Mitochondrial biogenesis drives tumor cell proliferation

Structure prediction analysis of human core TIM23 complex reveals conservation of the protein translocation mechanism

The majority of mitochondrial proteins are encoded in the nucleus, translated on cytosolic ribosomes, and subsequently targeted to the mitochondrial surface. Their further import into the organelle is facilitated by highly specialized protein translocases. Mitochondrial precursor proteins that are destined to the mitochondrial matrix and, to some extent, the inner membrane, utilize translocase of the inner membrane (TIM23). This indispensable import machinery has been extensively studied in yeast. The translocating unit of the TIM23 complex in yeast consists of two membrane proteins, Tim17 and Tim23. In contrast to previous findings, recent reports demonstrate the primary role of Tim17, rather than Tim23, in the translocation of newly synthesized proteins. Very little is known about human TIM23 translocase. Human cells have two orthologs of yeast Tim17, TIMM17A and TIMM17B. Here, using computational tools, we present the architecture of human core TIM23 variants with either TIMM17A or TIMM17B, forming two populations of highly similar complexes. The structures reveal high conservation of the core TIM23 complex between human and yeast. Interestingly, both TIMM17A and TIMM17B variants interact with TIMM23 and reactive oxygen species modulator 1 (ROMO1); a homolog of yeast Mgr2, a protein that can create a channel-like structure with Tim17. The high structural conservation of proteins that form the core TIM23 complex in yeast and humans raises an interesting question about mechanistic and functional differences that justify existence of the two variants of TIM23 in higher eukaryotes.

The bioenergetic landscape of cancer

BACKGROUND

Bioenergetic remodeling of core energy metabolism is essential to the initiation, survival, and progression of cancer cells through exergonic supply of adenosine triphosphate (ATP) and metabolic intermediates, as well as control of redox homeostasis. Mitochondria are evolutionarily conserved organelles that mediate cell survival by conferring energetic plasticity and adaptive potential. Mitochondrial ATP synthesis is coupled to the oxidation of a variety of substrates generated through diverse metabolic pathways. As such, inhibition of the mitochondrial bioenergetic system by restricting metabolite availability, direct inhibition of the respiratory Complexes, altering organelle structure, or coupling efficiency may restrict carcinogenic potential and cancer progression.

SCOPE OF REVIEW

Here, we review the role of bioenergetics as the principal conductor of energetic functions and carcinogenesis while highlighting the therapeutic potential of targeting mitochondrial functions.

MAJOR CONCLUSIONS

Mitochondrial bioenergetics significantly contribute to cancer initiation and survival. As a result, therapies designed to limit oxidative efficiency may reduce tumor burden and enhance the efficacy of currently available antineoplastic agents.

Telomerase and mitochondria inhibition promote apoptosis and TET2 and ANMT3a expression in triple negative breast cancer cell lines

Introduction

High metastasis, resistance to common treatments, and high mortality rate, has made triple-negative breast cancer (TNBC) to be the most invasive type of breast cancer. High telomerase activity and mitochondrial biogenesis are involved in breast cancer tumorigenesis. The catalytic subunit of telomerase, telomerase reverse transcriptase (hTERT), plays a role in telomere lengthening and extra-biological functions such as gene expression, mitochondria function, and apoptosis. In this study, it has been aimed to evaluate intrinsic-, extrinsic-apoptosis and DNMT3a and TET2 expression following the inhibition of telomerase and mitochondria respiration in TNBC cell lines.

Methods

TNBC cells were treated with IC50 levels of BIBR1532, tigecycline, and also their combination. Then, telomere length, and DNMT3a, TET2, and hTERT expression were evaluated. Finally, apoptosis rate, apoptosis-related proteins, and genes were analyzed.

Results

The present results showed that IC50 level of telomerase and inhibition of mitochondria respiration induced apoptosis but did not leave any significant effect on telomere length. The results also indicated that telomerase inhibition induced extrinsic-apoptosis in MDA-MB-231 and caused intrinsic- apoptosis in MDA-MB-468 cells. Furthermore, it was found that the expression of p53 decreased and was ineffective in cell apoptosis. The expressions of DNMT3a and TET2 increased in cells. In addition, combination treatment was better than BIBR1532 and tigecycline alone.

Conclusion

The inhibition of telomerase and mitochondria respiration caused intrinsic- and extrinsic- apoptosis and increased DNMT3a and TET2 expression and it could be utilized in breast cancer treatment.

A comprehensive pan-cancer analysis identifies a novel glycolysis score and its hub genes as prognostic and immunological biomarkers

Background

Glycolysis plays significant roles in tumor progression and immune response. However, the exact role of glycolysis in prognosis and immune regulation has not been explored in all cancer types. This study first calculated a novel glycolysis score and screened out 12 glycolytic hub genes, and comprehensively analyzed molecular expression, clinical implications, and immune features of glycolysis among pan-cancer.

Methods

The glycolysis score was derived by the single sample gene set enrichment analysis (ssGSEA) algorithm. The correlations of glycolysis with clinical parameters were analyzed using "limma" package. Downstream pathways of glycolysis were identified by Gene Set Enrichment Analysis (GSEA). The immune cell infiltration was explored and validated by three databases. The association between glycolysis and some immunotherapy biomarkers was explored by Pearson correlation analysis. Single-nucleotide variation (SNV), copy number variation (CNV), DNA methylation, and drug sensitivity analyses of 12 glycolytic hub genes were investigated. IMvigor210 and GSE91061 immunotherapeutic cohorts were retrieved to assess the ability of glycolysis score to predict immunotherapy efficacy. The expression of glycolysis key genes was detected in normal and endometrial cancer cell lines.

Results

We found that glycolysis score was generally higher in tumor tissues compared to normal tissues and a high glycolysis score predominated as a risk prognostic factor. A high glycolysis score was associated with decreased immunostimulatory natural killer (NK) cells and CD8+ T cells infiltration, well increased immunosuppressive M2-tumor-associated macrophages (M2-TAM) cells infiltration. Tumor mutational burden (TMB), microsatellite instability (MSI), and immune checkpoints (ICPs) all closely interacted with glycolysis score and the frequency of gene mutation was confirmed to be higher in colon adenocarcinoma (COAD) patients with higher glycolysis score. The SNV, CNV, and DNA methylation of 12 glycolysis key genes occurred at different frequencies and showed different impacts on survival outcomes. The predictive and prognostic value of glycolysis score for immunotherapy outcomes was validated in two immunotherapy cohorts. The expression levels of key genes differ in normal endometrial and three endometrial cancer cell lines.

Conclusions

This work indicated that glycolysis score and 12 glycolytic hub genes were correlated with an immunosuppressive microenvironment. They could be served as promising biomarkers aiding diagnosis, predicting prognosis and immunotherapy response for some tumor patients.

Prognostic Value of Circulating Mitochondrial DNA in Prostate Cancer and Underlying Mechanism

Circulating DNAs are considered as degraded DNA fragments of approximately 50-200 bp, found in blood plasma, consisting of cell-free mitochondrial and nuclear DNA. Such cell-free DNAs in the blood are found to be altered in different pathological conditions including lupus, heart disease, and malignancies. While nuclear DNAs are being used and being developed as a powerful clinical biomarker in liquid biopsies, mitochondrial DNAs (mtDNAs) are associated with inflammatory conditions including cancer progression. Patients with cancer including prostate cancer are found to have measurable concentrations of mitochondrial DNA in circulation in comparison with healthy controls. The plasma content of mitochondrial DNA is dramatically elevated in both prostate cancer patients and mouse models treated with the chemotherapeutic drug. Cell-free mtDNA, in its oxidized form, induced a pro-inflammatory condition and activates NLRP3-mediated inflammasome formation which causes IL-1β-mediated activation of growth factors. On the other hand, interacting with TLR9, mtDNAs trigger NF-κB-mediated complement C3a positive feedback paracrine loop and activate pro-proliferating signaling through upregulating AKT, ERK, and Bcl2 in the prostate tumor microenvironment. In this review, we discuss the growing evidence supporting cell-free mitochondrial DNA copy number, size, and mutations in mtDNA genes as potential prognostic biomarkers in different cancers and targetable prostate cancer therapeutic candidates impacting stromal-epithelial interactions essential for chemotherapy response.

Targeting mitochondria as a potential therapeutic strategy against chemoresistance in cancer

The importance of mitochondria is not only limited to energy generation but also in several physical and chemical processes critical for cell survival. Mitochondria play an essential role in cellular apoptosis, calcium ion transport and cellular metabolism. Mutation in the nuclear and mitochondrial genes, altered oncogenes/tumor suppressor genes, and deregulated signalling for cell viability are major reasons for cancer progression and chemoresistance. The development of drug resistance in cancer patients is a major challenge in cancer treatment as the resistant cells are often more aggressive. The drug resistant cells of numerous cancer types exhibit the deregulation of mitochondrial function. The increased biogenesis of mitochondria and its dynamic alteration contribute to developing resistance. Further, a small subpopulation of cancer stem cells in the heterogeneous tumor is primarily responsible for chemoresistance and has an attribute of mitochondrial dysfunction. This review highlights the critical role of mitochondrial dysfunction in chemoresistance in cancer cells through the processes of apoptosis, autophagy/mitophagy, and cancer stemness. Mitochondria-targeted therapeutic strategies might help reduce cancer progression and chemoresistance induced by various cancer drugs.

