Glioma 261 (GL261) is a frequently used murine glioma model. It was induced via intracranial injection of methylcholanthrene followed by serial intracranial and subcutaneous transplantations of tumor fragments into syngeneic C57BL/6 mice. By the mid-1990s, multiple groups had established a permanent cell line from the tumor. Other immunocompetent murine models used to study GBM include GL26, CT-2A, SMA-560, and 4C8.