Expression of peroxisome proliferator-activated receptor-gamma in colon cancer: correlation with histopathological parameters, cell cycle-related molecules, and patients' survival

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.

Evaluation of C-X-C chemokine receptor type 4 (CXCR4) and Peroxisome proliferator-activated receptor gamma (PPAR-γ) expression in colorectal carcinoma: Relation to the available clinicopathological parameters

Background

Colorectal carcinoma (CRC) is the most common malignancy of the gastrointestinal tract, representing an incredible health problem. It is essential to develop drugs against novel targets--involved in CRC tumorigenesis and progression--to improve the management of the disease. The aim of this study was to evaluate C-X-C chemokine receptor type 4 (CXCR4) and Peroxisome proliferator-activated receptor gamma (PPAR-γ) expression in CRC, and to associate their expression with the available clinicopathological parameters.

Materials and Methods

This study included 50 cases of primary CRC. All cases were stained by CXCR4 and PPAR-γ antibodies to assess their immunohistochemical expression. The relations between their expression and clinicopathological variables were assessed.

Results

CXCR4 expression was detected in 76% of studied cases. High CXCR4 expression showed significant associations with the depth of tumor invasion (P = 0.024), lymph node metastasis (P = 0.009), advanced tumor stage (P = 0.001) and the presence of vascular invasion (P = 0.035). PPAR-γ expression was detected in 78% of studied cases. PPAR-γ expression showed a statistically significant inverse relation with histologic types (P = 0.001), tumor grade (P = 0.005), depth of tumor invasion (P = 0.001), lymph node status (P = 0.001), TNM stage (P = 0.002), and vascular invasion (P = 0.001).

Conclusions

High CXCR4 and decreased PPAR-γ expressions are related to high tumor grade, advanced stage, and vascular invasion in colorectal carcinoma.

Peroxisome Proliferator-Activated Receptors and the Hallmarks of Cancer

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

Overexpression of the PPAR-γ protein in primary Ta/T1 non-muscle-invasive urothelial carcinoma

Peroxisome proliferator-activated receptor-γ (PPAR-γ) is a well-known nuclear receptor that is activated in the nucleus to regulate several transcription factors. Its expression patterns have been examined in various types of cancer. The present study investigated the expression patterns of PPAR-γ in non-muscle-invasive urothelial carcinoma. The expression rates of PPAR-γ, p53 and Ki-67 were compared to determine whether PPAR-γ may be considered as an immunobiomarker for bladder cancer. The intensity and extent of PPAR-γ expression were evaluated in 79 cases of non-muscle-invasive urothelial carcinoma (30 cases of papillary carcinoma low-grade, 30 cases of high-grade and 19 cases of carcinoma in situ) and 30 non-malignant cases. The nuclear overexpression of PPAR-γ was frequently observed in non-muscle-invasive urothelial carcinoma (63/79 cases) but was rarely detected in non-malignant cases (2/30 cases). The histological proliferation types of non-muscle-invasive urothelial carcinoma revealed that PPAR-γ was more frequently overexpressed in papillary carcinoma (54/60 cases) than in carcinoma in situ (9/19 cases). Immunohistochemical staining demonstrated that PPAR-γ was more useful as an immunobiomarker than p53 or Ki-67 (diagnostic odds ratios; 55.13, 16.82 and 11.13, respectively). In summary, this study demonstrated that the expression patterns of PPAR-γ were associated with histological proliferation type and that PPAR-γ was expressed in the nuclei of papillary carcinoma cells. These findings suggested that immunohistochemical staining for PPAR-γ may be used to comprehensively detect non-muscle-invasive urothelial carcinoma.

Combined COX-2/PPARγ Expression as Independent Negative Prognosticator for Vulvar Cancer Patients

Vulvar cancer incidence numbers have been rising steadily over the past decades. Especially the number of young patients with vulvar cancer increased recently. Therefore, the need to identify new prognostic factors for vulvar carcinoma is more apparent. Cyclooxygenase-2 (COX-2) has long been an object of scientific interest in the context of carcinogenesis. This enzyme is involved in prostaglandin synthesis and the latter binds to nuclear receptors like PPARγ. Therefore, the aim of this study was to investigate COX-2- and PPARγ- expression in tissues of vulvar carcinomas and to analyze their relevance as prognostic factors. The cytoplasmatic expression of COX-2 as well as PPARγ is associated with a significantly reduced survival, whereas nuclear expression of PPARγ results in a better survival. Especially the combined expression of both COX-2 and PPARγ in the cytoplasm is an independent negative prognosticator for vulvar cancer patients.

Common targets for a deadly duo of diabetes mellitus and colon cancer: Catching two fish with one worm

Colon cancer is a major health issue and number of cases are increasing every year. Diabetes mellitus is also a significant health issue that is growing day by day worldwide having negative influences on the survival of individuals. Research has shown a strong relationship between the two malignant diseases. The risk of colon cancer with patients who have type 2 diabetes mellitus has spiked by 30%. The scientific research suggests insulin has a major role in the spread of cancer and the condition unifying between the two diseases is hyperinsulinemia. Several anti-diabetic agents are used for the treatment of type 2 diabetesmellitus. However, their mechanism of action against cancer activity is a question and only a few agents have shown positive signs of action in colon cancer associated with type 2 diabetesmellitus. Hence, the identification of targets, which is common for both colon cancer, associated with type 2 diabetesmellitus has become an urgent requirement. Novel targets such as Liver X receptors, Histone deacetylase inhibitors (HDACi), Glucose Transporters (GLUTs), Peroxisome proliferator activator receptors (PPARs), Dipeptidyl peptidase-IV inhibitors (DPP4i), Cyclin-dependent kinase 4 inhibitors (CDK4i), Estrogen receptors,Mechanistic target of rapamycin (mTOR), Insulin-like growth factor receptors (IGF) are some of the targets which are common for both, type 2 diabetesmellitus and colon cancer. This current review gives an overview of the targets (using one worm) which are common for both viz. diabetes mellitus and colon cancer (two fish).

