Mitochondriotoxic compounds for cancer therapy

An Innovative Mitochondrial-targeted Gene Therapy for Cancer Treatment

Targeting cancer cell mitochondria holds great therapeutic promise, yet current strategies to specifically and effectively destroy cancer mitochondria in vivo are limited. Here, we introduce mLumiOpto, an innovative mitochondrial-targeted luminoptogenetics gene therapy designed to directly disrupt the inner mitochondrial membrane (IMM) potential and induce cancer cell death. We synthesize a blue light-gated channelrhodopsin (CoChR) in the IMM and co-express a blue bioluminescence-emitting Nanoluciferase (NLuc) in the cytosol of the same cells. The mLumiOpto genes are selectively delivered to cancer cells in vivo by using adeno-associated virus (AAV) carrying a cancer-specific promoter or cancer-targeted monoclonal antibody-tagged exosome-associated AAV. Induction with NLuc luciferin elicits robust endogenous bioluminescence, which activates mitochondrial CoChR, triggering cancer cell IMM permeability disruption, mitochondrial damage, and subsequent cell death. Importantly, mLumiOpto demonstrates remarkable efficacy in reducing tumor burden and killing tumor cells in glioblastoma or triple-negative breast cancer xenografted mouse models. These findings establish mLumiOpto as a novel and promising therapeutic strategy by targeting cancer cell mitochondria in vivo.

Anti-cancer activity of pyridoxal phosphate and metformin combination in human pancreatic cancer cells

Background: Pancreatic cancer is the foremost cause of cancer-related deaths in many developed countries with a poor prognosis. With advanced disease conditions chemotherapy, surgery followed by radiation is the regimen to prolong the survival. But a complete cure is questionable. Metformin is the first-line drug used for the treatment of type 2 diabetes in the world. Aim: The study aims to assess the anti-cancer activity of metformin with the combination of micronutrient pyridoxal phosphate (PLP) in the human pancreatic cancer cell line (PANC-1). Methods: Panc1 cells were maintained in vitro cell culture conditions. The IC50 concentrations of metformin and PLP were estimated and selected by using MTT assay. Morphological changes upon treatments were observed under microscope. Distribution of cells pattern was observed with propidium iodide dye in cell cycle assay. Different phases of cell distribution were studied with apoptosis assay. Results: More morphological changes were observed with PLP followed metformin. MTT assay revelled the IC50 concentrations of metformin and PLP were 20.95 ± 0.98 mM and 5.70 ± 0.07 mM. The cell cycle assay revealed that the percentage of cells was arrested in different phases with the treatments. Apoptosis assay revelled metformin increased necrosis population to 9.9%, whereas PLP has enhanced to 14.2% apoptosis. Tumour suppressor protein p53 levels had increased to 24.8% with PLP and 3.5% with metformin. Conclusion: In conclusion, PLP has significantly induced cell cycle arrest, apoptosis and enhanced p53 protein expression but a combination of PLP with metformin drug has not synergised anti-cancer activity in human PANC1 cells.

A viral interferon regulatory factor degrades RNA-binding protein hnRNP Q1 to enhance aerobic glycolysis via recruiting E3 ubiquitin ligase KLHL3 and decaying GDPD1 mRNA

Reprogramming of host metabolism is a common strategy of viral evasion of host cells, and is essential for successful viral infection and induction of cancer in the context cancer viruses. Kaposi's sarcoma (KS) is the most common AIDS-associated cancer caused by KS-associated herpesvirus (KSHV) infection. KSHV-encoded viral interferon regulatory factor 1 (vIRF1) regulates multiple signaling pathways and plays an important role in KSHV infection and oncogenesis. However, the role of vIRF1 in KSHV-induced metabolic reprogramming remains elusive. Here we show that vIRF1 increases glucose uptake, ATP production and lactate secretion by downregulating heterogeneous nuclear ribonuclear protein Q1 (hnRNP Q1). Mechanistically, vIRF1 upregulates and recruits E3 ubiquitin ligase Kelch-like 3 (KLHL3) to degrade hnRNP Q1 through a ubiquitin-proteasome pathway. Furthermore, hnRNP Q1 binds to and stabilizes the mRNA of glycerophosphodiester phosphodiesterase domain containing 1 (GDPD1). However, vIRF1 targets hnRNP Q1 for degradation, which destabilizes GDPD1 mRNA, resulting in induction of aerobic glycolysis. These results reveal a novel role of vIRF1 in KSHV metabolic reprogramming, and identifying a potential therapeutic target for KSHV infection and KSHV-induced cancers.

Mitochondrial Inhibition: a Treatment Strategy in Cancer?

PURPOSE OF REVIEW

Mitochondria have a major impact on virtually all processes linked to oncogenesis. Thus, mitochondrial metabolism inhibition has emerged as a promising anticancer strategy. In this review, we discuss the anticancer potential of mitochondrial inhibitors, with particular focus on metformin, in the context of more effective, targeted therapeutic modalities, and diagnostic strategies for cancer patients.

RECENT FINDINGS

Metformin has gained interest as an antitumor agent. However, promising results have not been translated into remarkable advances in the clinical practice. Recent findings emphasize the need of providing a metabolic context in which mitochondrial inhibitors may elicit its anticancerous effects. In addition, mitochondria are critical regulators in orchestrating immune responses. Thus, the immunomodulatory effect of mitochondrial inhibitors should also be taken into account to optimize its clinical use. Targeting mitochondrial metabolic network represents a promising therapeutic strategy in cancer. However, there is a need to define the metabolic context in which mitochondrial inhibitors are more effective, as well as how the cross-talk between many immunological functions and mitochondrial functionality may be exploited for a therapeutic benefit in cancer patients.

Cancer cell metabolism: Rewiring the mitochondrial hub

To adapt to tumoral environment conditions or even to escape chemotherapy, cells rapidly reprogram their metabolism to handle adversities and survive. Given the rapid rise of studies uncovering novel insights and therapeutic opportunities based on the role of mitochondria in tumor metabolic programing and therapeutics, this review summarizes most significant developments in the field. Taking in mind the key role of mitochondria on carcinogenesis and tumor progression due to their involvement on tumor plasticity, metabolic remodeling, and signaling re-wiring, those organelles are also potential therapeutic targets. Among other topics, we address the recent data intersecting mitochondria as of prognostic value and staging in cancer, by mitochondrial DNA (mtDNA) determination, and current inhibitors developments targeting mtDNA, OXPHOS machinery and metabolic pathways. We contribute for a holistic view of the role of mitochondria metabolism and directed therapeutics to understand tumor metabolism, to circumvent therapy resistance, and to control tumor development.

