Identification of putative c-Myc-responsive genes: characterization of rcl, a novel growth-related gene

Sepsis-induced changes in pyruvate metabolism: insights and potential therapeutic approaches

Sepsis is a heterogeneous syndrome resulting from a dysregulated host response to infection. It is considered as a global major health priority. Sepsis is characterized by significant metabolic perturbations, leading to increased circulating metabolites such as lactate. In mammals, pyruvate is the primary substrate for lactate production. It plays a critical role in metabolism by linking glycolysis, where it is produced, with the mitochondrial oxidative phosphorylation pathway, where it is oxidized. Here, we provide an overview of all cytosolic and mitochondrial enzymes involved in pyruvate metabolism and how their activities are disrupted in sepsis. Based on the available data, we also discuss potential therapeutic strategies targeting these pyruvate-related enzymes leading to enhanced survival.

ATF6 Promotes Colorectal Cancer Growth and Stemness by Regulating the Wnt Pathway

SIGNIFICANCE

ATF6 intervention reduces colorectal cancer cell and organoid viability by interrupting dysregulated Wnt signaling, identifying a novel facilitator and potential therapeutic target in colorectal cancer.

Functions and novel regulatory mechanisms of key glycolytic enzymes in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive vascular disease characterized by remodeling of the pulmonary vasculature and elevated pulmonary arterial pressure, ultimately leading to right heart failure and death. Despite its clinical significance, the precise molecular mechanisms driving PAH pathogenesis warrant confirmation. Compelling evidence indicates that during the development of PAH, pulmonary vascular cells exhibit a preference for energy generation through aerobic glycolysis, known as the "Warburg effect", even in well-oxygenated conditions. This metabolic shift results in imbalanced metabolism, increased proliferation, and severe pulmonary vascular remodeling. Exploring the Warburg effect and its interplay with glycolytic enzymes in the context of PAH has yielded current insights into emerging drug candidates targeting enzymes and intermediates involved in glucose metabolism. This sheds light on both opportunities and challenges in the realm of antiglycolytic therapy for PAH.

Cancer Metabolism Historical Perspectives: A Chronicle of Controversies and Consensus

A century ago, Otto Warburg's work sparked the field of cancer metabolism, which has since taken a tortuous path. As evidence accumulated over the decades, consensus views of causes of cancer emerged, whereby genetic and epigenetic oncogenic drivers promoted immune evasion and induced new blood vessels and neoplastic metabolism to support tumor growth. Neoplastic cells abandon social cues of intercellular cooperation, escape tissue confinement, metastasize, and ultimately kill the host. Herein, key milestones in the study of cancer metabolism are chronicled with an emphasis on carbohydrate metabolism. The field began with a cancer cell-autonomous view that has been refined by a richer understanding of solid cancers as growing, immune-suppressive, complex organs comprising different cell types that are nourished by a variety of nutrients and variable amounts of oxygen through abnormal neovasculatures. Based on foundational historical studies, our current understanding of cancer metabolism offers a hopeful outlook for targeting metabolism to enhance cancer therapy.

Ldha-Dependent Metabolic Programs in Sertoli Cells Regulate Spermiogenesis in Mouse Testis

Sertoli cells play indispensable roles in spermatogenesis by providing the advanced germ cells with structural, nutritional, and regulatory support. Lactate is regarded as an essential Sertoli-cell-derived energy metabolite that nurses various types of spermatogenic cells; however, this assumption has not been tested using genetic approaches. Here, we have reported that the depletion of lactate production in Sertoli cells by conditionally deleting lactate dehydrogenase A (Ldha) greatly affected spermatogenesis. Ldha deletion in Sertoli cells significantly reduced the lactate production and resulted in severe defects in spermatogenesis. Spermatogonia and spermatocytes did not show even mild impairments, but the spermiogenesis of Ldha conditional knockout males was severely disrupted. Further analysis revealed that 2456 metabolites were altered in the sperm of the knockout animals, and specifically, lipid metabolism was dysregulated, including choline, oleic acid, and myristic acid. Surprisingly, choline supplementation completely rescued the spermiogenesis disorder that was caused by the loss of Ldha activities. Collectively, these data have demonstrated that the interruption of Sertoli-cell-derived lactate impacted sperm development through a choline-mediated mechanism. The outcomes of these findings have revealed a novel function of lactate in spermatogenesis and have therapeutic applications in treating human infertility.

Metabolic Pathways, Enzymes, and Metabolites: Opportunities in Cancer Therapy

Metabolic reprogramming enables cancer cells to proliferate and produce tumor biomass under a nutrient-deficient microenvironment and the stress of metabolic waste. A cancer cell adeptly undergoes a variety of adaptations in metabolic pathways and differential expression of metabolic enzyme genes. Metabolic adaptation is mainly determined by the physiological demands of the cancer cell of origin and the host tissue. Numerous metabolic regulators that assist cancer cell proliferation include uncontrolled anabolism/catabolism of glucose metabolism, fatty acids, amino acids metabolism, nucleotide metabolism, tumor suppressor genes, microRNAs, and many regulatory enzymes and genes. Using this paradigm, we review the current understanding of metabolic reprogramming in tumors and discuss the new strategies of cancer metabolomics that can be tapped into for cancer therapeutics.

Curcumin and Wnt/β‑catenin signaling in exudative age‑related macular degeneration (Review)

Curcumin is a natural product widely used due to its pharmacological effects. Nevertheless, only a limited number of studies concerning the effects of curcumin on exudative age‑related macular degeneration (AMD) is currently available. Since ophthalmic diseases, including exudative AMD, have a marked impact on public health, the prevention and therapy of ophthalmic disorders remain of increasing concern. Exudative AMD is characterized by choroidal neovascularization (CNV) invading the subretinal space, ultimately enhancing exudation and hemorrhaging. The exudative AMD subtype corresponds to 10 to 15% of cases of macular degeneration; however, the occurrence of this subtype has been reported as the major cause of vision loss and blindness, with the occurrence of CNV being responsible for 80% of the cases with vision loss. In CNV increased expression of VEGF has been observed, stimulated by the overactivation of Wnt/β‑catenin signaling pathway. The stimulation of the Wnt/β‑catenin signaling pathway is responsible for the activation of several cellular mechanisms, simultaneously enhancing inflammation, oxidative stress and angiogenesis in numerous diseases, including ophthalmic disorders. Some studies have previously demonstrated the possible advantage of the use of curcumin for the inhibition of Wnt/β‑catenin signaling. In the present review article, the different mechanisms of curcumin are described concerning its effects on oxidative stress, inflammation and angiogenesis in exudative AMD, by interacting with Wnt/β‑catenin signaling.

CDCA7 Facilitates Tumor Progression by Directly Regulating CCNA2 Expression in Esophageal Squamous Cell Carcinoma

Background

CDCA7 is a copy number amplified gene identified not only in esophageal squamous cell carcinoma (ESCC) but also in various cancer types. Its clinical relevance and underlying mechanisms in ESCC have remained unknown.

Methods

Tissue microarray data was used to analyze its expression in 179 ESCC samples. The effects of CDCA7 on proliferation, colony formation, and cell cycle were tested in ESCC cells. Real-time PCR and Western blot were used to detect the expression of its target genes. Correlation of CDCA7 with its target genes in ESCC and various SCC types was analyzed using GSE53625 and TCGA data. The mechanism of CDCA7 was studied by chromatin immunoprecipitation (ChIP), luciferase reporter assays, and rescue assay.

Results

The overexpression of CDCA7 promoted proliferation, colony formation, and cell cycle in ESCC cells. CDCA7 affected the expression of cyclins in different cell phases. GSE53625 and TCGA data showed CCNA2 expression was positively correlated with CDCA7. The knockdown of CCNA2 reversed the malignant phenotype induced by CDCA7 overexpression. Furthermore, CDCA7 was found to directly bind to CCNA2, thus promoting its expression.

