Emerging role of the β-catenin-PPARγ axis in the pathogenesis of colorectal cancer

Serum Cytokine and miRNA Levels Are Differently Expressed in Right- and Left-Sided Colon Cancer

The tumor location in colorectal cancer (right- or left-sided colon cancer) is a key factor in determining disease progression. Right- and left-sided colon tumors are different in their clinical and molecular characteristics. Dysregulation of serum levels of proinflammatory cytokines, such as Transforming Growth Factor β (TGF-β) and Tumor Necrosis Factor-α (TNF-α), and Peroxisome Proliferator Activated Receptor-γ (PPAR-γ), known to be a growth-limiting and differentiation-promoting factor, as well as changes in miRNAs expression, are the major signaling pathways involved in the pathogenesis of this neoplasia. In the serum from 60 colorectal cancer (CRC) patients, we compared the differences in the expression of the levels of TGF-β, TNF-α, and PPAR-γ and in the expression of the main human miRNAs between right and left CRC. A significant over-expression in the TGF-β and TNF-α levels was observed in the serum from right-sided colon cancer patients. For the PPAR-γ, the patients with CRC located on the right-side showed lower levels than those detected in the serum from left-sided CRC subjects. Furthermore, significant differences also existed in the expression of specific circulating miRNAs between right- and left-sided CRC. In particular, the right upregulated miRNAs were all involved in the cell growth and proliferation related pathways. These findings confirm that the analysis of circulating levels of TGF-β, TNF-α, and PPAR-γ, as well as the study of the specific miRNAs in the serum, are able to identify specific characteristics of CRC patients, useful for choosing a personalized treatment protocol.

Combination of pioglitazone, a PPARγ agonist, and synthetic surfactant B-YL prevents hyperoxia-induced lung injury in adult mice lung explants

INTRODUCTION

Hyperoxia-induced lung injury is characterized by acute alveolar injury, disrupted epithelial-mesenchymal signaling, oxidative stress, and surfactant dysfunction, yet currently, there is no effective treatment. Although a combination of aerosolized pioglitazone (PGZ) and a synthetic lung surfactant (B-YL peptide, a surfactant protein B mimic) prevents hyperoxia-induced neonatal rat lung injury, whether it is also effective in preventing hyperoxia-induced adult lung injury is unknown.

METHOD

Using adult mice lung explants, we characterize the effects of 24 and 72-h (h) exposure to hyperoxia on 1) perturbations in Wingless/Int (Wnt) and Transforming Growth Factor (TGF)-β signaling pathways, which are critical mediators of lung injury, 2) aberrations of lung homeostasis and injury repair pathways, and 3) whether these hyperoxia-induced aberrations can be blocked by concomitant treatment with PGZ and B-YL combination.

RESULTS

Our study reveals that hyperoxia exposure to adult mouse lung explants causes activation of Wnt (upregulation of key Wnt signaling intermediates β-catenin and LEF-1) and TGF-β (upregulation of key TGF-β signaling intermediates TGF-β type I receptor (ALK5) and SMAD 3) signaling pathways accompanied by an upregulation of myogenic proteins (calponin and fibronectin) and inflammatory cytokines (IL-6, IL-1β, and TNFα), and alterations in key endothelial (VEGF-A and its receptor FLT-1, and PECAM-1) markers. All of these changes were largely mitigated by the PGZ + B-YL combination.

CONCLUSION

The effectiveness of the PGZ + B-YL combination in blocking hyperoxia-induced adult mice lung injury ex-vivo is promising to be an effective therapeutic approach for adult lung injury in vivo.

Potential Therapeutic Effects of PPAR Ligands in Glioblastoma

Glioblastoma (GB), also known as grade IV astrocytoma, represents the most aggressive form of brain tumor, characterized by extraordinary heterogeneity and high invasiveness and mortality. Thus, a great deal of interest is currently being directed to investigate a new therapeutic strategy and in recent years, the research has focused its attention on the evaluation of the anticancer effects of some drugs already in use for other diseases. This is the case of peroxisome proliferator-activated receptors (PPARs) ligands, which over the years have been revealed to possess anticancer properties. PPARs belong to the nuclear receptor superfamily and are divided into three main subtypes: PPAR-α, PPAR-β/δ, and PPAR-γ. These receptors, once activated by specific natural or synthetic ligands, translocate to the nucleus and dimerize with the retinoid X receptors (RXR), starting the signal transduction of numerous genes involved in many physiological processes. PPARs receptors are activated by specific ligands and participate principally in the preservation of homeostasis and in lipid and glucose metabolism. In fact, synthetic PPAR-α agonists, such as fibrates, are drugs currently in use for the clinical treatment of hypertriglyceridemia, while PPAR-γ agonists, including thiazolidinediones (TZDs), are known as insulin-sensitizing drugs. In this review, we will analyze the role of PPARs receptors in the progression of tumorigenesis and the action of PPARs agonists in promoting, or not, the induction of cell death in GB cells, highlighting the conflicting opinions present in the literature.

The Emerging Role of COX-2, 15-LOX and PPARγ in Metabolic Diseases and Cancer: An Introduction to Novel Multi-target Directed Ligands (MTDLs)

Emerging evidence supports an intertwining framework for the involvement of different inflammatory pathways in a common pathological background for a number of disorders. Of importance are pathways involving arachidonic acid metabolism by cyclooxygenase-2 (COX-2) and 15-lipoxygenase (15-LOX). Both enzyme activities and their products are implicated in a range of pathophysiological processes encompassing metabolic impairment leading to adipose inflammation and the subsequent vascular and neurological disorders, in addition to various pro- and antitumorigenic effects. A further layer of complexity is encountered by the disparate, and often reciprocal, modulatory effect COX-2 and 15-LOX activities and metabolites exert on each other or on other cellular targets, the most prominent of which is peroxisome proliferator-activated receptor gamma (PPARγ). Thus, effective therapeutic intervention with such multifaceted disorders requires the simultaneous modulation of more than one target. Here, we describe the role of COX-2, 15-LOX, and PPARγ in cancer and complications of metabolic disorders, highlight the value of designing multi-target directed ligands (MTDLs) modifying their activity, and summarizing the available literature regarding the rationale and feasibility of design and synthesis of these ligands together with their known biological effects. We speculate on the potential impact of MTDLs in these disorders as well as emphasize the need for structured future effort to translate these early results facilitating the adoption of these, and similar, molecules in clinical research.

