Mitochondrial metabolism and energy sensing in tumor progression

Peri active site catalysis of proline isomerisation is the molecular basis of allomorphy in β-phosphoglucomutase

Metabolic regulation occurs through precise control of enzyme activity. Allomorphy is a post-translational fine control mechanism where the catalytic rate is governed by a conformational switch that shifts the enzyme population between forms with different activities. β-Phosphoglucomutase (βPGM) uses allomorphy in the catalysis of isomerisation of β-glucose 1-phosphate to glucose 6-phosphate via β-glucose 1,6-bisphosphate. Herein, we describe structural and biophysical approaches to reveal its allomorphic regulatory mechanism. Binding of the full allomorphic activator β-glucose 1,6-bisphosphate stimulates enzyme closure, progressing through NAC I and NAC III conformers. Prior to phosphoryl transfer, loops positioned on the cap and core domains are brought into close proximity, modulating the environment of a key proline residue. Hence accelerated isomerisation, likely via a twisted anti/C4-endo transition state, leads to the rapid predominance of active cis-P βPGM. In contrast, binding of the partial allomorphic activator fructose 1,6-bisphosphate arrests βPGM at a NAC I conformation and phosphoryl transfer to both cis-P βPGM and trans-P βPGM occurs slowly. Thus, allomorphy allows a rapid response to changes in food supply while not otherwise impacting substantially on levels of important metabolites.

Active DNA Demethylase, TET1, Increases Oxidative Phosphorylation and Sensitizes Ovarian Cancer Stem Cells to Mitochondrial Complex I Inhibitor

Ten-eleven translocation 1 (TET1) is a methylcytosine dioxygenase involved in active DNA demethylation. In our previous study, we demonstrated that TET1 reprogrammed the ovarian cancer epigenome, increased stem properties, and activated various regulatory networks, including metabolic networks. However, the role of TET1 in cancer metabolism remains poorly understood. Herein, we uncovered a demethylated metabolic gene network, especially oxidative phosphorylation (OXPHOS). Contrary to the concept of the Warburg effect in cancer cells, TET1 increased energy production mainly using OXPHOS rather than using glycolysis. Notably, TET1 increased the mitochondrial mass and DNA copy number. TET1 also activated mitochondrial biogenesis genes and adenosine triphosphate production. However, the reactive oxygen species levels were surprisingly decreased. In addition, TET1 increased the basal and maximal respiratory capacities. In an analysis of tricarboxylic acid cycle metabolites, TET1 increased the levels of α-ketoglutarate, which is a coenzyme of TET1 dioxygenase and may provide a positive feedback loop to modify the epigenomic landscape. TET1 also increased the mitochondrial complex I activity. Moreover, the mitochondrial complex I inhibitor, which had synergistic effects with the casein kinase 2 inhibitor, affected ovarian cancer growth. Altogether, TET1-reprogrammed ovarian cancer stem cells shifted the energy source to OXPHOS, which suggested that metabolic intervention might be a novel strategy for ovarian cancer treatment.

Is There a Mitochondrial Protection via Remote Ischemic Conditioning in Settings of Anticancer Therapy Cardiotoxicity?

PURPOSE OF REVIEW

To provide an overview of (a) protective effects on mitochondria induced by remote ischemic conditioning (RIC) and (b) mitochondrial damage caused by anticancer therapy. We then discuss the available results of studies on mitochondrial protection via RIC in anticancer therapy-induced cardiotoxicity.

RECENT FINDINGS

In three experimental studies in healthy mice and pigs, there was a RIC-mediated protection against anthracycline-induced cardiotoxicity and there was some evidence of improved mitochondrial function with RIC. The RIC-mediated protection was not confirmed in the two available studies in cancer patients. In adult cancer patients, RIC was associated with an adverse outcome. There are no data on mitochondrial function in cancer patients. Studies in tumor-bearing animals are needed to determine whether RIC does not interfere with the anticancer properties of the drugs and whether RIC actually improves mitochondrial function, ultimately resulting in improved cardiac function.

CHEK2 knockout is a therapeutic target for TP53-mutated hepatocellular carcinoma

Currently, there is still a lack of novel and effective drug targets to improve the prognosis of hepatocellular carcinoma (HCC). Additionally, the role of CHEK2 in HCC has not been reported yet. The eQTLgen database and two HCC Genome-Wide Association Study (GWAS) datasets (ieu-b-4953, ICD10 C22.0) were used to find the drug target: CHEK2. Next, Colony, Edu, β-gal, and cell cycle analysis were facilitated to evaluate the role of CHEK2 knockout in HCC. In addition, Nultin-3 was added to evaluate the apoptosis of TP53-mutated HCC cells with CHEK2 knockout. Furthermore, MitoSox, electron microscopy, mitochondrial ATP, and NADH+/NADH levels were assessed in the CHEK2 knockout HCC cells with or without Metformin. Finally, cell-derived tumor xenograft was used to evaluate the role of CHEK2 knockout in vivo. We initially identified a potential drug target, CHEK2, through GWAS data analysis. Furthermore, we observed a significant upregulation of CHEK2 expression in HCC, which was found to be correlated with a poor prognosis. Subsequently, the results indicated that knocking out CHEK2 selectively affects the proliferation, cell cycle, senescence, and apoptosis of TP53-mutant HCC cells. Additionally, the introduction of Nultin-3 further intensified the functional impact on TP53-mutant cells. Then ClusterProfiler results showed high CHEK2 and TP53 mutation group was positively enriched in the mitochondrial ATP pathway. Then we used MitoSox, electron microscopy, mitochondrial ATP, and NADH + /NADH assay and found knockout of CHECK could induce the ATP pathway to inhibit the growth of HCC. Our research introduces a novel drug target for TP53-mutant HCC cells via mitochondrial ATP, addressing the limitation of Nultin-3 as a standalone treatment that does not induce tumor cell death.

Aldolase B-driven lactagenesis and CEACAM6 activation promote cell renewal and chemoresistance in colorectal cancer through the Warburg effect

Colorectal cancer (CRC) is a prevalent malignancy worldwide and is associated with a high mortality rate. Changes in bioenergy metabolism, such as the Warburg effect, are often observed in CRC. Aldolase B (ALDOB) has been identified as a potential regulator of these changes, but its exact role in CRC cell behavior and bioenergetic homeostasis is not fully understood. To investigate this, two cohorts of CRC patients were analyzed independently. The results showed that higher ALDOB expression was linked to unfavorable prognosis, increased circulating carcinoembryonic antigen (CEA) levels, and altered bioenergetics in CRC. Further analysis using cell-based assays demonstrated that ALDOB promoted cell proliferation, chemoresistance, and increased expression of CEA in CRC cells. The activation of pyruvate dehydrogenase kinase-1 (PDK1) by ALDOB-induced lactagenesis and secretion, which in turn mediated the effects on CEA expression. Secreted lactate was found to enhance lactate dehydrogenase B (LDHB) expression in adjacent cells and to be a crucial modulator of ALDOB-mediated phenotypes. Additionally, the effect of ALDOB on CEA expression was downstream of the bioenergetic changes mediated by secreted lactate. The study also identified CEA cell adhesion molecule-6 (CEACAM6) as a downstream effector of ALDOB that controlled CRC cell proliferation and chemoresistance. Notably, CEACAM6 activation was shown to enhance protein stability through lysine lactylation, downstream of ALDOB-mediated lactagenesis. The ALDOB/PDK1/lactate/CEACAM6 axis plays an essential role in CRC cell behavior and bioenergetic homeostasis, providing new insights into the involvement of CEACAM6 in CRC and the Warburg effect. These findings may lead to the development of new treatment strategies for CRC patients.