Increased Expression of the Mitochondrial Glucocorticoid Receptor Enhances Tumor Aggressiveness in a Mouse Xenograft Model

Mitochondria are important organelles for cellular physiology as they generate most of the energy requirements of the cell and orchestrate many biological functions. Dysregulation of mitochondrial function is associated with many pathological conditions, including cancer development. Mitochondrial glucocorticoid receptor (mtGR) is proposed as a crucial regulator of mitochondrial functions via its direct involvement in the regulation of mitochondrial transcription, oxidative phosphorylation (OXPHOS), enzymes biosynthesis, energy production, mitochondrial-dependent apoptosis, and regulation of oxidative stress. Moreover, recent observations revealed the interaction of mtGR with the pyruvate dehydrogenase (PDH), a key player in the metabolic switch observed in cancer, indicating direct involvement of mtGR in cancer development. In this study, by using a xenograft mouse model of mtGR-overexpressing hepatocarcinoma cells, we showed increased mtGR-associated tumor growth, which is accompanied by reduced OXPHOS biosynthesis, reduction in PDH activity, and alterations in the Krebs cycle and glucose metabolism, metabolic alterations similar to those observed in the Warburg effect. Moreover, autophagy activation is observed in mtGR-associated tumors, which further support tumor progression via increased precursors availability. Thus, we propose that increased mitochondrial localization of mtGR is associated with tumor progression possible via mtGR/PDH interaction, which could lead to suppression of PDH activity and modulation of mtGR-induced mitochondrial transcription that ends up in reduced OXPHOS biosynthesis and reduced oxidative phosphorylation versus glycolytic pathway energy production, in favor of cancer cells.

Mitochondrial plasticity supports proliferative outgrowth and invasion of ovarian cancer spheroids during adhesion

Background

Ovarian cancer cells aggregate during or after exfoliation from the primary tumor to form threedimensional spheroids. Spheroid formation provides a survival advantage during peritoneal dissemination in nutrient and oxygen-depleted conditions which is accompanied by a suppressed metabolic phenotype and fragmented mitochondria. Upon arrival to their metastatic sites, spheroids adhere to peritoneal organs and transition to a more epithelial phenotype to support outgrowth and invasion. In this study, we investigated the plasticity of mitochondrial morphology, dynamics, and function upon adhesion.

Methods

Using our slow-developing (MOSE-L) and fast-developing (MOSE-LTICv) ovarian cancer models, we mimicked adhesion and reoxygenation conditions by plating the spheroids onto tissue culture dishes and changing culture conditions from hypoxia and low glucose to normoxia with high glucose levels after adhesion. We used Western Blot, microscopy and Seahorse analyses to determine the plasticity of mitochondrial morphology and functions upon adhesion, and the impact on proliferation and invasion capacities.

Results

Independent of culture conditions, all spheroids adhered to and began to grow onto the culture plates. While the bulk of the spheroid was unresponsive, the mitochondrial morphology in the outgrowing cells was indistinguishable from cells growing in monolayers, indicating that mitochondrial fragmentation in spheroids was indeed reversible. This was accompanied by an increase in regulators of mitobiogenesis, PGC1a, mitochondrial mass, and respiration. Reoxygenation increased migration and invasion in both cell types but only the MOSE-L responded with increased proliferation to reoxygenation. The highly aggressive phenotype of the MOSE-LTICv was characterized by a relative independence of oxygen and the preservation of higher levels of proliferation, migration and invasion even in limiting culture conditions but a higher reliance on mitophagy. Further, the outgrowth in these aggressive cells relies mostly on proliferation while the MOSE-L cells both utilize proliferation and migration to achieve outgrowth. Suppression of proliferation with cycloheximide impeded aggregation, reduced outgrowth and invasion via repression of MMP2 expression and the flattening of the spheroids.

Discussion

Our studies indicate that the fragmentation of the mitochondria is reversible upon adhesion. The identification of regulatory signaling molecules and pathways of these key phenotypic alterations that occur during primary adhesion and invasion is critical for the identification of druggable targets for therapeutic intervention to prevent aggressive metastatic disease.

Ivermectin and gemcitabine combination treatment induces apoptosis of pancreatic cancer cells via mitochondrial dysfunction

Pancreatic cancer is an aggressive cancer characterized by high mortality and poor prognosis, with a survival rate of less than 5 years in advanced stages. Ivermectin, an antiparasitic drug, exerts antitumor effects in various cancer types. This is the first study to evaluate the anticancer effects of the combination of ivermectin and gemcitabine in pancreatic cancer. We found that the ivermectin–gemcitabine combination treatment suppressed pancreatic cancer more effectively than gemcitabine alone treatment. The ivermectin–gemcitabine combination inhibited cell proliferation via G1 arrest of the cell cycle, as evidenced by the downregulation of cyclin D1 expression and the mammalian target of rapamycin (mTOR)/signal transducer and activator of transcription 3 (STAT-3) signaling pathway. Ivermectin–gemcitabine increased cell apoptosis by inducing mitochondrial dysfunction via the overproduction of reactive oxygen species and decreased the mitochondrial membrane potential. This combination treatment also decreased the oxygen consumption rate and inhibited mitophagy, which is important for cancer cell death. Moreover, in vivo experiments confirmed that the ivermectin–gemcitabine group had significantly suppressed tumor growth compared to the gemcitabine alone group. These results indicate that ivermectin exerts synergistic effects with gemcitabine, preventing pancreatic cancer progression, and could be a potential antitumor drug for the treatment of pancreatic cancer.

Chemotherapy Resistance: Role of Mitochondrial and Autophagic Components

Simple Summary

Chemotherapy resistance is a common occurrence during cancer treatment that cancer researchers are attempting to understand and overcome. Mitochondria are a crucial intracellular signaling core that are becoming important determinants of numerous aspects of cancer genesis and progression, such as metabolic reprogramming, metastatic capability, and chemotherapeutic resistance. Mitophagy, or selective autophagy of mitochondria, can influence both the efficacy of tumor chemotherapy and the degree of drug resistance. Regardless of the fact that mitochondria are well-known for coordinating ATP synthesis from cellular respiration in cellular bioenergetics, little is known its mitophagy regulation in chemoresistance. Recent advancements in mitochondrial research, mitophagy regulatory mechanisms, and their implications for our understanding of chemotherapy resistance are discussed in this review.

Abstract

Cancer chemotherapy resistance is one of the most critical obstacles in cancer therapy. One of the well-known mechanisms of chemotherapy resistance is the change in the mitochondrial death pathways which occur when cells are under stressful situations, such as chemotherapy. Mitophagy, or mitochondrial selective autophagy, is critical for cell quality control because it can efficiently break down, remove, and recycle defective or damaged mitochondria. As cancer cells use mitophagy to rapidly sweep away damaged mitochondria in order to mediate their own drug resistance, it influences the efficacy of tumor chemotherapy as well as the degree of drug resistance. Yet despite the importance of mitochondria and mitophagy in chemotherapy resistance, little is known about the precise mechanisms involved. As a consequence, identifying potential therapeutic targets by analyzing the signal pathways that govern mitophagy has become a vital research goal. In this paper, we review recent advances in mitochondrial research, mitophagy control mechanisms, and their implications for our understanding of chemotherapy resistance.

Targeting the redox imbalance in mitochondria: A novel mode for cancer therapy

Changes in reactive oxygen species (ROS) levels affect many aspects of cell behavior. During carcinogenesis, moderate ROS production modifies gene expression to alter cell function, elevating metabolic activity and ROS. To avoid extreme ROS-activated death, cancer cells increase antioxidative capacity, regulating sustained ROS levels that promote growth. Anticancer therapies are exploring inducing supranormal, cytotoxic oxidative stress levels either inhibiting antioxidative capacity or promoting excess ROS to selectively destroy cancer cells, triggering mechanisms such as apoptosis, autophagy, necrosis, or ferroptosis. This review exemplifies pro-oxidants (natural/synthetic/repurposed drugs) and their clinical significance as cancer therapies providing revolutionary approaches.

Epstein-Barr virus noncoding small RNA (EBER1) induces cell proliferation by up-regulating cellular mitochondrial activity and calcium influx

Epstein-Barr virus encoded RNAs (EBER1 and EBER2) are two non-polyadenylated, non-protein coding small RNAs expressed at high levels in all forms of EBV latent infections. Although not directly involved in cell transformation, a number of studies have reported that these RNAs may be involved in cell proliferation. However, which of the two EBERs play a major role in this process and the mechanisms involved remains unknown. The aim of this study was to investigate the role and mechanism of EBER1-induced cell proliferation. Using stably transfected EBER1 cell lines, and multiple methodologies, we show that EBER1 transfected epithelial, B and T cell lines proliferate at a higher rate, have higher metabolic activity and increased DNA synthesis. The mitochondrial number and activity was also observed to be higher in the EBER1 transfected cells. Moreover, cytochrome c activity and store operated calcium entry (SOCE) were potentiated in the EBER1 expressing cells. Finally, the genes associated with cell proliferation were also observed to be up-regulated in the EBER1 transfected cells. Taken together, our data has unravelled the role of mitochondria and cellular calcium pathway that appear to be involved in EBER1 induced cell proliferation of EBV infected cells.

Oxygen sensing, mitochondrial biology and experimental therapeutics for pulmonary hypertension and cancer

The homeostatic oxygen sensing system (HOSS) optimizes systemic oxygen delivery. Specialized tissues utilize a conserved mitochondrial sensor, often involving NDUFS2 in complex I of the mitochondrial electron transport chain, as a site of pO₂-responsive production of reactive oxygen species (ROS). These ROS are converted to a diffusible signaling molecule, hydrogen peroxide (H₂O₂), by superoxide dismutase (SOD2). H₂O₂ exits the mitochondria and regulates ion channels and enzymes, altering plasma membrane potential, intracellular Ca²⁺ and Ca²⁺-sensitization and controlling acute, adaptive, responses to hypoxia that involve changes in ventilation, vascular tone and neurotransmitter release. Subversion of this O₂-sensing pathway creates a pseudohypoxic state that promotes disease progression in pulmonary arterial hypertension (PAH) and cancer. Pseudohypoxia is a state in which biochemical changes, normally associated with hypoxia, occur despite normal pO₂. Epigenetic silencing of SOD2 by DNA methylation alters H₂O₂ production, activating hypoxia-inducible factor 1α, thereby disrupting mitochondrial metabolism and dynamics, accelerating cell proliferation and inhibiting apoptosis. Other epigenetic mechanisms, including dysregulation of microRNAs (miR), increase pyruvate dehydrogenase kinase and pyruvate kinase muscle isoform 2 expression in both diseases, favoring uncoupled aerobic glycolysis. This Warburg metabolic shift also accelerates cell proliferation and impairs apoptosis. Disordered mitochondrial dynamics, usually increased mitotic fission and impaired fusion, promotes disease progression in PAH and cancer. Epigenetic upregulation of dynamin-related protein 1 (Drp1) and its binding partners, MiD49 and MiD51, contributes to the pathogenesis of PAH and cancer. Finally, dysregulation of intramitochondrial Ca²⁺, resulting from impaired mitochondrial calcium uniporter complex (MCUC) function, links abnormal mitochondrial metabolism and dynamics. MiR-mediated decreases in MCUC function reduce intramitochondrial Ca²⁺, promoting Warburg metabolism, whilst increasing cytosolic Ca²⁺, promoting fission. Epigenetically disordered mitochondrial O₂-sensing, metabolism, dynamics, and Ca²⁺ homeostasis offer new therapeutic targets for PAH and cancer. Promoting glucose oxidation, restoring the fission/fusion balance, and restoring mitochondrial calcium regulation are promising experimental therapeutic strategies.

