A metabolic perturbation by U0126 identifies a role for glutamine in resveratrol-induced cell death

Targeting mitochondria and programmed cell death as potential interventions for metastatic castration-resistant prostate cancer

Prostate cancer is one of the major causes of morbidity and mortality in men worldwide. Most patients with prostate cancer will turn into end-of-life stage when those tumor cells become metastatic castration-resistant prostate cancer (mCRPC). The mCRPC subsequently developed a resistance to androgen signaling. The current regimens for mCRPC therapy are still ineffective. Much evidence from in vitro and in vivo studies explored the roles of therapeutic interventions targeted at the mitochondria and programmed cell death for prostate cancer therapy. The present review will focus on the recent medications which targeted at mitochondria and programmed cell death in mCRPC and the significant findings from each study will be summarized and discussed. Development of therapeutic interventions, particularly at mitochondrial and cytotoxic targets for treatment of mCRPC without inducing cellular toxicity of normal tissues will be considered as the novel therapeutic strategy for mCRPC.

Akt and AMPK activators rescue hyperexcitability in neurons from patients with bipolar disorder

BACKGROUND

Bipolar disorder (BD) is a multifactorial psychiatric illness affecting ∼1% of the global adult population. Lithium (Li), is the most effective mood stabilizer for BD but works only for a subset of patients and its mechanism of action remains largely elusive.

METHODS

In the present study, we used iPSC-derived neurons from patients with BD who are responsive (LR) or not (LNR) to lithium. Combined electrophysiology, calcium imaging, biochemistry, transcriptomics, and phosphoproteomics were employed to provide mechanistic insights into neuronal hyperactivity in BD, investigate Li's mode of action, and identify alternative treatment strategies.

FINDINGS

We show a selective rescue of the neuronal hyperactivity phenotype by Li in LR neurons, correlated with changes to Na+ conductance. Whole transcriptome sequencing in BD neurons revealed altered gene expression pathways related to glutamate transmission, alterations in cell signalling and ion transport/channel activity. We found altered Akt signalling as a potential therapeutic effect of Li in LR neurons from patients with BD, and that Akt activation mimics Li effect in LR neurons. Furthermore, the increased neural network activity observed in both LR & LNR neurons from patients with BD were reversed by AMP-activated protein kinase (AMPK) activation.

INTERPRETATION

These results suggest potential for new treatment strategies in BD, such as Akt activators in LR cases, and the use of AMPK activators for LNR patients with BD.

FUNDING

Supported by funding from ERA PerMed, Bell Brain Canada Mental Research Program and Brain & Behavior Research Foundation.

Metabolomics Analysis Reveals Novel Targets of Chemosensitizing Polyphenols and Omega-3 Polyunsaturated Fatty Acids in Triple Negative Breast Cancer Cells

Triple negative breast cancer (TNBC) is a subtype of breast cancer with typically poorer outcomes due to its aggressive clinical behavior and lack of targeted treatment options. Currently, treatment is limited to the administration of high-dose chemotherapeutics, which results in significant toxicities and drug resistance. As such, there is a need to de-escalate chemotherapeutic doses in TNBC while also retaining/improving treatment efficacy. Dietary polyphenols and omega-3 polyunsaturated fatty acids (PUFAs) have been demonstrated to have unique properties in experimental models of TNBC, improving the efficacy of doxorubicin and reversing multi-drug resistance. However, the pleiotropic nature of these compounds has caused their mechanisms to remain elusive, preventing the development of more potent mimetics to take advantage of their properties. Using untargeted metabolomics, we identify a diverse set of metabolites/metabolic pathways that are targeted by these compounds following treatment in MDA-MB-231 cells. Furthermore, we demonstrate that these chemosensitizers do not all target the same metabolic processes, but rather organize into distinct clusters based on similarities among metabolic targets. Common themes in metabolic targets included amino acid metabolism (particularly one-carbon and glutamine metabolism) and alterations in fatty acid oxidation. Moreover, doxorubicin treatment alone generally targeted different metabolites/pathways than chemosensitizers. This information provides novel insights into chemosensitization mechanisms in TNBC.

Dual contribution of the mTOR pathway and of the metabolism of amino acids in prostate cancer

BACKGROUND

Prostate cancer is the leading cause of cancer in men, and its incidence increases with age. Among other risk factors, pre-existing metabolic diseases have been recently linked with prostate cancer, and our current knowledge recognizes prostate cancer as a condition with important metabolic anomalies as well. In malignancies, metabolic disorders are commonly associated with aberrations in mTOR, which is the master regulator of protein synthesis and energetic homeostasis. Although there are reports demonstrating the high dependency of prostate cancer cells for lipid derivatives and even for carbohydrates, the understanding regarding amino acids, and the relationship with the mTOR pathway ultimately resulting in metabolic aberrations, is still scarce.