Mitochondrial dysfunction at the crossroad of cardiovascular diseases and cancer

A large body of evidence indicates the existence of a complex pathophysiological relationship between cardiovascular diseases and cancer. Mitochondria are crucial organelles whose optimal activity is determined by quality control systems, which regulate critical cellular events, ranging from intermediary metabolism and calcium signaling to mitochondrial dynamics, cell death and mitophagy. Emerging data indicate that impaired mitochondrial quality control drives myocardial dysfunction occurring in several heart diseases, including cardiac hypertrophy, myocardial infarction, ischaemia/reperfusion damage and metabolic cardiomyopathies. On the other hand, diverse human cancers also dysregulate mitochondrial quality control to promote their initiation and progression, suggesting that modulating mitochondrial homeostasis may represent a promising therapeutic strategy both in cardiology and oncology. In this review, first we briefly introduce the physiological mechanisms underlying the mitochondrial quality control system, and then summarize the current understanding about the impact of dysregulated mitochondrial functions in cardiovascular diseases and cancer. We also discuss key mitochondrial mechanisms underlying the increased risk of cardiovascular complications secondary to the main current anticancer strategies, highlighting the potential of strategies aimed at alleviating mitochondrial impairment-related cardiac dysfunction and tumorigenesis. It is hoped that this summary can provide novel insights into precision medicine approaches to reduce cardiovascular and cancer morbidities and mortalities.

Mitochondria Deregulations in Cancer Offer Several Potential Targets of Therapeutic Interventions

Mitochondria play a key role in cancer and their involvement is not limited to the production of ATP only. Mitochondria also produce reactive oxygen species and building blocks to sustain rapid cell proliferation; thus, the deregulation of mitochondrial function is associated with cancer disease development and progression. In cancer cells, a metabolic reprogramming takes place through a different modulation of the mitochondrial metabolic pathways, including oxidative phosphorylation, fatty acid oxidation, the Krebs cycle, glutamine and heme metabolism. Alterations of mitochondrial homeostasis, in particular, of mitochondrial biogenesis, mitophagy, dynamics, redox balance, and protein homeostasis, were also observed in cancer cells. The use of drugs acting on mitochondrial destabilization may represent a promising therapeutic approach in tumors in which mitochondrial respiration is the predominant energy source. In this review, we summarize the main mitochondrial features and metabolic pathways altered in cancer cells, moreover, we present the best known drugs that, by acting on mitochondrial homeostasis and metabolic pathways, may induce mitochondrial alterations and cancer cell death. In addition, new strategies that induce mitochondrial damage, such as photodynamic, photothermal and chemodynamic therapies, and the development of nanoformulations that specifically target drugs in mitochondria are also described. Thus, mitochondria-targeted drugs may open new frontiers to a tailored and personalized cancer therapy.

Control of Mitochondrial Activity by the Ubiquitin Code in Health and Cancer

Cellular homeostasis is tightly connected to the broad variety of mitochondrial functions. To stay healthy, cells need a constant supply of nutrients, energy production and antioxidants defenses, undergoing programmed death when a serious, irreversible damage occurs. The key element of a functional integration of all these processes is the correct crosstalk between cell signaling and mitochondrial activities. Once this crosstalk is interrupted, the cell is not able to communicate its needs to mitochondria, resulting in oxidative stress and development of pathological conditions. Conversely, dysfunctional mitochondria may affect cell viability, even in the presence of nutrients supply and energy production, indicating the existence of feed-back control mechanisms between mitochondria and other cellular compartments. The ubiquitin proteasome system (UPS) is a multi-step biochemical pathway that, through the conjugation of ubiquitin moieties to specific protein substrates, controls cellular proteostasis and signaling, removing damaged or aged proteins that might otherwise accumulate and affect cell viability. In response to specific needs or changed extracellular microenvironment, the UPS modulates the turnover of mitochondrial proteins, thus influencing the organelle shape, dynamics and function. Alterations of the dynamic and reciprocal regulation between mitochondria and UPS underpin genetic and proliferative disorders. This review focuses on the mitochondrial metabolism and activities supervised by UPS and examines how deregulation of this control mechanism results in proliferative disorders and cancer.

Respiratory Complex I dysfunction in cancer: from a maze of cellular adaptive responses to potential therapeutic strategies

Mitochondria act as key organelles in cellular bioenergetics and biosynthetic processes producing signals that regulate different molecular networks for proliferation and cell death. This ability is also preserved in pathologic contexts such as tumorigenesis, during which bioenergetic changes and metabolic reprogramming confer flexibility favoring cancer cell survival in a hostile microenvironment. Although different studies epitomize mitochondrial dysfunction as a protumorigenic hit, genetic ablation or pharmacological inhibition of respiratory complex I causing a severe impairment is associated with a low-proliferative phenotype. In this scenario, it must be considered that despite the initial delay in growth, cancer cells may become able to resume proliferation exploiting molecular mechanisms to overcome growth arrest. Here, we highlight the current knowledge on molecular responses activated by complex I-defective cancer cells to bypass physiological control systems and to re-adapt their fitness during microenvironment changes. Such adaptive mechanisms could reveal possible novel molecular players in synthetic lethality with complex I impairment, thus providing new synergistic strategies for mitochondrial-based anticancer therapy.

MicroRNA and Metabolic Profiling of a Primary Ovarian Neuroendocrine Carcinoma Pulmonary-Type Reveals a High Degree of Similarity with Small Cell Lung Cancer

Small cell neuroendocrine carcinoma is most frequently found in the lung (SCLC), but it has been also reported, albeit with a very low incidence, in the ovary. Here, we analyze a case of primary small cell carcinoma of the ovary of pulmonary type (SCCOPT), a rare and aggressive tumor with poor prognosis, whose biology and molecular features have not yet been thoroughly investigated. The patient affected by SCCOPT had a residual tumor following chemotherapy which displayed pronounced similarity with neuroendocrine tumors and lung cancer in terms of its microRNA expression profile and mTOR-downstream activation. By analyzing the metabolic markers of the neoplastic lesion, we established a likely glycolytic signature. In conclusion, this in-depth characterization of SCCOPT could be useful for future diagnoses, possibly aided by microRNA profiling, allowing clinicians to adopt the most appropriate therapeutic strategy.

Versatile Functional Energy Metabolism Platform Working From Research to Patient: An Integrated View of Cell Bioenergetics

Mitochondrial dysfunctions that were not discovered during preclinical and clinical testing have been responsible for at least restriction of use as far as withdrawal of many drugs. To solve mitochondrial machinery complexity, integrative methodologies combining different data, coupled or not to mathematic modelling into systems biology, could represent a strategic way but are still very hard to implement. These technologies should be accurate and precise to avoid accumulation of errors that can lead to misinterpretations, and then alter prediction efficiency. To address such issue, we have developed a versatile functional energy metabolism platform that can measure quantitatively, in parallel, with a very high precision and accuracy, a high number of biological parameters like substrates or enzyme cascade activities in essential metabolism units (glycolysis, respiratory chain ATP production, oxidative stress...) Its versatility (our platform works on either cell lines or small animals and human samples) allows cell metabolism pathways fine tuning comparison from preclinical to clinical studies. Applied here to OXPHOS and/or oxidative stress as an example, it allows discriminating compounds with acute toxic effects but, most importantly, those inducing low noise chronic ones.