Conclusions

Our results reveal a novel mechanism of CDCA7 that it may act as an oncogene by directly upregulating CCNA2 to facilitate tumor progression in ESCC.

The Key Role of the WNT/β-Catenin Pathway in Metabolic Reprogramming in Cancers under Normoxic Conditions

Simple Summary

The canonical WNT/β-catenin pathway is upregulated in cancers and plays a major role in proliferation, invasion, apoptosis and angiogenesis. Recent studies have shown that cancer processes are involved under normoxic conditions. These findings completely change the way of approaching the study of the cancer process. In this review, we focus on the fact that, under normoxic conditions, the overstimulation of the WNT/β-catenin pathway leads to modifications in the tumor micro-environment and the activation of the Warburg effect, i.e., aerobic glycolysis, autophagy and glutaminolysis, which in turn participate in tumor growth.

Abstract

The canonical WNT/β-catenin pathway is upregulated in cancers and plays a major role in proliferation, invasion, apoptosis and angiogenesis. Nuclear β-catenin accumulation is associated with cancer. Hypoxic mechanisms lead to the activation of the hypoxia-inducible factor (HIF)-1α, promoting glycolytic and energetic metabolism and angiogenesis. However, HIF-1α is degraded by the HIF prolyl hydroxylase under normoxia, conditions under which the WNT/β-catenin pathway can activate HIF-1α. This review is therefore focused on the interaction between the upregulated WNT/β-catenin pathway and the metabolic processes underlying cancer mechanisms under normoxic conditions. The WNT pathway stimulates the PI3K/Akt pathway, the STAT3 pathway and the transduction of WNT/β-catenin target genes (such as c-Myc) to activate HIF-1α activity in a hypoxia-independent manner. In cancers, stimulation of the WNT/β-catenin pathway induces many glycolytic enzymes, which in turn induce metabolic reprogramming, known as the Warburg effect or aerobic glycolysis, leading to lactate overproduction. The activation of the Wnt/β-catenin pathway induces gene transactivation via WNT target genes, c-Myc and cyclin D1, or via HIF-1α. This in turn encodes aerobic glycolysis enzymes, including glucose transporter, hexokinase 2, pyruvate kinase M2, pyruvate dehydrogenase kinase 1 and lactate dehydrogenase-A, leading to lactate production. The increase in lactate production is associated with modifications to the tumor microenvironment and tumor growth under normoxic conditions. Moreover, increased lactate production is associated with overexpression of VEGF, a key inducer of angiogenesis. Thus, under normoxic conditions, overstimulation of the WNT/β-catenin pathway leads to modifications of the tumor microenvironment and activation of the Warburg effect, autophagy and glutaminolysis, which in turn participate in tumor growth.

Opposed Interplay between IDH1 Mutations and the WNT/β-Catenin Pathway: Added Information for Glioma Classification

Gliomas are the main common primary intraparenchymal brain tumor in the central nervous system (CNS), with approximately 7% of the death caused by cancers. In the WHO 2016 classification, molecular dysregulations are part of the definition of particular brain tumor entities for the first time. Nevertheless, the underlying molecular mechanisms remain unclear. Several studies have shown that 75% to 80% of secondary glioblastoma (GBM) showed IDH1 mutations, whereas only 5% of primary GBM have IDH1 mutations. IDH1 mutations lead to better overall survival in gliomas patients. IDH1 mutations are associated with lower stimulation of the HIF-1α a, aerobic glycolysis and angiogenesis. The stimulation of HIF-1α and the process of angiogenesis appears to be activated only when hypoxia occurs in IDH1-mutated gliomas. In contrast, the observed upregulation of the canonical WNT/β-catenin pathway in gliomas is associated with proliferation, invasion, aggressive-ness and angiogenesis.. Molecular pathways of the malignancy process are involved in early stages of WNT/β-catenin pathway-activated-gliomas, and this even under normoxic conditions. IDH1 mutations lead to decreased activity of the WNT/β-catenin pathway and its enzymatic targets. The opposed interplay between IDH1 mutations and the canonical WNT/β-catenin pathway in gliomas could participate in better understanding of the observed evolution of different tumors and could reinforce the glioma classification.

High expression of CDCA7 predicts poor prognosis for clear cell renal cell carcinoma and explores its associations with immunity

BACKGROUND

Cell division cycle-associated 7 (CDCA7), as a member of the cell division cycle associated family, was reported to be aberrantly expressed in both solid tumors and hematological tumors, suggesting its essential role in promoting tumorigenesis. Hence, we aimed to explore its comprehensive roles of overall survival (OS) in clear cell renal cell carcinoma (ccRCC) and emphasize its associations with immunity.

METHODS

The RNA sequencing data and corresponding clinical information were downloaded from The Cancer Genome Atlas (TCGA) database. Gene set enrichment analysis (GSEA) was adopted to explore CDCA7 associated signaling pathways. Univariate and multivariate Cox regression analyses were carried out to assess independent prognostic factors. Furthermore, roles of CDCA7 in human immunity were also investigated.

RESULTS

Our results suggested that CDCA7 was overexpressed in ccRCC and its elevated expression was related to shorter OS (P < 0.01). Univariate and multivariate Cox regression analyses identified CDCA7 as an independent prognostic factor (both P < 0.05). The prognostic nomogram integrating CDCA7 expression level and clinicopathologic variables was constructed to predict 1-, 3- and 5-year OS. GSEA indicated that high CDCA7 expression was related to the apoptosis pathway, cell cycle pathway, JAK-STAT pathway, NOD like receptor pathway, P53 pathway, T cell receptor pathway and toll like receptor pathway, etc. Moreover, CDCA7 was significantly related to microsatellite instability (MSI, P < 0.001) and tumor mutational burden (TMB, P < 0.001). As for immunity, CDCA7 was remarkably associated with immune infiltration, tumor microenvironment, immune checkpoint molecules and immune pathways.

CONCLUSIONS

CDCA7 could serve as an independent prognostic factor for ccRCC and it was closely related to MSI, TMB, and immunity.

Correlation analysis of serum cystatin C, uric acid and lactate dehydrogenase levels before chemotherapy on the prognosis of small-cell lung cancer

Related studies have reported that cystatin C (Cys C), uric acid (UA) and lactate dehydrogenase (LDH) affect tumor growth and invasion; however, the correlation between them and the prognosis of patients with small-cell lung cancer (SCLC) remains unclear. The present study aimed to investigate the effects of serum Cys C, UA and LDH concentrations on the prognosis of patients with SCLC prior to initial treatment, in order to identify potential targets for determining the clinical outcome of patients with SCLC. A total of 205 patients with SCLC were enrolled in the present study, and the clinical and laboratory data were obtained from the medical records. The receiver operating characteristic curve was used to determine the optimal cut-off values of Cys C, UA and LDH, while the Kaplan-Meier method was used for survival analysis. The Cox proportional hazard model was used for univariate and multivariate analyses to identify independent prognostic factors. The optimal cut-off values for Cys C, UA and LDH were 0.775 mg/l, 296.45 µmol/l and 198.5 U/l, respectively. The survival curves demonstrated that progression-free survival (PFS) and overall survival (OS) time were shorter in patients with high levels of Cys C, UA and LDH prior to chemotherapy. Univariate and multivariate analyses indicated that LDH concentration prior to chemotherapy may be an independent prognostic factor for both PFS and OS in patients with SCLC, while Cys C concentration may be an independent prognostic factor for PFS in patients with SCLC. The concentrations of Cys C, UA and LDH prior to chemotherapy were associated with prognosis of patients with SCLC. PFS and OS time were shorter, and the prognosis was poor in patients with elevated serum levels of Cys C, UA and LDH. Taken together, the results of the present study suggest that high concentrations of LDH and Cys C prior to chemotherapy may indicate rapid disease progression, thus it is important to focus on the progression and recurrence of the disease. High LDH concentration may also indicate a shorter survival time.

