Aspirin and gastrointestinal cancer

Rectal bleeding and previous anticoagulant treatment in patients with colorectal cancer do not predict outcome

BACKGROUND

The aim of this study was to determine whether the outcome of patients with colorectal cancer who presented with bleeding and a history of anticoagulant treatment was different from those who did not have bleeding or previous anticoagulant treatment.

METHODS

This was a single institution, retrospective study of patients with colorectal cancer with and without a history of rectal bleeding and treatment with anticoagulants, assessed for age, gender, tumor site, stage, recurrence rate, and survival.

RESULTS

A total of 621 consecutive patients (309 men) with a mean age of 70 years (range, 36-94 years) diagnosed with colorectal cancer between 1998 and 2004 were studied. Of these, 149 patients (24%) were referred for symptoms of rectal bleeding and 161 patients (26%) had been previously treated with anticoagulants. A total of 592 patients (95%) underwent curative or palliative surgery; endoscopic polypectomy was performed in 3 cases only and in 26 patients (4%) surgery was not performed due to advanced disease or critical illness. Patients with bleeding and a history of anticoagulant treatment presented commonly with stage I cancer. In addition, tumor stage III was less common in patients with previous anticoagulant treatment irrespective of presenting signs. Disease-free and overall survival rates were similar in all groups, irrespective of bleeding at presentation or anticoagulant treatment.

CONCLUSIONS

Rectal bleeding and anticoagulant treatment do not affect the outcome of newly diagnosed patients with colorectal cancer.

Nonsteroidal anti-inflammatory drugs induce colorectal cancer cell apoptosis by suppressing 14-3-3epsilon

To determine the role of 14-3-3 in colorectal cancer apoptosis induced by nonsteroidal anti-inflammatory drugs (NSAIDs), we evaluated the effects of sulindac on 14-3-3epsilon protein expression in colorectal cancer cells. Sulindac sulfide inhibited 14-3-3epsilon proteins in HT-29 and DLD-1 cells in a time- and concentration-dependent manner. Sulindac sulfone at 600 mumol/L inhibited 14-3-3epsilon protein expression in HT-29. Indomethacin and SC-236, a selective cyclooxygenase-2 (COX-2) inhibitor, exerted a similar effect as sulindac. Sulindac suppressed 14-3-3epsilon promoter activity. As 14-3-3epsilon promoter activation is mediated by peroxisome proliferator-activated receptor delta (PPARdelta), we determined the correlation between 14-3-3epsilon inhibition and PPARdelta suppression by NSAIDs. Sulindac sulfide inhibited PPARdelta protein expression and PPARdelta transcriptional activity. Overexpression of PPARdelta by adenoviral transfer rescued 14-3-3epsilon proteins from elimination by sulindac or indomethacin. NSAID-induced 14-3-3epsilon suppression was associated with reduced cytosolic Bad with elevation of mitochondrial Bad and increase in apoptosis which was rescued by Ad-PPARdelta transduction. Stable expression of 14-3-3epsilon in HT-29 significantly protected cells from apoptosis. Our findings shed light on a novel mechanism by which NSAIDs induce colorectal cancer apoptosis via the PPARdelta/14-3-3epsilon transcriptional pathway. These results suggest that 14-3-3epsilon is a target for the prevention and therapy of colorectal cancer.

Regular analgesic use and risk of multiple myeloma

Analgesic use has been implicated in the chemoprevention of a number of solid tumors, but to date no previous research has focused on the role of analgesics in the etiology of multiple myeloma (MM). We conducted a hospital-based case-control study of 117 patients with primary, incident MM and 483 age and residence matched controls without benign or malignant neoplasms. All participants received medical services at Roswell Park Cancer Institute in Buffalo, NY, and completed a comprehensive epidemiological questionnaire. Participants who reported analgesic use at least once a week for at least 6 months were classified as regular users; individuals who did not use analgesics regularly served as the reference group throughout the analyses. We used unconditional logistic regression analyses to compute crude and adjusted odds ratios (ORs) with corresponding 95% confidence intervals (CIs). Compared to non-users, regular aspirin users were not at reduced risk of MM (adjusted OR=0.99; 95% CI 0.65-1.49), nor were participants with the highest frequency or duration of aspirin use. A significant risk elevation was found for participants who were regular acetaminophen users (adjusted OR=2.95; 95% CI 1.72-5.08). Further, marked increases in risk of MM were noted with both greater frequency (>7 tablets weekly; adjusted OR=4.36; 95% CI 1.70-11.2) and greater duration (>10 years; adjusted OR=3.26; 95% CI 1.52-7.02) of acetaminophen use. We observed no evidence of a chemoprotective effect of aspirin on MM risk, but observed significant risk elevations with various measures of acetaminophen use. Our results warrant further investigation in population-based case-control and cohort studies and should be interpreted with caution in light of the limited sample size and biases inherent in hospital-based studies.

