APC-dependent suppression of colon carcinogenesis by PPARgamma

Probiotics in colorectal cancer prevention and therapy: mechanisms, benefits, and challenges

Colorectal cancer (CRC) is the third most diagnosed cancer and the second leading cause of morbidity worldwide. In Algeria, it ranks second in mortality-related deaths. Poor lifestyle, characterized by a low-fiber diet, insufficient physical activity, tobacco use, and alcohol consumption, is strongly associated with an increased risk of developing this disease. Probiotics have demonstrated anti-inflammatory and antitumor effects in preclinical and clinical studies. The World Health Organization (WHO) and European Food Safety Authority (EFSA) have recognized their safety and effectiveness, classifying them as Generally Recognized as Safe (GRAS) and Qualified Presumption of Safety (QPS), respectively. Probiotics exhibit immunomodulatory effects and maintain the equilibrium of the gut microbiota. However, the evidence for their clinical efficacy is inadequate, and additional research is requisite to establish them as therapeutic agents rather than simply as dietary supplements. Although probiotics are, in most cases, safe, high-risk patients should exercise caution due to the potential risk of infection. This review examines the current knowledge on probiotic strains, their therapeutic potential for colorectal cancer, limitations, and areas where further research is imperative to improve their efficacy.

Mechanic evaluation of Wu-Mei-Pill on colitis-associated colorectal cancer: An integrated transcriptomics, metabolomics, and experimental validation study

BACKGROUND

Chronic intestinal inflammatory diseases play a crucial role in the onset of colorectal cancer (CRC). Effectively impeding the progression of colitis-associated colorectal cancer (CAC) can be instrumental in hindering CRC development. Wu-Mei-Pill (WMP), a formulation comprising various herbal extracts, is clinically employed for CAC treatment, yet the underlying mechanism of WMP's efficacy in CAC remains unclear. Our study firstly demonstrated the effects and mechanisms of WMP on transcriptional and metabolic levels based on integrated transcriptomics and untargeted metabolomics and relative experimental validations.

MATERIALS AND METHODS

A CAC mouse model was established through a single injection of azoxymethane (AOM) followed by intermittent dextran sodium sulfate (DSS) intervention, with subsequent WMP administration. Initially, the therapeutic impact of WMP on the CAC model was assessed by observing survival rate, body weight change, colon length, tumor number, tumor load, and pathological changes in the colon tissue of CAC mice post-WMP intervention. Subsequently, differential genes and metabolites in the colorectal tissue of CAC mice following WMP intervention were identified through transcriptomics and non-targeted metabolomics. Finally, the influence of WMP on the peroxisome proliferator activated receptor (PPAR) pathway, Wnt pathway, and CC motif chemokine ligand 3 (CCL3)/ CC motif chemokine receptor 1 (CCR1) axis in CAC mice was verified through western blot, immunofluorescence, and ELISA based on the results of transcriptomics and non-targeted metabolomics.

RESULTS

WMP intervention enhanced survival, alleviated body weight loss, shortened colon length, tumor occurrence, and pathological changes in the colorectal tissue of CAC mice, such as glandular damage, tumourigenesis, and inflammatory cell infiltration. Transcriptomic and non-targeted metabolomic results revealed that WMP intervention up-regulated the expression of key regulatory mechanisms of fatty acid oxidation PPAR pathway-related genes (Pparg, Ppara, Cpt1a, and Acadm) and metabolites (L-carnitine and L-palmitoylcarnitine). Additionally, it down-regulated Wnt pathway-related genes (Wnt3, Axin2, Tcf7, Mmp7, Lgr5, Wnt5a, Fzd6, Wnt7b, Lef1, and Fzd10 etc.) and pro-inflammatory related genes (Il1b, Il6, Il17a, Ccl3, and Ccr1 etc.). Experimental validation demonstrated that WMP up-regulated PPAR pathway-related proteins [PPARγ, PPARα, carnitine palmitoyltransferase 1A (CPT1A), and acyl-CoA dehydrogenase medium chain (ACADM)] in the colorectal tissue of CAC mice. It also down-regulated Wnt pathway-related proteins [β-catenin, T-cell factor (TCF), lymphoid enhancer-binding factor (LEF), and matrix metallopeptidase 7 (MMP7)], inhibited the nuclear translocation of the key transcription factor β-catenin in the Wnt pathway, and suppressed epithelial-to-mesenchymal transition (EMT) activation induced by the Wnt pathway (up-regulated E-cadherin and down-regulated Vimentin). Furthermore, WMP intervention reduced pro-inflammatory factors [interleukin (IL)-6, IL-1β, and IL-17A] and decreased CCL3/CCR1 axis factors, including CCL3 protein levels and diminished F4/80+CCR1+ positive expressed cells.

CONCLUSION

WMP significantly inhibits CAC tumorigenesis by up-regulating PPARα-mediated fatty acid oxidation, inhibiting the Wnt signaling pathway-mediated EMT, and suppressing CCL3/CCR1-mediated inflammatory responses.

Peroxisome proliferator-activated receptors as therapeutic target for cancer

Peroxisome proliferator-activated receptors (PPARs) are transcription factors belonging to the nuclear receptor family. There are three subtypes of PPARs, including PPAR-α, PPAR-β/δ and PPAR-γ. They are expressed in different tissues and act by regulating the expression of target genes in the form of binding to ligands. Various subtypes of PPAR have been shown to have significant roles in a wide range of biological processes including lipid metabolism, body energy homeostasis, cell proliferation and differentiation, bone formation, tissue repair and remodelling. Recent studies have found that PPARs are closely related to tumours. They are involved in cancer cell growth, angiogenesis and tumour immune response, and are essential components in tumour progression and metastasis. As such, they have become a target for cancer therapy research. In this review, we discussed the current state of knowledge on the involvement of PPARs in cancer, including their role in tumourigenesis, the impact of PPARs in tumour microenvironment and the potential of using PPARs combinational therapy to treat cancer by targeting essential signal pathways, or as adjuvants to boost the effects of current chemo and immunotherapies. Our review highlights the complexity of PPARs in cancer and the need for a better understanding of the mechanism in order to design effective cancer therapies.

PPARG activation promotes the proliferation of colorectal cancer cell lines and enhances the antiproliferative effect of 5-fluorouracil

BACKGROUND

Peroxisome proliferator-activated receptor gamma (PPARG) is a member of the nuclear receptor family. It is involved in the regulation of adipogenesis, lipid metabolism, insulin sensitivity, vascular homeostasis and inflammation. In addition, PPARG agonists, known as thiazolidinediones, are well established in the treatment of type 2 diabetes mellitus. PPARGs role in cancer is a matter of debate, as pro- and anti-tumour properties have been described in various tumour entities. Currently, the specific role of PPARG in patients with colorectal cancer (CRC) is not fully understood.

MATERIAL AND METHODS

The prognostic impact of PPARG expression was investigated by immunohistochemistry in a case-control study using a matched pair selection of CRC tumours (n = 246) with either distant metastases to the liver (n = 82), lung (n = 82) or without distant metastases (n = 82). Its effect on proliferation as well as the sensitivity to the chemotherapeutic drug 5-fluorouracil (5-FU) was examined after activation, inhibition, and transient gene knockdown of PPARG in the CRC cell lines SW403 and HT29.

RESULTS

High PPARG expression was significantly associated with pulmonary metastasis (p = 0.019). Patients without distant metastases had a significantly longer overall survival with low PPARG expression in their tumours compared to patients with high PPARG expression (p = 0.045). In the pulmonary metastasis cohort instead, a trend towards longer survival was observed for patients with high PPARG expression in their tumour (p = 0.059). Activation of PPARG by pioglitazone and rosiglitazone resulted in a significant dose-dependent increase in proliferation of CRC cell lines. Inhibition of PPARG by its specific inhibitor GW9662 and siRNA-mediated knockdown of PPARG significantly decreased proliferation. Activating PPARG significantly increased the CRC cell lines sensitivity to 5-FU while its inhibition decreased it.

