COX-2 inhibitors for colorectal cancer

Using Theory To Extend the Scope of Azobenzene Drugs in Chemotherapy: Novel Combinations for a Specific Delivery

Gut microorganisms metabolize azobenzene compounds (Ph¹ -N=N-Ph² ) into free aniline products (Ph¹ -NH₂ +H₂ N-Ph² ), a process that has been largely investigated to reduce dyes residues in the textile industry. However, the action of bacterial core enzymes such as azoreductases (AzoR) might also help to deliver prodrugs that become active when they reach the colonic region, a mechanism with potential applications for the treatment of inflammatory bowel disease (IBD) and colorectal cancer. So far, three azo-bonded prodrugs of 5-aminosalicylic acid (5-ASA), for example, sulfasalazine, olsalazine and balsalazide, have been used for colon-targeted delivery. The present contribution describes the first rational design of a novel azobenzene prodrug thanks to a computational approach, with a focus on linking 5-ASA to another approved anti-inflammatory drug. The resulting prodrugs were assessed for their degradation upon AzoR action. Replacing the original carriers by irsogladine is found to improve action.

EP4 receptor as a novel promising therapeutic target in colon cancer

The most prevalent malignancy that can occur in the gastrointestinal tract is colon cancer. The current treatment options for colon cancer patients include chemotherapy, surgery, radiotherapy, immunotherapy, and targeted therapy. Although the chance of curing the disease in the early stages is high, there is no cure for almost all patients with advanced and metastatic disease. It has been found that over-activation of cyclooxygenase 2 (COX-2), followed by the production of prostaglandin E2 (PGE2) in patients with colon cancer are significantly increased. The tumorigenic function of COX-2 is mainly due to its role in the production of PGE2. PGE2, as a main generated prostanoid, has an essential role in growth and survival of colon cancer cell's. PGE2 exerts various effects in colon cancer cells including enhanced expansion, angiogenesis, survival, invasion, and migration. The signaling of PGE2 via the EP4 receptor has been shown to induce colon tumorigenesis. Moreover, the expression levels of the EP4 receptor significantly affect tumor growth and development. Overexpression of EP4 by various mechanisms increases survival and tumor vasculature in colon cancer cells. It seems that the pathway starting with COX2, continuing with PGE2, and ending with EP4 can promote the spread and growth of colon cancer. Therefore, targeting the COX-2/PGE2/EP4 axis can be considered as a worthy therapeutic approach to treat colon cancer. In this review, we have examined the role and different mechanisms that the EP4 receptor is involved in the development of colon cancer.

Mesenchymal Cells in Colon Cancer

Mesenchymal cells in the intestine comprise a variety of cell types of diverse origins, functions, and molecular markers. They provide mechanical and structural support and have important functions during intestinal organogenesis, morphogenesis, and homeostasis. Recent studies of the human transcriptome have revealed their importance in the development of colorectal cancer, and studies from animal models have provided evidence for their roles in the pathogenesis of colitis-associated cancer and sporadic colorectal cancer. Mesenchymal cells in tumors, called cancer-associated fibroblasts, arise via activation of resident mesenchymal cell populations and the recruitment of bone marrow-derived mesenchymal stem cells and fibrocytes. Cancer-associated fibroblasts have a variety of activities that promote colon tumor development and progression; these include regulation of intestinal inflammation, epithelial proliferation, stem cell maintenance, angiogenesis, extracellular matrix remodeling, and metastasis. We review the intestinal mesenchymal cell-specific pathways that regulate these processes, with a focus on their roles in mediating interactions between inflammation and carcinogenesis. We also discuss how increasing our understanding of intestinal mesenchymal cell biology and function could lead to new strategies to identify and treat colitis-associated cancers.

In vitro antiproliferative activity of 2,3-dihydroxy-9,10-anthraquinone induced apoptosis against COLO320 cells through cytochrome c release caspase mediated pathway with PI3K/AKT and COX-2 inhibition

The present study investigated the anticancer activity of 2,3-dihydroxy-9,10-anthraquinone against different cancer cells such as MCF-7, COLO320, HepG-2, Skov-3, MOLM-14, NB-4, CEM, K562, Jurkat, HL-60, U937, IM-9 and Vero. 2,3-dihydroxy-9,10-anthraquinone showed good antiproliferative activity against COLO320 cells when compared to other tested cells. The cytotoxicity results showed 79.8% activity at the dose of 2.07 μM with IC50 value of 0.13 μM at 24 h in COLO320 cells. So we chose COLO320 cells for further anticancer studies. mRNA expression was confirmed by qPCR analysis using SYBR green method. Treatment with 2,3-dihydroxy-9,10-anthraquinone was found to trigger intrinsic apoptotic pathway as indicated by down regulation of Bcl-2, Bcl-xl; up regulation of Bim, Bax, Bad; release of cytochrome c and pro-caspases cleaving to caspases. Furthermore, 2,3-dihydroxy-9,10-anthraquinone stopped at G0/G1 phase with modulation in protein levels of cyclins. On the other hand PI3K/AKT signaling plays an important role in cell metabolism. We found that 2,3-dihydroxy-9,10-anthraquinone inhibits PI3K/AKT activity after treatment. Also, COX-2 enzyme plays a major role in colorectal cancer. Our results showed that the treatment significantly reduced COX-2 enzyme in COLO320 cells. These results indicated antiproliferative activity of 2,3-dihydroxy-9,10-anthraquinone involving apoptotic pathways, mitochondrial functions, cell cycle checkpoint and controlling the over expression genes during the colorectal cancer. Molecular docking studies showed that the compound bound stably to the active sites of Bcl-2, COX-2, PI3K and AKT. This is the first report of anticancer mechanism involving 2,3-dihydroxy-9,10-anthraquinone in COLO320 cells. The present results might provide helpful suggestions for the design of antitumor drugs toward colorectal cancer treatment.

Direct Melanoma Cell Contact Induces Stromal Cell Autocrine Prostaglandin E2-EP4 Receptor Signaling That Drives Tumor Growth, Angiogenesis, and Metastasis

The stromal cells associated with tumors such as melanoma are significant determinants of tumor growth and metastasis. Using membrane-bound prostaglandin E synthase 1 (mPges1(-/-)) mice, we show that prostaglandin E2 (PGE2) production by host tissues is critical for B16 melanoma growth, angiogenesis, and metastasis to both bone and soft tissues. Concomitant studies in vitro showed that PGE2 production by fibroblasts is regulated by direct interaction with B16 cells. Autocrine activity of PGE2 further regulates the production of angiogenic factors by fibroblasts, which are key to the vascularization of both primary and metastatic tumor growth. Similarly, cell-cell interactions between B16 cells and host osteoblasts modulate mPGES-1 activity and PGE2 production by the osteoblasts. PGE2, in turn, acts to stimulate receptor activator of NF-κB ligand expression, leading to osteoclast differentiation and bone erosion. Using eicosanoid receptor antagonists, we show that PGE2 acts on osteoblasts and fibroblasts in the tumor microenvironment through the EP4 receptor. Metastatic tumor growth and vascularization in soft tissues was abrogated by an EP4 receptor antagonist. EP4-null Ptger4(-/-) mice do not support B16 melanoma growth. In vitro, an EP4 receptor antagonist modulated PGE2 effects on fibroblast production of angiogenic factors. Our data show that B16 melanoma cells directly influence host stromal cells to generate PGE2 signals governing neoangiogenesis and metastatic growth in bone via osteoclast erosive activity as well as angiogenesis in soft tissue tumors.