Interplay of Opposing Effects of the WNT/β-Catenin Pathway and PPARγ and Implications for SARS-CoV2 Treatment

The Coronavirus disease 2019 (COVID-19), caused by the novel coronavirus SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), has quickly reached pandemic proportions. Cytokine profiles observed in COVID-19 patients have revealed increased levels of IL-1β, IL-2, IL-6, and TNF-α and increased NF-κB pathway activity. Recent evidence has shown that the upregulation of the WNT/β-catenin pathway is associated with inflammation, resulting in a cytokine storm in ARDS (acute respire distress syndrome) and especially in COVID-19 patients. Several studies have shown that the WNT/β-catenin pathway interacts with PPARγ in an opposing interplay in numerous diseases. Furthermore, recent studies have highlighted the interesting role of PPARγ agonists as modulators of inflammatory and immunomodulatory drugs through the targeting of the cytokine storm in COVID-19 patients. SARS-CoV2 infection presents a decrease in the angiotensin-converting enzyme 2 (ACE2) associated with the upregulation of the WNT/β-catenin pathway. SARS-Cov2 may invade human organs besides the lungs through the expression of ACE2. Evidence has highlighted the fact that PPARγ agonists can increase ACE2 expression, suggesting a possible role for PPARγ agonists in the treatment of COVID-19. This review therefore focuses on the opposing interplay between the canonical WNT/β-catenin pathway and PPARγ in SARS-CoV2 infection and the potential beneficial role of PPARγ agonists in this context.

Arsenic trioxide induces differentiation of cancer stem cells in hepatocellular carcinoma through inhibition of LIF/JAK1/STAT3 and NF-kB signaling pathways synergistically

OBJECTIVE

Differentiation-inducing therapy for tumors is a strategy that aims to induce the differentiation and maturation of cancer stem cells (CSCs). The differentiation-inducing capacity of arsenic trioxide (ATO) in hepatocellular carcinoma (HCC) and the underlying mechanism were previously unknown.

METHODS

In the present study, we explored the ATO-induced differentiation of CSCs in HCC by detecting the expression of CSC-related markers and tumorigenicity variation in vivo and in vitro. We developed a combined chemotherapeutic approach to HCC by characterizing the effects of combinatorial treatment with 5-fluorouracil (5-FU)/cisplatin and ATO in vitro and in patient-derived xenograft models. Changes in gene expression patterns were investigated by gene microarray analysis.

RESULTS

ATO effectively induced differentiation of CSCs by downregulation of CSC-related genes and suppression of tumorigenicity capability. Combinatorial treatment with ATO and 5-FU/cisplatin significantly enhanced therapeutic effects in HCC cells compared with the treatment with 5-FU/cisplatin alone. Synergistic inhibition of the LIF/JAK1/STAT3 and NF-kB signaling pathways by ATO and 5-FU/cisplatin is a potential molecular mechanism underlying the differentiation effect.

CONCLUSIONS

ATO induced the differentiation of HCC CSCs and potentiated the cytotoxic effects of 5-FU/cisplatin through synergistic inhibition of the LIF/JAK1/STAT3 and NF-kB signaling pathways. These results offer new insights for the clinical treatment of HCC.

ICAT acts as a Coactivator in Regulating PPARγ Transcriptional Activity in Mesangial Cells

AIMS

Our study aims to explore the role of β-catenin interaction protein-1(ICAT) in regulating peroxisome proliferator-activated receptor γ (PPARγ) transcriptional activity in mesangial cells. The abnormal ICAT expression in mesangial cells under high glucose(HG) contributes to the development of diabetes and its complications such as diabetic nephropathy (DN).

METHODS

Human mesangial cells (HMCs) were cultured in either 5.5 (normal control) or 30 (high glucose) mmol/L glucose medium. Overexpression and knock-down of ICAT or β-catenin were carried out by transient transfection. PPARγ transcriptional activity was evaluated by luciferase assay. Protein-protein interactions were tested by Coimmunoprecipitation and GST-pull down assay. Cell phenotype transition of HMCs was detected by the expression level of α-SMA and fibronectin, as well as MTT assay.

RESULTS

High β-catenin protein expression but low ICAT was accompanied by low PPARγ transcriptional activity in HMCs cultured in HG. By using bioinformatics prediction, protein-protein and protein-DNA interaction experimental methods, ICAT and β-catenin were confirmed to act as coactivators in regulating PPARγ transcriptional activity. Overexpression of ICAT could mitigate the decrease of PPARγ transcriptional activity and partly relieve cell phenotype transition in HMCs.

CONCLUSIONS

β-catenin and ICAT interact as coactivator to modulate PPARγ transcriptional activation. In HMCs cultured in HG, the low expression of ICAT leads to low PPARγ transcriptional activation.

PPARG expression in colorectal cancer and its association with staging and clinical evolution

Purpose

To evaluate the gene expression of peroxisome proliferator activated receptors gamma (PPARG) in colorectal tumors and to correlate this data with clinical variables of the patients.

Methods

We analyzed the gene expression of PPARG in 50 samples of colorectal tumors using real-time reverse transcription polymerase chain reaction, and 20 adjacent normal tissue samples as control. The results of these quantifications were correlated with the respective patients’ medical records’ clinical information.

Results

PPARG expression was not different in the tumor tissue compared to the control tissue. Patients older than 60 years, histological type with mucinous differentiation, more advanced staging at the time of diagnosis, and patients who evolved with recurrence of the disease or death did not present higher PPARG expression.

Conclusion

Expression of PPARGD was not associated with worse prognosis.

