Determination of the Minimum Sample Amount for Capillary Electrophoresis-Fourier Transform Mass Spectrometry (CE-FTMS)-Based Metabolomics of Colorectal Cancer Biopsies

The minimum sample volume for capillary electrophoresis-Fourier transform mass spectrometry (CE-FTMS) useful for analyzing hydrophilic metabolites was investigated using samples obtained from colorectal cancer patients. One, two, five, and ten biopsies were collected from tumor and nontumor parts of the surgically removed specimens from each of the five patients who had undergone colorectal cancer surgery. Metabolomics was performed on the collected samples using CE-FTMS. To determine the minimum number of specimens based on data volume and biological interpretability, we compared the number of annotated metabolites in each sample with different numbers of biopsies and conducted principal component analysis (PCA), hierarchical cluster analysis (HCA), quantitative enrichment analysis (QEA), and random forest analysis (RFA). The number of metabolites detected in one biopsy was significantly lower than those in 2, 5, and 10 biopsies, whereas those detected among 2, 5, and 10 pieces were not significantly different. Moreover, a binary classification model developed by RFA based on 2-biopsy data perfectly distinguished tumor and nontumor samples with 5- and 10-biopsy data. Taken together, two biopsies would be sufficient for CE-FTMS-based metabolomics from a data content and biological interpretability viewpoint, which opens the gate of biopsy metabolomics for practical clinical applications.

Metabolomics with severity of radiographic knee osteoarthritis and early phase synovitis in middle-aged women from the Iwaki Health Promotion Project: a cross-sectional study

Background

Osteoarthritis (OA) is one of the costliest and most disabling forms of arthritis, and it poses a major public health burden; however, its detailed etiology, pathophysiology, and metabolism remain unclear. Therefore, the purpose of this study was to investigate the key plasma metabolites and metabolic pathways, especially focusing on radiographic OA severity and synovitis, from a large sample cohort study.

Methods

We recruited 596 female volunteers who participated in the Iwaki Health Promotion Project in 2017. Standing anterior-posterior radiographs of the knee were classified by the Kellgren-Lawrence (KL) grade. Radiographic OA was defined as a KL grade of ≥ 2. Individual effusion-synovitis was scored according to the Whole-Organ Magnetic Resonance Imaging Scoring System. Blood samples were collected, and metabolites were extracted from the plasma. Metabolome analysis was performed using capillary electrophoresis time-of-flight mass spectrometry. To investigate the relationships among metabolites, the KL grade, and effusion-synovitis scores, partial least squares with rank order of groups (PLS-ROG) analyses were performed.

Results

Among the 82 metabolites examined in this assay, PLS-ROG analysis identified 42 metabolites that correlated with OA severity. A subsequent metabolite set enrichment analysis using the significant metabolites showed the urea cycle and tricarboxylic acid cycle as key metabolic pathways. Moreover, further PLS-ROG analysis identified cystine (p = 0.009), uric acid (p = 0.024), and tyrosine (p = 0.048) as common metabolites associated with both OA severity and effusion-synovitis. Receiver operating characteristic analyses showed that cystine levels were moderately associated with radiographic OA (p < 0.001, area under the curve 0.714, odds ratio 3.7).

Conclusion

Large sample metabolome analyses revealed that cystine, an amino acid associated with antioxidant activity and glutamate homeostasis, might be a potential metabolic biomarker for radiographic osteoarthritis and early phase synovitis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02830-w.

Uncovering the Role of Gut Microbiota in Amino Acid Metabolic Disturbances in Heart Failure Through Metagenomic Analysis

Aims: Circulating amino acid (AA) abnormalities serve as predictors of adverse outcomes in patients with heart failure (HF). However, the role of the gut microbiota in AA disturbances remains unknown. Thus, we investigated gut microbial functions and their associations with AA metabolic alterations in patients with HF. Methods and Results: We performed whole-genome shotgun sequencing of fecal samples and mass spectrometry-based profiling of AAs in patients with compensated HF. Plasma levels of total essential AAs (EAAs) and histidine were significantly lower in patients with HF than in control subjects. HF patients also displayed increased and decreased abundance of gut microbial genes involved in the degradation and biosynthesis, respectively, of EAAs, including branched-chain AAs (BCAAs) and histidine. Importantly, a significant positive correlation was observed between the abundance of microbial genes involved in BCAA biosynthesis and plasma BCAA levels in patients with HF, but not in controls. Moreover, network analysis revealed that the depletion of Eubacterium and Prevotella, which harbor genes for BCAA and histidine biosynthesis, contributed to decreased abundance of microbial genes involved in the biosynthesis of those EAAs in patients with HF. Conclusions: The present study demonstrated the relationship between gut microbiota and AA metabolic disturbances in patients with HF.

Nontargeted Serum Lipid Profiling of Nonalcoholic Steatohepatitis by Multisegment Injection-Nonaqueous Capillary Electrophoresis-Mass Spectrometry: A Multiplexed Separation Platform for Resolving Ionic Lipids

New methods are needed for global lipid profiling due to the complex chemical structures and diverse physicochemical properties of lipids. Herein we introduce a robust data workflow to unambiguously select lipid features from serum ether extracts by multisegment injection-nonaqueous capillary electrophoresis-mass spectrometry (MSI-NACE-MS). An iterative three-stage screening strategy is developed for nontargeted lipid analyses when using multiplexed electrophoretic separations coupled to an Orbitrap mass analyzer under negative ion mode. This approach enables the credentialing of 270 serum lipid features annotated based on their accurate mass and relative migration time, including 128 ionic lipids reliably measured (median CV ≈ 13%) in most serum samples (>75%) from nonalcoholic steatohepatitis (NASH) patients (n = 85). A mobility map is introduced to classify charged lipid classes over a wide polarity range with selectivity complementary to chromatographic separations, including lysophosphatidic acids, phosphatidylcholines, phosphatidylinositols, phosphatidylethanolamines, and nonesterified fatty acids (NEFAs). Serum lipidome profiles were also used to differentiate high- from low-risk NASH patients using a k-means clustering algorithm, where elevated circulating NEFAs (e.g., palmitic acid) were associated with increased glucose intolerance, more severe liver fibrosis, and greater disease burden. MSI-NACE-MS greatly expands the metabolome coverage of conventional aqueous-based CE-MS protocols and is a promising platform for large-scale lipidomic studies.

