Expression of methionine adenosyltransferase 2A in renal cell carcinomas and potential mechanism for kidney carcinogenesis

Overview of Methionine Adenosyltransferase 2A (MAT2A) as an Anticancer Target: Structure, Function, and Inhibitors

Methionine adenosyltransferase 2A (MAT2A) is a rate-limiting enzyme in the methionine cycle that primarily catalyzes the synthesis of S-adenosylmethionine (SAM) from methionine and adenosine triphosphate (ATP). MAT2A has been recognized as a therapeutic target for the treatment of cancers. Recently, a few MAT2A inhibitors have been reported, and three entered clinical trials to treat solid tumorsor lymphoma with MTAP loss. This review aims to summarize the current understanding of the roles of MAT2A in cancer and the discovery of MAT2A inhibitors. Furthermore, a perspective on the use of MAT2A inhibitors for the treatment of cancer is also discussed. We hope to provide guidance for future drug design and optimization via analysis of the binding modes of known MAT2A inhibitors.

Blockade LAT1 Mediates Methionine Metabolism to Overcome Oxaliplatin Resistance under Hypoxia in Renal Cell Carcinoma

Simple Summary

The transformation and mechanism of methionine metabolism of renal cell carcinoma (RCC) under a hypoxic microenvironment is not well understood as yet. This study illustrated that the reprogramming of methionine metabolism and the subsequent glutathione (GSH) synthesis were mediated by amino acid transporter 1 (LAT1). Correspondingly, we proposed a combination strategy of LAT1 inhibitor JPH203 and oxaliplatin, which presented an enhanced therapeutic efficacy for RCC both in vivo and in vitro.

Abstract

Hypoxic microenvironment and metabolic dysregulation of tumor impairs the therapeutic efficacy of chemotherapeutic drugs, resulting in drug resistance and tumor metastasis, which has always been a challenge for the treatment of solid tumors, including renal cell carcinoma (RCC). Herein, starting from the evaluation of methionine metabolism in RCC cells, we demonstrated that the increased methionine accumulation in RCC cells was mediated by L-type amino acid transporter 1 (LAT1) under hypoxia. Glutathione (GSH), as a methionine metabolite, would attenuate the therapeutic efficacy of oxaliplatin through chemical chelation. Reducing methionine uptake by LAT1 inhibitor JPH203 significantly enhanced the sensitivity of RCC cells to oxaliplatin by reducing GSH production in vitro and in vivo. Therefore, we proposed an effective and stable therapeutic strategy based on the combination of oxaliplatin and LAT1 inhibitor, which is expected to solve the resistance of RCC to platinum-based drugs under hypoxia to a certain extent, providing a meaningful insight into the development of new therapeutic strategies and RCC treatment

Inhibition of MAT2A-Related Methionine Metabolism Enhances The Efficacy of Cisplatin on Cisplatin-Resistant Cells in Lung Cancer

Objective

Tumor drug resistance is a vital obstacle to chemotherapy in lung cancer. Methionine adenosyltransferase 2A has been considered as a potential target for lung cancer treatment because targeting it can disrupt the tumorigenicity of lung tumor-initiating cells. In this study, we primarily observed the role of methionine metabolism in cisplatin-resistant lung cancer cells and the functional mechanism of MAT2A related to cisplatin resistance.

Materials and Methods

In this experimental study, we assessed the half maximal inhibitory concentration (IC₅₀) of cisplatin in different cell lines and cell viability via Cell Counting Kit-8. Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR) was used to determine the expression of relative proteins and genes. Crystal violet staining was used to investigate cell proliferation. Additionally, we explored the transcriptional changes in lung cancer cells via RNA-seq.

Results

We found H460/DDP and PC-9 cells were more resistant to cisplatin than H460, and MAT2A was overexpressed in cisplatin-resistant cells. Interestingly, methionine deficiency enhanced the inhibitory effect of cisplatin on cell activity and the pro-apoptotic effect. Targeting MAT2A not only restrained cell viability and proliferation, but also contributed to sensitivity of H460/DDP to cisplatin. Furthermore, 4283 up-regulated and 5841 down-regulated genes were detected in H460/DDP compared with H460, and 71 signal pathways were significantly enriched. After treating H460/DDP cells with PF9366, 326 genes were up-regulated, 1093 genes were down-regulated, and 13 signaling pathways were significantly enriched. In TNF signaling pathway, CAS7 and CAS8 were decreased in H460/DDP cells, which increased by PF9366 treatment. Finally, the global histone methylation (H3K4me3, H3K9me2, H3K27me3, H3K36me3) was reduced under methionine deficiency conditions, while H3K9me2 and H3K36me3 were decreased specially via PF9366.