Indomethacin and juglone inhibit inflammatory molecules to induce apoptosis in colon cancer cells

Colorectal cancer (CRC) is the third most common fatal cancer. Indomethacin, a nonsteroidal anti-inflammatory drug, is known to reduce the occurrence of CRC. This study evaluated the potential anticolon cancer effects of juglone (5-hydroxy-1,4-naphthoquinone) in combination with indomethacin. Human colon adenocarcinoma cells (HT29) were subjected to treatment with indomethacin, juglone, and a combination of both. Morphological analysis, cell cycle regulation, and dual staining using acridine orange and ethidium bromide in control and treated cells revealed the apoptotic potential of these compounds. Bcl2 and inflammatory molecules (tumor necrosis factor-α, nuclear factor kappa B, and Cox-2) were found to be decreased with a concomitant increase in the expression of proapoptotic molecules (Bad, Bax, cytochrome c, and PUMA) as a result of the molecular regulation of Wnt, Notch, and peroxisome proliferator-activated receptor-γ signaling. Treatment with juglone was not as effective as with indomethacin; however, a combination of both was shown to be more effective, suggesting that juglone may be considered for therapeutic intervention of colon cancer.

Regulation of Ketogenic Enzyme HMGCS2 by Wnt/β-catenin/PPARγ Pathway in Intestinal Cells

The Wnt/β-catenin pathway plays a crucial role in development and renewal of the intestinal epithelium. Mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), a rate-limiting ketogenic enzyme in the synthesis of ketone body β-hydroxybutyrate (βHB), contributes to the regulation of intestinal cell differentiation. Here, we have shown that HMGCS2 is a novel target of Wnt/β-catenin/PPARγ signaling in intestinal epithelial cancer cell lines and normal intestinal organoids. Inhibition of the Wnt/β-catenin pathway resulted in increased protein and mRNA expression of HMGCS2 and βHB production in human colon cancer cell lines LS174T and Caco2. In addition, Wnt inhibition increased expression of PPARγ and its target genes, FABP2 and PLIN2, in these cells. Conversely, activation of Wnt/β-catenin signaling decreased protein and mRNA levels of HMGCS2, βHB production, and expression of PPARγ and its target genes in LS174T and Caco2 cells and mouse intestinal organoids. Moreover, inhibition of PPARγ reduced HMGCS2 expression and βHB production, while activation of PPARγ increased HMGCS2 expression and βHB synthesis. Furthermore, PPARγ bound the promoter of HMGCS2 and this binding was enhanced by β-catenin knockdown. Finally, we showed that HMGCS2 inhibited, while Wnt/β-catenin stimulated, glycolysis, which contributed to regulation of intestinal cell differentiation. Our results identified HMGCS2 as a downstream target of Wnt/β-catenin/PPARγ signaling in intestinal epithelial cells. Moreover, our findings suggest that Wnt/β-catenin/PPARγ signaling regulates intestinal cell differentiation, at least in part, through regulation of ketogenesis.

New Approaches to Cancer Therapy: Combining Fatty Acid Amide Hydrolase (FAAH) Inhibition with Peroxisome Proliferator-Activated Receptors (PPARs) Activation

Over the course of the past decade, peroxisome proliferator-activated receptors (PPARs) have been identified as part of the cannabinoid signaling system: both phytocannabinoids and endocannabinoids are capable of binding and activating these nuclear receptors. Fatty acid amide hydrolase (FAAH) hydrolyzes the endocannabinoid anandamide and other N-acylethanolamines. These substances have been shown to have numerous anticancer effects, and indeed the inhibition of FAAH has multiple beneficial effects that are mediated by PPARα subtype and by PPARγ subtype, especially antiproliferation and activation of apoptosis. The substrates of FAAH are also PPAR agonists, which explains the PPAR-mediated effects of FAAH inhibitors. Much like cannabinoid ligands and FAAH inhibitors, PPARγ agonists show antiproliferative effects on cancer cells, suggesting that additive or synergistic effects may be achieved through the positive modulation of both signaling systems. In this Miniperspective, we discuss the development of novel FAAH inhibitors able to directly act as PPAR agonists and their promising utilization as leads for the discovery of highly effective anticancer compounds.

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.

Metabolic reprogramming in atherosclerosis: Opposed interplay between the canonical WNT/β-catenin pathway and PPARγ

Atherosclerosis, a chronic inflammatory and age-related disease, is a complex mechanism presenting a dysregulation of vessel structures. During this process, the canonical WNT/β-catenin pathway is increased whereas PPARγ is downregulated. The two systems act in an opposite manner. This paper reviews the opposing interplay of these systems and their metabolic-reprogramming pathway in atherosclerosis. Activation of the WNT/β-catenin pathway enhances the transcription of targets involved in inflammation, endothelial dysfunction, the proliferation of vascular smooth muscle cells, and vascular calcification. This complex mechanism, which is partly controlled by the WNT/β-catenin pathway, presents several metabolic dysfunctions. This phenomenon, called aerobic glycolysis (or the Warburg effect), consists of a shift in ATP production from mitochondrial oxidative phosphorylation to aerobic glycolysis, leading to the overproduction of intracellular lactate. This mechanism is partially due to the injury of mitochondrial respiration and an increase in the glycolytic pathway. In contrast, PPARγ agonists downregulate the WNT/β-catenin pathway. Therefore, the development of therapeutic targets, such as PPARγ agonists, for the treatment of atherosclerosis could be an interesting and innovative way of counteracting the canonical WNT pathway.

PPARγ agonists: potential treatment for autism spectrum disorder by inhibiting the canonical WNT/β-catenin pathway

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is characterized by a deficit in social interactions and communication with repetitive and restrictive behavior. No curative treatments are available for ASD. Pharmacological treatments do not address the core ASD behaviors, but target comorbid symptoms. Dysregulation of the core neurodevelopmental pathways is associated with the clinical presentation of ASD, and the canonical WNT/β-catenin pathway is one of the major pathways involved. The canonical WNT/β-catenin pathway participates in the development of the central nervous system, and its dysregulation involves developmental cognitive disorders. In numerous tissues, the canonical WNT/β-catenin pathway and peroxisome proliferator-activated receptor gamma (PPARγ) act in an opposed manner. In ASD, the canonical WNT/β-catenin pathway is increased while PPARγ seems to be decreased. PPARγ agonists present a beneficial effect in treatment for ASD children through their anti-inflammatory role. Moreover, they induce the inhibition of the canonical WNT/β-catenin pathway in several pathophysiological states. We focus this review on the hypothesis of an opposed interplay between PPARγ and the canonical WNT/β-catenin pathway in ASD and the potential role of PPARγ agonists as treatment for ASD.

