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Widespread expression of ?-glutamyl cyclotransferase suggests it is not a general tumor marker.

ABSTRACT: ?-Glutamyl cyclotransferase (GGCT) contributes to the ?-glutamyl cycle that regulates glutathione metabolism. Although GGCT has been implicated in several studies as a possible cancer marker, little is known about its distribution in cells and tissues. The authors investigated GGCT expression in normal tissues and tumors using Western blots and immunohistochemistry with a novel anti-GGCT monoclonal antibody. GGCT was detected in most organs and was mainly found in epithelial cells. Although the intracellular distribution was mainly cytoplasmic, in some situations, nuclear staining was strong. A significant increase in the expression of GGCT was found in tumors of the lung, esophagus, stomach, bile duct, and uterine cervix. In contrast, there was a significant decrease in expression in renal and urothelial tumors. These results suggest that GGCT may be a biomarker of tumors in a limited range of organs.

SUBMITTER: Amano T

PROVIDER: S-EPMC3283131 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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Widespread expression of γ-glutamyl cyclotransferase suggests it is not a general tumor marker.

Amano Tomonari T Eishi Yoshinobu Y Yamada Tetsuo T Uchida Keisuke K Minegishi Kana K Tamura Tomoki T Kobayashi Daisuke D Hiroshi Kawachi K Suzuki Takashige T Board Philip G PG

The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society 20120101 1

γ-Glutamyl cyclotransferase (GGCT) contributes to the γ-glutamyl cycle that regulates glutathione metabolism. Although GGCT has been implicated in several studies as a possible cancer marker, little is known about its distribution in cells and tissues. The authors investigated GGCT expression in normal tissues and tumors using Western blots and immunohistochemistry with a novel anti-GGCT monoclonal antibody. GGCT was detected in most organs and was mainly found in epithelial cells. Although the ...[more]

PMID: 22205682

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Project description:The role of glutathione (GSH) in eukaryotic cells is well known. The biosynthesis of this γ-glutamine tripeptide is well studied. However, other γ-glutamyl peptides were found in various sources, and the pathways of their formation were not always clear. The aim of the present study was to determine whether Saccharomyces cerevisiae can produce γ-glutamyl tripeptides other than GSH and to identify the pathways associated with the formation of these peptides. The tripeptide γ-Glu-Val-Gly (γ-EVG) was used as a model. Wild-type yeast cells were shown to produce this peptide during cultivation in minimal synthetic medium. Two different biosynthetic pathways for this peptide were identified. The first pathway consisted of two steps. In the first step, γ-Glu-Val (γ-EV) was produced from glutamate and valine by the glutamate-cysteine ligase (GCL) Gsh1p or by the transfer of the γ-glutamyl group from GSH to valine by the γ-glutamyltransferase (GGT) Ecm38p or by the (Dug2p-Dug3p)2 complex. In the next step, γ-EV was combined with glycine by the glutathione synthetase (GS) Gsh2p. The second pathway consisted of transfer of the γ-glutamyl residue from GSH to the dipeptide Val-Gly (VG). This reaction was carried out mainly by the (Dug2p-Dug3p)2 complex, whereas the GGT Ecm38p did not participate in this reaction. The contribution of each of these two pathways to the intracellular pool of γ-EVG was dependent on cultivation conditions. In this work, we also found that Dug1p, previously identified as a Cys-Gly dipeptidase, played an essential role in the hydrolysis of the dipeptide VG in yeast cells. It was also demonstrated that γ-EV and γ-EVG could be effectively imported from the medium and that γ-EVG was imported by Opt1p, known to be a GSH importer. Our results demonstrated that γ-glutamyl peptides, particularly γ-EVG, are produced in yeast as products of several physiologically important reactions and are therefore natural components of yeast cells.

Project description:PurposeGamma-glutamyl transpeptidase (GGT) family genes play crucial roles in the formation and progression of several solid tumors. However, the expression patterns and the prognostic significance of GGT members in hepatocellular carcinoma (HCC) remain unknown. This study was designed to determine the expression profiles of GGT family members in HCC and validate the prognostic value of serum GGT protein in patients with HCC.MethodWe comprehensively searched public resources based on the LIHC dataset to determine the expression patterns, prognostic significance, DNA methylation status, immune infiltration, and biological pathways of GGT family genes in HCC. Subsequently, we validated the prognostic value of serum GGT protein in 85 patients with early-stage HCC subjected to curative hepatectomy from the Renmin Hospital of Wuhan University.ResultsExcept for GGT1, other GGT family members (GGT5, GGT6, and GGT7) were found to be differentially expressed in primary HCC samples (N = 371) and normal control tissues (N = 50). Furthermore, a positive relationship was not only observed between GGT1 and GGT5 (Spearman coefficient: 0.24, P = 5.143 × 10-6) but also between GGT5 and GGT6 (Spearman coefficient: 0.38, P = 1.24 × 10-13). The expression of GGT1, GGT5, and GGT7 was correlated with overall survival (OS), and GGT7 was associated with disease-free survival (DFS) in patients with HCC. Negative associations between DNA methylation and expression of mRNA were observed for GGT1 (Spearman coefficient: -0.38, P = 6.24e-14), GGT6 (Spearman coefficient: -0.29, P = 1.23e-8), and GGT7 (Spearman coefficient: -0.34, P=6.7e-11). GGT family genes were well correlated with the infiltration levels of immune cells in HCC, especially CD4+ T cells, macrophages, and dendritic cells. Finally, when validated with clinical data from the Renmin cohort, a high expression of serum GGT protein was identified as a strong prognostic element of unfavorable OS (HR = 3.114, P = 0.025), but not of DFS (HR = 1.198, P = 0.05) in patients with HCC subjected to curative hepatectomy.ConclusionTo our knowledge, this is the first comprehensive analysis of the expression patterns and clinical value of GGT family genes in patients with HCC. Our study laid the foundation for the clinical application of the GGT protein in the survival assessment of patients with HCC.

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Widespread expression of ?-glutamyl cyclotransferase suggests it is not a general tumor marker.

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Widespread expression of γ-glutamyl cyclotransferase suggests it is not a general tumor marker.

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