Conclusion

Methionine deficiency or MAT2A inhibition may modulate genes expression associated with apoptosis, DNA repair and TNF signaling pathways by regulating histone methylation, thus promoting the sensitivity of lung cancer cells to cisplatin.

Untargeted Metabolomics Showed Accumulation of One-Carbon Metabolites to Facilitate DNA Methylation during Extracellular Matrix Detachment of Cancer Cells

Tumor cells detached from the extracellular matrix (ECM) undergo anoikis resistance and metabolic reprogramming to facilitate cancer cell survival and promote metastasis. During ECM detachment, cancer cells utilize genomic methylation to regulate transcriptional events. One-carbon (1C) metabolism is a well-known contributor of SAM, a global substrate for methylation reactions, especially DNA methylation. DNA methylation-mediated repression of NK cell ligands MICA and MICB during ECM detachment has been overlooked. In the current work, we quantitated the impact of ECM detachment on one-carbon metabolites, expression of 1C regulatory pathway genes, and total methylation levels. Our results showed that ECM detachment promotes the accumulation of one-carbon metabolites and induces regulatory pathway genes and total DNA methylation. Furthermore, we measured the expression of well-known targets of DNA methylation in NK cell ligands in cancer cells, namely, MICA/B, during ECM detachment and observed low expression compared to ECM-attached cancer cells. Finally, we treated the ECM-detached cancer cells with vitamin C (a global methylation inhibitor) and observed a reduction in the promoter methylation of NK cell ligands, resulting in MICA/B re-expression. Treatment with vitamin C was also found to reduce global DNA methylation levels in ECM-detached cancer cells.

MAT2A Localization and Its Independently Prognostic Relevance in Breast Cancer Patients

(1) Background: methionine cycle is not only essential for cancer cell proliferation but is also critical for metabolic reprogramming, a cancer hallmark. Hepatic and extrahepatic tissues methionine adenosyltransferases (MATs) are products of two genes, MAT1A and MAT2A that catalyze the formation of S-adenosylmethionine (SAM), the principal biological methyl donor. Glycine N-methyltransferase (GNMT) further utilizes SAM for sarcosine formation, thus it regulates the ratio of SAM:S-adenosylhomocysteine (SAH). (2) Methods: by analyzing the TCGA/GTEx datasets available within GEPIA2, we discovered that breast cancer patients with higher MAT2A had worse survival rate (p = 0.0057). Protein expression pattern of MAT1AA, MAT2A and GNMT were investigated in the tissue microarray in our own cohort (n = 252) by immunohistochemistry. MAT2A C/N expression ratio and cell invasion activity were further investigated in a panel of breast cancer cell lines. (3) Results: GNMT and MAT1A were detected in the cytoplasm, whereas MAT2A showed both cytoplasmic and nuclear immunoreactivity. Neither GNMT nor MAT1A protein expression was associated with patient survival rate in our cohort. Kaplan–Meier survival curves showed that a higher cytoplasmic/nuclear (C/N) MAT2A protein expression ratio correlated with poor overall survival (5 year survival rate: 93.7% vs. 83.3%, C/N ratio ≥ 1.0 vs. C/N ratio < 1.0, log-rank p = 0.004). Accordingly, a MAT2A C/N expression ratio ≥ 1.0 was determined as an independent risk factor by Cox regression analysis (hazard ratio = 2.771, p = 0.018, n = 252). In vitro studies found that breast cancer cell lines with a higher MAT2A C/N ratio were more invasive. (4) Conclusions: the subcellular localization of MAT2A may affect its functions, and elevated MAT2A C/N ratio in breast cancer cells is associated with increased invasiveness. MAT2A C/N expression ratio determined by IHC staining could serve as a novel independent prognostic marker for breast cancer.

