Reverse transcriptase polymerase chain reaction as a reliable method to detect epidermal growth factor receptor exon 2-7 gene deletion in human glioblastomas

Epidermal growth factor receptor (EGFR) gene amplification has been reporte d to occur in diverse carcinoma types such as lung, ovarian, and breast car cinomas and in glioblastomas. A 801-bp in-frame deletion close to the amino terminus of the receptor protein has been found to occur more or less frequ ently within at least three of these tumor entities. We studied EGFR gene a lterations using the polymerase chain reaction and EGFR gene expression of 65 astrocytic tumors (51 glioblastomas World Health Organization [WHO] IV f ive anaplastic astrocytomas WHO III, and nine astrocytomas WHO II). EGFR ge ne amplification, as determined by Southern blotting. using a full-length c DNA probe, was observed in 22 of 51 glioblastomas (43%) but in none of the grade II astrocytomas. Two of five anaplastic astrocytomas at WHO In showed a considerable degree of EGFR amplification but, according to the neurorad iological data, these two tumors had to be considered as glioblastomas. The most frequently found genetic alteration was the 801-bp deletion near the receptor aminoterminus comprising a complete loss of exon 2 to exon 7 (del( 2-7)). We showed that RT-PCR is superior to Southern blot analysis in detec tion of this type of deletion and can be assigned to 9 of 38 (24%) glioblas tomas examined. Expression of a EGF receptor protein was enhanced in most o f the tumors with gene amplification. However, 5 of 18 tumors that express a receptor protein in the absence of EGFR gene amplification also showed el evated levels of EGFR gene expression. In addition to the full-length recep tor protein, a signal in the 140-kDa range was observed in 17 of 35 gliobla stomas (49%). This fragment may correspond to the truncated del(2-7) recept or protein or might be due to proteolysis of the full-length receptor prote in. HUM PATHOL 30:222-227. Copyright (C) 1999 by W.B. Saunders Company.