In vitro and in vivo effects of the PPAR-alpha agonists fenofibrate and retinoic acid in endometrial cancer

Low expression of fatty acid oxidation related gene ACADM indicates poor prognosis of renal clear cell carcinoma and is related to tumor immune infiltration

This research aims to identify the key fatty acid beta-oxidation (FAO) genes that are altered in kidney renal clear cell carcinoma (KIRC) and to analyze the role of these genes in KIRC. The Gene Expression Omnibus (GEO) and FAO datasets were used to identify these key genes. Wilcoxon rank sum test was used to assess the levels of acyl-CoA dehydrogenase medium chain (ACADM) between KIRC and non-cancer samples. The logistic regression and Wilcoxon rank sum test were used to explore the association between ACADM and clinical features. The diagnostic performance of ACADM for KIRC was assessed using a diagnostic receiver operating characteristic (ROC) curve. The co-expressed genes of ACADM were identified in LinkedOmics database, and their function and pathway enrichment were analyzed. The correlation between ACADM expression level and immune infiltration was analyzed by Gene Set Variation Analysis (GSVA) method. Additionally, the proliferation, migration, and invasion abilities of KIRC cells were assessed after overexpressing ACADM. Following differential analysis and intersection, we identified six hub genes, including ACADM. We found that the expression level of ACADM was decreased in KIRC tissues and had a better diagnostic effect (AUC = 0.916). Survival analysis suggested that patients with decreased ACADM expression had a worse prognosis. According to correlation analysis, a variety of clinical features were associated with the expression level of ACADM. By analyzing the infiltration level of immune cells, we found that ACADM may be related to the enrichment of immune cells. Finally, ACADM overexpression inhibited proliferation, migration, and invasion of KIRC cells. In conclusion, our findings suggest that reduced ACADM expression in KIRC patients is indicative of poor prognosis. These results imply that ACADM may be a diagnostic and prognostic marker for individuals with KIRC, offering a reference for clinicians in diagnosis and treatment.

Lipid-lowering drugs and cancer: an updated perspective

Statins and non-statin medications used for the management of dyslipidemia have been shown to possess antitumor properties. Since the use of these drugs has steadily increased over the past decades, more knowledge is required about their relationship with cancer. Lipid-lowering agents are heterogeneous compounds; therefore, it remains to be revealed whether anticancer potential is a class effect or related to them all. Here, we reviewed the literature on the influence of lipid-lowering medications on various types of cancer during development or metastasis. We also elaborated on the underlying mechanisms associated with the anticancer effects of antihyperlipidemic agents by linking the reported in vivo and in vitro studies.

Identification of a Difluorinated Alkoxy Sulfonyl Chloride as a Novel Antitumor Agent for Hepatocellular Carcinoma through Activating Fumarate Hydratase Activity

Fenofibrate is known as a lipid-lowering drug. Although previous studies have reported that fenofibrate exhibits potential antitumor activities, IC50 values of fenofibrate could be as high as 200 μM. Therefore, we investigated the antitumor activities of six synthesized fenofibrate derivatives. We discovered that one compound, SIOC-XJC-SF02, showed significant antiproliferative activity on human hepatocellular carcinoma (HCC) HCCLM3 cells and HepG2 cells (the IC50 values were 4.011 μM and 10.908 μM, respectively). We also found this compound could inhibit the migration of human HCC cells. Transmission electron microscope and flow cytometry assays demonstrated that this compound could induce apoptosis of human HCC cells. The potential binding sites of this compound acting on human HCC cells were identified by mass spectrometry-cellular thermal shift assay (MS-CETSA). Molecular docking, Western blot, and enzyme activity assay-validated binding sites in human HCC cells. The results showed that fumarate hydratase may be a potential binding site of this compound, exerting antitumor effects. A xenograft model in nude mice demonstrated the anti-liver cancer activity and the mechanism of action of this compound. These findings indicated that the antitumor effect of this compound may act via activating fumarate hydratase, and this compound may be a promising antitumor candidate for further investigation.

The Role of Peroxisome Proliferator-Activated Receptors in Endometrial Cancer

Endometrial carcinoma is the most common malignant tumor of the female genital tract in the United States. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptor proteins which regulate gene expression. In order to investigate the role of PPARs in endometrial cancer, we conducted a literature review using the MEDLINE and LIVIVO databases and were able to identify 27 relevant studies published between 2000 and 2023. The PPARα and PPARβ/δ isoforms seemed to be upregulated, whereas PPARγ levels were reported to be significantly lower in endometrial cancer cells. Interestingly, PPAR agonists were found to represent potent anti-cancer therapeutic alternatives. In conclusion, PPARs seem to play a significant role in endometrial cancer.

The role of peroxisome proliferator-activated receptors in the tumor microenvironment, tumor cell metabolism, and anticancer therapy

Peroxisome proliferator-activated receptors (PPARs) have been extensively studied for over 3 decades and consist of three isotypes, including PPARα, γ, and β/δ, that were originally considered key metabolic regulators controlling energy homeostasis in the body. Cancer has become a leading cause of human mortality worldwide, and the role of peroxisome proliferator-activated receptors in cancer is increasingly being investigated, especially the deep molecular mechanisms and effective cancer therapies. Peroxisome proliferator-activated receptors are an important class of lipid sensors and are involved in the regulation of multiple metabolic pathways and cell fate. They can regulate cancer progression in different tissues by activating endogenous or synthetic compounds. This review emphasizes the significance and knowledge of peroxisome proliferator-activated receptors in the tumor microenvironment, tumor cell metabolism, and anti-cancer treatment by summarizing recent research on peroxisome proliferator-activated receptors. In general, peroxisome proliferator-activated receptors either promote or suppress cancer in different types of tumor microenvironments. The emergence of this difference depends on various factors, including peroxisome proliferator-activated receptor type, cancer type, and tumor stage. Simultaneously, the effect of anti-cancer therapy based on drug-targeted PPARs differs or even opposes among the three peroxisome proliferator-activated receptor homotypes and different cancer types. Therefore, the current status and challenges of the use of peroxisome proliferator-activated receptors agonists and antagonists in cancer treatment are further explored in this review.

