Sulindac sulfide, an aspirin-like compound, inhibits proliferation, causes cell cycle quiescence, and induces apoptosis in HT-29 colon adenocarcinoma cells

Pro-apoptotic effect of a nitric oxide-donating NSAID, NCX 4040, on bladder carcinoma cells

Nitric oxide-releasing non steroidal anti-inflammatory drugs (NO-NSAIDs) are a promising class of compounds that cause cell cycle perturbations and induce apoptosis in cell lines from different tumors. We investigated the activity of a recently developed NO-NSAID (NCX 4040) in bladder cancer cell lines (HT1376 and MCR). Cells were treated with different drug concentrations for different exposure times. Cytostatic and cytocidal activity was tested by SRB assay and apoptosis was evaluated by TUNEL analysis, ANNEXIN V assay and fluorescence microscopy. To further investigate the cell death-inducing mechanisms of NCX 4040, we analyzed gp-170, caspase expression and mitochondrial membrane potential (Delta Psi) depolarization. NCX 4040 showed a striking cytocidal activity in both cell lines, reaching LC(50) at a 10-microM and 50-microM concentrations in HT1376 and in MCR cells, respectively, after an exposure of only 6 h followed by an 18-h washout. Apoptosis was triggered in up to 90% of cells and was associated with active caspase-3 expression and Delta Psi depolarization in both cell lines after a 6-h exposure. In conclusion, NCX 4040, which probably causes apoptosis via a mitochondrial-dependent mechanism, could prove to be a useful agent for improving bladder cancer treatment.

Sulindac activates nuclear translocation of AIF, DFF40 and endonuclease G but not induces oligonucleosomal DNA fragmentation in HT-29 cells

Sulindac is one of the most widely studied nonsteroidal anti-inflammatory drugs in the prevention of colon cancer. Thus, from the viewpoint of colon cancer chemotherapy it is important to reveal the mechanism of sulindac-induced cell death. This study was undertaken to dissect the molecular mechanism underlying sulindac-induced apoptosis in human colon cancer cell line HT-29 (mutant p53), focusing on nuclear translocation of AIF, DFF and endonuclease G. On induction of apoptosis by sulindac, it was associated with decreased mitochondrial membrane potential, nuclear expression of active caspase-3, cleavage of poly(ADP-ribose) polymerase, translocation of mitochondrial proteins to the nucleus, and morphological evidence of nuclear condensation. However, sulindac led to only disintegration of nuclear DNA into high molecular weight DNA fragments of about 100-300 kbp as determined by a pulse-field gel electrophoresis, suggesting a predominantly AIF-mediated cell death process. In summary, our findings indicate that sulindac induces large-scale DNA fragmentation without oligonucleosomal DNA fragmentation. This result suggests that nuclear translocation of DFF and endonuclease G are not sufficient for the induction of oligonucleosomal DNA fragmentation in HT-29 cells.

Effects of the combination of topoisomerase I inhibitors and celecoxib, a selective cylooxygenase-2 inhibitor on colorectal cancer

AIM: To investigate the antitumor properties of camptothecins (CPTs) combined with celecoxib, a selective cylooxygenase-2 (COX-2) inhibitor, in vitro and in vivo, and the effects of celecoxib on irinotecan (CPT-11)-induced diarrhea in mice.

METHODS: Four human colon cancer cell lines, HT-29, HCT-8, HCT-116 and Caco-2 were exposed to the increasing concentrations (10^-5, 10^-4, 10^-3,10^-2, 10^-1, 1, 10,100 μmol/L) of three topoisomerase I (Topo I) inhibitors, CPT-11, CPT and topotecan (TPT), and celecoxib (1 and 5 μmol/L) as well as a combination of each Topo I inhibitor. Then MTT assay was performed to evaluate the effects of adjunct use of celecoxib on the chemosensitivity of colon cancer cells to CPTs. HT-29 cells were divided into control group, celecoxib treatment group, CPT treatment group and combined CPT with celecoxib treatment group. Flow cytometry was used to evaluate the apoptotic rates and cell cycle distribution. The expression of COX-2 and apoptosis-related proteins (Bcl-2, Caspase-3 and P53) were determined by immunocytochemical method. HT-29 cell line-xenografts model was established. The nude mice bearing tumor were divided into five groups, namely control group, CPT-11 (25 mg/kg per day) treatment group, celecoxib (60 mg/kg) treatment group and combined celecoxib (30 mg/kg and 60 mg/kg, respectively) with CPT-11 treatment group. The effects of the drugs on tumor growth and the severity of late diarrhea induced by CPT-11 were assessed.

RESULTS: Celecoxib significantly decreased the IC₅₀ of the CPTs in the four colon cancer cell lines in vitro, but the reduction degrees of IC₅₀ depended on the level of COX-2 expression. In HT-29 cells, the apoptotic rates were 51.4% in co-treated groups (24.4% in CPT treated groups, P<0.01), and the proportion in the G0/G1 phase were 49.1% in co-treated group (5.5% in CPT treated groups, P<0.01). The expression of COX-2 and Bcl-2 were down-regulated, but the expression of P53 and Caspase-3 were up-regulated after co-treatment with CPT and celecoxib in HT-29 cells. In vivo, treatment with celecoxib at 60 mg/kg in conjunction with CPT-11 (25 mg/kg per day for three consecutive days) significantly reduced tumor growth by 78.77% (P<0.01 vs control group; P<0.05 vs CPT-11 group), and decreased the score and rate of diarrhea induced by CPT-11 (0.330.52 vs 2.33±0.82, P<0.01; 16.67% vs 83.33%, P<0.05). Besides, celecoxib at 60 mg/kg improved the body weight of the mice (17.54±1.13 g vs 14.56±2.16 g, P<0.05).

CONCLUSION: Celecoxib enhances antitumor properties of CPTs in colon cancer in vitro and in vivo, and this enhancement may be associated with the apoptosis increase and cell cycle arrest. Additionally, celecoxib reduces the severity of diarrhea and body weight loss induced by CPT-11.

The role of COX-2 in intestinal cancer

Cyclooxygenase (COX), the key regulatory enzyme for prostaglandin synthesis, is transcribed from two distinct genes. COX-1 is expressed constitutively in most tissues whereas COX-2 is induced by a wide variety of stimuli and was initially identified as an immediate-early growth response gene. In addition, COX-2 expression is markedly increased in 85-90% of human colorectal adenocarcinomas while COX-1 levels remain unchanged. Several epidemiological studies have reported a 40-50% reduction in the risk of developing colorectal cancer in persons who chronically take non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin, which are classic inhibitors of COX. Genetic evidence also supports a role for COX-2, since mice null for COX-2 have an 86% reduction in tumour multiplicity in a background containing a mutated APC allele. These results strongly suggest that COX-2 contributes to the development of intestinal tumours and that inhibition of COX is chemopreventative. It is hoped that the chemopreventative effects of NSAIDs will be enhanced by the recent development of COX-2-specific inhibitors.

The role of arachidonic acid regulatory enzymes in colorectal disease

PURPOSE

Nonsteroidal anti-inflammatory drugs have a wide ranging effect on diseases of the colon and rectum. Interestingly, nonsteroidal anti-inflammatory drugs seem to play a beneficial role in colorectal cancer chemoprevention and adenoma regression, but may have a deleterious effect in inflammatory bowel disease. Prostaglandin inhibition is central to both the beneficial and toxic effects of this class of drugs. Arachidonic acid metabolism is essential to prostaglandin synthesis.

METHODS

A Medline search using "nonsteroidal anti-inflammatory drugs," "colon cancer," "inflammatory bowel disease," "colitis," "COX inhibitors," "arachidonic acid," and "chemoprevention" as key words was performed for English-language articles. Further references were obtained through cross-referencing the bibliography cited in each work.

RESULTS

Based on numerous studies, nonsteroidal anti-inflammatory drugs have a beneficial role in colon cancer and colonic adenomas. However, they have been reported to have a deleterious effect on the colon in inflammatory bowel disease and have been shown to cause colitis. Nonsteroidal anti-inflammatory drugs work via multiple pathways, some well defined, and others unknown.

CONCLUSIONS

In the new millennium, nonsteroidal anti-inflammatory drugs may be used for chemoprevention of colorectal and other cancers. In addition, they may be used in combination with surgery and chemotherapy to primarily treat colorectal carcinoma. Undoubtedly, the use of novel cyclooxygenase inhibitors with less of a toxicity profile will allow more widespread use of nonsteroidal anti-inflammatory drugs for a variety of diseases. The future of this class of drugs is promising.

