Butyrate activates the monocarboxylate transporter MCT4 expression in breast cancer cells and enhances the antitumor activity of 3-bromopyruvate

Alleviation of allergic asthma by rosmarinic acid via gut-lung axis

BACKGROUND

Asthma affects 3% of the global population, leading to over 0.25 million deaths. Due to its complexity, asthma is difficult to cure or prevent, and current therapies have limitations. This has led to a growing demand for alternative asthma treatments. We found rosmarinic acid (RosA) as a potential new drug candidate from natural medicine. However, RosA has poor bioavailability and remains mainly in the gastrointestinal tract after oral administration, suggesting the involvement of gut microbiota in its bioactivity.

PURPOSE

To investigate the mechanism of RosA in alleviating allergic asthma by gut-lung axis.

METHODS

We used 16S rRNA gene sequencing and metabolites analysis to investigate RosA's modulation of gut microbiota. Techniques of molecular biology and metabolomics were employed to study the pharmacological mechanism of RosA. Cohousing was used to confirm the involvement of gut microbiota in RosA-induced improvement of allergic asthma.

RESULTS

RosA decreased cholate levels from spore-forming bacteria, leading to reduced 5-hydroxytryptamine (5-HT) synthesis, bronchoconstriction, vasodilation, and inflammatory cell infiltration. It also increased short-chain fatty acids (SCFAs) levels, facilitating the expression of intestinal tight junction proteins to promote intestinal integrity. SCFAs upregulated intestinal monocarboxylate transporters (MCTs), thereby improving their systemic delivery to reduce Th2/ILC2 mediated inflammatory response and suppress eosinophil influx and mucus production in lung. Additionally, RosA inhibited lipopolysaccharide (LPS) production and translocation, leading to reduced TLR4-NFκB mediated pulmonary inflammation and oxidative stress.

CONCLUSIONS

The anti-asthmatic mechanism of oral RosA is primarily driven by modulation of gut microbiota-derived 5-HT, SCFAs, and LPS, achieving a combined synergistic effect. RosA is a safe, effective, and reliable drug candidate that could potentially replace glucocorticoids for asthma treatment.

Targeting Glucose Metabolism in Cancer Cells as an Approach to Overcoming Drug Resistance

The "Warburg effect" consists of a metabolic shift in energy production from oxidative phosphorylation to glycolysis. The continuous activation of glycolysis in cancer cells causes rapid energy production and an increase in lactate, leading to the acidification of the tumour microenvironment, chemo- and radioresistance, as well as poor patient survival. Nevertheless, the mitochondrial metabolism can be also involved in aggressive cancer characteristics. The metabolic differences between cancer and normal tissues can be considered the Achilles heel of cancer, offering a strategy for new therapies. One of the main causes of treatment resistance consists of the increased expression of efflux pumps, and multidrug resistance (MDR) proteins, which are able to export chemotherapeutics out of the cell. Cells expressing MDR proteins require ATP to mediate the efflux of their drug substrates. Thus, inhibition of the main energy-producing pathways in cancer cells, not only induces cancer cell death per se, but also overcomes multidrug resistance. Given that most anticancer drugs do not have the ability to distinguish normal cells from cancer cells, a number of drug delivery systems have been developed. These nanodrug delivery systems provide flexible and effective methods to overcome MDR by facilitating cellular uptake, increasing drug accumulation, reducing drug efflux, improving targeted drug delivery, co-administering synergistic agents, and increasing the half-life of drugs in circulation.

The role of lactate in cardiovascular diseases

Cardiovascular diseases pose a major threat worldwide. Common cardiovascular diseases include acute myocardial infarction (AMI), heart failure, atrial fibrillation (AF) and atherosclerosis. Glycolysis process often has changed during these cardiovascular diseases. Lactate, the end-product of glycolysis, has been overlooked in the past but has gradually been identified to play major biological functions in recent years. Similarly, the role of lactate in cardiovascular disease is gradually being recognized. Targeting lactate production, regulating lactate transport, and modulating circulating lactate levels may serve as potential strategies for the treatment of cardiovascular diseases in the future. The purpose of this review is to integrate relevant clinical and basic research on the role of lactate in the pathophysiological process of cardiovascular disease in recent years to clarify the important role of lactate in cardiovascular disease and to guide further studies exploring the role of lactate in cardiovascular and other diseases. Video Abstract.

Novel Lipids to Regulate Obesity and Brain Function: Comparing Available Evidence and Insights from QSAR In Silico Models

Lipid molecules, such as policosanol, ergosterol, sphingomyelin, omega 3 rich phosphatidylcholine, α-tocopherol, and sodium butyrate, have emerged as novel additions to the portfolio of bioactive lipids. In this state-of-the-art review, we discuss these lipids, and their activity against obesity and mental or neurological disorders, with a focus on their proposed cellular targets and the ways in which they produce their beneficial effects. Furthermore, this available information is compared with that provided by in silico Absorption, Distribution, Metabolism, Excretion, and Toxicity (ADMET) models in order to understand the usefulness of these tools for the discovery of new bioactive compounds. Accordingly, it was possible to highlight how these lipids interact with various cellular targets related to the molecule transportation and absorption (e.g., α-tocopherol transfer protein for α-Tocopherol, ATP-binding cassette ABC transporters or Apolipoprotein E for sphingomyelins and phospholipids) or other processes, such as the regulation of gene expression (involving Sterol Regulatory Element-Binding Proteins for ergosterol or Peroxisome Proliferator-Activated Receptors in the case of policosanol) and inflammation (the regulation of interleukins by sodium butyrate). When comparing the literature with in silico Quantitative Structure-Activity Relationship (QSAR) models, it was observed that although they are useful for selecting bioactive molecules when compared in batch, the information they provide does not coincide when assessed individually. Our review highlights the importance of considering a broad range of lipids as potential bioactives and the need for accurate prediction of ADMET parameters in the discovery of new biomolecules. The information presented here provides a useful resource for researchers interested in developing new strategies for the treatment of obesity and mental or neurological disorders.

Butyrate inhibits the mitochondrial complex Ι to mediate mitochondria-dependent apoptosis of cervical cancer cells

BACKGROUND

Cervical cancer (CC) is a common gynecological malignancy with high morbidity worldwide. Butyrate, a short-chain fatty acid produced by intestinal flora, has been reported to inhibit cervical carcinogenesis. This study aimed to investigate the pro-apoptotic effects of butyrate on CC and the underlying mechanisms.

METHODS

Human HeLa and Ca Ski cells were used in this study. Cell proliferation, cell migration and invasion were detected by CCK-8 and EdU staining, transwell and wound healing assay, respectively. Cell cycle, mitochondrial membrane potential and apoptosis were evaluated by flow cytometry. Western blot and RT-qPCR were carried out to examine the related genes and proteins to the mitochondrial complex Ι and apoptosis. Metabolite changes were analyzed by energy metabolomics and assay kits. The association between G protein-coupled receptor 41, 43, 109a and CC prognosis was analyzed using data from The Cancer Genome Atlas (TCGA).

RESULTS

CCK-8 results showed significant inhibition of CC cell proliferation induced by butyrate treatment, which was confirmed by EdU staining and cell cycle detection. Data from the transwell and wound healing assay revealed that CC cell migration was dramatically reduced following butyrate treatment. Additionally, invasiveness was also decreased by butyrate. Western blot analysis showed that cleaved Caspase 3 and cleaved PARP, the enforcers of apoptosis, were increased by butyrate treatment. The results of Annexin V/PI staining and TUNEL also showed an increase in butyrate-induced apoptotic cells. Expression of Cytochrome C (Cytc), Caspase 9, Bax, but not Caspase 12 or 8, were up-regulated under butyrate exposure. Mechanistically, the decrease in mitochondrial NADH and NAD + levels after treatment with butyrate was observed by energy metabolomics and the NAD+/NADH Assay Kit, similar to the effects of the complex Ι inhibitor rotenone. Western blot results also demonstrated that the constituent proteins of mitochondrial complex Ι were reduced by butyrate. Furthermore, mitochondria-dependent apoptosis has been shown to be initiated by inhibition of the complex Ι.

CONCLUSION

Collectively, our results revealed that butyrate inhibited the proliferation, migration and invasion of CC cells, and induced mitochondrial-dependent apoptosis by inhibiting mitochondrial complex Ι.

