Inhibition of angiogenesis by nonsteroidal anti-inflammatory drugs: insight into mechanisms and implications for cancer growth and ulcer healing

A novel antioxidant and antiapoptotic role of omeprazole to block gastric ulcer through scavenging of hydroxyl radical

The mechanism of the antiulcer effect of omeprazole was studied placing emphasis on its role to block oxidative damage and apoptosis during ulceration. Dose-response studies on gastroprotection in stress and indomethacin-induced ulcer and inhibition of pylorus ligation-induced acid secretion indicate that omeprazole significantly blocks gastric lesions at lower dose (2.5 mg/kg) without inhibiting acid secretion, suggesting an independent mechanism for its antiulcer effect. Time course studies on gastroprotection and acid reduction also indicate that omeprazole almost completely blocks lesions at 1 h when acid inhibition is partial. The severity of lesions correlates well with the increased level of endogenous hydroxyl radical (*OH), which when scavenged by dimethyl sulfoxide causes around 90% reduction of the lesions, indicating that *OH plays a major role in gastric damage. Omeprazole blocks stress-induced increased generation of *OH and associated lipid peroxidation and protein oxidation, indicating that its antioxidant role plays a major part in preventing oxidative damage. Omeprazole also prevents stress-induced DNA fragmentation, suggesting its antiapoptotic role to block cell death during ulceration. The oxidative damage of DNA by *OH generated in vitro is also protected by omeprazole or its analogue, lansoprazole. Lansoprazole when incubated in a *OH-generating system scavenges *OH to produce four oxidation products of which the major one in mass spectroscopy shows a molecular ion peak at m/z 385, which is 16 mass units higher than that of lansoprazole (m/z 369). The product shows no additional aromatic proton signal for aromatic hydroxylation in (1)H NMR. The product absorbing at 278 nm shows no alkaline shift for phenols, thereby excluding the formation of hydroxylansoprazole. The product is assigned to lansoprazole sulfone formed by the addition of one oxygen atom at the sulfur center following attack by the *OH. Thus, omeprazole plays a significant role in gastroprotection by acting as a potent antioxidant and antiapoptotic molecule.

Oxidative stress regulates vascular endothelial growth factor-A gene transcription through Sp1- and Sp3-dependent activation of two proximal GC-rich promoter elements

Enhanced VEGF-A (vascular endothelial growth factor A) gene expression is associated with increased tumor growth and metastatic spread of solid malignancies including gastric cancer. Oxidative stress has been linked to tumor-associated neoangiogenesis; underlying mechanisms, however, remained poorly understood. Therefore, we studied the effect of oxidative stress on VEGF-A gene expression in gastric cancer cells. Oxidative stress generated by H(2)O(2) application potently stimulated VEGF-A protein and mRNA levels as determined by enzyme-linked immunosorbent assay and real-time PCR techniques, respectively, and elevated the activity of a transfected (-2018) VEGF-A promoter reporter gene construct in a time- and dose-dependent manner (4-8-fold). These effects were abolished by the antioxidant N-acetylcysteine, demonstrating specificity of oxidative stress responses. Functional 5' deletion analysis mapped the oxidative stress response element of the human VEGF-A promoter to the sequence -88/-50, and a single copy of this element was sufficient to confer basal promoter activity as well as oxidative stress responsiveness to a heterologous promoter system. Combination of EMSA studies, Sp1/Sp3 overexpression experiments in Drosophila SL-2 cells, and systematic promoter mutagenesis identified enhanced Sp1 and Sp3 binding to two GC-boxes at -73/-66 and -58/-52 as the core mechanism of oxidative stress-triggered VEGF-A transactivation. Additionally, in Gal4-Sp1/-Sp3-Gal4-luciferase assays, oxidative stress increased Sp1 but not Sp3 transactivating capacity, indicating additional mechanism(s) of VEGF-A gene regulation. Signaling studies identified a cascade comprising Ras --> Raf --> MEK1 --> ERK1/2 as the main pathway mediating oxidative stress-stimulated VEGF-A transcription. This study for the first time delineates the mechanisms underlying regulation of VEGF-A gene transcription by oxidative stress and thereby further elucidates potential pathways underlying redox control of neoangiogenesis.

Selective inhibitors of cyclooxygenase-2 delay the activation of nuclear factor kappa B and attenuate the expression of inflammatory genes in murine macrophages treated with lipopolysaccharide

The effect of rofecoxib, a selective cyclooxygenase-2 inhibitor, on inflammatory signaling has been investigated in elicited murine peritoneal macrophages. Macrophages treated with 10 microM rofecoxib exhibited an important inhibition in the early activation of nuclear factor kappa B (NF-kappa B) and the mitogen-activated protein kinase p38, the extracellular-regulated kinase p44, and the c-Jun N-terminal kinase. Moreover, this drug decreased the protein levels of nitric-oxide synthase-2 and cyclooxygenase-2 in lipopolysaccharide (LPS)-treated macrophages. Rofecoxib delayed and attenuated NF-kappa B activation, which impaired significantly the expression of kappa B-dependent genes. This drug and related coxibs did not affect cell viability and protected against LPS-induced apoptosis through the impairment of the inflammatory response. These data show an additional anti-inflammatory mechanism of selective cyclooxygenase-2 inhibitors through the attenuation of macrophage activation.

Alzheimer's disease and angiogenesis

Despite enormous investigative efforts, the pathological basis for Alzheimer's disease remains unclear. Suggested mechanisms for the disorder include cerebral hypoperfusion, inflammation, gene polymorphisms, and molecular lesions in the brain. In this Hypothesis, we argue that the vascular endothelial cell has a central role in the progressive destruction of cortical neurons in Alzheimer's disease. In Alzheimer's disease, the brain endothelium secretes the precursor substrate for the beta-amyloid plaque and a neurotoxic peptide that selectively kills cortical neurons. Large populations of endothelial cells are activated by angiogenesis due to brain hypoxia and inflammation. Results of epidemiological studies have shown that long-term use of non-steroidal anti-inflammatory drugs, statins, histamine H2-receptor blockers, or calcium-channel blockers seems to prevent Alzheimer's disease. We think this benefit is largely due to these drugs' ability to inhibit angiogenesis. If Alzheimer's disease is an angiogenesis-dependent disorder, then development of antiangiogenic drugs targeting the abnormal brain endothelial cell might be able to prevent and treat this disease. We suggest several laboratory and clinical approaches for testing our hypothesis.

Angiogenesis of the heart

Despite continued advances in the prevention and treatment of coronary artery disease, there are still a large number of patients who are not candidates for the conventional revascularization techniques of balloon angioplasty and stenting, or coronary artery bypass grafting (CABG). Therapeutic angiogenesis, in the form of the administration of growth factor protein or gene therapy, has emerged as a promising new method of treatment for patients with coronary artery disease. The goal of this strategy is to promote the development of supplemental blood conduits that will act as endogenous bypass vessels. New vessel formation occurs through the processes of angiogenesis, vasculogenesis, and arteriogenesis, under the control of growth factors such as those that belong to the vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF) and angiopoeitin (Ang) families of molecules. Preclinical studies have suggested that such an approach is both feasible and effective; however many questions remain to be answered. This review will address the elements of pharmacologic revascularization, focusing on gene and protein-based therapy. The important growth factors, the vector (for gene therapy), routes of delivery, the desired therapeutic effect, and quantifiable clinical end points for trials of angiogenesis will all be addressed.

Cyclooxygenase-2: a therapeutic target in angiogenesis

Angiogenesis has a role in the pathogenesis of several disorders, including cancer, chronic inflammatory diseases and retinopathies. Recent evidence demonstrates that the production of prostanoids by cyclooxygenase-2 (COX-2) promotes the expression of pro-angiogenic factors. Furthermore, inhibition of COX-2 by non-steroidal anti-inflammatory drugs leads to restricted angiogenesis and downregulated production of pro-angiogenic factors, such as vascular endothelial growth factor and basic fibroblast growth factor. These findings suggest that COX enzymes could be important therapeutic targets in the treatment of pathological angiogenesis.

Selective cyclooxygenase-2 inhibition does not affect the healing of cutaneous full-thickness incisional wounds in SKH-1 mice

BACKGROUND

The inducible cyclooxygenase-2 (COX-2) enzyme is upregulated in inflammatory diseases, as well as in epithelial cancers, and has an established role in angiogenesis and tissue repair.

OBJECTIVE

Because of these physiological effects and the widespread use of the selective COX-2 inhibitor, celecoxib, we wanted to determine if inhibition of COX-2 would affect incisional skin wound healing.

METHODS

Using a cutaneous full-thickness, sutured, incisional wound model in hairless SKH-1 mice, we evaluated the role of COX-2 in the wound healing process by comparing the effects of a nonselective COX inhibitor, diclofenac, with a selective COX-2 inhibitor, SC-791. Healing was monitored for up to 28 days postincision histologically and for recovery of wound strength.

