Peroxisome proliferator-activated receptor gamma ligands induce cell cycle arrest and apoptosis in human renal carcinoma cell lines

Integrated analyses reveal the prognostic, immunological features and mechanisms of cuproptosis critical mediator gene FDX1 in KIRC

The ferredoxin 1 (FDX1) gene had been recently reported as a critical mediator of cuproptosis, and without doubt, its roles in KIRC would be of importance. Hence, this paper was to explore the roles of FDX1 in kidney renal clear cell carcinoma (KIRC) and its potential molecular mechanisms via scRNA-sequencing and bulk RNA-sequencing analyses. FDX1 was lowly expressed in KIRC and validated both at the protein and mRNA levels (all p < 0.05). Moreover, its elevated expression was linked with a better overall survival (OS) prognosis in KIRC (p < 0.01). The independent impact of FDX1 on KIRC prognosis was demonstrated by univariate/multivariate regression analysis (p < 0.01). Gene set enrichment analysis (GSEA) identified seven pathways strongly associated with FDX1 in KIRC. Furthermore, FDX1 was also revealed to be significantly related with immunity (p < 0.05). In addition, patients with low expression of FDX1 might be more sensitive to immunotherapies. ScRNA-seq analysis found that FDX1 could be expressed in immune cells and was mainly differently expressed in Mono/Macro cells. Ultimately, we also identified several LncRNA/RBP/FDX1 mRNA networks to reveal its underlying mechanisms in KIRC. Taken together, FDX1 was closely related to prognosis and immunity in KIRC, and its RBP-involved mechanisms of LncRNA/RBP/FDX1 networks were also revealed by us.

CD200 ectodomain shedding into the tumor microenvironment leads to NK cell dysfunction and apoptosis

The basis of immune evasion, a hallmark of cancer, can differ even when cancers arise from one cell type such as in the human skin keratinocyte carcinomas: basal and squamous cell carcinoma. Here we showed that the basal cell carcinoma tumor-initiating cell surface protein CD200, through ectodomain shedding, was responsible for the near absence of NK cells within the basal cell carcinoma tumor microenvironment. In situ, CD200 underwent ectodomain shedding by metalloproteinases MMP3 and MMP11, which released biologically active soluble CD200 into the basal cell carcinoma microenvironment. CD200 bound its cognate receptor on NK cells to suppress MAPK pathway signaling that in turn blocked indirect (IFN-γ release) and direct cell killing. In addition, reduced ERK phosphorylation relinquished negative regulation of PPARγ-regulated gene transcription and led to membrane accumulation of the Fas/FADD death receptor and its ligand, FasL, which resulted in activation-induced apoptosis. Blocking CD200 inhibition of MAPK or PPARγ signaling restored NK cell survival and tumor cell killing, with relevance to many cancer types. Our results thus uncover a paradigm for CD200 as a potentially novel and targetable NK cell-specific immune checkpoint, which is responsible for NK cell-associated poor outcomes in many cancers.

PPAR-γ Partial Agonists in Disease-Fate Decision with Special Reference to Cancer

Peroxisome proliferator-activated receptor-γ (PPAR-γ) has emerged as one of the most extensively studied transcription factors since its discovery in 1990, highlighting its importance in the etiology and treatment of numerous diseases involving various types of cancer, type 2 diabetes mellitus, autoimmune, dermatological and cardiovascular disorders. Ligands are regarded as the key determinant for the tissue-specific activation of PPAR-γ. However, the mechanism governing this process is merely a contradictory debate which is yet to be systematically researched. Either these receptors get weakly activated by endogenous or natural ligands or leads to a direct over-activation process by synthetic ligands, serving as complete full agonists. Therefore, fine-tuning on the action of PPAR-γ and more subtle modulation can be a rewarding approach which might open new avenues for the treatment of several diseases. In the recent era, researchers have sought to develop safer partial PPAR-γ agonists in order to dodge the toxicity induced by full agonists, akin to a balanced activation. With a particular reference to cancer, this review concentrates on the therapeutic role of partial agonists, especially in cancer treatment. Additionally, a timely examination of their efficacy on various other disease-fate decisions has been also discussed.

Renal Cell Cancer and Obesity

Cancers are a frequent cause of morbidity and mortality. There are many risk factors for tumours, including advanced age, personal or family history of cancer, some types of viral infections, exposure to radiation and some chemicals, smoking and alcohol consumption, as well as obesity. Increasing evidence suggest the role of obesity in the initiation and progression of various cancers, including renal cell carcinoma. Since tumours require energy for their uncontrollable growth, it appears plausible that their initiation and development is associated with the dysregulation of cells metabolism. Thus, any state characterised by an intake of excessive energy and nutrients may favour the development of various cancers. There are many factors that promote the development of renal cell carcinoma, including hypoxia, inflammation, insulin resistance, excessive adipose tissue and adipokines and others. There are also many obesity-related alterations in genes expression, including DNA methylation, single nucleotide polymorphisms, histone modification and miRNAs that can promote renal carcinogenesis. This review focuses on the impact of obesity on the risk of renal cancers development, their aggressiveness and patients’ survival.

SRSF1 promotes the inclusion of exon 3 of SRA1 and the invasion of hepatocellular carcinoma cells by interacting with exon 3 of SRA1pre-mRNA

Steroid receptor RNA activator 1 (SRA1) has been described as a novel transcriptional co-activator that affects the migration of cancer cells. Through RT-PCR, we identified that skipping exon 3 of SRA1 produces two isoforms, including the truncated short isoform, SRA1-S, and the long isoform, SRA1-L. However, the effect of these two isomers on the migration of HCC cells, as well as the specific mechanism of exon 3 skipping remain unclear. In this study, we found up regulated expression of SRSF1 and SRA1-L in highly metastatic HCCLM3, as well as in HCCs with SRSF1 demonstrating the strongest correlation with SRA1-L. In contrast, we observed a constitutively low expression of SRA1-S and SRSF1 in lowly metastatic HepG2 cells. Overexpression of SRSF1 or SRA1-L promoted migration and invasion by increasing the expression of CD44, while SRA1-S reversed the effect of SRSF1 and SRA1-L in vitro. In addition, lung metastasis in mice revealed that, knockdown of SRSF1 or SRA1-L inhibited the migration of HCC cells, while SRA1-L overexpression abolished the effect of SRSF1 knockout and instead promoted HCC cells migration in vivo. More importantly, RNA immunoprecipitation and Cross-link immunoprecipitation analyses showed that SRSF1 interacts with exon 3 of SRA1 to up regulate the expression of SRA1-L in HCC cells. RNA pull-down results indicated that SRSF1 could also bind to exon 3 of SRA1 in vitro. Finally, minigene -MS2 mutation experiments showed that mutation of the SRA1 exon 3 binding site for SRSF1 prevented the binding of SRA1 pre-mRNA. In summary, our results provide experimental evidence that SRA1 exon 3 inclusion is up regulated by SRSF1 to promote tumor invasion and metastasis in hepatocellular carcinoma.