Characterization of butyrate-metabolism in colorectal cancer to guide clinical treatment

Colorectal cancer (CRC) is the third most prevalent one in the world among the most common malignant tumors. Numerous studies have shown that butyrate has demonstrated promise as an antitumor agent in a variety of human cancer types. However, butyrate remains understudied in CRC tumorigenesis and progression. In this study, we explored therapeutic strategies to treat CRC by examining the role of butyrate metabolism. First, from the Molecular Signature Database (MSigDB), we identified 348 butyrate metabolism-related genes (BMRGs). Next, we downloaded 473 CRC and 41 standard colorectal tissue samples from The Cancer Genome Atlas (TCGA) database and the transcriptome data of GSE39582 dataset from Gene Expression Omnibus (GEO) database. Then we evaluated the expression patterns of butyrate metabolism-related genes with difference analysis in CRC. Through univariate Cox regression and least absolute shrinkage and selection operator (LASSO) analysis, a prognostic model was constructed based on differentially expressed BMRGs. In addition, we discovered an independent prognostic marker for CRC patients. According to the expression levels and coefficients of identified BMRGs, the risk scores of all CRC samples were calculated. Utilizing differentially expressed genes in the high- and low-risk groups, we also constructed a Protein-Protein Interaction (PPI) network to visualize the interactions between proteins. Through the results of PPI network, we screened out differentially expressed target butyrate metabolism-related genes from ten hub genes. Finally, we performed clinical correlation analysis, immune cell infiltration analysis, and mutation analysis for these target genes. One hundred and seventy three differentially expressed butyrate metabolism-related genes were screened out in all the CRC samples. The prognostic model was established with univariate Cox regression and LASSO regression analysis. CRC patients' overall survival was significantly lower in the high-risk group than in the low-risk group for both training and validation set. Among the ten hub genes identified from the PPI network, four target butyrate metabolism-related genes were identified containing FN1, SERPINE1, THBS2, and COMP, which might provide novel markers or targets for treating CRC patients. Eighteen butyrate metabolism-related genes were used to develop a risk prognostic model that could be helpful for doctors to predict CRC patients' survival rate. Using this model, it is beneficial to forecast the response of CRC patients to immunotherapy and chemotherapy, thus making it easier to custom tailor cancer chemotherapy and immunotherapy to the individual patient.

Microbiota-Derived Short-Chain Fatty Acids: New Road in Colorectal Cancer Therapy

The colon microbiota is an important player in colorectal cancer (CRC) development, which is responsible for most of the cancer-related deaths worldwide. During carcinogenesis, the colon microbiota composition changes from a normobiosis profile to dysbiosis, interfering with the production of short-chain fatty acids (SCFAs). Each SCFA is known to play a role in several biological processes but, despite their reported individual effects, colon cells are exposed to these compounds simultaneously and the combined effect of SCFAs in colon cells is still unknown. Our aim was to explore the effects of SCFAs, alone or in combination, unveiling their biological impact on CRC cell phenotypes. We used a mathematical model for the prediction of the expected SCFA mixture effects and found that, when in mixture, SCFAs exhibit a concentration addition behavior. All SCFAs, alone or combined at the physiological proportions founded in the human colon, revealed to have a selective and anticancer effect by inhibiting colony formation and cell proliferation, increasing apoptosis, disturbing the energetic metabolism, inducing lysosomal membrane permeabilization, and decreasing cytosolic pH. We showed for the first time that SCFAs are specific towards colon cancer cells, showing promising therapeutic effects. These findings open a new road for the development of alternatives for CRC therapy based on the increase in SCFA levels through the modulation of the colon microbiota composition.

Glycolytic Inhibitors Potentiated the Activity of Paclitaxel and Their Nanoencapsulation Increased Their Delivery in a Lung Cancer Model

Antiglycolytic agents inhibit cell metabolism and modify the tumor’s microenvironment, affecting chemotherapy resistance mechanisms. In this work, we studied the effect of the glycolytic inhibitors 3-bromopyruvate (3BP), dichloroacetate (DCA) and 2-deoxyglucose (2DG) on cancer cell properties and on the multidrug resistance phenotype, using lung cancer cells as a model. All compounds led to the loss of cell viability, with different effects on the cell metabolism, migration and proliferation, depending on the drug and cell line assayed. DCA was the most promising compound, presenting the highest inhibitory effect on cell metabolism and proliferation. DCA treatment led to decreased glucose consumption and ATP and lactate production in both A549 and NCI-H460 cell lines. Furthermore, the DCA pretreatment sensitized the cancer cells to Paclitaxel (PTX), a conventional chemotherapeutic drug, with a 2.7-fold and a 10-fold decrease in PTX IC₅₀ values in A549 and NCI-H460 cell lines, respectively. To increase the intracellular concentration of DCA, thereby potentiating its effect, DCA-loaded poly(lactic-co-glycolic acid) nanoparticles were produced. At higher DCA concentrations, encapsulation was found to increase its toxicity. These results may help find a new treatment strategy through combined therapy, which could open doors to new treatment approaches.

Cytoskeleton disruption by the metabolic inhibitor 3-bromopyruvate: implications in cancer therapy

The small molecule 3-bromopyruvate (3BP), is an anticancer molecule that acts by hindering glycolysis and mitochondrial function leading to energy depletion and consequently, to cell death. In this work we have focused on understanding how the glycolytic inhibition affects cancer cell structural features. We showed that 3BP leads to a drastic decrease in the levels of β-actin and α-tubulin followed by disorganization and shrinkage of the cytoskeleton in breast cancer cells. 3BP inhibits cell migration and colony formation independently of the activity of metalloproteinases. To disclose if these structural alterations occurred prior to 3BP toxic effect, non-toxic concentrations of 3BP were used and we could observe that 3BP was able to inhibit energy production and induce loss of β-actin and α-tubulin proteins. This was accompanied with alterations in cytoskeleton organization and an increase in E-cadherin levels which may indicate a decrease in cancer cells aggressiveness. In this study we demonstrate that 3BP glycolytic inhibition of breast cancer cells is accompanied by cytoskeleton disruption and consequently loss of migration ability, suggesting that 3BP can potentially be explored for metastatic breast cancer therapy.

Consumption of Dairy Products and the Risk of Developing Breast Cancer in Polish Women

Lack of consistency in the relationship between dairy products consumption and breast cancer (BC) risk motivated us to evaluate this association in a case-control study of BC among Polish women. The study includes 1699 women 26–79 years of age, 823 BC cases identified in Cancer Registries and 876 randomly selected controls from the national population registry. Using a validated, semiquantitative food frequency questionnaire (FFQ), the consumption of dairy products was collected for a time period of 10–15 years prior to BC diagnosis. We used logistic regression, adjusting for potential confounders, to assess the relationship between total dairy consumption as well as individual dairy groups of milk, cottage cheese and hard cheese and BC risk for premenopausal and postmenopausal women. For total consumption, a significant decrease in BC risk was observed with increased consumption of one serving/week, OR _trend = 0.98, 2% decrease in risk, for premenopausal women only. For milk, a significant decrease in BC risk was observed for an increase in consumption of one glass/week, OR _trend = 0.95, 5% decrease, in both strata of menopause. In contrast, for hard cheese, a significant increase in the risk of 10% was observed only in premenopausal women, OR _trend = 1.10. Cottage cheese consumption significantly reduced BC risk by 20%, OR _trend = 0.80, for an increase in one serving/week for postmenopausal women only. Our results show that individual dairy products have a statistically significant but bi-directional relationship with BC risk, which differs for premenopausal and postmenopausal women.

Mechanistic basis and preliminary practice of butyric acid and butyrate sodium to mitigate gut inflammatory diseases: a comprehensive review

A key event featured in the early stage of chronic gut inflammatory diseases is the disordered recruitment and excess accumulation of immune cells in the gut lamina propria. This process is followed by the over-secretion of pro-inflammatory factors and the prolonged overactive inflammatory responses. Growing evidence has suggested that gut inflammatory diseases may be mitigated by butyric acid (BA) or butyrate sodium (NaB). Laboratory studies show that BA and NaB can enhance gut innate immune function through G-protein-mediated signaling pathways while mitigating the overactive inflammatory responses by inhibiting histone deacetylase. The regulatory effects may occur in both epithelial enterocytes and the immune cells in the lamina propria. Prior to further clinical trials, comprehensive literature reviews and rigid examination concerning the underlying mechanism are necessary. To this end, we collected and reviewed 197 published reports regarding the mechanisms, bioactivities, and clinical effects of BA and NaB to modulate gut inflammatory diseases. Our review found insufficient evidence to guarantee the safety of clinical practice of BA and NaB, either by anal enema or oral administration of capsule or tablet. The safety of clinical use of BA and NaB should be further evaluated. Alternatively, dietary patterns rich in "fruits, vegetables and beans" may be an effective and safe approach to prevent gut inflammatory disease, which elevates gut microbiota-dependent production of BA. Our review provides a comprehensive reference to future clinical trials of BA and NaB to treat gut inflammatory diseases.

