Gene Summary

Gene:GNMT; glycine N-methyltransferase
Summary:The protein encoded by this gene is an enzyme that catalyzes the conversion of S-adenosyl-L-methionine (along with glycine) to S-adenosyl-L-homocysteine and sarcosine. The encoded protein is found in the cytoplasm and acts as a homotetramer. Defects in this gene are a cause of GNMT deficiency (hypermethioninemia). [provided by RefSeq, Oct 2008]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:glycine N-methyltransferase
Source:NCBIAccessed: 11 August, 2015


What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 11 August 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Gene Expression
  • Histones
  • Chromosome 6
  • Cancer Gene Expression Regulation
  • Genotype
  • Transfection
  • Prostate Cancer
  • Sarcosine Oxidase
  • Genetic Predisposition
  • Methionine Adenosyltransferase
  • CpG Islands
  • Liver Cancer
  • Neoplastic Cell Transformation
  • Cell Proliferation
  • Uracil
  • Methyltransferases
  • Cancer DNA
  • Promoter Regions
  • ras Proteins
  • Neoplasm Proteins
  • Cell Nucleus
  • DNA Methylation
  • Knockout Mice
  • S-Adenosylmethionine
  • Hepatocellular Carcinoma
  • Enzymologic Gene Expression Regulation
  • Tumor Suppressor Proteins
  • Liver
  • alpha-Thalassemia
  • Wnt Proteins
  • Base Sequence
  • Glycine N-Methyltransferase
  • Polymerase Chain Reaction
  • Tissue Distribution
  • Recurrence
  • Tumor Markers
  • alpha 1-Antichymotrypsin
  • Messenger RNA
  • Signal Transduction
  • Immunohistochemistry
Tag cloud generated 11 August, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (2)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: GNMT (cancer-related)

Gao L, van den Hurk K, Moerkerk PT, et al.
Promoter CpG island hypermethylation in dysplastic nevus and melanoma: CLDN11 as an epigenetic biomarker for malignancy.
J Invest Dermatol. 2014; 134(12):2957-66 [PubMed] Related Publications
Dysplastic nevi are melanocytic lesions that represent an intermediate stage between common nevus and melanoma. Histopathological distinction of dysplastic nevus from melanoma can be challenging and there is a requirement for molecular diagnostic markers. In this study, we examined promoter CpG island methylation of a selected panel of genes, identified in a genome-wide methylation screen, across a spectrum of 405 melanocytic neoplasms. Promoter methylation analysis in common nevi, dysplastic nevi, primary melanomas, and metastatic melanomas demonstrated progressive epigenetic deregulation. Dysplastic nevi were affected by promoter methylation of genes that are frequently methylated in melanoma but not in common nevi. We assessed the diagnostic value of the methylation status of five genes in distinguishing primary melanoma from dysplastic nevus. In particular, CLDN11 promoter methylation was specific for melanoma, as it occurred in 50% of primary melanomas but in only 3% of dysplastic nevi. A diagnostic algorithm that incorporates methylation of the CLDN11, CDH11, PPP1R3C, MAPK13, and GNMT genes was validated in an independent sample set and helped distinguish melanoma from dysplastic nevus (area under the curve 0.81). Melanoma-specific methylation of these genes supports the utility as epigenetic biomarkers and could point to their significance in melanoma development.

Ottaviani S, Brooke GN, O'Hanlon-Brown C, et al.
Characterisation of the androgen regulation of glycine N-methyltransferase in prostate cancer cells.
J Mol Endocrinol. 2013; 51(3):301-12 [PubMed] Free Access to Full Article Related Publications
The development and growth of prostate cancer is dependent on androgens; thus, the identification of androgen-regulated genes in prostate cancer cells is vital for defining the mechanisms of prostate cancer development and progression and developing new markers and targets for prostate cancer treatment. Glycine N-methyltransferase (GNMT) is a S-adenosylmethionine-dependent methyltransferase that has been recently identified as a novel androgen-regulated gene in prostate cancer cells. Although the importance of this protein in prostate cancer progression has been extensively addressed, little is known about the mechanism of its androgen regulation. Here, we show that GNMT expression is stimulated by androgen in androgen receptor (AR) expressing cells and that the stimulation occurs at the mRNA and protein levels. We have identified an androgen response element within the first exon of the GNMT gene and demonstrated that AR binds to this element in vitro and in vivo. Together, these studies identify GNMT as a direct transcriptional target of the AR. As this is an evolutionarily conserved regulatory element, this highlights androgen regulation as an important feature of GNMT regulation.