Biochemical and Metabolomic Changes after Electromagnetic Hyperthermia Exposure to Treat Colorectal Cancer Liver Implants in Rats

Background: Hyperthermia (HT) therapy still remains relatively unknown, in terms of both its biological and therapeutic effects. This work aims to analyze the effects of exposure to HT, such as that required in anti-tumor magnetic hyperthermia therapies, using metabolomic and serum parameters routinely analyzed in clinical practice. Methods: WAG/RigHsd rats were assigned to the different experimental groups needed to emulate all of the procedures involved in the treatment of liver metastases by HT. Twelve hours or ten days after the electromagnetic HT (606 kHz and 14 kA/m during 21 min), blood samples were retrieved and liver samples were obtained. 1H-nuclear-magnetic-resonance spectroscopy (1H-NMR) was used to search for possible diagnostic biomarkers of HT effects on the rat liver tissue. All of the data obtained from the hydrophilic fraction of the tissues were analyzed and modeled using chemometric tools. Results: Hepatic enzyme levels were significantly increased in animals that underwent hyperthermia after 12 h, but 10 d later they could not be detected anymore. The metabolomic profile (main metabolic differences were found in phosphatidylcholine, taurine, glucose, lactate and pyruvate, among others) also showed that the therapy significantly altered metabolism in the liver within 12 h (with two different patterns); however, those changes reverted to a control-profile pattern after 10 days. Conclusions: Magnetic hyperthermia could be considered as a safe therapy to treat liver metastases, since it does not induce irreversible physiological changes after application.

Malic enzyme 2 connects the Krebs cycle intermediate fumarate to mitochondrial biogenesis

Mitochondria have an independent genome (mtDNA) and protein synthesis machinery that coordinately activate for mitochondrial generation. Here, we report that the Krebs cycle intermediate fumarate links metabolism to mitobiogenesis through binding to malic enzyme 2 (ME2). Mechanistically, fumarate binds ME2 with two complementary consequences. First, promoting the formation of ME2 dimers, which activate deoxyuridine 5'-triphosphate nucleotidohydrolase (DUT). DUT fosters thymidine generation and an increase of mtDNA. Second, fumarate-induced ME2 dimers abrogate ME2 monomer binding to mitochondrial ribosome protein L45, freeing it for mitoribosome assembly and mtDNA-encoded protein production. Methylation of the ME2-fumarate binding site by protein arginine methyltransferase-1 inhibits fumarate signaling to constrain mitobiogenesis. Notably, acute myeloid leukemia is highly dependent on mitochondrial function and is sensitive to targeting of the fumarate-ME2 axis. Therefore, mitobiogenesis can be manipulated in normal and malignant cells through ME2, an unanticipated governor of mitochondrial biomass production that senses nutrient availability through fumarate.

Extracellular Vesicles and Damage-Associated Molecular Patterns: A Pandora's Box in Health and Disease

Sterile inflammation develops as part of an innate immunity response to molecules released upon tissue injury and collectively indicated as damage-associated molecular patterns (DAMPs). While coordinating the clearance of potential harmful stimuli, promotion of tissue repair, and restoration of tissue homeostasis, a hyper-activation of such an inflammatory response may be detrimental. The complex regulatory pathways modulating DAMPs generation and trafficking are actively investigated for their potential to provide relevant insights into physiological and pathological conditions. Abnormal circulating extracellular vesicles (EVs) stemming from altered endosomal-lysosomal system have also been reported in several age-related conditions, including cancer and neurodegeneration, and indicated as a promising route for therapeutic purposes. Along this pathway, mitochondria may dispose altered components to preserve organelle homeostasis. However, whether a common thread exists between DAMPs and EVs generation is yet to be clarified. A deeper understanding of the highly complex, dynamic, and variable intracellular and extracellular trafficking of DAMPs and EVs, including those of mitochondrial origin, is needed to unveil relevant pathogenic pathways and novel targets for drug development. Herein, we describe the mechanisms of generation of EVs and mitochondrial-derived vesicles along the endocytic pathway and discuss the involvement of the endosomal-lysosomal in cancer and neurodegeneration (i.e., Alzheimer's and Parkinson's disease).

SIRT1 Activation Using CRISPR/dCas9 Promotes Regeneration of Human Corneal Endothelial Cells through Inhibiting Senescence

Human corneal endothelial cells (hCECs) are restricted in proliferative capacity in vivo. Reduction in the number of hCEC leads to persistent corneal edema requiring corneal transplantation. This study demonstrates the functions of SIRT1 in hCECs and its potential for corneal endothelial regeneration. Cell morphology, cell growth rates and proliferation-associated proteins were compared in normal and senescent hCECs. SIRT1 was activated using the CRISPR/dCas9 activation system (SIRT1a). The plasmids were transfected into CECs of six-week-old Sprague–Dawley rats using electroporation and cryoinjury was performed. Senescent cells were larger, elongated and showed lower proliferation rates and lower SIRT1 levels. SIRT1 activation promoted the wound healing of CECs. In vivo transfection of SIRT1a promoted the regeneration of CECs. The proportion of the S-phase cells was lower in senescent cells and elevated upon SIRT1a activation. SIRT1 regulated cell proliferation, proliferation-associated proteins, mitochondrial membrane potential, and oxidative stress levels. In conclusion, corneal endothelial senescence is related with a decreased SIRT1 level. SIRT1a promotes the regeneration of CECs by inhibiting cytokine-induced cell death and senescence. Gene function activation therapy using SIRT1a may serve as a novel treatment strategy for hCEC diseases.

Epigenetic alteration of mitochondrial biogenesis regulatory genes in arsenic exposed individuals (with and without skin lesions) and in skin cancer tissues: A case control study

Chronic arsenic toxicity has become a global concern due to its adverse pathophysiological outcome and carcinogenic potential. It is already established that arsenic induced reactive oxygen species alters mitochondrial functionality. Major regulatory genes for mitochondrial biogenesis, i.e., PGC1α, Tfam, NRF1and NRF2 are located in the nucleus. As a result, mitochondria-nucleus crosstalk is crucial for proper mitochondrial function. This previous hypothesis led us to investigateinvolvement of epigenetic alteration behindenhanced mitochondrial biogenesis in chronic arsenic exposure. An extensive case-control study was conducted with 390 study participants (unexposed, exposed without skin lesion, exposed with skin lesion and exposed skin tumour) from highly arsenic exposed areas ofWest Bengal, India. Methylation specific PCRrevealed significant promoter hypomethylation oftwo key biogenesis regulatory genes, PGC1αandTfam in arsenic exposed individuals and also in skin tumour tissues. Linear regression analysis indicated significant negative correlation between urinary arsenic concentration and promoter methylation status. Increased expression of biogenesis regulatory genes wasobtained by quantitative real-time PCR analysis. Moreover, altered mitochondrial fusion-fission regulatory gene expression was also observed in skin tumour tissues. miR663, having tumour suppressor gene like function was known to be epigenetically regulated through mitochondrial retrograde signal. Promoter hypermethylation with significantly decreased expression of miR663 was found in skin cancer tissues compared to non-cancerous control tissue. In conclusion, results indicated crucial role of epigenetic alteration in arsenic induced mitochondrial biogenesis and arsenical skin carcinogenesis for the first time. However, further mechanistic studies are necessary for detailed understanding of mitochondria-nucleus crosstalk in arsenic perturbation.

Manipulation of Mitochondrial Plasticity Changes the Metabolic Competition Between "Foe" and "Friend" During Tumor Malignant Transformation

Mitochondria as the cellular energy powerhouses provide a common site for multiple metabolic reactions in order to cover energy and biomolecule demands, thus integrating the diverse metabolic pathways to endow cells with metabolic adaptation. Mitochondrial plasticity is normally regulated by mitochondrial dynamics, mitochondrial metabolism and mitochondrial biogenesis. Given that tumor cells and T cells share the metabolic similarities of survival, proliferation, expansion as well as effector function, manipulation of mitochondrial plasticity would change the metabolic competition between “foe” and “friend” during tumor malignant progression. On the one hand, for “foe” tumor cells, mitochondrial plasticity provides the enhancement of tumor metastasis and the development of resistance to‘ diverse antitumor drugs. On the other hand, for “friend” T cells, mitochondrial plasticity promotes the generation of long-term memory T (T_M) cells and alleviates the exhaustion of tumor-infiltrating lymphocytes (TILs). Therefore, downregulation of mitochondrial plasticity of tumor cells through engineering tumor-targeting nanoparticles may effectively potentiate metabolic vulnerability and re-sensitize tumor to relevant therapeutic treatment. On the contrary, upregulation of mitochondrial plasticity of T cells through optimizing adoptive cellular immunotherapy (ACI) or chimeric antigen receptor (CAR)-T cell therapy would provide T cells with the robust metabolic fitness and the persistent immune function, thus blocking tumor metastasis and reoccurrence.

