Mitochondria as biosynthetic factories for cancer proliferation

Bone metastasis: mechanisms, therapies, and biomarkers

Skeletal metastases are frequent complications of many cancers, causing bone complications (fractures, bone pain, disability) that negatively affect the patient's quality of life. Here, we first discuss the burden of skeletal complications in cancer bone metastasis. We then describe the pathophysiology of bone metastasis. Bone metastasis is a multistage process: long before the development of clinically detectable metastases, circulating tumor cells settle and enter a dormant state in normal vascular and endosteal niches present in the bone marrow, which provide immediate attachment and shelter, and only become active years later as they proliferate and alter the functions of bone-resorbing (osteoclasts) and bone-forming (osteoblasts) cells, promoting skeletal destruction. The molecular mechanisms involved in mediating each of these steps are described, and we also explain how tumor cells interact with a myriad of interconnected cell populations in the bone marrow, including a rich vascular network, immune cells, adipocytes, and nerves. We discuss metabolic programs that tumor cells could engage with to specifically grow in bone. We also describe the progress and future directions of existing bone-targeted agents and report emerging therapies that have arisen from recent advances in our understanding of the pathophysiology of bone metastases. Finally, we discuss the value of bone turnover biomarkers in detection and monitoring of progression and therapeutic effects in patients with bone metastasis.

Metabolic regulation of prostate cancer heterogeneity and plasticity

Metabolic reprogramming is one of the main hallmarks of cancer cells. It refers to the metabolic adaptations of tumor cells in response to nutrient deficiency, microenvironmental insults, and anti-cancer therapies. Metabolic transformation during tumor development plays a critical role in the continued tumor growth and progression and is driven by a complex interplay between the tumor mutational landscape, epigenetic modifications, and microenvironmental influences. Understanding the tumor metabolic vulnerabilities might open novel diagnostic and therapeutic approaches with the potential to improve the efficacy of current tumor treatments. Prostate cancer is a highly heterogeneous disease harboring different mutations and tumor cell phenotypes. While the increase of intra-tumor genetic and epigenetic heterogeneity is associated with tumor progression, less is known about metabolic regulation of prostate cancer cell heterogeneity and plasticity. This review summarizes the central metabolic adaptations in prostate tumors, state-of-the-art technologies for metabolic analysis, and the perspectives for metabolic targeting and diagnostic implications.

Physiological and molecular aspects of heat-treated cultured granulosa cells of Egyptian buffalo (Bubalus bubalis)

The physiological and molecular responses of granulosa cells (GCs) from buffalo follicles were investigated when there were in vitro heat stress conditions imposed. The cultured GCs were heat-treated at 40.5 °C for 24, 48 or 72 h while GCs of the control group were not heat-treated (37 °C). There were no differences in viability between control and heat-treated groups. There was an upward trend in increase in E₂ secretion as the duration of heat stress advanced, being greater (P ≤ 0.05) for the GCs on which heat stress was imposed for 72 as compared with 24 h. In contrast, P₄ release was less (P ≤ 0.05) from GCs heat-treated for 48 h than those cultured for 24 h and GCs of the control group. The relative abundance of ATP5F1A and SOD2 mRNA transcripts was consistent throughout the period when there was imposing of heat stress to sustain mitochondrial function. The relative abundance of CPT2 transcript was less in heat-treated GCs than in GCs of the control group. There was a greater relative abundance of SREBP1 and TNF-α mRNA transcripts after 48 h of heat-treatment of GCs than GCs of the control group. In conclusion, the results from the current study indicate buffalo GCs cultured when there was imposing of heat stress maintained normal viability, steroidogenesis and transcriptional profile. The stability of antioxidant status and increased transcription of genes regulating cholesterol biosynthesis and stress resistance may be defense mechanisms of buffalo GCs against heat stress.

The yin and yang of mitochondrial Ca2+ signaling in cell physiology and pathology

Mitochondria are autonomous and dynamic cellular organelles orchestrating a diverse range of cellular activities. Numerous cell-signaling pathways target these organelles and Ca²⁺ is one of the most significant. Mitochondria are able to rapidly and transiently take up Ca²⁺, thanks to the mitochondrial Ca²⁺ uniporter complex, as well as to extrude it through the Na⁺/Ca²⁺ and H⁺/Ca²⁺ exchangers. The transient accumulation of Ca²⁺ in the mitochondrial matrix impacts on mitochondrial functions and cell pathophysiology. Here we summarize the role of mitochondrial Ca²⁺ signaling in both physiological (yang) and pathological (yin) processes and the methods that can be used to investigate mitochondrial Ca²⁺ homeostasis. As an example of the pivotal role of mitochondria in pathology, we described the state of the art of mitochondrial Ca²⁺ alterations in different pathological conditions, with a special focus on Alzheimer's disease.

Glutamine-Directed Migration of Cancer-Activated Fibroblasts Facilitates Epithelial Tumor Invasion

Tumors are complex tissues composed of transformed epithelial cells as well as cancer-activated fibroblasts (CAF) that facilitate epithelial tumor cell invasion. We show here that CAFs and other mesenchymal cells rely much more on glutamine than epithelial tumor cells; consequently, they are more sensitive to inhibition of glutaminase. Glutamine dependence drove CAF migration toward this amino acid when cultured in low glutamine conditions. CAFs also invaded a Matrigel matrix following a glutamine concentration gradient and enhanced the invasion of tumor cells when both cells were cocultured. Accordingly, glutamine directed invasion of xenografted tumors in immunocompromised mice. Stimulation of glutamine-driven epithelial tumor invasion by fibroblasts required previous CAF activation, which involved the TGFβ/Snail1 signaling axis. CAFs moving toward Gln presented a polarized Akt2 distribution that was modulated by the Gln-dependent activity of TRAF6 and p62 in the migrating front, and depletion of these proteins prevented Akt2 polarization and Gln-driven CAF invasion. Our results demonstrate that glutamine deprivation promotes CAF migration and invasion, which in turn facilitates the movement of tumor epithelial cells toward nutrient-rich territories. These results provide a novel molecular mechanism for how metabolic stress enhances invasion and metastasis. SIGNIFICANCE: Cancer-associated fibroblasts migrate and invade toward free glutamine and facilitate invasion of tumor epithelial cells, accounting for their movement away from the hostile conditions of the tumor towards nutrient-rich adjacent tissues. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/2/438/F1.large.jpg.

Redox Potential of Antioxidants in Cancer Progression and Prevention

The benevolent and detrimental effects of antioxidants are much debated in clinical trials and cancer research. Several antioxidant enzymes and molecules are overexpressed in oxidative stress conditions that can damage cellular proteins, lipids, and DNA. Natural antioxidants remove excess free radical intermediates by reducing hydrogen donors or quenching singlet oxygen and delaying oxidative reactions in actively growing cancer cells. These reducing agents have the potential to hinder cancer progression only when administered at the right proportions along with chemo-/radiotherapies. Antioxidants and enzymes affect signal transduction and energy metabolism pathways for the maintenance of cellular redox status. A decline in antioxidant capacity arising from genetic mutations may increase the mitochondrial flux of free radicals resulting in misfiring of cellular signalling pathways. Often, a metabolic reprogramming arising from these mutations in metabolic enzymes leads to the overproduction of so called ’oncometabolites’ in a state of ‘pseudohypoxia’. This can inactivate several of the intracellular molecules involved in epigenetic and redox regulations, thereby increasing oxidative stress giving rise to growth advantages for cancerous cells. Undeniably, these are cell-type and Reactive Oxygen Species (ROS) specific, which is manifested as changes in the enzyme activation, differences in gene expression, cellular functions as well as cell death mechanisms. Photodynamic therapy (PDT) using light-activated photosensitizing molecules that can regulate cellular redox balance in accordance with the changes in endogenous ROS production is a solution for many of these challenges in cancer therapy.

Cytochrome C Oxidase Assembly Factor 1 Homolog Predicts Poor Prognosis and Promotes Cell Proliferation in Colorectal Cancer by Regulating PI3K/AKT Signaling

Purpose

Colorectal cancer (CRC) is one of the most common malignancies in the world. The prognosis of advanced CRC is still poor. The purpose of this study was to identify a gene expression profile associated with CRC that may contribute to the early diagnosis of CRC and improve patient prognosis.