Upregulated claudin-1 expression promotes colitis-associated cancer by promoting β-catenin phosphorylation and activation in Notch/p-AKT-dependent manner

In IBD patients, integration between a hyper-activated immune system and epithelial cell plasticity underlies colon cancer development. However, molecular regulation of such a circuity remains undefined. Claudin-1(Cld-1), a tight-junction integral protein deregulation alters colonic epithelial cell (CEC) differentiation, and promotes colitis severity while impairing colitis-associated injury/repair. Tumorigenesis is a product of an unregulated wound healing process and therefore we postulated that upregulated Cld-1 levels render IBD patients susceptible to the colitis-associated cancer (CAC). Villin Cld-1 mice is used to carryout overexpressed studies in mice. The role of deregulated Cld-1 expression in CAC and underlying mechanism using a well-constructed study scheme and mouse models of DSS colitis/recovery and CAC. Using an inclusive investigative scheme, we here report that upregulated Cld-1 expression promotes susceptibility to the CAC and its malignancy. Increased mucosal inflammation, defective epithelial homeostasis accompanied the increased CAC in Villin-Cld1-Tg mice. We further found significantly increased levels of pro-tumorigenic M2 macrophages and β-CateninSer552 (β-CatSer552) expression in the CAC in Cld-1Tg versus WT mice. Mechanistic studies identified the role of PI3K/Akt signaling in Cld-1 dependent activation of the β-CatSer552, which, in turn, was dependent on pro-inflammatory signals. Our studies identify a critical role of Cld-1 in promoting susceptibility to CAC. Importantly, these effects of deregulated Cld-1 were not associated with altered tight junction integrity, but on its non-canonical role in regulating Notch/PI3K/Wnt/ β-CatSer552 signaling. Overall, outcome from our current studies identifies Cld-1 as potential prognostic biomarker for IBD severity and CAC, and a novel therapeutic target.

Differential Responses of Colorectal Cancer Cell Lines to Enterococcus faecalis' Strains Isolated from Healthy Donors and Colorectal Cancer Patients

The metabolites produced by the host’s gut microbiota have an important role in the maintenance of intestinal homeostasis, but can also act as toxins and induce DNA damage in colorectal epithelial cells increasing the colorectal cancer (CRC) chance. In this scenario, the impact of some of the components of the natural human gastrointestinal microbiota, such as Enterococcus faecalis (E. faecalis), at the onset of CRC progression remains controversial. Since under dysbiotic conditions it could turn into a pathogen, the aim of this study was to compare the effect of E. faecalis’ strains (isolated from CRC patients and healthy subjects’ stools) on the proliferation of different colorectal cells lines. First, we isolated and genotyping characterized the Enterococcus faecalis’ strains. Then, we analyzed the proliferation index (by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay) of three tumor and one normal intestinal cell lines, previously exposed to E. faecalis strains pre-cultured medium. Stool samples of CRC patients demonstrated a reduced frequency of E. faecalis compared to healthy subjects. In addition, the secreted metabolites of E. faecalis’ strains, isolated from healthy donors, decreased the human ileocecal adenocarcinoma cell line HCT-8 and human colon carcinoma cell line HCT-116 cell proliferation without effects on human colorectal adenocarcinoma cell line SW620 and on normal human diploid cell line CLR-1790. Notably, the metabolites of the strains isolated from CRC patients did not influence the cell growth of CRC cell lines. Our results demonstrated a new point of view in the investigation of E. faecalis’ role in CRC development, which raises awareness of the importance of not only associating the presence/absence of a unique microorganism, but also in defining the specific characteristics of the different investigated strains.

Estrogen-related receptor gamma functions as a tumor suppressor in gastric cancer

The principle factors underlying gastric cancer (GC) development and outcomes are not well characterized resulting in a paucity of validated therapeutic targets. To identify potential molecular targets, we analyze gene expression data from GC patients and identify the nuclear receptor ESRRG as a candidate tumor suppressor. ESRRG expression is decreased in GC and is a predictor of a poor clinical outcome. Importantly, ESRRG suppresses GC cell growth and tumorigenesis. Gene expression profiling suggests that ESRRG antagonizes Wnt signaling via the suppression of TCF4/LEF1 binding to the CCND1 promoter. Indeed, ESRRG levels are found to be inversely correlated with Wnt signaling-associated genes in GC patients. Strikingly, the ESRRG agonist DY131 suppresses cancer growth and represses the expression of Wnt signaling genes. Our present findings thus demonstrate that ESRRG functions as a negative regulator of the Wnt signaling pathway in GC and is a potential therapeutic target for this cancer.

Crosstalk Between Peroxisome Proliferator-Activated Receptor Gamma and the Canonical WNT/β-Catenin Pathway in Chronic Inflammation and Oxidative Stress During Carcinogenesis

