Recent genome-wide association studies identified FGFR2 as one of breast cancer susceptibility genes. FGFR2 expression was down-regulated in breast carcinomas when compared with paired normal epithelium. Stable retroviral transduction of FGFR2-IIIb and its alternatively spliced FGFR2-IIIc variants was achieved in breast cancer MDA-MB-231, T47D and near normal MCF-10A cells. Our findings revealed a direct reduction of breast cancer cell growth and motility, a significant arrest of transformed morphogenetic changes including the Epithelial to Mesenchymal transition (EMT), anchorage independent growth, and the formation of growth-arrested 3D acinar architectures, and suppressive actions on orthotopically xenografted epithelial neoplasms and surrounding tumor stroma. These tumor protective effects were concordant with physical interactions between the two FGFR2 isoforms and IKKβ. Consistent with these interactions we noted FGFR2 to inhibit NF-κB signaling, including decreased nuclear RelA/p65 NF-κB localization, down-regulation of a transfected NF-κB luciferase reporter, reduced production of NF-κB-dependent transcripts, Interleukin-6 and p-STAT3.

Recent genome-wide association studies identified FGFR2 as one of breast cancer susceptibility genes. FGFR2 expression was down-regulated in breast carcinomas when compared with paired normal epithelium. Stable retroviral transduction of FGFR2-IIIb and its alternatively spliced FGFR2-IIIc variants was achieved in breast cancer MDA-MB-231, T47D and near normal MCF-10A cells. Our findings revealed a direct reduction of breast cancer cell growth and motility, a significant arrest of transformed morphogenetic changes including the Epithelial to Mesenchymal transition (EMT), anchorage independent growth, and the formation of growth-arrested 3D acinar architectures, and suppressive actions on orthotopically xenografted epithelial neoplasms and surrounding tumor stroma. These tumor protective effects were concordant with physical interactions between the two FGFR2 isoforms and IKKβ. Consistent with these interactions we noted FGFR2 to inhibit NF-κB signaling, including decreased nuclear RelA/p65 NF-κB localization, down-regulation of a transfected NF-κB luciferase reporter, reduced production of NF-κB-dependent transcripts, Interleukin-6 and p-STAT3.

Single nucleotide polymorphisms present in the second intron of the fibroblast growth factor receptor 2 (FGFR2) gene have been linked with increased risk of breast cancer in several genome wide association studies. The potential effect of those SNPs appeared to be mediated through the differential binding of cis-regulatory elements, such as transcription factors, since all the SNPs in linkage disequilibrium were located in a regulatory DNA region. Preliminary studies have shown that a Runx2 binding site is functional only in the minor, disease associated allele of rs2981578, resulting in increased expression of FGFR2 in cancers from patients homozygous for that allele. Moreover, the increased risk conferred by the minor FGFR2 allele is associated most strongly in oestrogen receptor alpha positive (ERα) breast tumours, suggesting a potential interaction between ERα and FGFR signalling. Here, we have developed a human cell line model system to study the effect of those SNPs on cell behaviour. In an ERα positive breast cancer cell line, rs2981578 was edited using Zinc Finger Nucleases. Unexpectedly, the acquisition of the single risk allele in MCF7 cells failed to affect proliferation or cell cycle progression. Binding of Runx2 to the risk allele was not observed. However FOXA1 binding, an important ERα partner, appeared decreased at the rs2981578 locus in the risk allele cells. Additionally, differences in allele specific expression (ASE) of FGFR2 were not observed in a panel of 72 ERα positive breast cancer samples. Thus, the apparent increased risk of developing ERα positive breast cancer is not caused by rs2981578 alone. Rather, the observed increased risk of developing breast cancer might be the result of a coordinated effect of multiple SNPs forming a risk haplotype in the second intron of FGFR2.