Patients and Methods

Five pairs of CRC tissues and paracancerous tissues were used to identify causative genes using microarray assays. The prognostic value of Cytochrome C Oxidase Assembly Factor 1 Homolog (COA1) in CRC was assessed in 90 CRC patients. Loss-of-function assays, cell proliferation assays using Celigo and MTT, colony formation assays, a subcutaneous xenograft mouse model, and apoptosis assays were used to define the effects of downregulation of COA1 in CRC cells in vitro and in vivo. The underlying molecular mechanisms of COA1 in CRC were also investigated.

Results

The causative gene COA1 was identified through microarray analysis. COA1 expression in CRC was notably associated with pathologic differentiation, tumor size, and tumor depth. COA1 expression may act as an independent prognostic factor for overall survival of CRC. Knockdown of COA1 inhibited the proliferation of CRC cells in vitro and the tumorigenicity of CRC cells in vivo. Decreased COA1 expression induced apoptosis of CRC cells. Based on the microarray assay results comparing HCT116 cells transfected with lentivirus encoding anti-COA1 shRNA or negative control shRNA, ingenuity pathway analysis (IPA) revealed that the PI3K/AKT signaling pathway was significantly enriched. Moreover, CCND1, mTOR, AKT1, and MDM2 were identified as the downstream genes of COA1.

Conclusion

These findings demonstrate that COA1 promotes CRC cell proliferation and inhibits apoptosis by regulating the PI3K/AKT signaling pathway. Our results implicate COA1 as a potential oncogene involved in tumor growth and progression of CRC.

Targets (Metabolic Mediators) of Therapeutic Importance in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC), an extremely aggressive invasive cancer, is the fourth most common cause of cancer-related death in the United States. The higher mortality in PDAC is often attributed to the inability to detect it until it has reached advanced stages. The major challenge in tackling PDAC is due to its elusive pathology, minimal effectiveness, and resistance to existing therapeutics. The aggressiveness of PDAC is due to the capacity of tumor cells to alter their metabolism, utilize the diverse available fuel sources to adapt and grow in a hypoxic and harsh environment. Therapeutic resistance is due to the presence of thick stroma with poor angiogenesis, thus making drug delivery to tumor cells difficult. Investigating the metabolic mediators and enzymes involved in metabolic reprogramming may lead to the identification of novel therapeutic targets. The metabolic mediators of glucose, glutamine, lipids, nucleotides, amino acids and mitochondrial metabolism have emerged as novel therapeutic targets. Additionally, the role of autophagy, macropinocytosis, lysosomal transport, recycling, amino acid transport, lipid transport, and the role of reactive oxygen species has also been discussed. The role of various pro-inflammatory cytokines and immune cells in the pathogenesis of PDAC and the metabolites involved in the signaling pathways as therapeutic targets have been previously discussed. This review focuses on the therapeutic potential of metabolic mediators in PDAC along with stemness due to metabolic alterations and their therapeutic importance.

Pathogenic Heteroplasmic Somatic Mitochondrial DNA Mutation Confers Platinum-Resistance and Recurrence of High-Grade Serous Ovarian Cancer

Purpose

Platinum resistance is a primary barrier to improving the survival rate of ovarian cancer. The relationship between mtDNA somatic mutations and response to platinum-based chemotherapy in ovarian cancer has not been well clarified.

Patients and Methods

Here, we employed the next-generation sequencing (NGS) platform to identify mtDNA mutations of the unrelated high-grade serous ovarian cancer (HGSOC) patients.

Results

We identified 569 germline variants and 28 mtDNA somatic mutations, and found the platinum-sensitive relapsed HGSOC patients had more synonymous mutations while the platinum-resistant relapsed HGSOC patients had more missense mutations in the mtDNA somatic mutations. Meanwhile, we found that the HGSOC patients who harbored heteroplasmic pathogenic mtDNA somatic mutations had significantly higher prevalence of both platinum-resistance and relapse than those without (80.0% versus 16.7%, p=0.035). Additionally, we observed that the tumor tissues had significantly higher lactate-to-pyruvate (L/P) ratio than the paired nontumor tissues (p<0.001), and L/P ratio of tumors with any heteroplasmic pathogenic mtDNA mutations was significantly higher than that of the tumors free of pathogenic mtDNA mutations (p=0.025).

Conclusion

Our findings indicate that these heteroplasmic pathogenic mtDNA somatic mutations may cause decreased respiratory chain activity and lead to the metabolism remodeling that seem to be beneficial for progression of both platinum-based chemotherapy resistance and relapse.

Dissecting the Crosstalk between NRF2 Signaling and Metabolic Processes in Cancer

The transcription factor NRF2 (nuclear factor-erythroid 2 p45-related factor 2 or NFE2L2) plays a critical role in response to cellular stress. Following an oxidative insult, NRF2 orchestrates an antioxidant program, leading to increased glutathione levels and decreased reactive oxygen species (ROS). Mounting evidence now implicates the ability of NRF2 to modulate metabolic processes, particularly those at the interface between antioxidant processes and cellular proliferation. Notably, NRF2 regulates the pentose phosphate pathway, NADPH production, glutaminolysis, lipid and amino acid metabolism, many of which are hijacked by cancer cells to promote proliferation and survival. Moreover, deregulation of metabolic processes in both normal and cancer-based physiology can stabilize NRF2. We will discuss how perturbation of metabolic pathways, including the tricarboxylic acid (TCA) cycle, glycolysis, and autophagy can lead to NRF2 stabilization, and how NRF2-regulated metabolism helps cells deal with these metabolic stresses. Finally, we will discuss how the negative regulator of NRF2, Kelch-like ECH-associated protein 1 (KEAP1), may play a role in metabolism through NRF2 transcription-independent mechanisms. Collectively, this review will address the interplay between the NRF2/KEAP1 complex and metabolic processes.

Mitochondria as the decision makers for cancer cell fate: from signaling pathways to therapeutic strategies

As pivotal players in cellular metabolism, mitochondria have a double-faceted role in the final decision of cell fate. This is true for all cell types, but it is even more important and intriguing in the cancer setting. Mitochondria regulate cell fate in many diverse ways: through metabolism, by producing ATP and other metabolites deemed vital or detrimental for cancer cells; through the regulation of Ca²⁺ homeostasis, especially by the joint participation of the endoplasmic reticulum in a membranous tethering system for Ca²⁺ signaling called mitochondria-ER associated membranes (MAMs); and by regulating signaling pathways involved in the survival of cancer cells such as mitophagy. Recent studies have shown that mitochondria can also play a role in the regulation of inflammatory pathways in cancer cells, for example, through the release of mitochondrial DNA (mtDNA) involved in the activation of the cGAS-cGAMP-STING pathway. In this review, we aim to explore the role of mitochondria as decision makers in fostering cancer cell death or survival depending on the tumor cell stage and describe novel anticancer therapeutic strategies targeting mitochondria.

Translocase of the outer mitochondrial membrane complex subunit 20 (TOMM20) facilitates cancer aggressiveness and therapeutic resistance in chondrosarcoma

Chondrosarcoma is the second most common primary bone malignancy, representing one fourth of all primary bone sarcomas. It is typically resistant to radiation and chemotherapy treatments. However, the molecular mechanisms that contribute to cancer aggressiveness in chondrosarcomas remain poorly characterized. Here, we studied the role of mitochondrial transporters in chondrosarcoma aggressiveness including chemotherapy resistance. Histological grade along with stage are the most important prognostic biomarkers in chondrosarcoma. We found that high-grade human chondrosarcoma tumors have higher expression of the mitochondrial protein, translocase of the outer mitochondrial membrane complex subunit 20 (TOMM20), compared to low-grade tumors. TOMM20 overexpression in human chondrosarcoma cells induces chondrosarcoma tumor growth in vivo. TOMM20 drives proliferation, resistance to apoptosis and chemotherapy resistance. Also, TOMM20 induces markers of epithelial to mesenchymal transition (EMT) and metabolic reprogramming in these mesenchymal tumors. In conclusion, TOMM20 drives chondrosarcoma aggressiveness and resistance to chemotherapy.

