Adaptive landscapes and emergent phenotypes: why do cancers have high glycolysis?

pH-responsive targeted nanoparticles release ERK-inhibitor in the hypoxic zone and sensitize free gemcitabine in mutant K-Ras-addicted pancreatic cancer cells and mouse model

Therapeutic options for managing Pancreatic ductal adenocarcinoma (PDAC), one of the deadliest types of aggressive malignancies, are limited and disappointing. Therefore, despite suboptimal clinical effects, gemcitabine (GEM) remains the first-line chemotherapeutic drug in the clinic for PDAC treatment. The therapeutic limitations of GEM are primarily due to poor bioavailability and the development of chemoresistance resulting from the addiction of mutant-K-RAS/AKT/ERK signaling-mediated desmoplastic barriers with a hypoxic microenvironment. Several new therapeutic approaches, including nanoparticle-assisted drug delivery, are being investigated by us and others. This study used pH-responsive nanoparticles encapsulated ERK inhibitor (SCH772984) and surface functionalized with tumor-penetrating peptide, iRGD, to target PDAC tumors. We used a small molecule, SCH772984, to target ERK1 and ERK2 in PDAC and other cancer cells. This nanocarrier efficiently released ERKi in hypoxic and low-pH environments. We also found that the free-GEM, which is functionally weak when combined with nanoencapsulated ERKi, led to significant synergistic treatment outcomes in vitro and in vivo. In particular, the combination approaches significantly enhanced the GEM effect in PDAC growth inhibition and prolonged survival of the animals in a genetically engineered KPC (LSL-KrasG12D/+/LSL-Trp53R172H/+/Pdx-1-Cre) pancreatic cancer mouse model, which is not observed in a single therapy. Mechanistically, we anticipate that the GEM efficacy was increased as ERKi blocks desmoplasia by impairing the production of desmoplastic regulatory factors in PDAC cells and KPC mouse tumors. Therefore, 2nd generation ERKi (SCH 772984)-iRGD-pHNPs are vital for the cellular response to GEM and denote a promising therapeutic target in PDAC with mutant K-RAS.

Modeling tumors as species-rich ecological communities

Many advanced cancers resist therapeutic intervention. This process is fundamentally related to intra-tumor heterogeneity: multiple cell populations, each with different mutational and phenotypic signatures, coexist within a tumor and its metastatic nodes. Like species in an ecosystem, many cancer cell populations are intertwined in a complex network of ecological interactions. Most mathematical models of tumor ecology, however, cannot account for such phenotypic diversity nor are able to predict its consequences. Here we propose that the Generalized Lotka-Volterra model (GLV), a standard tool to describe complex, species-rich ecological communities, provides a suitable framework to describe the ecology of heterogeneous tumors. We develop a GLV model of tumor growth and discuss how its emerging properties, such as outgrowth and multistability, provide a new understanding of the disease. Additionally, we discuss potential extensions of the model and their application to three active areas of cancer research, namely phenotypic plasticity, the cancer-immune interplay and the resistance of metastatic tumors to treatment. Our work outlines a set of questions and a tentative road map for further research in cancer ecology.

Cancer resistance and metastasis are maintained through oxidative phosphorylation

Malignant tumors have increased energy requirements due to growth, differentiation or response to stress. A significant number of studies in recent years have described upregulation of mitochondrial genes responsible for oxidative phosphorylation (OXPHOS) in some tumors. Although OXPHOS is replaced by glycolysis in some tumors (Warburg effect), both processes can occur simultaneously during the evolution of the same malignancies. In particular, chemoresistant and/or cancer stem cells appear to find a way to activate OXPHOS and metastasize. In this paper, we discuss recent work showing upregulation of OXPHOS in chemoresistant tumors and cell models. In addition, we show an inverse correlation of OXPHOS gene expression with the survival time of cancer patients after chemotherapy and discuss combination therapies for resistant tumors.

Metabolic priming by multiple enzyme systems supports glycolysis, HIF1α stabilisation, and human cancer cell survival in early hypoxia

Adaptation to chronic hypoxia occurs through changes in protein expression, which are controlled by hypoxia-inducible factor 1α (HIF1α) and are necessary for cancer cell survival. However, the mechanisms that enable cancer cells to adapt in early hypoxia, before the HIF1α-mediated transcription programme is fully established, remain poorly understood. Here we show in human breast cancer cells, that within 3 h of hypoxia exposure, glycolytic flux increases in a HIF1α-independent manner but is limited by NAD+ availability. Glycolytic ATP maintenance and cell survival in early hypoxia rely on reserve lactate dehydrogenase A capacity as well as the activity of glutamate-oxoglutarate transaminase 1 (GOT1), an enzyme that fuels malate dehydrogenase 1 (MDH1)-derived NAD+. In addition, GOT1 maintains low α-ketoglutarate levels, thereby limiting prolyl hydroxylase activity to promote HIF1α stabilisation in early hypoxia and enable robust HIF1α target gene expression in later hypoxia. Our findings reveal that, in normoxia, multiple enzyme systems maintain cells in a primed state ready to support increased glycolysis and HIF1α stabilisation upon oxygen limitation, until other adaptive processes that require more time are fully established.

Exercise as a Promising Agent against Cancer: Evaluating Its Anti-Cancer Molecular Mechanisms

BACKGROUND

Cancer cases are continuously increasing, while the prevalence rates of physical inactivity are also continuously increasing. Physical inactivity is a causative factor in non-communicable diseases, including cancer. However, the potential beneficial effects of exercise on cancer treatment have not received much attention so far. The aim of this study was to highlight the relationship between cancer and exercise on a molecular basis.

METHODS

Comprehensive and in-depth research was conducted in the most accurate scientific databases by using relevant and effective keywords.

RESULTS

The mechanisms by which exercise may reduce cancer risk and/or progression may include the metabolic profile of hormones, systemic inflammation reduction, insulin sensitivity increase, antioxidant capacity augmentation, the boost to the immune system, and the direct effect on the tumor. There is currently substantial evidence that the effect of exercise may predict a stronger association with cancer and could supplementarily be embedded in cancer clinical practice to improve disease progression and prognosis.

CONCLUSION

The field of this study requires interconnecting the overall knowledge of exercise physiology with cancer biology and cancer clinical oncology to provide the basis for personalized targeting strategies that can be merged with training as a component of a holistic co-treatment approach to optimize cancer healthcare.

Lactate metabolic pathway regulates tumor cell metastasis and its use as a new therapeutic target

Abnormal energy metabolism is one of the ten hallmarks of tumors, and tumor cell metabolism provides energy and a suitable microenvironment for tumorigenesis and metastasis. Tumor cells can consume large amounts of glucose and produce large amounts of lactate through glycolysis even in the presence of oxygen, a process called aerobic glycolysis, also known as the Warburg effect. Lactate is the end product of the aerobic glycolysis. Lactate dehydrogenase A (LDHA), which is highly expressed in cancer cells, promotes lactate production and transports lactate to the tumor microenvironment and is taken up by surrounding stromal cells under the action of monocarboxylate transporter 1/4 (MCT1/4), which in turn influences the immune response and enhances the invasion and metastasis of cancer cells. Therapeutic strategies targeting lactate metabolism have been intensively investigated, focusing on its metastasis-promoting properties and various target inhibitors; AZD3965, an MCT1 inhibitor, has entered phase I clinical trials, and the LDHA inhibitor N-hydroxyindole (NHI) has shown cancer therapeutic activity in pre-clinical studies. Interventions targeting lactate metabolism are emerging as a promising option for cancer therapy, with chemotherapy or radiotherapy combined with lactate-metabolism-targeted drugs adding to the effectiveness of cancer treatment. Based on current research, this article outlines the role of lactate metabolism in tumor metastasis and the potential value of inhibitors targeting lactate metabolism in cancer therapy.

