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

Divergent molecular mechanisms underlying the pleiotropic functions of macrophage inhibitory cytokine-1 in cancer

Multifunctional macrophage inhibitory cytokine-1, MIC-1, is a member of the transforming growth factor-beta (TGF-beta) superfamily that plays key roles in the prenatal development and regulation of the cellular responses to stress signals and inflammation and tissue repair after acute injuries in adult life. The stringent control of the MIC-1 expression, secretion, and functions involves complex regulatory mechanisms and the interplay of other growth factor signaling networks that control the cell behavior. The deregulation of MIC-1 expression and signaling pathways has been associated with diverse human diseases and cancer progression. The MIC-1 expression levels substantially increase in cancer cells, serum, and/or cerebrospinal fluid during the progression of diverse human aggressive cancers, such as intracranial brain tumors, melanoma, and lung, gastrointestinal, pancreatic, colorectal, prostate, and breast epithelial cancers. Of clinical interest, an enhanced MIC-1 expression has been positively correlated with poor prognosis and patient survival. Secreted MIC-1 cytokine, like the TGF-beta prototypic member of the superfamily, may provide pleiotropic roles in the early and late stages of carcinogenesis. In particular, MIC-1 may contribute to the proliferation, migration, invasion, metastases, and treatment resistance of cancer cells as well as tumor-induced anorexia and weight loss in the late stages of cancer. Thus, secreted MIC-1 cytokine constitutes a new potential biomarker and therapeutic target of great clinical interest for the development of novel diagnostic and prognostic methods and/or cancer treatment against numerous metastatic, recurrent, and lethal cancers.

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.

Induction of p53-independent apoptosis by a novel synthetic hexahydrocannabinol analog is mediated via Sp1-dependent NSAID-activated gene-1 in colon cancer cells

Nonsteroidal anti-inflammatory drug (NSAID)-activated gene-1 (NAG-1) has received greater attention as a novel molecular target for anti-cancer therapeutics in recent years. We identified a novel synthetic hexahydrocannabinol analog, LYR-8 [(1-((9S)-1-hydroxy-6,6,9-trimethyl-6a,7,8,9,10,10a-hexahydro-6H-benzo[c]chromen-2-yl)ethanone)], as a potent NAG-1 and apoptosis inducer in a panel of human cancer cells. LYR-8 did not possess any affinity for cannabinoid receptor CB(1) or CB(2), which eliminates the concern about potential psychoactive side effects. LYR-8 dramatically induced NAG-1 expression and apoptosis in HCT116 (wild-type p53) and HT29 (mutant p53) colon cancer cells. The NAG-1 expression by LYR-8 was not blocked by pifithrin-alpha, a specific p53 inhibitor, which was different from doxorubicin that induced p53-dependent NAG-1 transcriptional activity. The induction of NAG-1 promoter activity by LYR-8 was strongly correlated with increased Sp1 activation as noted in various luc-promoter activities. Furthermore, pretreatment with the specific Sp1 inhibitor mithramycin A completely reversed the LYR-8-induced NAG-1 expression in both HCT116 and HT29 cells. Knockdown of NAG-1 using siRNA significantly reversed LYR-8-induced cell death in both wild-type and mutant p53-expressing colon cancer cells. Furthermore, sensitization with NAG-1 inducer sulindac sulfide synergized LYR-8-induced cell death in both colon cancer cells. These results suggest that induction of NAG-1 via Sp1 activation is a promising therapeutic approach in cancer treatment, and that a novel compound like LYR-8 could be a potent chemotherapeutic agent for colon cancers including p53-mutated cancer.

NSAID-activated gene-1 as a molecular target for capsaicin-induced apoptosis through a novel molecular mechanism involving GSK3beta, C/EBPbeta and ATF3

