Tumor invasiveness and liver metastasis of colon cancer cells correlated with cyclooxygenase-2 (COX-2) expression and inhibited by a COX-2-selective inhibitor, etodolac

Doxycycline inhibits cell proliferation and invasive potential: combination therapy with cyclooxygenase-2 inhibitor in human colorectal cancer cells

Matrix metalloproteinases (MMPs) and cyclooxygenase (COX) enzymes play pivotal roles in the metastatic process of colorectal cancers. Inhibition of both MMPs and COX could be an attractive option for the inhibition of cell growth and invasion. Two human colorectal cancer cell lines, LS174T and HT29, were challenged with MMP inhibitor (doxycycline), selective COX-2 inhibitor (NS-398), or a combination of these agents to evaluate cancer cell proliferation and invasion. Dose-dependent growth inhibition was observed in both cell lines when they were treated with a single therapy. These effects were not related to MMP-2 or MMP-9 expression potential of the cell lines. Doxycycline (10 microg/mL) induced G(0)/G(1) arrest, and 20 microg/mL provoked annexin V positivity and up-regulated caspase-3 activity in HT29 cells. However, 20 microg/mL doxycycline caused no distinct apoptotic change in LS174T cells. Although MMP expression was not inhibited by 5 to 10 microg/mL doxycycline or 50 to 100 micromol/L NS-398, MMPs' activities were down-regulated by these concentrations. Cellular invasion was noticed in LS174T cells, but their capacity for invasion was diminished by these inhibitors. The antiproliferative and antiinvasive effects of the combination therapy were more pronounced. Doxycycline (5 microg/mL) with 50 micromol/L NS-398 inhibited cell proliferation and doxycycline (5 microg/mL) with 100 micromol/L NS-398 attenuated MMP expression and activity, as well as capacity for invasion, compared with single therapy. These data suggest that combination therapy consisting of an MMP inhibitor with a COX-2 inhibitor is an attractive approach to the treatment of colorectal cancers. The use of this treatment regimen for chemoprevention or treatment of colorectal cancers should be considered in future clinical trials.

Protein kinase C (PKC) betaII induces cell invasion through a Ras/Mek-, PKC iota/Rac 1-dependent signaling pathway

Protein kinase C betaII (PKCbetaII) promotes colon carcinogenesis. Expression of PKCbetaII in the colon of transgenic mice induces hyperproliferation and increased susceptibility to colon cancer. To determine molecular mechanisms by which PKCbetaII promotes colon cancer, we established rat intestinal epithelial (RIE) cells stably expressing PKCbetaII. Here we show that RIE/PKCbetaII cells acquire an invasive phenotype that is blocked by the PKCbeta inhibitor LY379196. Invasion is not observed in RIE cells expressing a kinase-deficient PKCbetaII, indicating that PKCbetaII activity is required for the invasive phenotype. PKCbetaII induces activation of K-Ras and the Ras effector, Rac1, in RIE/PKCbetaII cells. PKCbetaII-mediated invasion is blocked by the Mek inhibitor, U0126, and by expression of either dominant negative Rac1 or kinase-deficient atypical PKCiota. Expression of constitutively active Rac1 induces Mek activation and invasion in RIE cells, indicating that Rac1 is the critical downstream effector of PKCbetaII-mediated invasion. Taken together, our results define a novel PKCbetaII --> Ras --> PKCiota /Rac1 --> Mek signaling pathway that induces invasion in intestinal epithelial cells. This pathway provides a plausible mechanism by which PKCbetaII promotes colon carcinogenesis.

Cyclooxygenase-2 selective inhibition with NS-398 suppresses proliferation and invasiveness and delays liver metastasis in colorectal cancer

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been reported to reduce the risk and mortality of colorectal cancer (CRC) by inhibiting the activity of cyclooxygenase (COX). The present studies were directed to determine whether selective COX-2 inhibition reduces CRC tumour cell proliferation and invasion/migration, and the possible cellular and molecular mechanisms involved. The MC-26 cells are a highly invasive mouse CRC cell line expressing COX-2 protein. NS-398 (100 μM), a highly selective COX-2 inhibitor, decreased cell proliferation by ∼35% of control, as determined using [³H]-thymidine incorporation. This reduction in cell proliferation was associated with decreased expression of cyclin D1 and proliferating cell nuclear antigen (PCNA). Furthermore, NS-398 inhibited cell invasion/migration through Matrigel extracellular matrix components at 24 h by ∼60%. The addition of exogenous prostaglandin E₂ partially attenuated the inhibition of cell invasion by 10 μM NS-398, but failed to reverse the effect of 100 μM NS-398. Matrix metalloproteinases-2 (MMP-2) and -9 (MMP-9) are two enzymes that facilitate cell invasion/migration by degrading the extracellular matrix. In the presence of 100 μM NS-398, Western blot hybridisation analysis and zymography demonstrated that both MMP-2 and MMP-9 protein levels and enzyme activity were decreased by ∼25–30%. In separate studies, NS-398 also inhibited tumour growth in vivo and retarded the formation of liver metastasis. The results of these studies indicate that the expression and activity of COX-2 appear to be associated with both the proliferative and invasive properties of CRC. Cyclooxygenase-2 inhibition suppresses tumour cell growth and invasion/migration, and retards liver metastasis in a mouse colon cancer model, via multiple cellular and molecular mechanisms.

