FGFR2 isoforms and anti-estrogen resistance. A) FGFR2 proteins in untreated and E2 treated (24 hours) MCF-7, OHTR, and Ful-R cells. Three cell types express different levels of FGFR2 proteins. B) FGFR2 C1, C2, and C3 mRNA levels in MCF-7, OHTR, and Ful-R cells. *, ** p<0.05 compared to parental MCF-7 cells. C) ERα is essential for the expression of slower migrating FGFR2 protein. siRNA experiments were performed as in Figure 5. Two exposures of ERα blot are shown to demonstrate the presence of residual ERα in Flu-R cells. D) The effect of KGF on proliferation of MCF-7, OHTR, and Ful-R cells. Cells were treated with KGF for six days and cell proliferation was measured using BrDU-ELISA. KGF stimulated proliferation of MCF-7 cells but not OHTR or Ful-R cells (*p=0.0001). OHTR and Ful-R cells displayed elevated basal proliferation compared to MCF-7 cells (**p=0.0001). E) Western blot analysis shows FGFR2 expression in vector control or FGFR2 C2 or C3 infected cells. F) E2 and tamoxifen sensitivity of FGFR2 C2 and C3 overexpressing cells. Cells were treated with E2 (10-10 M), 4-hydoxy tamoxifen (1 μM) or both for six days and cell proliferation was measured using BrDU-ELISA. Basal proliferation of FGFR2 C2 and C3 overexpressing cells was significantly higher compared to parental cells. E2 stimulated proliferation of all three-cell types.