Differential regulation of nonsteroidal anti-inflammatory drug-activated gene in normal human tracheobronchial epithelial and lung carcinoma cells by retinoids

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.

Reduced expression of GDF-15 is associated with atrophic inflammatory lesions of the prostate

BACKGROUND

Accumulating evidence suggests that chronic prostatic inflammation may lead to prostate cancer development. Growth differentiation factor-15 (GDF-15) is highly expressed in the prostate and has been associated with inflammation and tumorigenesis.

METHODS

To examine the relationship between GDF-15 and prostatic inflammation, GDF-15 expression was measured by immunohistochemical (IHC) staining in human prostatectomy specimens containing inflammation. The relationship between GDF-15 and specific inflammatory cells was determined using non-biased computer image analysis. To provide insight into a potential suppressive role for GDF-15 in inflammation, activation of inflammatory mediator nuclear factor of kappa B (NFκB) was measured in PC3 cells.

RESULTS

GDF-15 expression in luminal epithelial cells was decreased with increasing inflammation severity, suggesting an inverse association between GDF-15 and inflammation. Quantification of IHC staining by image analysis for GDF-15 and inflammatory cell markers revealed an inverse correlation between GDF-15 and CD3+, CD4+, CD8+, CD68+, and inos+ leukocytes. GDF-15 suppressed NFκB activity in luciferase reporter assays. Expression of the NFκB target, interleukin 8 (IL-8), was downregulated by GDF-15.

CONCLUSIONS

The inverse relationship between GDF-15 and inflammation demonstrates a novel expression pattern for GDF-15 in the human prostate and suppression of NFκB activity may shed light on a potential mechanism for this inverse correlation.

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.

Potential Therapeutic Role of Hispidulin in Gastric Cancer through Induction of Apoptosis via NAG-1 Signaling

Gastric cancer is one of the most common malignant cancers due to poor prognoses and high mortality rates worldwide. However, an effective chemotherapeutic drug without side effects remains lacking. Saussurea involucrata (SI) Kar. et Kir., also known as snow lotus, grows in mountainous rocky habitats at 2600 m elevation in the Tian Shan and A'er Tai regions of China. The ethyl acetate extract of SI had been shown to inhibit proliferation and induce apoptosis in various tumor cells. In this study, we demonstrated that Hispidulin, active ingredients in SI, inhibits the growth of AGS gastric cancer cells. After Hispidulin treatment, NAG-1 remained highly expressed, whereas COX-2 expression was downregulated. Flow cytometric analysis indicated that Hispidulin induces G1/S phase arrest and apoptosis in time- and concentration-dependent manners. G1/S arrest correlated with upregulated p21/WAF1 and p16 and downregulated cyclin D1 and cyclin E, independent of p53 pathway. In addition, Hispidulin can elevate Egr-1 expression and ERK1/2 activity, whereas ERK1/2 inhibitor markedly attenuated NAG-1 mediated apoptosis. Taken together, Hispidulin can efficiently activate ERK1/2 signaling followed by NAG-1 constitutive expression and trigger cell cycle arrest as well as apoptosis in cancer cell. It can be a potential compound for combination therapy of gastric cancer in the future.

Identification of TNM stage-specific genes in lung adenocarcinoma by genome-wide expression profiling

The present study aimed to investigate the molecular basis of lung cancer development using a microarray to identify the differentially-expressed genes associated with the various tumor-node-metastasis (TNM) stages of lung adenocarcinoma. This subtype of lung cancer has increased in incidence within recent years in China. A 35K oligo gene array covering ~25,100 genes was used to screen the differentially-expressed genes among 90 lung adenocarcinoma samples of various TNM stages. To verify the data from the gene arrays, three genes [human zinc finger-containing, Miz1, PIAS-like protein on chromosome 7 (Zimp7), GINS complex subunit 2 (GINS2) and NSAID activated gene 1 (NAG-1)] were validated using quantitative (q)PCR in an alternative set of samples to the gene array. A total of 640 genes were identified that were differentially-expressed in lung adenocarcinoma compared with the surrounding normal lung tissues. From these 640 candidate genes, 10 were observed to be differentially-expressed among TNM stages I, II and IIIA, of which, the Zimp7, GINS2 and NAG-1 genes were reported for the first time to be expressed at high levels in lung adenocarcinoma. The results of the qPCR for the three genes were consistent with those from the gene array. In total, 10 candidate genes were identified to be associated with the various TNM stages of lung adenocarcinoma in the population studied, which may provide new insights into the molecular basis underlying the development of lung adenocarcinoma and offer new targets for the diagnosis, therapy and prognosis.

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.

The role of NAG-1/GDF15 in the inhibition of intestinal polyps in APC/Min mice by sulindac

The antitumor effects of nonsteroidal anti-inflammatory drugs (NSAID) are assumed to be due to the inhibition of COX activity, but COX-independent mechanisms may also play an important role. NSAID-activated gene (NAG-1/GDF15) is induced by NSAIDs and has antitumorigenic activities. To determine the contribution of COX-2 inhibition and NAG-1/GDF15 expression to the prevention of colon carcinogenesis by NSAIDs, we evaluated several sulindac derivatives [des-methyl (DM)-sulindac sulfide and its prodrug DM-sulindac] that do not inhibit COX-2 activity. Sulindac sulfide and DM-sulindac induced the expression of NAG-1/GDF15 in HCT116 cells as determined by quantitative real-time PCR and Western blot. We fed APC/Min mice with 320 ppm of sulindac and doses of DM-sulindac. Only sulindac significantly inhibited tumor formation inAPC/Min mice. To determine the pharmacokinetic properties of sulindac and DM-sulindac in vivo, wild-type C57/B6 mice were fed with sulindac and DM-sulindac at 80, 160, and 320 ppm. High-performance liquid chromatography analysis revealed that the conversion of DM-sulindac to DM-sulindac sulfide (active form) was less efficient than the conversion of sulindac to sulindac sulfide (active form) in the mice. Lower levels of DM-sulindac sulfide accumulated in intestinal and colon tissues in comparison with sulindac sulfide. In addition, NAG-1/GDF15 was induced in the liver of sulindac-fed mice but not in the DM-sulindac-fed mice. Collectively, our results suggest that the tumor-inhibitory effects of sulindac in APC/Min mice may be due to, in part, NAG-1/GDF15 induction in the liver. Our study also suggests that pharmacologic properties should be carefully evaluated when developing drug candidates.

Activation of NAG-1 via JNK signaling revealed an isochaihulactone-triggered cell death in human LNCaP prostate cancer cells

Background

We explored the mechanisms of cell death induced by isochaihulactone treatment in LNCaP cells.

