Figure 1. PEITC inhibits MMP-9 activity and tumor invasion of various cancer cells.

(A) Cells in serum-free medium were treated with PEITC followed by TPA and incubated for 24 h. MMP-9 activity was analyzed by a zymography assay. (B and C) Cells were loaded into the upper chamber of Matrigel-coated Transwells and treated with PEITC and cultured for 24 h. (D and E) U2OS cells were treated with TPA plus isothiocyanates for 24 h. MMP-9 activity and expression were analyzed in a zymography assay and by western blotting, respectively. β-actin was used as a control. (F) U2OS cells were cultured on a dish, scratched, and then treated with isothiocyanates followed by TPA for 24 h. Migrating cells were photographed by phase contrast microscopy. (G) C57BL/6N mice (n = 4) were injected subcutaneously with a mixture of Matrigel (500 μL) and U2OS cells (3 × 10⁶ cells), along with the indicated drugs. Mice were euthanized 7 days after implantation, and the Matrigel plugs were removed and photographed. The amount of hemoglobin in the Matrigel plugs was quantified using Drabkin's reagent. Data represent the mean ± S.E. of three independent experiments. *p<0.05 vs. TPA.