Elements in potable groundwater in Rugao longevity area, China: Hydrogeochemical characteristics, enrichment patterns and health assessments

Rugao city is a typical longevity area taking shallow groundwater as the primary drinking water source. To determine the relationship between longevity and groundwater conditions, the hydrogeochemical characteristics and related causes of potable groundwater were investigated. On this basis, the water quality index (WQI) and hazard index (HI) of groundwater were evaluated. Meanwhile, the nutrient indicators beneficial to human health, like Ca and Mg concentrations, were also considered to explore the relationship. The results were as following: (1) 91.3% of water samples fell under the Ca/Mg-HCO3 water type, which resulted from the dissolution of silicate rock. Na, Cl-, Br, B in groundwater emanated from seawater intrusion. The abnormal concentrations of NO3- and As also indicated that anthropogenic activities had exerted significant influences on groundwater quality. (2) The average WQI value was 30.19, which meant that the overall groundwater quality in Rugao city was pretty good. However, 8 water samples were found to have HI values above 1, which might be attributed to the high concentration of As (maximum value 0.0407 mg/L; mean value 0.0076 mg/L). In general, low WQI and HI values corresponded to towns with a high longevity population; what's more, WQI and HI values of Rugao city were lower than those of non-longevity areas. (3) Comparing with adjacent non-longevity areas, the potable groundwater in Rugao city had the characteristics of high Ca (mean value 123.57 mg/L), high Mg (mean value 50.33 mg/L) and high SO42- (mean value 525.19 mg/L). The daily intake of Ca and Mg from drinking water could meet 12.4% and 22.4% of daily Ca and Mg requirements, respectively. Also, the areas where the Sr and B concentrations were higher usually had higher life expectancy. The high concentrations of Ca, Mg, SO42-, Sr and B in drinking water, as well as low WQI and HI values, probably contribute to physical health and longevity. This research helps provide an insight into the relationship between groundwater quality and health and can serve as a reference for drinking water quality management.

Differential Effects of Cancer-Associated Mutations Enriched in Helix H3 of PPARγ

Peroxisome proliferator-activated receptor gamma (PPARγ) has recently been revealed to regulate tumor microenvironments. In particular, genetic alterations of PPARγ found in various cancers have been reported to play important roles in tumorigenesis by affecting PPARγ transactivation. In this study, we found that helix H3 of the PPARγ ligand-binding domain (LBD) has a number of sites that are mutated in cancers. To uncover underlying molecular mechanisms between helix H3 mutations and tumorigenesis, we performed structure‒function studies on the PPARγ LBDs containing helix H3 mutations found in cancers. Interestingly, PPARγ Q286E found in bladder cancer induces a constitutively active conformation of PPARγ LBD and thus abnormal activation of PPARγ/RXRα pathway, which suggests tumorigenic roles of PPARγ in bladder cancer. In contrast, other helix H3 mutations found in various cancers impair ligand binding essential for transcriptional activity of PPARγ. These data indicate that cancer-associated mutations clustered in helix H3 of PPARγ LBD exhibit differential effects in PPARγ-mediated tumorigenesis and provide a basis for the development of new biomarkers targeting tumor microenvironments.

Pleiotropic effects of anti-diabetic drugs: A comprehensive review

Diabetes mellitus characterized by hyperglycaemia presents an array of comorbidities such as cardiovascular and renal failure, dyslipidemia, and cognitive impairments. Populations above the age of 60 are in an urgent need of effective therapies to deal with the complications associated with diabetes mellitus. Widely used anti-diabetic drugs have good safety profiles and multiple reports indicate their pleiotropic effects in diabetic patients or models. This review has been written with the objective of identifying the widely-marketed anti-diabetic drugs which can be efficiently repurposed for the treatment of other diseases or disorders. It is an updated, comprehensive review, describing the protective role of various classes of anti-diabetic drugs in mitigating the macro and micro vascular complications of diabetes mellitus, and differentiating these drugs on the basis of their mode of action. Notably, metformin, the anti-diabetic drug most commonly explored for cancer therapy, has also exhibited some antimicrobial effects. Unlike class specific effects, few instances of drug specific effects in managing cardiovascular complications have also been reported. A major drawback is that the pleiotropic effects of anti-diabetic drugs have been mostly investigated only in diabetic patients. Thus, for effective repurposing, more clinical trials devoted to analyse the effects of anti-diabetic drugs in patients irrespective of their diabetic condition, are required.

Drug rechanneling: A novel paradigm for cancer treatment

Cancer continues to be one of the leading contributors towards global disease burden. According to NIH, cancer incidence rate per year will increase to 23.6 million by 2030. Even though cancer continues to be a major proportion of the disease burden worldwide, it has the lowest clinical trial success rate amongst other diseases. Hence, there is an unmet need for novel, affordable and effective anti-neoplastic medications. As a result, a growing interest has sparkled amongst researchers towards drug repurposing. Drug repurposing follows the principle of polypharmacology, which states, "any drug with multiple targets or off targets can present several modes of action". Drug repurposing also known as drug rechanneling, or drug repositioning is an economic and reliable approach that identifies new disease treatment of already approved drugs. Repurposing guarantees expedited access of drugs to the patients as these drugs are already FDA approved and their safety and toxicity profile is completely established. Epidemiological studies have identified the decreased occurrence of oncological or non-oncological conditions in patients undergoing treatment with FDA approved drugs. Data from multiple experimental studies and clinical observations have depicted that several non-neoplastic drugs have potential anticancer activity. In this review, we have summarized the potential anti-cancer effects of anti-psychotic, anti-malarial, anti-viral and anti-emetic drugs with a brief overview on their mechanism and pathways in different cancer types. This review highlights promising evidences for the repurposing of drugs in oncology.

S. Ferreira KC, Neto JCR. Pharmacological Strategies for Insulin Sensitivity in Obesity and Cancer: Thiazolidinediones and Metformin

Background:

Chronic diseases, such as obesity and cancer, have high prevalence rates. Both diseases have hyperinsulinemia, hyperglycemia, high levels of IGF-1 and inflammatory cytokines in common. Therefore, these can be considered triggers for cancer development and growth. In addition, low-grade inflammation that modulates the activation of immune cells, cellular metabolism, and production of cytokines and chemokines are common in obesity, cancer, and insulin resistance. Pharmacological strategies are necessary when a change in lifestyle does not improve glycemic homeostasis. In this regard, thiazolidinediones (TZD) possess multiple molecular targets and regulate PPARγ in obesity and cancer related to insulin resistance, while metformin acts through the AMPK pathway.

Objective:

The aim of this study was to review TZD and metformin as pharmacological treatments for insulin resistance associated with obesity and cancer.