Capsaicin, a natural product of the Capsicum species of red peppers, is known to induce apoptosis and suppress growth. Non-steroidal anti-inflammatory drug-activated gene-1 (NAG-1) is a cytokine associated with pro-apoptotic and antitumorigenic property in colorectal and lung cancer. Our data demonstrate that capsaicin leads to induction of apoptosis and up-regulates NAG-1 gene expression at the transcriptional level. Overexpression of CCAAT/enhancer binding protein beta (C/EBPbeta) caused a significant increase of basal and capsaicin-induced NAG-1 promoter activity. We subsequently identified C/EBPbeta binding sites in the NAG-1 promoter responsible for capsaicin-induced NAG-1 transactivation. Electrophoretic mobility shift assay and chromatin immunoprecipitation assay confirmed binding of C/EBPbeta to the NAG-1 promoter. Capsaicin treatment resulted in an increase of phosphorylated serine/threonine residues on C/EBPbeta, and the immunoprecipitation study showed that capsaicin enhanced binding of C/EBPbeta with glycogen synthase kinase 3beta (GSK3beta) and activating transcription factor 3 (ATF3). The phosphorylation and interaction of C/EBPbeta with GSK3beta and ATF3 are decreased by the inhibition of the GSK3beta and Protein Kinase C pathways. Knockdown of C/EBPbeta, GSK3beta or ATF3 ameliorates NAG-1 expression induced by capsaicin treatment. These data indicate that C/EBPbeta phosphorylation through GSK3beta may mediate capsaicin-induced expression of NAG-1 and apoptosis through cooperation with ATF3 in human colorectal cancer cells.

A novel anticancer effect of Astragalus saponins: Transcriptional activation of NSAID-activated gene

Astragalus membranaceus has been used to ameliorate the side effects of antineoplastic drugs because of its immunomodulating nature. We had recently demonstrated that total Astragalus saponins (AST) possess anticarcinogenic and proapoptotic properties in human colon cancer cells and tumor xenograft. In this study, we identified NSAID-activated gene (NAG-1) as a potential molecular target of AST. The growth-inhibitory and proapoptotic effects of AST were assessed in a panel of human cancer cell lines. Hoechst 33342 nuclear staining, Annexin V-FITC/propidium iodide staining, Western immunoblotting, real-time PCR, luciferase reporter assay and electrophoretic mobility shift assay were conducted to determine the association of NAG-1 and related transcription factors with AST during its regulation of apoptotic activities. Moreover, the combined proapoptotic and NAG-1 promoting activities of AST and/or inhibitors of the PI3K-Akt pathway were also examined. AST caused overexpression of NAG-1, leading to PARP cleavage and apoptosis. The induction of NAG-1 promoter activity by the drug was associated with increased gene expression, in addition to prior increase in Egr-1 expression and DNA binding activity. AST-induced NAG-1 activation was intensified when PI3K inhibitor LY294002 or Akt inhibitor was co-treated and reversed by NAG-1 siRNA transfection. Nevertheless, the extent of NAG-1 induction could not be altered by the ERK inhibitor PD98059. Our results indicate that NAG-1 is a potential molecular target of AST in its antitumorigenic and proapoptotic actions, which would have additive effects when used along with PI3K-Akt inhibitors. The information obtained could facilitate future development of a novel target-specific chemotherapeutic agent with known molecular pathway.

Oncogenic Ras, but not (V600E)B-RAF, protects from cholesterol depletion-induced apoptosis through the PI3K/AKT pathway in colorectal cancer cells

Cholesterol is necessary for proliferation and survival of transformed cells. Here we analyse the effect of cholesterol depletion on apoptosis and the mechanisms underlying this effect in colorectal cancer cells carrying oncogenic Ras or (V600E)B-RAF mutations. We show that chronic cholesterol depletion achieved with lipoprotein-deficient serum (LPDS) and 25-hydroxycholesterol (25-HC) treatment results in a significant increase in apoptosis in HT-29 and Colo-205 cells containing the (V600E)B-RAF mutation, but not in HCT-116 and LoVo cells harbouring the (G13D)Ras mutation, or BE cells, which possess two mutations, (G13D)Ras and (G463V)B-RAF. We also demonstrate that oncogenic Ras protects from apoptosis induced by cholesterol depletion through constitutive activation of the phosphatidylinositol-3 kinase (PI3K)/AKT pathway. The specific activation of the PI3K/AKT pathway by overexpression of the (V12)RasC40 mutant or a constitutively active AKT decreases the LPDS plus 25-HC-induced apoptosis in HT-29 cells, whereas PI3K inhibition or abrogation of AKT expression renders HCT-116 sensitive to cholesterol depletion-induced apoptosis. Moreover, our data show that LPDS plus 25-HC increases the activity of c-Jun N-terminal kinase proteins only in HT-29 cells and that the inhibition of this kinase blocks the apoptosis induced by LPDS plus 25-HC. Finally, we demonstrate that AKT hyperactivation by oncogenic Ras protects from apoptosis, preventing the activation of c-Jun N-terminal kinase by cholesterol depletion. Thus, our data demonstrate that low levels of cholesterol induce apoptosis in colorectal cancer cells without oncogenic Ras mutations. These results reveal a novel molecular characteristic of colon tumours containing Ras or B-RAF mutations and should help in defining new targets for cancer therapy.

