Enhanced cyclooxygenase-2 expression in sporadic and familial adenomatous polyposis of the human colon

Butyric acid and prospects for creation of new medicines based on its derivatives: a literature review

The widespread use of antimicrobials causes antibiotic resistance in bacteria. The use of butyric acid and its derivatives is an alternative tactic. This review summarizes the literature on the role of butyric acid in the body and provides further prospects for the clinical use of its derivatives and delivery methods to the animal body. Thus far, there is evidence confirming the vital role of butyric acid in the body and the effectiveness of its derivatives when used as animal medicines and growth stimulants. Butyric acid salts stimulate immunomodulatory activity by reducing microbial colonization of the intestine and suppressing inflammation. Extraintestinal effects occur against the background of hemoglobinopathy, hypercholesterolemia, insulin resistance, and cerebral ischemia. Butyric acid derivatives inhibit histone deacetylase. Aberrant histone deacetylase activity is associated with the development of certain types of cancer in humans. Feed additives containing butyric acid salts or tributyrin are used widely in animal husbandry. They improve the functional status of the intestine and accelerate animal growth and development. On the other hand, high concentrations of butyric acid stimulate the apoptosis of epithelial cells and disrupt the intestinal barrier function. This review highlights the biological activity and the mechanism of action of butyric acid, its salts, and esters, revealing their role in the treatment of various animal and human diseases. This paper also discussed the possibility of using butyric acid and its derivatives as surface modifiers of enterosorbents to obtain new drugs with bifunctional action.

An increased CD25-positive intestinal regulatory T lymphocyte population is dependent upon Cox-2 activity in the Apcmin/+ model

Only mismatch repair (MMR)-deficient colorectal cancer (CRC) appears to respond well to programmed death (PD)-1 inhibition at the present time. Emerging evidence suggests a role for micro-environmental factors such as CD25⁺ cells modulating response to PD-1 inhibition. In the Apc^Min/+ model of familial adenomatous polyposis (MMR-proficient CRC), increased Cyclooxygenase-2 (Cox-2) expression by cells which include alternatively activated mononuclear phagocytes promotes intestinal tumorigenesis by mechanisms which may include immune suppression. To gain insight into this, we compared regulatory T cell (T_reg ) populations between Apc^Min/+ and wild-type mice prior to and after the phase of increased intestinal Cox-2-dependent prostaglandin E₂ (PGE₂ ) production. There was no difference in systemic T_reg function or numbers between Apc^Min/+ and wild-type mice. However, increased numbers of small intestinal CD25⁺ T_regs were observed with increased Cox-2 activity in the absence of any difference in the expression of Tgf-β or Tslp between Apc^Min/+ and wild-type mice. Cox-2 inhibitor therapy (Celecoxib) reversed the increase in Apc^Min/+ intestinal CD25⁺ T_reg numbers, without decreasing numbers of CD25⁺ systemic T_regs . Forkhead box protein 3 (FoxP3⁺ ) and Cox-2⁺ cells were co-localized to the interstitium of adenomas of Apc^min/+ mice. These results suggest selective dependence of an 'activated T_reg ' phenotype on paracrine Cox-2 activity in Apc^Min/+ small intestine. For therapeutic potential, further studies are required to evaluate the relevance of these findings to human cancer as well as the functional significance of CD25⁺ intestinal T_regs in cancer.

Methanolic extract of Boswellia serrata exhibits anti-cancer activities by targeting microsomal prostaglandin E synthase-1 in human colon cancer cells

BACKGROUND

Colorectal cancer (CRC) is the most common cancer. A proper method to reduce mortality of CRC is chemoprevention to prevent initiation and promotion of intestinal tumorgenesis. One of the promising and developing chemopreventive agents is natural compounds found in plants. Frankincense, the resin extract from the Boswellia specious, has been used in traditional and modern medicine for treating various diseases with very minimal side effects. In the current study, we investigated the anti-cancer activity of methanolic extract of Boswellia serrata (B. serrata) on HT-29 human colon cancer cells.

METHODS

HT-29 cells were treated with different concentrations of B. serrata and cell viability was assessed by MTT assay. mRNA expression of microsomal prostaglandin E synthase-1 (mPGES-1), vascular endothelial growth factor (VEGF), C-X-C chemokine receptor type 4 (CXCR4), matrix metalloproteinase-2 (MMP-2), MMP-9 and hypoxia-inducible factor-1 (HIF-1) were examined by quantitative real-time PCR. Apoptosis was evaluated by the proportion of sub-G1 cells. Prostaglandin E2 (PGE2) level and caspase 3 activity were determined by ELISA assay. Tube formation potential and HT-29 cells migration were assessed using three-dimensional vessel formation assay and scratch test.

RESULTS

B. serrata extract considerably decreased the expression of mPGES-1, VEGF, CXCR4, MMP-2, MMP-9 and HIF-1. The caspase 3 activity and percent of cells in sub-G1 phase were increased by B. serrata extract. Cell viability, PGE2 generation, in vitro tube formation and cell migration were decreased significantly in B. serrata-treated HT-29 compared to the control group.

CONCLUSION

Our findings suggest that B. serrata extract inhibits proliferation, angiogenesis and migration and induces apoptosis in HT-29 cells by inhibiting of mPGES-1 and decreasing the PGE2 level and its downstream targets.

Effects of naproxen on cell proliferation and genotoxicity in MG-63 osteosarcoma cell line

The purpose of this study was to determine the efficacy of naproxen, a nonsteroidal anti-inflammatory drug, on the MG-63 human osteosarcoma cell line. MG-63 cells were exposed to naproxen in a wide range of concentrations of 0.03, 0.05, 0.1, 0.42, 0.83, and 1.67 mg/ml for 72 h. The activity of naproxen was assessed by the following assays: cell morphology; 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) method; terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay; comet assay; and acridine orange and monodansylcadaverine (MDC) staining. Naproxen exerted a significant inhibitory effect on MG-63 cell proliferation, in a concentration-dependent manner, in all treatment groups compared with untreated cells. An increase in frequency of DNA damage, apoptotic bodies, apoptotic cells, and autophagic vacuoles was observed in MG-63-treated cells. Although future studies are needed, these findings suggest that naproxen may lead to improvements in treatment of patients with osteosarcoma.