Cancer epithelia-derived mitochondrial DNA is a targetable initiator of a paracrine signaling loop that confers taxane resistance

The work provides a conceptual advance in functionally defining the cross talk of tumor epithelia with cancer-associated fibroblastic cells contributing to tumor progression and therapeutic resistance. Independent of protein-based signaling molecules, prostate cancer cells secreted mitochondrial DNA to induce associated fibroblasts to generate anaphylatoxin C3a to support tumor progression in a positive feedback loop. Interestingly, the standard of care chemotherapy, docetaxel, used to treat castrate-resistant prostate cancer was found to further potentiate this paracrine-signaling axis to mediate therapeutic resistance. Blocking anaphylatoxin C3a signaling cooperatively sensitized prostate cancer tumors to docetaxel. We reveal that docetaxel resistance is not a cancer cell-autonomous phenomena and that targeting an immune modulator derived from cancer-associated fibroblasts can limit the expansion of docetaxel-resistant tumors.

Stromal-epithelial interactions dictate cancer progression and therapeutic response. Prostate cancer (PCa) cells were identified to secrete greater concentration of mitochondrial DNA (mtDNA) compared to noncancer epithelia. Based on the recognized coevolution of cancer-associated fibroblasts (CAF) with tumor progression, we tested the role of cancer-derived mtDNA in a mechanism of paracrine signaling. We found that prostatic CAF expressed DEC205, which was not expressed by normal tissue-associated fibroblasts. DEC205 is a transmembrane protein that bound mtDNA and contributed to pattern recognition by Toll-like receptor 9 (TLR9). Complement C3 was the dominant gene targeted by TLR9-induced NF-κB signaling in CAF. The subsequent maturation complement C3 maturation to anaphylatoxin C3a was dependent on PCa epithelial inhibition of catalase in CAF. In a syngeneic tissue recombination model of PCa and associated fibroblast, the antagonism of the C3a receptor and the fibroblastic knockout of TLR9 similarly resulted in immune suppression with a significant reduction in tumor progression, compared to saline-treated tumors associated with wild-type prostatic fibroblasts. Interestingly, docetaxel, a common therapy for advanced PCa, further promoted mtDNA secretion in cultured epithelia, mice, and PCa patients. The antiapoptotic signaling downstream of anaphylatoxin C3a signaling in tumor cells contributed to docetaxel resistance. The inhibition of C3a receptor sensitized PCa epithelia to docetaxel in a synergistic manner. Tumor models of human PCa epithelia with CAF expanded similarly in mice in the presence or absence of docetaxel. The combination therapy of docetaxel and C3 receptor antagonist disrupted the mtDNA/C3a paracrine loop and restored docetaxel sensitivity.

Mitochondrial determinants of chemoresistance

Chemoresistance constitute nowadays the major contributor to therapy failure in most cancers. There are main factors that mitigate cell response to therapy, such as target organ, inherent sensitivity to the administered compound, its metabolism, drug efflux and influx or alterations on specific cellular targets, among others. We now know that intrinsic properties of cancer cells, including metabolic features, substantially contribute to chemoresistance. In fact, during the last years, numerous reports indicate that cancer cells resistant to chemotherapy demonstrate significant alterations in mitochondrial metabolism, membrane polarization and mass. Metabolic activity and expression of several mitochondrial proteins are modulated under treatment to cope with stress, making these organelles central players in the development of resistance to therapies. Here, we review the role of mitochondria in chemoresistant cells in terms of metabolic rewiring and function of key mitochondria-related proteins.

Biological Functions and Molecular Mechanisms of Antibiotic Tigecycline in the Treatment of Cancers

As an FDA-approved drug, glycylcycline tigecycline has been used to treat complicated microbial infections. However, recent studies in multiple hematologic and malignant solid tumors reveal that tigecycline treatment induces cell cycle arrest, apoptosis, autophagy and oxidative stress. In addition, tigecycline also inhibits mitochondrial oxidative phosphorylation, cell proliferation, migration, invasion and angiogenesis. Importantly, combinations of tigecycline with chemotherapeutic or targeted drugs such as venetoclax, doxorubicin, vincristine, paclitaxel, cisplatin, and imatinib, have shown to be promising strategies for cancer treatment. Mechanism of action studies reveal that tigecycline leads to the inhibition of mitochondrial translation possibly through interacting with mitochondrial ribosome. Meanwhile, this drug also interferes with several other cell pathways/targets including MYC, HIFs, PI3K/AKT or AMPK-mediated mTOR, cytoplasmic p21 ^CIP1/Waf1, and Wnt/β-catenin signaling. These evidences indicate that antibiotic tigecycline is a promising drug for cancer treatment alone or in combination with other anticancer drugs. This review summarizes the biological function of tigecycline in the treatment of tumors and comprehensively discusses its mode of action.

Effects of nanoscale electric fields on the histology of liver cell dysplasia

Cells electrical fields have a significant role in cell function.

AIM

The current study examined the effects of nanoscale electric fields generated by magneto-electric nanoparticles (MENs) on precancerous liver tissue.

METHODS & RESULTS

A total of 30 nm MENs synthesized by sol-gel method were tested in vitro on HepG2 cells and in vivo on liver cell dysplasia in mice, which were exposed to 50 Hz 2 mT for 2 weeks, +/- MENs. MENs with alternating field (AF) reversed liver cells dysplastic features. In vitro cytotoxicity assay showed high lethal dose (LD 50) of 1.4 mg/ml. We also report on the expression of alpha-fetoprotein and cytochrome C.

CONCLUSION

MEN-generated nanoscale electric fields have significant biological effects on precancerous liver cells.

Early effector maturation of naïve human CD8+ T cells requires mitochondrial biogenesis

The role of mitochondrial biogenesis during naïve to effector differentiation of CD8⁺ T cells remains ill explored. In this study, we describe a critical role for early mitochondrial biogenesis in supporting cytokine production of nascent activated human naïve CD8⁺ T cells. Specifically, we found that prior to the first round of cell division activated naïve CD8⁺ T cells rapidly increase mitochondrial mass, mitochondrial respiration, and mitochondrial reactive oxygen species (mROS) generation, which were all inter-linked and important for CD8⁺ T cell effector maturation. Inhibition of early mitochondrial biogenesis diminished mROS dependent IL-2 production - as well as subsequent IL-2 dependent TNF, IFN-γ, perforin, and granzyme B production. Together, these findings point to the importance of mitochondrial biogenesis during early effector maturation of CD8⁺ T cells.

2-Methoxyestradiol Affects Mitochondrial Biogenesis Pathway and Succinate Dehydrogenase Complex Flavoprotein Subunit A in Osteosarcoma Cancer Cells

BACKGROUND/AIM

Dysregulation of mitochondrial pathways is implicated in several diseases, including cancer. Notably, mitochondrial respiration and mitochondrial biogenesis are favored in some invasive cancer cells, such as osteosarcoma. Hence, the aim of the current work was to investigate the effects of 2-methoxyestradiol (2-ME), a potent anticancer agent, on the mitochondrial biogenesis of osteosarcoma cells.

MATERIALS AND METHODS

Highly metastatic osteosarcoma 143B cells were treated with 2-ME separately or in combination with L-lactate, or with the solvent (non-treated control cells). Protein levels of α-syntrophin and peroxisome proliferator-activated receptor gamma, coactivator 1 alpha (PGC-1α) were determined by western blotting. Impact of 2-ME on mitochondrial mass, regulation of cytochrome c oxidase I (COXI) expression, and succinate dehydrogenase complex flavoprotein subunit A (SDHA) was determined by immunofluorescence analyses. Inhibition of sirtuin 3 (SIRT3) activity by 2-ME was investigated by fluorescence assay and also, using molecular docking and molecular dynamics simulations.

RESULTS

L-lactate induced mitochondrial biogenesis pathway via up-regulation of COXI. 2-ME inhibited mitochondrial biogenesis via regulation of PGC-1α, COXI, and SIRT3 in a concentration-dependent manner as a consequence of nuclear recruitment of neuronal nitric oxide synthase and nitric oxide generation. It was also proved that 2-ME inhibited SIRT3 activity by binding to both the canonical and allosteric inhibitor binding sites. Moreover, regardless of the mitochondrial biogenesis pathway, 2-ME affected the expression of SDHA.

CONCLUSION

Herein, mitochondrial biogenesis pathway regulation and SDHA were presented as novel targets of 2-ME, and moreover, 2-ME was demonstrated as a potent inhibitor of SIRT3. L-lactate was confirmed to exert pro-carcinogenic effects on osteosarcoma cells via the induction of the mitochondrial biogenesis pathway. Thus, L-lactate level may be considered as a prognostic biomarker for osteosarcoma.

Hypomethylation of mitochondrial D-loop and ND6 with increased mitochondrial DNA copy number in the arsenic-exposed population

Groundwater arsenic contamination has become a serious global concern due to its adverse effects on human health. Arsenic-induced reactive oxygen species trigger oxidative stress inside mitochondria, which initiate a cascade of events including altered mitochondrial (mt) membrane potential, uncoupling of electron transport chain, and mtDNA damage. A case-control study was conducted to examine the association between arsenic exposure and differences in mtDNA methylation and to assess the downstream consequences. We recruited 221 arsenic-exposed individuals, including 106 individuals with skin lesions (WSL) and 115 subjects without any skin lesions (WOSL) from the Murshidabad district, West Bengal, India. The unexposed group included 101 individuals from the arsenic unexposed area in East Midnapore. We analyzed the status of mtDNA methylation in D-loop region and ND6 gene by methylation-specific PCR. Gene expression was studied by quantitative real-time PCR. Significant hypomethylation in both D-loop and ND6 was observed with a consequent increase in their target gene expression and higher mtDNA copy number in arsenic-exposed populations compared to controls. Further mechanistic insights regarding mitochondrial epigenetic alteration in arsenic exposure will be of critical importance for the prevention of adverse health effects.

