Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0025202 (melanoma)
 69,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glutathione (GSH) and cysteine (CysH) have both been implicated in the biogenesis of the pheomelanin precursor 5-S-cysteinyldopa (5-S-CD). However, recent studies have shown that only CysH is transported across the membrane of isolated melanosomes, and that the positive regulation of CysH in pigment cells leads to an increased production of 5-S-CD. In the present study, the question was examined as to whether melanin precursors and tyrosinase could be coregulated by cellular thiols. To address this issue, the levels of CysH and GSH were varied in normal melanocytes and melanoma cells using buthionine sulfoximine (BSO), an inhibitor of GSH biosynthesis. Treatment with 50-100 microM BSO decreased GSH levels to less than 10% of control, and increased CysH levels between two- and five-fold in both cell types. Concomitant with this, an increase in the ratio of 5-S-CD to DOPA and a decrease in the pigment content of the cells were observed. The decrease in cell pigmentation was associated with strong decreases in tyrosine hydroxylase activity and 14C-melanin production. Only melanoma cells showed a modified tyrosinase isozyme pattern on Western immunoblots in response to BSO, while the mRNA expression of tyrosinase and TRP-1 were unchanged in both cell types. These results suggest that the balance between CysH and GSH, which is partly determined by the rate of utilization of CysH for GSH biosynthesis, regulates not only the levels of 5-S-CD and DOPA but also the melanogenic activity of pigment cells. Since DOPA functions as a cofactor in the monophenolase reaction of tyrosinase, it is proposed that the ratio of 5-S-CD to DOPA may be an important factor in the regulation of tyrosinase activity in situ.
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PMID:Co-regulation of melanin precursors and tyrosinase in human pigment cells: roles of cysteine and glutathione. 1064 2

Melanin biosynthesis is completely inhibited in the B16 melanoma cells following their incubation with inhibitors of the two ER glucosidases. This is primarily due to the inactivation of tyrosinase. Under the same conditions, the DOPA-oxidase activity of TRP-1 was only partially affected. In this report we investigate the effects of the perturbation of N-glycan processing in ER on the transport and activation of tyrosinase and TRP-1. We have localized the DOPA-oxidase activity in normal and inhibited cells and suggest that the first DOPA-reactive compartment of the secretory pathway (trans Golgi network) is also the site of tyrosinase activation. The inhibition of N-glycan processing does not affect the intracellular trafficking of the two melanogenic enzymes that are correctly transported to melanosomes. Immunoprecipitation experiments followed by analysis in SDS-PAGE under non-reducing conditions suggest that in inhibited cells, both tyrosinase and TRP-1 are synthesized in a modified conformation as compared to the normal proteins. These data suggest that the inhibition of melanin synthesis is not due to a defective transport but rather to conformational changes induced in the structure of tyrosinase and TRP-1 during their transit through the ER.
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PMID:Investigation of the intracellular transport of tyrosinase and tyrosinase related protein (TRP)-1. The effect of endoplasmic reticulum (ER)-glucosidases inhibition. 1064 4

The effects of calcium D-pantetheine-S-sulfonate (PaSSO3Ca) on human pigmentation were examined by in vitro assays using two types of human melanocytes: normal adult melanocytes (HNM) and M4Be melanoma cells. The compound, when added to a culture medium at doses indicating no cytotoxicity, causes a visually recognizable, reversible loss of pigment in both types of cells. Determination of melanin content, incorporation of 14C-DOPA into melanins and tyrosinase activities demonstrated that treatment of these cells with PaSSO3Ca resulted in a marked decrease in all three areas. When homogenates of these cells were assayed with lectins, the glycosylation pattern was modified, as tyrosinase activities were reduced in the cells treated with the compound. Immunoprecipitation of tyrosinase and tyrosinase-related protein 1 (Tyrp1 or TRP1) in cells incubated with radioactive glucosamine disclosed that glucosamine uptake by these enzymes was apparently increased, suggesting structural alterations in their sugar moieties. It is also noted that PaSSO3Ca is analogous in its chemical structure to Coenzyme A (CoA), which plays an important role in the intracellular transport of proteins. Based on these findings, it is likely that the compound exerts its depigmenting effects in human pigment cells through the modification of glycosylation of tyrosinase and TRP1, which are key enzymes for melanogenesis.
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PMID:Depigmenting effects of calcium D-pantetheine-S-sulfonate on human melanocytes. 1088 75