RESULTS

COX-2 expression was observed over the first week of healing, peaking at day 3 and was not affected by treatment with the selective COX-2 or nonselective COX inhibitors. Infiltrating macrophages, as well as keratinocytes and dermal fibroblasts at the wound site, expressed COX-2. Neither selective COX-2, nor nonselective COX inhibition had a significant effect on the macroscopic or microscopic morphology of the wounds, whereas dexamethasone treatment resulted in epidermal and granulation tissue atrophy. In addition, neither selective COX-2, nor nonselective COX inhibition altered keratinocyte proliferation and differentiation, dermal angiogenesis or the recovery of wound tensile strength, whereas dexamethasone reduced the tensile strength of the wounds by 30-38% throughout the healing period.

CONCLUSIONS

These data indicate that selective COX-2 inhibition does not affect the healing of surgical skin wounds.

Advances in the pathophysiology of constitutive and inducible cyclooxygenases: two enzymes in the spotlight

The aim of this commentary is to discuss recent data on the role of prostaglandins generated by both constitutive and inducible cyclooxygenases (COXs). According to a popular hypothesis, COX-1 generates 'good' prostaglandins for physiological 'housekeeping' functions like gastrointestinal (GI) mucosal integrity and regulation of renal blood flow, while COX-2 forms the 'bad' prostaglandins responsible for inflammatory symptoms. However, recent data show that the biological functions of prostanoids formed by the two enzymes are much more complex and interrelated than previously appreciated. Experimental evidence indicates that a full inflammatory response is likely sustained by prostanoids generated by both enzymes, and an effective anti-inflammatory effect requires the inhibition of the two enzymes. Similarly, the selective inhibition of either COX-1 or COX-2 does not elicit GI damage, but inhibition of both enzymes is necessary for GI mucosal damage to develop. Prostaglandins generated by both enzymes contribute to normal renal function by regulating the vascular tone and the normal blood flow. The synthesis of endothelial prostacyclin is mainly driven by COX-2, so that the selective COX-2 inhibition may bias vascular prostaglandin synthesis in favour of COX-1-derived thromboxane A(2) in platelets, leading to a prothrombotic outcome. Moreover, prostaglandins formed by COX-2 appear to have a major role in myocardial protection. We propose that the complexity of the situation in the field of COX-derived mediators should be borne in mind when anti-inflammatory therapy is required.

Human prostacyclin receptor

Prostacyclin, a member of the eicosanoid family of lipid mediators, is the major product of arachidonic acid metabolism formed in the marcovascular endothelium. It is a potent vasodilator, antithrombotic, and antiplatelet agent that mediates it effects through a membrane-associated receptor termed the IP. Cloning of the cDNA for IP, from human and other species, indicated its membership of the G protein-coupled receptor superfamily and has allowed detailed examination of the signaling and regulatory pathways utilized by this receptor. This article examines the current state of knowledge of the IP, its signaling and regulation, and its biological role in vivo and examines the possible existence of multiple PGI2 receptor sites.

Non steroidal anti-inflammatory drugs and COX-2 inhibitors as anti-cancer therapeutics: hypes, hopes and reality

Non-steroidal anti-inflammatory drugs (NSAIDs) and specific inhibitors of cyclooxygenase (COX)-2, are therapeutic groups widely used for the treatment of pain, inflammation and fever. There is growing experimental and clinical evidence indicating NSAIDs and COX-2 inhibitors also have anti-cancer activity. Epidemiological studies have shown that regular use of Aspirin and other NSAIDs reduces the risk of developing cancer, in particular of the colon. Molecular pathology studies have revealed that COX-2 is expressed by cancer cells and cells of the tumor stroma during tumor progression and in response to chemotherapy or radiotherapy. Experimental studies have demonstrated that COX-2 over expression promotes tumorigenesis, and that NSAIDs and COX-2 inhibitors suppress tumorigenesis and tumor progression. Clinical trials have shown that NSAIDs and COX-2 inhibitors suppress colon polyp formation and malignant progression in patients with familial adenomatous polyposis (FAP) syndrome. Recent advances in the understanding of the cellular and molecular mechanisms of the anti-cancer effects of NSAIDs and COX-2 inhibitors have demonstrated that these drugs target both tumor cells and the tumor vasculature. The therapeutic benefits of COX-2 inhibitors in the treatment of human cancer in combination with chemotherapy or radiotherapy are currently being tested in clinical trials. In this article we will review recent advances in the understanding of the anti-tumor mechanisms of these drugs and discuss their potential application in clinical oncology.

Overexpression of cyclooxygenase-2 in high-grade human transitional cell carcinoma of the upper urinary tract

OBJECTIVE

To examine cyclooxygenase (COX)-2 expression (a key enzyme in the synthesis of prostaglandins, and involved in carcinogenesis of human epithelial tumours) in human transitional cell carcinomas (TCCs) of the renal pelvis and ureter, and to determine whether COX-2 expression correlates with the clinicopathological characteristics of the disease.

MATERIALS AND METHODS

Specimens from 144 patients with TCC of the upper urinary tract who had undergone nephroureterectomy were analysed immunohistochemically, and 23 were also analysed by immunoblotting.

RESULTS

Immunoblot analysis showed COX-2 immunoreactivity in 17 (74%) of 23 tumours, but not in normal transitional epithelium. COX-2 was localized to the cytoplasm of cancer cells and expressed in 108 (75%) of 144 tumours, as assessed by immunohistochemical analysis. COX-2 expression correlated with tumour grade (P < 0.008), being detected in one of nine grade 1, 77 (79%) of 97 grade 2 and 30 (79%) of 38 grade 3 tumours. Other variables including tumour stage were not associated with COX-2 expression.

CONCLUSIONS

We show for the first time that COX-2 is frequently expressed in TCC of the upper urinary tract and is associated with the degree of tumour cell differentiation, indicating that COX-2 may be involved in TCC carcinogenesis at an early and/or late stage, and could be a useful target for chemoprevention of this type of cancer.

[Mucosa protective therapy with long-term nonsteroidal antirheumatic drugs]

Due to the extraordinary high prevalence of peptic lesions in the upper gastrointestine in the long-term treatment with nonsteroidal anti-inflammatory drugs, a prophylaxis in patients belonging to high-risk groups is essential. Misoprostol, proton pump inhibitors and histamine 2-receptor antagonists have been evaluated in prospective studies. The efficacy of Misoprostol is well documented, though its use in prevention is frequently limited due to side effects. Proton pump inhibitors are also well established, especially in the therapy of nonsteroidal anti-inflammatory drugs associated peptic ulcers and in consecutive secondary prevention. The histamine 2-receptor antagonist Famotidine in a high oral dosage is able to reduce the frequency of peptic lesions too, but not to the same degree as Misoprostol and proton pump inhibitors. It is very likely that helicobacter pylori eradication without any further mucosaprotective therapy will only decrease the incidence of upper gastrointestinal bleeding in low dose Aspirin application. In spite of controversial studies this eradication seems to be a useful additional therapy for ulcer prophylaxis in high risk groups. Selective Cyclooxygenase-2 inhibitors may become a promising alternative, from a pathophysiological perspective. However, to date there has been a lack of clear comparative studies with common nonsteroidal anti-inflammatory drugs plus mucosaprotecting agents. Daily therapy costs are higher with a Cyclooxygenase-2 inhibitor than using the traditional nonsteroidal anti-inflammatory drugs together with either proton pump inhibitors, histamine 2-receptor antagonists or Misoprostol--a fact that should be considered in primary therapeutic decisions. In the following review we will present the most important results of the different prophylactic and therapeutic modalities. On the basis of placebo-controlled, prospective studies on the one hand and the recommendations of the scientific societies on the other, a guideline for daily clinical practice will be suggested.

Trefoil peptides as proangiogenic factors in vivo and in vitro: implication of cyclooxygenase-2 and EGF receptor signaling

We previously established that the trefoil peptides (TFFs) pS2, spasmolytic polypeptide, and intestinal trefoil factor are involved in cellular scattering and invasion in kidney and colonic cancer cells. Using the chorioallantoic membrane (CAM) assay and the formation of tube-like structures by human umbilical vein endothelial cells (HUVEC) plated on the Matrigel matrix substratum, we report here that TFFs are proangiogenic factors. Angiogenic activity of TFFs is comparable to that induced by vascular endothelial growth factor, leptin, and transforming growth factor-alpha. Stimulation of angiogenesis by pS2 in the CAM assay is blocked by pharmacological inhibitors of cyclooxygenase COX-2 (NS-398) and epidermal growth factor receptor (EGF-R) tyrosine kinase (ZD1839), but is independent of KDR/Flk-1 and thromboxane A2 receptors. In contrast, the morphogenic switch induced by pS2 in HUVEC cells could be inhibited by the specific KDR heptapeptide antagonist ATWLPPR and by inhibitors of COX-2 and EGF-R signaling. These results implicate TFFs in the formation of new blood vessels during normal and pathophysiological processes linked to wound healing, inflammation, and cancer progression in the digestive mucosa and other human solid tumors associated with aberrant expression of TFFs.