Cancer prevention: a new era beyond cyclooxygenase-2

The seminal epidemiological observation that nonsteroidal anti-inflammatory drugs (NSAIDs) prevent colon and possibly other cancers has spurred novel approaches to cancer prevention. The known inhibitory effect of NSAIDs on the eicosanoid pathway prompted studies focusing on cyclooxygenase (COX) and its products. The increased prostaglandin E2 levels and the overexpression of COX-2 in colon and many other cancers provided the rationale for clinical trials with COX-2 inhibitors for cancer prevention or treatment. Their efficacy in the prevention of sporadic colon and other cancers remains unknown; one COX-2 inhibitor has been withdrawn because of side effects, and there are concerns about whether these effects are class-specific. There is evidence to suggest that COX-2 may not be the only or ideal eicosanoid pathway target for cancer prevention. Six sets of observations support this notion: the relatively late induction of COX-2 during carcinogenesis; the finding that NSAIDs may not require inhibition of COX-2 for their effect; the modest effect of coxibs in cancer prevention; that currently available coxibs have multiple non-COX-2 effects that may account for at least some of their efficacy; the possibility that concurrent inhibition of COX-2 in non-neoplastic cells may be harmful; and the possibility that COX-2 inhibition may modulate alternative eicosanoid pathways in a way that promotes carcinogenesis. Given the limitations of COX-2-specific inhibitors and the biological evidence mentioned above, we suggest that targets other than COX-2 should be pursued as alternative or complementary approaches to cancer prevention.

Cytoplasmic Phospholipase A2Deletion Enhances Colon Tumorigenesis

Cellular pools of free arachidonic acid are tightly controlled through enzymatic release of the fatty acid and subsequent utilization by downstream enzymes including the cyclooxygenases. Arachidonic acid cleavage from membrane phospholipids is accomplished by the actions of phospholipase A(2) (PLA(2)). Upon release, free arachidonic acid provides substrate for the synthesis of eicosanoids. However, under certain conditions, arachidonic acid may participate in ceramide-mediated apoptosis. Disruption of arachidonic acid homeostasis can shift the balance of cell turnover in favor of tumorigenesis, via overproduction of tumor-promoting eicosanoids or alternatively by limiting proapoptotic signals. In the following study, we evaluated the influence of genetic deletion of a key intracellular phospholipase, cytoplasmic PLA(2) (cPLA(2)), on azoxymethane-induced colon tumorigenesis. Heterozygous and null mice, upon treatment with the organotropic colon carcinogen, azoxymethane, developed a significant (P < 0.05) increase in colon tumor multiplicity (7.2-fold and 5.5-fold, respectively) relative to their wild-type littermates. This enhanced tumor sensitivity may be explained, in part, by the attenuated levels of apoptosis observed by terminal deoxynucleotidyl transferase-mediated nick end labeling staining within the colonic epithelium of heterozygous and null mice ( approximately 50% of wild type). The lower frequency of apoptotic cells corresponded with reduced ceramide levels (69% and 46% of wild-type littermates, respectively). Remarkably, increased tumorigenesis resulting from cPLA(2) deletion occurred despite a significant reduction in prostaglandin E(2) production, even in cyclooxygenase-2-overexpressing tumors. These data contribute new information that supports a fundamental role of cPLA(2) in the control of arachidonic acid homeostasis and cell turnover. Our findings indicate that the proapoptotic role of cPLA(2) in the colon may supercede its contribution to eicosanoid production in tumor development.

Colorectal cancer prevention: is an ounce of prevention worth a pound of cure?

Colorectal cancer (CRC) is among the most common human malignancies and remains a leading cause of cancer-related morbidity and mortality. Colorectal carcinogenesis is a multistep process characterized by molecular and cellular alterations that result in an identifiable precursor lesion, ie, the adenomatous polyp. The transition from normal mucosa to adenoma and its subsequent progression to carcinoma are protracted events that offer opportunities for preventive interventions. Suppression or reversal of the carcinogenic process in the colorectum with nonpharmacologic or pharmacologic agents, ie, chemoprevention, is an area of considerable research interest and activity. Interest in this field derives from multiple epidemiologic studies showing that regular and continued use of nonsteroidal anti-inflammatory drugs (NSAIDs), predominantly aspirin, is associated with significant reductions in both colorectal adenoma and carcinoma incidence. NSAIDs were first shown to be effective in patients with familial adenomatous polyposis (FAP). Subsequent randomized trials in FAP demonstrated that sulindac and the selective cyclooxygenase-2 (COX-2) inhibitor, celecoxib, can significantly regress existing adenomas, and resulted in Food and Drug Administration (FDA) approval of celecoxib for adjunctive management of these patients. Based on the aforementioned data, aspirin and coxibs have been or are currently being evaluated for the prevention of sporadic adenoma recurrence in high-risk patient populations. Evidence indicates that aspirin can reduce adenoma recurrence rates in patients with prior colorectal neoplasia; however, questions remain, including the optimal dosage, timing of initiation and duration of treatment, and clinical benefit versus potential harm to patients. These same issues apply to the nonpharmacologic agents such as calcium, folic acid, and selenium given as dietary supplements. Apart from aspirin, calcium carbonate is the only other agent that has been shown to modestly reduce sporadic adenoma recurrence rates in a randomized trial. Folate and selenium are being actively studied based on provocative preclinical data. In addition to demonstrating efficacy, chemopreventive agents must also be safe for long-term use, be well accepted by patients, and be cost-effective. In this review, the current status of CRC chemoprevention will be discussed, including the available evidence for selected pharmacologic and nonpharmacologic agents, particularly among high-risk populations.

Association between cyclooxygenase-2-expressing macrophages, ulceration and microvessel density in colorectal cancer

AIM

In colorectal carcinomas, cyclooxygenase-2 (COX-2) is expressed predominantly by epithelial cells and is implicated in tumour progression. Tumour-associated macrophages may influence tumour growth, proliferative rate and angiogenesis and also express COX-2 when activated. Thus they may play an important stromal-epithelial role in carcinogenesis. Tauhe aim of this study was to define the relationship between microvessel density (MVD), tumour COX-2 and macrophage COX-2 expression.

METHODS AND RESULTS

Sixty-five cases of formalin-fixed paraffin-embedded colorectal cancer were included in the study. Tissues were immunostained for COX-2, CD68 (macrophage marker) and CD34 (endothelial marker to assess MVD). Thirty-six cases were grossly ulcerated cancers and 29 cases showed focal/microscopic ulceration. Macrophages were in high concentration at the base of ulcerated areas, and were also diffusely dispersed within tumoral stroma. However, the pattern of macrophage COX-2 expression revealed two populations of macrophages--those deep within the tumour (negative for COX-2) and those at the base of ulcers (positive for COX-2). In all cases, the tumour epithelial cells expressed COX-2. MVD was higher at the base of ulcers, adjacent to COX-2+ macrophages, and was lower deep within the tumour.

CONCLUSIONS

In colorectal cancers, macrophages may have a dual role. Those concentrated at the base of the ulcers, where there is an associated high MVD, may induce angiogenesis, but their function may be in a healing/repair process. The lack of COX-2+ macrophages and lower MVD deep within the tumour suggests that it may be the epithelial COX-2 component that is important in tumour progression.

Selective inhibitors of MEK1/ERK44/42 and p38 mitogen-activated protein kinases potentiate apoptosis induction by sulindac sulfide in human colon carcinoma cells

The nonsteroidal anti-inflammatory drug (NSAID) sulindac prevents experimental colon cancer and can regress precancerous polyps in humans. Sulindac sulfide inhibits cyclooxygenase (COX)-mediated prostaglandin synthesis and retards the growth of cultured colon cell lines primarily by inducing apoptosis. Given the known role of mitogen-activated protein kinase (MAPK) in signal transduction and the regulation of cell survival and death, we determined the effect of sulindac sulfide on MAPK activation, COX-2 expression, and apoptosis induction in HCA-7 human colon cancer cells. Sulindac sulfide treatment was associated with activation of ERKp44/42 and p38 MAPK in a dosage- and time-dependent manner, and also activated upstream MEK. Similar results were seen in HCT-15 cells and also with the selective COX-2 inhibitor NS398. ERKp44/42 and p38 activation were accompanied by an induction of COX-2 protein expression. Selective inhibitors of sulindac sulfide–induced ERKp44/42 (PD98059) and p38 MAPK (SB203580) activation also suppressed the induction of COX-2 by this NSAID. Furthermore, both MAPK inhibitors significantly augmented sulindac sulfide–induced apoptosis, as did suppression of constitutive COX-2 using antisense oligonucleotides. In conclusion, MEK/ERK and p38 MAPK activation mediate COX-2 induction by sulindac sulfide. Selective inhibitors of these MAPKs potentiate apoptosis induction by this NSAID, suggesting a novel strategy for the prevention or treatment of colorectal cancer.