Role of macrophage inhibitory cytokine-1 in the development and progression of gastric cancer

Macrophage inhibitory cytokine-1 (MIC-1) is a divergent member of human transforming growth factor β (TGF-β) superfamily, which is overexpressed in a variety of human cancers, including gastric cancer. Numerous studies have shown that MIC-1 exerts tumor-suppressing activity through inducing apoptosis and inhibiting excessive proliferation in early gastric cancer. However, recent reports show that MIC-1 may contribute to the malignant progression of gastric cancer because of changes in internal environment in advanced gastric cancer. The mechanisms involved include: inhibiting the expression of catenin δ1 gene, upregulating the urokinase plasminogen activator (uPA) system to enhance invasiveness of gastric cancer cells, and inducing overexpression of ErbB2 receptor tyrosine kinase in human gastric cancer cells. The overexpression of MIC-1 and uPA in gastric cancer cells indicates a poor prognosis. Therefore, MIC-1 and uPA can be used as indicators to predict the prognosis of gastric cancer.

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.

A reciprocal relationship exists between non-steroidal anti-inflammatory drug-activated gene-1 (NAG-1) and cyclooxygenase-2

Non-steroidal anti-inflammatory drug (NSAID)-activated gene-1 (NAG-1) and COX-2 are involved in cellular processes such as inflammation, apoptosis, and tumorigenesis. To address the relationship between COX-2 and NAG-1 expression, we investigated the expression of NAG-1 and COX-2 in normal and tumor tissue from human patients, Apc(Min/+) mice, and COX-2(-/-) mice. While COX-2 expression is highly induced in tumor tissue, NAG-1 expression is reduced. Furthermore, PGE(2) reduces NAG-1 while celebrex induces NAG-1 expression. The results suggest that a possible inverse relationship exists between the expression of NAG-1 and COX-2 in tumor formation of colon tissue.

Macrophage inhibitory cytokine-1: a new player in melanoma development

Macrophage inhibitory cytokine-1 (MIC-1) is a divergent member of the TGF-beta superfamily. Although it has been reported to exhibit both tumorigenic and antitumorigenic activities, Boyle et al. report in this issue that MIC-1 expression was correlated with the tumorigenicity of melanoma cells. The elucidation of signaling pathways around MIC-1 might contribute to prospective targeting therapy for melanoma.

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.

Growth differentiation factor 15 production is necessary for normal erythroid differentiation and is increased in refractory anaemia with ring-sideroblasts

The disturbed erythropoiesis in patients with refractory anaemia with ring-sideroblasts (RARS) is characterized by intramedullary apoptosis of erythroid precursors and increased iron accumulation in mitochondria. To gain insight into these pathophysiological mechanisms we compared the gene expression profile (GEP) of erythroid precursors from RARS patients to the GEP of normal erythroid precursors. Three hundred sixty four probe sets were up-, and 253 probe sets downregulated in RARS cells. Interestingly, Growth Differentiation factor 15 (GDF15), a cytokine from the TGFbeta family, was dramatically upregulated in all RARS patients. Measurement of GDF15 in the sera from twenty RARS patients confirmed this finding by showing significantly, 7.2-fold, increased protein levels (3254 +/- 1400 ng/ml vs. 451 +/- 87 ng/ml in normals). In vitro studies demonstrated erythroid-specific production of GDF15 and dependence on erythropoietin. Induction of apoptosis by arsenic trioxide, a drug which acts via reduction of the mitochondrial membrane potential, also stimulated GDF15 production. Downregulation of endogenous GDF15 production in erythoblasts by specific siRNA led to diminished erythroid differentiation. Taken together, our findings demonstrate a new role for GDF15 in normal erythropoiesis as well as in the ineffective erythropoiesis of RARS patients.