Inflammation and oxidative stress are common and co-substantial pathological processes accompanying, promoting, and even initiating numerous cancers. The canonical WNT/β-catenin pathway and peroxisome proliferator-activated receptor gamma (PPARγ) generally work in opposition. If one of them is upregulated, the other one is downregulated and vice versa. WNT/β-catenin signaling is upregulated in inflammatory processes and oxidative stress and in many cancers, although there are some exceptions for cancers. The opposite is observed with PPARγ, which is generally downregulated during inflammation and oxidative stress and in many cancers. This helps to explain in part the opposite and unidirectional profile of the canonical WNT/β-catenin signaling and PPARγ in these three frequent and morbid processes that potentiate each other and create a vicious circle. Many intracellular pathways commonly involved downstream will help maintain and amplify inflammation, oxidative stress, and cancer. Thus, many WNT/β-catenin target genes such as c-Myc, cyclin D1, and HIF-1α are involved in the development of cancers. Nuclear factor-kappaB (NFκB) can activate many inflammatory factors such as TNF-α, TGF-β, interleukin-6 (IL-6), IL-8, MMP, vascular endothelial growth factor, COX2, Bcl2, and inducible nitric oxide synthase. These factors are often associated with cancerous processes and may even promote them. Reactive oxygen species (ROS), generated by cellular alterations, stimulate the production of inflammatory factors such as NFκB, signal transducer and activator transcription, activator protein-1, and HIF-α. NFκB inhibits glycogen synthase kinase-3β (GSK-3β) and therefore activates the canonical WNT pathway. ROS activates the phosphatidylinositol 3 kinase/protein kinase B (PI3K/Akt) signaling in many cancers. PI3K/Akt also inhibits GSK-3β. Many gene mutations of the canonical WNT/β-catenin pathway giving rise to cancers have been reported (CTNNB1, AXIN, APC). Conversely, a significant reduction in the expression of PPARγ has been observed in many cancers. Moreover, PPARγ agonists promote cell cycle arrest, cell differentiation, and apoptosis and reduce inflammation, angiogenesis, oxidative stress, cell proliferation, invasion, and cell migration. All these complex and opposing interactions between the canonical WNT/β-catenin pathway and PPARγ appear to be fairly common in inflammation, oxidative stress, and cancers.

Therapeutic strategies against cancer stem cells in human colorectal cancer

Colorectal cancer (CRC) is the third most frequent malignancy and represents the fourth most common cause of cancer-associated mortalities in the world. Despite many advances in the treatment of CRC, the 5-year survival rate of patients with CRC remains unsatisfactory due to tumor recurrence and metastases. Recently, cancer stem cells (CSCs), have been suggested to be responsible for the initiation and relapse of the disease, and have been identified in CRC. Due to their basic biological features, which include self-renewal and pluripotency, CSCs may be novel therapeutic targets for CRC and other cancer types. Conventional therapeutics only act on proliferating and mature cancer cells, while quiescent CSCs survive and often become resistant to chemotherapy. In this review, markers of CRC-CSCs are evaluated and the recently introduced experimental therapies that specifically target these cells by inducing CSC proliferation, differentiation and sensitization to apoptotic signals via molecules including Dickkopf-1, bone morphogenetic protein 4, Kindlin-1, tankyrases, and p21-activated kinase 1, are discussed. In addition, novel strategies aimed at inhibiting some crucial processes engaged in cancer progression regulated by the Wnt, transforming growth factor β and Notch signaling pathways (pyrvinium pamoate, silibinin, PRI-724, P17, and P144 peptides) are also evaluated. Although the metabolic alterations in cancer were first described decades ago, it is only recently that the concept of targeting key regulatory molecules of cell metabolism, such as sirtuin 1 (miR-34a) and AMPK (metformin), has emerged. In conclusion, the discovery of CSCs has resulted in the definition of novel therapeutic targets and the development of novel experimental therapies for CRC. However, further investigations are required in order to apply these novel drugs in human CRC.

Interactions between TGF-β1, canonical WNT/β-catenin pathway and PPAR γ in radiation-induced fibrosis

Radiation therapy induces DNA damage and inflammation leading to fibrosis. Fibrosis can occur 4 to 12 months after radiation therapy. This process worsens with time and years. Radiation-induced fibrosis is characterized by fibroblasts proliferation, myofibroblast differentiation, and synthesis of collagen, proteoglycans and extracellular matrix. Myofibroblasts are non-muscle cells that can contract and relax. Myofibroblasts evolve towards irreversible retraction during fibrosis process. In this review, we discussed the interplays between transforming growth factor-β1 (TGF-β1), canonical WNT/β-catenin pathway and peroxisome proliferator-activated receptor gamma (PPAR γ) in regulating the molecular mechanisms underlying the radiation-induced fibrosis, and the potential role of PPAR γ agonists. Overexpression of TGF-β and canonical WNT/β-catenin pathway stimulate fibroblasts accumulation and myofibroblast differentiation whereas PPAR γ expression decreases due to the opposite interplay of canonical WNT/β-catenin pathway. Both TGF-β1 and canonical WNT/β-catenin pathway stimulate each other through the Smad pathway and non-Smad pathways such as phosphatidylinositol 3-kinase/serine/threonine kinase (PI3K/Akt) signaling. WNT/β-catenin pathway and PPAR γ interact in an opposite manner. PPAR γ agonists decrease β-catenin levels through activation of inhibitors of the WNT pathway such as Smad7, glycogen synthase kinase-3 (GSK-3 β) and dickkopf-related protein 1 (DKK1). PPAR γ agonists also stimulate phosphatase and tensin homolog (PTEN) expression, which decreases both TGF-β1 and PI3K/Akt pathways. PPAR γ agonists by activating Smad7 decrease Smads pathway and then TGF-β signaling leading to decrease radiation-induced fibrosis. TGF-β1 and canonical WNT/β-catenin pathway promote radiation-induced fibrosis whereas PPAR γ agonists can prevent radiation-induced fibrosis.

PPARγ agonists: Potential treatments for exudative age-related macular degeneration

Choroidal neovascularization (CNV) characterizes the progression of exudative age-related macular degeneration (AMD) with the deterioration in the central vision. Vascular inflammation, and overproduction of inflammatory cytokines, growth factors and aberrant endothelial cell migration, initiate defective blood vessel proliferation in exudative AMD. CNV formation is initiated by the interplay between inflammation, the hallmark of exudative AMD, and the activation of WNT/β-catenin pathway. Upregulation of WNT/β-catenin pathway involves activation of PI3K/Akt pathway and then the Warburg effect to produce lactate. Lactate production generates VEGF expression and then participates to the initiation of CNV in exudative AMD. WNT/β-catenin pathway and PPARγ act in an opposite manner in several diseases. We focus this review on the interplay between PPARγ and canonical WNT/β-catenin pathway and the anti-inflammatory role of PPARγ in exudative AMD. In exudative AMD, PPARγ agonists downregulate inflammation and the WNT/β-catenin pathway. PPARγ agonists can appear as promising treatment against the initiation and the progression of CNV in exudative AMD.