Conclusions:

Thiazolidinediones restored adiponectin secretion and leptin sensitivity, reduced lipid droplets in hepatocytes and orexigen peptides in the hypothalamus. In cancer cells, TZD reduced proliferation, production of reactive oxygen species, and inflammation by acting through the mTOR and NFκB pathways. Metformin has similar effects, though these are AMPK-dependent. In addition, both drugs can be efficient against certain side effects caused by chemotherapy.

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.

Metabolic Syndrome Resolved within Two Years is Still a Risk Factor for Kidney Cancer

The prevalence of metabolic syndrome (MetS) and kidney cancer is increasing, but studies on the effects of MetS and its components on kidney cancer development have had ambiguous results. Overall, 7,613,865 patients from the Korean National Health Insurance System were analyzed and followed up until 2017. Patients with ≥3 of the necessary five components of MetS were diagnosed with MetS. Patients were divided into subgroups according to two consecutive physical examinations conducted every two years. The Cox proportional hazard regression model was used to survey the independent association between MetS and the risk of kidney cancer development. Kidney cancer risk was significantly higher in patients with MetS, and there was no difference according to sex. The hazards ratio of kidney cancer increased with increasing number of MetS components. For patients not diagnosed with MetS but with abdominal obesity and hypertension, the likelihood of developing kidney cancer was similar to that of patients diagnosed with MetS. Patients with improved MetS within two years had increased risk of kidney cancer compared with those without MetS. MetS is an independent risk factor for kidney cancer, and the obesity and hypertension components of MetS are also powerful risk factors.

Pioglitazone suppresses macrophage proliferation in apolipoprotein-E deficient mice by activating PPARγ

BACKGROUND AND AIMS

Local macrophage proliferation is linked to enhanced atherosclerosis progression. Our previous study found that troglitazone, a thiazolidinedione (TZD), suppressed oxidized low-density lipoprotein (Ox-LDL)-induced macrophage proliferation. However, its effects and mechanisms are unclear. Therefore, we investigated the effects of pioglitazone, another TZD, on macrophage proliferation.

METHODS

Normal chow (NC)- or high-fat diet (HFD)-fed apolipoprotein E-deficient (Apoe^-/-) mice were treated orally with pioglitazone (10 mg/kg/day) or vehicle (water) as a control. Mouse peritoneal macrophages were used in in vitro assays.

RESULTS

Atherosclerosis progression was suppressed in aortic sinuses of pioglitazone-treated Apoe^-/- mice, which showed fewer proliferating macrophages in plaques. Pioglitazone suppressed Ox-LDL-induced macrophage proliferation in a dose-dependent manner. However, treatment with peroxisome proliferator-activated receptor-γ (PPARγ) siRNA ameliorated pioglitazone-induced suppression of macrophage proliferation. Low concentrations (less than 100 μmol/L) of pioglitazone, which can suppress macrophage proliferation, activated PPARγ in macrophages, but did not induce macrophage apoptosis. Pioglitazone treatment did not induce TUNEL-positive cells in atherosclerotic plaques of aortic sinuses in Apoe^-/- mice.

CONCLUSIONS

Pioglitazone suppressed macrophage proliferation through PPARγ without inducing macrophage apoptosis. These findings imply that pioglitazone could prevent macrovascular complications in diabetic individuals.

Peroxisome Proliferator-Activated Receptor gamma negatively regulates liver regeneration after partial hepatectomy via the HGF/c-Met/ERK1/2 pathways

Peroxisome Proliferator-Activated Receptor gamma (PPARγ) is a nuclear receptor demonstrated to play an important role in various biological processes. The aim of this study was to determine the effect of PPARγ on liver regeneration upon partial hepatectomy (PH) in mice. Mice were subjected to two-thirds PH. Before surgery, mice were either treated with the PPARγ agonist rosiglitazone, the PPARγ antagonist GW9662 alone, or with the c-met inhibitor SGX523. Liver-to-body-weight ratio, lab values, and proliferation markers were assessed. Components of the PPARγ-specific signaling pathway were identified by western blot and qRT-PCR. Our results show that liver regeneration is being inhibited by rosiglitazone and accelerated by GW9662. Inhibition of c-Met by SGX523 treatment abrogates GW9662-induced liver regeneration and hepatocyte proliferation. Hepatocyte growth factor (HGF) protein levels were significantly downregulated after rosiglitazone treatment. Activation of HGF/c-Met pathways by phosphorylation of c-Met and ERK1/2 were inhibited in rosiglitazone-treated mice. In turn, blocking phosphorylation of c-Met significantly abrogated the augmented effect of GW9662 on liver regeneration. Our data support the concept that PPARγ abrogates liver growth and hepatocellular proliferation by inhibition of the HGF/c-Met/ERK1/2 pathways. These pathways may represent potential targets in response to liver disease and could impact on the development of molecular therapies.

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.

Concurrent inhibition of mTORC1 and mTORC2 by WYE-687 inhibits renal cell carcinoma cell growth in vitro and in vivo

Mammalian target of rapamycin (mTOR)in renal cell carcinoma (RCC) represents a valuable oncotarget for treatment. We here tested the potential anti-RCC activity by a novel mTOR kinase inhibitor WYE-687in vitro and in vivo.WYE-687 was cytotoxic and anti-proliferative to established RCC cell lines (786-O and A498) and primary human RCC cells. Yet, it was non-cytotoxic toHK-2 tubular epithelial cells.WYE-687 provoked caspase-dependent apoptosis in the RCC cells. At the molecular level, WYE-687 almost completely blocked mTORC1 (p-S6K1 and p-S6) and mTORC2 (p-Akt Ser 473) activation in both 786-Ocells and primary human RCC cells, where it downregulated both hypoxia-inducible factor (HIF)-1α and HIF-2α expression. Significantly, oral administration of WYE-687 potently suppressed786-O tumor xenograft growth in nude mice. mTORC1/2 activation and HIF-1α/2α expression were also remarkably downregulated in WYE-687-treated tumor tissues. Thus, our preclinical results imply that WYE-687 may have important translational value for the treatment of RCC.