COX-2 inhibitors for the prevention of breast cancer

The inducible prostaglandin synthase cyclooxygenase-2 (COX-2) is normally expressed predominantly in kidney and brain, and also has important roles in reproduction and inflammation. COX-2 misexpression has been observed in numerous human cancers, including the majority of colorectal cancers. Recently, COX-2 overexpression has been described in human breast cancer. COX-2 is present in about 40% of invasive breast carcinomas, particularly those that overexpress HER2/neu, and COX-2 expression correlates with poor patient prognosis. Manipulation of Cox-2 gene dosage by using transgenic overexpression and knockout approaches has revealed an important role for Cox-2 in tumorigenesis. Furthermore, translational experiments using rodent breast cancer models suggest COX-2 inhibition to be an effective strategy for both prevention and treatment of experimental breast cancers. Since COX-2 can contribute to multiple facets of tumorigenesis, including angiogenesis, several mechanisms are likely to underlie the anticancer action of COX inhibitors. Thus, selective COX-2 inhibitors offer considerable promise for the prevention and treatment of human breast cancer.

Prostaglandin E2 induces hypoxia-inducible factor-1alpha stabilization and nuclear localization in a human prostate cancer cell line

Hypoxia-induced up-regulation of vascular endothelial growth factor (VEGF) expression is a critical event leading to tumor neovascularization. Hypoxia stimulates hypoxia-inducible factor-1alpha (HIF-1alpha), a transcriptional activator of VEGF. Cyclooxygenase (COX)-2, an inducible enzyme that catalyzes the formation of prostaglandins (PGs) from arachidonic acid, is also induced by hypoxia. We reported previously that COX-2 inhibition prevents hypoxic up-regulation of VEGF in human prostate cancer cells and that prostaglandin E(2) (PGE(2)) restores hypoxic effects on VEGF. We hypothesized that PGE(2) mediates hypoxic effects on VEGF by modulating HIF-1alpha expression. Addition of PGE(2) to PC-3ML human prostate cancer cells had no effect on HIF-1alpha mRNA levels. However, PGE(2) significantly increased HIF-1alpha protein levels, particularly in the nucleus. This effect of PGE(2) largely results from the promotion of HIF-1alpha translocation from the cytosol to the nucleus. PGE(2) addition to PC-3 ML cells transfected with a GFP-HIF-1alpha vector induced a time-dependent nuclear accumulation of the HIF-1alpha protein. Two selective COX-2 inhibitors, meloxicam and NS398, decreased HIF-1alpha levels and nuclear localization, under both normoxic and hypoxic conditions. Of several prostaglandins tested, only PGE(2) reversed the effects of a COX-2 inhibitor in hypoxic cells. Finally, PGE(2) effects on HIF-1alpha were specifically inhibited by PD98059 (a MAPK inhibitor). These data demonstrate that PGE(2) production via COX-2-catalyzed pathway plays a critical role in HIF-1alpha regulation by hypoxia and imply that COX-2 inhibitors can prevent hypoxic induction of HIF-mediated gene transcription in cancer cells.

Correlation between nitric oxide and cyclooxygenase-2 pathways in head and neck squamous cell carcinomas

We investigated the interactions between inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) pathways in head and neck squamous cell carcinomas (HNSCCs) and in two carcinoma cell lines. HNSCCs showed an up-regulation of both pathways which were strongly correlated with each other (p=0.02) and with tumor vascularization (p=0.0001 and p=0.008, respectively). In carcinoma cells, Escherichia coli lipopolysaccharide (LPS) and EGF treatment up-regulated both pathways. NOS inhibitor N(G)-monomethyl-L-arginine methyl ester (L-NAME) inhibited this up-regulation. LPS or EGF induced iNOS expression that was not altered by NOS or COX-2 inhibitors. Conversely, LPS or EGF promoted COX-2 expression that was decreased by L-NAME. The NO donor S-nitroso-acetyl-penicillamine (SNAP) up-regulated COX-2 pathway and this effect was reduced by the guanylate cyclase inhibitor methylene blue. Thus, in squamous carcinoma cells, NO increases the activity of COX-2 pathway and this effect is probably mediated by endocellular cGMP level, with potential implications on tumor growth, angiogenesis, and therapy.

Aspirin and cancer risk: an update to 2001

Evidence of a protective role of aspirin on the risk of colorectal and other common cancers has been building up since the end of the 1980s. There are now more than 15 epidemiological (case-control and cohort) studies indicating that long-term use of aspirin is associated with a reduced risk of colorectal cancer. The overall relative risk (RR) estimate for regular aspirin users was 0.71 (95% confidence interval (CI) 0.66-0.77) from case-control studies, and 0.84 (95% CI 0.72-0.98) from cohort studies. A recent meta-analysis reported a RR of breast cancer for aspirin use of 0.70 (95% CI 0.61-0.81) in case-control studies, and of 0.79 (95% CI 0.59-1.06) in cohort studies. Furthermore, various epidemiological studies have suggested that aspirin use might have a favourable effect on ovarian cancer as well: the overall RR estimate was 0.82 (95% CI 0.69-0.99), although the evidence is too limited to permit firm conclusions. Data are more scanty, though in the same direction, for other neoplasms, including in particular stomach and oesophageal cancer.

Suppression of cyclooxygenase-2 and inducible nitric oxide synthase expression by conjugated linoleic acid in murine macrophages

Activated macrophages express inducible isoforms of cyclooxygenase (COX-2) and nitric oxide synthase (iNOS), and produce excessive amounts of prostaglandin E(2) (PGE(2)) and nitric oxide (NO) which play key roles in cancer pathogenesis. Conjugated linoleic acid (CLA) is an anticarcinogen while arachidonic acid (AA) may be a procarcinogen by increased PGE(2) production. This study examined the effects of CLA and AA on PGE(2) and NO synthesis in endotoxin-activated macrophages. RAW264.7 macrophages were incubated in medium containing no added lipid (control), 30 microM AA (AA medium), or 30 microM CLA (CLA medium) for 24 h followed by activation with bacterial endotoxin lipopolysaccharide (LPS; 100 ng/ml) for 9 h. CLA significantly depressed PGE(2) and NO production by 78% (P=0.003) and 57% (P=0.0001) respectively. Northern blot analysis of COX-2 and iNOS showed significant 33% (P=0.01) and 51% (P=0.04) decreases, respectively, paralleling those seen for PGE(2) and NO production. In contrast, AA significantly increased PGE(2) synthesis by 62% (P=0.02) and also suppressed NO production and iNOS expression in the same manner as observed for CLA. These results suggest that the anticarcinogenic effect of CLA in endotoxin-activated macrophages may be related to its ability to decrease both PGE(2) and NO synthesis by suppressing transcription of COX-2 and iNOS.

Seminal plasma activates cyclooxygenase-2 and prostaglandin E2 receptor expression and signalling in cervical adenocarcinoma cells

Enhanced cyclooxygenase (COX) expression and prostaglandin E2 (PGE2) synthesis are regarded as promoters of neoplastic cell proliferation and angiogenesis. Expression of COX-2 and synthesis of PGE2 are up-regulated in cervical carcinomas. In sexually active women, growth and invasiveness of neoplastic cervical epithelial cells may be also under the direct influence of PGE2 present in seminal plasma. The aims of this study were to investigate the effect of seminal plasma and PGE2 on the expression of COX-2 and expression and signalling of the PGE2 receptor subtypes (EP1-EP4) in HeLa (cervical adenocarcinoma) cells. Treatment of HeLa cells with seminal plasma or PGE2 resulted in up-regulation of COX-2 expression (P < 0.05). In addition, seminal plasma induced the mRNA expression of EP1, EP2 and EP4 receptors, whilst PGE2 treatment of HeLa cells induced the expression of the EP4 receptor (P < 0.05). This was coincident with a rapid accumulation of adenosine 3',5'-cyclic monophosphate (cAMP) in HeLa cells stimulated with seminal plasma or PGE2, which was greater in seminal plasma stimulated cells compared with PGE2 stimulated cells (P < 0.05). Subsequently, we investigated whether the effect of seminal plasma on cAMP signalling in HeLa cells was mediated via the cAMP-linked EP2/EP4 receptors. Stimulation of HeLa cells with seminal plasma or PGE2 resulted in an augmented cAMP accumulation in cells transfected with the EP2 or EP4 receptor cDNA compared with control transfected cells (P < 0.05). These data suggest that, in sexually active women, seminal plasma may play a role in modulating neoplastic cell function and cervical tumorigenesis.

