ACTIVITY OF 5-FORMYL TETRAHYDROFOLATE CYCLODEHYDRASE AND 5,10-METHENYL TETRAHYDROFOLATE CYCLOHYDROLASE IN PRIMARY BRAIN-TUMORS IN CHILDREN

The activity of the enzymes 5-formyl tetrahydrofolate cyclodehydrase a nd 5,10-methenyl tetrahydrofolate cyclohydrolase has been studied cyto chemically in children's primary brain tumors. These enzymes play a si gnificant role in purine biosynthesis. Thirty children, aged 1-12 year s, were studied, 12 with medulloblastoma, 14 with glioma grade I-IV, a nd 4 with ependymoma. The activity of the enzymes was apparent as cyto plasmic granules that sometimes overlie the nucleus of the tumor cells . This coincidence showed that different types of brain tumors exhibit different degrees of enzymic activity, which in some cases correlated positively with the malignant potential of the tumor. Approximately o ne third of the cases were negative for any activity of these enzymes. The intensity of the staining of 5,10-methenyl tetrahydrofolate cyclo hydrolase activity was actually higher than that of 5-formyl tetrahydr ofolate cyclodehydrase. The clinical or prognostic significance of the se findings remains to be clarified, but we believe that cytochemistry provides a sensitive technique for the detection, localization, and d escription of these enzymes in brain tumor cells. A clear understandin g of the mode of action of these enzymes may contribute to devising no vel therapeutic strategies.