Sweet as honey, bitter as bile: Mitochondriotoxic peptides and other therapeutic proteins isolated from animal tissues, for dealing with mitochondrial apoptosis

Mitochondria are subcellular organelles involved in cell metabolism and cell life-cycle. Their role in apoptosis regulation makes them an interesting target of new drugs for dealing with cancer or rare diseases. Several peptides and proteins isolated from animal and plant sources are known for their therapeutic properties and have been tested on cancer cell-lines and xenograft murine models, highlighting their ability in inducing cell-death by triggering mitochondrial apoptosis. Some of those molecules have been even approved as drugs. Conversely, many other bioactive compounds are still under investigation for their proapoptotic properties. In this review we report about a group of peptides, isolated from animal venoms, with potential therapeutic properties related to their ability in triggering mitochondrial apoptosis. This class of compounds is known with different names, such as mitochondriotoxins or mitocans.

Targeting Dormant Ovarian Cancer Cells In Vitro and in an In Vivo Mouse Model of Platinum Resistance

Spheroids exhibit drug resistance and slow proliferation, suggesting involvement in cancer recurrence. The protein kinase C inhibitor UCN-01 (7-hydroxystaurosporine) has shown higher efficacy against slow proliferating and/or quiescent ovarian cancer cells. In this study, tumorigenic potential was assessed using anchorage-independent growth assays and spheroid-forming capacity, which was determined with ovarian cancer cell lines as well as primary ovarian cancers. Of 12 cell lines with increased anchorage-independent growth, 8 formed spheroids under serum-free culture conditions. Spheroids showed reduced proliferation (P < 0.0001) and Ki-67 immunostaining (8% vs. 87%) relative to monolayer cells. Spheroid formation was associated with increased expression of mitochondrial pathway genes (P ≤ 0.001) from Affymetrix HT U133A gene expression data. UCN-01, a kinase inhibitor/mitochondrial uncoupler that has been shown to lead to Puma-induced mitochondrial apoptosis as well as ATP synthase inhibitor oligomycin, demonstrated effectiveness against spheroids, whereas spheroids were refractory to cisplatin and paclitaxel. By live in vivo imaging, ovarian cancer xenograft tumors were reduced after primary treatment with carboplatin. Continued treatment with carboplatin was accompanied by an increase in tumor signal, whereas there was little or no increase in tumor signal observed with subsequent treatment with UCN-01 or oltipraz. Taken together, our findings suggest that genes involved in mitochondrial function in spheroids may be an important therapeutic target in preventing disease recurrence.

Epigenetic Regulation and Dietary Control of Triple Negative Breast Cancer

Triple negative breast cancer (TNBC) represents a highly heterogeneous group of breast cancers, lacking expression of the estrogen (ER) and progesterone (PR) receptors, and human epidermal growth factor receptor 2 (HER2). TNBC are characterized by a high level of mutation and metastasis, poor clinical outcomes and overall survival. Here, we review the epigenetic mechanisms of regulation involved in cell pathways disrupted in TNBC, with particular emphasis on dietary food components that may be exploited for the development of effective strategies for management of TNBC.

Detection of 8-oxoguanine and apurinic/apyrimidinic sites using a fluorophore-labeled probe with cell-penetrating ability

BACKGROUND

Reactive oxygen species (ROS) produce different lesions in DNA by ROS-induced DNA damage. Detection and quantification of 8-oxo-7,8-dihydroguanine (8-oxoG) within cells are important for study. Human ribosomal protein S3 (hRpS3) has a high binding affinity to 8-oxoG. In this study, we developed an imaging probe to detect 8-oxoG using a specific peptide from hRpS3. Transactivator (TAT) proteins are known to have cell-penetrating properties. Therefore, we developed a TAT-S3 probe by attaching a TAT peptide to our imaging probe.

RESULTS

A DNA binding assay was conducted to confirm that our probe bound to 8-oxoG and apurinic/apyrimidinic (AP) sites. We confirmed that the TAT-S3 probe localized in the mitochondria, without permeabilization, and fluoresced in H₂O₂-treated HeLa cells and zebrafish embryos. Treatment with Mitoquinone (MitoQ), a mitochondria-targeted antioxidant, reduced TAT-S3 probe fluorescence. Additionally, treatment with O8, an inhibitor of OGG1, increased probe fluorescence. A competition assay was conducted with an aldehyde reaction probe (ARP) and methoxyamine (MX) to confirm binding of TAT-S3 to the AP sites. The TAT-S3 probe showed competitive binding to AP sites with ARP and MX.

CONCLUSIONS

These results revealed that the TAT-S3 probe successfully detected the presence of 8-oxoG and AP sites in damaged cells. The TAT-S3 probe may have applications for the detection of diseases caused by reactive oxygen species.

Uncoupling Effect of F16 Is Responsible for Its Mitochondrial Toxicity and Anticancer Activity

As a novel delocalized lipophilic cation, F16 selectively accumulates in mitochondria of carcinoma cells and shows a broad spectrum of antiproliferative action towards cancer cell lines. In order to reveal the mode of action and molecular mechanism of F16 inducing cytotoxicity, we investigated the effects of F16 on cancer cells and isolated mitochondria relative to its precursor compound (E)-3-(2-(pyridine-4yl)vinyl)-1 H-indole (PVI), which has a similar structure without positive charge. It was found that PVI did not accumulate in mitochondria, and exhibited lower cytotoxicity compared to F16. However, when they were directly incubated with mitochondria, both F16 and PVI were observed to induce damage to mitochondrial structure and function. Moreover, it was found that F16 as well as PVI acted as uncouplers on mitochondria, and further rescue experiments revealed that the addition of adenosine 5'-triphosphate was the most effective way to recover the cell viability decreased by F16. Thus it was concluded that the decreased intracellular adenosine 5'-triphosphate availability induced by the uncoupling effect of F16 was a major factor in F16-mediated cytotoxicity. Futhermore, the results indicated that the uncoupling effect of F16 is attributed to its chemical stucture in common with PVI but independent of its positive charge. The study may shed light on understanding the underlying mechanism of action for F16, and providing suggestions for the design of new mitochondria-targeted antitumor molecules.

