Nonsteroidal anti-inflammatory drug-activated gene-1 over expression in transgenic mice suppresses intestinal neoplasia

GDF15 and Growth Control

Growth/differentiation factor-15 (GDF-15) is a distant member of the transforming growth factor β (TGF-β) superfamily and is widely expressed in multiple mammalian tissues. Its expression is highly regulated and is often induced in response to conditions associated with cellular stress. GDF15 serum levels have a strong association with many diseases, including inflammation, cancer, cardiovascular diseases, and obesity, and potentially serve as reliable predictor of disease progression. A functional role for GDF15 has been suggested in cancer, cardiovascular disease, kidney disease and metabolic disease. However, the knowledge of its pathophysiological function at the molecular level is still limited and requires more investigation. Recent identification of the endogenous receptor for GDF15 may provide additional insight in to its' molecular mechanisms and relationship to disease states.

GDF15 Regulates Malat-1 Circular RNA and Inactivates NFκB Signaling Leading to Immune Tolerogenic DCs for Preventing Alloimmune Rejection in Heart Transplantation

Recombinant human growth differentiation factor 15 (rhGDF15) affects dendritic cell (DC) maturation. However, whether GDF15 is expressed in DCs and its roles and signaling in DCs remain largely unknown. It is unclear whether GDF15-DCs can induce immune tolerance in heart transplantation (HT). This study aims to understand the impact of endogenous GDF15 on DC's development, function, underlying molecular mechanism including circular RNA (circRNA). This study will also explore GDF15-DC-mediated immune modulation in HT. Bone marrow (BM) derived DCs were cultured and treated to up- or down regulate GDF15 expression. Phenotype and function of DCs were detected. Expression of genes and circRNAs was determined by qRT-PCR. The signaling pathways activated by GDF15 were examined. The impact of GDF15 treated DCs on preventing allograft immune rejection was assessed in a MHC full mismatch mouse HT model. Our results showed that GDF15 was expressed in DCs. Knockout of GDF15 promoted DC maturation, enhanced immune responsive functions, up-regulated malat-1 circular RNA (circ_Malat 1), and activated the nuclear factor kappa B (NFκB) pathway. Overexpression of GDF15 in DCs increased immunosuppressive/inhibitory molecules, enhanced DCs to induce T cell exhaustion, and promoted Treg generation through IDO signaling. GDF15 utilized transforming growth factor (TGF) β receptors I and II, not GFAL. Administration of GDF15 treated DCs prevented allograft rejection and induced immune tolerance in transplantation. In conclusion, GDF15 induces tolerogenic DCs (Tol-DCs) through inhibition of circ_Malat-1 and the NFκB signaling pathway and up-regulation of IDO. GDF15-DCs can prevent alloimmune rejection in HT.

Chitosan-based nanoparticles with damnacanthal suppress CRM1 expression

Cancer is one of the leading causes of mortality worldwide. Phytochemicals may be promising anticancer agents given their various chemical structures and diverse biological activities. Damnacanthal (DAM) is a major bioactive component of Noni, which has been investigated previously as a cancer-preventive or chemotherapeutic agent. DAM has also been reported to exhibit anti-proliferative activity in several cancer types. In the present study, it was identified that DAM downregulates chromosome maintenance protein 1 (CRM1) expression in human cancer cells. The application of chitosan-based nanoparticles (NPs) with DAM also induced CRM1 downregulation, which suggests that chitosan-based NPs may be effective vehicles for delivery of phytochemicals such as DAM. It was also identified that DAM increased the levels of the tumor suppressor non-steroidal anti-inflammatory drugs-activated gene 1 in the nucleus, thereby leading to enhanced anticancer effects. The results of the present study indicate that DAM and its nanoformulation may be a candidate anticancer drug.

The MIC-1/GDF15-GFRAL Pathway in Energy Homeostasis: Implications for Obesity, Cachexia, and Other Associated Diseases

MIC-1/GDF15 is a stress response cytokine and a distant member of the transforming growth factor beta (TGFb) superfamily, with no close relatives. It acts via a recently identified receptor called glial-derived neurotrophic factor (GDNF) receptor alpha-like (GFRAL), which is a distant orphan member of the GDNF receptor family that signals through the tyrosine kinase receptor Ret. MIC-1/GDF15 expression and serum levels rise in response to many stimuli that initiate cell stress and as part of a wide variety of disease processes, most prominently cancer and cardiovascular disease. The best documented actions of MIC-1/GDF15 are on regulation of energy homeostasis. When MIC-1/GDF15 serum levels are substantially elevated in diseases like cancer, it subverts a physiological pathway of appetite regulation to induce an anorexia/cachexia syndrome initiated by its actions on hindbrain neurons. These effects make it a potential target for the treatment of both obesity and anorexia/cachexia syndromes, disorders lacking any highly effective, readily accessible therapies.

Effects of postoperative non-steroidal anti-inflammatory drugs on long-term survival and recurrence of patients with non-small cell lung cancer

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used to relieve postoperative fever, surgery pain, and inflammation. In addition, NSAIDs have anticancer activity and may reduce the risk and mortality of several cancers. However, the association between postoperative NSAIDs and the clinical outcome of non-small cell lung cancer (NSCLC) patients with fever after surgery is not fully understood. We performed a retrospective study of NSCLC patients who underwent surgery between July 2011 and June 2012, aiming to evaluate the effect of postoperative NSAIDs on overall survival (OS) and progression-free survival (PFS). Differences in clinical data between the postoperative NSAIDs group and non-NSAIDs groups were analyzed by Chi-square tests. Kaplan-Meier curves method and Cox regression analysis were conducted for survival analysis. The primary and secondary endpoints were OS and PFS, respectively. This retrospective study included 347 NSCLC patients. There were no significant differences in the clinical characteristics between the NSAIDs group and non-NSAIDs group except for age (P = .024) and differential degree (P = .040). Administration of postoperative NSAIDs was related to longer OS (hazards ratio [HR] 0.528, 95% confidence interval [CI] 0.278-0.884, P = .006) and longer PFS (HR 0.557, 95% CI 0.317-0.841, P = .002) in the multivariate Cox regression model. Subgroup analysis showed statistically significant differences in elderly individuals, male subjects, low smoking index, poor differentiation, and non-adenocarcinoma subgroups, respectively. In conclusion, the administration of postoperative NSAIDs was related to longer OS and PFS in NSCLC patients with postoperative fever.

Uniting GDF15 and GFRAL: Therapeutic Opportunities in Obesity and Beyond

Growth differentiation factor-15 (GDF15) is a circulating protein that has been implicated in multiple biological processes, including energy homeostasis, body weight regulation, and cachexia driven by cancer and chronic disease. The potential to target GDF15 in the treatment of energy-intake disorders, including obesity and anorexia, is an area of intense investigation, but has been limited by the lack of an identified receptor, signaling mechanism, and target tissue. GDNF family receptor α-like (GFRAL) was recently identified as the neuronal brainstem receptor responsible for mediating the anorectic actions of GDF15. Herein, we provide a brief overview of GDF15 biology with a focus on energy homeostasis, and highlight the implications of the recent receptor identification to this field and beyond.

EZH2-Mediated Epigenetic Suppression of GDF15 Predicts a Poor Prognosis and Regulates Cell Proliferation in Non-Small-Cell Lung Cancer

Growth differentiation factor 15 (GDF15), a member of the TGF-β superfamily of cytokines, has been reported to exert very heterogeneous functions in various tumors. However, its expression and roles in mediating non-small-cell lung cancer (NSCLC) progression remain unknown. In this study, we found that GDF15 is downregulated in paired NSCLC tissues and correlated with poor clinical outcomes in NSCLC. A functional experiment demonstrated that overexpression of GDF15 significantly repressed NSCLC proliferation both in vitro and in vivo. Mechanistic studies reveal that inhibition of EZH2 expression prevented its binding to the GDF15 promoter region and reduced the trimethylation modification pattern of H3K27. Together, our data uncover that GDF15 is a direct target of EZH2 and, as a regulator of proliferation, might serve as a candidate prognostic biomarker and target for new therapies in human NSCLC.