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.

PPARγ Agonists in Combination Cancer Therapies

Peroxisome proliferator-activated receptor-gamma (PPARγ) is a nuclear receptor acting as a transcription factor involved in the regulation of energy metabolism, cell cycle, cell differentiation, and apoptosis. These unique properties constitute a strong therapeutic potential that place PPARγ agonists as one of the most interesting and widely studied anticancer molecules. Although PPARγ agonists exert significant, antiproliferative and tumoricidal activity in vitro, their anticancer efficacy in animal models is ambiguous, and their effectiveness in clinical trials in monotherapy is unsatisfactory. However, due to pleiotropic effects of PPARγ activation in normal and tumor cells, PPARγ ligands interact with many antitumor treatment modalities and synergistically potentiate their effectiveness. The most spectacular example is a combination of PPARγ ligands with tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML). In this setting, PPARγ activation sensitizes leukemic stem cells, resistant to any previous form of treatment, to targeted therapy. Thus, this combination is believed to be the first pharmacological therapy able to cure CML patients. Within the last decade, a significant body of data confirming the benefits of the addition of PPARγ ligands to various antitumor therapies, including chemotherapy, hormonotherapy, targeted therapy, and immunotherapy, has been published. Although the majority of these studies have been carried out in vitro or animal tumor models, a few successful attempts to introduce PPARγ ligands into anticancer therapy in humans have been recently made. In this review, we aim to summarize shines and shadows of targeting PPARγ in antitumor therapies.

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.

Telmisartan Influences the Antiproliferative Activity of Linoleic Acid in Human Colon Cancer Cells

Aim: Linoleic acid (LA) and telmisartan as PPARgamma agonists exhibit anticancer activity. The LA effect is observed for high non-achievable in vivo concentrations and in short treatment period, therefore we evaluate the effect of supplemental LA and pharmacological telmisartan plasma concentrations on human primary (SW480) and metastatic (SW620) colon cancer cells and immortal keratinocytes (HaCaT) cells in long-term treatment. Methods: Cell viability and proliferation were determined by TB and MTT and pro-apoptotic effect was measured by Annexin V binding assays, respectively.Results: LA decreased cancer cell viability and proliferation in a concentration-dependent manner, whereas no significant effect was found for HaCaT cells. Telmisartan (0.2 µM) suppresses antiproliferative effect of 60 µM LA on cancer cells in short-term treatment. Long-term administration of 60 µM LA reduced cancer cells viability after one week, while telmisartan delayed this effect by two weeks. Growth of all cell lines with 20 µM LA was unchanged during all treatment time. Telmisartan decreased late apoptosis of cancer and normal cells with 60 and 120 µM LA. Conclusion: The cytotoxic LA action depends not only on its concentration but also duration of treatment. Telmisartan exhibits biphasic but not synergistic effect on LA cytotoxicity in cancer cells.

Chiral phenoxyacetic acid analogues inhibit colon cancer cell proliferation acting as PPARγ partial agonists

Peroxisome Proliferator-Activated Receptor γ (PPARγ) is an important sensor at the crossroad of diabetes, obesity, immunity and cancer as it regulates adipogenesis, metabolism, inflammation and proliferation. PPARγ exerts its pleiotropic functions upon binding of natural or synthetic ligands. The molecular mechanisms through which PPARγ controls cancer initiation/progression depend on the different mode of binding of distinctive ligands. Here, we analyzed a series of chiral phenoxyacetic acid analogues for their ability to inhibit colorectal cancer (CRC) cells growth by binding PPARγ as partial agonists as assessed in transactivation assays of a PPARG-reporter gene. We further investigated compounds (R,S)-3, (S)-3 and (R,S)-7 because they combine the best antiproliferative activity and a limited transactivation potential and found that they induce cell cycle arrest mainly via upregulation of p21^waf1/cip1. Interestingly, they also counteract the β-catenin/TCF pathway by repressing c-Myc and cyclin D1, supporting their antiproliferative effect. Docking experiments provided insight into the binding mode of the most active compound (S)-3, suggesting that its partial agonism could be related to a better stabilization of H3 rather than H11 and H12. In conclusion, we identified a series of PPARγ partial agonists affecting distinct pathways all leading to strong antiproliferative effects. These findings may pave the way for novel therapeutic strategies in CRC.

