Fenofibrate-induced nuclear translocation of FoxO3A triggers Bim-mediated apoptosis in glioblastoma cells in vitro

Use of drugs for hyperlipidaemia and diabetes and risk of primary and secondary brain tumours: nested case-control studies using the UK Clinical Practice Research Datalink (CPRD)

OBJECTIVES

Previous studies have suggested that fibrates and glitazones may have a role in brain tumour prevention. We examined if there is support for these observations using primary care records from the UK Clinical Practice Research Datalink (CPRD).

DESIGN

We conducted two nested case-control studies using primary and secondary brain tumours identified within CPRD between 2000 and 2016. We selected cases and controls among the population of individuals who had been treated with any anti-diabetic or anti-hyperlipidaemic medication to reduce confounding by indication.

SETTING

Adults older than 18 years registered with a general practitioner in the UK contributing data to CPRD.

RESULTS

We identified 7496 individuals with any brain tumour (4471 primary; 3025 secondary) in total. After restricting cases and controls to those prescribed any anti-diabetic or anti-hyperlipidaemic medication, there were 1950 cases and 7791 controls in the fibrate and 480 cases with 1920 controls in the glitazone analyses. Longer use of glitazones compared with all other anti-diabetic medications was associated with a reduced risk of primary (adjusted OR (aOR) 0.89 per year, 95% CI 0.80 to 0.98), secondary (aOR 0.87 per year, 95% CI 0.77 to 0.99) or combined brain tumours (aOR 0.88 per year, 95% CI 0.81 to 0.95). There was little evidence that fibrate exposure was associated with risk of either primary or secondary brain tumours.

CONCLUSIONS

Longer exposure to glitazones was associated with reduced primary and secondary brain tumour risk. Further basic science and population-based research should explore this finding in greater detail, in terms of replication and mechanistic studies.

Forkhead box transcription factors (FOXOs and FOXM1) in glioma: from molecular mechanisms to therapeutics

Glioma is the most aggressive and malignant type of primary brain tumor, comprises the majority of central nervous system deaths, and is categorized into different subgroups according to its histological characteristics, including astrocytomas, oligodendrogliomas, glioblastoma multiforme (GBM), and mixed tumors. The forkhead box (FOX) transcription factors comprise a collection of proteins that play various roles in numerous complex molecular cascades and have been discovered to be differentially expressed in distinct glioma subtypes. FOXM1 and FOXOs have been recognized as crucial transcription factors in tumor cells, including glioma cells. Accumulating data indicates that FOXM1 acts as an oncogene in various types of cancers, and a significant part of studies has investigated its function in glioma. Although recent studies considered FOXO subgroups as tumor suppressors, there are pieces of evidence that they may have an oncogenic role. This review will discuss the subtle functions of FOXOs and FOXM1 in gliomas, dissecting their regulatory network with other proteins, microRNAs and their role in glioma progression, including stem cell differentiation and therapy resistance/sensitivity, alongside highlighting recent pharmacological progress for modulating their expression.

Bcl-2 inhibition combined with PPARα activation synergistically targets leukemic stem cell-like cells in acute myeloid leukemia

Persistence of leukemic stem cells (LSCs) is one of the determining factors to acute myeloid leukemia (AML) treatment failure and responsible for the poor prognosis of the disease. Hence, novel therapeutic strategies that target LSCs are crucial for treatment success. We investigated if targeting Bcl-2 and peroxisome proliferator activated receptor α (PPARα), two distinct cell survival regulating mechanisms could eliminate LSCs. This study demonstrate that the Bcl-2 inhibitor venetoclax combined with the PPARα agonist chiglitazar resulted in synergistic killing of LSC-like cell lines and CD34+ primary AML cells while sparing their normal counterparts. Furthermore, the combination regimen significantly suppressed AML progression in patient-derived xenograft (PDX) mouse models. Mechanistically, chiglitazar-mediated PPARα activation inhibited the transcriptional activity of the PIK3AP1 gene promoter and down-regulated the PI3K/Akt signaling pathway and anti-apoptotic Bcl-2 proteins, leading to cell proliferation inhibition and apoptosis induction, which was synergized with venetoclax. These findings suggest that combinatorial Bcl-2 inhibition and PPARα activation selectively eliminates AML cells in vivo and vitro, representing an effective therapy for patients with relapsed and refractory AML.

AMPK/FOXO3a Pathway Increases Activity and/or Expression of ATM, DNA-PKcs, Src, EGFR, PDK1, and SOD2 and Induces Radioresistance under Nutrient Starvation

Most solid tumors contain hypoxic and nutrient-deprived microenvironments. The cancer cells in these microenvironments have been reported to exhibit radioresistance. We have previously reported that nutrient starvation increases the expression and/or activity of ATM and DNA-PKcs, which are involved in the repair of DNA double-strand breaks induced by ionizing radiation. In the present study, to elucidate the molecular mechanisms underlying these phenomena, we investigated the roles of AMPK and FOXO3a, which play key roles in the cellular response to nutrient starvation. Nutrient starvation increased clonogenic cell survival after irradiation and increased the activity and/or expression of AMPKα, FOXO3a, ATM, DNA-PKcs, Src, EGFR, PDK1, and SOD2 in MDA-MB-231 cells. Knockdown of AMPKα using siRNA suppressed the activity and/or expression of FOXO3a, ATM, DNA-PKcs, Src, EGFR, PDK1, and SOD2 under nutrient starvation. Knockdown of FOXO3a using siRNA suppressed the activity and/or expression of AMPKα, ATM, DNA-PKcs, FOXO3a, Src, EGFR, PDK1, and SOD2 under nutrient starvation. Nutrient starvation decreased the incidence of apoptosis after 8 Gy irradiation. Knockdown of FOXO3a increased the incidence of apoptosis after irradiation under nutrient starvation. AMPK and FOXO3a appear to be key molecules that induce radioresistance under nutrient starvation and may serve as targets for radiosensitization.

Computational modeling and synthesis of pyridine variants of benzoyl-phenoxy-acetamide with high glioblastoma cytotoxicity and brain tumor penetration

Glioblastomas are highly aggressive brain tumors for which therapeutic options are very limited. In a quest for new anti-glioblastoma drugs, we focused on specific structural modifications to the benzoyl-phenoxy-acetamide (BPA) structure present in a common lipid-lowering drug, fenofibrate, and in our first prototype glioblastoma drug, PP1. Here, we propose extensive computational analyses to improve the selection of the most effective glioblastoma drug candidates. Initially, over 100 structural BPA variations were analyzed and their physicochemical properties, such as water solubility (- logS), calculated partition coefficient (ClogP), probability for BBB crossing (BBB_SCORE), probability for CNS penetration (CNS-MPO) and calculated cardiotoxicity (hERG), were evaluated. This integrated approach allowed us to select pyridine variants of BPA that show improved BBB penetration, water solubility, and low cardiotoxicity. Herein the top 24 compounds were synthesized and analyzed in cell culture. Six of them demonstrated glioblastoma toxicity with IC50 ranging from 0.59 to 3.24 µM. Importantly, one of the compounds, HR68, accumulated in the brain tumor tissue at 3.7 ± 0.5 µM, which exceeds its glioblastoma IC50 (1.17 µM) by over threefold.

Computational modeling and synthesis of Pyridine variants of Benzoyl-Phenoxy-Acetamide with high glioblastoma cytotoxicity and brain tumor penetration

Glioblastomas are highly aggressive brain tumors for which therapeutic options are very limited. In a quest for new anti-glioblastoma drugs, we focused on specific structural modifications of benzoyl-phenoxy-acetamide (BPA) present in a common lipid-lowering drug, fenofibrate, and in our first prototype glioblastoma drug, PP1. Here, we propose extensive computational analyses to improve selection of the most effective glioblastoma drug candidates. Initially over 100 structural BPA variations were analyzed and their physicochemical properties such as water solubility (-logS), calculated partition coefficient (ClogP), probability for BBB crossing (BBB_SCORE), probability for CNS penetration (CNS-MPO) and calculated cardiotoxicity (hERG), were evaluated. This integrated approach allowed us to select pyridine variants of BPA that show improved BBB penetration, water solubility, and low cardiotoxicity. Herein the top 24 compounds were synthesized and analyzed in cell culture. Six of them demonstrated glioblastoma toxicity with IC50 ranging from 0.59 to 3.24mM. Importantly, one of the compounds, HR68, accumulated in the brain tumor tissue at 3.7+/-0.5mM, which exceeds its glioblastoma IC50 (1.17mM) by over 3-fold.