PPAR-γ Agonists As Antineoplastic Agents in Cancers with Dysregulated IGF Axis

It is now widely accepted that insulin resistance and compensatory hyperinsulinemia are associated to increased cancer incidence and mortality. Moreover, cancer development and progression as well as cancer resistance to traditional anticancer therapies are often linked to a deregulation/overactivation of the insulin-like growth factor (IGF) axis, which involves the autocrine/paracrine production of IGFs (IGF-I and IGF-II) and overexpression of their cognate receptors [IGF-I receptor, IGF-insulin receptor (IR), and IR]. Recently, new drugs targeting various IGF axis components have been developed. However, these drugs have several limitations including the occurrence of insulin resistance and compensatory hyperinsulinemia, which, in turn, may affect cancer cell growth and survival. Therefore, new therapeutic approaches are needed. In this regard, the pleiotropic effects of peroxisome proliferator activated receptor (PPAR)-γ agonists may have promising applications in cancer prevention and therapy. Indeed, activation of PPAR-γ by thiazolidinediones (TZDs) or other agonists may inhibit cell growth and proliferation by lowering circulating insulin and affecting key pathways of the Insulin/IGF axis, such as PI3K/mTOR, MAPK, and GSK3-β/Wnt/β-catenin cascades, which regulate cancer cell survival, cell reprogramming, and differentiation. In light of these evidences, TZDs and other PPAR-γ agonists may be exploited as potential preventive and therapeutic agents in tumors addicted to the activation of IGF axis or occurring in hyperinsulinemic patients. Unfortunately, clinical trials using PPAR-γ agonists as antineoplastic agents have reached conflicting results, possibly because they have not selected tumors with overactivated insulin/IGF-I axis or occurring in hyperinsulinemic patients. In conclusion, the use of PPAR-γ agonists in combined therapies of IGF-driven malignancies looks promising but requires future developments.

Pioglitazone induces cell growth arrest and activates mitochondrial apoptosis in human uterine leiomyosarcoma cells by a peroxisome proliferator-activated receptor γ-independent mechanism

The peroxisome proliferator-activated receptor γ (PPARγ) agonists, thiazolidinediones, including pioglitazone (PIO) exhibit anti-tumour activities in cancer cells. The present study investigates the effects of PIO on cell proliferation and apoptosis in SK-UT-1 cells, a human uterine leiomyosarcoma cell line, and human uterine smooth muscle cells (HUtSMC). The proliferation and viability of SK-UT-1 cells treated with vehicle or PIO were assessed by cell counting and WST-1 assay. The activity of MEK/ERK and p38 MAPK signalling pathways and the expression of p53, the cyclin-dependent kinase inhibitor, p21, Bax, Bad and Bim proteins and cleaved caspase-3 were analysed by Western blotting. Quiescent SK-UT-1 cells intensively proliferate and display high levels of phosphorylated, activated MEK1/2, ERK1/2 and p38 MAPK. PIO (10 or 25 μM) induced time- and dose-dependently cell-growth arrest, reduced the cell numbers and effectively suppressed the over-activated MEK/ERK and p38 MAPK signalling pathways as evidenced by the abolished levels of phosphorylated MEK1/2, ERK1/2 and p38 MAPK. PIO activated the intrinsic apoptotic pathway, i.e. up-regulated the p53, p21, Bax and Bad proteins and cleaved caspase-3. PIO also reduced cell numbers of highly proliferative SK-UT-1 cells cultured in growth medium. The anti-proliferative and pro-apoptotic actions of PIO were not PPARγ dependent and exclusive for SK-UT-1 cells as PIO did not interfere with the proliferation of HUtSMC. The pronounced anti-tumorigenic effects of PIO in SK-UT-1 cells address an important issue about the relevance of the PPARγ agonist in the treatment of the human uterine leiomyosarcoma.

Cardioprotective effect of pioglitazone in diabetic and non-diabetic rats subjected to acute myocardial infarction involves suppression of AGE-RAGE axis and inhibition of apoptosis

Insulin resistance increases risk of cardiovascular diseases. This work investigated the protective effect of pioglitazone on myocardial infarction (MI) in non-diabetic and diabetic rats, focusing on its role on advanced glycated endproducts (AGEs) and cardiac apoptotic machinery. Male rats were divided into 2 experiments: experiment I and II (non-diabetic and diabetic rats) were assigned as saline, MI (isoproterenol, 85 mg/kg, daily), and MI+pioglitazone (5, 10, and 20 mg/kg). Injection of isoproterenol in diabetic rats produced greater ECG disturbances compared to non-diabetic rats. Treatment with pioglitazone (5 mg/kg) reduced the infarct size and improved some ECG findings. Pioglitazone (10 mg/kg) enhanced ECG findings, improved the histopathological picture and downregulated apoptosis in cardiac tissues. Whereas the higher dose of pioglitazone (20 mg/kg) did not improve most of the measured parameters but rather worsened some of them, such as proapoptotic markers. Importantly, a positive correlation was found between serum AGEs and cardiac AGE receptors (RAGEs) versus caspase 3 expression in the two experiments. Therefore, the current effect of pioglitazone was, at least in part, mediated through downregulation of AGE-RAGE axis and inhibition of apoptosis. Consequently, these data suggest that pioglitazone, at optimized doses, may have utility in protection from acute MI.

WIN induces apoptotic cell death in human colon cancer cells through a block of autophagic flux dependent on PPARγ down-regulation

Cannabinoids have been reported to possess anti-tumorigenic activity in cancer models although their mechanism of action is not well understood. Here, we show that the synthetic cannabinoid WIN55,212-2 (WIN)-induced apoptosis in colon cancer cell lines is accompanied by endoplasmic reticulum stress induction. The formation of acidic vacuoles and the increase in LC3-II protein indicated the involvement of autophagic process which seemed to play a pro-survival role against the cytotoxic effects of the drug. However, the enhanced lysosomal membrane permeabilization (LMP) blocked the autophagic flux after the formation of autophagosomes as demonstrated by the accumulation of p62 and LC3, two markers of autophagic degradation. Data also provided evidence for a role for nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) in cannabinoid signalling. PPARγ expression, at both protein and mRNA levels, was significantly down-regulated after WIN treatment and its inhibition, either by specific antagonists or by down-regulation via gene silencing, induced effects on cell viability as well as on ER stress and autophagic markers similar to those obtained in the presence of WIN. Moreover, the observation that the increase in p62 level and the induction of LMP were also modified by PPARγ antagonists seemed to indicate that PPARγ down-regulation was crucial to determinate the block of autophagic flux, thus confirming the critical role of PPARγ in WIN action. In conclusion, at our knowledge, our results are the first to show that the reduction of PPARγ levels contributes to WIN-induced colon carcinoma cell death by blocking the pro-survival autophagic response of cells.

Metabolic syndrome and renal cell carcinoma

BACKGROUND

Metabolic syndrome (MS) is a cluster of metabolic abnormalities, which has been regarded as a pivotal risk factor for cardiovascular diseases. Recent studies focusing on the relationship between MS and cancer have recognized the significant role of MS on carcinogenesis. Likewise, growing evidence suggests that MS has a strong association with increased renal cell carcinoma (RCC) risk. This review outlines the link between MS and RCC, and some underlying mechanisms responsible for MS-associated RCC.

MATERIALS AND METHODS

A National Center for Biotechnology Information PubMed search (http://www.pubmed.gov) was conducted using medical subject headings 'metabolic syndrome', 'obesity', 'hypertension', 'diabetes', 'dyslipidemia', and 'renal cell carcinoma'.