5-HT induces PPAR γ reduction and proliferation of pulmonary artery smooth muscle cells via modulating GSK-3β/β-catenin pathway

Studies have shown that peroxisome proliferator-activated receptor γ (PPAR γ) is down-regulated in pulmonary vascular lesions of patients with pulmonary hypertension (PH) and animal models of PH. Yet, the detailed molecular mechanisms underlying this alteration are not fully defined; the aim of this study is to address this issue. 5-HT dose- and time-dependently reduced PPAR γ expression and promoted pulmonary artery smooth muscle cells (PASMCs) proliferation; this was accompanied with the phosphorylation of Akt, inactivation of GSK-3β and up-regulation of β-catenin. Importantly, pre-treatment of cells with PI3K inhibitor (Ly294002) or prior silencing of β-catenin with siRNA blocked 5-HT-induced PPAR γ reduction and PASMCs proliferation. In addition, inactivation or lack of GSK-3β or inhibition of proteasome function up-regulated β-catenin protein without affecting its mRNA level and reduced PPAR γ protein expression. Taken together, our study indicates that 5-HT suppresses PPAR γ expression and stimulates PASMCs proliferation by modulating GSK-3β/β-catenin axis, and suggests that targeting this pathway might have potential value in the management of PH.

mRNA expression of nuclear factor of activated T-cells, cytoplasmic 2 (NFATc2) and peroxisome proliferator-activated receptor gamma (PPARG) transcription factors in colorectal carcinoma

Transcription factors are involved in cell cycle and apoptosis regulation and thus have a key role in the carcinogenesis of different tumors. Nuclear factor of activated T-cells, cytoplasmic 2 (NFATc2) and peroxisome proliferator-activated receptor gamma (PPARG) transcription factors are important in the carcinogenesis of colorectal cancer (CRC). In this study, we examined whether the expression of NFATc2 and PPARG genes is significantly altered during the carcinogenesis of CRC. A total of 47 tumor samples and matched normal tissue margins were collected during surgery from patients with CRC. In addition, three CRC cell lines (HCT119, SW480, and HT29) and healthy cell line were used. After total RNA extraction and cDNA synthesis, mRNA expression levels of NFATc2 and PPARG were examined by real-time polymerase chain reaction. The results showed that NFATc2 is overexpressed in the tumor tissues compared with normal tissue margins (p ≤ 0.05). However, the mRNA expression levels of PPARG were not significantly different between the tumor tissues and tissue margins. Our results indicate that NFATc2 may be used as an early diagnostic or predictive biomarker for CRC as well as a therapeutic target, providing that upcoming studies confirm these results.

Cardiovascular disease and cancer: Evidence for shared disease pathways and pharmacologic prevention

Cardiovascular disease (CVD) and cancer are leading causes of mortality and morbidity worldwide. Strategies to improve their treatment and prevention are global priorities and major focus of World Health Organization's joint prevention programs. Emerging evidence suggests that modifiable risk factors including diet, sedentary lifestyle, obesity and tobacco use are central to the pathogenesis of both diseases and are reflected in common genetic, cellular, and signaling mechanisms. Understanding this important biological overlap is critical and may help identify novel therapeutic and preventative strategies for both disorders. In this review, we will discuss the shared genetic and molecular factors central to CVD and cancer and how the strategies commonly used for the prevention of atherosclerotic vascular disease can be applied to cancer prevention.

The lncRNA H19 Promotes Cell Proliferation by Competitively Binding to miR-200a and Derepressing β-Catenin Expression in Colorectal Cancer

H19, a paternally imprinted noncoding RNA, has been found to be overexpressed in various cancers, including colorectal cancer (CRC), and may function as an oncogene. However, the mechanism by which H19 regulates CRC progression remains poorly understood. In this study, we aimed to assess H19 expression levels in CRC tissues, determine the effect of H19 on CRC proliferation, and explore the mechanism by which H19 regulates the proliferation of CRC. We measured H19 expression using qRT-PCR and analysed the effects of H19 on colon cancer cell proliferation via cell growth curve, cell viability assay, and colony formation assays. To elucidate the mechanism underlying these effects, we analysed the interactions between H19 and miRNAs and identified the target gene to which H19 and miRNA competitively bind using a series of molecular biological techniques. H19 expression was upregulated in CRC tissues compared with adjacent noncancerous tissues. H19 overexpression facilitated colon cancer cell proliferation, whereas H19 knockdown inhibited cell proliferation. miR-200a bound to H19 and inhibited its expression, thereby decreasing CRC cell proliferation. β-Catenin was identified as a target gene of miR-200a. H19 regulated β-catenin expression and activity by competitively binding to miR-200a. H19 promotes cell proliferation by competitively binding to miR-200a and derepressing β-catenin in CRC.

Prostaglandin terminal synthases as novel therapeutic targets

Non-steroidal anti-inflammatory drugs (NSAIDs) exert their anti-inflammatory and anti-tumor effects by reducing prostaglandin (PG) production via the inhibition of cyclooxygenase (COX). However, the gastrointestinal, renal and cardiovascular side effects associated with the pharmacological inhibition of the COX enzymes have focused renewed attention onto other potential targets for NSAIDs. PGH₂, a COX metabolite, is converted to each PG species by species-specific PG terminal synthases. Because of their potential for more selective modulation of PG production, PG terminal synthases are now being investigated as a novel target for NSAIDs. In this review, I summarize the current understanding of PG terminal synthases, with a focus on microsomal PGE synthase-1 (mPGES-1) and PGI synthase (PGIS). mPGES-1 and PGIS cooperatively exacerbate inflammatory reactions but have opposing effects on carcinogenesis. mPGES-1 and PGIS are expected to be attractive alternatives to COX as therapeutic targets for several diseases, including inflammatory diseases and cancer.