Enhancement of mitochondrial biogenesis and paradoxical inhibition of lactate dehydrogenase mediated by 14-3-3η in oncocytomas

Oncocytomas represent a subset of benign pituitary adenomas that are characterized by significant mitochondrial hyperplasia. Mitochondria are key organelles for energy generation and metabolic intermediate production for biosynthesis in tumour cells, so understanding the mechanism underlying mitochondrial biogenesis and its impact on cellular metabolism in oncocytoma is vital. Here, we studied surgically resected pituitary oncocytomas by using multi-omic analyses. Whole-exome sequencing did not reveal any nuclear mutations, but identified several somatic mutations of mitochondrial DNA, and dysfunctional respiratory complex I. Metabolomic analysis suggested that oxidative phosphorylation was reduced within individual mitochondria, and that there was no reciprocal increase in glycolytic activity. Interestingly, we found a reduction in the cellular lactate level and reduced expression of lactate dehydrogenase A (LDHA), which contributed to mitochondrial biogenesis in an in vitro cell model. It is of note that the hypoxia-response signalling pathway was not upregulated in pituitary oncocytomas, thereby failing to enhance glycolysis. Proteomic analysis showed that 14-3-3η was exclusively overexpressed in oncocytomas, and that 14-3-3η was capable of inhibiting glycolysis, leading to mitochondrial biogenesis in the presence of rotenone. In particular, 14-3-3η inhibited LDHA by direct interaction in the setting of complex I dysfunction, highlighting the role of 14-3-3η overexpression and inefficient oxidative phosphorylation in oncocytoma mitochondrial biogenesis. These findings deepen our understanding of the metabolic changes that occur within oncocytomas, and shine a light on the mechanism of mitochondrial biogenesis, providing a novel perspective on metabolic adaptation in tumour cells. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

C-fos upregulates P-glycoprotein, contributing to the development of multidrug resistance in HEp-2 laryngeal cancer cells with VCR-induced resistance

Background

Laryngeal cancer tends to have a very poor prognosis due to the unsatisfactory efficacy of chemotherapy for this cancer. Multidrug resistance (MDR) is the main cause of chemotherapy failure. The proto-oncogene c-fos has been shown to be involved in the development of MDR in several tumor types, but few studies have evaluated the relationship between c-fos and MDR in laryngeal cancer. We investigated the role of c-fos in MDR development in laryngeal cancer cells (cell line: human epithelial type 2, HEp-2) using the chemotherapeutic vincristine (VCR).

Methods

HEp-2/VCR drug resistance was established by selection against an increasing drug concentration gradient. The expressions of c-fos and multidrug resistance 1 (mdr1) were measured using qPCR and western blot. C-fos overexpression or knockdown was performed in various cells. The intracellular rhodamine-123 (Rh-123) accumulation assay was used to detect the transport capacity of P-glycoprotein (P-gp, which is encoded by the mdr1 gene).

Results

HEp-2 cells with VCR-induced resistance (HEp-2/VCR cells) were not only resistant to VCR but also evolved cross-resistance to other chemotherapeutic drugs. The expressions of the c-fos and mdr1genes were significantly higher in the HEp-2/VCR cells than in control cells. C-fos overexpression in HEp-2 cells (c-fos WT) resulted in increased P-gp expression and increased the IC₅₀ for 5-FU. C-fos knockdown in the HEp-2/VCR cells (c-fos shRNA) resulted in decreased P-gp expression and decreased IC₅₀ for 5-FU. An intracellular Rh-123 accumulation assay showed that the mean intracellular fluorescence intensity (MFI) was lower in the HEp-2/VCR cells than in HEp-2 cells. C-fos WT cells also showed lower MFI. By contrast, c-fos shRNA cells exhibited a higher MFI than the control group.

Conclusion

C-fos increased the expression of P-gp and mdr1 in the HEp-2/VCR cells, and enhanced the efflux function of the cells, thereby contributing to the development of MDR.

Metabolic cooperation between cancer and non-cancerous stromal cells is pivotal in cancer progression

The way cancer cells adapt to microenvironment is crucial for the success of carcinogenesis, and metabolic fitness is essential for a cancer cell to survive and proliferate in a certain organ/tissue. The metabolic remodeling in a tumor niche is endured not only by cancer cells but also by non-cancerous cells that share the same microenvironment. For this reason, tumor cells and stromal cells constitute a complex network of signal and organic compound transfer that supports cellular viability and proliferation.

The intensive dual-address cooperation of all components of a tumor sustains disease progression and metastasis. Herein, we will detail the role of cancer-associated fibroblasts, cancer-associated adipocytes, and inflammatory cells, mainly monocytes/macrophages (tumor-associated macrophages), in the remodeling and metabolic adaptation of tumors.

Potential interference of aluminum chlorohydrate with estrogen receptor signaling in breast cancer cells

Aluminum salts are widely used as the active antiperspirant in underarm cosmetic. Experimental observations indicate that its long term application may correlate with breast cancer development and progression. This action is proposed to be attributed, among others, to aluminum possible estrogen-like activities. In this study we showed that aluminum, in the form of aluminum chlorohydrate (ACH), caused increase in estrogen receptor alpha (ERα) protein levels, in ERα-positive MCF-7 cells. This effect was accompanied by moderate activation of Estrogen Response Elements (ERE)-driven reporter gene expression and 20%-50% increase in certain estrogen responsive, ERE-independent genes expression. Genes affected were ERα, p53, cyclin D1, and c-fos, crucial regulators of breast cancer development and progression. ACH-induced genes expression was eliminated in the presence of the estrogen antagonist: ICI 182780, in MCF-7 cells, whereas it was not observed in ERα-negative MDA-MB-231 breast cancer cells, indicating aluminum interference with estrogen signaling. Moreover, ACH caused increase in the perinuclear localization of estrogen receptor alpha in MCF-7 breast cancer cells and increase in the mitochondrial Bcl-2 protein, possibly affecting receptors-mediated mitochondrial actions and mitochondrial-dependent apoptosis. ACH-induced perinuclear localization of estrogen receptor beta was also observed in MDA-MB-231. Our findings indicate that aluminum actions on estrogen receptors protein level and subcellular localization possibly affect receptors-mediated actions and thus, aluminum interference with estrogen signaling.

Transcriptomic analysis of mitochondrial TFAM depletion changing cell morphology and proliferation

Human mitochondrial transcription factor A (TFAM) has been implicated in promoting tumor growth and invasion. TFAM activates mitochondrial DNA (mtDNA) transcription, and affects nuclear gene expression through mitochondrial retrograde signaling. In this study, we investigated the effects of TFAM depletion on the morphology and transcriptome of MKN45 gastric cancer cells. Morphology alteration became visible at 12 h after TFAM knockdown: the proportion of growth-arrested polygonal cells versus oval-shaped cells increased, reaching a half-maximum at 24 h and a near-maximum at 36 h. TFAM knockdown upregulated four genes and downregulated six genes by more than threefold at 24 h and similarly at 48 h. Among them, the knockdown of CFAP65 (cilia and flagella associated protein 65) or PCK1 (cytoplasmic phosphoenolpyruvate carboxykinase) rescued the effects of TFAM depletion on cell morphology and proliferation. PCK1 was found to act downstream of CFAP65 in calcium-mediated retrograde signaling. Furthermore, mtDNA depletion by 2',3'-dideoxycytidine was sufficient for induction of CFAP65 and PCK1 expression and inhibition of cell proliferation, but oxidative phosphorylation blockade or mitochondrial membrane potential depolarization was not. Thus, the TFAM-mtDNA-calcium-CFAP65-PCK1 axis participates in mitochondrial retrograde signaling, affecting tumor cell differentiation and proliferation.

Packaging and transfer of mitochondrial DNA via exosomes regulate escape from dormancy in hormonal therapy-resistant breast cancer

Increasing evidence suggests that extracellular vesicles (EVs) can transfer genetic material to recipient cells. However, the mechanism and role of this phenomenon are largely unknown. Here we have made a remarkable discovery: EVs can harbor the full mitochondrial genome. These extracellular vesicles can in turn transfer their mtDNA to cells with impaired metabolism, leading to restoration of metabolic activity. We determined that hormonal therapy induces oxidative phosphorylation-deficient breast cancer cells, which can be rescued via the transfer of mtDNA-laden extracellular vesicles. Horizontal transfer of mtDNA occurred in cancer stem-like cells and was associated with increased self-renewal potential of these cells, leading to resistance to hormonal therapy. We propose that mtDNA transfer occurs in human cancer via EVs.

The horizontal transfer of mtDNA and its role in mediating resistance to therapy and an exit from dormancy have never been investigated. Here we identified the full mitochondrial genome in circulating extracellular vesicles (EVs) from patients with hormonal therapy-resistant (HTR) metastatic breast cancer. We generated xenograft models of HTR metastatic disease characterized by EVs in the peripheral circulation containing mtDNA. Moreover, these human HTR cells had acquired host-derived (murine) mtDNA promoting estrogen receptor-independent oxidative phosphorylation (OXPHOS). Functional studies identified cancer-associated fibroblast (CAF)-derived EVs (from patients and xenograft models) laden with whole genomic mtDNA as a mediator of this phenotype. Specifically, the treatment of hormone therapy (HT)-naive cells or HT-treated metabolically dormant populations with CAF-derived mtDNA^hi EVs promoted an escape from metabolic quiescence and HTR disease both in vitro and in vivo. Moreover, this phenotype was associated with the acquisition of EV mtDNA, especially in cancer stem-like cells, expression of EV mtRNA, and restoration of OXPHOS. In summary, we have demonstrated that the horizontal transfer of mtDNA from EVs acts as an oncogenic signal promoting an exit from dormancy of therapy-induced cancer stem-like cells and leading to endocrine therapy resistance in OXPHOS-dependent breast cancer.

PGC1α induced by reactive oxygen species contributes to chemoresistance of ovarian cancer cells

Malignant cells are subjected to high levels of oxidative stress that arise from the increased production of reactive oxygen species (ROS) due to their altered metabolism. They activate antioxidant mechanisms to relieve the oxidative stress, and thereby acquire resistance to chemotherapeutic agents. In the present study, we found that PGC1α, a key molecule that both increases mitochondrial biogenesis and activates antioxidant enzymes, enhances chemoresistance in response to ROS generated by exposure of cells to ovarian sphere-forming culture conditions. Cells in the cultured spheres exhibited stem cell-like characteristics, and maintained higher ROS levels than their parent cells. Intriguingly, scavenging ROS diminished the aldehyde dehydrogenase (ALDH)-positive cell population, and inhibited proliferation of the spheres. ROS production triggered PGC1α expression, which in turn caused changes to mitochondrial biogenesis and activity within the spheres. The drug-resistant phenotype was observed in both spheres and PGC1α-overexpressing parent cells, and conversely, PGC1α knockdown sensitized the spheres to cisplatin treatment. Similarly, floating malignant cells derived from patient ascitic fluid included an ALDH-positive population and exhibited the tendency of a positive correlation between expressions of multidrug resistance protein 1 (MDR1) and PGC1α. The present study suggests that ROS-induced PGC1α mediates chemoresistance, and represents a novel therapeutic target to overcome chemoresistance in ovarian cancer.