Metagenomic analysis of gut microbiota reveals its role in trimethylamine metabolism in heart failure

BACKGROUND

We had previously reported an increase in trimethylamine N-oxide (TMAO) levels in patients with both compensated and decompensated heart failure (HF) and alteration in gut microbiota composition using 16S rRNA gene amplicon analysis. Although a metagenome-wide analysis showed that choline-TMA lyase levels increased in HF patients, which TMA generation pathway from choline, carnitine, or betaine contributes to the increase in TMAO levels in HF needs to be elucidated.

METHODS

We conducted a metagenome-wide shotgun sequencing analysis of gut microbiota and measured the TMAO levels in plasma of 22 HF patients during the compensated phase and 11 age-, sex-, and comorbidity-matched control subjects, whose gut microbiota compositions were reported in a previous 16S rRNA-based analysis.

RESULTS

The abundance of cntA/B was positively correlated with TMAO, especially in HF patients, whereas that of cutC/D or betaine reductase was not correlated either in controls or HF patients. The abundance of cntA/B was mainly derived from the genera Escherichia and Klebsiella either in controls or HF patients.

CONCLUSION

TMAO levels in plasma depend on the abundance of cntA/B in HF. Although it is difficult to exclude the involvement of confounding factors, microbial dysbiosis connecting the abundance of cntA/B in the gut and the increase of TMAO in plasma can be a therapeutic target for HF.

Capillary Electrophoresis Mass Spectrometry-Based Metabolomics of Plasma Samples from Healthy Subjects in a Cross-Sectional Japanese Population Study

For large-scale metabolomics, such as in cohort studies, normalization protocols using quality control (QC) samples have been established when using data from gas chromatography and liquid chromatography coupled to mass spectrometry. However, normalization protocols have not been established for capillary electrophoresis-mass spectrometry metabolomics. In this study, we performed metabolome analysis of 314 human plasma samples using capillary electrophoresis-mass spectrometry. QC samples were analyzed every 10 samples. The results of principal component analysis for the metabolome data from only the QC samples showed variations caused by capillary replacement in the first principal component score and linear variation with continuous measurement in the second principal component score. Correlation analysis between diagnostic blood tests and plasma metabolites normalized by the QC samples was performed for samples from 188 healthy subjects who participated in a Japanese population study. Five highly correlated pairs were identified, including two previously unidentified pairs in normal healthy subjects of blood urea nitrogen and guanidinosuccinic acid, and gamma-glutamyl transferase and cysteine glutathione disulfide. These results confirmed the validity of normalization protocols in capillary electrophoresis-mass spectrometry using large-scale metabolomics and comprehensive analysis.

Whole-body insulin resistance and energy expenditure indices, serum lipids, and skeletal muscle metabolome in a state of lipoprotein lipase overexpression

INTRODUCTION

Overexpression of lipoprotein lipase (LPL) protects against high-fat-diet (HFD)-induced obesity and insulin resistance in transgenic rabbits; however, the molecular mechanisms remain unclear. Skeletal muscle is a major organ responsible for insulin-stimulated glucose uptake and energy expenditure.

OBJECTIVES

The main purpose of the current study was to examine the effects of the overexpression of LPL on the skeletal muscle metabolomic profiles to test our hypothesis that the mitochondrial oxidative metabolism would be activated in the skeletal muscle of LPL transgenic rabbits and that the higher mitochondrial oxidative metabolism activity would confer better phenotypic metabolic outcomes.

METHODS

Under a HFD, insulin resistance index was measured using the intravenous glucose tolerance test, and total energy expenditure (TEE) was measured by doubly-labeled water in control and LPL transgenic rabbits (n = 12, each group). Serum lipids, such as triglycerides and free fatty acid, were also measured. The skeletal muscle metabolite profile was analyzed using capillary electrophoresis time-of flight mass spectrometry in the two groups (n = 9, each group). A metabolite set enrichment analysis (MSEA) with muscle metabolites and a false discovery rate q < 0.2 was performed to identify significantly different metabolic pathways between the 2 groups.

RESULTS

The triglycerides and free fatty acid levels and insulin resistance index were lower, whereas the TEE was higher in the LPL transgenic rabbits than in the control rabbits. Among 165 metabolites detected, the levels of 37 muscle metabolites were significantly different between the 2 groups after false discovery rate correction (q < 0.2). The MSEA revealed that the TCA cycle and proteinogenic amino acid metabolism pathways were significantly different between the 2 groups (P < 0.05). In the MSEA, all four selected metabolites for the TCA cycle (2-oxoglutaric acid, citric acid, malic acid, fumaric acid), as well as eight selected metabolites for proteinogenic amino acid metabolism (asparagine, proline, methionine, phenylalanine, histidine, arginine, leucine, isoleucine) were consistently increased in the transgenic rabbits compared with control rabbits, suggesting that these two metabolic pathways were activated in the transgenic rabbits. Some of the selected metabolites, such as citric acid and methionine, were significantly associated with serum lipids and insulin resistance (P < 0.05).

CONCLUSION

The current results suggest that the overexpression of LPL may lead to increased activities of TCA cycle and proteinogenic amino acid metabolism pathways in the skeletal muscle, and these enhancements may play an important role in the biological mechanisms underlying the anti-obesity/anti-diabetes features of LPL overexpression.

Extraction of Aqueous Metabolites from Cultured Adherent Cells for Metabolomic Analysis by Capillary Electrophoresis-Mass Spectrometry

Metabolomic analysis is a promising omics approach to not only understand the specific metabolic regulation in cancer cells compared to normal cells but also to identify biomarkers for early-stage cancer detection and prediction of chemotherapy response in cancer patients. Preparation of uniform samples for metabolomic analysis is a critical issue that remains to be addressed. Here, we present an easy and reliable protocol for extracting aqueous metabolites from cultured adherent cells for metabolomic analysis using capillary electrophoresis-mass spectrometry (CE-MS). Aqueous metabolites from cultured cells are analyzed by culturing and washing cells, treating cells with methanol, extracting metabolites, and removing proteins and macromolecules with spin columns for CE-MS analysis. Representative results using lung cancer cell lines treated with diamide, an oxidative reagent, illustrate the clearly observable metabolic shift of cells under oxidative stress. This article would be especially valuable to students and investigators involved in metabolomics research, who are new to harvesting metabolites from cell lines for analysis by CE-MS.

