EGF-R GENE COPY NUMBER CHANGES IN RENAL-CELL CARCINOMA DETECTED BY FLUORESCENCE IN-SITU HYBRIDIZATION

Expression of epidermal growth factor receptor (EGF-r) is a frequent e vent in renal cell carcinoma (RCC). To investigate the role of EGF-r g ene copy number changes related to EGF-r overexpression, 50 RCC specim ens were examined by fluorescence in situ hybridization (FISH) and imm unohistochemistry. Dual-labelling FISH with a repetitive pericentromer ic probe for chromosome 7 and a probe for the ECF-r gene (at 7p13) was performed to analyse the EGF-r copy number in relation to chromosome 7 copy number on a cell-by-cell basis. Polysony 7 was frequent in all histological types of RCC. Chromosome 7 polysomy was found in 26 of 35 clear cell (74 per cent), nine of nine papillary, and three of three chromophobe RCCs. EGF-r gene copy number was closely associated with t he chromosome 7 copy number on a cell-by-cell basis. No EGF-r gene amp lifications were found. EGF-r positivity was found in 37 of 50 cases ( 74 per cent) by immunohistochemistry. EGF-r positivity was more common in clear cell (81 per cent) than in papillary tumours (40 per cent; P =0.029). Neither chromosome 7 nor ECF-r gene copy number was associate d with ECF-r expression, indicating that an increased gene dosage is n ot a mechanism of EGF-r overexpression in RCC. (C) 1998 John Wiley & S ons, Ltd.