Health effects associated with phthalate activity on nuclear receptors

Phthalates are endocrine disruptors, widely used as plasticizers to impart flexibility in plastics, and as solvents in personal care products. Due to their nearly ubiquitous use in consumer products, most humans are exposed to phthalates daily. There has been extensive research on the reproductive health effects associated with phthalate exposure, but less attention has been paid to other actions. This review aims to summarize the known action of phthalates on different nuclear receptors. Some phthalates bind to and activate the estrogen receptor, making them weakly estrogenic. However, other phthalates antagonize androgen receptors. Some high molecular weight phthalates antagonize thyroid receptors, affecting metabolism. Several phthalates activate and interfere with the normal function of different peroxisome proliferator-activated receptors (PPARs), receptors that have critical roles in lipid metabolism and energy homeostasis. Some phthalates activate the aryl hydrocarbon receptor, which is critical for xenobiotic metabolism. Although phthalates have a short half-life in vivo, because people are continuously exposed, studies should examine the health effects of phthalates associated with long-term exposure. There is limited research on the effects of phthalates on health outcomes aside from reproductive function, particularly concerning are childhood adiposity, behavior, and learning. There is also limited information on actions of phthalates not mediated via nuclear receptors. Humans are exposed to multiple chemicals simultaneously, and how chemical mixtures act on nuclear receptor activity needs study. Although we know a great deal about phthalates, there is still much that remains uncertain. Future studies need to further examine their other potential health effects.

Peroxisome Proliferator-Activated Receptors and the Hallmarks of Cancer

Peroxisome proliferator-activated receptors (PPARs) function as nuclear transcription factors upon the binding of physiological or pharmacological ligands and heterodimerization with retinoic X receptors. Physiological ligands include fatty acids and fatty-acid-derived compounds with low specificity for the different PPAR subtypes (alpha, beta/delta, and gamma). For each of the PPAR subtypes, specific pharmacological agonists and antagonists, as well as pan-agonists, are available. In agreement with their natural ligands, PPARs are mainly focused on as targets for the treatment of metabolic syndrome and its associated complications. Nevertheless, many publications are available that implicate PPARs in malignancies. In several instances, they are controversial for very similar models. Thus, to better predict the potential use of PPAR modulators for personalized medicine in therapies against malignancies, it seems necessary and timely to review the three PPARs in relation to the didactic concept of cancer hallmark capabilities. We previously described the functions of PPAR beta/delta with respect to the cancer hallmarks and reviewed the implications of all PPARs in angiogenesis. Thus, the current review updates our knowledge on PPAR beta and the hallmarks of cancer and extends the concept to PPAR alpha and PPAR gamma.

Identification of the shared gene signatures and pathways between polycystic ovary syndrome and endometrial cancer: An omics data based combined approach

Objective

Polycystic ovary syndrome (PCOS) is a common endocrine disorder with high incidence. Recently it has been implicated as a significant risk factor for endometrial cancer (EC). Our study aims to detect shared gene signatures and biological mechanism between PCOS and EC by bioinformatics analysis.

Methods

Bioinformatics analysis based on GEO database consisted of data integration, network construction and functional enrichment analysis was applied. In addition, the pharmacological methodology and molecular docking was also performed.

Results

Totally 10 hub common genes, MRPL16, MRPL22, MRPS11, RPL26L1, ESR1, JUN, UBE2I, MRPL17, RPL37A, GTF2H3, were considered as shared gene signatures for EC and PCOS. The GO and KEGG pathway analysis of these hub genes showed that “mitochondrial translational elongation”, “ribosomal subunit”, “structural constituent of ribosome” and “ribosome” were highly correlated. Besides, associated transcription factors (TFs) and miRNAs network were constructed. We identified candidate drug molecules including fenofibrate, cinnarizine, propanil, fenthion, clindamycin, chloramphenicol, demeclocycline, hydrochloride, azacitidine, chrysene and artenimol according to these hub genes. Molecular docking analysis verified a good binding interaction of fenofibrate against available targets (JUN, ESR1, UBE2I).

Conclusion

Gene signatures and regulatory biological pathways were identified through bioinformatics analysis. Moreover, the molecular mechanisms of these signatures were explored and potential drug molecules associated with PCOS and EC were screened out.