The Role of Pi, Glutamine and the Essential Amino Acids in Modulating the Metabolism in Diabetes and Cancer

Purpose

Re-examine the current metabolic models.

Methods

Review of literature and gene networks.

Results

Insulin activates Pi uptake, glutamine metabolism to stabilise lipid membranes. Tissue turnover maintains the metabolic health. Current model of intermediary metabolism (IM) suggests glucose is the source of energy, and anaplerotic entry of fatty acids and amino acids into mitochondria increases the oxidative capacity of the TCA cycle to produce the energy (ATP). The reduced cofactors, NADH and FADH2, have different roles in regulating the oxidation of nutrients, membrane potentials and biosynthesis. Trans-hydrogenation of NADH to NADPH activates the biosynthesis. FADH2 sustains the membrane potential during the cell transformations. Glycolytic enzymes assume the non-canonical moonlighting functions, enter the nucleus to remodel the genetic programmes to affect the tissue turnover for efficient use of nutrients. Glycosylation of the CD98 (4F2HC) stabilises the nutrient transporters and regulates the entry of cysteine, glutamine and BCAA into the cells. A reciprocal relationship between the leucine and glutamine entry into cells regulates the cholesterol and fatty acid synthesis and homeostasis in cells. Insulin promotes the Pi transport from the blood to tissues, activates the mitochondrial respiratory activity, and glutamine metabolism, which activates the synthesis of cholesterol and the de novo fatty acids for reorganising and stabilising the lipid membranes for nutrient transport and signal transduction in response to fluctuations in the microenvironmental cues. Fatty acids provide the lipid metabolites, activate the second messengers and protein kinases. Insulin resistance suppresses the lipid raft formation and the mitotic slippage activates the fibrosis and slow death pathways.

Carbon Nanodots Derived from Urea and Citric Acid in Living Cells: Cellular Uptake and Antioxidation Effect

Carbon nanodots (CNDs), reported as polyatomic carbon domains surrounded by amorphous carbon frames, have drawn extensive attention due to their easy-to-synthesis, outstanding electronic properties, and superior biocompatibility. However, substantial assessments regarding their biological performance are still needed, considering the complex nature of this type of relatively new nanoparticles. In this report, CNDs derived from urea and citric acid (U-CNDs) are investigated in the treatment of two cell lines, EA.hy926 and A549 cells, to examine the biocompatibility, cellular uptake, and antioxidation effect. The intracellular uptake study suggests an energy-dependent transport process into the cells mainly involving macropinocytosis and lipid raft-mediated endocytosis pathways. Moreover, the U-CNDs mostly target the mitochondria and present strong antioxidative effects by scavenging reactive oxygen species (ROS) in cells. Overall the findings in this report manifest that the U-CNDs could serve as a bioimaging reagent and antioxidant causing little deleteriousness in the respects of viability, plasma membrane integrity, and mitochondrial activity in both cell lines, and demonstrate some efficacy for inhibiting the metabolic activities of A549 cancer cells at higher concentration.

Biodegradable hollow mesoporous organosilica nanotheranostics (HMON) for multi-mode imaging and mild photo-therapeutic-induced mitochondrial damage on gastric cancer

Background

CuS-modified hollow mesoporous organosilica nanoparticles (HMON@CuS) have been preferred as non-invasive treatment for cancer, as near infrared (NIR)-induced photo-thermal effect (PTT) and/or photo-dynamic effect (PDT) could increase cancer cells’ apoptosis. However, the certain role of HMON@CuS-produced-PTT&PDT inducing gastric cancer (GC) cells’ mitochondrial damage, remained unclear. Moreover, theranostic efficiency of HMON@CuS might be well improved by applying multi-modal imaging, which could offer an optimal therapeutic region and time window. Herein, new nanotheranostics agents were reported by Gd doped HMON decorated by CuS nanocrystals (called HMON@CuS/Gd).

Results

HMON@CuS/Gd exhibited appropriate size distribution, good biocompatibility, l-Glutathione (GSH) responsive degradable properties, high photo-thermal conversion efficiency (82.4%) and a simultaneous reactive oxygen species (ROS) generation effect. Meanwhile, HMON@CuS/Gd could efficiently enter GC cells, induce combined mild PTT (43–45 °C) and PDT under mild NIR power density (0.8 W/cm²). Surprisingly, it was found that PTT might not be the only factor of cell apoptosis, as ROS induced by PDT also seemed playing an essential role. The NIR-induced ROS could attack mitochondrial transmembrane potentials (MTPs), then promote mitochondrial reactive oxygen species (mitoROS) production. Meanwhile, mitochondrial damage dramatically changed the expression of anti-apoptotic protein (Bcl-2) and pro-apoptotic protein (Bax). Since that, mitochondrial permeability transition pore (mPTP) was opened, followed by inducing more cytochrome c (Cyto C) releasing from mitochondria into cytosol, and finally activated caspase-9/caspase-3-depended cell apoptosis pathway. Our in vivo data also showed that HMON@CuS/Gd exhibited good fluorescence (FL) imaging (wrapping fluorescent agent), enhanced T1 imaging under magnetic resonance imaging (MRI) and infrared thermal (IRT) imaging capacities. Guided by FL/MRI/IRT trimodal imaging, HMON@CuS/Gd could selectively cause mild photo-therapy at cancer region, efficiently inhibit the growth of GC cells without evident systemic toxicity in vivo.

Conclusion

HMON@CuS/Gd could serve as a promising multifunctional nanotheranostic platform and as a cancer photo-therapy agent through inducing mitochondrial dysfunction on GC.

Cancer cells with defective oxidative phosphorylation require endoplasmic reticulum-to-mitochondria Ca2+ transfer for survival

Spontaneous Ca²⁺ signaling from the InsP₃R intracellular Ca²⁺ release channel to mitochondria is essential for optimal oxidative phosphorylation (OXPHOS) and ATP production. In cells with defective OXPHOS, reductive carboxylation replaces oxidative metabolism to maintain amounts of reducing equivalents and metabolic precursors. To investigate the role of mitochondrial Ca²⁺ uptake in regulating bioenergetics in these cells, we used OXPHOS-competent and OXPHOS-defective cells. Inhibition of InsP₃R activity or mitochondrial Ca²⁺ uptake increased α-ketoglutarate (αKG) abundance and the NAD⁺/NADH ratio, indicating that constitutive endoplasmic reticulum (ER)-to-mitochondria Ca²⁺ transfer promoted optimal αKG dehydrogenase (αKGDH) activity. Reducing mitochondrial Ca²⁺ inhibited αKGDH activity and increased NAD⁺, which induced SIRT1-dependent autophagy in both OXPHOS-competent and OXPHOS-defective cells. Whereas autophagic flux in OXPHOS-competent cells promoted cell survival, it was impaired in OXPHOS-defective cells because of inhibition of autophagosome-lysosome fusion. Inhibition of αKGDH and impaired autophagic flux in OXPHOS-defective cells resulted in pronounced cell death in response to interruption of constitutive flux of Ca²⁺ from ER to mitochondria. These results demonstrate that mitochondria play a fundamental role in maintaining bioenergetic homeostasis of both OXPHOS-competent and OXPHOS-defective cells, with Ca²⁺ regulation of αKGDH activity playing a pivotal role. Inhibition of ER-to-mitochondria Ca²⁺ transfer may represent a general therapeutic strategy against cancer cells regardless of their OXPHOS status.

Systematic analysis reveals a functional role for STAMBPL1 in the epithelial-mesenchymal transition process across multiple carcinomas

Background

Deubiquitinating enzymes (DUBs) are linked to cancer progression and dissemination, yet less is known about their regulation and impact on epithelial–mesenchymal transition (EMT).

Methods

An integrative translational approach combining systematic computational analyses of The Cancer Genome Atlas cancer cohorts with CRISPR genetics, biochemistry and immunohistochemistry methodologies to identify and assess the role of human DUBs in EMT.