COX5B-Mediated Bioenergetic Alterations Modulate Cell Growth and Anticancer Drug Susceptibility by Orchestrating Claudin-2 Expression in Colorectal Cancers

Oxidative phosphorylation (OXPHOS) consists of four enzyme complexes and ATP synthase, and is crucial for maintaining physiological tissue and cell growth by supporting the main bioenergy pool. Cytochrome c oxidase (COX) has been implicated as a primary regulatory site of OXPHOS. Recently, COX subunit 5B (COX5B) emerged as a potential biomarker associated with unfavorable prognosis by modulating cell behaviors in specific cancer types. However, its molecular mechanism remains unclear, particularly in colorectal cancers (CRCs). To understand the role of COX5B in CRCs, the expression and postoperative outcome associations using independent in-house patient cohorts were evaluated. A higher COX5B tumor/nontumor expression ratio was associated with unfavorable clinical outcomes (p = 0.001 and 0.011 for overall and disease-free survival, respectively. In cell-based experiments, the silencing of COX5B repressed cell growth and enhanced the susceptibility of CRCs cells to anticancer drugs. Finally, downstream effectors identified by RNA sequencing followed by RT-qPCR and functional compensation experiments revealed that the tight junction protein Claudin-2 (CLDN2) acts downstream of COX5B-mediated bioenergetic alterations in controlling cell growth and the sensitivity to anticancer drugs in CRCs cells. In conclusion, it was found that COX5B promoted cell growth and attenuated anticancer drugs susceptibility in CRCs cells by orchestrating CLDN2 expression, which may contribute to unfavorable postoperative outcomes of patients with CRCs.

The Neglected Liaison: Targeting Cancer Cell Metabolic Reprogramming Modifies the Composition of Non-Malignant Populations of the Tumor Microenvironment

Metabolic reprogramming is a well-known hallmark of cancer, whereby the development of drugs that target cancer cell metabolism is gaining momentum. However, when establishing preclinical studies and clinical trials, it is often neglected that a tumor mass is a complex system in which cancer cells coexist and interact with several types of microenvironment populations, including endothelial cells, fibroblasts and immune cells. We are just starting to understand how such populations are affected by the metabolic changes occurring in a transformed cell and little is known about the impact of metabolism-targeting drugs on the non-malignant tumor components. Here we provide a general overview of the links between cancer cell metabolism and tumor microenvironment (TME), particularly focusing on the emerging literature reporting TME-specific effects of metabolic therapies.

Molecular Insights into the Recruiting Between UCP2 and DDX5/UBAP2L in the Metabolic Plasticity of Non-Small-Cell Lung Cancer

Mitochondrial uncoupling protein 2 (UCP2) is distributed in tumor cells with a link to the support of systemic metabolic deregulation, and the downregulation of UCP2 has been unveiled as a biomarker of oncogenesis and chemoresistance in non-small-cell lung cancer (NSCLC) cells. However, the underlying mechanism of how UCP2 cooperates with other proteins in this metabolic reprogramming remains largely unsolved. We employed a combined computational and experimental strategy to explore into the recruiting of DDX5 with other proteins, and we unraveled the underlying structural mechanisms. We found that recruiting by ATP-dependent RNA helicase DDX5 (DDX5)/ubiquitin-associated protein 2-like (UBAP2L) might help UCP2 to play the pathological roles in NSCLC cells. According to the view of thermodynamics in physics, UCP2 tends to recruit DDX5 rather than UBAP2L, as shown by the ensemble-based docking, molecular dynamics simulations and molecular mechanics generalized Born surface area (MM/GBSA) approach. Cellular immunofluorescence assays further demonstrated that UCP2 associate with DDX5, and the recruiting of DDX5 with UCP2 at least partially contribute to the metabolic plasticity of NSCLCs via the AKT/mTOR pathway. Our study proposed an efficient way for detecting the protein-protein association via the experimentally validated molecular simulation. Our results shed light on the functional annotation of UCP and DDX family proteins in dysregulated metabolism, and the identification of candidate therapeutic targets for NSCLC.

Knockdown of Gastrin Promotes Apoptosis of Gastric Cancer Cells by Decreasing ROS Generation

Overexpressed gastrin is reported to promote oncogenesis and development of gastric cancer by inhibiting apoptosis of cancer cells; however, the underlying mechanism remains unclear. Our study is aimed at revealing the mechanism underlying the effect of gastrin on apoptosis of gastric cancer cells. Gastrin-interfering cell line was constructed by stably transfecting gastrin-specific pshRNA plasmid to gastric cancer cell line BGC-823. Then, differentially expressed proteins between untreated BGC-823 and gastrin-interfering BGC-823 cell lines were detected by the iTRAQ technique. GO and KEGG analysis was used to analyze the differentially expressed genes that code these differentially expressed proteins. The Annexin V-FITC staining assay was used to detect gastric cancer cell apoptosis. The DCFH-DA fluorescent probe staining assay was used to measure intracellular ROS. Mitochondrial membrane potential was detected by flow cytometry. Western blot was used to analyze the mitochondria respiratory chain proteins and apoptosis-related proteins. A total of 107 differentially expressed proteins were identified by iTRAQ. GO and KEGG analysis showed that proteins coded by the corresponding differentially expressed genes were mainly enriched in the mitochondrial oxidative respiratory chain, and the expression of three proteins (COX17, COX5B, ATP5J) was upregulated. The three proteins with higher scores were verified by Western blot. The apoptosis rate of the gastrin knockdown cancer cell was significantly increased; meanwhile, gastrin knockdown leads to increase of membrane potential and decrease of intracellular ROS production. Additionally, Bax was significantly increased, whereas NF-κB-p65 and Bcl-2 were downregulated after knockdown of gastrin. Concomitantly, pretreatment with NAC reversed the effect of gastrin on the Bax and Bcl-2 expression. Gastrin promotes the production of ROS from mitochondria, activates NF-κB, and inhibits apoptosis via modulating the expression level of Bcl-2 and Bax.

Recent advances in understanding the role of metabolic heterogeneities in cell migration

Migration is an energy-intensive, multi-step process involving cell adhesion, protrusion, and detachment. Each of these steps require cells to generate and consume energy, regulating their morphological changes and force generation. Given the need for energy to move, cellular metabolism has emerged as a critical regulator of both single cell and collective migration. Recently, metabolic heterogeneity has been highlighted as a potential determinant of collective cell behavior, as individual cells may play distinct roles in collective migration. Several tools and techniques have been developed and adapted to study cellular energetics during migration including live-cell probes to characterize energy utilization and metabolic state and methodologies to sort cells based on their metabolic profile. Here, we review the recent advances in techniques, parsing the metabolic heterogeneities inherent in cell populations and their contributions to cell migration.

Signaling, metabolism, and cancer: An important relationship for therapeutic intervention

In cancerous cells, significant changes occur in the activity of signaling pathways affecting a wide range of cellular activities ranging from growth and proliferation to apoptosis, invasiveness, and metastasis. Extensive changes also happen with respect to the metabolism of a cancerous cell encompassing a wide range of functions that include: nutrient acquisition, biosynthesis of macromolecules, and energy generation. These changes are important and some therapeutic approaches for treating cancers have focused on targeting the metabolism of cancerous cells. Oncogenes and tumor suppressor genes have a significant effect on the metabolism of cells. There appears to be a close interaction between metabolism and the signaling pathways in a cancerous cell, in which the interaction provides the metabolic needs of a cancerous cell for uncontrolled proliferation, resistance to apoptosis, and metastasis. In this review, we have reviewed the latest findings in this regard and briefly review the most recent research findings regarding targeting the metabolism of cancer cells as a therapeutic approach for treatment of cancer.