Nutritional and botanical modulation of the inflammatory cascade--eicosanoids, cyclooxygenases, and lipoxygenases--as an adjunct in cancer therapy

Emerging on the horizon in cancer therapy is an expansion of the scope of treatment beyond cytotoxic approaches to include molecular management of cancer physiopathology. The goal in these integrative approaches, which extends beyond eradicating the affected cells, is to control the cancer phenotype. One key new approach appears to be modulation of the inflammatory cascade, as research is expanding that links cancer initiation, promotion, progression, angiogenesis, and metastasis to inflammatory events. This article presents a literature review of the emerging relationship between neoplasia and inflammatory eicosanoids (PGE2 and related prostaglandins), with a focus on how inhibition of their synthesizing oxidases, particularly cyclooxygenase (COX), offers anticancer actions in vitro and in vivo. Although a majority of this research emphasizes the pharmaceutical applications of nonsteroidal anti-inflammatory drugs and selective COX-2 inhibitors, these agents fail to address alternate pathways available for the synthesis of proinflammatory eicosanoids. Evidence is presented that suggests the inhibition of lipoxygenase and its by-products-LTB4, 5-HETE, and 12-HETE-represents an overlooked but crucial component in complementary cancer therapies. Based on the hypothesis that natural agents capable of modulating both lipoxygenase and COX may advance the efficacy of cancer therapy, an overview and discussion is presented of dietary modifications and selected nutritional and botanical agents (notably, omega-3 fatty acids, antioxidants, boswellia, bromelain, curcumin, and quercetin) that favorably influence eicosanoid production.

Cyclooxygenase-2 Expression in Right- and Left-Sided Colon Cancer: A Rationale For Optimization of Cyclooxygenase-2 Inhibitor Therapy

Cyclooxygenase-2 (COX-2) has been identified as a potential target for prevention and therapy of human colorectal cancers (CRC) and other cancers. Because right-sided colon cancers (RSCCs) exhibit clinicopathologic and genetic differences from left-sided colorectal cancers (LSCRCs), determination of COX-2 status in these subsets of CRCs may be clinically relevant in designing COX-2 inhibitor trials for CRC and in subsequent assessment of objective therapeutic response to such therapy. Thirty-six primary CRC resection specimens (18 left, 18 right) from 36 patients were evaluated. Representative tumor sections were subjected to immunohistochemical analysis of COX-2. A semiquantitative system was used to score cytoplasmic COX-2 immunostaining. The tumors were considered COX-2 positive if more than 10% tumor cells showed COX-2 staining. Clinicopathologic and COX-2 data were compared for LSCRCs versus RSCCs. All 18 LSCRCs and 13 of 18 (72%) RSCCs were well to moderately differentiated. Overall rates of COX-2 positivity for the LSCRCs versus RSCCs were 67% (12 of 18) and 33% (6 of 18), respectively (P = 0.04). Furthermore, 11 of 12 (92%) COX-2 positive LSCRCs and 3 of 6 (50%) COX-2 positive RSCCs were stage II-IV at resection. All 12 COX-2 positive LSCRCs were associated with advanced primary tumor and 4 of 12 (33%) LCRCs had distant metastases. These associations could not be evaluated for the RSCCs because of the limited number of COX-2 positive cases. The more frequent expression of COX-2 in LSCRCs as compared with RSCCs supports the hypothesis that COX-2 expression may be related to genetic alterations specific to right- or left-sided CRCs. Further studies are needed to elucidate such relationships. Our data also suggest that stratification of patients with CRC into right- and left-sided subsets may be important in optimal patient selection for COX-2 inhibitor therapy and for subsequent assessment of objective therapeutic response.

Selective inhibition of cyclooxygenase (COX)-2 inhibits endothelial cell proliferation by induction of cell cycle arrest

High-level expression of cyclooxygenase (COX)-2 is reported in 80-90% of colorectal adenocarcinomas. Selective inhibition of COX-2 was shown to reduce colorectal tumorigenesis in different models of carcinogenesis and to prevent metastasis in xenograft tumor models, as well as to suppress in vitro induced angiogenesis. Recently, COX-2 was reported to be expressed not only in malignant epithelial cells, but also in the neovasculature that feeds the tumor in a variety of solid human cancers. Thus, one of the possible mechanisms by which selective COX-2 inhibitor reduces tumor growth and metastasis is through inhibition of tumor angiogenesis. Although a report suggested a possible role of endothelial COX-1 in the process of angiogenesis, in a recent study, the selective inhibition of COX-2 was shown to strongly inhibit angiogenesis by inducing endothelial cell (EC) apoptosis. In the present study, using human umbilical vein endothelial cells (HUVECs) as a model of angiogenesis, we investigated the potential antiangiogenic effect of the selective COX-2 inhibitor and its mechanism of action, and clearly demonstrated that selective inhibition of COX-2 caused a dose-dependent decrease in the proliferative activity of ECs, as well as an inhibition of capillary-like tube formation. The inhibitory effect on EC proliferation was dependent on the cell cycle arrest to the G1 phase and not on cell apoptosis.

Suppression by nimesulide of bombesin-enhanced peritoneal metastasis of intestinal adenocarcinomas induced by azoxymethane in Wistar rats

The effects of the cyclooxygenase (COX)-2 inhibitor nimesulide on bombesin-enhanced peritoneal metastasis of azoxymethane (AOM)-induced intestinal adenocarcinomas were investigated in male Wistar rats. From the beginning of the study, the rats were given 10 weekly s.c. injections of AOM (7.4 mg/kg body weight) and s.c. injections of bombesin (40 microg/kg body weight) every other day. From week 16, the rats were given chow pellets containing 200 ppm or 400 ppm nimesulide ad libitum until termination of the study at week 45. Nimesulide at the higher dose significantly decreased the incidence of bombesin-enhanced metastasis to the peritoneum at week 45, although its administration had little or no effect on the location, histologic type, depth of involvement or infiltrating growth patterns of the tumors. Nimesulide also significantly decreased the incidence of bombesin-enhanced lymphatic vessel invasion by adenocarcinomas. Finally, it also inhibited bombesin-induced matrix metalloproteinase (MMP)-9 and pro-MMP-9 inductions. Our findings indicate that nimesulide may inhibit cancer metastasis through inhibition of pro-MMP-9 and MMP-9 inductions.