Targeting lactate dehydrogenase A (LDHA) exerts antileukemic effects on T-cell acute lymphoblastic leukemia

Background

T‐cell acute lymphoblastic leukemia (T‐ALL) is an uncommon and aggressive subtype of acute lymphoblastic leukemia (ALL). In the serum of T‐ALL patients, the activity of lactate dehydrogenase A (LDHA) is increased. We proposed that targeting LDHA may be a potential strategy to improve T‐ALL outcomes. The current study was conducted to investigate the antileukemic effect of LDHA gene‐targeting treatment on T‐ALL and the underlying molecular mechanism.

Methods

Primary T‐ALL cell lines Jurkat and DU528 were treated with the LDH inhibitor oxamate. MTT, colony formation, apoptosis, and cell cycle assays were performed to investigate the effects of oxamate on T‐ALL cells. Quantitative real‐time PCR (qPCR) and Western blotting analyses were applied to determine the related signaling pathways. A mitochondrial reactive oxygen species (ROS) assay was performed to evaluate ROS production after T‐ALL cells were treated with oxamate. A T‐ALL transgenic zebrafish model with LDHA gene knockdown was established using CRISPR/Cas9 gene‐editing technology, and then TUNEL, Western blotting, and T‐ALL tumor progression analyses were conducted to investigate the effects of LDHA gene knockdown on T‐ALL transgenic zebrafish.

Results

Oxamate significantly inhibited proliferation and induced apoptosis of Jurkat and DU528 cells. It also arrested Jurkat and DU528 cells in G0/G1 phase and stimulated ROS production (all P < 0.001). Blocking LDHA significantly decreased the gene and protein expression of c‐Myc, as well as the levels of phosphorylated serine/threonine kinase (AKT) and glycogen synthase kinase 3 beta (GSK‐3β) in the phosphatidylinositol 3′‐kinase (PI3K) signaling pathway. LDHA gene knockdown delayed disease progression and down‐regulated c‐Myc mRNA and protein expression in T‐ALL transgenic zebrafish.

Conclusion

Targeting LDHA exerted an antileukemic effect on T‐ALL, representing a potential strategy for T‐ALL treatment.

High expression of CDCA7 predicts tumor progression and poor prognosis in human colorectal cancer

Colorectal cancer (CRC) is one of the most fatal types of cancer worldwide. This study aimed to determine the predictive and prognostic values of cell division cycle associated protein 7 (CDCA7) in CRC. Firstly, the relationship between CDCA7 and CRC was assessed through bioinformatics analysis. Subsequently, CDCA7 expression levels were detected in various CRC cell lines, as well as 15 fresh human CRC tissues and their paired adjacent normal colorectal tissues using reverse transcription‑quantitative PCR and western blotting. Additionally, immunohistochemical staining was used to determine the levels of CDCA7 in 104 CRC tissues and their paired adjacent normal colorectal tissues. The present study revealed that CDCA7 expression was upregulated in CRC tissues and cell lines. The positive expression rates of CDCA7 in normal and CRC tissues were 26.92 and 75.96%, respectively. The intensities of CDCA7 immunostaining were significantly associated with CRC invasion depth, lymph node metastasis, tumor‑node‑metastasis stage and distant metastasis. However, no significant differences in sex, age, tumor size and CRC differentiation were found between high and low CDCA7 expression groups. Furthermore, patients with low CDCA7 expression exhibited a greater overall survival rate of CRC compared to those with high CDCA7 expression. The findings of this study indicated that CDCA7 may serve a significant role in CRC prognosis and progression, and may be considered a novel biomarker for the prediction of patient survival after colectomy.

BCG Vaccinations Upregulate Myc, a Central Switch for Improved Glucose Metabolism in Diabetes

Myc has emerged as a pivotal transcription factor for four metabolic pathways: aerobic glycolysis, glutaminolysis, polyamine synthesis, and HIF-1α/mTOR. Each of these pathways accelerates the utilization of sugar. The BCG vaccine, a derivative of Mycobacteria-bovis, has been shown to trigger a long-term correction of blood sugar levels to near normal in type 1 diabetics (T1D). Here we reveal the underlying mechanisms behind this beneficial microbe-host interaction. We show that baseline glucose transport is deficient in T1D monocytes but is improved by BCG in vitro and in vivo. We then show, using RNAseq in monocytes and CD4 T cells, that BCG treatment over 56 weeks in humans is associated with upregulation of Myc and activation of nearly two dozen Myc-target genes underlying the four metabolic pathways. This is the first documentation of BCG induction of Myc and its association with systemic blood sugar control in a chronic disease like diabetes.

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T1D has insufficient aerobic glycolysis; this causes insufficient sugar utilization

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BCG vaccine lowers blood sugar levels in T1D by augmenting aerobic glycolysis

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BCG-induced shift to aerobic glycolysis is associated with Myc activation

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Host-microbe BCG interactions through Myc activate sugar-regulating genes in T1D

Combining Hyperpolarized Real-Time Metabolic Imaging and NMR Spectroscopy To Identify Metabolic Biomarkers in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is a deadly cancer that progresses without any symptom, and oftentimes, it is detected at an advanced stage. The lack of prior symptoms and effective treatments have created a knowledge gap in the management of this lethal disease. This issue can be addressed by developing novel noninvasive imaging-based biomarkers in PDAC. We explored in vivo hyperpolarized (HP) ¹³C MRS of pyruvate to lactate conversion and ex vivo ¹H NMR spectroscopy in a panel of well-annotated patient-derived PDAC xenograft (PDXs) model and investigated the correlation between aberrant glycolytic metabolism and aggressiveness of the tumor. Real-time metabolic imaging data demonstrate the immediate intracellular conversion of HP ¹³C pyruvate to lactate after intravenous injection interrogating upregulated lactate dehydrogenase (LDH) activity in aggressive PDXs. Total ex vivo lactate measurement by ¹H NMR spectroscopy showed a direct correlation with in vivo dynamic pyruvate-to-lactate conversion and demonstrated the potential of dynamic metabolic flux as a biomarker of total lactate concentration and aggressiveness of the tumor. Furthermore, the metabolite concentrations were very distinct among all four tumor types analyzed in this study. Overexpression of LDH-A and hypoxia-inducible factor (HIF-1α) plays a significant role in the conversion kinetics of HP pyruvate-to-lactate in tumors. Collectively, these data identified aberrant metabolic characteristics of pancreatic cancer PDXs and could potentially delineate metabolic targets for therapeutic intervention. Metabolic imaging with HP pyruvate and NMR metabolomics may enable identification and classification of aggressive subtypes of patient-derived xenografts. Translation of this real-time metabolic technique to the clinic may have the potential to improve the management of patients at high risk of developing pancreatic diseases.

MYC Drives Group 3 Medulloblastoma through Transformation of Sox2+ Astrocyte Progenitor Cells

A subset of group 3 medulloblastoma frequently harbors amplification or overexpression of MYC lacking additional focal aberrations, yet it remains unclear whether MYC overexpression alone can induce tumorigenesis and which cells give rise to these tumors. Here, we showed that astrocyte progenitors in the early postnatal cerebellum were susceptible to transformation by MYC. The resulting tumors specifically resembled human group 3 medulloblastoma based on histology and gene-expression profiling. Gene-expression analysis of MYC-driven medulloblastoma cells revealed altered glucose metabolic pathways with marked overexpression of lactate dehydrogenase A (LDHA). LDHA abundance correlated positively with MYC expression and was associated with poor prognosis in human group 3 medulloblastoma. Inhibition of LDHA significantly reduced growth of both mouse and human MYC-driven tumors but had little effect on normal cerebellar cells or SHH-associated medulloblastoma. By generating a new mouse model, we demonstrated for the first time that astrocyte progenitors can be transformed by MYC and serve as the cells of origin for group 3 medulloblastoma. Moreover, we identified LDHA as a novel, specific therapeutic target for this devastating disease. SIGNIFICANCE: Insights from a new model identified LDHA as a novel target for group 3 medulloblastoma, paving the way for the development of effective therapies against this disease.