Metabolome analysis of esophageal cancer tissues using capillary electrophoresis-time-of-flight mass spectrometry

Reports of the metabolomic characteristics of esophageal cancer are limited. In the present study, we thus conducted metabolome analysis of paired tumor tissues (Ts) and non-tumor esophageal tissues (NTs) using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS). The Ts and surrounding NTs were surgically excised pair-wise from 35 patients with esophageal cancer. Following tissue homogenization and metabolite extraction, a total of 110 compounds were absolutely quantified by CE-TOFMS. We compared the concentrations of the metabolites between Ts and NTs, between pT1 or pT2 (pT1-2) and pT3 or pT4 (pT3-4) stage, and between node-negative (pN-) and node-positive (pN+) samples. Principal component analysis and hierarchical clustering analysis revealed clear metabolomic differences between Ts and NTs. Lactate and citrate levels in Ts were significantly higher (P=0.001) and lower (P<0.001), respectively, than those in NTs, which corroborated with the Warburg effect in Ts. The concentrations of most amino acids apart from glutamine were higher in Ts than in NTs, presumably due to hyperactive glutaminolysis in Ts. The concentrations of malic acid (P=0.015) and citric acid (P=0.008) were significantly lower in pT3-4 than in pT1-2, suggesting the downregulation of tricarboxylic acid (TCA) cycle activity in pT3-4. On the whole, in this study, we demonstrate significantly different metabolomic characteristics between tumor and non-tumor tissues and identified a novel set of metabolites that were strongly associated with the degree of tumor progression. A further understanding of cancer metabolomics may enable the selection of more appropriate treatment strategies, thereby contributing to individualized medicine.

CD44 variant 9 expression as a predictor for gastric cancer recurrence: immunohistochemical and metabolomic analysis of surgically resected tissues

CD44 variant 9 (CD44v9) and the heavy chain of 4F2 cell-surface antigen (CD98hc) appear important for regulation of reactive oxygen species defence and tumor growth in gastric cancer. This study examined the roles of CD44v9 and CD98hc as markers of gastric cancer recurrence, and investigated associations with energy metabolism. We applied capillary electrophoresis time-of-flight mass spectrometry to metabolome profiling of gastric cancer specimens from 103 patients who underwent resection with no residual tumor or microscopic residual tumor, and compared metabolite levels to immunohistochemical staining for CD44v9 and CD98hc. Positive expression rates were 40.7% for CD44v9 and 42.7% for CD98hc. Various tumor characteristics were significantly associated with CD44v9 expression. Five-year recurrence-free survival rate was significantly lower for CD44v9-positive tumors (39.1%) than for CD44v9-negative tumors (73.5%; P < 0.0001), but no significant differences in recurrence-free survival were seen according to CD98hc expression. Uni- and multivariate analyses identified positive CD44v9 expression as an independent predictor of poorer recurrence-free survival. Metabolome analysis of 110 metabolites found that levels of glutathione disulfide were significantly lower and reduced glutathione (GSH)/ glutathione disulfide (GSSG) ratio was significantly higher in CD44v9-positive tumors than in CD44v9-negative tumors, suggesting that CD44v9 may enhance pentose phosphate pathway flux and maintain GSH levels in cancer cells.

Metabolomic profling in gastric cancer tissues using time-of-flight mass spectrometry

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Background: To explore carcinogenic and prognostic biomarkers for gastric cancer, genomics, transcriptomics and proteomics approaches have been extensively applied;however, little has been investigated regarding the role of metabolomics profiles on progression and prognosis of gastric cancer. Therefore, in order to elucidate the role of metabolome on prognosis of gastric cancer, we investigated the metabolic profiles of gastric cancer tissue using time-of-flight mass spectrometry (TOFMS) Methods: A total of 162 patients with gastric cancer underwent gastrectomy from February 2010 to March 2013 were enrolled in this study. Cancer tissues (CA) and adjacent non-cancerous tissues (NC) were obtained from surgically resected sample and were snap-frozen in liquid nitrogen. The samples were then homogenized and then applied to capillary electrophoresis TOFMS (CE-TOFMS) The metabolomics dates were analyzed using principal component analysis (PCA) and hierachical clustering analysis(HCA) in order to compare the metabolic profiles of NC and CA. Metabolites date were further assessed according by the non-parametric Mann–Whitney U-test on the presence or absence of recurrence . Results: A total 96 metabolites were detected and quantified. PCA of the date well-distinguished CA from NC. In CA, lactate / pyruvate ratio was significantly higher, while adenylate energy charge was significantly lower than NC, which reaffirms the Warburug effect of cancer. Total glutathione and reducted glutathione/oxidized glutathione ratio in CA were significantly higher than in NC which possibly contributes to the homeostasis of redox status in CA. Intriguingly, in patients with recurrence, tumor concentrations of β-Ala, Asp, GDP and Gly were significantly lower than in those without recurrence. Conclusions: Metabolomic profiling clearly differentiated CA from NC. Considerably high lactate and amino acids levels expectedly highlighted the metabolome of tumors. Certain metabolite will be a candidate for biomarker in gastric cancer.

Arginine Deprivation Inhibits the Warburg Effect and Upregulates Glutamine Anaplerosis and Serine Biosynthesis in ASS1-Deficient Cancers

Targeting defects in metabolism is an underutilized strategy for the treatment of cancer. Arginine auxotrophy resulting from the silencing of argininosuccinate synthetase 1 (ASS1) is a common metabolic alteration reported in a broad range of aggressive cancers. To assess the metabolic effects that arise from acute and chronic arginine starvation in ASS1-deficient cell lines, we performed metabolite profiling. We found that pharmacologically induced arginine depletion causes increased serine biosynthesis, glutamine anaplerosis, oxidative phosphorylation, and decreased aerobic glycolysis, effectively inhibiting the Warburg effect. The reduction of glycolysis in cells otherwise dependent on aerobic glycolysis is correlated with reduced PKM2 expression and phosphorylation and upregulation of PHGDH. Concurrent arginine deprivation and glutaminase inhibition was found to be synthetic lethal across a spectrum of ASS1-deficient tumor cell lines and is sufficient to cause in vivo tumor regression in mice. These results identify two synthetic lethal therapeutic strategies exploiting metabolic vulnerabilities of ASS1-negative cancers.