Fatty acid-binding protein 1 is preferentially lost in microsatellite instable colorectal carcinomas and is immune modulated via the interferon γ pathway

Fatty acid-binding protein 1 (FABP1) is an intracellular protein responsible for the transportation of long chain fatty acids. Aside from its functions in lipid metabolism and cellular differentiation, FABP1 also plays a role in inflammation through its interaction with peroxisome proliferator-activated receptors (PPARs). Previously, we compared expression of colonic epithelium genes in a subset of microsatellite instable (MSI) colorectal carcinomas (medullary carcinomas) to normal colonic mucosa and found that FABP1 expression was markedly decreased in the tumors. Further analysis of RNA expression in the colorectal subtypes and The Cancer Genome Atlas data set found that FABP1 expression is decreased in the CMS1 subset of colorectal carcinomas, which is characterized by microsatellite instability. As MSI colorectal carcinomas are known for their robust immune response, we then aimed to link FABP1 to the immune microenvironment of MSI carcinomas. To confirm the gene expression results, we performed immunohistochemical analysis of a cohort of colorectal carcinomas. FABP1 was preferentially lost in MSI carcinomas (123/133, 93%) compared with microsatellite stable carcinomas (240/562, 43%, P<0.0001). In addition, higher numbers of tumor-infiltrating lymphocytes were present in tumors with loss of FABP1 (P<0.0001). Decreased expression of the fatty acid storage and glucose regulator, PPARγ, was associated with the loss of FABP1 (P<0.0001). Colorectal cancer cell lines treated with interferon γ exhibited decreased expression of FABP1. FABP1 expression was partially recovered with the treatment of the cell lines with rosiglitazone, a PPARγ agonist. This study demonstrated that the loss of FABP1 expression is associated with MSI carcinomas and that interferon γ stimulation plays a role in this process via its interaction with PPARγ.

Role of retinoids in the prevention and treatment of colorectal cancer

Vitamin A and its derivatives, retinoids, have been widely studied for their use as cancer chemotherapeutic agents. With respect to colorectal cancer (CRC), several critical mutations dysregulate pathways implicated in progression and metastasis, resulting in aberrant Wnt/β-catenin signaling, gain-of-function mutations in K-ras and phosphatidylinositol-3-kinase/Akt, cyclooxygenase-2 over-expression, reduction of peroxisome proliferator-activated receptor γ activation, and loss of p53 function. Dysregulation leads to increased cellular proliferation and invasion and decreased cell-cell interaction and differentiation. Retinoids affect these pathways by various mechanisms, many involving retinoic acid receptors (RAR). RAR bind to all-trans-retinoic acid (ATRA) to induce the transcription of genes responsible for cellular differentiation. Although most research concerning the chemotherapeutic efficacy of retinoids focuses on the ability of ATRA to decrease cancer cell proliferation, increase differentiation, or promote apoptosis; as CRC progresses, RAR expression is often lost, rendering treatment of CRCs with ATRA ineffective. Our laboratory focuses on the ability of dietary vitamin A to decrease CRC cell proliferation and invasion via RAR-independent pathways. This review discusses our research and others concerning the ability of retinoids to ameliorate the defective signaling pathways listed above and decrease tumor cell proliferation and invasion through both RAR-dependent and RAR-independent mechanisms.

Clinical Significance of Peroxisome Proliferator-Activated Receptor γ and TRAP220 in Patients with Operable Colorectal Cancer

Purpose

The peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear receptor that regulates expression of mediators of lipid metabolism and the inflammatory response. Thyroid hormone receptor-associated proteins 220 (TRAP220) is an essential component of the TRAP/Mediator complex. The objective of this study was to clarify whether PPARγ or TRAP220 are significant prognostic markers in resectable colorectal cancer (CRC).

Materials and Methods

A total of 399 patients who underwent curative resection for CRC were enrolled. We investigated the presence of PPARγ and TARP220 in CRC tissues and adjacent normal tissues by immunohistochemistry. Correlation between the expression of these factors and clinicopathologic features and survival was investigated.

Results

Median age of the patients was 63 years (range, 22 to 87 years), and median follow-up duration 61.1 months (range, 2 to 114 months). PPARγ and TRAP220 expression showed significant correlation with depth of invasion (p=0.013 and p=0.001, respectively). Expression of TRAP220 also showed association with lymph node metastasis and TNM stage (p=0.001). Compared with patients with TRAP220 negative tumors, patients with TRAP220 positive tumors had longer 5-year disease-free survival (DFS) tendency (p=0.051). Patients who were PPARγ positive combined with TRAP220 positive had a better 5-year DFS (64.8% vs. 79.3%, p=0.013). In multivariate analysis expression of both PPARγ and TRAP220 significantly affected DFS (hazard ratio, 0.620; 95% confidence interval, 0.379 to 0.997; p=0.048).

Conclusion

TRAP220 may be a valuable marker for nodal metastasis and TNM stage. Tumor co-expression of PPARγ and TRAP220 represents a biomarker for good prognosis in CRC patients.

Chemotherapy and chemoprevention by thiazolidinediones

Thiazolidinediones (TZDs) are synthetic ligands of Peroxisome-Proliferator-Activated Receptor gamma (PPARγ). Troglitazone, rosiglitazone, and pioglitazone have been approved for treatment of diabetes mellitus type II. All three compounds, together with the first TZD ciglitazone, also showed an antitumor effect in preclinical studies and a beneficial effect in some clinical trials. This review summarizes hypotheses on the role of PPARγ in tumors, on cellular targets of TZDs, antitumor effects of monotherapy and of TZDs in combination with other compounds, with a focus on their role in the treatment of differentiated thyroid carcinoma. The results of chemopreventive effects of TZDs are also considered. Existing data suggest that the action of TZDs is highly complex and that actions do not correlate with cellular PPARγ expression status. Effects are cell-, species-, and compound-specific and concentration-dependent. Data from human trials suggest the efficacy of TZDs as monotherapy in prostate cancer and glioma and as chemopreventive agent in colon, lung, and breast cancer. TZDs in combination with other therapies might increase antitumor effects in thyroid cancer, soft tissue sarcoma, and melanoma.