We previously reported that a melanoma antigen, recognized by tumor-specific cytotoxic T lymphocytes, was encoded by intron sequences retained in a partially spliced transcript of the tyrosinase-related protein-2/DOPAchrome tautomerase gene. At difference with the mRNA encoding tyrosinase-related protein-2, this anomalous transcript was not expressed in melanocytes. This study examined whether neoplastic and/or normal cells of the melanocytic lineage could express additional forms of tyrosinase-related protein-2 mRNA. Screening of a melanoma-derived cDNA library with a tyrosinase-related protein-2 probe allowed identification of two novel isoforms. The first, tyrosinase-related protein-2-long tail, corresponds to the dominant transcript detected on melanomas and melanocytes by northern blot analysis. Tyrosinase-related protein-2-long tail is identical to the tyrosinase-related protein-2-encoding published cDNA sequence except for an extended 3'-untranslated region and is originated by alternative polyadenylation. This novel 3'-untranslated region contains an alternatively spliced, tyrosinase-related protein-2 last exon in the second isoform (tyrosinase-related protein-2-8b). The protein encoded by tyrosinase-related protein-2-8b is identical to tyrosinase-related protein-2 in its first 460 amino acids but possesses a different carboxyl-terminus devoid of transmembrane domain. Tyrosinase-related protein-2-long tail exhibited DOPA-chrome tautomerase activity, when transiently transfected into COS-7 cells. On the contrary, no detectable activity was exhibited by tyrosinase-related protein-2-8b. Reverse transcription-polymerase chain reaction analysis indicated that tyrosinase-related protein-2-long tail and tyrosinase-related protein-2-8b are expressed by tyrosinase-related protein-2-positive melanomas and normal melanocytes. Moreover all cell lines positive for tyrosinase-related protein-2 isoforms expressed tyrosinase and, all but one, tyrosinase-related protein-1. These data show that the human tyrosinase-related protein-2/DOPAchrome tautomerase gene can yield different isoforms by alternative poly(A) site usage or by alternative splicing. The pattern of expression of these isoforms suggest that they might play a part in the normal pathway of melanin biosynthesis.
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PMID:Human melanocytes and melanomas express novel mRNA isoforms of the tyrosinase-related protein-2/DOPAchrome tautomerase gene: molecular and functional characterization. 1088 7

The screening of a series of arylsulfonylureido derivatives of amines (such as histamine, or dopamine), aliphatic/aromatic amino acids (such as Gly, beta-Ala, Val, Lys, Arg, Phe, Tyr, DOPA, etc.) and dipeptides (such as GlyGly, beta-AlaHis) led to the identification of three derivatives that possess tumor growth inhibitory properties against several leukemia, non-small cell lung, ovarian, melanoma, colon, CNS, renal, and breast cancer cell lines in vitro. The new derivatives were prepared by reaction of 4-toluenesulfonyl isocyanate with (protected) amines, amino acids or dipeptides. The mechanism of antitumor action with these new derivatives is not known at the moment but it may imply uncoupling of mitochondria, as for the structurally related diarylsulfonylurea sulofenur, an investigational anticancer agent.
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PMID:4-toluenesulfonylureido derivatives of amines, amino acids and dipeptides: a novel class of potential antitumor agents. 1103 76

Utilizing increased melanin pigmentation and accentuated melanogenesis seen in malignant melanoma, we newly developed melanoma-selective boron neutron capture therapy (BNCT) after designing and synthesizing the 10B-DOPA analogue, 10B-p-boronophenylalanine (10B-BPA). After multi-disciplined and extensive basic and pre-clinical investigations, we successfully treated 18 cases of human melanoma. Recently, we found that accentuated synthesis of melanin monomers, richest within coated vesicles (CV) in melanoma cells, plays a critical role in attracting 10B-BPA through chemical complex formation of monomers and 10B-BPA. CV are indeed BPA-localizing organelles. This led us to the new clinical endeavor that BPA may possess the potential ability to suppress melanin polymer formation through 'melanin monomer trapping' out of the melanogenic pathway which is highly regulated by the function of CV in pigment cells. It was soon found that melanin polymer formation can be suppressed by BPA at the chemical and cellular levels, then at the clinical level. Our discovery, that single molecule 10B-BPA possesses the dual nature of eradication of melanoma with BNCT and suppression of melanin hyperpigmentation, resulted from pursuing bilateral feedback at each stage from pure science to clinical application and vice versa. A further example of bilateral feedback is the development of gene-transfer applied BNCT (gBNCT). This also has its roots in clinical hurdles faced in treating amelanotic melanomas by 10B-BPA BNCT. The transfer of tyrosinase and melanin monomer synthesis-related genes into target cancer cells has produced more effective BNCT and may lead to gBNCT for non-melanoma cancers.
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PMID:Dual control of melanogenesis and melanoma growth: overview molecular to clinical level and the reverse. 1104 53