Mechanisms of the anti-cancer and anti-inflammatory actions of vitamin D

Calcitriol, the hormonally active form of vitamin D, is being evaluated in clinical trials as an anti-cancer agent. Calcitriol exerts multiple anti-proliferative, pro-apoptotic, and pro-differentiating actions on various malignant cells and retards tumor growth in animal models of cancer. Calcitriol also exhibits several anti-inflammatory effects including suppression of prostaglandin (PG) action, inhibition of p38 stress kinase signaling, and the subsequent production of pro-inflammatory cytokines and inhibition of NF-κB signaling. Calcitriol also decreases the expression of aromatase, the enzyme that catalyzes estrogen synthesis in breast cancer, both by a direct transcriptional repression and indirectly by reducing PGs, which are major stimulators of aromatase transcription. Other important effects include the suppression of tumor angiogenesis, invasion, and metastasis. These calcitriol actions provide a basis for its potential use in cancer therapy and chemoprevention. We summarize the status of trials involving calcitriol and its analogs, used alone or in combination with known anti-cancer agents.

Effects of intervention with sulindac and inulin/VSL#3 on mucosal and luminal factors in the pouch of patients with familial adenomatous polyposis

BACKGROUND/AIM

In order to define future chemoprevention strategies for adenomas or carcinomas in the pouch of patients with familial adenomatous polyposis (FAP), a 4-weeks intervention with (1) sulindac, (2) inulin/VSL#3, and (3) sulindac/inulin/VSL#3 was performed on 17 patients with FAP in a single center intervention study. Primary endpoints were the risk parameters cell proliferation and glutathione S-transferase (GST) detoxification capacity in the pouch mucosa; secondary endpoints were the short chain fatty acid (SCFA) contents, pH, and cytotoxicity of fecal water.

METHODS

Before the start and at the end of each 4-week intervention period, six biopsies of the pouch were taken and feces was collected during 24 h. Cell proliferation and GST enzyme activity was assessed in the biopsies and pH, SCFA contents, and cytotoxicity were assessed in the fecal water fraction. The three interventions (sulindac, inulin/VSL#3, sulindac/inulin/VSL#3) were compared with the Mann-Whitney U test.

RESULTS

Cell proliferation was lower after sulindac or VSL#3/inulin, the combination treatment with sulindac/inulin/VSL#3 showed the opposite. GST enzyme activity was increased after sulindac or VSL#3/inulin, the combination treatment showed the opposite effect. However, no significance was reached in all these measures. Cytotoxicity, pH, and SCFA content of fecal water showed no differences at all among the three treatment groups.

CONCLUSION

Our study revealed non-significant decreased cell proliferation and increased detoxification capacity after treatment with sulindac or VSL#3/inulin; however, combining both regimens did not show an additional effect.

Inherited Syndromes Predisposing to Inflammation and GI Cancer

Cancers arising within the gastrointestinal (GI) tract are commonly associated with an immune component at their inception and later in their maintenance. While many of the immune factors and immune cell types surrounding these lesions have been highlighted, the underlying pre-dispositions in immunesupported carcinogenesis are not well characterised. Inherited Mendelian GI disorders such as polyposis syndromes, while classically due to germline mutations in non-immune genes, commonly demonstrate alterations in key immune and inflammatory genes. In some cases immune based therapies have been shown to provide at least some benefit in animal models of these syndromes. The advent of genome wide association studies has begun to powerfully examine the genetic nature of complex non-Mendelian GI diseases highlighting polymorphisms within immune related genes and their potential to provide the niche in which GI cancers may originate. Here in the role in which Mendelian and non-Mendelian genetics of immune related factors supporting GI malignancy will be presented and discussed.

Progressive cellular response in the lamina propria of the colorectal adenoma-carcinoma sequence

AIMS

The lamina propria is inevitably involved in epithelial transformation. The aim was to evaluate the dynamic cellular changes in the tumour lamina propria throughout the colorectal adenoma-carcinoma sequence.

METHODS AND RESULTS

Using immunohistochemistry and double immunohistochemistry, we examined lamina propria cellular changes in 41 colorectal adenomas, 25 colorectal cancers and 15 control tissues. The results showed that the proliferation labelling index in lamina propria cells began to increase in the precancerous lesions (adenomas) and became even higher in the colorectal cancers; these proliferative cells were primarily identified as myofibroblasts and lymphocytes. Phenotypic analysis revealed gradually increasing lymphocytic infiltration in both the lamina propria and adenomatous epithelium, as well as myofibroblasts in the lamina propria. However, the intraepithelial macrophage density also showed a tendency to increase gradually. Furthermore, cyclooxygenase-2-expressing cell density and microvessel density gradually increased in the tumour lamina propria throughout the adenoma-carcinoma sequence.

CONCLUSIONS

Progressive cellular responses in the lamina propria could be involved in the adenoma-carcinoma transition.

Cyclooxygenase-2 and Hypoxia-Inducible Factor-1alpha protein expression is related to inflammation, and up-regulated since the early steps of colorectal carcinogenesis

Chronic mucosal inflammation is considered a risk factor for colorectal cancer. Neutrophils are a major source of oxidants, whereas cyclooxygenase 2 (COX-2) and Hypoxia Inducible Factor-1alpha (HIF-1alpha) protein expression levels are increased in inflammatory and malignant lesions. The main purpose of the present study was to evaluate myeloperoxidase (MPO) positive cell infiltration, COX-2 and HIF-1alpha protein expression in colorectal carcinogenesis, especially in its early phases, using immunohistochemistry and immunofluorescence confocal microscopy techniques. MPO, COX-2 and HIF-1alpha proteins were expressed at higher rates in the normal colorectal mucosa of patients with inflammatory bowel diseases and colorectal tumours than in patients with normal colonoscopy. A gradual increase in COX-2 and HIF-1alpha protein expression was observed in dysplastic aberrant crypt foci, adenomas and carcinomas, showing a strong relation to dysplasia. In conclusion, the present study supports the hypothesis of a key role of inflammation in malignant transformation of colorectal mucosa. The evaluation of some early markers related to inflammation in the mucosa of the large bowel may serve as potential tool for prognosis and therapeutic strategies.

