The 9L(LUC)/Wistar rat glioma model is not suitable for immunotherapy☆

The availability of a well-characterized animal brain tumor model will play an important role in identifying treatments for human brain tumors. Wistar rats bearing 9L glioma cells can develop solid, well-circumcised tumors, and may be a useful animal model for the evaluation of various therapeutic approaches for gliosarcomas. In this study, the 9L/Wistar rat glioma model was produced by intracerebral implantation of 9L(LUC) glioma cells syngenic to Fischer 344 (F344) rats. Bioluminescence imaging showed that tumors progressively grew from day 7 to day 21 in 9L(LUC)/F344 rats, and tumor regression was found in some 9L(LUC)/Wistar rats. Hematoxylin-eosin staining verified that intracranial tumors were gliomas. Immunohistochemistry results demonstrated that no CD(4)- and CD(8)-positive cells were found in the syngeneic 9L(LUC)/F344 model. However, many infiltrating CD(4)- and CD(8)-positive cells were observed within the tumors of the 9L(LUC)/Wistar model. Our data suggests that compared with 9L/F344 rats, 9L glioma Wistar rats may not be suitable for evaluating brain glioma immunotherapies, even though the model induced an immune response and exhibited tumor regression.