When Activator and Inhibitor of PPARα Do the Same: Consequence for Differentiation of Human Intestinal Cells

Peroxisome proliferator-activated receptor α (PPARα) is a ligand-dependent transcription factor that plays a role in various processes including differentiation of several cell types. We investigated the role of PPARα in the differentiation of intestinal cells using HT-29 and Caco2 cell lines as a model as well as human normal colon and colorectal carcinoma tissues. We detected a significant increase in PPARα expression in differentiated HT-29 cells as well as in normal surface colon epithelium where differentiated cells are localised. Thus, it seems that PPARα may play a role in differentiation of intestinal cells. Interestingly, we found that both PPARα activators (fenofibrate and WY-14643) as well as its inhibitor (GW6471) regulated proliferation and differentiation of HT-29 cells in vitro in the same way. Both compounds led to a decrease in proliferation accompanied by a significant increase in expression of villin, intestinal alkaline phosphatase (differentiation markers). Moreover, the same trend in villin expression was observed in Caco2 cells. Furthermore, villin expression was independent of subcellular localisation of PPARα. In addition, we found similar levels of PPARα expression in colorectal carcinomas in comparison to adjacent normal epithelium. All these findings support the hypothesis that differentiation of intestinal epithelium is PPARα-independent.

Cholesterol Metabolic Reprogramming in Cancer and Its Pharmacological Modulation as Therapeutic Strategy

Cholesterol is a ubiquitous sterol with many biological functions, which are crucial for proper cellular signaling and physiology. Indeed, cholesterol is essential in maintaining membrane physical properties, while its metabolism is involved in bile acid production and steroid hormone biosynthesis. Additionally, isoprenoids metabolites of the mevalonate pathway support protein-prenylation and dolichol, ubiquinone and the heme a biosynthesis. Cancer cells rely on cholesterol to satisfy their increased nutrient demands and to support their uncontrolled growth, thus promoting tumor development and progression. Indeed, transformed cells reprogram cholesterol metabolism either by increasing its uptake and de novo biosynthesis, or deregulating the efflux. Alternatively, tumor can efficiently accumulate cholesterol into lipid droplets and deeply modify the activity of key cholesterol homeostasis regulators. In light of these considerations, altered pathways of cholesterol metabolism might represent intriguing pharmacological targets for the development of exploitable strategies in the context of cancer therapy. Thus, this work aims to discuss the emerging evidence of in vitro and in vivo studies, as well as clinical trials, on the role of cholesterol pathways in the treatment of cancer, starting from already available cholesterol-lowering drugs (statins or fibrates), and moving towards novel potential pharmacological inhibitors or selective target modulators.

Roles of peroxisome proliferator-activated receptor α in the pathogenesis of ethanol-induced liver disease

Alcoholic liver disease (ALD) is a progressively aggravated liver disease with high incidence in alcoholics. Ethanol-induced fat accumulation and the subsequent lipopolysaccharide (LPS)-driven inflammation bring liver from reversible steatosis, to irreversible hepatitis, fibrosis, cirrhosis, and even hepatocellular carcinoma. Peroxisome proliferator-activated receptor α (PPARα) is a member of the nuclear receptor superfamily of ligand-activated transcription factors and plays pivotal roles in the regulation of fatty acid homeostasis as well as the inflammation control in the liver. It has been well documented that PPARα activity and/or expression are downregulated in liver of mice exposed to ethanol, which is thought to be one of the prime contributors to ethanol-induced steatosis, hepatitis and fibrosis. This article summarizes the current evidences from in vitro and animal models for the critical roles of PPARα in the onset and progression of ALD. Importantly, it should be noted that the expression of PPARα in human liver is reported to be similar to that in mice, and PPARα expression is downregulated in the liver of patients with nonalcoholic fatty liver disease (NAFLD), a disease sharing many similarities with ALD. Therefore, clinical trials investigating the expression of PPARα in the liver of ALD patients and the efficacy of strong PPARα agonists for the prevention and treatment of ALD are warranted.

Keratocytes promote corneal neovascularization through VEGFr3 induced by PPARα-inhibition

As the peroxisome proliferator - activated receptor alpha (PPARα) agonist, fenofibrate has been widely used to be a good lipid-regulating drug in the clinical application. In this study, we investigated the mechanism by which keratocytes inhibit the corneal neovascularization (CNV) through PPARα - activation. To do this, the CNV model was established by alkali burn, followed by being divided into three groups including control, fenofibrate and vehicle group. The expression of VEGFr3, MMP13 and PPARα in corneas of normal mouse and alkali-burned mouse was determined via quantitative RT- PCR (qRT-PCR) and Western blot analysis (WB). The CNV area was observed under a slit lamp microscope. The location of PPARα expression in the corneas was determined via immunohistochemistry. In cultured primary keratocytes, the effect of fenofibrate on PPARα, VEGFr3 and MMP13 expression was determined by qRT-PCR and WB. Besides, PPARα knockout (PPARα-/-) mouse CNV and keratocytes model were established to further confirm the effect of PPARα on VEGFr3 and MMP13 expression. We found that PPARα was expressed in epithelium, stroma and endothelium of the normal cornea, however, with relatively low level in the corneal stroma. Meanwhile, its expression was decreased markedly in the cornea during the stage of CNV formation. After treatment of fenofibrate, PPARα expression was promoted and the expression of VEGFr3 and MMP13 was inhibited in both CNV mice model and primary keratocytes, and CNV areas were decreased in CNV mice model. However, the results in PPARα-/- CNV and keratocytes model were opposite. Our results suggest that keratocytes could promote the expression of VEGFr3 and MMP13, and CNV formation through PPARα downregulation.