Over-expression of growth differentiation factor 15 (GDF15) preventing cold ischemia reperfusion (I/R) injury in heart transplantation through Foxo3a signaling

Ischemia reperfusion (I/R) injury which inevitably occurs during heart transplantation is the major factor leading to organ failure and graft rejection. In order to develop new therapies to prevent I/R injury, we used both a murine heart transplantation model with 24 hour cold I/R and an in vitro cell culture system to determine whether growth differentiation factor 15 (GDF15) is a protective factor in preventing I/R injury in heart transplantation and to further investigate underlying mechanisms of I/R injury. We found that cold I/R caused severe damage to the endocardium, epicardium and myocardium of heart grafts from wild type C57BL/6 mice, whereas grafts from GDF15 transgenic (TG) mice showed less damage as demonstrated by decreased cell apoptosis/death, decreased neutrophils infiltration and the preservation of the normal structure of the heart. Over-expression of GDF15 reduced expression of phosphorylated RelA p65, pre-inflammatory and pro-apoptotic genes while it enhanced Foxo3a phosphorylation in vitro and in vivo. Over-expression of GDF15 inhibited cell apoptosis/death and reduced neutrophil infiltration. In conclusion, this study, for the first time, demonstrates that GDF15 is a promising target for preventing cold I/R injury in heart transplantation. This study also shows that the resultant protective effects are mediated by the Foxo3 and NFκB signaling pathways.

YAP promotes breast cancer metastasis by repressing growth differentiation factor-15

The transcriptional co-activator Yes-associated protein (YAP) has been implicated as an oncogene and is found to promote breast cancer metastasis. However, the pro-metastatic mechanism of YAP remains unclear. Here, we demonstrated that YAP functions as a transcriptional repressor of growth differentiation factor-15 (GDF15), a divergent member of the transforming growth factor superfamily, in several breast cancer cell lines. Functionally, knockdown of YAP decreased, whereas knockdown of GDF15 increased, the metastatic potential of breast cancer cells. More than that, the reduced metastasis in YAP-depleted cells could be reversed by simultaneous knockdown of GDF15. Mechanistically, the repressive effect of YAP on GDF15 requires its transcriptional factor TEAD (TEA domain family). In addition, YAP recruits polycomb repressive complex 2 (PRC2) to tri-methylate histone H3 lysine 27 in the promoter region of GDF15. Co-immunoprecipitation experiments demonstrated that YAP and enhancer of zeste 2 PRC2 subunit (EZH2) physically interact with each other. In conclusion, our data reveal that YAP promotes metastasis of breast cancer cells by repressing GDF15 transcription and present a novel molecular mechanism underlying the pro-metastasis function of YAP oncoprotein, with the implication of a therapeutic avenue for breast cancer treatment.

Overproduction of growth differentiation factor 15 promotes human rhinovirus infection and virus-induced inflammation in the lung

Human rhinovirus (HRV) is the most common virus contributing to acute exacerbations of chronic obstructive pulmonary disease (COPD) nearly year round, but the mechanisms have not been well elucidated. Recent clinical studies suggest that high levels of growth differentiation factor 15 (GDF15) protein in the blood are associated with an increased yearly rate of all-cause COPD exacerbations. Therefore, in the current study, we investigated whether GDF15 promotes HRV infection and virus-induced lung inflammation. We first examined the role of GDF15 in regulating host defense and HRV-induced inflammation using human GDF15 transgenic mice and cultured human GDF15 transgenic mouse tracheal epithelial cells. Next, we determined the effect of GDF15 on viral replication, antiviral responses, and inflammation in human airway epithelial cells with GDF15 knockdown and HRV infection. Finally, we explored the signaling pathways involved in airway epithelial responses to HRV infection in the context of GDF15. Human GDF15 protein overexpression in mice led to exaggerated inflammatory responses to HRV, increased infectious particle release, and decreased IFN-λ2/3 (IL-28A/B) mRNA expression in the lung. Moreover, GDF15 facilitated HRV replication and inflammation via inhibiting IFN-λ1/IL-29 protein production in human airway epithelial cells. Lastly, Smad1 cooperated with interferon regulatory factor 7 (IRF7) to regulate airway epithelial responses to HRV infection partly via GDF15 signaling. Our results reveal a novel function of GDF15 in promoting lung HRV infection and virus-induced inflammation, which may be a new mechanism for the increased susceptibility and severity of respiratory viral (i.e., HRV) infection in cigarette smoke-exposed airways with GDF15 overproduction.

GL-V9 induced upregulation and mitochondrial localization of NAG-1 associates with ROS generation and cell death in hepatocellular carcinoma cells

We have previously reported that a newly synthesized compound, GL-V9 could induce mitochondria-mediated apoptosis in HepG2 cells. However, the underlying mechanisms have not been fully understood yet. In current study, we further showed that GL-V9 exhibited significant inhibitory effect on growth of several hepatocellular carcinoma cell lines. Moreover, GL-V9-induced growth inhibition was coincident with the strong upregulation of nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1), a TGFβ superfamily member, which has been linked with tumor suppression. Further analysis uncovered that GL-V9-activated p38 MAPK pathway contributed to enhancement of NAG-1 mRNA stability. Interestingly, we observed that the intracellular NAG-1 protein induced by GL-V9 could, at least in part, localize in mitochondria where it might affect protein expression, thereby resulting in dissipation of mitochondria membrane potential (MMP) and accumulation of mitochondrial superoxide, eventually facilitating to apoptosis events. Silence of NAG-1 could attenuate mitochondria related apoptosis caused by GL-V9. Moreover, GL-V9 suppressed tumor growth in xenograft model accompanied with upregulation of NAG-1 in tumor tissues. Collectively, these data demonstrated that NAG-1 could play an important role in mitochondria apoptosis triggered by GL-V9, thus providing novel mechanistic explanations and potential target for using GL-V9 as a chemotherapeutic agent against human hepatocellular carcinoma.

Macrophage inhibitory cytokine-1/growth differentiation factor-15 as a predictor of colonic neoplasia

BACKGROUND

Serum macrophage inhibitory cytokine-1 (MIC-1/GDF15) concentration has been associated with colonic adenomas and carcinoma.

AIMS

To determine whether circulating MIC-1/GDF15 serum concentrations are higher in the presence of adenomas and whether the level decreases after excision.

METHODS

Patients were recruited prospectively from a single centre and stratified into five groups: no polyps (NP); hyperplastic polyps (HP); sessile serrated ademona (SSA); adenomas (AP); and colorectal carcinoma (CRC). Blood samples were collected immediately before and 4 weeks after colonoscopy. MIC-1/GDF15 serum levels were quantified using ELISA.

RESULTS

Participants (n=301) were stratified as: NP; n=116 (52%), HP; n=37 (12%), SSA; n=19 (7%), AP; n=68 (23%); and CRC; n=3 (1%). Patients were excluded from the study due to nondiagnostic pathology (n=9, 3%) and exclusion criteria (n=20, 6%). In the 272 remaining subjects (M=149; F=123), age (P=.005), history of colonic polyps (P=.003) and family history of colonic polyps (P=.002) were associated with presence of adenomas. Baseline median MIC-1/GDF15 serum levels increased significantly from NP 609 (460-797) pg/mL, HP 582 (466-852) pg/mL, SSA 561 (446-837) pg/mL to AP 723 (602-1122) pg/mL and CRC 1107 (897-1107) pg/mL; (P<.001). In the pre- and postpolypectomy paired adenoma samples median MIC-1/GDF15 reduced significantly from 722 (603-1164) pg/mL to 685 (561-944) pg/mL (P=.002). A ROC analysis for serum MIC-1/GDF15 to identify adenomatous polyps indicated an area under the curve of 0.71.

CONCLUSIONS

Our data suggest that serum MIC-1/GDF15 has the diagnostic characteristics to increase the detection of colonic neoplasia and improve screening.

Growth Differentiation Factor-15 Deficiency Augments Inflammatory Response and Exacerbates Septic Heart and Renal Injury Induced by Lipopolysaccharide

Septic acute kidney injury (AKI) and myocardial dysfunction are leading causes of mortality with no accepted method of therapy. In this study we demonstrate the role of growth differentiating factor 15 (GDF15) in septic AKI and myocardial dysfunction using a murine lipopolysaccharide (LPS)-induced sepsis model and an in vitro cell culture system. Data show that GDF15 deficiency augments inflammatory response and exacerbates renal and cardiac injury induced by LPS, while over-expression of GDF15 protects the kidney and heart from LPS-induced organ dysfunction. Therefore, this study highlights the therapeutic potential of GDF15 in the treatment of endotoxin-induced sepsis.