Results

We identify a previously undiscovered biological function of STAM-binding protein like 1 (STAMBPL1) deubiquitinase in the EMT process in lung and breast carcinomas. We show that STAMBPL1 expression can be regulated by mutant p53 and that its catalytic activity is required to affect the transcription factor SNAI1. Accordingly, genetic depletion and CRISPR-mediated gene knockout of STAMBPL1 leads to marked recovery of epithelial markers, SNAI1 destabilisation and impaired migratory capacity of cancer cells. Reversely, STAMBPL1 expression reprogrammes cells towards a mesenchymal phenotype. A significant STAMBPL1-SNAI1 co-signature was observed across multiple tumour types. Importantly, STAMBPL1 is highly expressed in metastatic tissues compared to matched primary tumour of the same lung cancer patient and its expression predicts poor prognosis.

Conclusions

Our study provides a novel concept of oncogenic regulation of a DUB and presents a new role and predictive value of STAMBPL1 in the EMT process across multiple carcinomas.

Tumor microenvironment and epithelial mesenchymal transition as targets to overcome tumor multidrug resistance

It is well established that multifactorial drug resistance hinders successful cancer treatment. Tumor cell interactions with the tumor microenvironment (TME) are crucial in epithelial-mesenchymal transition (EMT) and multidrug resistance (MDR). TME-induced factors secreted by cancer cells and cancer-associated fibroblasts (CAFs) create an inflammatory microenvironment by recruiting immune cells. CD11b+/Gr-1+ myeloid-derived suppressor cells (MDSCs) and inflammatory tumor associated macrophages (TAMs) are main immune cell types which further enhance chronic inflammation. Chronic inflammation nurtures tumor-initiating/cancer stem-like cells (CSCs), induces both EMT and MDR leading to tumor relapses. Pro-thrombotic microenvironment created by inflammatory cytokines and chemokines from TAMs, MDSCs and CAFs is also involved in EMT and MDR. MDSCs are the most common mediators of immunosuppression and are also involved in resistance to targeted therapies, e.g. BRAF inhibitors and oncolytic viruses-based therapies. Expansion of both cancer and stroma cells causes hypoxia by hypoxia-inducible transcription factors (e.g. HIF-1α) resulting in drug resistance. TME factors induce the expression of transcriptional EMT factors, MDR and metabolic adaptation of cancer cells. Promoters of several ATP-binding cassette (ABC) transporter genes contain binding sites for canonical EMT transcription factors, e.g. ZEB, TWIST and SNAIL. Changes in glycolysis, oxidative phosphorylation and autophagy during EMT also promote MDR. Conclusively, EMT signaling simultaneously increases MDR. Owing to the multifactorial nature of MDR, targeting one mechanism seems to be non-sufficient to overcome resistance. Targeting inflammatory processes by immune modulatory compounds such as mTOR inhibitors, demethylating agents, low-dosed histone deacetylase inhibitors may decrease MDR. Targeting EMT and metabolic adaptation by small molecular inhibitors might also reverse MDR. In this review, we summarize evidence for TME components as causative factors of EMT and anticancer drug resistance.

Metabolomics markers in Neurology: current knowledge and future perspectives for therapeutic targeting

INTRODUCTION

Metabolomics is an emerging approach providing new insights into the metabolic changes and underlying mechanisms involved in the pathogenesis of neurological disorders.

AREAS COVERED

Here, the authors present an overview of the current knowledge of metabolic profiling (metabolomics) to provide critical insight on the role of biochemical markers and metabolic alterations in neurological diseases.

EXPERT OPINION

Elucidation of characteristic metabolic alterations in neurological disorders is crucial for a better understanding of their pathogenesis, and for identifying potential biomarkers and drug targets. Nevertheless, discrepancies in diagnostic criteria, sample handling protocols, and analytical methods still affect the generalizability of current study results.

Concerted Action of AMPK and Sirtuin-1 Induces Mitochondrial Fragmentation Upon Inhibition of Ca2+ Transfer to Mitochondria

Mitochondria are highly dynamic organelles constantly undergoing fusion and fission. Ca²⁺ regulates many aspects of mitochondrial physiology by modulating the activity of several mitochondrial proteins. We previously showed that inhibition of constitutive IP3R-mediated Ca²⁺ transfer to the mitochondria leads to a metabolic cellular stress and eventually cell death. Here, we show that the decline of mitochondrial function generated by a lack of Ca²⁺ transfer induces a DRP-1 independent mitochondrial fragmentation that at an early time is mediated by an increase in the NAD+/NADH ratio and activation of SIRT1. Subsequently, AMPK predominates and drives the fragmentation. SIRT1 activation leads to the deacetylation of cortactin, favoring actin polymerization, and mitochondrial fragmentation. Knockdown of cortactin or inhibition of actin polymerization prevents fragmentation. These data reveal SIRT1 as a new player in the regulation of mitochondrial fragmentation induced by metabolic/bioenergetic stress through regulating the actin cytoskeleton.

Mitochondria in cancer

The rediscovery and reinterpretation of the Warburg effect in the year 2000 occulted for almost a decade the key functions exerted by mitochondria in cancer cells. Until recent times, the scientific community indeed focused on constitutive glycolysis as a hallmark of cancer cells, which it is not, largely ignoring the contribution of mitochondria to the malignancy of oxidative and glycolytic cancer cells, being Warburgian or merely adapted to hypoxia. In this review, we highlight that mitochondria are not only powerhouses in some cancer cells, but also dynamic regulators of life, death, proliferation, motion and stemness in other types of cancer cells. Similar to the cells that host them, mitochondria are capable to adapt to tumoral conditions, and probably to evolve to ‘oncogenic mitochondria' capable of transferring malignant capacities to recipient cells. In the wider quest of metabolic modulators of cancer, treatments have already been identified targeting mitochondria in cancer cells, but the field is still in infancy.

Targeting Pyruvate Carboxylase by a Small Molecule Suppresses Breast Cancer Progression

Rapid metabolism differentiates cancer cells from normal cells and relies on anaplerotic pathways. However, the mechanisms of anaplerosis-associated enzymes are rarely understood. The lack of potent and selective antimetabolism drugs restrains further clinical investigations. A small molecule ZY-444 ((N 4-((5-(4-(benzyloxy)phenyl)-2-thiophenyl)methyl)-N 2-isobutyl-2,4-pyrimidinediamine) is discovered to inhibit cancer cell proliferation specifically, having potent efficacies against tumor growth, metastasis, and recurrence. ZY-444 binds to cellular pyruvate carboxylase (PC), a key anaplerotic enzyme of the tricarboxylic acid cycle, and inactivates its catalytic activity. PC inhibition suppresses breast cancer growth and metastasis through inhibiting the Wnt/β-catenin/Snail signaling pathway. Lower PC expression in patient tumors is correlated with significant survival benefits. Comparative profiles of PC expression in cancer versus normal tissues implicate the tumor selectivity of ZY-444. Overall, ZY-444 holds promise therapeutically as an anti-cancer metabolism agent.

Mitochondria in early development: linking the microenvironment, metabolism and the epigenome

Mitochondria, originally of bacterial origin, are highly dynamic organelles that have evolved a symbiotic relationship within eukaryotic cells. Mitochondria undergo dynamic, stage-specific restructuring and redistribution during oocyte maturation and preimplantation embryo development, necessary to support key developmental events. Mitochondria also fulfil a wide range of functions beyond ATP synthesis, including the production of intracellular reactive oxygen species and calcium regulation, and are active participants in the regulation of signal transduction pathways. Communication between not only mitochondria and the nucleus, but also with other organelles, is emerging as a critical function which regulates preimplantation development. Significantly, perturbations and deficits in mitochondrial function manifest not only as reduced quality and/or poor oocyte and embryo development but contribute to post-implantation failure, long-term cell function and adult disease. A growing body of evidence indicates that altered availability of metabolic co-factors modulate the activity of epigenetic modifiers, such that oocyte and embryo mitochondrial activity and dynamics have the capacity to establish long-lasting alterations to the epigenetic landscape. It is proposed that preimplantation embryo development may represent a sensitive window during which epigenetic regulation by mitochondria is likely to have significant short- and long-term effects on embryo, and offspring, health. Hence, mitochondrial integrity, communication and metabolism are critical links between the environment, the epigenome and the regulation of embryo development.