Fenofibrate-induced mitochondrial dysfunction and metabolic reprogramming reversal: the anti-tumor effects in gastric carcinoma cells mediated by the PPAR pathway

Cancer cells reprogram their metabolism to adapt to fast growth and environmental demands, which differ them from normal cells. Mitochondria are central to the malignant metabolism reprogramming process. Here, we report that PPARα was highly expressed in gastric cancer tissues and negatively correlated with prognosis. Fenofibrate, a common drug used to treat severe hypertriglyceridemia and mixed dyslipidemia, reversed cellular metabolism and mitochondrial dysfunction in gastric cancer cells through PPARα. Our results show that fenofibrate altered glucose and lipid metabolism, inhibited gastric cancer cell proliferation, and promoted apoptosis in gastric cancer cells. We further show that fenofibrate induced mitochondrial reprogramming via CPT1 and the fatty acid oxidation pathway, as well as by activating the AMPK pathway and inhibiting the HK2 pathway. Additionally, fenofibrate inhibited subcutaneous gastric cancer cell tumor growth without obvious toxicity in mice. Collectively, our results indicate that fenofibrate exhibits anti-tumor activity in vitro and in vivo via the mitochondria and metabolic reprogramming, demonstrating that mitochondrial regulation and the normalization of cancer cell metabolism are novel therapeutic strategies for cancer.

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.

Activation and Expression of Peroxisome Proliferator-Activated Receptor Alpha Are Associated with Tumorigenesis in Colorectal Carcinoma

Peroxisome proliferator-activated receptor alpha (PPAR-α) belongs to the PPAR family and plays a critical role in inhibiting cell proliferation and tumorigenesis in various tumors. However, the role of PPAR-α in colorectal tumorigenesis is unclear. In the present study, we found that fenofibrate, a PPAR-α agonist, significantly inhibited cell proliferation and induced apoptosis in colorectal carcinoma cells. In addition, PPAR-α was expressed in the nucleus of colorectal carcinoma cells, and the expression of nuclear PPAR-α increased in colorectal carcinoma tissue compared with that of normal epithelium tissue (P<0.01). The correlation between the expression of nuclear PPAR-α and clinicopathological factors was evaluated in human colorectal carcinoma tissues, and the nuclear expression of PPAR-α was significantly higher in well-to-moderately differentiated adenocarcinoma than in mucinous adenocarcinoma (P<0.05). These findings indicate that activation of PPAR-α may be involved in anticancer effects in colorectal carcinomas, and nuclear expression of PPAR-α may be a therapeutic target for colorectal adenocarcinoma treatment.

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.

Fenofibrate potentiates chemosensitivity to human breast cancer cells by modulating apoptosis via AKT/NF-κB pathway

Background

Cumulatively, evidences revealed that fenofibrate used in the therapy of hyperlipidemia and hypercholesterolemia has anti-cancer effect in multiple cancer types. However, its function and underlying mechanism of chemosensitization in breast cancer remain poorly understood.

Materials and methods

The cytotoxicity of fenofibrate and anti-cancer drugs in breast cancer cells was determined by MTT. Apoptosis and mitochondrial membrane potential were measured using flow cytometry. Caspases and PARP cleavage, the Bcl-2 family members’ protein expression, as well as the activation of AKT and NF-κB signaling pathways were evaluated using Western blot assay. Real-time PCR was used to determine the mRNA expression of Bcl-2 family members.

Results

Our data indicated that fenofibrate suppressed SKBR3 and MDA-MB-231 cell growth in a dose-dependent manner, in the same way as paclitaxel, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), ABT-737, and doxorubicin. Subtoxic levels of fenofibrate significantly augmented paclitaxel, TRAIL, ABT-737, and doxorubicin-induced apoptosis in both these two cell lines. Fenofibrate-promoted chemosensitivity is predominantly mediated by caspase-9 and caspase-3 activation and mitochondrial outer membrane permeabilization. Meanwhile, chemosensitivity promoted by fenofibrate also increased the expression of Bax and Bok and decreased the expression of Mcl-1 and Bcl-xl. Mechanistically, fenofibrate effectively reduced the phosphorylation levels of AKT and NF-κB. In addition, imiquimod, an NF-κB activator, could reverse fenofibrate-induced susceptibility to ABT-737-triggered apoptosis.

Conclusion

The present study provided the evidence of the underlying mechanisms on chemosensitization of fenofibrate by inducing the apoptosis of breast cancer in an AKT/NF-κB-dependent manner and implicated the potential application of fenofibrate in potentiating chemosensitivity in breast cancer therapy.

Fenofibrate Augments the Sensitivity of Drug-Resistant Prostate Cancer Cells to Docetaxel

Metronomic agents reduce the effective doses and adverse effects of cytostatics in cancer chemotherapy. Therefore, they can enhance the treatment efficiency of drug-resistant cancers. Cytostatic and anti-angiogenic effects of fenofibrate (FF) suggest that it can be used for the metronomic chemotherapy of drug-resistant prostate tumors. To estimate the effect of FF on the drug-resistance of prostate cancer cells, we compared the reactions of naïve and drug-resistant cells to the combined treatment with docetaxel (DCX)/mitoxantrone (MTX) and FF. FF sensitized drug-resistant DU145 and PC3 cells to DCX and MTX, as illustrated by their reduced viability and invasive potential observed in the presence of DCX/MTX and FF. The synergy of the cytostatic activities of both agents was accompanied by the inactivation of P-gp-dependent efflux, dysfunction of the microtubular system, and induction of polyploidy in DCX-resistant cells. Chemical inhibition of PPARα- and reactive oxygen species (ROS)-dependent pathways by GW6471 and N-acetyl-L-cysteine, respectively, had no effect on cell sensitivity to combined DCX/FF treatment. Instead, we observed the signs of adenosine triphosphate (ATP) deficit and autophagy in DCX/FF-treated drug-resistant cells. Furthermore, the cells that had been permanently propagated under DCX- and DCX/FF-induced stress did not acquire DCX/FF-resistance. Instead, relatively slow proliferation of DCX-resistant cells was efficiently inhibited by FF. Collectively, our observations show that FF reduces the effective doses of DCX by interfering with the drug resistance and energy metabolism of prostate cancer cells. Concomitantly, it impairs the chemotherapy-induced microevolution and expansion of DCX/FF-resistant cells. Therefore, FF can be applied as a metronomic agent to enhance the efficiency of palliative chemotherapy of prostate cancer.