Lee CM, Yen CH, Tzeng TY, et al.
Androgen response element of the glycine N-methyltransferase gene is located in the coding region of its first exon.
Biosci Rep. 2013; 33(5) [PubMed] Free Access to Full Article Related Publications
Androgen plays an important role in the pathogenesis of PCa (prostate cancer). Previously, we identified GNMT (glycine N-methyltransferase) as a tumour susceptibility gene and characterized its promoter region. Besides, its enzymatic product-sarcosine has been recognized as a marker for prognosis of PCa. The goals of this study were to determine whether GNMT is regulated by androgen and to map its AREs (androgen response elements). Real-time PCR analyses showed that R1881, a synthetic AR (androgen receptor) agonist induced GNMT expression in AR-positive LNCaP cells, but not in AR-negative DU145 cells. In silico prediction showed that there are four putative AREs in GNMT-ARE1, ARE2 and ARE3 are located in the intron 1 and ARE4 is in the intron 2. Consensus ARE motif deduced from published AREs was used to identify the fifth ARE-ARE5 in the coding region of exon 1. Luciferase reporter assay found that only ARE5 mediated the transcriptional activation of R1881. ARE3 overlaps with a YY1 [Yin and Yang 1 (motif (CaCCATGTT, +1118/+1126)] that was further confirmed by antibody supershift and ChIP (chromatin immunoprecipitation) assays. EMSA (electrophoretic mobility shift assay) and ChIP assay confirmed that AR interacts with ARE5 in vitro and in vivo. In summary, GNMT is an AR-targeted gene with its functional ARE located at +19/+33 of the first exon. These results are valuable for the study of the influence of androgen on the gene expression of GNMT especially in the pathogenesis of cancer.

Lin IY, Yen CH, Liao YJ, et al.
Identification of FKBP11 as a biomarker for hepatocellular carcinoma.
Anticancer Res. 2013; 33(6):2763-9 [PubMed] Related Publications
BACKGROUND: Glycine N-methyltransferase (GNMT) is a tumor suppressor of hepatocellular carcinoma (HCC). High proportions of GNMT knockout mice developed HCC. We previously identified a potential novel marker from Gnmt knockout mice, FK506 binding protein 11 (FKBP11). Here, we determined the clinical usefulness of FKBP11.
PATIENTS AND METHODS: FKBP11 expression levels were analyzed in 123 paired tumor and tumor-adjacent non-tumorous (TA) tissue samples from patients with HCC and in 29 benign liver samples from patients with hemangioma using quantitative real-time polymerase-chain-reaction.
RESULTS: FKBP11 was expressed at a higher level in tumor tissues compared to TA tissues (p<0.01). Moreover, we observed a significantly higher level of FKBP11 in TA tissues than in benign liver samples (p<0.01). Interestingly, expression of FKBP11 was higher in hepatitis viral-infected TA and benign tissues than in samples without viral etiology (p<0.05).
CONCLUSION: These results suggest a progressively elevated expression of FKBP11 during the development of HCC and FKBP11 has the potential to be an early marker for HCC.

Frau M, Feo F, Pascale RM
Pleiotropic effects of methionine adenosyltransferases deregulation as determinants of liver cancer progression and prognosis.
J Hepatol. 2013; 59(4):830-41 [PubMed] Related Publications
Downregulation of liver-specific MAT1A gene, encoding S-adenosylmethionine (SAM) synthesizing isozymes MATI/III, and upregulation of widely expressed MAT2A, encoding MATII isozyme, known as MAT1A:MAT2A switch, occurs in hepatocellular carcinoma (HCC). Being inhibited by its reaction product, MATII isoform upregulation cannot compensate for MATI/III decrease. Therefore, MAT1A:MAT2A switch contributes to decrease in SAM level in rodent and human hepatocarcinogenesis. SAM administration to carcinogen-treated rats prevents hepatocarcinogenesis, whereas MAT1A-KO mice, characterized by chronic SAM deficiency, exhibit macrovesicular steatosis, mononuclear cell infiltration in periportal areas, and HCC development. This review focuses upon the pleiotropic changes, induced by MAT1A/MAT2A switch, associated with HCC development. Epigenetic control of MATs expression occurs at transcriptional and post-transcriptional levels. In HCC cells, MAT1A/MAT2A switch is associated with global DNA hypomethylation, decrease in DNA repair, genomic instability, and signaling deregulation including c-MYC overexpression, rise in polyamine synthesis, upregulation of RAS/ERK, IKK/NF-kB, PI3K/AKT, and LKB1/AMPK axis. Furthermore, decrease in MAT1A expression and SAM levels results in increased HCC cell proliferation, cell survival, and microvascularization. All of these changes are reversed by SAM treatment in vivo or forced MAT1A overexpression or MAT2A inhibition in cultured HCC cells. In human HCC, MAT1A:MAT2A and MATI/III:MATII ratios correlate negatively with cell proliferation and genomic instability, and positively with apoptosis and global DNA methylation. This suggests that SAM decrease and MATs deregulation represent potential therapeutic targets for HCC. Finally, MATI/III:MATII ratio strongly predicts patients' survival length suggesting that MAT1A:MAT2A expression ratio is a putative prognostic marker for human HCC.

Khan AP, Rajendiran TM, Ateeq B, et al.
The role of sarcosine metabolism in prostate cancer progression.
Neoplasia. 2013; 15(5):491-501 [PubMed] Free Access to Full Article Related Publications
Metabolomic profiling of prostate cancer (PCa) progression identified markedly elevated levels of sarcosine (N-methyl glycine) in metastatic PCa and modest but significant elevation of the metabolite in PCa urine. Here, we examine the role of key enzymes associated with sarcosine metabolism in PCa progression. Consistent with our earlier report, sarcosine levels were significantly elevated in PCa urine sediments compared to controls, with a modest area under the receiver operating characteristic curve of 0.71. In addition, the expression of sarcosine biosynthetic enzyme, glycine N-methyltransferase (GNMT), was elevated in PCa tissues, while sarcosine dehydrogenase (SARDH) and pipecolic acid oxidase (PIPOX), which metabolize sarcosine, were reduced in prostate tumors. Consistent with this, GNMT promoted the oncogenic potential of prostate cells by facilitating sarcosine production, while SARDH and PIPOX reduced the oncogenic potential of prostate cells by metabolizing sarcosine. Accordingly, addition of sarcosine, but not glycine or alanine, induced invasion and intravasation in an in vivo PCa model. In contrast, GNMT knockdown or SARDH overexpression in PCa xenografts inhibited tumor growth. Taken together, these studies substantiate the role of sarcosine in PCa progression.

