9 production from mast cell progenitors. Gelatinolytic activities comparable to proMMP-9 and MMP-9 are observed in IL-3–dependent BMCMCs or IC-2 cells, but not in P-815, RBL-2H3, and HMC-1 cells (A). The addition of 50 ng/mL TPA enhances the gelatinolytic activities released from BMCMCs and IC-2 cells (B). The gelatinolytic activity released from IC-2 cells disappears in gels incubated in buffer containing 20 mmol/L EDTA or 2 mmol/L 1,10-phenanthroline. Enzymatic activity is not affected by incubation with serine protease inhibitors, 1 mmol/L ABSF, or 30 nmol/L aprotinin, respectively (C). Expression of MMP-9 mRNA is observed in BMCMCs and IC-2 cells; and treatment with 50 ng/mL TPA for 6 hours significantly increases the expression of MMP-9 mRNA of both the cells (D).