Induction of undifferentiated tumors by JC virus in the cerebrum of rats.

Newborn Sprague-Dawley rats were inoculated intracranially with JC virus (Tokyo-1), a human polyomavirus, which had been isolated by Nagashima et al. from the autopsied brain of a patient with progressive multifocal leukoencephalopathy in Japan. Twenty-one to 70 weeks later, 21 of 27 rats developed brain tumors in the cerebrum, but not in the cerebellum. Most of the tumor cells were of an undifferentiated neuroectodermal nature and showed nuclear palisades and pseudorosettes. In some tumor cells glial fibrillary acidic protein was positive immunohistochemically, and many glial filaments were demonstrated ultrastructurally. Neuronal differentiation was not proved. Two continuous lines of cultured tumor cells were established, and T antigen of JCV (Tokyo-1) was present in both cell lines. Glial differentiation was confirmed also in the tumors produced by subcutaneous transplantation of cultured tumor cells.