CONCLUSION

The prognostic effect of PPARG expression depends on the metastasis localization in advanced CRC patients. Activation of PPARG increased malignancy associated traits such as proliferation in CRC cell lines but also increases sensitivity towards the chemotherapeutic agent 5-FU. Based on this finding, a combination therapy of PPARG agonists and 5-FU-based chemotherapy constitutes a promising strategy which should be further investigated.

Galectin-9 in cancer therapy: from immune checkpoint ligand to promising therapeutic target

Galectin-9 (Gal-9) is a vital member of the galectin family, functioning as a multi-subtype galactose lectin with diverse biological roles. Recent research has revealed that Gal-9's interaction with tumors is an independent factor that influences tumor progression. Furthermore, Gal-9 in the immune microenvironment cross-talks with tumor-associated immune cells, informing the clarification of Gal-9's identity as an immune checkpoint. A thorough investigation into Gal-9's role in various cancer types and its interaction with the immune microenvironment could yield novel strategies for subsequent targeted immunotherapy. This review focuses on the latest advances in understanding the direct and indirect cross-talk between Gal-9 and hematologic malignancies, in addition to solid tumors. In addition, we discuss the prospects of Gal-9 in tumor immunotherapy, including its cross-talk with the ligand TIM-3 and its potential in immune-combination therapy.

Therapeutic Potential of a Small-Molecule STAT3 Inhibitor in a Mouse Model of Colitis

BACKGROUND AND AIMS

Inflammatory bowel disease (IBD) predisposes to colorectal cancer (CRC). In the current studies, we used the dextran sodium sulfate (DSS) murine model of colitis, which is widely used in preclinical studies, to determine the contribution of STAT3 to IBD. STAT3 has two isoforms: (STAT3 α; which has pro-inflammatory and anti-apoptotic functions, and STAT3β; which attenuates the effects of STAT3α). In the current study, we determined the contribution of STAT3 to IBD across all tissues by examining DSS-induced colitis in mice that express only STAT3α and in mice treated with TTI-101, a direct small-molecule inhibitor of both isoforms of STAT3.

METHODS

We examined mortality, weight loss, rectal bleeding, diarrhea, colon shortening, apoptosis of colonic CD4+ T-cells, and colon infiltration with IL-17-producing cells following 7-day administration of DSS (5%) to transgenic STAT3α knock-in (STAT3β-deficient; ΔβΔβ) mice and wild-type (WT) littermate cage control mice. We also examined the effect of TTI-101 on these endpoints in DSS-induced colitis in WT mice.

RESULTS

Each of the clinical manifestations of DSS-induced colitis examined was exacerbated in ΔβΔβ transgenic versus cage-control WT mice. Importantly, TTI-101 treatment of DSS-administered WT mice led to complete attenuation of each of the clinical manifestations and also led to increased apoptosis of colonic CD4+ T cells, reduced colon infiltration with IL-17-producing cells, and down-modulation of colon mRNA levels of STAT3-upregulated genes involved in inflammation, apoptosis resistance, and colorectal cancer metastases.

CONCLUSIONS

Thus, small-molecule targeting of STAT3 may be of benefit in treating IBD and preventing IBD-associated colorectal cancer.

RCAN1-mediated calcineurin inhibition as a target for cancer therapy

Cancer is the leading cause of mortality worldwide. Regulator of calcineurin 1 (RCAN1), as a patent endogenous inhibitor of calcineurin, plays crucial roles in the pathogenesis of cancers. Except for hypopharyngeal and laryngopharynx cancer, high expression of RCAN1 inhibits tumor progression. Molecular antitumor functions of RCAN1 are largely dependent on calcineurin. In this review, we highlight current research on RCAN1 characteristics, and the interaction between RCAN1 and calcineurin. Moreover, the dysregulation of RCAN1 in various cancers is reviewed, and the potential of targeting RCAN1 as a new therapeutic approach is discussed.

Effects of matcha tea extract on cell viability and peroxisome proliferator-activated receptor γ expression on T47D breast cancer cells

PURPOSE

In the following work, we investigated the nuclear peroxisome proliferator-activated receptor gamma (PPARγ)-dependent proliferation behavior of breast cancer cells after stimulation with matcha green tea extract (MTE).

METHODS

T47D cells were stimulated with MTE at concentrations of 5, 10 and 50 µg/ml. Cell viability was assessed using a WST-1 assay after an incubation time of 72 h. PPARγ expression was quantified at the gene level by real-time polymerase chain reaction (PCR). A western blot (WB) was carried out for the qualitative assessment of the expression behavior of on a protein level.

RESULTS

The WST-1 test showed a significant inhibition of viability in T47D cells after 72 h at 5, 10 and 50 µg/ml. The PCR showed an overexpression of PPARγ in T47D cells in all concentrations. At the concentration of 50 µg/ml the expression was significantly increased (p < 0.05). The WB demonstrated a significant quantitative increase of PPARγ at protein level with MTE concentrations of 10 and 50 µg/ml. In addition, there was a negative correlation between the overexpression of PPAR γ and the inhibition of proliferation.

CONCLUSION

MTE decreases the cell viability of T47D cells and furthermore leads to an overexpression of PPARγ on protein and mRNA level.

Pronounced Enhancement in Radiosensitization of Esophagus Cancer Cultivated in Docosahexaenoic Acid via the PPAR -γ Activation

Docosahexaenoic acid (DHA) has been reported to suppress the tumor growth and improve prognosis and has been used to cooperate with many other chemotherapy medicines. Up to now, surveys focused on the Interaction between DHA and radiation are relatively modest. Our study sought to evaluate the radiosensitivity changes caused by DHA on esophageal cancer cells. We selected TE-1 and TE-10 esophagus cancer cells as models and performed routine cell proliferation assay and cloning assay to detect the impact of DHA combined with X-ray. We used cell cycle assay, lipid peroxidation assay, comet assay, and apoptosis assay to unearth the potential causes. We also launched a mouse transplanted tumor experiment to verify the synergetic effect of DHA and irradiation. Finally, a western blot assay was used to find a novel mechanism. As a result, DHA improved TE-1 and TE-10 radiosensitivity in vivo and in vitro. What's more, PPAR-γ expression increased due to the DHA supplement. Inhibiting PPAR-γ could attenuate benefits brought out by DHA somehow. Due to its explicit usage and convenience, DHA would serve as an adjuvant therapy before radiotherapy if the clinical trials indicated positive.