Macrophage inhibitory cytokine-1 is overexpressed in malignant melanoma and is associated with tumorigenicity

The incidence of malignant melanoma has increased dramatically over the past four decades. Metastatic melanoma is associated with poor prognosis, as the current treatments do not have a significant impact on prolonging survival or decreasing mortality. We have identified a member of the transforming growth factor-beta superfamily, macrophage inhibitory cytokine (MIC)-1, which is highly expressed in melanoma cells. Of 53 melanoma cell lines that were examined for relative MIC-1 expression by western blot analysis, 35 (66%) showed significantly higher levels of MIC-1 compared to normal melanocytes. Primary melanoma biopsies (15 of 22) were found to contain cells expressing low levels of MIC-1 as determined by immunohistochemistry. In contrast, all metastatic melanoma biopsies examined (16 of 16) had strong expression of MIC-1. Expression of MIC-1 was found to be dependent on the mitogen-activated protein kinase pathway, and is a transcriptional target of the microphthalmia-associated transcription factor. Knockdown of MIC-1 expression using stable short-hairpin RNA in three melanoma cell lines showed a significant decrease in tumorigenicity (P<0.0001). These results indicate that MIC-1 may function to promote development of more aggressive melanoma tumors. MIC-1 may be suitable for development as a serum diagnostic and is a possible target for the treatment of metastatic melanoma.

Vitamin E succinate induces NAG-1 expression in a p38 kinase-dependent mechanism

NAG-1 (nonsteroidal anti-inflammatory drug-activated gene), a member of the transforming growth factor-beta superfamily, is involved in many cellular processes, such as inflammation, apoptosis/survival, and tumorigenesis. Vitamin E succinate (VES) is the succinate derivative of alpha-tocopherol and has antitumorigenic activity in a variety of cell culture and animal models. In the current study, the regulation and role of NAG-1 expression in PC-3 human prostate carcinoma cells by VES was examined. VES treatment induced growth arrest and apoptosis as well as an increase in NAG-1 protein and mRNA levels in a time- and concentration-dependent manner. VES treatment induced nuclear translocation and activation of p38 kinase. Pretreatment with p38 kinase inhibitor blocked the VES-induced increase in NAG-1 protein and mRNA levels, whereas an inhibition of protein kinase C, Akt, c-Jun NH(2)-terminal kinase, or MEK activity had no effect on VES-induced NAG-1 levels. Forced expression of constitutively active MKK6, an upstream kinase for p38, induced an increase in NAG-1 promoter activity, whereas p38 kinase inhibitor blocked MKK6-induced increase in NAG-1 promoter activity. VES treatment resulted in >3-fold increase in the half-life of NAG-1 mRNA in a p38 kinase-dependent manner and transient transfection experiment showed that VES stabilizes NAG-1 mRNA through AU-rich elements in 3'-untranslated region of NAG-1 mRNA. The inhibition of NAG-1 expression by small interfering RNA significantly blocked VES-induced poly(ADP-ribose) polymerase cleavage, suggesting that NAG-1 may play an important role in VES-induced apoptosis. These results indicate that VES-induced expression of NAG-1 mRNA/protein is regulated by transcriptional/post-transcriptional mechanism in a p38 kinase-dependent manner and NAG-1 can be chemopreventive/therapeutic target in prostate cancer.

DNA-dependent protein kinase catalytic subunit modulates the stability of c-Myc oncoprotein

Background

C-Myc is a short-lived oncoprotein that is destroyed by ubiquitin-mediated proteolysis. Dysregulated accumulation of c-Myc commonly occurs in human cancers. Some of those cases with the dysregulated c-Myc protein accumulation are attributed to gene amplification or increased mRNA expression. However, the abnormal accumulation of c-Myc protein is also a common finding in human cancers with normal copy number and transcription level of c-Myc gene. It seems that the mechanistic dysregulation in the control of c-Myc protein stabilization is another important hallmark associated with c-Myc accumulation in cancer cells. Here we report a novel mechanistic pathway through which DNA-dependent protein kinase catalytic subunit (DNA-PKcs) modulates the stability of c-Myc protein.

Results

Firstly, siRNA-mediated silencing of DNA-PKcs strikingly downregulated c-Myc protein levels in HeLa and HepG2 cells, and simultaneously decreased cell proliferation. The c-Myc protein level in DNA-PKcs deficient human glioma M059J cells was also found much lower than that in DNA-PKcs efficient M059K cells. ATM deficiency does not affect c-Myc expression level. Silencing of DNA-PKcs in HeLa cells resulted in a decreased stability of c-Myc protein, which was associated the increasing of c-Myc phosphorylation on Thr58/Ser62 and ubiquitination level. Phosphorylation of Akt on Ser473, a substrate of DNA-PKcs was found decreased in DNA-PKcs deficient cells. As the consequence, the phosphorylation of GSK3 β on Ser9, a negatively regulated target of Akt, was also decreased, and which led to activation of GSK 3β and in turn phosphorylation of c-Myc on Thr58. Moreover, inhibition of GSK3 activity by LiCl or specific siRNA molecules rescued the downregulation of c-Myc mediated by silencing DNA-PKcs. Consistent with this depressed DNA-PKcs cell model, overexpressing DNA-PKcs in normal human liver L02 cells, by sub-chronically exposing to very low dose of carcinogen 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), increased c-Myc protein level, the phosphorylation of Akt and GSK3 β, as well as cell proliferation. siRNA-mediated silencing of DNA-PKcs in this cell model reversed above alterations to the original levels of L02 cells.