Type B Lactic Acidosis in a Patient with Mantle Cell Lymphoma

Type B lactic acidosis is an uncommon medical emergency in which acid production overwhelms hepatic clearance. This specific etiology of lactic acidosis occurs without organ hypoperfusion and has been most commonly described in patients with hematologic malignancies but also in patients with solid tumors. The mechanism by which cancer cells switch their glucose metabolism toward increasingly anaerobic glycolytic phenotypes has been described as the "Warburg effect." Without treating the underlying malignancy, the prognosis for patients diagnosed with malignancy-related type B lactic acidosis is extremely poor. Here, we present a case of a 66-year-old male who was diagnosed with type B lactic acidosis secondary to mantle cell lymphoma. Bicarbonate drip was started to correct the lactic acidosis. The patient was also immediately treated with rituximab chemotherapy combined with rasburicase to avoid the hyperuricemia associated with tumor lysis syndrome. He responded to the early treatment and was discharged with normal renal function. Type B lactic acidosis secondary to hematologic malignancy is important to recognize. In order to successfully treat this syndrome, early diagnosis and simultaneous treatment of the imbalance of lactic acid levels and the underlying malignancy are necessary.

An appraisal of the current status of inhibition of glucose transporters as an emerging antineoplastic approach: Promising potential of new pan-GLUT inhibitors

Neoplastic cells displayed altered metabolism with accelerated glycolysis. Therefore, these cells need a mammoth supply of glucose for which they display an upregulated expression of various glucose transporters (GLUT). Thus, novel antineoplastic strategies focus on inhibiting GLUT to intersect the glycolytic lifeline of cancer cells. This review focuses on the current status of various GLUT inhibition scenarios. The GLUT inhibitors belong to both natural and synthetic small inhibitory molecules category. As neoplastic cells express multiple GLUT isoforms, it is necessary to use pan-GLUT inhibitors. Nevertheless, it is also necessary that such pan-GLUT inhibitors exert their action at a low concentration so that normal healthy cells are left unharmed and minimal injury is caused to the other vital organs and systems of the body. Moreover, approaches are also emerging from combining GLUT inhibitors with other chemotherapeutic agents to potentiate the antineoplastic action. A new pan-GLUT inhibitor named glutor, a piperazine-one derivative, has shown a potent antineoplastic action owing to its inhibitory action exerted at nanomolar concentrations. The review discusses the merits and limitations of the existing GLUT inhibitory approach with possible future outcomes.

Enhancing an Oxidative "Trojan Horse" Action of Vitamin C with Arsenic Trioxide for Effective Suppression of KRAS-Mutant Cancers: A Promising Path at the Bedside

The turn-on mutations of the KRAS gene, coding a small GTPase coupling growth factor signaling, are contributing to nearly 25% of all human cancers, leading to highly malignant tumors with poor outcomes. Targeting of oncogenic KRAS remains a most challenging task in oncology. Recently, the specific G12C mutant KRAS inhibitors have been developed but with a limited clinical outcome because they acquire drug resistance. Alternatively, exploiting a metabolic breach of KRAS-mutant cancer cells related to a glucose-dependent sensitivity to oxidative stress is becoming a promising indirect cancer targeting approach. Here, we discuss the use of a vitamin C (VC) acting in high dose as an oxidative "Trojan horse" agent for KRAS-mutant cancer cells that can be potentiated with another oxidizing drug arsenic trioxide (ATO) to obtain a potent and selective cytotoxic impact. Moreover, we outline the advantages of VC's non-natural enantiomer, D-VC, because of its distinctive pharmacokinetics and lower toxicity. Thus, the D-VC and ATO combination shows a promising path to treat KRAS-mutant cancers in clinical settings.

Investigating Two Modes of Cancer-Associated Antigen Heterogeneity in an Agent-Based Model of Chimeric Antigen Receptor T-Cell Therapy

Simple Summary

Chimeric antigen receptor (CAR) T-cell therapy has shown much promise in liquid tumors but often fails in solid tumors. This work uses a computational model to examine under what conditions this therapy might fail or be successful. The model includes interactions between cancer cells, CAR T-cells (treatment), and vascular cells (that feed and support tumor growth). From our results, we determined specific tumor conditions in which CAR T-cell therapy is predicted to fail and suggest a combination treatment that might improve the efficacy of the treatment.

Abstract

Chimeric antigen receptor (CAR) T-cell therapy has been successful in treating liquid tumors but has had limited success in solid tumors. This work examines unanswered questions regarding CAR T-cell therapy using computational modeling, such as, what percentage of the tumor must express cancer-associated antigens for treatment to be successful? The model includes cancer cell and vascular and CAR T-cell modules that interact with each other. We compare two different models of antigen expression on tumor cells, binary (in which cancer cells are either susceptible or are immune to CAR T-cell therapy) and gradated (where each cancer cell has a probability of being killed by a CAR T-cell). We vary the antigen expression levels within the tumor and determine how effective each treatment is for the two models. The simulations show that the gradated antigen model eliminates the tumor under more parameter values than the binary model. Under both models, shielding, in which the low/non-antigen-expressing cells protect high antigen-expressing cells, reduced the efficacy of CAR T-cell therapy. One prediction is that a combination of CAR T-cell therapies that targets the general population of cells as well as one that specifically targets cancer stem cells should increase its efficacy.

Physicochemical aspects of the tumour microenvironment as drivers of vasculogenic mimicry

Tumour vascularisation is vital for cancer sustainment representing not only the main source of nutrients and oxygen supply but also an escape route for single or clustered cancer cells that, once detached from the primary mass, enter the blood circulation and disseminate to distant organs. Among the mechanisms identified to contribute to tumour vascularisation, vasculogenic mimicry (VM) is gaining increasing interest in the scientific community representing an intriguing target for cancer treatment. VM indeed associates with highly aggressive tumour phenotypes and strongly impairs patient outcomes. Differently from vessels of healthy tissues, tumour vasculature is extremely heterogeneous and tortuous, impeding efficient chemotherapy delivery, and at the meantime hyperpermeable and thus extremely accessible to metastasising cancer cells. Moreover, tumour vessel disorganisation creates a self-reinforcing vicious circle fuelling cancer malignancy and progression. Because of the inefficient oxygen delivery and metabolic waste removal from tumour vessels, many cells within the tumour mass indeed experience hypoxia and acidosis, now considered hallmarks of cancer. Being strong inducers of vascularisation, therapy resistance, inflammation and metastasis, hypoxia and acidosis create a permissive microenvironment for cancer progression and dissemination. Along with these considerations, we decided to focus our attention on the relationship between hypoxia/acidosis and VM. Indeed, besides tumour angiogenesis, VM is strongly influenced by both hypoxia and acidosis, which could potentiate each other and fuel this vicious circle. Thus, targeting hypoxia and acidosis may represent a potential target to treat VM to impair tumour perfusion and cancer cell sustainment.

Current Progress and Perspectives on Using Gold Compounds for the Modulation of Tumor Cell Metabolism

Altered cellular metabolism, which is essential for the growth and survival of tumor cells in a specific microenvironment, is one of the hallmarks of cancer. Among the most significant changes in the metabolic pattern of tumor cells is the shift from oxidative phosphorylation to aerobic glycolysis for glucose utilization. Tumor cells also exhibit changes in patterns of protein and nucleic acid metabolism. Recently, gold compounds have been shown to target several metabolic pathways and a number of metabolites in tumor cells. In this review, we summarize how gold compounds modulate glucose, protein, and nucleic acid metabolism in tumor cells, resulting in anti-tumor effects. We also discuss the rationale underlying the anti-tumor effects of these gold compounds and highlight how to effectively utilize against various types of tumors.

