Regulation of interleukin-8 expression by nitric oxide in human pancreatic adenocarcinoma

Nitric oxide, thyroglobulin, and calcitonin: unraveling the nature of thyroid nodules

Background

Thyroid nodules (TN) are localized morphological changes in the thyroid gland and can be benign or malignant.

Objective

The present study investigates the relationships between biochemical markers in serum (s) and their homologs in washout (w) after fine-needle aspiration biopsy (FNAB) of the TN of interest and their correlation with cytology specimen findings.

Methods

We investigated the relationships between serum biochemical markers nitric oxide (NO), thyroglobulin (TG), and calcitonin (CT), their homologs in washout after FNAB of the TN of interest, and cytology findings of biopsy samples classified according to the Bethesda system for thyroid cytopathology in this study, which included 86 subjects.

Results

Washout TG (TGw) level positively correlates with the cytology finding of the biopsy. A higher level of TGw correlates with higher categories of the Bethesda classification and indicates a higher malignant potential. The levels of serum NO (NOs), serum TG (TGs), serum CT (CTs), and washout CT (CTw) do not correlate with the cytology finding of the biopsy, and the higher levels of washout NO (NOw) correspond to the more suspicious ultrasound findings.

Conclusion

The findings of our study suggest that TGw and NOw could be used as potential predictors of malignancy in TN.

Chronic nitric oxide exposure induces prostate cell carcinogenesis, involving genetic instability and a pro-tumorigenic secretory phenotype

Prostate cancer is a leading cause of cancer death in men. Inflammation and overexpression of inducible nitric oxide synthase (NOS2) have been implicated in prostate carcinogenesis. We aimed to explore the hypothesis that nitric oxide NO exerts pro-tumorigenic effects on prostate cells at physiologically relevant levels contributing to carcinogenesis. We investigated the impact of acute exposure of normal immortalised prostate cells (RWPE-1) to NO on cell proliferation and activation of DNA damage repair pathways. Furthermore we investigated the long term effects of chronic NO exposure on RWPE-1 cell migration and invasion potential and hallmarks of transformation. Our results demonstrate that NO induces DNA damage as indicated by γH2AX foci and p53 activation resulting in a G1/S phase block and activation of 53BP1 DNA damage repair protein. Long term adaption to NO results in increased migration and invasion potential, acquisition of anchorage independent growth and increased resistance to chemotherapy. This was recapitulated in PC3 and DU145 prostate cancer cells which upon chronic exposure to NO displayed increased cell migration, colony formation and increased resistance to chemotherapeutics. These findings indicate that NO may play a key role in the development of prostate cancer and the acquisition of an aggressive metastatic phenotype.

CAIX-Mediated Control of LIN28/let-7 Axis Contributes to Metabolic Adaptation of Breast Cancer Cells to Hypoxia

Solid tumors, including breast cancer, are characterized by the hypoxic microenvironment, extracellular acidosis, and chemoresistance. Hypoxia marker, carbonic anhydrase IX (CAIX), is a pH regulator providing a selective survival advantage to cancer cells through intracellular neutralization while facilitating tumor invasion by extracellular acidification. The expression of CAIX in breast cancer patients is associated with poor prognosis and metastases. Importantly, CAIX-positive hypoxic tumor regions are enriched in cancer stem cells (CSCs). Here we investigated the biological effects of CA9-silencing in breast cancer cell lines. We found that CAIX-downregulation in hypoxia led to increased levels of let-7 (lethal-7) family members. Simultaneously with the increase of let-7 miRNAs in CAIX-suppressed cells, LIN28 protein levels decreased, along with downstream metabolic pathways: pyruvate dehydrogenase kinase 1 (PDK1) and phosphorylation of its substrate, pyruvate dehydrogenase (PDH) at Ser-232, causing attenuation of glycolysis. In addition to perturbed glycolysis, CAIX-knockouts, in correlation with decreased LIN28 (as CSC reprogramming factor), also exhibit reduction of the further CSC-associated markers NANOG (Homeobox protein NANOG) and ALDH1 (Aldehyde dehydrogenase isoform 1). Oppositely, overexpression of CAIX leads to the enhancement of LIN28, ALDH1, and NANOG. In conclusion, CAIX-driven regulation of the LIN28/let-7 axis augments glycolytic metabolism and enhances stem cell markers expression during CAIX-mediated adaptation to hypoxia and acidosis in carcinogenesis.