Prognostic value of LINC02560 in colorectal cancer correlates with tumor microenvironment immunity

Background: LINC02560 is a new 477 bp long non-coding RNA located in 19q13.43. However, the expression of LINC02560 in colorectal cancer (CRC) has not been reported, and its correlation with tumor development and function is still unclear. Methods: The expression of LINC02560 in CRC was first analyzed in the cancer genome atlas (TCGA) combined with The Genotype-Tissue Expression(GTEx) databases and then validated by clinical CRC samples and cell lines. The association between LINC02560 expression and clinicopathologic variables was analyzed by the Wilcoxon Rank SUM test. Cox regression analysis and Kaplan-Meier plots were used to assess the prognostic value of LINC02560 in CRC. The correlation between the expression level of LINC02560 and the 24 immune cells in tumor microenvironment (TME) was analyzed by single sample gene set enrichment analysis (ssGSEA). Gene set enrichment analysis (GSEA) was conducted to detect potential biological processes associated with LINC02560 in CRC. Results: LINC02560 was significantly up-regulated in CRC in comparison to normal samples. There are significant differences in the expression of LINC02560 in different subgroups of N stage, M stage, carcinoembryonic antigen (CEA) level, residual tumor, TP53 status and pathological stage. The high LINC02560 expression indicated poor overall survival (OS) and progress free interval (PFI) in patients with CRC. Moreover, the multivariate Cox analysis demonstrated that the expression of LINC02560 was an independent prognosis-predicting factor for OS in CRC patients. GSEA indicated that high expression of LINC02560 was involved in MAPK, Wnt, and PPAR signaling pathways and participated in humoral immune processes. We also identified that LINC02560 expression had a negative correlation with 4 kinds of immune cells. Conclusions: In summary, our research results indicate that LINC02560 may be a potential prognostic biomarker. It is involved in the occurrence and development of CRC and may affect the prognosis of CRC patients by regulating immune cells in the TME.

Pparγ1 Facilitates ErbB2-Mammary Adenocarcinoma in Mice

HER2, which is associated with clinically aggressive disease, is overexpressed in 15-20% of breast cancers (BC). The host immune system participates in the therapeutic response of HER2⁺ breast cancer. Identifying genetic programs that participate in ErbB2-induced tumors may provide the rational basis for co-extinction therapeutic approaches. Peroxisome proliferator-activated receptor γ (PPARγ), which is expressed in a variety of malignancies, governs biological functions through transcriptional programs. Herein, genetic deletion of endogenous Pparγ1 restrained mammary tumor progression, lipogenesis, and induced local mammary tumor macrophage infiltration, without affecting other tissue hematopoietic stem cell pools. Endogenous Pparγ1 induced expression of both an EphA2-Amphiregulin and an inflammatory INFγ and Cxcl5 signaling module, that was recapitulated in human breast cancer. Pparγ1 bound directly to growth promoting and proinflammatory target genes in the context of chromatin. We conclude Pparγ1 promotes ErbB2-induced tumor growth and inflammation and represents a relevant target for therapeutic coextinction. Herein, endogenous Pparγ1 promoted ErbB2-mediated mammary tumor onset and progression. PPARγ1 increased expression of an EGF-EphA2 receptor tyrosine kinase module and a cytokine/chemokine 1 transcriptional module. The induction of a pro-tumorigenic inflammatory state by Pparγ1 may provide the rationale for complementary coextinction programs in ErbB2 tumors.

Peroxisome Proliferator-Activated Receptors as Molecular Links between Caloric Restriction and Circadian Rhythm

The circadian rhythm plays a chief role in the adaptation of all bodily processes to internal and environmental changes on the daily basis. Next to light/dark phases, feeding patterns constitute the most essential element entraining daily oscillations, and therefore, timely and appropriate restrictive diets have a great capacity to restore the circadian rhythm. One of the restrictive nutritional approaches, caloric restriction (CR) achieves stunning results in extending health span and life span via coordinated changes in multiple biological functions from the molecular, cellular, to the whole-body levels. The main molecular pathways affected by CR include mTOR, insulin signaling, AMPK, and sirtuins. Members of the family of nuclear receptors, the three peroxisome proliferator-activated receptors (PPARs), PPARα, PPARβ/δ, and PPARγ take part in the modulation of these pathways. In this non-systematic review, we describe the molecular interconnection between circadian rhythm, CR-associated pathways, and PPARs. Further, we identify a link between circadian rhythm and the outcomes of CR on the whole-body level including oxidative stress, inflammation, and aging. Since PPARs contribute to many changes triggered by CR, we discuss the potential involvement of PPARs in bridging CR and circadian rhythm.

Falcarindiol Purified From Carrots Leads to Elevated Levels of Lipid Droplets and Upregulation of Peroxisome Proliferator-Activated Receptor-γ Gene Expression in Cellular Models

Falcarindiol (FaDOH) is a cytotoxic and anti-inflammatory polyacetylenic oxylipin found in food plants of the carrot family (Apiaceae). FaDOH has been shown to activate PPARγ and to increase the expression of the cholesterol transporter ABCA1 in cells, both of which play an important role in lipid metabolism. Thus, a common mechanism of action of the anticancer and antidiabetic properties of FaDOH may be due to a possible effect on lipid metabolism. In this study, the effect of sub-toxic concentration (5 μM) of FaDOH inside human mesenchymal stem cells (hMSCs) was studied using white light microscopy and Raman imaging. Our results show that FaDOH increases lipid content in the hMSCs cells as well as the number of lipid droplets (LDs) and that this can be explained by increased expression of PPARγ2 as shown in human colon adenocarcinoma cells. Activation of PPARγ can lead to increased expression of ABCA1. We demonstrate that ABCA1 is upregulated in colorectal neoplastic rat tissue, which indicates a possible role of this transporter in the redistribution of lipids and increased formation of LDs in cancer cells that may lead to endoplasmic reticulum stress and cancer cell death.

Peroxisome Proliferator-Activated Receptors and Caloric Restriction-Common Pathways Affecting Metabolism, Health, and Longevity

Caloric restriction (CR) is a traditional but scientifically verified approach to promoting health and increasing lifespan. CR exerts its effects through multiple molecular pathways that trigger major metabolic adaptations. It influences key nutrient and energy-sensing pathways including mammalian target of rapamycin, Sirtuin 1, AMP-activated protein kinase, and insulin signaling, ultimately resulting in reductions in basic metabolic rate, inflammation, and oxidative stress, as well as increased autophagy and mitochondrial efficiency. CR shares multiple overlapping pathways with peroxisome proliferator-activated receptors (PPARs), particularly in energy metabolism and inflammation. Consequently, several lines of evidence suggest that PPARs might be indispensable for beneficial outcomes related to CR. In this review, we present the available evidence for the interconnection between CR and PPARs, highlighting their shared pathways and analyzing their interaction. We also discuss the possible contributions of PPARs to the effects of CR on whole organism outcomes.

Landscape of transcriptome variations uncovering known and novel driver events in colorectal carcinoma

We focused on an integrated view of genomic changes in Colorectal cancer (CRC) and distant normal colon tissue (NTC) to test the effectiveness of expression profiling on identification of molecular targets. We performed transcriptome on 16 primary coupled CRC and NTC tissues. We identified pathways and networks related to pathophysiology of CRC and selected potential therapeutic targets. CRC cells have multiple ways to reprogram its transcriptome: a functional enrichment analysis in 285 genes, 25% mutated, showed that they control the major cellular processes known to promote tumorigenesis. Among the genes showing alternative splicing, cell cycle related genes were upregulated (CCND1, CDC25B, MCM2, MCM3), while genes involved in fatty acid metabolism (ACAAA2, ACADS, ACAT1, ACOX, CPT1A, HMGCS2) were downregulated. Overall 148 genes showed differential splicing identifying 17 new isoforms. Most of them are involved in the pathogenesis of CRC, although the functions of these variants remain unknown. We identified 2 in-frame fusion events, KRT19-KRT18 and EEF1A1-HSP90AB1, encoding for chemical proteins in two CRC patients. We draw a functional interactome map involving integrated multiple genomic features in CRC. Finally, we underline that two functional cell programs are prevalently deregulated and absolutely crucial to determinate and sustain CRC phenotype.

