Activation of nicotinamide N-methyltransferase gene promoter by hepatocyte nuclear factor-1beta in human papillary thyroid cancer cells

NAD+ Metabolism and Immune Regulation: New Approaches to Inflammatory Bowel Disease Therapies

Inflammatory bowel disease (IBD), which includes Crohn's disease (CD) and ulcerative colitis (UC), is a multifactorial systemic inflammatory immune response. Nicotinamide adenine dinucleotide (NAD⁺) is a co-enzyme involved in cell signaling and energy metabolism. Calcium homeostasis, gene transcription, DNA repair, and cell communication involve NAD⁺ and its degradation products. There is a growing recognition of the intricate relationship between inflammatory diseases and NAD⁺ metabolism. In the case of IBD, the maintenance of intestinal homeostasis relies on a delicate balance between NAD⁺ biosynthesis and consumption. Consequently, therapeutics designed to target the NAD⁺ pathway are promising for the management of IBD. This review discusses the metabolic and immunoregulatory processes of NAD⁺ in IBD to examine the molecular biology and pathophysiology of the immune regulation of IBD and to provide evidence and theoretical support for the clinical use of NAD⁺ in IBD.

Systematic pan-cancer analysis of the nicotinamide n-methyltransferase in human cancer

In several tumors, Nicotinamide N-Methyltransferase (NNMT) was identified as a bridge between methylation metabolism and tumorigenesis and was associated with a poor prognosis. This research aims is to study the prognostic value of NNMT in cancer, its relationship with DNA methylation, and the immune microenvironment. On the basis of the Cancer Genome Atlas and the Cancer Cell Line Encyclopedia, Genotype Tissue-Expression, cBioPortal, Cellminer, Gene Expression Profiling Interactive Analysis, Human Protein Atlas and Clinical Proteomic Tumor Analysis Consortium, we used a series of bioinformatics strategies to investigate the potential carcinogenicity of NNMT, including the relationship between NNMT expression and prognosis, tumor mutational burden, microsatellite instability, and sensitivity analysis of anticancer drugs. The GeneMANIA, STRING, and BioGRID databases were examined for protein-protein interactions, and Gene Ontology and the Kyoto Encyclopedia of Genes were used to infer the signal pathway. The results indicated that NNMT was significantly expressed in several tumor tissues compared to the matching non-tumor tissues. Increased NNMT expression was linked to reduced OS, DSS, and DFI. In addition, there was a link between NNMT expression and TMB and MSI in 18 cancer types, and between NNMT expression and DNA methylation in 23 cancer types. Further study of NNMT gene alteration data revealed that deletion was the most prevalent form of NNMT mutation, and that there was a significant negative association between NNMT expression and mismatch repair genes. In addition, there was a strong positive connection between NNMT and immune infiltration in 28 types of tumors, and the immune cells that infiltrated the tumors displayed a characteristic NNMT pattern. According to the enrichment study, cell migration, cell motility, and cell adhesion were highly enriched in biological processes, and NNMT may be associated with the PI3K-Akt signaling pathway. By downregulating gene methylation or impacting the immunological microenvironment widely, NNMT may drive carcinogenesis and cause a poor prognosis. Our research showed that NNMT could be used as a biomarker of tumor immune infiltration and poor prognosis, thus providing a unique strategy for cancer therapy.

Nicotinamide N-Methyltransferase: A Promising Biomarker and Target for Human Cancer Therapy

Cancer cells typically exhibit a tightly regulated program of metabolic plasticity and epigenetic remodeling to meet the demand of uncontrolled cell proliferation. The metabolic-epigenetic axis has recently become an increasingly hot topic in carcinogenesis and offers new avenues for innovative and personalized cancer treatment strategies. Nicotinamide N-methyltransferase (NNMT) is a metabolic enzyme involved in controlling methylation potential, impacting DNA and histone epigenetic modification. NNMT overexpression has been described in various solid cancer tissues and even body fluids, including serum, urine, and saliva. Furthermore, accumulating evidence has shown that NNMT knockdown significantly decreases tumorigenesis and chemoresistance capacity. Most importantly, the natural NNMT inhibitor yuanhuadine can reverse epidermal growth factor receptor tyrosine kinase inhibitor resistance in lung cancer cells. In this review, we evaluate the possibility of NNMT as a diagnostic biomarker and molecular target for effective anticancer treatment. We also reveal the exact mechanisms of how NNMT affects epigenetics and the development of more potent and selective inhibitors.

Nicotinamide-N-methyltransferase is a promising metabolic drug target for primary and metastatic clear cell renal cell carcinoma

Background

The metabolic enzyme nicotinamide‐N‐methyltransferase (NNMT) is highly expressed in various cancer entities, suggesting tumour‐promoting functions. We systematically investigated NNMT expression and its metabolic interactions in clear cell renal cell carcinoma (ccRCC), a prominent RCC subtype with metabolic alterations, to elucidate its role as a drug target.

Methods

NNMT expression was assessed in primary ccRCC (n = 134), non‐tumour tissue and ccRCC‐derived metastases (n = 145) by microarray analysis and/or immunohistochemistry. Findings were validated in The Cancer Genome Atlas (kidney renal clear cell carcinoma [KIRC], n = 452) and by single‐cell analysis. Expression was correlated with clinicopathological data and survival. Metabolic alterations in NNMT‐depleted cells were assessed by nontargeted/targeted metabolomics and extracellular flux analysis. The NNMT inhibitor (NNMTi) alone and in combination with the inhibitor 2‐deoxy‐D‐glucose for glycolysis and BPTES (bis‐2‐(5‐phenylacetamido‐1,3,4‐thiadiazol‐2‐yl)ethyl‐sulfide) for glutamine metabolism was investigated in RCC cell lines (786‐O, A498) and in two 2D ccRCC‐derived primary cultures and three 3D ccRCC air–liquid interface models.

Results

NNMT protein was overexpressed in primary ccRCC (p = 1.32 × 10^–16) and ccRCC‐derived metastases (p = 3.92 × 10^–20), irrespective of metastatic location, versus non‐tumour tissue. Single‐cell data showed predominant NNMT expression in ccRCC and not in the tumour microenvironment. High NNMT expression in primary ccRCC correlated with worse survival in independent cohorts (primary RCC—hazard ratio [HR] = 4.3, 95% confidence interval [CI]: 1.5–12.4; KIRC—HR = 3.3, 95% CI: 2.0–5.4). NNMT depletion leads to intracellular glutamine accumulation, with negative effects on mitochondrial function and cell survival, while not affecting glycolysis or glutathione metabolism. At the gene level, NNMT‐depleted cells upregulate glycolysis, oxidative phosphorylation and apoptosis pathways. NNMTi alone or in combination with 2‐deoxy‐D‐glucose and BPTES resulted in inhibition of cell viability in ccRCC cell lines and primary tumour and metastasis‐derived models. In two out of three patient‐derived ccRCC air–liquid interface models, NNMTi treatment induced cytotoxicity.

Conclusions

Since efficient glutamine utilisation, which is essential for ccRCC tumours, depends on NNMT, small‐molecule NNMT inhibitors provide a novel therapeutic strategy for ccRCC and act as sensitizers for combination therapies.