RESULTS

This revealed that a variety of molecular mechanisms secondary to MS are involved in RCC formation, progression, and metastasis. A deeper understanding of these molecular mechanisms may provide some strategies for the prevention and treatment of RCC.

CONCLUSIONS

In summary, there is a large body of evidence regarding the link between MS and RCC, within which each component of MS is considered to have a close causal association with RCC.

Can an oral antidiabetic (rosiglitazone) be of benefit in leukemia treatment?

PPARs are ligand-regulated transcription factors and regulate expression of several gene products. Therefore, PPARs are being studied for their possible contribution to the treatment of cancer, atherosclerosis, inflammation, infertility and demyelinating diseases. Primary AML patients were observed to have significantly elevated PPARγ mRNA expression compared to normal peripheral blood or bone marrow mononuclear cells. This study investigated the cytotoxic effects of rosiglitazone maleate, a pure PPARγ agonist, in vitro in HL-60 cell line. This study obtained results which can provide guidance for future studies. Whether the PPARy agonist rosiglitazone maleate may provide additive effects in refractory or relapsing cases of acute leukemia may be set as an objective for the future studies.

Sphingoid bases from sea cucumber induce apoptosis in human hepatoma HepG2 cells through p-AKT and DR5

Biofunctional marine compounds have recently received substantial attention for their nutraceutical characteristics. In this study, we investigated the apoptosis-inducing effects of sphingoid bases prepared from sea cucumber using human hepatoma HepG2 cells. Apoptotic effects were determined by cell viability assay, DNA fragmentation assay, caspase-3 and caspase-8 activities. The expression levels of apoptosis-inducing death receptor-5 (DR5) and p-AKT were assayed by western blot analysis, and mRNA expression of bax, GADD45 and PPARγ was assayed by quantitative RT-PCR analysis. Sphingoid bases from sea cucumber markedly reduced the cell viability of HepG2 cells. DNA fragmentation indicative of apoptosis was observed in a dose-dependent manner. The expression levels of the apoptosis inducer protein Bax were increased by the sphingoid bases from sea cucumber. GADD45, which plays an important role in apoptosis-inducing pathways, was markedly upregulated by sphingoid bases from sea cucumber. Upregulation of PPARγ mRNA was also observed during apoptosis induced by the sphingoid bases. The expression levels of DR5 and p-AKT proteins were increased and decreased, respectively, as a result of the effects of sphingoid bases from sea cucumber. The results indicate that sphingoid bases from sea cucumber induce apoptosis in HepG2 cells through upregulation of DR5, Bax, GADD45 and PPARγ and downregulation of p-AKT. Our results show for the first time the functional properties of marine sphingoid bases as inducers of apoptosis in HepG2 cells.

Targeting the apoptotic pathway in chondrosarcoma using recombinant human Apo2L/TRAIL (dulanermin), a dual proapoptotic receptor (DR4/DR5) agonist

Recombinant human Apo2L/TRAIL (dulanermin) is based on the ligand for death receptors (DR4 and DR5), which promotes apoptosis. We report a patient with refractory chondrosarcoma who showed a prolonged response to dulanermin and explore mechanisms of response and resistance. This heavily pretreated patient had progressive metastatic chondrosarcoma to the lung. On dulanermin (8 mg/kg i.v. on days 1-5 in a 21-day cycle), the patient achieved a sustained partial response with only subcentimeter nodules remaining. After 62 months of dulanermin treatment, progressive disease in the lungs was noted, and the patient underwent a resection that confirmed chondrosarcoma. DR4 was detected (immunohistochemistry) in the patient's tumor, which may have enabled the response. However, upregulation of prosurvival proteins, namely, phosphorylated (p)-NF-κBp65 (Ser 536), p-STAT3 (Tyr 705), p-ERK 1/2 (Thr 202/Tyr 204), p-mTOR (Ser 2448), FASN, and Bcl-2, were also detected, which may have provided the underlying mechanisms for acquired dulanermin resistance. The patient was restarted on dulanermin and has continued on this treatment for an additional 16 months since surgery (78 months since initiation of treatment), with his most recent computed tomography (CT) scans showing no evidence of disease.

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.

Prognostic significance of P27 (Kip 1) and MUC1 in papillary transitional cell carcinoma of the urinary bladder

Aim:

To examine p27 (Kip 1) and MUC1 expression in specimens of papillary transitional cell carcinoma (PTCC) of the urinary bladder and to correlate their expression with the tumor grades,stages and outcome.

Patients and Methods:

Paraffin sections from previously diagnosed PTCC bladder were graded, staged and the patients were followed up for 5 years. Ten non-neoplastic urological lesions diagnosed as polypoid cystitis were taken as control. Three sections of 4 um thickness were obtained from every case. One was hematoxylin and eosin (H and E) stained for diagnosis, reviewing and confirmation. The other two sections were immunohistochemically stained for both p27and MUC1. The data of immunohistochemical results were correlated with the following conventional prognostic variables: tumor grade, stage, distant metastasis and 5 year survival.

Results:

The results showed a highly significant and an insignificant relationship between p27 expression and tumor grade and stage (P<0.01 and P>0.05), respectively. Correlating p27 expression with distant metastasis and overall survival showed a significant relationship with distant metastasis (P<0.05) and a highly significant one with overall survival (P<0.01). The results showed also a significant relationship between MUC1 expression and both tumor grade (P<0.01) and overall survival (P<0.05).

Conclusion:

p27 and MUC1 immunohistochemistry augment the classic histochemistry for the prognosis of PTCC of the bladder as well as improving the prediction of the patient outcome and survival.

Chondrosarcoma and peroxisome proliferator-activated receptor

Induction of differentiation and apoptosis in cancer cells by ligands of PPARγ is a novel therapeutic approach to malignant tumors. Chondrosarcoma (malignant cartilage tumor) and OUMS-27 cells (cell line established from grade III human chondrosarcoma) express PPARγ. PPARγ ligands inhibited cell proliferation in a dose-dependent manner, and induced apoptosis of OUMS-27. The higher-grade chondrosarcoma expressed a higher amount of antiapoptotic Bcl-xL in vivo. The treatment of OUMS-27 by 15d-PGJ₂, the most potent endogenous ligand for PPARγ, downregulated expression of Bcl-xL and induced transient upregulation of proapoptotic Bax, which could accelerate cytochrome c release from mitochondria to the cytosol, followed by induction of caspase-dependent apoptosis. 15d-PGJ₂ induced the expression of CDK inhibitor p21 protein in human chondrosarcoma cells, which appears to be involved in the mechanism of inhibition of cell proliferation. These findings suggest that targeted therapy with PPARγ ligands could be a novel strategy against chondrosarcoma.