PGC1α regulates mitochondrial oxidative phosphorylation involved in cisplatin resistance in ovarian cancer cells via nucleo-mitochondrial transcriptional feedback

Mitochondria play an important role in effective cell energy production and cell survival under stress conditions, such as treatment with chemotherapeutic drugs. Mitochondrial biogenesis is increased in ovarian cancer tissues, which is accompanied by alteration of mitochondrial energy metabolism, structure, and dynamics. These factors are involved in tumorigenesis and apoptosis resistance, highlighting the role of mitochondria in resisting cisplatin toxicity. Cisplatin-resistant ovarian cancer cells are dependent on mitochondrial OXPHOS for energy supply, and intracellular PGC1α-mediated mitochondrial biogenesis levels are increased in this cell line, indicating the important role of mitochondrial oxidative phosphorylation in cisplatin resistance. As PGC1α is a key molecule for integrating and coordinating nuclear DNA and mitochondrial DNA transcriptional machinery, an investigation into the regulatory mechanism PGC1α in mitochondrial energy metabolism via transcription may provide new clues for solving chemotherapy resistance. In the present study, it was demonstrated that inhibiting the expression of PGC1α decreased nuclear and mitochondrial DNA transcription factor expression, leading to increased lactic acid production and decreased cellular oxygen consumption and mitochondrial oxidative phosphorylation. Furthermore, mitochondrial stress-induced ROS production, as a feedback signal from mitochondria to the cell nucleus, increased PGC1α expression in SKOV3/DDP cells, which was involved in mitochondrial oxidative phosphorylation regulation. Collectively, the present study provides evidence that PGC1α-mediated nuclear and mitochondrial transcription feedback regulates energy metabolism and is involved in ovarian cancer cells escaping apoptosis during cisplatin treatment.

Allomorphy as a mechanism of post-translational control of enzyme activity

Enzyme regulation is vital for metabolic adaptability in living systems. Fine control of enzyme activity is often delivered through post-translational mechanisms, such as allostery or allokairy. β-phosphoglucomutase (βPGM) from Lactococcus lactis is a phosphoryl transfer enzyme required for complete catabolism of trehalose and maltose, through the isomerisation of β-glucose 1-phosphate to glucose 6-phosphate via β-glucose 1,6-bisphosphate. Surprisingly for a gatekeeper of glycolysis, no fine control mechanism of βPGM has yet been reported. Herein, we describe allomorphy, a post-translational control mechanism of enzyme activity. In βPGM, isomerisation of the K145-P146 peptide bond results in the population of two conformers that have different activities owing to repositioning of the K145 sidechain. In vivo phosphorylating agents, such as fructose 1,6-bisphosphate, generate phosphorylated forms of both conformers, leading to a lag phase in activity until the more active phosphorylated conformer dominates. In contrast, the reaction intermediate β-glucose 1,6-bisphosphate, whose concentration depends on the β-glucose 1-phosphate concentration, couples the conformational switch and the phosphorylation step, resulting in the rapid generation of the more active phosphorylated conformer. In enabling different behaviours for different allomorphic activators, allomorphy allows an organism to maximise its responsiveness to environmental changes while minimising the diversion of valuable metabolites.

β-phosphoglucomutase (βPGM) from Lactococcus lactis is a phosphoryl transfer enzyme required for catabolism of trehalose and maltose. Coupled analyses of multiple βPGM structures and enzymatic activity lead to the proposal of allomorphy — a post-translational mechanism controlling enzyme activity.

A systematic review of genes affecting mitochondrial processes in cancer

Malignant conversion of cancer cells requires efficient mitochondria reprogramming orchestrated by hundreds of genes. The transformation includes increased energy demand, biosynthesis of precursors, and reactive oxygen species needed to accelerate cell growth, proliferation, and survival. Reprogramming involves complex gene alterations that have not been methodically curated. Therefore, we systematically analyzed the literature of cancer-related genes in mitochondria. Through the analysis of >2500 PubMed abstracts and >1600 human genes, we identified 228 genes showing clear roles in cancer. Each gene was classified according to their homeostatic function, together with the pathological transitions that contribute to specific cancer hallmarks. The potential clinical relevance of these hallmarks and genes is discussed by representative examples and validated by detecting differences in gene expression levels across 16 different types of cancer. A compendium, including the gene functions and alterations underpinning cancer progression, can be explored at http://bioinformatica.mty.itesm.mx/MitoCancer.

Morphologic Variants of Pancreatic Neuroendocrine Tumors: Clinicopathologic Analysis and Prognostic Stratification

Better prognostication/stratification of pancreatic neuroendocrine tumors (PanNETs) is needed. In this detailed morpheomic study of 163 resected PanNETs, 11 unusual variants, some of which were not previously recognized, and others scarcely documented in the literature, were identified, and their pathologic characteristics were further analyzed. By behavior and clinicopathologic associations, these variants could be grouped into three prognostically different categories. I. More aggressive (20%). Included in this group were the variants that in average showed higher grade and stage and adverse outcome including oncocytic, plasmacytoid, lipid-rich and previously unrecognized hepatoid variants, which often had a more diffuse/broad-band growth pattern, with some also displaying discohesiveness. They were characterized by abundant cytoplasm and often had prominent nucleoli (as seen in metabolically active cells), thus the provisional name "metabolic cell phenotype." Because of their diversion from classical neuroendocrine cytomorphology, these variants created challenges on original diagnostic workup, particularly hepatoid examples, which revealed Arginase 1/Hep Par-1 expression in 50%. II. Less aggressive (10%). These cases either showed signs of maturation, including nested growth, paraganglioid pattern (which was previously unrecognized), and organoid PanNETs such as "ductulo-insular" growth, or showed symplastic/degenerative changes, and despite their paradoxically disconcerting histology, were more benevolent in behavior. III. Undetermined. There were other variants including mammary tubulolobular-like, pseudoglandular, peliotic, and sclerotic PanNETs, which although diagnostically challenging, their biologic significance could not be determined because of rarity or heterogeneous characteristics. Prognostic associations: Features that were significantly different in the more aggressive group than the less aggressive group were median size (5.0 vs 1.6 cm, p < 0.001), percentage of pT3+T4 cases (72% vs 12%, p < 0.001), Ki67 index (5.3% vs 2.3%, p = 0.001), % G2 and G3 cases (77% vs 27%, p < 0.001), and rate of lymph node and distant metastasis (96% vs 27%, p < 0.001). In stepwise logistic regression model using the 3 established prognosticators of T stage, size, and grade along with morphology, only aggressive-morphology (metabolic cell phenotype) was found to be associated with metastatic behavior with an odds ratio of 5.9 with 95% confidence interval (C.I.) 1.688 to 22.945 and p value 0.007. In conclusion, PanNETs display various morphologic patterns that are not only challenging and important diagnostically but appear to have biologic significance. Tumors with more diffuse growth of cells with nucleoli and abundant cytoplasm and/or discohesion (oncocytic, hepatoid, lipid-rich, plasmacytoid PanNETs), provisionally termed "metabolic cell phenotype," show aggressive characteristics and are an independent determinant of adverse outcome and thus may require closer post-surgical follow-up, whereas variants with more degenerative or mature features (ductuloinsular, pleomorphic, paraganglioma-like) appear to be more benevolent despite their more atypical and worrisome morphology.

UCP2 Deficiency Increases Colon Tumorigenesis by Promoting Lipid Synthesis and Depleting NADPH for Antioxidant Defenses

Colorectal cancer (CRC) is associated with metabolic and redox perturbation. The mitochondrial transporter uncoupling protein 2 (UCP2) controls cell proliferation in vitro through the modulation of cellular metabolism, but the underlying mechanism in tumors in vivo remains unexplored. Using murine intestinal cancer models and CRC patient samples, we find higher UCP2 protein levels in tumors compared to their non-tumoral counterparts. We reveal the tumor-suppressive role of UCP2 as its deletion enhances colon and small intestinal tumorigenesis in AOM/DSS-treated and Apc^Min/+ mice, respectively, and correlates with poor survival in the latter model. Mechanistically, UCP2 loss increases levels of oxidized glutathione and proteins in tumors. UCP2 deficiency alters glycolytic pathways while promoting phospholipid synthesis, thereby limiting the availability of NADPH for buffering oxidative stress. We show that UCP2 loss renders colon cells more prone to malignant transformation through metabolic reprogramming and perturbation of redox homeostasis and could favor worse outcomes in CRC.