A CXCL ortholog from Hippocampus abdominalis: Molecular features and functional delineation as a pro-inflammatory chemokine

Chemokines are a family of chemotactic cytokines that regulate leukocyte migration. They are classified into four groups namely, CXC, CC, C and CX₃C, based on the formation of a disulfide bridge. Among these, CXC chemokines have been identified as the largest group of chemokines in humans. In this study, we identified and functionally characterized a homolog of CXC chemokine from the big-belly seahorse, Hippocampus abdominalis, and designated it as ShCXCL. The cDNA of ShCXCL composed of a 342-bp open reading frame encoding 113 amino acids (aa). The CXC family-specific small cytokine domain (SCY) was identified from the mature peptide region, which comprised of a conserved CXC motif. As ShCXCL lacks an ELR (Glutamic acid-Leucine-Arginine) motif, it belongs to ELR^- subfamily. The recombinant ShCXCL protein strongly induced the nitric oxide (NO) production in macrophage cells (RAW 264.7 cell line) and showed the chemotactic effect on flounder peripheral blood leukocytes. Tissue profiling showed a ubiquitous expression pattern in all examined tissues, with a high abundance in spleen. The up-regulated mRNA expression pattern of ShCXCL was observed in blood and kidney tissues after immune stimulation by live bacteria, such as Streptococcus iniae and Edwardsiella tarda, and mitogens, such as lipopolysaccharides (LPS) and polyinosinic:polycytidylic acid (poly I:C), suggesting its important role in host immune defense against microbial infection.

Review of the mechanisms involved in the abscopal effect and future directions with a focus on thymic carcinoma

The abscopal effect is a rare phenomenon in radiotherapy, leading to impressive tumor regression outside the radiotherapy field. In this article we describe the occurrence of a postradiotherapy abscopal effect in an 89-year-old patient suffering from a metastatic neuroendocrine large-cell thymic carcinoma, the first case of the abscopal effect related to a thymic carcinoma reported in the literature. Along with the description of this case, we discuss and review the main potential mechanisms of bystander and abscopal effects in solid tumors so as to enable clinicians to identify and control these effects more resourcefully in the age of immunotherapy and stereotactic radiotherapy.

The yin and yang of nitric oxide in cancer progression

Nitric oxide (NO) is a short-lived, pleiotropic molecule that affects numerous critical functions in the body. Presently, there are markedly conflicting findings in the literature regarding NO and its role in carcinogenesis and tumor progression. NO has been shown to have dichotomous effects on cellular proliferation, apoptosis, migration, invasion, angiogenesis and many other important processes in cancer biology. It has been shown to be both pro- and antitumorigenic, depending on the concentration and the tumor microenvironment in question. NO is generated by three isoforms of NO synthase (NOS) that are widely expressed and sometimes upregulated in human tumors. Due to its vast array of physiological functions, it presents a huge challenge to researchers to discover its true potential in cancer biology and consequently, its use in anticancer therapies. In this study, we review the current knowledge in this area, with an emphasis placed on NO modulation as an anticancer therapy, focusing on NO-donating drugs and NOS inhibitors.

Role of Reactive Oxygen Species and Nitric Oxide in Mediating Chemotherapeutic Drug Induced Bystander Response in Human Cancer Cells Exposed In-Vitro

Background

The intention of cancer chemotherapy is to control the growth of cancer cells using chemical agents. However, the occurrence of second malignancies has raised concerns, leading to re-evaluation of the current strategy in use for chemotherapeutic agents. Although the mechanisms involved in second malignancy remain ambiguous, therapeutic-agent-induced non-DNA targeted effects like bystander response and genomic instability cannot be eliminated completely. Hence, Bleomycin (BLM) and Neocarzinostatin (NCS), chemotherapeutic drugs with a mode of action similar to ionizing radiation, were used to study the mechanism of bystander response in human cancer cells (A549, CCRF-CEM and HL-60) by employing co-culture methodology.

Methods

Bystander effect was quantified using micronucleus (MN) assay and in-situ immunofluorescence(γH2AX assay).The role of reactive oxygen species (ROS) and nitric oxide (NO) in mediating the bystander response was explored by pre-treating bystander cells with dimethylsulphoxide (DMSO) and C-PTIO respectively.

Results

Bystander response was observed only in CCRF-CEM and A549 cells (P < 0.001). A significant decrease in this response was observed with ROS scavenger, DMSO.

Conclusion

This significant attenuation in the bystander response on treatment with DMSO, suggests that ROS has a more significant role in mediating the bystander response.Since the possibility of the ROS and NO in mediating these bystander effect was confirmed, mechanistic control of these signaling molecules could either reduce radiation damage and potential carcinogenicity of normal tissues (by reducing bystander signaling) or maximize cell sterilization during chemotherapy (by amplifying bystander responses in tumors).