Nicotinamide N-Methyltransferase inhibits HBV replication by suppressing NR5A1 expression invitro

Chronic hepatitis B virus (HBV) infection can lead to fibrosis, liver cirrhosis, and primary hepatocellular carcinoma. Investigating host factors that regulate HBV replication helps to identify antiviral targets. In the current study, we identified Nicotinamide N-Methyltransferase gene (NNMT) as a novel factor that regulates HBV transcription. NNMT is up-regulated at both the mRNA and protein levels in HepG2.2.15 cells compared to HepG2 cells. Overexpression of NNMT reduces HBV replication in several cell models, while knockdown of NNMT enhances HBV DNA levels. Mechanistically, NNMT suppresses HBV DNA replication by inhibiting HBV RNA transcription. The region required for the inhibitory effect of NNMT was narrowed to nt 1672-1708 in enhancer II by luciferase assays. On the other hand, ChIP assays and EMSA results showed that NNMT does not bind to this region substantially, either directly or indirectly. Next, a collection of hepatic nuclear receptor transcription factors was screened to determine whether they were affected by NNMT overexpression. NR5A1, a positive regulator of HBV replication, decreased significantly after NNMT overexpression. Collectively, the findings of this study shed light on the regulation of HBV transcription.

Nicotinamide N-Methyltransferase in Head and Neck Tumors: A Comprehensive Review

The head and neck tumors (HNT) are a heterogeneous group of diseases ranging from benign to malignant lesions, with distinctive molecular and clinical behaviors. Several studies have highlighted the presence of an altered metabolic phenotype in HNT, such as the upregulation of nicotinamide N-methyltransferase (NNMT). However, its biological effects have not been completely disclosed and the role of NNMT in cancer cell metabolism remains unclear. Therefore, this comprehensive review aims to evaluate the available literature regarding the biological, diagnostic, and prognostic role of NNMT in HNT. NNMT was shown to be significantly overexpressed in all of the evaluated HNT types. Moreover, its upregulation has been correlated with cancer cell migration and adverse clinical outcomes, such as high-pathological stage, lymph node metastasis, and locoregional recurrences. However, in oral squamous cell carcinoma (OSCC) these associations are still debated, and several studies have failed to demonstrate the prognostic significance of NNMT. The shRNA-mediated gene silencing efficiently suppressed the NNMT gene expression and exhibited a clear inhibitory effect on cell proliferation, promoting the expression of apoptosis-related proteins and modulating the cell cycle. NNMT could represent a new molecular biomarker and a new target of molecular-based therapy, although further studies on larger patient cohorts are needed to explore its biological role in HNT.

Methylosystem for Cancer Sieging Strategy

As cancer is a genetic disease, methylation defines a biologically malignant phenotype of cancer in the association of one-carbon metabolism-dependent S-adenosylmethionine (SAM) as a methyl donor in each cell. Methylated substances are involved in intracellular metabolism, but via intercellular communication, some of these can also be secreted to affect other substances. Although metabolic analysis at the single-cell level remains challenging, studying the "methylosystem" (i.e., the intercellular and intracellular communications of upstream regulatory factors and/or downstream effectors that affect the epigenetic mechanism involving the transfer of a methyl group from SAM onto the specific positions of nucleotides or other metabolites in the tumor microenvironment) and tracking these metabolic products are important research tasks for understanding spatial heterogeneity. Here, we discuss and highlight the involvement of RNA and nicotinamide, recently emerged targets, in SAM-producing one-carbon metabolism in cancer cells, cancer-associated fibroblasts, and immune cells. Their significance and implications will contribute to the discovery of efficient methods for the diagnosis of and therapeutic approaches to human cancer.

Nicotinamide N-Methyltransferase: An Emerging Protagonist in Cancer Macro(r)evolution

Nicotinamide N-methyltransferase (NNMT) has progressed from being considered merely a Phase II metabolic enzyme to one with a central role in cell function and energy metabolism. Over the last three decades, a significant body of evidence has accumulated which clearly demonstrates a central role for NNMT in cancer survival, metastasis, and drug resistance. In this review, we discuss the evidence supporting a role for NNMT in the progression of the cancer phenotype and how it achieves this by driving the activity of pro-oncogenic NAD+-consuming enzymes. We also describe how increased NNMT activity supports the Warburg effect and how it promotes oncogenic changes in gene expression. We discuss the regulation of NNMT activity in cancer cells by both post-translational modification of the enzyme and transcription factor binding to the NNMT gene, and describe for the first time three long non-coding RNAs which may play a role in the regulation of NNMT transcription. We complete the review by discussing the development of novel anti-cancer therapeutics which target NNMT and provide insight into how NNMT-based therapies may be best employed clinically.

The Utility of Nicotinamide N-Methyltransferase as a Potential Biomarker to Predict the Oncological Outcomes for Urological Cancers: An Update

Nicotinamide N-methyltransferase (NNMT) catalyzes the N-methylation reaction of nicotinamide, using S-adenosyl-L-methionine as the methyl donor. Enzyme overexpression has been described in many non-neoplastic diseases, as well as in a wide range of solid malignancies. This review aims to report and discuss evidence available in scientific literature, dealing with NNMT expression and the potential involvement in main urologic neoplasms, namely, renal, bladder and prostate cancers. Data illustrated in the cited studies clearly demonstrated NNMT upregulation (pathological vs. normal tissue) in association with these aforementioned tumors. In addition to this, enzyme levels were also found to correlate with key prognostic parameters and patient survival. Interestingly, NNMT overexpression also emerged in peripheral body fluids, such as blood and urine, thus leading to candidate the enzyme as promising biomarker for the early and non-invasive detection of these cancers. Examined results undoubtedly showed NNMT as having the capacity to promote cell proliferation, migration and invasiveness, as well as its potential participation in fundamental events highlighting cancer progression, metastasis and resistance to chemo- and radiotherapy. In the light of this evidence, it is reasonable to attribute to NNMT a promising role as a potential biomarker for the diagnosis and prognosis of urologic neoplasms, as well as a molecular target for effective anti-cancer treatment.

Nicotinamide N-Methyltransferase in Acquisition of Stem Cell Properties and Therapy Resistance in Cancer

The activity of nicotinamide N-methyltransferase (NNMT) is tightly linked to the maintenance of the nicotinamide adenine dinucleotide (NAD⁺) level. This enzyme catalyzes methylation of nicotinamide (NAM) into methyl nicotinamide (MNAM), which is either excreted or further metabolized to N1-methyl-2-pyridone-5-carboxamide (2-PY) and H₂O₂. Enzymatic activity of NNMT is important for the prevention of NAM-mediated inhibition of NAD⁺-consuming enzymes poly-adenosine -diphosphate (ADP), ribose polymerases (PARPs), and sirtuins (SIRTs). Inappropriately high expression and activity of NNMT, commonly present in various types of cancer, has the potential to disrupt NAD⁺ homeostasis and cellular methylation potential. Largely overlooked, in the context of cancer, is the inhibitory effect of 2-PY on PARP-1 activity, which abrogates NNMT's positive effect on cellular NAD⁺ flux by stalling liberation of NAM and reducing NAD⁺ synthesis in the salvage pathway. This review describes, and discusses, the mechanisms by which NNMT promotes NAD⁺ depletion and epigenetic reprogramming, leading to the development of metabolic plasticity, evasion of a major tumor suppressive process of cellular senescence, and acquisition of stem cell properties. All these phenomena are related to therapy resistance and worse clinical outcomes.

