The first gene found to be amplified in human glioblastomas wasEGFRat 7pl2. More recently theMETgene at 7q31 was also reported amplified. We have studied chromosome 7 in a series of 47 glioblastomas by FISH, RFLP and microsatellite analysis. Four per cent (2/47) had 1 centromere, 26percnt; (12/47) 2, 32percnt; (15/47) 3, 4percnt; (2/47) 4, and 34percnt; (16/47) had subpopulations with variable numbers of chromosome 7 centromeres. In 25 of the 47 tumors (53percnt;) the pattern of allelic imbalance observed at each informative locus was similar and in accord with the FISH data, indicating loss or gain of complete chromosome copies. In 32percnt; of tumors (15/47) varying allelic imbalance was seen at different loci along the chromosome indicative of loss or gain of parts of chromosome 7 on a background of disomy, trisomy, tetrasomy, or polysomy. Amplification was studied in an extended series of 121 glioblastomas, and was seen at the 7pl2 region in 47 tumors (39percnt;). Forty-two tumors showed amplification ofEGFRand 12 of these had extensive amplicons including a number of adjacent loci, always involving only 1 allele. The amplicons of 5 tumors (11percnt;) did not includeEGFR,indicating that other unidentified genes in the region are targeted for amplification. Amplification ofMETwas not found. The findings show that copy number changes of chromosome 7 are common and that a number of genes may be targeted for amplification at 7pl2 in glioblastomas.
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