Metabolic changes associated with tumor metastasis, part 2: Mitochondria, lipid and amino acid metabolism

Redox-Mediated Mechanism of Chemoresistance in Cancer Cells

Cellular reactive oxygen species (ROS) status is stabilized by a balance of ROS generation and elimination called redox homeostasis. ROS is increased by activation of endoplasmic reticulum stress, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase family members and adenosine triphosphate (ATP) synthesis of mitochondria. Increased ROS is detoxified by superoxide dismutase, catalase, and peroxiredoxins. ROS has a role as a secondary messenger in signal transduction. Cancer cells induce fluctuations of redox homeostasis by variation of ROS regulated machinery, leading to increased tumorigenesis and chemoresistance. Redox-mediated mechanisms of chemoresistance include endoplasmic reticulum stress-mediated autophagy, increased cell cycle progression, and increased conversion to metastasis or cancer stem-like cells. This review discusses changes of the redox state in tumorigenesis and redox-mediated mechanisms involved in tolerance to chemotherapeutic drugs in cancer.

OGDH promotes the progression of gastric cancer by regulating mitochondrial bioenergetics and Wnt/β-catenin signal pathway

Background/aims

2-oxoglutarate dehydrogenase (OGDH) is the first rate-limiting E1 subunit of OGDH complex (OGDHC), which plays as a regulatory point in the cross-road of TCA cycle and glutamine metabolism. Until now, the role of OGDH in carcinogenesis has been unclear.

Methods

In the present study, we determined the expression of OGDH in human gastric cancer (GC) tissues and cell lines by RT-qPCR, Western blotting and immunohistochemical staining respectively. The biological impacts of OGDH on cell growth and migration were explored through modulation OGDH expression in GC cells. Furthermore, mitochondrial functions and Wnt/β-catenin signal were analyzed to elucidate the mechanism by which OGDH was involved in GC progression.

Results

The results showed that the levels of OGDH mRNA and protein were significantly higher in GC tissues, which was positively correlated with clinicalpathological parameters of GC patients. OGDH inhibitor SP significantly suppressed GC cell viability. Modulation of OGDH had distinct effects on cell proliferation, cell cycle and cell migration in the GC cell lines AGS and BGC823. Overexpression of OGDH resulted in the downregulation of the EMT molecular markers E-cadherin and ZO-1, the upregulation of N-cadherin and claudin-1. OGDH deficiency had the opposite outcomes in GC cells. Meantime, OGDH knockdown cells showed decreased mitochondrial membrane potential, oxygen consumption rate, intracellular ATP product, and increased ROS level and NADP⁺/NADPH ratio. Consistently, overexpression of OGDH enhanced the mitochondrial function in GC cells. Furthermore, OGDH knockdown reduced the expressions of β-catenin, slug and TCF8/ZEB1, and the downstream targets cyclin D1 and MMP9 in GC cells. OGDH overexpression facilitated the activation of Wnt/β-catenin signal pathway. Additionally, overexpression of OGDH promoted tumorigenesis of GC cells in nude mice.

Conclusion

Taken together, these results indicate that OGDH serves as a positive regulator of GC progression through enhancement of mitochondrial function and activation of Wnt/β-catenin signaling.

Glutamine Metabolism Is Essential for Stemness of Bone Marrow Mesenchymal Stem Cells and Bone Homeostasis

Skeleton has emerged as an endocrine organ which is both capable of regulating energy metabolism and being a target for it. Glutamine is the most bountiful and flexible amino acid in the body which provides adenosine 5′-triphosphate (ATP) demands for cells. Emerging evidences support that glutamine which acts as the second metabolic regulator after glucose exerts crucial roles in bone homeostasis at cellular level, including the lineage allocation and proliferation of bone mesenchymal stem cells (BMSCs), the matrix mineralization of osteoblasts, and the biosynthesis in chondrocytes. The integrated mechanism consisting of WNT, mammalian target of rapamycin (mTOR), and reactive oxygen species (ROS) signaling pathway in a glutamine-dependent pattern is responsible to regulate the complex intrinsic biological process, despite more extensive molecules are deserved to be elucidated in glutamine metabolism further. Indeed, dysfunctional glutamine metabolism enhances the development of degenerative bone diseases, such as osteoporosis and osteoarthritis, and glutamine or glutamine progenitor supplementation can partially restore bone defects which may promote treatment of bone diseases, although the mechanisms are not quite clear. In this review, we will summarize and update the latest research findings and clinical trials on the crucial regulatory roles of glutamine metabolism in BMSCs and BMSC-derived bone cells, also followed with the osteoclasts which are important in bone resorption.