Therapeutic inhibition of PPARα-HIF1α-PGK1 signaling targets leukemia stem and progenitor cells in acute myeloid leukemia

Treatment of acute myeloid leukemia (AML) with chemotherapeutic agents fails to eliminate leukemia stem cells (LSC)，and thus patients remain at high risk for relapse. Therefore, the identification of agents that target LSC is an important consideration for the development of new therapies. Enhanced glycolysis in LSC contributes to the aggressiveness of AML, which is difficult to be targeted. In this study, we showed that targeting peroxisome-proliferator-activated receptor α (PPARα), a ligand-activated transcription factor by chiglitazar provided a promising therapeutic approach. We first identified that chiglitazar reduced cell viability and proliferation of the leukemia stem-like cells population in AML. Treatment with chiglitazar blocked the ubiquitination of PPARα and increased its expression, resulting in the inhibition of glucose metabolism and apoptosis of AML cells. Consistent with its anti-leukemia stem-like cells activity in vitro, chiglitazar treatment in vivo resulted in the significant killing of leukemia stem-like cells as demonstrated in AML patient-derived xenograft (PDX) models. Mechanistically, PPARα overexpression inhibited the expression and promoter activity of PGK1 through blocking HIF1-α interaction on the PGK1 promoter. Thus, we concluded that targeting PPARα may serve as a novel approach for enhancing stem and progenitor cells elimination in AML.

Chelidonium majus Induces Apoptosis of Human Ovarian Cancer Cells via ATF3-Mediated Regulation of Foxo3a by Tip60

Forkhead transcription factor 3a (Foxo3a) is believed to be a tumor suppressor as its inactivation leads to cell transformation and tumor development. However, further investigation is required regarding the involvement of the activating transcription factor 3 (ATF3)-mediated Tat-interactive protein 60 (Tip60)/Foxo3a pathway in cancer cell apoptosis. This study demonstrated that Chelidonium majus upregulated the expression of ATF3 and Tip60 and promoted Foxo3a nuclear translocation, ultimately increasing the level of Bcl-2-associated X protein (Bax) protein. ATF3 overexpression stimulated Tip60 expression, while ATF3 inhibition by siRNA repressed Tip60 expression. Furthermore, siRNA-mediated Tip60 inhibition significantly promoted Foxo3a phosphorylation, leading to blockade of Foxo3a translocation into the nucleus. Thus, we were able to deduce that ATF3 mediates the regulation of Foxo3a by Tip60. Moreover, siRNA-mediated Foxo3a inhibition suppressed the expression of Bax and subsequent apoptosis. Taken together, our data demonstrate that Chelidonium majus induces SKOV-3 cell death by increasing ATF3 levels and its downstream proteins Tip60 and Foxo3a. This suggests a potential therapeutic role of Chelidonium majus against ovarian cancer.

Fenofibrate Exerts Anticancer Effects on Human Cervical Cancer HeLa Cells via Caspase-Dependent Apoptosis and Cell Cycle Arrest

<b><i>Objective:</i></b> In the present study, we attempted to identify the effects of fenofibrate on human cervical cancer cells. <b><i>Methods:</i></b> The cytotoxicity of fenofibrate in cervical cancer cells was determined by Cell Counting Kit-8. Immunoblotting assay was used to determine the protein expression of caspase-3, poly ADP-ribose polymerase cleavage, B-cell lymphoma 2 family protein expression, microtubule-associated protein 1A/1B-light chain 3 (LC3), as well as cyclins and cyclin-dependent kinases. Immunofluorescence imaging was used to determine the expression of cleaved caspase-3 and LC3. Flow cytometry was used to determine cell cycle and apoptosis. <b><i>Results:</i></b> We first showed that fenofibrate treatment reduced cell viability in HeLa cervical cancer cells in a dose-dependent manner at 24 h and 48 h. Importantly, fenofibrate-induced cell death was mediated through cell cycle arrest in the G0–G1 phase and caspase-dependent apoptosis. Moreover, fenofibrate also induced autophagy activation in a dose-dependent manner and pharmacological inhibition of autophagy led to increase of sub-G1 phase and caspase-dependent cell death in HeLa cells. <b><i>Conclusion:</i></b> In conclusion, these data demonstrated that fenofibrate initially induced cell cycle arrest, followed by caspase-3-dependent cell death in cervical cancer HeLa cells. However, fenofibrate also induced autophagy activation, which is closely related to the survival of diverse cancer cells, thus reducing the anticancer effects of fenofibrate. Therefore, the combination of an autophagy inhibitor and fenofibrate might have the potential to become a new therapeutic strategy for cervical cancer.

PPAR-α Modulators as Current and Potential Cancer Treatments

Cancer is one of the leading causes of mortality worldwide. PPAR modulators may hold great potential for the management of cancer patients. Indeed, PPARs are critical sensors and regulators of lipid, and they are able to promote eNOS activation, regulate immunity and inflammation response, and affect proliferation and differentiation of cancer cells. Cancer, a name given to a group of diseases, is characterized by multiple distinctive biological behaviors, including angiogenesis, abnormal cell proliferation, aerobic glycolysis, inflammation, etc. In the last decade, emerging evidence has shown that PPAR-α, a nuclear hormone receptor, can modulate carcinogenesis via exerting effects on one or several characteristic pathological behaviors of cancer. Therefore, the multi-functional PPAR modulators have substantial promise in various types of cancer therapies. This review aims to consolidate the functions of PPAR-α, as well as discuss the current and potential applications of PPAR-α agonists and antagonists in tackling cancer.

Functional analysis of Epinephelus coioides peroxisome proliferative-activated receptor α (PPARα): Involvement in response to viral infection

Peroxisome proliferative-activated receptor α (PPARα) belongs to the superfamily of nuclear receptors (NR). Studies have demonstrated that PPARα functions in energy metabolism, hepatic function, immune response, cell cycle, and apoptosis. In teleost fish, few studies have investigated the role of PPARα in the immune response. In this study, the grouper PPARα gene (EcPPARα) was investigated for its role in viral infection. The open reading frame of EcPPARα encoded a protein of 469 amino acids and contained an N-terminal domain (NTD), a DNA-binding domain (DBD), a hinge region, and a C-terminal ligand-binding domain (LBD). Phylogenetic analysis revealed that EcPPARα was most closely related to homologous genes in Sander lucioperca and Perca flavescens. Upon challenge with SGIV (Singapore grouper iridovirus) and RGNNV (Red-spotted grouper nervous necrosis virus), EcPPARα expression levels were significantly upregulated in different tissues. Subcellular localization analysis showed that the EcPPARα protein localized throughout the cytoplasm and nucleus with diffuse intracellular expression patterns, which is consistent with the localization pattern of mammalian PPARs. Based on morphological observation of cytopathic effect (CPEs), viral gene expression mRNAs, and virus titer assays, the results presented here showed that an overexpression of EcPPARα promoted SGIV production in grouper spleen cells. Overexpression of EcPPARα significantly inhibited the expression of several cytokines, including interferon-related genes (IFN-γ, ISG15, MXI, MXII, MAVS and MDA5), inflammatory cytokines (IL-1β, IL-6, IL-8, TNF-α) and Toll like receptor adaptors (TRAF6 and MyD88). Luciferase activity of IFN-α, IFN-γ, ISRE and NF-κB promoters was also significantly decreased in EcPPARα overexpression cells. Due to these detected interferon-related genes and inflammatory cytokines play important antiviral effect against SGIV in grouper, we speculated that the promotion effect of EcPPARα on SGIV replication may be caused by down-regulation of interferon and inflammatory response. In addition, through apoptotic body observation, capspase-3 activity detection, and flow cytometry analysis, it was found that overexpression of EcPPARα promoted SGIV-induced apoptosis in fathead minnow (FHM) cells. These data may increase an understanding of the role of PPARα in fish antiviral immune responses and apoptosis.