Role of lipoxins, resolvins, and other bioactive lipids in colon and pancreatic cancer

Unresolved inflammation, due to insufficient production of proresolving anti-inflammatory lipid mediators, can lead to an increased risk of tumorigenesis and tumor cell invasiveness. Various bioactive lipids, particularly those formed by cyclooxygenase (COX) and lipoxygenase (LOX) enzymes, have been well established as therapeutic targets for many epithelial cancers. Emerging studies suggest that there is a role for anti-inflammatory bioactive lipids and their mediators during the resolution phase of inflammation. These proresolving bioactive lipids, including lipoxins (LXs) and resolvins (RVs), have potent anti-inflammatory and anti-carcinogenic properties. The molecular signaling pathways controlling generation and degradation of the proresolving mediators LXs and RVs are now being elucidated, and the component molecules may serve as new targets for regulation of inflammation and inflammation-associated cancers like colon and pancreatic cancers. This review will highlight the recent advances in our understanding of how these bioactive lipids and proresolving mediators may function with various immune cells and cytokines in inhibiting tumor cell proliferation and progression and invasiveness of colon and pancreatic cancers.

Candidate pathways linking inducible nitric oxide synthase to a basal-like transcription pattern and tumor progression in human breast cancer

Inducible nitric oxide synthase (NOS2) is an inflammation responsive enzyme (EC 1.14.13.39) that is induced during acute and chronic inflammation and tissue injury as part of the host defense and wound healing process. NOS2 up-regulation leads to increased nitric oxide (NO) production, the means by which this enzyme can initiate NO-dependent signal transduction, influence the redox state of cells and induce modifications of proteins, lipids, and DNA. Aberrant expression of NOS2 has been observed in many types of human tumors. In breast cancer, increased NOS2 is associated with markers of poor outcome and decreased survival. Growth factor and cytokine signaling, tissue remodeling, NF-kB activation, and hypoxia are candidate mechanisms that induce NOS2 in tumor epithelial and tumor-infiltrating cells. NOS2 induction will trigger the release of variable amounts of NO into the tumor microenvironment and can activate oncogenic pathways, including the Akt, epidermal growth factor receptor and c-Myc signaling pathways, and stimulate tumor microvascularization. Constitutively increased NO levels may also select for mutant p53 cells to overcome the tumor suppressor function of NO-activated wild-type p53. More recent findings suggest that NO induces stem cell-like tumor characteristics in breast cancer. In this review, we will discuss the effects of NO in tumor biology and disease progression with an emphasis on breast cancer, and will examine the mechanisms that link increased NO to a basal-like transcription pattern in human breast tumors and poor disease outcome.

Antiangiogenic potential of three triterpenic acids in human liver cancer cells

Three triterpenic acids, oleanolic acid, ursolic acid and maslinic acid, at 2 or 4 μmol/L were used to study their antiangiogenic potential in human liver cancer Hep3B, Huh7 and HA22T cell lines. The effects of these compounds upon the level and/or expression of hypoxia-inducible factor (HIF)-1α, basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), interleukin (IL)-8, urokinase plasminogen activator (uPA), reactive oxygen species (ROS), nitric oxide (NO) and cell invasion and migration were examined. Results showed that these triterpenic acids at 4 μmol/L significantly suppressed HIF-1α expression in three cell lines (P < 0.05); and these compounds at test doses failed to affect bFGF expression (P > 0.05). Three triterpenic acids dose-dependently decreased production and expression of VEGF and IL-8, retained glutathione level, lowered ROS and NO levels, and declined cell invasion and migration in test cell lines (P < 0.05). These compounds also dose-dependently reduced uPA production and expression in Hep3B and Huh7 cell lines (P < 0.05); but these agents only at 4 μmol/L significantly suppressed uPA production and expression in HA22T cells (P < 0.05). These findings suggest that these triterpenic acids are potent antiangiogenic agents to retard invasion and migration in liver cancer cells.

Increased NOS2 predicts poor survival in estrogen receptor-negative breast cancer patients

Inducible nitric oxide synthase (NOS2) is involved in wound healing, angiogenesis, and carcinogenesis. NOS2 upregulation and increased nitric oxide (NO) production affect the redox state of cells and can induce protein, lipid, and DNA modifications. To investigate whether NOS2 levels influence survival of breast cancer patients, we examined NOS2 expression and its association with tumor markers and survival in 248 breast tumors. In multivariable survival analysis, increased NOS2 predicted inferior survival in women with estrogen receptor α-negative (ER-negative) tumors. Microdissected tumor epithelium from ER-negative tumors with high NOS2 had increased IL-8 and a gene expression signature characteristic of basal-like breast cancer with poor prognosis. In cell culture, NO only induced selected signature genes in ER-negative breast cancer cells. ER transgene expression in ER-negative cells inhibited NO-induced upregulation of the stem cell marker CD44 and other proteins encoded by signature genes, but not of IL-8. Exposure to NO also enhanced cell motility and invasion of ER-negative cells. Last, pathway analysis linked the tumor NOS2 gene signature to c-Myc activation. Thus, NOS2 is associated with a basal-like transcription pattern and poor survival of ER-negative patients.