Cancer and pulmonary hypertension: Learning lessons and real-life interplay

This article reviews the scientific reasons that support the intriguing vision of pulmonary hypertension (PH) as a disease with a cancer-like nature and to understand whether this point of view may have fruitful consequences for the overall management of PH. This review compares cancer and PH in view of Hanahan and Weinberg’s principles (i.e., hallmarks of cancer) with an emphasis on hyperproliferative, metabolic, and immune/inflammatory aspects of the disease. In addition, this review provides a perspective on the role of transcription factors and chromatin and epigenetic aberrations, besides genetics, as “common driving mechanisms” of PH hallmarks and the foreseeable use of transcription factor/epigenome targeting as multitarget approach against the hallmarks of PH. Thus, recognition of the widespread applicability and analogy of these concepts will increasingly affect the development of new means of PH treatment.

Metabolic pathway analyses identify proline biosynthesis pathway as a promoter of liver tumorigenesis

BACKGROUND & AIM

Under the regulation of various oncogenic pathways, cancer cells undergo adaptive metabolic programming to maintain specific metabolic states that support their uncontrolled proliferation. As it has been difficult to directly and effectively inhibit oncogenic signaling cascades with pharmaceutical compounds, focusing on the downstream metabolic pathways that enable indefinite growth may provide therapeutic opportunities. Thus, we sought to characterize metabolic changes in hepatocellular carcinoma (HCC) development and identify metabolic targets required for tumorigenesis.

METHODS

We compared gene expression profiles of Morris Hepatoma (MH3924a) and DEN (diethylnitrosamine)-induced HCC models to those of liver tissues from normal and rapidly regenerating liver models, and performed gain- and loss-of-function studies of the identified gene targets for their roles in cancer cell proliferation in vitro and in vivo.

RESULTS

The proline biosynthetic enzyme PYCR1 (pyrroline-5-carboxylate reductase 1) was identified as one of the most upregulated genes in the HCC models. Knockdown of PYCR1 potently reduced cell proliferation of multiple HCC cell lines in vitro and tumor growth in vivo. Conversely, overexpression of PYCR1 enhanced the proliferation of the HCC cell lines. Importantly, PYCR1 expression was not elevated in the regenerating liver, and KD or overexpression of PYCR1 had no effect on proliferation of non-cancerous cells. Besides PYCR1, we found that additional proline biosynthetic enzymes, such as ALDH18A1, were upregulated in HCC models and also regulated HCC cell proliferation. Clinical data demonstrated that PYCR1 expression was increased in HCC, correlated with tumor grade, and was an independent predictor of clinical outcome.

CONCLUSION

Enhanced expression of proline biosynthetic enzymes promotes HCC cell proliferation. Inhibition of PYCR1 or ALDH18A1 may be a novel therapeutic strategy to target HCC.

LAY SUMMARY

Even with the recently approved immunotherapies against liver cancer, currently available medications show limited clinical benefits or efficacy in the majority of patients. As such, it remains a top priority to discover new targets for effective liver cancer treatment. Here, we identify a critical role for the proline biosynthetic pathway in liver cancer development, and demonstrate that targeting key proteins in the pathway, namely PYCR1 and ALDH18A1, may be a novel therapeutic strategy for liver cancer.

Targeting metabolic dependencies in pediatric cancer

PURPOSE OF REVIEW

In an attempt to identify potential new therapeutic targets, efforts to describe the metabolic features unique to cancer cells are increasingly being reported. Although current standard of care regimens for several pediatric malignancies incorporate agents that target tumor metabolism, these drugs have been part of the therapeutic landscape for decades. More recent research has focused on the identification and targeting of new metabolic vulnerabilities in pediatric cancers. The purpose of this review is to describe the most recent translational findings in the metabolic targeting of pediatric malignancies.

RECENT FINDINGS

Across multiple pediatric cancer types, dependencies on a number of key metabolic pathways have emerged through study of patient tissue samples and preclinical modeling. Among the potentially targetable vulnerabilities are glucose metabolism via glycolysis, oxidative phosphorylation, amino acid and polyamine metabolism, and NAD metabolism. Although few agents have yet to move forward into clinical trials for pediatric cancer patients, the robust and promising preclinical data that have been generated suggest that future clinical trials should rationally test metabolically targeted agents for relevant disease populations.

SUMMARY

Recent advances in our understanding of the metabolic dependencies of pediatric cancers represent a source of potential new therapeutic opportunities for these diseases.

Metabolic Plasticity of Tumor Cells: How They Do Adapt to Food Deprivation

Dysregulated metabolism is a key hallmark of cancer cells and an enticing target for cancer treatment. Since the last 10 years, research on cancer metabolism has moved from pathway attention to network consideration. This metabolic complexity continuously adapt to new constraints in the tumor microenvironment. In this review, we will highlight striking changes in cancer cell metabolism compared to normal cells. Understanding this tumor metabolic plasticity suggests potential new targets and innovative combinatorial treatments for fighting cancer.

Energy Metabolism Rewiring Precedes UVB-Induced Primary Skin Tumor Formation

Although growing evidence indicates that bioenergetic metabolism plays an important role in the progression of tumorigenesis, little information is available on the contribution of reprogramming of energy metabolism in cancer initiation. By applying a quantitative proteomic approach and targeted metabolomics, we find that specific metabolic modifications precede primary skin tumor formation. Using a multistage model of ultraviolet B (UVB) radiation-induced skin cancer, we show that glycolysis, tricarboxylic acid (TCA) cycle, and fatty acid β-oxidation are decreased at a very early stage of photocarcinogenesis, while the distal part of the electron transport chain (ETC) is upregulated. Reductive glutamine metabolism and the activity of dihydroorotate dehydrogenase (DHODH) are both necessary for maintaining high ETC. Mice with decreased DHODH activity or impaired ETC failed to develop pre-malignant and malignant lesions. DHODH activity represents a major link between DNA repair efficiency and bioenergetic patterning during skin carcinogenesis.

Intramitochondrial Src kinase links mitochondrial dysfunctions and aggressiveness of breast cancer cells

High levels and activity of Src kinase are common among breast cancer subtypes, and several inhibitors of the kinase are currently tested in clinical trials. Alterations in mitochondrial activity is also observed among the different types of breast cancer. Src kinase is localized in several subcellular compartments, including mitochondria where it targets several proteins to modulate the activity of the organelle. Although the subcellular localization of other oncogenes modulates the potency of known treatments, nothing is known about the specific role of intra-mitochondrial Src (mtSrc) in breast cancer. The aim of this work was to determine whether mtSrc kinase has specific impact on breast cancer cells. We first observed that activity of mtSrc is higher in breast cancer cells of the triple negative subtype. Over-expression of Src specifically targeted to mitochondria reduced mtDNA levels, mitochondrial membrane potential and cellular respiration. These alterations of mitochondrial functions led to lower cellular viability, shorter cell cycle and increased invasive capacity. Proteomic analyses revealed that mtSrc targets the mitochondrial single-stranded DNA-binding protein, a regulator of mtDNA replication. Our findings suggest that mtSrc promotes aggressiveness of breast cancer cells via phosphorylation of mitochondrial single-stranded DNA-binding protein leading to reduced mtDNA levels and mitochondrial activity. This study highlights the importance of considering the subcellular localization of Src kinase in the development of potent therapy for breast cancer.

Rescue of TCA Cycle Dysfunction for Cancer Therapy

Mitochondrion, a maternally hereditary, subcellular organelle, is the site of the tricarboxylic acid (TCA) cycle, electron transport chain (ETC), and oxidative phosphorylation (OXPHOS)—the basic processes of ATP production. Mitochondrial function plays a pivotal role in the development and pathology of different cancers. Disruption in its activity, like mutations in its TCA cycle enzymes, leads to physiological imbalances and metabolic shifts of the cell, which contributes to the progression of cancer. In this review, we explored the different significant mutations in the mitochondrial enzymes participating in the TCA cycle and the diseases, especially cancer types, that these malfunctions are closely associated with. In addition, this paper also discussed the different therapeutic approaches which are currently being developed to address these diseases caused by mitochondrial enzyme malfunction.

