155 The role of dopachrome tautomerase in eumelanogenesis: Clone analyses of mouse B16 melanoma subclones and of TRP-2 cDNA transfected-human melanoma cells

Kondoh, H.; Wilczek, Adam; Mishima, Yutaka

doi:10.1016/0923-1811(95)93869-3

Cited by 2 publications

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“…Similar phenomena have been reported by us and other investigators. Kondoh et al (1994) reported that human TRP-2 cDNA-transfection into human Ihara melanoma cells upregulated both tyrosinase activity and melanin synthesis. Zhao et al (1996) also independently reported similar phenomena in human TRP-1 -deficient melanoma.…”

Section: Discussionmentioning

confidence: 99%

Enhanced Melanogenesis Induced by Tyrosinase Gene‐Transfer Increases Boron‐Uptake and Killing Effect of Boron Neutron Capture Therapy for Amelanotic Melanoma

Tsuboi¹,

Kondoh²,

Hoshino³

et al. 1998

Pigment Cell Research

149

105

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Specific and powerful cancer killing effect for melanoma by boron neutron capture therapy (BNCT) using DOPA analogue, 10B-p-boronophenylalanine (10B-BPA), has been established, but amelanotic melanoma is insufficiently responsive to 10B-BPA BNCT in comparison with actively melanin-producing melanoma. Although the accumulation mechanism of 10B-BPA within melanoma was not established, we have recently obtained findings suggesting that melanin monomers, key intermediates for melanin polymer formation, play a critical role in 10B-BPA accumulation. In addition, there are some kinds of human amelanotic melanomas, such as MEL2A, in which expression of tyrosinase is repressed or lacking though tyrosinase-related protein (TRP)-1 and TRP-2 are well expressed. Thus, by using a similarly tyrosinase-lacking mouse amelanotic melanoma cell line, A1059, we constructed TA1059 cells by transfecting human tyrosinase-cDNA into these cells. TA1059 cells acquired higher DOPA-oxidase and DOPAchrome tautomerase activity as well as eumelanin content at even higher levels than those of B16F10 cells. TA1059 cells showed about 2.5 times higher P-boronophenylalanine (BPA) uptake than A1059 cells in culture. In animal experiments, by using these cell lines, tumor growth of TA1059 was significantly suppressed by 10B-BPA BNCT as compared with A1059. These findings indicate that the induction of active melanin biosynthesis by melanogenic gene-transfer effectively improves the treatment of amelanotic melanoma by BNCT.

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Section: Discussionmentioning

confidence: 99%

Enhanced Melanogenesis Induced by Tyrosinase Gene‐Transfer Increases Boron‐Uptake and Killing Effect of Boron Neutron Capture Therapy for Amelanotic Melanoma

Tsuboi¹,

Kondoh²,

Hoshino³

et al. 1998

Pigment Cell Research

149

105

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“…The experiments carried out by Aroca et al ( 1992b) revealed that in the test tube assay system the melanin formation is accelerated by addition of DCT It is, however, difficult to predict without further in vivo experiments as to whether or not such a stimulatory effect occurs in the living pigment cell. We have recently transfected the human DCT gene into human Ihara melanoma cells that posses low DCT activity (Kondoh, 1994). The biochemical analysis of several clones of transfected cells revealed that the increase in DCT activity results in increase of not only the proportion of DHICAderived units in the eumelanin polymer, but also the total amount of eumelanin synthesized.…”

Section: Melanin Monomers [Mm]mentioning

confidence: 99%

Inhibitory Effects of Melanin Monomers, Dihydroxyindole‐2‐Carboxylic Acid (DHICA) and Dihydroxyindole (DHI) on Mammalian Tyrosinase, With a Special Reference to the Role of DHICA/DHI Ratio in Melanogenesis

Wilczek

Mishima

1995

Pigment Cell Research

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DOPAchrome tautomerase (DCT) is known to control the ratio of DHICA/DHI formed within the melanocyte, but physiologic significance of this activity is not yet fully elucidated. In this study the two melanin monomers are shown to inhibit with different efficacy the initial, tyrosinase-controlled, melanogenic reaction, namely conversion of L-tyrosine to DOPAchrome (2-carboxy-2,3-dihydroindole-5,6-quinone). This is demonstrated in the test tube assay system whereby formation of DOPAchrome is catalyzed by i) isolated premelanosomes (PMS), ii) tyrosinase-rich PMS glycoproteins, or iii) tyrosinase purified from fibroblasts transfected with human tyrosinase gene. Both DHI and DHICA suppress the conversion of L-tyrosine to DOPAchrome when added to reaction mixture but the inhibitory effect is far more strongly pronounced by DHI. DHI inhibits both activities of tyrosinase--tyrosine-hydroxylation and DOPA-oxidation--more strongly than DHICA. The different extent of inhibition is shown to reflect i) the ability of the two monomers to compete with tyrosinase substrates for the enzyme's active center and ii) the rate of interaction between melanin monomers and DOPAquinone. Consequently, we demonstrate that the tyrosinase-catalyzed DOPAchrome formation can be modulated by the ratio of DHICA/DHI among melanin monomers with the increased proportion of DHICA resulting in more efficient DOPAchrome formation. These results raise the possibility that DOPAchrome tautomerase plays a role in positive control of the tyrosinase-catalyzed early phase of melanogenesis.

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155 The role of dopachrome tautomerase in eumelanogenesis: Clone analyses of mouse B16 melanoma subclones and of TRP-2 cDNA transfected-human melanoma cells

Cited by 2 publications

References 0 publications

Enhanced Melanogenesis Induced by Tyrosinase Gene‐Transfer Increases Boron‐Uptake and Killing Effect of Boron Neutron Capture Therapy for Amelanotic Melanoma

Enhanced Melanogenesis Induced by Tyrosinase Gene‐Transfer Increases Boron‐Uptake and Killing Effect of Boron Neutron Capture Therapy for Amelanotic Melanoma

Inhibitory Effects of Melanin Monomers, Dihydroxyindole‐2‐Carboxylic Acid (DHICA) and Dihydroxyindole (DHI) on Mammalian Tyrosinase, With a Special Reference to the Role of DHICA/DHI Ratio in Melanogenesis

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