Development of a neurotoxicity assay that is tuned to detect mitochondrial toxicants

Many neurotoxicants affect energy metabolism in man, but currently available test methods may still fail to predict mito- and neurotoxicity. We addressed this issue using LUHMES cells, i.e., human neuronal precursors that easily differentiate into mature neurons. Within the NeuriTox assay, they have been used to screen for neurotoxicants. Our new approach is based on culturing the cells in either glucose or galactose (Glc-Gal-NeuriTox) as the main carbohydrate source during toxicity testing. Using this Glc-Gal-NeuriTox assay, 52 mitochondrial and non-mitochondrial toxicants were tested. The panel of chemicals comprised 11 inhibitors of mitochondrial respiratory chain complex I (cI), 4 inhibitors of cII, 8 of cIII, and 2 of cIV; 8 toxicants were included as they are assumed to be mitochondrial uncouplers. In galactose, cells became more dependent on mitochondrial function, which made them 2-3 orders of magnitude more sensitive to various mitotoxicants. Moreover, galactose enhanced the specific neurotoxicity (destruction of neurites) compared to a general cytotoxicity (plasma membrane lysis) of the toxicants. The Glc-Gal-NeuriTox assay worked particularly well for inhibitors of cI and cIII, while the toxicity of uncouplers and non-mitochondrial toxicants did not differ significantly upon glucose ↔ galactose exchange. As a secondary assay, we developed a method to quantify the inhibition of all mitochondrial respiratory chain functions/complexes in LUHMES cells. The combination of the Glc-Gal-NeuriTox neurotoxicity screening assay with the mechanistic follow up of target site identification allowed both, a more sensitive detection of neurotoxicants and a sharper definition of the mode of action of mitochondrial toxicants.

Non-canonical roles for metabolic enzymes and intermediates in malignant progression and metastasis

Metabolic alterations are established as a hallmark of cancer. Such hallmark changes in cancer metabolism are characterized by reprogramming of energy-producing pathways and increases in the generation of biosynthetic intermediates to meet the needs of rapidly proliferating tumor cells. Various metabolic phenotypes such as aerobic glycolysis, increased glutamine consumption, and lipolysis have also been associated with the process of metastasis. However, in addition to the energy and biosynthetic alterations, a number of secondary functions of enzymes and metabolites are emerging that specifically contribute to metastasis. Here, we describe atypical intracellular roles of metabolic enzymes, extracellular functions of metabolic enzymes, roles of metabolites as signaling molecules, and epigenetic regulation mediated by altered metabolism, all of which can affect metastatic progression. We highlight how some of these mechanisms are already being exploited for therapeutic purposes, and discuss how others show similar potential.

Progesterone Treatment Attenuates Glycolytic Metabolism and Induces Senescence in Glioblastoma

