Experimental model and immunohistochemical analyses of U87 human glioblastoma cell xenografts in immunosuppressed rat brains.

BACKGROUND: To study the neuropathology and selected tumour markers of malignant gliomas, an animal glioma model was developed using the implantation of human glioblastoma clone U87 into rat brains.
MATERIALS AND METHODS: The U87 cell suspension, or precultured U87 tumour spheroids, were inoculated into the brain of 4-week-old cyclosporin A immunosuppressed Wistar rats. The resulting first generation tumours were then transferred, through serial transplantations to rats, to obtain second and third generation tumours. Brain tumour sections were examined for various known tumour markers by routine HE staining and immunohistochemical analyses.
RESULTS: The immunohistochemical analyses showed that p53, S100 protein, glial fibrillary acidic protein (GFAP) and synaptophysin expressions, initially present in the tissue culture, were gradually lost in later tumour generations, whereas nestin and musashi expressions increased, possibly indicating progressive tumour cell dedifferentation. Persistent kallikrein, CD68 and vimentin expressions in U87 cells, as well as in all the generations of tumours, may be related to the preservation of the mesenchymal cell phenotype in this tumorigenesis model. Decreased cathepsins expression indicated lower invasive potential, but increasing Ki-67 expression marked higher proliferation activity in the subsequent tumour generations. The strong immune reaction for FVIII in the second and third generation tumours correlated with the observed increase in vascular proliferation in these tumours.
CONCLUSION: A simple, and well-defined rat model of fast-growing glioma was established, providing a basis for further experimental studies of genetic and protein expression fingerprints during human glioma tumorigenesis.