MOLECULAR VARIANTS OF EPIDERMAL GROWTH-FACTOR IN MALIGNANT ASTROCYTOMA

The present study has measured EGF levels in primary brain tumor tissu es. EGF levels were measured by specific radioimmunoassay (RIA) and fu rther analyzed by reversed-phase high performance liquid chromatograph y (RP-HPLC) followed by RIA and radioreceptor binding. The levels of E GF-like immunoreactivity (EGF-LI) in astrocytoma-IV tumors were fourfo ld greater than those in normal brain tissues. In astrocytoma-II and a strocytoma-III tumors, however, levels of EGF-LI were not different fr om those in normal brain. HPLC analysis of extracts from normal brain tissue and astrocytoma-II showed one peak of EGF-LI that coeluted with standard human EGF (retention time 22 min). Interestingly, EGF-LI in extracts of astrocytoma-IV tumors eluted in two distinct peaks with re tention times of 24 and 26 min (Astro-A and Astro-B, respectively). Ma terials in both Astro-A and Astro-B peaks reduced the specific binding of [I-125]hEGF to EGF receptors in human placental membranes. These s tudies demonstrate elevated levels of EGF-LI in malignant astrocytoma, but not in benign tumors. Furthermore, two different EGF-like molecul es that are different from native EGF are present in malignant astrocy toma.