We examined the effect of progesterone treatments on glycolytic metabolism and senescence as possible mechanisms in controlling the growth of glioblastoma multiforme (GBM). In an orthotopic mouse model, after tumor establishment, athymic nude mice received treatment with progesterone or vehicle for 40 days. Compared to controls, high-dose progesterone administration produced a significant reduction in tumor size (~47%) and an increased survival rate (~43%) without any demonstrable toxicity to peripheral organs (liver, kidney). This was accompanied by a significant improvement in spontaneous locomotor activity and reduced anxiety-like behavior. In a follow-up in vitro study of U87MG-luc, U87dEGFR and U118MG tumor cells, we observed that high-dose progesterone inhibited expression of Glut1, which facilitated glucose transport into the cytoplasm; glyceraldehyde 3-phosphate dehydrogenase (GAPDH; a glycolysis enzyme); ATP levels; and cytoplasmic FoxO1 and Phospho-FoxO1, both of which control glycolytic metabolism through upstream PI3K/Akt/mTOR signaling in GBM. In addition, progesterone administration attenuated EGFR/PI3K/Akt/mTOR signaling, which is highly activated in grade IV GBM. High-dose progesterone also induced senescence in GBM as evidenced by changes in cell morphology and β-galactocidase accumulation. In conclusion, progesterone inhibits the modulators of glycolytic metabolism and induces premature senescence in GBM cells and this can help to reduce/slow tumor progression.

Metabolic Regulation of Epithelial to Mesenchymal Transition: Implications for Endocrine Cancer

The last few decades have witnessed an outstanding advancement in our understanding of the hallmarks of endocrine cancers. This includes the epithelial to mesenchymal transition (EMT), a process that alters the morphology and functional characteristics of carcinoma cells. The mesenchymal stem cell like phenotype produced by EMT allows the dislocation of cancer cells from the primary tumor site with inheritance of motility, metastatic and invasive properties. A fundamental driver thought to initiate and propagate EMT is metabolic reprogramming that occur during these transitions. Though there remains a paucity of data regarding the alterations that occur during EMT in endocrine cancers, the contribution of deregulated metabolism is a prominent feature. This mini review focuses on metabolic reprogramming events that occur in cancer cells and in particular those of endocrine origin. It highlights the main metabolic reprogramming outcomes of EMT, encompassing glycolysis, mitochondria oxidative phosphorylation and function, glutamine and lipid metabolism. Comprehending the metabolic changes that occur during EMT will help formulate potential bioenergetic targets as therapies for endocrine cancer metastasis.

Roles of the mitochondrial genetics in cancer metastasis: not to be ignored any longer

Mitochondrial DNA (mtDNA) encodes for only a fraction of the proteins that are encoded within the nucleus, and therefore has typically been regarded as a lesser player in cancer biology and metastasis. Accumulating evidence, however, supports an increased role for mtDNA impacting tumor progression and metastatic susceptibility. Unfortunately, due to this delay, there is a dearth of data defining the relative contributions of specific mtDNA polymorphisms (SNP), which leads to an inability to effectively use these polymorphisms to guide and enhance therapeutic strategies and diagnosis. In addition, evidence also suggests that differences in mtDNA impact not only the cancer cells but also the cells within the surrounding tumor microenvironment, suggesting a broad encompassing role for mtDNA polymorphisms in regulating the disease progression. mtDNA may have profound implications in the regulation of cancer biology and metastasis. However, there are still great lengths to go to understand fully its contributions. Thus, herein, we discuss the recent advances in our understanding of mtDNA in cancer and metastasis, providing a framework for future functional validation and discovery.

Effects of tumor metabolic microenvironment on regulatory T cells

Recent studies have shown that on one hand, tumors need to obtain a sufficient energy supply, and on the other hand they must evade the body’s immune surveillance. Because of their metabolic reprogramming characteristics, tumors can modify the physicochemical properties of the microenvironment, which in turn affects the biological characteristics of the cells infiltrating them. Regulatory T cells (Tregs) are a subset of T cells that regulate immune responses in the body. They exist in large quantities in the tumor microenvironment and exert immunosuppressive effects. The main effect of tumor microenvironment on Tregs is to promote their differentiation, proliferation, secretion of immunosuppressive factors, and chemotactic recruitment to play a role in immunosuppression in tumor tissues. This review focuses on cell metabolism reprogramming and the most significant features of the tumor microenvironment relative to the functional effects on Tregs, highlighting our understanding of the mechanisms of tumor immune evasion and providing new directions for tumor immunotherapy.

