Invasion assay demonstrating the decreased invasiveness of pancreatic cancer cells after silencing of the expression of tumor associated MUC4 mucin. The CD/HPAF-siMUC4 (MUC4-specific shRNA-expressing) cells were seeded on Matrigel-coated porous membrane and allowed to invade under a chemotactic drive for 24 h. The cells that succeeded to invade through the Matrigel were fixed, stained, and photographed under bright-field microscopy (magnification, x100). Results from three independent experiments showed that MUC4 over expression is significantly associated (P<0.05) with an enhanced invasion capacity of pancreatic cancer cells. For details, see the article by Chaturvedi et al. on page 309.