Specific thiazolidinediones inhibit ovarian cancer cell line proliferation and cause cell cycle arrest in a PPARγ independent manner

BACKGROUND

Peroxisome Proliferator Activated Receptor gamma (PPARγ) agonists, such as the thiazolinediones (TZDs), have been studied for their potential use as cancer therapeutic agents. We investigated the effect of four TZDs--Rosiglitazone (Rosi), Ciglitazone (CGZ), Troglitazone (TGZ), and Pioglitazone (Pio)--on ovarian cancer cell proliferation, PPARγ expression and PPAR luciferase reporter activity. We explored whether TZDs act in a PPARγ dependent or independent manner by utilizing molecular approaches to inhibit or overexpress PPARγ activity.

PRINCIPAL FINDINGS

Treatment with CGZ or TGZ for 24 hours decreased proliferation in three ovarian cancer cell lines, Ovcar3, CaOv3, and Skov3, whereas Rosi and Pio had no effect. This decrease in Ovcar3 cell proliferation was due to a higher fraction of cells in the G(0)/G(1) stage of the cell cycle. CGZ and TGZ treatment increased apoptosis after 4 hours of treatment but not after 8 or 12 hours. Treatment with TGZ or CGZ increased PPARγ mRNA expression in Ovcar3 cells; however, protein levels were unchanged. Surprisingly, luciferase promoter assays revealed that none of the TZDs increased PPARγ activity. Overexpression of wild type PPARγ increased reporter activity. This was further augmented by TGZ, Rosi, and Pio indicating that these cells have the endogenous capacity to mediate PPARγ transactivation. To determine whether PPARγ mediates the TZD-induced decrease in proliferation, cells were treated with CGZ or TGZ in the absence or presence of a dominant negative (DN) or wild type overexpression PPARγ construct. Neither vector changed the TZD-mediated cell proliferation suggesting this effect of TZDs on ovarian cancer cells may be PPARγ independent.

CONCLUSIONS

CGZ and TGZ cause a decrease in ovarian cancer cell proliferation that is PPARγ independent. This concept is supported by the finding that a DN or overexpression of the wild type PPARγ did not affect the changes in cell proliferation and cell cycle.

Mechanisms by which thiazolidinediones induce anti-cancer effects in cancers in digestive organs

Increasing evidence suggests that thiazolidinediones (TZDs) could have a therapeutic potential for patients with cancers. Here, the evidence on the mechanisms by which TZDs could contribute to different steps of cancer biology in the digestive system is summarized. According to studies, TZDs induce anti-cancer actions through 3 main pathways: (1) cell growth arrest, (2) induction of apoptosis, and (3) inhibition of cell invasion. Cell growth arrest is induced by an increased level of p27(Kip1). p27(Kip1) accumulation results from the inhibition of the ubiquitin-proteasome system and/or inhibition of MEK-ERK signaling. TZDs induce apoptosis through increased levels of apoptotic molecules, such as p53 and PTEN and/or decreased level of anti-apoptotic molecules, such as Bcl-2 and survivin. Inhibition of MEK-ERK signaling-mediated up-regulation of E-cadherin and claudin-4, and/or decreased expression of matrix metalloproteinases (MMPs) such as MMP-2 and MMP-9, play a role in the TZD-induced inhibition of cancer cell invasion. Thus, TZDs are capable of inducing anti-tumor action in a variety of ways in gastrointestinal cancers.

Rosiglitazone enhances the radiosensitivity of p53-mutant HT-29 human colorectal cancer cells

Combined-modality treatment has improved the outcome in cases of various solid tumors, and radiosensitizers are used to enhance the radiotherapeutic efficiency. Rosiglitazone, a synthetic ligand of peroxisome proliferator-activated receptors gamma used in the treatment of type-2 diabetes, has been shown to reduce tumor growth and metastasis in human cancer cells, and may have the potential to be used as a radiosensitizer in radiotherapy for human colorectal cancer cells. In this study, rosiglitazone treatment significantly reduced the cell viability of p53-wild type HCT116 cells but not p53-mutant HT-29 cells. Interestingly, rosiglitazone pretreatment enhanced radiosensitivity in p53-mutant HT-29 cells but not HCT116 cells, and prolonged radiation-induced G(2)/M arrest and enhanced radiation-induced cell growth inhibition in HT-29 cells. Pretreatment with rosiglitazone also suppressed radiation-induced H2AX phosphorylation in response to DNA damage and AKT activation for cell survival; on the contrary, rosiglitazone pretreatment enhanced radiation-induced caspase-8, -9, and -3 activation and PARP cleavage in HT-29 cells. In addition, pretreatment with a pan-caspase inhibitor, zVAD-fmk, attenuated the levels of caspase-3 activation and PARP cleavage in radiation-exposed cancer cells in combination with rosiglitazone pretreatment. Our results provide proof for the first time that rosiglitazone suppresses radiation-induced survival signals and DNA damage response, and enhances the radiation-induced apoptosis signaling cascade. These findings can assist in the development of rosiglitazone as a novel radiosensitizer.

Thiazolidinediones alter growth and epithelial cell integrity, independent of PPAR-γ and MAPK activation, in mouse M1 cortical collecting duct cells

Peroxisome proliferator-activated receptor (PPAR)-γ is highly expressed in the collecting duct (CD), yet little is known about the effects of PPAR-γ ligands, thiazolidinediones (TZDs), on CD cell structure and function. M1 mouse cortical CD cells were treated with 5 μM troglitazone (TRO) and rosiglitazone (ROSI). First, growth was measured by [(3)H]thymidine and [(3)H]leucine incorporation, as well as analysis of cyclin D1 and the CDK inhibitor p27 by Western blot. [(3)H]thymidine incorporation was reduced by 56 and 24% by TRO and ROSI at 6 h, and [(3)H]leucine by 21 and 10%. A similar growth inhibition was also observed after 24 h for thymidine, but leucine was reduced by 48 and 24%, respectively. Likewise, cyclin D1 was diminished 60% by TRO, and p27 was elevated 1.6- and 1.7-fold in response to TRO and ROSI. Next, epithelial cell integrity was assessed by measuring different markers by Western blot analysis. While fibronectin and α-smooth muscle actin levels were unchanged, by 24 h E-cadherin was decreased by 50%, and β-catenin levels were reduced 2- and 1.5-fold in response to TRO and ROSI, respectively. GW9662, a PPAR-γ antagonist, did not reverse any of the TZD responses in M1 cells. Of interest, phosho-p38 levels were also elevated 2-fold in response to TRO and 2.3-fold to ROSI, but MAPK inhibition by PD98059 or SB203580 caused an additive inhibition of cell growth and did not alter E-cadherin or β-catenin in response to TZDs. Finally, apoptotic death was assessed by Western blot, but cleaved caspase-3 levels were unchanged from 15 min to 24 h in response to TZDs, and TRO did not affect cell viability or reactive oxygen species generation. Our data suggest that TZDs cause a disruption of M1 cell integrity that is preceded by an inhibition of cell growth. This response is independent of p38 or PPAR-γ activation.