Stimuli-Sheddable Nanomedicine Overcoming Pathophysiological Barriers for Potentiating Immunotherapy of Cancer

Immunotherapy displays potent potential for clinical cancer management by activating the protective immune response; however, the microenvironment of the immunosuppressive tumor restricts the efficiency of immunotherapies. Along with the complex pathophysiological barrier of the solid tumors, successful immunotherapeutic delivery remains a formidable challenge for conventional nanomedicine. Stimuli-sheddable nano vectors may facilitate the delivery of cargoes to tumors with minimal premature cargo leakage in blood circulation while enhancing the tumor penetration of nanomedicines by deshielding the polyethylene glycol (PEG) corona upon endogenous activity such as acidity, enzymes and glutathione, or external stimuli, such as laser irradiation. Throughout this study, researchers overviewed the recent advances of nanomedicine-based cancer immunotherapy using the stimuli-responsive deshielding nano vectors, which allowed researchers to integrate multiple therapeutic regimens for inducing immunogenic cell death. This aided in blocking the immune checkpoints, repolarizing the macrophages, and regulating the kynurenine metabolism. Furthermore, researchers discussed the critical issues in the development of stimuli-sheddable nanoimmunodulators, primarily aimed at speeding up their clinical translation. Finally, researchers provided novel perspectives for improving cancer management with the stimuli-sheddable nanomedicine.

VDAC1 Silencing in Cancer Cells Leads to Metabolic Reprogramming That Modulates Tumor Microenvironment

Simple Summary

Tumors are comprised of proliferating cancer cells, and their microenvironment consists of the extracellular matrix, blood vessels, and a variety of tissue cells. The tumor microenvironment functions in cell growth, proliferation, migration, immunity, malignant transformation, and apoptosis. Understanding the molecular interactions between cancer cells and their microenvironment would facilitate the development of therapeutic strategies to disrupt these interactions and fight cancer. Here, we demonstrate that depleting the mitochondrial gatekeeper VDAC1 in human cancer cells in tumors led to metabolic reprogramming, inhibited tumor growth, and disrupted tumor–host interactions. A next-generation sequencing analysis of human lung cell-derived tumors expressing or depleted of VDAC1 allows distinguishing genes of human or murine origin, thus enabling the separation of the bidirectional cross-talk between malignant cells and the tumor microenvironment. A battery of human cancer cell and mouse genes associated with tumor microenvironment formation and remodeling were altered. The results point to VDAC1 as a novel target for both inhibiting tumor growth and modulating the tumor microenvironment, thus influencing cancer progression, migration, and invasion.

Abstract

The tumor microenvironment (TME) plays an important role in cell growth, proliferation, migration, immunity, malignant transformation, and apoptosis. Thus, better insight into tumor–host interactions is required. Most of these processes involve the metabolic reprogramming of cells. Here, we focused on this reprogramming in cancerous cells and its effect on the TME. A major limitation in the study of tumor–host interactions is the difficulty in separating cancerous from non-cancerous signaling pathways within a tumor. Our strategy involved specifically silencing the expression of VDAC1 in the mitochondria of human-derived A549 lung cancer xenografts in mice, but not in the mouse-derived cells of the TME. Next-generation sequencing (NGS) analysis allows distinguishing the human or mouse origin of genes, thus enabling the separation of the bidirectional cross-talk between the TME and malignant cells. We demonstrate that depleting VDAC1 in cancer cells led to metabolic reprogramming, tumor regression, and the disruption of tumor–host interactions. This was reflected in the altered expression of a battery of genes associated with TME, including those involved in extracellular matrix organization and structure, matrix-related peptidases, angiogenesis, intercellular interacting proteins, integrins, and growth factors associated with stromal activities. We show that metabolic rewiring upon mitochondrial VDAC1 silencing in cancer cells affected several components of the TME, such as structural protein matrix metalloproteinases and Lox, and elicited a stromal response resembling the reaction to a foreign body in wound healing. As tumor progression requires a cooperative interplay between the host and cancer cells, and the ECM is intensively remodeled during cancer progression, VDAC1 depletion induced metabolic reprogramming that targeted both tumor cells and resulted in the alteration of the whole spectrum of TME-related genes, affecting the reciprocal feedback between ECM molecules, host cells, and cancer cells. Thus, VDAC1 depletion using si-VDAC1 represents therapeutic potential, inhibiting cancer cell proliferation and also inducing the modulation of TME components, which influences cancer progression, migration, and invasion.

High glucose induced c-Met activation promotes aggressive phenotype and regulates expression of glucose metabolism genes in HCC cells

Hepatocellular carcinoma (HCC) is strongly associated with metabolic dysregulations/deregulations and hyperglycemia is a common metabolic disturbance in metabolic diseases. Hyperglycemia is defined to promote epithelial to mesenchymal transition (EMT) of cancer cells in various cancers but its molecular contribution to HCC progression and aggressiveness is relatively unclear. In this study, we analyzed the molecular mechanisms behind the hyperglycemia-induced EMT in HCC cell lines. Here, we report that high glucose promotes EMT through activating c-Met receptor tyrosine kinase via promoting its ligand-independent homodimerization. c-Met activation is critical for high glucose induced acquisition of mesenchymal phenotype, survival under high glucose stress and reprogramming of cellular metabolism by modulating glucose metabolism gene expression to promote aggressiveness in HCC cells. The crucial role of c-Met in high glucose induced EMT and aggressiveness may be the potential link between metabolic syndrome-related hepatocarcinogenesis and/or HCC progression. Considering c-Met inhibition in hyperglycemic patients would be an important complementary strategy for therapy that favors sensitization of HCC cells to therapeutics.

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.

The harsh microenvironment in early breast cancer selects for a Warburg phenotype

Glucose is converted to energy through “fermentation” or “oxidation.” Generally, if oxygen is available, cells will oxidize glucose to CO₂ because it is more efficient than fermentation, which produces lactic acid. But Warburg noted that cancers ferment glucose at a “remarkable” rate even if O₂ is available! This “Warburg Effect” is still misunderstood because it doesn’t make sense that a cell would ferment glucose when it could get much more energy by oxidizing it. The current paper goes to the heart of this problem by defining the microenvironmental conditions that exist in early cancers that would select for a Warburg Effect. This is important because such cells are much more aggressive and like to lead to cancers that are lethal.

The harsh microenvironment of ductal carcinoma in situ (DCIS) exerts strong evolutionary selection pressures on cancer cells. We hypothesize that the poor metabolic conditions near the ductal center foment the emergence of a Warburg Effect (WE) phenotype, wherein cells rapidly ferment glucose to lactic acid, even in normoxia. To test this hypothesis, we subjected low-glycolytic breast cancer cells to different microenvironmental selection pressures using combinations of hypoxia, acidosis, low glucose, and starvation for many months and isolated single clones for metabolic and transcriptomic profiling. The two harshest conditions selected for constitutively expressed WE phenotypes. RNA sequencing analysis of WE clones identified the transcription factor KLF4 as potential inducer of the WE phenotype. In stained DCIS samples, KLF4 expression was enriched in the area with the harshest microenvironmental conditions. We simulated in vivo DCIS phenotypic evolution using a mathematical model calibrated from the in vitro results. The WE phenotype emerged in the poor metabolic conditions near the necrotic core. We propose that harsh microenvironments within DCIS select for a WE phenotype through constitutive transcriptional reprogramming, thus conferring a survival advantage and facilitating further growth and invasion.