Cyclo-oxygenase-2 over-expression in sporadic colorectal carcinoma without lymph node involvement

BACKGROUND

Cyclo-oxygenase-2 over-expression has been reported in most advanced human colorectal cancers.

AIMS

To assess the prevalence of cyclo-oxygenase-2 over-expression in non-advanced colorectal cancers, to investigate the correlation between cyclo-oxygenase-2 status and tumour clinicopathological features and molecular phenotype, and to determine the impact of cyclo-oxygenase-2 status on long-term clinical outcome.

METHODS

Sixty-one patients who had undergone surgery for colorectal cancer without lymph node involvement were evaluated retrospectively. Cyclo-oxygenase-2 expression was determined by immunohistochemistry. The tumour replication error phenotype was assessed by amplification of the two microsatellites, BAT-25 and BAT-26.

RESULTS

Thirty-six tumours were classified as cyclo-oxygenase-2 positive and 25 as cyclo-oxygenase-2 negative. No correlation was found between cyclo-oxygenase-2 over-expression and clinicopathological features or molecular phenotype. Cyclo-oxygenase-2 over-expression was an independent predictor of a poor prognosis. Indeed, the relative risk of tumour recurrence or death for patients with cyclo-oxygenase-2-positive tumours was 2.13 times that of patients with cyclo-oxygenase-2-negative tumours (P=0.008; 95% confidence interval, 1.22-3.73). This difference remained significant when post-operative deaths were censored in the multivariate analysis (P=0.014).

CONCLUSION

Cyclo-oxygenase-2 over-expression is not associated with tumour phenotype, but is indicative of a poorer clinical outcome in patients with non-advanced colorectal carcinoma.

Cyclooxygenase-2 inhibition decreases primary and metastatic tumor burden in a murine model of orthotopic lung adenocarcinoma

OBJECTIVE

To assess cyclooxygenase-2 inhibition on primary tumor and mediastinal metastases in a murine model of orthotopic lung adenocarcinoma.

METHODS

Human lung adenocarcinoma cells (CRL5908, female nonsmoker with cyclooxygenase-2 expression by Western blot) were implanted under direct visualization through the parietal pleura in the upper lobe of the left lung (2 x 10(6) cells/animal) of SCID mice. Mice were randomly assigned to 2 groups, either untreated (n = 62) or celecoxib-treated (n = 60). Celecoxib, a selective cyclooxygenase-2 antagonist, was solubilized in the animals' drink (25 mg/kg per day). Mice were arbitrarily killed at 1, 2, 3, and 4 weeks. A blinded observer assessed primary tumor volume and metastatic disease grossly and histologically.

RESULTS

Gross metastatic lymph nodes were present at 3 weeks in none of 15 (0%) treated and 12 of 15 (80.0%) untreated animals (P <.0001). Mean primary tumor volumes at 3 weeks for treated mice were 7.9 +/- 10.0 mm(3) and for untreated mice were 533.1 +/- 453.6 mm(3) (mean +/- SD, P <.0001). Gross metastatic lymph nodes were present at 4 weeks in 3 of 15 (20%) treated and 17 of 17 (100%) untreated animals (P <.0001). Mean primary tumor volumes at 4 weeks for treated mice were 37.1 +/- 46.2 mm(3) and for untreated mice were 809.6 +/- 1226.4 mm(3) (mean +/- SD, P <.0001). Mean blood levels of celecoxib in treated mice were 236.8 +/- 34.2 ng/mL (mean +/- SD).

CONCLUSIONS

Cyclooxygenase-2 inhibition results in decreased primary and metastatic tumor burden in a murine model using human lung adenocarcinoma. Cyclooxygenase-2 inhibition has the potential to decrease tumor progression and metastases in patients with lung adenocarcinoma.

Chemoprevention of gastrointestinal malignancies

BACKGROUND

There has been considerable interest in the use of chemical or dietary agents to suppress or inhibit the development of tumours in the early stages of carcinogenesis. This concept is known as chemoprevention and although the potential for such agents is tremendous, evaluating their clinical benefit is beset with difficulties.

AIMS

Using selected agents, such as curcumin and indole-3-carbinol, as examples, the present review will discuss the possible mechanisms of chemoprevention and the problems encountered in developing these agents into clinical drugs.

METHODS

A review of the published literature from 1985 to the present day was performed using Medline and Web of Science search engines. Key words used were 'gastrointestinal cancer' and 'chemoprevention'.

CONCLUSION

A huge number of agents with possible chemopreventive action has been identified. Pilot trials using molecular signatures of cancer activity can be used to select which agents should be included in large-scale phase III clinical trials. Publications concerning chemoprevention are concentrated in the scientific and oncological literature but surgeons with their greater exposure to premalignant gastrointestinal disease need to be aware of current concepts in this rapidly expanding field. This knowledge would allow collaboration between oncologists and surgeons in clinical trials to further evaluate chemopreventive compounds and ascertain their clinical impact.