Drug Combinatorial Therapies for the Treatment of KRAS Mutated Lung Cancers

KRAS is the most common oncogene to be mutated in lung cancer, and therapeutics directly targeting KRAS have proven to be challenging. The mutations of KRAS are associated with poor prognosis, and resistance to both adjuvant therapy and targeted EGFR TKI. EGFR TKIs provide significant clinical benefit for patients whose tumors bear EGFR mutations. However, tumors with KRAS mutations rarely respond to the EGFR TKI therapy. Thus, combination therapy is essential for the treatment of lung cancers with KRAS mutations. EGFR TKI combined with inhibitors of MAPKs, PI3K/mTOR, HDAC, Wee1, PARP, CDK and Hsp90, even miRNAs and immunotherapy, were reviewed. Although the effects of the combination vary, the combined therapeutics are one of the best options at present to treat KRAS mutant lung cancer.

PPARG rs3856806 C>T Polymorphism Increased the Risk of Colorectal Cancer: A Case-Control Study in Eastern Chinese Han Population

Purpose: Functional variants in the peroxisome proliferator-activated receptor gamma (PPARG) and PPARG co-activator 1 (PPARGC1) family (e.g., PPARGC1A and PPARGC1B) genes were predicted to confer susceptibility to colorectal cancer (CRC). The aim of the present study was to explore the relationship between PPARG, PPARGC1A, PPARGC1B polymorphism and the risk of CRC.

Patients and methods: We conducted a case-control study with 1,003 CRC cases and 1,303 controls. We selected the PPARG rs3856806 C>T, PPARGC1A rs2970847 C>T, rs8192678 C>T, rs3736265 G>A and PPARGC1B rs7732671 G>C and rs17572019 G>A SNPs to assess the relationship between PPARG, PPARGC1A, PPARGC1B their variants and risk of CRC.

Results: We found that the PPARG rs3856806 C>T polymorphism increased the risk of CRC (TT vs. CC: adjusted OR, 1.59, 95% CI 1.08–2.35, P = 0.020; TT/CT vs. CC: adjusted OR, 1.26; 95% CI 1.06–1.49; P = 0.009 and TT vs. CC/CT: adjusted OR, 1.54; 95% CI 1.05–2.26; P = 0.028), even after a Bonferroni correction test. The stratified analysis revealed that the PPARG rs3856806 C>T polymorphism also increased the risk of CRC, especially in male, ≥61 years old, never smoking, never drinking, BMI ≥ 24 kg/m², colon cancer and rectum cancer subgroups.

Conclusion: Our findings highlight that the PPARG rs3856806 C>T polymorphism may increase the risk of CRC. In the future larger sample size case-control studies with a detailed functional assessment are needed to further determine the relationship of the PPARG rs3856806 C>T polymorphism with CRC risk.

n-6 Linoleic Acid Induces Epigenetics Alterations Associated with Colonic Inflammation and Cancer

The farnesoid-X-receptor (FXR) protects against inflammation and cancer of the colon through maintenance of intestinal bile acid (BA) homeostasis. Conversely, higher levels of BA and cyclooxygenase-2 (COX-2) are risk factors for inflammation and cancer of the colon. In the United States, n-6 linoleic acid (LA) is the most commonly used dietary vegetable fat. Metabolism of n-6 fatty acids has been linked to a higher risk of intestinal cancer. The objectives of this study were to investigate in colonic mucosa the effects of a high-fat diet rich in LA (n-6HFD) on CpG methylation of Fxr and prostaglandin-endoperoxide synthase-2 (Ptsg-2) genes, and the impact on the expression of tumor suppressor adenomatous polyposis Coli (Apc) and proliferative cyclin D1 (Ccnd1) genes. Weaned C57BL/6J male mice were fed for 6 weeks either an n-6HFD containing 44% energy (44%E) from 22% safflower oil (SO, 76% LA by weight) or a 13% energy (13%E) control diet (Control) from SO (5% by weight). Mice fed the n-6HFD had reduced (60%) Fxr promoter CpG methylation and increased (~50%) Fxr mRNA. The expression of FXR-target ileal bile acid-binding protein (Ibabp), small heterodimer protein (Shp), and anti-inflammatory peroxisome proliferator-activated-γ1 genes was increased. The n-6HFD reduced Ptgs-2 CpG methylation, increased the expression of Cox-2, and increased Apc CpG methylation in colonic mucosa. Accordingly, reduced expression of Apc was coupled to accumulation of c-JUN and Ccnd1, respectively cofactor and gene targets for the β-catenin/Wnt signaling pathway. Finally, the n-6HFD reduced the expression of histone deacetylase-1 while favoring the accumulation of acetylated histone 3. We conclude that an n-6HFD epigenetically modifies Fxr, leading to the activation of downstream factors that participate in BA homeostasis. However, epigenetic activation of Ptsg-2 coupled with silencing of Apc and accumulation of C-JUN and Ccnd1 may increase the risk of inflammation and cancer of the colon.

β-catenin and PPAR-γ levels in bone marrow of myeloproliferative neoplasm: an immunohistochemical and ultrastructural study

In accordance with increased proliferation in myeloproliferative neoplasm (MPN), the goal is to evaluate the immunoexpression of: β-catenin, PPAR-γ and Ki67 protein, to compare them with bone marrow ultrastructural characteristics in patients with MPN. Immunoexpression and electron microscopy of bone marrow was analyzed in 30 Ph-negative MPN patients, including per 10 patients with polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF). The quantity of β-catenin immunoreactive cells was significantly higher in PV then in ET (p < 0.01) or PMF group of patients (p < 0.01) and also in ET versus PMF group of patients (p < 0.01). Erythroid lineage showed absent β-catenin staining without immunoreactivity in nucleus. In contrast, immunoreactivity for PPAR-γ was localized mostly in megakaryocytes and the highest number of PPAR-γ immunopositive cells was detected in PMF group of patients. In addition, the proliferative Ki67 index was significantly increased in the PMF and PV patients compared to patients with ET. Also, the megakaryocytes showed abnormal maturation in PMF group of patients as determined by ultrastructural analysis. These results indicated that PV dominantly expressed β-catenin and proliferation marker Ki67 in bone marrow, while PMF is linked preferentially to PPAR-γ immunopositive megakaryocytes characterized by abnormal maturation.

p-21 Activated Kinase as a Molecular Target for Chemoprevention in Diabetes

Hypothesis: Anti-diabetic drugs modulate p-21 activated kinase (PAK) signaling. Introduction: Type 2 diabetes mellitus (T2DM) is a chronic inflammatory disease associated with increased cancer risk. PAK signaling is implicated in cellular homeostasis when regulated, and cancer when unrestrained. Recent reports provided a role for PAK signaling in glucose homeostasis, but the role of PAKs in the pathogenesis of T2DM is unknown. Here, we performed a mini-meta-analysis to explore if anti-diabetic drugs modify PAK signaling pathways, and provide insight regarding modulation of these pathways, to potentially reduce diabetes-associated cancer risk. Methods: PAK interacting partners in T2DM were identified using the online STRING database. Correlation studies were performed via systematic literature review to understand the effect of anti-diabetic drugs on PAK signaling. A mini-meta-analysis correlated multiple clinical studies and revealed the overall clinical response rate and percentage of adverse events in piogliazone (n = 53) and metformin (n = 91) treated patients with PAK-associated diseases. Results: A total of 30 PAK interacting partners were identified (10: reduced beta-cell mass; 10: beta-cell dysfunction; 10: obesity-insulin resistance), which were highly associated with Wnt, and G-protein signaling. The anti-diabetic drug metformin activated signaling pathways upstream; whereas pioglitazone inhibited pathways downstream of PAK. Overall, clinical response upon pioglitazone treatment was 53%. Seventy-nine percent of pioglitazone and 75% of metformin treated patients had adverse events. Pioglitazone reduced molecular-PAK biomarkers of proliferation (Ki67 and CyclinD1), and metformin had the opposite effect. Conclusions: PAK signaling in T2DM likely involves Wnt and G-protein signaling, which may be altered by the anti-diabetic drugs metformin and pioglitazone. Apart from the therapeutic limitations of adverse events, pioglitazone may be promising in chemoprevention. However long-term multi-centered studies, which initiate pioglitazone treatment early will be required to fully assess the full potential of these drugs.