ASPirin Intervention for the REDuction of colorectal cancer risk (ASPIRED): a study protocol for a randomized controlled trial

BACKGROUND

Although aspirin is recommended for the prevention of colorectal cancer, the specific individuals for whom the benefits outweigh the risks are not clearly defined. Moreover, the precise mechanisms by which aspirin reduces the risk of cancer are unclear. We recently launched the ASPirin Intervention for the REDuction of colorectal cancer risk (ASPIRED) trial to address these uncertainties.

METHODS/DESIGN

ASPIRED is a prospective, double-blind, multidose, placebo-controlled, biomarker clinical trial of aspirin use in individuals previously diagnosed with colorectal adenoma. Individuals (n = 180) will be randomized in a 1:1:1 ratio to low-dose (81 mg/day) or standard-dose (325 mg/day) aspirin or placebo. At two study visits, participants will provide lifestyle, dietary and biometric data in addition to urine, saliva and blood specimens. Stool, grossly normal colorectal mucosal biopsies and cytology brushings will be collected during a flexible sigmoidoscopy without bowel preparation. The study will examine the effect of aspirin on urinary prostaglandin metabolites (PGE-M; primary endpoint), plasma inflammatory markers (macrophage inhibitory cytokine-1 (MIC-1)), colonic expression of transcription factor binding (transcription factor 7-like 2 (TCF7L2)), colonocyte gene expression, including hydroxyprostaglandin dehydrogenase 15-(NAD) (HPGD) and those that encode Wnt signaling proteins, colonic cellular nanocytology and oral and gut microbial composition and function.

DISCUSSION

Aspirin may prevent colorectal cancer through multiple, interrelated mechanisms. The ASPIRED trial will scrutinize these pathways and investigate putative mechanistically based risk-stratification biomarkers.

TRIAL REGISTRATION

This protocol is registered with the U.S. National Institutes of Health trial registry, ClinicalTrials.gov, under the identifier NCT02394769 . Registered on 16 March 2015.

High GDF-15 Serum Levels Independently Correlate with Poorer Overall Survival of Patients with Tumor-Free Stage III and Unresectable Stage IV Melanoma

Biomarkers are strongly needed for diagnostic surveillance of patients with metastatic melanoma. On the basis of its known association with tumor metastasis and its ability to induce cancer cachexia, we investigated serum levels of growth and differentiation factor 15 (sGDF-15) as a marker for overall survival (OS). sGDF-15 was retrospectively measured by ELISA in 761 samples obtained at distinct time points during routine clinical care of patients with stage III/IV melanoma. In the entire cohort, sGDF-15 ≥ 1.5 ng/ml was strongly associated with reduced OS after assessment. Subsequent analyses were performed separately for tumor-free stage III, tumor-free stage IV, and unresectable stage IV patients. For patients with unresectable distant metastasis (n = 206), sGDF-15 was independently associated with OS when considered together with the M-category and superior to serum level of lactate dehydrogenase. Analysis in tumor-free stage III patients during routine surveillance (n = 468) revealed sGDF-15 to be associated with OS and an independent factor when considered together with S100B and the pattern of locoregional metastasis. Only in tumor-free stage IV patients (n = 87) sGDF-15 was not associated with OS. sGDF-15 should thus be further validated as a marker for early detection of recurrence in stage III patients and as a prognostic or predictive marker particularly in the context newly available treatments in unresectable stage IV patients.

Expression of Human NSAID Activated Gene 1 in Mice Leads to Altered Mammary Gland Differentiation and Impaired Lactation

Transgenic mice expressing human non-steroidal anti-inflammatory drug activated gene 1 (NAG-1) have less adipose tissue, improved insulin sensitivity, lower insulin levels and are resistant to dietary induced obesity. The hNAG-1 expressing mice are more metabolically active with a higher energy expenditure. This study investigates female reproduction in the hNAG-1 transgenic mice and finds the female mice are fertile but have reduced pup survival after birth. Examination of the mammary glands in these mice suggests that hNAG-1 expressing mice have altered mammary epithelial development during pregnancy, including reduced occupancy of the fat pad and increased apoptosis via TUNEL positive cells on lactation day 2. Pups nursing from hNAG-1 expressing dams have reduced milk spots compared to pups nursing from WT dams. When CD-1 pups were cross-fostered with hNAG-1 or WT dams; reduced milk volume was observed in pups nursing from hNAG-1 dams compared to pups nursing from WT dams in a lactation challenge study. Milk was isolated from WT and hNAG-1 dams, and the milk was found to have secreted NAG-1 protein (approximately 25 ng/mL) from hNAG-1 dams. The WT dams had no detectable hNAG-1 in the milk. A decrease in non-esterified free fatty acids in the milk of hNAG-1 dams was observed. Altered milk composition suggests that the pups were receiving inadequate nutrients during perinatal development. To examine this hypothesis serum was isolated from pups and clinical chemistry points were measured. Male and female pups nursing from hNAG-1 dams had reduced serum triglyceride concentrations. Microarray analysis revealed that genes involved in lipid metabolism are differentially expressed in hNAG-1 mammary glands. Furthermore, the expression of Cidea/CIDEA that has been shown to regulate milk lipid secretion in the mammary gland was reduced in hNAG-1 mammary glands. This study suggests that expression of hNAG-1 in mice leads to impaired lactation and reduces pup survival due to altered milk quality and quantity.

Anorexia-cachexia and obesity treatment may be two sides of the same coin: role of the TGF-b superfamily cytokine MIC-1/GDF15

Anorexia-cachexia associated with cancer and other diseases is a common and often fatal condition representing a large area of unmet medical need. It occurs most commonly in advanced cancer and is probably a consequence of molecules released by tumour cells, or tumour-associated interstitial or immune cells. These may then act directly on muscle to cause atrophy and/or may cause anorexia, which then leads to loss of both fat and lean mass. Although the aetiological triggers for this syndrome are not well characterized, recent data suggest that MIC-1/GDF15, a transforming growth factor-beta superfamily cytokine produced in large amounts by cancer cells and as a part of other disease processes, may be an important trigger. This cytokine acts on feeding centres in the hypothalamus and brainstem to cause anorexia leading to loss of lean and fat mass and eventually cachexia. In animal studies, the circulating concentrations of MIC-1/GDF15 required to cause this syndrome are similar to those seen in patients with advanced cancer, and at least some epidemiological studies support an association between MIC-1/GDF15 serum levels and measures of nutrition. This article will discuss its mechanisms of central appetite regulation, and the available data linking this action to anorexia-cachexia syndromes that suggest it is a potential target for therapy of cancer anorexia-cachexia and conversely may also be useful for the treatment of severe obesity.

Moonlighting proteins in cancer

Since the 1980s, growing evidence suggested that the cellular localization of proteins determined their activity and biological functions. In a classical view, a protein is characterized by the single cellular compartment where it primarily resides and functions. It is now believed that when proteins appear in different subcellular locations, the cells surpass the expected activity of proteins given the same genomic information to fulfill complex biological behavior. Many proteins are recognized for having the potential to exist in multiple locations in cells. Dysregulation of translocation may cause cancer or contribute to poorer cancer prognosis. Thus, quantitative and comprehensive assessment of dynamic proteins and associated protein movements could be a promising indicator in determining cancer prognosis and efficiency of cancer treatment and therapy. This review will summarize these so-called moonlighting proteins, in terms of a coupled intracellular cancer signaling pathway. Determination of the detailed biological intracellular and extracellular transit and regulatory activity of moonlighting proteins permits a better understanding of cancer and identification of potential means of molecular intervention.

Association Between Plasma Levels of Macrophage Inhibitory Cytokine-1 Before Diagnosis of Colorectal Cancer and Mortality

BACKGROUND & AIMS

Patients with colorectal cancer (CRC) have high circulating levels of macrophage inhibitory cytokine-1 (MIC1 or growth differentiation factor 15), a marker of inflammation that might be involved in carcinogenesis. We analyzed blood samples collected from individuals before they were diagnosed with CRC to determine whether levels of MIC1 were associated with mortality.