Huidobro C, Toraño EG, Fernández AF, et al.
A DNA methylation signature associated with the epigenetic repression of glycine N-methyltransferase in human hepatocellular carcinoma.
J Mol Med (Berl). 2013; 91(8):939-50 [PubMed] Related Publications
The basic mechanisms underlying promoter DNA hypermethylation in cancer are still largely unknown. It has been proposed that the levels of the methyl donor group in DNA methylation reactions, S-adenosylmethionine (SAMe), might be involved. SAMe levels depend on the glycine-N-methyltransferase (GNMT), a one-carbon group methyltransferase, which catalyzes the conversion of SAMe to S-adenosylhomocysteine in hepatic cells. GNMT has been proposed to display tumor suppressor activity and to be frequently repressed in hepatocellular carcinoma (HCC). In this study, we show that GNMT shows aberrant DNA hypermethylation in some HCC cell lines and primary tumors (20 %). GNMT hypermethylation could contribute to gene repression and its restoration in cell lines displaying hypermethylation-reduced tumor growth in vitro. In agreement, human primary tumors expressing GNMT were of smaller size than tumors showing GNMT hypermethylation. Genome-wide analyses of gene promoter methylation identified 277 genes whose aberrant methylation in HCC was associated with GNMT methylation/expression. The findings in this manuscript indicate that DNA hypermethylation plays an important role in the repression of GNMT in HCC and that loss of GNMT in human HCC could promote the establishment of aberrant DNA methylation patterns at specific gene promoters.

Huidobro C, Fernandez AF, Fraga MF
The role of genetics in the establishment and maintenance of the epigenome.
Cell Mol Life Sci. 2013; 70(9):1543-73 [PubMed] Related Publications
Epigenetic mechanisms play an important role in gene regulation during development. DNA methylation, which is probably the most important and best-studied epigenetic mechanism, can be abnormally regulated in common pathologies, but the origin of altered DNA methylation remains unknown. Recent research suggests that these epigenetic alterations could depend, at least in part, on genetic mutations or polymorphisms in DNA methyltransferases and certain genes encoding enzymes of the one-carbon metabolism pathway. Indeed, the de novo methyltransferase 3B (DNMT3B) has been recently found to be mutated in several types of cancer and in the immunodeficiency, centromeric region instability and facial anomalies syndrome (ICF), in which these mutations could be related to the loss of global DNA methylation. In addition, mutations in glycine-N-methyltransferase (GNMT) could be associated with a higher risk of hepatocellular carcinoma and liver disease due to an unbalanced S-adenosylmethionine (SAM)/S-adenosylhomocysteine (SAH) ratio, which leads to aberrant methylation reactions. Also, genetic variants of chromatin remodeling proteins and histone tail modifiers are involved in genetic disorders like α thalassemia X-linked mental retardation syndrome, CHARGE syndrome, Cockayne syndrome, Rett syndrome, systemic lupus erythematous, Rubinstein-Taybi syndrome, Coffin-Lowry syndrome, Sotos syndrome, and facioescapulohumeral syndrome, among others. Here, we review the potential genetic alterations with a possible role on epigenetic factors and discuss their contribution to human disease.

Lu SC, Mato JM
S-adenosylmethionine in liver health, injury, and cancer.
Physiol Rev. 2012; 92(4):1515-42 [PubMed] Free Access to Full Article Related Publications
S-adenosylmethionine (AdoMet, also known as SAM and SAMe) is the principal biological methyl donor synthesized in all mammalian cells but most abundantly in the liver. Biosynthesis of AdoMet requires the enzyme methionine adenosyltransferase (MAT). In mammals, two genes, MAT1A that is largely expressed by normal liver and MAT2A that is expressed by all extrahepatic tissues, encode MAT. Patients with chronic liver disease have reduced MAT activity and AdoMet levels. Mice lacking Mat1a have reduced hepatic AdoMet levels and develop oxidative stress, steatohepatitis, and hepatocellular carcinoma (HCC). In these mice, several signaling pathways are abnormal that can contribute to HCC formation. However, injury and HCC also occur if hepatic AdoMet level is excessive chronically. This can result from inactive mutation of the enzyme glycine N-methyltransferase (GNMT). Children with GNMT mutation have elevated liver transaminases, and Gnmt knockout mice develop liver injury, fibrosis, and HCC. Thus a normal hepatic AdoMet level is necessary to maintain liver health and prevent injury and HCC. AdoMet is effective in cholestasis of pregnancy, and its role in other human liver diseases remains to be better defined. In experimental models, it is effective as a chemopreventive agent in HCC and perhaps other forms of cancer as well.