Cyclooxygenase-2 and thromboxane synthase in non-endocrine and endocrine tumors: a review

Prostaglandins (PG) are members of a large group of hormonally active fatty acids derived from free fatty acids. They are formed from arachidonic acid-the major PG precursor. Cyclooxygenase (COX)-1 and -2 are the rate-limiting steps in PG synthesis. COX-2 is overexpressed in many human non-endocrine and endocrine tumors including colon, breast, prostate, brain, thyroid, and pituitary. COX-2 has an important role in angiogenesis and tumor growth. Thromboxane synthase (TS) catalyzes the synthesis of thromboxane A2 (TXA2), which is derived from arachidonic acid and prostaglandin H2 and is a vasoconstrictor and inducer of platelet aggregation. TXA2 stimulates tumor growth and spread of some tumors and TS appears to have a critical role in tumorigenesis in some organ systems. In this review, we examine the role of COX-2 and TS in various non-endocrine tumors, especially colon, breast, prostate, and brain as well as in endocrine tumors. The accumulating evidence points to an increasingly important role of COX-2 and TS in tumor progression and metastasis.

Multifaceted roles of cyclooxygenase-2 in lung cancer

Lung cancer is the leading cause of cancer death in the United States. Although the low 5-year survival rate (under 15%) has changed minimally in the last 25 years, new agents and combinations of agents that target tumor proliferation, invasion, and survival may lead to improvement in patient outcomes. There is evidence that cyclooxygenase-2 (COX-2) is overexpressed in lung cancer and promotes tumor proliferation, invasion, angiogenesis, and resistance to apoptosis. COX-2 inhibitors have been found to inhibit tumor growth in animal models and have demonstrated responses when combined with conventional therapy in phase II clinical trials. Further understanding of the mechanisms involved in COX-2-mediated tumorigenesis and its interaction with other molecules in lung cancer may lead to improved therapeutic strategies for this disease. In addition, delineation of how COX-2-dependent genes modulate the malignant phenotype will provide novel insights in lung cancer pathogenesis.

Effects of Helicobacter pylori and NSAIDs on cytokinetics of gastric epithelium

AIM: To investigate the effects of Helicobacter pylori (H pylori ) and (NSAID) indomethacin and aspirin on the proliferation and apoptosis of gastric epithelial cells

METHODS: Gastric cancer cell line AGS cells were co-cultured with H pylori and/or NSAID, and then proliferation of AGS was examined by MTT assay, Western blotting and detection of proliferating cell nuclear antigen (PCNA). At the same time, cell apoptosis was detected with the FITC-Annexin-V/PI double staining, DNA gel eletrophoresis and transmission electron microscopy were used to confirm the results.

RESULTS: The CagA-positive H pylori strain NCTC11637 could enhance cell proliferation. Besides, low concentrations (range from 3.2×10⁷ CFU/L to 4×10⁹ CFU/L) of H pylori could promote proliferation (P <0.05) of AGS cell line while high concentrations (>2 ×10¹⁰ CFU/L) could inhibit the growth of AGS cells (P <0.05). When incubated with H pylori and NSAID together, proliferation of AGS cells was inhibited. Indomethacin and aspirin increased apoptosis of AGS cells significantly (P <0.05). No obvious apoptosis was observed in the H pylori-infected cells. When cells were co-cultured with H pylori and NSAID, the percentage of apoptosis also increased significantly (P <0.05), but the percentage was lower than that of cells incubated with NSAID alone. These results were confirmed by transmission electron microscopy and DNA gel electrophoresis.

CONCLUSION: CagA(+)H pylori strains are more prone to enhance the proliferation of gastric epithelial cells than cagA(-) H pylori strains. The effects of H pylori on the cell growth are associated with the concentrations of H pylori. NSAID can inhibit the gastric epithelial cell proliferation.

Methionine sulfoxide reductases: history and cellular role in protecting against oxidative damage

An enzyme that can reduce methionine sulfoxide in proteins was first discovered in Escherichia coli about 25 years ago. It is now apparent that there is a family of enzymes, referred to as methionine sulfoxide reductases (Msr), and in recent years there has been considerable interest in one of the members of the Msr family, MsrA. This enzyme has been shown to protect cells against oxidative damage, which suggests a possible role in a large number of age-related diseases. This review summarizes the history of the discovery of MsrA, properties of the enzyme and its role in protecting cells against oxidative damage. Other members of the Msr family that differ in substrate specificity and localization are described as well as a possible role for the Msr system in drug metabolism. The concept that the Msr system can be used to develop novel drugs that could be catalytic anti-oxidants is discussed.

Potency of arachidonic acid in polyunsaturated fatty acid-induced death of human monocyte-macrophages: implications for atherosclerosis

Evidence suggests that oxidation of LDL is involved in the progression of atherosclerosis by inducing apoptosis in macrophages. Polyunsaturated fatty acids (PUFAs) are prominent components of LDL and are highly peroxidisable. We therefore tested PUFAs for induction of apoptosis in human monocyte-macrophages in vitro. Arachidonic acid (AA) induced the highest levels of apoptosis followed by docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), despite DHA and EPA being more peroxidisable than AA. alpha-Linolenic acid induced lower levels of apoptosis. Linoleic and oleic acids were innocuous. Results of experiments with AA products and enzyme inhibitors suggest roles for peroxidation, cyclooxygenase and lipoxygenase in AA-induced apoptosis. Our results further suggest activation of PPARgamma by AA and DHA associated with apoptosis induction. These findings may be relevant to potential mechanisms of fatty acid influences on plaques and may suggest strategies for combating atherosclerosis progression.

Ibuprofen Inhibits Survival of Bladder Cancer Cells by Induced Expression of the p75NTR Tumor Suppressor Protein

Nonsteroidal anti-inflammatory drugs (NSAIDs) are used to reduce inflammation and as analgesics by inhibition of cyclooxygenase-2. At higher concentrations, some NSAIDs inhibit proliferation and induce apoptosis of cancer cells. Although several molecular mechanisms have been postulated to explain the anticancer effects of NSAIDs, they do not involve merely the inhibition of cyclooxygenase-2, and a more proximate initiator molecule may be regulated by NSAIDs to inhibit growth. The p75 neurotrophin receptor (p75NTR) is a proximate cell membrane receptor glycoprotein that has been identified as a tumor and metastasis suppressor. We observed that NSAID treatment of cell lines from bladder and other organs induced expression of the p75NTR protein. Of the different types of NSAIDs examined, ibuprofen was more efficacious than aspirin and acetaminophen and comparable with (R)-flurbiprofen and indomethacin in induction of p75NTR protein expression. This rank order NSAID induction of the p75NTR protein correlated with the ability of these NSAIDs to reduce cancer cell survival. To examine a mechanistic relationship between ibuprofen induction of p75NTR protein and inhibition of survival, bladder cancer cells were transfected with ponasterone A-inducible vectors that expressed a death domain-deleted (DeltaDD) or intracellular domain-deleted (DeltaICD) p75NTR product that acts as a dominant negative antagonist of the intact p75NTR protein. Expression of DeltaDD and DeltaICD rescued cells from ibuprofen inhibition of growth. These observations suggest that p75NTR is an important upstream modulator of the anticancer effects of NSAIDs and that ibuprofen induction of the p75NTR protein establishes an alternate mechanism by which ibuprofen may exert an anticancer effect.

New approaches to the role of diet in the prevention of cancers of the alimentary tract

Cancers of the alimentary tract are, collectively, amongst the major causes of morbidity and deaths from cancer across the world today. Of the 10 million new cases of cancer diagnosed in 2000, about 2.3 million were cancers of the pharynx, oesophagus, stomach or colorectum. Nevertheless, epidemiological studies indicate that cancers of the digestive organs are also amongst the most susceptible to modification by dietary factors. International variations in incidence suggest that round three quarters of all sporadic colorectal cancers are attributable to diet. Even within the relatively uniform environment of the European Union, there are variations in the incidence of colorectal and oesophageal cancers of about two- and six-fold, respectively. Carcinomas of the alimentary tract arise from epithelial cells via distinct sequences of neoplastic change, which require a large fraction of an individual's lifespan. The best characterised of these is the adenoma-carcinoma sequence of colorectal carcinogenesis, in which progressive loss of differentiation and normal morphology in a growing lesion is associated with the acquisition of somatic mutations, and of aberrant methylation of CpG-islands, leading to gene silencing. These molecular events are accompanied by functional changes, including increased mitosis and evasion of apoptosis. There is little evidence that diet exerts its effects primarily through food-borne carcinogens that can be identified and eliminated from the food-chain. It is far more probable that the adverse effects of diet are caused largely by over-consumption of energy, coupled with inadequate intakes of protective substances, including micronutrients, dietary fibre and a variety of phytochemicals. The latter are biologically active secondary plant metabolites, many of which modify cell proliferation and induce apoptosis in vitro. There is growing evidence that such effects also occur in vivo, and that they can suppress the progress of neoplasia. Carcinomas of the oesophagus, stomach and colon all appear to be partially preventable by diets rich in fruits and vegetables. Plant foods contain a variety of components including micronutrients, polyunsaturated fatty acids, and secondary metabolites such as glucosinolates and flavonoids, many of which can inhibit cell proliferation and induce apoptosis, and which may well act synergistically when combined in the human diet. The future challenge is to fully characterise and evaluate these effects at the cellular and molecular level, so at to exploit their full potential as protective mechanisms for the population as a whole.