Differential Glutamate Metabolism in Proliferating and Quiescent Mammary Epithelial Cells

Mammary epithelial cells transition between periods of proliferation and quiescence during development, menstrual cycles, and pregnancy, and as a result of oncogenic transformation. Utilizing an organotypic 3D tissue culture model coupled with quantitative metabolomics and proteomics, we identified significant differences in glutamate utilization between proliferating and quiescent cells. Relative to quiescent cells, proliferating cells catabolized more glutamate via transaminases to couple non-essential amino acid (NEAA) synthesis to α-ketoglutarate generation and tricarboxylic acid (TCA) cycle anaplerosis. As cells transitioned to quiescence, glutamine consumption and transaminase expression were reduced, while glutamate dehydrogenase (GLUD) was induced, leading to decreased NEAA synthesis. Highly proliferative human tumors display high transaminase and low GLUD expression, suggesting that proliferating cancer cells couple glutamine consumption to NEAA synthesis to promote biosynthesis. These findings describe a competitive and partially redundant relationship between transaminases and GLUD, and they reveal how coupling of glutamate-derived carbon and nitrogen metabolism can be regulated to support cell proliferation.

High-voltage capabilities of ultra-thin Nb2O5 nanosheet coated LiNi1/3Co1/3Mn1/3O2 cathodes

The surface coating of LiNi_1/3Co_1/3Mn_1/3 electrode with 1.1 nm Nb₂O₅ nanosheet enhanced the high voltage capability and long term stability of the charged state at 60 °C by reducing the contact area between electrode and electrolyte.

SHMT2 drives glioma cell survival in ischaemia but imposes a dependence on glycine clearance

Cancer cells adapt their metabolic processes to support rapid proliferation, but less is known about how cancer cells alter metabolism to promote cell survival in a poorly vascularized tumor microenvironment^1–3. Here, we identify a key role for serine and glycine metabolism in the survival of brain cancer cells within the ischemic zones of gliomas. In human glioblastoma multiforme (GBM), mitochondrial serine hydroxymethyltransferase (SHMT2) and glycine decarboxylase (GLDC) are highly expressed in the pseudopalisading cells that surround necrotic foci. We find that SHMT2 activity limits that of pyruvate kinase (PKM2) and reduces oxygen consumption, eliciting a metabolic state that confers a profound survival advantage to cells in poorly vascularized tumor regions. GLDC inhibition impairs cells with high SHMT2 levels as the excess glycine not metabolized by GLDC can be converted to the toxic molecules aminoacetone and methylglyoxal. Thus, SHMT2 is required for cancer cells to adapt to the tumor environment, but also renders these cells sensitive to glycine cleavage system inhibition.

Statistical hypothesis testing of factor loading in principal component analysis and its application to metabolite set enrichment analysis

Background

Principal component analysis (PCA) has been widely used to visualize high-dimensional metabolomic data in a two- or three-dimensional subspace. In metabolomics, some metabolites (e.g., the top 10 metabolites) have been subjectively selected when using factor loading in PCA, and biological inferences are made for these metabolites. However, this approach may lead to biased biological inferences because these metabolites are not objectively selected with statistical criteria.

Results

We propose a statistical procedure that selects metabolites with statistical hypothesis testing of the factor loading in PCA and makes biological inferences about these significant metabolites with a metabolite set enrichment analysis (MSEA). This procedure depends on the fact that the eigenvector in PCA for autoscaled data is proportional to the correlation coefficient between the PC score and each metabolite level. We applied this approach to two sets of metabolomic data from mouse liver samples: 136 of 282 metabolites in the first case study and 66 of 275 metabolites in the second case study were statistically significant. This result suggests that to set the number of metabolites before the analysis is inappropriate because the number of significant metabolites differs in each study when factor loading is used in PCA. Moreover, when an MSEA of these significant metabolites was performed, significant metabolic pathways were detected, which were acceptable in terms of previous biological knowledge.

Conclusions

It is essential to select metabolites statistically to make unbiased biological inferences from metabolomic data when using factor loading in PCA. We propose a statistical procedure to select metabolites with statistical hypothesis testing of the factor loading in PCA, and to draw biological inferences about these significant metabolites with MSEA. We have developed an R package “mseapca” to facilitate this approach. The “mseapca” package is publicly available at the CRAN website.

Abstract 1867: Metabolomic discrimination of undifferentiated and differentiated gastric cancer

Clinicopathological characteristics of gastric cancer patients strongly depend on histological type. In contrast with gene and protein expressions, metabolic properties of undifferentiated (UT) and differentiated (DT) gastric cancer have been largely unknown. Here, we conducted comparative metabolome analyses in UT and DT cell lines, uncovering characteristic differences between the levels of metabolites involved in energy metabolism. The metabolomic profile of DT cell lines was featured by its considerably high glycolytic intermediate, nucleotide, and glutathione levels, which highlight hallmarks of cancer metabolism represented by the Warburg effect and hyperactive nucleotide syntheses. In contrast, UT cell lines rather showed relatively low energy and redox statuses. We further confirmed the trends by measuring 392 metabolites of paired non-tumor and tumor gastric tissues obtained pairwise from 27 gastric cancer patients in order to metabolomically characterize non-tumors, UT (n=18), and DT (n=9) tumors. The results not only distinguished the profile of non-tumors from tumors, especially of DT, but also reaffirmed the distinctions between UT and DT tumors. Taken together, UT and DT cancers were metabolomically characterized both in vitro and in vivo; DT exhibited more typical cancer metabolic profiles than UT, whereas low glutathione ratios in UT imply their vulnerability to oxidative stress, which thus could be useful for developing more subtype-specific cancer therapeutics.