The Wnt-dependent signaling pathways as target in oncology drug discovery

Our current understanding of the Wnt-dependent signaling pathways is mainly based on studies performed in a number of model organisms including, Xenopus, Drosophila melanogaster, Caenorhabditis elegans and mammals. These studies clearly indicate that the Wnt-dependent signaling pathways are conserved through evolution and control many events during embryonic development. Wnt pathways have been shown to regulate cell proliferation, morphology, motility as well as cell fate. The increasing interest of the scientific community, over the last decade, in the Wnt-dependent signaling pathways is supported by the documented importance of these pathways in a broad range of physiological conditions and disease states. For instance, it has been shown that inappropriate regulation and activation of these pathways is associated with several pathological disorders including cancer, retinopathy, tetra-amelia and bone and cartilage disease such as arthritis. In addition, several components of the Wnt-dependent signaling pathways appear to play important roles in diseases such as Alzheimer’s disease, schizophrenia, bipolar disorder and in the emerging field of stem cell research. In this review, we wish to present a focused overview of the function of the Wnt-dependent signaling pathways and their role in oncogenesis and cancer development. We also want to provide information on a selection of potential drug targets within these pathways for oncology drug discovery, and summarize current data on approaches, including the development of small-molecule inhibitors, that have shown relevant effects on the Wnt-dependent signaling pathways.

Mining the Wnt pathway for cancer therapeutics

Aberrant activation of the Wnt pathway is implicated in driving the formation of various human cancers, particularly those of the digestive tract. Inhibition of aberrant Wnt pathway activity in cancer cell lines efficiently blocks their growth, highlighting the great potential of therapeutics designed to achieve this in cancer patients. Here we provide an overview of the promise and pitfalls of current drug development strategies striving to inhibit the Wnt pathway and present new opportunities for therapeutic intervention.

Association between Nonsteroidal Anti-inflammatory Drug Use and the Incidence of Lung Cancer in the Iowa Women's Health Study

BACKGROUND

Previous studies have suggested that use of aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs) may be associated with reduced risk of lung cancer, but the data are inconsistent and are limited particularly with respect to the effects of aspirin, separate from other NSAIDs.

METHODS

The Iowa Women's Health Study is a prospective cohort of 41,836 Iowa women ages 55 to 69 years old at baseline in 1986. NSAID use was assessed in 1992. Over 10 years of follow-up, 403 incident cases of lung cancer were identified. The association of incident lung cancer with current use of aspirin or non-aspirin NSAIDs was analyzed after adjustment for lung cancer risk factors. Hazard ratios (HR) were estimated using multivariate COX proportional hazards regression.

RESULTS

There were 27,162 women in the analytic cohort. After controlling for age, education, alcohol intake, pack-years, smoking status, body mass index, and total fruit intake, the RR of women taking six or more aspirin weekly was 1.21 (95% confidence interval, 0.92-1.59). The HR was 1.23 for women taking six or more non-aspirin NSAIDs weekly (95% confidence interval, 0.92-1.65). There was no statistically significant trend by frequency of use for either aspirin (P(trend) = 0.22) or non-aspirin NSAIDs (P(trend) = 0.53). Analyses by histologic type and smoking status yielded similar null results. Information on dosage and duration of use were not available for this analysis.

CONCLUSION

These findings do not suggest that aspirin or other NSAIDs reduce risk of lung cancer in this cohort of postmenopausal women.

Irreversible inhibition of glucose-6-phosphate dehydrogenase by the coenzyme A conjugate of ketoprofen: a key to oxidative stress induced by non-steroidal anti-inflammatory drugs?