CONCLUSIONS AND PERSPECTIVES

In this review, we briefly provide evidence supporting prostate cancer as a metabolic disease, and discuss what is known about mTOR signaling and prostate cancer. Next, we emphasized on the amino acids glutamine, leucine, serine, glycine, sarcosine, proline and arginine, commonly related to prostate cancer, to explore the alterations in their regulatory pathways and to link them with the associated metabolic reprogramming events seen in prostate cancer. Finally, we display potential therapeutic strategies for targeting mTOR and the referred amino acids, as experimental approaches to selectively attack prostate cancer cells.

Natural Compounds in Prostate Cancer Prevention and Treatment: Mechanisms of Action and Molecular Targets

Prostate cancer (PCa) represents a major cause of cancer mortality among men in developed countries. Patients with recurrent disease initially respond to androgen-deprivation therapy, but the tumor eventually progresses into castration-resistant PCa; in this condition, tumor cells acquire the ability to escape cell death and develop resistance to current therapies. Thus, new therapeutic approaches for PCa management are urgently needed. In this setting, natural products have been extensively studied for their anti-PCa activities, such as tumor growth suppression, cell death induction, and inhibition of metastasis and angiogenesis. Additionally, numerous studies have shown that phytochemicals can specifically target the androgen receptor (AR) signaling, as well as the PCa stem cells (PCSCs). Interestingly, many clinical trials have been conducted to test the efficacy of nutraceuticals in human subjects, and they have partially confirmed the promising results obtained in vitro and in preclinical models. This article summarizes the anti-cancer mechanisms and therapeutic potentials of different natural compounds in the context of PCa prevention and treatment.

Mitochondrial-targeted penetrating peptide delivery for cancer therapy

INTRODUCTION

Mitochondria are promising targeting organelles for anticancer strategies; however, mitochondria are difficult for antineoplastic drugs to recognize and bind. Mitochondria-penetrating peptides (MPPs) are unique tools to gain access to the cell interior and deliver a bioactive cargo into mitochondria. MPPs have combined or delivered a variety of antitumor cargoes and obviously inhibited the tumor growth in vivo and in vitro. MPPs create new opportunities to develop new treatments for cancer.

AREAS COVERED

We review the target sites of mitochondria and the target-penetration mechanism of MPPs, different strategies, and various additional strategies decorated MPPs for tumor cell mitochondria targeting, the decorating mattes including metabolism molecules, RNA, DNA, and protein, which exploited considered as therapeutic combined with MPPs and target in human cancer treatment.

EXPERT OPINION/COMMENTARY

Therapeutic selectivity that preferentially targets the mitochondrial abnormalities in cancer cells without toxic impact on normal cells still need to be deepen. Moreover, it needs appropriate study designs for a correct evaluation of the target delivery outcome and the degradation rate of the drug in the cell. Generally, it is optimistic that the advances in mitochondrial targeting drug delivery by MPPs plasticity outlined here will ultimately help to the discovery of new approaches for the prevention and treatment of cancers.

Transcriptional activation of glucose transporter 1 in orthodontic tooth movement-associated mechanical response

The interplay between mechanoresponses and a broad range of fundamental biological processes, such as cell cycle progression, growth and differentiation, has been extensively investigated. However, metabolic regulation in mechanobiology remains largely unexplored. Here, we identified glucose transporter 1 (GLUT1)-the primary glucose transporter in various cells-as a novel mechanosensitive gene in orthodontic tooth movement (OTM). Using an in vivo rat OTM model, we demonstrated the specific induction of Glut1 proteins on the compressive side of a physically strained periodontal ligament. This transcriptional activation could be recapitulated in in vitro cultured human periodontal ligament cells (PDLCs), showing a time- and dose-dependent mechanoresponse. Importantly, application of GLUT1 specific inhibitor WZB117 greatly suppressed the efficiency of orthodontic tooth movement in a mouse OTM model, and this reduction was associated with a decline in osteoclastic activities. A mechanistic study suggested that GLUT1 inhibition affected the receptor activator for nuclear factor-κ B Ligand (RANKL)/osteoprotegerin (OPG) system by impairing compressive force-mediated RANKL upregulation. Consistently, pretreatment of PDLCs with WZB117 severely impeded the osteoclastic differentiation of co-cultured RAW264.7 cells. Further biochemical analysis indicated mutual regulation between GLUT1 and the MEK/ERK cascade to relay potential communication between glucose uptake and mechanical stress response. Together, these cross-species experiments revealed the transcriptional activation of GLUT1 as a novel and conserved linkage between metabolism and bone remodelling.

