Insulin-like growth factor type I biology and targeting in malignant gliomas

Abstract

Growth factors such as insulin-like growth factor type I (IGF-I), epidermal growth factor (EGF), vascular-endothelial growth factor (VEGF) and transforming growth factor beta (TGF-beta) are present during the development of the CNS. When they reappear in the mature brain they are overexpressed in neoplastic glia, participating in the development of the most common human brain malignant tumor, glioblastoma multiforme, which is invariably fatal. Progress in treatment of this disease involves an increase in median survival from 8 to 11 months to an average of 15 months, rarely to 18 months. We do not know any therapy, which can make a complete stop of this neoplasm. To inhibit this process various anti-growth factor therapies have been proposed. We describe actual applications of growth factor inhibitors and antisense approaches. The review highlights results obtained with the promising treatment of glioblastoma multiforme: using inhibitors and antisense targeting growth factors, including IGF-I, their receptors, and their downstream signaling effectors including glycogenesis and oncogenes. The antisense strategies have been the subject of many clinical trials, especially the IGF-I antisense approach. Such antisense therapies, already introduced in clinical trial in the USA, Europe and Asia, will soon become the preferred alternative treatment for human glioblastoma multiforme. The inhibition of signal transduction pathways common to growth factors and glycogenesis appears as a parallel challenge to glioblastoma multiforme inhibition studies.