Fig. 2. Reduction of gastrin expression induces an epithelial-like morphology. (A) DLD-1 colorectal carcinoma cells stably transfected with an antisense gastrin construct (ASG, grey bars) produced (cell extracts) and secreted (conditioned media) significantly less progastrin (PG), Ggly and Gam than cells transfected with vector only (VO, black bars), as measured using the radioimmunoassays described previously (Hollande et al., 1997). The statistical significance of the differences between VO and ASG clones was assessed using ANOVA. *P<0.05; **P<0.01; n=3. The reduction of gastrin expression induced an epithelial-like morphology (B), as assessed by bright-field microscopy (bar, 20 µm, upper panels, or 10 µm, lower panels), and increased the expression of cortical actin (C), as assessed by immunofluorescent staining (bar, 7.5 µm). Both parameters were partially reversed by treatment of ASG clones with exogenous progastrin_6-80 (5 nM) for 4 hours (B,C).