Cyclooxygenase-1 and -2: molecular targets for cervical neoplasia

Cyclooxygenase (COX) is a key enzyme responsible for inflammation, converting arachidonic acid to prostaglandin and thromboxane. COX has at least two isoforms, COX-1 and COX-2. While COX-1 is constitutively expressed in most tissues for maintaining physiologic homeostasis, COX-2 is induced by inflammatory stimuli including cytokines and growth factors. Many studies have shown that COX-2 contributes to cancer development and progression in various types of malignancy including cervical cancer. Human papillomavirus, a necessary cause of cervical cancer, induces COX-2 expression via E5, E6 and E7 oncoproteins, which leads to prostaglandin E2 increase and the loss of E-cadherin, promotes cell proliferation and production of vascular endothelial growth factor. It is strongly suggested that COX-2 is associated with cancer development and progression such as lymph node metastasis. Many studies have suggested that non-selective COX-2 inhibitors such as non-steroidal anti-inflammatory drugs (NSAIDs), and selective COX-2 inhibitors might show anti-cancer activity in COX-2 -dependent and -independent manners. Two phase II trials for patients with locally advanced cervical cancer showed that celecoxib increased toxicities associated with radiotherapy. Contrary to these discouraging results, two phase II clinical trials, using rofecoxib and celecoxib, demonstrated the promising chemopreventive effect for patients with cervical intraepithelial neoplasia 2 or 3. However, these agents cause a rare, but serious, cardiovascular complication in spite of gastrointestinal protection in comparison with NSAIDs. Recent pharmacogenomic studies have showed that the new strategy for overcoming the limitation in clinical application of COX-2 inhibitors shed light on the use of them as a chemopreventive method.

Determination of Celecoxib in human plasma using liquid chromatography with high resolution time of flight-mass spectrometry

A sensitive method for the determination of Celecoxib (CXB) in human plasma samples was developed using liquid chromatography coupled to electrospray ionization and time of flight mass spectrometry (LC-ESI-TOF-MS). A full factorial design of experiments (FF-DOE) methodology was applied to optimize the ESI conditions for CXB determination and also to predict the effects of interactions of multiple parameters affecting ionization (i.e., capillary voltage, fragmentor voltage, electrolyte and electrolyte concentration). The optimum ionization voltages were 4500V and 220V for capillary and fragmentor, respectively. Even though the highest ESI efficiency was obtained without electrolytes, the addition of 1.0mM ammonium acetate was shown to be essential to buffer the matrix effect and ensure a consistent response. In contrast to previous studies, deuterated CXB was used as a recovery (surrogate) standard, which enabled the correction of CXB loss during sample preparation. The extraction recovery using solid phase extraction was 87-98%. The instrumental limit of detection of CXB (LOD), 0.33ng/mL, and matrix affected LOD, 0.55ng/mL, were similar and comparable to the previously reported LC-MS/MS LODs. This method was employed to determine CXB concentrations in human plasma samples. Upon administration of 400mg CXB to the healthy women, the concentrations found in the plasma were 440-3300ng/mL. The inter-day repeatability was less than 4% RSD.

Phytochemicals as chemosensitizers: from molecular mechanism to clinical significance

This review provides an overview of the clinical relevance of chemosensitization, giving special reference to the phenolic phytochemicals, curcumin, genistein, epigallocatechin gallate, quercetin, emodin, and resveratrol, which are potential candidates due to their ability to regulate multiple survival pathways without inducing toxicity. We also give a brief summary of all the clinical trials related to the important phytochemicals that emerge as chemosensitizers. The mode of action of these phytochemicals in regulating the key players of the death receptor pathway and multidrug resistance proteins is also abridged. Rigorous efforts in identifying novel chemosensitizers and unraveling their molecular mechanism have resulted in some of the promising candidates such as curcumin, genistein, and polyphenon E, which have gone into clinical trials. Even though considerable research has been conducted in identifying the salient molecular players either contributing to drug efflux or inhibiting DNA repair and apoptosis, both of which ultimately lead to the development of chemoresistance, the interdependence of the molecular pathways leading to chemoresistance is still the impeding factor in the success of chemotherapy. Even though clinical trials are going on to evaluate the chemosensitizing efficacy of phytochemicals such as curcumin, genistein, and polyphenon E, recent results indicate that more intense study is required to confirm their clinical efficacy. Current reports also warrant intense investigation about the use of more phytochemicals such as quercetin, emodin, and resveratrol as chemosensitizers, as all of them have been shown to modulate one or more of the key regulators of chemoresistance.

Chemopreventive properties of dietary rice bran: current status and future prospects

Emerging evidence suggests that dietary rice bran may exert beneficial effects against several types of cancer, such as breast, lung, liver, and colorectal cancer. The chemopreventive potential has been related to the bioactive phytochemicals present in the bran portion of the rice such as ferulic acid, tricin, β-sitosterol, γ-oryzanol, tocotrienols/tocopherols, and phytic acid. Studies have shown that the anticancer effects of the rice bran-derived bioactive components are mediated through their ability to induce apoptosis, inhibit cell proliferation, and alter cell cycle progression in malignant cells. Rice bran bioactive components protect against tissue damage through the scavenging of free radicals and the blocking of chronic inflammatory responses. Rice bran phytochemicals have also been shown to activate anticancer immune responses as well as affecting the colonic tumor microenvironment in favor of enhanced colorectal cancer chemoprevention. This is accomplished through the modulation of gut microflora communities and the regulation of carcinogen-metabolizing enzymes. In addition, the low cost of rice production and the accessibility of rice bran make it an appealing candidate for global dietary chemoprevention. Therefore, the establishment of dietary rice bran as a practical food-derived chemopreventive agent has the potential to have a significant impact on cancer prevention for the global population.

Control of cyclooxygenase-2 expression and tumorigenesis by endogenous 5-methoxytryptophan

Cyclooxygenase-2 (COX-2) expression is induced by mitogenic and proinflammatory factors. Its overexpression plays a causal role in inflammation and tumorigenesis. COX-2 expression is tightly regulated, but the mechanisms are largely unclear. Here we show the control of COX-2 expression by an endogenous tryptophan metabolite, 5-methoxytryptophan (5-MTP). By using comparative metabolomic analysis and enzyme-immunoassay, our results reveal that normal fibroblasts produce and release 5-MTP into the extracellular milieu whereas A549 and other cancer cells were defective in 5-MTP production. 5-MTP was synthesized from L-tryptophan via tryptophan hydroxylase-1 and hydroxyindole O-methyltransferase. 5-MTP blocked cancer cell COX-2 overexpression and suppressed A549 migration and invasion. Furthermore, i.p. infusion of 5-MTP reduced tumor growth and cancer metastasis in a murine xenograft tumor model. We conclude that 5-MTP synthesis represents a mechanism for endogenous control of COX-2 overexpression and is a valuable lead for new anti-cancer and anti-inflammatory drug development.