Monocarboxylate transporter 1 promotes proliferation and invasion of renal cancer cells by mediating acetate transport

One hallmark of renal cell carcinoma (RCC) is metabolic reprogramming, which involves elevation of glycolysis and upregulation of lipid metabolism. However, the mechanism of metabolic reprogramming is incompletely understood. Monocarboxylate transporter 1 (MCT1) promotes transport for lactate and pyruvate, which are crucial for cell metabolism. The aim of present study was to investigate the function of MCT1 on RCC development and its mechanism on metabolic reprogramming. The results showed that MCT1 messenger RNA and protein levels significantly increased in cancer tissues of ccRCC compared to normal tissue. MCT1 was further found to mainly located in the cell membrane of RCC. The knockdown of MCT1 by RNAi significantly inhibited proliferation and migration of 786-O and ACHN cells. MCT1 also induced the expressions of proliferation marker Ki-67 and invasion marker SNAI1. Moreover, we also showed that acetate treatment could upregulate the expression of MCT1, but not other MCT isoforms. On the other hand, MCT1 was involved in acetate transport and intracellular histone acetylation. In summary, this study revealed that MCT1 is abnormally high in ccRCC and promotes cancer development. The regulatory effect of MCT1 on cell proliferation and invasion maybe mediated by acetate transport.

Mutations in the S-Adenosylmethionine Synthetase Genes SAM1 and SAM2 Differentially Affect Genome Stability in Saccharomyces cerevisiae

Maintenance of genome integrity is a crucial cellular focus that involves a wide variety of proteins functioning in multiple processes. Defects in many different pathways can result in genome instability, a hallmark of cancer. Utilizing a diploid Saccharomyces cerevisiae model, we previously reported a collection of gene mutations that affect genome stability in a haploinsufficient state. In this work we explore the effect of gene dosage on genome instability for one of these genes and its paralog; SAM1 and SAM2 These genes encode S-Adenosylmethionine (AdoMet) synthetases, responsible for the creation of AdoMet from methionine and ATP. AdoMet is the universal methyl donor for methylation reactions and is essential for cell viability. It is the second most used cellular enzyme substrate and is exceptionally well-conserved through evolution. Mammalian cells express three genes, MAT1A, MAT2A, and MAT2B, with distinct expression profiles and functions. Alterations to these AdoMet synthetase genes, and AdoMet levels, are found in many cancers, making them a popular target for therapeutic intervention. However, significant variance in these alterations are found in different tumor types, with the cellular consequences of the variation still unknown. By studying this pathway in the yeast system, we demonstrate that losses of SAM1 and SAM2 have different effects on genome stability through distinctive effects on gene expression and AdoMet levels, and ultimately separate effects on the methyl cycle. Thus, this study provides insight into the mechanisms by which differential expression of the SAM genes have cellular consequences that affect genome instability.

Modulation of dietary methionine intake elicits potent, yet distinct, anticancer effects on primary versus metastatic tumors

Methionine dependency describes the characteristic rapid in vitro death of most tumor cells in the absence of methionine. Combining chemotherapy with dietary methionine deprivation [methionine-deficient diet (MDD)] at tolerable levels has vast potential in tumor treatment; however, it is limited by MDD-induced toxicity during extended deprivation. Recent advances in imaging and irradiation delivery have created the field of stereotactic body radiotherapy (SBRT), where fewer large-dose fractions delivered in less time result in increased local-tumor control, which could be maximally synergistic with an MDD short course. Identification of the lowest effective methionine dietary intake not associated with toxicity will further enhance the cancer therapy potential. In this study, we investigated the effects of MDD and methionine-restricted diet (MRD) in primary and metastatic melanoma models in combination with radiotherapy (RT). In vitro, MDD dose-dependently sensitized mouse and human melanoma cell lines to RT. In vivo in mice, MDD substantially potentiated the effects of RT by a significant delay in tumor growth, in comparison with administering MDD or RT alone. The antitumor effects of an MDD/RT approach were due to effects on one-carbon metabolism, resulting in impaired methionine biotransformation via downregulation of Mat2a, which encodes methionine adenosyltransferase 2A. Furthermore, and probably most importantly, MDD and MRD substantially diminished metastatic potential; the antitumor MRD effects were not associated with toxicity to normal tissue. Our findings suggest that modulation of methionine intake holds substantial promise for use with short-course SBRT for cancer treatment.

