A cell line of human malignant astrocytoma producing autocrine growth factor

A cell line was established from an anaplastic astrocytoma from a 69-yr-old female. The cells have been serially subcultured over 300 times for 6 yr without showing any sign of cell senescence. Their doubling time is about 36 h. The cells are fusiform and often hexagonal in sparse culture, but become spindle-shaped and formed mosaic structure in confluent culture. Under electron microscopy, intermediate filaments were randomly distributed in the cytoplasma, especially in the perinuclear space. The chromosome number was near tetraploid and varied from 86 to 94 chromosomes with a modal number of 91. The alpha and beta subunits of S-100 protein, vimentin, and glial fibrillary acidic protein (GFAP), which are reliable markers of astrocytic cells, were demonstrated in a large number of cells by immunoperoxidase staining. The results of immunoblotting showed that the expression of vimentin was much higher than that of GFAP. The tumorigenicity of the cells was revealed by xenografting into nude mice, which were X-irradiated before inoculation. Culture medium conditioned by the cells promoted growth of these cells in serum-free conditions and of normal rat glial cells in serum-depleted culture. The growth-promoting effect of conditioned medium was lost by trypsinization and reduced by boiling. These findings suggest that these cells are derived from neoplastic astrocytic cells and secrete a self-acting polypeptide growth-promoting factor into the culture medium.