Tpl2 ablation promotes intestinal inflammation and tumorigenesis in Apcmin mice by inhibiting IL-10 secretion and regulatory T-cell generation

To address the role of Tpl2, a MAP3K8 that regulates innate/adaptive immunity and inflammation, in intestinal tumorigenesis, we crossed a Tpl2 KO allele into the Apc(min/+) genetic background. Here, we show that Apc(min/+)/Tpl2(-/-) mice exhibit a fivefold increase in the number of intestinal adenomas. Bone marrow transplantation experiments revealed that the enhancement of polyposis was partially hematopoietic cell-driven. Consistent with this observation, Tpl2 ablation promoted intestinal inflammation. IL-10 levels and regulatory T-cell numbers were lower in the intestines of Tpl2(-/-) mice, independent of Apc and polyp status, suggesting that they were responsible for the initiation of the enhancement of tumorigenesis caused by the ablation of Tpl2. The low IL-10 levels correlated with defects in mTOR activation and Stat3 phosphorylation in Toll-like receptor-stimulated macrophages and with a defect in inducible regulatory T-cell generation and function. Both polyp numbers and inflammation increased progressively with time. The rate of increase of both, however, was more rapid in Apc(min/+)/Tpl2(-/-) mice, suggesting that the positive feedback initiated by inflammatory signals originating in developing polyps is more robust in these mice. This may be because these mice have a higher intestinal polyp burden as a result of the enhancement of tumor initiation.

Postpartum mammary gland involution drives progression of ductal carcinoma in situ through collagen and COX-2

The prognosis of breast cancer in young women is influenced by reproductive history. Women diagnosed within 5 years postpartum have worse prognosis than nulliparous women or women diagnosed during pregnancy. Here we describe a mouse model of postpartum breast cancer that identifies mammary gland involution as a driving force of tumor progression. In this model, human breast cancer cells exposed to the involuting mammary microenvironment form large tumors that are characterized by abundant fibrillar collagen, high cyclooxygenase-2 (COX-2) expression and an invasive phenotype. In culture, tumor cells are invasive in a fibrillar collagen and COX-2-dependent manner. In the involuting mammary gland, inhibition of COX-2 reduces the collagen fibrillogenesis associated with involution, as well as tumor growth and tumor cell infiltration to the lung. These data support further research to determine whether women at high risk for postpartum breast cancer would benefit from treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) during postpartum involution.

The proapoptotic BH3-only protein Bim is downregulated in a subset of colorectal cancers and is repressed by antiapoptotic COX-2/PGE(2) signalling in colorectal adenoma cells

Overexpression of cyclooxygenase-2 (COX-2) and elevated levels of its enzymatic product prostaglandin E2 (PGE₂) occur in the majority of colorectal cancers and play important roles in colorectal tumorigenesis. However, despite the established prosurvival role of PGE₂ in cancer, the underlying mechanisms are not fully understood. Here, we have shown that PGE₂ suppresses apoptosis via repression of the proapoptotic BH3-only protein Bim in human colorectal adenoma cells. Repression of Bim expression was dependent upon PGE₂-mediated activation of the Raf-MEK-ERK1/2 pathway which promoted Bim phosphorylation and proteasomal degradation. Reduction of Bim expression using RNA interference reduced spontaneous apoptosis in adenoma cells and abrogated PGE₂-dependent apoptosis suppression. Treatment of COX-2-expressing colorectal carcinoma cells with COX-2-selective NSAIDs induced Bim expression, suggesting that Bim repression via PGE₂ signalling may be opposed by COX-2 inhibition. Examination of Bim expression in two established in vitro models of the adenoma-carcinoma sequence revealed that downregulation of Bim expression was associated with tumour progression towards an anchorage-independent phenotype. Finally, immunohistochemical analyses revealed that Bim expression is markedly reduced in approximately 40% of human colorectal carcinomas in vivo. These observations highlight the COX-2/PGE₂ pathway as an important negative regulator of Bim expression in colorectal tumours and suggest that Bim repression may be an important step during colorectal cancer tumorigenesis.

The synergistic anticancer effect of troglitazone combined with aspirin causes cell cycle arrest and apoptosis in human lung cancer cells

Troglitazone (TGZ) is a synthetic thiazolidinedione drug belonging to a group of potent peroxisome proliferator-activated receptor gamma (PPAR gamma) agonists known to inhibit proliferation, alter cell cycle regulation, and induce apoptosis in various cancer cell types. TGZ is an oral anti-type II diabetes drug that can reverse insulin resistance. For more then 100 yr, aspirin, a nonselective cyclooxygenase (COX) inhibitor, has been successfully used as an anti-inflammatory drug. Recently, Aspirin (ASA) and some other nonsteroidal anti-inflammatory drugs (NSAIDs) have drawn much attention for their protective effects against colon cancer and cardiovascular disease; it has been observed that ASA's anti-tumor effect can be attributed to inhibition of cell cycle progression, induction of apoptosis, and inhibition of angiogenesis. In this report we demonstrate for the first time that, when administered in combination, TGZ and ASA can produce a strong synergistic effect in growth inhibition and G(1) arrest in lung cancer CL1-0 and A549 cells. Examination by colony formation assay revealed an even more profound synergy. In Western blot, combined TGZ and ASA also could downregulate Cdk2, E2F-1, cyclin B1, cyclin D3 protein, and the ratio of phospho-Rb/Rb. Importantly, apoptosis was synergistically induced by the combination treatment, as evidenced by caspase-3 activation and PARP cleavage. The involvement of PI3K/Akt inhibition and p27 upregulation, as well as hypophosphorylation of Rac1 at ser71, were demonstrated. Taken together, these results suggest that clinically achievable concentrations of TGZ and ASA used in combination may produce a strong anticancer synergy that warrants further investigation for its clinical applications.

The COX-2/PGE2 pathway: key roles in the hallmarks of cancer and adaptation to the tumour microenvironment

It is widely accepted that alterations to cyclooxygenase-2 (COX-2) expression and the abundance of its enzymatic product prostaglandin E(2) (PGE(2)) have key roles in influencing the development of colorectal cancer. Deregulation of the COX-2/PGE(2) pathway appears to affect colorectal tumorigenesis via a number of distinct mechanisms: promoting tumour maintenance and progression, encouraging metastatic spread, and perhaps even participating in tumour initiation. Here, we review the role of COX-2/PGE(2) signalling in colorectal tumorigenesis and highlight its ability to influence the hallmarks of cancer--attributes defined by Hanahan and Weinberg as being requisite for tumorigenesis. In addition, we consider components of the COX-prostaglandin pathway emerging as important regulators of tumorigenesis; namely, the prostanoid (EP) receptors, 15-hydroxyprostaglandin dehydrogenase and the prostaglandin transporter. Finally, based on recent findings, we propose a model for the cellular adaptation to the hypoxic tumour microenvironment that encompasses the interplay between COX-2, hypoxia-inducible factor 1 and dynamic switches in beta-catenin function that fine-tune signalling networks to meet the ever-changing demands of a tumour.