Substance P enhances wound closure in nitric oxide synthase knockout mice

INTRODUCTION

The neuropeptide, substance P (SP), up-regulates nitric oxide production (NO). The purpose of this study was to determine whether SP enhances response to cutaneous injury in nitric oxide synthase knockout (NOS null) mice.

METHODS

We studied mice with targeted deletions of the 3 NOS genes, neuronal NOS, inducible NOS, or endothelial NOS. Full thickness dorsal wounds were treated daily (d 0-6) with topical SP or normal saline (NaCl). Wounds were analyzed by flow cytometry for macrophage, leukocyte, endothelial, and dendritic cells. Healing time and wound epithelialization were compared using analysis of variance.

RESULTS

Wound closure in the 3 NOS null mice was slower than the control mice (P < 0.05). SP treatment enhanced wound closure in NOS null mice (P < 0.02). NOS null wounds exhibited reduced inflammation. SP increased macrophage, leukocyte, and dendritic cell densities at d 3 and d 7 (P < 0.05) in all NOS null mice. SP increased endothelial cell number in neuronal NOS and inducible NOS null mice, but not in endothelial NOS null mice (P > 0.05).

CONCLUSIONS

SP ameliorated the impaired wound healing response observed in NOS null mice by enhancing wound closure kinetics and epithelialization. SP increased inflammatory cell density in the wounds supporting the essential role of inflammatory cells, especially macrophages, in wound repair.

Interleukin-8 increases vascular endothelial growth factor and neuropilin expression and stimulates ERK activation in human pancreatic cancer

Interleukin-8 (IL-8) is associated with tumorigenesis by promoting angiogenesis and metastasis. Although up-regulation of IL-8 is indicated in many cancers, its function in pancreatic cancer has not been well characterized. In this study we examined the expression of IL-8 on pancreatic cancer cells and clinical tissue specimens, and investigated the effect of exogenous IL-8 on gene expression, and signaling in human pancreatic cancer cells. We found that pancreatic cancer cells expressed higher amount of IL-8 mRNA than normal human pancreatic ductal epithelium cells. IL-8 mRNA was also substantially overexpressed in 11 of 14 (79%) clinical pancreatic-adenocarcinoma samples compared with that in their surrounding normal tissues. Exogenous IL-8 up-regulated the expression of vascular endothelial growth factor(165), and neuropilin (NRP)-2 in BxPC-3 cells, one of human pancreatic cancer cell lines. IL-8 expression was inducible by hypoxia mimicking reagent cobalt chloride. In addition, IL-8 activated extracellular signal-regulated kinase (ERK)1/2 signaling pathway in BxPC-3 cells. Our studies suggest that IL-8 might be a malignant factor in human pancreatic cancer by induction of vascular endothelial growth factor and NRP-2 expression and ERK activation. Targeting IL-8 along with other antiangiogenesis therapy could be an effective treatment for this malignancy.

Acidic extracellular pH increases calcium influx-triggered phospholipase D activity along with acidic sphingomyelinase activation to induce matrix metalloproteinase-9 expression in mouse metastatic melanoma

Acidic extracellular pH is a common feature of tumor tissues. We have reported that culturing cells at acidic pH (5.4-6.5) induced matrix metalloproteinase-9 expression through phospholipase D, extracellular signal regulated kinase 1/2 and p38 mitogen-activated protein kinases and nuclear factor-kappaB. Here, we show that acidic extracellular pH signaling involves both pathways of phospholipase D triggered by Ca2+ influx and acidic sphingomyelinase in mouse B16 melanoma cells. We found that BAPTA-AM [1,2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid tetrakis (acetoxymethyl) ester], a chelator of intracellular free calcium, and the voltage dependent Ca2+ channel blockers, mibefradil (for T-type) and nimodipine (for L-type), dose-dependently inhibited acidic extracellular pH-induced matrix metalloproteinase-9 expression. Intracellular free calcium concentration ([Ca2+]i) was transiently elevated by acidic extracellular pH, and this [Ca2+]i elevation was repressed by EGTA and the voltage dependent Ca2+ channel blockers but not by phospholipase C inhibitor, suggesting that acidic extracellular pH increased [Ca2+]i through voltage dependent Ca2+ channel. In contrast, SR33557, an L-type voltage dependent Ca2+ channel blocker and acidic sphingomyelinase inhibitor, attenuated matrix metalloproteinase-9 induction but did not affect calcium influx. We found that acidic sphingomyelinase activity was induced by acidic extracellular pH and that the specific acidic sphingomyelinase inhibitors (perhexiline and desipramine) and siRNA targeting aSMase/smpd1 could inhibit acidic extracellular pH-induced matrix metalloproteinase-9 expression. BAPTA-AM reduced acidic extracellular pH-induced phospholipase D but not acidic sphingomyelinase acitivity. The acidic sphingomyelinase inhibitors did not affect the phosphorylation of extracellular signal regulated kinase 1/2 and p38, but they suppressed nuclear factor-kappaB activity. These data suggest that the calcium influx-triggered phospholipase D and acidic sphingomyelinase pathways of acidic extracellular pH induced matrix metalloproteinase-9 expression, at least in part, through nuclear factor-kappaB activation.