Glutathione-S-transferase P1-1 protects aberrant crypt foci from apoptosis induced by deoxycholic acid

BACKGROUND & AIMS

Aberrant crypt foci, precursors of colonic adenoma, are frequently positive for glutathione-S-transferase P1-1. Because deoxycholic acid is an apoptosis-inducing xenobiotic in the colon, we examined the possibility that aberrant crypt foci, through the cytoprotecting function of glutathione-S-transferase P1-1, resist deoxycholic acid-induced apoptosis, thereby surviving to become adenomas and subsequently cancer.

METHODS

Glutathione-S-transferase P1-1 or cyclooxygenase-2 expression and the percentage of apoptotic cells in aberrant crypt foci were examined by immunohistochemistry and by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling, respectively. Glutathione-S-transferase P1-1 was transfected into colon cancer cells (M7609) and human lung fibroblasts, and deoxycholic acid-induced apoptosis was evaluated by a dye-uptake assay and flow cytometry. Binding of deoxycholic acid to glutathione-S-transferase P1-1 was analyzed by circular dichroism and immunoprecipitation. Caspase activities were determined by colorimetric protease assay, and sulindac binding to glutathione-S-transferase P1-1 was determined by inhibition assay of glutathione-S-transferase P1-1 activity.

RESULTS

Aberrant crypt foci showed positive immunostaining for glutathione-S-transferase P1-1 but negative staining for cyclooxygenase-2. The percentage of apoptotic cells in aberrant crypt foci was significantly lower than in healthy epithelium, and the difference became more apparent with deoxycholic acid treatment. The impaired sensitivity of aberrant crypt foci to deoxycholic acid was restored by the glutathione-S-transferase P1-1-specific inhibitor gamma-glutamyl-S-(benzyl)cysteinyl-R-phenylglycine diethylester. By transfection of glutathione-S-transferase P1-1, M7609 cells became more resistant to deoxycholic acid-induced apoptosis than mock transfectants. Direct binding of glutathione-S-transferase P1-1 to deoxycholic acid was proven by circular dichroism and by immunoprecipitation. The aberrant crypt foci in adenoma patients treated with sulindac, which was shown to bind to glutathione-S-transferase P1-1, underwent apoptosis in 4 days and mostly regressed in 2-3 months.

CONCLUSIONS

Glutathione-S-transferase P1-1 protects aberrant crypt foci from deoxycholic acid-induced apoptosis and may play a pivotal role in early colon carcinogenesis.

Molecular mechanisms in C-Phycocyanin induced apoptosis in human chronic myeloid leukemia cell line-K562

C-Phycocyanin (C-PC), the major light harvesting biliprotein from Spirulina platensis is of greater importance because of its various biological and pharmacological properties. It is a water soluble, non-toxic fluorescent protein pigment with potent anti-oxidant, anti-inflammatory and anti-cancer properties. In the present study the effect of highly purified C-PC was tested on growth and multiplication of human chronic myeloid leukemia cell line (K562). The results indicate significant decrease (49%) in the proliferation of K562 cells treated with 50 microM C-PC up to 48 h. Further studies involving fluorescence and electron microscope revealed characteristic apoptotic features like cell shrinkage, membrane blebbing and nuclear condensation. Agarose electrophoresis of genomic DNA of cells treated with C-PC showed fragmentation pattern typical for apoptotic cells. Flow cytometric analysis of cells treated with 25 and 50 microM C-PC for 48 h showed 14.11 and 20.93% cells in sub-G0/G1 phase, respectively. C-PC treatment of K562 cells also resulted in release of cytochrome c into the cytosol and poly(ADP) ribose polymerase (PARP) cleavage. These studies also showed down regulation of anti-apoptotic Bcl-2 but without any changes in pro-apoptotic Bax and thereby tilting the Bcl-2/Bax ratio towards apoptosis. These effects of C-PC appear to be mediated through entry of C-PC into the cytosol by an unknown mechanism. The present study thus demonstrates that C-PC induces apoptosis in K562 cells by cytochrome c release from mitochondria into the cytosol, PARP cleavage and down regulation of Bcl-2.

Involvement of cell cycle regulatory proteins and MAP kinase signaling pathway in growth inhibition and cell cycle arrest by a selective cyclooxygenase 2 inhibitor, etodolac, in human hepatocellular carcinoma cell lines

Recent studies have shown that selective cyclooxygenase-2 (COX-2) inhibitors induce growth inhibition and cell cycle arrest in hepatocellular carcinoma (HCC) cell lines. However, the mechanism by which COX-2 inhibitors regulate the cell cycle and whether or not growth signal pathways are involved in the growth inhibition remain unclear. In this study, we investigated the mechanisms of growth inhibition and cell cycle arrest by etodolac, a selective COX-2 inhibitor, in HCC cell lines, HepG2 and PLC/PRF/5, by studying cell cycle regulatory proteins, and the MAP kinase and PDK1-PKB/AKT signaling pathways. Etodolac inhibited growth and PCNA expression and induced cell cycle arrest in both HCC cell lines. Etodolac induced p21WAF1/Cip1 and p27Kip1 expression and inhibited CDK2, CDK4, CDC2, cyclin A and cyclin B1 expression, but did not affect cyclin D1 or cyclin E. HGF and 10% FBS induced ERK phosphorylation, but phosphorylation of p38, JNK and AKT was down-regulated by etodolac. PD98059, a selective inhibitor of ERK phosphorylation, induced growth inhibition, the expression of p27Kip1 and cell cycle arrest. In conclusion, p21WAF1/Cip1, p27Kip1, CDK2, CDK4, CDC2, cyclin A, cyclin B1 and the MAP kinase signaling pathway are involved in growth inhibition and cell cycle arrest by a selective COX-2 inhibitor in HCC cell lines.

NO-donating nonsteroidal antiinflammatory drugs (NSAIDs) inhibit colon cancer cell growth more potently than traditional NSAIDs: a general pharmacological property?

The novel nitric oxide-donating nonsteroidal antiinflammatory drugs (NO-NSAIDs), consisting of a traditional NSAID to which a NO releasing moiety is covalently attached, may have an important role in colon cancer prevention and/or treatment. Preclinical studies have shown that NO-aspirin (NO-ASA) is more potent than traditional ASA in preventing colon cancer. Preclinical and clinical studies have also documented its superior safety, compared to traditional ASA. To evaluate the role of this structural modification on the cancer cell growth inhibitory effect of NSAIDs, we studied seven pairs of traditional NSAIDs (ASA, salicylic acid, indomethacin, sulindac, ibuprofen, flurbiprofen, piroxicam) and their corresponding NO-NSAIDs. All NO-NSAIDs (except NO-piroxicam which is a salt and not a true NO-NSAID) have greater potency in inhibiting HT-29 and HCT-15 colon cancer cell growth compared to their NSAID counterparts: the IC(50)s of the NO-NSAIDs were enhanced between 7- and 689-fold in HT-29 cells and 1.7- to 1083-fold in HCT-15 cells over those of the corresponding NSAIDs. Their growth inhibitory effect is due to a profound cell kinetic effect consisting of reduced cell proliferation and enhanced cell death. Since HT-29 cells express cyclooxygenases but HCT-15 do not, this effect appears independent of cyclooxygenase in the colon cancer cells. Thus the structural modification of these traditional NSAIDs leading to NO-NSAIDs enhances their potency in inhibiting colon cancer cell growth. Our findings suggest that the enhanced potency imparted on NSAIDs by this structural modification represents a pharmacological property that may be a general one for this class of compounds.

Should we eradicate Helicobacter pylori in non-steroidal anti-inflammatory drug users?