Celecoxib disrupts the canonical apoptotic network in HTLV-I cells through activation of Bax and inhibition of PKB/Akt

Adult T-cell leukemia/lymphoma (ATLL) is an aggressive lymphoproliferative disease of very poor clinical prognosis associated with infection by the human T-cell leukemia virus type I (HTLV-I). Treatment of patients with ATLL using conventional chemotherapy has limited benefit because HTLV-I cells are refractory to most apoptosis-inducing agents. In this study, we report that Celecoxib induces cell death via the intrinsic mitochondrial pathway in HTLV-I transformed leukemia cells. Treatment with Celecoxib was associated with activation of Bax, decreased expression of Mcl-1, loss of the mitochondrial membrane potential and caspase-9-dependent apoptosis. These effects were independent from Bcl-2 and Bcl-xL. We also found that Celecoxib inhibited the Akt/GSK3 beta survival pathway in HTLV-I cells.

Tumor size significantly correlates with postoperative liver metastases and COX-2 expression in patients with resectable pancreatic cancer

BACKGROUND/AIM

Local treatment often fails in patients with resectable pancreatic cancer due to the postoperative development of distant metastases, especially liver metastases. We determined the prognostic factors for postoperative liver metastases in pancreatic cancer patients following surgical resection with combined radiotherapy.

METHODS

Sixty-four patients with nonmetastatic, resectable pancreatic cancer were entered into this study. All of these patients had pancreatic resection surgery combined with radiotherapy. The development of postoperative liver metastases was carefully followed, and the survival ratio was evaluated using the Kaplan-Meier method. The prognostic importance of clinicopathological factors and molecular characteristics was analyzed by the Cox proportional hazards model. The correlation study was performed using Fisher's exact test.

RESULTS

Tumor size, curability, and histological type of differentiation were statistically significant independent prognostic factors. On multivariate analysis, curability and histological type of differentiation were statistically significant. Only tumor size (> or = 3 cm) was significantly correlated with postoperative liver metastases, as well as cyclooxygenase-2 expression.

CONCLUSIONS

There were three significant prognostic factors in patients with resectable pancreatic cancer who had local therapy. Patients who have a large tumor require particularly careful follow-up for postoperative liver metastases.

Prostaglandin E receptor EP4 antagonist suppresses osteolysis due to bone metastasis of mouse malignant melanoma cells

We examined the effects of prostaglandin E (PGE) receptor subtype EP4 antagonist on bone metastasis of cancer to clarify PGE's role in bone metastasis. Metastatic regions were detected in femurs accompanying severe bone loss in mice injected with B16 malignant melanoma cells. Administration of EP4 antagonist restored the bone loss induced by B16 melanoma. Adding B16 cells induced osteoclast formation in the coculture of bone marrow cells and osteoblasts without any exogenous bone-resorbing factor, and EP4 antagonist completely suppressed the osteoclast formation induced by B16 cells. Therefore, EP4 antagonist is a possible candidate for the therapy of bone metastasis of cancer.

Selenium regulates cyclooxygenase-2 and extracellular signal-regulated kinase signaling pathways by activating AMP-activated protein kinase in colon cancer cells

Epidemiologic and experimental evidences indicate that selenium, an essential trace element, can reduce the risk of a variety of cancers. Protection against certain types of cancers, particularly colorectal cancers, is closely associated with pathways involving cyclooxygenase-2 (COX-2). We found that AMP-activated protein kinase (AMPK), which functions as a cellular energy sensor, mediates critical anticancer effects of selenium via a COX-2/prostaglandin E(2) signaling pathway. Selenium activated AMPK in tumor xenografts as well as in colon cancer cell lines, and this activation seemed to be essential to the decrease in COX-2 expressions. Transduction with dominant-negative AMPK into colon cancer cells or application of cox-2(-/-)-negative cells supported the evidence that AMPK is an upstream signal of COX-2 and inhibits cell proliferation. In HT-29 colon cancer cells, carcinogenic agent 12-O-tetradecanoylphorbol-13-acetate (TPA) activated extracellular signal-regulated kinase (ERK) that led to COX-2 expression and selenium blocked the TPA-induced ERK and COX-2 activation via AMPK. We also showed the role of a reactive oxygen species as an AMPK activation signal in selenium-treated cells. We propose that AMPK is a novel and critical regulatory component in selenium-induced cancer cell death, further implying AMPK as a prime target of tumorigenesis.

Effects of selective PGE2 receptor antagonists in esophageal adenocarcinoma cells derived from Barrett's esophagus

Accumulating evidence suggests that COX-2-derived prostaglandin E(2) (PGE(2)) plays an important role in esophageal adenocarcinogenesis. Recently, PGE(2) receptors (EP) have been shown to be involved in colon cancer development. Since it is not known which receptors regulate PGE(2) signals in esophageal adenocarcinoma, we investigated the role of EP receptors using a human Barrett's-derived esophageal adenocarcinoma cell line (OE33). OE33 cells expressed COX-1, COX-2, EP(1), EP(2) and EP(4) but not EP(3) receptors as determined by real time RT-PCR and Western-blot. Treatment with 5-aza-dC restored expression, suggesting that hypermethylation is involved in EP(3) downregulation. Endogenous PGE(2) production was mainly due to COX-2, since this was significantly suppressed with COX-2 inhibitors (NS-398 and SC-58125), but not COX-1 inhibitors (SC-560). Cell proliferation ((3)H-thymidine uptake) was significantly inhibited by NS-398 and SC-58125, the EP(1) antagonist SC-51322, AH6809 (EP(1)/EP(2) antagonist), and the EP(4) antagonist AH23848B, but was not affected by exogenous PGE(2). However, treatment with the selective EP(2) agonist Butaprost or 16,16-dimethylPGE(2) significantly inhibited butyrate-induced apoptosis and stimulated OE33 cell migration. The effect of exogenous PGE(2) on migration was attenuated when cells were first treated with EP(1) and EP(4) antagonists. These findings suggest a potential role for EP selective antagonists in the treatment of esophageal adenocarcinoma.

Mediators of PGE2 synthesis and signalling downstream of COX-2 represent potential targets for the prevention/treatment of colorectal cancer

Colorectal cancer is a major cause of mortality and whilst up to 80% of sporadic colorectal tumours are considered preventable, trends toward increasing obesity suggest the potential for a further increase in its worldwide incidence. Novel methods of colorectal cancer prevention and therapy are therefore of considerable importance. Non-steroidal anti-inflammatory drugs (NSAIDs) are chemopreventive against colorectal cancer, mainly through their inhibitory effects on the cyclooxygenase isoform COX-2. COX enzymes represent the committed step in prostaglandin biosynthesis and it is predominantly increased COX-2-mediated prostaglandin-E2 (PGE2) production that has a strong association with colorectal neoplasia, by promoting cell survival, cell growth, migration, invasion and angiogenesis. COX-1 and COX-2 inhibition by traditional NSAIDs (for example, aspirin) although chemopreventive have some side effects due to the role of COX-1 in maintaining the integrity of the gastric mucosa. Interestingly, the use of COX-2 selective NSAIDs has also shown promise in the prevention/treatment of colorectal cancer while having a reduced impact on the gastric mucosa. However, the prolonged use of high dose COX-2 selective inhibitors is associated with a risk of cardiovascular side effects. Whilst COX-2 inhibitors may still represent viable adjuvants to current colorectal cancer therapy, there is an urgent need to further our understanding of the downstream mechanisms by which PGE2 promotes tumorigenesis and hence identify safer, more effective strategies for the prevention of colorectal cancer. In particular, PGE2 synthases and E-prostanoid receptors (EP1-4) have recently attracted considerable interest in this area. It is hoped that at the appropriate stage, selective (and possibly combinatorial) inhibition of the synthesis and signalling of those prostaglandins most highly associated with colorectal tumorigenesis, such as PGE2, may have advantages over COX-2 selective inhibition and therefore represent more suitable targets for long-term chemoprevention. Furthermore, as COX-2 is found to be overexpressed in cancers such as breast, gastric, lung and pancreatic, these investigations may also have broad implications for the prevention/treatment of a number of other malignancies.