Oxidative damage by non-steroidal anti-inflammatory drugs (NSAIDs) has been considered relevant to the occurrence of gastro-intestinal side-effects. In the case of chiral arylpropionate derivatives like ketoprofen (KPF), this mechanism has been evidenced for the R-enantiomer, especially when chiral inversion was observed, and lets us suppose the involvement of CoA conjugates. Glucose-6-phosphate dehydrogenase (G6PD) is the crucial enzyme to regenerate the GSH pool and maintain the intracellular redox potential. This enzyme is known to be down-regulated by palmitoyl-CoA thioester. We hypothesised then that G6PD is the target of carboxylic NSAIDs, via their CoA metabolites. We used molecular docking to localise a putative site in the human G6PD then we chose the Yeast orthologue, as the most suitable species to study experimentally the precise molecular interaction. KPF-CoA was effectively shown to bind covalently to the unique cysteine residue of the yeast enzyme. Binding was found to occur in the same site as palmitoyl-CoA. It was decreased in the presence of an allosteric inhibitor of G6PD, phospho(enol)pyruvate, and was not detected with G6PD of Leuconostoc mesenteroides, which does not possess the allosteric site. This site is distinct from the catalytic site, and probably allosteric, explaining the observed non-competitive inhibition of its activity by KPF-CoA. KPF-CoA was shown to induce the production of reactive oxygen species in Caco-2 cells, where its inhibition of G6PD activity was observed.

Opposing effects of aspirin and acetaminophen use on risk of adult acute leukemia

Regular use of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) has been hypothesized to be associated with reduced risk of hematologic cancer, although previous results have been inconsistent. The current study investigated the effects of aspirin or acetaminophen use on adult acute leukemia risk among 169 individuals with leukemia and 676 age and sex matched hospital controls with non-neoplastic conditions who completed a comprehensive epidemiologic questionnaire. Results indicate that regular aspirin use may be associated with a modest decrease in leukemia risk [adjusted odds ratio (aOR), 0.84; 95% confidence interval (CI), 0.59-1.21]. In contrast, ever using acetaminophen was associated with elevated leukemia risk (aOR, 1.53; 95% CI, 1.03-2.26). Results did not differ between men and women. Other studies have demonstrated that acetaminophen is associated with transient decreases in DNA repair, and lymphocytes may be particularly susceptible to DNA damage, suggesting a mechanism for the elevated acute leukemia risk observed among acetaminophen users.

Regular aspirin use and esophageal cancer risk

Given the high mortality rate and the rapidly increasing incidence rate of esophageal carcinoma, chemopreventive agents are highly desirable. Aspirin has been shown to be associated with reduced risk of developing colorectal carcinoma and other cancers. Even though previous studies have shown reduced risk of esophageal cancer associated with aspirin use, results were inconsistent with respect to frequency and duration of use. In this hospital-based case-control study, 163 esophageal cancer cases were compared to 482 age- and sex-matched hospital controls with nonneoplastic conditions. Participants were classified as regular aspirin users if they had taken the drug at least once a week for 6 months. Results suggest that esophageal cancer risk is significantly lower for regular aspirin users compared to nonusers [adjusted odds ratio (aOR) 0.54; 95% confidence interval (CI) 0.36-0.86]. Individuals who used an equivalent of at least 1 aspirin a day (> or =7 tablets/week) were half as likely to have been diagnosed with esophageal carcinoma (aOR 0.47; 95% CI 0.26-0.85), and a linear trend was noted with increasing frequency of use (p(trend) 0.007). Similar protective effects were noted with < or =20 years of use, whereas no risk reduction was noted with >20 years of use. Consistent reduction in risk associated with aspirin use was noted among both the major histological subtypes, but the protective effect appears to be more pronounced in adenocarcinoma compared to squamous cell carcinoma. Overall, results from the current study suggest that regular aspirin use may be associated with reduced risk of esophageal cancer.

Regular Analgesic Use and Risk of Endometrial Cancer

BACKGROUND

Analgesic use has been implicated in the chemoprevention of a number of solid tumors, but thus far, no previous research has focused on the role of aspirin in endometrial cancer etiology.

METHODS

We conducted a hospital-based case-control study of 427 women with primary, incident endometrial cancer, and 427 age- and residence-matched controls without benign or malignant neoplasms. All participants received medical services at Roswell Park Cancer Institute in Buffalo, NY, and completed a comprehensive epidemiologic questionnaire. Women who reported analgesic use at least once a week for at least 6 months were classified as regular users and served as the reference group throughout the analyses. We used unconditional logistic regression analyses to compute crude and adjusted odds ratios (OR) with corresponding 95% confidence intervals (CI).

RESULTS

Compared with nonusers, regular aspirin users were not at reduced risk of endometrial cancer (adjusted OR, 0.91; 95% CI, 0.66-1.26), nor were women with the highest frequency, duration, or cumulative lifetime aspirin use. When the sample was divided by body mass index status, regular aspirin use was not associated with risk among women classified as normal weight or overweight, but a significant risk reduction was seen for obese women (adjusted OR, 0.50; 95% CI, 0.27-0.92). Significant decreases in risk were also observed for obese women with the greatest frequency, duration, and cumulative aspirin use. No significant associations in the overall sample or among obese women were noted for acetaminophen use.

