Fig 1: Contribution of cell surface plasmin to activation of MMP9 and invasion of cancer cells. (A) A transwell-based invasion assay was performed on MDA-MB-231 cells treated with plasminogen (PLG; 10 µg/mL, 12 h) under the presence or absence of tranexamic acid (TXA) (1 or 10 mg/mL). (B) Prepared conditioned media from 1-day serum-free cultivation of the indicated cells were condensed 10-fold. The media specimens were subjected to sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) and then underwent Western blotting (WB) analysis to detect MMP9 after being transferred to a polyvinylidene difluoride (PVDF) membrane or Coomassie brilliant blue (CBB) staining of the running gel without the transfer procedure, which was used as a sample control for proper loading. (C) Zymography using the gelatin substrate was performed to detect MMP-secretory activity from the indicated cells. (D) Schematic representation of the in vivo experimental lung tropic cancer metastasis protocol. MDA-MB-231 GFP cells (8 × 105 cells) with or without TXA (0.5 g/kg) were injected intravenously into BALB/c-nu/nu female mice. (E) Lung metastasis was monitored by images (right) from cancer-based white foci in the dissected mouse lung, and the clear foci (left) were counted as total foci (more than 1 mm in diameter). (F) Schematic representation of the molecular interplay among the indicated vital molecules. Data from panels (A, E) are means ± SD. ns: not significant, *p < 0.05, **p < 0.01, ***p < 0.001.