Androgen-dependent alternative mRNA isoform expression in prostate cancer cells

Background: Androgen steroid hormones are key drivers of prostate cancer. Previous work has shown that androgens can drive the expression of alternative mRNA isoforms as well as transcriptional changes in prostate cancer cells. Yet to what extent androgens control alternative mRNA isoforms and how these are expressed and differentially regulated in prostate tumours is unknown. Methods: Here we have used RNA-Seq data to globally identify alternative mRNA isoform expression under androgen control in prostate cancer cells, and profiled the expression of these mRNA isoforms in clinical tissue. Results: Our data indicate androgens primarily switch mRNA isoforms through alternative promoter selection. We detected 73 androgen regulated alternative transcription events, including utilisation of 56 androgen-dependent alternative promoters, 13 androgen-regulated alternative splicing events, and selection of 4 androgen-regulated alternative 3' mRNA ends. 64 of these events are novel to this study, and 26 involve previously unannotated isoforms. We validated androgen dependent regulation of 17 alternative isoforms by quantitative PCR in an independent sample set. Some of the identified mRNA isoforms are in genes already implicated in prostate cancer (including LIG4, FDFT1 and RELAXIN), or in genes important in other cancers (e.g. NUP93 and MAT2A). Importantly, analysis of transcriptome data from 497 tumour samples in the TGCA prostate adenocarcinoma (PRAD) cohort identified 13 mRNA isoforms (including TPD52, TACC2 and NDUFV3) that are differentially regulated in localised prostate cancer relative to normal tissue, and 3 ( OSBPL1A, CLK3 and TSC22D3) which change significantly with Gleason grade and  tumour stage. Conclusions: Our findings dramatically increase the number of known androgen regulated isoforms in prostate cancer, and indicate a highly complex response to androgens in prostate cancer cells that could be clinically important.

Targeting S-adenosylmethionine biosynthesis with a novel allosteric inhibitor of Mat2A

S-Adenosyl-L-methionine (SAM) is an enzyme cofactor used in methyl transfer reactions and polyamine biosynthesis. The biosynthesis of SAM from ATP and L-methionine is performed by the methionine adenosyltransferase enzyme family (Mat; EC 2.5.1.6). Human methionine adenosyltransferase 2A (Mat2A), the extrahepatic isoform, is often deregulated in cancer. We identified a Mat2A inhibitor, PF-9366, that binds an allosteric site on Mat2A that overlaps with the binding site for the Mat2A regulator, Mat2B. Studies exploiting PF-9366 suggested a general mode of Mat2A allosteric regulation. Allosteric binding of PF-9366 or Mat2B altered the Mat2A active site, resulting in increased substrate affinity and decreased enzyme turnover. These data support a model whereby Mat2B functions as an inhibitor of Mat2A activity when methionine or SAM levels are high, yet functions as an activator of Mat2A when methionine or SAM levels are low. The ramification of Mat2A activity modulation in cancer cells is also described.

Identification of dysregulated genes in rheumatoid arthritis based on bioinformatics analysis

BACKGROUND

Rheumatoid arthritis (RA) is a chronic auto-inflammatory disorder of joints. The present study aimed to identify the key genes in RA for better understanding the underlying mechanisms of RA.

METHODS

The integrated analysis of expression profiling was conducted to identify differentially expressed genes (DEGs) in RA. Moreover, functional annotation, protein-protein interaction (PPI) network and transcription factor (TF) regulatory network construction were applied for exploring the potential biological roles of DEGs in RA. In addition, the expression level of identified candidate DEGs was preliminarily detected in peripheral blood cells of RA patients in the GSE17755 dataset. Quantitative real-time polymerase chain reaction (qRT-PCR) was conducted to validate the expression levels of identified DEGs in RA.

RESULTS

A total of 378 DEGs, including 202 up- and 176 down-regulated genes, were identified in synovial tissues of RA patients compared with healthy controls. DEGs were significantly enriched in axon guidance, RNA transport and MAPK signaling pathway. RBFOX2, LCK and SERBP1 were the hub proteins in the PPI network. In the TF-target gene network, RBFOX2, POU6F1, WIPF1 and PFKFB3 had the high connectivity with TFs. The expression status of 11 candidate DEGs was detected in GSE17755, the expression levels of MAT2A and NSA2 were significantly down-regulated and CD47 had the up-regulated tendency in peripheral blood cells of patients with RA compared with healthy individuals. qRT-PCR results of MAT2A, NSA2, CD47 were compatible with our bioinformatics analyses.