Exploring anticancer activity of structurally modified benzylphenoxyacetamide (BPA); I: Synthesis strategies and computational analyses of substituted BPA variants with high anti-glioblastoma potential

Structural variations of the benzylphenoxyacetamide (BPA) molecular skeleton were explored as a viable starting point for designing new anti-glioblastoma drug candidates. Hand-to-hand computational evaluation, chemical modifications, and cell viability testing were performed to explore the importance of some of the structural properties in order to generate, retain, and improve desired anti-glioblastoma characteristics. It was demonstrated that several structural features are required to retain the anti-glioblastoma activity, including a carbonyl group of the benzophenone moiety, as well as 4′-chloro and 2,2-dimethy substituents. In addition, the structure of the amide moiety can be modified in such a way that desirable anti-glioblastoma and physical properties can be improved. Via these structural modifications, more than 50 compounds were prepared and tested for anti-glioblastoma activity. Four compounds were identified (HR28, HR32, HR37, and HR46) that in addition to HR40 (PP1) from our previous study, have been determined to have desirable physical and biological properties. These include high glioblastoma cytotoxicity at low μM concentrations, improved water solubility, and the ability to penetrate the blood brain barrier (BBB), which indicate a potential for becoming a new class of anti-glioblastoma drugs.

Hydrogen Ion Dynamics of Cancer and a New Molecular, Biochemical and Metabolic Approach to the Etiopathogenesis and Treatment of Brain Malignancies

The treatment of cancer has been slowly but steadily progressing during the last fifty years. Some tumors with a high mortality in the past are curable nowadays. However, there is one striking exception: glioblastoma multiforme. No real breakthrough has been hitherto achieved with this tumor with ominous prognosis and very short survival. Glioblastomas, being highly glycolytic malignancies are strongly pH-dependent and driven by the sodium hydrogen exchanger 1 (NHE1) and other proton (H⁺) transporters. Therefore, this is one of those pathologies where the lessons recently learnt from the new pH-centered anticancer paradigm may soon bring a promising change to treatment. This contribution will discuss how the pH-centric molecular, biochemical and metabolic perspective may introduce some urgently needed and integral novel treatments. Such a prospective therapeutic approach for malignant brain tumors is developed here, either to be used alone or in combination with more standard therapies.

Deconvolution and network analysis of IDH-mutant lower grade glioma predict recurrence and indicate therapeutic targets

Aim: IDH-mutant lower grade glioma (LGG) has been proven to have a good prognosis. However, its high recurrence rate has become a major therapeutic difficulty. Materials & methods: We combined epigenomic deconvolution and a network analysis on The Cancer Genome Atlas IDH-mutant LGG data. Results: Cell type compositions between recurrent and primary gliomas are significantly different, and the key cell type that determines the prognosis and recurrence risk was identified. A scoring model consisting of four gene expression levels predicts the recurrence risk (area under the receiver operating characteristic curve = 0.84). Transcription factor PPAR-α explains the difference between recurrent and primary gliomas. A cell cycle-related module controls prognosis in recurrent tumors. Conclusion: Comprehensive deconvolution and network analysis predict the recurrence risk and reveal therapeutic targets for recurrent IDH-mutant LGG.

Chemically Modified Variants of Fenofibrate with Antiglioblastoma Potential

Anticancer effects of a common lipid-lowering drug, fenofibrate, have been described in the literature for a quite some time; however, fenofibrate has not been used as a direct anticancer therapy. We have previously reported that fenofibrate in its unprocessed form (ester) accumulates in the mitochondria, inhibits mitochondrial respiration, and triggers a severe energy deficit and extensive glioblastoma cell death. However, fenofibrate does not cross the blood brain barrier and is quickly processed by blood and tissue esterases to form the PPARα agonist fenofibric acid, which is practically ineffective effective in triggering cancer cell death. To address these issues, we have made several chemical modifications in fenofibrate structure to increase its stability, water solubility, tissue penetration, and ultimately anticancer potential. Our data show that, in comparison to fenofibrate, four new compounds designated here as PP1, PP2, PP3, and PP4 have improved anticancer activity in vitro. Like fenofibrate, the compounds block mitochondrial respiration and trigger massive glioblastoma cell death in vitro. In addition, one of the lead compounds, PP1, has improved water solubility and is significantly more stable when exposed to human blood in comparison to fenofibrate. Importantly, mice bearing large intracranial glioblastoma tumors demonstrated extensive areas of tumor cell death within the tumor mass following oral administration of PP1, and the treated mice did not show any major signs of distress, and accumulated PP1 at therapeutically relevant concentrations in several tissues, including brain and intracranial tumors.

Piperlongumine-induced nuclear translocation of the FOXO3A transcription factor triggers BIM-mediated apoptosis in cancer cells

The transcription factor forkhead box O 3A (FOXO3A) is a tumor suppressor that promotes cell cycle arrest and apoptosis. Piperlongumine (PL), a plant alkaloid, is known to selectively kill tumor cells while sparing normal cells. However, the mechanism of PL-induced cancer cell death is not fully understood. We report here that an association of FOXO3A with the pro-apoptotic protein BIM (also known as BCL2-like 11, BCL2L11) has a direct and specific function in PL-induced cancer cell death. Using HeLa cells stably expressing a FOXO3A-GFP fusion protein and several other cancer cell lines, we found that PL treatment induces FOXO3A dephosphorylation and nuclear translocation and promotes its binding to the BIM gene promoter, resulting in the up-regulation of BIM in the cancer cell lines. Accordingly, PL inhibited cell viability and caused intrinsic apoptosis in a FOXO3A-dependent manner. Of note, siRNA-mediated FOXO3A knockdown rescued the cells from PL-induced cell death. In vivo, the PL treatment markedly inhibited xenograft tumor growth, and this inhibition was accompanied by the activation of the FOXO3A-BIM axis. Moreover, PL promoted FOXO3A dephosphorylation by inhibiting phosphorylation and activation of Akt, a kinase that phosphorylates FOXO3A. In summary, our findings indicate that PL activates the FOXO3A-BIM apoptotic axis by promoting dephosphorylation and nuclear translocation of FOXO3A via Akt signaling inhibition. These findings uncover a critical mechanism underlying the effects of PL on cancer cells.

shRNA-mediated PPARα knockdown in human glioma stem cells reduces in vitro proliferation and inhibits orthotopic xenograft tumour growth

The overall survival for patients with primary glioblastoma is very poor. Glioblastoma contains a subpopulation of glioma stem cells (GSC) that are responsible for tumour initiation, treatment resistance and recurrence. PPARα is a transcription factor involved in the control of lipid, carbohydrate and amino acid metabolism. We have recently shown that PPARα gene and protein expression is increased in glioblastoma and has independent clinical prognostic significance in multivariate analyses. In this work, we report that PPARα is overexpressed in GSC compared to foetal neural stem cells. To investigate the role of PPARα in GSC, we knocked down its expression using lentiviral transduction with short hairpin RNA (shRNA). Transduced GSC were tagged with luciferase and stereotactically xenografted into the striatum of NOD-SCID mice. Bioluminescent and magnetic resonance imaging showed that knockdown (KD) of PPARα reduced the tumourigenicity of GSC in vivo. PPARα-expressing control GSC xenografts formed invasive histological phenocopies of human glioblastoma, whereas PPARα KD GSC xenografts failed to establish viable intracranial tumours. PPARα KD GSC showed significantly reduced proliferative capacity and clonogenic potential in vitro with an increase in cellular senescence. In addition, PPARα KD resulted in significant downregulation of the stem cell factors c-Myc, nestin and SOX2. This was accompanied by downregulation of the PPARα-target genes and key regulators of fatty acid oxygenation ACOX1 and CPT1A, with no compensatory increase in glycolytic flux. These data establish the aberrant overexpression of PPARα in GSC and demonstrate that this expression functions as an important regulator of tumourigenesis, linking self-renewal and the malignant phenotype in this aggressive cancer stem cell subpopulation. We conclude that targeting GSC PPARα expression may be a therapeutically beneficial strategy with translational potential as an adjuvant treatment. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Anticancer Properties of Fenofibrate: A Repurposing Use

Cancer is a leading cause of death throughout the world, and cancer therapy remains a big medical challenge in terms of both its therapeutic efficacy and safety. Therefore, to find out a safe anticancer drug has been long goal for oncologist and medical scientists. Among clinically used medicines with no or little toxicity, fenofibrate is a drug of the fibrate class that plays an important role in lowering the levels of serum cholesterol and triglycerides while elevating the levels of high-density lipoproteins. Recently, several studies have implied that fenofibrate may exert anticancer effects via a variety of pathways involved in apoptosis, cell-cycle arrest, invasion, and migration. Given the great potential that fenofibrate may have anticancer effects, this review was to investigate all published works which directly or indirectly support the anticancer activity of fenofibrate. These studies provide evidence that fenofibrate exerted antitumor effects in several human cancer cell lines, such as breast, liver, glioma, prostate, pancreas, and lung cancer cell lines. Among these studies some have further confirmed the possibility and efficacy of fenofibrate anticancer in xenograft mouse models. In the last part of this review, we also discuss the potential mechanisms of action of fenofibrate based on the available information. Overall, we may repurpose fenofibrate as an anticancer drug in cancer treatment, which urgently need further and comprehensively investigated.