Methods

LNCaP cells were treated with isochaihulactone and growth inhibition was assessed. Cell cycle profiles after isochaihulactone treatment were determined by flow cytometry. Expression levels of cell cycle regulatory proteins, caspase 9, caspase 3, and PARP were determined after isochaihulactone treatment. Signaling pathway was verified by inhibitors pre-treatment. Expression levels of early growth response gene 1 (EGR-1) and nonsteroidal anti-inflammatory drug-activated gene 1 (NAG-1) were determined to investigate their role in LNCaP cell death. NAG-1 expression was knocked down by si-NAG-1 siRNA transfection. Rate of cell death and proliferation were obtained by MTT assay.

Results

Isochaihulactone caused cell cycle arrest at G2/M phase in LNCaP cells, which was correlated with an increase of p53 and p21 levels and downregulation of the checkpoint proteins cdc25c, cyclin B1, and cdc2. Bcl-2 phosphorylation and caspase activation were also observed. Isochaihulactone induced phosphorylation of c-Jun-N-terminal kinase (JNK), and JNK inhibitor partially reduced isochaihulactone-induced cell death. Isochaihulactone also induced the expressions of EGR-1 and NAG-1. Expression of NAG-1 was reduced by JNK inhibitor, and knocking down of NAG-1 inhibited isochaihulactone-induced cell death.

Conclusions

Isochaihulactone apparently induces G2/M cell cycle arrest via downregulation of cyclin B1 and cdc2, and induces cellular death by upregulation of NAG-1 via JNK activation in LNCaP cells.

Molecular targets of apigenin in colorectal cancer cells: involvement of p21, NAG-1 and p53

Persuasive epidemiological and experimental evidence suggests that dietary flavonoids have anti-cancer activity. Since conventional therapeutic and surgical approaches have not been able to fully control the incidence and outcome of most cancer types, including colorectal neoplasia, there is an urgent need to develop alternative approaches for the management of cancer. We sought to develop the best flavonoids for the inhibition of cell growth, and apigenin (flavone) proved to be the most promising compound in colorectal cancer cell growth arrest. Subsequently, we found that pro-apoptotic proteins (NAG-1 and p53) and cell cycle inhibitor (p21) were induced in the presence of apigenin, and kinase pathways, including PKCδ and ataxia telangiectasia mutated (ATM), play an important role in activating these proteins. The data generated by in vitro experiments were confirmed in an animal study using APC(MIN+) mice. Apigenin is able to reduce polyp numbers, accompanied by increasing p53 activation through phosphorylation in animal models. Our data suggest apparent beneficial effects of apigenin on colon cancer.

Macrophage inhibitory cytokine-1 (MIC-1) and subsequent urokinase-type plasminogen activator mediate cell death responses by ribotoxic anisomycin in HCT-116 colon cancer cells

Ribosome-inactivating stresses possess a potent regulatory activity against tumor cell progression. In this study, we demonstrated that macrophage inhibitory cytokine-1 (MIC-1) and its associated signals determined the colon cancer cell response to the chemical ribotoxic stress. The ribotoxic stress agent anisomycin-induced MIC-1 gene expression which was involved in the ribotoxin-induced apoptotic pathway. MIC-1 was also a critical inducer of apoptosis-related gene products such as activated urokine-type plasminogen activator (PLAU) and PLAU receptor (uPAR). When MIC-1 or PLAU action was repressed in the tumor cells, the chemical ribotoxic stress triggered a survival-related MAP kinase such as ERK. Mechanistically, gene expression of apoptosis-mediator MIC-1 was enhanced by activating transcription factor 3 (ATF-3) via the p38 MAP kinase signaling pathway. Moreover, both promoter activity and mRNA stability of MIC-1 gene were up-regulated by ribotoxic anisomycin via the p38 MAP kinase signaling pathway. In conclusion, ribotoxic anisomycin-induced MIC-1 expression via p38-ATF3 pathway and subsequent apoptosis while suppressing survival ERK signal in the colon cancer cells. The results of this study provide mechanistic insight into tumor cell decision for death or survival pathways in response to ribosome-disrupting stresses from chemotherapeutics.

Nonsteroidal anti-inflammatory drug-activated gene-1 expression inhibits urethane-induced pulmonary tumorigenesis in transgenic mice

The expression of nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1) inhibits gastrointestinal tumorigenesis in NAG-1 transgenic mice (C57/BL6 background). In the present study, we investigated whether the NAG-1 protein would alter urethane-induced pulmonary lesions in NAG-1 transgenic mice on an FVB background (NAG-1(Tg+/FVB)). NAG-1(Tg+/FVB) mice had both decreased number and size of urethane-induced tumors, compared with control littermates (NAG-1(Tg+/FVB) = 16 +/- 4 per mouse versus control = 20 +/- 7 per mouse, P < 0.05). Urethane-induced pulmonary adenomas and adenocarcinomas were observed in control mice; however, only pulmonary adenomas were observed in NAG-1(Tg+/FVB) mice. Urethane-induced tumors from control littermates and NAG-1(Tg+/FVB) mice highly expressed proteins in the arachidonic acid pathway (cyclooxygenases 1/2, prostaglandin E synthase, and prostaglandin E(2) receptor) and highly activated several kinases (phospho-Raf-1 and phosphorylated extracellular signal-regulated kinase 1/2). However, only urethane-induced p38 mitogen-activated protein kinase (MAPK) phosphorylation was decreased in NAG-1(Tg+/FVB) mice. Furthermore, significantly increased apoptosis in tumors of NAG-1(Tg+/FVB) mice compared with control mice was observed as assessed by caspase-3/7 activity. In addition, fewer inflammatory cells were observed in the lung tissue isolated from urethane-treated NAG-1(Tg+/FVB) mice compared with control mice. These results paralleled in vitro assays using human A549 pulmonary carcinoma cells. Less phosphorylated p38 MAPK was observed in cells overexpressing NAG-1 compared with control cells. Overall, our study revealed for the first time that the NAG-1 protein inhibits urethane-induced tumor formation, probably mediated by the p38 MAPK pathway, and is a possible new target for lung cancer chemoprevention.

PLAB induction in fenretinide-induced apoptosis of ovarian cancer cells occurs via a ROS-dependent mechanism involving ER stress and JNK activation

Fenretinide [N-(4-hydroxyphenyl)-retinamide (4HPR)] is a synthetic retinoid with antitumor activity that induces apoptosis in various types of cancer cell. We showed previously that 4HPR upregulates the proapoptotic gene placental bone morphogenetic protein (PLAB), which is a mediator of 4HPR-induced apoptosis in ovarian cancer cells. Here, we investigated the signaling cascade involving PLAB that mediates the apoptotic effect. In 4HPR-sensitive ovarian cancer cells, 4HPR-induced reactive oxygen species (ROS) are involved in PLAB upregulation and apoptosis, both events abrogated by the antioxidants vitamin C and butylated hydroxyanisole. We analyzed the expression and activation of endoplasmic reticulum (ER) stress-associated molecules and show that 4HPR-induced ER stress is a consequence of ROS generation. Salubrinal, an ER stress inhibitor, abrogated 4HPR-induced PLAB upregulation and protected the cells from apoptosis. Downstream of ROS generation and ER stress, 4HPR activated c-Jun N-terminal kinase (JNK), which was inhibited by vitamin C and salubrinal. The JNK inhibitor SP600125 reduced 4HPR-induced PLAB upregulation, by decreasing PLAB mRNA half-life, and protected the cells from apoptosis. These data indicate that 4HPR-induced PLAB upregulation occurs downstream of a signaling cascade involving ROS generation, ER stress induction and JNK activation and that these steps are mediators of 4HPR-induced apoptosis.