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UCP2 protein expression, but not mRNA, is increased in CRC in both mice and humans

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UCP2 loss promotes AOM/DSS-induced CAC and Apc^Min-dependent intestinal cancer

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UCP2 loss-induced oxidative stress contributes to increased colon tumorigenesis

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UCP2 deficiency drives an imbalance between lipid metabolism and NADPH homeostasis

NRF-1 and HIF-1α contribute to modulation of human VDAC1 gene promoter during starvation and hypoxia in HeLa cells

VDAC (Voltage Dependent Anion Channel) is a family of pore forming protein located in the outer mitochondrial membrane. Its channel property ensures metabolites exchange between mitochondria and the rest of the cell resulting in metabolism and bioenergetics regulation, and in cell death and life switch. VDAC1 is the best characterized and most abundant isoform, and is involved in many pathologies, as cancer or neurodegenerative diseases. However, little information is available about its gene expression regulation in normal and/or pathological conditions. In this work, we explored VDAC1 gene expression regulation in normal conditions and in the contest of some metabolic and energetic mitochondrial dysfunction and cell stress as example. The core of the putative promoter region was characterized in terms of transcription factors responsive elements both by bioinformatic studies and promoter activity experiments. In particular, we found an abundant presence of NRF-1 sites, together with other transcription factors binding sites involved in cell growth, proliferation, development, and we studied their prevalence in gene activity. Furthermore, upon depletion of nutrients or controlled hypoxia, as detected in various pathologies, we found that VDAC1 transcripts levels were significantly increased in a time related manner. VDAC1 promoter activity was also validated by gene reporter assays. According to PCR real-time experiments, it was confirmed that VDAC1 promoter activity is further stimulated when cells are exposed to stress. A bioinformatic survey suggested HIF-1α, besides NRF-1, as a most active TFBS. Their validation was obtained by TFBS mutagenesis and TF overexpression experiments. In conclusion, we experimentally demonstrated the involvement of both NRF-1 and HIF-1α in the regulation of VDAC1 promoter activation at basal level and in some peculiar cell stress conditions.

Identification of Energy Metabolism Genes for the Prediction of Survival in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) samples were clustered into three energy metabolism-related molecular subtypes (C1, C2, and C3) with different prognosis using the gene expression data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO). HCC energy metabolism-related molecular subtype analysis was conducted based on the 594 energy metabolism genes. Differential expression analysis yielded 576 differentially expressed genes (DEGs) among the three subtypes, which were closely related to HCC progression. Six genes were finally selected from the 576 DEGs through LASSO-Cox regression and used in constructing a six-gene signature-associated prognostic risk model, which was validated using the TCGA internal and three GEO external validation cohorts. The risk model showed that high ANLN, ENTPD2, TRIP13, PLAC8, and G6PD expression levels were associated with bad prognosis, and high expression of ADH1C was associated with a good prognosis. The validation results showed that our risk model had a high distinguishing ability of prognosis in HCC patients. The four enriched pathways of the risk model were obtained by gene set enrichment analysis (GSEA) and found to be associated with the tumorigenesis and development of HCC, including the cell cycle, Wnt signaling pathway, drug metabolism cytochrome P450, and primary bile acid biosynthesis. The risk score calculated from the established risk model in 204 samples and other clinical characteristics were used in building a nomogram with a good prognostic prediction ability (C-index = 0.746, 95% CI = 0.714–0.777). The area under the curves (AUCs) of the nomogram model in 1-, 2-, and 3-years were 0.82, 0.77, and 0.79, respectively. Then, qRT-PCR and immunohistochemistry were used to validate the mRNA expression levels of the six genes, and significant differences in mRNA and gene expression were observed among the tumor and adjacent tissues. Overall, our study divided HCC patients into three energy metabolism-related molecular subtypes with different prognosis. Then, a risk model with a good performance in prognostic prediction was built using the TCGA dataset. This model can be used as an independent prognostic evaluation index for HCC patients.

COX5B-Mediated Bioenergetic Alteration Regulates Tumor Growth and Migration by Modulating AMPK-UHMK1-ERK Cascade in Hepatoma

The oxidative phosphorylation machinery in mitochondria, which generates the main bioenergy pool in cells, includes four enzyme complexes for electron transport and ATP synthase. Among them, the cytochrome c oxidase (COX), which constitutes the fourth complex, has been suggested as the major regulatory site. Recently, abnormalities in COX were linked to tumor progression in several cancers. However, it remains unclear whether COX and its subunits play a role in tumor progression of hepatoma. To search for the key regulatory factor(s) in COX for hepatoma development, in silico analysis using public transcriptomic database followed by validation for postoperative outcome associations using independent in-house patient cohorts was performed. In which, COX5B was highly expressed in hepatoma and associated with unfavorable postoperative prognosis. In addressing the role of COX5B in hepatoma, the loss- and gain-of-function experiments for COX5B were conducted. Consequently, COX5B expression was associated with increased hepatoma cell proliferation, migration and xenograft growth. Downstream effectors searched by cDNA microarray analysis identified UHMK1, an oncogenic protein, which manifested a positively correlated expression level of COX5B. The COX5B-mediated regulatory event on UHMK1 expression was subsequently demonstrated as bioenergetic alteration-dependent activation of AMPK in hepatoma cells. Phosphoproteomic analysis uncovered activation of ERK- and stathmin-mediated pathways downstream of UHMK1. Finally, comprehensive phenotypic assays supported the impacts of COX5B-UHMK1-ERK axis on hepatoma cell growth and migration.

Deregulated Mitochondrial DNA in Diseases

Mitochondria play various important roles in energy production, metabolism, and apoptosis. Mitochondrial dysfunction caused by alterations in mitochondrial DNA (mtDNA) can lead to the initiation and progression of cancers and other diseases. These alterations include mutations and copy number variations. Especially, the mutations in D-loop, MT-ND1, and MT-ND5 affect mitochondrial functions and are widely detected in various cancers. Meanwhile, several other mutations have been correlated with muscular and neuronal diseases, especially MT-TL1 is deeply related. These pieces of evidence indicated mtDNA alterations in diseases show potential as a novel therapeutic target. mtDNA repair enzymes are the target for delaying or stalling the mtDNA damage-induced cancer progression and metastasis. Moreover, some mutations reveal a prognosis ability of the drug resistance. Current efforts aim to develop mitochondrial transplantation technique as a direct cure for deregulated mitochondria-associated diseases. This review summarizes the implications of mitochondrial dysfunction in cancers and other pathologies; and discusses the relevance of mitochondria-targeted therapies, along with their contribution as potential biomarkers.

The CRISPR-Cas9 crADSL HeLa transcriptome: A first step in establishing a model for ADSL deficiency and SAICAR accumulation

Adenylosuccinate lyase (ADSL) catalyzes two steps in de novo purine synthesis (DNPS). Mutations in ADSL can result in inborn errors of metabolism characterized by developmental delay and disorder phenotypes, with no effective treatment options. Recently, SAICAR, a metabolic substrate of ADSL, has been found to have alternative roles in the cell, complicating the role of ADSL. crADSL, a CRISPR KO of ADSL in HeLa cells, was constructed to investigate DNPS and ADSL in a human cell line. Here we employ this cell line in an RNA-seq analysis to initially investigate the effect of DNPS and ADSL deficiency on the transcriptome as a first step in establishing a cellular model of ADSL deficiency. We report transcriptome changes in genes relevant to development, vascular development, muscle, and cancer biology, which provide interesting avenues for future research.