Cyclin D1 represses peroxisome proliferator-activated receptor alpha and inhibits fatty acid oxidation

Cyclin D1 is a cell cycle protein that promotes proliferation by mediating progression through key checkpoints in G1 phase. It is also a proto-oncogene that is commonly overexpressed in human cancers. In addition to its canonical role in controlling cell cycle progression, cyclin D1 affects other aspects of cell physiology, in part through transcriptional regulation. In this study, we find that cyclin D1 inhibits the activity of a key metabolic transcription factor, peroxisome proliferator-activated receptor α (PPARα), a member of nuclear receptor family that induces fatty acid oxidation and may play an anti-neoplastic role. In primary hepatocytes, cyclin D1 inhibits PPARα transcriptional activity and target gene expression in a cdk4-independent manner. In liver and breast cancer cells, knockdown of cyclin D1 leads to increased PPARα transcriptional activity, expression of PPARα target genes, and fatty acid oxidation. Similarly, cyclin D1 depletion enhances binding of PPARα to target sequences by chromatin immunoprecipitation. In proliferating hepatocytes and regenerating liver in vivo, induction of endogenous cyclin D1 is associated with diminished PPARα activity. Cyclin D1 expression is both necessary and sufficient for growth factor-mediated repression of fatty acid oxidation in proliferating hepatocytes. These studies indicate that in addition to playing a pivotal role in cell cycle progression, cyclin D1 represses PPARα activity and inhibits fatty acid oxidation. Our findings establish a new link between cyclin D1 and metabolism in both tumor cells and physiologic hepatocyte proliferation.

Regulatory effects of antitumor agent matrine on FOXO and PI3K-AKT pathway in castration-resistant prostate cancer cells

We previously demonstrated that matrine could inhibit the proliferating, migrating, as well as invading processes of both PC-3 and DU145 cells. However, the underlying molecular mechanisms have not yet been clearly defined. In this study, using various techniques such as high throughput sequencing technology, bioinformatics, quantitative real-time PCR, and immunoblot analysis, we aimed to understand whether matrine serves as a novel regulator of FOXO and PI3K-AKT signaling pathway. DU145 and PC-3 cell lines were cultured for 24 h in vitro. Cells were treated with either matrine or control serum for 48 h, followed by extraction of total RNA. The RNA was sequenced using HiSeq 2500 high-throughput sequencing platform (Illumina). A gene library was established and quality analysis of read data carried out. Integrated database from the website DAVID was used to analyze Gene Ontology (GO), and Kyoto encyclopedia of genes and genomes (KEGG) pathway of differential genes was used for pathway analysis, screening for fold differences of more than two times. The FOXO and PI3K-AKT signaling pathways were screened, and expression levels of mRNA and core protein detected by real-time PCR and immunoblotting, respectively. High throughput sequencing and GO analysis revealed that differentially expressed genes before and after treatment played an important role in cell metabolic process, growth process, anatomical structure formation, cellular component organization, and biological regulation. KEGG signal pathway analysis revealed that FOXO and PI3K-AKT signal pathways had a significant difference between before and after matrine-treated androgen-independent prostate cancer cells PC-3 and DU145. Real-time PCR showed that matrine treatment led to a significant increase in the expression levels of FOXO1A, FOXO3A, FOXO4, and FOXO6 in DU145 and PC-3 cells (P<0.01 or P<0.05), whereas the PI3K expression levels decreased (P<0.01). Similarly, immunoblotting revealed a significant increase (P<0.05) in the expression levels of FOXO1A FOXO3A, FOXO4, and FOXO6 in both PC-3 and DU145 cells, whereas PI3K expression levels decreased (P<0.05). Matrine had a broad regulating effect on the mRNA expression profiles of both PC-3 and DU145 cells. Matrine may inhibit cell proliferation, migration, as well as invasion, and induce apoptosis in both PC-3 and DU145 cells through FOXO and PI3K-AKT signaling pathways. Matrine could therefore be used as a complementary drug to present chemotherapeutic agents, for treating androgen-independent prostate cancer.

Fork Head Box Class O1 (FOXO1) Activates Bim Expression to Mediate Cardiac Apoptosis in Chronic Intermittent Hypoxia-Induced Cardiac Hypertrophy

Background

Obstructive sleep apnea syndrome (OSAS) is characterized by chronic intermittent episodes of upper-airway obstruction with hypoxia and is associated with increased risk of cardiovascular diseases, including myocardial hypertrophy. Chronic intermittent hypoxia (CIH) has been shown to induce apoptosis in cardiomyocytes. However, the mechanisms of cardiomyocytes apoptosis under CIH largely remain unclear.

Material/Methods

We used male Sprague-Dawley rats and human cardiomyocyte cell line H9C2, and Annexin V/PI, Western blot analysis, co-immunoprecipitation, RT-PCR, immunohistochemistry, and TUNEL assay were carried out.

Results

We show that Bim was significantly up-regulated by CIH in cardiomyocytes, and the function of Bim in CIH-induced apoptosis was supported by the genetic suppression of Bim with si-RNA. We also observed that CIH-motivated expression of Bim was directly related to fork head box class O1 (FOXO1), which is increased in CIH. Genetic ablation and pharmacological inhibition of FOXO1 in cardiomyocytes attenuated CIH-induced apoptosis, hypertrophy, and features of perivascular fibrosis in cardiomyocytes in vitro and in vivo.

Conclusions

FOXO1 is a key integrator of the apoptosis signal transduction pathway, driving chronic intermittent hypoxia-induced cardiac hypertrophy, and inhibition of FOXO1 provides a potential target for the treatment of OSAS with cardiac hypertrophy.

Metabolic Reprogramming in Glioma

Many cancers have long been thought to primarily metabolize glucose for energy production—a phenomenon known as the Warburg Effect, after the classic studies of Otto Warburg in the early twentieth century. Yet cancer cells also utilize other substrates, such as amino acids and fatty acids, to produce raw materials for cellular maintenance and energetic currency to accomplish cellular tasks. The contribution of these substrates is increasingly appreciated in the context of glioma, the most common form of malignant brain tumor. Multiple catabolic pathways are used for energy production within glioma cells, and are linked in many ways to anabolic pathways supporting cellular function. For example: glycolysis both supports energy production and provides carbon skeletons for the synthesis of nucleic acids; meanwhile fatty acids are used both as energetic substrates and as raw materials for lipid membranes. Furthermore, bio-energetic pathways are connected to pro-oncogenic signaling within glioma cells. For example: AMPK signaling links catabolism with cell cycle progression; mTOR signaling contributes to metabolic flexibility and cancer cell survival; the electron transport chain produces ATP and reactive oxygen species (ROS) which act as signaling molecules; Hypoxia Inducible Factors (HIFs) mediate interactions with cells and vasculature within the tumor environment. Mutations in the tumor suppressor p53, and the tricarboxylic acid cycle enzymes Isocitrate Dehydrogenase 1 and 2 have been implicated in oncogenic signaling as well as establishing metabolic phenotypes in genetically-defined subsets of malignant glioma. These pathways critically contribute to tumor biology. The aim of this review is two-fold. Firstly, we present the current state of knowledge regarding the metabolic strategies employed by malignant glioma cells, including aerobic glycolysis; the pentose phosphate pathway; one-carbon metabolism; the tricarboxylic acid cycle, which is central to amino acid metabolism; oxidative phosphorylation; and fatty acid metabolism, which significantly contributes to energy production in glioma cells. Secondly, we highlight processes (including the Randle Effect, AMPK signaling, mTOR activation, etc.) which are understood to link bio-energetic pathways with oncogenic signals, thereby allowing the glioma cell to achieve a pro-malignant state.