COX-2 expression in sporadic colorectal adenomatous polyps is linked to adenoma characteristics

AIMS

To assess cyclooxygenase-2 (COX-2) expression in sporadic colonic adenomas and to explore the association of COX-2 positivity with adenoma characteristics linked to increased risk of malignant transformation.

METHODS AND RESULTS

COX-2 expression and localization were assessed in 64 colorectal adenomas and 35 paired adjacent normal colonic mucosal biopsy specimens. The number of adenoma specimens was then extended to include polyps exhibiting an increasing degree of epithelial dysplasia. Forty colonic hyperplastic polyps were also identified from the pathology diagnostic database and included in the analysis. Immunohistochemistry was performed with the Envision+ peroxidase-linked biotin-free system incorporating a signal amplification step. There was a statistically significant increase in COX-2 expression in colonic polyps compared with paired adjacent normal mucosa, chi(2) = 40.1, P = 0.001. The probability of COX-2 expression increased along with increasing adenoma size and increasing degree of epithelial dysplasia. Fifty-five per cent of the hyperplastic polyp specimens expressed COX-2.

CONCLUSIONS

This study associates COX-2 epithelial expression with a number of adenoma characteristics that convey an increased risk of malignant transformation. This is in keeping with a positive role for COX-2 in early colorectal carcinogenesis.

PTGS2 (COX-2) -765 G > C functional promoter polymorphism and its association with risk and lymph node metastasis in nasopharyngeal carcinoma

Cyclooxygenase-2 (Cox-2) is a key enzyme in the conversion of arachidonic acid to prostaglandins that has been shown to have a particular importance in the progression of several malignancies including nasopharyngeal carcinoma (NPC). In the current report, we designed a case-controlled study to evaluate the susceptibility and prognostic implications of the functional -765 G > C genetic variation in NPC. A PCR and restriction fragment length polymorphism analysis was used to determine the polymorphism in a Tunisian population of patients with NPC (n = 180) and in healthy control subjects (n = 169). A higher risk for NPC was observed for carriers of COX-2 -765 C allele (OR = 1.76; P = 0.01). This association remains significant after adjustments for age and sex (OR = 1.89; P = 0.008). Regarding prognostic indicators, a significant association was found between -765 C allele carriers and the presence of lymph node metastasis (OR = 2.28; P = 0.01), as well as, with tumor stage (OR = 2.73; P = 0.03). This is the first report on the studies of COX-2 SNPs in NPC and our data suggest that this genetic variant may play a role in mediating susceptibility to NPC, as well as, in neoplastic progression, a finding which further supports the involvement of COX-2 in NPC etiology.

Reversal of expression of 15-lipoxygenase-1 to cyclooxygenase-2 is associated with development of colonic cancer

AIMS

Two different pathways of linoleic acid (LA) metabolism have opposite effects on the development of colonic cancer: a protumoral prostaglandin cascade metabolized by cyclooxygenase (COX)-2, and an antitumoral peroxisome proliferator-activated receptor (PPAR)-gamma ligands metabolized by 15-lipooxygenase (LOX)-1. The aim was to examine the switching of the two LA metabolic pathways in colonic adenomas and carcinomas.

MATERIALS AND METHODS

The expression of 15LOX-1 mRNA and COX-2 protein was examined in 54 adenomas, 21 pTis carcinoma-in-adenoma lesions and 36 pT3/p Stage II carcinomas of the colon by in-situ hybridization and immunohistochemistry, respectively.

RESULTS

15LOX-1 expression was found in 89% (48 of 54) of adenomas, 43% (nine of 21) of adenomas and 10% (two of 21) of carcinomas in carcinoma-in-adenoma lesions, but not in pT3 carcinomas (P < 0.0001). In contrast, COX-2 production was found in 11% (six of 54) of adenomas, 52% (11 of 21) of adenomas and 71% (15 of 21) of carcinomas in carcinoma-in-adenoma lesions, and 92% (33 of 36) of pT3 carcinomas (P < 0.0001). Concurrence of 15LOX-1 down-regulation and COX-2 up-regulation was found in 6% (three of 54) of adenomas, 33% (seven of 21) of adenomas and 71% (15 of 21) of carcinomas in carcinoma-in-adenoma lesions, and 92% (33 of 36) of pT3 carcinomas (P < 0.0001).

CONCLUSIONS

These results suggest that switching of LA metabolism by reversal of the expression of 15LOX-1 and COX-2 is associated with acquisition of malignant potential in colonic neoplasia.

Cyclooxygenase-2 (cox-2) and the inflammogenesis of cancer

Cohesive scientific evidence from molecular, animal, and human investigations supports the hypothesis that aberrant induction of COX-2 and up-regulation of the prostaglandin cascade play a significant role in carcinogenesis, and reciprocally, blockade of the process has strong potential for cancer prevention and therapy. Supporting evidence includes the following: [1] expression of constitutive COX-2-catalyzed prostaglandin biosynthesis is induced by most cancer-causing agents including tobacco smoke and its components (polycylic aromatic amines, heterocyclic amines, nitrosamines), essential polyunsaturated fatty acids (unconjugated linoleic acid), mitogens, growth factors, proinflammatory cytokines, microbial agents, tumor promoters, and other epigenetic factors, [2] COX-2 expression is a characteristic feature of all premalignant neoplasms, [3] COX-2 expression is a characteristic feature of all malignant neoplasms, and expression intensifies with stage at detection and cancer progression and metastasis, [4] all essential features of carcinogenesis (mutagenesis, mitogenesis, angiogenesis, reduced apoptosis, metastasis, and immunosuppression) are linked to COX-2-driven prostaglandin (PGE-2) biosynthesis, [5] animal studies show that COX-2 up-regulation (in the absence of genetic mutations) is sufficient to stimulate the transformation of normal cells to invasive cancer and metastatic disease, [6] non-selective COX-2 inhibitors, such as aspirin and ibuprofen, reduce the risk of human cancer and precancerous lesions, and [7] selective COX-2 inhibitors, such as celecoxib, reduce the risk of human cancer and precancerous lesions at all anatomic sites thus far investigated. Results confirming that COX-2 blockade is effective for both cancer prevention and therapy have been tempered by observations that some COX2 inhibitors pose a risk to the cardiovascular system, and more studies are needed in order to determine if certain of these drugs can be taken at dosages that prevent cancer without increasing cardiovascular risk. It is emphasized that the "inflammogenesis model of cancer" is not mutually exclusive and may in fact be synergistic with the accumulation of somatic mutations in tumor suppressor genes and oncogenes or epigenetic factors in the development of cancer.