Cryptolepine inhibits melanoma cell growth through coordinated changes in mitochondrial biogenesis, dynamics and metabolic tumor suppressor AMPKα1/2-LKB1

Dysregulated mitochondrial dynamics and biogenesis have been associated with various pathological conditions including cancers. Here, we assessed the therapeutic effect of cryptolepine, a pharmacologically active alkaloid derived from the roots of Cryptolepis sanguinolenta, on melanoma cell growth. Treatment of human melanoma cell lines (A375, Hs294t, SK-Mel28 and SK-Mel119) with cryptolepine (1.0, 2.5, 5.0 and 7.5 μM) for 24 and 48 h significantly (P < 0.001) inhibited the growth of melanoma cells but not normal melanocytes. The inhibitory effect of cryptolepine was associated with loss of mitochondrial membrane potential and reduced protein expression of Mfn1, Mfn2, Opa1 and p-Drp1 leading to disruption of mitochondrial dynamics. A decrease in the levels of ATP and mitochondrial mass were associated with activation of the metabolic tumor suppressor AMPKα1/2-LKB1, and a reduction in mTOR signaling. Decreased expression of SDH-A and COX-I demonstrated that cryptolepine treatment reduced mitochondrial biogenesis. In vivo treatment of A375 xenograft-bearing nude mice with cryptolepine (10 mg/Kg body weight, i.p.) resulted in significant inhibition of tumor growth, which was associated with disruption of mitochondrial dynamics and a reduction in mitochondrial biogenesis. Our study suggests that low toxicity phytochemicals like cryptolepine may be tested for the treatment of melanoma.

Connective tissue growth factor decreases mitochondrial metabolism through ubiquitin-mediated degradation of mitochondrial transcription factor A in oral squamous cell carcinoma

BACKGROUND/PURPOSE

Deregulation of metabolic pathways is one of the hallmarks of cancer progression. Connective tissue growth factor (CTGF/CCN2) acts as a tumor suppressor in oral squamous cell carcinoma (OSCC). However, the role of CTGF in modulating cancer metabolism is still unclear.

METHODS

OSCC cells stably overexpressing CTGF (SAS/CTGF) and shRNA against CTGF (TW2.6/shCTGF) were established. Oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) were examined by the Seahorse XF24 analyzer. The expression of CTGF and mitochondrial biogenesis related genes was measured by real-time polymerase chain reaction or Western blot analysis.

RESULTS

CTGF decreased OCR, ECAR, adenosine triphosphate (ATP) generation, mitochondrial DNA (mtDNA), and mitochondrial transcription factor A (mtTFA) protein expression in OSCC cells. Overexpression of mtTFA restored CTGF-decreased OCR, ECAR, mtDNA copy number, migration and invasion of SAS/CTGF cells. Immunoprecipitation assay showed a higher level of ubiquitinated mtTFA protein after CTGF treatment. MG132, an inhibitor of proteasomal degradation, reversed the effect of CTGF on mtTFA protein expression in SAS cells.

CONCLUSION

CTGF can decrease glycolysis, mitochondrial oxidative phosphorylation, ATP generation, and mtDNA copy number by increasing mtTFA protein degradation through ubiquitin proteasome pathway and in turn reduces migration and invasion of OSCC cells. Therefore, CTGF may be developed as a potential additive therapeutic drug for oral cancer in the near future.

Exposure to Inorganic Arsenic Is Associated with Increased Mitochondrial DNA Copy Number and Longer Telomere Length in Peripheral Blood

Background: Exposure to inorganic arsenic (iAs) through drinking water causes cancer. Alterations in mitochondrial DNA copy number (mtDNAcn) and telomere length in blood have been associated with cancer risk. We elucidated if arsenic exposure alters mtDNAcn and telomere length in individuals with different arsenic metabolizing capacity.

Methods: We studied two groups in the Salta province, Argentina, one in the Puna area of the Andes (N = 264, 89% females) and one in Chaco (N = 169, 75% females). We assessed arsenic exposure as the sum of arsenic metabolites [iAs, methylarsonic acid (MMA), dimethylarsinic acid (DMA)] in urine (U-As) using high-performance liquid chromatography coupled with hydride generation and inductively coupled plasma mass spectrometry. Efficiency of arsenic metabolism was expressed as percentage of urinary metabolites. MtDNAcn and telomere length were determined in blood by real-time PCR.

Results: Median U-As was 196 (5–95 percentile: 21–537) μg/L in Andes and 80 (5–95 percentile: 15–1637) μg/L in Chaco. The latter study group had less-efficient metabolism, with higher %iAs and %MMA in urine compared with the Andean group. U-As was significantly associated with increased mtDNAcn (log2 transformed to improve linearity) in Chaco (β = 0.027 per 100 μg/L, p = 0.0085; adjusted for age and sex), but not in Andes (β = 0.025, p = 0.24). U-As was also associated with longer telomere length in Chaco (β = 0.016, p = 0.0066) and Andes (β = 0.0075, p = 0.029). In both populations, individuals with above median %iAs showed significantly higher mtDNAcn and telomere length compared with individuals with below median %iAs.

Conclusions: Arsenic was associated with increased mtDNAcn and telomere length, particularly in individuals with less-efficient arsenic metabolism, a group who may have increased risk for arsenic-related cancer.

Estrogen receptor-β in mitochondria: implications for mitochondrial bioenergetics and tumorigenesis

Estrogen enhances mitochondrial function by enhancing mitochondrial biogenesis and sustaining mitochondrial energy-transducing capacity. Shifts in mitochondrial bioenergetic pathways from oxidative phosphorylation to glycolysis have been hypothesized to be involved in estrogen-induced tumorigenesis. Studies have shown that mitochondria are an important target of estrogen. Estrogen receptor-β (ERβ) has been shown to localize to mitochondria in a ligand-dependent or -independent manner and can affect mitochondrial bioenergetics and anti-apoptotic signaling. However, the functional role of mitochondrial ERβ in tumorigenesis remains unclear. Clinical studies of ERβ-related tumorigenesis have shown that ERβ stimulates mitochondrial metabolism to meet the high energy demands of processes such as cell proliferation, cell survival, and transformation. Thus, in elucidating the precise role of mitochondrial ERβ in cell transformation and tumorigenesis, it will be particularly valuable to explore new approaches for the development of medical treatments targeting mitochondrial ERβ-mediated mitochondrial function and preventing apoptosis.

Expression of BTG1 in hepatocellular carcinoma and its correlation with cell cycles, cell apoptosis, and cell metastasis

This study aimed to analyze the expression, clinical significance of B cell translocation gene 1 (BTG1) in hepatocellular carcinoma, and the biological effect in its cell line by BTG1 overexpression. Immunohistochemistry and Western blot were used to analyze BTG1 protein expression in 70 cases of hepatocellular cancer and 32 cases of normal tissues to study the relationship between BTG1 expression and clinical factors. Recombinant lentiviral vector was constructed to overexpress BTG1 and then infect hepatocellular cancer HepG2 cell line. The level of BTG1 protein expression was found to be significantly lower in hepatocellular cancer tissue than normal tissues (P < 0.05). Decreased expression of BTG1 was significantly correlated with tumor invasion, lymph node metastasis, clinic stage, and histological grade of patients with hepatocellular cancer (P < 0.05). Meanwhile, loss of BTG1 expression correlated significantly with poor overall survival time by Kaplan-Meier analysis (P < 0.05). The result of biological function has shown that HepG2 cell-transfected BTG1 had a lower survival fraction; higher percentage of the G0/G1 phases; higher cell apoptosis; significant decrease in migration and invasion; and lower Cyclin D1 (CND1), B cell lymphoma 2 (Bcl-2), and matrix metalloproteinases (MMP)-9 protein expression compared with HepG2 cell-untransfected BTG1 (P < 0.05). BTG1 expression decreased in hepatocellular cancer and correlated significantly with lymph node metastasis, clinic stage, histological grade, poor overall survival, proliferation, and metastasis in hepatocellular cancer cell by regulating CND1, Bcl-2, and MMP-9 protein expression, suggesting that BTG1 may play important roles as a negative regulator to hepatocellular cancer cell.

BTG1 expression in thyroid carcinoma: diagnostic indicator and prognostic marker

We determined the expression and function of B cell translocation gene 1 (BTG1) in thyroid carcinoma. Thyroid samples were obtained from cancer lesions (n=83) and adjacent normal tissue (n=35) in thyroid cancer patients immediately after endoscopic biopsy. BTG1 expression was determined by immunohistochemistry and western blotting. The effect of BTG1 overexpression was examined in vitro utilizing the human thyroid cancer cell line FTC-133, stably transfected with a recombinant lentivirus (LeBTG1 cells) and compared to empty vector transfected controls (LeEmpty). BTG1 overexpression was verified by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blotting. The expression of proteins involved in cell cycle regulation (cyclin D1), apoptosis (Bcl-2) and cell migration (MMP-9) in LeBTG1 cells was analyzed by western blotting. The effect of BTG1 overexpression on cell viability and proliferation was assessed by MTT assay in LeBTG1 and LeEmpty cells. Flow cytometric analyses were used to evaluate the effect of BTG1 expression on cell cycle distribution and apoptosis. The migration and invasion potential of LeBTG1 cells was examined by plating cells in Matrigel-coated chambers. BTG1 protein expression was significantly lower in thyroid cancer tissue biopsies compared to normal tissue as measured by immunohistochemistry (36.1 vs. 80.0% of tissues; P<0.05) and western blotting (0.251±0.021 vs. 0.651±0.065; P<0.05). Decreased expression of BTG1 was significantly correlated with thyroid cancer lymph node metastasis, clinical stage and pathological differentiation (P<0.05), as well as with reduced overall 10‑year survival rates compared to patients with higher expression levels (30.2 vs. 66.7%; P<0.05). In vitro analyses revealed that LeBTG1 cells had a reduced survival fraction compared to control LeEmpty cells, with higher rates of apoptosis (11.6±2.1 vs. 2.1±0.4%; P<0.05). The proportion of LeBTG1 cells in G0/G1 stage and S phase was also significantly different from LeEmpty cells (81.8±6.3 and 10.2±1.0%, vs. 62.4±4.9 and 25.5±2.6%, respectively; P<0.05), and the migration and invasion of LeBTG1 cells was significantly impaired with respect to LeEmpty cells (72.0±8.0 and 55.0±7.0 vs. 113.0±16.0 and 89.0±9.0, respectively; P<0.05). These effects were accompanied by decreased protein expression of cyclin D1, Bcl-2 and MMP-9 in LeBTG1 cells (0.234±0.018, 0.209±0.021, 0.155±0.017, respectively) compared to control LeEmpty cells (0.551±0.065, 0.452±0.043, 0.609±0.072, respectively; P<0.05). Reduced BTG1 expression is associated with increased disease severity, suggesting it is a negative regulator of thyroid cancer and can serve as a prognostic indicator.

