Enzymatic deamination of 8-azaguanine in normal human brain and in glioblastoma multiforme.

Abstract

Summary 1.The human brain tumor, glioblastoma multiforme, when grown in tissue culture, is severely damaged by exposure to 8-azaguanine. 2.Fetal human brain, the only available nonneoplastic control for tissue culture experiments, is less severely damaged by exposure to this agent and recovers more rapidly and more completely when the agent is removed. 3.8-Azaxanthine, the end product of the enzymatic deamination of 8-azaguanine, causes no damage of any kind to either of these tissues in tissue culture. 4.Homogenates of glioblastoma are devoid of measurable a zaguanine deaminase activity; homogenates of non-neoplastic adult brain exhibit the highest deaminase activity of any animal tissue which has been studied. 5.Chromatographic analysis of feeding fluids after incubation with glioblastoma explants in tissue culture confirms the virtual absence of azaguanine deaminase activity from the cells of this tissue. Fetal brain is somewhat better able to carry out the deamination of this agent, but even this slightly greater deaminase activity is very small when compared to the activity of adult human brain.