An Anti-tumorigenic Role of the Warburg Effect at Emergence of Transformed Cells

The Warburg effect is one of the hallmarks of cancer cells, characterized by enhanced aerobic glycolysis. Despite intense research efforts, its functional relevance or biological significance to facilitate tumor progression is still debatable. Hence the question persists when and how the Warburg effect contributes to carcinogenesis. Especially, the role of metabolic changes at a very early stage of tumorigenesis has received relatively little attention, and how aerobic glycolysis impacts tumor incidence remains largely unknown. Here we discuss a novel paradigm for the effect of the Warburg effect that provides a suppressive role in oncogenesis.Key words: Warburg effect, aerobic glycolysis, cell competition, EDAC.

Antiproliferative Effects of Pancratium Maritimum Extracts on Normal and Cancerous Cells

BACKGROUND

Plants are an important natural source of compounds used in cancer therapy. Pancratium maritimum contains potential anti-cancer agents such as alkaloids. In this study, we investigated the anti-proliferative effects of P. maritimum extracts on MDA-MB-231 human epithelial adenocarcinoma cell line and on normal lymphocytes in vitro.

METHODS

Leaves, flowers, roots, and bulbs of P. maritimum were collected and their contents were extracted and diluted to different concentrations that were applied on MDA-MB-231 cells and normal human lymphocytes cell in vitro for different intervals. Cells viability, proliferation, cell cycle distribution, apoptosis, and growth were evaluated by flow cytometry and microscopy. Parametric unpaired t-test was used to compare effects of plant extracts on treated cell cultures with untreated control cell cultures. IC₅₀ was also calculated.

RESULTS

P. maritimum extract had profound effects on MDA-MB-321 cells. It inhibited cell proliferation in a dose- and time-dependent manner. The IC₅₀ values were 0.039, 0.035, and 0.026 mg/ml after 48, 72, and 96 hours of treatment with 0.1 mg/ml concentration of bulb extract, respectively. Those values were 0.051 and 0.03 mg/ml after 72 and 96 hours for root extract, respectively, and 0.048 mg/ml after 96 hours for flower extract. There were no significant effects of P. maritimum bulb extracts on normal lymphocytes proliferation.

CONCLUSION

P. maritimum extract has anti-proliferative effects on MDA-MB-231 cell line in vitro. The effects imply the involvement of mechanisms that inhibits cell growth and arresting cells at S and G₂/M phases. Cyclin B1, Bcl-2, and Ki67 expression was also affected.

Dual subcellular compartment delivery of doxorubicin to overcome drug resistant and enhance antitumor activity

In order to overcome drug resistant and enhance antitumor activity of DOX, a new pH-sensitive micelle (DOX/DQA-DOX@DSPE-hyd-PEG-AA) was prepared to simultaneously deliver DOX to nucleus and mitochondria. Drug released from DOX/DQA-DOX@DSPE-hyd-PEG-AA showed a pH-dependent manner. DOX/DQA-DOX@DSPE-hyd-PEG-AA induced the depolarization of mitochondria and apoptosis in MDA-MB-231/ADR cells and A549 cells, which resulted in the high cytotoxicity of DOX/DQA-DOX@DSPE-hyd-PEG-AA against MDA-MB-231/ADR cells and A549 cells. Confocal microscopy confirmed that DOX/DQA-DOX@DSPE-hyd-PEG-AA simultaneously delivered DQA-DOX and DOX to the mitochondria and nucleus of tumor cell. After DOX/DQA-DOX@DSPE-hyd-PEG-AA was injected to the tumor-bearing nude mice by the tail vein, DOX was mainly found in tumor tissue. But DOX was widely distributed in the whole body after the administration of free DOX. Compared with free DOX, the same dose of DOX/DQA-DOX@DSPE-hyd-PEG-AA significantly inhibited the growth of DOX-resistant tumor in tumor-bearing mice without obvious systemic toxicity. Therefore, dual subcellular compartment delivery of DOX greatly enhanced the antitumor activity of DOX on DOX-resistant tumor. DOX/DQA-DOX@DSPE-hyd-PEG-AA has the potential in target therapy for DOX-resistant tumor.

Metformin combined with aspirin significantly inhibit pancreatic cancer cell growth in vitro and in vivo by suppressing anti-apoptotic proteins Mcl-1 and Bcl-2

Metformin and aspirin have been studied extensively as cancer preventive or therapeutic agents. However, the effects of their combination on pancreatic cancer cells have not been investigated. Herein, we evaluated the effects of metformin and aspirin, alone or in combination, on cell viability, migration, and apoptosis as well as the molecular changes in mTOR, STAT3 and apoptotic signaling pathways in PANC-1 and BxPC3 cells. Metformin and aspirin, at relatively low concentrations, demonstrated synergistically inhibitory effects on cell viability. Compared to the untreated control or individual drug, the combination of metformin and aspirin significantly inhibited cell migration and colony formation of both PANC-1 and BxPC-3 cells. Metformin combined with aspirin significantly inhibited the phosphorylation of mTOR and STAT3, and induced apoptosis as measured by caspase-3 and PARP cleavage. Remarkably, metformin combined with aspirin significantly downregulated the anti-apoptotic proteins Mcl-1 and Bcl-2, and upregulated the pro-apoptotic proteins Bim and Puma, as well as interrupted their interactions. The downregulation of Mcl-1 and Bcl-2 was independent of AMPK or STAT3 pathway but partially through mTOR signaling and proteasome degradation. In a PANC-1 xenograft mouse model, we demonstrated that the combination of metformin and aspirin significantly inhibited tumor growth and downregulated the protein expression of Mcl-1 and Bcl-2 in tumors. Taken together, the combination of metformin and aspirin significantly inhibited pancreatic cancer cell growth in vitro and in vivo by regulating the pro- and anti-apoptotic Bcl-2 family members, supporting the continued investigation of this two drug combination as chemopreventive or chemotherapeutic agents for pancreatic cancer.