Effect of gap junctional intercellular communication on radiation responses in neoplastic human cells

Gap junctional intercellular communication (GJIC) is an important function of metazoan cells and is believed to have beneficial effects in anti-tumor therapy. In this study, we found that, when neoplastic human salivary gland (HSG) cells were irradiated with a 100 keV/microm carbon-ion beam, micronuclei, G(2)/M-phase arrest, and cell killing were induced and that their induction increased with dose. Treatment of confluent HSG cells with 8-Br-cAMP increased GJIC between cells. After release from this treatment, the cell cycle progress and the formation of binucleated cells were still similar to those of untreated cells. However, radiation-induced cellular damage, including micronucleus (MN) formation and G(2)/M-phase arrest of that cAMP-treated population, was less than that of the untreated population and that the surviving fraction was slightly enhanced by cAMP treatment, suggesting that increased GJIC protects HSG cells from lethal radiation damage. Moreover, when confluent HSG cells were treated with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO), a scavenger of nitric oxide (NO) free radical, MN induction and cell killing in the irradiated population were increased. Our results indicate that NO may be involved in GJIC-mediated radioprotection of HSG cells, which may have implications for radiotherapy.

Current update of cytokines in pancreatic cancer: pathogenic mechanisms, clinical indication, and therapeutic values

Pancreatic cancer is the fourth leading cause of cancer death with a 5-year survival less than 5 percent despite rigorous interventions. This largely is due to its late presentation, aggressive metastasis, and a lack of effective adjuvant therapies. Cytokines have been studied in many tumor types, where they have been shown to be an important influence in cancer cell behavior and to have potential as tumor markers, therapeutic targets, or as treatments themselves. Recently, the roles cytokines play in pancreatic cancer have become the subject of intense investigation. However, the story is complicated, largely because of the pleiotropic and overlapping nature of cytokine functions. This article attempts to provide a focused review of recent discoveries in this area by organizing the material along the pathophysiologic tasks a cancer cell must accomplish to achieve malignancy. We examined how cytokines act to create a microenvironment conducive to tumor cell survival and growth, discussed how cytokines affect proliferation, invasion, metastasis, and apoptosis in pancreatic cancer cells, and we summarized how this knowledge has been applied either to target cytokines or use them therapeutically.

Radiation-induced bystander effects in malignant trophoblast cells are independent from gap junctional communication

It is controversially discussed that irradiation induces bystander effects via gap junction channels and/or diffusible cellular factors such as nitric oxide or cytokines excreted from the cells into the environment. But up to now the molecular mechanism leading to a bystander response is not well understood. To discriminate between both mechanisms of bystander response, (i) mediated by gap junctional communication and/or (ii) mediated by diffusible molecules, we used non-communicating Jeg3 malignant trophoblast cells transfected with inducible gap junction proteins, connexin43 and connexin26, respectively, based on the Tet-On system. We co-cultivated X-ray irradiated and non-irradiated bystander Jeg3 cells for 4 h, separated both cell populations by flow cytometry and evaluated the expression of activated p53 by Western blot analysis. The experimental design was proven with communicating versus non-communicating Jeg3 cells. Interestingly, our results revealed a bystander effect which was independent from gap junctional communication properties and the connexin isoform expressed. Therefore, it seems more likely that the bystander effect is not mediated via gap junction channels but rather by paracrine mechanisms via excreted molecules in Jeg3 cells.