ATM deficiency promotes progression of CRPC by enhancing Warburg effect

ATM is a well-known master regulator of double strand break (DSB) DNA repair and the defective DNA repair has been therapeutically exploited to develop PARP inhibitors based on the synthetic lethality strategy. ATM mutation is found with increased prevalence in advanced metastatic castration-resistant prostate cancer (mCRPC). However, the molecular mechanisms underlying ATM mutation-driving disease progression are still largely unknown. Here, we report that ATM mutation contributes to the CRPC progression through a metabolic rather than DNA repair mechanism. We showed that ATM deficiency generated by CRISPR/Cas9 editing promoted CRPC cell proliferation and xenograft tumor growth. ATM deficiency altered cellular metabolism and enhanced Warburg effect in CRPC cells. We demonstrated that ATM deficiency shunted the glucose flux to aerobic glycolysis by upregulating LDHA expression, which generated more lactate and produced less mitochondrial ROS to promote CRPC cell growth. Inhibition of LDHA by siRNA or inhibitor FX11 generated less lactate and accumulated more ROS in ATM-deficient CRPC cells and therefore potentiated the cell death of ATM-deficient CRPC cells. These findings suggest a new therapeutic strategy for ATM-mutant CRPC patients by targeting LDHA-mediated glycolysis metabolism, which might be effective for the PARP inhibitor resistant mCRPC tumors.

Vasculogenesis and angiogenesis initiation under normoxic conditions through Wnt/β-catenin pathway in gliomas

The canonical Wnt/β-catenin pathway is up-regulated in gliomas and involved in proliferation, invasion, apoptosis, vasculogenesis and angiogenesis. Nuclear β-catenin accumulation correlates with malignancy. Hypoxia activates hypoxia-inducible factor (HIF)-1α by inhibiting HIF-1α prolyl hydroxylation, which promotes glycolytic energy metabolism, vasculogenesis and angiogenesis, whereas HIF-1α is degraded by the HIF prolyl hydroxylase under normoxic conditions. We focus this review on the links between the activated Wnt/β-catenin pathway and the mechanisms underlying vasculogenesis and angiogenesis through HIF-1α under normoxic conditions in gliomas. Wnt-induced epidermal growth factor receptor/phosphatidylinositol 3-kinase (PI3K)/Akt signaling, Wnt-induced signal transducers and activators of transcription 3 (STAT3) signaling, and Wnt/β-catenin target gene transduction (c-Myc) can activate HIF-1α in a hypoxia-independent manner. The PI3K/Akt/mammalian target of rapamycin pathway activates HIF-1α through eukaryotic translation initiation factor 4E-binding protein 1 and STAT3. The β-catenin/T-cell factor 4 complex directly binds to STAT3 and activates HIF-1α, which up-regulates the Wnt/β-catenin target genes cyclin D1 and c-Myc in a positive feedback loop. Phosphorylated STAT3 by interleukin-6 or leukemia inhibitory factor activates HIF-1α even under normoxic conditions. The activation of the Wnt/β-catenin pathway induces, via the Wnt target genes c-Myc and cyclin D1 or via HIF-1α, gene transactivation encoding aerobic glycolysis enzymes, such as glucose transporter, hexokinase 2, pyruvate kinase M2, pyruvate dehydrogenase kinase 1 and lactate dehydrogenase-A, leading to lactate production, as the primary alternative of ATP, at all oxygen levels, even in normoxic conditions. Lactate released by glioma cells via the monocarboxylate lactate transporter-1 up-regulated by HIF-1α and lactate anion activates HIF-1α in normoxic endothelial cells by inhibiting HIF-1α prolyl hydroxylation and preventing HIF labeling by the von Hippel-Lindau protein. Increased lactate with acid environment and HIF-1α overexpression induce the vascular endothelial growth factor (VEGF) pathway of vasculogenesis and angiogenesis under normoxic conditions. Hypoxia and acidic pH have no synergistic effect on VEGF transcription.

Pim1 supports human colorectal cancer growth during glucose deprivation by enhancing the Warburg effect

Cancer cells metabolize glucose mainly by glycolysis and are well adapted to metabolic stress. Pim1 is an oncogene that promotes colorectal cancer (CRC) growth and metastasis, and its expression is positively correlated with CRC progression. However, the mechanism underlying Pim1 overexpression during CRC progression and the role of Pim1 in CRC metabolism remains unclear. In the present study, we discovered that Pim1 expression was significantly upregulated in response to glucose deprivation‐induced metabolic stress by AMP‐activated protein kinase signaling. Pim1 promoted CRC cell proliferation in vitro and tumorigenicity in vivo. Clinical observations showed that Pim1 expression was higher in CRC tissues than in adjacent normal tissues. Pim1 overexpression in CRC tissues not only predicted CRC prognosis in patients but also showed a positive relationship with ¹⁸F‐fluorodeoxyglucose uptake. Further in vitro experiments showed that Pim1 promoted the Warburg effect and that Pim1 expression was positively correlated with hexokinase 2 and lactate dehydrogenase A expression. Pim1‐silenced cells were more vulnerable to glucose starvation, and Pim1‐induced tumor proliferation or tolerance to glucose starvation was attenuated by blocking the Warburg effect. In conclusion, glucose deprivation is one of the mechanisms that leads to elevated Pim1 expression in CRC, and Pim1 upregulation ensures CRC growth in response to glucose deprivation by facilitating the Warburg effect in a compensatory way.

Deoxynucleoside 5-monophosphate N-glycosidase from a phylogenetically distant metazoa, sponge

Deoxynucleoside 5-monophosphate N-glycosidase or DNPH1 (former name Rcl) is a nucleotide hydrolase whose expression in mammalian cancer tissues has been associated with its tumorigenic potential. Therefore, the enzyme has been studied principally in rat and human models. We found the corresponding gene also in the freshwater sponge Ephydatia muelleri, an animal phylogenetically very distant from mammals. Here we report the expression and characterization of the recombinant DNPH1 from E. muelleri. The ancient homolog of mammalian enzyme in a sponge showed the substrate specificity and catalytic efficiency similar to that in higher animals. E. muelleri DNPH1 is inhibited by the purine nucleotides with different numbers of 5'-phosphate groups (n = 1-4). Our results demonstrate that GTP but also dGTP are the best inhibitors, followed by all other purine nucleotides that were tested. Hence, the functioning of DNPH1 in cells where the natural ATP and GTP concentrations are much higher than those of the substrates, dNMPs, should normally be downregulated. We demonstrate for the first time the existence of biologically relevant natural inhibitors of DNPH1, namely ATP and GTP.

PPARγ agonists: Potential treatments for exudative age-related macular degeneration

Choroidal neovascularization (CNV) characterizes the progression of exudative age-related macular degeneration (AMD) with the deterioration in the central vision. Vascular inflammation, and overproduction of inflammatory cytokines, growth factors and aberrant endothelial cell migration, initiate defective blood vessel proliferation in exudative AMD. CNV formation is initiated by the interplay between inflammation, the hallmark of exudative AMD, and the activation of WNT/β-catenin pathway. Upregulation of WNT/β-catenin pathway involves activation of PI3K/Akt pathway and then the Warburg effect to produce lactate. Lactate production generates VEGF expression and then participates to the initiation of CNV in exudative AMD. WNT/β-catenin pathway and PPARγ act in an opposite manner in several diseases. We focus this review on the interplay between PPARγ and canonical WNT/β-catenin pathway and the anti-inflammatory role of PPARγ in exudative AMD. In exudative AMD, PPARγ agonists downregulate inflammation and the WNT/β-catenin pathway. PPARγ agonists can appear as promising treatment against the initiation and the progression of CNV in exudative AMD.