Ion Channels, Transporters, and Sensors Interact with the Acidic Tumor Microenvironment to Modify Cancer Progression

Solid tumors, including breast carcinomas, are heterogeneous but typically characterized by elevated cellular turnover and metabolism, diffusion limitations based on the complex tumor architecture, and abnormal intra- and extracellular ion compositions particularly as regards acid-base equivalents. Carcinogenesis-related alterations in expression and function of ion channels and transporters, cellular energy levels, and organellar H⁺ sequestration further modify the acid-base composition within tumors and influence cancer cell functions, including cell proliferation, migration, and survival. Cancer cells defend their cytosolic pH and HCO₃^- concentrations better than normal cells when challenged with the marked deviations in extracellular H⁺, HCO₃^-, and lactate concentrations typical of the tumor microenvironment. Ionic gradients determine the driving forces for ion transporters and channels and influence the membrane potential. Cancer and stromal cells also sense abnormal ion concentrations via intra- and extracellular receptors that modify cancer progression and prognosis. With emphasis on breast cancer, the current review first addresses the altered ion composition and the changes in expression and functional activity of ion channels and transporters in solid cancer tissue. It then discusses how ion channels, transporters, and cellular sensors under influence of the acidic tumor microenvironment shape cancer development and progression and affect the potential of cancer therapies.

Mitochondrial Function Are Disturbed in the Presence of the Anticancer Drug, 3-Bromopyruvate

3-bromopuryvate (3-BP) is a compound with unique antitumor activity. It has a selective action against tumor cells that exhibit the Warburg effect. It has been proven that the action of 3-BP is pleiotropic: it acts on proteins, glycolytic enzymes, reduces the amount of ATP, induces the formation of ROS (reactive oxygen species), and induces nuclear DNA damage. Mitochondria are important organelles for the proper functioning of the cell. The production of cellular energy (ATP), the proper functioning of the respiratory chain, or participation in the production of amino acids are one of the many functions of mitochondria. Here, for the first time, we show on the yeast model that 3-BP acts in the eukaryotic cell also by influence on mitochondria and that agents inhibiting mitochondrial function can potentially be used in cancer therapy with 3-BP. We show that cells with functional mitochondria are more resistant to 3-BP than rho⁰ cells. Using an MTT assay (a colorimetric assay for assessing cell metabolic activity), we demonstrated that 3-BP decreased mitochondrial activity in yeast in a dose-dependent manner. 3-BP induces mitochondrial-dependent ROS generation which results in ∆sod2, ∆por1, or ∆gpx1 mutant sensitivity to 3-BP. Probably due to ROS mtDNA lesions rise during 3-BP treatment. Our findings may have a significant impact on the therapy with 3-BP.

Metabolic Strategies for Inhibiting Cancer Development

The tumor microenvironment is a complex mix of cancerous and noncancerous cells (especially immune cells and fibroblasts) with distinct metabolisms. These cells interact with each other and are influenced by the metabolic disorders of the host. In this review, we discuss how metabolic pathways that sustain biosynthesis in cancer cells could be targeted to increase the effectiveness of cancer therapies by limiting the nutrient uptake of the cell, inactivating metabolic enzymes (key regulatory ones or those linked to cell cycle progression), and inhibiting ATP production to induce cell death. Furthermore, we describe how the microenvironment could be targeted to activate the immune response by redirecting nutrients toward cytotoxic immune cells or inhibiting the release of waste products by cancer cells that stimulate immunosuppressive cells. We also examine metabolic disorders in the host that could be targeted to inhibit cancer development. To create future personalized therapies for targeting each cancer tumor, novel techniques must be developed, such as new tracers for positron emission tomography/computed tomography scan and immunohistochemical markers to characterize the metabolic phenotype of cancer cells and their microenvironment. Pending personalized strategies that specifically target all metabolic components of cancer development in a patient, simple metabolic interventions could be tested in clinical trials in combination with standard cancer therapies, such as short cycles of fasting or the administration of sodium citrate or weakly toxic compounds (such as curcumin, metformin, lipoic acid) that target autophagy and biosynthetic or signaling pathways.

The Anticancer Drug 3-Bromopyruvate Induces DNA Damage Potentially Through Reactive Oxygen Species in Yeast and in Human Cancer Cells

3-bromopyruvate (3-BP) is a small molecule with anticancer and antimicrobial activities. 3-BP is taken up selectively by cancer cells’ mono-carboxylate transporters (MCTs), which are highly overexpressed by many cancers. When 3-BP enters cancer cells it inactivates several glycolytic and mitochondrial enzymes, leading to ATP depletion and the generation of reactive oxygen species. While mechanisms of 3-BP uptake and its influence on cell metabolism are well understood, the impact of 3-BP at certain concentrations on DNA integrity has never been investigated in detail. Here we have collected several lines of evidence suggesting that 3-BP induces DNA damage probably as a result of ROS generation, in both yeast and human cancer cells, when its concentration is sufficiently low and most cells are still viable. We also demonstrate that in yeast 3-BP treatment leads to generation of DNA double-strand breaks only in S-phase of the cell cycle, possibly as a result of oxidative DNA damage. This leads to DNA damage, checkpoint activation and focal accumulation of the DNA response proteins. Interestingly, in human cancer cells exposure to 3-BP also induces DNA breaks that trigger H2A.X phosphorylation. Our current data shed new light on the mechanisms by which a sufficiently low concentration of 3-BP can induce cytotoxicity at the DNA level, a finding that might be important for the future design of anticancer therapies.

MCT1, MCT4 and CD147 expression and 3-bromopyruvate toxicity in colorectal cancer cells are modulated by the extracellular conditions

Monocarboxylate transporters (MCTs) inhibition leads to disruption in glycolysis, induces cell death and decreases cell invasion, revealing the importance of MCT activity in intracellular pH homeostasis and tumor aggressiveness. 3-Bromopyruvate (3BP) is an anti-tumor agent, whose uptake occurs via MCTs. It was the aim of this work to unravel the importance of extracellular conditions on the regulation of MCTs and in 3BP activity. HCT-15 was found to be the most sensitive cell line, and also the one that presented the highest basal expression of both MCT1 and of its chaperone CD147. Glucose starvation and hypoxia induced an increased resistance to 3BP in HCT-15 cells, in contrast to what happens with an extracellular acidic pH, where no alterations in 3BP cytotoxicity was observed. However, no association with MCT1, MCT4 and CD147 expression was observed, except for glucose starvation, where a decrease in CD147 (but not of MCT1 and MCT4) was detected. These results show that 3BP cytotoxicity might include other factors beyond MCTs. Nevertheless, treatment with short-chain fatty acids (SCFAs) increased the expression of MCT4 and CD147 as well as the sensitivity of HCT-15 cells to 3BP. The overall results suggest that MCTs influence the 3BP effect, although they are not the only players in its mechanism of action.

Glycogen storage in a zebrafish Pompe disease model is reduced by 3-BrPA treatment

Pompe disease (PD) is an autosomal recessive muscular disorder caused by deficiency of the glycogen hydrolytic enzyme acid α-glucosidase (GAA). The enzyme replacement therapy, currently the only available therapy for PD patients, is efficacious in improving cardiomyopathy in the infantile form, but not equally effective in the late onset cases with involvement of skeletal muscle. Correction of the skeletal muscle phenotype has indeed been challenging, probably due to concomitant dysfunctional autophagy. The increasing attention to the pathogenic mechanisms of PD and the search of new therapeutic strategies prompted us to generate and characterize a novel transient PD model, using zebrafish. Our model presented increased glycogen content, markedly altered motor behavior and increased lysosome content, in addition to altered expression of the autophagy-related transcripts and proteins Beclin1, p62 and Lc3b. Furthermore, the model was used to assess the beneficial effects of 3-bromopyruvic acid (3-BrPA). Treatment with 3-BrPA induced amelioration of the model phenotypes regarding glycogen storage, motility behavior and autophagy-related transcripts and proteins. Our zebrafish PD model recapitulates most of the defects observed in human patients, proving to be a powerful translational model. Moreover, 3-BrPA unveiled to be a promising compound for treatment of conditions with glycogen accumulation.

Effect of Short Chain Fatty Acids on Age-Related Disorders

Recent studies have indicated a prominent role of intestinal microbiota in regulation of several physiological aspects of the host including development and activation of the immune system and control of metabolism. In this review, we focused our discussion on bacterial metabolites produced from dietary fiber fermentation called short-chain fatty acids, which act as a link between the microbiota and host cells. Specifically, we described how modifications in their intestinal levels are associated with development of age-related pathologies including metabolic diseases and type 2 diabetes, hypertension, cardiovascular and neurodegenerative diseases. We also highlight their impact on the development of cancer.

