IN-VITRO AND IN-VIVO MODELS FOR THE STUDY OF BRAIN-TUMOR INVASION

Since it is difficult to study the dynamic biological aspects of brain tumour invasion using histological sections of surgical biopsy and au topsy tissues, various laboratory systems have been devised. Animal mo dels are less than ideal as chemically-induced brain tumours suffer fr om the fact that they have a low incidence and a long latency, while t ransplanted tumours grow predominantly by expansion, due to high proli ferative activity and not by diffuse local invasion as in human brain tumours. Various in vitro assays have, therefore, been established for both migration and invasion. These include the simple scratch techniq ue in a confluent cell monolayer, the use of cloning rings and the ''T ranswell'' modified Boyden chamber technique. More complex, three-dime nsional culture model systems have also been developed, using chick he art, optic nerve or reaggregated fetal brain as ''targets'' for the in vasion of neoplastic glia. Each method has yielded important informati on on the mechanisms which underlie brain tumour invasion. Moreover, i ndividual microenvironmental factors may be modulated in these laborat ory systems to determine their influence on the migration/invasion pro cess.