The expression of BTG1 is downregulated in nasopharyngeal carcinoma and possibly associated with tumour metastasis

To determine the expression and function of B cell translocation gene 1 (BTG1) in nasopharyngeal carcinoma. Nasopharyngeal samples were taken from cancer lesions (n = 75) and adjacent normal tissue (n = 33) in nasopharyngeal cancer patients immediately after endoscopic biopsy. BTG1 expression was determined by immunohistochemistry and Western blotting. The effect of BTG1 overexpression was examined in vitro utilizing a human nasopharyngeal cancer cell line CNE2 stably transfected with a recombinant lentivirus (LeBTG1 cells) and compared to empty vector-transfected controls (LeEmpty). BTG1 overexpression was verified by real-time reverse transcriptase polymerase chain reaction and Western blot. The expression of proteins involved in cell cycle regulation (cyclin D1), apoptosis (Bcl-2) and cell migration (MMP-9) in LeBTG1 cells were analyzed by Western blot. The effect of BTG1 overexpression on cell viability and proliferation was assessed by an MTT assay in LeBTG1 and LeEmpty cells. Flow cytometric analyses were used to evaluate the effect of BTG1 expression on cell cycle distribution and apoptosis. The migration and invasion potential of LeBTG1 cells was examined by plating cells in Matrigel-coated chambers. BTG1 protein expression was significantly lower in nasopharyngeal cancer tissue biopsies than normal tissue as measured by immunohistochemistry (36.0 vs. 81.8 % of tissues; P < 0.05) and Western blotting (0.221 ± 0.019 vs. 0.652 ± 0.055; P < 0.05). Decreased expression of BTG1 was significantly correlated with nasopharyngeal cancer tumor stage, lymph node metastasis, clinical stage and pathologic differentiation (P < 0.05), as well as with reduced overall five-year survival rates compared to patients with higher expression levels (31.2 vs. 70.2 %; P < 0.05). In vitro analyses revealed that LeBTG1 cells had a reduced survival fraction compared to control LeEmpty cells, with higher rates of apoptosis (9.3 ± 0.7 vs. 2.3 ± 0.3 %; P < 0.05). The proportion of LeBTG1 cells in G0/G1 stage and S phase was also significantly different from LeEmpty cells (82.6 ± 3.8 and 10.1 ± 1.0 %, vs. 62.2 ± 2.4 and 28.9 ± 2.0 %, respectively; Ps < 0.05), and the migration and invasion of LeBTG1 cells was significantly impaired with respect to LeEmpty cells (96.0 ± 13.0 and 91.0 ± 11.0 vs. 158.0 ± 17.0 and 142.0 ± 15.0, respectively; Ps < 0.05). These effects were accompanied by decreased protein expression of cyclin D1, Bcl-2 and MMP-9 in LeBTG1 cells (0.231 ± 0.021, 0.413 ± 0.046, 0.131 ± 0.011, respectively) compared to control LeEmpty cells (0.636 ± 0.067, 0.821 ± 0.083, 0.451 ± 0.041, respectively; Ps < 0.05). Reduced BTG1 expression is associated with increased disease severity, suggesting it is a negative regulator of nasopharyngeal cancer and can serve as a prognostic indicator.

BTG1 underexpression is an independent prognostic marker in esophageal squamous cell carcinoma

To determine the expression and function of B cell translocation gene 1 (BTG1) in esophageal carcinoma, esophageal samples were taken from cancer lesions (n = 74) and adjacent normal tissue (n = 34) in esophageal cancer patients immediately after endoscopic biopsy. BTG1 expression was determined by immunohistochemistry and Western blotting. The effect of BTG1 overexpression was examined in vitro utilizing a human esophageal cancer cell line ECA-109 stably transfected with a recombinant lentivirus (LeBTG1 cells) and compared to empty vector-transfected controls (LeEmpty). BTG1 overexpression was verified by real-time reverse transcriptase polymerase chain reaction (RT-PCR) and Western blot. The expression of proteins involved in cell cycle regulation (cyclin D1) and apoptosis (Bcl-2) and cell migration (MMP-9) in LeBTG1 cells was analyzed by Western blot. The effect of BTG1 overexpression on cell viability and proliferation was assessed by an MTT assay in LeBTG1 and LeEmpty cells. Flow cytometric analyses were used to evaluate the effect of BTG1 expression on cell cycle distribution and apoptosis. The migration and invasion potential of LeBTG1 cells was examined by plating cells in Matrigel-coated chambers. The level of BTG1 protein expression was found to be significantly lower in esophageal cancer tissue than normal tissues (P < 0.05). Decreased expression of BTG1 was significantly correlated with lymph node metastasis, clinical stage, and histological grade of patients with esophageal cancer (P < 0.05). Meanwhile, loss of BTG1 expression correlated significantly with poor overall survival time by Kaplan-Meier analysis (P < 0.05). The result of biological function shown that Eca-109 cell-transfected BTG1 had a lower survival fraction, higher percentage of the G0/G1 phases, higher cell apoptosis, significant decrease in migration and invasion, and lower cylin D1, Bcl-2, and MMP-9 protein expression compared with Eca-109 cell-untransfected BTG1 (P < 0.05). Reduced BTG1 expression is associated with increased disease severity, suggesting it is a negative regulator of esophageal cancer and can serve as a prognostic indicator.

Cancer metabolism: new validated targets for drug discovery

Recent studies in cancer metabolism directly implicate catabolic fibroblasts as a new rich source of i) energy and ii) biomass, for the growth and survival of anabolic cancer cells. Conversely, anabolic cancer cells upregulate oxidative mitochondrial metabolism, to take advantage of the abundant fibroblast fuel supply. This simple model of “metabolic-symbiosis” has now been independently validated in several different types of human cancers, including breast, ovarian, and prostate tumors. Biomarkers of metabolic-symbiosis are excellent predictors of tumor recurrence, metastasis, and drug resistance, as well as poor patient survival. New pre-clinical models of metabolic-symbiosis have been generated and they genetically validate that catabolic fibroblasts promote tumor growth and metastasis. Over 30 different stable lines of catabolic fibroblasts and >10 different lines of anabolic cancer cells have been created and are well-characterized. For example, catabolic fibroblasts harboring ATG16L1 increase tumor cell metastasis by >11.5-fold, despite the fact that genetically identical cancer cells were used. Taken together, these studies provide >40 novel validated targets, for new drug discovery and anti-cancer therapy. Since anabolic cancer cells amplify their capacity for oxidative mitochondrial metabolism, we should consider therapeutically targeting mitochondrial biogenesis and OXPHOS in epithelial cancer cells. As metabolic-symbiosis promotes drug-resistance and may represent the escape mechanism during anti-angiogenic therapy, new drugs targeting metabolic-symbiosis may also be effective in cancer patients with recurrent and advanced metastatic disease.

Tumor microenvironment and metabolic synergy in breast cancers: critical importance of mitochondrial fuels and function

Metabolic synergy or metabolic coupling between glycolytic stromal cells (Warburg effect) and oxidative cancer cells occurs in human breast cancers and promotes tumor growth. The Warburg effect or aerobic glycolysis is the catabolism of glucose to lactate to obtain adenosine triphosphate (ATP). This review summarizes the main findings on this stromal metabolic phenotype, and the associated signaling pathways, as well as the critical role of oxidative stress and autophagy, all of which promote carcinoma cell mitochondrial metabolism and tumor growth. Loss of Caveolin 1 (Cav-1) and the upregulation of monocarboxylate transporter 4 (MCT4) in stromal cells are novel markers of the Warburg effect and metabolic synergy between stromal and carcinoma cells. MCT4 and Cav-1 are also breast cancer prognostic biomarkers. Reactive oxygen species (ROS) are key mediators of the stromal Warburg effect. High ROS also favors cancer cell mitochondrial metabolism and tumorigenesis, and anti-oxidants can reverse this altered stromal and carcinoma metabolism. A pseudo-hypoxic state with glycolysis and low mitochondrial metabolism in the absence of hypoxia is a common feature in breast cancer. High ROS induces loss of Cav-1 in stromal cells and is sufficient to generate a pseudo-hypoxic state. Loss of Cav-1 in the stroma drives glycolysis and lactate extrusion via HIF-1α stabilization and the upregulation of MCT4. Stromal cells with loss of Cav-1 and/or high expression of MCT4 also show a catabolic phenotype, with enhanced macroautophagy. This catabolic state in stromal cells is driven by hypoxia-inducible factor (HIF)-1α, nuclear factor κB (NFκB), and JNK activation and high ROS generation. A feed-forward loop in stromal cells regulates pseudo-hypoxia and metabolic synergy, with Cav-1, MCT4, HIF-1α, NFκB, and ROS as its key elements. Metabolic synergy also may occur between cancer cells and cells in distant organs from the tumor. Cancer cachexia, which is due to severe organismal metabolic dysregulation in myocytes and adipocytes, shares similarities with stromal-carcinoma metabolic synergy, as well. In summary, metabolic synergy occurs when breast carcinoma cells induce a nutrient-rich microenvironment to promote tumor growth. The process of tumor metabolic synergy is a multistep process, due to the generation of ROS, and the induction of catabolism with autophagy, mitophagy and glycolysis. Studying epithelial-stromal interactions and metabolic synergy is important to better understand the ecology of cancer and the metabolic role of different cell types in tumor progression.