PPAR-γ agonists and their effects on IGF-I receptor signaling: Implications for cancer

It is now well established that the development and progression of a variety of human malignancies are associated with dysregulated activity of the insulin-like growth factor (IGF) system. In this regard, promising drugs have been developed to target the IGF-I receptor or its ligands. These therapies are limited by the development of insulin resistance and compensatory hyperinsulinemia, which in turn, may stimulate cancer growth. Novel therapeutic approaches are, therefore, required. Synthetic PPAR-γ agonists, such as thiazolidinediones (TZDs), are drugs universally used as antidiabetic agents in patients with type 2 diabetes. In addition of acting as insulin sensitizers, PPAR-γ agonists mediate in vitro and in vivo pleiotropic anticancer effects. At least some of these effects appear to be linked with the downregulation of the IGF system, which is induced by the cross-talk of PPAR-γ agonists with multiple components of the IGF system signaling. As hyperinsulinemia is an emerging cancer risk factor, the insulin lowering action of PPAR-γ agonists may be expected to be also beneficial to reduce cancer development and/or progression. In light of these evidences, TZDs or other PPAR-γ agonists may be exploited in those tumors "addicted" to the IGF signaling and/or in tumors occurring in hyperinsulinemic patients.

Combining the receptor tyrosine kinase inhibitor AEE788 and the mammalian target of rapamycin (mTOR) inhibitor RAD001 strongly inhibits adhesion and growth of renal cell carcinoma cells

BACKGROUND

Treatment options for metastatic renal cell carcinoma (RCC) are limited due to resistance to chemo- and radiotherapy. The development of small-molecule multikinase inhibitors has now opened novel treatment options. We evaluated the influence of the receptor tyrosine kinase inhibitor AEE788, applied alone or combined with the mammalian target of rapamycin (mTOR) inhibitor RAD001, on RCC cell adhesion and proliferation in vitro.

METHODS

RCC cell lines Caki-1, KTC-26 or A498 were treated with various concentrations of RAD001 or AEE788 and tumor cell proliferation, tumor cell adhesion to vascular endothelial cells or to immobilized extracellular matrix proteins (laminin, collagen, fibronectin) evaluated. The anti-tumoral potential of RAD001 combined with AEE788 was also investigated. Both, asynchronous and synchronized cell cultures were used to subsequently analyze drug induced cell cycle manipulation. Analysis of cell cycle regulating proteins was done by western blotting.

RESULTS

RAD001 or AEE788 reduced adhesion of RCC cell lines to vascular endothelium and diminished RCC cell binding to immobilized laminin or collagen. Both drugs blocked RCC cell growth, impaired cell cycle progression and altered the expression level of the cell cycle regulating proteins cdk2, cdk4, cyclin D1, cyclin E and p27. The combination of AEE788 and RAD001 resulted in more pronounced RCC growth inhibition, greater rates of G0/G1 cells and lower rates of S-phase cells than either agent alone. Cell cycle proteins were much more strongly altered when both drugs were used in combination than with single drug application. The synergistic effects were observed in an asynchronous cell culture model, but were more pronounced in synchronous RCC cell cultures.

CONCLUSION

Potent anti-tumoral activitites of the multikinase inhibitors AEE788 or RAD001 have been demonstrated. Most importantly, the simultaneous use of both AEE788 and RAD001 offered a distinct combinatorial benefit and thus may provide a therapeutic advantage over either agent employed as a monotherapy for RCC treatment.

In vitro and in vivo anti-melanoma effects of ciglitazone

Activation of PPARgamma by synthetic ligands, thiazolidinediones, inhibits the proliferation of cancer cells. In this report, focusing our attention on ciglitazone, we show that ciglitazone inhibits melanoma growth by inducing apoptosis and cell-cycle arrest, whereas normal melanocytes are resistant to ciglitazone. In melanoma cells, ciglitazone-induced apoptosis is associated with caspase activations and a loss of mitochondrial membrane potential. Induction of cell-cycle arrest by ciglitazone is associated with changes in expression of key cell-cycle regulators such as p21, cyclin D1, and pRB hypophosphorylation. Cell-cycle arrest occurs at low ciglitazone concentrations and through a PPARgamma-dependent pathway, whereas the induction of apoptosis is caused by higher ciglitazone concentrations and independently of PPARgamma. These results allow an effective molecular dissociation between proapoptotic effects and growth inhibition evoked by ciglitazone in melanoma cells. Finally, we show that in vivo treatment of nude mice by ciglitazone dramatically inhibits human melanoma xenograft development. The data presented suggest that ciglitazone might be a better candidate for clinical trials in melanoma treatment than the thiazolidinediones currently used in the treatment of type 2 diabetes, such as rosiglitazone, which is devoid of a proapoptotic PPARgamma-independent function.

Relationship between arachidonic acid pathway and human renal cell carcinoma

Recent epidemiological studies and animal experiments have demonstrated that nonsteroidal antiinflammatory drugs (NSAIDs) reduce the incidence of colorectal carcinoma. Cyclooxygenase (COX) is the principal target of NSAIDs. COX is the first oxidase in the process of prostaglandin production from arachidonic acid. COX enzyme may be involved in the initiation and/or the promotion of carcinogenesis due to NSAIDs inhibition of COX. Lipoxygenase (LOX) is also an initial enzyme in the pathway for producing leukotrienes from arachidonic acid. Similar to COX, LOX enzyme may also be involved in the initiation and/or promotion of carcinogenesis. Peroxisome proliferator activator-receptor (PPAR)-γ is a ligand-activated transcriptional factor belonging to the steroid receptor superfamily. PPAR-γ plays a role in both adipocyte differentiation and carcinogenesis. PPAR-γ is one target for cell growth modulation of NSAIDs. In this review, we report the expression of COX-2, LOX and PPAR-γ in human renal cell carcinoma tissues as well as the effects of COX-2 and LOX inhibitors and PPAR-γ ligand.

Chemotherapeutic drugs induce PPAR-gamma expression and show sequence-specific synergy with PPAR-gamma ligands in inhibition of non-small cell lung cancer

Preclinical studies have shown that peroxisome proliferator-activated receptor gamma (PPAR-gamma) ligands can exert antitumor effects against non-small cell lung cancer (NSCLC) and a variety of other cancers. In this study, we investigate the potential use of a PPAR-gamma ligand, troglitazone (Tro), in combination with either of two chemotherapeutic agents, cisplatin (Cis) or paclitaxel (Pac), for the treatment of NSCLC. In vitro, treatment of NSCLC cell lines with Tro potentiated Cis- or Pac-induced growth inhibition. The potentiation of growth inhibition was observed only when Cis or Pac treatment was followed by Tro and not vice versa, demonstrating a sequence-specific effect. Median effect analysis revealed a synergistic interaction between Tro and Cis in the inhibition of NSCLC cell growth and confirmed the sequence-specific effect. We also found that Cis or Pac up-regulated the expression of PPAR-gamma protein, accounting for the observed sequence-specific synergy. Similarly, experiments performed using a NSCLC xenograft model demonstrated enhanced effectiveness of combined treatment with Cis and PPAR-gamma ligands, Tro or pioglitazone. Tumors from Cis-treated mice also demonstrated enhanced PPAR-gamma expression. Together, our data demonstrate a novel sequence-specific synergy between PPAR-gamma ligands and chemotherapeutic agents for lung cancer treatment.