METHODS

We collected data on survival of 618 participants diagnosed with CRC who provided prediagnosis blood specimens in 1990 (Nurses' Health Study) and 1994 (Health Professionals' Follow-up Study) and were followed through 2010. Levels of MIC1 were measured by enzyme-linked immunosorbent assay and then were categorized into quartiles based on the known distribution of MIC1 levels among previously matched individuals without CRC (controls) within each cohort. We then examined the association of MIC1 levels with overall and CRC-specific mortality using Cox proportional hazards models, with adjustments for mortality-associated risk factors and other plasma markers of inflammation. We also assessed the relationship between levels of MIC1 and levels of prostaglandin-endoperoxide synthase 2 expression (PTGS2 or cyclooxygenase-2), measured in 245 tumor samples by immunohistochemistry.

RESULTS

Compared with participants in the lowest quartile for plasma level of MIC1, the multivariate hazard ratio for CRC-specific death for participants in the highest quartile of MIC1 level was 2.40 (95% confidence interval: 1.33-4.34; P for linear trend = .009). The association of MIC1 with survival varied with level of PTGS2 expression in tumor samples (Pinteraction = .04). For individuals with PTGS2-positive tumors, the hazard ratio for CRC-specific death among those with high levels of MIC1 (equal to or greater than the median) was 2.13 (95% confidence interval: 0.99-4.58) compared with participants with low levels of MIC1 (below the median). In individuals with PTGS2-negative CRC, a high level of MIC1 was not associated with an increased risk of CRC-specific death (multivariate hazard ratio = 0.61; 95% confidence interval: 0.13-2.93).

CONCLUSIONS

Based on an analysis of blood and colorectal tumor samples from 2 large studies, high plasma levels of MIC1 (growth differentiation factor 15) before diagnosis of CRC are associated with greater CRC-specific mortality, particularly in individuals with PTGS2-positive tumors.

Chemoprevention in gastrointestinal physiology and disease. Anti-inflammatory approaches for colorectal cancer chemoprevention

Colorectal cancer (CRC) is one of the most common human malignancies and a leading cause of cancer-related deaths in developed countries. Identifying effective preventive strategies aimed at inhibiting the development and progression of CRC is critical for reducing the incidence and mortality of this malignancy. The prevention of carcinogenesis by anti-inflammatory agents including nonsteroidal anti-inflammatory drugs (NSAIDs), selective cyclooxygenase-2 (COX-2) inhibitors, and natural products is an area of considerable interest and research. Numerous anti-inflammatory agents have been identified as potential CRC chemopreventive agents but vary in their mechanism of action. This review will discuss the molecular mechanisms being studied for the CRC chemopreventive activity of NSAIDs (i.e., aspirin, sulindac, and ibuprofen), COX-2 inhibitors (i.e., celecoxib), natural products (i.e., curcumin, resveratrol, EGCG, genistein, and baicalein), and metformin. A deeper understanding of how these anti-inflammatory agents inhibit CRC will provide insight into the development of potentially safer and more effective chemopreventive drugs.

hNAG-1 increases lifespan by regulating energy metabolism and insulin/IGF-1/mTOR signaling

Nonsteroidal anti-inflammatory drug-activated gene (NAG-1) or GDF15 is a divergent member of the transforming growth factor beta (TGF-β) superfamily and mice expressing hNAG-1/hGDF15 have been shown to be resistant to HFD-induced obesity and inflammation. This study investigated if hNAG-1 increases lifespan in mice and its potential mechanisms. Here we report that female hNAG-1 mice had significantly increased both mean and median life spans in two transgenic lines, with a larger difference in life spans in mice on a HFD than on low fat diet. hNAG-1 mice displayed significantly reduced body and adipose tissue weight, lowered serum IGF-1, insulin and glucose levels, improved insulin sensitivity, and increased oxygen utilization, oxidative metabolism and energy expenditure. Gene expression analysis revealed significant differences in conserved gene pathways that are important regulators of longevity, including IGF-1, p70S6K, and PI3K/Akt signaling cascades. Phosphorylation of major components of IGF-1/mTOR signaling pathway was significantly lower in hNAG-1mice. Collectively, hNAG-1 is an important regulator of mammalian longevity and may act as a survival factor. Our study suggests that hNAG-1 has potential therapeutic uses in obesity-related diseases where life span is frequently shorter.

NAG-1/GDF15 accumulates in the nucleus and modulates transcriptional regulation of the Smad pathway

Protein dynamics, modifications, and trafficking are all processes that can modulate protein activity. Accumulating evidence strongly suggests that many proteins play distinctive roles dependent on cellular location. Nonsteroidal anti-inflammatory drug activated gene-1 (NAG-1) is a TGF-β superfamily protein that plays a role in cancer, obesity, and inflammation. NAG-1 is synthesized and cleaved into a mature peptide, which is ultimately secreted into the extracellular matrix (ECM). In this study, we have found that full-length NAG-1 is expressed in not only the cytoplasm and ECM, but also in the nucleus. NAG-1 is dynamically moved to the nucleus, exported into cytoplasm, and further transported into the ECM. We have also found that nuclear NAG-1 contributes to inhibition of the Smad pathway by interrupting the Smad complex. Overall, our study indicates that NAG-1 is localized in the nucleus and provides new evidence that NAG-1 controls transcriptional regulation in the Smad pathway.

Evasion of anti-growth signaling: A key step in tumorigenesis and potential target for treatment and prophylaxis by natural compounds

The evasion of anti-growth signaling is an important characteristic of cancer cells. In order to continue to proliferate, cancer cells must somehow uncouple themselves from the many signals that exist to slow down cell growth. Here, we define the anti-growth signaling process, and review several important pathways involved in growth signaling: p53, phosphatase and tensin homolog (PTEN), retinoblastoma protein (Rb), Hippo, growth differentiation factor 15 (GDF15), AT-rich interactive domain 1A (ARID1A), Notch, insulin-like growth factor (IGF), and Krüppel-like factor 5 (KLF5) pathways. Aberrations in these processes in cancer cells involve mutations and thus the suppression of genes that prevent growth, as well as mutation and activation of genes involved in driving cell growth. Using these pathways as examples, we prioritize molecular targets that might be leveraged to promote anti-growth signaling in cancer cells. Interestingly, naturally occurring phytochemicals found in human diets (either singly or as mixtures) may promote anti-growth signaling, and do so without the potentially adverse effects associated with synthetic chemicals. We review examples of naturally occurring phytochemicals that may be applied to prevent cancer by antagonizing growth signaling, and propose one phytochemical for each pathway. These are: epigallocatechin-3-gallate (EGCG) for the Rb pathway, luteolin for p53, curcumin for PTEN, porphyrins for Hippo, genistein for GDF15, resveratrol for ARID1A, withaferin A for Notch and diguelin for the IGF1-receptor pathway. The coordination of anti-growth signaling and natural compound studies will provide insight into the future application of these compounds in the clinical setting.

ATF3 Mediates Anti-Cancer Activity of Trans-10, cis-12-Conjugated Linoleic Acid in Human Colon Cancer Cells

Conjugated linoleic acids (CLA) are a family of isomers of linoleic acid. CLA increases growth arrest and apoptosis of human colorectal cancer cells through an isomer-specific manner. ATF3 belongs to the ATF/CREB family of transcription factors and is associated with apoptosis in colorectal cancer. The present study was performed to investigate the molecular mechanism by which t10, c12-CLA stimulates ATF3 expression and apoptosis in human colorectal cancer cells. t10, c12-CLA increased an apoptosis in human colorectal cancer cells in dose dependent manner. t10, c12-CLA induced ATF3 mRNA and luciferase activity of ATF3 promoter in a dose-dependent manner. The responsible region for ATF3 transcriptional activation by t10, c12-CLA is located between −147 and −1850 of ATF3 promoter. mRNA stability of ATF3 was not affected by t10, c12-CLA treatment. t10, c12-CLA increases GSK3β expression and suppresses IGF-1-stimulated phosphorylation of Akt. The knockdown of ATF3 suppressed expression of GSK3β and NAG-1 and PARP cleavage. The results suggest that t10, c12-CLA induces apoptosis through ATF3-mediated pathway in human colorectal cancer cells.