The interaction between Helicobacter pylori and non-steroidal anti-inflammatory drugs (NSAIDs) in ulcerogenesis has been visited by many studies. Apparently these studies yielded conflicting results. This is a result of a wide diversity of methodology, selection of patient groups and definitions of outcome used by different investigators. This review attempts to analyse separately studies dealing with new or chronic NSAID users, primary or secondary prophylaxis, complicated or uncomplicated ulcers in NSAID or aspirin users. Evidence suggests that eradication of Helicobacter pylori infection may reduce the risk of ulcer and ulcer complications in patients requiring NSAIDs and aspirin. Whether or not one should test-and-treat H. pylori before prescribing NSAIDs is a complicated issue. Factors such as the ulcer risk of patients, previous history of NSAID usage and the use of aspirin or NSAIDs would guide the strategy.

Cell Proliferation and Apoptotic Indices Predict Adenoma Regression in a Placebo-Controlled Trial of Celecoxib in Familial Adenomatous Polyposis Patients

Background: Celecoxib was shown to regress colorectal adenomas in familial adenomatous polyposis (FAP) patients relative to placebo. To address the mechanism of polyp regression, we determined whether celecoxib can modulate cell proliferation, apoptosis, and prostaglandin E2 (PGE2) levels in colorectal epithelia from FAP trial participants and whether such alterations correlate with observed reductions in polyp number. Materials and Methods: Colorectal mucosal biopsies were obtained at baseline and on last day of celecoxib (100 or 400 mg twice daily) or placebo administration (6 months). Residual paraffin-embedded adenomas and normal mucosa from the same patients (n = 17) or normal tissue alone (n = 15) were analyzed. Immunoperoxidase staining for Ki-67 was performed and apoptotic cells were identified by their morphology. Ki-67 and apoptotic labeling indices and their ratios were calculated in superficials (s) and nonsuperficial (ns) regions of adenomas and normal mucosa, and baseline to 6-month differences were calculated. PGE2 levels were analyzed by mass spectroscopy (normal, n = 64; adenoma, n = 56). Biomarkers were analyzed by treatment arm and correlated with previously determined mean percentage reductions in colorectal polyp number. Results: In adenomas, a reduction in the superficial proliferative activity i.e., Ki-67s labeling index, accompanied polyp regression (r = −0.76, P = 0.006). An increase in the apoptotic ratio [i.e., superficial apoptotic index (AIs)/nonsuperficial apoptotic index (AIns)] was found to correlate with reduced polyp counts in that higher apoptotic ratios correlated with better response to celecoxib (r = 0.71, P = 0.004). Furthermore, the AIs/Ki-67s ratio (r = 0.58, P = 0.026) accompanied polyp regression. In normal mucosa, a trend toward increased AIs (r = 0.33, P = 0.053) and polyp regression was found. PGE2 levels did not significantly correlate with polyp regression. Changes in biomarker levels (baseline to 6 months) were correlated in adenomas and normal mucosa (AIs, r = 0.29, P = 0.024; AIns, r = 0.34, P = 0.009; PGE2, r = 0.50, P = 0.059) within individual patients. Conclusion: Suppression of cell proliferation and an increased apoptotic ratio, as well as the ratio of apoptosis to cell proliferation, accompany polyp regression in a chemoprevention trial in FAP patients. These findings suggest potential mechanisms for the efficacy of celecoxib and warrant further study of these biomarkers as intermediate endpoints in FAP patients.

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

BACKGROUND AND AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Role of apoptosis and CD95-receptor/ligand system in aspirin- and Helicobacter pylori-induced cell death

BACKGROUND

Helicobacter pylori and aspirin both induce gastric epithelial apoptosis. However, the apoptosis-inducing mechanism of aspirin is still unknown.

MATERIAL AND METHODS

Apoptosis induction was measured in several gastric epithelial cell lines after incubation with either aspirin or H. pylori supernatant or with a combination of both. CD95 expression was assessed by FACS analysis and CD95L mRNA was measured by reverse transcription polymerase chain reaction.

RESULTS

It could be demonstrated that aspirin- and H. pylori supernatant-induced apoptosis involves increased CD95 expression in three different gastric epithelial cell lines. The combined exposure of H. pylori supernatant and aspirin had synergistic effects on both apoptotic cell death and CD95 expression. Blockade of CD95 signalling with an antagonistic antibody was partially prevented from H. pylori- but not from aspirin-induced apoptosis. Furthermore, CD95L expression was detected after treatment with H. pylori only.

CONCLUSIONS

These data suggest that although aspirin-mediated CD95 up-regulation is not relevant for its direct apoptotic effect it may sensitize gastric epithelial cells for H. pylori-induced apoptosis. Collectively our data demonstrate the relation of aspirin- and H. pylori-induced apoptosis from a new perspective.

Reduction of Sulindac to its active metabolite, sulindac sulfide: assay and role of the methionine sulfoxide reductase system

Sulindac is a known anti-inflammatory drug that functions by inhibition of cyclooxygenases 1 and 2 (COX). There has been recent interest in Sulindac and other non-steroidal anti-inflammatory drugs (NSAID) because of their anti-tumor activity against colorectal cancer. Studies with sulindac have indicated that it may also function as an anti-tumor agent by stimulating apoptosis. Sulindac is a pro-drug, containing a methyl sulfoxide group, that must be reduced to sulindac sulfide to be active as a COX inhibitor. In the present studies we have developed a simple assay to measure sulindac reduction and tested sulindac as a substrate for 6 known members of the methionine sulfoxide reductase (Msr) family that have been identified in Escherichia coli. Only MsrA and a membrane associated Msr can reduce sulindac to the active sulfide. The reduction of sulindac also has been demonstrated in extracts of calf liver, kidney, and brain. Sulindac reductase activity is also present in mitochondria and microsomes.

Apoptosis-modulating agents in combination with radiotherapy-current status and outlook

PURPOSE

To increase the therapeutic efficacy of ionizing radiation or to reduce radiation-mediated side effects, diverse research centers for translational radiation oncology have headed for a specific modulation of defined cellular death pathways. In this regard, several signaling systems have proved to be of high potential value.

RESULTS

It has previously been shown that apoptotic pathways induced by ionizing radiation are distinct from death pathways triggered by death ligands such as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). The combination of both radiation and TRAIL was highly efficient in vitro and in preclinical mouse models. However, several aspects of normal tissue toxicity have not been solved, and no Phase I data are available yet. A second approach tested in a Phase I trial is based on the observation that synthetic phospholipid derivatives (alkyllysophospholipids and alkylphosphocholines) strongly enhance apoptotic effects by modulating the balance among the mitogenic, anti-apoptotic MAPK, phosphatidylinositol 3'-kinase (PI3K)/Akt, and the pro-apoptotic SAPK/JNK signaling pathways. Furthermore, others have provided evidence that inhibition of anti-apoptotic signals generated by mitogenic stimuli may increase radiation responses. In this context, controversial data are available regarding the influence of a pharmacologic abrogation of MEK1, Erk1/2 signaling on apoptotic sensitivity but no Phase I trials of MEK inhibitors either alone or in combination with radiation have yet been published. However, inhibition of the PI3K/Akt survival pathway using compounds such as the protein kinase C (PKC) inhibitor PKC412 has been shown to induce apoptosis or to increase the apoptotic sensitivity of tumor cells. Therefore, these drugs may be used alone or in combination with radiation to increase tumor control; however, Phase I data are lacking. Several other drugs, including cyclooxygenase-2 inhibitors, betulinic acid, and proteasome inhibitors, have been shown to interact with apoptotic signal transduction. Again, most of the drugs have not been tested in combination with radiation in vivo or-in the case of cyclooxygenase-2 inhibitors-exert pleiotropic effects.

CONCLUSION

Although the examples do not reflect all available strategies, it is clear that several promising approaches targeting defined cell death pathways have been developed and entered into clinical trials. The use of synthetic phospholipid derivatives in a Phase I trial is an important example, proving that basic research in radiation biology finally guides the development of new treatment strategies. This, and other approaches, will hopefully increase tumor control rates and reduce side effects in the future.

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.

N/A

N/A

Cyclooxygenase-2 expression in stromal tumors of the gastrointestinal tract

Cyclooxygenase (COX) is a key enzyme in the conversion of arachidonic acid to prostaglandins, prostacyclin, and thromboxane. COX-2 is expressed in many epithelial malignancies, particularly those of the gastrointestinal (GI) tract. COX-2 has been implicated in the pathogenesis of cancers and has a significant negative effect on survival. To date, little is known about the expression of COX-2 in nonepithelial tumors. The objective of this study was to evaluate the expression of COX-2 in GI stromal tumors (GISTs). We evaluated 15 GISTs using tissue microarray. Tissue blocks were retrieved and stained with hematoxylin and eosin to evaluate the histological tumor type. In addition, immunohistochemistry was performed for COX-2, the macrophage marker, CD68 (KP-1), and KIT (CD117). Two pathologists then evaluated the tissues to determine the extent and intensity of COX-2 expression. The location of CD68-positive cells, and whether these cells were COX-2 positive, was also evaluated. The results showed that 80% (12 of 15) of the tumors expressed COX-2. Expression was noted in the cytoplasm of the tumor cells, with variable intensity of staining among the tumors. COX-2 was expressed in both epithelial cell and spindle cell tumors, but appeared stronger in epithelial lesions. In mixed lesions, COX-2 was expressed to a greater extent in epithelial areas. There was a greater extent of COX-2 expression in malignant tumors and tumors located within the stomach. Tumor-infiltrating macrophages (CD68-positive cells) were identified in all of the lesions; in 80% of cases, those macrophages also expressed COX-2. This study is the first to demonstrate COX-2 expression in stromal lesions of the GI tract. The enzyme may play a role in the proliferation of these lesions, suggesting the potential use of nonsteroidal anti-inflammatory drugs in treatment.