Proteasome inhibitor MG132 induces thyroid cancer cell apoptosis by modulating the activity of transcription factor FOXO3a

Proteasome inhibitors are promising antitumor drugs with preferable cytotoxicity in malignant cells and have exhibited clinical efficiency in several hematologic malignancies. P53-dependent apoptosis has been reported to be a major mechanism underlying. However, apoptosis can also be found in cancer cells with mutant-type p53, suggesting the involvement of p53-independent mechanism. Tumor suppressor forkhead Box O3 is another substrate of proteasomal degradation, which also functions partially through inducing apoptosis. The aim of this study was to explore the effect of proteasome inhibition on the expression and activity of forkhead Box O3 in thyroid cancer cells. Using flow cytometry, western blot, immunofluorescence staining and quantitative RT-PCR assays, we assessed proteasome inhibitor MG132-induced apoptosis in thyroid cancer cells and its effect on the expression and activity of forkhead Box O3. The resulted showed that MG132 induced significant apoptosis, and caused the accumulation of p53 protein in both p53 wild-type and mutant-type thyroid cancer cell lines, whereas the proapoptotic targets of p53 were transcriptionally upregulated only in the p53 wild-type cells. Strikingly, upon MG132 administration, the accumulation and nuclear translocation of transcription factor forkhead Box O3 as well as transcriptional upregulation of its proapoptotic target genes were found in thyroid cancer cells regardless of p53 status. Cell apoptosis was enhanced by ectopic overexpression while attenuated by silencing of forkhead Box O3. Altogether, we demonstrated that proteasome inhibitor MG132 induces thyroid cancer cell apoptosis at least partially through modulating forkhead Box O3 activity.

The transcription factor PPARα is overexpressed and is associated with a favourable prognosis in IDH-wildtype primary glioblastoma

AIMS

PPARα agonists are in current clinical use as hypolipidaemic agents and show significant antineoplastic effects in human glioblastoma models. To date however, the expression of PPARα in large-scale glioblastoma datasets has not been examined. We aimed to investigate the expression of the transcription factor PPARα in primary glioblastoma, the relationship between PPARα expression and patients' clinicopathological features and other molecular markers associated with gliomagenesis.

METHODS AND RESULTS

With protein immunoblotting techniques and reverse transcription quantitative real-time PCR, PPARα was found to be significantly overexpressed in glioblastoma compared with control brain tissue (P = 0.032 and P = 0.005). PPARA gene expression was found to be enriched in the classical glioblastoma subtype within The Cancer Genome Atlas (TCGA) dataset. Although not associated with overall survival when assessed by immunohistochemistry, cross-validation with the TCGA dataset and multivariate analyses identified PPARA gene expression as an independent prognostic marker for overall survival (P = 0.042). Finally, hierarchical clustering revealed novel, significant associations between high PPARA expression and a putative set of glioblastoma molecular mediators including EMX2, AQP4, and NTRK2.

CONCLUSIONS

PPARα is overexpressed in primary glioblastoma and high PPARA expression functions as an independent prognostic marker in the glioblastoma TCGA dataset. Further studies are required to explore genetic associations with high PPARA expression and to analyse the predictive role of PPARα expression in glioblastoma models in response to PPARα agonists.

Peroxisome proliferator-activated receptor α (PPARα) contributes to control of melanogenesis in B16 F10 melanoma cells

Recent studies revealed the cooperation between peroxisome proliferator-activated receptor gamma (PPARγ) and α-MSH signaling, which results in enhanced melanogenesis in melanocytes and melanoma cells. However, the agonists of PPARα, such as fenofibrate, exert depigmenting effect. Therefore, we aimed to check how the PPARα expression level affects the antimelanogenic activity of fenofibrate and whether PPARα modulates melanogenesis independently of its agonist. To answer these questions, we used three B16 F10-derived cell lines, which varied in the PPARα expression level and were developed by stable transfection with plasmids driving shRNA-based PPARα silencing or overexpression of PPARα-emerald GFP fusion protein. Melanin contents were assessed with electron paramagnetic resonance spectroscopy along with color component image analysis-a novel approach to pigment content characteristics in melanoma cells. B16 F10 wt and Ctrl shRNA lines showed intermediate pigmentation, whereas the pigmentation of the B16 F10-derived cell lines was inversely correlated with the PPARα expression level. We observed that cells overexpressing PPARα were almost amelanotic and cells with reduced PPARα protein level were heavily melanized. Furthermore, fenofibrate down-regulated the melanogenic apparatus (MITF, tyrosinase, and tyrosinase-related proteins) in the cells with the regular PPARα expression level resulting in their visibly lower total melanin content in all the cell lines. From these observations, we conclude that fenofibrate works as a strong depigmenting agent, which acts independently of PPARα, but in an additive fashion. Our results also indicate that alterations in PGC-1a acetylation and expression level might contribute to the regulation of melanogenesis by PPARα and fenofibrate.

PPARα induces cell apoptosis by destructing Bcl2

PPARα belongs to the peroxisome-proliferator-activated receptors (PPARs) family, which plays a critical role in inhibiting cell proliferation and tumorigenesis, while the molecular mechanism is still unclear. Here we report that PPARα serves as an E3 ubiquitin ligase to govern Bcl2 protein stability. PPARα physically bound to Bcl2 protein. In this process, PPARα/C102 was critical for PPARα binding to BH3 domain of Bcl2, subsequently, PPARα transferred K48-linked polyubiquitin to lysine-22 site of Bcl2 resulting in its ubiquitination and proteasome-dependent degradation. Importantly, overexpression of PPARα enhanced cancer cell chemotherapy sensitivity. In contrast, silenced PPARα decreased this event. These findings revealed a novel mechanism of PPARα governed endogenous Bcl2 protein stability leading to reduced cancer cell chemoresistance, which provides a potential drug target for cancer treatment.

Ergosterol purified from medicinal mushroom Amauroderma rude inhibits cancer growth in vitro and in vivo by up-regulating multiple tumor suppressors

We have previously screened thirteen medicinal mushrooms for their potential anti-cancer activities in eleven different cell lines and found that the extract of Amauroderma rude exerted the highest capacity in inducing cancer cell death. The current study aimed to purify molecules mediating the anti-cancer cell activity. The extract of Amauroderma rude was subject to fractionation, silica gel chromatography, and HPLC. We purified a compound and identified it as ergosterol by EI-MS and NMR, which was expressed at the highest level in Amauroderma rude compared with other medicinal mushrooms tested. We found that ergosterol induced cancer cell death, which was time and concentration dependent. In the in vivo experiment, normal mice were injected with murine cancer cell line B16 that is very aggressive and caused mouse death severely. We found that treatment with ergosterol prolonged mouse survival. We found that ergosterol-mediated suppression of breast cancer cell viability occurred through apoptosis and that ergosterol up-regulated expression of the tumor suppressor Foxo3. In addition, the Foxo3 down-stream signaling molecules Fas, FasL, BimL, and BimS were up-regulated leading to apoptosis in human breast cancer cells MDA-MB-231. Our results suggest that ergosterol is the main anti-cancer ingredient in Amauroderma rude, which activated the apoptotic signal pathway. Ergosterol may serve as a potential lead for cancer therapy.

Fenofibrate Induces Ketone Body Production in Melanoma and Glioblastoma Cells

Ketone bodies [beta-hydroxybutyrate (bHB) and acetoacetate] are mainly produced in the liver during prolonged fasting or starvation. bHB is a very efficient energy substrate for sustaining ATP production in peripheral tissues; importantly, its consumption is preferred over glucose. However, the majority of malignant cells, particularly cancer cells of neuroectodermal origin such as glioblastoma, are not able to use ketone bodies as a source of energy. Here, we report a novel observation that fenofibrate, a synthetic peroxisome proliferator-activated receptor alpha (PPARa) agonist, induces bHB production in melanoma and glioblastoma cells, as well as in neurospheres composed of non-transformed cells. Unexpectedly, this effect is not dependent on PPARa activity or its expression level. The fenofibrate-induced ketogenesis is accompanied by growth arrest and downregulation of transketolase, but the NADP/NADPH and GSH/GSSG ratios remain unaffected. Our results reveal a new, intriguing aspect of cancer cell biology and highlight the benefits of fenofibrate as a supplement to both canonical and dietary (ketogenic) therapeutic approaches against glioblastoma.