Citation Format: Kenjiro Kami, Tamaki Fujimori, Masanori Terashima, Masatoshi Kusuhara, Masanori Tokunaga, Yutaka Tanizawa, Etsuro Bando, Taiichi Kawamura, Hiroyuki Yamamoto, Yoshiaki Ohashi. Metabolomic discrimination of undifferentiated and differentiated gastric cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1867. doi:10.1158/1538-7445.AM2013-1867

Abstract 5429: Robust in vitro cancer metabolism in non-tumorigenic microglial cells

It is well documented that energy metabolism differs between cancerous tissue and normal tissue for a large variety of human and animal tumors. The murine J2 retrovirus contributes to oncogenesis in macrophage cells. The BV-2 microglia cells were immortalized using the v-raf/v-myc carrying J2 retrovirus. These cells, however, do not form tumors when grown in vivo in the natural C57BL/6 host. Consistent with v-raf/v-myc expression, the in vitro metabolic and proliferation rate of the BV-2 cells greatly exceeded that of the tumorigenic and metastatic VM-M3 microglia cells when grown in DMEM containing 25 mM glucose. When controlling for proliferation and ATP production, the BV-2 cells produced more lactate than did the VM-M3 cells under aerobic conditions, thus demonstrating a robust Warburg effect in the BV-2 cells. The Warburg effect is associated with HIF stabilization under aerobic conditions. Mutations in the IDH1 gene produce 2-hydroxyglutarate (2HG), a recognized “onco-metabolite” that also contributes to HIF stabilization under aerobic conditions. Mass spectrometry analysis showed that the non-tumorigenic BV-2 cells made 2-HG only under anoxic conditions. 2-HG was not detected under anoxia or normoxia in VM-M3LM cells, a less malignant clonal variant of VM-M3. It appears that the BV-2 cells have a more robust cancer metabolism than either the high malignant VM-M3 cells or the low malignant VM-M3LM cells. The VM-M3LM cells consumed more oxygen and produced less lactate per ATP than did either the BV-2 cells or the VM-M3 cells, thus displaying a reduced Warburg effect. In other words, the Warburg effect was greatest in the non-tumorigenic BV-2 cells, was lowest in the low malignant VM-M3LM cells, but was intermediate in the high malignant VM-M3 cells. The results suggest that over expression of the v-raf/v-myc oncogenes, production of the IDH1 onco-metabolite, and a robust Warburg effect are not sufficient to drive tumorigenesis in the BV-2 cells. Supported in part from Boston College Res. Expense Fund.

Citation Format: Roberto Flores, Kenjiro Kami, Thomas Seyfried. Robust in vitro cancer metabolism in non-tumorigenic microglial cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5429. doi:10.1158/1538-7445.AM2013-5429

Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Metabolomic profiling of lung and prostate tumor tissues by capillary electrophoresis time-of-flight mass spectrometry

Metabolic microenvironment of tumor cells is influenced by oncogenic signaling and tissue-specific metabolic demands, blood supply, and enzyme expression. To elucidate tumor-specific metabolism, we compared the metabolomics of normal and tumor tissues surgically resected pairwise from nine lung and seven prostate cancer patients, using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS). Phosphorylation levels of enzymes involved in central carbon metabolism were also quantified. Metabolomic profiles of lung and prostate tissues comprised 114 and 86 metabolites, respectively, and the profiles not only well distinguished tumor from normal tissues, but also squamous cell carcinoma from the other tumor types in lung cancer and poorly differentiated tumors from moderately differentiated tumors in prostate cancer. Concentrations of most amino acids, especially branched-chain amino acids, were significantly higher in tumor tissues, independent of organ type, but of essential amino acids were particularly higher in poorly differentiated than moderately differentiated prostate cancers. Organ-dependent differences were prominent at the levels of glycolytic and tricarboxylic acid cycle intermediates and associated energy status. Significantly high lactate concentrations and elevated activating phosphorylation levels of phosphofructokinase and pyruvate kinase in lung tumors confirmed hyperactive glycolysis. We highlighted the potential of CE-TOFMS-based metabolomics combined with phosphorylated enzyme analysis for understanding tissue-specific tumor microenvironments, which may lead to the development of more effective and specific anticancer therapeutics.

Metabolomic profiling rationalized pyruvate efficacy in cybrid cells harboring MELAS mitochondrial DNA mutations

Pyruvate treatment was found to alleviate clinical symptoms of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome and is highly promising therapeutic. Using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS), we measured time-changes of 161 intracellular and 85 medium metabolites to elucidate metabolic effects of pyruvate treatment on cybrid human 143B osteosarcoma cells harboring normal (2SA) and MELAS mutant (2SD) mitochondria. The results demonstrated dramatic and sustainable effects of pyruvate administration on the energy metabolism of 2SD cells, corroborating pyruvate as a metabolically rational treatment regimen for improving symptoms associated with MELAS and possibly other mitochondrial diseases.

Metabolomic discrimination of intestinal- and diffuse-type gastric cancer tissues using capillary electrophoresis time-of-flight mass spectrometry

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Background: Clinicopathological characteristics of gastric cancer patients strongly depend on histological type. In contrast with gene and protein expressions, metabolic properties of intestinal- and diffuse-type gastric cancer have been largely unknown. Here, we conducted metabolome analysis of paired non-tumor and tumor gastric tissues by using capillary electrophoresis and liquid chromatography combined with time-of-flight mass spectrometry (CE- and LC-TOFMS, respectively) in order to metabolomically characterize non-tumors (NTs), intestinal-type tumors (ITs), and diffuse-type tumors (DTs). Methods: Tumor and surrounding non-tumor tissues were surgically excised pair-wise from 27 gastric cancer patients (18 ITs and 9 DTs) who underwent gastrectomy at our institution between February and May 2011. Following tissue homogenization and metabolite extraction, we measured 254 and 138 metabolites, respectively, by CE-TOFMS and LC-TOFMS. Results: Metabolomic profiles of tumor tissues, especially ITs, were well-distinguished from those of NTs: Lactate and most glycolytic intermediate levels in ITs were significantly higher than those in NTs, which reaffirms the Warburg effect of cancer, but the significance was lesser in DTs. Levels of all the measured amino acids were significantly higher in ITs and relatively higher in DTs than in NTs, showing high capacities of cancer cells for protein synthesis. Although levels of ATP, GTP, and energy charge in ITs and DTs were lower than those in NTs, purine contents were rather higher in the tumors than in NTs, which may support their high demand for DNA replication. Moreover, reduced glutathione in DTs were the lowest among others, implying their potential vulnerability against oxidative stress. Conclusions: Metabolomic profiles of NTs, ITs, and DTs were discriminated by CE- and LC-TOFMS analyses: Considerably high lactate, amino acid, and purine levels highlighted the metabolome of tumors, especially of ITs. Relatively low energy and redox statuses of DTs, however, could be targeted for developing more effective cancer therapeutics.