Transcriptomic analysis of pancreatic cancer cells in response to metformin and aspirin: an implication of synergy

Metformin and aspirin have been studied extensively as cancer preventative and therapeutic agents. However, the underlying molecular mechanisms for the inhibitory effects of pancreatic cancer development remain undefined. To gain further insight into their biological function in pancreatic cancer, we conducted a transcriptomic analysis using RNA sequencing to assess the differential gene expression induced by metformin (5 mM) and aspirin (2 mM), alone or in combination, after treatment of PANC-1 cells for 48 hours. Compared to an untreated control, metformin down-regulated 58 genes and up-regulated 91 genes, aspirin down-regulated 12 genes only, while metformin plus aspirin down-regulated 656 genes and up-regulated 449 genes (fold-change > 2, P < 10⁻⁵). Of the top 10 genes (fold-change > 10, P < 10⁻¹⁰) regulated by metformin plus aspirin, PCDH18, CCL2, RASL11A, FAM111B and BMP5 were down-regulated ≥ 20-fold, while NGFR, NPTX1, C7orf57, MRPL23AS1 and UNC5B were up-regulated ≥ 10-fold. Ingenuity Pathway Analysis (IPA) revealed that the pathways, “cholesterol biosynthesis”, “cell cycle: G1/S checkpoint regulation”, and “axonal guidance signaling” were the most statistically significant pathways modulated by metformin plus aspirin. Although the results need further functional validation, these data provide the first evidence for the synergistic action between metformin and aspirin in modulating the transcriptional profile of pancreatic cancer cells.

Cochlioquinone derivatives with apoptosis-inducing effects on HCT116 colon cancer cells from the phytopathogenic fungus Bipolaris luttrellii L439

A new cochlioquinone derivative, cochlioquinone F (1), as well as three known compounds, anhydrocochlioquinone A (2), isocochlioquinone A (3), and isocochlioquinone C (4), were isolated from the PDB (potato dextrose broth) culture of the phytopathogenic fungus Bipolaris luttrellii. The structure of 1 was elucidated on the basis of NMR techniques. The apoptosis-inducing effects of compounds 1-4 were evaluated against HCT116 cancer cells. Compound 2 exhibited the strongest activity in inducing apoptosis on HCT116 cells within the range of 10-30 μM. In addition, the caspase activation, the release of cytochrome c from mitochondria, and the downregulation of Bcl-2 protein in HCT116 cells treated with compound 2 were detected.

Pathophysiological implications of mitochondrial oxidative stress mediated by mitochondriotropic agents and polyamines: the role of tyrosine phosphorylation

Mitochondria, once merely considered as the "powerhouse" of cells, as they generate more than 90 % of cellular ATP, are now known to play a central role in many metabolic processes, including oxidative stress and apoptosis. More than 40 known human diseases are the result of excessive production of reactive oxygen species (ROS), bioenergetic collapse and dysregulated apoptosis. Mitochondria are the main source of ROS in cells, due to the activity of the respiratory chain. In normal physiological conditions, ROS generation is limited by the anti-oxidant enzymatic systems in mitochondria. However, disregulation of the activity of these enzymes or interaction of respiratory complexes with mitochondriotropic agents may lead to a rise in ROS concentrations, resulting in oxidative stress, mitochondrial permeability transition (MPT) induction and triggering of the apoptotic pathway. ROS concentration is also increased by the activity of amine oxidases located inside and outside mitochondria, with oxidation of biogenic amines and polyamines. However, it should also be recalled that, depending on its concentration, the polyamine spermine can also protect against stress caused by ROS scavenging. In higher organisms, cell signaling pathways are the main regulators in energy production, since they act at the level of mitochondrial oxidative phosphorylation and participate in the induction of the MPT. Thus, respiratory complexes, ATP synthase and transition pore components are the targets of tyrosine kinases and phosphatases. Increased ROS may also regulate the tyrosine phosphorylation of target proteins by activating Src kinases or phosphatases, preventing or inducing a number of pathological states.

Anticancer/antiviral agent Akt inhibitor-IV massively accumulates in mitochondria and potently disrupts cellular bioenergetics

Inhibitors of the PI3-kinase/Akt (protein kinase B) pathway are under investigation as anticancer and antiviral agents. Akt inhibitor-IV (ChemBridge 5233705, CAS 681281-88-9, AKTIV), a small molecule reported to inhibit this pathway, exhibits potent anticancer and broad-spectrum antiviral activity. However, depending on concentration, this cationic benzimidazole derivative exhibits paradoxical positive or negative effects on the phosphorylation of Akt that are not well understood. To elucidate its mechanism of action, we investigated its spectroscopic properties. This compound proved to be sufficiently fluorescent (excitation λ_max = 388 nm, emission λ_max = 460 nm) to enable examination of its uptake and distribution in living mammalian cells. Despite a low quantum yield of 0.0016, imaging of HeLa cells treated with AKTIV (1 μM, 5 min) by confocal laser scanning microscopy, with excitation at 405 nm, revealed extensive accumulation in mitochondria. Treatment of Jurkat lymphocytes with 1 μM AKTIV for 15 min caused accumulation to over 250 μM in these organelles, whereas treatment with 5 μM AKTIV yielded concentrations of over 1 mM in mitochondria, as analyzed by flow cytometry. This massive loading resulted in swelling of these organelles, followed by their apparent disintegration. These effects were associated with profound disruption of cellular bioenergetics including mitochondrial depolarization, diminished mitochondrial respiration, and release of reactive oxygen species. Because mitochondria play key roles in both cancer proliferation and viral replication, we conclude that the anticancer and antiviral activities of AKTIV predominantly result from its direct and immediate effects on the structure and function of mitochondria.

Apoptotic efficacy of etomoxir in human acute myeloid leukemia cells. Cooperation with arsenic trioxide and glycolytic inhibitors, and regulation by oxidative stress and protein kinase activities

Fatty acid synthesis and oxidation are frequently exacerbated in leukemia cells, and may therefore represent a target for therapeutic intervention. In this work we analyzed the apoptotic and chemo-sensitizing action of the fatty acid oxidation inhibitor etomoxir in human acute myeloid leukemia cells. Etomoxir caused negligible lethality at concentrations up to 100 µM, but efficaciously cooperated to cause apoptosis with the anti-leukemic agent arsenic trioxide (ATO, Trisenox), and with lower efficacy with other anti-tumour drugs (etoposide, cisplatin), in HL60 cells. Etomoxir-ATO cooperation was also observed in NB4 human acute promyelocytic cells, but not in normal (non-tumour) mitogen-stimulated human peripheral blood lymphocytes. Biochemical determinations in HL60 cells indicated that etomoxir (25–200 µM) dose-dependently inhibited mitochondrial respiration while slightly stimulating glycolysis, and only caused marginal alterations in total ATP content and adenine nucleotide pool distribution. In addition, etomoxir caused oxidative stress (increase in intracellular reactive oxygen species accumulation, decrease in reduced glutathione content), as well as pro-apoptotic LKB-1/AMPK pathway activation, all of which may in part explain the chemo-sensitizing capacity of the drug. Etomoxir also cooperated with glycolytic inhibitors (2-deoxy-D-glucose, lonidamine) to induce apoptosis in HL60 cells, but not in NB4 cells. The combined etomoxir plus 2-deoxy-D-glucose treatment did not increase oxidative stress, caused moderate decrease in net ATP content, increased the AMP/ATP ratio with concomitant drop in energy charge, and caused defensive Akt and ERK kinase activation. Apoptosis generation by etomoxir plus 2-deoxy-D-glucose was further increased by co-incubation with ATO, which is apparently explained by the capacity of ATO to attenuate Akt and ERK activation. In summary, co-treatment with etomoxir may represent an interesting strategy to increase the apoptotic efficacy of ATO and (with some limitations) 2-deoxy-D-glucose which, although clinically important anti-tumour agents, exhibit low efficacy in monotherapy.