Copy number variation is highly correlated with differential gene expression: a pan-cancer study

BACKGROUND

Cancer is a heterogeneous disease with many genetic variations. Lines of evidence have shown copy number variations (CNVs) of certain genes are involved in development and progression of many cancers through the alterations of their gene expression levels on individual or several cancer types. However, it is not quite clear whether the correlation will be a general phenomenon across multiple cancer types.

METHODS

In this study we applied a bioinformatics approach integrating CNV and differential gene expression mathematically across 1025 cell lines and 9159 patient samples to detect their potential relationship.

RESULTS

Our results showed there is a close correlation between CNV and differential gene expression and the copy number displayed a positive linear influence on gene expression for the majority of genes, indicating that genetic variation generated a direct effect on gene transcriptional level. Another independent dataset is utilized to revalidate the relationship between copy number and expression level. Further analysis show genes with general positive linear influence on gene expression are clustered in certain disease-related pathways, which suggests the involvement of CNV in pathophysiology of diseases.

CONCLUSIONS

This study shows the close correlation between CNV and differential gene expression revealing the qualitative relationship between genetic variation and its downstream effect, especially for oncogenes and tumor suppressor genes. It is of a critical importance to elucidate the relationship between copy number variation and gene expression for prevention, diagnosis and treatment of cancer.

Human Ovarian Cancer Tissue Exhibits Increase of Mitochondrial Biogenesis and Cristae Remodeling

Ovarian cancer (OC) is the most lethal gynecologic cancer characterized by an elevated apoptosis resistance that, potentially, leads to chemo-resistance in the recurrent disease. Mitochondrial oxidative phosphorylation was found altered in OC, and mitochondria were proposed as a target for therapy. Molecular evidence suggests that the deregulation of mitochondrial biogenesis, morphology, dynamics, and apoptosis is involved in carcinogenesis. However, these mitochondrial processes remain to be investigated in OC. Eighteen controls and 16 OC tissues (serous and mucinous) were collected. Enzymatic activities were performed spectrophotometrically, mitochondrial DNA (mtDNA) content was measured by real-time-PCR, protein levels were determined by Western blotting, and mitochondrial number and structure were measured by electron microscopy. Statistical analysis was performed using Student’s t-test, Mann-Whitney U test, and principal component analysis (PCA). We found, in OC, that increased mitochondrial number associated with increased peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) and mitochondrial transcription factor A (TFAM) protein levels, as well as mtDNA content. The OC mitochondria presented an increased maximum length, as well as reduced cristae width and junction diameter, associated with increased optic atrophy 1 protein (OPA1) and prohibitin 2 (PHB2) protein levels. In addition, in OC tissues, augmented cAMP and sirtuin 3 (SIRT3) protein levels were observed. PCA of the 25 analyzed biochemical parameters classified OC patients in a distinct group from controls. We highlight a “mitochondrial signature” in OC that could result from cooperation of the cAMP pathway with the SIRT3, OPA1, and PHB2 proteins.

The Tangled Mitochondrial Metabolism in Cancer: An Innovative Pharmacological Approach

BACKGROUND

Mitochondria are remarkably gaining significant and different pathogenic roles in cancer (i.e., to sustain specific metabolism, to activate signaling pathways, to promote apoptosis resistance, to favor cancer cell dissemination, and finally to facilitate genome instability). Interestingly, all these roles seem to be linked to the fundamental activity of mitochondria, i.e. oxidative metabolism. Intriguingly, a typical modification of mitochondrial oxidative metabolism and reactive oxygen species production/ neutralization seems to have a central role in all these tangled pathogenic roles in cancer. On these bases, a careful understanding of the molecular relationships between cancer and mitochondria may represent a fundamental step to realize therapeutic approaches blocking the typical cancer progression. The main aim of this review is to stress some neglected aspects of oxidative mitochondrial metabolism of cancer cells to promote more translational research with diagnostic and therapeutic potential.

METHODS

We reviewed the available literature regarding clinical and experimental studies on various roles of mitochondria in cancer, with attention to the cancer cell mitochondrial metabolism.

RESULTS

Mitochondria are an important source of reactive oxygen species. Their toxic effects seem to increase in cancer cells. However, it is not clear if damage depends on ROS overproduction and/or defect in detoxification. Failure of both these processes is likely a critical component of the cancer process and is strictly related to the actual microenvironment of cancer cells.

CONCLUSIONS

Mitochondria, also by ROS production, have a fundamental pathogenetic role in promoting and maintaining cancer and its spreading. To carefully understand the tangled redox state of cancer cells mitochondria represents a fundamental step to realize therapeutic approaches blocking the typical cancer progression.

The Quiescent Metabolic Phenotype of Glioma Stem Cells

Introduction

Glioblastoma (GBM) is the most common primary malignant brain tumor in humans and, even with aggressive treatment that includes surgical resection, radiation (IR), and chemotherapy administration, prognosis is poor due to tumor recurrence. There is evidence that within GBMs a small number of glioma stem-like cells (GSLCs) exist, which are thought to be therapy resistant and are thus capable of repopulating a tumor after treatment. Like most cancers, GBMs largely employ aerobic glycolysis to create ATP, a phenomenon known as the Warburg Effect. There is no consensus on the metabolic characteristics of cancer stem cells. GSLCs have been shown to rely more heavily on oxidative phosphorylation, but there is also evidence that cancer stem cells can adapt their metabolism by fluctuating between energy pathways or acquiring intermediate metabolic phenotypes. We hypothesized that the metabolism of GSLCs differs from that of differentiated GBM tumor cell lines, and that the steady state metabolism would be differentially altered following radiation treatment.

Materials and Methods

We evaluated the oxygen consumption rate, extracellular acidification rate, and metabolic enzyme levels of GBM cell lines and GSLCs before and after irradiation using extracellular flux assays. We also measured absolute metabolite levels in these cells via mass spectroscopy with and without radiation treatment.

Results

GSLCs were found to be significantly more quiescent in comparison to adherent GBM cell lines, highlighted by lower glycolytic and maximal respiratory capacities as well as lower oxygen consumption and extracellular acidification rates. Analysis of individual metabolite concentrations revealed lower total metabolite concentrations overall but also elevated levels of metabolites in different energy pathways for GSLCs compared to GBM cell lines. Additionally, the metabolism of both GSLCs and GBM cell lines were found to be altered by IR.

Conclusions

While there is not one metabolic alteration that distinguishes irradiated GSLC metabolism from that of GBM cell lines, therapies targeting more metabolically quiescent tumor cells and thus the resistant GSLC population may increase a cancer's sensitivity to radiotherapy.

C9-13 chlorinated paraffins cause immunomodulatory effects in adult C57BL/6 mice

Short-chain chlorinated paraffins (SCCPs, C_10-13) were listed as persistent organic pollutants (POPs) by the Stockholm Convention in 2017 and pose extensive exposure risks to humans. To our knowledge, there have been no studies reporting the immmunomodulatory effects of SCCPs until now. C₉-CPs have also been shown to be present in the environment. In this study, adult male C57BL/6 mice were exposed to 1, 10, or 100 mg/kg/d C_9-13-CPs by gavage for 28 d. The results showed that compared to those of the controls, exposure to C_9-13-CPs led to increased spleen weight, delimited germinal centers, enhanced energy metabolism, and elevated glutathione content, but no variation in the malonaldehyde level in the spleen was observed. Exposure to C_9-13-CPs also increased the populations of splenic lymphocytes, T lymphocytes, NK cells, and the ratio of the CD3⁺/CD19⁺ subsets and CD4⁺/CD8⁺ subsets compared to those of the controls. RNA-seq revealed 424 differentially expressed genes (DEGs) (fold change ≥ 1.5, FDR < 0.05) in the spleen between the control group and the 100 mg/kg/d C_9-13-CPs-treated group. KEGG analysis demonstrated that folate biosynthesis, pathways in cancer and thyroid hormone signaling were the three most significantly enriched pathways, and despite not reaching statistical significance, some immune-related pathways were also enriched in the KEGG functional enrichment analysis, including the chemokine signaling pathway (FDR < 0.0584), the NF-κB signaling pathway (FDR < 0.0663), Th17 cell differentiation (FDR < 0.0839), and the Jak-STAT signaling pathway. Moreover, compared to those of the controls, exposure to C_9-13-CPs enhanced the Concanavalin A (Con A)-stimulated cultured splenocyte proliferation, while the exposure showed no effect on the splenocyte proliferation that was stimulated by lipopolysaccharides (LPS). Taken together, these results demonstrated that subacute exposure to C_9-13-CPs could have immunomodulatory effects in mice. The present study helps to provide an understanding of the comprehensive health risks posed by C_9-13-CPs.