NRH:quinone oxidoreductase 2 (NQO2) and glutaminase (GLS) both play a role in large extracellular vesicles (LEV) formation in preclinical LNCaP-C4-2B prostate cancer model of progressive metastasis

In the course of studies aimed at the role of oxidative stress in the development of metastatic potential in the LNCaP-C4-2B prostate cancer progression model system, we found a relative decrease in the level of expression of the cytoplasmic nicotinamide riboside: quinone oxidoreductase (NQO2) and an increase in the oxidative stress in C4-2B cells compared to that in LNCaP or its derivatives C4 and C4-2. It was also found that C4-2B cells specifically shed large extracellular vesicles (LEVs) suggesting that these LEVs and their cargo could participate in the establishment of the osseous metastases. The level of expression of caveolin-1 increased as the system progresses from LNCaP to C4-2B. Since NQO2 RNA levels were not changed in LNCaP, C4, C4-2, and C4-2B, we tested an altered cellular distribution hypothesis of NQO2 being compartmentalized in the membrane fractions of C4-2B cells which are rich in lipid rafts and caveolae. This was confirmed when the detergent resistant membrane fractions were probed on immunoblots. Moreover, when the LEVs were analyzed for membrane associated caveolin-1 as possible cargo, we noticed that the enzyme NQO2 was also a component of the cargo along with caveolin-1 as seen in double immunofluorescence studies. Molecular modeling studies showed that a caveolin-1 accessible site is present in NQO2. Specific interaction between NQO2 and caveolin-1 was confirmed using deletion constructs of caveolin-1 fused with glutathione S-transferase (GST). Interestingly, whole cell lysate and mitochondrial preparations of LNCaP, C4, C4-2, and C4-2B showed an increasing expression of glutaminase (GLS, kidney type). The extrusion of LEVs appears to be a specific property of the bone metastatic C4-2B cells and this process could be inhibited by a GLS specific inhibitor BPTES, suggesting the critical role of a functioning glutamine metabolism. Our results indicate that a high level of expression of caveolin-1 in C4-2B cells contributes to an interaction between caveolin-1 and NQO2 and to their packaging as cargo in the shed LEVs. These results suggest an important role of membrane associated oxidoreductases in the establishment of osseous metastases in prostate cancer.

Berberine Ameliorates High Glucose-Induced Cardiomyocyte Injury via AMPK Signaling Activation to Stimulate Mitochondrial Biogenesis and Restore Autophagic Flux

Background: Type II diabetes (T2D)-induced cardiomyocyte hypertrophy is closely linked to the impairment of mitochondrial function. Berberine has been shown to be a promising effect for hypoglycemia in T2D models. High glucose-induced cardiomyocyte hypertrophy in vitro has been reported. The present study investigated the protective effect and the underlying mechanism of berberine on high glucose-induced H9C2 cell line.

Methods: High glucose-induced H9C2 cell line was used to mimic the hyperglycemia resulting in cardiomyocyte hypertrophy. Berberine was used to rescue in this model and explore the mechanism in it. Confocal microscopy, immunofluorescence, RT-PCR, and western blot analysis were performed to evaluate the protective effects of berberine in high glucose-induced H9C2 cell line.

Results: Berberine dramatically alleviated hypertrophy of H9C2 cell line and significantly ameliorated mitochondrial function by rectifying the imbalance of fusion and fission in mitochondrial dynamics. Furthermore, berberine further promoted mitogenesis and cleared the damaged mitochondria via mitophagy. In addition, berberine also restored autophagic flux in high glucose-induced cardiomyocyte injury via AMPK signaling pathway activation.

Conclusion: Berberine ameliorates high glucose-induced cardiomyocyte injury via AMPK signaling pathway activation to stimulate mitochondrial biogenesis and restore autophagicflux in H9C2 cell line.

