Abstract 3211: FGFR1 and FGFR2 gene copy number variations in prostate cancer

Abstract

Abstract Patients with hormone refractory prostate cancer (HRPC) have very few clinical options. A bottle neck in development of new therapies is the poor understanding of the molecular basis of hormone independency. A pathway thought to be important in this progression is FGFR. Amplification of FGFR1 has been observed in breast cancer and has led to the hypothesis that it is involved in Tamoxifen resistance (Turner et al., 2010). Here we evaluated the copy number variations (CNV) of the gene loci of FGFR1 (8p12) and FGFR2 (10q26) by dual color FISH in FFPE tissue of recurrent PC patients (n=28), non-recurrent PC patients (n=15), PC patients undergoing palliative RPE (n=15), patients with benign prostate hyperplasia (n=17) and tumor free tissue samples (n=12). We analyzed CNV between different clinical patient subgroups. Two types of CNV for the gene loci of FGFR1 and FGFR2 were observed. Either the gene dose of the target gene locus occurred to be amplified or the gene dose was elevated due to polysomy of the respective chromosome. Furthermore patients with CNV of FGFR1 or FGFR2 exhibited in 40-50% intra tumor heterogeneity by presenting normal cells and cells with CNV. FGFR1 gene dose elevations (either due to gene locus amplification or polysomy of chromosome 8) were observed in 7% (1/15) of patients without recurrence but in 49% (17/35) of the patients with recurrence. Also, in patients undergoing palliative RPE 75% (12/16) of the patients exhibited FGFR1 gene dose elevation. In the case of FGFR2, gene dose elevations (gene locus amplification or polysomy of chromosome 10) were observed in none of the patients without recurrence but in 13% of the patients with recurrence and in 20% of patients undergoing palliative RPE. In the control groups such variations were not found. Interestingly, the gene dose variations differed in the prostate cancer patients depending on their hormone sensitivity. 47% (7/15) of hormone refractory patients and 30% (6/20) of the hormone sensitive patients showed elevated FGFR1 gene dose, for FGFR2, 30% and 20% of the respective subgroups were affected. In summary we conclude that this is first evidence that CNV of FGFR1 and FGFR2 might have implications for hormone resistance in PC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3211. doi:10.1158/1538-7445.AM2011-3211