Non-apoptotic cell death in malignant tumor cells and natural compounds

Traditional cancer therapy is mainly targeting on enhancing cell apoptosis, however, it is well established that many cancer cells are chemo-resistant and defective in apoptosis induction. Therefore, it may have important therapeutic implications to exploit some novel natural compounds based on non-apoptotic programmed cell death. Currently, accumulating evidence shows that the compounds from nature source can induce non-apoptotic programmed cell death in cancer cells, and therefore these natural compounds have gained a great promise for the future anticancer therapeutics. In this review, we will concentrate our efforts on the latest developments regarding major forms of non-apoptotic programmed cell death--autophagic cell death, necroptosis, ferroptosis, pyroptosis, glutamoptosis and exosome-associated cell death. Our increased understanding of the role of natural compounds in regulating non-apoptotic programmed cell death will hopefully provide prospective strategies for cancer therapy.

Cancer Chemoprevention by Phytochemicals: Nature's Healing Touch

Phytochemicals are an important part of traditional medicine and have been investigated in detail for possible inclusion in modern medicine as well. These compounds often serve as the backbone for the synthesis of novel therapeutic agents. For many years, phytochemicals have demonstrated encouraging activity against various human cancer models in pre-clinical assays. Here, we discuss select phytochemicals—curcumin, epigallocatechin-3-gallate (EGCG), resveratrol, plumbagin and honokiol—in the context of their reported effects on the processes of inflammation and oxidative stress, which play a key role in tumorigenesis. We also discuss the emerging evidence on modulation of tumor microenvironment by these phytochemicals which can possibly define their cancer-specific action. Finally, we provide recent updates on how low bioavailability, a major concern with phytochemicals, is being circumvented and the general efficacy being improved, by synthesis of novel chemical analogs and nanoformulations.

mTOR inhibitor temsirolimus and MEK1/2 inhibitor U0126 promote chromosomal instability and cell type-dependent phenotype changes of glioblastoma cells

The phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) and the RAF/mitogen-activated and extracellular signal-regulated kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathways are frequently deregulated in cancer. Temsirolimus (TEM) and its primary active metabolite rapamycin allosterically block mTOR complex 1 substrate recruitment. The context-/experimental setup-dependent opposite effects of rapamycin on the multiple centrosome formation, aneuploidy, DNA damage/repair, proliferation, and invasion were reported. Similarly, the context-dependent either tumor-promoting or suppressing effects of RAF-MEK-ERK pathway and its inhibitors were demonstrated. Drug treatment-mediated stress may promote chromosomal instability (CIN), accelerating changes in the genomic landscape and phenotype diversity. Here, we characterized the genomic and phenotypic changes of U251 and T98G glioblastoma cell lines long-term treated with TEM or U0126, an inhibitor of MEK1/2. TEM significantly increased clonal and non-clonal chromosome aberrations. Both TEM and U0126 affected copy number alterations (CNAs) pattern. A proliferation rate of U251TEM and U251U0126 cells was lower and higher, respectively, than control cells. Colony formation efficiency of U251TEM significantly decreased, whereas U251U0126 did not change. U251TEM and U251U0126 cells decreased migration. In contrast, T98GTEM and T98GU0126 cells did not change proliferation, colony formation efficiency, and migration. Changes in the sensitivity of inhibitor-treated cells to the reduction of the glucose concentration were observed. Our results suggest that CIN and adaptive reprogramming of signal transduction pathways may be responsible for the cell type-dependent phenotype changes of long-term TEM- or U0126-treated tumor cells.

Large oncosomes contain distinct protein cargo and represent a separate functional class of tumor-derived extracellular vesicles

Large oncosomes (LO) are atypically large (1-10μm diameter) cancer-derived extracellular vesicles (EVs), originating from the shedding of membrane blebs and associated with advanced disease. We report that 25% of the proteins, identified by a quantitative proteomics analysis, are differentially represented in large and nano-sized EVs from prostate cancer cells. Proteins enriched in large EVs included enzymes involved in glucose, glutamine and amino acid metabolism, all metabolic processes relevant to cancer. Glutamine metabolism was altered in cancer cells exposed to large EVs, an effect that was not observed upon treatment with exosomes. Large EVs exhibited discrete buoyant densities in iodixanol (OptiPrep^TM) gradients. Fluorescent microscopy of large EVs revealed an appearance consistent with LO morphology, indicating that these structures can be categorized as LO. Among the proteins enriched in LO, cytokeratin 18 (CK18) was one of the most abundant (within the top 5^th percentile) and was used to develop an assay to detect LO in the circulation and tissues of mice and patients with prostate cancer. These observations indicate that LO represent a discrete EV type that may play a distinct role in tumor progression and that may be a source of cancer-specific markers.