Conclusion

A suitable DNA-PKcs level in cells is necessary for maintaining genomic stability, while abnormal overexpression of DNA-PKcs may contribute to cell proliferation and even oncogenic transformation by stabilizing the c-Myc oncoprotein via at least the Akt/GSK3 pathway. Our results suggest DNA-PKcs a novel biological role beyond its DNA repair function.

Multiple mechanisms are involved in 6-gingerol-induced cell growth arrest and apoptosis in human colorectal cancer cells

6-Gingerol, a natural product of ginger, has been known to possess anti-tumorigenic and pro-apoptotic activities. However, the mechanisms by which it prevents cancer are not well understood in human colorectal cancer. Cyclin D1 is a proto-oncogene that is overexpressed in many cancers and plays a role in cell proliferation through activation by beta-catenin signaling. Nonsteroidal anti-inflammatory drug (NSAID)-activated gene-1 (NAG-1) is a cytokine associated with pro-apoptotic and anti-tumorigenic properties. In the present study, we examined whether 6-gingerol influences cyclin D1 and NAG-1 expression and determined the mechanisms by which 6-gingerol affects the growth of human colorectal cancer cells in vitro. 6-Gingerol treatment suppressed cell proliferation and induced apoptosis and G(1) cell cycle arrest. Subsequently, 6-gingerol suppressed cyclin D1 expression and induced NAG-1 expression. Cyclin D1 suppression was related to inhibition of beta-catenin translocation and cyclin D1 proteolysis. Furthermore, experiments using inhibitors and siRNA transfection confirm the involvement of the PKCepsilon and glycogen synthase kinase (GSK)-3beta pathways in 6-gingerol-induced NAG-1 expression. The results suggest that 6-gingerol stimulates apoptosis through upregulation of NAG-1 and G(1) cell cycle arrest through downregulation of cyclin D1. Multiple mechanisms appear to be involved in 6-gingerol action, including protein degradation as well as beta-catenin, PKCepsilon, and GSK-3beta pathways.

Macrophage inhibitory cytokine-1 activates AKT and ERK-1/2 via the transactivation of ErbB2 in human breast and gastric cancer cells

Macrophage inhibitory cytokine-1 (MIC-1) is a member of the transforming growth factor-beta superfamily, which is overexpressed in a variety of human cancers, including breast and gastric cancer. The function of MIC-1 in cancer remains controversial and its signaling pathways remain poorly understood. In this study, we demonstrate that MIC-1 induces the transactivation of ErbB2 in SK-BR-3 breast and SNU-216 gastric cancer cells. MIC-1 induced a significant phosphorylation of Akt and ERK-1/2, and also effected an increase in the levels of tyrosine phosphorylation of ErbB1, ErbB2 and ErbB3 in SK-BR-3 and SNU-216 cells. The treatment of these cells with AG825 and AG1478, inhibitors specific for ErbB2 tyrosine kinase, resulted in the complete abolition of MIC-1-induced Akt and ERK-1/2 phosphorylation. Furthermore, the small-interfering RNA-mediated downregulation of ErbB2 significantly reduced not only the phosphorylation of Akt and ERK-1/2 but also the invasiveness of the cells induced by MIC-1. Our results show that ErbB2 activation performs a crucial function in MIC-1-induced signaling pathways. Further investigations revealed that MIC-1 induced the expression of the hypoxia inducible factor-1alpha protein and the expression of its target genes, including vascular endothelial growth factor, via the activation of the mammalian target of rapamycin (mTOR) signaling pathway. Stimulation of SK-BR-3 with MIC-1 profoundly induces the phosphorylation of mTOR and its downstream substrates, including p70S6K and 4E-BP1. Collectively, these results show that MIC-1 may participate in the malignant progression of certain human cancer cells that overexpress ErbB2 through the transactivation of ErbB2 tyrosine kinase.

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.

