Invading C6 glioma cells maintaining tumorigenicity

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Abstract
✓ To characterize rat glioma cell invasion, 2 × 106 fluorophore-labeled or transfection-labeled C6 rat glioma cells were implanted in the rat frontal lobe. Eighty percent of the rats implanted formed bulk tumors (3–4 mm in diameter). Two weeks after implantation, fluorescence microscopy revealed single tumor cells in sites over 16 mm from the bulk brain tumor. Tumor cells distant from the bulk tumor remained single without mass formation and invaded primarily along white matter tracts. Two weeks after tumor implantation, three cell lines were created from each brain by disaggregation and initiation in culture of 1) bulk tumor, 2) contralateral hemisphere, and 3) cerebellum; all disaggregated specimens generated viable cultures. Cells cultured from the contralateral hemisphere were morphologically indistinguishable from cells from the bulk tumor and from the original C6 cell line. Cells cultured from the cerebellum were morphologically quite distinct from the C6 cell line. Cells from disaggregated specimens obtained from the tumor, contralateral hemisphere, and cerebellum were implanted in the frontal lobe of naive rats to test tumorgenicity. Bulk tumor formed in 58% of the rats implanted with specimens from tumor, in 75% of the rats implanted with specimens from contralateral hemisphere, and in only 12.5% of the rats implanted with specimens from the cerebellar hemispheres. Experiments using C6 cells labeled by transfection with the p3′ss DNA vector prior to implantation confirmed that the cells cultured from the contralateral hemisphere were derived from the implanted C6 cells. Experiments 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.