FGFR1 and FGF Coamplification in Breast Cancer.

Abstract

Abstract Background:FGFR1 is a tyrosine kinase receptor involved in cell proliferation, migration and differentiation. FGFR1 gene is amplified in about 10% of breast cancer. Several studies have previously reported that FGFR1 inhibition could lead to a decrease in cell proliferation. Recent data obtained in prostate cancer have shown that FGFR1 activation could mediate epithelial to mesenchymal transition. In the present study, we evaluated the rational to target FGFR1 in clinical setting.Material and methods:We first assessed whether FGFR1 amplification was associated with a specific breast cancer phenotype. We assessed FGFR1 amplification by CGH array on 235 samples and by FISH (Z-2072, Spec FGFR1/Cen8 dual color probe, Zytovision®) on 260 samples, not included in the CGH part. We then assessed the functional effects of FGFR1 inhibitions in vitro. The antiproliferative effect of E3810 (FGFR1 inhibitor) was assessed both on FGFR1-non amplified (T47D/MCF7) and FGFR1 amplified (SUM44PE/MDA134) cell lines. Effect of FGFR1 inhibition was assessed on gene expression profiling.Results:When assessed by FISH, FGFR1 amplification was observed in 23/260 cases. Most of the samples (62%) exhibited an ER+/PR- phenotype, suggesting activation of intracellular kinase. FGFR1 amplification was observed in 24 out of 235 samples (10%). Interestingly, FGFR1 amplification was associated with gene gain in FGF3/FGF4/FGF19 (11q13) (55% versus 22%, p=0.05). FGFR1 inhibition by E-3810 inhibits MAPk phosphorylation, cell proliferation. A differential IC 50 for cell proliferation was observed between amplified cell lines and control cell lines. Preliminary data on gene expression profiling suggest that FGFR1 inhibition on breast cancer cells could lead to significant decrease in the Sox9 expression, a protein involved in epithelial to mesenchymal transition.Conclusion:FGFR1-amplified breast cancers present a discrete phenotype, including a high rate of ER+/PR- and high rate of FGF3/4/19 gains. Pharmacologic inhibition of FGFR1 leads to cell proliferation decrease and modulation of genes involved in EMT. These data suggest that there is a rational to target FGFR1 in clinical setting in patients with FGFR1-amplified breast cancer. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4170.