Tyrosinase is essential for pigmentation and is a source of tumor-derived antigenic peptides and cellular immune response. Wild type tyrosinase in melanoma cells and certain albino mutants in untransformed melanocytes are targeted to proteolytic degradation by the 26 S proteasome due to retention of the misfolded protein in the endoplasmic reticulum and its subsequent retranslocation to the cytosol. Here, we demonstrate that the substrates DOPA and tyrosine induced in melanoma cells a transition of misfolded wild type tyrosinase to the native form that is resistant to proteolysis, competent to exit the endoplasmic reticulum, and able to produce melanin. Because the enzymatic activity of tyrosinase is induced by DOPA, we propose that proper folding of the wild type protein, just like mutant forms, is tightly linked to its catalytic state. Loss of pigmentation, therefore, in tyrosinase-positive melanoma cells is a consequence of tumor-induced metabolic changes that suppress tyrosinase activity and DOPA production within these cells.
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PMID:Proper folding and endoplasmic reticulum to golgi transport of tyrosinase are induced by its substrates, DOPA and tyrosine. 1112 58

Tyrosinase-related protein 2 (TRP-2), also known as DOPAchrome tautomerase, is an enzyme in melanin biosynthesis and may play an important role in detoxification of a metabolite derived from DOPA. TRP-2 is expressed in melanocytes of neural crest origin and retinal pigment epithelium (RPE), derived from the optic cup. TRP-2 has been established as an early differentiation marker for melanoblasts and RPE. It is therefore of significance to study the regulation of TRP-2/DOPAchrome tautomerase expression. Here we show that TRP-2 mRNA is expressed in Y79 human retinoblastoma cell line, derived from a primitive multipotential retinal cell. Retinoblastoma is the common primary intraocular tumor of childhood. Basal expression levels in Y79 retinoblastoma cells of TRP-2 mRNA and protein are comparable to those in melanoma cells, whereas mRNA for tyrosinase, the rate-limiting enzyme in melanogenesis, is undetectable in retinoblastoma cells. Transient transfection assays showed that the TRP-2 gene promoter efficiently directs the reporter gene expression in retinoblastoma cells as it does in melanoma cells. Moreover, the expression of TRP-2 mRNA was induced by retinoic acid in retinoblastoma cells but not noticeably affected by forskolin, a cAMP-elevating reagent, whereas in melanoma cells its expression was induced by forskolin but not by retinoic acid. These results suggest a difference in the regulation of TRP-2 expression between retinoblastoma and melanoma cells. Moreover, TRP-2 mRNA is expressed in the excised retinoblastoma specimens, as assessed by RT-PCR. The present study shows unexpected features of TRP-2 and may enhance our understanding of the pathophysiology of retinoblastoma.
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PMID:Expression of tyrosinase-related protein 2/DOPAchrome tautomerase in the retinoblastoma. 1118 Sep 71

The highest incidences of cancer are found in the skin, but endogenous pigmentation is associated with markedly reduced risk. Agents that enhance skin pigmentation have the potential to reduce both photodamage and skin cancer incidence. The purpose of this review is to evaluate agents that have the potential to increase skin pigmentation. These include topically applied substances that simulate natural pigmentation: dihydroxyacetone and melanins; and substances that stimulate the natural pigmentation process: psoralens with UVA (PUVA), dimethylsulfoxide (DMSO), L-tyrosine, L-Dopa, lysosomotropic agents, diacylglycerols, thymidine dinucleotides, DNA fragments, melanocyte stimulating hormone (MSH) analogs, 3-isobutyl-1-methylxanthine (IBMX), nitric oxide donors, and bicyclic monoterpene (BMT) diols. These agents are compared with regards to efficacy when administered to melanoma cells, normal human epidermal melanocytes, animal skin, and human skin. In addition, mechanisms of action are reviewed since these may reveal issues related to both efficacy and safety. Both dihydroxyacetone and topically applied melanins are presently available to the consumer, and both of these have been shown to provide some photoprotection. Of the pigmentation stimulators, only PUVA and MSH analogs have been tested extensively on humans, but there are concerns about the safety and side effects of both. At least some of the remaining pigmentation stimulators under development have the potential to safely induce a photoprotective tan.
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PMID:Skin pigmentation enhancers. 1168 62

Two new nitrosoureas (TNUs), containing tyrosine derivatives as carriers of nitrosourea cytotoxic group have been synthesised. The physicochemical properties such as half-life time (tau(0.5)), alkylating and carbamoylating activities were determined. The nitrosoureas showed a higher inhibiting effect on the DOPA-oxidase activity of mushroom tyrosinase than that of the antitumour drug N'-cyclohexyl-N-(2-chloroethyl)-N-nitrosourea (lomustine, CCNU). In vitro cytotoxic effects of newly synthesised tyrosine containing nitrosoureas have been studied and compared to those of CCNU. A higher cytotoxicity to B16 melanoma cells than to YAC-1 and to lymphocytes was demonstrated for the tyrosine containing nitrosoureas in comparison with CCNU. Based on the results presented, we accept that a new trend for synthesis of more selective and less toxic nitrosourea derivatives as potential antimelanomic drugs might be developed.
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PMID:Structure-based design of nitrosoureas containing tyrosine derivatives as potential antimelanoma agents. 1196 Jun 64


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