High-throughput tissue microarray analysis of 3p25 (RAF1) and 8p12 (FGFR1) copy number alterations in urinary bladder cancer

Abstract

Studies by comparative genomic hybridization revealed that the chromosomal regions 3p25 and 8p11-p12 are recurrently amplified in bladder cancer. To investigate the prevalence of DNA copy number alterations in these chromosomal regions and study their clinical significance, we used probes for the RAF1 (3p25) and FGFR1 (8p12) genes for fluorescence in situ hybridization. A tissue microarray containing 2317 tumors was analyzed. The analysis revealed RAF1 amplification in 4.0% and FGFR1 amplification in 3.4% of interpretable tumors. In addition, deletions were found at the 3p25 locus in 2.2% and at the 8p11-12 locus in 9.9% of interpretable tumors. Both amplifications and deletions of RAF1 and FGFR1 were significantly associated with high tumor grade (P < 0.0001), advanced stage (P < 0.0001), and poor survival (P < 0.05) if tumors of all of the stages where analyzed together. RAF1 amplifications were associated with subsequent tumor progression in pT1 carcinomas (P < 0.05). The marked differences in the frequency of all of the analyzed changes between pTa grade 1/grade 2 and pT1-4 carcinomas support the concept of these tumor groups representing different tumor entities.