Constitutive nitric oxide acting as a possible intercellular signaling molecule in the initiation of radiation-induced DNA double strand breaks in non-irradiated bystander cells

The initiation and propagation of the early processes of bystander signaling induced by low-dose alpha-particle irradiation are very important for understanding the underlying mechanism of the bystander process. Our previous investigation showed that the medium collected from cell culture exposed to low-dose alpha-particle rapidly induced phosphorylated form of H2AX protein foci formation among the non-irradiated medium receptor cells in a time-dependent manner. Using N(G)-methyl-L-arginine, 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate and N(omega)-nitro-L-arginine (L-NNA) treatment before exposure to 1 cGy alpha-particle, we showed in the present study that nitric oxide (NO(*)) produced in the irradiated cells was important and necessary for the DNA double strand break inducing activity (DIA) of conditioned medium and the generation of NO(*) in irradiated confluent AG1522 cells is in a time-dependent manner and that almost all NO(*) was generated within 15 min post-irradiation. Concurrently, the kinetics of NO(*) production in the medium of irradiated cells after irradiation was rapid and in a time-dependent manner as well, with a maximum yield observed at 10 min after irradiation with electron spin resonance analysis. Furthermore, our results that 7-Nitroindazole and L-NNA, but not aminoguanidine hemisulfate, treatment before exposure to 1 cGy alpha-particle significantly decrease the DIA of the conditioned medium suggested that constitutive NO(*) from the irradiated cells possibly acted as an intercellular signaling molecule to initiate and activate the early process (<or=30 min) of bystander response after low-dose irradiation.

Inducible nitric oxide synthase (iNOS) in tumor biology: the two sides of the same coin

Inducible nitric oxide synthase (iNOS) is one of three key enzymes generating nitric oxide (NO) from the amino acid l-arginine. iNOS-derived NO plays an important role in numerous physiological (e.g. blood pressure regulation, wound repair and host defence mechanisms) and pathophysiological (inflammation, infection, neoplastic diseases, liver cirrhosis, diabetes) conditions. iNOS is the synthase isoform most commonly associated with malignant disease. Nevertheless, the role of iNOS during tumor development is highly complex, and incompletely understood. Both promoting and deterring actions have been described, presumably depending upon the local concentration of iNOS within the tumor microenvironment. In particular, pivotal effects such as malingnant transformation, angiogenesis, and metastasis are modulated by iNOS. On the other hand, NO derived from macrophages has a potentially cytotoxic/cytostatic effect upon tumor cells. Hence, therapeutical interference with iNOS activity is of considerable interest, especially in tumors where metastatic activity, host defence mechanisms and the level of differentiation seem to be correlated to iNOS expression. This review will aim to summarize the dual actions of iNOS as simultaneous tumor promoter and suppressor.

Mechanism of radiation-induced bystander effect: role of the cyclooxygenase-2 signaling pathway

The radiation-induced bystander effect is defined as "the induction of biological effects in cells that are not directly traversed by a charged particle but are in close proximity to cells that are." Although these bystander effects have been demonstrated with a variety of biological endpoints in both human and rodent cell lines (as well as in 3D tissue samples), the mechanism of the phenomenon is not known. Although gap junction communication and the presence of soluble mediator(s) are both known to play important roles in the bystander response, the precise signaling molecules have yet to be identified. By using the Columbia University charged particle beam in conjunction with a strip dish design, we show here that the cyclooxygenase-2 (COX-2, also known as prostaglandin endoperoxide synthase-2) signaling cascade plays an essential role in the bystander process. Treatment of bystander cells with NS-398, which suppresses COX-2 activity, significantly reduced the bystander effect. Because the critical event of the COX-2 signaling is the activation of the mitogen-activated protein kinase pathways, our finding that inhibition of the extracellular signal-related kinase phosphorylation suppressed bystander response further confirmed the important role of mitogen-activated protein kinase signaling cascade in the bystander process. These results provide evidence that the COX-2-related pathway, which is essential in mediating cellular inflammatory response, is the critical signaling link for the bystander phenomenon.

Role of inflammation in pancreatic carcinogenesis and the implications for future therapy

BACKGROUND

The link between inflammation and pancreatic cancer has been observed for a number of gastrointestinal neoplasms. This review examines the role of inflammation in pancreatic carcinogenesis and how it can be utilised to develop new therapies against pancreatic cancer.

METHODS

A literature review of Pubmed, Medline and Web of Science databases was undertaken using the key words, pancreatic cancer, inflammation, inducible nitric oxide, interleukins, pro-inflammatory cytokines, cyclooxygenase-2, NF-kappa B, reactive oxygen species, DNA adducts, lipoxygenases, chemoprevention.

RESULTS

Epidemiological evidence and molecular studies both in vitro and in vivo all support the hypothesis that inflammation plays an important in the initiation and progression of pancreatic tumours.

