Soluble factors involved in glioma invasion.

Recent studies using molecular and cellular techniques of the factors regulating the invasion process have revealed a crucial role for a number of growth factors and cytokines. Their function lies on the one hand in the autocrine stimulation of the tumor cells themselves, resulting in the stimulation of protease expression and an enhancement of migratory potential. On the other hand, the growth factors and cytokines seem to play a major role in the paracrine activation of the tumor surrounding stroma. Through stimulation of the strong angiogenic response that is characteristic for gliomas and also of the expression of proteases in the stromal cells, they contribute critically to the generation of a stromal environment that is permissive or even inductive for tumor cell invasion. Understanding of the mechanisms by which soluble factors modulate glioma cell invasion therefore will help to determine targets for the modification of existing therapies and lead to the development of novel therapeutic strategies in the management of gliomas.