Diverse Stakeholders of Tumor Metabolism: An Appraisal of the Emerging Approach of Multifaceted Metabolic Targeting by 3-Bromopyruvate

Malignant cells possess a unique metabolic machinery to endure unobstructed cell survival. It comprises several levels of metabolic networking consisting of 1) upregulated expression of membrane-associated transporter proteins, facilitating unhindered uptake of substrates; 2) upregulated metabolic pathways for efficient substrate utilization; 3) pH and redox homeostasis, conducive for driving metabolism; 4) tumor metabolism-dependent reconstitution of tumor growth promoting the external environment; 5) upregulated expression of receptors and signaling mediators; and 6) distinctive genetic and regulatory makeup to generate and sustain rearranged metabolism. This feat is achieved by a "battery of molecular patrons," which acts in a highly cohesive and mutually coordinated manner to bestow immortality to neoplastic cells. Consequently, it is necessary to develop a multitargeted therapeutic approach to achieve a formidable inhibition of the diverse arrays of tumor metabolism. Among the emerging agents capable of such multifaceted targeting of tumor metabolism, an alkylating agent designated as 3-bromopyruvate (3-BP) has gained immense research focus because of its broad spectrum and specific antineoplastic action. Inhibitory effects of 3-BP are imparted on a variety of metabolic target molecules, including transporters, metabolic enzymes, and several other crucial stakeholders of tumor metabolism. Moreover, 3-BP ushers a reconstitution of the tumor microenvironment, a reversal of tumor acidosis, and recuperative action on vital organs and systems of the tumor-bearing host. Studies have been conducted to identify targets of 3-BP and its derivatives and characterization of target binding for further optimization. This review presents a brief and comprehensive discussion about the current state of knowledge concerning various aspects of tumor metabolism and explores the prospects of 3-BP as a safe and effective antineoplastic agent.

The Cryptococcus neoformans monocarboxylate transporter Jen4 is responsible for increased 3-bromopyruvate sensitivity

In the last decades, 3-bromopyruvate (3BP) has been intensively studied as a promising anticancer and antimicrobial agent. The transport of this drug inside the cell is a critical step for its toxicity in cancer and microorganisms. The Cryptococcus neoformans is the most sensitive species of microorganisms toward 3BP. Its cells exhibit the highest uptake rate of 3BP among all tested fungal strains. In Saccharomyces cerevisiae cells, the Jen1 transporter was found to be responsible for 3BP sensitivity. The deletion of Jen1 resulted in the abolishment of 3BP mediated transport. We functionally characterized the Jen4 protein, a Jen1 homologue of C. neoformans, and its role in the phenotypic 3BP sensitivity. The deletion of the CNAG_04704 gene, which encodes Jen4, was found to impair the mediated transport of 3BP and decrease 3BP sensitivity. Further heterologous expression of Jen4 in the S. cerevisiae jen1Δ ady2Δ strain restored the mediated transport of 3BP. The application of a green fluorescent protein fusion tag with the CNAG_04704, revealed the Jen4 labeled on the plasma membrane. The identification of 3BP transporters in pathogen cells is of great importance for understanding the mechanisms of 3BP action and to anticipate the application of this compound as an antimicrobial drug.

Residual feed intake in beef cattle and its association with carcass traits, ruminal solid-fraction bacteria, and epithelium gene expression

Background

Residual feed intake (RFI) describes an animal’s feed efficiency independent of growth performance. The objective of this study was to determine differences in growth performance, carcass traits, major bacteria attached to ruminal solids-fraction, and ruminal epithelium gene expression between the most-efficient and the least-efficient beef cattle. One-hundred and forty-nine Red Angus cattle were allocated to three contemporary groups according to sex and herd origin. Animals were fed a finishing diet in confinement for 70 d to determine the RFI category for each. Within each group, the two most-efficient (n = 6; RFI coefficient = − 2.69 ± 0.58 kg dry matter intake (DMI)/d) and the two least-efficient animals (n = 6; RFI coefficient = 3.08 ± 0.55 kg DMI/d) were selected. Immediately after slaughter, ruminal solids-fraction and ruminal epithelium were collected for bacteria relative abundance and epithelial gene expression analyses, respectively, using real-time PCR.

Results

The most-efficient animals consumed less feed (P = 0.01; 5.03 kg less DMI/d) compared with the least-efficient animals. No differences (P > 0.10) in initial body weight (BW), final BW, and average daily gain (ADG) were observed between the two RFI classes. There were no significant RFI × sex effects (P > 0.10) on growth performance. Compared with the least-efficient group, hot carcass weight (HCW), ribeye area (REA), and kidney, pelvic, and heart fat (KPH) were greater (P ≤ 0.05) in the most-efficient cattle. No RFI × sex effect (P > 0.10) for carcass traits was detected between RFI groups. Of the 10 bacterial species evaluated, the most-efficient compared with least efficient cattle had greater (P ≤ 0.05) relative abundance of Eubacterium ruminantium, Fibrobacter succinogenes, and Megasphaera elsdenii, and lower (P ≤ 0.05) Succinimonas amylolytica and total bacterial density. No RFI × sex effect on ruminal bacteria was detected between RFI groups. Of the 34 genes evaluated in ruminal epithelium, the most-efficient cattle had greater (P ≤ 0.05) abundance of genes involved in VFA absorption, metabolism, ketogenesis, and immune/inflammation-response. The RFI × sex interactions indicated that responses in gene expression between RFI groups were due to differences in sex. Steers in the most-efficient compared with least-efficient group had greater (P ≤ 0.05) expression of SLC9A1, HIF1A, and ACO2. The most-efficient compared with least-efficient heifers had greater (P ≤ 0.05) mRNA expression of BDH1 and lower expression (P ≤ 0.05) of SLC9A2 and PDHA1.

Conclusions

The present study revealed that greater feed efficiency in beef cattle is associated with differences in bacterial species and transcriptional adaptations in the ruminal epithelium that might enhance nutrient delivery and utilization by tissues. The lack of RFI × sex interaction for growth performance and carcass traits indicates that sex may not play a major role in improving these phenotypes in superior RFI beef cattle. However, it is important to note that this result should not be considered a solid biomarker of efficient beef cattle prior to further examination due to the limited number of heifers compared with steers used in the study.

Electronic supplementary material

The online version of this article (10.1186/s40104-018-0283-8) contains supplementary material, which is available to authorized users.

Valproate sensitizes human glioblastoma cells to 3-bromopyruvate-induced cytotoxicity

Glioblastoma (GBM) is the most common brain tumor; however, no effective treatment for it is available yet. Monocarboxylate transporters, which are highly expressed in GBM, play a role in transporting antitumor agents, such as 3-bromopyruvate (3-BrPA). Valproate, primarily used to treat epilepsy, has been considered a possible treatment option for malignant GBM. In this study, we aimed to investigate the combined effects of 3-BrPA and valproate on GBM cell growth and elucidate the underlying mechanisms. Valproate enhanced 3-BrPA-induced cell death in T98G cells, used as a GBM model. Multidrug resistance-associated protein 2 (MRP2) and breast cancer resistance protein (BCRP) mRNA levels significantly increased after valproate treatment. 3-BrPA-induced cell death, which was enhanced by valproate, was inhibited in the presence of MK571, a MRP inhibitor, or Ko143, a BCRP inhibitor. In addition, treatment with 3-BrPA and valproate for 48 h reduced cellular ATP levels compared to those in the 3-BrPA alone treatment group. However, cellular ATP levels were recovered in the presence of MK571 or Ko143, compared to those in the 3-BrPA and valproate treatment groups. In conclusion, we suggested that valproate enhanced 3-BrPA-induced cell death. This might be attributable to the increase in cellular ATP consumption owing to valproate-induced MRP2 or BCRP expression.

GLUT1 expression in pediatric adrenocortical tumors: a promising candidate to predict clinical behavior

Background

Discrimination between benign and malignant tumors is a challenging process in pediatric adrenocortical tumors. New insights in the metabolic profile of pediatric adrenocortical tumors may contribute to this distinction, predict prognosis, as well as identify new molecular targets for therapy. The aim of this work is to characterize the expression of the metabolism-related proteins MCT1, MCT2, MCT4, CD147, CD44, GLUT1 and CAIX in a series of pediatric adrenocortical tumors.

Methods

A total of 50 pediatric patients presenting adrenocortical tumors, including 41 clinically benign and 9 clinically malignant tumors, were included. Protein expression was evaluated using immunohistochemistry in samples arranged in tissue microarrays.

Results

The immunohistochemical analysis showed a significant increase in plasma membrane expression of GLUT1 in malignant lesions, when compared to benign lesions (p=0.004), being the expression of this protein associated with shorter overall and disease-free survival (p=0.004 and p=0.001, respectively). Although significant differences were not observed for proteins other than GLUT1, MCT1, MCT4 and CD147 were highly expressed in pediatric adrenocortical neoplasias (around 90%).

Conclusion

GLUT1 expression was differentially expressed in pediatric adrenocortical tumors, with higher expression in clinically malignant tumors, and associated with shorter survival, suggesting a metabolic remodeling towards a hyperglycolytic phenotype in this malignancy.