Sialic Acid Metabolism: A Key Player in Breast Cancer Metastasis Revealed by Metabolomics

Metastatic breast cancer is currently incurable. It has recently emerged that different metabolic pathways support metastatic breast cancer. To further uncover metabolic pathways enabling breast cancer metastasis, we investigated metabolic differences in mouse tumors of differing metastatic propensities using mass spectrometry-based metabolomics. We found that sialic acid metabolism is upregulated in highly metastatic breast tumors. Knocking out a key gene in sialic acid metabolism, Cmas, inhibits synthesis of the activated form of sialic acid, cytidine monophosphate-sialic acid and decreases the formation of lung metastases in vivo. Thus, the sialic acid pathway may be a new target against metastatic breast cancer.

The emerging co-regulatory role of long noncoding RNAs in epithelial-mesenchymal transition and the Warburg effect in aggressive tumors

Malignant tumor cells have several unique characteristics, and their ability to undergo epithelial-mesenchymal transition (EMT) is a molecular gateway to invasive behavior. Rapid proliferation and increased invasiveness during EMT enhance aberrant glucose metabolism in tumor cells. Meanwhile, aerobic glycolysis provides energy, biosynthesis precursors, and an appropriate microenvironment to facilitate EMT. Reciprocal crosstalk between the processes synergistically contributes to malignant cancer behaviors, but the regulatory mechanisms underlying this interaction remain unclear. Long non-coding RNAs (lncRNAs) are a recently recognized class of RNAs involved in multiple physiological and pathological tumor activities. Increasing evidence indicates that lncRNAs play overlapping roles in both EMT and cancer metabolism. In this review, we describe the lncRNAs reportedly involved in the two biological processes and explore the detailed mechanisms that could help elucidate this co-regulatory network and provide a theoretical basis for clinical management of EMT-related malignant phenotypes.

Metabolome analysis of esophageal cancer tissues using capillary electrophoresis-time-of-flight mass spectrometry

Reports of the metabolomic characteristics of esophageal cancer are limited. In the present study, we thus conducted metabolome analysis of paired tumor tissues (Ts) and non-tumor esophageal tissues (NTs) using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS). The Ts and surrounding NTs were surgically excised pair-wise from 35 patients with esophageal cancer. Following tissue homogenization and metabolite extraction, a total of 110 compounds were absolutely quantified by CE-TOFMS. We compared the concentrations of the metabolites between Ts and NTs, between pT1 or pT2 (pT1-2) and pT3 or pT4 (pT3-4) stage, and between node-negative (pN-) and node-positive (pN+) samples. Principal component analysis and hierarchical clustering analysis revealed clear metabolomic differences between Ts and NTs. Lactate and citrate levels in Ts were significantly higher (P=0.001) and lower (P<0.001), respectively, than those in NTs, which corroborated with the Warburg effect in Ts. The concentrations of most amino acids apart from glutamine were higher in Ts than in NTs, presumably due to hyperactive glutaminolysis in Ts. The concentrations of malic acid (P=0.015) and citric acid (P=0.008) were significantly lower in pT3-4 than in pT1-2, suggesting the downregulation of tricarboxylic acid (TCA) cycle activity in pT3-4. On the whole, in this study, we demonstrate significantly different metabolomic characteristics between tumor and non-tumor tissues and identified a novel set of metabolites that were strongly associated with the degree of tumor progression. A further understanding of cancer metabolomics may enable the selection of more appropriate treatment strategies, thereby contributing to individualized medicine.

Metformin and propranolol combination prevents cancer progression and metastasis in different breast cancer models

Discovery of new drugs for cancer treatment is an expensive and time-consuming process and the percentage of drugs reaching the clinic remains quite low.

Drug repositioning refers to the identification and development of new uses for existing drugs and represents an alternative drug development strategy.

In this work, we evaluated the antitumor effect of metronomic treatment with a combination of two repositioned drugs, metformin and propranolol, in triple negative breast cancer models.

By in vitro studies with five different breast cancer derived cells, we observed that combined treatment decreased proliferation (P < 0.001), mitochondrial activity (P < 0.001), migration (P < 0.001) and invasion (P < 0.001). In vivo studies in immunocompetent mice confirmed the potential of this combination in reducing tumor growth (P < 0.001) and preventing metastasis (P < 0.05).

Taken together our results suggest that metformin plus propranolol combined treatment might be beneficial for triple negative breast cancer control, with no symptoms of toxicity.