Gene expression profiling in familial adenomatous polyposis adenomas and desmoid disease

Gene expression profiling is a powerful method by which alterations in gene expression can be interrogated in a single experiment. The disease familial adenomatous polyposis (FAP) is associated with germline mutations in the APC gene, which result in aberrant β-catenin control. The molecular mechanisms underlying colorectal cancer development in FAP are being characterised but limited information is available about other symptoms that occur in this disorder. Although extremely rare in the general population, desmoid tumours in approximately 10% of FAP patients. The aim of this study was to determine the similarities and differences in gene expression profiles in adenomas and compare them to those observed in desmoid tumours. Illumina whole genome gene expression BeadChips were used to measure gene expression in FAP adenomas and desmoid tumours. Similarities between gene expression profiles and mechanisms important in regulating formation of FAP adenomas and desmoid tumours were identified. This study furthers our understanding of the mechanisms underlying FAP and desmoid tumour formation.

Functional antagonism between RNA binding proteins HuR and CUGBP2 determines the fate of COX-2 mRNA translation

BACKGROUND AND AIMS

Cyclooxygenase-2 (COX-2) expression is regulated at the levels of messenger RNA (mRNA) stability and translation by AU-rich elements (ARE) located in its 3' untranslated region (3'UTR). Although structurally homologous RNA binding proteins HuR and CUGBP2 stabilize COX-2 mRNA, HuR induces whereas CUGBP2 inhibits COX-2 mRNA translation. This study aimed to determine the antagonism between these proteins on COX-2 expression.

METHODS

COX-2 ARE binding activity was determined by nitrocellulose filter binding and UV cross-linking assays using recombinant glutathione S-transferase (GST)/HuR and GST/CUGBP2. Protein:protein interactions were determined by GST pull-down, yeast 2-hybrid, and immunocytochemistry assays. Nucleocytoplasmic shutting was determined by heterokaryon analyses. The effect of CUGBP2 and HuR on COX-2 ARE-dependent translation was shown by a chimeric luciferase mRNA containing COX-2 3'UTR. HT-29 cells were subjected to 12 Gy gamma-irradiation in a cesium irradiator.

RESULTS

CUGBP2 and HuR bind with similar affinities to COX-2 ARE, but CUGBP2 competes with HuR for binding. In vitro, HuR and CUGBP2 heterodimerize. Furthermore, FLAG-tagged HuR and myc-tagged CUGBP2 colocalize in the nucleus of HCT-116 cells. Moreover, both proteins shuttled between the nucleus and cytoplasm. In vitro, HuR enhanced whereas CUGBP2 inhibited translation of the chimeric luciferase COX-2 3'UTR mRNA. Furthermore, CUGBP2 competitively inhibited HuR-mediated translation of the transcript. In HT-29 cells transfected with HuR and CUGBP2, a switch in COX-2 mRNA binding from predominantly HuR to CUGBP2 occurred after radiation treatment, which was coupled with increased silencing of the COX-2 mRNA.

CONCLUSIONS

CUGBP2 overrides HuR and suppresses COX-2 mRNA translation.

Global Tumor RNA Expression in Early Establishment of Experimental Tumor Growth and Related Angiogenesis following Cox-Inhibition Evaluated by Microarray Analysis

Altered expression of COX-2 and overproduction of prostaglandins, particularly prostaglandin E2, are common in malignant tumors. Consequently, non-steroidal anti-inflammatory drugs (NSAIDs) attenuate tumor net growth, tumor related cachexia, improve appetite and prolong survival. We have also reported that COX-inhibition (indomethacin) interfered with early onset of tumor endothelial cell growth, tumor cell proliferation and apoptosis. It is however still unclear whether such effects are restricted to metabolic alterations closely related to eicosanoid pathways and corresponding regulators, or whether a whole variety of gene products are involved both up- and downstream effects of eicosanoids. Therefore, present experiments were performed by the use of an in vivo, intravital chamber technique, where micro-tumor growth and related angiogenesis were analyzed by microarray to evaluate for changes in global RNA expression caused by indomethacin treatment.

Indomethacin up-regulated 351 and down-regulated 1852 genes significantly (p < 0.01); 1066 of these genes had unknown biological function. Genes with altered expression occurred on all chromosomes.

Our results demonstrate that indomethacin altered expression of a large number of genes distributed among a variety of processes in the carcinogenic progression involving angiogenesis, apoptosis, cell-cycling, cell adhesion, inflammation as well as fatty acid metabolism and proteolysis. It remains a challenge to distinguish primary key alterations from secondary adaptive changes in transcription of genes altered by cyclooxygenase inhibition.

Effects of cyclooxygenase inhibition on the gastrointestinal tract

Cyclooxygenase (COX) is a rate-limiting enzyme that catalyzes the conversion of arachidonic acid, an essential fatty acid present in cell membrane phospholipids and liberated by phospholipase, into prostaglandins (PGs) and prostanoids. COX has two distinct membrane-anchored isoenzymes; COX-1 and COX-2. COX-1 is a constitutively expressed and found in most normal body tissues; COX-2 is expressed in normal tissues at low levels and is highly induced by pro-inflammatory mediators in the setting of inflammation, injury, and pain. Inhibitors of COX activity include: (1) conventional non-selective non-steroidal anti-inflammatory drugs (ns-NSAIDs); (2) selective COX-2 inhibitors (COXIBs); and (3) COX-1 inhibitors. Non-selective NSAIDs, at therapeutic doses, inhibit both COX-1 and COX-2. The anti-inflammatory benefits of these drugs are primarily derived from COX-2 inhibition, while inhibition of COX-1 often elicits gastrointestinal (GI) toxicity. Therefore, COXIBs were developed to provide a selective COX-2 agent, i.e., one, that at fully therapeutic doses demonstrated comparable therapeutic benefit to non-selective NSAIDs, without the attendant COX-1-mediated GI toxicities. In this review, we evaluate available literature describing the pathophysiologic role of cyclooxygenases and the effects of their inhibition in GI system in experimental and domestic animal species.