Reexamining cancer metabolism: lactate production for carcinogenesis could be the purpose and explanation of the Warburg Effect

Herein, we use lessons learned in exercise physiology and metabolism to propose that augmented lactate production (‘lactagenesis’), initiated by gene mutations, is the reason and purpose of the Warburg Effect and that dysregulated lactate metabolism and signaling are the key elements in carcinogenesis. Lactate-producing (‘lactagenic’) cancer cells are characterized by increased aerobic glycolysis and excessive lactate formation, a phenomenon described by Otto Warburg 93 years ago, which still remains unexplained. After a hiatus of several decades, interest in lactate as a player in cancer has been renewed. In normal physiology, lactate, the obligatory product of glycolysis, is an important metabolic fuel energy source, the most important gluconeogenic precursor, and a signaling molecule (i.e. a ‘lactormone’) with major regulatory properties. In lactagenic cancers, oncogenes and tumor suppressor mutations behave in a highly orchestrated manner, apparently with the purpose of increasing glucose utilization for lactagenesis purposes and lactate exchange between, within and among cells. Five main steps are identified (i) increased glucose uptake, (ii) increased glycolytic enzyme expression and activity, (iii) decreased mitochondrial function, (iv) increased lactate production, accumulation and release and (v) upregulation of monocarboxylate transporters MTC1 and MCT4 for lactate exchange. Lactate is probably the only metabolic compound involved and necessary in all main sequela for carcinogenesis, specifically: angiogenesis, immune escape, cell migration, metastasis and self-sufficient metabolism. We hypothesize that lactagenesis for carcinogenesis is the explanation and purpose of the Warburg Effect. Accordingly, therapies to limit lactate exchange and signaling within and among cancer cells should be priorities for discovery.

Aerobic Glycolysis Hypothesis Through WNT/Beta-Catenin Pathway in Exudative Age-Related Macular Degeneration

Exudative age-related macular degeneration (AMD) is characterized by molecular mechanisms responsible for the initiation of choroidal neovascularization (CNV). Inflammatory processes are associated with upregulation of the canonical WNT/beta-catenin pathway in exudative AMD. We focus this review on the link between WNT/beta-catenin pathway activation and neovascular progression in exudative AMD through activation of aerobic glycolysis for production of angiogenic factors. Increased WNT/beta-catenin pathway involves hexokinase 2 (HK2) and pyruvate kinase M2 (PKM2). WNT/beta-catenin pathway stimulates PI3K/Akt pathway and then HIF-1alpha which activates glycolytic enzymes: glucose transporter (Glut), pyruvate dehydrogenase kinase 1 (PDK1), lactate dehydrogenase A (LDH-A), and monocarboxylate lactate transporter (MCT-1). This phenomenon is called aerobic glycolysis or the Warburg effect. Consequently, phosphorylation of PDK-1 inhibits the pyruvate dehydrogenase complex (PDH). Thus, a large part of pyruvate cannot be converted into acetyl-CoA in mitochondria and only a part of acetyl-CoA can enter the tricarboxylic acid cycle. Cytosolic pyruvate is converted into lactate through the action of LDH-A. In exudative AMD, high level of cytosolic lactate is correlated with increase of VEGF expression, the angiogenic factor of CNV. Photoreceptors in retina cells can metabolize glucose through aerobic glycolysis to protect them against oxidative damage, as cancer cells do.

Lateral cortical Cdca7 expression levels are regulated by Pax6 and influence the production of intermediate progenitors

Background

We studied whether regulation of Cdca7 (Cell division cycle associated 7) expression by transcription factor Pax6 contributes to Pax6’s cellular actions during corticogenesis. The function of Cdca7 in mediating Pax6’s effects during corticogenesis has not been explored. Pax6 is expressed by radial glial progenitors in the ventricular zone of the embryonic cortical neuroepithelium, where it is required for the development of a normal complement of Tbr2-expressing intermediate progenitor cells in the subventricular zone. Pax6’s expression levels are graded across the ventricular zone, with highest levels laterally where Tbr2-expressing progenitors are generated in greatest numbers at early stages of corticogenesis.

Methods

We used in situ hybridization and immunohistochemistry to analyse patterns of Cdca7 and Pax6 expression in cortical tissue from wild-type and Pax6^−/− embryos. In each genotype we compared the graded expression of the two genes quantitatively at several ages. To test whether defects in Cdca7 expression in lateral cortical cells might contribute to the cellular defects in this region caused by Pax6 loss, we electroporated a Cdca7 expression vector into wild-type lateral cortex and examined the effect on the production of Tbr2-expressing cells.

Results

We found that Cdca7 is co-expressed with Pax6 in cortical progenitors, at levels opposite to those of Pax6. Lowest levels of Cdca7 are found in the radial glial progenitors of lateral cortex, where Pax6 levels are highest. Higher levels of Cdca7 are found in ventral telencephalon, where Pax6 levels are low. Loss of Pax6 causes Cdca7 expression to increase in the lateral cortex. Elevating Cdca7 in normal lateral cortical progenitors to levels close to those normally found in ventral telencephalon reduces their production of Tbr2-expressing cells early in lateral cortical formation.

Conclusion

Our results suggest that Pax6 normally represses Cdca7 expression in the lateral cortex and that repression of Cdca7 in cells of this region is required for their production of a normal complement of Tbr2-expressing intermediate progenitors.

HIF1/2α mediates hypoxia-induced LDHA expression in human pancreatic cancer cells

Glycolysis is a typical conduit for energy metabolism in pancreatic cancer (PC) due to the hypoxic microenviroment. Lactate dehydrogenase A (LDHA) catalyzes the conversion of pyruvate to lactate and is considered to be a key checkpoint of anaerobic glycolysis. The aim of the present study was to explore the mechanism of interactions between hypoxia, HIF-1/2α and LDHA, and the function of LDHA on PC cells by analyzing 244 PC and paratumor specimens. It was found that LDHA was over-expressed and related to tumor stages. The result of in vitro study demonstrated that hypoxia induced LDHA expression. To explore the relationship between HIF and LDHA, chromatin immunoprecipitation assay and luciferase assay were performed. The result showed that HIF-1/2α bound to LDHA at 89bp under the hypoxic condition. Furthermore, knockdown of endogenous HIF-1α and HIF-2α decreased the LDHA expression even in the hypoxic condition, which was accompanied with a significant decrease in lactate production and glucose utilization (p < 0.01). Immunofluorescence in the 244 specimens showed that HIF-1/2α was over-expressed and associated with LDHA over-expression (p < 0.0001). Forced expression of LDHA promoted the growth and migration of PC cells, while knocking down the expression of LDHA inhibited the cell growth and migration markedly. In summary, the present study proved that HIF1/2α could activate LDHA expression in human PC cells, and high expression of LDHA promoted the growth and migration of PC cells.

