Mitogens as motogens

Numerous in vivo methodologies have documented the invasive behavior of glioma cells through normal brain parenchyma. Glioma cell locomotion has also been assessed with a number of in vitro assays including the Boyden chamber and other chemotaxis assays, colloidal gold cell tracking, analysis of migration of cells tumor cells from spheroids, confrontation cultures of glioma cells with aggregates of non-neoplastic tissue, time-lapse video microscopy, electron microscopic examination of the cytomorphologic correlates of cell motility, the radial dish assay, and quantitative enzyme immunoassay of proteins associated with invasion (e.g. laminin). Several of these techniques have been specifically modified to assess the effects of cytokines on glioma cell motility in vitro. Cytokines studied utilizing these methods include: epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), the bb dimer of platelet-derived growth factor (PDGFbb), nerve growth factor (NGF), interleukin 2 (IL-2), transforming growth factors alpha and beta 1 (TGFα and TGFstraat₁), and tumor necrosis factor alpha (TNFα). This review summarizes the investigational methods used to evaluate random and directional glioma cell motility and invasion in vivo and in vitro. The roles of specific mitogens as motogens, as evaluated with these methods are then presented.