Amplified genes in human gliomas.
The most common types of brain tumors in adults are collectively known as gliomas. The most common glioma is the most malignant, the glioblastoma. Double minute chromosomes, known to represent amplified genes, are found in 50% of glioblastomas. Four genes have been identified as being amplified in more than single cases of glioblastomas; MYCN, GLI, PDGFRA and EGFR. The first three have been reported in a few per cent of malignant gliomas, and EGFR in around 40% of glioblastomas. The latter two genes code for growth factor receptors. On amplification, the genes for these receptors frequently become rearranged, resulting in changes in the regions of their transcripts that code for the extra-cellular domains of these proteins. Such aberrant proteins may provide us with cell-surface, tumor-specific, epitopes. These findings provide simple examples of the impact the use of modern molecular biological techniques will have for our understanding and treatment of tumors in the future.