Prostaglandin E2 promotes integrin alpha Vbeta 3-dependent endothelial cell adhesion, rac-activation, and spreading through cAMP/PKA-dependent signaling

We have recently reported that the inhibition of endothelial cell COX-2 by non-steroidal anti-inflammatory drugs suppresses alpha(V)beta(3)- (but not alpha(5)beta(1)-) dependent Rac activation, endothelial cell spreading, migration, and angiogenesis (Dormond, O., Foletti, A., Paroz, C., and Ruegg, C. (2001) Nat. Med. 7, 1041-1047). Here we investigated the role of the COX-2 metabolites PGE(2) and TXA2 in regulating human umbilical vein endothelial cell (HUVEC) adhesion and spreading. We report that PGE(2) accelerated alpha(V)beta(3)-mediated HUVEC adhesion and promoted Rac activation and cell spreading, whereas the TXA2 agonist retarded adhesion and inhibited spreading. We show that the cAMP level and the cAMP-regulated protein kinase A (PKA) activity are critical mediators of these PGE(2) effects. alpha(V)beta(3)-mediated adhesion induced a transient COX-2-dependent rise in cAMP levels, whereas the cell-permeable cAMP analogue 8-brcAMP accelerated adhesion, promoted Rac activation, and cell spreading in the presence of the COX-2 inhibitor NS-398. Pharmacological inhibition of PKA completely blocked alpha(V)beta(3)-mediated adhesion. A constitutively active Rac mutant (L61Rac) rescued alpha(V)beta(3)-dependent spreading in the presence of NS398 or, but did not accelerate adhesion, whereas a dominant negative Rac mutant (N17Rac) suppressed spreading without affecting adhesion. alpha(5)beta(1)-mediated HUVEC adhesion, Rac activation, and spreading were not affected by PGE(2), 8-brcAMP, or the inhibition of PKA. In conclusion, these results demonstrate that PGE(2) accelerates alpha(V)beta(3)-mediated endothelial cell adhesion through cAMP-dependent PKA activation and induces alpha(V)beta(3)-dependent spreading via cAMP- and PKA-dependent Rac activation and may contribute to the further understanding of the regulation of vascular integrins alpha(V)beta(3) by COX-2/PGE(2) during tumor angiogenesis and inflammation.

Autocrine/paracrine regulation of apoptosis in epithelial cells by prostaglandin E2

This study was designed to investigate the effect of IL-1alpha-induced up-regulation of cyclooxygenase-2 (COX-2) on prostaglandin E(2) (PGE(2)) secretion and the subsequent phenotypic effects of PGE(2) on epithelial cells. The effect of IL-1alpha on COX-2 expression was investigated in the T24 bladder epithelial cell line following treatment with 0, 0.05, 0.5, 1 or 10 ng/ml IL-1alpha for 1, 2, 4 or 6 h. Quantitative PCR confirmed up-regulation of expression of COX-2 with maximal expression observed following treatment with 0.5 ng/ml IL-1alpha for 1 h. Co-treatment of the cells with 0.5 ng/ml IL-1alpha in the presence or absence of 100 ng/ml IL-1 receptor antagonist (RA) abolished the up-regulation in COX-2 expression confirming that the effect of IL-1alpha is mediated via its membrane-bound receptors. Treatment with 0.5 ng/ml IL-1alpha resulted in a time-dependent increase in PGE(2) secretion with maximal secretion detected at 24 and 48 h after stimulation with IL-1alpha. Co-treatment of the cells with IL-1alpha and IL-1RA or the COX-2 enzyme inhibitor NS398 abolished the IL-1alpha mediated secretion of PGE(2). Treatment of T24 cells with 100 nM PGE(2) resulted in a significant elevation in cAMP generation confirming the expression of functional PGE(2) receptors. Finally, the effect of exogenous treatment with PGE(2) on apoptosis of T24 cells was assessed using cell death detection ELISA. T24 cells were treated with camptothecin to induce apoptosis in the presence or absence of 50 or 100 nM PGE(2) or 10 microM forskolin. Treatment of T24 cells with increasing doses of camptothecin alone resulted in a significant increase in the induction of apoptosis (P<0.01). However, co-treatment of the cells with 50 or 100 nM PGE(2) or 10 microM forskolin resulted in the inhibition of induction of the apoptotic pathway by camptothecin. These data demonstrate that PGE(2) inhibits apoptosis of epithelial cells possibly via cAMP-dependent pathway.

Real-time changes in 1H and 31P NMR spectra of malignant human mammary epithelial cells during treatment with the anti-inflammatory agent indomethacin

Choline metabolites in malignant human mammary epithelial cells (HMECs) are significantly altered compared to normal HMECs. (1)H NMR studies of cell extracts have shown that treatment of malignant HMECs with a nonsteroidal anti-inflammatory agent, indomethacin, results in a distribution of choline compounds more typical of nonmalignant HMECs. To follow the time course of these changes, in this study real-time monitoring of choline compounds of malignant MDA-MB-231 cells was performed during treatment with indomethacin. The contribution of changes in intra- and extracellular pH to changes in choline compounds was also examined. Changes in water-soluble choline phospholipid metabolites, such as phosphocholine (PC), glycerophosphocholine (GPC), and total choline, as well as intracellular pH, were monitored by (31)P and diffusion-weighted (1)H NMR spectroscopy of living cells using an NMR-compatible perfusion system. An accumulation of GPC and a decrease of PC, resulting in an increased [GPC]/[PC] ratio, were detected within 2 hr of treatment with 200 microM indomethacin. Since a decreased [GPC]/[PC] ratio is associated with increased malignancy, these data demonstrate that nonspecific cyclooxygenase inhibition by indomethacin alters the choline metabolite profile of malignant cells towards a less malignant phenotype. These changes were not related to alterations of intra- or extracellular pH.

Gastroprotective effect of Neem (Azadirachta indica) bark extract: possible involvement of H(+)-K(+)-ATPase inhibition and scavenging of hydroxyl radical

The antisecretory and antiulcer effects of aqueous extract of Neem (Azadirachta indica) bark have been studied along with its mechanism of action, standardisation and safety evaluation. The extract can dose dependently inhibit pylorus-ligation and drug (mercaptomethylimidazole)-induced acid secretion with ED(50) value of 2.7 and 2 mg Kg(-1) b.w. respectively. It is highly potent in dose-dependently blocking gastric ulcer induced by restraint-cold stress and indomethacin with ED(50) value of 1.5 and 1.25 mg Kg(-1) b.w. respectively. When compared, bark extract is equipotent to ranitidine but more potent than omeprazole in inhibiting pylorus-ligation induced acid secretion. In a stress ulcer model, it is more effective than ranitidine but almost equipotent to omeprazole. Bark extract inhibits H(+)-K(+)-ATPase activity in vitro in a concentration dependent manner similar to omeprazole. It offers gastroprotection against stress ulcer by significantly preventing adhered mucus and endogenous glutathione depletion. It prevents oxidative damage of the gastric mucosa by significantly blocking lipid peroxidation and by scavenging the endogenous hydroxyl radical ((z.rad;)OH)-the major causative factor for ulcer. The (z.rad;)OH-mediated oxidative damage of human gastric mucosal DNA is also protected by the extract in vitro. Bark extract is more effective than melatonin, vitamin E, desferrioxamine and alpha-phenyl N-tert butylnitrone, the known antioxidants having antiulcer effect. Standardisation of the bioactive extract by high pressure liquid chromatography indicates that peak 1 of the chromatogram coincides with the major bioactive compound, a phenolic glycoside, isolated from the extract. The pharmacological effects of the bark extract are attributed to a phenolic glycoside which is apparently homogeneous by HPLC and which represents 10% of the raw bark extract. A single dose of 1g of raw extract per kg b.w. (mice) given in one day and application of 0.6g raw extract per kg b.w. per day by oral route over 15 days to a cumulative dose of 9g per kg was well tolerated and was below the LD(50). It is also well tolerated by rats with no significant adverse effect. It is concluded that Neem bark extract has therapeutic potential for the control of gastric hyperacidity and ulcer.