Manipulation of the small intestine as a cause of the increased inflammatory response after open compared with laparoscopic surgery

BACKGROUND

Laparoscopic surgery of the gastrointestinal tract involves a reduced immune response compared with open surgery. The aim of this study was to assess manual handling of the gut in open procedures as the principal cause of the enhanced immune response.

METHODS

Eighteen Landrace pigs underwent gastrectomy by three different methods: conventional open wound with bowel manipulation, laparoscopically assisted gastrectomy, and gastrectomy without manipulation using a combination of open wound and laparoscopic surgical devices. Local inflammatory changes were assessed by ascites formation, intestinal adhesion development and intestinal inflammatory gene expression. Associated systemic inflammatory changes were determined by measuring portal and systemic plasma endotoxin levels, plasma inflammatory cytokine levels, liver inflammatory gene expression and transaminase levels.

RESULTS

Significantly more postoperative intra-abdominal fluid and adhesions were seen in the open group. The expression of inflammatory cytokines was significantly greater in the intestine and liver in the open group. Portal and systemic levels of endotoxin, inflammatory cytokines and transaminases were also higher.

CONCLUSION

Manual handling of organs during gastrectomy is an important contributor to the molecular and humoral inflammatory response to surgery, supporting the use of minimally invasive techniques in gastrointestinal surgery.

Localization of MyoD, myogenin and cell cycle regulatory factors in hypertrophying rat skeletal muscles

AIM

MyoD, myogenin, proliferating cell nuclear antigen (PCNA) and cyclin-dependent kinase inhibitor p21 (p21) proteins are key molecules in inducing the growth of myogenic cells in vitro. However, it has not been determined which cell types express these factors in hypertrophying skeletal muscles in vivo.

METHODS

Using immunohistochemical techniques, we examined the spatial and temporal expression patterns of MyoD, myogenin, PCNA and p21 proteins in functionally overloaded rat plantaris muscles induced by ablation of the soleus and gastrocnemius muscles.

RESULTS

MyoD and myogenin were detected in myonuclei located inside the dystrophin-positive plasma membrane of myofibres, m-cadherin-positive satellite cell nuclei and nuclei located in the interstitial spaces between myofibres on days 1, 3, 5 and 7 post-surgery. Entry of satellite cells into the cell cycle was indicated by the expression of PCNA on day 3 post-surgery, and withdrawal from the cell cycle was observed by the expression of p21 in satellite cell nuclei on day 5 post-surgery. However, the expression of both PCNA and p21 in satellite cell nuclei disappeared on day 7 post-surgery.

CONCLUSION

These results indicate that proliferated satellite cell-derived myoblasts and undefined myogenic cells located in the interstitial spaces may contribute to an increase in myonuclear number and/or hyperplasia. Furthermore, we provide evidence that all of myonuclei, satellite cells and undefined myogenic cells express both MyoD and myogenin proteins. These results suggest that continual expression of MyoD and myogenin proteins in these cells is an essential molecular event which induces the successful hypertrophy of skeletal muscles.

Solution structure of micelle-bound H5 peptide (427-452): a primary structure corresponding to the pore forming region of the voltage dependent potassium channel

A 26-mer peptide with the sequence of the pore forming region (residues 427-452) of the Shaker K(+) channel (H5 region) was chemically synthesized. Analyses by CD and two-dimensional 1H NMR spectroscopy were used to investigate the structure of the peptide bound to SDS micelles in solution, which are commonly used in biophysical studies. The tertiary structure of the peptide as a monomer was composed of an alpha-helix (431-438), a turn (439-442), and random coils (427-430, 443-452), and was very similar to that of the pore forming region of the native K(+) channel from Streptomyces lividans determined by X-ray analysis. This result suggests that even an isolated peptide forms a native-like conformation for residues from 431 to 442, depending on its intrinsic amino acid sequence and the surrounding environment.

Gene expression of receptors for IL-6, LIF, and CNTF in regenerating skeletal muscles

The biological actions of interleukin-6 (IL-6), leukemia inhibitory factor (LIF), and ciliary neurotrophic factor (CNTF) are mediated via respective functional receptor complexes consisting of a common signal-transducing component, gp130, and other specific receptor components, IL-6 receptor alpha (IL-6R), LIF receptor beta (LIFR), and CNTF receptor alpha (CNTFR). IL-6, LIF, and CNTF are implicated in skeletal muscle regeneration. However, the cell populations that express these receptor components in regenerating muscles are unknown. Using in situ hybridization histochemistry, we examined spatiotemporal expression patterns of gp130, IL-6R, LIFR, and CNTFR mRNAs in regenerating muscles after muscle contusion. At the early stages of regeneration (from 3 hr to Day 2 post contusion), significant signals for gp130 and LIFR mRNAs were detected in myonuclei and/or nuclei of muscle precursor cells (mpcs) and in mononuclear cells located in extracellular spaces between myofibers after muscle contusion, but IL-6R mRNA was expressed only in mononuclear cells. At Day 7 post contusion, signals for gp130, LIFR, and IL-6R mRNAs were not detected in newly formed myotubes, whereas the CNTFR mRNA level was upregulated in myotubes. These findings suggest that the upregulation of receptor subunits in distinct cell populations plays an important role in the effective regeneration of both myofibers and motor neurons. (J Histochem Cytochem 48:1203-1213, 2000)

A novel NMR method for determining the interfaces of large protein-protein complexes

Identification of the interfaces of large (Mr > 50,000) protein-protein complexes in solution by high resolution NMR has typically been achieved using experiments involving chemical shift perturbation and/or hydrogen-deuterium exchange of the main chain amide groups of the proteins. Interfaces identified using these techniques, however, are not always identical to those revealed using X-ray crystallography. In order to identify the contact residues in a large protein-protein complex more accurately, we developed a novel NMR method that uses cross-saturation phenomena in combination with TROSY detection in an optimally deuterium labeled system.