The chemopreventive agent sulindac attenuates expression of the antiapoptotic protein survivin in colorectal carcinoma cells

Nonsteroidal anti-inflammatory drugs (NSAIDs) such as sulindac have chemopreventive activity against colorectal tumors. Although the molecular mechanism has not been fully established, it is thought to involve the ability of NSAIDs to induce apoptosis. Because the majority of colon carcinomas are known to overexpress antiapoptotic proteins such as survivin and Bcl-2 and show only limited ability to undergo apoptosis, we hypothesized that the ability of sulindac to cause regression of adenomas and to inhibit colon carcinogenesis is mediated, at least in part, by down-regulation of one or more of these antiapoptotic proteins. To test this hypothesis, we exposed HT-29 colon carcinoma cells to sulindac. Sulindac induced a sustained decrease in mRNA and protein expression for survivin but not for Bcl-2. This finding suggests that sulindac is selectively acting through a survivin-related pathway. This is consistent with our earlier finding that inhibition of the beta-catenin:T-cell factor 4 (Tcf-4) pathway by the adenomatous polyposis coli protein down-regulates survivin expression and with recent evidence that sulindac induces beta-catenin degradation, which would reduce Tcf-4 activation. This suggests that the beta-catenin:Tcf-4:survivin mechanism may be a useful target for therapy or chemoprevention of colon cancer.

Celecoxib: a potent cyclooxygenase-2 inhibitor in cancer prevention

Non-steroidal anti-inflammatory drugs (NSAIDs) are the most widely used therapeutic agents in the treatment of pain, inflammation and fever. They may also have a role in the management of cancer prevention, Alzheimer's disease and prophylaxis against cardiovascular disease. These drugs act primarily by inhibiting cyclooxygenase enzyme, which has two isoforms, cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). Selective COX-2 inhibitors provide potent anti-inflammatory and analgesic effects without the side effects of gastric and renal toxicity and inhibition of platelet function. Celecoxib is a potent COX-2 inhibitor being developed for the treatment of rheumatoid arthritis and osteoarthritis. Chemoprevention is the use of pharmacological or natural agents to prevent, suppress, interrupt or reverse the process of carcinogenesis. For this purpose, celecoxib is being used for different cancer types. The effects of NSAIDs on tumor growth remain unclear, but are most likely to be multifocal. In this article, we reviewed COX-2 selectivity, the pharmacological properties of celecoxib, the use of celecoxib for cancer prevention and the mechanisms of chemoprevention.

Effects of low dose aspirin (81 mg) on proliferating cell nuclear antigen and Amaranthus caudatus labeling in normal-risk and high-risk human subjects for colorectal cancer

Epidemiological, experimental, and clinical observations provide support for a colorectal cancer chemopreventive role for aspirin. We have evaluated the effects of aspirin on proliferation biomarkers in normal-risk and high-risk human subjects for colorectal cancer. Colorectal biopsies were obtained at baseline and at 24h after 28 daily doses of 81 mg of aspirin from 13 high-risk and 15 normal-risk subjects for colorectal cancer. We evaluated aspirin's effects on proliferating cell nuclear antigen (PCNA) immunohistochemistry and epithelial mucin histochemistry using the lectin, Amaranthus caudatus agglutinin (ACA) in crypt sections from rectal biopsies. The baseline whole crypt PCNA LIs differed significantly between normal-risk and high-risk subjects. PCNA LIs are not affected by 28 days of aspirin at 81 mg daily. ACA LIs are decreased by 28 days of aspirin at 81 mg daily in both normal-risk and high-risk subjects. Aspirin's effects on ACA LIs may have mechanistic and biological implications that deserve further attention. PCNA and ACA LIs are not useful as proliferation biomarkers for aspirin's chemopreventive activity in morphologically normal human colorectal mucosa.

Cyclooxygenase-2 inhibitor (SC-236) suppresses activator protein-1 through c-Jun NH2-terminal kinase

BACKGROUND AND AIMS

Aspirin exerts antitumor effect partly through blocking tumor promoter-induced activator protein-1 (AP-1) activation. The aim of this study is to determine how specific COX-2 inhibitor SC-236 mediates antitumor effect by modulation of AP-1-signaling pathway.

METHODS

AP-1 transcriptional activity and DNA-binding activity were detected by luciferase reporter assay and gel shift assay, separately. Mitogen-activated protein kinase (MAPK) activation was determined by Western blot and in vitro kinase assay. Antisense oligonucleotide against c-Jun-N-terminal kinase (JNK) was used to suppress JNK expression.

RESULTS

We showed that SC-236 inhibited 12-O-tetradecanoylphorbol-13-acetate (PMA)-induced cell transformation in a dose-dependent manner in JB6 cells. At a dose range (12.5-50 micromol/L) that inhibited cell transformation, SC-236 also inhibited anchorage-independent cell growth and AP-1-activation in 3 gastric cancer cells, independent of COX-prostaglandin synthesis. SC-236 down-regulated c-Jun-NH2-terminal kinase phosphorylation and activity. Suppression of JNK activity reversed the inhibitory effect on AP-1 activity by SC-236 and suppressed gastric cancer cell growth, indicating that the inhibitory effect of SC-236 on AP-1 activation and cell growth was through interaction with JNK.

CONCLUSIONS

The inhibitory effect on JNK-c-Jun/AP-1 activation contributes to the antitumor effect of COX-2-specific inhibitor, and inhibition of JNK activation may have a therapeutic benefit against gastric cancer.

MEK inhibition of pancreatic carcinoma cells by U0126 and its effect in combination with sulindac

OBJECTIVES

The MAP kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) pathway is critical for cell growth and survival. In the current study, we examined the effect of inhibiting the MEK-ERK pathway in pancreatic tumor cells with the MEK-specific inhibitor U0126. In addition, we investigated whether the MEK-ERK pathway influenced the response of pancreatic cancer cells to nonsteroidal antiinflammatory drugs (NSAIDs).

METHODS

Cell growth was monitored by a colorimetric proliferation assay and cell counts. Cell cycle analysis was performed using flow cytometry. Apoptosis was measured using a DNA fragmentation ELISA. Protein expression was detected by Western blot.

CONCLUSION

Treatment with U0126 dose dependently inhibited the growth of 3 human pancreatic carcinoma cell lines (BxPC-3, PANC-1, and MIA PaCa-2). U0126 treatment resulted in cell-cycle alterations but did not induce apoptosis. Growth inhibitory concentrations of NSAIDs unexpectedly increased ERK phosphorylation in BxPC-3 and MIA PaCa-2 cells. We therefore evaluated the effect of treating pancreatic tumor cells with the combination of the NSAID sulindac and U0126. Treatment with U0126 complemented sulindac-induced growth inhibition in BxPC-3 and PANC-1 cells. The expression of several cell cycle (p21, p27, cyclin D1) and apoptotic (survivin, Bcl-xL) regulatory proteins was altered after U0126 and/or sulindac treatment. Our findings suggest that inhibition of the MEK-ERK signaling pathway may sensitize pancreatic tumor cells to NSAID therapy.