Ianni M, Porcellini E, Carbone I, et al.
Genetic factors regulating inflammation and DNA methylation associated with prostate cancer.
Prostate Cancer Prostatic Dis. 2013; 16(1):56-61 [PubMed] Related Publications
BACKGROUND: Prostate cancer (PCa) displays a strong familiarity component and genetic factors; genes regulating inflammation may have a pivotal role in the disease. Epigenetic changes control chromosomal integrity, gene functions and ultimately carcinogenesis. The enzyme glycine-N-methyltransferase (GNMT) contributes to S-adenosylmethionine level regulation and, by affecting DNA methylation, influences gene expression. The genotype and allele distribution of single-nucleotide polymorphisms (SNPs) in the promoter regions of vascular endothelial growth factor (VEGF), interleukin (IL)-10, IL-1β, alpha-1-antichymotrypsin (ACT) and GNMT genes, the level of global DNA methylation and the influence of GNMT SNP upon DNA methylation in a PCa case-control study have been investigated.
METHODS: SNPs of VEGF (rs699947), ACT (rs1884082), IL-1β (rs16944), IL-10 (rs1800896) and GNMT (rs9462856) genes were assessed by PCR or by real-time PCR methods. DNA methylation was assessed by an ELISA assay.
RESULTS: Frequencies of the VEGF AA genotype, the IL-10 A allele and GNMT T allele were higher in PCa. The concomitant presence of the AA genotype of VEGF, the A allele of IL-10 and T allele of GNMT increased the risk of PCa. Total DNA methylation was decreased in PCa; control GNMT T carriers (T+) showed the highest level of DNA methylation.
CONCLUSIONS: SNPs in VEGF, IL-10 and GNMT genes might have a synergistic role in the development of PCa. The GNMT T allele may influence PCa risk by affecting DNA methylation and prostate gene expression. Our observations might help implement the screening of unaffected subjects with an increased susceptibility to develop PCa.

Frau M, Simile MM, Tomasi ML, et al.
An expression signature of phenotypic resistance to hepatocellular carcinoma identified by cross-species gene expression analysis.
Cell Oncol (Dordr). 2012; 35(3):163-73 [PubMed] Free Access to Full Article Related Publications
BACKGROUND AND AIMS: Hepatocarcinogenesis is under polygenic control. We analyzed gene expression patterns of dysplastic liver nodules (DNs) and hepatocellular carcinomas (HCCs) chemically-induced in F344 and BN rats, respectively susceptible and resistant to hepatocarcinogenesis.
METHODS: Expression profiles were performed by microarray and validated by quantitative RT-PCR and Western blot.
RESULTS: Cluster analysis revealed two distinctive gene expression patterns, the first of which included normal liver of both strains and BN nodules, and the second one F344 nodules and HCC of both strains. We identified a signature predicting DN and HCC progression, characterized by highest expression of oncosuppressors Csmd1, Dmbt1, Dusp1, and Gnmt, in DNs, and Bhmt, Dmbt1, Dusp1, Gadd45g, Gnmt, Napsa, Pp2ca, and Ptpn13 in HCCs of resistant rats. Integrated gene expression data revealed highest expression of proliferation-related CTGF, c-MYC, and PCNA, and lowest expression of BHMT, DMBT1, DUSP1, GADD45g, and GNMT, in more aggressive rat and human HCC. BHMT, DUSP1, and GADD45g expression predicted patients' survival.
CONCLUSIONS: Our results disclose, for the first time, a major role of oncosuppressor genes as effectors of genetic resistance to hepatocarcinogenesis. Comparative functional genomic analysis allowed discovering an evolutionarily conserved gene expression signature discriminating HCC with different propensity to progression in rat and human.

Balassiano K, Lima S, Jenab M, et al.
Aberrant DNA methylation of cancer-associated genes in gastric cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC-EURGAST).
Cancer Lett. 2011; 311(1):85-95 [PubMed] Related Publications
Epigenetic events have emerged as key mechanisms in the regulation of critical biological processes and in the development of a wide variety of human malignancies, including gastric cancer (GC), however precise gene targets of aberrant DNA methylation in GC remain largely unknown. Here, we have combined pyrosequencing-based quantitative analysis of DNA methylation in 98 GC cases and 64 controls nested within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort and in cancer tissue and non-tumorigenic adjacent tissue of an independent series of GC samples. A panel of 10 cancer-associated genes (CHRNA3, DOK1, MGMT, RASSF1A, p14ARF, CDH1, MLH1, ALDH2, GNMT and MTHFR) and LINE-1 repetitive elements were included in the analysis and their association with clinicopathological characteristics (sex, age at diagnosis, anatomical sub-site, histological sub-type) was examined. Three out of the 10 genes analyzed exhibited a marked hypermethylation, whereas two genes (ALDH2 and MTHFR) showed significant hypomethylation, in gastric tumors. Among differentially methylated genes, we identified new genes (CHRNA3 and DOK1) as targets of aberrant hypermethylation in GC, suggesting that epigenetic deregulation of these genes and their corresponding cellular pathways may promote the development and progression of GC. We also found that global demethylation of tumor cell genomes occurs in GC, consistent with the notion that abnormal hypermethylation of specific genes occurs concomitantly with genome-wide hypomethylation. Age and gender had no significant influence on methylation states, but an association was observed between LINE-1 and MLH1 methylation levels with histological sub-type and anatomical sub-site. This study identifies aberrant methylation patters in specific genes in GC thus providing information that could be exploited as novel biomarkers in clinics and molecular epidemiology of GC.

