Kinetics and glial fibrillary acidic (GFA) protein production in a transplantable human giant cell glioblastoma (D-212 MG) of near haploid karyotype maintained in an organ culture system. An immunohistochemistry study

A transplantable subcutaneous tumour (designated D-212 MG), sequentially passaged in athymic nude mice and originally derived from a human giant cell glioblastoma, was maintained in an organ culture (matrix) system and studied immunohistochemically after in vitro pulse-labelling with bromodeoxyuridine (BrdU) and for the presence of glial fibrillary acidic (GFA) protein, after 1, 2 and 3 weeks in culture. The histological characteristics of the tumour, showing two cell populations of giant multinucleated cells and small cells, were preserved in the explants. An increased percentage of multinucleated giant cells was found after 3 weeks in vitro. A small but constant fraction (4-6%) of these cells continued to synthesize DNA. The labelling index of the small cells was somewhat higher, but decreased slightly although significantly over the 3-week period in vitro (from approximately 10.5 to 8%). The percentage of small cells that were positive for GFA protein was in the region of 75% and that of the giant multinucleated cells was in the region of 45%; it did not change significantly during the 3 weeks in vitro. The in vitro results confirm the astrocytic nature of both the small cells and the giant multinucleated cells in this tumour, the capacity of both cell populations to synthesize DNA in culture and to demonstrate invasiveness, and suggest the possibility that some of the giant multinucleated cells may have originated from the conversion of a number of small tumour cells.