Metabolic alterations during the growth of tumour spheroids

Solid tumours undergo considerable alterations in their metabolism of nutrients in order to generate sufficient energy and biomass for sustained growth and proliferation. During growth, the tumour microenvironment exerts a number of influences (e.g. hypoxia and acidity) that affect cellular biology and the flux or utilisation of fuels including glucose. The tumour spheroid model was used to characterise the utilisation of glucose and describe alterations to the activity and expression of key glycolytic enzymes during the tissue growth curve. Glucose was avidly consumed and associated with the production of lactate and an acidified medium, confirming the reliance on glycolytic pathways and a diminution of oxidative phosphorylation. The expression levels and activities of hexokinase, phosphofructokinase-1, pyruvate kinase and lactate dehydrogenase in the glycolytic pathway were measured to assess glycolytic capacity. Similar measurements were made for glucose-6-phosphate dehydrogenase, the entry point and regulatory step of the pentose-phosphate pathway (PPP) and for cytosolic malate dehydrogenase, a key link to TCA cycle intermediates. The parameters for these key enzymes were shown to undergo considerable variation during the growth curve of tumour spheroids. In addition, they revealed that the dynamic alterations were influenced by both transcriptional and posttranslational mechanisms.

Metformin directly acts on mitochondria to alter cellular bioenergetics

BACKGROUND

Metformin is widely used in the treatment of diabetes, and there is interest in 'repurposing' the drug for cancer prevention or treatment. However, the mechanism underlying the metabolic effects of metformin remains poorly understood.

METHODS

We performed respirometry and stable isotope tracer analyses on cells and isolated mitochondria to investigate the impact of metformin on mitochondrial functions.

RESULTS

We show that metformin decreases mitochondrial respiration, causing an increase in the fraction of mitochondrial respiration devoted to uncoupling reactions. Thus, cells treated with metformin become energetically inefficient, and display increased aerobic glycolysis and reduced glucose metabolism through the citric acid cycle. Conflicting prior studies proposed mitochondrial complex I or various cytosolic targets for metformin action, but we show that the compound limits respiration and citric acid cycle activity in isolated mitochondria, indicating that at least for these effects, the mitochondrion is the primary target. Finally, we demonstrate that cancer cells exposed to metformin display a greater compensatory increase in aerobic glycolysis than nontransformed cells, highlighting their metabolic vulnerability. Prevention of this compensatory metabolic event in cancer cells significantly impairs survival.

CONCLUSIONS

Together, these results demonstrate that metformin directly acts on mitochondria to limit respiration and that the sensitivity of cells to metformin is dependent on their ability to cope with energetic stress.

p53-mediated activation of the mitochondrial protease HtrA2/Omi prevents cell invasion

Oncogenic Ras induces cell transformation and promotes an invasive phenotype. The tumor suppressor p53 has a suppressive role in Ras-driven invasion. However, its mechanism remains poorly understood. Here we show that p53 induces activation of the mitochondrial protease high-temperature requirement A2 (HtrA2; also known as Omi) and prevents Ras-driven invasion by modulating the actin cytoskeleton. Oncogenic Ras increases accumulation of p53 in the cytoplasm, which promotes the translocation of p38 mitogen-activated protein kinase (MAPK) into mitochondria and induces phosphorylation of HtrA2/Omi. Concurrently, oncogenic Ras also induces mitochondrial fragmentation, irrespective of p53 expression, causing the release of HtrA2/Omi from mitochondria into the cytosol. Phosphorylated HtrA2/Omi therefore cleaves β-actin and decreases the amount of filamentous actin (F-actin) in the cytosol. This ultimately down-regulates p130 Crk-associated substrate (p130Cas)-mediated lamellipodia formation, countering the invasive phenotype initiated by oncogenic Ras. Our novel findings provide insights into the mechanism by which p53 prevents the malignant progression of transformed cells.

Kinetic and structural characterization of an alternatively spliced variant of human mitochondrial 5'(3')-deoxyribonucleotidase

Human mitochondrial 5'(3')-deoxyribonucleotidase (mdN) catalyzes dephosphorylation of nucleoside monophosphates, and thus helps maintain homeostasis of deoxynucleosides required for mitochondrial DNA synthesis. Mature mdN is a 23-kDa dimeric protein with highest expression levels in the heart, brain and skeletal muscle. We have identified an alternative splice variant of the mdN gene containing an 18-nucleotide insertion encoding 6 amino acids (GKWPAT) at the 3'-end of the penultimate exon 4. We recombinantly expressed this enzyme variant and characterized its biochemical and kinetic properties as well as its three-dimensional structure. Our high-resolution (1.27 Å) crystal structure revealed that the insertion forms a loop located in the vicinity of the active site pocket and affects enzyme kinetic parameters as well as protein thermal stability.

Honokiol analogs: a novel class of anticancer agents targeting cell signaling pathways and other bioactivities

Honokiol (3,5-di-(2-propenyl)-1,1-biphenyl-2,2-diol) is a natural bioactive neolignan isolated from the genus Magnolia. In recent studies, honokiol has been observed to have anti-angiogenic, anticancer, anti-inflammatory, neuroprotective and GABA-modulating properties in vitro and in preclinical models. Honokiol and its analogs target multiple signaling pathways including NF-κB, STAT3, EGFR, mTOR and caspase-mediated common pathway, which regulate cancer initiation and progression. Honokiol and its targets of action may be helpful in the development of effective analogs and targeted cancer therapy. In this review, recent data describing the molecular targets of honokiol and its analogs with anticancer and some other bioactivities are discussed.