Hepatocyte nuclear factor 1 beta: A perspective in cancer

Hepatocyte nuclear factor 1 beta (HNF1 β/B) exists as a homeobox transcription factor having a vital role in the embryonic development of organs mainly liver, kidney and pancreas. Initially described as a gene causing maturity‐onset diabetes of the young (MODY), HNF1β expression deregulation and single nucleotide polymorphisms in HNF1β have now been associated with several tumours including endometrial, prostate, ovarian, hepatocellular, renal and colorectal cancers. Its function has been studied either as homodimer or heterodimer with HNF1α. In this review, the role of HNF1B in different cancers will be discussed along with the role of its splice variants, and its emerging role as a potential biomarker in cancer.

Nicotinamide N-methyltransferase: At the crossroads between cellular metabolism and epigenetic regulation

Background

The abundance of energy metabolites is intimately interconnected with the activity of chromatin-modifying enzymes in order to guarantee the finely tuned modulation of gene expression in response to cellular energetic status. Metabolism-induced epigenetic gene regulation is a key molecular axis for the maintenance of cellular homeostasis, and its deregulation is associated with several pathological conditions. Nicotinamide N-methyltransferase (NNMT) is a metabolic enzyme that catalyzes the methylation of nicotinamide (NAM) using the universal methyl donor S-adenosyl methionine (SAM), directly linking one-carbon metabolism with a cell's methylation balance and nicotinamide adenine dinucleotide (NAD⁺) levels. NNMT expression and activity are regulated in a tissue-specific-manner, and the protein can act either physiologically or pathologically depending on its distribution. While NNMT exerts a beneficial effect by regulating lipid parameters in the liver, its expression in adipose tissue correlates with obesity and insulin resistance. NNMT upregulation has been observed in a variety of cancers, and increased NNMT expression has been associated with tumor progression, metastasis and worse clinical outcomes. Accordingly, NNMT represents an appealing druggable target for metabolic disorders as well as oncological and other diseases in which the protein is improperly activated.

Scope of review

This review examines emerging findings concerning the complex NNMT regulatory network and the role of NNMT in both NAD metabolism and cell methylation balance. We extensively describe recent findings concerning the physiological and pathological regulation of NNMT with a specific focus on the function of NNMT in obesity, insulin resistance and other associated metabolic disorders along with its well-accepted role as a cancer-associated metabolic enzyme. Advances in strategies targeting NNMT pathways are also reported, together with current limitations of NNMT inhibitor drugs in clinical use.

Major conclusions

NNMT is emerging as a key point of intersection between cellular metabolism and epigenetic gene regulation, and growing evidence supports its central role in several pathologies. The use of molecules that target NNMT represents a current pharmaceutical challenge for the treatment of several metabolic-related disease as well as in cancer.

Hepatoblastomas exhibit marked NNMT downregulation driven by promoter DNA hypermethylation

Hepatoblastomas exhibit the lowest mutational burden among pediatric tumors. We previously showed that epigenetic disruption is crucial for hepatoblastoma carcinogenesis. Our data revealed hypermethylation of nicotinamide N-methyltransferase, a highly expressed gene in adipocytes and hepatocytes. The expression pattern and the role of nicotinamide N-methyltransferase in pediatric liver tumors have not yet been explored, and this study aimed to evaluate the effect of nicotinamide N-methyltransferase hypermethylation in hepatoblastomas. We evaluated 45 hepatoblastomas and 26 non-tumoral liver samples. We examined in hepatoblastomas if the observed nicotinamide N-methyltransferase promoter hypermethylation could lead to dysregulation of expression by measuring mRNA and protein levels by real-time quantitative polymerase chain reaction, immunohistochemistry, and Western blot assays. The potential impact of nicotinamide N-methyltransferase changes was evaluated on the metabolic profile by high-resolution magic angle spinning nuclear magnetic resonance spectroscopy. Significant nicotinamide N-methyltransferase downregulation was revealed in hepatoblastomas, with two orders of magnitude lower nicotinamide N-methyltransferase expression in tumor samples and hepatoblastoma cell lines than in hepatocellular carcinoma cell lines. A specific TSS1500 CpG site (cg02094283) of nicotinamide N-methyltransferase was hypermethylated in tumors, with an inverse correlation between its methylation level and nicotinamide N-methyltransferase expression. A marked global reduction of the nicotinamide N-methyltransferase protein was validated in tumors, with strong correlation between gene and protein expression. Of note, higher nicotinamide N-methyltransferase expression was statistically associated with late hepatoblastoma diagnosis, a known clinical variable of worse prognosis. In addition, untargeted metabolomics analysis detected aberrant lipid metabolism in hepatoblastomas. Data presented here showed the first evidence that nicotinamide N-methyltransferase reduction occurs in hepatoblastomas, providing further support that the nicotinamide N-methyltransferase downregulation is a wide phenomenon in liver cancer. Furthermore, this study unraveled the role of DNA methylation in the regulation of nicotinamide N-methyltransferase expression in hepatoblastomas, in addition to evaluate the potential effect of nicotinamide N-methyltransferase reduction in the metabolism of these tumors. These preliminary findings also suggested that nicotinamide N-methyltransferase level may be a potential prognostic biomarker for hepatoblastoma.

ER stress-induced upregulation of NNMT contributes to alcohol-related fatty liver development

BACKGROUND & AIMS

N-nicotinamide methyltransferase (NNMT) is emerging as an important enzyme in the regulation of metabolism. NNMT is highly expressed in the liver. However, the exact regulatory mechanism(s) underlying NNMT expression remains unclear and its potential involvement in alcohol-related liver disease (ALD) is completely unknown.

METHODS

Both traditional Lieber-De Carli and the NIAAA mouse models of ALD were employed. A small-scale chemical screening assay and a chromatin immunoprecipitation assay were performed. NNMT inhibition was achieved via both genetic (adenoviral short hairpin RNA delivery) and pharmacological approaches.

RESULTS

Chronic alcohol consumption induces endoplasmic reticulum (ER) stress and upregulates NNMT expression in the liver. ER stress inducers upregulated NNMT expression in both AML12 hepatocytes and mice. PERK-ATF4 pathway activation is the main contributor to ER stress-mediated NNMT upregulation in the liver. Alcohol consumption fails to upregulate NNMT in liver-specific Atf4 knockout mice. Both adenoviral NNMT knockdown and NNMT inhibitor administration prevented fatty liver development in response to chronic alcohol feeding; this was also associated with the downregulation of an array of genes involved in de novo lipogenesis, including Srebf1, Acaca, Acacb and Fasn. Further investigations revealed that activation of the lipogenic pathway by NNMT was independent of its NAD⁺-enhancing action; however, increased cellular NAD⁺, resulting from NNMT inhibition, was associated with marked liver AMPK activation.

CONCLUSIONS

ER stress, specifically PERK-ATF4 pathway activation, is mechanistically involved in hepatic NNMT upregulation in response to chronic alcohol exposure. Overexpression of NNMT in the liver plays an important role in the pathogenesis of ALD.

LAY SUMMARY

In this study, we show that nicotinamide methyltransferase (NNMT) - the enzyme that catalyzes nicotinamide degradation - is a pathological regulator of alcohol-related fatty liver development. NNMT inhibition protects against alcohol-induced fatty liver development and is associated with suppressed de novo lipogenic activity and enhanced AMPK activation. Thus, our data suggest that NNMT may be a potential therapeutic target for the treatment of alcohol-related liver disease.