The natural cytokinin 2OH3MeOBAR induces cell death by a mechanism that is different from that of the "classical" cytokinin ribosides

Cytokinin ribosides (N⁶-substituted adenosines) have demonstrated anticancer activity in various cultured cell lines, several xenografts and even a small clinical trial. Effects of kinetin riboside, N⁶-benzyladenosine (BAR) and N⁶-isopentenyladenosine on various parameters related to apoptosis have also been reported, but not directly compared with those of the highly active naturally occurring aromatic cytokinins oTR (ortho-topolin riboside) and 2OH3MeOBAR (N⁶-(2-hydroxy-3-methoxybenzyl)adenosine). Here we show that 2OH3MeOBAR is the most active cytokinin riboside studied to date (median, 1st quartile, 3rd quartile and range of GI50 in tests with the NCI60 cell panel: 0.19, 0.10, 0.43 and 0.02 to 15.7 μM, respectively) and it differs from other cytokinins by inducing cell death without causing pronounced ATP depletion. Analysis of NCI60 test data suggests that its activity is independent of p53 status. Further we demonstrate that its 5'-monophosphate, the dominant cancer cell metabolite, inhibits the candidate oncogene DNPH1. Synthesis, purification, HPLC-MS identification and HPLC-UV quantification of 2OH3MeOBAR metabolites are also reported.

Activation of WNT/β-Catenin Signaling Enhances Pancreatic Cancer Development and the Malignant Potential Via Up-regulation of Cyr61

Pancreatic ductal adenocarcinoma (PDAC), a poor prognostic cancer, commonly develops following activating mutations in the KRAS oncogene. Activation of WNT signaling is also commonly observed in PDAC. To ascertain the impact of postnatal activation of WNT-stimulated signaling pathways in PDAC development, we combined the Elastase-tva-based RCAS-TVA pancreatic cancer model with the established LSL-Kras^G12D, Ptf1a-cre model. Delivery of RCAS viruses encoding β-catenin^S37A and WNT1 stimulated the progression of premalignant pancreatic intraepithelial neoplasias (PanIN) and PDAC development. Moreover, mice injected with RCAS-β-catenin^S37A or RCAS-Wnt1 had reduced survival relative to RCAS-GFP-injected controls (P < .05). Ectopic expression of active β-catenin, or its DNA-binding partner TCF4, enhanced transformation associated phenotypes in PDAC cells. In contrast, these phenotypes were significantly impaired by the introduction of ICAT, an inhibitor of the β-catenin/TCF4 interaction. By gene expression profiling, we identified Cyr61 as a target molecule of the WNT/β-catenin signaling pathway in pancreatic cancer cells. Nuclear β-catenin and CYR61 expression were predominantly detected in moderately to poorly differentiated murine and human PDAC. Indeed, nuclear β-catenin- and CYR61-positive PDAC patients demonstrated poor prognosis (P < .01). Knockdown of CYR61 in a β-catenin-activated pancreatic cancer cell line reduced soft agar, migration and invasion activity. Together, these data suggest that the WNT/β-catenin signaling pathway enhances pancreatic cancer development and malignancy in part via up-regulation of CYR61.

Anticancer strategies based on the metabolic profile of tumor cells: therapeutic targeting of the Warburg effect

Tumor cells rely mainly on glycolysis for energy production even in the presence of sufficient oxygen, a phenomenon termed the Warburg effect, which is the most outstanding characteristic of energy metabolism in cancer cells. This metabolic adaptation is believed to be critical for tumor cell growth and proliferation, and a number of onco-proteins and tumor suppressors, including the PI3K/Akt/mTOR signaling pathway, Myc, hypoxia-inducible factor and p53, are involved in the regulation of this metabolic adaptation. Moreover, glycolytic cancer cells are often invasive and impervious to therapeutic intervention. Thus, altered energy metabolism is now appreciated as a hallmark of cancer and a promising target for cancer treatment. A better understanding of the biology and the regulatory mechanisms of aerobic glycolysis has the potential to facilitate the development of glycolysis-based therapeutic interventions for cancer. In addition, glycolysis inhibition combined with DNA damaging drugs or chemotherapeutic agents may be effective anticancer strategies through weakening cell damage repair capacity and enhancing drug cytotoxicity.

A novel KLF6-Rho GTPase axis regulates hepatocellular carcinoma cell migration and dissemination

The presence of invasion into the extra-hepatic portion of the portal vein or the development of distant metastases renders hepatocellular carcinoma (HCC) patients ineligible for the only potential curative options for this malignancy-tumor resection or organ transplantation. Gene expression profiling of murine HCC cell lines identified KLF6 as a potential regulator of HCC cell migration. KLF6 knockdown increases cell migration, consistent with the correlation between decreased KLF6 mRNA levels and the presence of vascular invasion in human HCC. Concordantly, single-copy deletion of Klf6 in a HCC mouse model results in increased tumor formation, increased metastasis to the lungs and decreased survival, indicating that KLF6 suppresses both HCC development and metastasis. By combining gene expression profiling and chromatin immunoprecipitation coupled to deep sequencing, we identified novel transcriptional targets of KLF6 in HCC cells including VAV3, a known activator of the RAC1 small GTPase. Indeed, RAC1 activity is increased in KLF6-knockdown cells in a VAV3-dependent manner, and knockdown of either RAC1 or VAV3 impairs HCC cell migration. Together, our data demonstrate a novel function for KLF6 in constraining HCC dissemination through the regulation of a VAV3-RAC1 signaling axis.

The druggability of intracellular nucleotide-degrading enzymes

Nucleotide metabolism is the target of a large number of anticancer drugs including antimetabolites and specific enzyme inhibitors. We review scientific findings that over the last 10-15 years have allowed the identification of several intracellular nucleotide-degrading enzymes as cancer drug targets, and discuss further potential therapeutic applications for Rcl, SAMHD1, MTH1 and cN-II. We believe that enzymes involved in nucleotide metabolism represent potent alternatives to conventional cancer chemotherapy targets.

The Regulation and Function of Lactate Dehydrogenase A: Therapeutic Potential in Brain Tumor

There are over 120 types of brain tumor and approximately 45% of primary brain tumors are gliomas, of which glioblastoma multiforme (GBM) is the most common and aggressive with a median survival rate of 14 months. Despite progress in our knowledge, current therapies are unable to effectively combat primary brain tumors and patient survival remains poor. Tumor metabolism is important to consider in therapeutic approaches and is the focus of numerous research investigations. Lactate dehydrogenase A (LDHA) is a cytosolic enzyme, predominantly involved in anaerobic and aerobic glycolysis (the Warburg effect); however, it has multiple additional functions in non‐neoplastic and neoplastic tissues, which are not commonly known or discussed. This review summarizes what is currently known about the function of LDHA and identifies areas that would benefit from further exploration. The current knowledge of the role of LDHA in the brain and its potential as a therapeutic target for brain tumors will also be highlighted. The Warburg effect appears to be universal in tumors, including primary brain tumors, and LDHA (because of its involvement with this process) has been identified as a potential therapeutic target. Currently, there are, however, no suitable LDHA inhibitors available for tumor therapies in the clinic.

Atlantic salmon (Salmo salar) liver transcriptome response to diets containing Camelina sativa products

Due to increasing demand for fish oil (FO) and fish meal (FM) in aquafeeds, more sustainable alternatives such as plant-derived oils and proteins are needed. Camelina sativa products are viable feed ingredients given the high oil and crude protein content in the seed. Atlantic salmon were fed diets with complete or partial replacement of FO and/or FM with camelina oil (CO) and/or camelina meal (CM) in a 16-week trial [Control diet: FO; Test diets: 100% CO replacement of FO (100CO), or 100CO with solvent-extracted FM (100COSEFM), 10% CM (100CO10CM), or SEFM+10% CM (100COSEFM10CM)]. Diet composition, growth, and fatty acid analyses for this feeding trial were published previously. A 44K microarray experiment identified liver transcripts that responded to 100COSEFM10CM (associated with reduced growth) compared to controls, yielding 67 differentially expressed features (FDR<5%). Ten microarray-identified genes [cpt1, pcb, bar, igfbp-5b (2 paralogues), btg1, dnph1, lect-2, clra, klf9, and fadsd6a], and three additional genes involved in lipid metabolism [elovl2, elovl5 (2 paralogues), and fadsd5], were subjected to QPCR with liver templates from all 5 dietary treatments. Of the microarray-identified genes, only bar was not QPCR validated. Both igfbp-5b paralogues were significantly down-regulated, and fadsd6a was significantly up-regulated, in all 4 camelina-containing diet groups compared with controls. Multivariate statistics were used to correlate hepatic desaturase and elongase gene expression data with tissue fatty acid profiles, indicating the involvement of these genes in LC-PUFA biosynthesis. This nutrigenomic study provides molecular biomarkers for use in developing novel aquafeeds using camelina products.

