Brain tumour migration and invasion: the role of in vitro model systems

Human primary (intrinsic) brain tumours rarely metastasis to distant organs, however they do show a marked propensity for diffuse infiltrative invasion of the contiguous, normal brain tissue. This is arguably the most important biological feature of this group of – predominantly glial – neoplasms. Single neoplastic glia may migrate several millimetres, or even centimetres from the major tumour mass and there is increasing evidence that during the migratory phase these cells transiently arrest from the cell cycle therefore rendering them refractory to therapeutic radiation. Moreover, they are protected from the action of the majority of cytotoxic drugs by virtue of their investment within areas of intact blood-brain barrier. These migratory, socalled “guerrilla” cells later return to the division phase, under hitherto unknown microenvironmental cues, to form local recurrences of the primary tumour