Pitfalls of the MTT assay: Direct and off-target effects of inhibitors can result in over/underestimation of cell viability

The MTT assay (to a less degree MTS, XTT or WST) is a widely exploited approach for measuring cell viability/drug cytotoxicity. MTT reduction occurs throughout a cell and can be significantly affected by a number of factors, including metabolic and energy perturbations, changes in the activity of oxidoreductases, endo-/exocytosis and intracellular trafficking. Over/underestimation of cell viability by the MTT assay may be due to both adaptive metabolic and mitochondrial reprogramming of cells subjected to drug treatment-mediated stress and inhibitor off-target effects. Previously, imatinib, rottlerin, ursolic acid, verapamil, resveratrol, genistein nanoparticles and some polypeptides were shown to interfere with MTT reduction rate resulting in inconsistent results between the MTT assay and alternative assays. Here, to test the under/overestimation of viability by the MTT assay, we compared results derived from the MTT assay with the trypan blue exclusion assay after treatment of glioblastoma U251, T98G and C6 cells with three widely used inhibitors with the known direct and side effects on energy and metabolic homeostasis - temozolomide (TMZ), a DNA-methylating agent, temsirolimus (TEM), an inhibitor of mTOR kinase, and U0126, an inhibitor of MEK1/2 kinases. Inhibitors were applied shortly as in IC50 evaluating studies or long as in studies focusing on drug resistance acquisition. We showed that over/underestimation of cell viability by the MTT assay and its significance depends on a cell line, a time point of viability measurement and other experimental parameters. Furthermore, we provided a comprehensive survey of factors that should be accounted in the MTT assay. To avoid result misinterpretation, supplementation of the tetrazolium salt-based assays with other non-metabolic assays is recommended.

Differential Regulation of ERK1/2 and mTORC1 Through T1R1/T1R3 in MIN6 Cells

The MAPKs ERK1/2 respond to nutrients and other insulin secretagogues in pancreatic β-cells and mediate nutrient-dependent insulin gene transcription. Nutrients also stimulate the mechanistic target of rapamycin complex 1 (mTORC1) to regulate protein synthesis. We showed previously that activation of both ERK1/2 and mTORC1 in the MIN6 pancreatic β-cell-derived line by extracellular amino acids (AAs) is at least in part mediated by the heterodimeric T1R1/T1R3, a G protein-coupled receptor. We show here that AAs differentially activate these two signaling pathways in MIN6 cells. Pretreatment with pertussis toxin did not prevent the activation of either ERK1/2 or mTORC1 by AAs, indicating that G(I) is not central to either pathway. Although glucagon-like peptide 1, an agonist for a G(s-)coupled receptor, activated ERK1/2 well and mTORC1 to a small extent, AAs had no effect on cytosolic cAMP accumulation. Ca(2+) entry is required for ERK1/2 activation by AAs but is dispensable for AA activation of mTORC1. Pretreatment with UBO-QIC, a selective G(q) inhibitor, reduced the activation of ERK1/2 but had little effect on the activation of mTORC1 by AAs, suggesting a differential requirement for G(q). Inhibition of G(12/13) by the overexpression of the regulator of G protein signaling domain of p115 ρ-guanine nucleotide exchange factor had no effect on mTORC1 activation by AAs, suggesting that these G proteins are also not involved. We conclude that AAs regulate ERK1/2 and mTORC1 through distinct signaling pathways.

By reducing hexokinase 2, resveratrol induces apoptosis in HCC cells addicted to aerobic glycolysis and inhibits tumor growth in mice

Cancer cells exhibit an altered metabolic phenotype known as the aerobic glycolysis. The expression of HK2 changes the metabolic phenotype of cells to support cancerous growth. In the present study, we investigated the inhibitory effect of resveratrol on HK2 expression and hepatocellular carcinoma (HCC) cell glycolysis. Aerobic glycolysis was observed in four HCC cell lines compared to the normal hepatic cells. Resveratrol sensitized aerobic glycolytic HCC cells to apoptosis, and this effect was attenuated by glycolytic inhibitors. The induction of mitochondrial apoptosis was associated with the decrease of HK2 expression by resveratrol in HCC cells. In addition, resveratrol enhanced sorafenib induced cell growth inhibition in aerobic glycolytic HCC cells. Combination treatment with both reagents inhibited the growth and promoted apoptosis of HCC-bearing mice. The reduction of HK2 by resveratrol provides a new dimension to clinical HCC therapies aimed at preventing disease progression.