Prostaglandins promote colon cancer cell invasion; signaling by cross-talk between two distinct growth factor receptors

Colorectal cancer is the second most frequent cancer in the Western world, often lethal when invasion and/or metastasis occur. In addition to hepatocyte growth factor (HGF), colon cancer invasion may be driven by prostaglandins, especially the E2 series (PGE2), generated by the cyclooxygenase-2 (Cox-2) enzyme. While concentration of PGE2 as well as expression of Cox-2, HGF receptor (c-Met-R), epidermal growth factor receptor (EGFR), and beta-catenin are all dramatically increased in colon cancers and implicated in their growth and invasion, the precise role of PGE2 in the latter process remains unclear. Here we provide evidence that PGE2 transactivates c-Met-R (contingent upon functional EGFR), increases tyrosine phosphorylation and nuclear accumulation of beta-catenin, and induces urokinase-type plasminogen activator receptor (uPAR) mRNA expression. This is accompanied by increased beta-catenin association with c-Met-R and enhanced colon cancer cell invasiveness. Inactivation of EGFR and c-Met-R significantly reduced PGE2-induced cancer cell invasiveness. Clinical relevance of these findings is confirmed by our immunohistochemical studies demonstrating that cancer cells in the invasive front overexpress Cox-2, c-Met-R, and beta-catenin. Our findings explain a functional relationship between prostaglandins, EGFR, and c-Met-R in colon cancer growth and invasion.

Cyclo-oxygenase 2 inhibition in colorectal cancer therapy

BACKGROUND

Cyclo-oxygenase inhibition for the treatment of colorectal neoplasia has been studied with renewed interest since the discovery of cyclo-oxygenase (Cox) 2 and the introduction of specific Cox-2 inhibitors. These drugs have implications for both the prevention of colorectal carcinoma and the potential treatment of the disease.

METHODS AND RESULTS

A Medline database search was performed for articles using the keywords "colonic, colon or rectal and neoplasia or cancer" and "cyclo-oxygenase or Cox-2." Cross-references of relevant historical papers were also included. There is substantial evidence that Cox-2 plays a role in the development and progression of colorectal cancer. The specific inhibition of this enzyme has been shown to inhibit cancer growth in in vitro and in vivo models. The mechanisms of action for these effects are poorly understood and potential clinical applications at present remain under investigation.

CONCLUSION

Cox-2 inhibitors have great promise as useful additions to current cancer treatments. There is a need for randomized clinical trials to define a role for these drugs in chemoprevention, recurrence prophylaxis, and adjuvant therapy for colorectal and other solid tumours.

Development of COX inhibitors in cancer prevention and therapy

On the strength of in vitro, in vivo, observational, and clinical data, nonsteroidal antiinflammatory drugs (NSAIDs)-also referred to as COX inhibitors-have emerged as lead compounds for cancer prevention, and possible adjuncts to cancer therapy. Thus far, the routine use of NSAIDs for these indications is limited, largely owing to toxicity concerns, the paucity of efficacy data for any specific target organ, and uncertainties with regard to the most appropriate regimen (i.e., the best agent, formulation, dose, route of administration, and duration). Strategies to address these concerns primarily aim to improve the therapeutic index (i.e., benefit:risk ratio) of COX inhibitors by 1) minimizing systemic exposures whenever feasible, 2) achieving greater mechanistic specificity, 3) coadministering agents that provide prophylaxis against common toxicities, and 4) coadministering other effective anticancer agents. Clinical trials testing most of these strategies have been completed or are under way. The National Cancer Institute has a substantial research portfolio dedicated to the identification, testing, and development of NSAIDs as preventive and therapeutic anticancer agents. Discovering how to apply NSAIDs in persons with-or at risk for-cancer, although challenging, has the potential for considerable clinical and public health benefits.

Cyclooxygenase-2 expression and angiogenesis in colorectal cancer

AIM: Cyclooxygenase-2 is involved in a variety of important cellular functions, including cell growth and differentiation, cancer cell motility and invasion, angiogenesis and immune function. However, the role of cyclooxygenase-2 as an angiogenic factor in colorectal cancer tissue is still unclear. We investigated the relationship between cyclooxygenase-2 and angiogenesis by analyzing the expression of cyclooxygenase-2 in colorectal cancer tissue, as well as its association with vascular endothelial growth factor (VEGF) and microvascular density (MVD).

METHODS: The expression of cyclooxygenase-2, VEGF, as well as MVD was detected in 128 cases of colorectal cancer by immunohistochemical staining. The relationship between the cyclooxygenase-2 and VEGF expression and MVD was evaluated. Our objective was to determine the effect of cyclooxygenase-2 on the angiogenesis of colorectal cancer tissue.

RESULTS: Among 128 cases of colorectal cancer, 87 were positive for cyclooxygenase-2 (67.9%), and 49 for VEGF (38.3%), respectively. The microvessel counts ranged from 23 to 142, with a mean of 51.7 (standard deviation, 19.8). The expression of cyclooxygenase-2 was correlated significantly with the depth of invasion, stage of disease, metastasis (lymph node and liver), VEGF expression and MVD. Patients in T3-T4, stage III-IV and with metastasis had much higher expression of cyclooxygenase-2 than patients in T1-T2, stage I-II and without metastasis (P < 0.05). The positive expression rate of VEGF (81.6%) in the cyclooxygenase-2 positive group was higher than that in the cyclooxygenase-2 negative group (18.4%, P < 0.05). Also, the microvessel count (56 ± 16) in cyclooxygenase-2 positive group was significantly higher than that in cyclooxygenase-2 negative group (43 ± 12, P < 0.05). The microvessel count in tumors with positive cyclooxygenase-2 and VEGF was the highest (60 ± 18, 41-142, P < 0.05), whereas that in tumors with negative cyclooxygenase-2 and VEGF was the lowest (39 ± 16, 23-68, P < 0.05).