The E3 ubiquitin ligase TRIM25 regulates adipocyte differentiation via proteasome-mediated degradation of PPARγ

Peroxisome proliferator-activated receptor gamma (PPARγ) is a ligand-dependent transcription factor that regulates adipocyte differentiation and glucose homeostasis. The transcriptional activity of PPARγ is regulated not only by ligands but also by post-translational modifications (PTMs). In this study, we demonstrate that a novel E3 ligase of PPARγ, tripartite motif-containing 25 (TRIM25), directly induced the ubiquitination of PPARγ, leading to its proteasome-dependent degradation. During adipocyte differentiation, both TRIM25 mRNA and protein expression significantly decreased and negatively correlated with the expression of PPARγ. The stable expression of TRIM25 reduced PPARγ protein levels and suppressed adipocyte differentiation in 3T3-L1 cells. In contrast, the specific knockdown of TRIM25 increased PPARγ protein levels and stimulated adipocyte differentiation. Furthermore, TRIM25-knockout mouse embryonic fibroblasts (MEFs) exhibited an increased adipocyte differentiation capability compared with wild-type MEFs. Taken together, these data indicate that TRIM25 is a novel E3 ubiquitin ligase of PPARγ and that TRIM25 is a novel target for PPARγ-associated metabolic diseases.

Relationship of PPARG, PPARGC1A, and PPARGC1B polymorphisms with susceptibility to hepatocellular carcinoma in an eastern Chinese Han population

Background

PPARG, PPARGC1A, and PPARGC1B polymorphisms may be implicated in the development of cancer.

Participants and methods

In this study, we selected PPARG rs1801282 C>G and rs3856806 C>T, PPARGC1A rs2970847 C>T, and PPARGC1B rs7732671 G>C and rs17572019 G>A single-nucleotide polymorphisms to explore the relationship between these polymorphisms and hepatocellular carcinoma (HCC) risk. A total of 584 HCC patients and 923 controls were enrolled.

Results

We found that PPARG rs1801282 C>G polymorphism was correlated with a decreased susceptibility of HCC (CG vs CC, adjusted OR 0.47, 95% CI 0.27-0.82, P=0.007; CG/GG vs CC, adjusted OR 0.52, 95% CI 0.31-0.88, P=0.015). However, PPARG rs3856806 C>T polymorphism was a risk factor for HCC (TT vs CC, adjusted OR 2.33, 95% CI 1.25-4.36, P=0.008; TT vs CT/CC, adjusted OR 2.26, 95% CI 1.22-4.17, P=0.010). In a subgroup analysis by chronic hepatitis B virus (HBV)-infection status, age, sex, alcohol use, and smoking status, a significant association between PPARG rs1801282 C>G polymorphism and a decreased risk of HCC in male, ≥53 years, never-smoking, never-drinking, and nonchronic HBV-infection-status subgroups was found. However, we found PPARG rs3856806 C>T polymorphism increased the risk of HCC in never-smoking, never-drinking, and nonchronic HBV-infection-status subgroups. Haplotype-comparison analysis indicated that C_rs1801282T_rs3856806C_rs2970847G_rs7732671G_rs17572019, C_rs1801282T_rs3856806T_rs2970847G_rs7732671G_rs17572019, and C_rs1801282C_rs3856806C_rs2970847C_rs7732671A_rs17572019 haplotypes increased the risk of HCC. PPARG C_rs1801282T_rs3856806 and G_rs1801282C_rs3856806 haplotypes also influenced the risk of HCC.

Conclusion

In conclusion, our findings suggest PPARG polymorphisms may influence the susceptibility of HCC. The PPARG, PPARGC1A, and PPARGC1B haplotypes might be associated with HCC risk.

PPARγ is dispensable for clear cell renal cell carcinoma progression

OBJECTIVE

Clear cell renal cell carcinoma (ccRCC) is a subtype of kidney cancer defined by robust lipid accumulation, which prior studies have indicated plays an important role in tumor progression. We hypothesized that the peroxisome proliferator-activated receptor gamma (PPARγ), detected in both ccRCC tumors and cell lines, promotes lipid storage in ccRCC and contributes to tumorigenesis in this setting. PPARγ transcriptionally regulates a number of genes involved in lipid and glucose metabolism in adipocytes, yet its role in ccRCC has not been described. The objective of this study was to elucidate endogenous PPARγ function in ccRCC cells.

METHODS AND RESULTS

Using chromatin immunoprecipitation followed by deep sequencing (ChIP-seq), we found that PPARγ and its heterodimer RXR occupy the canonical DR1 PPAR binding motif at approximately 1000 locations throughout the genome that can be subdivided into adipose-shared and ccRCC-specific sites. CRISPR-Cas9 mediated, loss-of-function studies determined that PPARγ is dispensable for viability, proliferation, and migration of ccRCC cells in vitro and in vivo. Also, surprisingly, PPARγ deletion had little effect on the robust lipid accumulation that typifies the "clear cell" phenotype of kidney cancer.

CONCLUSION

Our results suggest that PPARγ plays neither a tumor suppressive nor oncogenic role in advanced ccRCC, and thus single-agent therapeutics targeting PPARγ are unlikely to be effective for the treatment of this disease. The unique cistrome of PPARγ in ccRCC cells demonstrates the importance of cell type in determining the functions of PPARγ.

Enteric Microbiota⁻Gut⁻Brain Axis from the Perspective of Nuclear Receptors

Nuclear receptors (NRs) play a key role in regulating virtually all body functions, thus maintaining a healthy operating body with all its complex systems. Recently, gut microbiota emerged as major factor contributing to the health of the whole organism. Enteric bacteria have multiple ways to influence their host and several of them involve communication with the brain. Mounting evidence of cooperation between gut flora and NRs is already available. However, the full potential of the microbiota interconnection with NRs remains to be uncovered. Herewith, we present the current state of knowledge on the multifaceted roles of NRs in the enteric microbiota–gut–brain axis.

Identification of prostate cancer hub genes and therapeutic agents using bioinformatics approach

BACKGROUND

Prostate cancer (PCa) is the most common and the second leading cause of cancer-related death among men in America. As the molecular mechanism of PCa has not yet been completely discovered, identification of hub genes and potential drug of this disease is an important area of research that could provide new insights into exploring the mechanisms underlying PCa.

OBJECTIVE

The aim of this study was to identify potential biomarkers and novel drug for prostate cancer treatment.

METHODS

The differentially expressed genes (DEGs) between prostate cancer and normal cells were screened using microarray data obtained from the Gene Expression Omnibus database. Gene ontology (GO) and pathway enrichment analyses were performed in order to investigate the functions of DEGs, and the protein-protein interaction (PPI) network of the DEGs was constructed using the Cytoscape software. DEGs were then mapped to the connectivity map database to identify molecular agents associated with the underlying mechanisms of PCa.

RESULTS

Totally, 359 genes (155 upregulated and 204 downregulated genes) were found to be differentially expressed between prostate cancer and normal cells. The GO terms significantly enriched by DEGs included cell adhesion, protein binding involved in cell-cell adhesion, response to BMP, extracellular region and extracellular region part. KEGG pathway analysis showed that the most significant pathways included cell adhesion molecules (CAMs) and TGF-beta signaling pathway. The PPI network of up-regulated DEGs and down-regulated DEGs were established, respectively. While CDH1, BMP2, NKX3-1, PPARG and PRKAR2B were identified as the hub genes in the PPI network.