Resveratrol in prostate diseases - a short review

Introduction

Resveratrol is a plant–derived polyphenol suggested to have many beneficial health effects, including antioxidant, anti–inflammatory, anti–proliferative, proapoptotic, and anti–angiogenic. It is even specu- lated that uptake of resveratrol by red wine consumption could be behind the so–called French paradox the lower incidence of cardiovascular diseases in the French population. These properties, together with good absorption and tolerance, would make it an attractive agent in prostatic diseases, especially in cancer prevention and treatment.

Material and methods

MEDLINE search (keywords “prostate res- veratrol”) resulted in 39 research papers published since 2007. It has been shown that resveratol down–regulate androgen receptor expression, inhibit proliferation, and promote apop- tosis in prostate cancer cell lines and enhance their sensitivity to ionizing radiation. Several studies on animal prostate cancer development also suggest that resveratrol is able do delay or prevent carcino- genesis in prostate. Despite these promising results, there is no proof of any therapeutic properties of resveratrol in prostate diseases from human clinical trials nor any information about ongoing trials in this field.

Conclusions

Resveratrol is produced and sold as a nutritional supplement, there is not enough clinical evidence to justify a recommendation for the administration of resveratrol in humans at present.

Off-target effects of MEK inhibitors

The mitogen-activated protein kinases (MAPKs) ERK1/2 regulate numerous cellular processes, including gene transcription, proliferation, and differentiation. The only known substrates of the MAP2Ks MEK1/2 are ERK1/2; thus, MEK inhibitors PD98059, U0126, and PD0325901 have been important tools in determining the functions of ERK1/2. By using these inhibitors and genetically manipulating MEK, we found that ERK1/2 activation is neither sufficient nor necessary for regulated secretion of insulin from pancreatic β cells or secretion of epinephrine from chromaffin cells. We show that both PD98059 and U0126 reduce agonist-induced entry of calcium into cells in a manner independent of their ability to inhibit ERK1/2. Caution should be used when interpreting results from experiments using these compounds.

Targeting cancer cell mitochondria as a therapeutic approach

Mitochondria are double membrane-enveloped organelles that play a central role in cellular metabolism, calcium homeostasis, redox signaling and cell fates. They function as main generators of ATP, metabolites for the construction of macromolecules and reactive oxygen species. In many cancer cells, mitochondria seem dysfunctional, manifested by a shift of energy metabolism from oxidative phosphorylation to active glycolysis and an increase in reactive oxygen species generation. These metabolic changes are often associated with upregulation of NAD(P)H oxidase. Importantly, the metabolic reprogramming in a cancer cell is mechanistically linked to oncogenic signals. Targeting mitochondria as a cancer therapeutic strategy has attracted much attention in the recent years and multiple review articles in this area have been published. This article attempts to provide an update on recent progress in identification of mitochondria-associated molecules as potential anticancer targets and the respective targeting compounds.

The antimetastatic effects of resveratrol on hepatocellular carcinoma through the downregulation of a metastasis-associated protease by SP-1 modulation

BACKGROUND

The mortality and morbidity rates from cancer metastasis have not declined in Taiwan, especially because of hepatocellular carcinoma (HCC). Resveratrol has been shown to have benefits such as cardioprotection, providing antioxidative, anti-inflammatory, anti-cancer properties in previous studies. Therefore, HCC cells were subjected to treatment with resveratrol and then analyzed to determine the effects of resveratrol on the migration and invasion.

METHODOLOGY AND PRINCIPAL FINDINGS

Modified Boyden chamber assays revealed that resveratrol treatment significantly inhibited cell migration and invasion capacities of Huh7 cell lines that have low cytotoxicity in vitro, even at a high concentration of 100 µM. The results of casein zymography and western blotting revealed that the activities and protein levels of the urokinase-type plasminogen activator (u-PA) were inhibited by resveratrol. Western blot analysis also showed that resveratrol inhibits phosphorylation of JNK1/2. Tests of the mRNA level, real-time PCR, and promoter assays evaluated the inhibitory effects of resveratrol on u-PA expression in HCC cells. The chromatin immunoprecipitation (ChIP) assay showed that reactive in transcription protein of nuclear factor SP-1 was inhibited by resveratrol.

CONCLUSIONS

Resveratrol inhibits u-PA expression and the metastasis of HCC cells and is a powerful chemopreventive agent. The inhibitory effects were associated with the downregulation of the transcription factors of SP-1 signaling pathways.