Polyphenolic Proanthocyanidin-B2 suppresses proliferation of liver cancer cells and hepatocellular carcinogenesis through directly binding and inhibiting AKT activity

The well-documented anticarcinogenic properties of natural polyphenolic proanthocyanidins (OPC) have been primarily attributed to their antioxidant and anti-inflammatory potency. Emerging evidence suggests that OPC may target canonical oncogenic pathways, including PI3K/AKT; however, the underlying mechanism and therapeutic potential remain elusive. Here we identify that proanthocyanidin B2 (OPC-B2) directly binds and inhibits AKT activity and downstream signalling, thereby suppressing tumour cell proliferation and metabolism in vitro and in a xenograft and diethyl-nitrosamine (DEN)-induced hepatocellular carcinoma (HCC) mouse models. We further find that OPC-B2 binds to the catalytic and regulatory PH domains to lock the protein in a closed conformation, similar to the well-studied AKT allosteric inhibitor MK-2206. Molecular docking and dynamic simulation suggest that Lys297 and Arg86 are critical sites of OPC-B2 binding; mutation of Lys297 or Arg86 to alanine completely abolishes the antitumor effects of OPC-B2 but not MK-2206. Together, our study reveals that OPC-B2 is a novel allosteric AKT inhibitor with potent anti-tumour efficacy beyond its antioxidant and anti-inflammatory properties.

Delicate Balances in Cancer Chemotherapy: Modeling Immune Recruitment and Emergence of Systemic Drug Resistance

Metronomic chemotherapy can drastically enhance immunogenic tumor cell death. However, the mechanisms responsible are still incompletely understood. Here, we develop a mathematical model to elucidate the underlying complex interactions between tumor growth, immune system activation, and therapy-mediated immunogenic cell death. Our model is conceptually simple, yet it provides a surprisingly excellent fit to empirical data obtained from a GL261 SCID mouse glioma model treated with cyclophosphamide on a metronomic schedule. The model includes terms representing immune recruitment as well as the emergence of drug resistance during prolonged metronomic treatments. Strikingly, a single fixed set of parameters, adjusted neither for individuals nor for drug schedule, recapitulates experimental data across various drug regimens remarkably well, including treatments administered at intervals ranging from 6 to 12 days. Additionally, the model predicts peak immune activation times, rediscovering experimental data that had not been used in parameter fitting or in model construction. Notably, the validated model suggests that immunostimulatory and immunosuppressive intermediates are responsible for the observed phenomena of resistance and immune cell recruitment, and thus for variation of responses with respect to different schedules of drug administration.

Characterizing the Motility of Chemotherapeutics-Treated Acute Lymphoblastic Leukemia Cells by Time-Lapse Imaging

Drug resistance is an obstacle in the therapy of acute lymphoblastic leukemia (ALL). Whether the physical properties such as the motility of the cells contribute to the survival of ALL cells after drug treatment has recently been of increasing interest, as they could potentially allow the metastasis of solid tumor cells and the migration of leukemia cells. We hypothesized that chemotherapeutic treatment may alter these physical cellular properties. To investigate the motility of chemotherapeutics-treated B-cell ALL (B-ALL) cells, patient-derived B-ALL cells were treated with chemotherapy for 7 days and left for 12 h without chemotherapeutic treatment. Two parameters of motility were studied, velocity and migration distance, using a time-lapse imaging system. The study revealed that compared to non-chemotherapeutically treated B-ALL cells, B-ALL cells that survived chemotherapy treatment after 7 days showed reduced motility. We had previously shown that Tysabri and P5G10, antibodies against the adhesion molecules integrins α4 and α6, respectively, may overcome drug resistance mediated through leukemia cell adhesion to bone marrow stromal cells. Therefore, we tested the effect of integrin α4 or α6 blockade on the motility of chemotherapeutics-treated ALL cells. Only integrin α4 blockade decreased the motility and velocity of two chemotherapeutics-treated ALL cell lines. Interestingly, integrin α6 blockade did not affect the velocity of chemoresistant ALL cells. This study explores the physical properties of the movements of chemoresistant B-ALL cells and highlights a potential link to integrins. Further studies to investigate the underlying mechanism are warranted.

Reactive Oxygen Species, Metabolic Plasticity, and Drug Resistance in Cancer

The metabolic abnormality observed in tumors is characterized by the dependence of cancer cells on glycolysis for their energy requirements. Cancer cells also exhibit a high level of reactive oxygen species (ROS), largely due to the alteration of cellular bioenergetics. A highly coordinated interplay between tumor energetics and ROS generates a powerful phenotype that provides the tumor cells with proliferative, antiapoptotic, and overall aggressive characteristics. In this review article, we summarize the literature on how ROS impacts energy metabolism by regulating key metabolic enzymes and how metabolic pathways e.g., glycolysis, PPP, and the TCA cycle reciprocally affect the generation and maintenance of ROS homeostasis. Lastly, we discuss how metabolic adaptation in cancer influences the tumor’s response to chemotherapeutic drugs. Though attempts of targeting tumor energetics have shown promising preclinical outcomes, the clinical benefits are yet to be fully achieved. A better understanding of the interaction between metabolic abnormalities and involvement of ROS under the chemo-induced stress will help develop new strategies and personalized approaches to improve the therapeutic efficiency in cancer patients.

Radioiodination of Pimonidazole as a Novel Theranostic Hypoxia Probe

BACKGROUND

Tumors are defined as abnormal tissue masses, and one of the most important factors leading to the growth of these abnormal tissue masses is Vascular Endothelial Growth Factor, which stimulates angiogenesis by releasing cells under hypoxic conditions. Hypoxia has a vital role in cancer therapy, thus it is important to monitor hypoxia. The hypoxia marker Pimonidazole (PIM) is a candidate biomarker of cancer aggressiveness.

OBJECTIVE

The study aimed to perform radioiodination of PIM with Iodine-131 (¹³¹I) to join a theranostic approach. For this purpose, PIM was derived as PIM-TOS to be able to be radioiodinated.

METHODS

PIM was derived via a tosylation reaction. Derivatization product (PIM-TOS) was radioiodinated by using iodogen method and was analyzed by High-Performance Liquid Chromatography and Liquid chromatography-mass spectrometry. Thin layer radiochromatography was utilized for its quality control studies.

RESULTS

PIM was derived successfully after the tosylation reaction. The radioiodination yield of PIM-TOS was over 85%.

CONCLUSION

In the current study, radioiodination potential of PIM with ¹³¹I, as a potential theranostic hypoxia agent was investigated. Further experimental studies should be performed for developing a novel hypoxia probe including theranostics approaches.

Causes and Consequences of Variable Tumor Cell Metabolism on Heritable Modifications and Tumor Evolution

When cancer research advanced into the post-genomic era, it was widely anticipated that the sought-after cure will be delivered promptly. Instead, it became apparent that an understanding of cancer genomics, alone, is unable to translate the wealth of information into successful cures. While gene sequencing has significantly improved our understanding of the natural history of cancer and identified candidates for therapeutic targets, it cannot predict the impact of the biological response to therapies. Hence, patients with a common mutational profile may respond differently to the same therapy, due in part to different microenvironments impacting on gene regulation. This complexity arises from a feedback circuit involving epigenetic modifications made to genes by the metabolic byproducts of cancer cells. New insights into epigenetic mechanisms, activated early in the process of carcinogenesis, have been able to describe phenotypes which cannot be inferred from mutational analyses per se. Epigenetic changes can propagate throughout a tumor via heritable modifications that have long-lasting consequences on ensuing phenotypes. Such heritable epigenetic changes can be evoked profoundly by cancer cell metabolites, which then exercise a broad remit of actions across all stages of carcinogenesis, culminating with a meaningful impact on the tumor's response to therapy. This review outlines some of the cross-talk between heritable epigenetic changes and tumor cell metabolism, and the consequences of such changes on tumor progression.