CONCLUSION

We observed no evidence of an overall chemoprotective effect of aspirin on endometrial cancer risk, but the significant risk reductions among obese women warrant further investigation.

Arachidonic acid, an omega-6 fatty acid, induces cytoplasmic phospholipase A2 in prostate carcinoma cells

For the past 60 years, dietary intake of essential fatty acids has increased. Moreover, the omega-6 fatty acids have recently been found to play an important role in regulation of gene expression. Proliferation of human prostate cells was significantly increased 48 h after arachidonic acid (AA) addition. We have analyzed initial uptake using nile red fluorescence and we found that the albumin conjugated AA is endocytosed into the cells followed by the induction of RNA within minutes, protein and PGE2 synthesis within hours. Here we describe that AA induces expression of cytosolic phospholipase A2 (cPLA2) in a dose-dependent manner and that this upregulation is dependent upon downstream synthesis of PGE2. The upregulation of cox-2 and cPLA2 was inhibited by flurbiprofen, a cyclooxygenase (COX) inhibitor, making this a second feed-forward enzyme in the eicosanoid pathway. Cox-2 specific inhibitors are known to inhibit colon and prostate cancer growth in humans; however, recent findings show that some of these have cardiovascular complications. Since cPLA2 is upstream in the eicosanoid pathway, it may be a good alternative for a pharmaceutical target for the treatment of cancer.

Regular use of aspirin or acetaminophen and risk of non-Hodgkin lymphoma

Regular use of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) has been hypothesized to be associated with reduced risk of non-Hodgkin lymphoma (NHL), although previous results have been inconsistent. The current study investigated the effects of regular aspirin or acetaminophen use on non-Hodgkin lymphoma risk among 625 individuals with primary, incident NHL and 2512 age and sex matched hospital controls with non-neoplastic conditions who completed a comprehensive epidemiologic questionnaire. Results indicate that regular aspirin use may be associated with decreased NHL risk among men [adjusted odds ratio (aOR) 0.82, 95% confidence interval (CI), 0.65--1.04], but not among women (aOR 0.93, 95% CI, 0.71--1.23). In contrast, regular acetaminophen use was associated with elevated NHL risk among women (aOR 1.71, 95% CI, 1.18--2.50) but not among men (aOR 0.75, 95% CI, 0.48--1.17). Other studies have demonstrated that acetaminophen is associated with transient decreases in DNA repair, and lymphocytes may be particularly susceptible to DNA damage, suggesting a mechanism for the elevated NHL risk observed.

Screening, prevention and socioeconomic costs associated with the treatment of colorectal cancer

Colorectal cancer (CRC), the third most prevalent cancer worldwide, imposes a significant economic and humanistic burden on patients and society. One study conservatively estimated the annual expenditures for colorectal cancer to be approximately dollars US 5.3 billion in 2000, including both direct and indirect costs. However, other investigators estimated inpatient costs alone incurred in the US in 1994 to be around dollars US 5.14 billion. Therefore, the economic burden of colorectal cancer in the US could be projected to be somewhere in the range of dollars US 5.5-6.5 billion by considering that inpatient costs approximate 80% of total direct costs. No worldwide data have been published, but assuming that the US represents 25-40% of total expenditures in oncology, as seen for breast and lung cancers, a rough estimate for colorectal cancer would be in the range of dollars US 14-22 billion. Screening helps increase patient survival by diagnosing colorectal cancer early. The ideal method among the four tests most used (faecal occult blood test, flexible sigmoidoscopy, colonoscopy and double contrast barium enema) has not been identified. Economic studies of colorectal cancer screening are complex because of the many variables involved, as well as the fact that the outcomes must be followed for many years, and the lack of consensus on screening guidelines. Intuitively, modelling colorectal cancer is one way to overcome these hurdles; published modelling studies predict colorectal cancer screening programs to be within the threshold of dollars US 40000 per life-year saved. The faecal occult blood test appears to be the only clearly effective test, both from a clinical and an economic viewpoint. Important limitations are the invasiveness and inconvenience of the screening procedures, except faecal occult blood test. Patients' comfort and satisfaction are essential in improving compliance with screening recommendations, which appears to be low even in the US (35% of the general population aged over 40 years and 60% of the high-risk population), the country with the highest awareness and compliance in the world. Since colorectal cancer is generally a disease of the elderly, its economic burden is expected to grow in the near future, mainly due to population aging. Potential avenues to pursue in order to contain or reduce the economic burden of colorectal cancer would be the design and implementation of efficient screening programmes, the improvement of patient awareness and compliance with screening guidelines, the development of appropriate prevention programs (i.e. primary and secondary), and earlier diagnosis.