Wilop S, Fernandez AF, Jost E, et al.
Array-based DNA methylation profiling in acute myeloid leukaemia.
Br J Haematol. 2011; 155(1):65-72 [PubMed] Related Publications
Methylation in the promoter region of many genes is involved in regulating gene expression patterns. Using the Illumina GoldenGate© methylation assay, we examined the methylation status of 1505 CpG-sites from 807 genes in 32 samples from patients with acute myeloid leukaemia (AML) at diagnosis, nine at relapse and 15 normal controls and performed additional pyrosequencing and semiquantitative methylation specific polymerase chain reaction (MSP) of the GNMT promoter in 113 diagnostic AML samples. We found a gain of overall methylation in AML samples with a further increase at relapse. Regional hypermethylation as assessed by array analysis could be confirmed by both MSP and pyrosequencing. Additionally, large-scale methylation analysis identified interesting candidate genes. Cluster analysis indicated that cytogenetic subgroups seemed to be characterized by additional distinct epigenetic modifications and that basic DNA methylation patterns remain at relapse. Therefore, promoter hypermethylation is a frequent event in AML and is accentuated at relapse. Array-based methylation analysis determined distinct methylation profiles for non-malignant controls and AML samples with specific chromosomal aberrations and can identify target genes for further evaluation.

Song YH, Shiota M, Kuroiwa K, et al.
The important role of glycine N-methyltransferase in the carcinogenesis and progression of prostate cancer.
Mod Pathol. 2011; 24(9):1272-80 [PubMed] Related Publications
Glycine N-methyltransferase (GNMT) has a role in the metabolism of methionine as well as in gluconeogenesis. It has recently been reported that the GNMT gene acts as a tumor-susceptible gene. However, little is known about the specific function of GNMT in carcinogenesis and malignant progression. To better our understanding of the function of GNMT in prostate cancer, we used siRNAs to examine the effects of GNMT knockdown on cell proliferation and the cell cycle. In addition, the relation between immunohistochemical GNMT expression and clinicopathologic parameters was investigated in 148 prostate cancer tissues. Here, we show that siRNA-mediated GNMT knockdown results in an inhibition of proliferation, and induces G1 arrest and apoptosis in prostate cancer cell lines. Moreover, high cytoplasmic GNMT expression was also correlated with a higher Gleason score (P<0.001) and higher pT stage (P=0.027). The patients with high GNMT cytoplasmic expression showed significantly lower disease-free survival rates than patients with low expression (P<0.001). High GNMT cytoplasmic expression had a significant impact on patient disease-free survival in multivariate analysis (P=0.005). This is the first investigation to reveal the novel finding that GNMT may have an important role in promoting prostate cancer cell growth via the regulation of apoptosis and contribute to the progression of prostate cancer. The modulation of GNMT expression or function may be a strategy for developing novel therapeutics for prostate cancer. GNMT may represent a novel marker of malignant progression and poor prognosis in prostate cancer.

Wang YC, Tang FY, Chen SY, et al.
Glycine-N methyltransferase expression in HepG2 cells is involved in methyl group homeostasis by regulating transmethylation kinetics and DNA methylation.
J Nutr. 2011; 141(5):777-82 [PubMed] Related Publications
Glycine-N methyltransferase (GNMT) is a potential tumor suppressor that is commonly inactivated in human hepatoma. We systematically investigated how GNMT regulates methyl group kinetics and global DNA methylation. HepG2 cells (GNMT inactive, GNMT-) and cells transfected with GNMT expressed vector (GNMT+) were cultured in low (10 μmol/L), adequate (100 μmol/L), or high (500 μmol/L) l-methionine, each with 2.27 μmol/L folate. Transmethylation kinetics were studied using stable isotopic tracers and GC-MS. Methylation status was determined by S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) levels, SAM:SAH ratio, DNA methyltransferase (DNMT) activity, and methylated cytidine levels in DNA. Compared with GNMT- cells, GNMT+ cells had lower homocysteine and greater cysteine concentrations. GNMT expression increased methionine clearance by inducing homocysteine transsulfuration and remethylation metabolic fluxes when cells were cultured in high or adequate l-methionine. In contrast, homocysteine remethylation flux was lower in GNMT+ cells than in GNMT- cells and homocysteine transsulfuration fluxes did not differ when cells were cultured in low methionine, suggesting that normal GNMT function helps to conserve methyl groups. Furthermore, GNMT expression decreased SAM and increased SAH levels and reduced DNMT activity in high or adequate, but not low, methionine cultures. In low methionine cultures, restoring GNMT in HepG2 cells did not lead to sarcosine synthesis, which would waste methyl groups. Methylated cytidine levels were significantly lower in GNMT- cells than in GNMT+ cells. In conclusion, we have shown that GNMT affects transmethylation kinetics and SAM synthesis and facilitates the conservation of methyl groups by limiting homocysteine remethylation fluxes.