PKM2: A Potential Regulator of Rheumatoid Arthritis via Glycolytic and Non-Glycolytic Pathways

Immunometabolism provides a new perspective on the pathogenesis of rheumatoid arthritis (RA). In recent years, there have been investigations focusing on the role of intracellular glucose metabolism in the pathogenesis of RA. Previous studies have shown that glycolysis of synovial tissue is increased in RA patients, while glycolysis inhibitors can significantly inhibit synovitis. Pyruvate kinase (PK) is a key enzyme in glycolysis, catalyzing the final rate-limiting step in the process. An isoform of PK, PKM2, provides favorable conditions for the survival of tumor cells via its glycolytic or non-glycolytic functions and has become a potential therapeutic target in tumors. RA synovium has the characteristic of tumor-like growth, and, moreover, increased expression of PKM2 was identified in the synovial tissue of RA patients in recent studies, indicating the underlying role of PKM2 in RA. PKM2 has potential value as a new therapeutic target or biomarker for RA, but its exact role in RA remains unclear. In this review, the properties of PKM2 and existing research concerning PKM2 and RA are thoroughly reviewed and summarized, and the possible role and mechanism of PKM2 in RA are discussed.

In vivo 13 C and 1 H-[13 C] MRS studies of neuroenergetics and neurotransmitter cycling, applications to neurological and psychiatric disease and brain cancer

In the last 25 years ¹³ C MRS has been established as the only noninvasive method for measuring glutamate neurotransmission and cell specific neuroenergetics. Although technically and experimentally challenging ¹³ C MRS has already provided important new information on the relationship between neuroenergetics and neuronal function, the high energy cost of brain function in the resting state and the role of altered neuroenergetics and neurotransmitter cycling in disease. In this paper we review the metabolic and neurotransmitter pathways that can be measured by ¹³ C MRS and key findings on the linkage between neuroenergetics, neurotransmitter cycling, and brain function. Applications of ¹³ C MRS to neurological and psychiatric disease as well as brain cancer are reviewed. Recent technological developments that may help to overcome spatial resolution and brain coverage limitations of ¹³ C MRS are discussed.

Immunity, Hypoxia, and Metabolism-the Ménage à Trois of Cancer: Implications for Immunotherapy

It is generally accepted that metabolism is able to shape the immune response. Only recently we are gaining awareness that the metabolic crosstalk between different tumor compartments strongly contributes to the harsh tumor microenvironment (TME) and ultimately impairs immune cell fitness and effector functions. The major aims of this review are to provide an overview on the immune system in cancer; to position oxygen shortage and metabolic competition as the ground of a restrictive TME and as important players in the anti-tumor immune response; to define how immunotherapies affect hypoxia/oxygen delivery and the metabolic landscape of the tumor; and vice versa, how oxygen and metabolites within the TME impinge on the success of immunotherapies. By analyzing preclinical and clinical endeavors, we will discuss how a metabolic characterization of the TME can identify novel targets and signatures that could be exploited in combination with standard immunotherapies and can help to predict the benefit of new and traditional immunotherapeutic drugs.

Dendritic Polyglycerol-Derived Nano-Architectures as Delivery Platforms of Gemcitabine for Pancreatic Cancer

Dendritic polyglycerol-co-polycaprolactone (PG-co-PCL)-derived block copolymers are synthesized and explored as nanoscale drug delivery platforms for a chemotherapeutic agent, gemcitabine (GEM), which is the cornerstone of therapy for pancreatic ductal adenocarcinoma (PDAC). Current treatment strategies with GEM result in suboptimal therapeutic outcome owing to microenvironmental resistance and rapid metabolic degradation of GEM. To address these challenges, physicochemical and cell-biological properties of both covalently conjugated and non-covalently stabilized variants of GEM-containing PG-co-PCL architectures have been evaluated. Self-assembly behavior, drug loading and release capacity, cytotoxicity, and cellular uptake properties of these constructs in monolayer and in spheroid cultures of PDAC cells are investigated. To realize the covalently conjugated carrier systems, GEM, in conjunction with a tertiary amine, is attached to the polycarbonate block grafted from the PG-co-PCL core. It is observed that pH-dependent ionization properties of these amine side-chains direct the formation of self-assembly of block copolymers in the form of nanoparticles. For non-covalent encapsulation, a facile "solvent-shifting" technique is adopted. Fabrication techniques are found to control colloidal and cellular properties of GEM-loaded nanoconstructs. The feasibility and potential of these newly developed architectures for designing carrier systems for GEM to achieve augmented prognosis for pancreatic cancer are reported.

Proteomics-Metabolomics Combined Approach Identifies Peroxidasin as a Protector against Metabolic and Oxidative Stress in Prostate Cancer

Peroxidasin (PXDN), a human homolog of Drosophila PXDN, belongs to the family of heme peroxidases and has been found to promote oxidative stress in cardiovascular tissue, however, its role in prostate cancer has not been previously elucidated. We hypothesized that PXDN promotes prostate cancer progression via regulation of metabolic and oxidative stress pathways. We analyzed PXDN expression in prostate tissue by immunohistochemistry and found increased PXDN expression with prostate cancer progression as compared to normal tissue or cells. PXDN knockdown followed by proteomic analysis revealed an increase in oxidative stress, mitochondrial dysfunction and gluconeogenesis pathways. Additionally, Liquid Chromatography with tandem mass spectrometry (LC-MS/MS)-based metabolomics confirmed that PXDN knockdown induced global reprogramming associated with increased oxidative stress and decreased nucleotide biosynthesis. We further demonstrated that PXDN knockdown led to an increase in reactive oxygen species (ROS) associated with decreased cell viability and increased apoptosis. Finally, PXDN knockdown decreased colony formation on soft agar. Overall, the data suggest that PXDN promotes progression of prostate cancer by regulating the metabolome, more specifically, by inhibiting oxidative stress leading to decreased apoptosis. Therefore, PXDN may be a biomarker associated with prostate cancer and a potential therapeutic target.

Correlation and expression analysis of hypoxia-inducible factor 1α, glucose transporter 1 and lactate dehydrogenase 5 in human gastric cancer

The development and identification of novel potential targeting sites for intervention therapy are essential in the search for improved treatment methods for gastric cancer (GC). Previously, it has been reported that hypoxia inducible factor-1α (HIF-1α) is a potential target gene involved in the endogenous hypoxic response and bioenergetic metabolism of GC cells. In the present study, with the assumption of a close interplay among HIF-1α, glucose transporter 1 (GLUT1) and lactate dehydrogenase-5 (LDH-5), 85 patients with GC were recruited and the protein and gene expression levels of HIF-1α, GLUT1 and LDH-5 in tumor tissues were evaluated in order to assess clinical correlations and co-expression patterns, using Immunohistochemical staining and reverse transcription-quantitative polymerase chain reaction. The results demonstrated that the protein and gene expression levels of HIF-1α were significantly associated with the depth of invasion, nodal metastasis, clinical stage, differentiation and distant metastasis. Consistent with the protein expression results, the mRNA expression levels of the genes coding for GLUT1 and LDH-5 were clearly associated with tumor size, depth of invasion, distant metastasis, clinical stage and differentiation. Correlation analysis of HIF-1α with GLUT1 and LDH-5 at the protein and mRNA expression levels in gastric carcinoma indicated that HIF-1α expression was positively correlated with the expression of GLUT1 (P<0.01, r=0.765 for mRNA expression; P<0.01, r=0.697 for protein expression) and LDH-5 (P<0.01, r=0.892 for mRNA expression; P<0.01, r=0.783 for protein expression) at the mRNA and protein levels. Therefore, it may be concluded that HIF-1α, GLUT1 and LDH-5 are potential target genes involved in the endogenous tumor response to hypoxia and the inhibition of tumor energy metabolism, highlighting a novel therapeutic target for GC.

