Inhibiting 6-phosphogluconate dehydrogenase selectively targets breast cancer through AMPK activation

Single-cell senescence identification reveals senescence heterogeneity, trajectory, and modulators

Cellular senescence underlies many aging-related pathologies, but its heterogeneity poses challenges for studying and targeting senescent cells. We present here a machine learning program senescent cell identification (SenCID), which accurately identifies senescent cells in both bulk and single-cell transcriptome. Trained on 602 samples from 52 senescence transcriptome datasets spanning 30 cell types, SenCID identifies six major senescence identities (SIDs). Different SIDs exhibit different senescence baselines, stemness, gene functions, and responses to senolytics. SenCID enables the reconstruction of senescent trajectories under normal aging, chronic diseases, and COVID-19. Additionally, when applied to single-cell Perturb-seq data, SenCID helps reveal a hierarchy of senescence modulators. Overall, SenCID is an essential tool for precise single-cell analysis of cellular senescence, enabling targeted interventions against senescent cells.

Some pyrroles as inhibitors of the pentose phosphate pathways enzymes: An in vitro and molecular docking study

Glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD) are pentose phosphate pathway enzymes. Compounds with a heterocyclic pyrrole ring system containing this atom can be derivatized with various functional groups into highly effective bioactive agents. In this study, pyrrole derivatives on these enzyme's activity were investigated. The IC50 values of different concentrations of pyrrole derivatives for G6PD were found in the range of 0.022-0.221 mM Ki values 0.021 ± 0.003-0.177 ± 0.021 and for 6PGD IC50 values 0.020-0.147, mM Ki values 0.013 ± 0.002-0.113 ± 0.030 mM. The 2-acetyl-1-methylpyrrole (1g) showed the best inhibition value for G6PD and 6PGD enzymes. In addition, in silico molecular docking experiments were performed to elucidate how these pyrrole derivatives (1a-g) interact with the binding sites of the target enzymes. The study's findings on pyrrole derivatives could be used to create innovative therapeutics that could be a treatment for many diseases, especially cancer manifestations.

The enzymes of the oxidative phase of the pentose phosphate pathway as targets of reactive species: consequences for NADPH production

The pentose phosphate pathway (PPP) is a key metabolic pathway. The oxidative phase of this process involves three reactions catalyzed by glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconolactonase (6PGL) and 6-phosphogluconate dehydrogenase (6PGDH) enzymes. The first and third steps (catalyzed by G6PDH and 6PGDH, respectively) are responsible for generating reduced nicotinamide adenine dinucleotide phosphate (NAPDH), a key cofactor for maintaining the reducing power of cells and detoxification of both endogenous and exogenous oxidants and electrophiles. Despite the importance of these enzymes, little attention has been paid to the fact that these proteins are targets of oxidants. In response to oxidative stimuli metabolic pathways are modulated, with the PPP often up-regulated in order to enhance or maintain the reductive capacity of cells. Under such circumstances, oxidation and inactivation of the PPP enzymes could be detrimental. Damage to the PPP enzymes may result in a downward spiral, as depending on the extent and sites of modification, these alterations may result in a loss of enzymatic activity and therefore increased oxidative damage due to NADPH depletion. In recent years, it has become evident that the three enzymes of the oxidative phase of the PPP have different susceptibilities to inactivation on exposure to different oxidants. In this review, we discuss existing knowledge on the role that these enzymes play in the metabolism of cells, and their susceptibility to oxidation and inactivation with special emphasis on NADPH production. Perspectives on achieving a better understanding of the molecular basis of the oxidation these enzymes within cellular environments are given.

Effects of Arbutin on Potassium Bromate-Induced Erythrocyte Toxicity in Rats: Biochemical Evaluation of Some Metabolic Enzyme Activities In Vivo and In Vitro

In the present study, the inhibitory effect of potassium bromate on the pentose phosphate pathway and intracellular antioxidant systems enzymes (glucose 6-phosphate dehydrogenase (G6PD), 6-phosphogluconate dehydrogenase (6PGD), glutathione reductase (GR), glutathione S-transferase (GST), and thioredoxin reductase (TrxR)) and the role of arbutin in ameliorating this inhibition were investigated. In the in vivo phase of the study, Wistar Albino rats (28 male adults) were randomly divided into four groups. Control (n = 7): isotonic serum (0.5 mL, i.p), potassium bromate group (n = 7): potassium bromate (100 mg/kg), arbutin group (n = 7): arbutin (i.p.) (50 mg/kg/day), potassium bromate + arbutin, and Group (n = 7): potassium bromate (100 mg/kg) + arbutin (50 mg/kg/day) (i.p). The results of in vivo study showed that the activities of G6PD, 6PGD, GR, and TrxR enzymes were strongly inhibited in potassium bromate groups (p < 0.05). It was determined that GST enzyme activity decreased in the potassium bromate group, but this decrease was not statistically significant compared to the control group (p ⩾ 0.05). A statistically significant increase was found in G6PD, 6PGD, GST, and TrxR enzyme activities in the arbutin group compared to the control group (p < 0.05). The increase in GR enzyme activity was not statistically significant (p ⩾ 0.05). The potassium bromate + arbutin group's enzyme activity increased in comparison to the potassium bromate group and was discovered to be closer to the control group. It was found that potassium bromate inhibited the 6PGD enzyme obtained from rat erythrocyte tissues with IC50 = 346 μM value and Ki = 434.4 μM ± 6.1 value, and the inhibition was noncompetitive.

Hyperosmolar Potassium Inhibits Corneal Myofibroblast Transformation and Prevent Corneal Scar

PURPOSE

Corneal myofibroblasts play a crucial role in the process of corneal scarring. Potassium has been documented to reduce skin scar tissue formation. Herein, we investigated the ability of potassium to prevent corneal fibrosis in cell culture and in vivo.

METHODS

Corneal fibroblasts (CFs) were isolated from the corneal limbus and treated with TGF-β1 to transform into corneal myofibroblasts. Corneal myofibroblast markers were detected by quantitative real-time PCR, Western blot, and immunofluorescence. The contractive functions of corneal myofibroblast were evaluated by the scratch assay and the collagen gel contraction assay. RNA sequencing in corneal fibroblasts was performed to explore the mechanisms underlying hyperosmolar potassium treatment. GO and KEGG analysis were performed to explore the underlying mechanism by hyperosmolar potassium treatment. The ATP detection assay assessed the level of cell metabolism. KCl eye drops four times per day were administered to mice models of corneal injury to evaluate the ability to prevent corneal scar formation. Corneal opacity area was evaluated by Image J software.

RESULTS

Treatment with hyperosmolar potassium could suppress corneal myofibroblast transformation and collagen I synthesis induced by TGF-β1 in cell culture. Hyperosmolar potassium could inhibit wound healing and gel contraction in CFs. RNA sequencing results suggested that genes involved in the metabolic pathway were downregulated after KCl treatment. ATP levels were significantly decreased in the KCl group compared with the control group. Hyperosmolar potassium could prevent corneal myofibroblast transformation after corneal injury and corneal scar formation in mice.

CONCLUSION

Potassium can suppress corneal myofibroblast transformation and collagen I protein synthesis. Moreover, given that KCl eye drops can prevent corneal scar formation, it has been suggested to have huge prospects as a novel treatment approach during clinical practice.