Vázquez-Chantada M, Fernández-Ramos D, Embade N, et al.
HuR/methyl-HuR and AUF1 regulate the MAT expressed during liver proliferation, differentiation, and carcinogenesis.
Gastroenterology. 2010; 138(5):1943-53 [PubMed] Free Access to Full Article Related Publications
BACKGROUND & AIMS: Hepatic de-differentiation, liver development, and malignant transformation are processes in which the levels of hepatic S-adenosylmethionine are tightly regulated by 2 genes: methionine adenosyltransferase 1A (MAT1A) and methionine adenosyltransferase 2A (MAT2A). MAT1A is expressed in the adult liver, whereas MAT2A expression primarily is extrahepatic and is associated strongly with liver proliferation. The mechanisms that regulate these expression patterns are not completely understood.
METHODS: In silico analysis of the 3' untranslated region of MAT1A and MAT2A revealed putative binding sites for the RNA-binding proteins AU-rich RNA binding factor 1 (AUF1) and HuR, respectively. We investigated the posttranscriptional regulation of MAT1A and MAT2A by AUF1, HuR, and methyl-HuR in the aforementioned biological processes.
RESULTS: During hepatic de-differentiation, the switch between MAT1A and MAT2A coincided with an increase in HuR and AUF1 expression. S-adenosylmethionine treatment altered this homeostasis by shifting the balance of AUF1 and methyl-HuR/HuR, which was identified as an inhibitor of MAT2A messenger RNA (mRNA) stability. We also observed a similar temporal distribution and a functional link between HuR, methyl-HuR, AUF1, and MAT1A and MAT2A during fetal liver development. Immunofluorescent analysis revealed increased levels of HuR and AUF1, and a decrease in methyl-HuR levels in human livers with hepatocellular carcinoma (HCC).
CONCLUSIONS: Our data strongly support a role for AUF1 and HuR/methyl-HuR in liver de-differentiation, development, and human HCC progression through the posttranslational regulation of MAT1A and MAT2A mRNAs.

Liao YJ, Liu SP, Lee CM, et al.
Characterization of a glycine N-methyltransferase gene knockout mouse model for hepatocellular carcinoma: Implications of the gender disparity in liver cancer susceptibility.
Int J Cancer. 2009; 124(4):816-26 [PubMed] Related Publications
Hepatocellular carcinoma (HCC) is the fifth common cancer in the world and it mainly occurs in men. Glycine N-methyltransferase (GNMT) participates in one-carbon metabolism and affects DNA methylation by regulating the ratio of S-adenosylmethionine to S-adenosylhomocystine. Previously, we described that the expression of GNMT was diminished in human HCC. Here, we showed that 50% (3/6) male and 100% (7/7) female Gnmt-/- mice developed HCC, and their mean ages of HCC development were 17 and 16.5 months, respectively. In addition, 42.9% (3/7) of female Gnmt-/- mice had hemangioma. Wnt reporter assay demonstrated that Gnmt is a negative regulator for canonical Wnt signaling pathway. Beta-catenin, cyclin D1 and c-Myc, genes related to Wnt pathway, were upregulated in the liver tissues from both 11 weeks and HCC stage of Gnmt-/- mice. Furthermore, global DNA hypomethylation and aberrant expression of DNA methyltransferases 1 and 3b were found in the early and late stages of HCC development. Hierarchical cluster analysis of 6,023 transcripts from microarray data found that gene expression patterns of HCC tumors from male and female Gnmt-/- mice were distinctively different. Real-time PCR confirmed that Gadd45a, Pak1, Mapk3 and Dsup3 genes of mitogen-activated protein kinase (MAPK) pathway were activated in Gnmt-/- mice, especially in the female mice. Therefore, GNMT is a tumor suppressor gene for liver cancer, and it is associated with gender disparity in liver cancer susceptibility.

Huang YC, Chen M, Shyr YM, et al.
Glycine N-methyltransferase is a favorable prognostic marker for human cholangiocarcinoma.
J Gastroenterol Hepatol. 2008; 23(9):1384-9 [PubMed] Related Publications
BACKGROUND AND AIM: Glycine N-methyltransferase (GNMT) is a susceptibility gene for human hepatocellular carcinoma (HCC). We previously reported that GNMT expression is diminished in HCC. Here we report our examination of GNMT expression patterns in cholangiocarcinoma and the relationship between its expression and prognosis.
METHODS: We analyzed GNMT expression in tumor tissues from 33 cholangiocarcinoma patients (19 male) using immunohistochemistry (IHC) procedures with a GNMT monoclonal antibody (mAb 4-17). GNMT expression intensity and percentages were scored on a scale of 0 to 6. The association between GNMT expression and survival was analyzed using the Kaplan-Meier method, and prognostic factors were evaluated with a multivariate Cox proportional hazards regression model.
RESULTS: High GNMT expression was found in epithelial cells of normal bile ducts. Six of 33 (18.2%) cholangiocarcinoma tissues had no GNMT expression. A statistically significant difference was noted in GNMT expression between male and female patients (68.4% vs 100%, P < 0.05). Compared to patients with GNMT expression scores > 3, the death hazard ratio for patients with GNMT scores CONCLUSIONS: GNMT expression is a favorable prognosis predictor for cholangiocarcinoma.