Prognostic significance of cyclin D1 expression in colorectal cancer: a meta-analysis of observational studies

Objective

Cyclin D1 plays a vital role in cancer cell cycle progression and is overexpressed in many human cancers, including colorectal cancer (CRC). However, the prognostic value of cyclin D1 overexpression in colorectal cancer is conflicting and heterogeneous. We conducted a meta-analysis to more precisely evaluate its prognostic significance.

Methods

A comprehensive literature search for relevant studies published up to January 2014 was performed using PubMed, EMBASE, and ISI Web of Science. The pooled hazard ratio (HR) with 95% confidence intervals (CI) was used to estimate the effects.

Results

22 studies with 4150 CRC patients were selected to evaluate the association between cyclin D1 and overall survival (OS), disease-free survival (DFS) and clinicopathological parameters. In a random-effects model, the results showed that cyclin D1 overexpression in CRC was significantly associated with both poor OS (HR = 0.73, 95% CI: 0.63–0.85, P<0.001) and DFS (HR = 0.60, 95% CI: 0.44–0.82, P = 0.001). Additionally, cyclin D1 overexpression was significantly associated with more relative older patients (≥60 years) (OR 0.62, 95% CI 0.44–0.89, P = 0.009), T3,4 tumor invasion (OR 0.70, 95% CI 0.57–0.85, P<0.001), N positive (OR 0.75, 95% CI 0.60–0.95, P = 0.016) and distant metastasis (OR 0.60, 95% CI 0.36–0.99, P = 0.047) of CRC.

Conclusion

The meta-analysis results indicated that cyclin D1 is an unfavorable prognostic factor for CRC. Cyclin D1 overexpression might be associated with poor clinical outcome and some clinicopathological factors such as age, T category, N category and distant metastasis in CRC patients.

Rosiglitazone amplifies the sensitivity of docetaxel and reduces the expression of CD44v6

Breast cancer seriously impairs physical and mental health in females. Currently, with further investigation into drugs, a number of new pharmacological effects have been found that offer new methods for clinical application in the treatment of breast cancer. As a widely used antidiabetic drug, rosiglitazone (Ros) has become well known for its anticancer effects, mediated by the activation of peroxisome proliferator-activated receptor γ and downregulated expression of the associated invasion gene. The objective of the present study was to investigate the combination of Ros and docetaxel (DOC) and whether DOC has any effect on breast cancer cell lines. The results showed that the combination of Ros and DOC may cooperate to increase anti-growth efficacy. The additive inhibitory effects on cell proliferation were sequence-dependent and are not likely to be associated with cell cycle arrest. This suggested that the target activation of associated factors of the signaling pathway by Ros may be a compelling ally in cancer treatment. In addition, evidence was provided for a convergence of Ros and DOC to induce the reduced expression of CD44v6. Future studies are required to confirm which associated gene of Ros is significant in blocking the signaling pathway.

Rosiglitazone and AS601245 decrease cell adhesion and migration through modulation of specific gene expression in human colon cancer cells

PPARs are nuclear receptors activated by ligands. Activation of PPARγ leads to a reduction of adhesion and motility in some cancer models. PPARγ transcriptional activity can be negatively regulated by JNK-mediated phosphorylation. We postulated that the use of agents able to inhibit JNK activity could increase the effectiveness of PPARγ ligands. We analysed the effects of rosiglitazone (PPARγ ligand) and AS601245 (a selective JNK inhibitor) alone or in association on adhesion and migration of CaCo-2, HT29, and SW480 human colon cancer cells and investigated, through microarray analysis, the genes involved in these processes. Cell adhesion and migration was strongly inhibited by rosiglitazone and AS601245. Combined treatment with the two compounds resulted in a greater reduction of the adhesion and migration capacity. Affymetrix analysis in CaCo-2 cells revealed that some genes which were highly modulated by the combined treatment could be involved in these biological responses. Rosiglitazone, AS601245 and combined treatment down-regulated the expression of fibrinogen chains in all three cell lines. Moreover, rosiglitazone, alone or in association with AS601245, caused a decrease in the fibrinogen release. ARHGEF7/β-PIX gene was highly down-regulated by combined treatment, and western blot analysis revealed that β-PIX protein is down-modulated in CaCo-2, HT29 and SW480 cells, also. Transfection of cells with β-PIX gene completely abrogated the inhibitory effect on cell migration, determined by rosiglitazone, AS601245 and combined treatment. Results demonstrated that β-PIX protein is involved in the inhibition of cell migration and sustaining the positive interaction between PPARγ ligands and anti-inflammatory agents in humans.

Expression of peroxisome proliferator activated receptor-gamma (PPAR-γ) in human non-small cell lung carcinoma: correlation with clinicopathological parameters, proliferation and apoptosis related molecules and patients' survival