CONCLUSIONS

The BMP2, PPARG and PRKAR2B genes may therefore be potential biomarkers in the treatment of PCa. Additionally, the small molecular agent phenoxybenzamine may be a potential drug for PCa.

The Involvement of PPARs in the Peculiar Energetic Metabolism of Tumor Cells

Energy homeostasis is crucial for cell fate, since all cellular activities are strongly dependent on the balance between catabolic and anabolic pathways. In particular, the modulation of metabolic and energetic pathways in cancer cells has been discussed in some reports, but subsequently has been neglected for a long time. Meanwhile, over the past 20 years, a recovery of the study regarding cancer metabolism has led to an increasing consideration of metabolic alterations in tumors. Cancer cells must adapt their metabolism to meet their energetic and biosynthetic demands, which are associated with the rapid growth of the primary tumor and colonization of distinct metastatic sites. Cancer cells are largely dependent on aerobic glycolysis for their energy production, but are also associated with increased fatty acid synthesis and increased rates of glutamine consumption. In fact, emerging evidence has shown that therapeutic resistance to cancer treatment may arise from the deregulation of glucose metabolism, fatty acid synthesis, and glutamine consumption. Cancer cells exhibit a series of metabolic alterations induced by mutations that lead to a gain-of-function of oncogenes, and a loss-of-function of tumor suppressor genes, including increased glucose consumption, reduced mitochondrial respiration, an increase of reactive oxygen species, and cell death resistance; all of these are responsible for cancer progression. Cholesterol metabolism is also altered in cancer cells and supports uncontrolled cell growth. In this context, we discuss the roles of peroxisome proliferator-activated receptors (PPARs), which are master regulators of cellular energetic metabolism in the deregulation of the energetic homeostasis, which is observed in cancer. We highlight the different roles of PPAR isotypes and the differential control of their transcription in various cancer cells.

Genome-wide analysis of long noncoding RNA and mRNA co-expression profile in intrahepatic cholangiocarcinoma tissue by RNA sequencing

Long noncoding RNAs (lncRNAs), which are pervasively transcribed in the genome, are emerging in molecular biology as crucial regulators of cancer. RNA-seq data were downloaded from GEO of NCBI and further analyzed to identify novel targets in intrahepatic cholangiocarcinoma (iCCA). We investigated differences in lncRNA and mRNA profiles between 7 pairs of iCCA and adjacent normal tissues. 230 lncRNAs were differentially expressed more than four-fold change in iCCA tissues. Among these, 97 were upregulated and 133 downregulated relatively to normal tissues. Moreover, 169 lncRNAs and 597 mRNAs formed the lncRNA-mRNA co-expression network which consist 766 network nodes and 769 connection edges. Bioinformatics analysis identified these dysregulated lncRNAs were associated with cholesterol homeostasis, insoluble fraction and lipid binding activity and were enriched in complement and coagulation cascades and PPAR signaling pathway. These results uncovered the landscape of iCCA-associated lncRNAs and co-expression network, providing insightful information about dysregulated lncRNAs in iCCA.

Anti-leukemic effects of PPARγ ligands

The peroxisome proliferator-activated receptor (PPAR) γ, a subtype of PPARs, is a member of the nuclear receptor family. PPARγ and its ligands contribute to various types of diseases including cancer. Given that currently developed therapies against leukemia are not very effective or safe, PPARγ ligands have been shown to be a new class of compounds with the potential to treat hematologic malignancies, particularly leukemia. The capability of PPARγ ligands to induce apoptosis, inhibit proliferation, and promote differentiation of leukemia cells suggests it has significant potential as a drug against leukemia. However, the specific mechanisms and molecules involved are not well-understood, although a number of PPARγ ligands with anti-leukemic effects have been identified. This may explain why PPARγ ligands have not been widely evaluated in clinical trials. To fill the gaps in the lack of understanding of specific anti-leukemic processes of PPARγ ligands and further adapt these molecules as anti-leukemic agents, this review describes previous studies of the anti-leukemic effects of PPARγ ligands.

Peroxisome proliferator activating receptor-γ and the podocyte

Over the past two decades it has become clear that the glomerular podocyte is a key cell in preventing albuminuria, kidney failure and cardiovascular morbidity. Understanding the key pathways that protect the podocyte in times of glomerular stress, which can also be therapeutically manipulated, are highly attractive. In the following review we assess the evidence that the peroxisome proliferator activating receptor (PPAR) agonists are beneficial for podocyte and kidney function with a focus on PPAR-γ. We explain our current understanding of the mechanisms of action of these agonists and the evidence they are beneficial in diabetic and non-diabetic kidney disease. We also outline why these drugs have not been widely used for kidney disease in the past but they may be in the future.

Alpha-Tocopherol prevents esophageal squamous cell carcinoma by modulating PPARγ-Akt signaling pathway at the early stage of carcinogenesis

The poor prognosis of esophageal squamous cell carcinoma (ESCC) emphasizes the urgent need to better understand the carcinogenesis and develop prevention strategies. Previous studies have highlighted the potential of using Vitamin E (tocopherols) for cancer chemoprevention, but the preventive activity of α-Tocopherol against ESCC remains to be elucidated. Our data showed that early-stage supplementation with α-Tocopherol significantly prevented esophageal carcinogenesis induced by N-nitrosomethylbenzylamine (NMBA) in ESCC rat model. In the Het-1A cell model, α-Tocopherol markedly suppressed cell proliferation, promoted cell cycle G2-phase arrest and increased apoptosis. Gene microarray and proteins array analysis indicated that Akt signaling was a potential target for α-Tocopherol. We further demonstrated that α-Tocopherol increased the expression of PPARγ and its downstream tumor suppressor PTEN. Knockdown of PPARγ activated Akt signaling transduction, whereas this process was attenuated by the presence of α-Tocopherol and PPARγ agonist Rosiglitazone. In contrast, the effect of α-Tocopherol on Akt inhibition was not observed in established tumors, neither in cancerous cell lines which constitutively expressed higher levels of PPARγ. These results were closely correlated with the ineffectiveness of α-Tocopherol in the late stage of ESCC carcinogenesis. Taken together, our study suggested that α-Tocopherol may serve as a PPARγ agonist for the chemoprevention of esophageal cancer.

Association of PPARG rs 1801282 C>G polymorphism with risk of colorectal cancer: from a case-control study to a meta-analysis

The functional single nucleotide polymorphisms in peroxisome proliferator-activated receptor gamma (PPARG) gene were predicted to be correlated with the susceptibility of colorectal cancer (CRC). The aim of the present study was to explore the relationship between PPARG rs1801282 C>G polymorphism and the risk of CRC. First, we conducted a case-control study with 387 CRC cases and 1,536 controls. We used the SNPscan method to determine the genotypes of PPARG rs1801282 C>G polymorphism. We found PPARG rs1801282 C>G polymorphism had a tendency of decreased risk to CRC risk (CG vs. CC: adjusted OR, 0.67, 95% CI = 0.43–1.04 for CG vs. CC, P = 0.073; GG vs. CC: adjusted OR, 0.68; 95% CI, 0.44–1.05; P = 0.078). The stratified analysis revealed PPARG rs1801282 C>G polymorphism also had a tendency of decreased risk to colon cancer (CG vs. CC: adjusted OR = 0.54, 95% CI = 0.27–1.08, P = 0.083). The results of subsequent meta-analysis suggested that PPARG rs1801282 C>G polymorphism might be a protective factor for CRC, especially in Asians, colon cancer and rectum cancer subgroups. In conclusion, our study indicates that PPARG rs1801282 C>G polymorphism might decrease the risk of overall CRC. Larger sample size and well-designed case-control studies are needed to confirm the potential association.