Phytoestrogens and colorectal cancer prevention

Because colorectal cancer (CRC) is a leading cause of cancer mortality in the Western industrialized world, future chemopreventive strategies will be of high socioeconomic importance. Lower CRC incidences in Far Eastern countries in part may be attributed to high nutritional intake of soy and its abundance in phytoestrogens. Phytoestrogens are plant-derived substances which, due to molecular similarities to endogenous estrogens, distinctly interact with estrogen receptors ERalpha and ERbeta. Both genomic and nongenomic mechanisms have been shown to be responsible for possible anticarcinogenic properties of phytoestrogens, such as induction of apoptosis and inhibition of tyrosine kinases and DNA topoisomerases. This chapter provides a comprehensive review of a variety of studies exploring possible relations between phytoestrogen uptake and CRC risk. While in vitro and animal studies in general are somewhat supportive of a protective role of phytoestrogens against CRC, epidemiological work so far performed does not allow any conclusion on this issue. Studies about mechanisms of phytoestrogenic action against CRC development have been evaluated as well. Because estrogens, vitamin D, and calcium are frequently suggested to be important in CRC prevention, studies concentrating on interactions of phytoestrogens with these substances have been performed. Although support in evidence for a protective effect of phytoestrogens against CRC has increased over the last decade, it is still too early to give a definite recommendation, especially in view of enduring inconsistencies about concentrations most likely to be effective. Further experimental, and particularly epidemiological, studies are required to advance our understanding of the role of phytoestrogens against colon carcinogenesis.

Celecoxib induces apoptosis in cervical cancer cells independent of cyclooxygenase using NF-kappaB as a possible target

PURPOSE

Recently, many studies have shown that celecoxib induces apoptosis in various cancer cells by different mechanisms depending on the cell type. This study examined the apoptotic effect of celecoxib in cervical cancer cells and its mechanism.

METHODS

Cell viability was measured by MTT assay and apoptosis was examined by DNA fragmentation and flow cytometry. Western blotting and immunoprecipitation were used to explore various mechanisms of celecoxib-induced apoptosis. The activation of NF-kappaB was confirmed by EMSA.

RESULTS

Celecoxib induced apoptosis independent of COX-2 activity. This event accompanied the activation of caspase-8 and -9 with Bid cleavage and the loss of mitochondrial membrane potential. The protective effect of caspase-8 and -9 inhibitors on celecoxib-induced apoptosis suggests the importance of caspase-8 and -9 activation in this apoptotic pathway. Fas/FADD-mediated apoptotic pathway was detected only in C33A cells, demonstrated by the immunoprecipitation of Fas-FADD in celecoxib-treated cells and the protective effect of FADD dominant negative mutant. Finally, NF-kappaB appeared to be involved in celecoxib-induced apoptosis, as revealed by increased NF-kB DNA binding activity in a time-dependent manner and attenuation of its proapoptotic effect by N-tosyl-L-phenylalanyl-chloromethyl ketone, an NF-kB blocker.

CONCLUSIONS

These data show that caspase-8 and -9 are involved in the apoptotic effect of celecoxib in cervical cancer cells. This requires the FADD-dependent pathway in a cell type-specific manner. In addition, NF-kappaB may play a key role in celecoxib-induced apoptosis.

Increased NF-kappaB DNA binding but not transcriptional activity during apoptosis induced by the COX-2-selective inhibitor NS-398 in colorectal carcinoma cells

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit colorectal neoplasia, an effect that is associated with their ability to induce apoptosis. Although NSAIDs have been reported to inhibit NF-κB, more recent studies show activation of NF-κB by NSAIDs. NF-κB commonly shows antiapoptotic activity and is implicated in the therapeutic resistance of cancer cells. The effects of highly COX-2-selective NSAIDs such as NS-398 on NF-κB in colorectal tumour cells have not been reported. Therefore, we addressed whether NF-κB has a role in NS-398-induced apoptosis of colorectal cancer cells. Treatment of HT-29 colorectal carcinoma cells with doses of NS-398 (50–75 μM) known to induce apoptosis had no effect on NF-κB for up to 48 h. However after 72 and 96 h NF-κB DNA-binding activity was increased by NS-398, in parallel with apoptosis induction. NS-398-treated HT-29 cells showed increased p50 homodimer binding and an induction of p50/p65 heterodimers, as demonstrated by supershift assay. However, although NS-398 increased NF-κB DNA binding it did not increase NF-κB-dependent reporter activity and inhibition of NF-κB DNA binding did not enhance NS-398-induced apoptosis. This indicates that NF-κB activated by NS-398 is transcriptionally inactive and is an encouraging result for the use of COX-2-selective NSAIDs not only in chemoprevention but also as novel therapies for colon cancer.

Cyclooxygenase-2 inhibitor NS398 enhances antitumor effect of irradiation on hormone refractory human prostate carcinoma cells

PURPOSE

We examined the potential therapeutic effect of NS398, a selective cyclooxygenase-2 (COX-2) inhibitor, combined with irradiation on human prostate adenocarcinoma DU145 cells.

MATERIALS AND METHODS

The effect on tumor growth, proliferation testing and clonogenic survival was determined to evaluate its antitumor effect when exposed to NS398 or combined with irradiation. Immunoblotting analyses were done to detect the expression of COX-2, nuclear factor-kappaB p50 and Rel A p65 because evidence suggested a biological association of COX-2 with alterations in these markers. Reverse transcriptase-polymerase chain reaction was also performed to show its effect on the transcription level of COX-2.

RESULTS

Exposure of DU145 cells to NS398 alone suppressed proliferation in a dose and time dependent manner. Examination of the NS398 effect on the radiation response showed marked enhancement of radiosensitivity. Western blot indicated that NS398 down-regulated the expression of COX-2, nuclear factor-kappaB, p50 and Rel A p65, whereas the effect was more pronounced when combined with irradiation. Reverse transcriptase-polymerase chain reaction showed that the NS398 antitumor effect was associated with COX-2 transcription inhibition. Importantly COX-2 expression was enhanced by irradiation but this phenomenon was abolished when cells were exposed to NS398. Inhibition of tumor growth in animal model was observed when mice were treated with NS398 alone and irradiation alone, and this effect was maximal when treated with NS398 and irradiation.