6-Phosphogluconate dehydrogenase inhibition arrests growth and induces apoptosis in gastric cancer via AMPK activation and oxidative stress

Poor outcomes in advanced gastric cancer necessitate alternative therapeutic strategies. 6-Phosphogluconate dehydrogenase (6-PGDH), an enzyme that catalyzes the decarboxylation step in the oxidative pentose phosphate pathway, has been identified as a promising therapeutic target in many cancers. In this study, we systematically investigated the expression and function of 6-PGDH in gastric cancer. We found that 6-PGDH expression and activity were aberrantly elevated in gastric cancer tissues compared to their adjacent normal tissues. 6-PGDH knockdown using two independent shRNAs resulted in minimal 6-PGDH levels and activity, decreased growth, and enhanced gastric cancer cell sensitivity to 5-flurorouracil. However, 6-PGDH knockdown did not affect the cancer cells. Mechanistic studies showed that 6-PGDH inhibition disrupted lipid biosynthesis and redox homeostasis in gastric cancer, inhibited growth, and induced apoptosis. Notably, the in vitro findings were validated using an in vivo gastric cancer xenograft mouse model. This study established that 6-PGDH is broadly elevated in gastric cancer patients and that 6-PGDH inhibition can sensitize gastric cancer cells in response to chemotherapy.

Novel Anti-Cancer Products Targeting AMPK: Natural Herbal Medicine against Breast Cancer

Breast cancer is a common cancer in women worldwide. The existing clinical treatment strategies have been able to limit the progression of breast cancer and cancer metastasis, but abnormal metabolism, immunosuppression, and multidrug resistance involving multiple regulators remain the major challenges for the treatment of breast cancer. Adenosine 5'-monophosphate (AMP)-Activated Protein Kinase (AMPK) can regulate metabolic reprogramming and reverse the "Warburg effect" via multiple metabolic signaling pathways in breast cancer. Previous studies suggest that the activation of AMPK suppresses the growth and metastasis of breast cancer cells, as well as stimulating the responses of immune cells. However, some other reports claim that the development and poor prognosis of breast cancer are related to the overexpression and aberrant activation of AMPK. Thus, the role of AMPK in the progression of breast cancer is still controversial. In this review, we summarize the current understanding of AMPK, particularly the comprehensive bidirectional functions of AMPK in cancer progression; discuss the pharmacological activators of AMPK and some specific molecules, including the natural products (including berberine, curcumin, (-)-epigallocatechin-3-gallate, ginsenosides, and paclitaxel) that influence the efficacy of these activators in cancer therapy; and elaborate the role of AMPK as a potential therapeutic target for the treatment of breast cancer.

Inhibition of 6-Phosphogluconate Dehydrogenase Reverses Epirubicin Resistance Through Metabolic Reprograming in Triple-Negative Breast Cancer Cells

At present, chemotherapy is the most effective strategy for treating triple-negative breast cancer (TNBC), but its efficacy was limited by the development of chemo-resistance. The exact mechanism of chemoresistance still remains unclear. This study aims to examine whether 6-phosphogluconate dehydrogenase (6PGD), a key enzyme in the oxidative pentose phosphate pathway (PPP), could promote the resistance of TNBC cells to epirubicin. A TNBC epirubicin-resistant cell line was developed by increasing concentration and the effectiveness was tested. The expression and knockdown efficiency of 6PGD were further validated by performing quantitative real-time PCR (qPCR) and Western blot. The effects of 6PGD on parental and drug-resistant TNBC cell lines were verified based on proliferation and apoptosis experiments. Finally, nicotinamide adenine dinucleotide phosphate (NADPH) and lactate quantitative experiments were performed to examine the mechanism of 6PGD in promoting drug resistance. Epirubicin-resistant cancer cells exhibited a higher level of 6PGD in contrast to epirubicin-sensitive cells. In addition, 6PGD inhibited by genetic and pharmacological approaches significantly suppressed the growth and survival of both epirubicin-sensitive and epirubicin-resisteant TNBC cells. It should be noted that 6PGD inhibition sensitized epirubicin-resistant TNBC cells to epirubicin treatment. Moreover, it was also found that the levels of NADPH and lactate increased in epirubicin-resistant TNBC cells but decreased in response to 6PGD inhibition. The present results indicated that 6PGD inhibition disrupted metabolic reprogramming in epirubicin-resistant TNBC cells. Our work demonstrated that 6PGD inhibition reversed the resistance of TNBC cells to epirubicin, providing an alternative therapeutic choice to tackle the challenge of epirubicin resistance in TNBC treatment.

Identification of Lignan Compounds as New 6-Phosphogluconate Dehydrogenase Inhibitors for Lung Cancer

Targeting pentose phosphate pathway (PPP) enzymes has emerged as a promising strategy to combat cancer. 6-Phosphogluconate dehydrogenase (6-PGD), the third critical enzyme of the PPP, catalyzes oxidative decarboxylation of 6-phosphogluconate (6-PG) to produce ribulose-5-phosphate (Ru-5-P) and CO2. Overexpression of 6-PGD has been reported in multiple cancers and is recognized as a potential anticancer drug target. The current study is focused on the utilization of indispensable virtual screening tools for structure-based drug discovery. During the study, 17,000 natural compounds were screened against the 3-phosphoglycerate (3-PG) binding site of 6-PGD through a molecular operating environment (MOE), which revealed 115 inhibitors with higher selectivity and binding affinity. Out of the 115 best-fit compounds within the 6-PGD binding cavity, 15 compounds were selected and optimized through stringent in silico ADMET assessment models that justified the desirable pharmacokinetic, pharmacodynamic and physicochemical profiles of 5 ligands. Further protein−ligand stability assessment through molecular dynamics (MD) simulation illustrated three potential hits, secoisolariciresinol, syringaresinol and cleomiscosin A, with stable confirmation. Moreover, 6-PGD inhibitor validation was performed by an in vitro enzymatic assay using human erythrocytes purified 6-PGD protein and A549 cell lysate protein. The results of the in vitro assays supported the in silico findings. In order to gain insight into the anticancer activity of the aforementioned compounds, they were subjected to CLC-Pred, an in silico cytotoxicity browsing tool, which proved their anticancer activity against several cancer cell lines at Pa > 0.5. Additionally, a confirmation for in silico cytotoxicity was made by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for commercially available hits syringaresinol and cleomiscosin A against lung cancer (A549) cells. The results demonstrated that syringaresinol has an IC50 value of 36.9 μg/mL, while cleomiscosin A has an IC50 value of 133 μg/mL. After MTT, flow cytometry analysis confirmed that compounds induced apoptosis in A549 cells in a dose-dependent manner. This study suggested that the respective lignan compounds can serve as lead candidates for lung cancer therapy via 6-PGD inhibition. Furthermore, in vivo experiments need to be conducted to confirm their efficacy.

