CHARACTERIZATION OF GLIOMA-CELLS DERIVED FROM HUMAN POLYOMAVIRUS-INDUCED BRAIN-TUMORS IN HAMSTERS

Intracerebral injection of human polyomavirus, JCV, into neonatal hamsters causes tumors of,glial origin. HJC is an established cell Line derived from a JCV-induced mixed hamster brain tumor with astrocytic and ependymal components. Flow cytometric and immunohistochemical analysis of HJC suggests that it is comprised of a mixed population of cells all of which contain the JCV early protein, T-antigen, in the nuclei. Five individual clonal lines, called HJC-15a to HJC-15e, were isolated by limiting dilution and were found to exhibit distinct morphological characteristics with 25-30% variation in their sizes. It was evident that each clone has unique growth rates, doubling times, and cell cycle parameters with different G(1), S, and G(2) phase times. All clonal cells showed the presence of the JCV early protein in the nucleus. Of interest was the observation from immunoprecipitation and Western analysis indicating qualitative and quantitative differences in the T-antigen isoforms produced in these cells. Similar to the parental clone, HJC-15b produced two distinct forms of JCV T-antigen isoforms, 88 kDa and 92 kDa proteins. In addition, HJC-15c was able to produce a 23-25 kDa protein which was recognized by anti-T-antigen antibody. The activity of cyclin-dependent kinases, in particular cdc2, was higher in HJC-15c than in the other cell lines. The data presented herein indicates that glioblastomas induced by viral T-antigen expression are composed of a multitude of distinct cells that possess a variety of different characteristics.