Suppression of tumorigenesis in the Apc(min) mouse: down-regulation of beta-catenin signaling by a combination of tea plus sulindac

Epidemiological and animal studies suggest that tea may be protective towards cancers of the GI tract. White tea, the least processed form of tea, contains high levels of polyphenols and, like green tea, is chemopreventive towards heterocyclic amine-initiated colonic aberrant crypt formation in male F344 rats. We examined for the first time the relative effectiveness of white and green tea in suppressing intestinal tumorigenesis in C57BL/6J-Apc(Min/+) (Apc(min)) mice. Each tea was also compared with sulindac, a non-steroidal anti-inflammatory drug known to be highly effective in Apc(min) mice. Male C57BL/6J (+/+) (wild-type) and Apc(min) mice were treated in the drinking water with white tea or green tea (1.5% w/v, 2 min brew-time), 80 p.p.m. sulindac, a combination of 80 p.p.m. sulindac in 1.5% white tea, or pH buffered water. After 12 weeks of treatment, Apc(min) mice given white tea, green tea, or sulindac had significantly fewer tumors than controls (P < 0.05). The protection provided by 1.5% green or white tea was comparable to that provided by 80 p.p.m. sulindac. Mice treated with a combination of white tea plus sulindac had significantly fewer tumors than either treatment alone (P < 0.05). beta-catenin and beta-catenin/Tcf-4 regulated proteins Cyclin D(1) and c-Jun were readily detected in polyps, but markedly reduced in normal-looking intestines of mice treated with both tea and sulindac. This research provides evidence that teas, particularly when administered in combination with sulindac, are highly effective at inhibiting intestinal neoplasia in male Apc(min) mice via direct or indirect effects on the beta-catenin/APC pathway.

Regular aspirin use and lung cancer risk

BACKGROUND

Although a large number of epidemiological studies have examined the role of aspirin in the chemoprevention of colon cancer and other solid tumors, there is a limited body of research focusing on the association between aspirin and lung cancer risk.

METHODS

We conducted a hospital-based case-control study to evaluate the role of regular aspirin use in lung cancer etiology. Study participants included 868 cases with primary, incident lung cancer and 935 hospital controls with non-neoplastic conditions who completed a comprehensive epidemiological questionnaire. Participants were classified as regular aspirin users if they had taken the drug at least once a week for at least one year.

RESULTS

Results indicated that lung cancer risk was significantly lower for aspirin users compared to non-users (adjusted OR = 0.57; 95% CI 0.41-0.78). Although there was no clear evidence of a dose-response relationship, we observed risk reductions associated with greater frequency of use. Similarly, prolonged duration of use and increasing tablet years (tablets per day x years of use) was associated with reduced lung cancer risk. Risk reductions were observed in both sexes, but significant dose response relationships were only seen among male participants. When the analyses were restricted to former and current smokers, participants with the lowest cigarette exposure tended to benefit most from the potential chemopreventive effect of aspirin. After stratification by histology, regular aspirin use was significantly associated with reduced risk of small cell lung cancer and non-small cell lung cancer.

CONCLUSIONS

Overall, results from this hospital-based case-control study suggest that regular aspirin use may be associated with reduced risk of lung cancer.

Regular use of aspirin and pancreatic cancer risk

BACKGROUND

Regular use of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) has been consistently associated with reduced risk of colorectal cancer and adenoma, and there is some evidence for a protective effect for other types of cancer. As experimental studies reveal a possible role for NSAIDs is reducing the risk of pancreatic cancer, epidemiological studies examining similar associations in human populations become more important.

METHODS

In this hospital-based case-control study, 194 patients with pancreatic cancer were compared to 582 age and sex-matched patients with non-neoplastic conditions to examine the association between aspirin use and risk of pancreatic cancer. All participants received medical services at the Roswell Park Cancer Institute in Buffalo, NY and completed a comprehensive epidemiologic questionnaire that included information on demographics, lifestyle factors and medical history as well as frequency and duration of aspirin use. Patients using at least one tablet per week for at least six months were classified as regular aspirin users. Unconditional logistic regression was used to compute crude and adjusted odds ratios (ORs) with 95% confidence intervals (CIs).

RESULTS

Pancreatic cancer risk in aspirin users was not changed relative to non-users (adjusted OR = 1.00; 95% CI 0.72-1.39). No significant change in risk was found in relation to greater frequency or prolonged duration of use, in the total sample or in either gender.