Fenofibrate Interferes with the Diapedesis of Lung Adenocarcinoma Cells through the Interference with Cx43/EGF-Dependent Intercellular Signaling

Extravasation of circulating cancer cells is regulated by the intercellular/intracellular signaling pathways that locally impair the endothelial barrier function. Co-cultures of human umbilical vein endothelial cells (HUVECs) with lung adenocarcinoma A549 cells enabled us to identify these pathways and to quantify the effect of fenofibrate (FF) on their activity. A549 cells induced the disruption and local activation of endothelial continuum. These events were accompanied by epidermal growth factor (EGF) up-regulation in endothelial cells. Impaired A549 diapedesis and HUVEC activation were seen upon the chemical inhibition of connexin(Cx)43 functions, EGF/ERK1/2-dependent signaling, and RhoA/Rac1 activity. A total of 25 μM FF exerted corresponding effects on Cx43-mediated gap junctional coupling, EGF production, and ERK1/2 activation in HUVEC/A549 co-cultures. It also directly augmented endothelial barrier function via the interference with focal adhesion kinase (FAK)/RhoA/Rac1-regulated endothelial cell adhesion/contractility/motility and prompted the selective transmigration of epithelioid A549 cells. N-acetyl-L-cysteine abrogated FF effects on HUVEC activation, suggesting the involvement of PPARα-independent mechanism(s) in its action. Our data identify a novel Cx43/EGF/ERK1/2/FAK/RhoA/Rac1-dependent signaling axis, which determines the efficiency of lung cancer cell diapedesis. FF interferes with its activity and reduces the susceptibility of endothelial cells to A549 stimuli. These findings provide the rationale for the implementation of FF in the therapy of malignant lung cancers.

Fenofibrate inhibits the growth of prostate cancer through regulating autophagy and endoplasmic reticulum stress

Fenofibrate is a fibric acid derivative which exhibits a role of peroxisome proliferator-activated receptor-alpha agonist. It is widely utilized in therapy of hyperlipidemia and hypercholesterolemia. Its anticancer function is discovered in recent years. However, the role of fenofibrate in prostate cancer (PCa) is poorly understood. In this study, we investigated the function and mechanism of fenofibrate in PCa cells. Firstly, fenofibrate treated PCa cells showed more apoptosis compared with the control group. Further, we found that fenofibrate induced autophagy but finally blocked its complete flux in PCa cells through regulating AMPK-mTOR pathway. The intermediate metabolite from uncompleted autophagy induced endoplasmic reticulum stress (ER stress) via PERK and IRE1 signalings. In vivo mice model confirmed that fenofibrate inhibited the growth of PCa. This study suggests that fenofibrate is an effective inhibitor of PCa by regulating autophagy and ER stress.

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.

PPARα, a predictor of patient survival in glioma, inhibits cell growth through the E2F1/miR-19a feedback loop

Nuclear receptors such as peroxisome proliferator-activated receptor α (PPARα) are potential therapeutic targets. In this study, we found that PPARα expression was lower in high grade gliomas and PPARα was an independent prognostic factor in GBM patients. PPARα agonism or overexpression inhibited glioma cell proliferation, invasion, and aerobic glycolysis as well as suppressed glioma growth in an orthotopic model. Bioinformatic analysis and luciferase reporter assays showed that miR-19a decreased PPARα expression. E2F1 knockdown up-regulated PPARα and inhibited cell proliferation, invasion, and aerobic glycolysis, but this activity was blocked by miR-19a. Knockdown of E2F1 decreased miR-19a by inhibiting the miR-19a promoter. Moreover, PPARα repressed E2F1 via the p21 pathwayby modulating the transcriptional complexes containing E2F1 and pRB proteins. These results suggest that the E2F1/miR19a/PPARα feedback loop is critical for glioma progression.

Fenofibrate induced PPAR alpha expression was attenuated by oestrogen receptor alpha overexpression in Hep3B cells

The physiological regulation of Oestrogen receptor α (ERα) and peroxisome proliferator-activated receptor alpha (PPARα) in Hepatocellular carcinoma (HCC) remains unknown. The present study we first treat the cells with fenofibrate and further investigated the possible mechanisms of 17β-estradiol (E₂ ) and/or ERα on regulating PPARα expression. We also found higher PPARα expression in the tumor area than adjacent areas and subsequently compared PPARα expression in four different hepatic cancer cell lines. Hep3B cells were found to express more PPARα than the other cell lines. Using the PPARα agonist fenofibrate, we found that fenofibrate increased Hep3B cell proliferation efficiency by increasing cell cycle proteins, such as cyclin D1 and PCNA, and inhibiting p27 and caspase 3 expressions. Next, we performed transient transfections and immuno-precipitation studies using the pTRE2/ERα plasmid to evaluate the interaction between ERα and PPARα. ERα interacted directly with PPARα and negatively regulated its function. Moreover, in Tet-on ERα over-expressed Hep3B cells, E₂ treatment inhibited PPARα, its downstream gene acyl-CoA oxidase (ACO), cyclin D1 and PCNA expression and further increased p27 and caspase 3 expressions. However, over-expressed ERα plus 17-β-estradiol (10^-8 M) reversed the fenofibrate effect and induced apoptosis, which was blocked in ICI/melatonin/fenofibrate-treated cells. This study illustrates that PPARα expression and function were negatively regulated by ERα expression in Hep3B cells.