Nicotinamide N-Methyltransferase: Genomic Connection to Disease

Single-nucleotide polymorphisms (SNPs) in and around the nicotinamide N-methyltransferase (NNMT) gene are associated with a range of cancers and other diseases and conditions. The data on these associations have been assembled, and their strength discussed. There is no evidence that the presence of either the major or minor base in any SNP affects the expression of nicotinamide N-methyltransferase. Nevertheless, suggestions have been put forward that some of these SNPs do affect NNMT expression and thus homocysteine metabolism. An alternative idea involving non-coding messenger RNAs (mRNAs) is suggested as a possible mechanism whereby health is influenced. It is postulated that these long, non-coding NNMT mRNAs may exert deleterious effects by interfering with the expression of other genes. Neither hypothesis, however, has experimental proof, and further work is necessary to elucidate NNMT genetic interactions.

Thyroid Dysfunction and Diabetes Mellitus: Two Closely Associated Disorders

Thyroid dysfunction and diabetes mellitus are closely linked. Several studies have documented the increased prevalence of thyroid disorders in patients with diabetes mellitus and vice versa. This review critically discusses the different underlying mechanisms linking type 1 and 2 diabetes and thyroid dysfunction to demonstrate that the association of these two common disorders is unlikely a simple coincidence. We assess the current state of knowledge on the central and peripheral control of thyroid hormone on food intake and glucose and lipid metabolism in target tissues (such as liver, white and brown adipose tissue, pancreatic β cells, and skeletal muscle) to explain the mechanism linking overt and subclinical hypothyroidism to type 2 diabetes and metabolic syndrome. We also elucidate the common susceptibility genes and the pathogenetic mechanisms contributing to the autoimmune mechanism involved in the onset of type 1 diabetes mellitus and autoimmune thyroid disorders. An untreated thyroid dysfunction can impair the metabolic control of diabetic patients, and this association can have important repercussions on the outcome of both of these disorders. Therefore, we offer recommendations for the diagnosis, management, and screening of thyroid disorders in patients with diabetes mellitus, including the treatment of diabetic patients planning a pregnancy. We also discuss the major causes of failure to achieve an optimal management of thyroid dysfunction in diabetic patients and provide recommendations for assessing and treating these disorders during therapy with antidiabetic drugs. An algorithm for a correct approach of these disorders when linked is also provided.

Development of a Suicide Inhibition-Based Protein Labeling Strategy for Nicotinamide N-Methyltransferase

Nicotinamide N-methyltransferase (NNMT) catalyzes the S-adenosyl-l-methionine-dependent methylation of nicotinamide to form N-methylnicotinamide. This enzyme detoxifies xenobiotics and regulates NAD⁺ biosynthesis. Additionally, NNMT is overexpressed in various cancers. Herein, we describe the first NNMT-targeted suicide substrates. These compounds, which include 4-chloropyridine and 4-chloronicotinamide, exploit the broad substrate scope of NNMT; methylation of the pyridine nitrogen enhances the electrophilicity of the C4 position, thereby promoting an aromatic nucleophilic substitution by C159, a noncatalytic cysteine. On the basis of this activity, we developed a suicide inhibition-based protein labeling strategy using an alkyne-substituted 4-chloropyridine that selectively labels NNMT in vitro and in cells. In total, this study describes the first NNMT-directed activity-based probes.

Citrullination Inactivates Nicotinamide- N-methyltransferase

Nicotinamide- N-methyltransferase (NNMT) catalyzes the irreversible methylation of nicotinamide (NAM) to form N-methyl nicotinamide using S-adenosyl methionine as a methyl donor. NNMT is implicated in several chronic disease conditions, including cancers, kidney disease, cardiovascular disease, and Parkinson's disease. Although phosphorylation of NNMT in gastric tumors is reported, the functional effects of this post-translational modification has not been investigated. We previously reported that citrullination of NNMT by Protein Arginine Deiminases abolished its methyltransferase activity. Herein, we investigate the mechanism of inactivation. Using tandem mass spectrometry, we identified three sites of citrullination in NNMT. With this information in hand, we used a combination of site-directed mutagenesis, kinetics, and circular dichoism experiments to demonstrate that citrullination of R132 leads to a structural perturbation that ultimately promotes NNMT inactivation.

Nicotinamide N-methyltransferase enhances resistance to 5-fluorouracil in colorectal cancer cells through inhibition of the ASK1-p38 MAPK pathway

Nicotinamide N-methyltransferase (NNMT), which converts nicotinamide to 1-methylnicotinamide (1-MNA), is overexpressed in a variety of human cancers and serves as a potential anti-cancer target. In this study, we investigated the effect of NNMT on 5-fluorouracil (5-FU) sensitivity of colorectal cancer (CRC) cells, and the underlying mechanisms. Our results show that down-regulation of NNMT in CRC HT-29 cells diminishes 5-FU resistance, while over expression of NNMT in SW480 cells enhances it. NNMT reduces reactive oxygen species (ROS) production induced by 5-FU by increasing 1-MNA in CRC cells. The reduction in ROS leads to inactivation of the ASK1-p38 mitogen-activated protein kinase (MAPK) pathway, which reduces 5-FU-induced apoptosis. In vivo, NNMT attenuates 5-FU-induced inhibition of CRC tumor growth in nude mice. These observations suggest that NNMT and the 1-MNA it produces inhibit the ASK1-p38 MAPK pathway, resulting in increased CRC cell resistance to 5-FU.

Hepatocyte nuclear factor-1beta enhances the stemness of hepatocellular carcinoma cells through activation of the Notch pathway

Hepatocyte nuclear factor-1beta plays an important role in the development and progression of liver cancer. In recent years, the expression of HNF-1β has been reported to be associated with risk for a variety of cancers. The purpose of this study is to investigate whether the expression of HNF-1β promotes the malignancy of HCC and its mechanism. We retrospectively investigated the expression of HNF-1β in 90 patients with hepatocellular carcinoma and found that the high expression of HNF-1β indicated poor prognosis. We overexpressed HNF-1β in liver cancer cell lines and found the expression of liver progenitor cell markers and stemness were upregulated. The invasion ability and epithelial-mesenchymal transition (EMT)-associated genes were also significantly higher in liver cancer cells overexpressing HNF-1β than in the control group. A mechanistic study suggested the activation of the Notch signalling pathway probably plays a key role downstream of HNF-1β. More importantly, HNF-1β promoted tumourigenesis of HCC cells in vivo. In conclusion, high expression of HNF-1β not only promoted the de-differentiation of HCC cells into liver cancer stem cells through activating the Notch pathway but also enhanced the invasive potential of HCC cells and EMT occurrence, which would contribute to the enhancement of cell migration and invasion.

Nicotinamide N-Methyltransferase in Health and Cancer

Over the past decade, the roles of nicotinamide N-methyltransferase and its product 1-methyl nicotinamide have emerged from playing merely minor roles in phase 2 xenobiotic metabolism as actors in some of the most important scenes of human life. In this review, the structures of the gene, messenger RNA, and protein are discussed, together with the role of the enzyme in many of the common cancers that afflict people today.