CONCLUSIONS

These data suggest that regular aspirin use may not be associated with lower risk of pancreatic cancer.

Treatment and prevention of aspirin-induced gastroduodenal ulcers and gastrointestinal bleeding

Aspirin use is associated with gastroduodenal mucosal damage and increased risk of upper gastrointestinal (GI) bleeding. Many aspirin users should receive prophylactic treatment since they often have several risk factors for upper GI complications. The best therapeutic approach for reducing GI toxicity in low-dose aspirin users is still ill-defined as only a few studies have focused on this problem. Omeprazole appears to be very effective in reducing both acute gastroduodenal mucosal damage and upper GI bleeding in the high-risk patient taking low-dose aspirin, but data with other anti-ulcer agents are lacking (misoprostol) or inconsistent (ranitidine) at present. The role of Helicobacter pylori is controversial in NSAID users, but there is now wide agreement that H. pylori infection increases mucosal damage and the risk of upper GI bleeding in low-dose aspirin users.

JTE-522-induced apoptosis in human gastric adenocarinoma cell line AGS cells by caspase activation accompanying cytochrome C release, membrane translocation of Bax and loss of mitochondrial membrane potential

AIM: To investigate the role of the mitochondrial pathway in JTE-522-induced apoptosis and to investigate the relationship between cytochrome C release, caspase activity and loss of mitochondrial membrane potential (△Ψm).

METHODS: Cell culture, cell counting, ELISA assay, TUNEL, flow cymetry, Western blot and fluorometric assay were employed to investigate the effect of JTE-522 on cell proliferation and apoptosis in AGS cells and related molecular mechanism.

RESULTS: JTE-522 inhibited the growth of AGS cells and induced the apoptosis. Caspases 8 and 9 were activated during apoptosis as judged by the appearance of cleavage products from procaspase and the caspase activities to cleave specific fluorogenic substrates. To elucidate whether the activation of caspases 8 and 9 was required for the apoptosis induction, we examined the effect of caspase-specific inhibitors on apoptosis. The results showed that caspase inhibitors significantly inhibited the apoptosis induced by JTE-522. In addition, the membrane translocation of Bax and cytosolic release of cytochrome C accompanying with the decrease of the uptake of Rhodamin 123, were detected at an early stage of apoptosis. Furthermore, Bax translocation, cytochrome C release, and caspase 9 activation were blocked by Z-VAD.fmk and Z-IETD-CHO.

CONCLUSION: The present data indicate a crucial association between activation of caspases 8, 9, cytochrome C release, membrane translocation of Bax, loss of △Ψm and JTE-522-induced apoptosis in AGS cells.

The role of eicosanoids, cyclooxygenases, and nonsteroidal anti-inflammatory drugs in colorectal tumorigenesis and chemoprevention

There is mounting evidence from studies on experimental cancer in rodents, interventional studies in patients with familial adenomatous polyposis, and some, but not all, epidemiologic investigations, that suggests a chemopreventive effect of aspirin and nonaspirin nonsteroidal anti-inflammatory drugs (NSAIDs) against colorectal cancer. In addition, the mechanisms by which these agents modulate tumorigenesis are being elucidated in laboratory experiments. Currently available NSAIDs are unlikely to have an acceptable benefit-to-risk ratio for long-term use in an asymptomatic population. Once the discrete chemopreventive mechanisms are established and the genetic background and risk factor profile of individuals who will benefit from chemoprevention are clarified, a low-dose combination of NSAIDs with different targets may optimize efficacy and minimize toxicity. At present, however, colectomy is still the treatment of choice for patients with familial adenomatous polyposis, and early screening and regular surveillance colonoscopies are the choices for those at risk for hereditary nonpolyposis colorectal cancer. In the average-risk individual, endoscopic screening and surveillance will remain the core of efforts to prevent sporadic colorectal cancer.