Moringin activates Wnt canonical pathway by inhibiting GSK3β in a mouse model of experimental autoimmune encephalomyelitis

Aberrant canonical Wnt-β-catenin signaling has been reported in multiple sclerosis (MS), although the results are controversial. The present study aimed to examine the role of the Wnt-β-catenin pathway in experimental MS and also to test moringin (4-[α-L-rhamnopyranosyloxy]-benzyl isothiocyanate), resulting from exogenous myrosinase hydrolysis of the natural phytochemical glucomoringin 4(α-L-rhamnosyloxy)-benzyl glucosinolate as a modulator of neuroinflammation via the β-catenin-PPARγ axis. Experimental autoimmune encephalomyelitis (EAE), the most common model of MS, was induced in C57BL/6 mice by immunization with MOG35-55. Released moringin (10 mg/kg glucomoringin +5 μL myrosinase/mouse) was administered daily for 1 week before EAE induction and continued until mice were killed on day 28 after EAE induction. Our results clearly showed that the Wnt-β-catenin pathway was downregulated in the EAE model, whereas moringin pretreatment was able to avert this. Moringin pretreatment normalizes the aberrant Wnt-β-catenin pathway, resulting in GSK3β inhibition and β-catenin upregulation, which regulates T-cell activation (CD4 and FoxP3), suppresses the main inflammatory mediators (IL-1β, IL-6, and COX2), through activation of PPARγ. In addition, moringin attenuates apoptosis by reducing the expression of the Fas ligand and cleaved caspase 9, and in parallel increases antioxidant Nrf2 expression in EAE mice. Taken together, our results provide an interesting discovery in identifying moringin as a modulator of the Wnt-β-catenin signaling cascade and as a new potential therapeutic target for MS treatment.

Proteomic characterization of peroxisome proliferator-activated receptor-γ (PPARγ) overexpressing or silenced colorectal cancer cells unveils a novel protein network associated with an aggressive phenotype

Peroxisome proliferator-activated receptor-γ (PPARγ) is a transcription factor of the nuclear hormone receptor superfamily implicated in a wide range of processes, including tumorigenesis. Its role in colorectal cancer (CRC) is still debated; most reports support that PPARγ reduced expression is associated with poor prognosis. We employed 2-Dimensional Differential InGel Electrophoresis (2-D DIGE) followed by Liquid Chromatography (LC)-tandem Mass Spectrometry (MS/MS) to identify differentially expressed proteins and the molecular pathways underlying PPARγ expression in CRC progression. We identified several differentially expressed proteins in HT29 and HCT116 CRC cells and derived clones either silenced or overexpressing PPARγ, respectively. In Ingenuity Pathway Analysis (IPA) they showed reciprocal relation with PPARγ and a strong relationship with networks linked to cell death, growth and survival. Interestingly, five of the identified proteins, ezrin (EZR), isoform C of prelamin-A/C (LMNA), alpha-enolase (ENOA), prohibitin (PHB) and RuvB-like 2 (RUVBL2) were shared by the two cell models with opposite expression levels, suggesting a possible regulation by PPARγ. mRNA and western blot analysis were undertaken to obtain a technical validation and confirm the expression trend observed by 2-D DIGE data. We associated EZR upregulation with increased cell surface localization in PPARγ-overexpressing cells by flow cytometry and immunofluorescence staining. We also correlated EZR and PPARγ expression in our series of CRC specimens and the expression profiling of all five proteins levels in the publicly available colon cancer genomic data from Oncomine and Cancer Genome Atlas (TCGA) colon adenocarcinoma (COAD) datasets. In summary, we identified a panel of proteins correlated with PPARγ expression that could be associated with CRC unveiling new pathways to be investigated for the selection of novel potential prognostic/predictive biomarkers and/or therapeutic targets.

Inhibition of Prostaglandin Reductase 2, a Putative Oncogene Overexpressed in Human Pancreatic Adenocarcinoma, Induces Oxidative Stress-Mediated Cell Death Involving xCT and CTH Gene Expressions through 15-Keto-PGE2

Prostaglandin reductase 2 (PTGR2) is the enzyme that catalyzes 15-keto-PGE₂, an endogenous PPARγ ligand, into 13,14-dihydro-15-keto-PGE₂. Previously, we have reported a novel oncogenic role of PTGR2 in gastric cancer, where PTGR2 was discovered to modulate ROS-mediated cell death and tumor transformation. In the present study, we demonstrated the oncogenic potency of PTGR2 in pancreatic cancer. First, we observed that the majority of the human pancreatic ductal adenocarcinoma tissues was stained positive for PTGR2 expression but not in the adjacent normal parts. In vitro analyses showed that silencing of PTGR2 expression enhanced ROS production, suppressed pancreatic cell proliferation, and promoted cell death through increasing 15-keto-PGE₂. Mechanistically, silencing of PTGR2 or addition of 15-keto-PGE₂ suppressed the expressions of solute carrier family 7 member 11 (xCT) and cystathionine gamma-lyase (CTH), two important providers of intracellular cysteine for the generation of glutathione (GSH), which is widely accepted as the first-line antioxidative defense. The oxidative stress-mediated cell death after silencing of PTGR2 or addition of 15-keto-PGE₂ was further abolished after restoring intracellular GSH concentrations and cysteine supply by N-acetyl-_L-cysteine and 2-Mercaptomethanol. Our data highlight the therapeutic potential of targeting PTGR2/15-keto-PGE₂ for pancreatic cancer.