CONCLUSION: Cyclooxygenase-2 may be associated with tumor progression by madulating the angiogenesis in colorectal cancer tissue and used as a possible biomarker.

A low toxicity maintenance regime, using eicosapentaenoic acid and readily available drugs, for mantle cell lymphoma and other malignancies with excess cyclin D1 levels

Mantle cell lymphoma is a difficult to treat non-Hodgkin's lymphoma (NHL) whose biochemistry is unusually well characterised. Almost all and perhaps all patients overexpress the cyclin D1 protein which is crucial in driving cells from the G1 to the S phase. This overexpression may be responsible for the refractoriness. Despite this understanding, treatments for mantle cell lymphoma are based on standard NHL regimes of cyclophosphamide, doxorubicin, vincristine and prednisone, perhaps supplemented with the monoclonal antibody rituximab. There has never been any attempt to direct treatment to the cyclin D1 mechanism or to angiogenesis which is now known to be important in all lymphomas. Both these targets lend themselves to long-term maintenance regimes of relatively low toxicity which can be used as adjuvants to standard therapy. Agents which have recently been shown to block cyclin D1 translation by regulating calcium levels are the unsaturated essential fatty acid, eicosapentaenoic acid (EPA), the antidiabetic thiazolidinediones, and the antifungal agent, clotrimazole. Two types of agent which have been shown to inhibit angiogenesis are the teratogen, thalidomide, and the selective inhibitors of cyclo-oxygenase 2 (COX-2). Retinoids exert synergistic effects with EPA and have been shown to inhibit both tumour growth and angiogenesis. The mechanisms of action of these various agents are discussed, and specific suggestions are made for low toxicity maintenance therapy of mantle cell lymphoma and of other tumours which overexpress cyclin D1.

Molecular biomarkers of colorectal carcinogenesis and their role in surveillance and early intervention

Modern medicine is increasingly focused towards population surveillance for disease, coupled with the implementation of preventative measures applied to 'at-risk' patients. Surveillance in colorectal cancer is limited by the cost and risk of endoscopy. Trials of putative chemopreventive agents in colorectal cancer are hampered by difficulties in following up large cohorts of patients over long periods of time to ascertain the clinical effect. Research into possible pathways of colorectal carcinogenesis has revealed a range of biological intermediates which could be used in surveillance, the identification of high risk populations and early diagnosis of cancer. The aim of this paper was to review the possible role of biomarkers in surveillance and the timing of intervention. A literature review using both Medline and Web of Science was performed from 1995 onwards using keywords: biomarkers, colorectal cancer, carcinogenesis, chemoprevention, surveillance and screening. Research has identified many potential biomarkers, such as cyclooxygenase-2 (COX-2), oxidative DNA adducts and glutathione S-transferase (GST) polymorphisms, which could be applied in a clinical setting to screen for and detect colorectal cancer. Molecular biomarkers, such as COX-2, oxidative DNA adducts and GST polymorphisms offer new prospects in the detection of early colorectal cancer, surveillance of high-risk populations and prediction of the clinical effectiveness of chemopreventive drugs. Their role could be extended into surgical surveillance for potentially operable disease and post-operative follow-up for disease recurrence. Research should be directed at assessing complementary biomarkers to increase clinical effectiveness in determining management options for patients.

Cancer-associated immunodeficiency and dendritic cell abnormalities mediated by the prostaglandin EP2 receptor

Prostaglandin E(2) (PGE(2)), a major COX metabolite, plays important roles in several facets of tumor biology. We characterized the contribution of the PGE(2) EP2 receptor to cancer-associated immune deficiency using EP2(-/-) mice. EP2(-/-) mice exhibited significantly attenuated tumor growth and longer survival times when challenged with MC26 or Lewis lung carcinoma cell lines as compared with their wild-type littermates. While no differences in T cell function were observed, PGE(2) suppressed differentiation of DCs from wild-type bone marrow progenitors, whereas EP2-null cells were refractory to this effect. Stimulation of cells in mixed lymphocyte reactions by wild-type DCs was suppressed by treatment with PGE(2), while EP2(-/-)-derived DCs were resistant to this effect. In vivo, DCs, CD4(+), and CD8(+) T cells were significantly more abundant in draining lymph nodes of tumor-bearing EP2(-/-) mice than in tumor-bearing wild-type mice, and a significant antitumor cytotoxic T lymphocyte response could be observed only in the EP2(-/-) animals. Our data demonstrate an important role for the EP2 receptor in PGE(2)-induced inhibition of DC differentiation and function and the diminished antitumor cellular immune responses in vivo.

Recent advances in the pharmacological treatment of colorectal cancer

Recent advances in the treatment of colorectal cancer have lead to significant gains in response rates and survival. The combination of newer agents such as irinotecan and oxaliplatin with 5-fluorouracil/leucovorin using various dosing schedules in the metastatic setting has resulted in a steady improvement in the outcome of patients with colorectal cancer. Experimental therapies such as epidermal growth factor receptor inhibitors, vascular endothelial growth factor inhibitors and cyclooxygenase-2 inhibitors, have shown promise in early clinical trials and have acceptable toxicity profiles. Efforts towards improving risk-stratification of stage II colorectal cancer patients and optimising therapy in patients with advanced disease, have focused on molecular and genetic markers. It is hoped that the addition of new therapies to existing drug combinations, as well as further advances in the understanding of colorectal cancer biology, will lead to further improvement in survival and quality of life for patients.