Review Paper: Cancer Chemopreventive Compounds and Canine Cancer

Canine cancer has become more prevalent in recent years because of increased life expectancy and greater attention to the health of pets. The range of cancers seen in dogs is as diverse as that in human patients, and despite more intensive therapeutic interventions, fatality rates remain unacceptably high in both species. Chemoprevention is therefore an important means of confronting this disease. Because domestic pets share our environment, greater cross-application and study of the protumorigenic and antitumorigenic factors in our shared environment will benefit all species, leading to the development of new families of less toxic antitumorigenic compounds based on novel and established molecular targets. Currently, the most interesting cancer preventive agents are nonsteroidal anti-inflammatory drugs, peroxisome proliferator-activated receptor-γ ligands, and dietary compounds. This article provides an overview of what is known about how these agents affect molecular signaling in neoplastic disease, with reference to reported application and/or study in dogs where available.

p53 controls prostate-derived factor/macrophage inhibitory cytokine/NSAID-activated gene expression in response to cell density, DNA damage and hypoxia through diverse mechanisms

The p53 tumor suppressor modulates cellular response to stress through both transcriptional and post-transcriptional mechanisms. Elucidation of the downstream targets of p53 following cell stress will aid in our understanding of the pathways involved in cellular adaptation to stressful stimuli. Here, we demonstrate that the TGF-beta superfamily member, and putative tumor suppressor, prostate-derived factor (PDF)/NSAID-activated gene (NAG)-1/macrophage inhibitory cytokine (MIC)-1 is induced in LNCaP human prostate cancer cells following treatment with the DNA-damaging agent, doxorubicin, culture under hypoxic conditions and by the hypoxia mimetic, cobalt chloride. Additionally, PDF expression was induced by increasing cell density. Expression of dominant negative p53 in LNCaP cells blocked induction of PDF mRNA and protein demonstrating the requirement for functional p53 in PDF induction by these stimuli. DNA damage and hypoxia resulted in increased p53 protein accumulation indicating that PDF expression may be controlled by cellular levels of p53. We also show the requirement for de novo protein synthesis in PDF induction by hypoxia and DNA damage. Increased PDF mRNA stability in response to hypoxia and cobalt chloride, but not doxorubicin, indicates that p53-dependent induction of PDF expression occurs via diverse mechanisms. Thus, PDF may represent a novel target of p53 in response to cell stress.

Nonsteroidal anti-inflammatory drug-activated gene (NAG-1/GDF15) expression is increased by the histone deacetylase inhibitor trichostatin A

Nonsteroidal anti-inflammatory drug-activated gene (NAG-1) is a putative tumor suppressor whose expression can be increased by drug treatment. Glioblastoma is the most common central nervous system tumor, is associated with high morbidity and mortality, and responds poorly to surgical, chemical, and radiation therapy. The histone deacetylase inhibitors are under current consideration as therapeutic agents in treating glioblastoma. We investigated whether trichostatin A (TSA) would alter the expression of NAG-1 in glioblastoma cells. The DNA demethylating agent 5-aza-dC did not increase NAG-1 expression, but TSA up-regulated NAG-1 expression and acted synergistically with 5-aza-dC to induce NAG-1 expression. TSA indirectly increases NAG-1 promoter activity and increases NAG-1 mRNA and protein expression in the T98G human glioblastoma cell line. TSA also increases the expression of transcription factors Sp-1 and Egr-1. Small interfering RNA experiments link NAG-1 expression to apoptosis induced by TSA. Reporter gene assays, specific inhibition by small interfering RNA transfections, and chromatin immunoprecipitation assays indicate that Egr-1 and Sp-1 mediate TSA-induced NAG-1 expression. TSA also increases the stability of NAG-1 mRNA. TSA-induced NAG-1 expression involves multiple mechanisms at the transcriptional and post-transcriptional levels.

Cyclooxygenase inhibitors induce apoptosis in sinonasal cancer cells by increased expression of nonsteroidal anti-inflammatory drug-activated gene

Nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1) has recently been shown to be induced by nonsteroidal anti-inflammatory drugs (NSAIDs) and to have proapoptotic and antitumorigenic activities. Although sulindac sulfide induced apoptosis in sinonasal cancer cells, the relationship between NAG-1 and NSAIDs has not been determined. In this study, we investigated the induction of apoptosis in sinonasal cancer cells treated by various NSAIDs and the role of NAG-1 expression in this induction. The effect of NSAIDs on normal human nasal epithelial (NHNE) cells was also examined to evaluate their safety on normal cells. Finally, the in vivo anti-tumorigenic activity of NSAIDs in mice was investigated. In AMC-HN5 human sinonasal carcinoma cells, indomethacin was the most potent NAG-1 inducer and caused NAG-1 expression in a time- and dose-dependent manner. The induction of NAG-1 expression preceded the induction of apoptosis. Conditioned medium from NAG-1-overexpressing Drosophila cells inhibited proliferation of sinonasal cancer cells and induced apoptosis. In addition, in NAG-1 small interfering RNA-transfected cells, apoptosis induced by indomethacin was suppressed. In contrast, NAG-1 expression and apoptosis were not induced by NSAIDs or conditioned medium in NHNE cells. Furthermore, indomethacin induced a dose-dependent in vivo increase in the expression of NAG-1 mRNA in the mice tumors and the volume of xenograft tumors of AMC-HN5 cells in indomethacin-treated nude mice was reduced compared to that in control mice. In conclusion, indomethacin exerts proapoptotic and antitumorigenic effects in sinonasal cancer cells through the induction of NAG-1 and can be considered a safe and effective chemopreventive agent against sinonasal cancer.

Implication of NAG-1 in synergistic induction of apoptosis by combined treatment of sodium salicylate and PI3K/MEK1/2 inhibitors in A549 human lung adenocarcinoma cells

Aspirin is used as chemopreventive agents in a variety of human cancer cells including those of colon, lung, breast, and leukemia. Sodium salicylate (NaSal, the natural deacetylated form of aspirin) induced cell cycle arrest and apoptosis in a dose-dependent manner in A549 cells; high dose (20mM) of NaSal-induced apoptosis, whereas low dose (2-10mM) induced cell cycle arrest. We found that NaSal-activated Akt/PKB, ERK1/2, and p38MAPK signal cascades. Twenty micromolar of NaSal-induced apoptotic response of A549 cells was enhanced by the PI3K inhibitors (LY294002 and wortmannin) and in a less extent by the MEK1/2 inhibitors (U0126 and PD98059), whereas it was suppressed by the p38MAPK inhibitor (SB203580). Furthermore, simultaneous inhibition of the Akt/PKB and ERK1/2 signal cascades could lower the dose of NaSal to induce apoptosis to 2mM in A549 lung cancer cells. Similar enhancement was observed in cells treated with 2mM NaSal and 100muM genistein, an inhibitor of receptor tyrosine kinases (RTKs) that are upstream of PI3K and MEK1/2 signaling. We further demonstrated that NAG-1 plays a key role in apoptosis by NaSal-based combined treatment. Collectively, our findings indicate that inhibition of the pro-survival Akt/PKB and ERK1/2 signaling may increase the chemopreventive effects of NaSal and combined treatment of two natural compounds (NaSal and genistein) results in a highly synergistic induction of apoptosis, thereby increasing the chemopreventive effects of NaSal against cancer.