Nicotinamide N-Methyltransferase: More Than a Vitamin B3 Clearance Enzyme

Nicotinamide (NAM) N-methyltransferase (NNMT) was originally identified as the enzyme responsible for the methylation of NAM, one of the forms of vitamin B3. Methylated NAM is eventually excreted from the body. Recent evidence has expanded the role of NNMT beyond clearance of excess vitamin B3. NNMT has been implicated in the regulation of multiple metabolic pathways in tissues such as adipose and liver as well as cancer cells through the consumption of methyl donors and generation of active metabolites. This review examines recent findings regarding the function of NNMT in physiology and disease and highlights potential new avenues for therapeutic intervention. Finally, key gaps in our knowledge about this enzymatic system and future areas of investigation are discussed.

N-methylnicotinamide and nicotinamide N-methyltransferase are associated with microRNA-1291-altered pancreatic carcinoma cell metabolome and suppressed tumorigenesis

The cell metabolome comprises abundant information that may be predictive of cell functions in response to epigenetic or genetic changes at different stages of cell proliferation and metastasis. An unbiased ultra-performance liquid chromatography-mass spectrometry-based metabolomics study revealed a significantly altered metabolome for human pancreatic carcinoma PANC-1 cells with gain-of-function non-coding microRNA-1291 (miR-1291), which led to a lower migration and invasion capacity as well as suppressed tumorigenesis in a xenograft tumor mouse model. A number of metabolites, including N-methylnicotinamide, involved in nicotinamide metabolism, and l-carnitine, isobutyryl-carnitine and isovaleryl-carnitine, involved in fatty acid metabolism, were elevated in miR-1291-expressing PANC-1. Notably, N-methylnicotinamide was elevated to the greatest extent, and this was associated with a sharp increase in nicotinamide N-methyltransferase (NNMT) mRNA level in miR-1291-expressing PANC-1 cells. In addition, expression of NNMT mRNA was inversely correlated with pancreatic tumor size in the xenograft mouse model. These results indicate that miR-1291-altered PANC-1 cell function is associated with the increase in N-methylnicotinamide level and NNMT expression, and in turn NNMT may be indicative of the extent of pancreatic carcinogenesis.

Upregulation of tissue and urinary nicotinamide N-methyltransferase in bladder cancer: potential for the development of a urine-based diagnostic test

Carcinoma of the bladder is one of the most common urologic malignancies occurring worldwide. Diagnosis and monitoring of bladder urothelial carcinoma (UC) are based on cystoscopy and urinary cytology. However, these diagnostic methods still have some limitations, mainly related to invasive nature and lack of sensitivity. New reliable and non-invasive biomarkers for bladder cancer detection are therefore required. To explore the involvement of enzymes of drug metabolism in bladder cancer, in the present study, we analyzed the gene expression profiles of tumor and normal looking tissues obtained from the same patient by cDNA macroarray. The enzyme nicotinamide N-methyltransferase (NNMT) was identified as a highly expressed gene in bladder cancer. RT-PCR, Real-Time PCR, Western blot analysis, and catalytic activity assay, performed on a large cohort of patients with bladder UC, confirmed NNMT upregulation. NNMT mRNA and protein levels were also determined in urine specimens obtained from patients with bladder UC and healthy subjects. We found that NNMT expression levels were significantly higher in patients with bladder tumor compared to controls that showed very low or undetectable amounts of NNMT transcript and protein. Our results indicate that a marked NNMT increase is a peculiar feature of bladder UC and suggest the potential suitability of urine NNMT expression levels determination for early and non-invasive diagnosis of bladder cancer.

Association of nicotinamide-N-methyltransferase gene rs694539 variant with patients with nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of abnormal hepatic steatosis in the absence of a history of alcohol use and with a prevalence of 15%-45% in developed nations. Nonalcoholic steatohepatitis (NASH) is an advanced stage of NAFLD with a pronounced major inflammatory component. The aim of this study was to investigate the possible role of nicotinamide-N-methyltransferase (NNMT) gene rs694539 variant in the development of NASH. Therefore, we analyzed 80 NASH patients and 183 healthy controls using a polymerase chain reaction-restriction fragment length polymorphism method developed in our laboratory. The NNMT rs694539 variant was found to be significantly associated with NASH (χ(2)=9.349, p=0.009). The individuals with the GG genotype had protection against NASH (χ(2)=3.793, p=0.051, odds ratio [OR]=0.580, 95% confidence interval [CI]=0.334-1.006), whereas the individuals with the AA genotype showed statistically significant increased risk for NASH (χ(2)=7.748, p=0.005, OR=7.338, 95% CI=1.448-37.190). Moreover, the G allele was protective against NASH (χ(2)=7.748, p=0.005, OR=0.136, and 95% CI=0.027-0.691). On the other hand, the A allele was a risk factor for NASH (χ(2)=3.793, p=0.051, OR=1.725, and 95% CI=0.994-2.996). Consequently, the rs694539 variant of NNMT gene is a genetic risk factor for developing NASH.

RNA-mediated gene silencing of nicotinamide N-methyltransferase is associated with decreased tumorigenicity in human oral carcinoma cells

Oral squamous cell carcinoma (OSCC) is the most common type of oral cancer. Despite progress in the treatment of OSCC, overall survival has not improved substantially in the last three decades. Therefore, identification of reliable biomarkers becomes essential to develop effective anti-cancer therapy. In this study, we focused on the enzyme Nicotinamide N-methyltransferase (NNMT), which plays a fundamental role in the biotransformation of many xenobiotics. Although several tumors have been associated with abnormal NNMT expression, its role in cancer cell metabolism remains largely unknown. In this report, 7 human oral cancer cell lines were examined for NNMT expression by Real-Time PCR, Western blot and HPLC-based catalytic assay. Subsequently, we evaluated the in vitro effect of shRNA-mediated silencing of NNMT on cell proliferation. In vivo tumorigenicity of oral cancer cells with stable knockdown of NNMT was assayed by using xenograft models. High expression levels of NNMT were found in PE/CA PJ-15 cells, in keeping with the results of Western blot and catalytic activity assay. PE/CA PJ-15 cell line was stably transfected with shRNA plasmids against NNMT and analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and soft agar Assays. Transfected and control cells were injected into athymic mice in order to evaluate the effect of NNMT silencing on tumor growth. NNMT downregulation resulted in decreased cell proliferation and colony formation ability on soft agar. In athymic mice, NNMT silencing induced a marked reduction in tumour volume. Our results show that the downregulation of NNMT expression in human oral carcinoma cells significantly inhibits cell growth in vitro and tumorigenicity in vivo. All these experimental data seem to suggest that NNMT plays a critical role in the proliferation and tumorigenic capacity of oral cancer cells, and its inhibition could represent a potential molecular approach to the treatment of oral carcinoma.

New molecular insights into peripheral T cell lymphomas

Peripheral T cell lymphomas (PTCLs) are heterogeneous neoplasms and represent about 12% of all lymphoid malignancies. They are often regarded as "orphan diseases," a designation that does not reflect their real incidence but rather signifies the difficulties encountered in their classification, diagnosis, and treatment. Here we revise the current understanding of the pathobiological characteristics of the most common nodal PTCLs by focusing on the contribution given by high-throughput technologies and the identification of potential therapeutic targets proposed by translational studies.

Effect of orally administered phenethyl isothiocyanate on hepatic gene expression in rats

SCOPE

Phenethyl isothiocyanate (PEITC) is a constituent of cruciferous vegetables that has demonstrated cancer preventive activity in a number of cancer models including lung, prostate, and breast cancer. Our objective was to examine the effects of the oral administration of PEITC for 7 days on the hepatic expression of genes important in drug metabolism and toxicity in Sprague Dawley rats. The liver is the major site for the metabolism of various xenobiotics and carcinogens, and determining the effects of PEITC on the gene expression of hepatic enzymes may provide insight into mechanisms underlying the cancer preventive activity of PEITC.