DISCUSSION

Our study might provide valuable information for exploring the pathogenesis mechanism of RA and identifying the potential biomarkers for RA diagnosis.

Cellular Stress and p53-Associated Apoptosis by Juniperus communis L. Berry Extract Treatment in the Human SH-SY5Y Neuroblastoma Cells

Plant phenolics have shown to activate apoptotic cell death in different tumourigenic cell lines. In this study, we evaluated the effects of juniper berry extract (Juniperus communis L.) on p53 protein, gene expression and DNA fragmentation in human neuroblastoma SH-SY5Y cells. In addition, we analyzed the phenolic composition of the extract. We found that juniper berry extract activated cellular relocalization of p53 and DNA fragmentation-dependent cell death. Differentially expressed genes between treated and non-treated cells were evaluated with the cDNA-RDA (representational difference analysis) method at the early time point of apoptotic process when p53 started to be activated and no caspase activity was detected. Twenty one overexpressed genes related to cellular stress, protein synthesis, cell survival and death were detected. Interestingly, they included endoplasmic reticulum (ER) stress inducer and sensor HSPA5 and other ER stress-related genes CALM2 and YKT6 indicating that ER stress response was involved in juniper berry extract mediated cell death. In composition analysis, we identified and quantified low concentrations of fifteen phenolic compounds. The main groups of them were flavones, flavonols, phenolic acids, flavanol and biflavonoid including glycosides of quercetin, apigenin, isoscutellarein and hypolaetin. It is suggested that juniper berry extract induced the p53-associated apoptosis through the potentiation and synergism by several phenolic compounds.

Methionine and cystine double deprivation stress suppresses glioma proliferation via inducing ROS/autophagy

Cancer cells are highly dependent on methionine and cystine (Met-Cys) for survival and proliferation. However, the molecular mechanism is not fully clear. The present study is to investigate the effects of Met-Cys deprivation on glioma cells proliferation. The results showed that Met-Cys double deprivation had synergistic action on elevating ROS level, decreased GSH level and inhibition of glioma cell proliferation. Moreover, both of them deprivation triggered autophagy of glioma cells both in vitro and in vivo. Importantly, Met-Cys double restriction diet inhibited growth of glioma. These results provided a new regulation mechanism of Met-Cys metabolism on affecting glioma cell proliferation, suggesting that targeting Met-Cys metabolism may be a potential strategy for glioma therapy.

Pioglitazone does not affect the risk of kidney cancer in patients with type 2 diabetes

OBJECTIVE

To investigate whether pioglitazone treatment of patients with type 2 diabetes mellitus was associated with an increased risk of kidney cancer.

METHODS

The reimbursement databases of all Taiwanese patients with type 2 diabetes who received oral anti-diabetic agents or insulin from 1996 to 2009 were retrieved from the National Health Insurance. An entry date was set at 1 January 2006, and a total of 1,093,675 patients with type 2 diabetes were followed up for kidney cancer incidence until the end of 2009. The incidences of kidney cancer among patients who had and had not received pioglitazone, as well as among subgroups of those treated with pioglitazone (sorted by time since starting pioglitazone, duration of treatment and cumulative dose) were calculated and hazard ratios (HRs) estimated by Cox regression analysis.

RESULTS

Of the 1,093,675 patients, 58,172 (5.3%) had and 1,035,503 (94.7%) had not received pioglitazone, with incident kidney cancer developing in 208 (0.36%) and 3304 (0.32%) patients, respectively, and a respective incidence of 97.7 and 90.5 per 100,000 person-years. Pioglitazone and kidney cancer were not significantly associated in unadjusted (HR 1.04; 95% confidence interval (CI), 0.90-1.20), age-sex-adjusted (HR 1.09; 95% CI, 0.95-1.25), and fully adjusted (HR 1.09; 95% CI, 0.94-1.26) models. None of the dose-response parameters showed a significant trend of risk association, with all P-trends >0.10.

CONCLUSIONS

Pioglitazone does not affect the risk of kidney cancer.