Molecular characterisation of canine nonsteroidal anti-inflammatory drug-activated gene (NAG-1)

Nonsteroidal anti-inflammatory drug (NSAID)-activated gene (NAG-1), a divergent member of the transforming growth factor beta superfamily, was previously identified as a gene induced by several anti-tumorigenic compounds, including NSAIDs and peroxisome proliferator-activated receptor gamma (PPARgamma) ligands in humans. In this study, canine NAG-1 was characterised from a canine genomic database. Gene induction by some NSAIDs and PPARgamma ligands was demonstrated in canine osteosarcoma cell lines. Phylogenetic analysis indicates that canine NAG-1 is more homologous with the corresponding mouse and rat genes than with human NAG-1. Expression of canine NAG-1 was increased by treatment with piroxicam and SC-560 (NSAIDs) and the PPARgamma ligand rosiglitazone. This study demonstrates that canine NAG-1 is up-regulated by some anti-tumorigenic compounds in osteosarcoma cell lines and may provide an important target of chemotherapy in canine cancer.

Celecoxib induces apoptosis in COX-2 deficient human gastric cancer cells through Akt/GSK3beta/NAG-1 pathway

In this study, we analyzed the mechanisms of the apoptotic effects of celecoxib on COX-2 deficient gastric cancer cell line, MGC-803. We found celecoxib treatment induced caspase-dependent apoptosis in MGC-803 cells. Celecoxib inhibited Ser473 Akt and Ser9 GSK3beta phosphorylation and induced upregulation of nonsteroidal anti-inflammatory drugs-activated gene-1 (NAG-1) expression. The effects of celecoxib on NAG-1 expression were abolished by pretreatment with GSK3beta inhibitor, SB216763. Furthermore, GSK3beta gene silencing by siRNA inhibited the celecoxib-induced NAG-1 expression. Our study demonstrated that Akt/GSK3beta/NAG-1 signal pathway may represent as the major mechanism of the COX-2-independent effects of celecoxib on gastric cancer cells.

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.

The epidemiology of prostate cancer--with a focus on nonsteroidal anti-inflammatory drugs

Aspirin and other NSAIDs have a potential role in the primary and secondary prevention of many common diseases associated with aging, including the top two causes of mortality in the United States-cardiovascular disease and cancer. These agents may be beneficial in the management of Alzheimer's disease,other forms of dementia, and Parkinson's. disease. Because men with prostate cancer or precancer are likely to present with coexisting conditions that would be affected by systemic aspirin, NSAID, or other COX-2 inhibitor therapies, it is important to consider any possible preventive studies or future clinical recommendations of aspirin or NSAIDs for prostate cancer within the context of these comorbid conditions. Aspirin or nonaspirin NSAIDs may be appropriate prevention therapy for patients at high risk of prostate cancer, myocardial infarction, Parkinson's disease, Alzheimer's disease, lung cancer, or colorectal cancer, but low risk for gastrointestinal complications or stroke. Further quantitative comparative studies of the risks and benefits of these common comorbidities in older Americans, with special attention to dose and duration parameters, are warranted.

Role of macrophage inhibitory cytokine-1 in tumorigenesis and diagnosis of cancer

Macrophage inhibitory cytokine-1 (MIC-1), a transforming growth factor-beta superfamily cytokine, is involved in tumor pathogenesis, and its measurement can be used as a clinical tool for the diagnosis and management of a wide range of cancers. Although generally considered to be part of the cell's antitumorigenic repertoire, MIC-1 secretion, processing, and latent storage suggest a complex, dynamic variability in MIC-1 bioavailability in the tumor microenvironment, potentially modulating tumor progression and invasiveness.

A novel peroxisome proliferator–activated receptor γ ligand, MCC-555, induces apoptosis via posttranscriptional regulation of NAG-1 in colorectal cancer cells

