Biosynthesis of Eumelanin in Melanoma and Biochemical Markers of Melanoma

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1. Simplified method for preparing enmelanin-related metabolites Dopachrome solution, firepared by chemical oxidation of dopa, was kept under different pH to yield 5,6DHI and 5,6DHI2C. Treatment with diazomethane afforded their O-methyl derivatives. This enabled us to obtain standard compounds necessary for the following research.2. Importance of enmelanin-related metabolites as biochemical markers of melanoma (1) Excretion of melanin-related metabolites was examined in mice bearing B16 melanoma. In early stage of tumor progression, the increase of 5H6MI2C was found to be more pronounced than of 5-S-CD, a commonly used marker. (2) Correlation among the contents of melanin-related metabolites in tumor, serum, and urine was examined in mice bearing B16 melanoma. Good correlation was found between serum indoles (5H6MI2C + 6H5MI2C) or 5-S-CD and tumor weight (r = 0.92, 0.89, respectively). Urinary metabolites did not show a significant correlation. These results suggest that melanin-related metabolites in serum may better reflect progression of melanoma than those in urine. (3) High levels of glucronide and sulfate conjugates of indoles were found in urine of a melanoma patient. Only sulfate conjugates were detected in urine of melanoma-bearing mice.Serum and urine samples from healthy subjects and melanoma patients will be analyzed for indoles and 5-S-CD to compare their usefulness in early diagnosis and prognosis of melanoma.