Thermodynamics in cancers: opposing interactions between PPAR gamma and the canonical WNT/beta-catenin pathway

Cancer cells are the site of numerous metabolic and thermodynamic abnormalities. We focus this review on the interactions between the canonical WNT/beta-catenin pathway and peroxisome proliferator-activated receptor gamma (PPAR gamma) in cancers and their implications from an energetic and metabolic point of view. In numerous tissues, PPAR gamma activation induces inhibition of beta-catenin pathway, while the activation of the canonical WNT/beta-catenin pathway inactivates PPAR gamma. In most cancers but not all, PPAR gamma is downregulated while the WNT/beta-catenin pathway is upregulated. In cancer cells, upregulation of the WNT/beta-catenin signaling induces dramatic changes in key metabolic enzymes that modify their thermodynamic behavior. This leads to activation of pyruvate dehydrogenase kinase1 (PDK-1) and monocarboxylate lactate transporter. Consequently, phosphorylation of PDK-1 inhibits the pyruvate dehydrogenase complex (PDH). Thus, a large part of pyruvate cannot be converted into acetyl-coenzyme A (acetyl-CoA) in mitochondria and only a part of acetyl-CoA can enter the tricarboxylic acid cycle. This leads to aerobic glycolysis in spite of the availability of oxygen. This phenomenon is referred to as the Warburg effect. Cytoplasmic pyruvate is converted into lactate. The WNT/beta-catenin pathway induces the transcription of genes involved in cell proliferation, i.e., MYC and CYCLIN D1. This ultimately promotes the nucleotide, protein and lipid synthesis necessary for cell growth and multiplication. In cancer, activation of the PI3K-AKT pathway induces an increase of the aerobic glycolysis. Moreover, prostaglandin E2 by activating the canonical WNT pathway plays also a role in cancer. In addition in many cancer cells, PPAR gamma is downregulated. Moreover, PPAR gamma contributes to regulate some key circadian genes. In cancers, abnormalities in the regulation of circadian rhythms (CRs) are observed. CRs are dissipative structures which play a key-role in far-from-equilibrium thermodynamics. In cancers, metabolism, thermodynamics and CRs are intimately interrelated.

Hepatocyte nuclear factor 1α suppresses steatosis-associated liver cancer by inhibiting PPARγ transcription

Worldwide epidemics of metabolic diseases, including liver steatosis, are associated with an increased frequency of malignancies, showing the highest positive correlation for liver cancer. The heterogeneity of liver cancer represents a clinical challenge. In liver, the transcription factor PPARγ promotes metabolic adaptations of lipogenesis and aerobic glycolysis under the control of Akt2 activity, but the role of PPARγ in liver tumorigenesis is unknown. Here we have combined preclinical mouse models of liver cancer and genetic studies of a human liver biopsy atlas with the aim of identifying putative therapeutic targets in the context of liver steatosis and cancer. We have revealed a protumoral interaction of Akt2 signaling with hepatocyte nuclear factor 1α (HNF1α) and PPARγ, transcription factors that are master regulators of hepatocyte and adipocyte differentiation, respectively. Akt2 phosphorylates and inhibits HNF1α, thus relieving the suppression of hepatic PPARγ expression and promoting tumorigenesis. Finally, we observed that pharmacological inhibition of PPARγ is therapeutically effective in a preclinical murine model of steatosis-associated liver cancer. Taken together, our studies in humans and mice reveal that Akt2 controls hepatic tumorigenesis through crosstalk between HNF1α and PPARγ.

Interactions between PPAR Gamma and the Canonical Wnt/Beta-Catenin Pathway in Type 2 Diabetes and Colon Cancer

In both colon cancer and type 2 diabetes, metabolic changes induced by upregulation of the Wnt/beta-catenin signaling and downregulation of peroxisome proliferator-activated receptor gamma (PPAR gamma) may help account for the frequent association of these two diseases. In both diseases, PPAR gamma is downregulated while the canonical Wnt/beta-catenin pathway is upregulated. In colon cancer, upregulation of the canonical Wnt system induces activation of pyruvate dehydrogenase kinase and deactivation of the pyruvate dehydrogenase complex. As a result, a large part of cytosolic pyruvate is converted into lactate through activation of lactate dehydrogenase. Lactate is extruded out of the cell by means of activation of monocarboxylate lactate transporter-1. This phenomenon is called Warburg effect. PPAR gamma agonists induce beta-catenin inhibition, while inhibition of the canonical Wnt/beta-catenin pathway activates PPAR gamma.

Mouse Models of Human Familial Cancer Syndromes

As many as 5% of human cancers appear to be of hereditable etiology. Of the more than 50 characterized familial cancer syndromes, most involve disease affecting multiple organs and many can be traced to one or more abnormalities in specific genes. Studying these syndromes in humans is a difficult task, especially when it comes to genes that may manifest themselves early in gestation. It has been made somewhat easier with the development of genetically engineered mice (GEM) that phenotypically mimic many of these inheritable human cancers. The past 15 years has seen the establishment of mouse lines heterozygous or homozygous null for genes known or suspected of being involved in human cancer syndromes, including APC, ATM, BLM, BRCA1, BRCA2, LKB1, MEN1, MLH, MSH, NF1, TP53, PTEN, RB1, TSC1, TSC2, VHL, and XPA. These lines not only provide models for clinical disease and pathology, but also provide avenues to investigate molecular pathology, gene-gene and protein-tissue interaction, and, ultimately, therapeutic intervention. Possibly of even greater importance, they provide a means of looking at placental and fetal tissues, where genetic abnormalities are often first detected and where they may be most easily corrected. We will review these mouse models, examine their usefulness in medical research, and furnish sources of animals and references.

Alzheimer Disease: Crosstalk between the Canonical Wnt/Beta-Catenin Pathway and PPARs Alpha and Gamma

The molecular mechanisms underlying the pathophysiology of Alzheimer's disease (AD) are still not fully understood. In AD, Wnt/beta-catenin signaling has been shown to be downregulated while the peroxisome proliferator-activated receptor (PPAR) gamma (mARN and protein) is upregulated. Certain neurodegenerative diseases share the same Wnt/beta-catenin/PPAR gamma profile, such as bipolar disorder and schizophrenia. Conversely, other NDs share an opposite profile, such as amyotrophic lateral sclerosis, Parkinson's disease, Huntington's disease, multiple sclerosis, and Friedreich's ataxia. AD is characterized by the deposition of extracellular Abeta plaques and the formation of intracellular neurofibrillary tangles in the central nervous system (CNS). Activation of Wnt signaling or inhibition of both glycogen synthase kinase-3beta and Dickkopf 1, two key negative regulators of the canonical Wnt pathway, are able to protect against Abeta neurotoxicity and to ameliorate cognitive performance in AD patients. Although PPAR gamma is upregulated in AD patients, and despite the fact that it has been shown that the PPAR gamma and Wnt/beta catenin pathway systems work in an opposite manner, PPAR gamma agonists diminish learning and memory deficits, decrease Abeta activation of microglia, and prevent hippocampal and cortical neurons from dying. These beneficial effects observed in AD transgenic mice and patients might be partially due to the anti-inflammatory properties of PPAR gamma agonists. Moreover, activation of PPAR alpha upregulates transcription of the alpha-secretase gene and represents a new therapeutic treatment for AD. This review focuses largely on the behavior of two opposing pathways in AD, namely Wnt/beta-catenin signaling and PPAR gamma. It is hoped that this approach may help to develop novel AD therapeutic strategies integrating PPAR alpha signaling.