Impact of mitonuclear interactions on life-history responses to diet

Mitochondria are central to both energy metabolism and biosynthesis. Mitochondrial function could therefore influence resource allocation. Critically, mitochondrial function depends on interactions between proteins encoded by the mitochondrial and nuclear genomes. Severe incompatibilities between these genomes can have pervasive effects on both fitness and longevity. How milder deficits in mitochondrial function affect life-history trade-offs is less well understood. Here, we analyse how mitonuclear interactions affect the trade-off between fecundity and longevity in Drosophila melanogaster. We consider a panel of 10 different mitochondrial DNA haplotypes against two contrasting nuclear backgrounds (w¹¹¹⁸ (WE) and Zim53 (ZIM)) in response to high-protein versus standard diet. We report strikingly different responses between the two nuclear backgrounds. WE females have higher fecundity and decreased longevity on high protein. ZIM females have much greater fecundity and shorter lifespan than WE flies on standard diet. High protein doubled their fecundity with no effect on longevity. Mitochondrial haplotype reflected nuclear life-history trade-offs, with a negative correlation between longevity and fecundity in WE flies and no correlation in ZIM flies. Mitonuclear interactions had substantial effects but did not reflect genetic distance between mitochondrial haplotypes. We conclude that mitonuclear interactions can have significant impact on life-history trade-offs, but their effects are not predictable by relatedness. This article is part of the theme issue 'Linking the mitochondrial genotype to phenotype: a complex endeavour'.

Cytoproliferative and Anti-Oxidant Effects Induced by Tannic Acid in Human Embryonic Kidney (Hek-293) Cells

Tannic acid (TA) portrays a myriad of beneficial properties and has forthwith achieved incessant significance for its cytoprotective qualities in traditional and modern-day medicine. However, TA displays an ambiguous nature demonstrating anti-oxidant and pro-oxidant traits, beckoning further research. Although vast literature on the anti-proliferative effects of TA on cancer cell lines exist, the effects on normal cells remain unchartered. Herein, the cytoproliferative and anti-oxidant effects induced by TA in human embryonic kidney (Hek-293) cells were investigated. Data obtained from the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay demonstrated that TA increased the cell viability and cellular proliferation rate at higher concentrations. Hoechst assay, examining proliferation marker Ki67 supported these findings. DNA fragmentation and oxidative stress-inducers were specifically noted at IC25 and IC50 treatments via biochemical assays. This alluded to TA's pro-oxidant characteristics. However, the countervailing anti-oxidant defence mechanisms as the endogenous anti-oxidants and phase2 detoxification enzymes were significantly upregulated. Luminometry fortified the anti-oxidant capacity of TA, whereby executioner caspase-3/7 were not activated subservient to the activation of initiator caspases-8 and -9. Thus, proving that TA has anti-apoptotic traits, inter alia. Therefore, TA proved to harbour anti-oxidant, anti-apoptotic, and proliferative effects in Hek-293 cells with its partial cytotoxic responses being outweighed by its cytoprotective mechanisms.

The Metabolic Landscape of Lung Cancer: New Insights in a Disturbed Glucose Metabolism

Metabolism encompasses the biochemical processes that allow healthy cells to keep energy, redox balance and building blocks required for cell development, survival, and proliferation steady. Malignant cells are well-documented to reprogram their metabolism and energy production networks to support rapid proliferation and survival in harsh conditions via mutations in oncogenes and inactivation of tumor suppressor genes. Despite the histologic and genetic heterogeneity of tumors, a common set of metabolic pathways sustain the high proliferation rates observed in cancer cells. This review with a focus on lung cancer covers several fundamental principles of the disturbed glucose metabolism, such as the “Warburg” effect, the importance of the glycolysis and its branching pathways, the unanticipated gluconeogenesis and mitochondrial metabolism. Furthermore, we highlight our current understanding of the disturbed glucose metabolism and how this might result in the development of new treatments.

MicroRNA-519d-3p inhibits cell proliferation and cell cycle G1/S transition in glioma by targeting CCND1

Glioma is the most common highly malignant primary brain tumor. MicroRNA-519d-3p exerts important effects in several tumors, but its functional role in glioma remained poorly understood. In this study, we found miR-519d-3p expression was significantly decreased in glioma tissues and cell lines. Moreover, the in vitro experiments showed that overexpression of miR-519d-3p suppressed cell proliferation and induced cell cycle G0/G1 phase arrest using MTT and flow cytometry assays in glioma cell lines, U87 and U251. Mechanistically, Cyclin D1 (CCND1) was predicted and confirmed as the direct target genes of miR-519d-3p using luciferase report assay. In addition, knockdown of CCND1 imitated the suppressive effects of miR-519d-3p on cell proliferation and cell cycle progression. Furthermore, restoration of CCND1 reversed the effects of miR-519d-3p overexpression in glioma cells. Taken together, these data demonstrate that suppression of CCND1 by miR-519d-3p might be a therapeutic target for glioma.Abbreviations miR-519d-3p: microRNA-519d-3p; CCND1: Cyclin D1; ATCC: American Type Culture Collection; MTT: 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide; PI: propidium iodide; WT: wild type; MUT: mutant type; SD: standard deviation.

Cancer-specific metabolism: Promising approaches for colorectal cancer treatment

Investigation of cancer-specific metabolism has made it possible to establish the principle that atypically reconstituted metabolism is considered a hallmark of cancer due to changes in physiological property. Recently, a variety of targets depending on the prompted aerobic glycolysis process, starting from the abnormal uptake of glucose, and cancer-specific metabolism due to impaired mitochondrial function and abnormal expression of drug-metabolizing enzymes have been investigated and discovered. Given that most solid cancers rely on cancer-specific metabolism to support their growth, it is necessary to examine closely the specific processes of cancer metabolism and have a detailed understanding of how cellular metabolism is altered in colorectal cancer (CRC) related to CRC survival and proliferation. The development of key methods to regulate efficiently cancer-specific metabolism in CRC is still in the initial stage. Therefore, targeting cancer-specific metabolism will yield treatable methods that are critical as a new area of development strategies for CRC treatment.

Cancer-specific metabolism: Promising approaches for colorectal cancer treatment

Investigation of cancer-specific metabolism has made it possible to establish the principle that atypically reconstituted metabolism is considered a hallmark of cancer due to changes in physiological property. Recently, a variety of targets depending on the prompted aerobic glycolysis process, starting from the abnormal uptake of glucose, and cancer-specific metabolism due to impaired mitochondrial function and abnormal expression of drug-metabolizing enzymes have been investigated and discovered. Given that most solid cancers rely on cancer-specific metabolism to support their growth, it is necessary to examine closely the specific processes of cancer metabolism and have a detailed understanding of how cellular metabolism is altered in colorectal cancer (CRC) related to CRC survival and proliferation. The development of key methods to regulate efficiently cancer-specific metabolism in CRC is still in the initial stage. Therefore, targeting cancer-specific metabolism will yield treatable methods that are critical as a new area of development strategies for CRC treatment.

Metabolic crosstalk in the breast cancer microenvironment

During tumorigenesis, breast tumour cells undergo metabolic reprogramming, which generally includes enhanced glycolysis, tricarboxylic acid cycle activity, glutaminolysis and fatty acid biosynthesis. However, the extension and functional importance of these metabolic alterations may diverge not only according to breast cancer subtypes, but also depending on the interaction of cancer cells with the complex surrounding microenvironment. This microenvironment comprises a variety of non-cancerous cells, such as immune cells (e.g. macrophages, lymphocytes, natural killer cells), fibroblasts, adipocytes and endothelial cells, together with extracellular matrix components and soluble factors, which influence cancer progression and are predictive of clinical outcome. The continuous interaction between cancer and stromal cells results in metabolic competition and symbiosis, with oncogenic-driven metabolic reprogramming of cancer cells shaping the metabolism of neighbouring cells and vice versa. This review addresses current knowledge on this metabolic crosstalk within the breast tumour microenvironment (TME). Improved understanding of how metabolism in the TME modulates cancer development and evasion of tumour-suppressive mechanisms may provide clues for novel anticancer therapeutics directed to metabolic targets.