Cyclooxygenase-independent induction of apoptosis by sulindac sulfone is mediated by polyamines in colon cancer

Sulindac, a non-steroidal anti-inflammatory prodrug, is metabolized into pharmacologically active sulfide and sulfone derivatives. Sulindac sulfide, but not sulindac sulfone, inhibits cyclooxygenase (COX) enzyme activities, yet both derivatives have growth inhibitory effects on colon cancer cells. Microarray analysis was used to detect COX-independent effects of sulindac on gene expression in human colorectal cells. Spermidine/sperm-ine N1-acetyltransferase (SSAT) gene, which encodes a polyamine catabolic enzyme, was induced by clinically relevant sulindac sulfone concentrations. Northern blots confirmed increased SSAT RNA levels in these colon cancer cells. Deletion analysis and mutational studies were done to map the sulindac sulfone-dependent response sequences in the SSAT 5'-flanking sequences. This led us to the identification of two peroxisome proliferator-activated receptor (PPAR) response elements (PPREs) in the SSAT gene. PPRE-2, at +48 bases relative to the transcription start site, is required for the induction of SSAT by sulindac sulfone and is specifically bound by PPAR gamma in the Caco-2 cells as shown by transfection and gel shift experiments. PPRE-1, at-323 bases relative to the start site, is not required for the induction of SSAT by sulindac sulfone but can be bound by both PPAR delta and PPAR gamma. Sulindac sulfone reduced cellular polyamine contents in the absence but not in the presence of verapamil, an inhibitor of the export of monoacetyl diamines, inhibited cell proliferation and induced apoptosis. The induced apoptosis could be partially rescued by exogenous putrescine. These data suggest that apoptosis induced by sulindac sulfone is mediated, in part, by the COX-independent, PPAR-dependent transcriptional activation of SSAT, leading to reduced tissue polyamine contents in human colon cancer cells.

The 15-lipoxygenase-1 product 13-S-hydroxyoctadecadienoic acid down-regulates PPAR-delta to induce apoptosis in colorectal cancer cells

Diminished apoptosis, a critical event in tumorigenesis, is linked to down-regulated 15-lipoxygenase-1 (15-LOX-1) expression in colorectal cancer cells. 13-S-hydroxyoctadecadienoic acid (13-S-HODE), which is the primary product of 15-LOX-1 metabolism of linoleic acid, restores apoptosis. Nonsteroidal antiinflammatory drugs (NSAIDs) transcriptionally up-regulate 15-LOX-1 expression to induce apoptosis. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors for linoleic and arachidonic acid metabolites. PPAR-delta promotes colonic tumorigenesis. NSAIDs suppress PPAR-delta activity in colon cancer cells. The mechanistic relationship between 15-LOX-1 and PPAR-delta was previously unknown. Our current study shows that (i) 13-S-HODE binds to PPAR-delta, decreases PPAR-delta activation, and down-regulates PPAR-delta expression in colorectal cancer cells; (ii) the induction of 15-LOX-1 expression is a critical step in NSAID down-regulation of PPAR-delta and the resultant induction of apoptosis; and (iii) PPAR-delta is an important signaling receptor for 13-S-HODE-induced apoptosis. The in vivo relevance of these mechanistic findings was demonstrated in our tumorigenesis studies in nude mouse xenograft models. Our findings indicate that the down-regulation of PPAR-delta by 15-LOX-1 through 13-S-HODE is an apoptotic signaling pathway that is activated by NSAIDs.

Molecular mechanisms involved in the antiproliferative effect of two COX-2 inhibitors, nimesulide and NS-398, on colorectal cancer cell lines

BACKGROUND

Cyclooxygenase (COX)-2 is up-regulated in most colorectal cancers. Chronic use of non-steroidal anti-inflammatory drugs, which target cyclooxygenases, have been shown to reduce the risk of these cancers. However, the mechanisms underlying this protective effect remain unclear.

AIMS

The aim of our study was to characterize the effects of two COX-2 selective inhibitors, NS-398 and nimesulide, on colorectal cancer cell proliferation, and to describe the molecular mechanisms involved.

MATERIALS AND METHODS

HT-29 and SW-1116 cell lines were cultured with either NS-398 or nimesulide. Cell proliferation was assessed by staining DNA with crystal violet. Cell cycle repartition and apoptosis were analysed by flow cytometry. The expression of COX-1 and COX-2. and of two cyclin dependent kinase inhibitors, p21Cip1 and p27Kip1, was analysed by Western blotting and RT-PCR.

RESULTS

Both drugs dose-dependently inhibited cell proliferation and induced G1 cell cycle blockade. HT-29 cells were more sensitive to both drugs than SW-1116 cells. p21Cip1 and p27Kip1 were induced on both cell lines. Concomitant induction of p21Cip1 mRNA indicates transcriptional modulation, whereas induction of p27Kip1 only at the protein level suggests post-translational modulation.

CONCLUSION

NS-398 and nimesulide inhibit colorectal cell proliferation through induction of p21Cip1 and p27Kip1.

Celecoxib activates a novel mitochondrial apoptosis signaling pathway

The cyclooxygenase (COX)-2 inhibitor Celecoxib may inhibit cancer cell growth independently of its capacity to block the COX-2 enzyme. The growth inhibitory effect had been attributed to its pro-apoptotic effects. However, the molecular details of Celecoxib-induced apoptosis have not been analyzed yet. To differentiate between death receptor and mitochondrial signaling pathways, induction of apoptosis upon treatment with Celecoxib was tested in Jurkat T- and BJAB B-lymphoma cell lines with defects in either pathway. Celecoxib-induced dose- and time-dependent apoptosis in Jurkat and BJAB cells involving i) activation of caspases-9, -8, and -3, ii) cleavage of poly(ADP-ribose) polymerase and inhibitor of caspase-activated DNAase, iii) breakdown of the mitochondrial membrane potential, and iv) release of cytochrome c. Lack of Fas-associated death domain protein (FADD), overexpression of a dominant negative FADD, lack of caspase-8, and treatment with caspase-8-specific inhibitors had no influence on Celecoxib-induced apoptosis. In contrast, overexpression of a dominant negative caspase-9 or pharmacological inhibition of caspase-9 strongly interfered with Celecoxib-induced cell death. Furthermore, expression of Apaf-1 was required for Celecoxib-induced apoptosis. Importantly, Bcl-2 overexpression did not abrogate caspase activation, mitochondrial alterations, and apoptosis upon Celecoxib treatment while inhibiting radiation induced apoptosis. In conclusion, Celecoxib induces apoptosis via a novel apoptosome-dependent but Bcl-2-independent mitochondrial pathway.

Activity of the non-steroidal anti-inflammatory drug indomethacin against colorectal cancer

A substantial body of evidence from rodent colon carcinogenesis models, in vitro experiments with human colorectal cancer cells and limited clinical observations in humans suggest that the non-steroidal anti-inflammatory drug indomethacin has anti-colorectal cancer activity. However, although many mechanisms of the anti-neoplastic activity of indomethacin have been suggested, e.g., cyclooxygenase inhibition and peroxisome proliferator-activated receptor gamma activation, the precise relevance of the majority of in vitro pharmacological observations to the in vivo anti-neoplastic activity of indomethacin remains unclear. Herein, we review the existing literature describing the chemopreventative and chemotherapeutic efficacy of indomethacin against colorectal cancer, and draw together the disparate literature describing potential mechanisms of action of indomethacin in human colorectal cancer cells in vitro. Although indomethacin itself has significant adverse effects, including serious upper gastrointestinal toxicity, the development of novel derivatives that may have an improved safety profile means that further investigation of the anti-colorectal cancer activity of indomethacin is warranted.

Inhibition of apoptosis in normal and transformed intestinal epithelial cells by cAMP through induction of inhibitor of apoptosis protein (IAP)-2

Cyclooxygenase (COX)-2, a rate-limiting enzyme of prostaglandin (PG) production, is overexpressed in colorectal adenomas and adenocarcinomas, and its inhibition by nonsteroidal antiinflammatory drugs protects against colorectal cancer. Mechanisms of cancer promotion by COX-2 are not fully understood, but signaling through prostaglandin (PG)E2 receptors is a contributing factor. The major PGE2 receptors on epithelial cells, EP2 and EP4, increase cAMP production, which promotes growth and inhibits apoptosis in some cell types. Here, we show that cAMP agonists, including PGE2, cholera toxin, and a membrane-permeant cAMP analog, protect normal and transformed intestinal epithelial cells from apoptosis induced by diverse stimuli. This protection is associated with cAMP-mediated, rapid induction of cellular inhibitor of apoptosis protein (c-IAP)-2 and delayed induction of LIVIN, but not of six other members of the IAP family. Concurrently and characteristic of IAP functions, the activity, but not generation, of the cleaved form of the central executioner caspase 3 is inhibited. Induction of c-IAP2 expression by cAMP agonists is accompanied by phosphorylation of cAMP response element binding protein and cAMP response element-dependent activation of transcriptional reporters. Furthermore, inhibition of COX-2 in cells overexpressing the enzyme decreases c-IAP2 expression and promotes apoptosis, both of which are reversible by PGE2 addition, suggesting that COX-2-promoted antiapoptosis is mediated by release of PGE2 and subsequent cAMP-dependent c-IAP2 induction. These results help to explain the cancer chemoprotective effects of nonsteroidal antiinflammatory drugs by defining a mechanism through which cAMP signaling can promote the development of colorectal and possibly other epithelial cancers by means of disruption of normal apoptotic processes.