Apoptosis and/or differentiation induction caused by the peroxisome proliferator-activated receptor gamma (PPARgamma) ligand is a promising approach to cancer therapy. The thiazolidinedione derivative MCC-555 has an apoptotic activity in human colorectal cancer cells, accompanied by up-regulation of a proapoptotic nonsteroidal anti-inflammatory drug-activated gene (NAG-1) in a PPARgamma-independent manner. Treatment with MCC-555 resulted in the induction of NAG-1 expression and apoptosis in HCT-116 cells. Down-regulation of NAG-1 by small interfering RNA suppressed MCC-555-induced apoptosis. MCC-555 was found to affect NAG-1 mRNA stability. To further define the underlying mechanism of RNA stability affected by MCC-555, we cloned the 3'-untranslated region (3'UTR) of human NAG-1 mRNA, which contains four copies of an AU-rich element (ARE), downstream from the luciferase gene. The reporter activity was reduced to approximately 70% by inserting the 3'UTR. In addition, deletion of ARE sequences in the 3'UTR or MCC-555 treatment substantially restored activity. This effect of MCC-555 on the ARE-mediated mRNA degradation was inhibited by extracellular signal-regulated kinase (ERK) pathway inhibitors. Subsequently, rapid phosphorylation of ERK1/2 by MCC-555 treatment was detected. Moreover, ERK small interfering RNA suppressed MCC-555-induced NAG-1 expression. These results suggest that ARE sequences in the 3'UTR of the NAG-1 gene contribute to mRNA degradation and ERK1/2 phosphorylation is responsible for the stabilization of NAG-1 mRNA. These findings may provide a novel explanation for the antitumorigenic and/or proapoptotic action of MCC-555 in human colorectal cancer and the ability of pharmacologic approaches to be used against diseases caused by alterations of RNA stability.

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.

Activating transcription factor 3 and early growth response 1 are the novel targets of LY294002 in a phosphatidylinositol 3-kinase-independent pathway

LY294002, a phosphatidylinositol 3-kinase (PI3K) inhibitor, has been widely used to study the function of PI3K in cellular responses. Based on its inhibitory effect on PI3K, LY294002 has been shown to exert antitumorigenic effect in vivo and in vitro. Here, we report that LY294002 alters early growth response 1 (EGR-1) phosphorylation and subsequently enhances activating transcription factor 3 (ATF3) expression independently of PI3K inhibition. This pathway may be, in part, responsible for the antitumorigenic effect of LY294002 in human colorectal cancer cells. ATF3 expression was increased by LY294002, followed by the induction of apoptosis in several colorectal cancer cell lines. This is consistent with results showing that the down-regulation of the ATF3 gene by small interfering RNA suppressed LY294002-induced apoptosis in HCT-116 cells. On the other hand, ATF3 expression was not affected by another PI3K inhibitor, wortmannin, as well as phosphatase and tensin homologue or dominant-negative Akt overexpression. We also found that LY294002 increases ATF3 promoter activity and the transactivation is partly mediated by a GC-rich sequence located in the promoter. EGR-1 binds to the ATF3 promoter as assessed by gel shift assay. Furthermore, phosphorylated EGR-1 was highly increased in LY294002-treated cells, indicating that EGR-1 phosphorylation induced by LY294002 may facilitate ATF3 transactivation. Our data suggest that EGR-1 acts as a mediator in LY294002-induced ATF3 expression via a PI3K-independent pathway. ATF3 and EGR-1 may provide a novel explanation for the antitumorigenic properties of LY294002 in human colorectal cancer cells.

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.

Morphine promotes Jurkat cell apoptosis through pro-apoptotic FADD/P53 and anti-apoptotic PI3K/Akt/NF-kappaB pathways

Opiates have been shown to inhibit cell growth and trigger apoptosis, but the underlying molecular mechanisms remain unclear. We have previously shown that morphine induces Fas expression and promotes Fas-mediated apoptosis. Here, we investigated the mechanisms by which morphine modulates apoptosis in human Jurkat cells. Morphine-induced apoptosis was inhibited by transfection with a dominant negative Fas-associated death domain (FADD) plasmid, revealing that morphine-induced apoptosis is dependent on FADD. Furthermore, suppression of endogenous p53 expression by RNA interference technology considerably attenuated the morphine-induced apoptosis. In addition, morphine-induced apoptosis seems to be dependent on the activation of phosphatidylinositol 3-kinase (PI3K), as PI3K inhibition by the PI3K inhibitor LY294002 significantly enhanced morphine-induced apoptosis. Moreover, inhibition of Akt or nuclear factor-kappaB (NF-kappaB) expression by RNA interference technology also dramatically increased morphine-induced apoptosis. Our study thus demonstrates that morphine induces Jurkat cell apoptosis through FADD/p53, anti-apoptotic PI3K/Akt and NF-kappaB 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 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.