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

Non-steroidal anti-inflammatory drugs (NSAIDs) have been reported to reduce the risk and mortality of colorectal cancer (CRC). Although the exact mechanisms remain unclear, the inhibition of cyclooxygenase (COX) by NSAIDs appears to abort, if not prevent, CRC carcinogenesis or metastatic tumor progression. The aim of our study was to investigate the association between COX-2 expression and CRC tumor cell invasiveness. The differences in immunoblot-detectable COX-2 protein contents in primary CRCs, metastatic hepatic lesions and corresponding normal mucosa from the same individual were evaluated in 17 patients. Three different colon cancer cell lines, SW620, Lovo, HT-29 and a metastatic variant of HT-29, HT-29/Inv3, were employed to evaluate COX-2 expression and prostaglandin E(2) (PGE2) production in relation to their invasive abilities in vitro. The effects of a COX-2-selective inhibitor, etodolac, on cell proliferation and invasive activity were also determined. The results showed that 15 of 17 (88%) metastatic CRC cells from the liver and 14 of 17 (82%) primary CRC tissue exhibited much higher levels of COX-2 than corresponding adjacent normal mucosa from the same patient. Among those patients with relatively high COX-2 expression in the primary tumors, almost all exhibited even higher levels of COX-2 in their hepatic metastases. Among the 4 colon cancer cell lines, HT-29/Inv3 manifested the highest COX-2 expression, PGE2 production and in vitro invasive activity. The selective COX-2 inhibitor, etodolac, could especially exert cytotoxicity and markedly suppress the invasive property and PGE(2) production, although not the COX-2 protein level, in HT-29/Inv3 cells. Our results imply that COX-2 expression may be associated with the invasive and metastatic properties of CRC tumor cells.

Current approaches to reducing gastrointestinal toxicity of low-dose aspirin

Use of low-dose aspirin is associated with gastroduodenal mucosal damage and increased risk of upper gastrointestinal (GI) bleeding. Many patients on low-dose aspirin should receive prophylactic treatment, because they often present several risk factors that may lead to upper GI complications in nonsteroidal anti-inflammatory drug (NSAID) users. It is reasonable to assume that effective therapy (e.g., omeprazole, misoprostol, and high-dose famotidine) in the prevention of NSAID-induced gastroduodenal ulcers will also be effective in this setting. However, the best therapeutic approach to reducing GI toxicity in low-dose aspirin users is not defined, because only a few studies have focused on this problem. Omeprazole seems very effective in reducing both acute gastroduodenal mucosal damage and upper GI bleeding in the high-risk patient taking low-dose aspirin, but data with other antiulcer agents are lacking (misoprostol) or inconsistent (ranitidine) at present. No data are available on the effect of these drugs on dyspepsia or chronic gastroduodenal ulcers in the long-term use of low-dose aspirin. The role of Helicobacter pylori is controversial, but it may increase mucosal damage and the risk of upper GI bleeding in these patients. More data are needed to define the best therapeutic regimen in patients taking low-dose aspirin.

Biochemistry of cyclooxygenase (COX)-2 inhibitors and molecular pathology of COX-2 in neoplasia

Several types of human tumors overexpress cyclooxygenase (COX) -2 but not COX-1, and gene knockout transfection experiments demonstrate a central role of COX-2 in experimental tumorigenesis. COX-2 produces prostaglandins that inhibit apoptosis and stimulate angiogenesis and invasiveness. Selective COX-2 inhibitors reduce prostaglandin synthesis, restore apoptosis, and inhibit cancer cell proliferation. In animal studies they limit carcinogen-induced tumorigenesis. In contrast, aspirin-like nonselective NSAIDs such as sulindac and indomethacin inhibit not only the enzymatic action of the highly inducible, proinflammatory COX-2 but the constitutively expressed, cytoprotective COX-1 as well. Consequently, nonselective NSAIDs can cause platelet dysfunction, gastrointestinal ulceration, and kidney damage. For that reason, selective inhibition of COX-2 to treat neoplastic proliferation is preferable to nonselective inhibition. Selective COX-2 inhibitors, such as meloxicam, celecoxib (SC-58635), and rofecoxib (MK-0966), are NSAIDs that have been modified chemically to preferentially inhibit COX-2 but not COX-1. For instance, meloxicam inhibits the growth of cultured colon cancer cells (HCA-7 and Moser-S) that express COX-2 but has no effect on HCT-116 tumor cells that do not express COX-2. NS-398 induces apoptosis in COX-2 expressing LNCaP prostate cancer cells and, surprisingly, in colon cancer S/KS cells that does not express COX-2. This effect may due to induction of apoptosis through uncoupling of oxidative phosphorylation and down-regulation of Bcl-2, as has been demonstrated for some nonselective NSAIDs, for instance, flurbiprofen. COX-2 mRNA and COX-2 protein is constitutively expressed in the kidney, brain, spinal cord, and ductus deferens, and in the uterus during implantation. In addition, COX-2 is constitutively and dominantly expressed in the pancreatic islet cells. These findings might somewhat limit the use of presently available selective COX-2 inhibitors in cancer prevention but will probably not deter their successful application for the treatment of human cancers.