PPAR gamma regulates MITF and beta-catenin expression and promotes a differentiated phenotype in mouse melanoma S91

Melanoma represents one of the most rapidly metastasizing, hence deadly tumors due to its high proliferation rate and invasiveness, characteristics of undifferentiated embryonic tissues. Given the absence of effective therapy for metastatic melanoma, understanding more fully the molecular mechanisms underlying melanocyte differentiation may provide opportunities for novel therapeutic intervention. Here we show that in mouse melanoma S91 cells activation of the peroxisome proliferator activated receptor (PPAR) gamma induces events resembling differentiation, such as growth arrest accompanied by apoptosis, spindle morphology and enhanced tyrosinase expression. These events are preceded by an initial transient increase in expression from the Microphthalmia-associated transcription factor gene, (MITF) promoter, whereas exposure to a PPAR gamma ligand- ciglitazone that exceeds 8 h, causes a gradual decrease of MITF, until by 48 h MITF expression is substantially reduced. Beta-catenin, an MITF transcriptional activator, shows a similar pattern of decline during ciglitazone treatment, consistent with previous reports that activated PPAR gamma inhibits the Wnt/beta-catenin pathway through induction of beta-catenin proteasomal degradation. We suggest that the PPAR gamma-mediated beta-catenin down-regulation is likely to be responsible for changes in MITF levels. The data suggest that PPAR gamma, besides its well-established role in mesenchymal cell differentiation towards adipocytes, might regulate differentiation in the melanocytic lineage.

Troglitazone, a peroxisome proliferator-activated receptor γ ligand, induces growth inhibition and apoptosis of HepG2 human liver cancer cells

AIM: To examine the effect of troglitazone, a peroxisome proliferator-activated receptor γ (PPARγ) ligand, on the proliferation and apoptosis of human liver cancer cells.

METHODS: Liver cancer cell line HepG2 was cultured and treated with troglitazone. Cell proliferation was detected by 3-(4-,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay; apoptosis was detected by flow cytometry and terminal deoxynucleotidyl transferase-mediated nick end labeling of DNA fragmentation sites (TUNEL) assay; and apoptosis-related protein was detected by immunocytochemistry and Western blotting.

RESULTS: Troglitazone inhibited growth and induced apoptosis of HepG2 cells in a dose-dependent manner, and induced activation of caspase-3 expression. Troglitazone not only drove apoptosis-inhibiting factor survivin to translocate incompletely from the nucleus to the cytoplasm, but also inhibited expression of survivin, while it did not affect expression of apoptosis-promoting factor Bax.

CONCLUSION: PPARγ ligands inhibit growth and induce apoptosis of liver cancer cells, and may have applications for the prevention and treatment of liver cancer.

1,1-bis(3'-indolyl)-1-(p-substitutedphenyl)methanes induce apoptosis and inhibit renal cell carcinoma growth

PURPOSE

1,1-Bis(3'-indolyl)-1-(p-substitutedphenyl)methanes [methylene-substituted diindolylmethanes (C-DIM)] containing p-trifluoromethyl, p-t-butyl, and p-phenyl substituents activate peroxisome proliferator-activated receptor gamma (PPARgamma) and inhibit growth of several different cancer cell lines through receptor-dependent and receptor-independent pathways. The purpose of this study is to investigate the anticancer activity of these compounds in renal cell carcinoma.

EXPERIMENTAL DESIGN

The anticancer activity of the p-t-butyl-substituted C-DIM compound (DIM-C-pPhtBu) was investigated in ACHN and 786-0 renal cell carcinoma cell lines and in an orthotopic model for renal carcinogenesis using ACHN cells injected directly into the kidney.

RESULTS

PPARgamma is overexpressed in ACHN cells and barely detectable in 786-0 cells, and treatment with DIM-C-pPhtBu induces proteasome-dependent degradation of cyclin D1 and variable effects on p21 and p27 expression in both cell lines. DIM-C-pPhtBu also induced several common proapoptotic responses in ACHN and 786-0 cells, including increased expression of nonsteroidal anti-inflammatory drug-activated gene-1 and endoplasmic reticulum stress, which activates death receptor 5 and the extrinsic pathway of apoptosis. Activation of these responses was PPARgamma independent. In addition, DIM-C-pPhtBu (40 mg/kg/d) also inhibited tumor growth in an orthotopic mouse model for renal carcinogenesis, and this was accompanied by induction of apoptosis in renal tumors treated with DIM-C-pPhtBu but not in tumors treated with the corn oil vehicle (control).

CONCLUSIONS

DIM-C-pPhtBu and related compounds are cytotoxic to renal cancer cells and activate multiple proapoptotic and growth-inhibitory pathways. The results coupled with in vivo anticancer activity show the potential of DIM-C-pPhtBu and related C-DIMs for clinical treatment of renal adenocarcinoma.

Cimicifuga foetida extract inhibits proliferation of hepatocellular cells via induction of cell cycle arrest and apoptosis

The purpose of this study is to determine whether the ethyl acetate fraction (EAF) from the aerial part of Cimicifuga foetida Linnaeus possesses the anti-tumor action on hepatoma, and therefore, provide evidence for the traditional use of the plant as a detoxification agent. EAF was extracted and its cytotoxicity was evaluated on a panel of Hepatocytes by MTT assay. The IC(50) values of EAF on HepG2, R-HepG2 and primary cultured normal mouse hepatocytes were 21, 43 and 80 microg/mL, respectively. Morphology observation, Annexin V-FITC/PI staining, cell cycle analysis and western blot were used to further elucidate the cytotoxic mechanism of EAF. EAF induced G(0)/G(1)cell cycle arrest at lower concentration (25 microg/mL), and triggered G(2)/M arrest and apoptosis at higher concentrations (50 and 100 microg/mL, respectively). An increase in the ratio of Bax/Bcl-2, activation of downstream effector Caspase 3, and cleavage of poly-ADP-ribose polymerase (PARP) were implicated in EAF-induced apoptosis. In addition, EAF inhibited the growth of the implanted mouse H(22) tumor in a dose-dependent manner with the growth inhibitory rate of 63.32% at 200 mg/kg. In conclusion, EAF may potentially find use as a new therapy for the treatment of hepatoma.