Leukemia inhibitory factor, glial cell line-derived neurotrophic factor, and their receptor expressions following muscle crush injury

Using in situ hybridization histochemistry, we characterized the spatiotemporal gene expression patterns of leukemia inhibitory factor (LIF) and glial cell line-derived neurotrophic factor (GDNF), and their receptor components (LIFR, GFR-alpha1, RET) induced in muscle cells, intramuscular nerves, and motoneurons in the regeneration processes of both muscle cells and nerves following muscle contusion. Muscle contusion induced upregulation of GDNF and GFR-alpha1 mRNAs in Schwann cell-like cells in the intramuscular nerves and of LIFR mRNA in damaged muscle cells. LIFR, GFR-alpha1, and RET mRNA expressions in motoneurons were upregulated following muscle contusion. Muscle contusion also induced more rapid, prominent transactivations of GFR-alpha1 and RET genes in motoneurons than did sciatic nerve axotomy. These findings suggest that rapid and prominent upregulation of the receptor components for LIF and GDNF in motoneurons is important for the regeneration of intramuscular motor nerves damaged by muscle contusion.

Tissue expression of the S100 protein family-related MRP8 gene in human chorionic villi by in situ hybridization techniques

The present study examined the tissue-expression of MRP8 in human placenta using a biotinylated DNA-probe for in situ hybridization. During the first and second trimesters high level and synchronous expression of MRP8 was detected in cytotrophoblasts (Langhans' cells), placental-tissue macrophages (Hofbauer cells), fibroblast-like cells, endothelial cells and monocytic lineages in the foetal capillaries. The highest expression was seen in large and oval-shaped cytotrophoblasts and stromal-cell populations at around 8-11 weeks. At term placentas had low level MRP8 expression chiefly in the myelomonocytic lineages in foetal blood vessels. The peripheral monocytes in the maternal space also expressed MRP8 at high levels during the first and second trimesters, which subsequently decreased at term. We suggest three hypotheses based on these results; (1) The initial expression of MRP8 may occur in two cell lineages of extra-embryonic and intra-embryonic origin in the first two trimesters; (2) the cytotrophoblasts, placental-tissue macrophages and fibroblasts may play important roles in the production of placental hormones and the immuno-regulation of foetal acceptance; and (3) MRP8-expression may be synchronously inhibited once the trophoblasts and stromal cell-constituents have differentiated in the chorionic villi.

Expressions of a 68kDa-glycoprotein (GP68) and laminin in the mesodermal tissue of the developing mouse embryo

Immunohistochemistry revealed initial expression of the stage-specific glycoprotein, GP68, in various mesenchymal tissue substructures of mouse embryos. During the 11-15th days of gestation, GP68 was localized in the primitive meninges, chondroblasts and perichondrium of pre-cartilaginous vertebral bodies and ribs, connective tissue cells of the dermis, the epicardium and endocardium of the heart, the epimysium and perimysium of skeleton musclature, and the basement membranes of splanchnic organs. Double staining for laminin expression indicated coincidental expression in identical tissue substructures. However, laminin was expressed in days 10-18 embryos and the neonate. Therefore, GP68 is coincidentally expressed with laminin in mesenchymal tissues between the 11th and 15th day of gestation, and may play a role as a laminin-associated protein. In the light of these results, a hypothesis concerning the relationship between these two proteins and the mechanisms of non-integrin laminin-associated proteins during normal embryogenesis is discussed further.

Localization of leukemia inhibitory factor and interleukin-6 messenger ribonucleic acids in regenerating rat skeletal muscle

In the present study, we characterized both temporal and spatial expression patterns of leukemia inhibitory factor (LIF) and interleukin-6 (IL-6) messenger ribonucleic acids (mRNAs) in injured skeletal muscle using in situ hybridization. LIF and IL-6 mRNAs were expressed in mononucleated cells and damaged muscle cells. Further, signals for LIF mRNA were also detected in Schwann cell-like cells of intramuscular nerves. These results suggest that the earliest events involved in the repair of injured muscles and nerves may be triggered by these cytokines.

Cellular characterization of the 91kDa-ectopic ascitic antigen sharing antigenicity with MRP8 in the human placenta as revealed by immunoelectron microscopical colloidal-gold techniques

Cellular characterization of the 91kDa-ectopic ascitic protein that exhibits pregnancy-associated and tumour-related dynamics has been examined in the human placenta using an electron microscopic immunocolloidal-gold technique. This protein was initially isolated from the ascitic fluids of a patient suffered from ovarian and uterine cancers with mixed mesodermal tumours, and determined to be sharing antigenicity with the 28kDa-oncodevelopmental protein and a calcium-binding protein; MRP8/CFA, respectively. Placentas obtained were divided into three groups by their gestational periods. Small chorionic villous tissues were embedded in Lowicryl K4M resin or Epon 812 resin. Specific and higher labelings by gold-particles were obtained in sections of Lowicryl resin and, then, recognized in mesenchyme-derived cells and/or myeloid lineages; such as placental tissue macrophages (Hofbauer cells), fibroblasts, foetal myelomonocytic cells including endothelial cells, etc., in the first and second trimesters. So far, the pattern of antigenic appearances changed depending on the stage of gestation. On the other hand, 91kDa-protein was also determined in the syncytiotrophoblast, but not in cytotrophoblasts at whenever been examined. It is assumed that the antigenic expression in syncytiotrophoblasts might be reflected to be absorbed or incorporated from those of foetal or maternal origins, and the antibody used in this study should be sensitive to the antigenic epitope derived from those of myeloid lineages. In the light of these results, hypotheses concerning mechanisms of both transplacental permeability of substances by the placental barrier and cell/tissue differentiation by calcium-binding (and/or -depending) proteins such as 91kDa-protein, MRP8, etc.; presumable the S-100 protein family, are discussed further.

