Children’s Brain Tumour Cells Produce RNA Particles with Incomplete Retrovirus Characteristics

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Abstract
Short-term cultures of cells from human brain tumors have been reported to synthesize RNA particles of density in the range characteristic of C type RNA retroviruses, with associated DNA polymerase activity. Fresh tumor cells obtained from 6 children with astrocytoma and 7 children with medulloblastoma, together with 1 sample of normal brain tissue and normal leukocytes from brain tumor patients were assayed by several characteristics for the presence of primate retrovirus. One of 6 (17%) astrocytomas and 4 of 7 (57%) medulloblastomas released RNA particles which banded in sucrose gradients at a density of 1.16-1.18 g/cm3 together with a short segment of DNA, which was eliminated by prior RN treatment and 2 proteins of 28 and 16kD (kilodalton). These findings were compatible with the presence of a primate retrovirus. Immune coprecipitation of 125I-labeled proteins from the 1.16-1.18 g/cm3 gradient region failed to show any reactivity with antisera to p28 core antigens or the p70 reverse transcriptase antigens of simian sarcoma virus, baboon endogenous virus or Mason Pfizer virus. Assays for DNA polymerase activity in culture supernatant fluid showed only a low amount of activity with template preferences not characteristic of retroviral reverse transcriptase enzyme.