Experimental model and immunohistochemical comparison of U87 human glioblastoma cell xenografts on the chicken chorioallantoic membrane and in rat brains.

Background: To study the neuropathology and selected tumour markers of malignant gliomas, an animal glioma model was developed using the implantation of U87 human glioblastoma cells into chick chorioallantoic membrane. The immunohistochemical characteristics were studied and compared with an orthotopic rodent model.

Materials And Methods: The U87 cell suspension was inoculated onto the chick chorioallantoic membrane on embryonic day seven and into the brain of nude rats. Brain tumour sections were examined for various known tumour markers by routine haematoxylin and eosin staining and immunohistochemical analyses.

Results: The immunohistochemical analyses showed that S100 protein, glial fibrillary acidic protein and synaptophysin expressions, initially present in tissue culture, were lost in both models. Persistent kallikrein, CD68 and vimentin expressions in U87 cells, as well as in both animal tumour models, were detected. The percentage of p53-positive nuclei, which was higher in the tumours grown on the chick chorioallantoic membrane than in rats, did not correlate with the Ki-67 labelling index. Strong cathepsin expression was maintained from the cell culture to both tumour models. CD3-positive cells and numerous leukocytes, but no CD20-positive cells were detected in any of the animal samples, indicating the immunological response of the host to be primarily cellular. Stronger immune reaction for vascular endothelial growth factor in rats correlated with an observed increase in vascular proliferation in these tumours.

Conclusion: A simple, fast-growing, cheap and well-defined chick chorioallantoic membrane model of glioma was established, providing a basis for further experimental studies of genetic and protein expression during human glioma tumourigenesis. This model may possibly replace some rodent models for selective studies.