The antimalarial amodiaquine causes autophagic-lysosomal and proliferative blockade sensitizing human melanoma cells to starvation- and chemotherapy-induced cell death

Pharmacological inhibition of autophagic-lysosomal function has recently emerged as a promising strategy for chemotherapeutic intervention targeting cancer cells. Repurposing approved and abandoned non-oncological drugs is an alternative approach to the identification and development of anticancer therapeutics, and antimalarials that target autophagic-lysosomal functions have recently attracted considerable attention as candidates for oncological repurposing. Since cumulative research suggests that dependence on autophagy represents a specific vulnerability of malignant melanoma cells, we screened a focused compound library of antimalarials for antimelanoma activity. Here we report for the first time that amodiaquine (AQ), a clinical 4-aminoquinoline antimalarial with unexplored cancer-directed chemotherapeutic potential, causes autophagic-lysosomal and proliferative blockade in melanoma cells that surpasses that of its parent compound chloroquine. Monitoring an established set of protein markers (LAMP1, LC3-II, SQSTM1) and cell ultrastructural changes detected by electron microscopy, we observed that AQ treatment caused autophagic-lysosomal blockade in malignant A375 melanoma cells, a finding substantiated by detection of rapid inactivation of lysosomal cathepsins (CTSB, CTSL, CTSD). AQ-treatment was associated with early induction of energy crisis (ATP depletion) and sensitized melanoma cells to either starvation- or chemotherapeutic agent-induced cell death. AQ displayed potent antiproliferative effects, and gene expression array analysis revealed changes at the mRNA (CDKN1A, E2F1) and protein level (TP53, CDKN1A, CCND1, phospho-RB1 [Ser 780]/[Ser 807/811], E2F1) consistent with the observed proliferative blockade in S-phase. Taken together, our data suggest that the clinical antimalarial AQ is a promising candidate for repurposing efforts that aim at targeting autophagic-lysosomal function and proliferative control in malignant melanoma cells.

Visualizing chemical structure-subcellular localization relationships using fluorescent small molecules as probes of cellular transport

Background

To study the chemical determinants of small molecule transport inside cells, it is crucial to visualize relationships between the chemical structure of small molecules and their associated subcellular distribution patterns. For this purpose, we experimented with cells incubated with a synthetic combinatorial library of fluorescent, membrane-permeant small molecule chemical agents. With an automated high content screening instrument, the intracellular distribution patterns of these chemical agents were microscopically captured in image data sets, and analyzed off-line with machine vision and cheminformatics algorithms. Nevertheless, it remained challenging to interpret correlations linking the structure and properties of chemical agents to their subcellular localization patterns in large numbers of cells, captured across large number of images.

Results

To address this challenge, we constructed a Multidimensional Online Virtual Image Display (MOVID) visualization platform using off-the-shelf hardware and software components. For analysis, the image data set acquired from cells incubated with a combinatorial library of fluorescent molecular probes was sorted based on quantitative relationships between the chemical structures, physicochemical properties or predicted subcellular distribution patterns. MOVID enabled visual inspection of the sorted, multidimensional image arrays: Using a multipanel desktop liquid crystal display (LCD) and an avatar as a graphical user interface, the resolution of the images was automatically adjusted to the avatar’s distance, allowing the viewer to rapidly navigate through high resolution image arrays, zooming in and out of the images to inspect and annotate individual cells exhibiting interesting staining patterns. In this manner, MOVID facilitated visualization and interpretation of quantitative structure-localization relationship studies. MOVID also facilitated direct, intuitive exploration of the relationship between the chemical structures of the probes and their microscopic, subcellular staining patterns.

Conclusion

MOVID can provide a practical, graphical user interface and computer-assisted image data visualization platform to facilitate bioimage data mining and cheminformatics analysis of high content, phenotypic screening experiments.

Oxyphenisatin acetate (NSC 59687) triggers a cell starvation response leading to autophagy, mitochondrial dysfunction, and autocrine TNFα-mediated apoptosis

Oxyphenisatin (3,3-bis(4-hydroxyphenyl)-1H-indol-2-one) and several structurally related molecules have been shown to have in vitro and in vivo antiproliferative activity. This study aims to confirm and extend mechanistic studies by focusing on oxyphenisatin acetate (OXY, NSC 59687), the pro-drug of oxyphenisatin. Results confirm that OXY inhibits the growth of the breast cancer cell lines MCF7, T47D, HS578T, and MDA-MB-468. This effect is associated with selective inhibition of translation accompanied by rapid phosphorylation of the nutrient sensing eukaryotic translation initiation factor 2α (eIF2α) kinases, GCN2 and PERK. This effect was paralleled by activation of AMP-activated protein kinase (AMPK) combined with reduced phosphorylation of the mammalian target of rapamycin (mTOR) substrates p70S6K and 4E-BP1. Microarray analysis highlighted activation of pathways involved in apoptosis induction, autophagy, RNA/protein metabolism, starvation responses, and solute transport. Pathway inhibitor combination studies suggested a role for AMPK/mTOR signaling, de novo transcription and translation, reactive oxygen species (ROS)/glutathione metabolism, calcium homeostasis and plasma membrane Na(+) /K(+) /Ca(2+) transport in activity. Further examination confirmed that OXY treatment was associated with autophagy, mitochondrial dysfunction, and ROS generation. Additionally, treatment was associated with activation of both intrinsic and extrinsic apoptotic pathways. In the estrogen receptor (ER) positive MCF7 and T47D cells, OXY induced TNFα expression and TNFR1 degradation, indicating autocrine receptor-mediated apoptosis in these lines. Lastly, in an MCF7 xenograft model, OXY delivered intraperitoneally inhibited tumor growth, accompanied by phosphorylation of eIF2α and degradation of TNFR1. These data suggest that OXY induces a multifaceted cell starvation response, which ultimately induces programmed cell death.

Boosting antioxidants by lipophilization: a strategy to increase cell uptake and target mitochondria

PURPOSE

To explore the possibility to boost phenolic antioxidants through their structural modification by lipophilization and check the influence of such covalent modification on cellular uptake and mitochondria targeting.

METHODS

Rosmarinic acid was lipophilized by various aliphatic chain lengths (butyl, octyl, decyl, dodecyl, hexadecyl, and octadecyl) to give rosmarinate alkyl esters which were then evaluated for their ability (i) to reduce the level of reactive oxygen species (ROS) using 2',7'-dichlorodihydrofluorescein diacetate probe, (ii) to cross fibroblast cell membranes using confocal microscopy, and (iii) to target mitochondria using MitoTracker® Red CMXRos.

