The metabolism of tryptophan in patients with bladder cancer and other urological diseases

The excretion of tryptophan metabolites was followed in the urine of 201 patients with bladder tumour, of 55 subjects with cancer of genito-urinary organs (ex. tra-bladder), and of 112 patients with various urological diseases (non-neoplastic). All 3 groups contained patients excreting abnormal amounts of kynurenine, 3-hydroxykynurenine and 3-hydroxyanthranilic acid. The urinary kynurenine excretion was followed for several days in 9 bladder tumour patients during simultaneous administration of daily large doses of vitamin B 6. In some cases pyridoxine slightly decreased, but never completely inhibited the abnormal excretion of kynurenine. In addition to these investigations on spontaneous excretion, l-tryptophan was administered (100 mg/kg body weight) to 4 bladder tumour patients. Kynurenine, N-α-acetylkynurenine, 3-hydroxykynurenine, kynurenic acid, xanthurenic acid and 3-hydroxyanthranilic acid were measured after loading. Small differences in the sum of compounds excreted were found between these patients and normal controls. The data presented are difficult to reconcile with the hypothesis that the excretion of abnormal quantities of tryptophan metabolites, suggested as endogenous carcinogens, might have caused the induction of cancer only when excreted by bladder tumour patients. In fact such an excretion occurs in patients with extra-bladder tumours and with various urological diseases, as well as in other human pathological conditions.