Screening the yeast genome for energetic metabolism pathways involved in a phenotypic response to the anti-cancer agent 3-bromopyruvate

In this study the detailed characteristic of the anti-cancer agent 3-bromopyruvate (3-BP) activity in the yeast Saccharomyces cerevisiae model is described, with the emphasis on its influence on energetic metabolism of the cell. It shows that 3-BP toxicity in yeast is strain-dependent and influenced by the glucose-repression system. Its toxic effect is mainly due to the rapid depletion of intracellular ATP. Moreover, lack of the Whi2p phosphatase results in strongly increased sensitivity of yeast cells to 3-BP, possibly due to the non-functional system of mitophagy of damaged mitochondria through the Ras-cAMP-PKA pathway. Single deletions of genes encoding glycolytic enzymes, the TCA cycle enzymes and mitochondrial carriers result in multiple effects after 3-BP treatment. However, it can be concluded that activity of the pentose phosphate pathway is necessary to prevent the toxicity of 3-BP, probably due to the fact that large amounts of NADPH are produced by this pathway, ensuring the reducing force needed for glutathione reduction, crucial to cope with the oxidative stress. Moreover, single deletions of genes encoding the TCA cycle enzymes and mitochondrial carriers generally cause sensitivity to 3-BP, while totally inactive mitochondrial respiration in the rho⁰ mutant resulted in increased resistance to 3-BP.

Metabolic reprogramming: a new relevant pathway in adult adrenocortical tumors

Adrenocortical carcinomas (ACCs) are complex neoplasias that may present unexpected clinical behavior, being imperative to identify new biological markers that can predict patient prognosis and provide new therapeutic options. The main aim of the present study was to evaluate the prognostic value of metabolism-related key proteins in adrenocortical carcinoma. The immunohistochemical expression of MCT1, MCT2, MCT4, CD147, CD44, GLUT1 and CAIX was evaluated in a series of 154 adult patients with adrenocortical neoplasia and associated with patients' clinicopathological parameters. A significant increase in was found for membranous expression of MCT4, GLUT1 and CAIX in carcinomas, when compared to adenomas. Importantly MCT1, GLUT1 and CAIX expressions were significantly associated with poor prognostic variables, including high nuclear grade, high mitotic index, advanced tumor staging, presence of metastasis, as well as shorter overall and disease free survival. In opposition, MCT2 membranous expression was associated with favorable prognostic parameters. Importantly, cytoplasmic expression of CD147 was identified as an independent predictor of longer overall survival and cytoplasmic expression of CAIX as an independent predictor of longer disease-free survival. We provide evidence for a metabolic reprogramming in adrenocortical malignant tumors towards the hyperglycolytic and acid-resistant phenotype, which was associated with poor prognosis.

Transport of haloacids across biological membranes

Haloacids are considered to be environmental pollutants, but some of them have also been tested in clinical research. The way that haloacids are transported across biological membranes is important for both biodegradation and drug delivery purposes. In this review, we will first summarize putative haloacids transporters and the information about haloacids transport when studying carboxylates transporters. We will then introduce MCT1 and SLC5A8, which are respective transporter for antitumor agent 3-bromopyruvic acid and dichloroacetic acid, and monochloroacetic acid transporters Deh4p and Dehp2 from a haloacids-degrading bacterium. Phylogenetic analysis of these haloacids transporters and other monocarboxylate transporters reveals their evolutionary relationships. Haloacids transporters are not studied to the extent that they deserve compared with their great application potentials, thus future inter-discipline research are desired to better characterize their transport mechanisms for potential applications in both environmental and clinical fields.

Characterization of acetate transport in colorectal cancer cells and potential therapeutic implications

Acetate, together with other short chain fatty acids has been implicated in colorectal cancer (CRC) prevention/therapy. Acetate was shown to induce apoptosis in CRC cells. The precise mechanism underlying acetate transport across CRC cells membrane, that may be implicated in its selectivity towards CRC cells, is not fully understood and was addressed here. We also assessed the effect of acetate in CRC glycolytic metabolism and explored its use in combination with the glycolytic inhibitor 3-bromopyruvate (3BP). We provide evidence that acetate enters CRC cells by the secondary active transporters MCT1 and/or MCT2 and SMCT1 as well as by facilitated diffusion via aquaporins. CRC cell exposure to acetate upregulates the expression of MCT1, MCT4 and CD147, while promoting MCT1 plasma membrane localization. We also observed that acetate increases CRC cell glycolytic phenotype and that acetate-induced apoptosis and anti-proliferative effect was potentiated by 3BP. Our data suggest that acetate selectivity towards CRC cells might be explained by the fact that aquaporins and MCTs are found overexpressed in CRC clinical cases. Our work highlights the importance that acetate transport regulation has in the use of drugs such as 3BP as a new therapeutic strategy for CRC.

The anticancer agent 3-bromopyruvate: a simple but powerful molecule taken from the lab to the bedside

At the beginning of the twenty-first century, 3-bromopyruvate (3BP), a simple alkylating chemical compound was presented to the scientific community as a potent anticancer agent, able to cause rapid toxicity to cancer cells without bystander effects on normal tissues. The altered metabolism of cancers, an essential hallmark for their progression, also became their Achilles heel by facilitating 3BP's selective entry and specific targeting. Treatment with 3BP has been administered in several cancer type models both in vitro and in vivo, either alone or in combination with other anticancer therapeutic approaches. These studies clearly demonstrate 3BP's broad action against multiple cancer types. Clinical trials using 3BP are needed to further support its anticancer efficacy against multiple cancer types thus making it available to more than 30 million patients living with cancer worldwide. This review discusses current knowledge about 3BP related to cancer and discusses also the possibility of its use in future clinical applications as it relates to safety and treatment issues.

Mutant IDH1 expression is associated with down-regulation of monocarboxylate transporters

Mutations in isocitrate dehydrogenase 1 (IDH1) are characteristic of low-grade gliomas. We recently showed that mutant IDH1 cells reprogram cellular metabolism by down-regulating pyruvate dehydrogenase (PDH) activity. Reduced pyruvate metabolism via PDH could lead to increased pyruvate conversion to lactate. The goal of this study was therefore to investigate the impact of the IDH1 mutation on the pyruvate-to-lactate flux. We used 13C magnetic resonance spectroscopy and compared the conversion of hyperpolarized [1-13C]-pyruvate to [1-13C]-lactate in immortalized normal human astrocytes expressing mutant or wild-type IDH1 (NHAIDHmut and NHAIDHwt). Our results indicate that hyperpolarized lactate production is reduced in NHAIDHmut cells compared to NHAIDHwt. This reduction was associated with lower expression of the monocarboxylate transporters MCT1 and MCT4 in NHAIDHmut cells. Furthermore, hyperpolarized lactate production was comparable in lysates of NHAIDHmut and NHAIDHwt cells, wherein MCTs do not impact hyperpolarized pyruvate delivery and lactate production. Collectively, our findings indicated that lower MCT expression was a key contributor to lower hyperpolarized lactate production in NHAIDHmut cells. The SLC16A3 (MCT4) promoter but not SLC16A1 (MCT1) promoter was hypermethylated in NHAIDHmut cells, pointing to possibly different mechanisms mediating reduced MCT expression. Finally analysis of low-grade glioma patient biopsy data from The Cancer Genome Atlas revealed that MCT1 and MCT4 expression was significantly reduced in mutant IDH1 tumors compared to wild-type. Taken together, our study shows that reduced MCT expression is part of the metabolic reprogramming of mutant IDH1 gliomas. This finding could impact treatment and has important implications for metabolic imaging of mutant IDH1 gliomas.

The metabolic microenvironment of melanomas: Prognostic value of MCT1 and MCT4

BRAF mutations are known drivers of melanoma development and, recently, were also described as players in the Warburg effect, while this reprogramming of energy metabolism has been identified as a possible strategy for treating melanoma patients. Therefore, the aim of this work was to evaluate the expression and prognostic value of a panel of glycolytic metabolism-related proteins in a series of melanomas. The immunohistochemical expression of MCT1, MCT4, GLUT1, and CAIX was evaluated in 356 patients presenting melanoma and 20 patients presenting benign nevi. Samples included 20 benign nevi, 282 primary melanomas, 117 lymph node and 54 distant metastases samples. BRAF mutation was observed in 29/92 (31.5%) melanoma patients and 17/20 (85%) benign nevi samples. NRAS mutation was observed in 4/36 (11.1%) melanoma patients and 1/19 (5.3%) benign nevi samples. MCT4 and GLUT1 expression was significantly increased in metastatic samples, and MCT1, MCT4 and GLUT1 were significantly associated with poor prognostic variables. Importantly, MCT1 and MCT4 were associated with shorter overall survival. In conclusion, the present study brings new insights on metabolic aspects of melanoma, paving the way for the development of new-targeted therapies.

