The role of growth factors in the malignant and invasive progression of intrinsic brain tumours.

Although growth factors are acknowledged for their mitogenic activity, a number of other functions are fulfilled by such peptides. These include control of motile and invasive behaviour, angiogenesis and phenotype. Various growth factors including epidermal growth factor, fibroblast growth factor, platelet derived growth factor, transforming growth factor and vascular endothelial growth factor have been described in human glial tumours. These factors may act in either autocrine or paracrine loop systems to determine the malignant potential of intrinsic brain tumours. This review examines each of these factors and their various isoforms and outlines the influence they may exert on the behaviour of neoplastic glia. Moreover, the role of growth factors in the control of the various mechanisms which underlie diffuse infiltrative invasion, neovascularisation and proliferation are explored. Finally, the potential of growth factors and their receptors as therapeutic targets is considered.