METHODS AND RESULTS

Using a microarray containing 282 genes, we observed that PEITC significantly up-regulated UDP-glucuronosyltransferase UGT1A6 and strongly down-regulated nicotinamide N-methyltransferase (NNMT). We also confirmed the down-regulation of NNMT by real-time quantitative RT-PCR. Other genes that were significantly up-regulated were the drug metabolizing enzyme cyp2b15, the anti-apoptotic gene bcl2l2, and the stress regulators Gadd45b, Dnajb9, Dnajb5 and Hspb1.

CONCLUSION

Our results indicate new targets that may be important in the mechanisms of the anticancer effects of PEITC. Of particular significance was the down-regulation of NNMT which may represent a new target for the treatment of a variety of cancers.

Inhibiting Proliferation in KB Cancer Cells by RNA Interference-Mediated Knockdown of Nicotinamide N-Methyltransferase Expression

The enzyme Nicotinamide N-methyltransferase (NNMT) catalyzes the methylation of nicotinamide and other pyridines, playing a pivotal role in the biotransformation and detoxification of many drugs and xenobiotic compounds. Several tumours have been associated with abnormal NNMT expression, however its role in tumour development remains largely unknown. In this study we investigated expression levels of Nicotinamide N-methyltransferase in a cancer cell line and we evaluated the effect of shRNA-mediated silencing of NNMT on cell proliferation. Cancer cells were examined for NNMT expression by semiquantitative RT-PCR and Western blot analysis. A HPLC-based catalytic assay was performed to assess enzyme activity. Cells were transfected with four shRNA plasmids against NNMT and control cells were treated with transfection reagent only (mock). The efficiency of gene silencing was detected by Real-Time PCR and Western blot analysis. MTT cell proliferation assay and the soft agar colony formation assay were then applied to investigate the functional changes in cancerous cell. NNMT mRNA was detected in cancer cells, showing a very high expression level. In keeping with the results of RT-PCR analysis, the protein level and NNMT enzyme activity were particularly high in KB cells. ShRNA vectors targeted against NNMT efficiently suppressed gene expression, showing inhibition observed at both the mRNA and protein levels. Down-regulation of NNMT significantly inhibited cell proliferation and decreased colony formation ability on soft agar. The present data support the hypothesis that the enzyme plays a role in tumour expansion and its inhibition could represent a possible molecular approach to the treatment of cancer.

Nicotinamide N-methyltransferase protein expression in renal cell cancer

OBJECTIVE

To understand the function of nicotinamide N-methyltransferase (NNMT) protein as tumor biomarker in renal carcinoma.

METHODS

Recombinant NNMT protein was used to prepare monoclonal antibodies by hybridoma technique. The diagnostic and prognostic function of NNMT protein in renal carcinoma was evaluated by analyzing 74 renal cancer tissues through immunohistochemical staining for NNMT by using the prepared antibodies.

RESULTS

Two hybridomas named 2F8 and 1E7 stably secreting the monoclonal antibodies were isolated successfully, and characters such as isotypes and specificity were determined. NNMT protein was significantly up-regulated in renal cancer and significantly associated with tumor histology and ages. The univariate survival analysis demonstrated that the pT-status, high levels of NNMT, and distant metastasis were significant prognosticators.

CONCLUSION

NNMT is over-expressed in a large proportion in renal cell cancers. High NNMT expression is significantly associated with unfavorable prognosis. However, the prognostic value of NNMT needs further verification in larger sample sizes.

The role of hepatocyte nuclear factor-1beta in the pathogenesis of clear cell carcinoma of the ovary

PROBLEM

Clear cell carcinoma (CCC) of the ovary has a number of features distinguishing it from other epithelial ovarian carcinomas (EOC) because of its characteristic histology and biology, frequent concurrence with endometriotic lesion, and highly chemoresistant nature resulting in an extremely poor prognosis. The incidence of CCC has been steadily increasing in Japan. They comprise approximately 20% of all EOC. Understanding the mechanisms of CCC development and elucidating pathogenesis and pathophysiology are intrinsic to prevention and effective therapies for CCC.

METHOD OF STUDY

This article reviews the English language literature for biology, pathogenesis, and pathophysiological studies on endometriosis-associated EOC. Several data are discussed in the context of endometriosis and CCC biology.

RESULTS

Recent studies based on genome-wide expression analysis technology have noted specific expression of hepatocyte nuclear factor-1beta (HNF-1beta) in endometriosis and CCC, suggesting that early differentiation into the clear cell lineage takes place in the endometriosis. The HNF-1beta-dependent pathway of CCC will be discussed, which are providing new insights into regulation of apoptosis and glycogen synthesis and resistance of CCC to anticancer agents.

CONCLUSIONS

This review summarizes recent advances in the HNF-1beta and its target genes; the potential challenges to the understanding of carcinogenesis, pathogenesis, and pathophysiology of CCC; and a possible novel model is proposed.

Activation of nicotinamide N-methyltrasferase and increased formation of 1-methylnicotinamide (MNA) in atherosclerosis

Nicotinamide N-methyltrasferase (NMMT) catalyzes the conversion of nicotinamide (NA) to 1-methylnicotinamide (MNA). Recent studies have reported that exogenous MNA exerts anti-thrombotic and anti-inflammatory activity, suggesting that endogenous NMMT-derived MNA may play a biological role in the cardiovascular system. In the present study, we assayed changes in hepatic NNMT activity and MNA plasma levels along the progression of atherosclerosis in apoE/LDLR(-/-) mice, as compared to age-matched wild-type mice. Atherosclerosis progression in apoE/LDLR(-/-) mice was quantified in aortic root, while hepatic NNMT activity and MNA plasma concentrations were concomitantly measured in 2-, 3-, 4-, and 6-month-old mice. In apoE/LDLR(-/-) mice, atherosclerotic plaques developed in the aortic roots beginning at the age of 3 months and gradually increased in size, macrophage content, and inflammation intensity over time, as detected by Oil-Red O staining, CD68 immunostaining, and in situ zymography (MMP2/MMP9 activity). Hepatic NNMT activity was upregulated approximately two-fold in apoE/LDLR(-/-) mice by the age of 2 months, as compared to wild-type mice (1.03 +/- 0.14 vs. 0.64 +/- 0.23 pmol/min/mg, respectively). MNA plasma concentrations were also elevated approximately two-fold (0.30 +/- 0.13 vs. 0.17 +/- 0.04 micromol/l, respectively). As atherosclerosis progressed, hepatic NMMTactivity and MNA plasma concentrations increased five-fold in 6-month-old apoE/LDLR(-/-) mice at the stage of advanced atherosclerotic plaques (NMMT activity: 2.29 +/- 0.34 pmol/min/mg, MNA concentration: 1.083 +/- 0.33 micromol/l). In summary, the present study demonstrated that the progression of vascular inflammation and atherosclerosis was associated with the upregulation of hepatic NNMT activity and subsequent increase in endogenous MNA plasma levels. Given the anti-thrombotic and anti-inflammatory properties of exogenous MNA, robust activation of an endogenous NA-MNA pathway in atherosclerosis may play an important compensatory role.