Peroxisome proliferator-activated receptor-γ (PPAR-γ) has currently been considered as molecular target for the treatment of human metabolic disorders. PPAR-γ has also been implicated in the pathogenesis and progression of several types of cancer, being associated with cell differentiation, growth and apoptosis. The present study aimed to evaluate the clinical significance of PPAR-γ expression in non-small cell lung carcinoma (NSCLC). PPAR-γ protein expression was assessed immunohistochemically in tumoral samples of 67 NSCLC patients and was statistically analyzed in relation to clinicopathological parameters, proliferation and apoptosis related molecules and patients' survival. Positive PPAR-γ expression was prominent in 30 (45 %) out of 67 NSCLC cases. PPAR-γ positivity was more frequently observed in squamous cell lung carcinoma cases compared to lung adenocarcinoma ones (p = 0.048). PPAR-γ positivity was significantly associated with bcl-2 positivity (p = 0.016) and borderline with c-myc positivity (p = 0.052), whereas non associations with grade of differentiation, TNM stage, Ki-67, p53, bax proteins' expression and patients' survival were noted. In the subgroup of squamous cell lung carcinoma cases, PPAR-γ positivity was significantly associated with tumor size (p = 0.038), while in lung adenocarcinoma ones with histopathological grade of differentiation (p = 0.026). The present study supported evidence for possible participation of PPAR-γ in the biological mechanisms underlying the carcinogenic evolution of the lung. Although the survival prediction using PPAR-γ expression as a marker seems uncertain, the observed correlation with apoptosis related proteins reinforces the potential utility of PPAR-γ ligands as cell cycle modulators in future therapeutic approaches in lung cancer.

Peroxisome proliferator-activated receptor-γ in mobile tongue squamous cell carcinoma: associations with clinicopathological parameters and patients survival

PURPOSE

Peroxisome proliferator-activated receptor-γ (PPAR-γ) is a ligand-activated transcription factor, implicated in various aspects of cancer biology, such as differentiation, proliferation, invasion and angiogenesis. The present study aimed to evaluate the clinical significance of PPAR-γ in mobile tongue squamous cell carcinoma (SCC).

METHODS

PPAR-γ protein expression was assessed immunohistochemically on 49 mobile tongue SCC tissue samples obtained from an equal number of patients. PPAR-γ expression and intensity of immunostaining were statistically analyzed in relation with clinicopathological characteristics, mitotic index and patients' survival.

RESULTS

Elevated PPAR-γ expression was more frequently observed in patients with reduced depth of invasion (P = 0.0111). Moderate/intense PPAR-γ staining intensity was more frequently observed in patients with no evidence of muscular infiltration (P = 0.0229) and reduced depth of invasion (P = 0.0176). Mobile tongue SCC patients presenting enhanced PPAR-γ expression had significantly longer overall and disease-free survival times compared to those with low PPAR-γ expression (log-rank test, P = 0.0162 and P = 0.0114, respectively).

CONCLUSIONS

PPAR-γ immunoreactivity in mobile tongue SCC was correlated with clinicopathological characteristics crucial for patients' management and prognosis. PPAR-γ may be considered as a useful prognostic marker in mobile tongue SCC and a potential therapeutic target for tongue cancer chemoprevention and treatment.

Rosiglitazone and retinoic acid inhibit proliferation and induce apoptosis in the HCT-15 human colorectal cancer cell line

The aim of this study was to explore the effects of rosiglitazone (RSG) in combination with all-trans retinoic acid (ATRA) on the proliferation and apoptosis of the HCT-15 human colorectal cancer cell line. HCT-15 cells were divided into a blank control group, a vehicle control group and experimental groups (RSG only or ATRA only or RSG plus ATRA). Growth inhibition was examined using the MTT assay. Apoptosis and cell cycle progression were examined by flow cytometry. The expression of COX-2, MMP-7 and TIMP-1 was examined by immunocytochemistry. RSG alone inhibited HCT-15 cell proliferation in a concentration- and time-dependent manner (P<0.05). The combination of RSG and ATRA exhibited significant synergy (q>1.15). RSG or ATRA alone effectively increased the proportion of cells in the G0/G1 phase and decreased the proportion of cells in the S phase, thus inducing apoptosis (P<0.05). The combination of RSG and ATRA resulted in even stronger G1 cell cycle arrest (P<0.05). HCT-15 cells expressed COX-2, MMP-7 and TIMP-1, with positive expression rates in the control group of 66.79, 73.21 and 64.08%, respectively. After the combined application of RSG and ATRA, the positive rates significantly declined to only 19.33, 20.58 and 13.13%, respectively (P<0.01). In conclusion, the combination of RSG and ATRA reduced the expression of COX-2, MMP-7 and TIMP-1, caused cell cycle arrest at the G1 phase and induced apoptosis, which resulted in the inhibition of cell proliferation in the HCT-15 human colorectal cancer cell line.

MCM-2 and MCM-5 expression in gastric adenocarcinoma: clinical significance and comparison with Ki-67 proliferative marker

BACKGROUND

Minichromosome maintenance (MCM) proteins are essential components of DNA replication, being related to cell proliferation, and serve as useful biomarkers for cancer screening, surveillance and prognosis. The aim of the present study was to evaluate the clinical significance of MCM-2 and MCM-5 expression in gastric adenocarcinoma in comparison with Ki-67 proliferative marker.

METHODS

MCM-2, MCM-5 and Ki-67 expression was assessed immunohistochemically in 66 tumoral samples of gastric adenocarcinoma patients and was statistically analyzed in relation to clinicopathological characteristics and patient survival.