Multiomics Integration Reveals the Landscape of Prometastasis Metabolism in Hepatocellular Carcinoma

The systematic investigation of gene mutation and expression is important to discover novel biomarkers and therapeutic targets in cancers. Here, we integrated genomics, transcriptomics, proteomics, and metabolomics to analyze three hepatocellular carcinoma (HCC) cell lines with differential metastatic potentials. The results revealed the profile of the prometastasis metabolism potentially associated with HCC metastasis. The multiomic analysis identified 12 genes with variations at multiple levels from three metabolic pathways, including glycolysis, starch, and sucrose metabolism, and glutathione metabolism. Furthermore, uridine diphosphate (UDP)-glucose pyrophosphorylase 2 (UGP2), was observed to be persistently up-regulated with increased metastatic potential. UGP2 overexpression promoted cell migration and invasion and enhanced glycogenesis in vitro The role of UGP2 in metastasis was further confirmed using a tumor xenograft mouse model. Taken together, the compendium of multiomic data provides valuable insights in understanding the roles of shifted cellular metabolism in HCC metastasis.

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.

(+)-Catechin in a 1:2 Complex with Lysine Inhibits Cancer Cell Migration and Metastatic Take in Mice

Metastasis is of dismal prognosis for cancer patients, but recent evidence in mouse models of cancer shows that metastasis prevention is a reachable clinical objective. These experiments indicate that altered mitochondrial activities are associated with the metastatic phenotype. Mitochondrial transfer from metastatic to non-metastatic cells can indeed transfer the metastatic phenotype, and metastatic progenitor cells differ from other cancer cells by a higher sublethal production of mitochondrial reactive oxygen species (ROS). Moreover, mitochondria-targeted antioxidants can prevent metastatic dissemination in mouse models of cancer. Comparatively, general antioxidants have unpredictable effects on cancer metastasis, most probably because they affect several cell types, several subcellular ROS production sites and, often, several endogenous oxidant species. Thus, targeting antioxidants to mitochondria could improve their antimetastatic activities, as previously exemplified with mitochondria-targeted mitoTEMPO and mitoQ that can prevent metastatic dissemination in cancer-bearing mice. Our objective in this study was to identify whether catechins, which are known to be potent antioxidants, can inhibit cancer cell migration in vitro and metastatic take in vivo. Comparative analysis of the response to epigallocatechin-3-gallate, (+)-catechin and (+)-catechin:lysine complexes revealed that, whereas all compounds had similar general antioxidant properties, (+)-catechin:lysine 1:2, but not epigallocatechin-3-gallate, can prevent metastatic take of melanoma cells to the lungs of mice. (+)-Catechin:lysine 1:2 possesses two net positive charges provided by lysines at physiological pH, which could provide high affinity for the negatively charged mitochondrial matrix. While this study reveals that (+)-catechin:lysine 1:2 has interesting antimetastatic effects, future experiments are needed to formally demonstrate the stability of the complex, its effective tropism for mitochondria and whether or not its activity can be globally attributed to its antioxidant activity at this precise subcellular location.

Mitochondrial Dysfunction: A Novel Potential Driver of Epithelial-to-Mesenchymal Transition in Cancer

Epithelial-to-mesenchymal transition (EMT) allows epithelial cancer cells to assume mesenchymal features, endowing them with enhanced motility and invasiveness, thus enabling cancer dissemination and metastatic spread. The induction of EMT is orchestrated by EMT-inducing transcription factors that switch on the expression of “mesenchymal” genes and switch off the expression of “epithelial” genes. Mitochondrial dysfunction is a hallmark of cancer and has been associated with progression to a metastatic and drug-resistant phenotype. The mechanistic link between metastasis and mitochondrial dysfunction is gradually emerging. The discovery that mitochondrial dysfunction owing to deregulated mitophagy, depletion of the mitochondrial genome (mitochondrial DNA) or mutations in Krebs’ cycle enzymes, such as succinate dehydrogenase, fumarate hydratase, and isocitrate dehydrogenase, activate the EMT gene signature has provided evidence that mitochondrial dysfunction and EMT are interconnected. In this review, we provide an overview of the current knowledge on the role of different types of mitochondrial dysfunction in inducing EMT in cancer cells. We place emphasis on recent advances in the identification of signaling components in the mito-nuclear communication network initiated by dysfunctional mitochondria that promote cellular remodeling and EMT activation in cancer cells.