Wild type- and mutant p53 proteins in mitochondrial dysfunction: emerging insights in cancer disease

Deregulated cell metabolism is one of the cancer hallmarks. Mitochondrial DNA mutations and enzyme defects, aberrant tumor suppressor or oncogenic activities cause mitochondrial dysfunction leading to deregulated cellular energetics. The tumor suppressor protein, p53 is a tetrameric transcription factor that in response to diverse genotoxic and non-genotoxic insults activates a plethora of target genes to preserve genome integrity. In the last two decades the discovery of cytoplasmic p53 localization focused intense research on its extra-nuclear functions. The ability of p53 to induce apoptosis acting directly at mitochondria and the related mechanisms of p53 localization and translocation in the cytoplasm have been investigated. A role of cytoplasmic p53 in autophagy, pentose phosphate pathway, fatty acid synthesis and oxidation, and drug response has been proposed. TP53 gene is mutated in more than half of human cancers. In parallel to loss of tumor suppressive functions, mutant p53 proteins often gain new tumorigenic activities (GOF, gain of function). It has been recently shown that mutant p53 proteins mediate metabolic changes thereby promoting cancer development and metastases. Here we review the contribution of either wild-type p53 or mutant p53 proteins to the fine-tuning of mitochondrial metabolism of both normal and cancer cells. Greater knowledge at the mechanistic level might provide insights to develop new cancer therapeutic approaches.

The multifaceted effects of metformin on tumor microenvironment

The efficacy of metformin in treating cancer has been extensively investigated since epidemiologic studies associated this anti-diabetic drug with a lower risk of cancer incidence. Since tumors are complex systems, in which cancer cells coexist and interact with several different types of non-malignant cells, it is not surprising that anti-cancer drugs affect not only cancer cells, but also the abundance and functions of cells of the tumor microenvironment. Recent years have seen a wide collection of reports showing how metformin, as well as other complex I inhibitors, may influence cancer progression by modulating the phenotype of non-transformed cells in a tumor. In this review, we particularly focus on the effect of metformin on angiogenesis, cancer-associated fibroblasts, tumor-associated macrophages and cancer immunosuppression.

Anticancer Thiosemicarbazones: Chemical Properties, Interaction with Iron Metabolism, and Resistance Development

SIGNIFICANCE

During the past decades, thiosemicarbazones were clinically developed for a variety of diseases, including tuberculosis, viral infections, malaria, and cancer. With regard to malignant diseases, the class of α-N-heterocyclic thiosemicarbazones, and here especially 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (Triapine), was intensively developed in multiple clinical phase I/II trials. Recent Advances: Very recently, two new derivatives, namely COTI-2 and di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) have entered phase I evaluation. Based on the strong metal-chelating/metal-interacting properties of thiosemicarbazones, interference with the cellular iron (and copper) homeostasis is assumed to play an important role in their biological activity.

CRITICAL ISSUES

In this review, we summarize and analyze the data on the interaction of (α-N-heterocyclic) thiosemicarbazones with iron, with the special aim of bridging the current knowledge on their mode of action from chemistry to (cell) biology. In addition, we highlight the difference to classical iron(III) chelators such as desferrioxamine (DFO), which are used for the treatment of iron overload.

FUTURE DIRECTIONS

We want to emphasize that thiosemicarbazones are not solely removing iron from the cells/organism. In contrast, they should be considered as iron-interacting drugs influencing diverse biological pathways in a complex and multi-faceted mode of action. Consequently, in addition to the discussion of physicochemical properties (e.g., complex stability, redox activity), this review contains an overview on the diversity of cellular thiosemicarbazone targets and drug resistance mechanisms.

Metabolic reprogramming in breast cancer results in distinct mitochondrial bioenergetics between luminal and basal subtypes

Mitochondrial dysfunction is a key feature of cancer and is frequently associated with increased aggressiveness and metastatic potential. Recent evidence has brought to light a metabolic rewiring that takes place during the epithelial-to-mesenchymal transition (EMT), a process that drives the invasive capability of malignant tumors, and highlights a mechanistic link between mitochondrial dysfunction and EMT that has been only partially investigated. In this study, we characterized mitochondrial function and bioenergetic status of cultured human breast cancer cell lines, including luminal-like and basal-like subtypes. Through a combination of biochemical and functional studies, we demonstrated that basal-like cell lines exhibit impaired, but not completely inactive, mitochondrial function, and rely on a consequent metabolic switch to glycolysis to support their ATP demand. These altered metabolic activities are linked to modifications of key electron transport chain proteins and a significant increase in levels of reactive oxygen species compared to luminal cells. Furthermore, we observed that the stable knockdown of EMT markers caused functional changes in mitochondria that result in acquisition of a hybrid glycolysis/OXPHOS phenotype in cancer cells as a means to sustain their metabolic demand.

Mitochondrial cytochrome P450 (CYP) 1B1 is responsible for melatonin-induced apoptosis in neural cancer cells

Melatonin is an endogenous indoleamine with a wide range of biological functions in the various organisms from bacteria to mammals. Evidence indicates that melatonin facilitates apoptosis in cancer cells and enhances the antitumor activity of chemotherapy in animals and clinical studies. However, the melatonin metabolism and the key metabolic targets in cancer cells still remain unknown. In this study, U118 and SH-SY5Y tumor cell lines were used to investigate the metabolic pathways of melatonin in cancer cells. Interestingly, the inhibitory effect of melatonin on proliferation in SH-SY5Y cells is more potent than that in U118 cells. In contrast, this inhibitory effect on the normal cells is absent. The antitumor effects of melatonin are positively associated with its metabolite N-acetylserotonin (NAS). Unexpectedly, CYP1B1 is, for first time, identified to localize in the mitochondria of tumor cells, and it metabolizes melatonin to form NAS in situ, which subsequently triggers mitochondria-dependent apoptosis in cancer cells. In normal cells, NAS does not induce apoptosis. A remarkable individual variation on CYP1B1 expression was also detected in human tumor tissue. These findings provide the novel mechanisms regarding the antitumor effects of melatonin in the level of mitochondria. Thus, we hypothesize that CYP1B1 overexpression in mitochondria would significantly enhance the antitumor effects of melatonin. Mitochondrial CYP1B1 can potentially serve as a specific target to modify the therapeutic and biological effects of melatonin on cancer patients.

Melanoma metabolism contributes to the cellular responses to MAPK/ERK pathway inhibitors

BACKGROUND

Besides its influence on survival, growth, proliferation, invasion and metastasis, cancer cell metabolism also greatly influences the cellular responses to molecular-targeted therapies.

SCOPE OF THE REVIEW

To review the recent advances in elucidating the metabolic effects of BRAF and MEK inhibitors (clinical inhibitors of the MAPK/ERK pathway) in melanoma and discuss the underlying mechanisms involved in the way metabolism can influence melanoma cell death and resistance to BRAF and MEK inhibitors. We also underlined the therapeutic perspectives in terms of innovative drug combinations.