microRNAs and cancer metabolism reprogramming: the paradigm of metformin

Increasing evidence witnesses that cancer metabolism alterations represent a critical hallmark for many types of human tumors. There is a strong need to understand and dissect the molecular mechanisms underlying cancer metabolism to envisage specific biomarkers and underpin critical molecular components that might represent novel therapeutic targets. One challenge, that is the focus of this review, is the reprogramming of the altered metabolism of a cancer cell toward that of un-transformed cell. The anti-hyperglicemic agent, metformin has proven to be effective in reprogramming the metabolism of cancer cells even from those subpopulations endowed with cancer stem like features and very high chemoresistenace to conventional anticancer treatments. A functional interplay involving selective modulation of microRNAs (miRNAs) takes place along the anticancer metabolic effects exerted by metformin. The implications of this interplay will be also discussed in this review.

The Caenorhabditis elegans Myc-Mondo/Mad complexes integrate diverse longevity signals

The Myc family of transcription factors regulates a variety of biological processes, including the cell cycle, growth, proliferation, metabolism, and apoptosis. In Caenorhabditis elegans, the "Myc interaction network" consists of two opposing heterodimeric complexes with antagonistic functions in transcriptional control: the Myc-Mondo:Mlx transcriptional activation complex and the Mad:Max transcriptional repression complex. In C. elegans, Mondo, Mlx, Mad, and Max are encoded by mml-1, mxl-2, mdl-1, and mxl-1, respectively. Here we show a similar antagonistic role for the C. elegans Myc-Mondo and Mad complexes in longevity control. Loss of mml-1 or mxl-2 shortens C. elegans lifespan. In contrast, loss of mdl-1 or mxl-1 increases longevity, dependent upon MML-1:MXL-2. The MML-1:MXL-2 and MDL-1:MXL-1 complexes function in both the insulin signaling and dietary restriction pathways. Furthermore, decreased insulin-like/IGF-1 signaling (ILS) or conditions of dietary restriction increase the accumulation of MML-1, consistent with the notion that the Myc family members function as sensors of metabolic status. Additionally, we find that Myc family members are regulated by distinct mechanisms, which would allow for integrated control of gene expression from diverse signals of metabolic status. We compared putative target genes based on ChIP-sequencing data in the modENCODE project and found significant overlap in genomic DNA binding between the major effectors of ILS (DAF-16/FoxO), DR (PHA-4/FoxA), and Myc family (MDL-1/Mad/Mxd) at common target genes, which suggests that diverse signals of metabolic status converge on overlapping transcriptional programs that influence aging. Consistent with this, there is over-enrichment at these common targets for genes that function in lifespan, stress response, and carbohydrate metabolism. Additionally, we find that Myc family members are also involved in stress response and the maintenance of protein homeostasis. Collectively, these findings indicate that Myc family members integrate diverse signals of metabolic status, to coordinate overlapping metabolic and cytoprotective transcriptional programs that determine the progression of aging.

Clinicopathological significance and prognostic value of lactate dehydrogenase A expression in gastric cancer patients

INTRODUCTION

LDH-A, the enzyme responsible for transforming pyruvate into lactate, has been demonstrated to be up-regulated in many types of cancer and to give rise to more aggressive behavior by regulating proliferation and anti-apoptosis. However, its expression in gastric cancer (GC) has not been characterized thoroughly. The purpose of this study was to clarify the expression and potential impact of LDH-A in GC.

METHODS

We examined LDH-A expression by immunohistochemistry on GC tissue microarray (TMA) and using Western blot on fresh GC tissues and cell lines. Prognostic value and correlation with other clinicopathologic factors were evaluated. We transfected siRNA into GC cells against LDH-A. LDH-A was analyzed by Western blotting and real-time RT-PCR. Cell growth was evaluated in vitro and in vivo. Lactate and ATP production by cells were determined.

RESULTS

There was significantly higher LDH-A expression in carcinoma than in non-neoplastic mucosa (NNM). There was a positive correlation of LDH-A expression with age, histological type and Lymph node metastases. Survival analysis demonstrated that high expression of LDH-A in GC was associated with lower overall survival (OS). When stratified by Lauren grade and histological classification, significance appeared in diffuse type and undifferentiated type GC. In multivariate analysis, the LDH-A expression in GC was an independent prognostic risk factor for OS (hazard ratio = 1.829, 95%CI 1.375-2.433,P<0.0001). Specific siRNA against LDH-A in GC cell line retarded cell growth both in vitro and in mouse models. LDH-A knockdown also reduced lactate and ATP production in GC cells.

CONCLUSIONS

Our study indicated the oncogenic role of LDH-A in GC. LDH-A expression is an independent prognostic risk factor in GC patients and up-regulated expression of LDH-A could be predictive of poor outcomes in diffuse type and undifferentiated type GC. Our results suggested that LDH-A might be a potential therapeutic target in gastric cancer.

N (6)-substituted AMPs inhibit mammalian deoxynucleotide N-hydrolase DNPH1

The gene dnph1 (or rcl) encodes a hydrolase that cleaves the 2’-deoxyribonucleoside 5’-monophosphate (dNMP) N-glycosidic bond to yield a free nucleobase and 2-deoxyribose 5-phosphate. Recently, the crystal structure of rat DNPH1, a potential target for anti-cancer therapies, suggested that various analogs of AMP may inhibit this enzyme. From this result, we asked whether N⁶-substituted AMPs, and among them, cytotoxic cytokinin riboside 5’-monophosphates, may inhibit DNPH1. Here, we characterized the structural and thermodynamic aspects of the interactions of these various analogs with DNPH1. Our results indicate that DNPH1 is inhibited by cytotoxic cytokinins at concentrations that inhibit cell growth.

Metformin: On Ongoing Journey across Diabetes, Cancer Therapy and Prevention

Cancer metabolism is the focus of intense research, which witnesses its key role in human tumors. Diabetic patients treated with metformin exhibit a reduced incidence of cancer and cancer-related mortality. This highlights the possibility that the tackling of metabolic alterations might also hold promising value for treating cancer patients. Here, we review the emerging role of metformin as a paradigmatic example of an old drug used worldwide to treat patients with type II diabetes which to date is gaining strong in vitro and in vivo anticancer activities to be included in clinical trials. Metformin is also becoming the focus of intense basic and clinical research on chemoprevention, thus suggesting that metabolic alteration is an early lesion along cancer transformation. Metabolic reprogramming might be a very efficient prevention strategy with a profound impact on public health worldwide.

p16 Stimulates CDC42-dependent migration of hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related deaths worldwide. Tumor dissemination to the extra-hepatic region of the portal vein, lymph nodes, lungs or bones contributes to the high mortality seen in HCC; yet, the molecular mechanisms responsible for HCC metastasis remain unclear. Prior studies have suggested a potential link between accumulated cytoplasm-localized p16 and tumor progression. Here we report that p16 enhances metastasis-associated phenotypes in HCC cells – ectopic p16 expression increased cell migration in vitro, and lung colonization after intravenous injection, whereas knockdown of endogenous p16 reduced cell migration. Interestingly, analysis of p16 mutants indicated that the Cdk4 interaction domain is required for stimulation of HCC cell migration; however, knockdown of Cdk4 and Cdk6 showed that these proteins are dispensable for this phenomenon. Intriguingly, we found that in p16-positive HCC samples, p16 protein is predominantly localized in the cytoplasm. In addition, we identified a potential role for nuclear-cytoplasmic shuttling in p16-stimulated migration, consistent with the predominantly cytoplasmic localization of p16 in IHC-positive HCC samples. Finally, we determined that p16-stimulated cell migration requires the Cdc42 GTPase. Our results demonstrate for the first time a pro-migratory role for p16, and suggest a potential mechanism for the observed association between cytoplasmic p16 and tumor progression in diverse tumor types.

