INVADING C6 GLIOMA-CELLS MAINTAINING TUMORIGENICITY

To characterize rat glioma cell invasion, 2 X 10(6) fluorophore-labele d or transfection-labeled C6 rat glioma cells were implanted in the ra t frontal lobe. Eighty percent of the rats implanted formed bulk tumor s (3-4 mm in diameter). Two weeks after implantation, fluorescence mic roscopy revealed single tumor cells in sites over 16 mm from the bulk brain tumor. Tumor cells distant from the bulk tumor remained single w ithout mass formation and invaded primarily along white matter tracts. Two weeks after tumor implantation, three cell lines were created fro m each brain by disaggregation and initiation in culture of 1) bulk tu mor, 2) contralateral hemisphere, and 3) cerebellum; all disaggregated specimens generated viable cultures. Cells cultured from the contrala teral hemisphere were morphologically indistinguishable from cells fro m the bulk tumor and from the original C6 cell line. Cells cultured fr om the cerebellum were morphologically quite distinct from the C6 cell line. Cells from disaggregated specimens obtained from the tumor, con tralateral hemisphere, and cerebellum were implanted in the frontal lo be of naive rats to test tumorgenicity. Bulk tumor formed in 58% of th e rats implanted with specimens from tumor, in 75% of the rats implant ed with specimens from contralateral hemisphere, and in only 12.5% of the rats implanted with specimens from the cerebellar hemispheres. Exp eriments using C6 cells labeled by transfection with the p3'ss DNA vec tor prior to implantation confirmed that the cells cultured from the c ontralateral hemisphere were derived from the implanted C6 cells. Expe riments with C6 cells anchored in agar served to verify that movement to the contralateral hemisphere was secondary to parenchymal invasion rather than dispersion in the cerebrospinal fluid.