CONCLUSIONS

These results suggest that NS398 could be used as a potential therapeutic agent combined with irradiation for prostate adenocarcinoma.

Development and validation of an automated SPE-LC-MS/MS assay for valdecoxib and its hydroxylated metabolite in human plasma

A sensitive and specific liquid chromatography-tandem mass spectrometry assay was developed to quantitate valdecoxib (I) and its hydroxylated metabolite (II) in human plasma. The analytes (I and II) and a structurally analogue internal standard (IS) were extracted on a C(18) solid phase extraction (SPE) cartridge using a Zymark RapidTrace automation system. The chromatographic separation was performed on a narrow-bore reverse phase Zorbax XDB-C(8) HPLC column with a mobile phase of acetonitrile:water (50:50, v/v) containing 10 mM ammonium acetate. The analytes were ionized using negative electrospray mass spectrometry, then detected by multiple reaction monitoring (MRM) with a tandem mass spectrometer. The precursor to product ion transitions of m/z 313-->118 and m/z 329-->196 were used to measure I and II, respectively. The assay exhibited a linear dynamic range of 0.5-200 ng/ml of I and II in human plasma with absolute recoveries from plasma at 91 and 86%, respectively. The lower limit of quantitation was 0.5 ng/ml for I and II. Acceptable precision and accuracy were obtained for concentrations over the calibration curve ranges (0.5-200 ng/ml). Sample analysis time for each injection was 5 min, a throughput of 70 human plasma standards and samples per run was achieved. The assay has been successfully used to analyze human plasma samples to support clinical phase I and II studies.

Antiinflammatory property of 3-aryl-5-(n-propyl)-1,2,4-oxadiazoles and antimicrobial property of 3-aryl-5-(n-propyl)-4,5-dihydro-1,2,4-oxadiazoles: their syntheses and spectroscopic studies

The synthesis of six 3-aryl-5-(n-propyl)-4,5dihydro-1,2,4-oxadiazoles 3a-f has been achieved in a facile manner by the reaction of an appropriate arylamidoxime 1a-f with butyraldehyde 2. Oxidation of 3a-f individually using MnO(2) in CH(2)Cl(2) or sodium hypochlorite in THF/H(2)O furnished 1,2,4-oxadiazoles 4a-f in good to excellent yields. Compounds 4a-f were also evaluated against inflammation. Except 4e, all of them reduced inflammation, however, 4c presented better antiinflammatory activity. A preliminary antimicrobial activity tests of 3a-f showed that these compounds possess activity against some microorganisms. In fact, 3c and 3f have been found to be more effective against Staphylococcus aureus, Mycobacterium smegmatis, and Candida albicans.

Pharmacokinetics and metabolism of a COX-2 inhibitor, valdecoxib, in mice

The pharmacokinetics and metabolism of valdecoxib, a potent cyclooxygenase-2 selective inhibitor, were investigated in mice. Valdecoxib was extensively metabolized after a single 5 mg/kg oral administration of [(14)C]valdecoxib and elimination of unchanged drug was minor (less than 1%) in male and female mice. The total mean percentage of administered radioactive dose recovered was 99.8% in the male mice and 94.7% in the female mice. Sixteen metabolites were identified in mouse plasma, red blood cells, urine, and feces. The main phase I metabolic pathway of valdecoxib in mice involved the oxidation of the 5-methyl group to form the active hydroxymethyl metabolite M1. M1 was further oxidized to the carboxylic acid metabolite M4, which underwent opening of the isoxazole ring to form M6 and M13. Phase II metabolism included glucuronide, glucoside, and methyl sulfone conjugations. M1 was also conjugated with glucuronic acid and glucose to yield M-G and M1-glucose, respectively. Three novel methylsulfone conjugates M20, M21, and M21-G were detected in blood or urine. Valdecoxib and M1 were the major radioactive components in plasma and red blood cells. The plasma area under the curve from zero to infinity (AUC(0-infinity)) values for valdecoxib and M1 were 3.58 and 0.850 microg. h/ml in males and 2.08 and 1.63 microg. h/ml in females, respectively. The RBC AUC(0-infinity) values for valdecoxib and M1 were 12.1 and 22.6 microg. h/g in males and 6.42 and 35.2 microg. h/g in females, respectively.

Role of prostaglandin E produced by osteoblasts in osteolysis due to bone metastasis

Prostaglandin E2 (PGE2) is produced in bone mainly by osteoblasts and stimulates bone resorption. Osteolytic bone metastasis of cancers is accompanied by bone resorption. In this study, we examined the roles of PGE2 in osteolysis due to bone metastasis of breast cancer. Injection of human breast cancer cells, MDA-MB-231 (MDA-231), into nude mice causes severe osteolysis in the femur and tibia. The expression of cyclo-oxygenase-2 (COX-2) and the receptor activator of NF-kappaB ligand (RANKL), a key molecule in osteoclast differentiation, mRNAs was markedly elevated in bone with metastasis. When MDA-231 cells were cocultured with mouse calvaria, COX-2-induced PGE2 production and bone resorption progressed. The contact with MDA-231 cells could induce the expression of COX-2 and RANKL in osteoblasts by mechanisms involving MAP kinase and NF-kappaB. The blockage of PGE2 signal by indomethacin and EP4 antagonist abrogated the osteoclast formation induced by the breast cancer cells. Here, we show a PGE-dependent mechanism of osteolysis due to bone metastasis.

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.

Syntheses of ferulic acid derivatives and their suppressive effects on cyclooxygenase-2 promoter activity

Novel ferulic acid derivatives in which feruloyl groups were attached to the hydroxyl groups of myo-inositol 1,3,5-orthoformate derivatives were synthesized. These feruloyl-myo-inositols suppressed the cyclooxygenase-2 (COX-2) promoter activity in a concentration-dependent manner. Among the examined compounds, compound 9 showed the highest activity. A treatment with 100 microM of compound 9 for 24 h resulted in a 50% decrease of COX-2 promoter activity without marked cytotoxicity. Both the molecular structure in which two ferulic acid moieties are facing each other and the molecular hydrophobicity may be essential for the suppression of COX-2 promoter activity.

Diclofenac antagonizes peroxisome proliferator-activated receptor-gamma signaling

Although nonsteroidal anti-inflammatory drugs (NSAIDs) are used as cancer chemopreventative agents, their mechanism is unclear because NSAIDs have cyclooxygenase-independent actions. We investigated an alternative target for NSAIDs, peroxisome proliferator-activated receptor-gamma (PPARgamma), activation of which decreases cancer cell proliferation. NSAIDs have been shown to activate this receptor, but only at high concentrations. Here, we have examined binding of diclofenac to PPARgamma using a cis-parinaric acid displacement assay and studied the effect of diclofenac effect on PPARgamma trans-activation in a COS-1 cell reporter assay. Unexpectedly, diclofenac bound PPARgamma at therapeutic concentrations (K(i) = 700 nM) but induced only 2-fold activation of PPARgamma at a concentration of 25 microM and antagonized PPARgamma trans-activation by rosiglitazone. This antagonism was overcome with increasing rosiglitazone concentrations, indicating that diclofenac is a partial agonist. No effect of diclofenac was seen without exogenous receptor, confirming that it was working through a PPARgamma-specific mechanism. This is the first description of an NSAID that can antagonize PPARgamma. In addition, this is the first time that an NSAID has been shown to bind this receptor at clinically meaningful concentrations. The physiological relevance of these findings was tested using adipocyte differentiation and cancer cell proliferation assays. Diclofenac decreased PPARgamma-mediated adipose cell differentiation by 60% and inhibited the action of rosiglitazone on the prostate cancer cell line, DU-145, allowing a 3-fold increase in proliferation. This work shows that standard doses of diclofenac may have pharmacodynamic interactions with rosiglitazone and this has therapeutic implications, both in the management of type 2 diabetes and during cancer treatment.