Gene modulation by the cyclooxygenase inhibitor, sulindac sulfide, in human colorectal carcinoma cells: possible link to apoptosis

The mechanisms underlying the anti-tumorigenic properties of cyclooxygenase inhibitors are not well understood. One novel hypothesis is alterations in gene expression. To test this hypothesis sulindac sulfide, which is used to treat familial adenomatous polyposis, was selected to detect gene modulation in human colorectal cells at physiological concentrations with microarray analysis. At micromolar concentrations, sulindac sulfide stimulated apoptosis and inhibited the growth of colorectal cancer cells on soft agar. Sulindac sulfide (10 microm) altered the expression of 65 genes in SW-480 colorectal cancer cells, which express cyclooxygenase-1 but little cyclooxygenase-2. A more detailed study of 11 genes revealed that their expression was altered in a time- and dose-dependent manner as measured by real-time RT-PCR. Northern analysis confirmed the expression of 9 of these genes, and Western analysis supported the conclusion that sulindac sulfide altered the expression of these proteins. Cyclooxygenase-deficient HCT-116 cells were more responsive to sulindac sulfide-induced gene expression than SW-480 cells. However, this response was diminished in HCT-116 cells overexpressing cyclooxygenase-1 compared with normal HCT-116 cells suggesting the presence of cyclooxygenase attenuates this response. However, prostaglandin E2, the main product of cyclooxygenase, only suppressed the sulindac sulfide-induced expression of two genes, with little known biological function while it modulated the expression of two more. The most likely explanation for this finding is the metabolism of sulindac sulfide to inactive metabolites by the peroxidase activity of cyclooxygenase. In conclusion, this is the first report showing sulindac sulfide, independent of cyclooxygenase, altered the expression of several genes possibly linked to its anti-tumorigenic and pro-apoptotic activity.

Nonsteroidal anti-inflammatory drug reduces neutrophil and macrophage accumulation but does not improve tendon regeneration

Whether nonsteroidal anti-inflammatory drugs have a beneficial effect on tendon regeneration is still a matter of debate. Given that inflammatory cells are thought to induce nonspecific damage following an injury, we tested the hypothesis that a 3-day treatment with diclofenac would protect tendons from inflammatory cell injury and would promote healing. Neutrophil and ED1(+) macrophage concentrations were determined in the paratenon and the core of the rat Achilles tendon following collagenase-induced injury. Hydroxyproline content, edema, and mechanical properties were also evaluated at 1, 3, 7, 14, and 28 days post-trauma. Collagenase injections induced a 70% decrease in the ultimate rupture point at Day 3. Diclofenac treatments (1 mg/kg bid) selectively decreased the accumulation of neutrophils and ED1(+) macrophages by 59% and 35%, respectively, in the paratenon, where blood vessels are numerous, but did not reduce the accumulation of neutrophils and ED1(+) macrophages in the core of the tendon. Edema was significantly reduced on Day 3 but persisted during the remodeling phase in the diclofenac-treated group only. The inhibition of leukocyte accumulation by diclofenac did not translate into a reduction of tissue damage or a promotion of tissue healing, because the mechanical properties of injured Achilles tendons were identical in placebo and diclofenac-treated groups. These results indicate that diclofenac reduced both edema and the accumulation of inflammatory cells within the paratenon but provided no biochemical or functional benefits for the Achilles tendon.

Application of gene expression profiling to colon cell maturation, transformation and chemoprevention

Methods for high-throughput analysis of profiles of gene expression that assay thousands of genes simultaneously are powerful approaches for understanding and classifying cell and tissue phenotype. This includes analysis of normal pathways of cell maturation and their perturbation in transformation, the sensitivity and mechanism of response of normal and tumor cells to physiological and pharmacological agents, and modulation of tumor risk and progression by nutritional factors. However, the complex data generated by such approaches raise difficulties in analysis. We will describe some of the methods we have used in analyzing databases generated in a number of projects in our laboratories. These include: the role of k-ras mutations in colon cell transformation; the role of p21(WAF1/cip1) in intestinal tumor formation and response to sulindac; the development of the absorptive and goblet cell lineages; sensitivity of colonic cells to chemotherapeutic agents; mechanisms that regulate c-myc expression utilizing novel methods of transcriptional imaging; and interaction of nutritional and genetic factors in modulation of intestinal tumor formation.

Aspirin and indomethacin exhibit antiproliferative effects and induce apoptosis in T98G human glioblastoma cells

The in vitro antiproliferative and apoptosis inducing properties of the nonsteroidal anti-inflammatory drugs (NSAIDs) like acetyl salicylic acid (aspirin) and indomethacin were investigated in T98G human glioblastoma cells to explore their potential role in the chemoprevention of human glioma. The biological effects induced by aspirin and indomethacin on T98G cells, in which the expression of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) were confirmed by RT-PCR and immunostaining, were investigated by studying cell proliferation and apoptosis assays. The antiproliferative effects occurred in a dose- and time-dependent manner on T98G cells by the treatment with 0.1 -2 mM aspirin and 25-100 microM indomethacin. Moreover, aspirin displayed the greatest growth inhibition within 24 h. Approximately 90% growth inhibition occurred following treatment either with 2 mM aspirin or 100 microM indomethacin by 72 h and induction of apoptosis was confirmed by DNA laddering and TUNEL assay. Our in vitro findings indicate that aspirin and indomethacin have an antiproliferative effect on T98G human glioblastoma cells at toxic concentrations.

Effect of monensin liposomes on the cytotoxicity of anti-My9-bR immunotoxin

The purpose of the study was to evaluate the utility of monensin liposomes in the enhancement of in-vitro cytotoxicity, apoptosis and in-vivo antitumour activity of anti-My9-bR immunotoxin. Monensin liposomes were prepared and studied for the enhancement of in-vitro cytotoxicity and apoptotic response of anti-My9-bR immunotoxin against both sensitive and resistant human promyelocytic leukemia HL-60 cells by MTS/PES method and acridine orange staining, respectively. Further, the in-vivo cytotoxicity enhancement of anti-My9-bR immunotoxin by monensin liposomes was studied in a survival model of severe combined immunodeficient (SCID) mice bearing intraperitoneal HL-60 tumours. The in-vitro cytotoxicity of anti-My9-bR immunotoxin was enhanced 580 fold and 4.7 fold against sensitive and resistant HL-60 cells, respectively, by monensin liposomes (5 x 10(-8) M). The combination of anti-My9-bR immunotoxin (50ng mL(-1)) with monensin liposomes (5 x 10(-8) M) produced apoptosis in 40% of cells, whereas the apoptotic response was minimal (< 10%) in anti-My9-bR immunotoxin- or monensin liposome (alone)-treated HL-60 (resistant) cells. In SCID mice bearing HL-60 tumours, anti-My9-bR immunotoxin (75 microg kg(-1) administered intravenously every other day for a total of five courses) showed a median survival time of 20 days, which was no different than that of vehicle control- or monensin liposome-treated mice. However, anti-My9-bR immunotoxin (75 microg kg(-1)) in combination with monensin liposomes (4 microg kg(-1) monensin), administered every other day for a total of five courses, was found to prolong the survival of 20% of mice for more than 46 days. Our results indicate that, despite anti-My9-bR immunotoxin being ineffective in the HL-60 tumour model, its combination with monensin liposomes could improve the antitumour response.

Butyrate downregulates alpha2beta1 integrin: a possible role in the induction of apoptosis in colorectal cancer cell lines

BACKGROUND

Integrins mediate cell matrix adhesion and regulate cell growth and survival. In colonic epithelial cells, alpha(2)beta(1) integrin controls glandular differentiation and proliferation. Butyrate stimulates differentiation and induces apoptosis in vitro.

AIMS

We investigated whether butyrate induction of apoptosis was associated with perturbation of integrin mediated cell matrix adhesion.

METHODS

Three colonic cancer cell lines (SW1222, SW620, LS174T) were studied. Adhesion to extracellular matrix proteins, expression of alpha(2)beta(1) integrin, and apoptosis were studied in adherent cells after treatment with 4 mM butyrate.

RESULTS

Butyrate decreased the attachment to type I collagen in SW620 cells and type I and IV collagen in LS174T cells. The decreased cell attachment was associated with downregulation of alpha(2)beta(1) integrin and increased apoptosis in adherent cells. No changes in alpha(2)beta(1) expression or matrix adhesion were seen in SW1222 cells, which were also found to be less sensitive to butyrate induction of apoptosis. Downregulation of alpha(2)beta(1) integrin preceded the detection of apoptosis.

CONCLUSION

Apoptosis induced by butyrate is associated with downregulation of expression and functional activity of alpha(2)beta(1) integrin. Perturbation of cell matrix adhesion may be a novel mechanism by which butyrate induces apoptosis in colorectal cancer cells.