Role of the AMPK/SIRT1 pathway in non‑alcoholic fatty liver disease (Review)

Non‑alcoholic fatty liver disease (NAFLD) is an increasingly prevalent ailment worldwide. Moreover, de novo lipogenesis (DNL) is considered a critical factor in the development of NAFLD; hence, its inhibition is a promising target for the prevention of fatty liver disease. There is evidence to indicate that AMP‑activated protein kinase (AMPK) and sirtuin 1 (SIRT1) may play a crucial role in DNL and are the regulatory proteins in type 2 diabetes mellitus, obesity and cardiovascular disease. Therefore, AMPK and SIRT1 may be promising targets for the treatment of NAFLD. The present review article thus aimed to summarize the findings of clinical studies published during the past decade that suggested the beneficial effects of AMPK and SIRT1, using their specific activators and their combined effects on fatty liver disease.

Energy metabolism pathways in breast cancer progression: The reprogramming, crosstalk, and potential therapeutic targets

Breast cancer (BC) is a malignant tumor that seriously endangers health in women. BC, like other cancers, is accompanied by metabolic reprogramming. Among energy metabolism-related pathways, BC exhibits enhanced glycolysis, tricarboxylic acid (TCA) cycle, pentose phosphate pathway (PPP), glutamate metabolism, and fatty acid metabolism activities. These pathways facilitate the proliferation, growth and migration of BC cells. The progression of BC is closely related to the alterations in the activity or expression level of several metabolic enzymes, which are regulated by the intrinsic factors such as the key signaling and transcription factors. The metabolic reprogramming in the progression of BC is attributed to the aberrant expression of the signaling and transcription factors associated with the energy metabolism pathways. Understanding the metabolic mechanisms underlying the development of BC will provide a druggable potential for BC treatment and drug discovery.

Phosphogluconate dehydrogenase is a predictive biomarker for immunotherapy in hepatocellular carcinoma

Background

Phosphogluconate dehydrogenase (PGD) is involved in the regulation of various tumors. However, its role in hepatocellular carcinoma (HCC) is poorly understood. This study tried to determine the prognostic efficacy of PGD and its value for immunotherapy in HCC.

Methods

The data from the TCGA database was used to explore the predictive power of PGD expression and methylation on the overall survival (OS) of HCC through Cox regression and the Kaplan-Meier analysis. Then, we used the GEO and ICGC database to further verify the predictive power. Finally, the relationship between PGD and immune cells and the relationship between PGD and the efficacy of immunotherapy were explored through bioinformatics analysis in HCC.

Results

PGD is highly expressed in HCC tissues, which is negatively regulated by PGD methylation. Low PGD expression and PGD hypermethylation predict better OS in HCC patients. Besides, a meta-analysis based on the TCGA, GSE14520, and ICGC databases further confirms that low PGD expression is closely related to favorable OS. Then, we find significant differences of immune cell infiltrations between high and low PGD expression groups. Expressions of immune checkpoints, most HLA members and tumor mutation burden (TMB) are higher in the high PGD expression group, which indicates beneficial efficacy of immunotherapy in this group. And the potential mechanisms of PGD are exhibited.

Conclusion

PGD is an independent prognostic factor of HCC patients and plays an important role in immune cell infiltration and immunotherapy, which indicates that PGD can be used as a predictive biomarker for HCC immunotherapy.

Glucose deprivation reduces proliferation and motility, and enhances the anti-proliferative effects of paclitaxel and doxorubicin in breast cell lines in vitro

Background

Breast cancer chemotherapy with high dose alkylating agents is severely limited by their collateral toxicity to crucial normal tissues such as immune and gut cells. Taking advantage of the selective dependence of cancer cells on high glucose and combining glucose deprivation with these agents could produce therapeutic synergy.

Methods

In this study we examined the effect of glucose as well as its deprivation, and antagonism using the non-metabolized analogue 2-deoxy glucose, on the proliferation of several breast cancer cell lines MCF7, MDA-MB-231, YS1.2 and pII and one normal breast cell line, using the MTT assay. Motility was quantitatively assessed using the wound healing assay. Lactate, as the end product of anaerobic glucose metabolism, secreted into culture medium was measured by a biochemical assay. The effect of paclitaxel and doxorubicin on cell proliferation was tested in the absence and presence of low concentrations of glucose using MTT assay.

Results

In all cell lines, glucose supplementation enhanced while glucose deprivation reduced both their proliferation and motility. Lactate added to the medium could substitute for glucose. The inhibitory effects of paclitaxel and doxorubicin were significantly enhanced when glucose concentration was decreased in the culture medium, requiring 1000-fold lesser concentration to achieve a similar degree of inhibition to that seen in glucose-containing medium.

Conclusion

Our data show that a synergy was obtained by combining paclitaxel and doxorubicin with glucose reduction to inhibit cancer cell growth, which in vivo, might be achieved by applying a carbohydrate-restricted diet during the limited phase of application of chemotherapy; this could permit a dose reduction of the cytotoxic agents, resulting in greater tolerance and lesser side effects.

6-Phosphogluconate dehydrogenase and its crystal structures

6-Phosphogluconate dehydrogenase (6PGDH; EC 1.1.1.44) catalyses the oxidative decarboxylation of 6-phosphogluconate to ribulose 5-phosphate in the context of the oxidative part of the pentose phosphate pathway. Depending on the species, it can be a homodimer or a homotetramer. Oligomerization plays a functional role not only because the active site is at the interface between subunits but also due to the interlocking tail-modulating activity, similar to that of isocitrate dehydrogenase and malic enzyme, which catalyse a similar type of reaction. Since the pioneering crystal structure of sheep liver 6PGDH, which allowed motifs common to the β-hydroxyacid dehydrogenase superfamily to be recognized, several other 6PGDH crystal structures have been solved, including those of ternary complexes. These showed that more than one conformation exists, as had been suggested for many years from enzyme studies in solution. It is inferred that an asymmetrical conformation with a rearrangement of one of the two subunits underlies the homotropic cooperativity. There has been particular interest in the presence or absence of sulfate during crystallization. This might be related to the fact that this ion, which is a competitive inhibitor that binds in the active site, can induce the same 6PGDH configuration as in the complexes with physiological ligands. Mutagenesis, inhibitors, kinetic and binding studies, post-translational modifications and research on the enzyme in cancer cells have been complementary to the crystallographic studies. Computational modelling and new structural studies will probably help to refine the understanding of the functioning of this enzyme, which represents a promising therapeutic target in immunity, cancer and infective diseases. 6PGDH also has applied-science potential as a biosensor or a biobattery. To this end, the enzyme has been efficiently immobilized on specific polymers and nanoparticles. This review spans the 6PGDH literature and all of the 6PGDH crystal structure data files held by the Protein Data Bank.

Metabolic remodeling maintains a reducing environment for rapid activation of the yeast DNA replication checkpoint

Nucleotide metabolism fuels normal DNA replication and is also primarily targeted by the DNA replication checkpoint when replication stalls. To reveal a comprehensive interconnection between genome maintenance and metabolism, we analyzed the metabolomic changes upon replication stress in the budding yeast S. cerevisiae. We found that upon treatment of cells with hydroxyurea, glucose is rapidly diverted to the oxidative pentose phosphate pathway (PPP). This effect is mediated by the AMP-dependent kinase, SNF1, which phosphorylates the transcription factor Mig1, thereby relieving repression of the gene encoding the rate-limiting enzyme of the PPP. Surprisingly, NADPH produced by the PPP is required for efficient recruitment of replication protein A (RPA) to single-stranded DNA, providing the signal for the activation of the Mec1/ATR-Rad53/CHK1 checkpoint signaling kinase cascade. Thus, SNF1, best known as a central energy controller, determines a fast mode of replication checkpoint activation through a redox mechanism. These findings establish that SNF1 provides a hub with direct links to cellular metabolism, redox, and surveillance of DNA replication in eukaryotes.