Divergent effects of new cyclooxygenase inhibitors on gastric ulcer healing: Shifting the angiogenic balance

Delayed gastric ulcer healing is a well recognized problem associated with the use of cyclooxygenase (COX) inhibitors. In contrast, NO-releasing COX inhibitors do not interfere with ulcer healing. These divergent effects may in part be due to differences in their effects on platelets, which are known to influence ulcer healing. Therefore, we compared the effects of a nonselective COX inhibitor (flurbiprofen), a nitric oxide-releasing COX inhibitor (HCT-1026), and a selective COX-2 inhibitor (celecoxib) on gastric ulcer healing, angiogenesis, and platelet/serum levels of vascular endothelial growth factor (VEGF) and endostatin. Gastric ulcers were induced in rats by serosal application of acetic acid. Daily treatment with the test drugs was started 3 days later and continued for 1 week. Celecoxib and flurbiprofen impaired angiogenesis and delayed ulcer healing, as well as increasing serum endostatin levels relative to those of VEGF. HCT-1026 did not delay ulcer healing nor impair angiogenesis, and also did not change the ratio of serum endostatin to VEGF. Incubation of human umbilical vein endothelial cells with serum from celecoxib- or flurbiprofen-treated rats resulted in suppressed proliferation and increased apoptosis, effects that were reversed by an antiendostatin antibody. These results demonstrate a previously unrecognized mechanism through which nonsteroidal antiinflammatory drugs can delay ulcer healing, namely, through altering the balance of anti- and proangiogenic factors in the serum. The absence of a delaying effect of HCT-1026 on ulcer healing may be related to the maintenance of a more favorable balance in serum levels of pro- and antiangiogenic growth factors.

Gastric damage induced by subchronic administration of preferential cyclooxygenase-1 and cyclooxygenase-2 inhibitors in rats

Nonsteroidal anti-inflammatory drugs (NSAIDs) are well known to induce gastrointestinal damage including bleeding, ulceration and perforation in humans and animals. The aim of this study was to compare the effects of two oxicams, preferential cyclooxygenase (COX)-1 or COX-2 inhibitors, on both gastric mucosa and some biological parameters (hematological, hepatic and renal) after subchronic administration (14 and 28 days) in rats. Neutrophil infiltration was also assessed. Equipotent doses of meloxicam (3.75 and 7.5 mg/kg) and piroxicam (5 and 10 mg/kg) were administered. Both drugs dose-dependently caused multiple gastric erosions and hemorrhage in rats after 14 and 28 days of administration. Treatment with meloxicam led to a higher gastric damage than with piroxicam on day 14 although these results were not significant. The levels of myeloperoxidase activity (as an index of neutrophil infiltration) were not changed compared with control after drug treatment. All the hematological parameters obtained after drugs administration for 14 and 28 days were in the range of normal values, and a significant increase in platelet levels could be observed in the group treated with 5 mg/kg of piroxicam for 14 days. Aspartate aminotransferase (AST or GOT) increased significantly after 14 days, but after 28 days the values returned to normality. Creatinine and urea did not undergo significant changes except for the piroxicam 14-day 5 mg/kg group, in which uremia increased significantly over normal values. In conclusion, our results show that meloxicam, a preferential COX-2 inhibitor, causes rates of gastric lesion comparable to those seen with traditional NSAIDs, without inducing important changes in biological parameters.

Induction of COX-2 by LPS in macrophages is regulated by Tpl2-dependent CREB activation signals

Macrophage activation by bacterial lipopolysaccharide (LPS) promotes the secretion of pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta), and of secondary mediators, such as leukotrienes and prostaglandins (PGs). Mice lacking the gene encoding the serine/threonine protein kinase Tpl2/Cot produce low levels of TNF-alpha in response to LPS because of an ERK-dependent post-transcriptional defect, and they are resistant to LPS/D-galactosamine-induced endotoxin shock. In this study we demonstrate that prostaglandin E2 and its regulatory enzyme, COX-2, are also targets of Tpl2-transduced LPS signals in bone marrow-derived mouse macrophages. Thus, LPS-stimulated Tpl2(-/-) macrophages express low levels of COX-2 and PGE2, compared with wild-type Tpl2(+/+) cells. The ability of Tpl2 to regulate COX-2 expression depends on ERK signals that activate p90Rsk and Msk1, which in turn phosphorylate CREB, a key regulator of COX-2 transcription. These data identify physiological targets of Tpl2 signaling downstream of ERK and further implicate Tpl2 in the pathophysiology of inflammation.

Mechanisms and future directions for angiogenesis-based cancer therapies

Targeting angiogenesis represents a new strategy for the development of anticancer therapies. New targets derived from proliferating endothelial cells may be useful in developing anticancer drugs that prolong or stabilize the progression of tumors with minimal systemic toxicities. These drugs may also be used as novel imaging and radiommunotherapeutic agents in cancer therapy. In this review, the mechanisms and control of angiogenesis are discussed. Genetic and proteomic approaches to defining new potential targets on tumor vasculature are then summarized, followed by discussion of possible antiangiogenic treatments that may be derived from these targets and current clinical trials. Such strategies involve the use of endogenous antiangiogenic agents, chemotherapy, gene therapy, antiangiogenic radioligands, immunotherapy, and endothelial cell-based therapies. The potential biologic end points, toxicities, and resistance mechanisms to antiangiogenic agents must be considered as these therapies enter clinical trials.

The cyclo-oxygenase-2 inhibitor celecoxib perturbs intracellular calcium by inhibiting endoplasmic reticulum Ca2+-ATPases: a plausible link with its anti-tumour effect and cardiovascular risks

Substantial evidence indicates that the cyclo-oxygenase-2 (COX-2) inhibitor celecoxib, a widely prescribed anti-inflammatory agent, displays anti-tumour effect by sensitizing cancer cells to apoptosis. As part of our effort to understand the mechanism by which celecoxib mediates apoptosis in androgen-independent prostate cancer cells, we investigated its effect on intracellular calcium concentration ([Ca(2+)](i)). Digital ratiometric imaging analysis indicates that exposure of PC-3 cells to celecoxib stimulates an immediate [Ca(2+)](i) rise in a dose- and time-dependent manner. Kinetic data show that this Ca(2+) signal arises from internal Ca(2+) release in conjunction with external Ca(2+) influx. Examinations of the biochemical mechanism responsible for this Ca(2+) mobilization indicate that celecoxib blocks endoplasmic reticulum (ER) Ca(2+)-ATPases. Consequently, inhibition of this Ca(2+) reuptake mechanism results in Ca(2+) mobilization from ER stores followed by capacitative calcium entry, leading to [Ca(2+)](i) elevation. In view of the important role of Ca(2+) in apoptosis regulation, this Ca(2+) perturbation may represent part of the signalling mechanism that celecoxib uses to trigger rapid apoptotic death in cancer cells. This Ca(2+)-ATPase inhibitory activity is highly specific for celecoxib, and is not noted with other COX inhibitors tested, including aspirin, ibuprofen, naproxen, rofecoxib (Vioxx), DuP697 and NS398. Moreover, it is noteworthy that this activity is also observed in many other cell lines examined, including A7r5 smooth muscle cells, NIH 3T3 fibroblast cells and Jurkat T cells. Consequently, this Ca(2+)-perturbing effect may provide a plausible link with the reported toxicities of celecoxib such as increased cardiovascular risks in long-term anti-inflammatory therapy.

Angiogenic markers, neovascularization and malignant deformation of Barrett's esophagus

The molecular events underlying progression of Barrett's esophagus to adenocarcinoma remain an area of active investigation. Neovascularization and angiogenesis have been studied in esophageal adenocarcinomas by counting of microvessels after staining with vascular markers, and by immunohistochemistry for vascular endothelial growth factor. Angiogenesis appears to be increased early in the neoplastic process, but has poor prognostic value. We have demonstrated that expression levels of two important genes that regulate cell growth, namely inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, are frequently upregulated in Barrett's esophagus and associated adenocarcinomas. COX-2 expression may be related to reflux of bile salts, which induce COX-2 expression in Barrett's tissues and esophageal adenocarcinoma cells in vitro. COX-2 inhibition induces apoptosis and blocks proliferation in COX-2-expressing esophageal adenocarcinoma cells in vitro, and blocks angiogenesis in both in vivo and in vitro models. Although controversial, recent evidence suggest that iNOS-derived NO can inhibit angiogenesis in some model systems. In conclusion, both iNOS and COX-2 appear to be involved in Barrett's-associated neoplastic progression, but COX-2 inhibition is more promising as a chemopreventive strategy. COX-2 inhibition may exert beneficial effects by decreasing angiogenesis and epithelial proliferation, and by facilitating apoptosis of epithelial cells that have undergone DNA damage.