Huang YC, Lee CM, Chen M, et al.
Haplotypes, loss of heterozygosity, and expression levels of glycine N-methyltransferase in prostate cancer.
Clin Cancer Res. 2007; 13(5):1412-20 [PubMed] Related Publications
PURPOSE: Glycine N-methyltransferase (GNMT) affects genetic stability by regulating DNA methylation and interacting with environmental carcinogens. In a previous study, we showed that GNMT acts as a susceptibility gene for hepatocellular carcinoma. Here, we report on our efforts to characterize the haplotypes, loss of heterozygosity (LOH), and expression levels of the GNMT in prostate cancer.
EXPERIMENTAL DESIGN: Peripheral blood mononuclear cell DNA collected from 326 prostate cancer patients and 327 age-matched controls was used to determine GNMT haplotypes. Luciferase reporter constructs were used to compare the promoter activity of different GNMT haplotypes. GNMT LOH rates in tumorous specimens were investigated via a comparison with peripheral blood mononuclear cell genotypes. Immunohistochemical staining was used to analyze GNMT expression in tissue specimens collected from 5 normal individuals, 33 benign prostatic hyperplasia patients, and 45 prostate cancer patients.
RESULTS: Three major GNMT haplotypes were identified in 92% of the participants: A, 16GAs/DEL/C (58%); B, 10GAs/INS/C (19.9%); and C, 10GAs/INS/T (14.5%). Haplotype C carriers had significantly lower risk for prostate cancer compared with individuals with haplotype A (odds ratio, 0.68; 95% confidence interval, 0.48-0.95). Results from a phenotypic analysis showed that haplotype C exhibited the highest promoter activity (P < 0.05, ANOVA test). In addition, 36.4% (8 of 22) of the prostatic tumor tissues had LOH of the GNMT gene. Immunohistochemical staining results showed abundant GNMT expression in normal prostatic and benign prostatic hyperplasia tissues, whereas it was diminished in 82.2% (37 of 45) of the prostate cancer tissues.
CONCLUSIONS: Our findings suggest that GNMT is a tumor susceptibility gene for prostate cancer.

Chen SY, Lin JR, Darbha R, et al.
Glycine N-methyltransferase tumor susceptibility gene in the benzo(a)pyrene-detoxification pathway.
Cancer Res. 2004; 64(10):3617-23 [PubMed] Related Publications
Glycine N-methyltransferase (GNMT) affects genetic stability by (a) regulating the ratio of S-adenosylmethionine to S-adenosylhomocystine and (b) binding to folate. Based on the identification of GNMT as a 4 S polyaromatic hydrocarbon-binding protein, we used liver cancer cell lines that expressed GNMT either transiently or stably in cDNA transfections to analyze the role of GNMT in the benzo(a)pyrene (BaP) detoxification pathway. Results from an indirect immunofluorescent antibody assay showed that GNMT was expressed in cell cytoplasm before BaP treatment and translocated to cell nuclei after BaP treatment. Compared with cells transfected with the vector plasmid, the number of BaP-7,8-diol 9,10-epoxide-DNA adducts that formed in GNMT-expressing cells was significantly reduced. Furthermore, the dose-dependent inhibition of BaP-7,8-diol 9,10-epoxide-DNA adduct formation by GNMT was observed in HepG2 cells infected with different multiplicities of infection of recombinant adenoviruses carrying GNMT cDNA. According to an aryl hydrocarbon hydroxylase enzyme activity assay, GNMT inhibited BaP-induced cytochrome P450 1A1 enzyme activity. Automated BaP docking using a Lamarckian genetic algorithm with GNMT X-ray crystallography revealed a BaP preference for the S-adenosylmethionine-binding domain of the dimeric form of GNMT, a novel finding of a cellular defense against potentially damaging exposures. In addition to GNMT, results from docking experiments showed that BaP binds readily with other DNA methyltransferases, including HhaI, HaeIII, PvuII methyltransferases and human DNA methyltransferase 2. We therefore hypothesized that BaP-DNA methyltransferase and BaP-GNMT interactions may contribute to carcinogenesis.

Liu HH, Chen KH, Shih YP, et al.
Characterization of reduced expression of glycine N-methyltransferase in cancerous hepatic tissues using two newly developed monoclonal antibodies.
J Biomed Sci. 2003 Jan-Feb; 10(1):87-97 [PubMed] Related Publications
Glycine N-methyltransferase (GNMT) is a protein with multiple functions. Recently, two Italian siblings who had hepatomegaly and chronic elevation of serum transaminases were diagnosed to have GNMT deficiency caused by inherited compound heterozygosity of the GNMT gene with missence mutations. To evaluate the expression of GNMT in cell lines and tissues from hepatocellular carcinoma (HCC) patients, we produced two monoclonal antibodies (mAbs) 4-17 and 14-1 using two recombinant GNMT fusion proteins. M13 phage peptide display showed that the reactive epitopes of mAbs 4-17 and 14-1 were amino acid residues 11-15 and 272-276 of human GNMT, respectively. The dissociation constants of the binding between GNMT and mAbs were 1.7 x 10(-8) M for mAb 4-17 and 1.8 x 10(-9) M for mAb 14-1. Both mAbs can identify GNMT present in normal human and mouse liver tissues using Western blotting (WB) and immunohistochemical staining assay (IHC). In addition, WB with both mAbs showed that none of 2 hepatoblastoma and 5 HCC cell lines expressed GNMT. IHC demonstrated that 50% (13/26) of nontumorous liver tissues and 96% (24/25) of HCC tissues did not express GNMT. Therefore, the expression of GNMT was downregulated in human HCC.