PPARα regulates tumor progression, foe or friend?

PPARα belongs to the peroxisome-proliferator-activated receptors (PPARs) family that consists of PPARα, PPARδ, and PAPRγ. Activation of PPARα by ligands including fatty acids and their derivatives as well as some synthetic compounds regulates tumor progression in various tissues. Activated PPARα inhibits or promotes tumorigenesis depending on the specific tissues, but the molecular mechanism is still unclear. In this review, the recent progress of PPARα regulating tumorigenesis is discussed.

NF-κB/RelA-PKM2 mediates inhibition of glycolysis by fenofibrate in glioblastoma cells

Aerobic glycolysis (production of lactate from glucose in the presence of oxygen) is a hallmark of cancer. Fenofibrate is a lipid-lowering drug and an agonist of the peroxisome proliferator-activated receptor alpha (PPARα). We found that FF inhibited glycolysis in a PPARα-dependent manner in glioblastoma cells. Fenofibrate inhibited the transcriptional activity of NF-κB/RelA and also disrupted its association with hypoxia inducible factor1 alpha (HIF1α), which is required for the binding of NF-κB/RelA to the PKM promoter and PKM2 expression. High ratios of PKM2/PKM1 promote glycolysis and inhibit oxidative phosphorylation, thus favoring aerobic glycolysis. Fenofibrate decreased the PKM2/PKM1 ratio and caused mitochondrial damage. Given that fenofibrate is a widely used non-toxic drug, we suggest its use in patients with glioblastoma multiforme (GBM).

Expression Profiling Identifies Bezafibrate as Potential Therapeutic Drug for Lung Adenocarcinoma

Drug-induced gene expression patterns that invert disease profiles have recently been illustrated to be a new strategy for drug-repositioning. In the present study, we validated this approach and focused on prediction of novel drugs for lung adenocarcinoma (AC), for which there is a pressing need to find novel therapeutic compounds. Firstly, connectivity map (CMap) analysis computationally predicted bezafibrate as a putative compound against lung AC. Then this hypothesis was verified by in vitro assays of anti-proliferation and cell cycle arrest. In silico docking evidence indicated that bezafibrate could target cyclin dependent kinase 2(CDK2), which regulates progression through the cell cycle. Furthermore, we found that bezafibrate can significantly down-regulate the expression of CDK2 mRNA and p-CDK2. Using a nude mice xenograft model, we also found that bezafibrate could inhibit tumor growth of lung AC in vivo. In conclusion, this study proposed bezafibrate as a potential therapeutic option for lung AC patients, illustrating the potential of in silico drug screening.

Fenofibrate increases radiosensitivity in head and neck squamous cell carcinoma via inducing G2/M arrest and apoptosis

Radiation therapy is an important treatment for head and neck squamous cell carcinoma (HNSCC). However, how to promote radiation sensitivity in HNSCC remains a challenge. This study aimed to investigate the radiosensitizing effects of fenofibrate on HNSCC and explore the underlying mechanisms. HNSCC cell lines CNE-2 and KB were subjected to ionizing radiation (IR), in the presence or absence of fenofibrate treatment. Cell growth and survival, apoptosis and cell cycle were evaluated. In addition, CNE-2 cells were xenografted into nude mice and subjected to IR and/ or fenofibrate treatment. The expression of cyclinB and CDK1 was detected by Western blotting. Our results showed that fenofibrate efficiently radiosensitized HNSCC cells and xenografts in mice, and induced apoptosis and G2/M arrest via reducing the activity of the CDK1/cyclinB1 kinase complex. These data suggest that fenofibrate could be a promising radiosensitizer for HNSCC radiotherapy.

Enhancement of radiosensitivity in human esophageal carcinoma cells by fenofibrate and its potential mechanism

AIMS AND BACKGROUND

Fenofibrate is a specific agonist of PPARα, and is characterized by relatively low systemic toxicity. Recent studies have revealed that fenofibrate suppresses the growth of several cancer lines in vitro, but the exact relation between fenofibrate and irradiation has not been explored. The purpose of this study was to investigate the radiosensitivity enhancement effects of fenofibrate combined with radiation on the human esophageal carcinoma cell lines Eca-109 and TE1, and the potential mechanism underlying these effects.

METHODS AND STUDY DESIGN

The Eca-109 and TE1 cell lines were tested by the CCK-8 assay for cell proliferation. The multitarget click model was used to delineate the survival curve and radiosensitivity was determined after cells were treated with fenofibrate and/or x-ray radiation. Flow cytometry was used to examine the effect of fenofibrate and radiation on the cell cycle. The expression of vascular endothelial growth factor (VEGF) protein was detected by Western blot analysis.

RESULTS

When given alone, fenofibrate had a time- and concentration-dependent cytotoxic effect on cells. The dose-enhancement ratio for combined fenofibrate and radiation increased markedly compared with fenofibrate alone. Further, the ratio of cells in the G2/M phase after fenofibrate and radiation was higher than that after fenofibrate or irradiation alone. The expression of VEGF protein was suppressed after treatment with fenofibrate alone or fenofibrate plus radiation.

CONCLUSIONS

Fenofibrate can enhance the radiosensitivity of human esophageal carcinoma cells by increasing G2/M phase arrest. Modulation of VEGF expression could contribute in vivo to a favorable interaction.

FOXO3a mediates the cytotoxic effects of cisplatin in lung cancer cells

Cisplatin is one of the major chemotherapeutic agents used against different human cancers. A better understanding of the downstream cellular targets of cisplatin will provide information on its mechanism of action. FOXO3a is a member of the FOXO transcription factor family, which modulates the expression of genes involved in cell cycle arrest, apoptosis, and other cellular processes. In this study, we have investigated the effects of cisplatin in a panel of lung cancer cell lines. The results showed that cisplatin inhibited the proliferation of these lung cancer cell lines by inhibiting the PI3K/AKT pathway, with evidence of decreasing phosphorylation of PI3K and AKT under cisplatin treatment, and constitutively activating AKT1 could reduce cisplatin-induced cell apoptosis. More importantly, cisplatin significantly inhibited FOXO3a phosphorylation (at Thr32, AKT phosphorylation site) and induced FOXO3a nuclear accumulation, which in turn increased the expression of FOXO3a-dependent apoptotic protein Bim. Knockdown of FOXO3a expression using small interfering RNA attenuated cisplatin-induced apoptosis. Furthermore, activation of FOXO3a induced cell apoptosis irrespective of p53 status, whereas p53 may act as FOXO3a downstream molecules involved in cisplatin-induced cell apoptosis. Together, our findings suggested that FOXO3a is a relevant mediator of the cytotoxic effects of cisplatin in lung cancer cells.

Fenofibrate subcellular distribution as a rationale for the intracranial delivery through biodegradable carrier

Fenofibrate, a well-known normolipidemic drug, has been shown to exert strong anticancer effects against tumors of neuroectodermal origin including glioblastoma. Although some pharmacokinetic studies were performed in the past, data are still needed about the detailed subcellular and tissue distribution of fenofibrate (FF) and its active metabolite, fenofibric acid (FA), especially in respect to the treatment of intracranial tumors. We used high performance liquid chromatography (HPLC) to elucidate the intracellular, tissue and body fluid distribution of FF and FA after oral administration of the drug to mice bearing intracranial glioblastoma. Following the treatment, FF was quickly cleaved to FA by blood esterases and FA was detected in the blood, urine, liver, kidney, spleen and lungs. We have also detected small amounts of FA in the brains of two out of six mice, but not in the brain tumor tissue. The lack of FF and FA in the intracranial tumors prompted us to develop a new method for intracranial delivery of FF. We have prepared and tested in vitro biodegradable poly-lactic-co-glycolic acid (PLGA) polymer wafers containing FF, which could ultimately be inserted into the brain cavity following resection of the brain tumor. HPLC-based analysis demonstrated a slow and constant diffusion of FF from the wafer, and the released FF abolished clonogenic growth of glioblastoma cells. On the intracellular level, FF and FA were both present in the cytosolic fraction. Surprisingly, we also detected FF, but not FA in the cell membrane fraction. Electron paramagnetic resonance spectroscopy applied to spin-labeled phospholipid model-membranes revealed broadening of lipid phase transitions and decrease of membrane polarity induced by fenofibrate. Our results indicate that the membrane-bound FF could contribute to its exceptional anticancer potential in comparison to other lipid-lowering drugs, and advocate for intracranial delivery of FF in the combined pharmacotherapy against glioblastoma.