Macrophage inhibitory cytokine-1 (MIC-1/GDF15) gene deletion promotes cancer growth in TRAMP prostate cancer prone mice

The divergent TGF-β superfamily member, macrophage inhibitory cytokine-1 (MIC-1/GDF15), is overexpressed by most cancers, including prostate cancer (PCa). Whilst its circulating levels are linked to cancer outcome, the role MIC-1/GDF15 plays in cancer development and progression is incompletely understood. To investigate its effect on PCa development and spread, we have used TRAMP prostate cancer prone mice bearing a germline deletion of MIC-1/GDF15 (TRAMPMIC-/-). On average TRAMPMIC-/- mice died about 5 weeks earlier and had larger prostatic tumors compared with TRAMP mice that were wild type for MIC-1/GDF15 (TRAMPMIC+/+). Additionally, at the time of death or ethical end point, even when adjusted for lifespan, there were no significant differences in the number of mice with metastases between the TRAMPMIC+/+ and TRAMPMIC-/- groups. However, consistent with our previous data, more than twice as many TRAMP mice overexpressing MIC-1/GDF15 (TRAMPfmsmic-1) had metastases than TRAMPMIC+/+ mice (p<0.0001). We conclude that germ line gene deletion of MIC-1/GDF15 leads to increased local tumor growth resulting in decreased survival consistent with an overall protective role for MIC-1/GDF15 in early primary tumor development. However, in advancing disease, as we have previously noted, MIC-1/GDF15 overexpression may promote local invasion and metastatic spread.

Knockdown of platinum-induced growth differentiation factor 15 abrogates p27-mediated tumor growth delay in the chemoresistant ovarian cancer model A2780cis

Molecular mechanisms underlying the development of resistance to platinum-based treatment in patients with ovarian cancer remain poorly understood. This is mainly due to the lack of appropriate in vivo models allowing the identification of resistance-related factors. In this study, we used human whole-genome microarrays and linear model analysis to identify potential resistance-related genes by comparing the expression profiles of the parental human ovarian cancer model A2780 and its platinum-resistant variant A2780cis before and after carboplatin treatment in vivo. Growth differentiation factor 15 (GDF15) was identified as one of five potential resistance-related genes in the A2780cis tumor model. Although A2780-bearing mice showed a strong carboplatin-induced increase of GDF15 plasma levels, the basal higher GDF15 plasma levels of A2780cis-bearing mice showed no further increase after short-term or long-term carboplatin treatment. This correlated with a decreased DNA damage response, enhanced AKT survival signaling and abrogated cell cycle arrest in the carboplatin-treated A2780cis tumors. Furthermore, knockdown of GDF15 in A2780cis cells did not alter cell proliferation but enhanced cell migration and colony size in vitro. Interestingly, in vivo knockdown of GDF15 in the A2780cis model led to a basal-enhanced tumor growth, but increased sensitivity to carboplatin treatment as compared to the control-transduced A2780cis tumors. This was associated with larger necrotic areas, a lobular tumor structure and increased p53 and p16 expression of the carboplatin-treated shGDF15-A2780cis tumors. Furthermore, shRNA-mediated GDF15 knockdown abrogated p27 expression as compared to control-transduced A2780cis tumors. In conclusion, these data show that GDF15 may contribute to carboplatin resistance by suppressing tumor growth through p27. These data show that GDF15 might serve as a novel treatment target in women with platinum-resistant ovarian cancer.

H2S-releasing drugs: anti-inflammatory, cytoprotective and chemopreventative potential

Hydrogen sulfide exerts a number of cytoprotective and anti-inflammatory effects in many organ systems. In an effort to exploit these potent and beneficial effects, a number of hydrogen sulfide-releasing derivatives of existing drugs have been developed and extensively tested in pre-clinical models. In particular, efforts have been made by several groups to develop hydrogen sulfide-releasing derivatives of a number of nonsteroidal anti-inflammatory drugs. The main goal of this approach is to reduce the gastrointestinal ulceration and bleeding caused by this class of drugs, particularly when used chronically such as in the treatment of arthritis. However, these drugs may also have utility for prevention of various types of cancer. This paper provides an overview of some of the mechanisms underlying the anti-inflammatory and cytoprotective actions of hydrogen sulfide. It also gives some examples of hydrogen sulfide-releasing anti-inflammatory drugs, and their actions in terms of reducing inflammation and attenuating the development of cancer in experimental models.

Ginger compound [6]-shogaol and its cysteine-conjugated metabolite (M2) activate Nrf2 in colon epithelial cells in vitro and in vivo

In this study, we identified Nrf2 as a molecular target of [6]-shogaol (6S), a bioactive compound isolated from ginger, in colon epithelial cells in vitro and in vivo. Following 6S treatment of HCT-116 cells, the intracellular GSH/GSSG ratio was initially diminished but was then elevated above the basal level. Intracellular reactive oxygen species (ROS) correlated inversely with the GSH/GSSG ratio. Further analysis using gene microarray showed that 6S upregulated the expression of Nrf2 target genes (AKR1B10, FTL, GGTLA4, and HMOX1) in HCT-116 cells. Western blotting confirmed upregulation, phosphorylation, and nuclear translocation of Nrf2 protein followed by Keap1 decrease and upregulation of Nrf2 target genes (AKR1B10, FTL, GGTLA4, HMOX1, and MT1) and glutathione synthesis genes (GCLC and GCLM). Pretreatment of cells with a specific inhibitor of p38 (SB202190), PI3K (LY294002), or MEK1 (PD098059) attenuated these effects of 6S. Using ultra-high-performance liquid chromatography-tandem mass spectrometry, we found that 6S modified multiple cysteine residues of Keap1 protein. In vivo 6S treatment induced Nrf2 nuclear translocation and significantly upregulated the expression of MT1, HMOX1, and GCLC in the colon of wild-type mice but not Nrf2(-/-) mice. Similar to 6S, a cysteine-conjugated metabolite of 6S (M2), which was previously found to be a carrier of 6S in vitro and in vivo, also activated Nrf2. Our data demonstrated that 6S and its cysteine-conjugated metabolite M2 activate Nrf2 in colon epithelial cells in vitro and in vivo through Keap1-dependent and -independent mechanisms.

Growth differentiation factor-15 (GDF-15) suppresses in vitro angiogenesis through a novel interaction with connective tissue growth factor (CCN2)

Growth differentiation factor-15 (GDF-15) and the CCN family member, connective tissue growth factor (CCN2), are associated with cardiac disease, inflammation, and cancer. The precise role and signaling mechanism for these factors in normal and diseased tissues remains elusive. Here we demonstrate an interaction between GDF-15 and CCN2 using yeast two-hybrid assays and have mapped the domain of interaction to the von Willebrand factor type C domain of CCN2. Biochemical pull down assays using secreted GDF-15 and His-tagged CCN2 produced in PC-3 prostate cancer cells confirmed a direct interaction between these proteins. To investigate the functional consequences of this interaction, in vitro angiogenesis assays were performed. We demonstrate that GDF-15 blocks CCN2-mediated tube formation in human umbilical vein endothelial (HUVEC) cells. To examine the molecular mechanism whereby GDF-15 inhibits CCN2-mediated angiogenesis, activation of αV β3 integrins and focal adhesion kinase (FAK) was examined. CCN2-mediated FAK activation was inhibited by GDF-15 and was accompanied by a decrease in αV β3 integrin clustering in HUVEC cells. These results demonstrate, for the first time, a novel signaling pathway for GDF-15 through interaction with the matricellular signaling molecule CCN2. Furthermore, antagonism of CCN2 mediated angiogenesis by GDF-15 may provide insight into the functional role of GDF-15 in disease states.

Lower NLRP3 inflammasome activity in NAG-1 transgenic mice is linked to a resistance to obesity and increased insulin sensitivity

OBJECTIVE

The NLRP3 inflammasome plays an important regulatory role in obesity-induced insulin resistance. NSAID activated gene-1 (NAG-1) is a divergent member of the TGF-β superfamily. NAG-1 Tg mice are resistant to dietary- and genetic-induced obesity and have improved insulin sensitivity. The objective was to examine whether NLRP3 inflammasome activity is associated with this observed phenotype in NAG-1 Tg mice.

METHODS

Key components of the NLRP3 inflammasome were examined in NAG-1 Tg mice on both regular and high fat diet (HFD) conditions.