Serum levels of nicotinamide N-methyltransferase in patients with lung cancer

PURPOSE

The aim of this study was to determine if nicotinamide N-methyltransferase (NNMT) is useful as a biomarker of lung cancer (stages I-III).

METHODS

We established an ELISA system for NNMT. We determined the levels of NNMT and carcinoembryonic antigen (CEA) in sera of 113 non-small cell lung cancer (NSCLC) patients undergoing surgery and sera of 50 non-neoplastic lung disease patients with chronic obstructive pulmonary disease (COPD) and of 24 healthy donors.

RESULTS

The serum levels of NNMT were significantly higher in lung cancer patients than in COPD patients and healthy donors. The relationship between the specificity and sensitivity of NNMT and CEA measurements for the detection of lung cancer was analyzed by means of receiver-operating characteristic curves. The corresponding areas under the curves were 0.703 for NNMT and 0.621 for CEA, indicating slightly better sensitivity of NNMT. With 90% specificity, the sensitivities of NNMT and CEA as lung cancer markers were 25 and 24%, respectively. There was no significant correlation between NNMT and CEA. Therefore, the sensitivity of NSCLC detection at 90% specificity increased from 25 to 32% when NNMT was used in combination with CEA.

CONCLUSION

The NNMT serum level may have significance in the early detection of NSCLC patients.

Expression of nicotinamide N-methyltransferase in hepatocellular carcinoma is associated with poor prognosis

BACKGROUND

Hepatocellular carcinoma (HCC) is the most common tumor in the adult liver, with high relapse and mortality rates despite diverse treatment modalities. In this study, nicotinamide N-methyltransferase (NNMT), a key enzyme in drug metabolism, was investigated as a potential prognostic factor.

METHODS

Frozen tumors and non-cancerous surrounding tissues from 120 patients with primary HCC were studied. Expressions of NNMT and internal control genes were measured by real-time reverse-transcription PCR (RT-PCR). The relationship of NNMT mRNA level with clinicopathologic parameters and clinical outcome was evaluated.

RESULTS

NNMT mRNA level is markedly reduced in HCCs compared to non-cancerous surrounding tissues (P < 0.0001), and NNMT expression in tumors was significantly correlated with tumor stage (P = 0.010). Moreover, stratification of patients based on tumor NNMT mRNA levels revealed that the patients who expressed higher NNMT mRNA levels tended to have a shorter overall survival (OS) time (P = 0.053) and a significantly shorter disease-free survival (DFS) time (P = 0.016). Both NNMT expression (P = 0.0096) and tumor stage (P = 0.0017) were found to be significant prognostic factors for DFS in a multivariate analysis.

CONCLUSION

The results of this study indicated that NNMT gene expression is associated with tumor stage and DFS time in HCC cases. Because of the broad substrate specificity of NNMT, which could alter the efficacy and adverse effects of chemotherapy, NNMT merits further investigation regarding its role as a prognostic factor with a larger cohort of HCC patients.

Peripheral T cell lymphoma, not otherwise specified: the stuff of genes, dreams and therapies

Peripheral T cell lymphomas (PTCL) account for about 12% of lymphoid tumours worldwide. Almost half show such morphological and molecular variability as to hamper any further classification, and to justify their inclusion in a waste-basket category termed “not otherwise specified (NOS)”. The latter term is used for neoplasms with aggressive presentation, poor response to therapy and dismal prognosis. In contrast to B cell lymphomas, PTCL have been the subject of only a limited number of studies to elucidate their pathobiology and identify novel pharmacological approaches. Herewith, the authors revise the most recent contributions on the subject based on the experience they have gained in the extensive application of microarray technologies. PTCL/NOS are characterised by erratic expression of T cell associated antigens, including CD4 and CD52, which have recently been proposed as targets for ad hoc immunotherapies. PTCL/NOS also show variable Ki-67 marking, with rates >80% heralding a worse prognosis. Gene expression profiling studies have revealed that PTCL/NOS derive from activated T lymphocytes, more often of the CD4+ type, and bear a signature composed of 155 genes and related products that play a pivotal role in cell signalling transduction, proliferation, apoptosis and matrix remodelling. This observation seems to pave the way for the use of innovative drugs such as tyrosine kinase and histone deacetylase inhibitors whose efficacy has been proven in PTCL primary cell cultures. Gene expression profiling also allows better distinction of PTCL/NOS from angioimmunoblastic T cell lymphoma, the latter being characterised by follicular T helper lymphocyte derivation and CXCL13, PD1 and vascular endothelial growth factor expression.

Expression of hepatocyte nuclear factor-1alpha mRNA in human anaplastic thyroid cancer cell lines and tumors

BACKGROUND

Hepatocyte nuclear factor (HNF)-1alpha and HNF-1beta are related transcription factors that are mainly expressed in liver cells. Our previous study showed that HNF-1beta was highly expressed in papillary thyroid cancer cell lines and tumors. HNF-1alpha mRNA, however, was not detected in differentiated thyroid cancer cell lines. The objective of this study was to determine whether HNF-1alpha is expressed in dedifferentiated anaplastic thyroid cancer cells.

METHODS

Total RNA isolated from six anaplastic thyroid cancer cell lines and 38 surgical samples was analyzed for HNF-1alpha mRNA by conventional reverse-transcription polymerase chain reaction (RT-PCR) or real-time RT-PCR. HNF-1alpha DNA binding activity was measured by gel retardation assay and HNF-1alpha protein was identified by Western blotting.

RESULTS

HNF-1alpha mRNA was expressed in four of the six anaplastic cell lines. The presence of HNF-1alpha protein and DNA binding activity was detected in three lines with higher HNF-1alpha mRNA level. Three cell lines also expressed HNF-1beta. HNF-1alpha transcripts were also detected in five out of six anaplastic tumors, but not in the papillary tumors except one with weak PCR signal.

CONCLUSION

HNF-1alpha mRNA was detected in high frequency in anaplastic thyroid cancer cell lines and tumors. HNF-1alpha might play a role in the pathogenesis of anaplastic thyroid cancer.

Nicotinamide N-methyltransferase upregulation inversely correlates with lymph node metastasis in oral squamous cell carcinoma

We investigated expression levels of Nicotinamide N-Methyltransferase (NNMT), an enzyme involved in the biotransformation of many drugs and xenobiotic compounds, in oral squamous cell carcinoma (OSCC). Measurements were performed by semi-quantitative RT-PCR and quantitative real-time PCR in tumor and matched adjacent healthy tissue. Interestingly, NNMT was up-regulated in most of the favorable OSCCs, while no marked NNMT expression alterations between tumor and normal mucosa were detected in most of the unfavorable OSCCs. Western blot and immunohistochemical analyses also were performed and the relationship between tumor characteristics and NNMT levels in OSCC were studied to evaluate the effectiveness of NNMT as a prognostic marker in the squamous cell carcinoma of the oral cavity. In summary, the present study suggests that NNMT may have potential as a biomarker and a therapeutic target for OSCC.

Stat3 up-regulates expression of nicotinamide N-methyltransferase in human cancer cells

PURPOSE

To discover new molecular targets for cancer therapy and diagnosis, we surveyed signal transducers and activators of transcription 3 (Stat3)-regulated genes, because constitutive activation of Stat3 is associated with a wide variety of human malignancies.