Effect of in vivo loss of GDF-15 on hepatocellular carcinogenesis

BACKGROUND

Growth/differentiation factor-15(GDF-15) is a divergent TGF-beta family member that is expressed following liver injury and carcinogen exposure. GDF-15 expression is highly associated with gastrointestinal cancer stage, size, and metastasis and has been implicated in inhibition of tumor growth and increased tumor invasiveness. The current study sought to determine the effect of GDF-15 ablation on the development of hepatocellular carcinoma (HCC) in vivo.

MATERIALS AND METHODS

Male mice genetically deleted for the gene encoding GDF-15 (Gdf15 (-/-) mice) and wild-type controls were exposed to the hepatocarcinogen diethylnitrosamine (DEN). Mice were killed at 6 months of age and their livers dissected and processed for histology. Tumor number and size relative to total liver area examined were determined.

RESULTS

At 6 months of age, tumors were identified in 16 of 20 (80%) Gdf15 (-/-) mice and 16 of 19 wild-type mice (84%). No significant difference in tumor-occupied area was observed in Gdf15 (-/-) mice versus wild-type mice. In addition, no difference in invasiveness was observed in HCC arising in Gdf15 (-/-) as compared to wild-type mice. In wild type mice strong immunohistochemical staining for GDF-15 was noted on small HCC foci, whereas a loss of GDF-15 expression was found in a number of advanced HCC tumors.

CONCLUSIONS

Although highly expressed in association with multiple gastrointestinal cancers, and lost in some advanced HCC, genetic ablation of GDF-15 has no apparent effect on HCC tumor formation rate, growth rate or invasiveness in diethylnitrosamine-induced HCC in vivo.

The anticancer agent prodigiosin induces p21WAF1/CIP1 expression via transforming growth factor-beta receptor pathway

The anticancer agent prodigiosin has been shown to act as an efficient immunosuppressant, eliciting cell cycle arrest at non-cytotoxic concentrations, and potent proapoptotic and antimetastatic effects at higher concentrations. Gene expression profiling of MCF-7 cells after treatment with a non-cytotoxic concentration of prodigiosin showed that expression of the p21WAF1/CIP1 gene, a negative cell cycle regulator was induced. In this study, we show that prodigiosin induces p21 expression leading to cell cycle blockade. Subsequently, we attempted to elucidate the molecular mechanisms involved in prodigiosin-mediated p21 gene expression. We demonstrate that prodigiosin induces p21 in a p53-independent manner as prodigiosin induced p21 in cells with both mutated and dominant negative p53. Conversely, the transforming growth factor-beta (TGF-beta) pathway has been found to be necessary for p21 induction. Prodigiosin-mediated p21 expression was blocked by SB431542, a TGF-beta receptor inhibitor. Nevertheless, this pathway alone is not enough to induce p21 expression. The TGF-beta family member (nonsteroidal anti-inflammatory drug)-activated gene 1/growth differentiation factor 15 (NAG-1) may activate this pathway, as it has previously been suggested to signal through the TGF-beta pathway and is overexpressed in response to prodigiosin treatment. We show that NAG-1 colocalizes with TGF-beta receptor type I, suggesting a possible interaction between them. Taken together, these results suggest the TGF-beta pathway is required for induction of p21 expression after prodigiosin treatment of MCF-7 cells.

Activation of Nonsteroidal Anti-Inflammatory Drug-Activated Gene-1 via Extracellular Signal-Regulated Kinase 1/2 Mitogen-Activated Protein Kinase Revealed a Isochaihulactone-Triggered Apoptotic Pathway in Human Lung Cancer A549 Cells

The novel lignan isochaihulactone inhibits cell proliferation and is an effective inducer of apoptosis in a variety of carcinoma cell lines. To determine the mechanisms underlying these effects, we examined isochaihulactone-induced changes in gene expression using oligodeoxynucleotide-based microarray screening of a human lung carcinoma cell line, A549. Isochaihulactone-inducible genes included the early growth response gene-1 (EGR-1) and nonsteroidal anti-inflammatory drug-activated gene (NAG-1). Isochaihulactone increased EGR-1 and then NAG-1 mRNA and protein expression. Pure isochaihulactone induced phosphorylation of extracellular signal-regulated kinase (ERK) 1/2. Isochaihulactone-induced increases in EGR-1 and NAG-1 expression were reduced by the mitogen-activated protein kinase kinase 1/2 inhibitor 2'-amino-3'-methoxyflavone (PD98059), and this effect was not blocked by the phosphatidylinositol 3-kinase/protein kinase B pathway inhibitor 2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one hydrochloride (LY294002). Inhibition of isochaihulactone-induced NAG-1 expression by EGR-1 small interfering RNA blocked isochaihulactone-induced apoptosis in A549 cells, suggesting that induction of EGR-1 expression decreases survival of A549 cells. RNA interference using double-stranded RNA specific for NAG-1 also inhibited isochaihulactone-induced apoptosis, and cells transfected to increased NAG-1 expression had a greater apoptotic response to isochaihulactone and reduced colony formation efficiency. In addition, treatment of nude mice with isochaihulactone increased the in vivo NAG-1 expression as examined by immunohistochemistry from tumor biopsy. Isochaihulactone treatment increased the luciferase activity of NAG-1 in A549 cells transfected with the NAG-1 promoter construct. This induction increased expression of NAG-1 that was p53-independent and Sp1-dependent. Our findings suggest that NAG-1 expression is up-regulated by isochaihulactone through an ERK-dependent pathway involving the activation of EGR-1.