Catabolic cancer-associated fibroblasts transfer energy and biomass to anabolic cancer cells, fueling tumor growth

Fibroblasts are the most abundant "non-cancerous" cells in tumors. However, it remains largely unknown how these cancer-associated fibroblasts (CAFs) promote tumor growth and metastasis, driving chemotherapy resistance and poor clinical outcome. This review summarizes new findings on CAF signaling pathways and their emerging metabolic phenotypes that promote tumor growth. Although it is well established that altered cancer metabolism enhances tumor growth, little is known about the role of fibroblast metabolism in tumor growth. New studies reveal that metabolic coupling occurs between catabolic fibroblasts and anabolic cancer cells, in many types of human tumors, including breast, prostate, and head & neck cancers, as well as lymphomas. These catabolic phenotypes observed in CAFs are secondary to a ROS-induced metabolic stress response. Mechanistically, this occurs via HIF1-alpha and NFκB signaling, driving oxidative stress, autophagy, glycolysis and senescence in stromal fibroblasts. These catabolic CAFs then create a nutrient-rich microenvironment, to metabolically support tumor growth, via the local stromal generation of mitochondrial fuels (lactate, ketone bodies, fatty acids, glutamine, and other amino acids). New biomarkers of this catabolic CAF phenotype (such as caveolin-1 (Cav-1) and MCT4), which are reversible upon treatment with anti-oxidants, are strong predictors of poor clinical outcome in various types of human cancers. How cancer cells metabolically reprogram fibroblasts can also help us to understand the effects of cancer cells at an organismal level, explaining para-neoplastic phenomena, such as cancer cachexia. In conclusion, cancer should be viewed more as a systemic disease, that engages the host-organism in various forms of energy-transfer and metabolic co-operation, across a whole-body "ecosystem".

BTG1 expression correlates with the pathogenesis and progression of breast carcinomas

This study aimed to analyze the expression, clinical significance of B cell translocation gene 1 (BTG1) in breast carcinoma and the biological effect in its cell line by BTG1 overexpression. Immunohistochemistry and western blot were used to analyze BTG1 protein expression in 72 cases of breast cancer and 36 cases of normal tissues to study the relationship between BTG1 expression and clinical factors. Recombinant lentiviral vector was constructed to over-express EMP-1 and then infect breast cancer MCF-7 cell line. Quantitative real-time RT-PCR (qRT-PCR) and western blot were used to detect the mRNA level and protein of BTG1. MTT assay, cell apoptosis, cell cycles, migration and invasion assays were also conducted as to the influence of the upregulated expression of BTG1 that might be found on MCF-7 cells biological effect. The level of BTG1 protein expression was found to be significantly lower in breast cancer tissue than normal tissues (P < 0.05). Decreased expression of BTG1 was significantly correlated with tumor invasion, lymph node metastasis, clinic stage and histological grade of patients with breast cancer (P < 0.05). Meanwhile, loss of BTG1 expression correlated significantly with poor overall survival time by Kaplan-Meier analysis (P < 0.05). The result of biological function shown that MCF-7 cell transfected BTG1 had a lower survival fraction, higher percentage of the G0/G1 phases, higher cell apoptosis, significant decrease in migration and invasion, and lower CyclinD1, Bcl-2, and MMP-9 protein expression compared with MCF-7 cell untransfected BTG1 (P < 0.05). BTG1 expression decreased in breast cancer and correlated significantly lymph node metastasis, clinic stage, histological grade, poor overall survival, proliferation, and metastasis in breast cancer cell by regulating CyclinD1, Bcl-2, and MMP-9 protein expression, suggesting that BTG1 may play important roles as a negative regulator to breast cancer cell.

The expression of BTG1 is downregulated in NSCLC and possibly associated with tumor metastasis

This study aimed to analyze the expression, clinical significance of B cell translocation gene 1 (BTG1) in nonsmall cell lung cancer (NSCLC) and the biological effect in its cell line by BTG1 overexpression. Immunohistochemistry and western blot were used to analyze BTG1 protein expression in 82 cases of NSCLC and 38 cases of normal tissues to study the relationship between BTG1 expression and clinical factors. Recombinant lentiviral vector was constructed to overexpress EMP-1 and then infect NSCLC H1299 cell line. Quantitative real-time RT-PCR and western blot were used to detect the mRNA level and protein of BTG1. 3-[4,5-dimethylthiazol -2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay, cell apoptosis, cell cycles, and migration and invasion assays were also conducted as to the influence of the upregulated expression of BTG1 that might be found on H1299 cells biological effect. The level of BTG1 protein expression was found to be significantly lower in NSCLC tissue than normal tissues (P < 0.05). Decreased expression of BTG1 was significantly correlated with lymph node metastasis, clinic stage, and histological grade of patients with NSCLC (P < 0.05). Meanwhile, loss of BTG1 expression correlated significantly with poor overall survival time by Kaplan-Meier analysis (P < 0.05). The result of biological function show that H1299 cell transfected BTG1 had a lower survival fraction; higher percentage of the G0/G1 phases; higher cell apoptosis; significant decrease in migration and invasion; and lower CyclinD1, Bcl-2, and MMP-9 protein expression compared with H1299 cell untransfected BTG1 (P < 0.05). BTG1 expression decreased in NSCLC and correlated significantly with lymph node metastasis; clinical stage; histological grade; poor overall survival; cell proliferation; cell cycles; cell apoptosis; and migration and invasion in NSCLC cell by regulating CyclinD1, Bcl-2, and MMP-9 protein expression, suggesting that BTG1 may play important roles as a negative regulator to NSCLC cell.

Oncogenes induce the cancer-associated fibroblast phenotype: metabolic symbiosis and "fibroblast addiction" are new therapeutic targets for drug discovery

Metabolic coupling, between mitochondria in cancer cells and catabolism in stromal fibroblasts, promotes tumor growth, recurrence, metastasis, and predicts anticancer drug resistance. Catabolic fibroblasts donate the necessary fuels (such as L-lactate, ketones, glutamine, other amino acids, and fatty acids) to anabolic cancer cells, to metabolize via their TCA cycle and oxidative phosphorylation (OXPHOS). This provides a simple mechanism by which metabolic energy and biomass are transferred from the host microenvironment to cancer cells. Recently, we showed that catabolic metabolism and "glycolytic reprogramming" in the tumor microenvironment are orchestrated by oncogene activation and inflammation, which originates in epithelial cancer cells. Oncogenes drive the onset of the cancer-associated fibroblast phenotype in adjacent normal fibroblasts via paracrine oxidative stress. This oncogene-induced transition to malignancy is "mirrored" by a loss of caveolin-1 (Cav-1) and an increase in MCT4 in adjacent stromal fibroblasts, functionally reflecting catabolic metabolism in the tumor microenvironment. Virtually identical findings were obtained using BRCA1-deficient breast and ovarian cancer cells. Thus, oncogene activation (RAS, NFkB, TGF-β) and/or tumor suppressor loss (BRCA1) have similar functional effects on adjacent stromal fibroblasts, initiating "metabolic symbiosis" and the cancer-associated fibroblast phenotype. New therapeutic strategies that metabolically uncouple oxidative cancer cells from their glycolytic stroma or modulate oxidative stress could be used to target this lethal subtype of cancers. Targeting "fibroblast addiction" in primary and metastatic tumor cells may expose a critical Achilles' heel, leading to disease regression in both sporadic and familial cancers.

Oncogenes and inflammation rewire host energy metabolism in the tumor microenvironment: RAS and NFκB target stromal MCT4

Here, we developed a model system to evaluate the metabolic effects of oncogene(s) on the host microenvironment. A matched set of "normal" and oncogenically transformed epithelial cell lines were co-cultured with human fibroblasts, to determine the "bystander" effects of oncogenes on stromal cells. ROS production and glucose uptake were measured by FACS analysis. In addition, expression of a panel of metabolic protein biomarkers (Caveolin-1, MCT1, and MCT4) was analyzed in parallel. Interestingly, oncogene activation in cancer cells was sufficient to induce the metabolic reprogramming of cancer-associated fibroblasts toward glycolysis, via oxidative stress. Evidence for "metabolic symbiosis" between oxidative cancer cells and glycolytic fibroblasts was provided by MCT1/4 immunostaining. As such, oncogenes drive the establishment of a stromal-epithelial "lactate-shuttle", to fuel the anabolic growth of cancer cells. Similar results were obtained with two divergent oncogenes (RAS and NFκB), indicating that ROS production and inflammation metabolically converge on the tumor stroma, driving glycolysis and upregulation of MCT4. These findings make stromal MCT4 an attractive target for new drug discovery, as MCT4 is a shared endpoint for the metabolic effects of many oncogenic stimuli. Thus, diverse oncogenes stimulate a common metabolic response in the tumor stroma. Conversely, we also show that fibroblasts protect cancer cells against oncogenic stress and senescence by reducing ROS production in tumor cells. Ras-transformed cells were also able to metabolically reprogram normal adjacent epithelia, indicating that cancer cells can use either fibroblasts or epithelial cells as "partners" for metabolic symbiosis. The antioxidant N-acetyl-cysteine (NAC) selectively halted mitochondrial biogenesis in Ras-transformed cells, but not in normal epithelia. NAC also blocked stromal induction of MCT4, indicating that NAC effectively functions as an "MCT4 inhibitor". Taken together, our data provide new strategies for achieving more effective anticancer therapy. We conclude that oncogenes enable cancer cells to behave as selfish "metabolic parasites", like foreign organisms (bacteria, fungi, viruses). Thus, we should consider treating cancer like an infectious disease, with new classes of metabolically targeted "antibiotics" to selectively starve cancer cells. Our results provide new support for the "seed and soil" hypothesis, which was first proposed in 1889 by the English surgeon, Stephen Paget.