Identification of Macrolepiota procera extract as a novel G6PD inhibitor for the treatment of lung cancer

Tumor metabolism, an emerging hallmark of cancer, is characterized by aberrant expression of enzymes from various metabolic pathways including glycolysis and PPP (pentose phosphate pathway). Glucose 6 phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD), oxidative carboxylases of PPP, have been reported to accomplish different biosynthetic and energy requirements of cancer cells. G6PD and 6PGD have been proposed as potential therapeutic targets for cancer therapy during recent years due to their overexpression in various cancers. Here, we have employed enzymatic assay based screening using in-house G6PD and 6PGD assay protocols for the identification of mushroom extracts which could inhibit G6PD or 6PGD enzymatic activity for implications in cancer therapy. For the fulfillment of the objectives of present study, nine edible mushrooms were subjected to green extraction for preparation of ethanolic extracts. 6xhis-G6PD and pET-28a-h6PGD plasmids were expressed in BL21-DE3 E. coli cells for the expression and purification of protein of interests. Using purified proteins, in house enzymatic assay protocols were established. The preliminary screening identified two extracts (Macrolepiota procera and Terfezia boudieri) as potent and selective G6PD inhibitors, while no extract was found highly active against 6PGD. Further, evaluation of anticancer potential of mushroom extracts against lung cancer cells revealed Macrolepiota procera as potential inhibitor of cancer cell proliferation with IC₅₀ value of 6.18 μg/ml. Finally, screening of M. procera-derived compounds against G6PD via molecular docking has identified paraben, quercetin and syringic acid as virtual hit compounds possessing good binding affinity with G6PD. The result of present study provides novel findings for possible mechanism of action of M. procera extract against A549 via G6PD inhibition suggesting that M. procera might be of therapeutic interest for lung cancer treatment.

Are we still on the right path(way)?: the altered expression of the pentose phosphate pathway in solid tumors and the potential of its inhibition in combination therapy

INTRODUCTION

The pentose phosphate pathway (PPP) branches from glycolysis and is crucial for cell growth, since it provides necessary compounds for anabolic reactions, nucleotide synthesis, and detoxification of reactive-oxygen-species (ROS). Overexpression of PPP enzymes has been reported in multiple cancer types and linked to therapy resistance, making their inhibition interesting targets for anti-cancer therapies.

AREAS COVERED

This review summarizes the extent of PPP upregulation across different cancer types, and the non-metabolic functions that PPP-enzymes might contribute to cancer initiation and maintenance. The effects of PPP-inhibition and their combinations with chemotherapeutics are summarized. We searched the databases provided by the University of Amsterdam to characterize the altered expression of the PPP across different cancer types, and to identify the effects of PPP-inhibition.

EXPERT OPINION

It can be concluded that there are synergistic and additive effects of PPP-inhibition and various classes of chemotherapeutics. These effects may be attributed to the increased susceptibility to ROS. However, the toxicity, low efficacy, and off-target effects of PPP-inhibitors make application in clinical practice challenging. Novel inhibitors are currently being developed, which could make PPP-inhibition a potential therapeutic strategy in the future, especially in combination with conventional chemotherapeutics and the inhibition of other metabolic pathways.

Prognostic Model and Nomogram Construction Based on a Novel Ferroptosis-Related Gene Signature in Lower-Grade Glioma

Background: Low-grade glioma (LGG) is considered a fatal disease for young adults, with overall survival widely ranging from 1 to 15 years depending on histopathologic and molecular subtypes. As a novel type of programmed cell death, ferroptosis was reported to be involved in tumorigenesis and development, which has been intensively studied in recent years.

Methods: For the discovery cohort, data from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) were used to identify the differentially expressed and prognostic ferroptosis-related genes (FRGs). The least absolute shrinkage and selection operator (LASSO) and multivariate Cox were used to establish a prognostic signature with the above-selected FRGs. Then, the signature was developed and validated in TCGA and Chinese Glioma Genome Atlas (CGGA) databases. By combining clinicopathological features and the FRG signature, a nomogram was established to predict individuals’ one-, three-, and five-year survival probability, and its predictive performance was evaluated by Harrell’s concordance index (C-index) and calibration curves. Enrichment analysis was performed to explore the signaling pathways regulated by the signature.

Results: A novel risk signature contains seven FRGs that were constructed and were used to divide patients into two groups. Kaplan–Meier (K−M) survival curve and receiver-operating characteristic (ROC) curve analyses confirmed the prognostic performance of the risk model, followed by external validation based on data from the CGGA. The nomogram based on the risk signature and clinical traits was validated to perform well for predicting the survival rate of LGG. Finally, functional analysis revealed that the immune statuses were different between the two risk groups, which might help explain the underlying mechanisms of ferroptosis in LGG.

Conclusion: In conclusion, this study constructed a novel and robust seven-FRG signature and established a prognostic nomogram for LGG survival prediction.

Nuclear Receptor-Mediated Metabolic Reprogramming and the Impact on HR+ Breast Cancer

Simple Summary

Breast cancer is the most commonly diagnosed and second leading cause of cancer-related deaths in women in the United States, with hormone receptor positive (HR+) tumors representing more than two-thirds of new cases. Recent evidence has indicated that dysregulation of multiple metabolic programs, which can be driven through nuclear receptor activity, is essential for tumor genesis, progression, therapeutic resistance and metastasis. This study will review the current advances in our understanding of the impact and implication of altered metabolic processes driven by nuclear receptors, including hormone-dependent signaling, on HR+ breast cancer.

Abstract

Metabolic reprogramming enables cancer cells to adapt to the changing microenvironment in order to maintain metabolic energy and to provide the necessary biological macromolecules required for cell growth and tumor progression. While changes in tumor metabolism have been long recognized as a hallmark of cancer, recent advances have begun to delineate the mechanisms that modulate metabolic pathways and the consequence of altered signaling on tumorigenesis. This is particularly evident in hormone receptor positive (HR+) breast cancers which account for approximately 70% of breast cancer cases. Emerging evidence indicates that HR+ breast tumors are dependent on multiple metabolic processes for tumor progression, metastasis, and therapeutic resistance and that changes in metabolic programs are driven, in part, by a number of key nuclear receptors including hormone-dependent signaling. In this review, we discuss the mechanisms and impact of hormone receptor mediated metabolic reprogramming on HR+ breast cancer genesis and progression as well as the therapeutic implications of these metabolic processes in this disease.