CONCLUSION

Sustained damage caused by chronic inflammation may precede the onset of frank malignancy by a significant interval. As such, suppression of inflammatory changes and oxidative damage, may help delay or even prevent the inception of pancreatic neoplasia.

A molecular cascade showing nitric oxide-heme oxygenase-1-vascular endothelial growth factor-interleukin-8 sequence in human endothelial cells

Heme oxygenase (HO)-1 has been shown to be an important biological target of nitric oxide (NO). NO can induce HO-1 expression and IL-8 production, particularly, in endothelial cells. Interestingly, HO-1 tends to induce the production of vascular endothelial growth factor (VEGF) that is involved in endothelial IL-8 syntheses. Whether HO-1 expression by NO may provide a link with IL-8 or VEGF synthesis was investigated in human umbilical vein endothelial cells (HUVECs). The NO donor S-nitroso-N-acetyl-penicillamine (SNAP) dose-dependently increased IL-8 and VEGF productions and HO-1 expression in HUVECs. Transfection with either HO-1 small interfering RNA or HO-1 antisense oligodeoxynucleotide abrogated the ability of SNAP to induce HO-1 expression and IL-8 and VEGF productions. Both pharmacological induction and gene transfer of HO-1 directly induced IL-8 and VEGF productions. Anti-VEGF neutralizing antibody blocked SNAP-mediated IL-8 production and VEGF itself induced IL-8 production, whereas anti-IL-8 neutralizing antibody had no effect on VEGF production in SNAP-treated HUVECs. Neither anti-VEGF nor anti-IL-8 antibodies influenced SNAP-induced HO-1 expression. Moreover, neither VEGF nor IL-8 showed an additive effect on SNAP-induced HO-1 expression. HO-1 transfection had no significant effect on productions of other CXC chemokines, such as growth-related oncogen-alpha and epithelial neutrophil activation peptide-78. Taken together, these results provide a molecular cascade showing NO-HO-1-VEGF-IL-8 sequence in human endothelial cells.

Acidic extracellular pH induces matrix metalloproteinase-9 expression in mouse metastatic melanoma cells through the phospholipase D-mitogen-activated protein kinase signaling

The extracellular pH (pHe) of tumor tissues is often acidic, which can induce the expression of several proteins. We previously showed that production of matrix metalloproteinase-9 (MMP-9) was induced by culturing cells at acidic pHe (5.4-6.5). Here we have investigated the signal transduction pathway by which acidic pHe induces MMP-9 expression. We found that acidic pHe (5.9) activated phospholipase D (PLD), and inhibition of PLD activity by 1-butanol and Myr-ARF6 suppressed the acidic pHe-induced MMP-9 expression. Exogenous PLD, but not phosphatidylinositol-specific PLC or PLA2, mimicked MMP-9 induction by acidic pHe. Western blot analysis revealed that acidic pHe increased the steady-state levels of phosphorylated extracellular signal-regulated kinases 1/2 and p38 and that the PLD inhibitors suppressed these increases. Using 5'-deletion mutant constructs of the MMP-9 promoter, we found that the acidic pHe-responsive region was located at nucleotide -670 to -531, a region containing the NF kappa B binding site. A mutation into the NF kappa B binding site reduced, but not completely, the acidic pHe-induced MMP-9 promoter activity, and NF kappa B activity was induced by acidic pHe. Pharmacological inhibitors specific for mitogen-activated protein kinase kinase 1/2 (PD098059) and p38 (SB203580) attenuated the acidic pHe-induced NF kappa B activity and MMP-9 expression. These data suggest that PLD, mitogen-activated protein kinases (extracellular signal-regulated kinases 1/2 and p38), and NF kappa B mediate the acidic pHe signaling to induce MMP-9 expression. A transcription factor(s) other than NF kappa B may also be involved in the MMP-9 expression.

Nitric Oxide-Derived Nitrosating Species and Gene Expression in Human Monocytic Cells