Fenofibrate in cancer: mechanisms involved in anticancer activity

Objective: To review the mechanisms of anti-cancer activity of fenofibrate (FF) and other Peroxisome Proliferator Activator Receptor α (PPARα) agonists based on evidences reported in the published literature.Methods: We extensively reviewed the literature concerning FF as an off target anti-cancer drug. Controversies regarding conflicting findings were also addressed.Results: The main mechanism involved in anti-cancer activity is anti-angiogenesis through down-regulation of  Vascular Endothelial Growth Factor (VEGF), Vascular Endothelial Growth Factor Receptor (VEGFR) and Hypoxia Inducible factor-1 α (HIF-1α), inhibition of endothelial cell migration, up-regulation of endostatin and thrombospondin-1, but there are many other contributing mechanisms like apoptosis and cell cycle arrest, down-regulation of Nuclear Factor Kappa B (NF-kB) and Protein kinase B (Akt) and decrease of cellular energy by impairing mitochondrial function. Growth impairment is related to down-regulation of Phospho-Inositol 3 Kinase (PI3K)/Akt axis and down-regulation of the p38 map kinase (MAPK) cascade. A possible role should be assigned to FF stimulated over-expression of Tribbles Homolog-3 (TRIB3) which inhibits Akt phosphorylation. Important anti-cancer and anti-metastatic activities are due to down-regulation of MCP-1 (monocyte chemotactic protein-1), decreased Metalloprotease-9 (MMP-9) production, weak down-regulation of adhesion molecules like E selectin, intercellular adhesion molecules (ICAM) and Vascular Endothelial Adhesion Molecules (VCAM), and decreased secretion of chemokines like Interleukin-6 (IL-6), and down-regulation of cyclin D-1. There is no direct link between FF activity in lipid metabolism and anticancer activity, except for the fact that many anticancer actions are dependent from PPARα agonism. FF exhibits also PPARα independent anti-cancer activities.Conclusions: There are strong evidences indicating that FF can disrupt growth-related activities in many different cancers, due to anti-angiogenesis and anti-inflammatory effects. Therefore FF may be useful as a complementary adjunct treatment of cancer, particularly included in anti-angiogenic protocols like those currently increasingly used in glioblastoma. There are sound reasons to initiate well planned phase II clinical trials for FF as a complementary adjunct treatment of cancer.

Anti-tumoral effects of miR-3189-3p in glioblastoma

Glioblastoma is one of the most aggressive brain tumors. We have previously found up-regulation of growth differentiation factor 15 (GDF15) in glioblastoma cells treated with the anticancer agent fenofibrate. Sequence analysis of GDF15 revealed the presence of a microRNA, miR-3189, in the single intron. We then asked whether miR-3189 was expressed in clinical samples and whether it was functional in glioblastoma cells. We found that expression of miR-3189-3p was down-regulated in astrocytoma and glioblastoma clinical samples compared with control brain tissue. In vitro, the functionality of miR-3189-3p was tested by RNA-binding protein immunoprecipitation, and miR-3189-3p coimmunoprecipitated with Argonaute 2 together with two of its major predicted gene targets, the SF3B2 splicing factor and the guanine nucleotide exchange factor p63RhoGEF. Overexpression of miR-3189-3p resulted in a significant inhibition of cell proliferation and migration through direct targeting of SF3B2 and p63RhoGEF, respectively. Interestingly, miR-3189-3p levels were increased by treatment of glioblastoma cells with fenofibrate, a lipid-lowering drug with multiple anticancer activities. The attenuated expression of miR-3189-3p in clinical samples paralleled the elevated expression of SF3B2, which could contribute to the activation of SF3B2 growth-promoting pathways in these tumors. Finally, miR-3189-3p-mediated inhibition of tumor growth in vivo further supported the function of this microRNA as a tumor suppressor.

FoxO proteins' nuclear retention and BH3-only protein Bim induction evoke mitochondrial dysfunction-mediated apoptosis in berberine-treated HepG2 cells

Mammalian forkhead-box family members belonging to the 'O' category (FoxO) manipulate a plethora of genes modulating a wide array of cellular functions including cell cycle regulation, apoptosis, DNA damage repair, and energy metabolism. FoxO overexpression and nuclear accumulation have been reported to show correlation with hindered tumor growth in vitro and size in vivo, while FoxO's downregulation via phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway has been linked with tumor promotion. In this study, we have explored for the first time intervention of berberine, a plant-derived isoquinoline alkaloid, with FoxO family proteins in hepatoma cells. We observed that berberine significantly upregulated the mRNA expression of both FoxO1 and FoxO3a. Their phosphorylation-mediated cytoplasmic sequestration followed by degradation was prevented by berberine-induced downmodulation of the PI3K/Akt/mTOR pathway which promoted FoxO nuclear retention. PTEN, a tumor suppressor gene and negative regulator of the PI3K/Akt axis, was upregulated while phosphorylation of its Ser380 residue (possible mechanism of PTEN degradation) was significantly decreased in treated HepG2 cells. Exposure to berberine induced a significant increase in transcriptional activity of FoxO, as shown by GFP reporter assay. FoxO transcription factors effectively heightened BH3-only protein Bim expression, which in turn, being a direct activator of proapoptotic protein Bax, altered Bax/Bcl-2 ratio, culminating into mitochondrial dysfunction, caspases activation, and DNA fragmentation. The pivotal role of Bim in berberine-mediated cytotoxicity was further corroborated by knockdown experiments where Bim-silencing partially restored HepG2 cell viability during berberine exposure. In addition, a correlation between oxidative overload and FoxO's nuclear accumulation via JNK activation was evident as berberine treatment led to a pronounced increase in JNK phosphorylation together with enhanced ROS generation, lipid peroxidation, decreased activities of superoxide dismutase and catalase, and diminished glutathione levels. Thus, our findings suggest that the antiproliferative effect of berberine may in part be due to mitochondria-mediated apoptosis with Bim acting as a pivotal downstream factor of FoxO-induced transcriptional activation.

Molecular mechanisms of fenofibrate-induced metabolic catastrophe and glioblastoma cell death

Fenofibrate (FF) is a common lipid-lowering drug and a potent agonist of the peroxisome proliferator-activated receptor alpha (PPARα). FF and several other agonists of PPARα have interesting anticancer properties, and our recent studies demonstrate that FF is very effective against tumor cells of neuroectodermal origin. In spite of these promising anticancer effects, the molecular mechanism(s) of FF-induced tumor cell toxicity remains to be elucidated. Here we report a novel PPARα-independent mechanism explaining FF's cytotoxicity in vitro and in an intracranial mouse model of glioblastoma. The mechanism involves accumulation of FF in the mitochondrial fraction, followed by immediate impairment of mitochondrial respiration at the level of complex I of the electron transport chain. This mitochondrial action sensitizes tested glioblastoma cells to the PPARα-dependent metabolic switch from glycolysis to fatty acid β-oxidation. As a consequence, prolonged exposure to FF depletes intracellular ATP, activates the AMP-activated protein kinase-mammalian target of rapamycin-autophagy pathway, and results in extensive tumor cell death. Interestingly, autophagy activators attenuate and autophagy inhibitors enhance FF-induced glioblastoma cytotoxicity. Our results explain the molecular basis of FF-induced glioblastoma cytotoxicity and reveal a new supplemental therapeutic approach in which intracranial infusion of FF could selectively trigger metabolic catastrophe in glioblastoma cells.

Fenofibrate induces apoptosis of triple-negative breast cancer cells via activation of NF-κB pathway

Background

There are a lot of unmet needs in patients with triple-negative breast cancer (TNBC). Fenofibrate, a peroxisome proliferator-activated receptor alpha (PPAR-α) agonist, has been used for decades to treat hypertriglyceridaemia and mixed dyslipidaemia. Recent studies show that it might have anti-tumor effects, however, the mechanism remains unclear. Here, we assessed the ability of fenofibrate to induce apoptosis of TNBC in vitro and in vivo and explored involved mechanisms.