Cancer prevention: a new era beyond cyclooxygenase-2

The seminal epidemiological observation that nonsteroidal anti-inflammatory drugs (NSAIDs) prevent colon and possibly other cancers has spurred novel approaches to cancer prevention. The known inhibitory effect of NSAIDs on the eicosanoid pathway prompted studies focusing on cyclooxygenase (COX) and its products. The increased prostaglandin E2 levels and the overexpression of COX-2 in colon and many other cancers provided the rationale for clinical trials with COX-2 inhibitors for cancer prevention or treatment. Their efficacy in the prevention of sporadic colon and other cancers remains unknown; one COX-2 inhibitor has been withdrawn because of side effects, and there are concerns about whether these effects are class-specific. There is evidence to suggest that COX-2 may not be the only or ideal eicosanoid pathway target for cancer prevention. Six sets of observations support this notion: the relatively late induction of COX-2 during carcinogenesis; the finding that NSAIDs may not require inhibition of COX-2 for their effect; the modest effect of coxibs in cancer prevention; that currently available coxibs have multiple non-COX-2 effects that may account for at least some of their efficacy; the possibility that concurrent inhibition of COX-2 in non-neoplastic cells may be harmful; and the possibility that COX-2 inhibition may modulate alternative eicosanoid pathways in a way that promotes carcinogenesis. Given the limitations of COX-2-specific inhibitors and the biological evidence mentioned above, we suggest that targets other than COX-2 should be pursued as alternative or complementary approaches to cancer prevention.

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.

Protein kinase C-dependent regulation of NAG-1/placental bone morphogenic protein/MIC-1 expression in LNCaP prostate carcinoma cells

NAG-1 (nonsteroidal anti-inflammatory drug-activated gene), a member of the transforming growth factor beta superfamily, is involved in cellular processes such as inflammation, apoptosis/survival, and tumorigenesis and is regulated by p53, Sp1, and Egr-1. In the current study, the regulation of NAG-1 expression in LNCaP human prostate carcinoma cells by 12-O-tetradecanoylphorbol-13-acetate (TPA) was examined. TPA treatment increased NAG-1 protein and mRNA levels in a time- and concentration-dependent manner as well as NF-kappa B binding/transcriptional activity in LNCaP cells. Pretreatment with protein kinase C (PKC) inhibitor blocked the TPA-induced increase in NAG-1 protein levels and NF-kappa B binding/transcriptional activity, whereas an inhibition of p38, JNK, MEK activity had no effect on TPA-induced NAG-1 levels and NF-kappa B transcriptional activity. Expression of constitutively active PKCs induced an increase in NF-kappa B transcriptional activity and NAG-1 protein levels in LNCaP cells. The expression of NF-kappa B p65 induced NAG-1 promoter activity, and chromatin immunoprecipitation assay for p65 showed that NF-kappa B binds the NAG-1 promoter in LNCaP cells. Inhibition of TPA-induced NAG-1 expression by NAG-1 short interfering RNA blocked TPA-induced apoptosis in LNCaP cells, suggesting induction of NAG-1 negatively affects LNCaP cell survival. These results demonstrate that NAG-1 expression is up-regulated by TPA in LNCaP cells through a PKC-dependent pathway involving the activation of NF-kappa B.

Evaluation of polycyclic aromatic hydrocarbons in the activation of early growth response-1 and peroxisome proliferator activated receptors

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental and food contaminants with known or suspected carcinogenic properties. In this study, we have evaluated whether PAHs activate the early growth response (EGR-1) gene and bind to peroxisome proliferator-activated receptor alpha (PPAR alpha) and delta (PPAR beta/delta) in cell culture systems. Luciferase reporter systems were employed and several PAHs were evaluated for their ability to activate EGR-1 and PPARs. Some PAHs enhanced EGR-1 expression and activated PPAR alpha and PPAR beta. Among them, benz(a)anthracene was found to act as a relatively potent activator of PPAR alpha and PPAR beta/delta, and to significantly enhance EGR-1 transcription. These in vitro assays were confirmed by Western blot analysis, using cell lysates of tissue samples from mouse trapped at a highly contaminated Superfund site in the Chattanooga Creek floodplain in Chattanooga, Tennessee. We have found that a PPAR target gene, glycogen synthase kinase-3beta (GSK-3beta), was down-regulated and EGR-1 was up-regulated in the mouse samples of Chattanooga Creek. In addition, select PAHs repressed GSK-3beta and induced CYP4A in FaO rat hepatoma cells. In conclusion, PAHs activate PPAR alpha and PPAR beta/delta, and up-regulate EGR-1 expression in vitro as well as in vivo. These data may provide a diversity of PAH activity in several biological pathways.