Expression of cyclooxygenase-2 and clinicopathologic features in human gastric adenocarcinoma

AIM: To study the expression of cyclooxygenase-2 (COX-2) gene in gastric cancer and the relationship between COX-2 expression and clinicopathologic features of gastric cancer.

METHODS: With reference to the expression of β-actin gene, COX-2 mRNA level was examined in cancerous tissues and adjacent noncancerous mucosa from 33 patients by semiquantitative reverse transcription- polymerase chain reaction (RT-PCR). Quantitation of relative band Adj volume counts was performed using molecular Analyst for windows software. The COX-2 index was determined from the band Adj volume counts ratio of COX-2 to constitutively expressed actin.

RESULTS: The COX-2 index in gastric carcinoma was significantly higher than that in normal mucosa (0.5966 ± 0.2659 vs 0.2979 ± 0.171, u = 5.4309, P < 0.01). Significantly higher expression of COX-2 mRNA was also observed in patients with lymph node involvement than that in those without (0.6775 ± 0.2486 vs 0.4105 ± 0.2182, t = 2.9341, P < 0.01). Furthermore, the staging in the UICC TNM classification significantly correlated with COX-2 overexpression (F = 3.656, P < 0.05), the COX-2 index in stage III and IV was significantly higher than those in stage I and II (q = 3.2728 and q = 3.4906, P < 0.05). The COX-2 index showed no correlation with patient抯 age, sex, blood group, tumor location, gross typing, depth of invasion, differentiation, and the greatest tumor dimension (P > 0.05).

CONCLUSION: Expression of COX-2 mRNA in gastric carcinoma was significantly higher, which may enhance lymphatic metastasis in patients with gastric carcinoma. The staging in the UICC TNM classification was significantly correlated with COX-2 over-expression. COX-2 may contribute to progression of tumor in human gastric adenocarcinoma.

Predictive markers for colorectal cancer: current status and future prospects

Colorectal cancer (CRC) is the second leading cause of cancer death in the United States. Although there is clear evidence of the benefit of chemotherapy in adjuvant and metastatic settings, its use continues to be suboptimal because of intrinsic or acquired drug resistance. 5-Fluorouracil continues to be the mainstay of CRC therapy, and combinations with newer chemotherapeutic agents such as irinotecan and oxaliplatin have resulted in improved response rates and survival. The role of other agents including cyclooxygenase-2 inhibitors, epidermal growth factor receptor, and farnsyl transferase inhibitors remains to be elucidated. Despite these improvements, many patients undergo chemotherapy without benefit. Increased understanding of the biology of CRC has led to the identification of prognostic markers that may help identify patients who will benefit from chemotherapy. Furthermore, studies have also begun to identify markers that predict whether a tumor will respond to a particular chemotherapy. The ultimate goal of this research is to prospectively identify patients who should receive chemotherapy and, thus, to tailor treatment to the molecular profile of the tumor and patient. Such an approach has the potential to dramatically improve response rates. This review highlights potentially important prognostic and predictive factors in CRC and discusses the potential for their use in the treatment of this disease.

Requirement of cyclooxygenase-2 expression and prostaglandins for human prostate cancer cell invasion

The PC-3 Low Invasive cells and the PC-3 High Invasive cells were used to investigate the correlation of the COX-2 expression and its arachidonic acid metabolites, prostaglandins, with their invasiveness through Matrigel using a Boyden chamber assay. The COX-2 expression in PC-3 High Invasive cells was approximately 3-fold higher than in PC-3 Low Invasive cells while the COX-1 expression was similar in both cell sublines. When incubated with arachidonic acid, PGE2 was the major prostaglandin produced by these cells. PC-3 High Invasive cells produced PGE2 approximately 2.5-fold higher than PC-3 Low Invasive cells. PGD2 was the second most abundant prostaglandin produced by these cells. Both indomethacin (a nonspecific COX inhibitor) and NS-398 (a specific COX-2 inhibitor) inhibited the production of prostaglandins and the cell invasion. PGE2 alone did not induce the cell invasion of PC-3 Low Invasive cells. However, PGE2 reversed the inhibition of cell invasion by NS-398 and enhanced the cell invasion of the PC-3 High Invasive cells. In contrast, PGD2 slightly inhibited the cell invasion. These results suggest that in the PC-3 Low Invasive cells, COX-2-derived PGE2 may not be sufficient to induce cell invasion while in the PC-3 High Invasive cells, PGE2 may be sufficient to act as an enhancer for the cell invasion. Further, PGD2 may represent a weak inhibitor and counteracts the effect of PGE2 in the cell invasion.

Molecular pathology of tumor metastasis III. Target array and combinatorial therapies

Therapy of tumor progression and the metastatic disease is the biggest challenge of clinical oncology. Discovery of the diverse molecular pathways behind this complex disease outlined an approach to better treatment strategies. The development of combined cytotoxic treatment protocols has produced promising results but no breakthrough in the clinical management of metastatic disease. The multiple - specific and non-specific pathways and cellular targets of tumor progression are outlined in this review. Such an approach, individually designed for various cancer types, may have a better chance to treat or even cure cancer patients with progressive disease.

Biology of colorectal liver metastases

The elucidation of the interaction of the tumor and its microenvironment has increased surgeons' understanding of the biologic mechanisms mediating metastases formation. The ability to develop effective biologic therapies will depend on understanding the complex interactions among endothelial cells and tumor cells and on the cytokine cross-talk among all cells within a particular tumor at a particular site. Biologic therapies must be targeted to both the site and the tumor. By the time metastases form, most steps in the metastatic cascade have been completed. Therapy to down-regulate or interrupt the last stages of metastases, proliferation, and angiogenesis and mechanisms to disrupt cell survival signals appear to be the most promising areas of investigation.