Methods

MTT method was used to evaluate the anti-proliferation effect of fenofibrate, and invert microscope to observe the apoptotic morphological changes. The percentage of apoptotic cells and distribution ratios of cell cycle were determined by flow cytometric analysis. The related protein levels were measured by Western blot method. The changes of genes and pathways were detected by gene expression profiling. The tumor growth in vivo was assessed by MDA-MB-231 xenograft mouse model. Terminal deoxytransferase-catalyzed DNA nick-end labeling (TUNEL) assay was employed to estimate the percentage of apoptotic cells in vivo. In order to evaluate the safety of fenofibrate, blood sampled from rat eyes was detected.

Results

We found that fenofibrate had anti-proliferation effects on breast cancer cell lines, of which the first five most sensitive ones were all TNBC cell lines. Its induction of apoptosis was independent on PPAR-α status with the highest apoptosis percentage of 41.8 ± 8.8%, and it occurred in a time- and dose-dependent manner accompanied by up-regulation of Bad, down-regulation of Bcl-xl, Survivin and activation of caspase-3. Interestingly, activation of NF-κB pathway played an important role in the induction of apoptosis by fenofibtate and the effect could be almost totally blocked by a NF-κB specific inhibitor, pyrrolidine dithiocarbamate (PDTC). In addition, fenofibrate led to cell cycle arrest at G0/G1 phase accompanied by down-regulation of Cyclin D1, Cdk4 and up-regulation of p21, p27/Kip1. In vivo, fenofibrate slowed down tumor growth and induced apoptosis with a good safety profile in the MDA-MB-231 xengograft mouse model.

Conclusions

It is concluded that fenofibrate induces apoptosis of TNBC via activation of NF-κB pathway in a PPAR-α independent way, and may serve as a novel therapeutic drug for TNBC therapy.

Characterization of fenofibrate-mediated anti-proliferative pro-apoptotic effects on high-grade gliomas and anti-invasive effects on glioma stem cells

Glioblastoma is the most common, and at the same time, most aggressive type of high-grade glioma (HGG). The prognosis of glioblastoma patients treated with standard therapy including surgery, temozolomide and radiation therapy remains poor. Peroxisome proliferator-activated receptor-α (PPARα) agonists are in widespread clinical use for the treatment of hyperlipidemia. Recent evidence has suggested a potential role in various cancers including glioblastoma. In this study, we characterized the effects of PPARα agonist, fenofibrate, directly on HGG cells and glioma stem cells (GSC). Fenofibrate exhibited dose-dependent p53-independent anti-proliferative effects on HGG starting at 25 μM and pro-apoptotic effects starting at 50 μM, suggesting that the anti-proliferative actions are present only at 25 μM. PPARα was expressed in all HGG cell lines. Inhibition of PPARα with specific inhibitor GW6471 did not affect either proliferation or apoptosis suggesting that these are PPARα-independent effects. Fenofibrate treatment of HGG cells robustly diminished the expression of key signaling pathways, including NF-κB and cyclin D1. Phosphorylation of Akt was also diminished, with no change in total Akt. Effects on apoptotic signaling molecules, Bax and Bcl-xL, had a trend towards pro-apoptotic effects. With respect to GSC, fenofibrate treatment at 25 μM significantly decreased invasion in association with a decrease in CD133 and Oct4 expression. Overall, results support consideration of fenofibrate as an anti-glioma agent and establish its potential as an adjunct treatment strategy for HGG. Translation to the clinical setting could be rapid given its current use as a clinical agent and its low toxicity profile.

Fenofibrate suppresses melanogenesis in B16-F10 melanoma cells via activation of the p38 mitogen-activated protein kinase pathway

Fenofibrate and ciglitazone belong to the classes of fibrates and thiazolidinediones, respectively. Their pharmacological actions on peroxisome proliferator-activated receptors (PPARs) present a potential therapy for hyperlipidemia and hyperglycemia. However, the melanogenesis affected by PPAR ligands in melanocytes has not been well investigated. By determining the melanin content of cells treated with PPAR agonists, we showed that fenofibrate significantly reduced melanin synthesis, but its major active metabolite, fenofibric acid, did not. Notably, the suppression of melanogenesis by fenofibrate could not be prevented by the PPARα specific antagonist GW6471. In addition, T0901317, a liver X receptor (LXR) agonist, restored the antimelanogenic activity of fenofibrate. Accordingly, fenofibrate may suppress melanogenesis through a PPARα-independent pathway. Treatment of cells with fenofibrate led to the down-regulated gene expression of melanocortin 1 receptor (MC1R). Fenofibrate also attenuated the dihydroxyphenylalanine (DOPA)-staining activity and expression of tyrosinase as well as the expression of microphthalmia-associated transcription factor (MITF). The phosphorylation of p38 mitogen-activated protein kinase (MAPK) was stimulated by fenofibrate. Furthermore, the p38 MAPK inhibitor SB203580 prevented the repressive effects of fenofibrate on the melanin production. Taken together, the results of the present study suggest that fenofibrate inhibits melanin synthesis via the down-regulation of MC1R, the up-regulation of p38 MAPK, and interference with LXR signaling pathways to decrease the expression of tyrosinase in B16-F10 melanoma cells.

Wnt/β-catenin signaling protects mouse liver against oxidative stress-induced apoptosis through the inhibition of forkhead transcription factor FoxO3

Numerous liver diseases are associated with extensive oxidative tissue damage. It is well established that Wnt/β-catenin signaling directs multiple hepatocellular processes, including development, proliferation, regeneration, nutrient homeostasis, and carcinogenesis. It remains unexplored whether Wnt/β-catenin signaling provides hepatocyte protection against hepatotoxin-induced apoptosis. Conditional, liver-specific β-catenin knockdown (KD) mice and their wild-type littermates were challenged by feeding with a hepatotoxin 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet to induce chronic oxidative liver injury. Following the DDC diet, mice with β-catenin-deficient hepatocytes demonstrate increased liver injury, indicating an important role of β-catenin signaling for liver protection against oxidative stress. This finding was further confirmed in AML12 hepatocytes with β-catenin signaling manipulation in vitro using paraquat, a known oxidative stress inducer. Immunofluorescence staining revealed an intense nuclear FoxO3 staining in β-catenin-deficient livers, suggesting active FoxO3 signaling in response to DDC-induced liver injury when compared with wild-type controls. Consistently, FoxO3 target genes p27 and Bim were significantly induced in β-catenin KD livers. Conversely, SGK1, a β-catenin target gene, was significantly impaired in β-catenin KD hepatocytes that failed to inactivate FoxO3. Furthermore, shRNA-mediated deletion of FoxO3 increased hepatocyte resistance to oxidative stress-induced apoptosis, confirming a proapoptotic role of FoxO3 in the stressed liver. Our findings suggest that Wnt/β-catenin signaling is required for hepatocyte protection against oxidative stress-induced apoptosis. The inhibition of FoxO through its phosphorylation by β-catenin-induced SGK1 expression reduces the apoptotic function of FoxO3, resulting in increased hepatocyte survival. These findings have relevance for future therapies directed at hepatocyte protection, regeneration, and anti-cancer treatment.

Differential Effects of MicroRNAs on Glioblastoma Growth and Migration

Glioblastoma multiforme is characterized by rapid proliferation, aggressive metastatic potential, and resistance to radio- and chemotherapy. The matricellular protein CYR61 regulates cellular proliferation and migration and is highly expressed in Glioblastomas. MicroRNAs are 22-nucleotides long RNAs that regulate gene expression post-transcriptionally. Here, we utilized the LN229 glioblastoma cell line and found that CYR61 is a target of miR-136, miR-155, and miR-634. Over-expression of miR-136 and miR-634 miRNAs negatively affected proliferation, but not migration, while expression of miR-155 reduced migration but did not affect the proliferation of LN229 cells. Investigation of the molecular mechanisms affected by expression of miR-634 revealed an increased phosphorylation of p70S6 kinase, suggesting an induction of the mammalian target of rapamycin (mTOR) complex 1 pathway. Additionally, in miR-634 overexpressing cells, TSC2, a negative regulator of mTOR signaling, was found to be decreased. Altogether, our study provides insights on the differential roles of miRs-136, -155, and -634 in regulating glioblastoma cell growth and migration, and how microRNAs could be manipulated to decrease the aggressiveness and metastatic potential of tumor cells.