Cyproheptadine exhibits antitumor activity in urothelial carcinoma cells by targeting GSK3β to suppress mTOR and β-catenin signaling pathways

Cyproheptadine, a serotonin antagonist, has recently been reported to function as a novel therapeutic agent by inhibiting PI3K/AKT signaling in several human cancers. However, the therapeutic effect of cyproheptadine in urothelial carcinoma (UC) has never been explored. In this study, we determined the effect of cyproheptadine on the growth of five human UC cell lines and an in vivo xenograft model. The results showed that cyproheptadine exerted an inhibitory effect on the proliferation of UC cells both in vitro and in vivo. Cyproheptadine also induced cell cycle arrest in the G1 phase, subsequently followed by apoptosis and necrosis. The underlying mechanisms of cell cycle arrest were associated with the reduction of c-Myc, induction of p21 and p27, and the stabilization of Rb expression. In addition, the suppression of the GSK3β/TSC2/mTOR pathway and deregulation of the GSK3β/β-catenin signaling were observed in cyproheptadine-treated UC cells. Furthermore, cyproheptadine-induced apoptosis was associated with ANGPTL4 expression followed by activation of caspase3 and PARP in UC cells. Our experimental results provide evidence that cyproheptadine is a suitable therapeutic agent for the treatment of UC.

Epigenetics and Colorectal Neoplasia: the Evidence for Physical Activity and Sedentary Behavior

Studies demonstrate that regular physical activity and, more recently, limited sedentary behavior are associated with reduced risk of colorectal neoplasia. However, the biological mechanisms of action for physical activity versus sedentary behavior are not clear. Epigenetic variation is suggested as a potential mechanism that would allow for independent, or possibly even synergistic, effects of activity and inactivity on colorectal epithelium. We describe the evidence for epigenetic variation as a link between physical activity and sedentary behavior in colorectal neoplasia risk. There are few studies that directly evaluate this relationship. However, the growing literature describes a variety of gene targets influenced by activity that are also important to colorectal neoplasia etiology. Future studies may identify epigenetic markers with translational significance in identifying high-risk individuals or those for whom a personalized activity regimen could significantly alter the methylation signature in colon epithelial cells, and thus future risk of colorectal cancer.

Scutellaria barbata D. Don inhibits growth and induces apoptosis by suppressing IL-6-inducible STAT3 pathway activation in human colorectal cancer cells

One of the most critical cellular signal transduction pathways known to malfunction in colorectal cancer is the interleukin-6/signal transducer and activator of transcription 3 (IL-6/STAT3) pathway. Scutellaria barbata D. Don (SB) is well-known traditional medicine in China that targets STAT3 signaling, and it has long been used to treat various types of cancer; however, the precise mechanism of its antitumor activity remains largely unclear. In order to further elucidate this underlying mechanism, an ethanol extract of SB (EESB) in cancer treatment. The aim of the present study was to evaluate the effects of EESB on the IL-6-inducible STAT3 pathway. We tested the dose-response association between EESB, IL-6-induced proliferaion and apoptosis using an MTT assay, colony formation and flow cytometry analysis in vitro. In addition, caspase-9 and caspase-3 activation was determined using a colorimetric assay, the activity of IL-6-induced STAT3 pathway was evaluated using western blot analysis, and the expression levels of cyclin D1, cyclin-dependent kinase 4, Bcl2 and Bcl2-associated X were determined using reverse transcription-polymerase chain reaction and western blot analysis. In the present study it was found that EESB could significantly inhibit the IL-6-mediated increase in STAT3 phosphorylation levels and transcriptional activity in HT-29 human colon carcinoma cells, resulting in the suppression of cell proliferation and the induction of apoptosis. In addition, treatment with EESB markedly inhibited the IL-6-induced upregulation of cyclin D1 and B-cell lymphoma-2, two key target genes of the STAT3 pathway. These results suggest that treatment with EESB could effectively inhibit the proliferation and promote the apoptosis of human colon carcinoma cells via modulation of the IL-6/STAT3 signaling pathway and its target genes.

Vitamin D3 enhances the tumouricidal effects of 5-Fluorouracil through multipathway mechanisms in azoxymethane rat model of colon cancer

Background

Vitamin D3 and its analogues have recently been shown to enhance the anti-tumour effects of 5- Fluorouracil (5-FU) both in vitro and in xenograft mouse model of colon cancer. This study measured the potential mechanism(s) by which vitamin D3 could synergise the tumouricidal activities of 5-FU in azoxymethane (AOM) rat model of colon cancer.

Methods

Seventy-five male Wistar rats were divided equally into 5 groups: Control, AOM, AOM-treated by 5-FU (5-FU), AOM-treated by vitamin D3 (VitD3), and AOM-treated by 5-FU + vitamin D3 (5-FU/D). The study duration was 15 weeks. AOM was injected subcutaneously for 2 weeks (15 mg/kg/week). 5-FU was injected intraperitoneally in the 9th and 10th weeks post AOM (8 total injections were given: 12 mg/kg/day for 4 successive days, then 6 mg/kg every other day for another 4 doses) and oral vitamin D3 (500 IU/rat/day; 3 days/week) was given from week 7 post AOM till the last week of the study. The colons were collected following euthanasia for gross and histopathological examination. The expression of β-catenin, transforming growth factor-β1 (TGF-β1), TGF-β type 2 receptor (TGF-βR2), smad4, inducible nitric oxide synthase (iNOS), and heat shock protein-90 (HSP-90) proteins was measured by immunohistochemistry. In colonic tissue homogenates, quantitative RT-PCR was used to measure the mRNA expression of Wnt, β-catenin, Dickkopf-1 (DKK-1) and cyclooxygenase-2 (COX-2) genes, while ELISA was used to measure the concentrations of TGF-β1, HSP-90 and COX-2 proteins.

Results

Monotherapy with 5-FU or vitamin D3 significantly decreased the number of grown tumours induced by AOM (P < 0.05); however, their combination resulted in more significant tumouricidal effects (P < 0.05) compared with monotherapy groups. Mechanistically, vitamin D3/5-FU co-therapy significantly decreased the expression of Wnt, β-catenin, iNOS, COX-2 and HSP-90 and significantly increased the expression of DKK-1, TGF-β1, TGF-βR2, smad4 (P < 0.05), in comparison with their corresponding monotherapy groups.

Conclusions

Vitamin D3 and 5-FU synergise together and exhibit better anticancer effects by modulating Wnt/β-catenin pathway, TGF-β1 signals, iNOS, COX-2 and HSP-90. Further studies are required to illustrate the clinical value of vitamin D supplementation during the treatment of colon cancer with 5-FU in human patients.