MAJOR CONCLUSION

BRAF and MEK inhibitors inhibit aerobic glycolysis and induce high levels of metabolic stress leading to effective cell death by apoptosis in BRAF-mutated cancer cells. An increase in mitochondrial metabolism is required to survive to MAPK/ERK pathway inhibitors and the sub-population of cells that survives to these inhibitors are characterized by mitochondrial OXPHOS phenotype. Consequently, mitochondrial inhibition could be combined with oncogenic "drivers" inhibitors of the MAPK/ERK pathway for improving the efficacy of molecular-targeted therapy.

GENERAL SIGNIFICANCE

Metabolism is a key component of the melanoma response to BRAF and/or MEK inhibitors. Mitochondrial targeting may offer novel therapeutic approaches to overwhelm the mitochondrial addiction that limits the efficacy of BRAF and/or MEK inhibitors. These therapeutic approaches might be quickly applicable to the clinical situation.

The role of compartmentalized signaling pathways in the control of mitochondrial activities in cancer cells

Mitochondria are the powerhouse organelles present in all eukaryotic cells. They play a fundamental role in cell respiration, survival and metabolism. Stimulation of G-protein coupled receptors (GPCRs) by dedicated ligands and consequent activation of the cAMP·PKA pathway finely couple energy production and metabolism to cell growth and survival. Compartmentalization of PKA signaling at mitochondria by A-Kinase Anchor Proteins (AKAPs) ensures efficient transduction of signals generated at the cell membrane to the organelles, controlling important aspects of mitochondrial biology. Emerging evidence implicates mitochondria as essential bioenergetic elements of cancer cells that promote and support tumor growth and metastasis. In this context, mitochondria provide the building blocks for cellular organelles, cytoskeleton and membranes, and supply all the metabolic needs for the expansion and dissemination of actively replicating cancer cells. Functional interference with mitochondrial activity deeply impacts on cancer cell survival and proliferation. Therefore, mitochondria represent valuable targets of novel therapeutic approaches for the treatment of cancer patients. Understanding the biology of mitochondria, uncovering the molecular mechanisms regulating mitochondrial activity andmapping the relevant metabolic and signaling networks operating in cancer cells will undoubtly contribute to create a molecular platform to be used for the treatment of proliferative disorders. Here, we will highlight the emerging roles of signaling pathways acting downstream to GPCRs and their intersection with the ubiquitin proteasome system in the control of mitochondrial activity in different aspects of cancer cell biology.

Mitochondrial metabolism and cancer

Glycolysis has long been considered as the major metabolic process for energy production and anabolic growth in cancer cells. Although such a view has been instrumental for the development of powerful imaging tools that are still used in the clinics, it is now clear that mitochondria play a key role in oncogenesis. Besides exerting central bioenergetic functions, mitochondria provide indeed building blocks for tumor anabolism, control redox and calcium homeostasis, participate in transcriptional regulation, and govern cell death. Thus, mitochondria constitute promising targets for the development of novel anticancer agents. However, tumors arise, progress, and respond to therapy in the context of an intimate crosstalk with the host immune system, and many immunological functions rely on intact mitochondrial metabolism. Here, we review the cancer cell-intrinsic and cell-extrinsic mechanisms through which mitochondria influence all steps of oncogenesis, with a focus on the therapeutic potential of targeting mitochondrial metabolism for cancer therapy.

PGC1α: Friend or Foe in Cancer?

The PGC1 family (Peroxisome proliferator-activated receptor γ (PPARγ) coactivators) of transcriptional coactivators are considered master regulators of mitochondrial biogenesis and function. The PGC1α isoform is expressed especially in metabolically active tissues, such as the liver, kidneys and brain, and responds to energy-demanding situations. Given the altered and highly adaptable metabolism of tumor cells, it is of interest to investigate PGC1α in cancer. Both high and low levels of PGC1α expression have been reported to be associated with cancer and worse prognosis, and PGC1α has been attributed with oncogenic as well as tumor suppressive features. Early in carcinogenesis PGC1α may be downregulated due to a protective anticancer role, and low levels likely reflect a glycolytic phenotype. We suggest mechanisms of PGC1α downregulation and how these might be connected to the increased cancer risk that obesity is now known to entail. Later in tumor progression PGC1α is often upregulated and is reported to contribute to increased lipid and fatty acid metabolism and/or a tumor cell phenotype with an overall metabolic plasticity that likely supports drug resistance as well as metastasis. We conclude that in cancer PGC1α is neither friend nor foe, but rather the obedient servant reacting to metabolic and environmental cues to benefit the tumor cell.

Oxidative stress regulates cellular bioenergetics in esophageal squamous cell carcinoma cell

The aim of the present study was to explore the effects of oxidative stress induced by CoCl₂ and H₂O₂ on the regulation of bioenergetics of esophageal squamous cell carcinoma (ESCC) cell line TE-1 and analyze its underlying mechanism. Western blot results showed that CoCl₂ and H₂O₂ treatment of TE-1 cells led to significant reduction in mitochondrial respiratory chain complex subunits expression and increasing intracellular reactive oxygen species (ROS) production. We further found that TE-1 cells treated with CoCl₂, a hypoxia-mimicking reagent, dramatically reduced the oxygen consumption rate (OCR) and increased the extracellular acidification rate (ECAR). However, H₂O₂ treatment decreased both the mitochondrial respiration and aerobic glycolysis significantly. Moreover, we found that H₂O₂ induces apoptosis in TE-1 cells through the activation of PARP, Caspase 3, and Caspase 9. Therefore, our findings indicate that CoCl₂ and H₂O₂ could cause mitochondrial dysfunction by up-regulation of ROS and regulating the cellular bioenergy metabolism, thus affecting the survival of tumor cells.

Non-Canonical Mechanisms Regulating Hypoxia-Inducible Factor 1 Alpha in Cancer

Hypoxia-inducible factor 1 alpha (HIF-1α) orchestrates cellular adaptation to low oxygen and nutrient-deprived environment and drives progression to malignancy in human solid cancers. Its canonical regulation involves prolyl hydroxylases (PHDs), which in normoxia induce degradation, whereas in hypoxia allow stabilization of HIF-1α. However, in certain circumstances, HIF-1α regulation goes beyond the actual external oxygen levels and involves PHD-independent mechanisms. Here, we gather and discuss the evidence on the non-canonical HIF-1α regulation, focusing in particular on the consequences of mitochondrial respiratory complexes damage on stabilization of this pleiotropic transcription factor.

¹H-NMR-Based Metabonomics of the Protective Effect of Coptis chinensis and Berberine on Cinnabar-Induced Hepatotoxicity and Nephrotoxicity in Rats

Coptis chinensis Franch has been used in Traditional Chinese Medicine (TCM) for treating infectious and inflammatory diseases for over two thousand years. Berberine (BN), an isoquinoline alkaloid, is the main component of Coptis chinensis. The pharmacological basis for its therapeutic effects, which include hepatoprotective effects on liver injuries, has been studied intensively, yet the therapy of liver injuries and underlying mechanism remain unclear. We investigated the detoxification mechanism of Coptis chinensis and berberine using metabolomics of urine and serum in the present study. After the treatment with Coptis chinensis and berberine, compared with the cinnabar group, Coptis chinensis and berberine can regulate the concentration of the endogenous metabolites. PLS-DA score plots demonstrated that the urine and serum metabolic profiles in rats of the Coptis chinensis and berberine groups were similar those of the control group, yet remarkably apart from the cinnabar group. The mechanism may be related to the endogenous metabolites including energy metabolism, amino acid metabolism and metabolism of intestinal flora in rats. Meanwhile, liver and kidney histopathology examinations and serum clinical chemistry analysis verified the experimental results of metabonomics.