RESULTS

The expression of caspase-1 and ASC, key components of the NLRP3 inflammasome, is significantly reduced at mRNA and protein levels in white adipose tissue (WAT) of NAG-1 Tg mice. HFD increases the expression of caspase-1 and ASC in WT mice, but their expression is reduced in NAG-1 Tg mice. Furthermore, there is reduced IL-18, IL-1β, and TNF-α expression in the WAT of NAG-1 Tg mice. NAG-1 Tg mice have significantly lower serum leptin and insulin levels and reduced expression of macrophage infiltration markers (F4/80, CD11b, and CD11c) in WAT.

CONCLUSIONS

The study suggests the lower NLRP3 inflammasome activity may play a role in the resistance of NAG-1 Tg mice to diet-induced obesity and improved insulin sensitivity.

Obesity, rather than diet, drives epigenomic alterations in colonic epithelium resembling cancer progression

While obesity represents one of several risk factors for colorectal cancer in humans, the mechanistic underpinnings of this association remain unresolved. Environmental stimuli, including diet, can alter the epigenetic landscape of DNA cis-regulatory elements affecting gene expression and phenotype. Here, we explored the impact of diet and obesity on gene expression and the enhancer landscape in murine colonic epithelium. Obesity led to the accumulation of histone modifications associated with active enhancers at genomic loci downstream of signaling pathways integral to the initiation and progression of colon cancer. Meanwhile, colon-specific enhancers lost the same histone mark, poising cells for loss of differentiation. These alterations reflect a transcriptional program with many features shared with the program driving colon cancer progression. The interrogation of enhancer alterations by diet in colonic epithelium provides insights into the biology underlying high-fat diet and obesity as risk factors for colon cancer.

A prospective study of macrophage inhibitory cytokine-1 (MIC-1/GDF15) and risk of colorectal cancer

BACKGROUND

Chronic inflammation plays a role in the development of colorectal cancer (CRC). The novel plasma inflammatory biomarker macrophage inhibitory cytokine-1 (MIC-1, GDF15) may have a direct mechanistic role in colorectal carcinogenesis.

METHODS

We conducted a prospective, nested, case-control study of incident CRC among men and women who provided a prediagnostic blood specimen. We used an enzyme-linked immunosorbent assay to measure MIC-1 and examined associations between quintiles of MIC-1 and CRC using logistic regression adjusted for matching factors (age and date of blood draw), risk factors, and other plasma inflammatory markers. We also assessed the relationship between MIC-1 levels and prostaglandin-endoperoxide synthase 2 (PTGS2)/cyclooxygenase-2 (COX-2) enzyme status in tumors with available tissue for analysis. All statistical tests were two-sided.

RESULTS

Compared with men and women within the lowest quintile of plasma MIC-1, the multivariable relative risk (RR) for CRC was 1.93 (95% confidence interval [CI] = 1.27 to 2.94) for the highest quintile (P linear trend = .004). In an exploratory analysis, we found that among individuals with high plasma MIC-1 levels (quintiles 2-5), compared with nonuse, regular use of aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) was associated with a lower risk of PTGS2-positive CRC (multivariable RR = 0.60; 95% confidence interval = 0.41 to 0.88) but not PTGS2-negative CRC (multivariable RR = 1.21; 95% CI = 0.71 to 2.07). In contrast, among individuals with low MIC-1 levels (quintile 1), aspirin and NSAID use was not associated with a lower risk of PTGS2-positive CRC (multivariable RR = 0.57; 95% CI = 0.21 to 1.54) or PTGS2-negative CRC (multivariable RR = 1.41; 95% CI = 0.47 to 4.23).

CONCLUSIONS

Our results support an association between higher levels of circulating MIC-1 (GDF15) and CRC. Aspirin/NSAID use appeared to lower risk of PTGS2-positive cancers, particularly among individuals with high levels of circulating MIC-1.

NAG-1/GDF-15 prevents obesity by increasing thermogenesis, lipolysis and oxidative metabolism

Objective

Obesity is a major health problem associated with high morbidity and mortality. NSAID activated gene, (NAG-1) is a TGF-β superfamily member reported to alter adipose tissue levels in mice. We investigated whether hNAG-1 acts as a regulator of adiposity and energy metabolism.

Design/Subjects

hNAG-1 mice, ubiquitously expressing hNAG-1, were placed on a control or high fat diet (HFD) for 12 weeks. hNAG-1 expressing B16/F10 melanoma cells were used in a xenograft model to deliver hNAG-1 to obese C57BL/6 mice.

Results

As compared to wild-type littermates, transgenic hNAG-1 mice have less white fat and brown fat despite equivalent food intake, improved glucose tolerance, lower insulin levels and are resistant to dietary- and genetic-induced obesity. hNAG-1 mice are more metabolically active with higher energy expenditure. Obese C57BL/6 mice treated with hNAG-1 expressing xenografts show decreases in adipose tissue and serum insulin levels. hNAG-1 mice and obese mice treated with hNAG-1 expressing xenografts show increased thermogenic gene expression (UCP1, PGC1α, ECH1, Cox8b, Dio2, Cyc1, PGC1β, PPARα, Elvol3) in brown adipose tissue (BAT) and increased expression of lipolytic genes (Adrb3, ATGL, HSL) in both white adipose tissue (WAT) and BAT, consistent with higher energy metabolism

Conclusion

hNAG-1 modulates metabolic activity by increasing the expression of key thermogenic and lipolytic genes in BAT and WAT. hNAG-1 appears to be a novel therapeutic target in preventing and treating obesity and insulin resistance.

Anti-tumor activity of non-steroidal anti-inflammatory drugs: cyclooxygenase-independent targets

Non-steroidal anti-inflammatory drugs (NSAIDs) are used extensively for analgesic and antipyretic treatments. In addition, NSAIDs reduce the risk and mortality to several cancers. Their mechanisms in anti-tumorigenesis are not fully understood, but both cyclooxygenase (COX)-dependent and -independent pathways play a role. We and others have been interested in elucidating molecular targets of NSAID-induced apoptosis. In this review, we summarize updated literature regarding cellular and molecular targets modulated by NSAIDs. Among those NSAIDs, sulindac sulfide and tolfenamic acid are emphasized in this review because these two drugs have been well investigated for their anti-tumorigenic activity in many different types of cancer.

Serum growth differentiation factor 15 levels in newly diagnosed multiple myeloma patients

BACKGROUND/AIMS

Multiple myeloma (MM) is a hematological cancer associated with increased clonal malignant plasma cells. Growth differentiation factor 15 (GDF 15) is a protein that is highly expressed in the bone marrow mesenchymal stem cells of patients with MM. This study investigated whether the clinical stage of the disease, treatment response and survival are affected by pretreatment serum GDF 15 levels.

METHODS

Serum GDF 15 levels were measured in 35 newly diagnosed MM patients and 27 healthy controls. The correlation between serum GDF 15 levels and various clinical and laboratory parameters was analyzed.

RESULTS

The study demonstrated significantly higher levels of GDF 15 in MM patients. There was a negative correlation between GDF 15 levels, hemoglobin and albumin levels, and a positive correlation between GDF 15 levels, CRP, creatinine, β-2-microglobulin and stage. GDF 15 levels were lower in patients who could receive autologous stem cell transplantation compared to other groups, representing a statistically significant difference. However, in the survival analyses, GDF 15 level did not have an impact on survival.

CONCLUSION

High serum levels of GDF 15 may indicate a poor treatment response. Our study supports the prognostic value of GDF 15 in MM.

Concise review: growth differentiation factor 15 in pathology: a clinical role?

Growth differentiation factor 15 (GDF15) is a divergent member of the transforming growth factor β family discovered in a broad range of cells, as indicated by the diversity of its nomenclature. However, the only tissue that expresses a high amount of GDF15 in the physiologic state is placenta. GDF15 is easily detected in blood, and its concentration varies with age. In fact, increased blood concentration of GDF15 is associated with numerous pathological conditions. However, the biological significance underlying these observations is far from clear. GDF15 could have a positive or negative role depending on the state of cells or their environment. Furthermore, study of its biology is hampered by lack of knowledge of its receptor and thus the signaling pathways that drive its action. GDF15 seems to be an integrative signal in pathologic conditions, giving information on severity of disease. Its effectiveness in classifying patients to modulate treatment remains to be shown. Development of therapeutic interventions with GDF15 or anti-GDF15 agents remains difficult until we uncover the mechanism that drives its activity.