Glucose Metabolism and Glucose Transporters in Breast Cancer

Breast cancer is the most common malignancy in women worldwide and is associated with high mortality rates despite the continuously advancing treatment strategies. Glucose is essential for cancer cell metabolism owing to the Warburg effect. During the process of glucose metabolism, various glycolytic metabolites, such as serine and glycine metabolites, are produced and other metabolic pathways, such as the pentose phosphate pathway (PPP), are associated with the process. Glucose is transported into the cell by glucose transporters, such as GLUT. Breast cancer shows high expressions of glucose metabolism-related enzymes and GLUT, which are also related to breast cancer prognosis. Triple negative breast cancer (TNBC), which is a high-grade breast cancer, is especially dependent on glucose metabolism. Breast cancer also harbors various stromal cells such as cancer-associated fibroblasts and immune cells as tumor microenvironment, and there exists a metabolic interaction between these stromal cells and breast cancer cells as explained by the reverse Warburg effect. Breast cancer is heterogeneous, and, consequently, its metabolic status is also diverse, which is especially affected by the molecular subtype, progression stage, and metastatic site. In this review, we will focus on glucose metabolism and glucose transporters in breast cancer, and we will additionally discuss their potential applications as cancer imaging tracers and treatment targets.

Biochemical and structural insights into 6-phosphogluconate dehydrogenase from Leishmania donovani

6-phosphogluconate dehydrogenase (6PGDH) participates in pentose phosphate pathway of glucose metabolism by catalyzing oxidative decarboxylation of 6-phsophogluconate (6PG) and its absence has been lethal for several eukaryotes. Despite being a validated drug target in many organisms like Plasmodium, the enzyme has not been explored in leishmanial parasites. In the present study, 6PGDH of Leishmania donovani (Ld6PGDH) is cloned and purified followed by its characterization using biochemical and structural approaches. Ld6PGDH lacks the glycine-serine-rich sequence at its C-terminal that is present in other eukaryotes including humans. Leishmanial 6PGDH possesses more affinity for substrate (6PG) and cofactor (NADP) in comparison to that of human. The enzymatic activity is inhibited by gentamicin and cefuroxime through competitive mode with functioning more potently towards leishmanial 6PGDH than its human counterpart. CD analysis has shown higher α-helical content in the secondary structure of Ld6PGDH, while fluorescence studies revealed that tryptophan residues are not completely accessible to solvent environment. The three-dimensional structure was generated through homology modelling and docked with substrate and cofactor. The docking studies demonstrated two separate binding pockets for 6PG and NADP with higher affinity for the cofactor binding, and Asn105 is interacting with substrate as well as the cofactor. Additionally, MD simulation has shown complexes of Ld6PGDH with 6PG and NADP to be more stable than its apo form. Altogether, the present study might provide the foundation to investigate this enzyme as potential target against leishmaniasis. KEY POINTS: • Ld6PGDH enzymatic activity is competitively inhibited by gentamicin and cefuroxime. • It displays more helical contents and all structural characteristics of 6PGDH family. • Interaction studies demonstrate higher affinity of cofactor than substrate for Ld6PGDH.

Overcoming chemoresistance by targeting reprogrammed metabolism: the Achilles' heel of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer-related death due to its late diagnosis that removes the opportunity for surgery and metabolic plasticity that leads to resistance to chemotherapy. Metabolic reprogramming related to glucose, lipid, and amino acid metabolism in PDAC not only enables the cancer to thrive and survive under hypovascular, nutrient-poor and hypoxic microenvironments, but also confers chemoresistance, which contributes to the poor prognosis of PDAC. In this review, we systematically elucidate the mechanism of chemotherapy resistance and the relationship of metabolic programming features with resistance to anticancer drugs in PDAC. Targeting the critical enzymes and/or transporters involved in glucose, lipid, and amino acid metabolism may be a promising approach to overcome chemoresistance in PDAC. Consequently, regulating metabolism could be used as a strategy against PDAC and could improve the prognosis of PDAC.

USP8 is a Novel Therapeutic Target in Melanoma Through Regulating Receptor Tyrosine Kinase Levels

Introduction

The hyperactivation of receptor tyrosine kinase (RTK)-mediated pathways plays an important role in melanoma progression and resistance to therapy. The ubiquitin-specific protease 8 (USP8) is a deubiquitinating enzyme and its inhibition induces degradation of RTKs. This work explored the expression and role of USP8 in melanoma.

Methods

ELISA and qPCR were performed to assess USP8 expression in melanoma tissues and cells, as well as their normal counterparts. Cellular proliferation, migration and apoptosis assays were performed to determine USP8 functions in three melanoma cell lines. Western blot was performed to analyze RTK signaling in melanoma cells after USP8 inhibition.

Results

mRNA and protein level of USP8 were higher in melanoma cells than normal melanocytes. Higher USP8 expression was also found in tumors in the majority of melanoma patients. USP8 expression was not associated with clinicopathological features, such as age, disease stage, histology, ulceration and BRAF status. Functional analysis demonstrated that USP8 overexpression promoted melanoma cell activities and alleviated the inhibitory effects of therapeutic drugs. In contrast, USP8 knockdown suppressed melanoma cell growth, survival and migration, and augmented the inhibitory effects of therapeutic drugs. Mechanism studies revealed that USP8 inhibition remarkably reduced the expression level of multiple oncogenic RTKs, including c-Met, Kit, EGFR and GPCR. Consistently, RTK-mediated downstream pathways were disrupted in USP8-depleted cells, leading to the increased level of pro-apoptotic proteins and decreased level of anti-apoptotic proteins.

Conclusion

Inhibition of USP8 activity is a novel sensitizing strategy to overcome therapy resistance in melanoma.

Physcion and Physcion 8-O-β-D-glucopyranoside: Natural Anthraquinones with Potential Anticancer Activities

Nature has provided prodigious reservoirs of pharmacologically active compounds for drug development since times. Physcion and physcion 8-O-β-D-glucopyranoside (PG) are bioactive natural anthraquinones which exert anti-inflammatory and anticancer properties with minimum or no adverse effects. Moreover, physcion also exhibits anti-microbial and hepatoprotective properties, while PG is known to have anti-sepsis as well as ameliorative activities against dementia. This review aims to highlight the natural sources and anticancer activities of physcion and PG, along with associated mechanisms of actions. On the basis of the literature, physcion and PG regulate multitudinous cell signaling pathways through the modulation of various regulators of cell cycle, protein kinases, microRNAs, transcriptional factors, and apoptosis linked proteins resulting in the effective killing of cancerous cells in vitro as well as in vivo. Both compounds effectively suppress metastasis, furthermore, physcion acts as an inhibitor of 6PGD and also plays an important role in chemosensitization. This review article suggests that physcion and PG are potent anticancer drug candidates, but further investigations on their mechanism of action and pre-clinical trials are mandatory in order to comprehend the full potential of these natural cancer killers in anticancer remedies.

Oxidative Pentose Phosphate Pathway Enzyme 6-Phosphogluconate Dehydrogenase Plays a Key Role in Breast Cancer Metabolism

The pentose phosphate pathway (PPP) plays an essential role in the metabolism of breast cancer cells for the management of oxidative stress and the synthesis of nucleotides. 6-phosphogluconate dehydrogenase (6PGD) is one of the key enzymes of the oxidative branch of PPP and is involved in nucleotide biosynthesis and redox maintenance status. Here, we aimed to analyze the functional importance of 6PGD in a breast cancer cell model. Inhibition of 6PGD in MCF7 reduced cell proliferation and showed a significant decrease in glucose consumption and an increase in glutamine consumption, resulting in an important alteration in the metabolism of these cells. No difference in reactive oxygen species (ROS) production levels was observed after 6PGD inhibition, indicating that 6PGD, in contrast to glucose 6-phosphate dehydrogenase, is not involved in redox balance. We found that 6PGD inhibition also altered the stem cell characteristics and mammosphere formation capabilities of MCF7 cells, opening new avenues to prevent cancer recurrance after surgery or chemotherapy. Moreover, inhibition of 6PGD via chemical inhibitor S3 resulted in an induction of senescence, which, together with the cell cycle arrest and apoptosis induction, might be orchestrated by p53 activation. Therefore, we postulate 6PGD as a novel therapeutic target to treat breast cancer.