Relationship between APC genotype, polyp distribution, and oral sulindac treatment in the colon and rectum of patients with familial adenomatous polyposis

PURPOSE

Familial adenomatous polyposis is an inherited colorectal cancer syndrome characterized by the presence of multiple adenomatous colorectal polyps. Molecular studies have revealed that germline mutations in the APC gene are the underlying cause of the disease. The nonsteroidal anti-inflammatory agent sulindac has been shown to reduce the number of colorectal adenomas. Most sulindac trials in the large bowel have focused on the distal colon and relatively little is known about its effect on the proximal colon. Moreover, it is unknown whether the site of the APC mutation affects the efficacy of sulindac.

METHODS

This study investigated whether there were regional differences in the effect of sulindac on the colon and whether response to sulindac was dependent on the site of mutation in the APC gene. In an open prospective study 17 patients with familial adenomatous polyposis were treated with 300 mg oral sulindac daily for four months followed by a washout phase of six months. Ten of the patients had an intact colon and seven had rectal stumps only. The number, size, and the degree of dysplasia of the adenomas were evaluated by colonoscopy at entry, end of treatment and end of the study.

RESULTS

Overall, a statistically significant decrease in the number of adenomas was observed (120 +/- 112 to 28 +/- 64, P = 0.007). After cessation of sulindac treatment the number of adenomas increased to 48 +/- 44.5, but remained significantly lower than the values observed at baseline. In the ten patients with intact colons, adenomas decreased by sevenfold in the proximal colon (103 +/- 73 to 15.1 +/- 47.4, P = 0.011) and twofold in the distal colon (80 +/- 52 to 29.6 +/- 37.2, P = 0.005). The size of adenomas and the grade of dysplasia also decreased. No correlation could be seen between the APC mutation site and the response to treatment.

CONCLUSION

These data indicate that sulindac reduces the number of adenomas in the entire colon and that the effect seems to be more pronounced in the proximal colon.

A decrease in remodeling accounts for the accumulation of arachidonic acid in murine mast cells undergoing apoptosis

The goal of this study was to examine arachidonic acid (AA) metabolism by murine bone marrow-derived mast cells (BMMC) during apoptosis induced by cytokine depletion. BMMC deprived of cytokines for 12-48 h displayed apoptotic characteristics. During apoptosis, levels of AA, but not other unsaturated fatty acids, correlated with the percentage of apoptotic cells. A decrease in both cytosolic phospholipase A(2) expression and activity indicated that cytosolic phospholipase A(2) did not account for AA mobilization during apoptosis. Free AA accumulation is also unlikely to be due to decreases in 5-lipoxygenase and/or cyclooxygenase activities, since BMMC undergoing apoptosis produced similar amounts of leukotriene B(4) and significantly greater amounts of PGD(2) than control cells. Arachidonoyl-CoA synthetase and CoA-dependent transferase activities responsible for incorporating AA into phospholipids were not altered during apoptosis. However, there was an increase in arachidonate in phosphatidylcholine (PC) and neutral lipids concomitant with a 40.7 +/- 8.1% decrease in arachidonate content in phosphatidylethanolamine (PE), suggesting a diminished capacity of mast cells to remodel arachidonate from PC to PE pools. Further evidence of a decrease in AA remodeling was shown by a significant decrease in microsomal CoA-independent transacylase activity. Levels of lyso-PC and lyso-PE were not altered in cells undergoing apoptosis, suggesting that the accumulation of lysophospholipids did not account for the decrease in CoA-independent transacylase activity or the induction of apoptosis. Together, these data suggest that the mole quantities of free AA closely correlated with apoptosis and that the accumulation of AA in BMMC during apoptosis was mediated by a decreased capacity of these cells to remodel AA from PC to PE.

Inhibition of store-operated calcium entry contributes to the anti-proliferative effect of non-steroidal anti-inflammatory drugs in human colon cancer cells

Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit proliferation and angiogenesis in colorectal cancer. We examined a possible involvement of store-operated calcium (SOC) entry in human colon carcinoma cells (HRT-18), which require calcium for proliferation. Acetyl-salicylic-acid (ASA), mefenamic acid (MEF) and sulindac sulfide (SUS) inhibited cell proliferation with the following order of potency: SUS > MEF >> ASA. SUS but not MEF and ASA induced apoptosis following low-dose treatment. Furthermore, SUS and MEF significantly altered the cell cycle distribution. The ability of NSAIDs to inhibit SOC entry was assessed by measuring the intracellular calcium concentration ([Ca2+]i) in response to calcium store depletion using the endoplasmic calcium ATPase inhibitor thapsigargin. SUS and MEF, but not ASA significantly inhibited SOC entry. A causal link between SOC entry inhibition and anti-proliferative activity was tested using the inorganic SOC entry inhibitor La3+ and the specific organic inhibitor N-1-n-octyl-3,5-bis-(4-pyridyl)triazole (DPT). Both La3+ and DPT inhibited cell proliferation and SOC entry. Analogous to MEF, the anti-proliferative effect of DPT was mediated by cell cycle arrest and not by induction of apoptosis. These data indicate a role of SOC entry for cell proliferation in cancer cells and suggest a novel anti-proliferative NSAID mechanism in addition to its known influence on lipid metabolism.

Cyclooxygenase (COX)-1 expressing macrophages/microglial cells and COX-2 expressing astrocytes accumulate during oligodendroglioma progression

Cyclooxygenases (COX, prostaglandin endoperoxide synthases, PGG/H synthases) are potent mediators of edema, impeding blood flow and immunomodulation in the pathologically altered brain. Two COX iso-enzymes have been associated with brain disease, the constitutively expressed COX-1 and the cytokine-inducible COX-2. We have used single and double labeling immunohistochemistry to analyse COX-1 and COX-2 expression in twenty-six primary WHO grade II oligodendrogliomas, sixteen primary WHO grade III anaplastic oligodendrogliomas, twenty-seven matched recurrences and ten neuropathologically unaltered brains. COX-1 immunoreactivity was predominantly observed in macrophages/microglial cells. The number of COX-1 expressing macrophages/microglial cells was significantly lower in primary oligodendrogliomas than in primary anaplastic oligodendrogliomas (P<0.0001) and in anaplastic oligodendroglioma relapses (P=0.011). Patients with low COX-1 labeling scores in the primary tumors had significantly longer time to progression and overall survival (P=0.0285) than those with high COX-1 labeling scores. COX-2 immunoreactivity was predominantly observed in disseminated neurons and astrocytes. In glioblastoma multiforme relapses, accumulation of COX-2 expressing astrocytes was observed surrounding areas of focal necrosis. The number of COX-2 expressing astrocytes was significantly (P=0.0471) lower in primary oligodendrogliomas than in high grade oligodendroglioma relapses. These data provide convincing evidence for the differential accumulation of cyclooxygenase isoforms during oligodendroglioma progression in vivo.