RESULTS

MCM-2 expression did not show significant associations with any clinicopathological parameters, while Ki-67 expression was merely significantly associated with tumor size (P = 0.0150). MCM-2 and Ki-67 expression were more frequently in intestinal (median values: 67.5 and 60%) compared to diffuse-type (median values: 60 and 45%) gastric adenocarcinoma cases without though reaching statistical significance (P > 0.05). MCM-5 expression was significantly associated with tumor size (P = 0.0295), presence of lymph node metastases (P = 0.0216) and tumor histopathological stage (P = 0.0098). Patients presenting high MCM-5 expression had significantly shorter survival times (log-rank test, P = 0.0042), whereas neither MCM-2 nor Ki-67 expression showed significant prognostic value (log-rank test, P = 0.9618 and P = 0.7174, respectively). In multivariate analysis, patient age, histopathological stage and grade of differentiation, but not MCM-5 expression, were identified as independent prognostic factors (Cox regression analysis, P = 0.0097, P = 0.0195, P = 0.0035 and P = 0.3245, respectively).

CONCLUSIONS

The present study showed that MCM-5 expression was associated with clinicopathological parameters in gastric adenocarcinoma. However, further studies highlighting the distinct impact of the two histopathological types, intestinal and diffuse, are warranted to delineate whether MCMs could be used as diagnostic and prognostic markers in gastric neoplasia.

Suppression of NF-kappaB and GSK-3beta is involved in colon cancer cell growth inhibition by the PPAR agonist troglitazone

Peroxisome proliferator-activated receptor (PPAR)-gamma agonists such as troglitazone, pioglitazone and thiazolidine have been shown to induce apoptosis in human colon cancer cells. The molecular mechanism of PPARgamma agonist-induced apoptosis of colon cancer cells, however, is not clear. Glycogen synthase kinase-3beta (GSK-3beta) is an indispensable element for the activation of nuclear factor-kappa B (NF-kappaB) which plays a critical role in the mediation of survival signals in cancer cells. To investigate the mechanisms of PPARgamma agonist-induced apoptosis of colon cancer cells, we examined the effect of troglitazone (0-16muM) on the activation of GSK-3beta and NF-kappaB. Our study showed that the inhibitory effect of troglitazone on colon cancer cell growth was associated with inhibition of NF-kappaB activity and GSK-3beta expression in a dose-dependent manner. Cells were arrested in G(0)/G(1) phase followed by the induction of apoptosis after treatment of troglitazone with concomitant decrease in the expression of the G(0)/G(1) phase regulatory proteins; Cdk2, Cdk4, cyclin B1, D1, and E as well as in the anti-apoptosis protein Bcl-2 along with an increase in the expression of the pro-apoptosis-associated proteins; Caspase-3, Caspase-9 and Bax. Transient transfection of GSK-3beta recovered troglitazone-induced cell growth inhibition and NF-kappaB inactivation. In contrast, co-treatment of troglitazone with a GSK-3beta inhibitor (AR-a014418) or siRNA against GSK-3beta, significantly augmented the inhibitory effect of troglitazone on the NF-kappaB activity, the cancer cell growth and on the expression of G(0)/G(1) phase regulatory proteins and pro-apoptosis regulatory proteins. These results suggest that the PPARgamma agonist, troglitazone, inhibits colon cancer cell growth via inactivation of NF-kappaB by suppressing GSK-3beta activity.

Peroxisome proliferator activated receptor-γ and the ubiquitin-proteasome system in colorectal cancer

Peroxisome proliferator activated receptor-γ (PPARγ), a transcription factor of the nuclear receptor superfamily plays a significant role in colorectal cancer pathogenesis. In most experimental systems PPARγ activation has tumor suppressing effects in the colon. PPARγ is regulated at multiple levels by the ubiquitin-proteasome system (UPS). At a first level, UPS regulates PPARγ transcription. This regulation involves both PPARγ transcription specific factors and the general transcription machinery. At a second level UPS regulates PPARγ and its co-factors themselves, as PPARγ and many co-factors are proteasome substrates. At a third level of regulation, transduction pathways working in parallel but also having interrelations with PPARγ are regulated by the UPS, creating a network of regulation in the colorectal carcinogenesis-related pathways that are under UPS control. Activation of PPARγ transcription by direct pharmacologic activators and by stabilization of its molecule by proteasome inhibitors could be strategies to be exploited in colorectal cancer treatment.

Significance of LRP and PPAR-gamma Expression in Lipomatous Soft Tissue Tumors

Background:

Molecular mechanism of differentiation in lipogenic tumor is still unknown in detail. Low-density lipoprotein receptor-related protein (LRP) and peroxisome proliferator-activated receptor gamma (PPAR-γ), representative regulatory molecules of lipogenic differentiation, have been reported today as multi-functional molecules and to modulate tumorigenesis in various kind of cancer. To date, diagnostic and therapeutic significance of the expression of these molecules in lipogenic tumors are not defined.

Methods:

The immunohistochemical expression status of LRP and PPAR-γ in various grades of 54 lipogenic tumors was analyzed. Correlation between the expression levels and the differentiation of the tumors was confirmed. For statistical analyses, the Kruskal-Wallis test, the Steel-Dwass test and the Mann–Whitney U test were used.

Results:

LRP and PPAR-γ expression was detected in 50 (92.6%) and 44 (81.5%) cases, respectively. The expression level in LRP was significantly higher in cases with well differentiated liposarcoma, pleomorphic liposarcoma and dedifferentiated liposarcoma than in lipoma. Compared with lipoma or well differentiated liposarcoma, significant elevation in expression level of PPAR-γ was confirmed in myxoid liposarcoma, pleomorphic liposarcoma, dedifferentiated liposarcoma and the differentiated area of dedifferentiated liposarcoma.

Conclusion:

The up-regulation of LRP and PPAR-γ in higher grade cases, i.e. less differentiated tumors than in low grade cases was shown, suggesting the candidate role of these molecules as tumor progression modulators rather than regulatory molecules of differentiation in lipogenic tumors.