Cryptotanshinone strengthens the effect of gefitinib against non-small cell lung cancer through inhibiting transketolase

Lung cancer is the leading cause of cancer-related mortality and causes more than a million deaths per year. Gefitinib is the first-line agent of advanced lung cancer, however, resistance to gefitinib becomes a major problem in clinical application. Transketolase (TKT) is a key enzyme functioning between the oxidative arm and the non-oxidative arm of the pentose phosphate pathway. In this study, we firstly found that the expression of TKT was remarkably up-regulated in NSCLC cells, while the knockdown of TKT could inhibit cell proliferation and enhance the effect of gefitinib on NSCLC cells, which indicated the role of TKT in treating advanced lung cancer. Cryptotanshinone (CTS) is a natural active compound possessing anti-cancer effect. Here we demonstrated that CTS could strengthen the effect of gefitinib on NSCLC cells via inhibition of TKT in vitro and in vivo. Moreover, Nrf2 was involved in the repression of CTS on TKT expression. Collectively, these findings indicated the role of TKT in lung cancer progression and may provide novel therapeutic strategies to overcome resistance to gefitinib. Furthermore, CTS may serve as a new candidate in adjuvant treatment of advanced lung cancer.

Exploring Dysregulated Signaling Pathways in Cancer

Cancer cell biology takes advantage of identifying diverse cellular signaling pathways that are disrupted in cancer. Signaling pathways are an important means of communication from the exterior of cell to intracellular mediators, as well as intracellular interactions that govern diverse cellular processes. Oncogenic mutations or abnormal expression of signaling components disrupt the regulatory networks that govern cell function, thus enabling tumor cells to undergo dysregulated mitogenesis, to resist apoptosis, and to promote invasion to neighboring tissues. Unraveling of dysregulated signaling pathways may advance the understanding of tumor pathophysiology and lead to the improvement of targeted tumor therapy. In this review article, different signaling pathways and how their dysregulation contributes to the development of tumors have been discussed.

Metabolism and immunity in breast cancer

Breast cancer is one of the most common malignancies that seriously threaten women's health. In the process of the malignant transformation of breast cancer, metabolic reprogramming and immune evasion represent the two main fascinating characteristics of cancer and facilitate cancer cell proliferation. Breast cancer cells generate energy through increased glucose metabolism. Lipid metabolism contributes to biological signal pathways and forms cell membranes except energy generation. Amino acids act as basic protein units and metabolic regulators in supporting cell growth. For tumor-associated immunity, poor immunogenicity and heightened immunosuppression cause breast cancer cells to evade the host's immune system. For the past few years, the complex mechanisms of metabolic reprogramming and immune evasion are deeply investigated, and the genes involved in these processes are used as clinical therapeutic targets for breast cancer. Here, we review the recent findings related to abnormal metabolism and immune characteristics, regulatory mechanisms, their links, and relevant therapeutic strategies.

Rac1 repression reverses chemoresistance by targeting tumor metabolism

Tumor metabolism is exemplified by the increased rate of glucose utilization, a biochemical signature of cancer cells. The enhanced glucose hydrolysis enabled by the augmentation of glycolytic flux and the pentose phosphate pathway (PPP) plays a pivotal role in the growth and survival of neoplastic cells. In a recent report, it has been shown that in human breast cancer the GTP binding protein, Rac1 enables resistance to therapy, particularly against the DNA-damaging therapeutics. Significantly, the findings demonstrate that Rac1-dependent chemoresistance involves the upregulation of glycolytic flux as well as PPP. Using multiple approaches, the study demonstrates that disruption of Rac1 activity sensitizes cancer cells to DNA-damaging agents. More importantly, the data uncover a previously unknown PPP regulatory role of Rac1 in breast cancer. Finally, the authors also show the effectiveness and the feasibility of in vivo targeting of Rac1 to enhance the chemosensitivity of breast cancer. This elegant report provokes scientific curiosity to expand our understanding of the intricacies of the role and regulation of Rac1 in cancer.

Discovery of Ebselen as an Inhibitor of 6PGD for Suppressing Tumor Growth

Introduction

The 6-phosphogluconate dehydrogenase (6PGD) was upregulated in many solid cancers and plays an important role in tumorigenesis. In the present study, we want to discover an old drug as an inhibitor of 6PGD for suppressing tumor growth.

Methods

We determined the expression of 6PGD in cancer tissues using Gene Expression Omnibus (GEO) profiles and explored the importance of 6PGD expression in cancer progression by using Kaplan–Meier Plotter. We identified Ebselen as a 6PGD inhibitor by using 6PGD in vitro enzyme activity assay. Cell viability, cell proliferation, tumor growth and cell metabolism assay were used to explore the role of 6PGD and its inhibitor in cancer cells.

Results

We found that the expression of 6PGD was upregulated in different cancer tissues and it can promote tumorigenesis. Here, we analyzed our 6PGD inhibitor screening data again and found an old drug Ebselen, which blocks cancer cell proliferation and tumor growth by inhibiting 6PGD enzyme activity, while knocking down 6PGD would partially abolish the inhibition of Ebselen on cell proliferation and cell metabolism.

Conclusion

Our results suggested that the conventional drug Ebselen could serve as a novel inhibitor of 6PGD for suppressing cancer growth by inhibiting 6PGD enzyme activity.

The structure of a novel membrane-associated 6-phosphogluconate dehydrogenase from Gluconacetobacter diazotrophicus (Gd6PGD) reveals a subfamily of short-chain 6PGDs

The enzyme 6-phosphogluconate dehydrogenase catalyzes the conversion of 6-phosphogluconate to ribulose-5-phosphate. It represents an important reaction in the oxidative pentose phosphate pathway, producing a ribose precursor essential for nucleotide and nucleic acid synthesis. We succeeded, for the first time, to determine the three-dimensional structure of this enzyme from an acetic acid bacterium, Gluconacetobacter diazotrophicus (Gd6PGD). Active Gd6PGD, a homodimer (70 kDa), was present in both the soluble and the membrane fractions of the nitrogen-fixing microorganism. The Gd6PGD belongs to the newly described subfamily of short-chain (333 AA) 6PGDs, compared to the long-chain subfamily (480 AA; e.g., Ovis aries, Homo sapiens). The shorter amino acid sequence in Gd6PGD induces the exposition of hydrophobic residues in the C-terminal domain. This distinct structural feature is key for the protein to associate with the membrane. Furthermore, in terms of function, the short-chain 6PGD seems to prefer NAD⁺ over NADP⁺ , delivering NADH to the membrane-bound NADH dehydrogenase of the microorganisms required by the terminal oxidases to reduce dioxygen to water for energy conservation. ENZYME: ECnonbreakingspace1.1.1.343. DATABASE: Structural data are available in PDB database under the accession number 6VPB.