RA and ω-3 PUFA co-treatment activates autophagy in cancer cells

Retinoic acid (RA), is a promising therapeutic agent for the treatment of breast cancer. However, metabolic disorders and drug resistance reduce the efficacy of RA. In this study, we found that RA and ω-3 polyunsaturated fatty acids (ω-3 PUFAs) synergistically induced cell death in vitro and in vivo and autophagy activation. Moreover, RA-induced hypercholesterolemia was completely corrected by ω-3 PUFA supplementation. In addition, we demonstrated that the effects of this combination on the autophagic flux were independent of the two major canonic regulatory complexes controlling autophagic vesicle formation. The treatment activated Gαq-p38 MAPK signaling pathways, which resulted in autophagy of breast cancer cells. Knockdown of Gαq or P38 expression prevented RA and ω-3 PUFAs from inducing autophagy. Data indicated that Gαq-p38activation was mediated by the co-activation of GPR40 and RARα in lipid rafts, rather than by the activation of GPR120, RARβ, or RARγ. The results of this study suggest that hyperlipidemic drug side effects may be ameliorated by the administration of ω-3 PUFAs. Thus, the therapeutic indexes of the corresponding drugs may be increased.

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.

A CD47-associated super-enhancer links pro-inflammatory signalling to CD47 upregulation in breast cancer

CD47 is a cell surface molecule that inhibits phagocytosis of cells that express it by binding to its receptor, SIRPα, on macrophages and other immune cells. CD47 is expressed at different levels by neoplastic and normal cells. Here, to reveal mechanisms by which different neoplastic cells generate this dominant 'don't eat me' signal, we analyse the CD47 regulatory genomic landscape. We identify two distinct super-enhancers (SEs) associated with CD47 in certain cancer cell types. We show that a set of active constituent enhancers, located within the two CD47 SEs, regulate CD47 expression in different cancer cell types and that disruption of CD47 SEs reduces CD47 gene expression. Finally we report that the TNF-NFKB1 signalling pathway directly regulates CD47 by interacting with a constituent enhancer located within a CD47-associated SE specific to breast cancer. These results suggest that cancers can evolve SE to drive CD47 overexpression to escape immune surveillance.

Stimulating effect of normal-dosing of fibrates on cell proliferation: word of warning

BACKGROUND

Fibrates are widely used hypolipidemic drugs, which serve as ligand of peroxisome proliferator-activated receptor α (PPARα). Recently, they have also been considered as potential anticancer agents. We studied effect of fibrates treatment on cell proliferation, expression of CYP2J2 and concomitant changes in expression of cell cycle regulatory proteins in three different human cell lines: HEK293, HepG2, and HT-29.

METHODS

We used WST-1 viability test, western blot and immunocytochemistry for detection of proteins of interests and analysis of cell cycle.

RESULTS

Our results showed that at lower concentrations of all tested fibrates, viability of all tested cell lines is increased, whereas at higher concentrations, repression is apparent. Unfortunately, the viability of tested cells is predominantly increased in a range of concentration which is reached in patient plasma. This phenomenon is accompanyed by elevation of CYP2J2, increased number of cyclin E-positive cells and decreased number of Cdc25A-positive cells in all tested cell lines, and elevated cyclin A expression in HepG2 and HT-29. These changes are concentration-dependent. We suppose that increased level of CYP2J2 could explain enhanced cell proliferation in lower concentration of fibrates.

CONCLUSION

Based on our results, we suggested there is no anti-cancer effect of fibrates in tested carcinoma cell lines.

Fenofibrate Suppresses Oral Tumorigenesis via Reprogramming Metabolic Processes: Potential Drug Repurposing for Oral Cancer

One anticancer strategy suggests targeting mitochondrial metabolism to trigger cell death through slowing down energy production from the Warburg effect. Fenofibrate is a clinical lipid-lowering agent and an effective anticancer drug. In the present study, we demonstrate that fenofibrate provided novel mechanisms for delaying oral tumor development via the reprogramming of metabolic processes. Fenofibrate induced cytotoxicity by decreasing oxygen consumption rate (OCR) that was accompanied with increasing extracellular acidification rate (ECAR) and reducing ATP content. Moreover, fenofibrate caused changes in the protein expressions of hexokinase II (HK II), pyruvate kinase, pyruvate dehydrogenase, and voltage-dependent anion channel (VDAC), which are associated with the Warburg effect. In addition, fenofibrate reprogrammed the metabolic pathway by interrupting the binding of HK II to VDAC. In an oral cancer mouse model, fenofibrate exhibited both preventive and therapeutic efficacy on oral tumorigenesis. Fenofibrate administration suppressed the incidence rate of tongue lesions, reduced the tumor sizes, decreased the tumor multiplicity, and decreased the immunoreactivities of VDAC and mTOR. The molecular mechanisms involved in fenofibrate's ability to delay tumor development included the down-regulation of mTOR activity via TSC1/2-dependent signaling through activation of AMPK and inactivation of Akt, or via a TSC1/2-independent pathway through direct suppression of raptor. Our findings provide a molecular rationale whereby fenofibrate exerts anticancer and additional beneficial effects for the treatment of oral cancer patients.