3-OH flavone inhibition of epidermal growth factor-induced proliferaton through blocking prostaglandin E2 production

Epidermal growth factor (EGF) has been shown to induce proliferation in cells, however, the role of prostaglandin E(2) (PGE(2)) plays in EGF-induced proliferation in still unclear. EGF and PGE(2) showed proliferation responses in epidermoid carcinoma cell A431 by MTT and [(3)H] thymidine incorporation assay. Activation of the EGF receptor and extracellular signal-regulated protein kinases (ERK1/2), but not p38 and JNK, appeared 10 min after EGF treatment, whereas total amounts of ERK1/2, p38 and JNK remained unchanged in A431 cells, accompanied by induction of COX-2 and PGE(2) production. PD98059, a specific ERK1/2 inhibitor, inhibited EGF-induced proliferation with concomitant decreases in ERK1/2 phosphorylation and COX-2/PGE(2) induction. Non-steroid anti-inflammatory drugs (NSAIDs) such as aspirin and diclofenac, a COX activity inhibitor, inhibited EGF-induced proliferation by blocking PGE(2) production. The addition of PGE(2) reversed the inhibitory effects of PD98059, aspirin, and diclofenac on EGF-induced proliferation. This suggests that COX-2/PGE(2) activation involves in EGF-induced proliferation and locates at the downstream of ERK1/2 activation. Furthermore, the natural product, 3-OH flavone, showed the most-potent inhibitory activity on EGF-induced proliferation among 9 structurally-related compounds, and suppression of EGF receptor phosphorylation, ERK1/2 phosphorylation, and COX-2/PGE(2) production by 3-OH flavone was identified. PGE(2) addition attenuates the inhibitory activity of 3-OH flavone on EGF-induced proliferation by MTT assay and colony formation by soft agar assay. Additionally, 3-OH flavone also showed more-specific inhibition on EGF- than on fetal bovine serum (FBS)-induced proliferation in A431 cells. Results of our present study provide evidence to demonstrate that PGE(2) is an important downstream molecule in EGF-induced proliferation, and 3-OH flavone, which inhibits PGE(2) production by blocking MAPK cascade, might reserve potential for development as an anti-cancer drug.

Loss of the EP2 prostaglandin E2 receptor in immortalized human keratinocytes results in increased invasiveness and decreased paxillin expression

Prostaglandin E(2) (PGE(2)) receptor subtype EP(2), which is coupled to cAMP metabolism, is known to mediate proliferation of primary human keratinocytes in vitro. The effect of gain or loss of EP(2) receptors in immortalized human keratinocytes (HaCat cells) was examined. HaCat keratinocytes were transfected with sense or anti-sense constructs of the EP(2) receptor. Loss or gain of EP(2) expression was documented by immunoblot and associated changes in agonist-stimulated cAMP production. Loss or gain of EP(2) receptor expression correlated with alterations in plating efficiencies but with modest affects on growth. When cell lines were studied in an organ culture model, anti-sense clones were highly invasive compared with vector controls and sense transfectants. A marked increase in prostaglandin production is commonly seen in malignant lesions. Because prostaglandin receptors are known to undergo ligand-induced receptor down-regulation, we sought to determine whether EP(2) receptor down-regulation results in increased invasiveness. In vector controls, invasiveness was reproduced by ligand-dependent EP(2) receptor down-regulation as assessed by immunohistochemistry. In addition, loss of EP(2) receptor expression was associated with decreased paxillin expression, a critical component of focal adhesion assembly. Thus, down-regulation of EP(2) receptors represents a potential mechanism for neoplastic progression to an invasive phenotype.

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.

Cyclooxygenase-2 expression correlates with uPAR levels and is responsible for poor prognosis of colorectal cancer

Considering recent findings that cyclooxygensase-2 (COX-2) is involved in the progression of colorectal carcinoma (CRC), the role of COX-2 in promoting invasion and angiogenesis was investigated by evaluating the relationship of COX-2 expression to various clinicopathological variables, including plasminogen activating system (PA system) and vascular endothelial growth factor (VEGF). Tumor tissues from 71 patients with CRC were assayed to determine the antigen levels of urokinase-type plasminogen activator (uPA), uPA receptor (uPAR), and plasminogen activator inhibitor-1 and -2 (PAI-1 and PAI-2), as well as immunohistochemical expression of VEGF. COX-2 was assayed immunohistochemically in 56 patients. COX-2 expression was detected in cancer cells and it was also expressed by stromal cells in some patients. Fourteen patients (25%) were COX-2 positive, whereas 42 were negative. COX-2 expression was significantly related to lymphatic invasion (P = 0.0317), but was not related to microvessel density or VEGF expression. In the PA system, uPAR antigen levels were significantly higher in tumors with COX-2 expression than in tumors without (P = 0.0233). Univariate analysis showed that significant prognostic variables for survival were tumor size, lymph node involvement, lymphatic invasion, vascular invasion, liver metastasis, high uPAR level, and COX-2 expression, but only liver metastasis was an independent prognostic factor (P = 0.0065) in multivariate analysis. COX-2 expression was a more important prognostic indicator than any other factor except liver metastasis (P = 0.0526). The significant relationship between the presence of COX-2 protein and uPAR antigen levels contributed to the enhancement of tumor invasion and the poor outcome in patients with CRC.