Expression of cyclo-oxygenase-2 in gastrointestinal carcinoid tumors

BACKGROUND

Cyclo-oxygenase (COX)-2 overexpression is observed in various neoplasms and COX-2 inhibition has been attempted as prevention and/or therapy in these neoplasms. Carcinoid tumors are thought to arise from neuroendocrine cells and originate mainly in the gastrointestinal tract. Cyclo-oxygenase-2 is reportedly expressed in neuroendocrine cells of normal colorectal mucosa. The role of COX in carcinoids has not previously been investigated. The aim of the present paper was to clarify the expression of COX-1 and -2, and their role in human gastrointestinal carcinoids.

METHODS

Expression of COX-1 and -2 was studied immunohistochemically in 38 gastrointestinal carcinoids. Five bronchopulmonary and seven metastatic carcinoids were also examined, for comparison with gastrointestinal carcinoids. The immunohistochemical score (IHS) was calculated from staining intensity and immunoreactive cell population, and ranked according to four grades (negative to strong).

RESULTS

Cyclo-oxygenase-2 was expressed in all gastrointestinal carcinoids (weak, 1; moderate, 13; strong, 24) and bronchopulmonary carcinoids (weak, 1; moderate, 4), as well as their metastases (moderate, 3; strong, 4). The IHS of COX-2 in larger tumors was significantly lower than that in smaller tumors. However, the IHS of COX-2 at the advancing tumor edge was significantly higher than that at the centers of tumors >or=10 mm in size. Faint COX-1 expression was detected in only one duodenal, one rectal and four bronchopulmonary carcinoids.

CONCLUSIONS

Enhanced COX-2 expression was observed in gastrointestinal as well as bronchopulmonary carcinoids and their metastases, especially at the advancing edges of the tumors. Cyclo-oxygenase-2 may play a role in carcinoid progression.

Cyclooxygenase-2 (COX-2)-independent anticarcinogenic effects of selective COX-2 inhibitors

Nonsteroidal antiinflammatory drugs (NSAIDs) appear to reduce the risk of developing cancer. One mechanism through which NSAIDs act to reduce carcinogenesis is to inhibit the activity of cyclooxygenase-2 (COX-2), an enzyme that is overexpressed in various cancer tissues. Overexpression of COX-2 increases cell proliferation and inhibits apoptosis. However, selective COX-2 inhibitors can also act through COX-independent mechanisms. In this review, we describe the COX-2-independent molecular targets of these COX-2 inhibitors and discuss how these targets may be involved in the anticarcinogenic activities of these selective COX-2 inhibitors. We also compare the concentrations of these inhibitors used in in vitro and in vivo experiments and discuss the implications of the in vitro studies for clinical management of cancer with these drugs.

Increased Cyclooxygenase-2 Expression in Duodenal Compared with Colonic Tissues in Familial Adenomatous Polyposis and Relationship to the −765G → C COX-2 Polymorphism

BACKGROUND

Colorectal cancers arising in patients with familial adenomatous polyposis (FAP) can be largely prevented by polyp surveillance and prophylactic colectomy. As a result, duodenal adenocarcinoma has become a leading cause of death in patients with FAP. Cyclooxygenase 2 (COX-2) inhibition is effective against colorectal polyposis in FAP, but is less effective in treating duodenal polyps. We compared the expression of COX-2 in duodenal and colorectal adenomas from patients with FAP and from patients with sporadic neoplasms and correlated expression to a COX-2 promoter polymorphism (-765G/-->C) that is reported to influence COX-2 expression.

METHODS

The study population included 36 FAP patients with colonic adenomas, 22 FAP patients with duodenal adenomas, 22 patients with sporadic duodenal adenomas, and 17 patients with sporadic duodenal adenocarcinoma. Neoplastic and corresponding normal tissue COX-2 expressions were determined using immunohistochemistry on tissue microarrays. The prevalence and ethnic distribution of a polymorphism in the COX-2 promoter that influences COX-2 expression (-765G --> C) were determined in DNA from 274 individuals by real-time quantitative PCR.

RESULTS

Among patients with FAP, histologically normal duodenal mucosa showed higher COX-2 expression than normal colonic mucosa (P < 0.02), and duodenal adenomas had higher COX-2 expression than colonic adenomas (P </= 0.01). In addition, the normal duodenum of patients with FAP showed higher COX-2 expression than the normal duodenal mucosa of patients with sporadic adenomas (P < 0.05). COX-2 expression was significantly higher in the normal-appearing (P < 0.01) mucosa of patients with FAP carrying the -765GG genotype compared with those carrying the -765GC or -765CC genotypes. The -765C genotype was more common in African Americans than in Caucasians (52% versus 33%, P < 0.01).

CONCLUSIONS

High COX-2 expression in the normal and adenomatous duodenal mucosa of patients with FAP may explain the poorer response of these neoplasms to chemoprevention with COX-2 inhibitors.

Subepithelial myofibroblasts express cyclooxygenase-2 in colorectal tubular adenomas

PURPOSE

Recent data support the hypothesis that the inducible isoform of cyclooxygenase (COX-2) plays a role in the early stages of colonic carcinogenesis and that nonsteroidal anti-inflammatory drugs (NSAIDs) retard the development of colon cancer by modulating COX-2. However, the cell types responsible for producing COX-2 in colorectal adenomas remain a subject of controversy.

EXPERIMENTAL DESIGN

COX-2 expression in normal colonic mucosa (n = 50), hyperplastic polyps (n = 43), sporadic adenomas (n = 67), and invasive colonic adenocarcinoma (n = 39) was studied in formalin-fixed and paraffin-embedded tissue sections from endoscopy biopsy and colonic resection specimens. Immunohistochemistry (avidin-biotin complex technique with double immunolabeling) was used to identify the phenotypes of COX-2-producing cells.