Nonsteroidal anti-inflammatory drugs inhibit matrix metalloproteinase-2 via suppression of the ERK/Sp1-mediated transcription

Our previous data showed that nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit matrix metalloproteinase-2 (MMP-2) expression via repression of gene transcription in lung cancer cells. In this study, we investigate the molecular mechanism by which NSAIDs inhibit MMP-2. Promoter deletion and mutation analysis indicate that NSAIDs act via the Sp1 transcription factor binding site located between -91 and -84 in the MMP-2 promoter to suppress gene expression. Electrophoretic mobility shift assays show that Sp1 and Sp3 proteins constitutively bind to this consensus sequence and overexpression of Sp1 may enhance MMP-2 expression. NSAID treatment reduces Sp1 DNA binding activity and phosphorylation and attenuates MMP-2 expression. We also investigate the signaling pathway that mediates the effect of NSAIDs. Our results suggest that ERKs are involved in this process. First, NSAIDs suppress basal and serum-stimulated ERK activity. Second, a MEK inhibitor PD98059 inhibits MMP-2 promoter activity and Sp1 phosphorylation. Third, overexpression of constitutively active MEK1 stimulates Sp1 phosphorylation and MMP-2 promoter activity and antagonizes the inhibition of NSAIDs. Collectively, our data suggest that NSAIDs inhibit MMP-2 by blocking ERK/Sp1-mediated transcription.

Novel target for induction of apoptosis by cyclo-oxygenase-2 inhibitor SC-236 through a protein kinase C-beta(1)-dependent pathway

Nonsteroidal anti-inflammatory drugs (NSAIDs) reduce the risk of gastrointestinal cancers. Recently, a similar protective effect has been demonstrated by the specific cyclo-oxygenase-2 (COX-2) inhibitors. However, the exact mechanism that accounts for the anti-proliferative effect of specific COX-2 inhibitors is still not fully understood, and it is still controversial whether these protective effects are predominantly mediated through the inhibition of COX-2 activity and prostaglandin synthesis. Identification of molecular targets regulated by COX-2 inhibitors could lead to a better understanding of their pro-apoptotic and anti-neoplastic activities. In the present study, we investigated the effect and the possible molecular target of a COX-2-specific inhibitor SC-236 on gastric cancer. We showed that SC-236 induced apoptosis in gastric cancer cells. However, this effect was not dependent on COX-2 inhibition. SC-236 down-regulated the protein expression and kinase activity of PKC-beta(1), increased the expression of PKCdelta and PKCeta, but did not alter the expression of other PKC isoforms in AGS cells. Moreover, exogenous prostaglandins or PGE(2) receptor antagonists could not reverse the inhibition effect on PKCbeta(1) by SC-236, which suggested that this effect occurred through a mechanism independent of cyclo-oxygenase activity and prostaglandin synthesis. Overexpression of PKCbeta(1) attenuated the apoptotic response of AGS cells to SC-236 and was associated with overexpression of p21(waf1/cip1). Inhibition of PKCbeta(1)-mediated overexpression of p21(waf1/cip1) partially reduced the anti-apoptotic effect of PKCbeta(1). The down-regulation of PKCbeta(1) provides an explanation for COX-independent apoptotic effects of specific COX-2 inhibitor in cultured gastric cancer cells. We also suggest that PKCbeta(1) act as survival mediator in gastric cancer, and its down-regulation by COX-2 inhibitor SC-236 may provide new target for future treatment of gastric cancer.

Inflammation and cancer, the mastocytoma P815 tumor model revisited: triggering of macrophage activation in vivo with pro-tumorigenic consequences

Subcutaneous in vivo injections of cells of the mastocytoma line P815 in syngenic DBA/2 mice induce locally fast growing solid tumors. These have been used extensively as a cancer model to analyze and manipulate the relationship between tumor cells and host's immune defenses. We report that progression of P815 tumors in vivo was accompanied by a burst (Days 5-7) of local inflammatory cells recruitment and angiogenesis observed histologically, corroborated in vivo by MRI with gadolinium, overtranscription of macrophage activation marker genes, secretion of TNF-alpha by regional lymph node cells and concomitant systemic inflammation. No substantial overtranscriptions of either VEGF or IL-10 or TGF-beta genes were observed. Induction of COX-2 gene was a late event. To establish a possible relationship between the tumor-induced local, regional and systemic increase of pro-inflammatory mediators and progression of tumors in vivo, we carried out experiments deliberately modulating the inflammatory status of the recipient animals. Pretreatment of recipient animals by i.p. injection of thioglycolate accelerated P815 tumor growth. At the opposite, treatment of mice with either a COX-1 + COX-2 inhibitor (aspirin, 1 mg/day/mouse) or a specific COX-2 inhibitor (celecoxib, 0.13 mg/day/mouse) for 2 weeks after injection of tumor cells, significantly reduced the size and growth rate of tumors compared to control mice. Experiments carried out in vitro indicated that peritoneal macrophages from untreated animals were strongly activated by live P815 cells and by P815 membrane preparations. The tumor-induced inflammatory reaction could establish a local micro environment favoring tumor progression. The P815 tumor model might be helpful to recognize important factors controlling host/tumor relationship.

Purification and characterization of a cyclooxygenase-2 and angiogenesis suppressing factor produced by human fibroblasts

Cyclooxygenase-2 (COX-2) is an inducible enzyme that plays an important role in several pathophysiological processes, including inflammation, angiogenesis, and tumorigenesis. We have recently observed that COX-2 induction is restrained in proliferating fibroblasts. The mechanism by which this occurs is unclear. Here, we report the detection and isolation from the conditioned medium of proliferating fibroblasts a factor that suppressed COX-2 expression. This factor, which was named cytoguardin, suppressed COX-2 protein levels induced by phorbol 12-myristate 13-acetate, interleukin-1beta, tumor necrosis factor alpha, and lipopolysaccharide (LPS) in fibroblasts and LPS-induced COX-2 protein levels and promoter activities in human endothelial cells and murine RAW 264.7 cells in a comparable concentration-dependent manner. It inhibited COX-2 expression induced by angiogenic factors and endothelial tube formation induced by angiogenic factors and colon cancer cell medium. These findings provide evidence for the control of COX-2 transcription by an endogenous cellular factor.

Cyclooxygenases and colon cancer

There is considerable interest in the involvement of cyclooxygenase-2 (COX-2) in colon carcinogenesis and its progression, because nonsteroidal anti-inflammatory drugs (NSAIDs) reduce mortality from colon cancer and COX-2 is one of the known targets of NSAIDs. COX-2 mRNA and protein levels are increased in colon cancer tissues from patients and in some colon cancer cell lines. The relationship between COX-2 and colon cancer is further confirmed by studies using the murine models of adenomatous polyposis coli, in which NSAIDs and gene knockouts reduce the number of spontaneously developing intestinal polyps. COX-2 expression in intestinal epithelial cells increases resistance to apoptosis, promotes tumor angiogenesis, and enhances invasion and metastasis. COX-2 expression in stromal cells appears to have a role in tumor angiogenesis because tumor growth is attenuated when colon cancer cells are implanted in COX-2 knockout mice due to a decreased vascular supply to the tumors. Although NSAIDs act via COX-2 to inhibit colon cancer growth, there also appear to be COX-2 independent actions for NSAIDs. COX-2 selective inhibitors can be the core drugs for the prevention and the treatment of colon cancer.

Prognostic significance of cyclooxygenase-2 pathway and angiogenesis in head and neck squamous cell carcinoma

Prostaglandins play a critical role in tumor development and growth by regulating numerous biologic processes, including tumor angiogenesis, with clear prognostic and therapeutic implications. The aim of this study was to investigate the prognostic relevance of cyclooxygenase-2 (COX-2) pathway activation in head and neck squamous cell carcinoma (HNSCC). COX-2 activity was analyzed in 52 consecutive patients by assessing protein expression and prostaglandin E(2) (PgE(2)) levels and was then correlated to vascular endothelial growth factor (VEGF) expression and tumor angiogenesis. We evaluated the prognostic impact of these parameters by Kaplan-Meier and Cox survival analysis. COX-2 expression by tumor cells was closely correlated to VEGF expression and to tumor vascularization. According to Kaplan-Meier analysis, patients with COX-2 tumor overexpression and with higher PgE(2) tumor levels had significantly shorter overall survival estimates (P = 0.022 and P = 0.033, respectively). Analogously, patients with more-vascularized tumors had worse survival than those with less-vascularized cancers (P = 0.032). Cox multivariate analysis demonstrated that the most significant prognostic factors were presence of lymph node metastasis, tumor vascularization, COX-2 protein expression, and PgE(2) tumor levels. This study demonstrates a close correlation between COX-2 pathway, VEGF expression, and tumor angiogenesis in HNSCC. In addition, COX-2 overexpression and higher tumor vascularization appear to predict a shorter survival in patients with head and neck cancer.

Cellular and molecular mechanisms responsible for progression of Barrett's metaplasia to esophageal carcinoma

Barrett's metaplasia is found in approximately 12% to 18% of patients undergoing upper endoscopy for symptoms of reflux. Barrett's metaplasia is a premalignant condition and remains the number one risk factor for developing esophageal adenocarcinoma. There has been an increase in the incidence of esophageal adenocarcinoma in the past two decades, making it the most rapidly rising cancer in the United States and Western Europe. This article describes the progression from Barrett's metaplasia to esophageal adenocarcinoma and predictors for the development of adenocarcinoma in Barrett's metaplasia. Barrett's metaplasia represents a histological mosaic, with dysplastic tissue adjacent to non-dysplastic tissue. The histologic changes leading to adenocarcinoma are accompanied by alterations at the molecular level, including the accumulation of gene mutations and changes in gene expression. The determination of the molecular events that occur in the transition from normal esophageal squamous mucosa to dysplasia and to esophageal adenocarcinoma have lead to a better understanding of the process of the transformation to adenocarcinoma. This knowledge will lead to better biomarkers to diagnose and assess cancer risk.