Prodigiosin induces the proapoptotic gene NAG-1 via glycogen synthase kinase-3beta activity in human breast cancer cells

Prodigiosin (2-methyl-3-pentyl-6-methoxyprodigiosene) is a bacterial metabolite that has anticancer and antimetastatic properties. However, the molecular mechanisms responsible for these abilities are not fully understood. Gene expression profiling of the human breast cancer cell line MCF-7 treated with prodigiosin was analyzed by cDNA array technology. The majority of the significantly modified genes were related to apoptosis, cell cycle, cellular adhesion, or transcription regulation. The dramatic increase of the nonsteroidal anti-inflammatory drug-activated gene 1 (NAG-1) made this gene an interesting candidate regarding the possible mechanism by which prodigiosin induces cytotoxicity in MCF-7 cells. Our results show that prodigiosin triggers accumulation of the DNA-damage response tumor-suppressor protein p53 but that NAG-1 induction was independent of p53 accumulation. Moreover, prodigiosin caused AKT dephosphorylation and glycogen synthase kinase-3beta (GSK-3beta) activation, which correlated with NAG-1 expression. Prodigiosin-induced apoptosis was recovered by inhibiting GSK-3beta, which might be due, at least in part, to the blockade of the GSK-3beta-dependent up-regulation of death receptors 4 and 5 expression. These findings suggest that prodigiosin-mediated GSK-3beta activation is a key event in regulating the molecular pathways that trigger the apoptosis induced by this anticancer agent.

Analysis of gene expression identifies PLAB as a mediator of the apoptotic activity of fenretinide in human ovarian cancer cells

Fenretinide (4-HPR) is a synthetic retinoid with antitumor activity, which induces apoptosis in cancer cell lines of different histotypes. To identify genes contributing to its apoptotic activity in ovarian cancer cells, we monitored, by cDNA arrays, gene expression changes after 4-HPR exposure in A2780, a human ovarian carcinoma cell line sensitive to the retinoid. Among the differentially expressed transcripts, PLAcental Bone morphogenetic protein (PLAB), a proapoptotic gene, was the most highly induced. In a panel of ovarian carcinoma cell lines with different 4-HPR sensitivities, PLAB upregulation was associated with cellular response to 4-HPR, its overexpression increased basal apoptosis and its silencing by small interfering RNA decreased the ability of 4-HPR to induce apoptosis. PLAB induction by 4-HPR was p53- and EGR-1 independent and was regulated, at least in part, by increased stability of PLAB mRNA. PLAB up-modulation by 4-HPR also occurred in vivo: in ascitic cells collected from patients with ovarian cancer before and after 4-HPR treatment, PLAB was upmodulated in 2/4 patients. Our results in certain ovarian cancer cell lines indicate a role for PLAB as a mediator of 4-HPR-induced apoptosis. The correlation of increased PLAB in vivo with antitumor activity remains to be established.

NSAID activated gene (NAG-1), a modulator of tumorigenesis

The NSAID activated gene (NAG-1), a member of the TGF-beta superfamily, is involved in tumor progression and development. The over-expression of NAG-1 in cancer cells results in growth arrest and increase in apoptosis, suggesting that NAG-1 has anti-tumorigenic activity. This conclusion is further supported by results of experiments with transgenic mice that ubiquitously express human NAG-1. These transgenic mice are resistant to the development of intestinal tumors following treatment with azoxymethane or by introduction of a mutant APC gene. In contrast, other data suggest a pro-tumorigenic role for NAG-1, for example, high expression of NAG-1 is frequently observed in tumors. NAG-1 may be like other members of the TGF-beta superfamily, acting as a tumor suppressor in the early stages, but acting pro-tumorigenic at the later stages of tumor progression. The expression of NAG-1 can be increased by treatment with drugs and chemicals documented to prevent tumor formation and development. Most notable is the increase in NAG-1 expression by the inhibitors of cyclooxygenases that prevent human colorectal cancer development. The regulation of NAG-1 is complex, but these agents act through either p53 or EGR-1 related pathways. In addition, an increase in NAG-1 is observed in inhibition of the AKT/GSK-3beta pathway, suggesting NAG-1 alters cell survival. Thus, NAG-1 expression is regulated by tumor suppressor pathways and appears to modulate tumor progression.

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

BACKGROUND & AIMS

The nonsteroidal anti-inflammatory drug-activated gene (NAG-1) was identified as a proapoptotic, antitumorigenic protein in vitro, induced by many antitumorigenic and chemopreventive drugs including cyclooxygenase inhibitors. However, its antitumorigenic activity has not been elucidated in vivo.

METHODS

Transgenic mice were generated that ubiquitously overexpress human NAG-1 under the control of a chicken beta-actin promoter (CAG). The NAG-1 transgenic mice (NAG-(Tg+)) were characterized, and then the antitumorigenic activity was evaluated with 2 colorectal carcinogenesis models: chemical induction with azoxymethane and genetic induction using the Apc(Min+) mutation.

RESULTS

NAG-(Tg+) showed no apparent phenotype other than a reduction in body weight, particularly in males. To examine whether NAG-1 expression would suppress intestinal tumorigenesis, the NAG-(Tg+) mice were treated with the colorectal carcinogen azoxymethane. NAG-(Tg+) mice developed 50% fewer aberrant crypt foci and no tumors, in comparison with nontransgenic littermates. This result demonstrates that expression of this human protein in vivo can suppress chemically induced carcinogenesis in the colon. The NAG-(Tg+) mice were also crossed with Apc(Min+) mice to determine the effect of the transgene on intestinal polyp formation. NAG-(Tg+) mice heterozygous for the Apc(Min+) mutation had a significantly reduced polyp load (60%) compared with nontransgenic Apc(Min+) littermates.

CONCLUSIONS

Our results support NAG-1 as an important regulator of intestinal adenoma growth in vivo and suggest that NAG-1 may act as a tumor suppressor gene.

Prostate derived factor in human prostate cancer cells: gene induction by vitamin D via a p53-dependent mechanism and inhibition of prostate cancer cell growth

The secosteroid hormone 1alpha, 25-dihydroxyvitamin D3 (1,25D) has been shown to regulate the growth and differentiation of human prostate cancer (PCa) cells, although the precise molecular mechanisms mediating these effects have not been defined. Previous studies in our laboratory demonstrated that the antiproliferative effects of 1,25D on PCa cells are mediated through the nuclear vitamin D receptor (VDR). In the present study, we performed gene profiling of LNCaP human PCa cells following 1,25D treatment and identified the antitumorigenic gene, prostate derived factor (PDF), as being highly induced by 1,25D. PDF is a member of the TGF-beta superfamily and has been implicated in a variety of functions directly related totumorigenicity including antiproliferative and pro-apoptotic effects. Gene expression studies using 1,25D analogs and a VDR antagonist demonstrate that 1,25D-mediated induction of PDF message and protein in PCa cells is dependent on VDR action. PDF is a transcriptional target of the tumor suppressor, p53. Here we show that the expression of PDF in nine PCa cell lines is dependent on functional p53. Additionally, transfection of p53-null ALVA-31 PCa cells with a p53 expression plasmid, and expression of dominant negative p53 in LNCaP PCa cells, show that the ability of VDR to induce PDF requires functional p53. Importantly, forced PDF expression in PC-3 cells results in decreased cell proliferation, soft agar cloning, and xenograft tumor size. These data demonstrate that PDF exerts antitumorigenic properties on PCa cells and its regulation by 1,25D may provide insights into the action of 1,25D in PCa.