Variations in NAG-1 expression of human gastric carcinoma and normal gastric tissues

Nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1), a member of the transforming growth factor β (TGF-β) superfamily, has been demonstrated to possess antitumorigenic and proapoptotic activities in gastric cancer cells. In the present study, the expression of NAG-1 was assessed in human gastric carcinoma, tumor-adjacent normal tissues and normal gastric mucosa, with the aim to investigate the role of NAG-1 in the carcinogenesis and development of gastric carcinoma. NAG-1 protein expression was evaluated using immunohistochemical staining, while the expression of NAG-1 mRNA was evaluated using reverse transcription-polymerase chain reaction. It was observed that adenocarcinoma tissues had a lower expression of NAG-1 than normal gastric tissues. Furthermore, moderately and well-differentiated adenocarcinoma tissues expressed more NAG-1 protein than the poorly differentiated adenocarcinoma tissues. The expression of NAG-1 protein in adenocarcinoma tissues did not correlate with tumor-node-metastasis staging, infiltration degree or tumor size. The NAG-1 mRNA expression in adenocarcinoma tissues was also lower than that in normal gastric tissues. In conclusion, NAG-1 was poorly expressed in adenocarcinoma tissues and inversely correlated with the degree of tumor differentiation. These results indicate that NAG-1 may have an anti-oncogenic function in the carcinogenesis and development of gastric carcinoma, and that its attenuated or absent expression may lead to gastric carcinogenesis.

The involvement of endoplasmic reticulum stress in the suppression of colorectal tumorigenesis by tolfenamic acid

The nonsteroidal anti-inflammatory drug tolfenamic acid has been shown to suppress cancer cell growth and tumorigenesis in different cancer models. However, the underlying mechanism by which tolfenamic acid exerts its antitumorigenic effect remains unclear. Previous data from our group and others indicate that tolfenamic acid alters expression of apoptosis- and cell-cycle arrest-related genes in colorectal cancer cells. Here, we show that tolfenamic acid markedly reduced the number of polyps and tumor load in APC(min)(/+) mice, accompanied with cyclin D1 downregulation in vitro and in vivo. Mechanistically, tolfenamic acid promotes endoplasmic reticulum (ER) stress, resulting in activation of the unfolded protein response (UPR) signaling pathway, of which PERK-mediated phosphorylation of eukaryotic translation initiation factor 2α (eIF2α) induces the repression of cyclin D1 translation. Moreover, the PERK-eIF2α-ATF4 branch of the UPR pathway plays a role in tolfenamic acid-induced apoptosis in colorectal cancer cells, as silencing ATF4 attenuates tolfenamic acid-induced apoptosis. Taken together, these results suggest ER stress is involved in tolfenamic acid-induced inhibition of colorectal cancer cell growth, which could contribute to antitumorigenesis in a mouse model.

NAG-1/GDF15 transgenic mouse has less white adipose tissue and a reduced inflammatory response

NAG-1/GDF15 is a TGF-β superfamily member with poorly characterized biological activity proposed to inhibit inflammatory cytokine production. Transgenic mice expressing human NAG-1/GDF15 (NAG-1^Tg/Lox) are leaner with lower body weight and are resistant to chemically or genetically induced intestinal tumors. Because of the link between obesity, inflammation, and cancer, we examined whether these mice exhibit a reduced response to inflammatory stimuli. The NAG-1^Tg/Lox mice had a reduced inflammatory response to LPS based on the serum levels of cytokines KC, IL-6, MCP-1, and TNFα. In contrast to literature reports and our in vivo results, NAG-1 did not inhibit LPS-induced cytokine expression in vitro in RAW264.7 cells, mouse peritoneal macrophages, or mouse liver Kupffer cells, suggesting that NAG-1/GDF15 does not directly inhibit LPS-induced inflammatory cytokine production. However, NAG-1^Tg/Lox mice have less white adipose tissue, the major source of inflammatory adipokines including leptin. Basal and LPS-treated serum leptin and mRNA levels in the adipose tissue of NAG-1^Tg/Lox mice were lower than those in WT mice. We propose that the reduced white adipose tissue and reduced leptin expression may be responsible, in part, for the reduced inflammatory response to LPS and the decrease in intestinal tumors observed in NAG-1^Tg/Lox mice.

Characterization of PPAR dual ligand MCC-555 in AOM-induced colorectal tumorigenesis

Colorectal cancer (CRC) is one of the most commonly diagnosed cancers. Peroxisome proliferator-activated receptor γ (PPARγ) agonists represent a potentially important family of chemopreventive/therapeutic compounds for cancer treatment by affecting cell proliferation, differentiation, and apoptosis. Dual ligands for PPARα and PPARγ, such as netoglitazone (MCC-555), have been developed to improve treatment of metabolic syndromes, including hyperglycemia and hyperlipidemia. Interestingly, these dual ligands also possess anti-proliferative activities against a variety of cancer cell lines with a greater potency than conventional PPARγ specific ligands. In this study, chemopreventive properties of MCC-555 in colorectal tumorigenesis were evaluated using azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) in A/J mice. We found that MCC-555 suppressed AOM-induced ACF in A/J mice, compared to the control group. Administration of MCC-555 resulted in decreased mitoses and increased apoptotic cells in the colon. Furthermore, expression of tumor suppressor protein MUC2 was increased in MCC-555 treated mice. Our data clearly suggest that MCC-555 has an effect on the early events of colon carcinogenesis, thus providing evidence that MCC-555 could be a potential preventive compound for CRC.

Proteasome inhibitor MG132 induces NAG-1/GDF15 expression through the p38 MAPK pathway in glioblastoma cells

The expression of nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1) is regulated by the p53 and Egr-1 tumor suppressor pathways. Many anti-cancer drugs and chemicals induce NAG-1 expression, but the mechanisms are not fully understood. Transgenic mice expressing human NAG-1 are resistant to intestinal and prostate cancer, suggesting that NAG-1 is a tumor suppressor. Proteasome inhibitors exhibit anti-glioblastoma activities in preclinical studies. Here, we show that the proteasome inhibitors MG132 and bortezomib induced NAG-1 expression and secretion in glioblastoma cells. MG132 increased NAG-1 expression through transcriptional and post-transcriptional mechanisms. At the transcriptional level, the induction of NAG-1 required the -133 to +41 bp region of the promoter. At post-transcriptional levels, MG132 stabilized NAG-1 mRNA by increasing the half-life from 1.5 h to >8 h. Because of the dramatic increase in mRNA stability, this is likely the major contributor to MG132-mediated NAG-1 induction. Further probing into the mechanism revealed that MG132 increased phosphorylation of the p38 MAPK pathway. Consequently, inhibiting p38 phosphorylation blocked activation of the NAG-1 promoter and decreased mRNA stability, indicating that p38 MAPK activation mediates both MG132-dependent promoter activation and mRNA stabilization of NAG-1. We propose that the induction of NAG-1 by p38 MAPK is a potential contributor to the anti-glioblastoma activity of proteasome inhibitors.

The diverse roles of nonsteroidal anti-inflammatory drug activated gene (NAG-1/GDF15) in cancer

Nonsteroidal anti-inflammatory drug (NSAID) activated gene-1, NAG-1, is a divergent member of the transforming growth factor-beta (TGF-β) superfamily that plays a complex but poorly understood role in several human diseases including cancer. NAG-1 expression is substantially increased during cancer development and progression especially in gastrointestinal, prostate, pancreatic, colorectal, breast, melanoma, and glioblastoma brain tumors. Aberrant increases in the serum levels of secreted NAG-1 correlate with poor prognosis and patient survival rates in some cancers. In contrast, the expression of NAG-1 is up-regulated by several tumor suppressor pathways including p53, GSK-3β, and EGR-1. NAG-1 expression is also induced by many drugs and dietary compounds which are documented to prevent the development and progression of cancer in mouse models. Studies with transgenic mice expressing human NAG-1 demonstrated that the expression of NAG-1 inhibits the development of intestinal tumors and prostate tumors in animal models. Laboratory and clinical evidence suggest that NAG-1, like other TGF-β family members, may have different or pleiotropic functions in the early and late stages of carcinogenesis. Upon understanding the molecular mechanism and function of NAG-1 during carcinogenesis, NAG-1 may serve as a potential biomarker for the diagnosis and prognosis of cancer and a therapeutic target for the inhibition and treatment of cancer development and progression.