Factors influencing results and outcome after transmyocardial laser revascularization

BACKGROUND

Transmyocardial laser revascularization (TMR) has been increasingly used during the recent past for patients with diffuse coronary artery disease. Because this operation is associated with significant morbidity and mortality, it is important to select patients for TMR who are likely to benefit from the procedure.

METHODS

We performed an univariate logistic regression analysis of 20 factors on the benefits and outcomes of 134 patients who underwent isolated TMR at our institution between November 1994 and May 2000.

RESULTS

Responders and nonresponders differed significantly with regard to the incidence of diabetes mellitus. For diabetic patients the chance of profiting from the TMR operation was only 43% of that of nondiabetic patients (odds ratio = 0.43 [0.20 to 0.92]). Furthermore, patients with a preoperative body mass index of less than 25 had a threefold increase in the probability of death during the first year after TMR as compared to patients whose body mass index was 25 or more (odds ratio = 2.97 [1.05 to 8.40]). The incidence of diabetes was also slightly but not significantly different between 1-year survivors and nonsurvivors.

CONCLUSIONS

In diabetic patients we recommend caution in selecting therapeutic TMR because outcomes are less satisfactory than in nondiabetics. Furthermore, patients with a body mass index below 25 have a significantly higher risk for death during the first postoperative year. Studies based on larger patient populations should follow.

Cyclo-oxygenase 2 function is essential for bone fracture healing

Despite the molecular and histological similarities between fetal bone development and fracture healing, inflammation is an early phase of fracture healing that does not occur during development. Cyclo-oxygenase 2 (COX-2) is induced at inflammation sites and produces proinflammatory prostaglandins. To determine if COX-2 functions in fracture healing, rats were treated with COX-2-selective nonsteroidal anti-inflammatory drugs (NSAIDs) to stop COX-2-dependent prostaglandin production. Radiographic, histological, and mechanical testing determined that fracture healing failed in rats treated with COX-2-selective NSAIDs (celecoxib and rofecoxib). Normal fracture healing also failed in mice homozygous for a null mutation in the COX-2 gene. This shows that COX-2 activity is necessary for normal fracture healing and confirms that the effects of COX-2-selective NSAIDs on fracture healing is caused by inhibition of COX-2 activity and not from a drug side effect. Histological observations suggest that COX-2 is required for normal endochondral ossification during fracture healing. Because mice lacking Cox2 form normal skeletons, our observations indicate that fetal bone development and fracture healing are different and that COX-2 function is specifically essential for fracture healing.

Inhibition of programmed cell death impairs in vitro vascular-like structure formation and reduces in vivo angiogenesis

Tissue remodeling during embryonic development and in the adult organism relies on a subtle balance between cell growth and apoptosis. As angiogenesis involves restructuring of preexisting endothelium, we examined the role of apoptosis in new vessel formation. We show that apoptosis occurs before capillary formation but not after vessels have assembled. Using the human umbilical vein endothelial cell (HUVEC) in vitro Matrigel angiogenesis model, we show that vascular-like structure formation requires apoptotic cell death through activation of a caspase-dependent mechanism and mitochondrial cytochrome c release. Vascular-like structure formation was further blocked by caspase inhibitors such as z-VAD or Ac-DEVD-CHO, using HUVEC and human lung microvascular endothelial cells. Overexpression of anti-apoptotic human Bcl-2 or baculovirus p35 genes in HUVEC altered endothelial cell rearrangement during in vitro angiogenesis, causing impaired vessel-like structure formation. Caspase inhibitors blocked VEGF- or bFGF-induced HUVEC angiogenesis on 2- or 3-D collagen gels, respectively, confirming that apoptosis was not the result of nonspecific cell death after seeding on the matrix. In an in vivo angiogenesis assay, caspase inhibitors blocked VEGF-dependent vascular formation at the alignment step, as demonstrated histologically. This evidence indicates that endothelial cell apoptosis may be relevant for precise vascular tissue rearrangement in in vitro and in vivo angiogenesis.

Indomethacin delays gastric restitution: association with the inhibition of focal adhesion kinase and tensin phosphorylation and reduced actin stress fibers

Repair of superficial gastric mucosal injury is accomplished by the process of restitution-migration of epithelial cells to restore continuity of the mucosal surface. Actin filaments, focal adhesions, and focal adhesion kinase (FAK) play crucial roles in cell motility essential for restitution. We studied whether epidermal growth factor (EGF) and/or indomethacin (IND) affect cell migration, actin stress fiber formation, and/or phosphorylation of FAK and tensin in wounded gastric monolayers. Human gastric epithelial monolayers (MKN 28 cells) were wounded and treated with either vehicle or 0.5 mM IND for 16 hr followed by EGF. EGF treatment significantly stimulated cell migration and actin stress fiber formation, and increased FAK localization to focal adhesions, and phosphorylation of FAK and tensin, whereas IND inhibited all these at the baseline and EGF-stimulated conditions. IND-induced inhibition of FAK phosphorylation preceded changes in actin polymerization, indicating that actin depolymerization might be the consequence of decreased FAK activity. In in vivo experiments, rats received either vehicle or IND (5 mg/kg i.g.), and 3 min later, they received water or 5% hypertonic NaCl; gastric mucosa was obtained at 1, 4, and 8 hr after injury. Four and 8 hr after hypertonic injury, FAK phosphorylation was induced in gastric mucosa compared with controls. IND pretreatment significantly delayed epithelial restitution in vivo, and reduced FAK phosphorylation and recruitment to adhesion points, as well as actin stress fiber formation in migrating surface epithelial cells. Our study indicates that FAK, tensin, and actin stress fibers are likely mediators of EGF-stimulated cell migration in wounded human gastric monolayers and potential targets for IND-induced inhibition of restitution.

Cyclooxygenase-2: a therapeutic target

Cyclooxygenase (COX), also known as prostaglandin endoperoxide synthase, is the key enzyme required for the conversion of arachidonic acid to prostaglandins. Two COX isoforms have been identified, COX-1 and COX-2. In many situations, the COX-1 enzyme is produced constitutively (e.g., in gastric mucosa), whereas COX-2 is highly inducible (e.g., at sites of inflammation and cancer). Traditional nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit both enzymes, and a new class of COX-2 selective inhibitors (COXIBs) preferentially inhibit the COX-2 enzyme. This review summarizes our current understanding of the role of COX-1 and COX-2 in normal physiology and disease.

Selective cyclooxygenase-2 inhibition impairs glomerular capillary healing in experimental glomerulonephritis

Selective cyclooxygenase-2 (COX-2) inhibitors have anti-inflammatory activity and reduce proteinuria in experimental membranous glomerulonephritis. Antiangiogenic properties of COX-2 inhibitors were recently reported. Whether these properties are relevant to the glomerular healing process in inflammatory glomerular diseases was investigated. For evaluation of the effects of selective COX-2 inhibitors on the glomerular healing process in a rat model of mesangioproliferative glomerulonephritis (induced by anti-Thy 1.1 antibody), a selective COX-2 inhibitor (rofecoxib or celecoxib) or vehicle was administered daily from day 1 after disease induction until euthanasia on day 6. Additional nephritic rats were treated with rofecoxib or vehicle from day 1 to day 10 and were monitored until day 28. Selective COX-2 inhibition led to significant increases in mesangiolysis (up to +71%) on days 2 and 6 and in albuminuria (up to 3.1-fold) on day 6. This augmentation of glomerular capillary damage was associated with rarefaction of glomerular endothelial cells, whereas the proliferation and activation of mesangial cells were not affected. No significant effects on the glomerular influx of polymorphonuclear neutrophils or the infiltration and proliferation of monocytes/macrophages at day 2 were noted. These effects were independent of systemic hemodynamic features, because rofecoxib did not affect systolic BP on day 2 or 5. Nephritic rats treated with rofecoxib for 10 d demonstrated persistent glomerular injury at day 28, as indicated by increased albuminuria (10-fold) and mesangial type IV collagen deposition (+24%). In normal rats, 5-d administration of rofecoxib failed to induce albuminuria or morphologic renal damage. In conclusion, selective COX-2 inhibitors impair glomerular capillary repair after mesangiolysis in rats with anti-Thy 1.1 glomerulonephritis. These data suggest that selective COX-2 inhibitors should be used with caution among patients with inflammatory endocapillary glomerular disorders.