SLC1A3 contributes to L-asparaginase resistance in solid tumors

L‐asparaginase (ASNase) serves as an effective drug for adolescent acute lymphoblastic leukemia. However, many clinical trials indicated severe ASNase toxicity in patients with solid tumors, with resistant mechanisms not well understood. Here, we took a functional genetic approach and identified SLC1A3 as a novel contributor to ASNase resistance in cancer cells. In combination with ASNase, SLC1A3 inhibition caused cell cycle arrest or apoptosis, and myriads of metabolic vulnerabilities in tricarboxylic acid (TCA) cycle, urea cycle, nucleotides biosynthesis, energy production, redox homeostasis, and lipid biosynthesis. SLC1A3 is an aspartate and glutamate transporter, mainly expressed in brain tissues, but high expression levels were also observed in some tumor types. Here, we demonstrate that ASNase stimulates aspartate and glutamate consumptions, and their refilling through SLC1A3 promotes cancer cell proliferation. Lastly, in vivo experiments indicated that SLC1A3 expression promoted tumor development and metastasis while negating the suppressive effects of ASNase by fueling aspartate, glutamate, and glutamine metabolisms despite of asparagine shortage. Altogether, our findings identify a novel role for SLC1A3 in ASNase resistance and suggest that restrictive aspartate and glutamate uptake might improve ASNase efficacy with solid tumors.

Mitochondrial supercomplex assembly promotes breast and endometrial tumorigenesis by metabolic alterations and enhanced hypoxia tolerance

Recent advance in cancer research sheds light on the contribution of mitochondrial respiration in tumorigenesis, as they efficiently produce ATP and oncogenic metabolites that will facilitate cancer cell growth. Here we show that a stabilizing factor for mitochondrial supercomplex assembly, COX7RP/COX7A2L/SCAF1, is abundantly expressed in clinical breast and endometrial cancers. Moreover, COX7RP overexpression associates with prognosis of breast cancer patients. We demonstrate that COX7RP overexpression in breast and endometrial cancer cells promotes in vitro and in vivo growth, stabilizes mitochondrial supercomplex assembly even in hypoxic states, and increases hypoxia tolerance. Metabolomic analyses reveal that COX7RP overexpression modulates the metabolic profile of cancer cells, particularly the steady-state levels of tricarboxylic acid cycle intermediates. Notably, silencing of each subunit of the 2-oxoglutarate dehydrogenase complex decreases the COX7RP-stimulated cancer cell growth. Our results indicate that COX7RP is a growth-regulatory factor for breast and endometrial cancer cells by regulating metabolic pathways and energy production.

Breast cancer risk in relation to plasma metabolites among Hispanic and African American women

PURPOSE

The metabolic etiology of breast cancer has been explored in the past several years using metabolomics. However, most of these studies only included non-Hispanic White individuals.

METHODS

To fill this gap, we performed a two-step (discovery and validation) metabolomics profiling in plasma samples from 358 breast cancer patients and 138 healthy controls. All study subjects were either Hispanics or non-Hispanic African Americans.

RESULTS

A panel of 14 identified metabolites significantly differed between breast cancer cases and healthy controls in both the discovery and validation sets. Most of these identified metabolites were lipids. In the pathway analysis, citrate cycle (TCA cycle), arginine and proline metabolism, and linoleic acid metabolism pathways were observed, and they significantly differed between breast cancer cases and healthy controls in both sets. From those 14 metabolites, we selected 9 non-correlated metabolites to generate a metabolic risk score. Increased metabolites risk score was associated with a 1.87- and 1.63-fold increased risk of breast cancer in the discovery and validation sets, respectively (Odds ratio (OR) 1.87, 95% Confidence interval (CI) 1.50, 2.32; OR 1.63, 95% CI 1.36, 1.95).

CONCLUSIONS

In summary, our study identified metabolic profiles and pathways that significantly differed between breast cancer cases and healthy controls in Hispanic or non-Hispanic African American women. The results from our study might provide new insights on the metabolic etiology of breast cancer.

CHCHD4 regulates tumour proliferation and EMT-related phenotypes, through respiratory chain-mediated metabolism

BACKGROUND

Mitochondrial oxidative phosphorylation (OXPHOS) via the respiratory chain is required for the maintenance of tumour cell proliferation and regulation of epithelial to mesenchymal transition (EMT)-related phenotypes through mechanisms that are not fully understood. The essential mitochondrial import protein coiled-coil helix coiled-coil helix domain-containing protein 4 (CHCHD4) controls respiratory chain complex activity and oxygen consumption, and regulates the growth of tumours in vivo. In this study, we interrogate the importance of CHCHD4-regulated mitochondrial metabolism for tumour cell proliferation and EMT-related phenotypes, and elucidate key pathways involved.

RESULTS

Using in silico analyses of 967 tumour cell lines, and tumours from different cancer patient cohorts, we show that CHCHD4 expression positively correlates with OXPHOS and proliferative pathways including the mTORC1 signalling pathway. We show that CHCHD4 expression significantly correlates with the doubling time of a range of tumour cell lines, and that CHCHD4-mediated tumour cell growth and mTORC1 signalling is coupled to respiratory chain complex I (CI) activity. Using global metabolomics analysis, we show that CHCHD4 regulates amino acid metabolism, and that CHCHD4-mediated tumour cell growth is dependent on glutamine. We show that CHCHD4-mediated tumour cell growth is linked to CI-regulated mTORC1 signalling and amino acid metabolism. Finally, we show that CHCHD4 expression in tumours is inversely correlated with EMT-related gene expression, and that increased CHCHD4 expression in tumour cells modulates EMT-related phenotypes.

CONCLUSIONS

CHCHD4 drives tumour cell growth and activates mTORC1 signalling through its control of respiratory chain mediated metabolism and complex I biology, and also regulates EMT-related phenotypes of tumour cells.

Comprehensive Metabolomic Analysis of IDH1R132H Clinical Glioma Samples Reveals Suppression of β-oxidation Due to Carnitine Deficiency

Gliomas with Isocitrate dehydrogenase 1 (IDH1) mutation have alterations in several enzyme activities, resulting in various metabolic changes. The aim of this study was to determine a mechanism for the better prognosis of gliomas with IDH mutation by performing metabolomic analysis. To understand the metabolic state of human gliomas, we analyzed clinical samples obtained from surgical resection of glioma patients (grades II–IV) with or without the IDH1 mutation, and compared the results with U87 glioblastoma cells overexpressing IDH1 or IDH1^R132H. In clinical samples of gliomas with IDH1 mutation, levels of D-2-hydroxyglutarate (D-2HG) were increased significantly compared with gliomas without IDH mutation. Gliomas with IDH mutation also showed decreased intermediates in the tricarboxylic acid cycle and pathways involved in the production of energy, amino acids, and nucleic acids. The marked difference in the metabolic profile in IDH mutant clinical glioma samples compared with that of mutant IDH expressing cells includes a decrease in β-oxidation due to acyl-carnitine and carnitine deficiencies. These metabolic changes may explain the lower cell division rate observed in IDH mutant gliomas and may provide a better prognosis in IDH mutant gliomas.

Synthesis, characterization and efficacy of mitochondrial targeted delivery of TPP-curcumin in rotenone-induced toxicity

BACKGROUND

Mitochondrial impairments due to free radicals are implicated in a wide range of neurotoxicological alterations. Curcumin, an active ingredient of turmeric has shown protective efficacy against oxidative damage due to its strong antioxidant potential, but its efficiency is restricted due to low bioavailability in the mitochondria. In view of this, we have synthesized mitochondria-targeted curcumin (MTC) with an aim to investigate its efficacy against rotenone-induced oxidative damage in mice and isolated mitochondria.

METHODS

MTC was synthesized by attaching the triphenylphosphonium cation (TPP) as a cationic carrier to the curcumin to assess its protective efficacy in rotenone-induced in-vitro and in-vivo toxicity in mice.

