Limitations of the C6/Wistar rat intracerebral glioma model: Implications for evaluating immunotherapy

OBJECTIVE: Intracranial rat glioma models are a useful method for evaluatin g the efficacy and toxicity of novel therapies for malignant glioma. The C6 /Wistar model has been used extensively as a reproducible in vivo model for studying primary brain tumors including anti-glioma immune responses. The objective of the present study is to provide in vivo evidence that the C6 r at glioma model is allogeneic within Wistar rats and is therefore inappropr iate for evaluating immune responses. METHODS: Growth patterns and immune responses of C6 cells implanted into th e brain and flank of Wistar rats were analyzed and compared to an immunogen ic syngeneic model (9L/Fischer). RESULTS: Wistar rats with C6 tumors developed a potent humoral and cellular immune response to the tumor. Wistar rats given simultaneous flank and int racerebral tumors had a survival rate of 100% compared to an 11% survival r ate in control animals receiving only intracranial C6 cells. CONCLUSION: The CS rat glioma induces a vigorous immune reaction that may m imic a specific anti-tumor response in Wistar rats. Efficacy of immunothera py within this model must be cautiously interpreted.