RESULTS

In colorectal adenomas, increased expression of COX-2 was detected and localized to alpha smooth muscle actin ( proportional, variant SMA)-positive subepithelial stromal cells (myofibroblasts) in the periluminal region of the lamina propria in 63 (94%) of 67 cases. In contrast, in normal colonic mucosa and in hyperplastic polyps with intact epithelium, COX-2 expression was found only in macrophages and endothelial cells. In areas in which the surface epithelium was ulcerated in normal mucosa as well as hyperplastic or neoplastic polyps, COX-2 expression was increased in granulation tissue (and present in macrophages, endothelium, and myofibroblasts). In invasive carcinoma, COX-2 expression in myofibroblasts was limited to the adenomatous portion of the tumor and was detected in 62% of cases (n = 39). In addition, focal expression of COX-2 by malignant epithelial cells was observed in 23% of invasive adenocarcinoma.

CONCLUSIONS

These results show that increased COX-2 expression in sporadic adenoma of the colon is common and is localized specifically to subepithelial intestinal myofibroblasts. These findings further support the hypothesis that myofibroblasts are important target cells for NSAID-mediated chemoprevention of colorectal cancer.

Cyclooxygenases in cancer: progress and perspective

Aspirin has been used to control pain and inflammation for over a century. Epidemiological studies first associated a decreased incidence of colorectal cancer with the long-term use of aspirin in the early 1980s. Near the same time the first reports showing regression of colorectal adenomas in response to the non-steroidal anti-inflammatory drug (NSAID) sulindac were reported. In subsequent years, the use of other NSAIDs, which inhibit cyclooxygenase (COX) enzymes, was linked to reduced cancer risk in multiple tissues including those of the breast, prostate, and lung. Together these studies resulted in the identification of a new cancer preventive and/or therapeutic target-COX enzymes, especially COX-2. Meanwhile, the overexpression of COX-2, and less consistently, the upstream and downstream enzymes of the prostaglandin synthesis pathway, was demonstrated in multiple cancer types and some pre-neoplastic lesions. Direct interactions of prostaglandins with their receptors through autocrine or paracrine pathways to enhance cellular survival or stimulate angiogenesis have been proposed as the molecular mechanisms underlying the pro-carcinogenic functions of COX-2. The rapid development of safe and effective inhibitors targeting individual COX enzymes not only dramatically improved our understanding of the function of COX-2, but also resulted in discovery of COX independent functions of NSAIDs, providing important hints for future drug design. Here we review the fundamental features of COX enzymes, especially as related to carcinogenesis, their expression and function in both animal tumor models and clinical cancers and the proposed mechanisms behind their roles in cancer.

Prognostic significance of vascular endothelial growth factor and cyclooxygenase 2 expression in patients receiving preoperative chemoradiation for esophageal cancer

OBJECTIVE

Both vascular endothelial growth factor and cyclooxygenase 2 overexpression have been associated with poor prognosis in a variety of human malignancies. In this study we assessed the effect of preoperative chemotherapy and radiation on expression levels of vascular endothelial growth factor and cyclooxygenase 2 in patients with esophageal cancer and determined whether these markers were associated with treatment response and overall survival.

METHODS

Expression levels of vascular endothelial growth factor and cyclooxygenase 2 were measured in a cohort of 46 patients with esophageal cancer receiving preoperative chemoradiation followed by surgical resection. Immunohistochemical stains were performed on both pretreatment biopsy specimens and posttreatment resection specimens for each patient. Differences in vascular endothelial growth factor and cyclooxygenase 2 expression before and after treatment were measured, and pretreatment expression levels were correlated with treatment response and overall survival.

RESULTS

We found that preoperative chemotherapy and radiation induced expression of cyclooxygenase 2 in stromal cells and induced vascular endothelial growth factor expression in both tumor and stromal cells. Pretreatment vascular endothelial growth factor expression did not correlate with treatment response, and cyclooxygenase 2 expression correlated with treatment response only in the subset of patients with squamous cell carcinoma. Although patients whose tumors expressed high levels of vascular endothelial growth factor and cyclooxygenase 2 tended to have shorter overall survival times, this trend did not reach statistical significance.

CONCLUSIONS

Neither vascular endothelial growth factor nor cyclooxygenase 2 are strong predictors of treatment response and survival in patients undergoing preoperative chemoradiation for esophageal cancer. This lack of prognostic significance might be explained by changes in the expression levels of these markers during treatment.

The relationship between cyclooxygenase-2 expression and characteristics of malignant transformation in human colorectal adenomas

BACKGROUND AND AIMS

Cyclooxygenase 2 (COX-2) is a target of aspirin and other non-steroidal anti-inflammatory drugs and is implicated in the pathogenesis of colorectal cancer. The objective of this study was to evaluate the extent of COX-2 in pre-malignant colorectal polyps and to assess the relationship between COX-2 and the level of dysplasia in these lesions.

METHODS

Whole polypectomy specimens were retrieved from 123 patients by endoscopic or surgical resection. Following formalin fixation and paraffin embedding, the polyps were evaluated histologically for size, type and grade of dysplasia. The extent of COX-2 expression was measured by the avidin-biotin immunohistochemical technique using a monoclonal COX-2 antibody. The extent of COX-2 expression was graded according to percentage epithelial COX-2 expression.

RESULTS

The polyps were of the following histological types: 10 hyperplastic, 35 tubular adenomas, 61 tubulovillous adenomas and 17 villous adenomas. Twenty showed mild dysplasia, 65 moderate dysplasia, and 28 focal or severe dysplasia (including eight with focal invasion). The average polyp size was 1.7 cm. Nine hyperplastic polyps were COX-2-negative and one was COX-2-positive. COX-2 expression was more extensive in larger polyps and in polyps with a higher villous component. There was a significant increase in the extent of COX-2 protein with increasing severity of dysplasia. Within a polyp, there was a focal corresponding increase in COX-2 expression within epithelium showing a higher grade of dysplasia.

CONCLUSIONS

COX-2 expression is related directly to colorectal adenomatous polyp size, type and grade of dysplasia. This suggests that the role of COX-2 in colorectal cancer may be at an early stage in the adenoma-to-carcinoma sequence and supports the suggestion that inhibition of COX-2 may be useful chemoprevention for this disease.

Prostanoids, ornithine decarboxylase, and polyamines in primary chemoprevention of familial adenomatous polyposis

BACKGROUND & AIMS

Familial adenomatous polyposis because of germline mutation of the adenomatous polyposis coli gene is characterized by development of colorectal adenomas and, ultimately, colorectal cancer. The usefulness of colorectal mucosal compounds to predict the effect on adenoma development of primary chemoprevention with the nonsteroidal anti-inflammatory drug sulindac was evaluated.