Anorexia/cachexia of chronic diseases: a role for the TGF-β family cytokine MIC-1/GDF15

Anorexia/cachexia is a common and currently mostly untreatable complication of advanced cancer. It is also a feature of a number of chronic diseases and can also occur as part of the normal ageing process. Over recent years, two different, but sometimes overlapping, processes have been identified to mediate anorexia/cachexia: those that act primarily on muscle reducing its mass and function, and processes that decrease nutrition leading to loss of both fat and muscle. In the case of at least some cancers, the latter process is sometimes driven by marked overexpression of macrophage inhibitory cytokine-1/growth differentiation factor 15 (MIC-1/GDF15). MIC-1/GDF15 is a transforming growth factor beta (TGF-β) family cytokine that is found in the serum of all normal individuals at an average concentration of about 0.6 ng/ml. Its increased expression in both cancers and other diseases can result in 10-100-fold or more elevation of its serum levels. In experimental animals, serum MIC-1/GDF15 levels at the lower end of this range induce anorexia by direct actions of the circulating cytokine on feeding centres in the brain. Mice with tumours overexpressing MIC-1/GDF15 display decreased food intake, loss of lean and fat mass and cachexia. That this process also mediates anorexia/cachexia in humans is suggested by the fact that there is a direct correlation between the degree of serum MIC-1/GDF15 elevation and the amount of cancer-related weight loss, the first such relationship demonstrated. Further, in experimental animals, weight loss can be reversed by neutralisation of tumour-produced MIC-1/GDF15 with a specific monoclonal antibody, suggesting the possibility of effective therapy of patients with the devastating complication of anorexia/cachexia.

Macrophage inhibitory cytokine-1 (MIC-1/GDF15) slows cancer development but increases metastases in TRAMP prostate cancer prone mice

Macrophage inhibitory cytokine-1 (MIC-1/GDF15), a divergent member of the TGF-β superfamily, is over-expressed by many common cancers including those of the prostate (PCa) and its expression is linked to cancer outcome. We have evaluated the effect of MIC-1/GDF15 overexpression on PCa development and spread in the TRAMP transgenic model of spontaneous prostate cancer. TRAMP mice were crossed with MIC-1/GDF15 overexpressing mice (MIC-1(fms)) to produce syngeneic TRAMP(fmsmic-1) mice. Survival rate, prostate tumor size, histopathological grades and extent of distant organ metastases were compared. Metastasis of TC1-T5, an androgen independent TRAMP cell line that lacks MIC-1/GDF15 expression, was compared by injecting intravenously into MIC-1(fms) and syngeneic C57BL/6 mice. Whilst TRAMP(fmsmic-1) survived on average 7.4 weeks longer, had significantly smaller genitourinary (GU) tumors and lower PCa histopathological grades than TRAMP mice, more of these mice developed distant organ metastases. Additionally, a higher number of TC1-T5 lung tumor colonies were observed in MIC-1(fms) mice than syngeneic WT C57BL/6 mice. Our studies strongly suggest that MIC-1/GDF15 has complex actions on tumor behavior: it limits local tumor growth but may with advancing disease, promote metastases. As MIC-1/GDF15 is induced by all cancer treatments and metastasis is the major cause of cancer treatment failure and cancer deaths, these results, if applicable to humans, may have a direct impact on patient care.

A peroxisome proliferator-activated receptor ligand MCC-555 imparts anti-proliferative response in pancreatic cancer cells by PPARgamma-independent up-regulation of KLF4

MCC-555 is a novel PPARα/γ dual ligand of the thiazolidinedione class and was recently developed as an anti-diabetic drug with unique properties. MCC-555 also has anti-proliferative activity through growth inhibition and apoptosis induction in several cancer cell types. Our group has shown that MCC-555 targets several proteins in colorectal tumorigenesis including nonsteroidal anti-inflammatory drug (NSAID)-activated gene (NAG-1) which plays an important role in chemoprevention responsible for chemopreventive compounds. NAG-1 is a member of the TGF-β superfamily and is involved in tumor progression and development; however, NAG-1's roles in pancreatic cancer have not been studied. In this report, we found that MCC-555 alters not only NAG-1 expression, but also p21 and cyclin D1 expression. NAG-1 and p21 expression was not blocked by PPARγ-specific antagonist GW9662, suggesting that MCC-555-induced NAG-1 and p21 expression is independent of PPARγ activation. However, decreasing cyclin D1 by MCC-555 seems to be affected by PPARγ activation. Further, we found that the GC box located in the NAG-1 promoter play an important role in NAG-1 transactivation by MCC-555. Subsequently, we screened several transcription factors that may bind to the GC box region in the NAG-1 promoter and found that KLF4 potentially binds to this region. Expression of KLF4 precedes NAG-1 and p21 expression in the presence of MCC-555, whereas blocking KLF4 expression using specific KLF4 siRNA showed that both NAG-1 and p21 expression by MCC-555 was blocked. In conclusion, MCC-555's actions on anti-proliferation involve both PPARγ-dependent and -independent pathways, thereby enhancing anti-tumorigenesis in pancreatic cancer cells.

The H6D variant of NAG-1/GDF15 inhibits prostate xenograft growth in vivo

BACKGROUND

Non-steroidal anti-inflammatory drug-activated gene (NAG-1), a divergent member of the transforming growth factor-beta superfamily, has been implicated in many cellular processes, including inflammation, early bone formation, apoptosis, and tumorigenesis. Recent clinical studies suggests that a C to G single nucleotide polymorphism at position 6 (histidine to aspartic acid substitution, or H6D) of the NAG-1 protein is associated with lower human prostate cancer incidence. The objective of the current study is to investigate the activity of NAG-1 H6D variant in prostate cancer tumorigenesis in vivo.

METHODS

Human prostate cancer DU145 cells expressing the H6D NAG-1 or wild-type (WT) NAG-1 were injected subcutaneously into nude mice and tumor growth was monitored. Serum and tumor samples were collected for subsequent analysis.

RESULTS

The H6D variant was more potent than the WT NAG-1 and inhibited tumor growth significantly compared to control mice. Mice with tumors expressing the WT NAG-1 have greater reduced both body weight and abdominal fat than mice with H6D variant tumors suggesting different activities of the WT NAG-1 and the H6D NAG-1. A significant reduction in adiponectin, leptin, and IGF-1 serum levels was observed in the tumor-bearing mice with a more profound reduction observed with expression of H6D variant. Cyclin D1 expression was suppressed in the tumors with a dramatic reduction observed in the tumor expressing the H6D variant.

CONCLUSION

Our data suggest that the H6D variant of NAG-1 inhibits prostate tumorigenesis by suppressing IGF-1 and cyclin D1 expression but likely additional mechanisms are operative.

COX inhibitors directly alter gene expression: role in cancer prevention?

Inflammation is an important contributor to the development and progression of human cancers. Inflammatory lipid metabolites, prostaglandins, formed from arachidonic acid by prostaglandin H synthases commonly called cyclooxygenases (COXs) bind to specific receptors that activate signaling pathways driving the development and progression of tumors. Inhibitors of prostaglandin formation, COX inhibitors, or nonsteroidal anti-inflammatory drugs (NSAIDs) are well documented as agents that inhibit tumor growth and with long-term use prevent tumor development. NSAIDs also alter gene expression independent of COX inhibition and these changes in gene expression also appear to contribute to the anti-tumorigenic activity of these drugs. Many NSAIDs, as illustrated by sulindac sulfide, alter gene expressions by altering the expression or phosphorylation status of the transcription factors specificity protein 1 and early growth response-1 with the balance between these two events resulting in increases or decreases in specific target genes. In this review, we have summarized and discussed the various genes altered by this mechanism after NSAID treatment and how these changes in expression relate to the anti-tumorigenic activity. A major focus of the review is on NSAID-activated gene (NAG-1) or growth differentiation factor 15. This unique member of the TGF-β superfamily is highly induced by NSAIDs and numerous drugs and chemicals with anti-tumorigenic activities. Investigations with a transgenic mouse expressing the human NAG-1 suggest it acts to suppress tumor development in several mouse models of cancer. The biochemistry and biology of NAG-1 were discussed as potential contributor to cancer prevention by COX inhibitors.