Drug-induced expression of nonsteroidal anti-inflammatory drug-activated gene/macrophage inhibitory cytokine-1/prostate-derived factor, a putative tumor suppressor, inhibits tumor growth

A common in vitro response for many chemopreventive and antitumor agents, including some cyclooxygenase inhibitors, is the increased expression of nonsteroidal anti-inflammatory drug-activated gene (NAG)-1/macrophage inhibitory cytokine (MIC)-1/prostate-derived factor (PDF). The experimental anticancer drug 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F203) was a potent inducer of NAG-1 expression, and in MCF-7 cells, it inhibited cell growth and induced apoptosis. NAG-1 small interfering RNA blocked NAG-1 expression and 5F203-induced apoptosis in MCF-7 cells, indicating that NAG-1 may mediate the apoptosis and anticancer activity. One mechanism by which 5F203 increases NAG-1 expression is by increasing the stability of NAG-1 mRNA, dependent of de novo protein synthesis. Extracellular signal-regulated kinase (ERK) 1/2 phosphorylation was increased by 5F203, and inhibition of ERK1/2 phosphorylation abolished the induction of NAG-1 protein expression and increased the stability of NAG-1 mRNA. Thus, 5F203 regulates NAG-1 expression by a unique mechanism compared with other drugs. A mouse orthotopic mammary tumor model was used to determine whether 5F203 increased NAG-1 expression in vivo and suppressed tumor growth. Treatment of the mice with Phortress, the prodrug of 5F203, increased the in vivo expression of NAG-1 as measured by real-time reverse transcription-polymerase chain reaction from RNA obtained by needle biopsy, and the expression correlated with a reduction of tumor volume. These results confirm that NAG-1 suppresses tumor growth, and its in vivo expression can be controlled by treating mice with anticancer drugs, such as Phortress. Drugs that target NAG-1 could lead to a unique strategy for the development of chemotherapeutic and chemopreventive agents.

Ionizing radiation enhances the expression of the nonsteroidal anti-inflammatory drug-activated gene (NAG1) by increasing the expression of TP53 in human colon cancer cells

The induction of apoptosis in cells of human colon cancer cell lines after gamma irradiation was investigated to determine whether apoptosis was mediated by TP53 and the subsequent expression of its downstream target, the NSAID-activated gene (NAG1). HCT116 (TP53(+/+)), HCT15 (TP53 mutant) and TP53 null HCT116 (TP53(-/-)) cells were irradiated with gamma rays, and apoptosis was measured at various times after irradiation. In HCT116 TP53(+/+) cells, apoptosis was increased after irradiation; the increase was dependent on the time after treatment and the dose of gamma rays. However, in HCT15 TP53 mutant cells and HCT116 TP53(-/-) cells, there were no remarkable changes in apoptosis. The expression of TP53 protein in HCT116 cells was increased after irradiation and was followed by an increase in the expression of NAG1 protein. In contrast, the expression of NAG1 protein in TP53 mutant cells and TP53(-/-) cells was not increased by the radiation treatment, suggesting that NAG1 was required for apoptosis. The expression of NAG1 increased apoptosis in HCT116 cells, but radiation treatment did not further increase apoptosis. The transfection of a NAG1 siRNA into HCT116 cells suppressed radiation-induced apoptosis and inhibited the induction of NAG1 protein without altering the expression of TP53. a NAG1 luciferase promoter construct that included both of the TP53 binding sites, was activated by radiation in dose-dependent manner, while the promoters lacking one or both of the TP53 binding sites in the NAG1 promoter activity either was less responsive or did not respond. The findings reported here indicate that gamma radiation activates the TP53 tumor suppressor, which then increases the expression of NAG1. NAG1 mediates the induction of apoptosis in human colorectal cells.

Growth Differentiation Factor-15: Induction in Liver Injury Through p53 and Tumor Necrosis Factor-Independent Mechanisms1

Expression of macrophage inhibitory cytokine-1 (MIC-1), a divergent transforming growth factor-beta family member, and its murine ortholog, growth/differentiation factor-15 (GDF-15), is induced in hepatocytes by surgical and chemical injury and heat shock. Here, we demonstrate that the regulation of GDF-15/MIC-1 expression may be evolutionarily conserved because MIC-1 was induced in diseased human livers. Gdf15 induction was independent of protein synthesis, a hallmark of immediate-early gene regulation. Although tumor necrosis factor (TNF) induced GDF-15 expression, injury-elicited Gdf15 expression was not reduced in mice deficient for both TNF receptor subtypes. Furthermore, although the stress sensor p53 is known to induce GDF-15/MIC-1 expression, injury-elicited Gdf15 expression was unchanged in p53 null mice. Our results demonstrate that GDF-15 induction is an immediate early response to liver injury that can occur through TNF and p53 independent pathways.

Conjugated linoleic acid stimulates an anti-tumorigenic protein NAG-1 in an isomer specific manner

Conjugated linoleic acids (CLAs), naturally occurring fatty acids in ruminant food products, have anti-tumorigenic and pro-apoptotic properties in animal as well as in vitro models of cancer. However, the cellular mechanism has not been fully understood. NAG-1 (non-steroidal anti-inflammatory drug-activated gene-1) is induced by several dietary compounds and belongs to a TGF-beta superfamily gene associated with pro-apoptotic and anti-tumorigenic activities. The present study was performed to elucidate the molecular mechanism by which CLA stimulates anti-tumorigenic activity in human colorectal cancer (CRC) cells. The trans-10, cis-12-CLA (t10,c12-CLA) repressed cell proliferation and induced apoptosis, whereas linoleic acid or c9,t11-CLA showed no effect on cell proliferation and apoptosis. We also found that t10,c12-CLA induced the expression of a pro-apoptotic gene, NAG-1, in human CRC cells. Inhibition of NAG-1 expression by small interference RNA (siRNA) results in repression of t10,c12-CLA-induced apoptosis. Microarray analysis using t10,c12-CLA-treated HCT-116 cells revealed that activating transcription factor 3 (ATF3) was induced and its expression was confirmed by western analysis. The t10,c12-CLA treatment followed by the overexpression of ATF3 increased NAG-1 promoter activity in HCT-116 cells. We further provide the evidence that t10,c12-CLA inhibited the phosphorylation of AKT and the blockage of GSK-3 by siRNA abolished t10,c12-CLA-induced ATF3 and NAG-1 expression. The current study demonstrates that t10,c12-CLA stimulates ATF3/NAG-1 expression and subsequently induces apoptosis in an isomer specific manner. These effects may be through inhibition of AKT/GSK-3beta pathway in human CRC cells.