Acidosis and cancer: from mechanism to neutralization

The extracellular pH of solid tumors is unequivocally acidic due to a combination of high rates of lactic acid production (a consequence of fermentative glycolytic metabolism) and poor perfusion. This has been documented by us and others in a wide variety of solid tumor models, primarily using magnetic resonance spectroscopic imaging (MRSI). This acidity contributes to tumor progression by inducing genome instability, promoting local invasion and metastases, inhibiting anti-tumor immunity, and conferring resistance to chemo- and radio-therapies. Systemic buffer therapies can neutralize tumor acidity and has been shown to inhibit local invasion and metastasis and improve immune surveillance in a variety of cancer model systems. This review will revisit the causes and consequences of acidosis by summarizing strategies used by cancer cells to adapt to acidosis, and how this acidity associated with carcinogenesis, metastasis, and immune function. Finally, this review will discuss how neutralization of acidity can be used to inhibit carcinogenesis and metastasis and improve anti-cancer immunotherapy.

Acidification of Tumor at Stromal Boundaries Drives Transcriptome Alterations Associated with Aggressive Phenotypes

Acidosis is a fundamental feature of the tumor microenvironment, which directly regulates tumor cell invasion by affecting immune cell function, clonal cell evolution, and drug resistance. Despite the important association of tumor microenvironment acidosis with tumor cell invasion, relatively little is known regarding which areas within a tumor are acidic and how acidosis influences gene expression to promote invasion. Here, we injected a labeled pH-responsive peptide to mark acidic regions within tumors. Surprisingly, acidic regions were not restricted to hypoxic areas and overlapped with highly proliferative, invasive regions at the tumor-stroma interface, which were marked by increased expression of matrix metalloproteinases and degradation of the basement membrane. RNA-seq analysis of cells exposed to low pH conditions revealed a general rewiring of the transcriptome that involved RNA splicing and enriched for targets of RNA binding proteins with specificity for AU-rich motifs. Alternative splicing of Mena and CD44, which play important isoform-specific roles in metastasis and drug resistance, respectively, was sensitive to histone acetylation status. Strikingly, this program of alternative splicing was reversed in vitro and in vivo through neutralization experiments that mitigated acidic conditions. These findings highlight a previously underappreciated role for localized acidification of tumor microenvironment in the expression of an alternative splicing-dependent tumor invasion program. SIGNIFICANCE: This study expands our understanding of acidosis within the tumor microenvironment and indicates that acidosis induces potentially therapeutically actionable changes to alternative splicing.

Emerging Technologies to Image Tissue Metabolism

Due to the implication of altered metabolism in a large spectrum of tissue function and disease, assessment of metabolic processes becomes essential in managing health. In this regard, imaging can play a critical role in allowing observation of biochemical and physiological processes. Nuclear imaging methods, in particular positron emission tomography, have been widely employed for imaging metabolism but are mainly limited by the use of ionizing radiation and the sensing of only one parameter at each scanning session. Observations in healthy individuals or longitudinal studies of disease could markedly benefit from non-ionizing, multi-parameter imaging methods. We therefore focus this review on progress with the non-ionizing radiation methods of MRI, hyperpolarized magnetic resonance and magnetic resonance spectroscopy, chemical exchange saturation transfer, and emerging optoacoustic (photoacoustic) imaging. We also briefly discuss the role of nuclear and optical imaging methods for research and clinical protocols.

Enhanced nitric oxide signaling amplifies vasorelaxation of human colon cancer feed arteries

Inadequate perfusion of solid cancer tissue results in low local nutrient and oxygen levels and accumulation of acidic waste products. Previous investigations have focused primarily on tumor blood vessel architecture, and we lack information concerning functional differences between arteries that deliver blood to solid cancer tissue versus normal tissue. Here, we use isometric myography to study resistance-sized arteries from human primary colon adenocarcinomas and matched normal colon tissue. Vasocontraction of colon cancer feed arteries in response to endothelin-1 and thromboxane stimulation is attenuated compared with normal colon arteries despite similar wall dimensions and comparable contractions to arginine vasopressin and K+-induced depolarization. Acetylcholine-induced vasorelaxation and endothelial NO synthase expression are increased in colon cancer feed arteries compared with normal colon arteries, whereas vasorelaxation to exogenous NO donors is unaffected. In congruence, the differences in vasorelaxant and vasocontractile function between colon cancer feed arteries and normal colon arteries decrease after NO synthase inhibition. Rhythmic oscillations in vascular tone, known as vasomotion, are of lower amplitude but similar frequency in colon cancer feed arteries compared with normal colon arteries. In conclusion, higher NO synthase expression and elevated NO signaling amplify vasorelaxation and attenuate vasocontraction of human colon cancer feed arteries. We propose that enhanced endothelial function augments tumor perfusion and represents a potential therapeutic target.

NEW & NOTEWORTHY Local vascular resistance influences tumor perfusion. Arteries supplying human colonic adenocarcinomas show enhanced vasorelaxation and reduced vasocontraction mainly due to elevated nitric oxide-mediated signaling. Rhythmic oscillations in tone, known as vasomotion, are attenuated in colon cancer feed arteries.

Magmas inhibition as a potential treatment strategy in malignant glioma

PURPOSE

Magmas (mitochondria-associated protein involved in granulocyte-macrophage colony-stimulating factor signal transduction) is a nuclear gene that encodes the mitochondrial import inner membrane translocase subunit Tim16. Magmas is highly conserved, ubiquitously expressed in mammalian cells, and is essential for cell viability. Magmas expression levels are increased in prostate cancers and pituitary adenomas. Moreover, silencing Magmas by RNAi sensitizes pituitary adenoma cells to pro-apoptotic stimuli and induces a G0/G1 accumulation. The aim of this study was to examine whether inhibition of Magmas by small molecule inhibitors could be beneficial for the treatment of malignant gliomas.

METHODS

We evaluated the expression of Magmas in patient-derived glioblastoma tissue samples and xenograft models. We studied the feasibility of a small molecule Magmas inhibitor (BT#9) as a therapeutic agent in stable human glioma cell lines and high-grade patient derived glioma stem-like cells.

RESULTS

Magmas was overexpressed in tissue sections from glioma patients and xenografts. In vivo studies revealed that BT#9 could cross the blood-brain barrier in the animal model. Magmas inhibition by BT#9 in glioma cell lines significantly decreased cell proliferation, induced apoptosis along with vacuole formation, and blocked migration and invasion. In addition, BT#9 treatment decreased the respiratory function of glioma cells, supporting the role that Magmas serves as a reactive oxygen species regulator.

CONCLUSIONS

This is the first study on the role of Magmas in glioma. Our findings suggest that Magmas plays a key role in glioma cell survival and targeting Magmas by small molecule inhibitors may be a therapeutic strategy in gliomas.