RESULTS

Increasing the chain length led to an improvement of the antioxidant activity until a threshold is reached for medium chain (10 carbon atoms) and beyond which lengthening resulted in a decrease of activity. This nonlinear phenomenon-also known as the cut-off effect-is discussed here in connection to the previously similar results observed in emulsified, liposomal, and cellular systems. Moreover, butyl, octyl, and decyl rosmarinates passed through the membranes in less than 15 min, whereas longer esters did not cross membranes and formed extracellular aggregates. Besides cell uptake, alkyl chain length also determined the subcellular localization of esters: mitochondria for medium chains esters, cytosol for short chains and extracellular media for longer chains.

CONCLUSION

The localization of antioxidants within mitochondria, the major site and target of ROS, conferred an advantage to medium chain rosmarinates compared to both short and long chains. In conjunction with changes in cellular uptake, this result may explain the observed decrease of antioxidant activity when lengthening the lipid chain of esters. This brings a proof-of-concept that grafting medium chain allows the design of mitochondriotropic antioxidants.

Cadmium-induced apoptosis in primary rat cerebral cortical neurons culture is mediated by a calcium signaling pathway

Cadmium (Cd) is an extremely toxic metal, capable of severely damaging several organs, including the brain. Studies have shown that Cd disrupts intracellular free calcium ([Ca²⁺]_i) homeostasis, leading to apoptosis in a variety of cells including primary murine neurons. Calcium is a ubiquitous intracellular ion which acts as a signaling mediator in numerous cellular processes including cell proliferation, differentiation, and survival/death. However, little is known about the role of calcium signaling in Cd-induced apoptosis in neuronal cells. Thus we investigated the role of calcium signaling in Cd-induced apoptosis in primary rat cerebral cortical neurons. Consistent with known toxic properties of Cd, exposure of cerebral cortical neurons to Cd caused morphological changes indicative of apoptosis and cell death. It also induced elevation of [Ca²⁺]_i and inhibition of Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase activities. This Cd-induced elevation of [Ca²⁺]_i was suppressed by an IP₃R inhibitor, 2-APB, suggesting that ER-regulated Ca²⁺ is involved. In addition, we observed elevation of reactive oxygen species (ROS) levels, dysfunction of cytochrome oxidase subunits (COX-I/II/III), depletion of mitochondrial membrane potential (ΔΨm), and cleavage of caspase-9, caspase-3 and poly (ADP-ribose) polymerase (PARP) during Cd exposure. Z-VAD-fmk, a pan caspase inhibitor, partially prevented Cd-induced apoptosis and cell death. Interestingly, apoptosis, cell death and these cellular events induced by Cd were blocked by BAPTA-AM, a specific intracellular Ca²⁺ chelator. Furthermore, western blot analysis revealed an up-regulated expression of Bcl-2 and down-regulated expression of Bax. However, these were not blocked by BAPTA-AM. Thus Cd toxicity is in part due to its disruption of intracellular Ca²⁺ homeostasis, by compromising ATPases activities and ER-regulated Ca²⁺, and this elevation in Ca²⁺ triggers the activation of the Ca²⁺-mitochondria apoptotic signaling pathway. This study clarifies the signaling events underlying Cd neurotoxicity, and suggests that regulation of Cd-disrupted [Ca²⁺]_i homeostasis may be a new strategy for prevention of Cd-induced neurodegenerative diseases.

Stress-related mitochondrial components and mitochondrial genome as targets of anticancer therapy

In addition to their role as cell powerhouse mitochondria are key organelles in the processes deciding about cell life or death that are crucial for tumor cell growth and survival, as well as for tumor cell ability to metastasize. Alterations in mitochondrial structure and functions have long been observed in cancer cells, thus targeting mitochondria as an anticancer therapeutic strategy has gained momentum recently. We will review the achievements and perspectives in the elucidation of the molecular basis for developing mitochondrial-targeted compounds as potential anticancer agents with special attention to mitochondrial DNA mutations and mitochondrial dysfunction. Molecules/agents candidate to affect mitochondrial metabolism in cancer cells will be dealt with, with a particular focus on approaches targeting defects in the mitochondrial genome.

Oncogenic BRAF regulates oxidative metabolism via PGC1α and MITF

Activating mutations in BRAF are the most common genetic alterations in melanoma. Inhibition of BRAF by small molecules leads to cell-cycle arrest and apoptosis. We show here that BRAF inhibition also induces an oxidative phosphorylation gene program, mitochondrial biogenesis, and the increased expression of the mitochondrial master regulator, PGC1α. We further show that a target of BRAF, the melanocyte lineage factor MITF, directly regulates the expression of PGC1α. Melanomas with activation of the BRAF/MAPK pathway have suppressed levels of MITF and PGC1α and decreased oxidative metabolism. Conversely, treatment of BRAF-mutated melanomas with BRAF inhibitors renders them addicted to oxidative phosphorylation. Our data thus identify an adaptive metabolic program that limits the efficacy of BRAF inhibitors.

Glycolysis inhibitor screening identifies the bis-geranylacylphloroglucinol protonophore moronone from Moronobea coccinea

Tumor cells exhibit enhanced glucose consumption and lactate production even when supplied with adequate oxygen (a phenomenon known as the Warburg effect, or aerobic glycolysis). Pharmacological inhibition of aerobic glycolysis represents a potential tumor-selective approach that targets the metabolic differences between normal and malignant tissues. Human breast tumor MDA-MB-231 cells were used to develop an assay system to discover natural product-based glycolysis inhibitors. The assay employed was based on hypersensitivity to glycolytic inhibition in tumor cells treated with the mitochondrial electron transport inhibitor rotenone. Under such conditions, ATP supply, and hence cell viability, depends exclusively on glycolysis. This assay system was used to evaluate 10648 plant and marine organism extracts from the U.S. National Cancer Institute's Open Repository. Bioassay-guided isolation of an active Moronobea coccinea extract yielded the new bis-geranylacylphloroglucinol derivative moronone (1). Compound 1 exhibited enhanced antiproliferative/cytotoxic activity in the presence of rotenone-imposed metabolic stress on tumor cells. Surprisingly, mechanistic studies revealed that 1 did not inhibit glycolysis, but rather functions as a protonophore that dissipates the mitochondrial proton gradient. In the presence of rotenone, tumor cells may be hypersensitive to protonophores due to increased ATP utilization by the ATP synthase.