1,1-Bis(3'-indolyl)-1-(p-substitutedphenyl)methanes are peroxisome proliferator-activated receptor gamma agonists but decrease HCT-116 colon cancer cell survival through receptor-independent activation of early growth response-1 and nonsteroidal anti-inflammatory drug-activated gene-1

1,1-Bis-(3'-indolyl)-1-(p-substitutedphenyl)methanes containing p-trifluoromethyl (DIM-C-pPhCF3), p-t-butyl (DIM-C-pPhtBu), and phenyl (DIM-C-pPhC6H5) substituents decrease survival of HCT-116 colon cancer cells and activate peroxisome proliferator-activated receptor (PPAR) gamma in this and other cancer cell lines. These PPARgamma-active compounds had minimal effects on expression of cell cycle proteins and did not induce caveolin-1 in HCT-116 cells. However, these compounds induced nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1) and apoptosis in HCT-116 cells, and in time-course studies, the PPARgamma agonists maximally induced early growth response-1 (Egr-1) protein within 2 h, whereas a longer time course was observed for induction of NAG-1 protein. These data, coupled with deletion and mutation analysis of both the Egr-1 and NAG-1 gene promoters, indicate that activation of NAG-1 by these compounds was dependent on prior induction of Egr-1, and induction of these responses was PPARgamma-independent. Results of kinase inhibitor studies also demonstrated that activation of Egr-1/NAG-1 by methylene-substituted diindolylmethanes (C-DIMs) was phosphatidylinositol 3-kinase-dependent, and this represents a novel receptor-independent pathway for C-DIM-induced growth inhibition and apoptosis in colon cancer cells.

The transforming growth factor-beta family members bone morphogenetic protein-2 and macrophage inhibitory cytokine-1 as mediators of the antiangiogenic activity of N-(4-hydroxyphenyl)retinamide

PURPOSE

Tumor growth appears to be an angiogenesis-dependent process. N-(4-hydroxyphenyl)retinamide (fenretinide; 4HPR) has been found to inhibit and/or prevent tumor growth under diverse conditions. Although 4HPR is antiangiogenic, the molecular mechanisms of this effect remain largely unknown.

EXPERIMENTAL DESIGN

Endothelial cells were treated with 4HPR in vitro to study the effects on migration, invasion, and organization, as well as gene expression by microarray and quantitative PCR studies. In vivo angiogenesis was evaluated in the Matrigel model.

RESULTS

4HPR treatment substantially modified the biological activities of endothelial cells, repressing their capacity to migrate, invade, and organize into capillary-like structures. The inhibition of invasion induced by 4HPR was also associated with decreased activities of the metalloproteases matrix metalloproteinase-2 and CD13/APN. Using oligonucleotide microarrays, we observed that bone morphogenetic protein-2 and macrophage inhibitory cytokine-1, two multifunctional cytokines of the transforming growth factor-beta family that regulate the growth, differentiation, apoptosis, and matrix accumulation of a variety of cells, are up-regulated in vitro by 4HPR. Both these molecules specifically inhibited endothelial cell growth, migration, and invasion in vitro and suppressed angiogenesis in the Matrigel plug assay in vivo. Blocking antibodies to bone morphogenetic protein-2 were able to reverse the suppressive effects of 4HPR in vitro and in vivo.

CONCLUSIONS

These data support the conclusion that 4HPR inhibits tumor growth by repression of new vessel growth and identify novel points of regulation of angiogenesis in transforming growth factor-beta family proteins.

The conventional nonsteroidal anti-inflammatory drug sulindac sulfide arrests ovarian cancer cell growth via the expression of NAG-1/MIC-1/GDF-15

Although the chemopreventive and antitumorigenic activities of nonsteroidal anti-inflammatory drug (NSAID) against colorectal cancer are well established, the molecular mechanisms responsible for these properties in ovarian cancer have not been elucidated. Therefore, there is an urgent need to develop mechanism-based approaches for the management of ovarian cancer. To this end, the effect of several NSAIDs on ovarian cancer cells was investigated as assessed by the induction of NAG-1/MIC-1/GDF-15, a proapoptotic gene belonging to the transforming growth factor-beta superfamily. Sulindac sulfide was the most significant NSAID activated gene 1 (NAG-1) inducer and its expression was inversely associated with cell viability as determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay. This growth suppression by sulindac sulfide was recovered by transfection of NAG-1 small interfering RNA. These results indicate that NAG-1 is one of the genes responsible for growth suppression by sulindac sulfide. Furthermore, we observed down-regulation of p21 WAF1/CIP1 by introduction of NAG-1 small interfering RNA into sulindac sulfide-treated cells. In addition, to elucidate other potential molecular mechanisms involved in sulindac sulfide treatment of ovarian cancer cells, we did a membrane-based microarray experiment. We found that cyclin D1, MMP-1, PI3KR1, and uPA were down-regulated by sulindac sulfide. In conclusion, a novel molecular mechanism is proposed to explain the experimental results and provide a rationale for the chemopreventive activity of NSAIDs in ovarian cancer.

Indole-3-carbinol and 3,3'-diindolylmethane induce expression of NAG-1 in a p53-independent manner

Indole-3-carbinol (I3C), present in cruciferous vegetables, and its major in vivo product 3,3'-diindolylmethane (DIM), have been reported to suppress cancer development. However, the responsible molecular mechanisms are not fully understood. Nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1) is a TGF-beta superfamily gene associated with pro-apoptotic and anti-tumorigenic activities. The present study was performed to investigate whether I3C and DIM influence NAG-1 expression and to provide the potential molecular mechanism of their effects on anti-tumorigenesis. The I3C repressed cell proliferation and induced NAG-1 expression in a concentration-dependent manner. In addition, DIM increased the expression of NAG-1 as well as activating transcription factor 3 (ATF3), and the induction of ATF3 was earlier than that of NAG-1. The DIM treatment increased luciferase activity of NAG-1 in HCT-116 cells transfected with NAG-1 promoter construct. The results suggest that I3C represses cell proliferation through up-regulation of NAG-1 and that ATF3 may play a pivotal role in DIM-induced NAG-1 expression in human colorectal cancer cells. Furthermore, the mixture of I3C with resveratrol enhances NAG-1 expression, suggesting the synergistic effect of these two unrelated compounds on NAG-1 expression.

Cyclooxygenase inhibitors induce apoptosis in oral cavity cancer cells by increased expression of nonsteroidal anti-inflammatory drug-activated gene

We have investigated whether NAG-1 is induced in oral cavity cancer cells by various NSAIDs and if apoptosis induced by NSAIDs can be linked directly with the induction of NAG-1. NAG-1 expression was increased by diclofenac, aceclofenac, indomethacin, ibuprofen, and sulindac sulfide, in the order of NAG-1 induction, but not by acetaminophen, piroxicam or NS-398. Diclofenac was the most effective NAG-1 inducer. Incubation with diclofenac inhibited cell proliferation and induced apoptosis. The expression of NAG-1 was observed in advance of the induction of apoptosis. Conditioned medium from NAG-1-overexpressing Drosophila cells inhibited SCC 1483 cells proliferation and induced apoptosis. In summary, some NSAIDs induce NAG-1 expression in oral cavity cancer cells and the induced NAG-1 protein appears to mediate apoptosis. Therefore, NSAIDs may be considered as a possible chemopreventive agent against oral cavity cancer.