Immunolocalization of 91 kDa ascitic protein in the human placenta

A 91 kDa protein, sharing antigenicity with a pregnancy-associated antigen, was isolated from the ascitic fluid of a patient suffered from the gynaecological malignant neoplasms. It was revealed in the human placenta by immunocytochemical techniques, and found to be localized in the stroma, including a fibrous network, fibroblasts and the Hofbauer cells of the terminal and stem villi in the first trimester. Immunoreactive staining was also found in macrophage-like cells, presumable the precursor of the Hofbauer cell, in the stem villi of placenta. It is assumed that macrophage-like cells containing the protein would be originated from the extraembryonic mesoderm or blood vessels, and then migrated to the stroma of terminal villi. During the second trimester, the protein was observed in numerous vesicles among the syncytial trophoblasts. The density of these immunoreactive vesicles and the cytoplasm of Hofbauer cells was rapidly increased with gestational stages, whereas it was gradually reduced towards the late-second trimester. The highest labellings occurred at around 17 weeks or later. On the other hand, at term, the protein was mainly observed in numerous villous blood vessels including endothelial cells. In the light of these results, a hypothesis concerning mechanisms of transplacental permeability of the protein by the placental barrier is discussed further.

Localization of myogenin, c-fos, c-jun, and muscle-specific gene mRNAs in regenerating rat skeletal muscle

It has been suggested that myogenin is an important factor for the differentiation of myoblasts and that its function in myogenesis is regulated by proto-oncogenes in in vitro experiments. We have characterized the spatial and temporal expression patterns of myogenin, c-fos, c-jun, and muscle creatine kinase mRNAs during the skeletal muscle regeneration process using in situ hybridization histochemistry. Myogenin transcripts are first detected in the myonuclei/nuclei of satellite cells at 6 h after induction of regeneration. Myogenin mRNA is expressed in desmin-positive myoblasts, yet no muscle creatine kinase mRNA is detected in this cell type. Both the muscle creatine kinase and myogenin mRNAs are expressed in the newly formed myotubes, but not at earlier stages. Transcripts for c-fos and c-jun mRNAs are expressed first in the myonuclei/nuclei of satellite cells at 3 h post-trauma. c-jun mRNA is expressed in both myoblasts and myotubes, while c-fos mRNA was not detected in these cells. These results suggest that myogenin plays important role in the regeneration of injured muscle and that c-jun and c-fos may have different roles in this process.

Changes of vinculin and extracellular matrix components following blunt trauma to rat skeletal muscle

The purpose of the present study was to determine changes in the localization of vinculin, Type IV collagen, laminin, and fibronectin during the damage-repair process in the skeletal muscle over several days following acute blunt trauma. A single blunt trauma to the gastrocnemius muscle of the rat was induced by applying 1.57 J of kinetic energy to one leg. By day 2 after trauma, vinculin had disappeared rapidly from the intracellular submembraneous region corresponding to the costamere, whereas Type IV collagen and laminin persisted around the degenerating myofibers (corresponding to the basement membrane). Fibronectin could be observed filling the widened endomysium and in the ruptured myofibers. In the early phase of muscle regeneration (day 5 after trauma), newly synthesized vinculin, Type IV collagen, and laminin formed ring-like structures around the regenerating myotubes. Fibronectin could also be observed filling the widened endomysium around the regenerating myotubes. Further, when small newly formed or splitted myofibers were observed in the areas of regenerating myofibers (day 10 after trauma), vinculin, Type IV collagen, laminin, and fibronectin were localized in specialized regions corresponding to the costamere, basement membrane, and endomysium. These results demonstrated that restoration of the costamere, basement membrane, and endomysium are essential to the maturation of regenerating myofibers after injury.

Secretory pathway of vitellogenesis in the liver of the cockerel as revealed by immuno-gold and computer-assisted digitization techniques

The protein A-gold immunocytochemical technique was used to localize the secretory pathway of oestradiol-induced vitellogenin in hepatic parenchymal cells of the cockerel. Liver was removed from experimental birds on the 1st, 4th and 8th day following oestradiol-treatment, and embedded in Lowicryl K4M resin cured at -20 degrees C. In selected electron micrographs the fractional surface area of each of the intracellular compartments was measured by the computer-assisted digitization technique. Labelling was detected over the cisternae of the rough endoplasmic reticulum (RER), the Golgi apparatus, the immature secretory vacuoles (ISV) including condensing vacuoles and the mature secretory vacuoles (MSV). Counts of the gold particles demonstrated an increasing concentration which progressed in the order RER less than Golgi less than ISV less than MSV and identified the secretory pathway of the protein. The highest density of labelling was obtained on the 4th day, when vitellogenin reaches its peak activity. Autophagic activity (or crinophagy) was also found in lysosomes and its labelling intensity increased daily. A hypothesis concerning the secretory pathway of non-stored proteins by the liver is discussed further.

Immunoelectron microscopical demonstration of egg-yolk plasma precursor vitellogenin in the hepatocyte of oestradiol-treated cockerels

Vitellogenin has been localized at the electron microscopical level in the liver of the cockerel using a colloidal gold technique. White leghorn cockerels were treated with 17 beta-oestradiol to induce vitellogenesis. Pieces of liver were removed from control and experimental birds on the 4th and 8th days following hormone treatment, and embedded in Lowicryl K4M. Vitellogenin was isolated from the plasma of oestradiol-treated cockerels, and the antibody to it elicited in rabbits and made vitellogenin-specific by affinity chromatography on lipovitellin-Sepharose columns. At the light microscopical level, the intensity of immunohistochemical staining was considerably above background levels in oestradiol-treated cockerels. At the electron microscopical level, gold particles indicating antigenic sites of vitellogenin were largely confined to the rough endoplasmic reticulum, Golgi apparatus, immature and lysosomes and phagosomes within hepatocytes and sinusoidal cells respectively. These observations strongly suggest that the intracellular pathway of vitellogenin secretion in chicken hepatocytes under the experimental conditions studied involves external stimuli and secretory vacuoles. The labelling of lysosomes may reflect catabolic turnover (crinophagy).