Characterization of metabolites of Celecoxib in rabbits by liquid chromatography/tandem mass spectrometry

The metabolism of the anti-inflammatory drug Celecoxib in rabbits was characterized using liquid chromatography (LC)/tandem mass spectrometry (MS/MS) with precursor ion and constant neutral loss scans followed by product ion scans. After separation by on-line liquid chromatography, the crude urine samples and plasma and fecal extracts were analyzed with turbo-ionspray ionization in negative ion mode using a precursor ion scan of m/z 69 (CF(3)) and a neutral loss scan of 176 (dehydroglucuronic acid). The subsequent product ion scans of the [M - H] ions of these metabolites yielded the identification of three phase I and four phase II metabolites. The phase I metabolites had hydroxylations at the methyl group or on the phenyl ring of Celecoxib, and the subsequent oxidation product of the hydroxymethyl metabolite formed the carboxylic acid metabolite. The phase II metabolites included four positional isomers of acyl glucuronide conjugates of the carboxylic acid metabolite. These positional isomers were caused by the alkaline pH of the rabbit urine and were not found in rabbit plasma. The chemical structures of the metabolites were characterized by interpretation of their product ion spectra and comparison of their LC retention times and the product ion spectra with those of the authentic synthesized standards.

Suppression by flavonoids of cyclooxygenase-2 promoter-dependent transcriptional activity in colon cancer cells: structure-activity relationship

Cyclooxygenase-2 (COX-2) plays an important role in carcinogenesis. Investigation of the suppressive action of twelve flavonoids of different chemical classes on the transcriptional activity of the COX-2 gene in human colon cancer DLD-1 cells using a reporter gene assay have revealed quercetin to be the most potent suppressor of COX-2 transcription (IC50 = 10.5 microM), while catechin and epicatechin showed weak activity (IC50 = 415.3 microM). Flavonoids have three heterocyclic rings as a common structure. A structure-activity study indicated that the number of hydroxyl groups on the B ring and an oxo group at the 4-position of the C ring are important in the suppression of COX-2 transcriptional activity. A low electron density of the oxygen atom in the hydroxyl group of the A ring was also important. Further examination of the role of the hydroxyl group in the A ring showed that bromination of resacetophenone to give 3,5-dibromo-2,4-dihydroxyacetophenone resulted in a 6.8-fold increase in potency for suppressing COX-2 promoter activity. These results provide a basis for the design of improved suppressors of COX-2 transcriptional activity.

Familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is a dominantly inherited familial cancer syndrome characterized by an increased predisposition to colorectal cancer and other benign and malignant extra-colonic lesions. FAP has been linked to germline mutations of the adenomatous polyposis coli (APC) gene that encodes a protein with 2,843 amino acids that has important functions in the regulation of cell growth. A genotype-phenotype correlation has also been observed between mutations in the APC gene and polyp phenotype. We review the clinical and genetic features of this disorder and provide information on the diagnostic approaches and treatment options available for this disease.

The action mechanism of cyclooxygenase-2 inhibitor for treatment of experimental allergic neuritis

We previously reported the effect of a cyclooxygenase (COX)-2 inhibitor, nimesulide, on experimental allergic neuritis (EAN) in both the induction and effector phases, in contrast to the usual COX inhibitor, which was effective only when administered in the induction phase. To assess the mechanism of action of a COX-2 inhibitor, we studied the expression of COX-2 and assayed plasma levels of prostaglandins, and also compared the clinical effect of a COX-2 inhibitor with a 5-lipoxygenase (LO) inhibitor, which is responsible for another pathway of arachidonic acid metabolism. Nerves of EAN rats showed distinct expression of COX-2, which is derived mostly from endoneurial macrophages. Treatment with a COX-2 inhibitor had no effect on its expression. However, prostaglandin estradiol (E(2)) concentration of plasma was significantly lower compared with the control group. The LO inhibitor showed no clinical effect. These results suggest that a selective COX-2 inhibitor is effective in the effector phase by its influence on macrophages that are responsible for nerve degeneration.

Aspirin induces cell death and caspase-dependent phosphatidylserine externalization in HT-29 human colon adenocarcinoma cells

The induction of cell death by aspirin was analysed in HT-29 colon carcinoma cells. Aspirin induced two hallmarks of apoptosis: nuclear chromatin condensation and increase in phosphatidylserine externalization. However, aspirin did not induce either oligonucleosomal fragmentation of DNA, decrease in DNA content or nuclear fragmentation. The effect of aspirin on Annexin V binding was inhibited by the caspase inhibitor Z-VAD.fmk, indicating the involvement of caspases in the apoptotic action of aspirin. However, aspirin did not induce proteolysis of PARP, suggesting that aspirin does not increase nuclear caspase 3-like activity in HT-29 cells. This finding may be related with the 'atypical' features of aspirin-induced apoptosis in HT-29 cells.

The economic burden associated with colon cancer in the United States

Colon cancer, the second most frequent cause of cancer deaths in the United States, is primarily a disease of the elderly. As the current population ages in the coming decades, the economic burden of colon cancer is expected to increase substantially. The primary objective of this study was to estimate the economic burden of hospitalizations for colon cancer. Secondary objectives were to assess the relationship between risk factors, including age, and treatment charges and to estimate the number of hospital admissions through the year 2050. We examined hospital discharge data for the years 1991 through 1994 from the Healthcare Cost and Utilization Project of the US Agency for Health Care Policy and Research to assess the characteristics of hospitalizations forcolon cancer in the United States. Census data were used to project the annual number of admissions through the year 2050. The mean number of admissions for colon cancer was 237,754 per year, the mean length of stay was 11.1 days per admission, and mean total hospital charges were $4.57 billion per year. Most of the charges were incurred by people aged > or = 60 years (83.08%) and by people with no known risk factors for colon cancer (93.96%). Based on census projections, between 1992 and 2050 the annual number of colon cancer-related admissions will increase from 215,000 to 471,000 in people aged > or = 50 years and from 192,000 to 448,000 in people aged > or = 60 years. Knowledge of additional risk factors and more effective preventive, screening, diagnostic, and treatment procedures may help prevent the predicted increase in colon cancer-related hospitalizations in the next century.

Non steroidal anti-inflammatory drugs and colorectal cancer: is there a way forward?

Non steroidal anti-inflammatory drugs (NSAIDs) have diverse clinical applications through modulation of oxidative processes and cell signalling. Observations that these agents may inhibit human colorectal carcinogenesis have produced great excitement. However, comparative data relating to their chemopreventative effectiveness or to relevant mechanisms of action remains unclear. This review considers the clinical and epidemiological evidence for colorectal tumour prevention by NSAIDs against current concepts of drug mechanisms. We also propose areas of further research for potential therapeutic advancement.