METHODS

A randomized, double-blind, placebo-controlled study of 41 subjects genotypically affected with familial adenomatous polyposis but phenotypically unaffected was conducted. Patients received either sulindac or placebo for 48 months, and development of new adenomas was evaluated. The levels of 5 prostanoids, ornithine decarboxylase, and polyamines were measured serially in normal-appearing rectal mucosa.

RESULTS

There were no statistically significant differences between treatment groups in baseline levels of prostanoids, ornithine decarboxylase, or polyamines. At conclusion of the study, 4 of 5 prostaglandin levels were statistically significantly lower in the sulindac group than in the placebo group. Among the subset of patients taking sulindac, 3 of 5 prostaglandin levels were statistically significantly lower in patients who were polyp free than in those who developed polyps. By contrast, there were no statistically significant differences in ornithine decarboxylase or polyamines between treatment groups or in those on sulindac who were polyp free compared with those who developed polyps.

CONCLUSIONS

Colorectal mucosal prostaglandin levels, but not ornithine decarboxylase or polyamines, may be valuable biomarkers to assess appropriate drug dosage and medication compliance in patients undergoing primary chemoprevention therapy with sulindac. Reduction of mucosal prostaglandin levels may be necessary to achieve chemopreventive benefit from this agent.

Enhanced expression of Cyclooxygenase-2 in glaucomatous dog eyes

OBJECTIVE

Cyclooxygenase-2 (COX-2)-derived prostaglandins (PGs) are shown to play important pathophysiologic roles in various disease states. Recently, the effectiveness of topical PGs in reducing intraocular pressure (IOP) has stimulated further interest in the physiologic function of COX-2 and PGs in normal and glaucomatous eyes. Therefore, we investigated the cell-type distribution and expression of COX-2 in normal and glaucomatous dog eyes.

PROCEDURES

Using isoform-specific antibodies, we immunohistochemically evaluated COX-2 expression in formalin-fixed and paraffin-embedded normal (n = 5) and glaucomatous (n = 17) dog eyes.

RESULTS

In the normal eyes, only minimal COX-2 immunoreactivity was observed in the ciliary epithelium. In the glaucomatous eyes, COX-2 expression was further observed in the cornea and corneoscleral limbus. In the cornea, moderate to strong COX-2 expression was observed in all corneal layers (epithelium, stromal cells and endothelium), with the greatest expression present in the epithelial layer. In the corneoscleral limbus area, COX-2 immunoreactivity was noted in the stromal cells of sclera, trabecular meshwork and endothelial cells of the angular aqueous plexus.

CONCLUSIONS

Increased expression of COX-2 in dog glaucomatous eyes suggests that COX-2-derived PGs may have a potential role in the pathogenesis of canine glaucoma.

The cox-2-specific inhibitor celecoxib inhibits adenylyl cyclase

Nonsteroidal anti-inflammatory drugs (NSAIDs) are well-known causes of acute renal insufficiency and gastropathy in patients with chronic inflammatory diseases. This action is presumed to result from nonselective inhibition of both constitutive and inducible forms of prostaglandin H synthases, also known as the cyclooxygenase enzymes (i.e., COX-1 amd COX-2). Celecoxib (Celebrex) is a COX-2 enzyme inhibitor and has emerged as a preferred therapeutic agent for the treatment of rheumatoid arthritis as compared to other NSAIDs. Celecoxib has recently been the subject of criticism for its side effects, mainly arterial thrombosis and renal hemorrhage, although it is considered a superior drug in protecting the gastrointestinal tract. In the present study, we report that celecoxib not only inhibited COX-2, but also exhibited the property of inhibiting adenylyl cyclase, an important enzyme forming the intracellular second messenger 3',5'-adenosine monophosphate (cAMP) from adenosine triphosphate (ATP). Celecoxib also inhibited cholera toxin-stimulated cAMP formation, which indicated its ability to permeate cell membranes in order to reach intracellular adenylyl cyclase. It inhibited in vitro adenylyl cyclase activity in both human colonic epithelial cells and purified adenylyl cyclase from Bordetella pertussis. The IC50 of celecoxib for B. pertussis adenylyl cyclase was calculated to be 0.375 mM. Lineweaver-Burk analysis showed that the type of enzyme inhibition was competitive. The apparent Km and Vm of adenylyl cyclase was calculated as 25.0 nM and 7.14 nmol/min/mg, respectively. Celecoxib changed the Km value to 66.6 nM without affecting the Vmax. The current study suggests that apart from inflammation, celecoxib therapy could be further extended to diseases involving cAMP upregulation either by endogenous reactions or exogenous agents. These new data showing inhibition of adenylyl cyclase should be considered in light of the drug's pathological effects or in patients specifically excluded from treatment (e.g., asthmatics).

Human colorectal adenomas demonstrate a size-dependent increase in epithelial cyclooxygenase-2 expression

Non-steroidal anti-inflammatory drugs are chemopreventive for colorectal cancer. This effect is due in part to their ability to inhibit the inducible isoform of cyclooxygenase (COX-2). However, the cellular expression and role of COX-2 in the premalignant stages of colorectal tumourigenesis is unclear. COX-2 expression was assessed in 35 human colorectal adenomas and 38 sporadic invasive colorectal adenocarcinomas. Adenomas were classified as small (<5 mm in diameter), medium (5-10 mm), and large (>10 mm). All tissues were paraffin-embedded and formalin-fixed. COX-2 protein expression was determined using immunohistochemistry. COX-2 was detected in the epithelial cells in 35 of 38 carcinomas (92%) and in 8 of 8 (100%) lymph node metastases. All of the epithelial cells expressed COX-2 in 30 of 35 (86%) carcinomas and in 100% of the lymph node metastases. Twenty-three of 35 (66%) adenomas expressed COX-2 in the tumour epithelium. With an increase in the size of adenoma (<5 mm, 5-10 mm, >10 mm), there was an increase in (i) the proportion of adenomas with immunoreactive COX-2 in the epithelium (p = 0.036)-this was 38% in small adenomas and 82% in large adenomas; (ii) the extent of epithelial COX-2 staining within a given tumour (p = 0.003)-100% of epithelial cells were COX-2-positive in 15% of small adenomas and in 73% of large adenomas; and (iii) the intensity of epithelial COX-2 staining (p = 0.009)-strong COX-2 staining occurred in 8% of small adenomas and in 36% of large adenomas. COX-2 immunoreactivity was not detected in adjacent normal epithelium but was apparent in fibroblasts and inflammatory mononuclear cells of adjacent normal, adenoma, and carcinoma tissue. These results suggest that epithelial COX-2 activity is important for the growth and/or survival of adenomatous epithelial cells from an adenoma diameter of less than 5 mm and that there is a selective advantage for adenoma epithelial cells expressing higher levels of COX-2.