RESULTS

In-vitro treatment of rotenone in isolated mitochondria caused a significant increase in lipid peroxidation (2.74 fold, 3.62 fold), protein carbonyl contents (2.62 fold, 1.81 fold), and decrease in levels of reduced glutathione (2.02 fold, 1.70 fold) as compared to control. Pre-treatment of curcumin and MTC along with rotenone in the isolated mitochondria significantly reduce the oxidative stress as compared to those treated with rotenone alone. Rotenone treatment in mice significantly increased lipid peroxidation (2.02 fold) and decreased the levels of reduced glutathione (2.99 fold), superoxide dismutase (2.09 fold) and catalase (3.60 fold) in the liver as compared to controls. Co-treatment of curcumin and MTC along with rotenone significantly reduced lipid peroxidation (1.26 fold, 1.76 fold) and increased the levels of reduced glutathione (1.60 fold, 2.43 fold), superoxide dismutase (1.45 fold, 1.99 fold) and catalase (2.32 fold, 2.90 fold) as compared to those treated with rotenone alone.

CONCLUSION

The results of the present study indicate that the protective efficacy of MTC against rotenone-induced oxidative damage was more promising than curcumin in both in-vitro and in-vivo system which indicates the enhanced bioavailability of MTC. Graphical abstract Effect of mitochondrial targeted delivery of TPP-curcumin in rotenone-induced toxicity.

Global serum metabolomics profiling of colorectal cancer

Accurate diagnosis of colorectal cancer (CRC) relies on the use of invasive tools such as colonoscopy and sigmoidoscopy. Non-invasive tools are less sensitive in detecting the disease, particularly in the early stage. A number of researchers have used metabolomics analyses on serum/plasma samples of patients with CRC compared with normal healthy individuals in an effort to identify biomarkers for CRC. The aim of the present review is to compare reported serum metabolomics profiles of CRC and to identify common metabolites affected among these studies. A literature search was performed to include any experimental studies on global metabolomics profile of CRC using serum/plasma samples published up to March 2018. The Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool was used to assess the quality of the studies reviewed. In total, nine studies were included. The studies used various analytical platforms and were performed on different populations. A pathway enrichment analysis was performed using the data from all the studies under review. The most affected pathways identified were protein biosynthesis, urea cycle, ammonia recycling, alanine metabolism, glutathione metabolism and citric acid cycle. The metabolomics analysis revealed levels of metabolites of glycolysis, tricarboxylic acid cycle, anaerobic respiration, protein, lipid and glutathione metabolism were significantly different between cancer and control samples. Although the majority of differentiating metabolites identified were different in the different studies, there were several metabolites that were common. These metabolites include pyruvic acid, glucose, lactic acid, malic acid, fumaric acid, 3-hydroxybutyric acid, tryptophan, phenylalanine, tyrosine, creatinine and ornithine. The consistent dysregulation of these metabolites among the different studies suggest the possibility of common diagnostic biomarkers for CRC.

Mito-Nuclear Communication in Hepatocellular Carcinoma Metabolic Rewiring

As the main metabolic and detoxification organ, the liver constantly adapts its activity to fulfill the energy requirements of the whole body. Despite the remarkable adaptive capacity of the liver, prolonged exposure to noxious stimuli such as alcohol, viruses and metabolic disorders results in the development of chronic liver disease that can progress to hepatocellular carcinoma (HCC), which is currently the second leading cause of cancer-related death worldwide. Metabolic rewiring is a common feature of cancers, including HCC. Altered mito-nuclear communication is emerging as a driving force in the metabolic reprogramming of cancer cells, affecting all aspects of cancer biology from neoplastic transformation to acquired drug resistance. Here, we explore relevant aspects (and discuss recent findings) of mito-nuclear crosstalk in the metabolic reprogramming of hepatocellular carcinoma.

Early mitochondrial fragmentation is a potential in vitro biomarker of environmental stress

Mitochondria are essential dynamic organelles that ordinarily balance between fragmentation and fusion. Under stress conditions, a shift toward fragmentation or hyper-fusion is observed as a pro-survival reaction. Fragmentation of mitochondria occurs within minutes or hours after the beginning of the stress and occurs in response to a large number of stress stimuli, including those triggered by environmental contaminants. In this study, we tested whether the change in the mitochondrial phenotype, from tubular to fragmented, could be used as a potential environmental stress biomarker in cells and compared this response with the standard MTT-based viability assay. Firstly, we show that mitochondrial fragmentation induced by selected stressors not only increases with concentrations, but also correlates positively with the cytotoxicity. Secondly, we found that the mitochondrial fragmentation that occurs in the first hour of stress correlated with the viability measured after a 24-h stress, allowing the establishment of a linear relation between mitochondrial fragmentation at 1 h and the predictable associated cytotoxicity of environmental contaminants alone or in mixture. In conclusion, we have succeeded in developing a model of predictable 24 h-cytotoxicity given mitochondrial fragmentation at 1 h with a set of chemicals. This model has been successful applied to three environmental toxicants and to a set of two chemical mixtures. We thus propose that mitochondrial fragmentation is a response that could be used as an early in vitro biomarker of environmental stress for toxicants alone or in mixture.

Metabolic reprogramming of mitochondrial respiration in metastatic cancer

Tumor initiation, progression, and metastasis are tissue context-dependent processes. Cellular and non-cellular factors provide the selective microenvironment that determines the fate of the evolving tumor through mechanisms that include metabolic reprogramming. Genetic and epigenetic changes contribute to this reprogramming process, which is orchestrated through ongoing communication between the mitochondrial and nuclear genomes. Metabolic flexibility, in particular the ability to rapidly adjust the balance between glycolytic and mitochondrial energy production, is a hallmark of aggressive, invasive, and metastatic cancers. Tumor cells sustain damage to both nuclear and mitochondrial DNA during tumorigenesis and as a consequence of anticancer treatments. Nuclear and mitochondrial DNA mutations and polymorphisms are increasingly recognized as factors that influence metabolic reprogramming, tumorigenesis, and tumor progression. Severe mitochondrial DNA damage compromises mitochondrial respiration. When mitochondrial respiration drops below a cell-specific threshold, metabolic reprogramming and plasticity fail to compensate and tumor formation is compromised. In these scenarios, tumorigenesis can be restored by acquisition of respiring mitochondria from surrounding stromal cells. Thus, intercellular mitochondrial transfer has the potential to confer treatment resistance and to promote tumor progression and metastasis. Understanding the constraints of metabolic, and in particular bioenergetic reprogramming, and the role of intercellular mitochondrial transfer in tumorigenesis provides new insights into addressing tumor progression and treatment resistance in highly aggressive cancers.

Topotecan induces apoptosis via ASCT2 mediated oxidative stress in gastric cancer

BACKGROUND

Topotecan (TPT) is a Topo I inhibitor and shows obvious anti-cancer effects on gastric cancer. Cancer cells reprogram their metabolic pathways to increase nutrients uptake, which has already been a hallmark of cancer. But the effect of TPT on metabolism in gastric cancer remains unknown.

PURPOSE

To investigate the effect of TPT on metabolism in gastric cancer.

METHODS

ATP production was measured by ATP Assay kit. Glucose and glutamine uptake were measured by Glucose (HK) Assay Kit and Glutamine/Glutamate Determination Kit respectively. To detect glutathione (GSH) concentration and reactive oxygen species (ROS) generation, GSH and GSSG Assay Kit and ROS Assay Kit were adopted. Apoptosis rates, mitochondrial membrane potential (MMP) were determined by flow cytometry and protein levels were analyzed by immumohistochemical staining and western blotting.

RESULTS

TPT increased ATP production. TPT promoted glucose uptake possibly via up-regulation of hexokinase 2 (HK2) or glucose transporter 1 (GLUT1) expression, while decreased glutamine uptake by down-regulation of ASCT2 expression. ASCT2 inhibitor GPNA and ASCT2 knockdown significantly suppressed the growth of gastric cancer cells. Inhibition of ASCT2 reduced glutamine uptake which led to decreased production of GSH and increased ROS level. ASCT2 knockdown induced apoptosis via the mitochondrial pathway and weakened anti-cancer effect of TPT.

CONCLUSION

TPT inhibits glutamine uptake via down-regulation of ASCT2 which causes oxidative stress and induces apoptosis through the mitochondrial pathway. Moreover, TPT inhibits proliferation partially via ASCT2. These observations reveal a previously undescribed mechanism of ASCT2 regulated gastric cancer proliferation and demonstrate ASCT2 is a potential anti-cancer target of TPT.