THE BIOCHEMICAL AND CLINICAL SIGNIFICANCE OF MELANOGENURIA

Role of the clinical laboratory in the diagnosis and management of malignant melanoma

The biosynthesis of melanin from tyrosine is reviewed as the basis for assessment of laboratory tests that might potentially aid in the diagnosis and management of patients with malignant melanoma. These tests include qualitative and quantitative assays for the intermediates in metabolism of melanin and catecholamines, enzyme assays, metal ion analyses, and, most recently, immunoassays. Although currently no role exists for the clinical laboratory in the early diagnosis of malignant melanoma, serial quantitative analyses of total or individual melanogens or of catecholamine metabolites in urine or plasma specimens may be of value in the management of patients with this disorder. Immunologically based methods for the diagnosis and management of malignant melanoma hold some promise for the future.

Identification of 5-Hydroxy-6-indolyl-O-sulfate in Urine of Patients with Malignant Melanoma

It has previously been shown that enzymatically hydrolyzed urine of patients with malignant melanoma contains 5,6-dihydroxyindole (5, 6DHI ). In this study we describe the elucidation of the entire structure of urinary 5, 6DHI -conjugate. Differential hydrolysis of melanotic urine revealed that, in contrast to beta-glucuronidase, sulfatase can liberate 5, 6DHI from its conjugated form. 5, 6DHI -sulfate was synthetized by reacting 5, 6DHI with sulfur trioxide trimethylamine complex. Thin-layer chromatography (TLC) documented its close similarity to the Thorm ahlen -positive compound usually entitled "C." Gas chromatographic-mass spectrometric (GC-MS) analysis of methylated and subsequently hydrolyzed synthetic 5, 6DHI -sulfate showed that the synthetic product consisted of a mixture of 5-hydroxy-6-indolyl-O-sulfate and 6-hydroxy-5-indolyl-O-sulfate (with a certain amount of 5, 6DHI -disulfate). 5, 6DHI -sulfate was purified with use of DEAE-cellulose column chromatography from melanotic urine. Methylation of this conjugate with deuterated dimethylsulfate and subsequent GC-MS analysis of the hydrolyzed product provided evidence that 5, 6DHI from melanotic urine was almost exclusively sulfated in position 6. It was concluded (1) that 5, 6DHI is excreted as a 6-O-sulfate, and (2) that this compound is consistent with Thorm ahlen -positive compound "C".

The urinary melanogen cysteinyldopa in melanoma and in suntanning: Australian experience

Determination of urine cysteinyldopa excretion is the most sensitive chemical test for the detection of melanoma metastases and has been successfully applied during the Scandinavian winter, when sun irradiation is low. The value of this determination, under Australian conditions of greater sun irradiation, has been assessed by comparing the cysteinyldopa excretion of patients with that of normal subjects exposed to sunlight. Cysteinyldopa is an intermediate in the biosynthesis of the red-brown phaeomelanin. Of 20 patients without known secondary melanoma, the cysteinyldopa concentration of "spot" urines ranged from 0 to 190 (mean 48) microgram/ml; of six known to have local metastases, 0 to 80 (mean 19) microgram/ml; and of four known to have extensive metastases 80 to 1350 (mean 330) microgram/ml. The effect of sun irradiation alone was assessed in nine healthy subjects followed one to 11 weeks before and after recorded periods of sun exposure. The cysteinyldopa concentrations of 24-hour urines ranged from 40 to 3100 microgram/ml. Increases occurred three to 10 days following sun exposure and were greatest following multiple small exposures in an individual with "Celtic" complexion. It is concluded that measurement of cysteinyldopa concentration would be of value in the follow-up of melanoma patients in Australia only if patients could be persuaded to live under conditions free of all direct sun-irradiation.

Simple and sensitive test for the determination of phenolic compounds in urine and its application to melanoma

A simple procedure is outlined for the determination of phenolic compounds in urine. The method involves the diazotization of p-nitroaniline and subsequent coupling of the diazonium chloride with phenolic compounds. The diazo compound formed is determined by measuring the absorbance at 400 nm. The extinction coefficients for several compounds have been determined. Application of this method to determine the levels of phenolic compounds in urine in patients with melanoma showed that the assay may be of diagnostic value. The amounts of phenols in 24-hr urine samples from patients with melanoma, patients with various other diseases, and healthy individuals were determined. A statistical analysis of these results showed that the results for patients with melanoma were higher than those for healthy individuals and patients with other diseases at 1 percent probability level. A comparison of this test with three other methods (Thormählen test, ferric chloride test, and ferrocitrate test) for determination of melanogens showed that the diazo test is the most sensitive one for detecting melanoma.