Expression of annexin II in gastric carcinoma and its role in gastric cancer metastasis

AIM

To investigate the expression of annexin II in gastric carcinoma and its role in the metastasis of gastric cancer.

METHODS

The expression of annexin II in 51 cases of gastric carcinoma and 24 cases of adjacent tissues was detected by immunohistochemistry. The relationship between annexin II and clinical features of gastric cancer was analyzed. Annexin II specific siRNA was used to inhibit the expression of annexin II in gastric cancer HGC-27 cells, and the effects of annexin II on the migration and secretion of matrix metalloproteinases (MMPs) were observed.

RESULTS

The positive rate of annexin II protein was 82.4% in gastric cancer tissues and 37.5% in adjacent tissues. There was significant difference between the two groups (P < 0.01); and the positive expression of annexin II was not related to the sex and age of the patients (P > 0.05). The expression of annexin II protein was correlated with tumor size, histological differentiation, TNM stage, Lymph node metastasis and other clinical features were significantly correlated, the difference was statistically significant (P < 0.05). Inhibition of annexin II expression, gastric cancer HGC-27 cells migration and secretion of MMPs were significantly decreased, the difference was statistically significant (P < 0.05).

CONCLUSION

Annexin II is highly expressed in gastric cancer tissues, annexin II protein expression is related to tumor size, histological differentiation, TNM staging, lymph node metastasis and other clinical features were significantly correlated. Annexin II high expression can promote the invasion and metastasis of gastric cancer.

The KISS1 metastasis suppressor appears to reverse the Warburg effect by shifting from glycolysis to mitochondrial beta-oxidation

The shift by cancer cells toward aerobic glycolysis (Warburg effect) confers selective advantages by utilizing nutrients (e.g., lipids, amino acids, and nucleotides) to build biomass. Lipogenesis is generally enhanced, and its inhibition diminishes proliferation and survival. Re-expression of the metastasis suppressor KISS1 in human melanoma cells results in greater mitochondrial biogenesis, inhibition of glycolysis, utilization of beta-oxidation to provide energy, elevated oxidation of exogenous fatty acids, and increased expression of early-phase lipogenesis genes at both mRNA and protein levels. Correspondingly, the energy sensor AMPKβ is phosphorylated, resulting in inhibitory phosphorylation of acetyl-CoA carboxylase (ACC), which is linked to enhanced beta-oxidation. Furthermore, PGC1α is required for KISS1-mediated phosphorylation of ACC and metastasis suppression. Collectively, these data further support the linkages between macromolecular metabolism and metastasis.

KEY MESSAGES

• KISS1 alters fatty acid metabolism. • There may be connections between metastasis and metabolism. • PGC1alpha appears to be downstream mediator of KISS1 metastasis suppression.

Metabolic reprogramming and epithelial-to-mesenchymal transition in cancer

Several lines of evidence indicate that during transformation epithelial cancer cells can acquire mesenchymal features via a process called epithelial-to-mesenchymal transition (EMT). This process endows cancer cells with increased invasive and migratory capacity, enabling tumour dissemination and metastasis. EMT is associated with a complex metabolic reprogramming, orchestrated by EMT transcription factors, which support the energy requirements of increased motility and growth in harsh environmental conditions. The discovery that mutations in metabolic genes such as FH, SDH and IDH activate EMT provided further evidence that EMT and metabolism are intertwined. In this review, we discuss the role of EMT in cancer and the underpinning metabolic reprogramming. We also put forward the hypothesis that, by altering chromatin structure and function, metabolic pathways engaged by EMT are necessary for its full activation.