Nullomer derived anticancer peptides (NulloPs): differential lethal effects on normal and cancer cells in vitro

We demonstrate the first use of the nullomer (absent sequences) approach to drug discovery and development. Nullomers are the shortest absent sequences determined in a species, or group of species. By identifying the shortest absent peptide sequences from the NCBI databases, we screened several potential anti-cancer peptides. In order to improve cell penetration and solubility we added short poly arginine tails (5Rs), and initially solubilized the peptides in 1M trehalose. The results for one of the absent sequences 9R (RRRRRNWMWC), and its scrambled version 9S1R (RRRRRWCMNW) are reported here. We refer to these peptides derived from nullomers as PolyArgNulloPs. A control PolyArgNulloP, 124R (RRRRRWFMHW), was also included. The lethal effects of 9R and 9S1R are mediated by mitochondrial impairment as demonstrated by increased ROS production, ATP depletion, cell growth inhibition, and ultimately cell death. These effects increase over time for cancer cells with a concomitant drop in IC-50 for breast and prostate cancer cells. This is in sharp contrast to the effects in normal cells, which show a decreased sensitivity to the NulloPs over time.

Rapamycin induces autophagy in the melanoma cell line M14 via regulation of the expression levels of Bcl-2 and Bax

Cancer therapy with rapamycin has been successfully implemented for kidney cancer, glioblastoma and prostate cancer. However, there are few studies concerning the effects of rapamycin on the treatment of human melanoma. In this study, we investigated whether rapamycin may be a promising strategy for the effective treatment of melanoma and explored the possible mechanism for this by culturing M14 cells in vitro and treating with rapamycin at three concentrations (10, 50 or 100 nmol/l). MDC and LC3B staining, western blot analysis, flow cytometry and transmission electron microscopy were employed. We revealed that rapamycin induced autophagy and inhibited the proliferation of M14 cells in a concentration-dependent manner, Furthermore, western blot analysis revealed an upregulated expression of Bcl-2 and downregulated expression of Bax in M14 cells. In conclusion, rapamycin induced autophagy and inhibited the growth of M14 cells. The mechanism may involve regulation of the expression of Bcl-2 family proteins. Rapamycin appears to be a promising strategy for the effective treatment of melanoma.

Warburg meets autophagy: cancer-associated fibroblasts accelerate tumor growth and metastasis via oxidative stress, mitophagy, and aerobic glycolysis

SIGNIFICANCE

Here, we review certain recent advances in oxidative stress and tumor metabolism, which are related to understanding the contributions of the microenvironment in promoting tumor growth and metastasis. In the early 1920s, Otto Warburg, a Nobel Laureate, formulated a hypothesis to explain the "fundamental basis" of cancer, based on his observations that tumors displayed a metabolic shift toward glycolysis. In 1963, Christian de Duve, another Nobel Laureate, first coined the phrase auto-phagy, derived from the Greek words "auto" and "phagy," meaning "self" and "eating."

RECENT ADVANCES

Now, we see that these two ideas (autophagy and aerobic glycolysis) physically converge in the tumor stroma. First, cancer cells secrete hydrogen peroxide. Then, as a consequence, oxidative stress in cancer-associated fibroblasts drives autophagy, mitophagy, and aerobic glycolysis.

CRITICAL ISSUES

This "parasitic" metabolic coupling converts the stroma into a "factory" for the local production of recycled and high-energy nutrients (such as L-lactate)-to fuel oxidative mitochondrial metabolism in cancer cells. We believe that Warburg and de Duve would be pleased with this new two-compartment model for understanding tumor metabolism. It adds a novel stromal twist to two very well-established cancer paradigms: aerobic glycolysis and autophagy.

FUTURE DIRECTIONS

Undoubtedly, these new metabolic models will foster the development of novel biomarkers, and corresponding therapies, to achieve the goal of personalized cancer medicine. Given the central role that oxidative stress plays in this process, new powerful antioxidants should be developed in the fight against cancer.

Subcellular localization and activity of gambogic acid

The natural product gambogic acid (GA) has shown significant potential as an anticancer agent as it is able to induce apoptosis in multiple tumor cell lines, including multidrug-resistant cell lines, as well as displaying antitumor activity in animal models. Despite the fact that GA has entered phase I clinical trials, the primary cellular target and mode of action of this compound remain unclear, although many proteins have been shown to be affected by it. By thorough analysis of several cellular organelles, at both the morphological and functional levels, we demonstrate that the primary effect of GA is at the mitochondria. We found that GA induces mitochondrial damage within minutes of incubation at low-micromolar concentrations. Moreover, a fluorescent derivative of GA was able to localize specifically to the mitochondria and was displaced from these organelles after competition with unlabeled GA. These findings indicate that GA directly targets the mitochondria to induce the intrinsic pathway of apoptosis, and thus represents a new member of the mitocans.

Aerobic glycolysis: meeting the metabolic requirements of cell proliferation

Warburg's observation that cancer cells exhibit a high rate of glycolysis even in the presence of oxygen (aerobic glycolysis) sparked debate over the role of glycolysis in normal and cancer cells. Although it has been established that defects in mitochondrial respiration are not the cause of cancer or aerobic glycolysis, the advantages of enhanced glycolysis in cancer remain controversial. Many cells ranging from microbes to lymphocytes use aerobic glycolysis during rapid proliferation, which suggests it may play a fundamental role in supporting cell growth. Here, we review how glycolysis contributes to the metabolic processes of dividing cells. We provide a detailed accounting of the biosynthetic requirements to construct a new cell and illustrate the importance of glycolysis in providing carbons to generate biomass. We argue that the major function of aerobic glycolysis is to maintain high levels of glycolytic intermediates to support anabolic reactions in cells, thus providing an explanation for why increased glucose metabolism is selected for in proliferating cells throughout nature.

The diverse role of the PPARγ coactivator 1 family of transcriptional coactivators in cancer

The critical role that altered cellular metabolism plays in promoting and maintaining the cancer phenotype has received considerable attention in recent years. For many years it was believed that aerobic glycolysis, also known as the Warburg Effect, played an important role in cancer. However, recent studies highlight the requirement of mitochondrial function, oxidative phosphorylation and biosynthetic pathways in cancer. This has promoted interest into mechanisms controlling these metabolic pathways. The PPARγ coactivator (PGC)-1 family of transcriptional coactivators have emerged as key regulators of several metabolic pathways including oxidative metabolism, energy homeostasis and glucose and lipid metabolism. While PGC-1s have been implicated in a number of metabolic diseases, recent studies highlight an important role in cancer. Studies show that PGC-1s have both pro and anticancer functions and suggests a dynamic role for the PGC-1s in cancer. We discuss in this review the links between PGC-1s and cancer, with a focus on the most well studied family member, PGC-1α.