Paracrine cyclooxygenase-2-mediated signalling by macrophages promotes tumorigenic progression of intestinal epithelial cells

In human colorectal adenomas or polyps, cyclooxygenase-2 is expressed predominantly by stromal (or interstitial) macrophages. Therefore, we tested the hypothesis that macrophage cyclooxygenase-2 has paracrine pro-tumorigenic activity using in vitro models of macrophage-epithelial cell interactions. We report that macrophages can promote tumorigenic progression of intestinal epithelial cells (evidenced by decreased cell-cell contact inhibition, increased proliferation and apoptosis, gain of anchorage-independent growth capability, decreased membranous E-cadherin expression, up-regulation of cyclooxygenase-2 expression, down-regulation of transforming growth factor-beta type II receptor expression and resistance to the anti-proliferative activity of transforming growth factor-beta(1)) in a paracrine, cyclooxygenase-2-dependent manner. Pharmacologically relevant concentrations (1-2 microM) of a selective cyclooxygenase-2 inhibitor had no detectable, direct effect on intestinal epithelial cells but inhibited the macrophage-epithelial cell signal mediating tumorigenic progression. Cyclooxygenase-2-mediated stromal-epithelial cell signalling during the early stages of intestinal tumorigenesis provides a novel target for chemoprevention of colorectal cancer (and other gastro-intestinal epithelial malignancies, which arise on a background of chronic inflammation, such as gastric cancer) and may explain the discrepancy between the concentrations of cyclooxygenase inhibitors required to produce anti-neoplastic effects in vitro and in vivo.

Analysis of cyclooxygenase expression in human colorectal adenomas

INTRODUCTION

Evidence from rodent intestinal tumorigenesis models suggests that both cyclooxygenase-1 and cyclooxygenase-2 may play important roles in the development and progression of human sporadic colorectal adenomas. However, previous studies of cyclooxygenase isoform expression in human colorectal adenomas have produced conflicting data. Cyclooxygenase-1 expression has been poorly studied, and cyclooxygenase-2 positivity of adenomas has been variable depending on the detection technique used. It also remains unclear whether villous adenomas express cyclooxygenase-2.

METHODS

Cyclooxygenase isoform expression in human sporadic colorectal adenomas was analyzed by reverse transcription-polymerase chain reaction, Western blot analysis, and immunohistochemistry.

RESULTS

Variable cyclooxygenase-1 expression was detected in all adenomas (n = 9) by both reverse transcription-polymerase chain reaction and Western blot analysis. Cyclooxygenase-2 expression was detected in eight (89 percent) of nine adenomas by reverse transcription-polymerase chain reaction and immunohistochemistry. Cyclooxygenase-2 protein was not detected by Western blot analysis in any adenoma. Cyclooxygenase-2 was expressed by all histopathologic types of adenoma and localized predominantly to superficial interstitial cells, in which it was associated with increased adenoma size.

CONCLUSION

Cyclooxygenase-1 is expressed at variable levels by all adenomas. Cyclooxygenase-2 is expressed by the majority of adenomas, including those of the villous type, at levels below the sensitivity of Western blot analysis.

Structure-activity relationship of indomethacin analogues for MRP-1, COX-1 and COX-2 inhibition. identification of novel chemotherapeutic drug resistance modulators

We report the screening of analogues of indomethacin to investigate the structure-activity relationship (SAR) of indomethacin-mediated multidrug resistance associated protein-1 (MRP-1) inhibition. By examining the activities of compounds with minor variations of the parent structure, we were able to separate MRP-1, glutathione-S-transferase (GST), cyclooxygenase (COX)-1 and COX-2 inhibitory activities. Combination cytotoxicity assays were utilised to identify agents which possess synergistic potential in MRP-1-expressing cell lines. MRP-1 Inside Out Vesicles (IOVs) were utilised to demonstrate the ability of the indomethacin analogues to inhibit the pump directly. Most of the indomethacin analogues active as MRP-1 inhibitors were poor GST inhibitors when compared with the GST-inhibitory activity of indomethacin. Two of the MRP-1 inhibitory analogues were found to have no COX-1 inhibitory activity and low COX-2 inhibitory activity, suggesting potentially reduced clinical toxicity. One MRP-1 inhibitory indomethacin analogue was also found to have low COX-1 inhibitory activity, but significant COX-2 inhibitory activity, making this analogue again interesting in terms of low potential toxicity, but with the possibility of direct inhibitory effects on tumour growth.

Pharmacology of cyclooxygenase-2 inhibition in the kidney

Cyclooxygenase (COX) exists as two unique isoforms (that is, COX-1 and COX-2) which are poorly understood with regard to their roles in renal function. The renal effects of conventional non-steroidal anti-inflammatory drugs (NSAIDs) are believed to result from the inhibition of one or both isoforms. Drugs that selectively inhibit COX-2 provide useful pharmacological tools for discerning the effects associated with the inhibition of the individual isoforms, and may help clarify the renal roles of COX-1 and COX-2. This review summarizes the current data on the renal expression of COX isoforms and their potential roles in renal function, and reviews the studies that have attempted to correlate renal functional changes with selective isoform inhibition. Since there are significant differences in the expression of COX isoforms in the kidneys of laboratory animals and humans, this review also examines the correlation of the results of COX inhibition in experimental studies in laboratory animals with clinical data. Because of potential interspecies differences in the roles of COX isoforms in renal function, animal models may have limited predictive value for patients, particularly those with renal risk factors. Accordingly, any uncertainty concerning the safety or therapeutic benefit of COX-2-specific drugs in these patient populations will need to be resolved with clinical investigations.