Gelsolin Induces Cancer Invasion via uPA Cascade Figure 5. Gelsolin increases uPA secretion of colorectal tumor cells and enhances invasion via the urokinase-type plasminogen (uPA) cascade. (A) Increased gelsolin in HCT116 cells augmented the secretion and activity of uPA. The levels of secreted uPA by cells cultured for 48 hours in serum-free conditions were detected in the supernatant using ELISA. Gelsolin-overexpressing HCT116 cells secreted significantly higher uPA levels compared to control cells (left), which correlated with higher uPA enzymatic activity, as evident from uPA zymographic analysis using 16- PLOS ONE | www.plosone.org 8 August 2012 | Volume 7 | Issue 8 | e43594