Peroxisome Proliferator-Activated Receptor Ligands and Their Role in Chronic Myeloid Leukemia: Therapeutic Strategies

Imatinib therapy remains the gold standard for treatment of chronic myeloid leukemia; however, the acquired resistance to this therapeutic agent in patients has urged the scientists to devise modalities for overcoming this chemoresistance. For this purpose, initially therapeutic agents with higher tyrosine kinase activity were introduced, which had the potential for inhibiting even mutant forms of Bcr-Abl. Furthermore, coupling imatinib with peroxisome proliferator-activated receptor ligands also showed beneficial effects in chronic myeloid leukemia cell proliferation. These combination protocols inhibited cell growth and induced apoptosis as well as differentiation in chronic myeloid leukemia cell lines. In addition, peroxisome proliferator-activated receptors ligands increased imatinib uptake by upregulating the expression of human organic cation transporter 1. Taken together, peroxisome proliferator-activated receptors ligands are currently being considered as novel promising therapeutic candidates for chronic myeloid leukemia treatment, because they can synergistically enhance the efficacy of imatinib. In this article, we reviewed the potential of peroxisome proliferator-activated receptors ligands for use in chronic myeloid leukemia treatment. The mechanism of action of these therapeutics modalities are also presented in detail.

PPARα modulates gene expression profiles of mitochondrial energy metabolism in oral tumorigenesis

Metabolic reprogramming plays a crucial role in the development of cancer. The aim of this study was to explore the effect of fenofibrate, an agonist of peroxisome proliferator-activated receptor alpha (PPARα), on gene expression profiles of mitochondrial energy metabolism. Our results showed that PPARα expression was negatively correlated with tumor progression in an oral cancer mouse model. Activation of PPARα through fenofibrate suppressed migration of oral cancer cells. Differential protein profiling demonstrated that expressions of genes related to mitochondrial energy metabolism were either up-regulated (Atp5g3, Cyc1, Ndufa5, Ndufa10, and Sdhd) or down-regulated (Cox5b, Ndufa1, Ndufb7, and Uqcrh) through PPARα activation and response. Our results indicate that PPARα exhibits a great potential for anti-oral cancer therapies by modulating cancer cell mitochondrial energy metabolism.

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.

The truncated splice variant of peroxisome proliferator-activated receptor alpha, PPARα-tr, autonomously regulates proliferative and pro-inflammatory genes

BACKGROUND

The peroxisome proliferator-activated receptor alpha (PPARα) controls lipid/energy homeostasis and inflammatory responses. The truncated splice variant PPARα-tr was suggested to exert a dominant negative function despite being unable to bind consensus PPARα DNA response elements.

METHODS

The distribution and variability factor of each PPARα variant were assessed in the well-characterized cohort of human liver samples (N = 150) on the mRNA and protein levels. Specific siRNA-mediated downregulation of each transcript as well as specific overexpression with subsequent qRT-PCR analysis of downstream genes was used for investigation of specific functional roles of PPARα-wt and PPARα-tr forms in primary human hepatocytes.

RESULTS

Bioinformatic analyses of genome-wide liver expression profiling data suggested a possible role of PPARα-tr in downregulating proliferative and pro-inflammatory genes. Specific gene silencing of both forms in primary human hepatocytes showed that induction of metabolic PPARα-target genes by agonist WY14,643 was prevented by PPARα-wt knock-down but neither prevented nor augmented by PPARα-tr knock-down. WY14,643 treatment did not induce proliferative genes including MYC, CDK1, and PCNA, and knock-down of PPARα-wt had no effect, while PPARα-tr knock-down caused up to 3-fold induction of these genes. Similarly, induction of pro-inflammatory genes IL1B, PTGS2, and CCL2 by IL-6 was augmented by knock-down of PPARα-tr but not of PPARα-wt. In contrast to human proliferative genes, orthologous mouse genes were readily inducible by WY14,643 in PPARα-tr non-expressing AML12 mouse hepatocytes. Induction was augmented by overexpression of PPARα-wt and attenuated by overexpression of PPARα-tr. Pro-inflammatory genes including IL-1β, CCL2 and TNFα were induced by WY14,643 in mouse and human cells and both PPARα forms attenuated induction. As potential mechanism of PPARα-tr inhibitory action we suggest crosstalk with WNT/β-catenin pathway. Finally, treatment with WY14,643 in the presence of PPARα-tr resulted in the significant reduction of cell viability of AML12 and human ovarian cancer cell line, SKOV3.

CONCLUSIONS

Our data suggest that the truncated PPARα splice variant functions as an endogenous inhibitor of proliferative and pro-inflammatory genes in human cells and that its absence in mouse may explain species-specific differences in fibrate-induced hepatocarcinogenesis.

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.

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.

Fenofibrate enhances barrier function of endothelial continuum within the metastatic niche of prostate cancer cells

OBJECTIVE

Extravasation of circulating cancer cells is an important step of the metastatic cascade and a potential target for anti-cancer strategies based on vasoprotective drugs. Reports on anti-cancer effects of fenofibrate (FF) prompted us to analyze its influence on the endothelial barrier function during prostate cancer cell diapedesis.

RESEARCH DESIGN AND METHODS

In vitro co-cultures of endothelial cells with cancer cells imitate the 'metastatic niche' in vivo. We qualitatively and quantitatively estimated the effect of 25 μM FF on the events which accompany prostate carcinoma cell diapedesis, with the special emphasis on endothelial cell mobilization.