The effect of 3-bromopyruvate on human colorectal cancer cells is dependent on glucose concentration but not hexokinase II expression

Cancer cells heavily rely on the glycolytic pathway regardless of oxygen tension. Hexokinase II (HKII) catalyses the first irreversible step of glycolysis and is often overexpressed in cancer cells. 3-Bromopyruvate (3BP) has been shown to primarily target HKII, and is a promising anti-cancer compound capable of altering critical metabolic pathways in cancer cells. Abnormal vasculature within tumours leads to heterogeneous microenvironments, including glucose availability, which may affect drug sensitivity. The aim of the present study was to elucidate the mechanisms by which 3BP acts on colorectal cancer (CRC) cells with focus on the HKII/Akt signalling axis. High HKII-expressing cell lines were more sensitive to 3BP than low HKII-expressing cells. 3BP-induced rapid Akt phosphorylation at site Thr-308 and cell death via both apoptotic and necrotic mechanisms. Cells grown under lower glucose concentrations showed greater resistance towards 3BP. Cells with HKII knockdown showed no changes in 3BP sensitivity, suggesting the effects of 3BP are independent of HKII expression. These results emphasize the importance of the tumour microenvironment and glucose availability when considering therapeutic approaches involving metabolic modulation.

Effect of 3-bromopyruvate acid on the redox equilibrium in non-invasive MCF-7 and invasive MDA-MB-231 breast cancer cells

Novel approaches to cancer chemotherapy employ metabolic differences between normal and tumor cells, including the high dependence of cancer cells on glycolysis ("Warburg effect"). 3-Bromopyruvate (3-BP), inhibitor of glycolysis, belongs to anticancer drugs basing on this principle. 3-BP was tested for its capacity to kill human non-invasive MCF-7 and invasive MDA-MB-231 breast cancer cells. We found that 3-BP was more toxic for MDA-MB-231 cells than for MCF-7 cells. In both cell lines, a statistically significant decrease of ATP and glutathione was observed in a time- and 3-BP concentration-dependent manner. Transient increases in the level of reactive oxygen species and reactive oxygen species was observed, more pronounced in MCF-7 cells, followed by a decreasing tendency. Activities of glutathione peroxidase, glutathione reductase (GR) and glutathione S-transferase (GST) decreased in 3-BP treated MDA-MB-231 cells. For MCF-7 cells decreases of GR and GST activities were noted only at the highest concentration of 3-BP.These results point to induction of oxidative stress by 3-BP via depletion of antioxidants and inactivation of antioxidant enzymes, more pronounced in MDA-MB-231 cells, more sensitive to 3-BP.

Reprogramming energy metabolism and inducing angiogenesis: co-expression of monocarboxylate transporters with VEGF family members in cervical adenocarcinomas

Background

Deregulation of cellular energetic metabolism was recently pointed out as a hallmark of cancer cells. This deregulation involves a metabolic reprogramming that leads to a high production of lactate. Lactate efflux, besides contributing for the glycolytic flux, also acts in the extracellular matrix, contributing for cancer malignancy, by, among other effects, induction of angiogenesis. However, studies on the interplay between cancer metabolism and angiogenesis are scarce. Therefore, the aim of the present study was to evaluate the metabolic and vascular molecular profiles of cervical adenocarcinomas, their co-expression, and their relation to the clinical and pathological behavior.

Methods

The immunohistochemical expression of metabolism-related proteins (MCT1, MCT4, CD147, GLUT1 and CAIX) as well as VEGF family members (VEGF-A, VEGF-C, VEGF-D, VEGFR-1, VEGFR-2 and VEGFR-3) was assessed in a series of 232 cervical adenocarcinomas. The co-expression among proteins was assessed and the expression profiles were associated with patients’ clinicopathological parameters.

Results

Among the metabolism-related proteins, MCT4 and CAIX were the most frequently expressed in cervical adenocarcinomas while CD147 was the less frequently expressed protein. Overall, VEGF family members showed a strong and extended expression with VEGF-C and VEGFR-2 as the most frequently expressed and VEGFR-1 as the less expressed member. Co-expression of MCT isoforms with VEGF family members was demonstrated. Finally, MCT4 was associated with parametrial invasion and HPV18 infection, CD147 and GLUT1 with distant metastasis, CAIX with tumor size and HPV18 infection, and VEGFR-1 with local and lymphnode metastasis.

Conclusions

The results herein presented provide additional evidence for a crosstalk between deregulating cellular energetics and inducing angiogenesis. Also, the metabolic remodeling and angiogenic switch are relevant to cancer progression and aggressiveness in adenocarcinomas.

Metabolic targeting of oncogene MYC by selective activation of the proton-coupled monocarboxylate family of transporters

Deregulation of the MYC oncogene produces Myc protein that regulates multiple aspects of cancer cell metabolism, contributing to the acquisition of building blocks essential for cancer cell growth and proliferation. Therefore, disabling Myc function represents an attractive therapeutic option for cancer treatment. However, pharmacological strategies capable of directly targeting Myc remain elusive. Here, we identified that 3-bromopyruvate (3-BrPA), a drug candidate that primarily inhibits glycolysis, preferentially induced massive cell death in human cancer cells overexpressing the MYC oncogene, in vitro and in vivo, without appreciable effects on those exhibiting low MYC levels. Importantly, pharmacological inhibition of glutamine metabolism synergistically potentiated the synthetic lethal targeting of MYC by 3-BrPA due in part to the metabolic disturbance caused by this combination. Mechanistically, we identified that the proton-coupled monocarboxylate transporter 1 (MCT1) and MCT2, which enable efficient 3-BrPA uptake by cancer cells, were selectively activated by Myc. Two regulatory mechanisms were involved: first, Myc directly activated MCT1 and MCT2 transcription by binding to specific recognition sites of both genes; second, Myc transcriptionally repressed miR29a and miR29c, resulting in enhanced expression of their target protein MCT1. Of note, expressions of MCT1 and MCT2 were each significantly elevated in MYCN-amplified neuroblastomas and C-MYC-overexpressing lymphomas than in tumors without MYC overexpression, correlating with poor prognosis and unfavorable patient survival. These results identify a novel mechanism by which Myc sensitizes cells to metabolic inhibitors and validate 3-BrPA as potential Myc-selective cancer therapeutics.

3-BrPA eliminates human bladder cancer cells with highly oncogenic signatures via engagement of specific death programs and perturbation of multiple signaling and metabolic determinants

BACKGROUND

Urinary bladder cancer is one of the most fatal and expensive diseases of industrialized world. Despite the strenuous efforts, no seminal advances have been achieved for its clinical management. Given the importance of metabolic reprogramming in cancer cell survival and growth, we have herein employed 3-BrPA, a halogenated derivative of pyruvate and historically considered inhibitor of glycolysis, to eliminate bladder cancer cells with highly oncogenic molecular signatures.

METHODS

Bladder cancer cells were exposed to 3-BrPA in the absence or presence of several specific inhibitors. Cell viability was determined by MTT and flow-cytometry assays; cell death, signaling activity and metabolic integrity by Western blotting and immunofluorescence; mutant-gene profiling by DNA sequencing; and gene expression by RT-sqPCR.

RESULTS

3-BrPA could activate dose-dependent apoptosis (type 1 PCD) and regulated necrosis (type 3 PCD) of T24 (grade III; H-Ras(G12V); p53(ΔY126)), but not RT4 (grade I), cells, with PARP, MLKL, Drp1 and Nec-7-targeted components critically orchestrating necrotic death. However, similarly to RIPK1 and CypD, p53 presented with non-essential contribution to 3-BrPA-induced cellular collapse, while reactivation of mutant p53 with PRIMA-1 resulted in strong synergism of the two agents. Given the reduced expression of MPC components (likely imposing mitochondrial dysfunction) in T24 cells, the suppression of constitutive autophagy (required by cells carrying oncogenic Ras; also, type 2 PCD) and derangement of glucose-homeostasis determinants by 3-BrPA critically contribute to drug-directed depletion of ATP cellular stores. This bioenergetic crisis is translated to severe dysregulation of Akt/FoxO/GSK-3, mTOR/S6, AMPK and MAPK (p44/42, p38 and SAPK/JNK) signaling pathways in 3-BrPA-treated T24 cells. Sensitivity to 3-BrPA (and tolerance to glucose deprivation) does not rely on B-Raf(V600E) or K-Ras(G13D) mutant oncogenic proteins, but partly depends on aberrant signaling activities of Akt, MAPK and AMPK kinases. Interestingly, MCT1- and macropinocytosis-mediated influx of 3-BrPA in T24 represents the principal mechanism that regulates cellular responsiveness to the drug. Besides its capacity to affect transcription in gene-dependent manner, 3-BrPA can also induce GLUT4-specific splicing silencing in both sensitive and resistant cells, thus dictating alternative routes of drug trafficking.