Extracellular vesicles swarm the cancer microenvironment: from tumor-stroma communication to drug intervention

Intercellular communication sets the pace for transformed cells to survive and to thrive. Extracellular vesicles (EVs), such as exosomes, microvesicles and large oncosomes, are involved in this process shuttling reciprocal signals and other molecules between transformed and stromal cells, including fibroblasts, endothelial and immune cells. As a result, these cells are adapted or recruited to a constantly evolving cancer microenvironment. Moreover, EVs take part in the response to anticancer therapeutics not least by promoting drug resistance throughout the targeted tumor. Finally, circulating EVs can also transport important molecules to remote destinations in order to prime metastatic niches in an otherwise healthy tissue. Although the understanding of EV biology remains a major challenge in the field, their characteristics create new opportunities for advances in cancer diagnostics and therapeutics.

Serine and one-carbon metabolism in cancer

The non-essential amino acid serine supports several metabolic processes that are crucial for the growth and survival of proliferating cells, including protein, amino acid and glutathione synthesis. As an important one-carbon donor to the folate cycle, serine contributes to nucleotide synthesis, methylation reactions and the generation of NADPH for antioxidant defence. Many cancer cells are highly dependent on serine, a trait that provides several novel therapeutic opportunities, either through the inhibition of de novo serine synthesis or by limiting the availability or uptake of exogenous serine.

Adipophilin expression in lung adenocarcinoma is associated with apocrine-like features and poor clinical prognosis: an immunohistochemical study of 328 cases

AIMS

The lipogenic pathway is up-regulated in proliferating cells. However, the clinical impact of neoplastic steatogenesis in lung cancer is unclear. The aim of the present study was to evaluate the association of intracytoplasmic lipids with the clinicopathological features of lung adenocarcinoma (ADC), by immunohistochemical analysis of adipophilin (ADP), a coating protein found on intracytoplasmic lipid droplets.

METHODS AND RESULTS

Tissue microarrays consisting of 328 primary lung ADCs surgically resected at Kyoto University Hospital were immunostained for ADP. Subsequently, correlations between ADP expression and clinical, molecular and survival data were performed. Fifty-one (15.5%) cases were ADP-positive. The presence of vascular invasion (P = 0.003), predominantly solid histology (P < 0.001), poorly differentiated type (P < 0.001), wild-type EGFR (P = 0.002), ALK fusion (P < 0.001), strong/diffuse mitochondrial staining (P < 0.001), a lack of surfactant protein B expression (P = 0.014) and a high Ki67 index (P < 0.001) were significantly correlated with ADP-positive ADC. In contrast, there were no correlations between ADP-positive ADC and sex, age, smoking history, tumour stage, thyroid transcription factor-1 expression, or KRAS mutational status. ADP-positive ADCs had apocrine-like features (P < 0.001). Patients with ADP-positive ADC had worse disease-free and overall survival (P = 0.047 and P = 0.013, respectively) than those with ADP-negative ADC.

CONCLUSIONS

ADP was expressed in a small proportion of lung ADCs. ADP-positive lung ADC was significantly associated with apocrine-like features, wild-type EGFR, and poor prognosis, suggesting that ADP-positive lung ADC could be a distinct subtype of lung adenocarcinoma, induced by up-regulation of the lipogenic pathway.

Elevated amino acids in gastric juice as potential biomarkers for gastric cancer

Early diagnosis plays a vital role in the improvement of the curative rate of gastric cancer. However, the poor specificity and sensitivity of traditional gastric cancer biomarkers, such as carcino-embryonic antigen and carbohydrate antigen 199, make it difficult to screen early gastric cancer. Gastric juice amino acid profile may be an alternative tumor marker, since abnormal elevation of amino acids in gastric juice has been reported in precancerous patients. Normal concentration of amino acids is extremely low in gastric juice, and special techniques are required to detect amino acids in gastric juice. The change of amino acids in gastric juice is more significant than in blood and tumor tissue. The amino acid profile in gastric juice may work as efficient biomarkers for gastric cancer with the development of amino acid detection technique.