RESULTS

Fenofibrate attenuated cancer cell diapedesis via augmenting endothelial cell adhesion to the substratum rather than through the effect on intercellular communication networks within the metastatic niche. The inhibition of endothelial cell motility was accompanied by the activation of PPARα-dependent and PPARα-independent reactive oxygen species signaling, Akt and focal adhesion kinase (FAK) phosphorylation, in the absence of cytotoxic effects in endothelial cells.

CONCLUSIONS

Fenofibrate reduces endothelial cell susceptibility to the paracrine signals received from prostate carcinoma cells, thus inhibiting endothelial cell mobilization and reducing paracellular permeability of endothelium in the metastatic niche. Our data provide a mechanistic rationale for extending the clinical use of FF and for the combination of this well tolerated vasoactive drug with the existing multidrug regimens used in prostate cancer therapy.

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.

Targeting tumor suppressor networks for cancer therapeutics

Cancer is a consequence of mutations in genes that control cell proliferation, differentiation and cellular homeostasis. These genes are classified into two categories: oncogenes and tumor suppressor genes. Together, overexpression of oncogenes and loss of tumor suppressors are the dominant driving forces for tumorigenesis. Hence, targeting oncogenes and tumor suppressors hold tremendous therapeutic potential for cancer treatment. In the last decade, the predominant cancer drug discovery strategy has relied on a traditional reductionist approach of dissecting molecular signaling pathways and designing inhibitors for the selected oncogenic targets. Remarkable therapies have been developed using this approach; however, targeting oncogenes is only part of the picture. Our understanding of the importance of tumor suppressors in preventing tumorigenesis has also advanced significantly and provides a new therapeutic window of opportunity. Given that tumor suppressors are frequently mutated, deleted, or silenced with loss-of-function, restoring their normal functions to treat cancer holds tremendous therapeutic potential. With the rapid expansion in our knowledge of cancer over the last several decades, developing effective anticancer regimens against tumor suppressor pathways has never been more promising. In this article, we will review the concept of tumor suppression, and outline the major therapeutic strategies and challenges of targeting tumor suppressor networks for cancer therapeutics.

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.

Peroxisome proliferator activated receptor α ligands as anticancer drugs targeting mitochondrial metabolism

Tumor cells show metabolic features distinctive from normal tissues, with characteristically enhanced aerobic glycolysis, glutaminolysis and lipid synthesis. Peroxisome proliferator activated receptor α (PPAR α) is activated by nutrients (fatty acids and their derivatives) and influences these metabolic pathways acting antagonistically to oncogenic Akt and c-Myc. Therefore PPAR α can be regarded as a candidate target molecule in supplementary anticancer pharmacotherapy as well as dietary therapeutic approach. This idea is based on hitting the cancer cell metabolic weak points through PPAR α mediated stimulation of mitochondrial fatty acid oxidation and ketogenesis with simultaneous reduction of glucose and glutamine consumption. PPAR α activity is induced by fasting and its molecular consequences overlap with the effects of calorie restriction and ketogenic diet (CRKD). CRKD induces increase of NAD+/NADH ratio and drop in ATP/AMP ratio. The first one is the main stimulus for enhanced protein deacetylase SIRT1 activity; the second one activates AMP-dependent protein kinase (AMPK). Both SIRT1 and AMPK exert their major metabolic activities such as fatty acid oxidation and block of glycolysis and protein, nucleotide and fatty acid synthesis through the effector protein peroxisome proliferator activated receptor gamma 1 α coactivator (PGC-1α). PGC-1α cooperates with PPAR α and their activities might contribute to potential anticancer effects of CRKD, which were reported for various brain tumors. Therefore, PPAR α activation can engage molecular interplay among SIRT1, AMPK, and PGC-1α that provides a new, low toxicity dietary approach supplementing traditional anticancer regimen.

Regulation of URG4/URGCP and PPARα gene expressions after retinoic acid treatment in neuroblastoma cells

Neuroblastoma (NB), originating from neural crest cells, is the most common extracranial tumor of childhood. Retinoic acid (RA) which is the biological active form of vitamin A regulates differentiation of NB cells, and RA derivatives have been used for NB treatment. PPARα (peroxisome proliferator-activated receptor) plays an important role in the oxidation of fatty acids, carcinogenesis, and differentiation. URG4/URGCP gene is a proto-oncogene and that overexpression of URG4/URGCP is associated with metastasis and tumor recurrence in osteosarcoma. It has been known that URG4/URGCP gene is an overexpressed gene in hepatocellular carcinoma and gastric cancers. This study aims to detect gene expression patterns of PPARα and URG4/URGCP genes in SH-SY5Y NB cell line after RA treatment. Expressions levels of PPARα and URG4/URGCP genes were analyzed after RA treatment for reducing differentiation in SH-SY5Y NB cell line. To induce differentiation, the cells were treated with 10 μM RA in the dark for 3-10 days. Gene expression of URG4/URGCP and PPARα genes were presented as the yield of polymerase chain reaction (PCR) products from target genes compared with the yield of PCR products from the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene. SH-SY5Y cells possess small processes in an undifferentiated state, and after treatment with RA, the cells developed long neurites, resembling a neuronal phenotype. PPARα gene expression increased in RA-treated groups; URG4/URGCP gene expression decreased in SH-SY5Y cells after RA treatment compared with that in the control cells. NB cell differentiation might associate with PPARα and URG4/URGCP gene expression profile after RA treatment.