ABSTRACT
Previous studies indicating the importance of catecholamine metabolism in neuroblastoma were briefly reviewed. Metabolic pathways were presented showing how the major urinary metabolites 3-methoxy-4-hydroxymandelic acid (VMA) and 3-methoxy-4-hydroxy-phenylacetic acid (HVA) are formed from norepinephrine and from dopamine plus 3,4-dihydroxyphenylalanine (DOPA), respectively. For 289 neuroblastoma patients at the time of diagnosis, the urinary excretion of VMA was significantly elevated in 75%, and HVA was elevated in 80%. Periodic assay of these metabolites during the course of the disease revealed that the excretion trends were of prognostic value with 80-90% reliability. By contrast, when the excretion in only the initial urine specimens was considered, the survival rate was the same for patients with normal, and with significantly elevated, excretion. Review of the results of tracer studies aimed at elucidating the in vivo metabolic origins of the urinary metabolites suggested that a) in neuroblastoma, the catecholamines were largely inactivated by intracellular metabolism in the tumor cells; b) there was excess production and excretion of the norepinephrine precursors, DOPA and dopamine; and c) in the tumors of most neuroblastoma patients, the initial enzyme in catecholamine synthesis, tyrosine hydroxylase, had an activity comparable with that in normal adrenal glands. The importance of the metabolism of catecholamines in patients with neuroblastoma was stressed: a) The excretion of elevated levels of urinary catecholamine metabolites were useful in diagnosis and in following the course of the disease, and b) study of the catecholamine metabolism in these patients permitted examination of possible relationships between the activity of the enzymes involved in catecholamine synthesis and the malignancy of this tumor.
Subject(s)
Catecholamines/metabolism , Neuroblastoma/metabolism , Child, Preschool , Dihydroxyphenylalanine/metabolism , Dopamine/metabolism , Homovanillic Acid/urine , Humans , Methoxyhydroxyphenylglycol/metabolism , Norepinephrine/metabolism , Tyrosine 3-Monooxygenase/metabolism , Vanilmandelic Acid/urine , Wilms Tumor/metabolismABSTRACT
Tyrosine hydroxylase (TH) activity has been determined in 22 neuroblastoma tumors from 15 patients, in 1 pheochromocytoma, 20 adrenal glands, 10 other tumors and organs, and 4 specimens of sera. The enzyme activity was found only in the neural crest tumors and adrenal glands, but the levels were too low to be detected in the other tumors and in normal liver and kidney tissues. The average specific activity (mean +/- SE) of TH in 23 neural crest tumors was 0.559 +/- 0.101; in 20 adrenal glands was 0.418 +/- 0.124 nmol/mg protein/minute. In 13 patients with neuroblastoma and 1 patient with pheochromocytoma, both TH levels in the primary tumors and urinary excretion of vanillylmandelic acid (VMA) and homovanillic acid (HVA) were studied. The urinary excretion of VMA by 10 of 13 neuroblastoma patients and by the patient with pheochromocytoma was significantly to markedly elevated above normal levels; excretion of HVA by 12 of 13 neuroblastoma patients was similarly elevated. These results indicate that tyrosine hydroxylase, an enzyme specifically located in the adrenal medulla and monoaminergic neurons, is also present in neuroblastoma, a malignant tumor of similar embryologic origin, and in pheochromocytoma. Not only can TH activity in these tumors be demonstrated in vitro, but the elevated urinary excretion of VMA and/or HVA by the majority of patients with these tumors also indicates TH activity of the tumors in vivo.