CONCLUSIONS

Altogether, it seems that 3-BrPA represents a promising agent for bladder cancer targeted therapy.

The cytotoxicity of 3-bromopyruvate in breast cancer cells depends on extracellular pH

Although the anti-cancer properties of 3BP (3-bromopyruvate) have been described previously, its selectivity for cancer cells still needs to be explained [Ko et al. (2001) Cancer Lett. 173, 83-91]. In the present study, we characterized the kinetic parameters of radiolabelled [14C] 3BP uptake in three breast cancer cell lines that display different levels of resistance to 3BP: ZR-75-1 < MCF-7 < SK-BR-3. At pH 6.0, the affinity of cancer cells for 3BP transport correlates with their sensitivity, a pattern that does not occur at pH 7.4. In the three cell lines, the uptake of 3BP is dependent on the protonmotive force and is decreased by MCTs (monocarboxylate transporters) inhibitors. In the SK-BR-3 cell line, a sodium-dependent transport also occurs. Butyrate promotes the localization of MCT-1 at the plasma membrane and increases the level of MCT-4 expression, leading to a higher sensitivity for 3BP. In the present study, we demonstrate that this phenotype is accompanied by an increase in affinity for 3BP uptake. Our results confirm the role of MCTs, especially MCT-1, in 3BP uptake and the importance of cluster of differentiation (CD) 147 glycosylation in this process. We find that the affinity for 3BP transport is higher when the extracellular milieu is acidic. This is a typical phenotype of tumour microenvironment and explains the lack of secondary effects of 3BP already described in in vivo studies [Ko et al. (2004) Biochem. Biophys. Res. Commun. 324, 269-275].

Limitations of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay when compared to three commonly used cell enumeration assays

Background

The tetrazolium-based MTT assay has long been regarded as the gold standard of cytotoxicity assays as it is highly sensitive and has been miniaturised for use as a high-throughput screening assay. However, various reports refer to interference by different test compounds, including the glycolysis inhibitor 3-bromopyruvate, with the conversion of the dye to coloured formazan crystals. This study assessed the linear range and reproducibility of three commonly used cell enumeration assays; the neutral red uptake (NRU), resazurin reduction (RES) and sulforhodamine B (SRB) assays, in comparison to the MTT assay. Interference between the MTT assay and three glycolysis inhibitors, 2-deoxyglucose, 3-bromopyruvate and lonidamine, was investigated.

Results

Data indicate that the NRU, RES and SRB assays showed the smallest variability across the linear range, while the largest variation was observed for the MTT assay. This implies that these assays would more accurately detect small changes in cell number than the MTT assay. The SRB assay provided the most reproducible results as indicated by the coefficient of determination after a limited number of experiments. The SRB assay also produced the lowest variance in the derived 50% inhibitory concentration (IC₅₀), while IC₅₀ concentrations of 3-bromopyruvate could not be detected using either the MTT or RES assays after 24 hours incubation. Interference in the MTT assay was observed for all three tested glycolysis inhibitors in a cell-free environment. No interferences were observed for the NRU, SRB or RES assays.

Conclusions

This study demonstrated that the MTT assay was not the best assay in a number of parameters that must be considered when a cell enumeration assay is selected: the MTT assay was less accurate in detecting changes in cell number as indicated by the variation observed in the linear range, had the highest variation when the IC₅₀ concentrations of the glycolysis inhibitors were determined, and interference between the MTT assay and all the glycolysis inhibitors tested were observed. The SRB assay performed best overall considering all of the parameters, suggesting that it is the most suitable assay for use in preclinical screening of novel therapeutic compounds with oxido-reductive potential.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-015-1000-8) contains supplementary material, which is available to authorized users.

Lactate transporters and vascular factors in HPV-induced squamous cell carcinoma of the uterine cervix

Background

Tumour microenvironment is a fundamental aspect of tumour behaviour, modulating important events as cancer cell migration and invasion, as well as angiogenesis and metastisation. Among other microenvironment features, hypoxia and acidity play important roles in this modulation. As the metabolic reprogramming of cancer cells induces extracellular acidity, which in turn induces angiogenesis, and hypoxia induces both the metabolic reprogramming and angiogenesis, the present study aims to evaluate the immunohistochemical expression of a variety of metabolic and vascular markers as common targets of the hypoxic microenvironment in a series of cervical squamous cells carcinoma, as well as using an in vitro 3D culture model.

Methods

Immunohistochemical expression of MCT1, MCT4, CD147, GLUT1 and CAIX was assessed in a series of 28 chronic cervicitis, 34 LSIL, 29 HSIL, 38 cases of squamous cells carcinoma (SCC), as well as in in vitro 3D culture of keratinocytes expressing HPV genes. Furthermore, VEGF family members’ expression was assessed in the SCC cases. The expression profiles were associated with patients’ clinicopathological parameters.

Results

We found an increase of MCT4 expression along progression to malignancy in cervical samples. Also, MCT4 was associated with CD147 and CAIX expression. VEGF-A expression was more frequently found in cases without MCT1 expression. Both MCT4 and CD147 were more frequently expressed in younger patients at diagnosis while no associations were found between VEGF family and clinicopathological parameters. Finally, we show evidence for the upregulation of MCT4, as well as CD147 and CAIX, after HPV transfection.

Conclusions

The results herein presented point at MCT4 as a promising therapeutic target in squamous cells carcinoma of the uterine cervix. Importantly, we show a possible association between lactate transport and angiogenesis, which should be further explored.

Comprehensive review on lactate metabolism in human health

Metabolic pathways involved in lactate metabolism are important to understand the physiological response to exercise and the pathogenesis of prevalent diseases such as diabetes and cancer. Monocarboxylate transporters are being investigated as potential targets for diagnosis and therapy of these and other disorders. Glucose and alanine produce pyruvate which is reduced to lactate by lactate dehydrogenase in the cytoplasm without oxygen consumption. Lactate removal takes place via its oxidation to pyruvate by lactate dehydrogenase. Pyruvate may be either oxidized to carbon dioxide producing energy or transformed into glucose. Pyruvate oxidation requires oxygen supply and the cooperation of pyruvate dehydrogenase, the tricarboxylic acid cycle, and the mitochondrial respiratory chain. Enzymes of the gluconeogenesis pathway sequentially convert pyruvate into glucose. Congenital or acquired deficiency on gluconeogenesis or pyruvate oxidation, including tissue hypoxia, may induce lactate accumulation. Both obese individuals and patients with diabetes show elevated plasma lactate concentration compared to healthy subjects, but there is no conclusive evidence of hyperlactatemia causing insulin resistance. Available evidence suggests an association between defective mitochondrial oxidative capacity in the pancreatic β-cells and diminished insulin secretion that may trigger the development of diabetes in patients already affected with insulin resistance. Several mutations in the mitochondrial DNA are associated with diabetes mellitus, although the pathogenesis remains unsettled. Mitochondrial DNA mutations have been detected in a number of human cancers. d-lactate is a lactate enantiomer normally formed during glycolysis. Excess d-lactate is generated in diabetes, particularly during diabetic ketoacidosis. d-lactic acidosis is typically associated with small bowel resection.

Mitochondria: 3-bromopyruvate vs. mitochondria? A small molecule that attacks tumors by targeting their bioenergetic diversity

Enhanced glycolysis, the classic bioenergetic phenotype of cancer cells was described by Otto Warburg approximately 90 years ago. However, the Warburg hypothesis does not necessarily imply mitochondrial dysfunction. The alkyl-halogen, 3-bromopyruvate (3BP), would not be expected to have selective targets for cancer therapy due to its high potential reactivity toward many SH side groups. Contrary to predictions, 3BP interferes with glycolysis and oxidative phosphorylation in cancer cells without side effects in normal tissues. The mitochondrial hexokinase II has been claimed as the main target. This "Organelle in focus" article presents a historical view of the use of 3BP in biochemistry and its effects on ATP-producing pathways of cancer cells. I will discuss how the alkylated enzymes contribute to the cooperative collapse of mitochondria and apoptosis. Perspectives for targeting 3BP to bioenergetics enzymes for cancer treatment will be considered.