Differential expression of peroxisome proliferator activated receptor gamma and cyclin D1 does not affect proliferation of asthma- and non-asthma-derived airway smooth muscle cells

PPARgamma levels in asthma- and non-asthma-derived airway smooth muscle cells and PPARgamma activation-induced cell proliferation were investigated. In the presence of FBS, PPARgamma levels were higher in subconfluent asthma-derived cells but lower in confluent cells compared with non-asthma-derived. However, PPARgamma activation did not alter cell proliferation.

BACKGROUND AND OBJECTIVE

Airway remodelling involves thickening of the airway smooth muscle (ASM) bulk. Proliferation of asthma-derived ASM cells is increased in vitro, but underlying mechanisms remain unknown. Peroxisome proliferators activated receptor-gamma (PPARgamma) regulates the cell cycle. It is suggested that PPARgamma agonists have anti-inflammatory effects, which may be valuable in the treatment of asthma, but information regarding their antiproliferative properties in ASM is lacking. Although corticosteroids reduce airway inflammation, in vitro they inhibit proliferation in only non-asthma ASM cells by reducing cyclin D1. We therefore investigated the effects of mitogenic stimulation (foetal bovine serum (FBS)), and a PPARgamma ligand (ciglitazone), on PPARgamma and cyclin D1 expression and proliferation of ASM cells. In addition, we examined the effects of ciglitazone on ASM cell proliferation.

METHODS

We assessed PPARgamma and cyclin D1 mRNA and protein levels using quantitative PCR and immunoblotting. Cell proliferation was assessed using bromodeoxyuridine uptake.

RESULTS

In the presence of 5% FBS, PPARgamma and cyclin D1 expression decreased over time in non-asthmatic cells but increased in asthmatic cells (compared with sub-confluent cells). FBS-induced proliferation of asthmatic cells increased at all time points, but occurred only at day 7 with non-asthmatic cells (compared with unstimulated time-matched control). Ciglitazone increased PPARgamma expression in both groups, but did not alter cell proliferation, while fluticasone increased PPARgamma protein only in asthmatic cells.

CONCLUSIONS

Although in the presence of a mitogenic stimulus, PPARgamma was differentially expressed in asthma- and non-asthma-derived ASM; its expression was not related to the increased proliferation observed in asthmatic ASM.

Metabolic syndrome and risk of subsequent colorectal cancer

The metabolic syndrome and visceral obesity have an increasing prevalence and incidence in the general population. The actual prevalence of the metabolic syndrome is 24% in US population and between 24.6% and 30.9% in Europe. As demonstrated by many clinical trials (NAHANES III, INTERHART) the metabolic syndrome is associated with an increased risk of both diabetes and cardiovascular disease. In addition to cardiovascular disease, individual components of the metabolic syndrome have been linked to the development of cancer, particularly to colorectal cancer. Colorectal cancer is an important public health problem; in the year 2000 there was an estimated total of 944 717 incident cases of colorectal cancer diagnosed world-wide. This association is sustained by many epidemiological studies. Recent reports suggest that individuals with metabolic syndrome have a higher risk of colon or rectal cancer. Moreover, the clusters of metabolic syndrome components increase the risk of associated cancer. The physiopathological mechanism that links metabolic syndrome and colorectal cancer is mostly related to abdominal obesity and insulin resistance. Population and experimental studies demonstrated that hyperinsulinemia, elevated C-peptide, elevated body mass index, high levels of insulin growth factor-1, low levels of insulin growth factor binding protein-3, high leptin levels and low adiponectin levels are all involved in carcinogenesis. Understanding the pathological mechanism that links metabolic syndrome and its components to carcinogenesis has a major clinical significance and may have profound health benefits on a number of diseases including cancer, which represents a major cause of mortality and morbidity in our societies.

Obesity and breast cancer: the roles of peroxisome proliferator-activated receptor-γ and plasminogen activator inhibitor-1

Breast cancer is the most prominent cancer among females in the United States. There are a number of risk factors associated with development of breast cancer, including consumption of a high-fat diet and obesity. Plasminogen activator inhibitor-1 (PAI-1) is a cytokine upregulated in obesity whose expression is correlated with a poor prognosis in breast cancer. As a key mediator of adipogenesis and regulator of adipokine production, peroxisome proliferator-activated receptor-γ (PPAR-γ) is involved in PAI-1 expression from adipose tissue. We summarize the current knowledge linking PPAR-γ and PAI-1 expression to high-fat diet and obesity in the risk of breast cancer.

A cohort study of cyclin D1 expression and prognosis in 602 colon cancer cases

PURPOSE

Cyclin D1 and cyclin-dependent kinases (CDK) are commonly activated in colorectal cancer. The activity of cyclin D1 can be blocked by CDK inhibitors, including p27 (CDKN1B) and p21 (CDKN1A, which is induced by p53). However, prognostic significance of tumoral cyclin D1 remains uncertain, and no previous study has considered potential confounding effect of p53, p21, p27, and related molecular events [microsatellite instability (MSI), CpG island methylator phenotype, and LINE-1 hypomethylation].

EXPERIMENTAL DESIGN

Among 602 colon cancer patients (stage I-IV) in two prospective cohort studies, cyclin D1 overexpression was detected in 330 (55%) tumors by immunohistochemistry. Cox proportional hazard models computed hazard ratios (HR) of colon cancer-specific and overall mortalities, adjusted for patient characteristics and tumoral molecular features, including p53, p21, p27, cyclooxygenase-2, fatty acid synthase, LINE-1 methylation, CpG island methylator phenotype, MSI, BMI, KRAS, and BRAF.