Transcription Factor YY1 Promotes Cell Proliferation by Directly Activating the Pentose Phosphate Pathway

Tumor cells alter their metabolism to meet their demand for macromolecules and support a high rate of proliferation as well as cope with oxidative stress. The transcription factor yin yang 1 (YY1) is upregulated in various types of tumors and is crucial for tumor cell proliferation and metastasis. However, its role in tumor cell metabolic reprogramming is poorly understood. Here, we show that YY1 alters tumor cell metabolism by activating glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme in the pentose phosphate pathway. By stimulating the pentose phosphate pathway, YY1 enhanced production of nucleotides and DNA synthesis, decreased intracellular reactive oxygen species levels, and promoted antioxidant defense by supplying increased reducing power in the form of NADPH. Importantly, YY1-mediated regulation of the pentose phosphate pathway in tumor cells occurred not through p53, but rather through direct activation of G6PD transcription by YY1. Regulation of pentose phosphate pathway activity through G6PD was strongly related to YY1-induced proliferation of tumor cells and tumorigenesis. Together, our results describe a novel role for YY1 in regulating G6PD in a p53-independent manner, which links its function in tumorigenesis to metabolic reprogramming in tumor cells.Significance: This study reveals a novel role for YY1 in regulating G6PD and activating the pentose phosphate pathway, linking its function in tumorigenesis to metabolic reprogramming. Cancer Res; 78(16); 4549-62. ©2018 AACR.

Modeling triple-negative breast cancer heterogeneity: Effects of stromal macrophages, fibroblasts and tumor vasculature

A hallmark of breast tumors is its spatial heterogeneity that includes its distribution of cancer stem cells and progenitor cells, but also heterogeneity in the tumor microenvironment. In this study we focus on the contributions of stromal cells, specifically macrophages, fibroblasts, and endothelial cells on tumor progression. We develop a computational model of triple-negative breast cancer based on our previous work and expand it to include macrophage infiltration, fibroblasts, and angiogenesis. In vitro studies have shown that the secretomes of tumor-educated macrophages and fibroblasts increase both the migration and proliferation rates of triple-negative breast cancer cells. In vivo studies also demonstrated that blocking signaling of selected secreted factors inhibits tumor growth and metastasis in mouse xenograft models. We investigate the influences of increased migration and proliferation rates on tumor growth, the effect of the presence on fibroblasts or macrophages on growth and morphology, and the contributions of macrophage infiltration on tumor growth. We find that while the presence of macrophages increases overall tumor growth, the increase in macrophage infiltration does not substantially increase tumor growth and can even stifle tumor growth at excessive rates.

α-cyano-4-hydroxycinnamate impairs pancreatic cancer cells by stimulating the p38 signaling pathway

Multiple studies are currently targeting dysregulated cancer cell metabolism with distinct combinations of inhibitors. In this study, we evaluated in pancreatic cancer cells metformin, which blocks oxidative phosphorylation, in combination with α-cyano-4-hydroxycinnamate, which has been reported to inhibit the export of lactate from the cytosol. The combination of metformin with α-cyano-4-hydroxycinnamate had a major inhibitory effect on the migration of 6606PDA cells. Monotherapy with α-cyano-4-hydroxycinnamate and especially the combination with metformin also caused significant inhibition of cell proliferation and induced cell death. α-cyano-4-hydroxycinnamate in combination with metformin reduced the export of lactate significantly, whereas α-cyano-4-hydroxycinnamate monotherapy only modestly influenced lactate export. None of these two drugs inhibited the expression of distinct glycolytic enzymes. Interestingly, α-cyano-4-hydroxycinnamate rather inhibited the ERK and very strongly stimulated the p38 signaling pathway in 6606PDA as well as in 7265PDA cells. In addition, the inhibition of the p38 signaling pathway by PH-797804 partially reversed the effect of α-cyano-4-hydroxycinnamate on cell apoptosis in both cell lines. We conclude that α-cyano-4-hydroxycinnamate monotherapy and especially the combinatorial therapy with metformin has strong anti-cancerous effects. α-cyano-4-hydroxycinnamate causes cancer cell apoptosis by a novel mechanism for this drug, namely the stimulation of the p38 signaling pathway.

Mitochondrial Lon is over-expressed in high-grade gliomas, and mediates hypoxic adaptation: potential role of Lon as a therapeutic target in glioma

Mitochondrial dysfunction is a hallmark of cancer biology. Tumor mitochondrial metabolism is characterized by an abnormal ability to function in scarce oxygen conditions through glycolysis (the Warburg effect), and accumulation of mitochondrial DNA defects are present in both hereditary neoplasia and sporadic cancers. Mitochondrial Lon is a major regulator of mitochondrial metabolism and the mitochondrial response to free radical damage, and plays an essential role in the maintenance and repair of mitochondrial DNA. Despite these critical cellular functions of Lon, very little has been reported regarding its role in glioma. Lon expression in gliomas and its relevance with patient survival was examined using published databases and human tissue sections. The effect of Lon in glioma biology was investigated through siRNA targeting Lon. We also tested the in vitro antitumor activity of Lon inhibitor, CC4, in the glioma cell lines D-54 and U-251. High Lon expression was associated with high glioma tumor grade and poor patient survival. While Lon expression was elevated in response to a variety of stimuli, Lon knockdown in glioma cell lines decreased cell viability under normal conditions, and dramatically impaired glioma cell survival under hypoxic conditions. Furthermore, the Lon inhibitor, CC4, efficiently prohibited glioma cell proliferation and synergistically enhanced the therapeutic efficacy of the chemotherapeutic agents, temozolomide (TMZ) and cisplatin. We demonstrate that Lon plays a key role in glioma cell hypoxic survival and mitochondrial respiration, and propose Lon as a promising therapeutic target in the treatment of malignant gliomas.

Cancer and Exercise: Warburg Hypothesis, Tumour Metabolism and High-Intensity Anaerobic Exercise

There is ample evidence that regular moderate to vigorous aerobic physical activity is related to a reduced risk for various forms of cancer to suggest a causal relationship. Exercise is associated with positive changes in fitness, body composition, and physical functioning as well as in patient-reported outcomes such as fatigue, sleep quality, or health-related quality of life. Emerging evidence indicates that exercise may also be directly linked to the control of tumour biology through direct effects on tumour-intrinsic factors. Beside a multitude of effects of exercise on the human body, one underscored effect of exercise training is to target the specific metabolism of tumour cells, namely the Warburg-type highly glycolytic metabolism. Tumour metabolism as well as the tumour–host interaction may be selectively influenced by single bouts as well as regularly applied exercise, dependent on exercise intensity, duration, frequency and mode. High-intensity anaerobic exercise was shown to inhibit glycolysis and some studies in animals showed that effects on tumour growth might be stronger compared with moderate-intensity aerobic exercise. High-intensity exercise was shown to be safe in patients; however, it has to be applied carefully with an individualized prescription of exercise.

Lactate metabolism: historical context, prior misinterpretations, and current understanding

Lactate (La^-) has long been at the center of controversy in research, clinical, and athletic settings. Since its discovery in 1780, La^- has often been erroneously viewed as simply a hypoxic waste product with multiple deleterious effects. Not until the 1980s, with the introduction of the cell-to-cell lactate shuttle did a paradigm shift in our understanding of the role of La^- in metabolism begin. The evidence for La^- as a major player in the coordination of whole-body metabolism has since grown rapidly. La^- is a readily combusted fuel that is shuttled throughout the body, and it is a potent signal for angiogenesis irrespective of oxygen tension. Despite this, many fundamental discoveries about La^- are still working their way into mainstream research, clinical care, and practice. The purpose of this review is to synthesize current understanding of La^- metabolism via an appraisal of its robust experimental history, particularly in exercise physiology. That La^- production increases during dysoxia is beyond debate, but this condition is the exception rather than the rule. Fluctuations in blood [La^-] in health and disease are not typically due to low oxygen tension, a principle first demonstrated with exercise and now understood to varying degrees across disciplines. From its role in coordinating whole-body metabolism as a fuel to its role as a signaling molecule in tumors, the study of La^- metabolism continues to expand and holds potential for multiple clinical applications. This review highlights La^-'s central role in metabolism and amplifies our understanding of past research.