Both butyrate incubation and hypoxia upregulate genes involved in the ruminal transport of SCFA and their metabolites

Butyrate modulates the differentiation, proliferation and gene expression profiles of various cell types. Ruminal epithelium is exposed to a high intraluminal concentration and inflow of n-butyrate. We aimed to investigate the influence of n-butyrate on the mRNA expression of proteins involved in the transmembranal transfer of n-butyrate metabolites and short-chain fatty acids in ruminal epithelium. N-butyrate-induced changes were compared with the effects of hypoxia because metabolite accumulation after O2 depletion is at least partly comparable to the accumulation of metabolites after n-butyrate exposure. Furthermore, in various tissues, O2 depletion modulates the expression of transport proteins that are also involved in the extrusion of metabolites derived from n-butyrate breakdown in ruminal epithelium. Sheep ruminal epithelia mounted in Ussing chambers were exposed to 50 mM n-butyrate or incubated under hypoxic conditions for 6 h. Electrophysiological measurements showed hypoxia-induced damage in the epithelia. The mRNA expression levels of monocarboxylate transporters (MCT) 1 and 4, anion exchanger (AE) 2, downregulated in adenoma (DRA), putative anion transporter (PAT) 1 and glucose transporter (GLUT) 1 were assessed by RT-qPCR. We also examined the mRNA expression of nuclear factor (NF) κB, cyclooxygenase (COX) 2, hypoxia-inducible factor (HIF) 1α and acyl-CoA oxidase (ACO) to elucidate the possible signalling pathways involved in the modulation of gene expression. The mRNA expression levels of MCT 1, MCT 4, GLUT 1, HIF 1α and COX 2 were upregulated after both n-butyrate exposure and hypoxia. ACO and PAT 1 were upregulated only after n-butyrate incubation. Upregulation of both MCT isoforms and NFκB after n-butyrate incubation could be detected on protein level as well. Our study suggests key roles for MCT 1 and 4 in the adaptation to an increased intracellular load of metabolites, whereas an involvement of PAT 1 in the transport of n-butyrate also seems possible.

Metabolic control analysis of respiration in human cancer tissue

Bioenergetic profiling of cancer cells is of great potential because it can bring forward new and effective therapeutic strategies along with early diagnosis. Metabolic Control Analysis (MCA) is a methodology that enables quantification of the flux control exerted by different enzymatic steps in a metabolic network thus assessing their contribution to the system‘s function. Our main goal is to demonstrate the applicability of MCA for in situ studies of energy metabolism in human breast and colorectal cancer cells as well as in normal tissues. We seek to determine the metabolic conditions leading to energy flux redirection in cancer cells. A main result obtained is that the adenine nucleotide translocator exhibits the highest control of respiration in human breast cancer thus becoming a prospective therapeutic target. Additionally, we present evidence suggesting the existence of mitochondrial respiratory supercomplexes that may represent a way by which cancer cells avoid apoptosis. The data obtained show that MCA applied in situ can be insightful in cancer cell energetic research.

Ascorbic acid and a cytostatic inhibitor of glycolysis synergistically induce apoptosis in non-small cell lung cancer cells

Ascorbic acid (AA) exhibits significant anticancer activity at pharmacologic doses achievable by parenteral administration that have minimal effects on normal cells. Thus, AA has potential uses as a chemotherapeutic agent alone or in combination with other therapeutics that specifically target cancer-cell metabolism. We compared the effects of AA and combinations of AA with the glycolysis inhibitor 3-(3-pyridinyl)-1-(4-pyridinyl)-2-propen-1-one (3-PO) on the viability of three non-small cell lung cancer (NSCLC) cell lines to the effects on an immortalized lung epithelial cell line. AA concentrations of 0.5 to 5 mM caused a complete loss of viability in all NSCLC lines compared to a <10% loss of viability in the lung epithelial cell line. Combinations of AA and 3-PO synergistically enhanced cell death in all NSCLC cell lines at concentrations well below the IC₅₀ concentrations for each compound alone. A synergistic interaction was not observed in combination treatments of lung epithelial cells and combination treatments that caused a complete loss of viability in NSCLC cells had modest effects on normal lung cell viability and reactive oxygen species (ROS) levels. Combination treatments induced dramatically higher ROS levels compared to treatment with AA and 3-PO alone in NSCLC cells and combination-induced cell death was inhibited by addition of catalase to the medium. Analyses of DNA fragmentation, poly (ADP-ribose) polymerase cleavage, annexin V-binding, and caspase activity demonstrated that AA-induced cell death is caused via the activation of apoptosis and that the combination treatments caused a synergistic induction of apoptosis. These results demonstrate the effectiveness of AA against NSCLC cells and that combinations of AA with 3-PO synergistically induce apoptosis via a ROS-dependent mechanism. These results support further evaluation of pharmacologic concentrations of AA as an adjuvant treatment for NSCLC and that combination of AA with glycolysis inhibitors may be a promising therapy for the treatment of NSCLC.

MCT1-mediated transport of a toxic molecule is an effective strategy for targeting glycolytic tumors

There is increasing evidence that oncogenic transformation modifies the metabolic program of cells. A common alteration is the upregulation of glycolysis, and efforts to target glycolytic enzymes for anti-cancer therapy are underway. Here, we performed a genome-wide haploid genetic screen to identify resistance mechanisms to 3-bromopyruvate (3-BrPA), a drug candidate that inhibits glycolysis in a poorly understood fashion. We identified the SLC16A1 gene product, MCT1, as the main determinant of 3-BrPA sensitivity. MCT1 is necessary and sufficient for 3-BrPA uptake by cancer cells. Additionally, MCT1 mRNA levels are the best predictor of 3-BrPA sensitivity and are most elevated in glycolytic cancer cells. Lastly, forced MCT1 expression in 3-BrPA resistant cancer cells sensitizes tumor xenografts to 3-BrPA treatment in vivo. Our results identify a potential biomarker for 3-BrPA sensitivity and provide proof of concept that the selectivity of cancer-expressed transporters can be exploited for delivering toxic molecules to tumors.

3-Bromopyruvate (3BP) a fast acting, promising, powerful, specific, and effective "small molecule" anti-cancer agent taken from labside to bedside: introduction to a special issue

Although the "Warburg effect", i.e., elevated glucose metabolism to lactic acid (glycolysis) even in the presence of oxygen, has been recognized as the most common biochemical phenotype of cancer for over 80 years, its biochemical and genetic basis remained unknown for over 50 years. Work focused on elucidating the underlying mechanism(s) of the "Warburg effect" commenced in the author's laboratory in 1969. By 1985 among the novel findings made two related most directly to the basis of the "Warburg effect", the first that the mitochondrial content of tumors exhibiting this phenotype is markedly decreased relative to the tissue of origin, and the second that such mitochondria have markedly elevated amounts of the enzyme hexokinase-2 (HK2) bound to their outer membrane. HK2 is the first of a number of enzymes in cancer cells involved in metabolizing the sugar glucose to lactic acid. At its mitochondrial location HK2 binds at/near the protein VDAC (voltage dependent anion channel), escapes inhibition by its product glucose-6-phosphate, and gains access to mitochondrial produced ATP. As shown by others, it also helps immortalize cancer cells, i.e., prevents cell death. Based on these studies, the author's laboratory commenced experiments to elucidate the gene basis for the overexpression of HK2 in cancer. These studies led to both the discovery of a unique HK2 promoter region markedly activated by both hypoxic conditions and moderately activated by several metabolites (e.g., glucose), Also discovered was the promoter's regulation by epigenetic events (i.e., methylation, demethylation). Finally, the author's laboratory turned to the most important objective. Could they selectively and completely destroy cancerous tumors in animals? This led to the discovery in an experiment conceived, designed, and conducted by Young Ko that the small molecule 3-bromopyruvate (3BP), the subject of this mini-review series, is an incredibly powerful and swift acting anticancer agent. Significantly, in subsequent experiments with rodents (19 animals with advanced cancer) Ko led a project in which 3BP was shown in a short treatment period to eradicate all (100%). Ko's and co-author's findings once published attracted global attention leading world-wide to many other studies and publications related to 3BP and its potent anti-cancer effect. This Issue of the Journal of Bioenergetics and Biomembranes (JOBB 44-1) captures only a sampling of research conducted to date on 3BP as an anticancer agent, and includes also a Case Report on the first human patient known to the author to be treated with specially formulated 3BP. Suffice it to say in this bottom line, "3BP, a small molecule, results in a remarkable therapeutic effect when it comes to treating cancers exhibiting a "Warburg effect". This includes most cancer types.

Glutamine deprivation enhances antitumor activity of 3-bromopyruvate through the stabilization of monocarboxylate transporter-1

Anticancer drug efficacy might be leveraged by strategies to target certain biochemical adaptations of tumors. Here we show how depriving cancer cells of glutamine can enhance the anticancer properties of 3-bromopyruvate, a halogenated analog of pyruvic acid. Glutamine deprival potentiated 3-bromopyruvate chemotherapy by increasing the stability of the monocarboxylate transporter-1, an effect that sensitized cells to metabolic oxidative stress and autophagic cell death. We further elucidated mechanisms through which resistance to chemopotentiation by glutamine deprival could be circumvented. Overall, our findings offer a preclinical proof-of-concept for how to employ 3-bromopyruvate or other monocarboxylic-based drugs to sensitize tumors to chemotherapy.