Aspirin and NS-398 inhibit hepatocyte growth factor-induced invasiveness of human hepatoma cells

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit cyclooxygenase (COX) activity and are considered to exert antitumor actions in a variety of cancer cells, although the effects are unlikely entirely due to COX inhibition. Because clinical observations suggest that hepatocyte growth factor (HGF) can promote metastasis of hepatoma cells while stimulating tumor invasiveness, we investigated the effect of aspirin and NS-398, a selective COX-2 inhibitor, on HGF-mediated invasiveness of HepG2 human hepatoma cells. HGF stimulated the invasiveness of HepG2 cells in Matrigel cell invasion assay, together with increased expression of matrix metalloproteinase (MMP) 9. Addition of aspirin or NS-398, similar to PD98059, which acts as a specific inhibitor of mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK), an upstream kinase regulating extracellular signal-regulated kinase (ERK)1/2, abrogated such actions of HGF without affecting cell viability. Aspirin and NS-398, in contrast to PD98059, did not suppress ERK1/2 phosphorylation induced by HGF. However, both agents inhibited the kinase activity of ERK1/2 induced by HGF and repressed HGF-induced phosphorylation of 90-kd ribosomal S6 kinase (RSK) and Elk-1, key downstream substrates of ERK1/2, resulting in the suppression of transcriptional activity of Elk-1 as well as nuclear factor kappaB (NF-kappaB) and AP-1, which are involved in MMP-9 gene regulation. In conclusion, our results suggest that aspirin and NS-398 inhibit HGF-induced invasiveness of HepG2 human hepatoma cells through ERK1/2.

Chemoprevention of gastrointestinal malignancies with nonsteroidal antiinflammatory drugs

In multiple studies, the chronic use of nonsteroidal antiinflammatory drugs (NSAIDs) has been associated with a decreased incidence of several types of gastrointestinal (GI) neoplasia. This effect may be mediated by one of several intracellular mechanisms, some of which involve the inhibition of the cyclooxygenase-2 (COX-2) isoenzyme. In multiple studies of colorectal carcinoma, chronic NSAID use has shown a protective effect, with the majority of studies demonstrating a 30-70% risk reduction associated with NSAID use. The effect of NSAIDs on other types of GI neoplasia is less clear, but evidence suggests that chronic NSAID use may diminish the risk of esophageal and gastric carcinomas. Data assessing the effects of NSAIDs on the incidence of pancreatic and hepatic malignancies currently are too sparse and inconsistent to draw any conclusions. The newer COX-2 specific agents may provide a less GI-toxic alternative to nonselective NSAIDs as chemoprotective agents.

Inhibition of proliferation of gastric epithelial cells by a cyclooxygenase 2 inhibitor, JTE522, is also mediated by a PGE2-independent pathway

BACKGROUND

Cyclooxygenase-2 (COX-2) is one of the rate-limiting enzymes for prostaglandin synthesis from arachidonic acid. Although it is known that inhibition of cyclooxygenase activity delays ulcer healing, the regulatory relationship between COX-2 and its metabolites in gastric epithelial cell proliferation is not well known.

AIM

To investigate whether COX-2 has an effect on gastric mucosal cell proliferation and further studied whether such effect is mediated only by prostaglandin E2 (PGE2), a representative metabolite of arachidonates in the gastric mucosa.

METHODS

Artificial wounds of defined area size were created on complete monolayer cell sheets of isolated rat gastric epithelial cells and rat gastric cell line RGM1 under the addition of arachidonic acid or a COX-2 selective inhibitor, JTE522. Repair of wounds was assessed by monitoring wound size, with cell proliferation detected using 5-bromodeoxyuridine staining. Quantity of secreted PGE2 was measured by enzyme immunoassay.

RESULTS

Stimulation of foetal calf serum increased the expression of COX-2 protein and inhibition of COX-2 retarded wound healing with reduction of cell proliferation. Arachidonic acid increased PGE2 production and accelerated restoration. Combination of JTE522 and arachidonic acid resulted in a marked retardation of wound healing compared to the control, but JTE522 did not completely suppress the increase in cellular PGE2 content following the addition of arachidonate.

CONCLUSIONS

The difference in the effects of JTE522 on PGE2 production and on wound healing suggest that the involvement of COX-2 in gastric epithelial cell proliferation is not mediated solely by PGE2.

Frequent co-localization of Cox-2 and laminin-5 gamma2 chain at the invasive front of early-stage lung adenocarcinomas

Laminin-5 is an extracellular matrix protein that plays a key role in cell migration and tumor invasion. Cox-2 is an induced isoform of cyclooxygenases that plays an important role in carcinogenesis, suppression of apoptosis, angiogenesis, and metastasis of colon cancer. We report frequent co-expression of cox-2 and laminin-5 at the invasive front of early-stage lung adenocarcinomas. We investigated the expression of cox-2 and laminin-5 immunohistochemically in 102 cases of small-sized lung adenocarcinoma (maximum dimension, 2 cm or less). Cox-2 and laminin-5 were expressed in 97 (95.1%) and 82 (80.4%) cases, respectively. Both were preferentially localized in cancer cells at the cancer-stroma interface, although cox-2 tended to show a diffuse staining pattern in some cases. A comparison of their staining patterns revealed a striking similarity in their distribution in 24 cases, and a partial overlap between their localization in another 20 cases. Moreover, an overall correlation was found between the expression levels of cox-2 and laminin-5 (P = 0.018). To gain insight into the mechanisms that regulate the expression of these proteins, we additionally studied their expression in 58 cases of stage I lung adenocarcinoma, in which p53 status was determined by immunohistochemistry, polymerase chain reaction-single strand conformation polymorphism analysis, and direct sequencing. The results showed that tumors with mutant p53 tended to express more cox-2 than those with wild-type p53 (P = 0.080). Also, tumors that overexpressed p53 had higher levels of cox-2 and laminin-5 than those without p53 overexpression (P = 0.032 and 0.047, respectively). Further immunohistochemical analysis showed that tumors that overexpressed both epidermal growth factor receptor (EGFR) and erbB-2 had higher levels of cox-2 and laminin-5 than those without concomitant overexpression of these proteins (P = 0.014 and P = 0.018, respectively). To see whether EGFR signaling is involved in cox-2 and laminin-5 expression, we further conducted in vitro analyses using six lung adenocarcinoma cell lines (A549, HLC-1, ABC-1, LC-2/ad, VMRC-LCD, and L27). Western blot analyses showed that cox-2 mRNA levels, and to a lesser extent laminin-5 gamma2 mRNA levels, correlated with the expression levels of erbB-2 and the phosphorylated form of MAPK/ERK-1/2 protein. The addition of transforming growth factor-alpha increased both cox-2 and laminin-5 gamma2 mRNA levels in A549, ABC-1, and L27 with different kinetics; the induction of cox-2 occurred earlier than that of laminin-5 gamma2. Finally, the migration of ABC-1 cells was inhibited by MAP kinase kinase inhibitor PD98059 and a selective cox-2 inhibitor NS-398. In contrast, the migration of A549 cells was inhibited by PD98059, but much less effectively by NS-398. These results suggest that co-stimulatory mechanisms may exist that increase the expression of cox-2 and laminin-5 at the invasive front of lung adenocarcinomas and that EGFR signaling could be one of the mechanisms. Further investigations are warranted concerning the role of cox-2 and laminin-5 in cancer cell invasion and the significance of p53 and EGFR signaling in the regulation of cox-2 and laminin-5 expression.

NSAID inhibition of GI cancer growth: clinical implications and molecular mechanisms of action

Epidemiological studies suggest that aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) reduce the incidence of and mortality from colorectal, gastric, and esophageal cancers. The precise mechanisms by which NSAIDs exert their chemopreventive effects are not fully explained, but likely involve inhibition of cyclo-oxygenase, the enzyme that converts arachidonic acid to prostaglandins. Two isoforms of this enzyme, cyclo-oxygenase 1 (COX-1) and COX-2, have been identified. COX-2 is absent in normal mucosa but is overexpressed in colonic, gastric, and esophageal cancers, as well as their precursor lesions. The inhibition of COX-2 through either pharmacological agents or gene deletion results in suppression of colonic polyp formation. NSAIDs reduce colonic, gastric, and esophageal cancer cell growth, in part, by inducing apoptosis. However, the antineoplastic effects of NSAIDs may be partly independent of their ability to inhibit COX-2. The mechanisms involved in the antineoplastic actions of NSAIDs include inhibition of angiogenesis (essential for delivery of oxygen and nutrients to a growing tumor), induction of apoptosis (which is usually reduced in cancer cells) by stimulation of proapoptotic genes, and direct inhibition of cancer cell growth by blocking signal transduction pathways responsible for cell proliferation.