Expression of the intracellular domain of FGFR1 in MCF-7 cells increased cell migration and bypassed GrB inhibition. (A) Western blotting confirmed successful transfection of the intracellular C-terminal FGFR1 (IC-FGFR1-MYC) fragment in MCF-7 cells. A 55-kD band was present with both anti-FGFR1 antibody or an anti–c-MYC antibody. Similarly, immunofluorescence showed enhanced nuclear FGFR1 in the cells transfected with the IC-FGFR1-MYC construct. Bar, 25 µm. (B) Transwell migration assays showed that, under control conditions, MCF-7 cells transfected with both full-length FGFR1b and IC-FGFR1-MYC migrated more compared with empty vector (pcDNA4/TO) cells. GrB inhibition decreased migration in all cells transfected with empty vector, full-length (FL) FGFR1b, or IC-FGFR1-MYC compared with untreated cells, but there was a significant difference in the cells transfected with IC-FGFR1-MYC compared with empty vector, whether or not there was no difference between cell transfected with full-length FGFR1b. *, P ≤ 0.05; **, P < 0.01; ***, P < 0.001 (paired Student’s t test and ANOVA). Error bars show means ± SEM.