Targeting the methionine cycle for melanoma therapy with 3‐O‐(3,4,5‐trimethoxybenzoyl)‐(−)‐epicatechin

Abstract

The higher expression of methionine cycle genes in melanoma cells than in normal melanocytes may be related with increased protein synthesis and transmethylation reactions and the subsequent need for high levels of methionine. 3-O-(3,4,5-trimethoxybenzoyl)-(2)-epicatechin (TMECG), a trimethoxy derivative of epicatechin-3-gallate (ECG), effectively suppressed proliferation of melanoma cells in cultures by inducing apoptosis. TMECG modulates the expression of genes involved in methionine metabolism, cellular methylation and glutathione synthesis in melanoma cells. TMECG treatment of melanoma cells resulted in the downregulation of antiapoptotic Bcl-2, the upregulation of proapoptotic Bax and the activation of caspase-3; however, it did not induce the expression of the apoptosis protease-activating factor-1 (Apaf-1). Having elucidated the effects of TMECG on the melanoma methionine cycle, we designed therapeuthical strategies to increase its effectiveness. Combinations of TMECG with S-adenosylmethionine or compounds that modulate the intracellular concentration of adenosine strongly increase the antiproliferative effects of TMECG. The ability of TMECG to target multiple aspects related with melanoma survival, with a high degree of potency, points to its clinical value in melanoma therapy. ' 2008 Wiley-Liss, Inc.Key words: methionine; 3-O-(3,4,5-trimethoxybenzoyl)-(2)-epicatechin; DNA methylation; melanoma therapy; glutathione Malignant tumors are characterized by a high rate of growth. Tumor cells deplete the energy of the host, particularly glucose but also amino acids. Methionine is an essential amino acid with at least 4 major functions (Fig. 1). 1 First, methionine participates in protein synthesis. Second, methionine is a precursor of glutathione, a tripeptide that reduces reactive oxygen species (ROS), thereby protecting cells from oxidative stress. 2 Third, it is required for the formation of polyamines, which have far-ranging effects on nuclear and cell division. 3 Fourth, methionine is the major source of the methyl groups necessary for the methylation of DNA and other molecules. 1 It is important to bear in mind the wellestablished connection of the methionine cycle with 2 crucial cell metabolites, folic acid and adenosine (Fig. 1). Folic acid acts as the fuel for the methionine cycle, which after transformation by folate cycle enzymes such as dihydrofolate reductase (DHFR), thymine synthase (TS) and 5,10-methylene-tetrahydrofolate reductase (MTHFR), forms N 5 -methyl-tetrahydrofolate (N 5 -CH 3 -THF), the cofactor of methionine synthase (MS), the enzyme responsible for methionine synthesis. Adenosine, in contrast, is a product of the methionine cycle and is produced at high concentrations in tumor cells. The efficient intracellular elimination of this product by adenosine-transforming enzymes, such as adenosine deaminase (ADA), or its transport out of the cells by specific adenosine transporters, including the equilibrate nucleoside transporters (ENTs), is of vital importance for cancer cell survival.Me...

Promoting E2F1-mediated apoptosis in oestrogen receptor-α-negative breast cancer cells

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“…mRNA extraction, cDNA synthesis, and conventional and semiquantitative real-time PCR (qRT-PCR) were performed as previously described [19]. The primers were designed using Primer Express version 2.0 software (Applied Biosystems, Foster City, CA, USA) and synthesised by Life Technologies.…”

Binding of Natural and Synthetic Polyphenols to Human Dihydrofolate Reductase

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Differential Volatile Signatures from Skin, Naevi and Melanoma: A Novel Approach to Detect a Pathological Process

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