METHODS

We investigated the Stat3-regulated genes in 293 cells with cDNA microarray analysis and found that Nicotinamide N-methyltransferase (NNMT) was induced on stimulation of the cells with leukemia inhibitory factor. We examined the expression of NNMT in several types of cancer cells by real-time quantitative RT-PCR. To examine the role of Stat3, Hep-G2 hepatocellular carcinoma cells were transfected with NNMT promoter-luciferase reporter construct together with conditionally active Stat3 (Stat3ER) or dominant-negative Stat3 expression vector and NNMT promoter activity was determined. The expression of NNMT and activated Stat3 in 88 colon cancer tissues and 17 normal colon tissues was examined with immunohistochemical analysis.

RESULTS

In Hep-G2 cells and SW480 colon cancer cells, NNMT expression increased on stimulation of the cells with interleukin 6. NNMT promoter activity in Hep-G2 cells was dependent on the activation of Stat3. MDA-MB-468 breast cancer cells and HT29 colon cancer cells expressed constitutively a high level of NNMT. Treatment of these cells with Stat3 siRNA or curcumin, which inhibited Stat3 phosphorylation, resulted in reduction of the NNMT level. We found a correlation between the expression of NNMT and activated Stat3 (P<0.001) in the colon cancer tissues.

CONCLUSION

NNMT is a novel Stat3-regulated gene. Its expression is enhanced with the activation of Stat3 in colon cancer tissues. NNMT may be a potential candidate for a tumor marker of various kinds of cancers.

Nicotinamide N-methyltransferase upregulation inversely correlates with lymph node metastasis in oral squamous cell carcinoma

We investigated expression levels of Nicotinamide N-Methyltransferase (NNMT), an enzyme involved in the biotransformation of many drugs and xenobiotic compounds, in oral squamous cell carcinoma (OSCC). Measurements were performed by semi-quantitative RT-PCR and quantitative real-time PCR in tumor and matched adjacent healthy tissue. Interestingly, NNMT was up-regulated in most of the favorable OSCCs, while no marked NNMT expression alterations between tumor and normal mucosa were detected in most of the unfavorable OSCCs. Western blot and immunohistochemical analyses also were performed and the relationship between tumor characteristics and NNMT levels in OSCC were studied to evaluate the effectiveness of NNMT as a prognostic marker in the squamous cell carcinoma of the oral cavity. In summary, the present study suggests that NNMT may have potential as a biomarker and a therapeutic target for OSCC.

Gene expression analysis of peripheral T cell lymphoma, unspecified, reveals distinct profiles and new potential therapeutic targets

Peripheral T cell lymphoma, unspecified (PTCL/U), the most common form of PTCL, displays heterogeneous morphology and phenotype, poor response to treatment, and poor prognosis. We demonstrate that PTCL/U shows a gene expression profile clearly distinct from that of normal T cells. Comparison with the profiles of purified T cell subpopulations (CD4+, CD8+, resting [HLA-DR-], and activated [HLA-DR+]) reveals that PTCLs/U are most closely related to activated peripheral T lymphocytes, either CD4+ or CD8+. Interestingly, the global gene expression profile cannot be surrogated by routine CD4/CD8 immunohistochemistry. When compared with normal T cells, PTCLs/U display deregulation of functional programs often involved in tumorigenesis (e.g., apoptosis, proliferation, cell adhesion, and matrix remodeling). Products of deregulated genes can be detected in PTCLs/U by immunohistochemistry with an ectopic, paraphysiologic, or stromal location. PTCLs/U aberrantly express, among others, PDGFRalpha, a tyrosine-kinase receptor, whose deregulation is often related to a malignant phenotype. Notably, both phosphorylation of PDGFRalpha and sensitivity of cultured PTCL cells to imatinib (as well as to an inhibitor of histone deacetylase) were found. These results, which might be extended to other more rare PTCL categories, provide insight into tumor pathogenesis and clinical management of PTCL/U.

Identification of Nicotinamide N-Methyltransferase as a Novel Tumor Marker for Renal Clear Cell Carcinoma

PURPOSE

To explore the involvement of enzymes of drug metabolism in renal cell carcinoma we analyzed the gene expression profiles of tumor and nontumor tissues from the same patient by DNA macroarray. The enzyme nicotinamide N-methyltransferase was selected for further evaluation.

MATERIALS AND METHODS

Nicotinamide N-methyltransferase mRNA expression was investigated in paired tissue samples from cancerous and noncancerous parts of the kidneys of 30 patients with clear cell renal cell carcinoma who underwent tumor nephrectomy. Measurements were performed by semiquantitative reverse transcriptase-polymerase chain reaction and quantitative real-time polymerase chain reaction. Paired tissue samples were also obtained from 1 patient with chromophobe renal cell carcinoma and from another with oncocytoma to compare the specificity of changes in nicotinamide N-methyltransferase expression among tumors that are related to different renal epithelial cell types. Western blot analysis and catalytic activity assay were also performed to study nicotinamide N-methyltransferase expression. Expression correlated with tumor characteristics.

RESULTS

A marked increased expression in tumor tissue was found for nicotinamide N-methyltransferase, which is an enzyme involved in the biotransformation of many drugs and xenobiotic compounds. Differential gene expression measurements in tumor vs normal tissue revealed up-regulation in all clear cell renal cell carcinomas at between 3 and 294-fold (mean 41). In contrast, in chromophobe renal cell carcinoma and oncocytoma nicotinamide N-methyltransferase expression did not increase. In addition, nicotinamide N-methyltransferase expression significantly correlated inversely with tumor size.

CONCLUSIONS

Our results indicate that a marked nicotinamide N-methyltransferase increase is a peculiar feature of clear cell renal cell carcinoma. Additional studies may establish the role of nicotinamide N-methyltransferase in tumor formation and progression.

Histone deacetylase inhibitor depsipeptide represses nicotinamide N-methyltransferase and hepatocyte nuclear factor-1beta gene expression in human papillary thyroid cancer cells

Nicotinamide N-methyltransferase (NNMT) catalyzes N-methylation of nicotinamide and other structural analogues. NNMT gene expression is enhanced in many papillary thyroid cancer cells and activated by hepatocyte nuclear factor (HNF)-1beta. In this work, we studied the effects of depsipeptide, a histone deacetylase inhibitor, on NNMT gene expression in BHP 18-21 papillary thyroid cancer cells. Depsipeptide reduced NNMT mRNA level in a dose-dependent and time-dependent manner as determined by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR). In contrast, expression of the sodium iodide symporter (NIS), a gene with differentiated function, waas enhanced in the treated cells. NNMT protein level determined by Western blot analysis and NNMT catalytic activity was also reduced significantly in the depsipeptide-treated cells. To study the mechanism of NNMT gene repression by depsipeptide, effects of depsipeptide on NNMT promoter activity were determined by luciferase reporter gene assay. NNMT promoter activity was significantly reduced in the HNF-1beta-positive BHP 18-21 cells but not in the HNF-1beta-negative BHP 14-9 papillary cancer cells. A mutant reporter construct with mutations in a HNF-1 site in the NNMT basal promoter region did not respond to depsipeptide in both HNF-1beta protein levels, and abolished activity of DNA binding to the HNF-1 site in the NNMT promoter region. Protein synthesis inhibitor cycloheximide and proteasome inhibitor MG-132 enhanced HNF-1beta stability in the depsipeptide-treated cells. In summary, depsipeptide represses NNMT and HNF-1beta gene expression in some papillary thyroid cancer cells. the repression of NNMT by depsipeptide is at the transcription level through downregulation of transcription activator HNF-1beta.