The Pentose Phosphate Pathway Dynamics in Cancer and Its Dependency on Intracellular pH

The Pentose Phosphate Pathway (PPP) is one of the key metabolic pathways occurring in living cells to produce energy and maintain cellular homeostasis. Cancer cells have higher cytoplasmic utilization of glucose (glycolysis), even in the presence of oxygen; this is known as the "Warburg Effect". However, cytoplasmic glucose utilization can also occur in cancer through the PPP. This pathway contributes to cancer cells by operating in many different ways: (i) as a defense mechanism via the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) to prevent apoptosis, (ii) as a provision for the maintenance of energy by intermediate glycolysis, (iii) by increasing genomic material to the cellular pool of nucleic acid bases, (iv) by promoting survival through increasing glycolysis, and so increasing acid production, and (v) by inducing cellular proliferation by the synthesis of nucleic acid, fatty acid, and amino acid. Each step of the PPP can be upregulated in some types of cancer but not in others. An interesting aspect of this metabolic pathway is the shared regulation of the glycolytic and PPP pathways by intracellular pH (pHi). Indeed, as with glycolysis, the optimum activity of the enzymes driving the PPP occurs at an alkaline pHi, which is compatible with the cytoplasmic pH of cancer cells. Here, we outline each step of the PPP and discuss its possible correlation with cancer.

6-Phosphogluconate dehydrogenase fuels multiple aspects of cancer cells: From cancer initiation to metastasis and chemoresistance

Reprogrammed metabolism is key biochemical characteristic of malignant cells, which represents one of the emerging hallmarks of cancer. Currently, there is rising contemplation on oxidative pentose phosphate pathway (PPP) enzymes as potential therapeutic hits due to their affiliation with tumor metabolism. 6-Phosphogluconate dehydrogenase (6PGD), third oxidative decarboxylase of PPP, has received a great deal of attention during recent years due to its critical role in tumorigenesis and redox homeostasis. 6PGD has been reported to overexpress in number of cancer types and its hyperactivation is mediated through post-transcriptional and post-translational modifications by YTH domain family 2 (YTHDF2), Nrf2 (nuclear factor erythroid 2-related factor 2), EGFR (epidermal growth factor receptor) and via direct structural interactions with ME1 (malic enzyme 1). Upregulated expression of 6PGD provides metabolic as well as defensive advantage to cancer cells, thus, promoting their proliferative and metastatic potential. Moreover, enhanced 6PGD expression also performs key role in development of chemoresistance as well as radiation resistance in cancer. This review aims to discuss the historical timeline and cancer-specific role of 6PGD, pharmacological and genetic inhibitors of 6PGD and 6PGD as prognostic biomarker in order to explore its potential for therapeutic interventions. We anticipate that targeting this imperative supplier of NADPH might serve as tempting avenue to combat the deadly disease like cancer.

6PGD Upregulation is Associated with Chemo- and Immuno-Resistance of Renal Cell Carcinoma via AMPK Signaling-Dependent NADPH-Mediated Metabolic Reprograming

BACKGROUND

The essential role of 6-phosphogluconate dehydrogenase (6PGD), the enzyme catalyzing the oxidative pentose phosphate pathway, in tumor growth and metabolism has garnered attention in recent years. In this work, we are the first to demonstrate that aberrant activation of 6PGD is a feature in renal cell carcinoma (RCC) and is critically involved in renal carcinogenesis and chemo- and immuno-resistance.

MATERIALS AND METHODS

6PGD expression and activity were systematically analyzed in normal and malignant renal cells and tissues. The roles of 6PGD and its downstream mechanism were investigated using gain-of-function and loss-of-function approaches.

RESULTS

6PGD expression and enzyme activity were increased in RCC cells and patients' samples. Activation of 6PGD via gain-of-function approach promoted growth of normal kidney but not RCC cells, and alleviated the efficacy of chemotherapeutic (e.g., 5-FU) and immunotherapeutic (e.g., IFN-α) agents. In contrast, 6PGD inhibition using siRNA knockdown and pharmacological inhibitor physcion augmented the inhibitory effects of 5-FU and IFN-α in RCC. Mechanistic studies demonstrated that 6PGD inhibition activated AMPK signaling, leading to ACC1 enzyme inhibition and reduction of lipid synthesis. In addition, 6PGD inhibition disrupted NADPH and NADH homeostasis in RCC cells as shown by the decreased level of NADPH and NADH, and suppressed SIRT-1 activity. AMPK inhibition by siRNA knockdown reversed the inhibitory effects of physcion, demonstrating that the effect of 6PGD inhibition is AMPK activation dependent.

CONCLUSIONS

Our work provides preclinical evidence that 6PGD inhibition may represent a potential therapeutic strategy to augment the efficacy of RCC standard of care drugs.

The Role of the Pentose Phosphate Pathway in Diabetes and Cancer

The pentose phosphate pathway (PPP) branches from glucose 6-phosphate (G6P), produces NADPH and ribose 5-phosphate (R5P), and shunts carbons back to the glycolytic or gluconeogenic pathway. The PPP has been demonstrated to be a major regulator for cellular reduction-oxidation (redox) homeostasis and biosynthesis. Enzymes in the PPP are reported to play important roles in many human diseases. In this review, we will discuss the role of the PPP in type 2 diabetes and cancer.

P-MAPA and IL-12 Differentially Regulate Proteins Associated with Ovarian Cancer Progression: A Proteomic Study

To investigate the potential role of immunotherapies in the cellular and molecular mechanisms associated with ovarian cancer (OC), we applied a comparative proteomic toll using protein identification combined with mass spectrometry. Herein, the effects of the protein aggregate magnesium-ammonium phospholinoleate-palmitoleate anhydride, known as P-MAPA, and the human recombinant interleukin-12 (hrIL-12) were tested alone or in combination in human SKOV-3 cells. The doses and period were defined based on a previous study, which showed that 25 μg/mL P-MAPA and 1 ng/mL IL-12 are sufficient to reduce cell metabolism after 48 h. Indeed, among 2,881 proteins modulated by the treatments, 532 of them were strictly concordant and common. P-MAPA therapy upregulated proteins involved in tight junction, focal adhesion, ribosome constitution, GTP hydrolysis, semaphorin interactions, and expression of SLIT and ROBO, whereas it downregulated ERBB4 signaling, toll-like receptor signaling, regulation of NOTCH 4, and the ubiquitin proteasome pathway. In addition, IL-12 therapy led to upregulation of leukocyte migration, tight junction, and cell signaling, while cell communication, cell metabolism, and Wnt signaling were significantly downregulated in OC cells. A clear majority of proteins that were overexpressed by the combination of P-MAPA with IL-12 are involved in tight junction, focal adhesion, DNA methylation, metabolism of RNA, and ribosomal function; only a small number of downregulated proteins were involved in cell signaling, energy and mitochondrial processes, cell oxidation and senescence, and Wnt signaling. These findings suggest that P-MAPA and IL-12 efficiently regulated important proteins associated with OC progression; these altered proteins may represent potential targets for OC treatment in addition to its immunoadjuvant effects.