Mapping Extracellular pH of Gliomas in Presence of Superparamagnetic Nanoparticles: Towards Imaging the Distribution of Drug-Containing Nanoparticles and Their Curative Effect on the Tumor Microenvironment

Since brain's microvasculature is compromised in gliomas, intravenous injection of tumor-targeting nanoparticles containing drugs (D-NPs) and superparamagnetic iron oxide (SPIO-NPs) can deliver high payloads of drugs while allowing MRI to track drug distribution. However, therapeutic effect of D-NPs remains poorly investigated because superparamagnetic fields generated by SPIO-NPs perturb conventional MRI readouts. Because extracellular pH (pH_e) is a tumor hallmark, mapping pH_e is critical. Brain pH_e is measured by biosensor imaging of redundant deviation in shifts (BIRDS) with lanthanide agents, by detecting paramagnetically shifted resonances of nonexchangeable protons on the agent. To test the hypothesis that BIRDS-based pH_e readout remains uncompromised by presence of SPIO-NPs, we mapped pH_e in glioma-bearing rats before and after SPIO-NPs infusion. While SPIO-NPs accumulation in the tumor enhanced MRI contrast, the pH_e inside and outside the MRI-defined tumor boundary remained unchanged after SPIO-NPs infusion, regardless of the tumor type (9L versus RG2) or agent injection method (renal ligation versus coinfusion with probenecid). These results demonstrate that we can simultaneously and noninvasively image the specific location and the healing efficacy of D-NPs, where MRI contrast from SPIO-NPs can track their distribution and BIRDS-based pH_e can map their therapeutic impact.

Probing the metabolic phenotype of breast cancer cells by multiple tracer stable isotope resolved metabolomics

Breast cancers vary by their origin and specific set of genetic lesions, which gives rise to distinct phenotypes and differential response to targeted and untargeted chemotherapies. To explore the functional differences of different breast cell types, we performed Stable Isotope Resolved Metabolomics (SIRM) studies of one primary breast (HMEC) and three breast cancer cells (MCF-7, MDAMB-231, and ZR75-1) having distinct genotypes and growth characteristics, using 13C6-glucose, 13C-1+2-glucose, 13C5,15N2-Gln, 13C3-glycerol, and 13C8-octanoate as tracers. These tracers were designed to probe the central energy producing and anabolic pathways (glycolysis, pentose phosphate pathway, Krebs Cycle, glutaminolysis, nucleotide synthesis and lipid turnover). We found that glycolysis was not associated with the rate of breast cancer cell proliferation, glutaminolysis did not support lipid synthesis in primary breast or breast cancer cells, but was a major contributor to pyrimidine ring synthesis in all cell types; anaplerotic pyruvate carboxylation was activated in breast cancer versus primary cells. We also found that glucose metabolism in individual breast cancer cell lines differed between in vitro cultures and tumor xenografts, but not the metabolic distinctions between cell lines, which may reflect the influence of tumor architecture/microenvironment.

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.

The emerging role and targetability of the TCA cycle in cancer metabolism

The tricarboxylic acid (TCA) cycle is a central route for oxidative phosphorylation in cells, and fulfills their bioenergetic, biosynthetic, and redox balance requirements. Despite early dogma that cancer cells bypass the TCA cycle and primarily utilize aerobic glycolysis, emerging evidence demonstrates that certain cancer cells, especially those with deregulated oncogene and tumor suppressor expression, rely heavily on the TCA cycle for energy production and macromolecule synthesis. As the field progresses, the importance of aberrant TCA cycle function in tumorigenesis and the potentials of applying small molecule inhibitors to perturb the enhanced cycle function for cancer treatment start to evolve. In this review, we summarize current knowledge about the fuels feeding the cycle, effects of oncogenes and tumor suppressors on fuel and cycle usage, common genetic alterations and deregulation of cycle enzymes, and potential therapeutic opportunities for targeting the TCA cycle in cancer cells. With the application of advanced technology and in vivo model organism studies, it is our hope that studies of this previously overlooked biochemical hub will provide fresh insights into cancer metabolism and tumorigenesis, subsequently revealing vulnerabilities for therapeutic interventions in various cancer types.

An agent-based model of triple-negative breast cancer: the interplay between chemokine receptor CCR5 expression, cancer stem cells, and hypoxia

Background

Triple-negative breast cancer lacks estrogen, progesterone, and HER2 receptors and is thus not possible to treat with targeted therapies for these receptors. Therefore, a greater understanding of triple-negative breast cancer is necessary for the treatment of this cancer type. In previous work from our laboratory, we found that chemokine ligand-receptor CCL5-CCR5 axis is important for the metastasis of human triple-negative breast cancer cell MDA-MB-231 to the lymph nodes and lungs, in a mouse xenograft model. We collected relevant experimental data from our and other laboratories for numbers of cancer stem cells, numbers of CCR5+ cells, and cell migration rates for different breast cancer cell lines and different experimental conditions.

Results

Using these experimental data we developed an in silico agent-based model of triple-negative breast cancer that considers surface receptor CCR5-high and CCR5-low cells and breast cancer stem cells, to predict the tumor growth rate and spatio-temporal distribution of cells in primary tumors. We find that high cancer stem cell percentages greatly increase tumor growth. We find that anti-stem cell treatment decreases tumor growth but may not lead to dormancy unless all stem cells get eliminated. We further find that hypoxia increases overall tumor growth and treatment with a CCR5 inhibitor maraviroc slightly decreases overall tumor growth. We also characterize 3D shapes of solid and invasive tumors using several shape metrics.

Conclusions

Breast cancer stem cells and CCR5+ cells affect the overall growth and morphology of breast tumors. In silico drug treatments demonstrate limited efficacy of incomplete inhibition of cancer stem cells after which tumor growth recurs, and CCR5 inhibition causes only a slight reduction in tumor growth.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-017-0445-x) contains supplementary material, which is available to authorized users.

Warburg effect-damping of electromagnetic oscillations

Mitochondrial dysfunction is a central defect in cells creating the Warburg and reverse Warburg effect cancers. However, the link between mitochondrial dysfunction and cancer has not yet been clearly explained. Decrease of mitochondrial oxidative energy production to about 50 % in comparison with healthy cells may be caused by inhibition of pyruvate transfer into mitochondrial matrix and/or disturbed H⁺ ion transfer across inner mitochondrial membrane into cytosol. Lowering of the inner membrane potential and shifting of the working point of mitochondria to high values of pH above an intermediate point causes reorganization of the ordered water layer at the mitochondrial membrane. The reorganized ordered water layers at high pH values release electrons which are transferred to the cytosol rim of the layer. The electrons damp electromagnetic activity of Warburg effect cancer cells or fibroblasts associated with reverse Warburg effect cancer cells leading to lowered electromagnetic activity, disturbed coherence, increased frequency of oscillations and decreased level of biological functions. In reverse Warburg effect cancers, associated fibroblasts supply energy-rich metabolites to the cancer cell resulting in increased power of electromagnetic field, fluctuations due to shift of oscillations to an unstable nonlinear region, decreased frequency and loss of coherence.