Distinct gene regulatory programs define the inhibitory effects of liver X receptors and PPARG on cancer cell proliferation

Background

The liver X receptors (LXRs, NR1H2 and NR1H3) and peroxisome proliferator-activated receptor gamma (PPARG, NR1C3) nuclear receptor transcription factors (TFs) are master regulators of energy homeostasis. Intriguingly, recent studies suggest that these metabolic regulators also impact tumor cell proliferation. However, a comprehensive temporal molecular characterization of the LXR and PPARG gene regulatory responses in tumor cells is still lacking.

Methods

To better define the underlying molecular processes governing the genetic control of cellular growth in response to extracellular metabolic signals, we performed a comprehensive, genome-wide characterization of the temporal regulatory cascades mediated by LXR and PPARG signaling in HT29 colorectal cancer cells. For this analysis, we applied a multi-tiered approach that incorporated cellular phenotypic assays, gene expression profiles, chromatin state dynamics, and nuclear receptor binding patterns.

Results

Our results illustrate that the activation of both nuclear receptors inhibited cell proliferation and further decreased glutathione levels, consistent with increased cellular oxidative stress. Despite a common metabolic reprogramming, the gene regulatory network programs initiated by these nuclear receptors were widely distinct. PPARG generated a rapid and short-term response while maintaining a gene activator role. By contrast, LXR signaling was prolonged, with initial, predominantly activating functions that transitioned to repressive gene regulatory activities at late time points.

Conclusions

Through the use of a multi-tiered strategy that integrated various genomic datasets, our data illustrate that distinct gene regulatory programs elicit common phenotypic effects, highlighting the complexity of the genome. These results further provide a detailed molecular map of metabolic reprogramming in cancer cells through LXR and PPARG activation. As ligand-inducible TFs, these nuclear receptors can potentially serve as attractive therapeutic targets for the treatment of various cancers.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-016-0328-6) contains supplementary material, which is available to authorized users.

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.

Proliferation and fission of peroxisomes - An update

In mammals, peroxisomes perform crucial functions in cellular metabolism, signalling and viral defense which are essential to the health and viability of the organism. In order to achieve this functional versatility peroxisomes dynamically respond to molecular cues triggered by changes in the cellular environment. Such changes elicit a corresponding response in peroxisomes, which manifests itself as a change in peroxisome number, altered enzyme levels and adaptations to the peroxisomal structure. In mammals the generation of new peroxisomes is a complex process which has clear analogies to mitochondria, with both sharing the same division machinery and undergoing a similar division process. How the regulation of this division process is integrated into the cell's response to different stimuli, the signalling pathways and factors involved, remains somewhat unclear. Here, we discuss the mechanism of peroxisomal fission, the contributions of the various division factors and examine the potential impact of post-translational modifications, such as phosphorylation, on the proliferation process. We also summarize the signalling process and highlight the most recent data linking signalling pathways with peroxisome proliferation.

Transglutaminase 2--a novel inhibitor of adipogenesis

Differentiation of preadipocytes to lipid storing adipocytes involves extracellular signaling pathways, matrix remodeling and cytoskeletal changes. A number of factors have been implicated in maintaining the preadipocyte state and preventing their differentiation to adipocytes. We have previously reported that a multifunctional and protein crosslinking enzyme, transglutaminase 2 (TG2) is present in white adipose tissue. In this study, we have investigated TG2 function during adipocyte differentiation. We show that TG2 deficient mouse embryonic fibroblasts (Tgm2-/- MEFs) display increased and accelerated lipid accumulation due to increased expression of major adipogenic transcription factors, PPARγ and C/EBPα. Examination of Pref-1/Dlk1, an early negative regulator of adipogenesis, showed that the Pref-1/Dlk1 protein was completely absent in Tgm2-/- MEFs during early differentiation. Similarly, Tgm2-/- MEFs displayed defective canonical Wnt/β-catenin signaling with reduced β-catenin nuclear translocation. TG2 deficiency also resulted in reduced ROCK kinase activity, actin stress fiber formation and increased Akt phosphorylation in MEFs, but did not alter fibronectin matrix levels or solubility. TG2 protein levels were unaltered during adipogenic differentiation, and was found predominantly in the extracellular compartment of MEFs and mouse WAT. Addition of exogenous TG2 to Tgm2+/+ and Tgm2-/- MEFs significantly inhibited lipid accumulation, reduced expression of PPARγ and C/EBPα, promoted the nuclear accumulation of β-catenin, and recovered Pref-1/Dlk1 protein levels. Our study identifies TG2 as a novel negative regulator of adipogenesis.

Protective Effects of Turbinaria ornata and Padina pavonia against Azoxymethane-Induced Colon Carcinogenesis through Modulation of PPAR Gamma, NF-κB and Oxidative Stress

The aim of this study was to investigate the antiproliferative and protective effects of the brown seaweeds, Turbinaria ornata and Padina pavonia, against azoxymethane (AOM)-induced colon carcinogenesis in mice. Both algal extracts showed anti-proliferative effects on the human carcinoma cell line HCT-116 in vitro, with T. ornata demonstrating a more potent effect. Male albino Swiss mice received intraperitoneal injections of AOM (10 mg/kg) once a week for two consecutive weeks and 100 mg/kg of either T. ornata or P. pavonia extracts. AOM-induced mice exhibited alterations in the histological structure of the colon, elevated lipid peroxidation and nitric oxide, declined glutathione content and reduced activity of superoxide dismutase and glutathione peroxidase. In addition, AOM induced downregulation of peroxisome proliferator activated receptor gamma (PPARγ) and p53 mRNA expression, with concomitant upregulation of nuclear factor-kappa B (NF-κB) in colon tissue. Administration of either algal extract markedly alleviated the recorded alterations. In conclusion, the current study suggests that T. ornata and P. pavonia, through their antioxidant and anti-inflammatory effects, are able to attenuate colon inflammation by downregulating NF-κB expression. Furthermore, the protective effects of both algae against AOM-initiated carcinogenesis were attributed, at least in part, to their ability to upregulate colonic PPARγ and p53 expression.

Peroxisome proliferator-activated receptor γ upregulates galectin-9 and predicts prognosis in intestinal-type gastric cancer

The importance of PPARγ (peroxisome proliferator-activated receptor γ) in gastric cancer (GC) is unclear. We investigated the role of PPARγ in GC cell lines and an animal model, and its prognostic significance of PPARγ in GC patients. We controlled PPARγ and galectin-9 expression by using siRNAs and lentiviral constructs. Interaction between PPARγ and galectin-9 was evaluated using luciferase and chromatin immunoprecipitation assays. PPARγ expression in GCs was determined by immunohistochemical staining of tissue microarrays and survival analysis was done. Overexpression of PPARγ was accompanied by increased galectin-9. Enhanced PPARγ or galectin-9 expression increased E-cadherin expression; decreased expression of N-cadherin, fibronectin, snail, twist and slug and reduced cell invasion and migration. PPARγ bound to the galectin-9 promoter region. Galectin-9 activity increased in PPARγ-overexpressing cells but decreased in PPARγ siRNA-treated cells. In a zebrafish xenograft model, the number of migrated cancer cells and number of fish with AGS cells in the tail vein were reduced in PPARγ-overexpressing GC cells. PPARγ was expressed in 462 of the 688 patients (69.2%) with GC. In 306 patients with intestinal-type GC, those with PPARγ-positive tumors had lower overall and cancer-specific mortalities than those with PPARγ-negative tumors. PPARγ expression was an independent prognostic factor for overall and GC-specific mortality in patients with intestinal-type GC (adjusted hazard ratio, 0.42; 95% CI, 0.22-0.81). PPARγ inhibits cell invasion, migration and epithelial-mesenchymal transition through upregulation of galectin-9 in vitro and in vivo.