Reversal of the substrate specificity of CMP N-glycosidase to dCMP

MilB is a CMP hydrolase involved in the early steps of biosynthesis of the antifungal compound mildiomycin. An enzyme from the bacimethrin biosynthetic pathway, BcmB, is closely related to MilB in both sequence and function. These two enzymes belong to the nucleoside 2'-deoxyribosyltransferase (NDT) superfamily. NDTs catalyze N-glycosidic bond cleavage of 2'-deoxynucleosides via a covalent 2-deoxyribosyl-enzyme intermediate. Conservation of key active site residues suggests that members of the NDT superfamily share a common mechanism; however, the enzymes differ in their substrate preferences. Substrates vary in the type of nucleobase, the presence or absence of a 2'-hydroxyl group, and the presence or absence of a 5'-phosphate group. We have determined the structures of MilB and BcmB and compared them to previously determined structures of NDT superfamily members. The comparisons reveal how these enzymes differentiate between ribosyl and deoxyribosyl nucleotides or nucleosides and among different nucleobases. The 1.6 Å structure of the MilB-CMP complex reveals an active site feature that is not obvious from comparisons of sequence alone. MilB and BcmB that prefer substrates containing 2'-ribosyl groups have a phenylalanine positioned in the active site, whereas NDT family members with a preference for 2'-deoxyribosyl groups have a tyrosine residue. Further studies show that the phenylalanine is critical for the specificity of MilB and BcmB toward CMP, and mutation of this phenylalanine residue to tyrosine results in a 1000-fold reversal of substrate specificity from CMP to dCMP.

c-Myc and cancer metabolism

The processes of cellular growth regulation and cellular metabolism are closely interrelated. The c-Myc oncogene is a "master regulator" which controls many aspects of both of these processes. The metabolic changes which occur in transformed cells, many of which are driven by c-Myc overexpression, are necessary to support the increased need for nucleic acids, proteins, and lipids necessary for rapid cellular proliferation. At the same time, c-Myc overexpression results in coordinated changes in level of expression of gene families which result in increased cellular proliferation. This interesting duality of c-Myc effects places it in the mainstream of transformational changes and gives it a very important role in regulating the "transformed phenotype." The effects induced by c-Myc can occur either as a "primary oncogene" which is activated by amplification or translocation or as a downstream effect of other activated oncogenes. In either case, it appears that c-Myc plays a central role in sustaining the changes which occur with transformation. Although efforts to use c-Myc as a therapeutic target have been quite frustrating, it appears that this may change in the next few years.

Lysine-5 acetylation negatively regulates lactate dehydrogenase A and is decreased in pancreatic cancer

Tumor cells commonly have increased glucose uptake and lactate accumulation. Lactate is produced from pyruvate by lactate dehydrogenase A (LDH-A), which is frequently overexpressed in tumor cells and is important for cell growth. Elevated transcription by c-Myc or HIF1α may contribute to increased LDH-A in some cancer types. Here, we show that LDH-A is acetylated at lysine 5 (K5) and that this acetylation inhibits LDH-A activity. Furthermore, the K5-acetylated LDH-A is recognized by the HSC70 chaperone and delivered to lysosomes for degradation. Replacement of endogenous LDH-A with an acetylation mimetic mutant decreases cell proliferation and migration. Importantly, K5 acetylation of LDH-A is reduced in human pancreatic cancers. Our study reveals a mechanism of LDH-A upregulation in pancreatic cancers.

Lactate dehydrogenase A is overexpressed in pancreatic cancer and promotes the growth of pancreatic cancer cells

The prognosis for pancreatic cancer is very poor, and developing new therapeutic strategies for this cancer is needed. Recently, the Warburg effect (aerobic glycolysis) has attracted much attention for its function in the tumorigenesis. Lactate dehydrogenase A (LDHA) executes the final step of aerobic glycolysis and has been reported to be involved in the tumor progression. However, the function of LDHA in pancreatic cancer has not been studied. Here, we found that the expression of LDHA was elevated in the clinical pancreatic cancer samples. Forced expression of LDHA promoted the growth of pancreatic cancer cells, while knocking down the expression of LDHA inhibited cell growth dramatically. Moreover, silencing the expression of LDHA inhibited the tumorigenicity of pancreatic cancer cells in vivo. Mechanistically, knocking down the expression of LDHA activated apoptosis pathway. Taken together, our study revealed the oncogenic role of LDHA in pancreatic cancer and suggested that LDHA might be a potential therapeutic target.

LDHA is necessary for the tumorigenicity of esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common lethal tumors in the world, and the development of new therapeutic targets is needed. Recent studies have shown that aerobic glycolysis, also known as the Warburg effect, mediated the anti-apoptotic effects in cancer cells. Lactate dehydrogenase A (LDHA) which executed the final step of aerobic lactate production has been reported to be involved in the tumor progression. However, the function of LDHA in ESCC has not been investigated. In this study, it was found that LDHA was up-regulated in ESCC clinical samples. Knockdown of the expression of LDHA inhibited cell growth and cell migration in vitro as well as tumorigenesis in vivo. With regard to the molecular mechanism, silencing the expression of LDHA was related to decreased AKT activation and cyclin D1 expression and increased cleavage of PARP and caspase 8. Taken together, our findings suggest that LDHA plays an important role in the progression of ESCC by modulating cell growth, and LDHA might be a potential therapeutic target in ESCC.

Functional specific roles of H-ras and N-ras. A proteomic approach using knockout cell lines

Ras small GTPases function as transducers of extracellular signals regulating cell survival, growth and differentiation. There are three major ras isoforms: H-, N- and K-Ras. To improve the understanding of H- and N-Ras protein signalling networks, we compared total proteome changes in mouse embryonic fibroblasts knock out for H-ras and/or N-ras, using proteomics tools combining 2DE, semi-quantitative image analysis, in-gel trypsin digestion and mass spectrometry. There are four up-regulated proteins due to the loss of expression of H-Ras (including cyclin-dependent kinase inhibitor 2A) and eight down-regulated (including stress-70 protein, dihydropyrimidinase-related-protein 3, heat shock cognate 71 kDa protein, tropomyosin beta chain, Rho GDP-dissociation inhibitor 1) and six up-regulated proteins (e.g. leukocyte elastase inhibitor A, L-lactate dehydrogenase B chain, c-Myc-responsive protein Rcl, interleukin-1 receptor antagonist protein) due to the loss of expression of both N- and H-Ras. Most of these proteins are related to Ras signalling in one way or another. Changes in expression of some of these proteins were further confirmed by Western blot. This proteomic comparative analysis from loss of function of H- and N-Ras knockout fibroblasts yields interpretable data to elucidate the differential protein expression, and contributes to evaluate the possibilities for physiological and therapeutic targets.

Alterations of metabolic genes and metabolites in cancer

Altered metabolic regulation has long been observed in human cancer and broadly used in the clinic for tumor detection. Two recent findings--the direct regulation of metabolic enzymes by frequently mutated cancer genes and frequent mutations of several metabolic enzymes themselves in cancer--have renewed interest in cancer metabolism. Supporting a causative role of altered metabolic enzymes in tumorigenesis, abnormal levels of several metabolites have been found to play a direct role in cancer development. The alteration of metabolic genes and metabolites offer not only new biomarkers for diagnosis and prognosis, but also potential new targets for cancer therapy.