RESULTS

Cyclin D1 overexpression was associated with a low cancer-specific mortality in Kaplan-Meier analysis (P = 0.006), and in both univariate Cox regression [unadjusted HR, 0.64; 95% confidence interval (CI), 0.47-0.88; P = 0.0063] and multivariate analyses (adjusted HR, 0.57; 95% CI, 0.39-0.84; P = 0.0048). Similar findings were observed for an overall mortality (adjusted HR, 0.74; 95% CI, 0.57-0.98; P = 0.036). Notably, the effect of cyclin D1 on survival might differ by MSI status (P(interaction) = 0.008). Compared with tumors that were both cyclin D1-negative and MSI-low/microsatellite stable, the presence of either cyclin D1 or MSI-high or both seemed to confer better clinical outcome (adjusted HR point estimates, 0.10-0.65).

CONCLUSIONS

Cyclin D1 overexpression is associated with longer survival in colon cancer.

Colorectal cancer expression of peroxisome proliferator-activated receptor gamma (PPARG, PPARgamma) is associated with good prognosis

BACKGROUND & AIMS

The peroxisome proliferator-activated receptor gamma (PPARG, PPARgamma) is a nuclear receptor that regulates expression of mediators of lipid metabolism and the inflammatory response. There is controversy over the pro-oncogenic or antioncogenic effects of PPARG, and little is known about its prognostic significance in colon cancer.

METHODS

Among 470 patients with colorectal cancer (stages I-IV) identified in 2 independent prospective cohorts, PPARG expression was detected in 102 tumors (22%) by immunohistochemistry. Cox proportional hazards models were used to compute hazard ratios (HRs) of colorectal cancer-specific and overall mortalities, adjusted for patient characteristics and molecular features including cyclooxygenase 2, fatty acid synthase, KRAS, BRAF, PIK3CA, p53, p21, beta-catenin, LINE-1 hypomethylation, microsatellite instability (MSI), and the CpG island methylation phenotype (CIMP).

RESULTS

Compared with patients with PPARG-negative tumors, patients with PPARG-positive tumors had significantly lower overall mortality, determined by Kaplan-Meier analysis (P=.0047), univariate Cox regression (HR, 0.55; 95% confidence interval [CI], 0.37-0.84; P=.0053), and multivariate analysis (adjusted HR, 0.43; 95% CI, 0.27-0.69; P=.0004). Patients with PPARG-positive tumors experienced lower colorectal cancer-specific mortality (adjusted HR, 0.44; 95% CI, 0.25-0.79; P=.0054). The relationship between PPARG and lower mortality did not appear to be significantly modified by MSI, CIMP, LINE-1, or the other clinical and molecular variables examined (all P(interaction)>.05).

CONCLUSIONS

Tumor expression of PPARG is independently associated with longer survival of patients. PPARG expression appears to mark an indolent subset of colorectal cancers.

Expression of the peroxisome proliferator-activated receptors-alpha, -beta, and -gamma in ovarian carcinoma effusions is associated with poor chemoresponse and shorter survival

Peroxisome proliferator-activated receptors regulate lipid metabolism, affecting inflammation and cancer. The present study analyzed the anatomical site-related expression and prognostic role of peroxisome proliferator-activated receptors in ovarian carcinoma. Fresh-frozen effusions (n = 79), primary carcinomas (n = 44), and solid metastases (n = 16) were studied for peroxisome proliferator-activated receptor-alpha, -beta, and -gamma messenger RNA expression using reverse transcriptase polymerase chain reaction. Peroxisome proliferator-activated receptor-gamma messenger RNA expression was further assessed in 60 tumors (30 effusions, 20 primary carcinomas, 10 metastases) using in situ hybridization. Peroxisome proliferator-activated receptor-gamma protein expression was immunohistochemically analyzed in 160 effusions. All peroxisome proliferator-activated receptors were expressed in most tumors at all anatomical sites using reverse transcriptase polymerase chain reaction, but peroxisome proliferator-activated receptor-alpha (P = .004) and peroxisome proliferator-activated receptor-beta (P = .002) messenger RNA levels were higher in effusions compared with primary carcinomas and solid metastases. In situ hybridization localized peroxisome proliferator-activated receptor-gamma messenger RNA to carcinoma cells in both effusions and solid lesions. Peroxisome proliferator-activated receptor-gamma protein was detected in carcinoma cells in 102 of 160 (64%) effusions. Higher effusion messenger RNA levels of all peroxisome proliferator-activated receptors were associated with less favorable response to chemotherapy at diagnosis (P = .009). In univariate survival analysis, higher messenger RNA expression of all peroxisome proliferator-activated receptors was associated with poor progression-free (P = .045) and overall (P = .014) survival. Higher peroxisome proliferator-activated receptor-gamma protein expression was similarly associated with poor overall survival for the entire cohort (P = .046) and for patients with disease recurrence effusions (P = .009). Peroxisome proliferator-activated receptors were not independent predictors of survival in Cox multivariate analysis. Peroxisome proliferator-activated receptor members are frequently expressed in ovarian carcinoma, with upregulated expression in effusions. Peroxisome proliferator-activated receptor expression in effusions is associated with poor response to chemotherapy at disease recurrence and poor survival, suggesting a role in tumor biology at this unique microenvironment.