Tseng TL, Shih YP, Huang YC, et al.
Genotypic and phenotypic characterization of a putative tumor susceptibility gene, GNMT, in liver cancer.
Cancer Res. 2003; 63(3):647-54 [PubMed] Related Publications
Glycine N-methyltransferase (GNMT), a multifunctional protein involved in the maintenance of the genetic stability, is often down-regulated in hepatocellular carcinoma (HCC). Using genotypic characterization of GNMT in hepatoma cell lines and in a Taiwanese population with a high incidence of liver cancer we have investigated the role of this gene in the progression of liver cancer. Six novel polymorphisms, including two short tandem repeats, one 4-nucleotide insertion/deletion polymorphism, and three single nucleotide polymorphisms, in GNMT were identified in this study. The rates of loss of heterozygosity at the GNMT locus in pairs of normal and tumor tissue from the HCC patients were approximately 36-47%. In addition, the observed heterozygosity of GNMT decreases in tumor adjacent liver DNA from HCC patients compared with that observed in blood DNA from normal individuals and HCC patients. This may result from the early event of loss of heterozygosity within the GNMT gene in the liver tissues of HCC patients. However, in this study, we did not observe the association of polymorphic GNMT alleles as inherited risk factors for HCC. We also elucidated the functional impact of genetic markers in the GNMT promoter by performing luciferase reporter gene and gel mobility shift assays. The results indicate that two polymorphisms, short tandem repeat 1 and insertion/deletion polymorphism, in the promoter region could cause allelic specific effects on the transcriptional activity of GNMT. The risk genotypes of GNMT, which presumably have a lower expression level, as estimated from in vitro functional studies, are over-represented in tumor-adjacent tissues from HCC patients. In summary, our results suggest that GNMT alteration may be an early event in HCC development and that GNMT could be a new tumor susceptibility gene for HCC.

Avila MA, Berasain C, Torres L, et al.
Reduced mRNA abundance of the main enzymes involved in methionine metabolism in human liver cirrhosis and hepatocellular carcinoma.
J Hepatol. 2000; 33(6):907-14 [PubMed] Related Publications
BACKGROUND/AIMS: It has been known for at least 50 years that alterations in methionine metabolism occur in human liver cirrhosis. However, the molecular basis of this alteration is not completely understood. In order to gain more insight into the mechanisms behind this condition, mRNA levels of methionine adenosyltransferase (MAT1A), glycine methyltransferase (GNMT), methionine synthase (MS), betaine homocysteine methyltransferase (BHMT) and cystathionine beta-synthase (CBS) were examined in 26 cirrhotic livers, five hepatocellular carcinoma (HCC) tissues and ten control livers.
METHODS: The expression of the above-mentioned genes was determined by quantitative RT-PCR analysis. Methylation of MAT1A promoter was assessed by methylation-sensitive restriction enzyme digestion of genomic DNA.
RESULTS: When compared to normal livers MAT1A, GNMT, BHMT, CBS and MS mRNA contents were significantly reduced in liver cirrhosis. Interestingly, MAT1A promoter was hypermethylated in the cirrhotic liver. HCC tissues also showed decreased mRNA levels of these enzymes.
CONCLUSIONS: These findings establish that the abundance of the mRNA of the main genes involved in methionine metabolism is markedly reduced in human cirrhosis and HCC. Hypermethylation of MAT1A promoter could participate in its reduced expression in cirrhosis. These observations help to explain the hypermethioninemia, hyperhomocysteinemia and reduced hepatic glutathione content observed in cirrhosis.

Chen YM, Chen LY, Wong FH, et al.
Genomic structure, expression, and chromosomal localization of the human glycine N-methyltransferase gene.
Genomics. 2000; 66(1):43-7 [PubMed] Related Publications
The glycine N-methyltransferase (GNMT) gene encodes a protein that not only acts as an enzyme to regulate the ratio of S-adenosylmethionine to S-adenosylhomocysteine, but also participates in the detoxification pathway in liver cells. Previously, we reported that the expression level of GNMT was diminished in human hepatocellular carcinoma. In this study, the human GNMT gene was cloned and characterized. It contains six exons and spans about 10 kb. Instead of a TATA box, it has a transcriptional initiator located 801 bp upstream from the translation start codon. The gene was localized to chromosome 6p12 using fluorescence in situ hybridization. Northern blot analysis of 16 tissues from different human organs showed that GNMT was expressed only in liver, pancreas, and prostate.

Chen YM, Shiu JY, Tzeng SJ, et al.
Characterization of glycine-N-methyltransferase-gene expression in human hepatocellular carcinoma.
Int J Cancer. 1998; 75(5):787-93 [PubMed] Related Publications
Messenger RNA differential display was used to study liver-gene expression in paired tumor and non-tumor tissues from hepatocellular carcinoma (HCC) patients. mRNA differential display and Northern-blot analyses showed that a 0.8-kb cDNA fragment was diminished or absent from the tumorous tissues of 7 HCC patients. The cDNA fragment was sequenced and found to have 98.7% nucleotide sequence homology with human glycine-N-methyltransferase cDNA (GNMT). In addition, there was no detectable level of GNMT expression in 4 human HCC cell lines, SK-Hep1, Hep 3B, HuH-7 and HA22T, examined by Northern-blot assay. A full-length GNMT cDNA clone-9-1-2 was obtained by screening a Taiwanese liver cDNA library. In comparison with the GNMT cDNA sequence reported elsewhere, clone 9-1-2 had 4 nucleotide differences resulting in 1 amino-acid change. Immunohistochemical staining with rabbit anti-recombinant GNMT serum showed that GNMT protein almost completely disappeared in liver-cancer cells, while it was abundant in the non-tumorous liver cells. Down-regulation of GNMT gene expression may be involved in the pathogenesis of liver cancer.

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