GROWTH-FACTOR RECEPTORS AND THEIR LIGANDS

The understanding of the signal transduction cascade involving growth factors and their receptors is one major key for diagnostic and therap eutic improvements in human neoplasms. Using receptor autoradiography, an inverse relationship for the incidence of somatostatin receptors ( SSR) and epidermal growth factor receptors (EGFR) was found in gliomas [1]. In the majority of low grade gliomas, SSR were present but EGFR were absent. In contrast, EGFR were present in most glioblastomas, but no SSR were detected. Recently, the amplification of the EGFR gene an d its overexpression was demonstrated to be associated with the develo pment of glioblastomas. Several independent reports revealed that 40-5 0% of tumors show amplified EGFR [2-4]. The frequency of EGFR amplific ation was directly associated with tumor malignancy. In addition, ampl ified EGFR levels indicate a bad prognosis and shorter overall surviva l [5]. Recent analysis of the EGFR gene in tumors has shown that regio ns of this gene frequently undergo alteration. Hence, not only amplifi cation but also mutation may be the cause of the increased malignancy in EGFR overexpressing cells [6].