Cyclooxygenase inhibitors induce the expression of the tumor suppressor gene EGR-1, which results in the up-regulation of NAG-1, an antitumorigenic protein

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to have chemopreventive activity, but the mechanisms involved are not clearly understood. Although NSAIDs inhibit cyclooxygenase activity, they also increase the expression of a divergent member of the transforming growth factor-beta superfamily, termed NSAID-activated gene 1 (NAG-1), a protein with an antitumorigenic and proapoptotic activity that could in part be linked to the chemoprevention activity of NSAIDs. NAG-1 is induced by some NSAIDs, but the mechanisms responsible are not clear. In this report, we have identified a cis-acting element responsive to NSAIDs located within the -73 to -51 region of the NAG-1 promoter. This region contains overlapping EGR-1 and Sp1 binding sites, and mutations in this region suggest that the transcription factors have an important role in NSAID-induced NAG-1 expression. EGR-1 was found to play a critical role in the induction of NAG-1 by sulindac sulfide and other NSAIDs. NSAIDs increase EGR-1 protein expression that occurs before the induction of NAG-1 expression, supporting the hypothesis that EGR-1 is necessary for NSAID-induced NAG-1 expression. Thus, NSAIDs induce the expression of EGR-1, a tumor suppressor gene, providing a novel mechanism to explain, in part, the antitumorigenic properties of some NSAIDs. NAG-1 seems to be an important downstream target protein of this transcription factor, EGR-1, and may mediate the chemopreventive activity of some NSAIDs.

Identification of nonsteroidal anti-inflammatory drug-activated gene (NAG-1) as a novel downstream target of phosphatidylinositol 3-kinase/AKT/GSK-3beta pathway

The signaling pathway of phosphatidylinositol 3-kinase (PI3K)/AKT, which is involved in cell survival, proliferation, and growth, has become a major focus in targeting cancer therapeutics. Nonsteroidal anti-inflammatory drug-activated gene (NAG-1) was previously identified as a gene induced by several anti-tumorigenic compounds including nonsteroidal anti-inflammatory drugs, peroxisome proliferator-activated receptor gamma ligands, and dietary compounds. NAG-1 has been shown to exhibit anti-tumorigenic and/or pro-apoptotic activities in vivo and in vitro. In this report, we showed a PI3K/AKT/glycogen synthase kinase-3beta (GSK-3beta) pathway regulates NAG-1 expression in human colorectal cancer cells as assessed by the inhibition of PI3K, AKT, and GSK-3beta. PI3K inhibition by LY294002 showed an increase in NAG-1 protein and mRNA expression, and 1l-6-hydroxymethyl-chiro-inositol 2(R)-2-O-methyl-3-O-octadecylcarbonate (AKT inhibitor) also induced NAG-1 expression. LY294002 caused increased apoptosis, cell cycle, and cell growth arrest in HCT-116 cells. Inhibition of GSK-3beta, which is negatively regulated by AKT, using AR-A014418 and lithium chloride completely abolished LY294002-induced NAG-1 expression as well as the NAG-1 promoter activity. Furthermore, the down-regulation of GSK-3 gene using small interference RNA resulted in a decline of the NAG-1 expression in the presence of LY294002. These data suggest that expression of NAG-1 is regulated by PI3K/AKT/GSK-3beta pathway in HCT-116 cells and may provide a further understanding of the important role of PI3K/AKT/GSK-3beta pathway in tumorigenesis.

Calcitriol-induced prostate-derived factor: Autocrine control of prostate cancer cell growth

Calcitriol (1alpha,25-dihydroxycholecalciferol) seems to play an important role in the complex control of prostate cell growth. It inhibits proliferation and induces differentiation and apoptosis in prostate cancer cells. However, the molecular mechanisms of the antiproliferative activity of calcitriol are not completely understood. The expression of prostate-derived factor (PDF), a member of the transforming growth factor-beta (TGF-beta) superfamily, has been shown to be associated with proapoptotic and antimitotic activities. We show that calcitriol induces PDF expression in LNCaP human prostate cancer cells in a concentration- and time-dependent manner. In LNCaP cells, the suppression of cell growth by calcitriol is accompanied by stimulation of PDF mRNA and protein synthesis. Human recombinant PDF inhibits LNCaP cell growth. We do not detect any effect of PDF-specific antibody on the basal growth of LNCaP cells, but this antibody partially reverses the suppression of LNCaP cell growth by calcitriol, suggesting that the effect of calcitriol on cell growth is at least partially mediated by PDF. In PC-3 cells, which are less responsive to the growth-inhibitory effect of calcitriol, it has no effect on PDF expression. We do not detect an effect of recombinant PDF on SMAD phosphorylation in LNCaP cells, but ERK1/2 kinases are transiently phosphorylated in response to PDF, which suggests that in LNCaP cells PDF may exert its action through pathway alternative to the classical TGF-beta signaling pathway. The present study describes the regulation of PDF, the proapoptotic protein of the TGF-beta superfamily, by calcitriol in androgen-responsive prostate cancer cells. This is a new link between calcitriol and growth factors of TGF-beta superfamily in the control of prostate cell growth.

Expression of NAG-1, a transforming growth factor-beta superfamily member, by troglitazone requires the early growth response gene EGR-1

Troglitazone (TGZ) and 15-deoxy-Delta(12,14)-prostaglandin J2 (PGJ2) are peroxisome proliferator-activated receptor-gamma (PPARgamma) ligands that have been shown to possess pro-apoptotic activity in human colon cancer. Although these compounds bind to PPARgamma transcription factors as agonists, emerging evidence suggests that TGZ acts independently of PPARgamma in many functions, including apoptosis. We previously reported that TGZ induces an early growth response transcription factor (EGR-1) by the ERK phosphorylation pathway rather than by the PPARgamma pathway (Baek, S. J., Wilson, L. C., Hsi, L. C., and Eling, T. E. (2003) J. Biol. Chem. 278, 5845-5853). In this report, we show that the expression of the antitumorigenic and/or pro-apoptotic gene NAG-1 (nonsteroidal anti-inflammatory drug-activated gene-1) is induced by TGZ and correlates with EGR-1 induction. In cotransfection and gel shift assays, we show that EGR-1-binding sites are located within region -73 to -51 of the NAG-1 promoter and have an important role in the transactivation of TGZ-induced NAG-1 expression. In contrast, PGJ2 induced NAG-1 protein expression, but PGJ2 may not affect the same region that TGZ does in the NAG-1 promoter. The effect of PGJ2 is probably PPARgamma-dependent because a PPARgamma antagonist inhibited the PGJ2-induced expression of NAG-1. TGZ-induced NAG-1 expression was not inhibited by the PPARgamma antagonist. The fact that TGZ-induced NAG-1 expression was accompanied by the biosynthesis of EGR-1 also suggests that EGR-1 plays a pivotal role in TGZ-induced NAG-1 expression. Our results suggest that EGR-1 induction is a unique property of TGZ, but is independent of PPARgamma activation. The up-regulation of NAG-1 may provide a novel explanation for the antitumorigenic property of TGZ.