Role of coenzymes in cancer metabolism

Cancer is a heterogeneous set of diseases characterized by the rewiring of cellular signaling and the reprogramming of metabolic pathways to sustain growth and proliferation. In past decades, studies were focused primarily on the genetic complexity of cancer. Recently, increasing number of studies have discovered several mutations among metabolic enzymes in different tumor cells. Most of the enzymes are regulated by coenzymes, organic cofactors, that function as intermediate carrier of electrons or functional groups that are transferred during the reaction. However, the precise role of cofactors is not well elucidated. In this review, we discuss several metabolic enzymes associated to cancer metabolism rewiring, whose inhibition may represent a therapeutic target. Such enzymes, upon expression or inhibition, may impact also the coenzymes levels, but only in few cases, it was possible to direct correlate coenzymes changes with a specific enzyme. In addition, we also summarize an up-to-date information on biological role of some coenzymes, preclinical and clinical studies, that have been carried out in various cancers and their outputs.

Crucial role of the pentose phosphate pathway in malignant tumors

Interest in cancer metabolism has increased in recent years. The pentose phosphate pathway (PPP) is a major glucose catabolism pathway that directs glucose flux to its oxidative branch and leads to the production of a reduced form of nicotinamide adenine dinucleotide phosphate and nucleic acid. The PPP serves a vital role in regulating cancer cell growth and involves many enzymes. The aim of the present review was to describe the recent discoveries associated with the deregulatory mechanisms of the PPP and glycolysis in malignant tumors, particularly in hepatocellular carcinoma, breast and lung cancer.

Optimizing Size Exclusion Chromatography for Extracellular Vesicle Enrichment and Proteomic Analysis from Clinically Relevant Samples

The field of extracellular vesicle (EV) research has rapidly expanded in recent years, with particular interest in their potential as circulating biomarkers. Proteomic analysis of EVs from clinical samples is complicated by the low abundance of EV proteins relative to highly abundant circulating proteins such as albumin and apolipoproteins. To overcome this, size exclusion chromatography (SEC) has been proposed as a method to enrich EVs whilst depleting protein contaminants; however, the optimal SEC parameters for EV proteomics have not been thoroughly investigated. Here, quantitative evaluation and optimization of SEC are reported for separating EVs from contaminating proteins. Using a synthetic model system followed by cell line-derived EVs, it is found that a 10 mL Sepharose 4B column in PBS produces optimal resolution of EVs from background protein. By spiking-in cancer cell-derived EVs to healthy plasma, it is shown that some cancer EV-associated proteins are detectable by nano-LC-MS/MS when as little as 1% of the total plasma EV number are derived from a cancer cell line. These results suggest that an optimized SEC and nanoLC-MS/MS workflow may be sufficiently sensitive for disease EV protein biomarker discovery from patient-derived clinical samples.

6PGD inhibition sensitizes hepatocellular carcinoma to chemotherapy via AMPK activation and metabolic reprogramming

Better understanding of the molecular mechanism involved in hepatocellular carcinoma (HCC) progression is essential for the development of therapeutic strategies to overcome chemoresistance in HCC patients. In this work, we show that 6-phosphogluconate dehydrogenase (6PGD), a key enzyme of the oxidative pentose phosphate pathway, is important for HCC growth and survival. Compared to normal liver tissues, we demonstrate that 6PGD expression is upregulated in HCC tissues. 6PGD overexpression increases 6PGD activity and promotes growth in normal liver cells. In contrast, targeting 6PGD using both genetic and pharmacological approaches inhibits HCC growth and survival. Combination of chemotherapeutic agents with 6PGD inhibition achieves greater efficacy in inhibiting HCC growth and survival than chemotherapeutic agent alone. We further show that inhibition of 6PGD activates AMP-activated protein kinase (AMPK) and acetyl-coenzyme A carboxylase 1 (ACC1), and decreases level of NADPH/NAD + and NADH in HCC, leading to SIRT1 activity reduction and oxidative stress. Conversely, AMPK depletion significantly abolishes the effects of physcion (a selective small-molecule 6PGD inhibitor) in decreasing NADPH/NAD + ratio, growth and survival, confirming the role of AMPK as the relevant upstream activator with 6PGD inhibition in HCC cells. Our work is the first to demonstrate the upregulation of 6PGD and its critical involvement in growth and survival in HCC. Our findings suggest 6PGD as a promising therapeutic target to overcome chemoresistance in HCC.

Inhibition of mitochondrial translation as a therapeutic strategy for human ovarian cancer to overcome chemoresistance

Aberrant increase in mitochondrial biogenesis is common in human ovarian cancer and has great therapeutic value. In this work, we demonstrate that tigecycline, a FDA-approved broad spectrum antibiotic, selectively targets ovarian cancer cells through inhibition of mitochondrial translation. Tigecycline dose-dependently inhibits proliferation of ovarian cancer cells via arresting them at G2/M phase and induces apoptosis through caspase pathway. At the same concentration, tigecycline either does not or inhibits normal cells in a less extent than ovarian cancer cells. Mechanistically, tigecycline specifically inhibits translation by mitochondrial ribosome but not nuclear or cytosolic ribosome, leading to mitochondrial dysfunction, oxidative stress and damage, AMPK activation and inhibition of mTOR signaling in ovarian cancer cells. We further show that the inhibitory effects on ovarian cancer cell by tigecycline is mediated by its suppression of mitochondrial respiration. Importantly, the combination of tigecycline and cisplatin at sublethal concentration results in much greater efficacy than cisplatin alone in vitro and in vivo. Additionally, the effective dose of tigecycline in ovarian cancer is clinically achievable. Our study suggests that tigecycline is a useful addition to the treatment of ovarian cancer. Our work also highlights the targeted therapeutic potential of mitochondrial respiration in ovarian cancer.

Inhibiting 6-phosphogluconate dehydrogenase enhances chemotherapy efficacy in cervical cancer via AMPK-independent inhibition of RhoA and Rac1

BACKGROUND

The oxidative pentose phosphate pathway (PPP) is essential for cancer metabolism and growth. However, the contribution of 6-phosphogluconate dehydrogenase (6PGD), a key enzyme of PPP, to cervical cancer development remains largely unknown.

METHODS

mRNA and protein levels of 6PGD were analyzed in cervical cancer cells and tissues derived from patients and compared to normal counterparts. Using cell culture system and xenograft mouse model, the functions of 6PGD in cervical cancer are determined and its molecular mechanism is analyzed. 6PGD inhibitor physcion and siRNA knockdown were used.

RESULTS

In this work, we demonstrate that 6PGD is aberrantly upregulated and activated in cervical cancer cells and patient tissues compared to normal counterparts. Using different approaches and preclinical models, we show that 6PGD inhibition decreases growth and migration, and enhances chemosensitivity in cervical cancer. Mechanistically, inhibition of 6PGD activates AMP-activated protein kinase (AMPK) and decreases RhoA and Rac1 activities. AMPK depletion significantly reduces the effects of 6PGD inhibition in decreasing RhoA and Rac1 activities, growth and migration in cervical cancer cells.

CONCLUSIONS

Our work is the first to demonstrate the aberrant expression of 6PGD and its predominant roles in cervical cancer cell growth and migration, via a AMPK-dependent activation. Our findings suggest 6PGD as a potential therapeutic target to enhance chemosensitivity in cervical cancer.