Cyclopentenone prostaglandins induce caspase activation and apoptosis in dendritic cells by a PPAR-gamma-independent mechanism: regulation by inflammatory and T cell-derived stimuli

OBJECTIVE

Dendritic cells (DC) are professional antigen-presenting cells playing a pivotal role in the induction of immunological responses. There is evidence that DC survival during ongoing immune responses is finite. However, little is known about the mechanisms regulating apoptosis in these cells. Here, we have investigated the effects of the anti-inflammatory cyclopentenone prostaglandins on human monocyte-derived DC.

MATERIALS AND METHODS

Phenotype of DC was determined by flow cytometry and their allostimulatory potential in mixed leukocyte reaction. Induction of apoptosis in DC was monitored by staining with annexin-V-FITC and propidium iodide, propidium iodide staining of cell nuclei, and fluorimetric assay of caspase activity. Induction of maturation in DC was obtained by stimulation with TNF-alpha, LPS, IFN-gamma, CD40-ligand, or different combinations of these stimuli. PPAR-gamma expression in DC was determined by RT-PCR.

RESULTS

Exposure of immature DC to cyclopentenone prostaglandins blunted their allostimulatory capacity and skewed their phenotype by downregulating CD1a and costimulatory molecules. These effects were due to activation of caspases and induction of apoptotic cell death in DC by cyclopentenone prostaglandins. Mature DC showed enhanced susceptibility to apoptosis via cyclopentenone prostaglandins as compared with immature DC. Although DC express PPAR-gamma, the corresponding receptor for some of these metabolites, PPAR-gamma activation by a synthetic high-affinity agonist failed to impair DC viability.

CONCLUSIONS

Cyclopentenone prostaglandins induce apoptosis of human DC by a PPAR-gamma-independent mechanism. Since these compounds are released during an inflammatory event and show anti-inflammatory properties, they may contribute to the downregulation of DC function through apoptotic cell death.

Osteoprotegerin levels increased by interleukin-1beta in human periodontal ligament cells are suppressed through prostaglandin E(2) synthesized de novo

Osteoprotegerin (OPG) is a novel tumor necrosis factor receptor superfamily that inhibits osteoclast differentiation, activity, and survival. Interleukin-1beta (IL-1beta) increases OPG expression. IL-1beta also increases prostaglandin E(2) (PGE(2)) production and stimulates bone resorption. In the present study, we examined the involvement of PGE(2) in IL-1beta-induced increases in OPG levels in human periodontal ligament cells (HPL cells) in an effort to clarify apparently conflicting IL-1beta actions on bone resorption and understand IL-1beta-induced increases in secretion of OPG and PGE(2) in HPL cells. 5,6-dichloro-1-beta-D-ribofuranosyl-benzimidazole, a mRNA synthesis inhibitor, partly inhibited the increase in OPG mRNA levels induced by IL-1beta. Cycloheximide, a protein synthesis inhibitor, enhanced the stimulatory effect of IL-1beta. Etodolac, a selective cyclooxygenase-2 inhibitor, suppressed the increase in PGE(2) levels. Furthermore, etodolac reinforced the promotion of OPG expression by IL-1beta at the mRNA and protein levels. PGE(2) added to cultures of HPL cells decreased OPG mRNA levels in a dose- and time- dependent manner. These findings suggest that the increase in OPG levels induced by IL-1beta in HPL cells is suppressed through PGE(2) synthesized de novo.

Celecoxib: a specific COX-2 inhibitor with anticancer properties

In addition to the well-established pathophysiological role that COX-2 plays in inflammation, recent evidence implies that this isoform may also be involved in multiple biologic events throughout the tumorigenic process. Many epidemiological studies demonstrate that nonsteroidal anti-inflammatory drugs (NSAIDs) reduce the risk of a wide range of tumors. Further, COX-2 is chronically overexpressed in many premalignant, malignant, and metastatic human cancers, and levels of overexpression have been shown to significantly correlate to invasiveness, prognosis, and survival in some cancers. Pharmacological studies consistently demonstrate that COX-2 inhibitors dose-dependently inhibit tumor growth and metastasis in various relevant animal models of cancer. Importantly, several investigators have also shown COX-2 inhibitors may act additively or synergistically with currently used cytotoxics and molecularly targeted agents. Here we present a broad overview of the growing evidence that COX-2 plays a pivotal role throughout oncogenesis and summarize the rationale to explore the use of COX-2 inhibitors for the prevention and/or treatment of cancer as a single agent or in combination with current anticancer modalities.

Many actions of cyclooxygenase-2 in cellular dynamics and in cancer

Cyclooxygenase-2 (COX-2) is the inducible isoform of cyclooxygenase, the enzyme that catalyzes the rate-limiting step in prostaglandin synthesis from arachidonic acid. Various prostaglandins are produced in a cell type-specific manner, and they elicit cellular functions via signaling through G-protein coupled membrane receptors, and in some cases, through the nuclear receptor PPAR. COX-2 utilization of arachidonic acid also perturbs the level of intracellular free arachidonic acid and subsequently affects cellular functions. In a number of cell and animal models, induction of COX-2 has been shown to promote cell growth, inhibit apoptosis and enhance cell motility and adhesion. The mechanisms behind these multiple actions of COX-2 are largely unknown. Compelling evidence from genetic and clinical studies indicates that COX-2 upregulation is a key step in carcinogenesis. Overexpression of COX-2 is sufficient to cause tumorigenesis in animal models and inhibition of the COX-2 pathway results in reduction in tumor incidence and progression. Therefore, the potential for application of non-steroidal anti-inflammatory drugs as well as the recently developed COX-2 specific inhibitors in cancer clinical practice has drawn tremendous attention in the past few years. Inhibition of COX-2 promises to be an effective approach in the prevention and treatment of cancer, especially colorectal cancer.