In living cells, NO signaling is mediated by NO-derived metabolites and is therefore dependent on the rate of formation of these so-called reactive nitrogen intermediates (RNIs). We have examined the effects of NO-oxidizing agents, the nitronyl nitroxide PTIO and its less hydrophobic analogue carboxy-PTIO (CPTIO), on the expression of NO-sensitive genes in monocytic U937 and Mono Mac 6 cells. We have observed that pretreatment of cells with PTIO boosted expression of IL-8 and heme oxygenase 1 (HOX) genes to a high level in cells treated with the NO donor DPTA-NO. In contrast, pretreatment of cells with CPTIO significantly inhibited NO-dependent expression of IL-8 and hardly stimulated HOX gene expression by DPTA-NO. The effect of PTIO was abrogated by reduced glutathione, suggesting that upregulation of the IL-8 and HOX genes is dependent on RNI-mediated S-nitrosation of specific regulator(s). The concentration of PTIO required to enhance mRNA level was different for IL-8 and HOX genes. Analysis of 4,5-diaminofluorescein (DAF) nitrosation in the presence of PTIO and DPTA-NO showed that optimal PTIO concentrations required for maximal N(2)O(3) synthesis and for highest IL-8 gene expression are similar. Furthermore, we have shown that, besides IL-8 and HOX, PTIO superactivates NO-dependent expression of TNF-alpha and p21/WAF1 genes. In contrast, the level of MIP-1alpha, c-jun, and c-fos genes was not changed by the presence of PTIO in U937 cells and was even reduced in Mono Mac 6 cells.

Nitric oxide post-transcriptionally up-regulates LPS-induced IL-8 expression through p38 MAPK activation

Nitric oxide (NO(.-)) contributes to vascular collapse in septic shock and regulates inflammation. Here, we demonstrate in lipopolysaccharide (LPS)-stimulated human THP-1 cells and monocytes that NO(.-) regulates interleukin (IL)-8 and tumor necrosis factor alpha (TNF-alpha) by distinct mechanisms. Dibutyryl-cyclic guanosine 5'-monophosphate (cGMP) failed to simulate NO(.-)-induced increases in TNF-alpha or IL-8 production. In contrast, dibutyryl-cyclic adenosine monophosphate blocked NO(.-)-induced production of TNF-alpha (P=0.009) but not IL-8. NO(.-) increased IL-8 (5.7-fold at 4 h; P=0.04) and TNF-alpha mRNA levels (2.2-fold at 4 h; P=0.037). However, nuclear run-on assays demonstrated that IL-8 transcription was slightly decreased by NO(.-) (P=0.08), and TNF-alpha was increased (P=0.012). Likewise, NO(.-) had no effect on IL-8 promoter activity (P=0.84) as measured by reporter gene assay. In THP-1 cells and human primary monocytes treated with actinomycin D, NO(.-) had no effect on TNF-alpha mRNA stability (P>0.3 for both cell types) but significantly stabilized IL-8 mRNA (P=0.001 for both cell types). Because of its role in mRNA stabilization, the p38 mitogen-activated protein kinase (MAPK) pathway was examined and found to be activated by NO(.-) in LPS-treated THP-1 cells and human monocytes. Further, SB202190, a p38 MAPK inhibitor, was shown to block NO(.-)-induced stabilization of IL-8 mRNA (P<0.02 for both cell types). Thus, NO(.-) regulates IL-8 but not TNF-alpha post-transcriptionally. IL-8 mRNA stabilization by NO(.-) is independent of cGMP and at least partially dependent on p38 MAPK activation.

Nitric oxide synergistically potentiates interleukin-1 beta-induced increase of cyclooxygenase-2 mRNA levels, resulting in the facilitation of substance P release from primary afferent neurons: involvement of cGMP-independent mechanisms

We previously demonstrated that cultured rat dorsal root ganglion (DRG) cells respond to stimulation with interleukin-1 beta (IL-1 beta) by releasing substance P (SP), and this response is regulated via the cyclooxygenase (COX)-2 pathway. In this study, to ascertain the interaction between nitric oxide (NO) and prostaglandins in primary afferent neurons, we investigated the effect of NO on the IL-1 beta-induced release of SP in cultured DRG cells. An NO donor, S-nitroso-N-acetyl-DL-penicillamine (SNAP), did not in itself evoke SP release. However, it potentiated the IL-1 beta-induced release of SP. Similarly, while SNAP did not elicit the expression of COX-2 mRNA, it potentiated the expression induced by IL-1 beta in cultured DRG cells, and this potentiation was significantly suppressed by the NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (carboxy-PTIO). Moreover, SNAP also potentiated the expression of COX-2 protein induced by IL-1 beta in cultured DRG cells. The stimulatory effect of SNAP on the IL-1 beta-induced release of SP was completely inhibited on co-incubation with a selective COX-2 inhibitor, NS-398. 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ), a potent inhibitor of soluble guanylate cyclase, did not suppress, and a membrane-permeable cGMP analogue, 8-Br-cGMP, did not mimic the stimulatory effects of SNAP in DRG cells. These results suggest that in cultured DRG cells, NO potentiates the IL-1 beta-induced increase in COX-2 expression via a soluble guanylate cyclase-cGMP-independent pathway, resulting in facilitation of SP release. The interaction between NO and COX in primary afferent neurons might contribute to the change in nociceptive perception in inflammatory hyperalgesia.