Helicobacter pylori infection and gastrin and cyclooxygenase expression in gastric and colorectal malignancies

Helicobacter pylori, infecting more than 50% of the world population, results in gastritis, usually located in the antral portion of the stomach, accompanied by hypergastrinemia, the key factor in gastric and colorectal carcinogenesis. Excessive mucosal cell proliferation for many years may eventually result in gastric atrophy, cell mutation and transformation of gastric mucosal cells into gastrin-producing cells, which also express gastrin receptors serving to stimulate cell proliferation and tumor growth. These processes may be completed by the expression of cyclooxygenase-2 (COX-2) as an inflammation enzyme to release excessive amounts of PGE(2), leading to further proliferation, reduction in apoptosis, angiogenesis and tumor growth. H. pylori eradication results in complete regression of MALT lymphoma and subsequent normalisation of excessive gastrin release and COX-2 expression. Reduction of gastrin by active immunisation (gastrimmune), blocking of gastrin receptors with specific blockers and suppression of COX-2 might be helpful in inhibiting tumor growth and invasion.

Non-steroidal anti-inflammatory drugs and apoptosis in the gastrointestinal tract: potential role of the pentose phosphate pathways

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most widely prescribed drugs, primarily for treatment of arthritis. NSAIDs can have two effects independent of their anti-inflammatory action. In the stomach and small bowel long term NSAID consumption can lead to ulceration, whereas in the colon NSAID use can regress existing tumours. In this review, we hypothesise that NSAID-induced damage occurs predominantly by promoting apoptosis, involving a number of mechanisms depending on the type and the redox state of the cell. In addition to inhibiting cyclooxygenase (COX) activity, this includes interfering with glucose metabolism through both arms of the pentose phosphate pathways and energy production via glycolysis and oxidative phosphorylation. Shifting the cellular balance from proliferation to apoptosis is probably the most important outcome by which NSAIDs exhibit their differing actions. Understanding how these different pathways can be reconciled and their contribution to the balance between cell birth and cell death is the challenge for the future. The pentose phosphate pathways may provide a pivotal point for understanding links between factors which alter proliferative activity (e.g. COXs), provide energy metabolism (particularly aerobic and anaerobic metabolism of glucose), and change the redox state of the cell leading to apoptosis.

Low-dose misoprostol for the prevention of low-dose aspirin-induced gastroduodenal injury

INTRODUCTION

The harmful effects of non-steroidal anti-inflammatory drugs (NSAIDs) on the gastric mucosa and the prophylactic effects of misoprostol are both dose-dependent.

AIM

To investigate whether a low-dose of misoprostol is sufficient to prevent gastric mucosal injury caused by low-dose aspirin.

METHODS

We conducted a double-blind placebo controlled parallel group endoscopic study in 32 evaluable volunteers. The main outcome measure was erosive injury (ulcers and superficial erosions) in the gastric mucosa over 28 days.

RESULTS

Most subjects developed erosions on aspirin 300 mg daily. This was significantly reduced by misoprostol 100 microg daily. (Odds ratio 0.18, 95% CI: 0.07-0.48). There were no drug-related or gastrointestinal adverse events in subjects receiving misoprostol.

CONCLUSION

Misoprostol 100 microg daily can prevent low-dose aspirin induced gastric mucosal injury without causing identifiable adverse effects.

Cyclooxygenase-2 and carcinogenesis

Numerous investigations have shown that COX-2 is a participant in the pathway of colon carcinogenesis, especially when mutation of the APC tumor suppressor is the initiating event. Moreover, it seems that the amount of COX-2 is important, since there is a correlation between its level of expression and the size of the tumors and their propensity to invade underlying tissue [40]. Inhibiting COX-2 at an early stage blocks the development of malignant tumors, causes pre-malignant tumors to regress and may improve the outcome once the cancer is completely established. This set of findings seems to link very strongly with the traditional observation that chronic inflammation is a precursor to a variety of types of cancer. By this formulation, inflammatory stimuli increase COX-2 and the downstream events that it induces promote tumor formation. All of these finding suggest that existing NSAIDs will be useful for the prophylaxis of colon cancer and polyps and we eagerly await clinical investigations that will generate guidelines that suggest those individuals that are the most appropriate recipients for such therapy. Although this field has progressed rapidly in the last few years, many important questions remain.

Clinical preventive medicine in primary care: background and practice: 2. Delivering primary preventive services

Strategies to incorporate preventive services into primary care settings have been underutilized. The first component of delivering preventive services in the primary care setting is the health risk assessment followed by establishment of practice guidelines and protocols for preventive services--who is eligible for what service (based on age, sex, and other clinical characteristics) and when. A computerized reminder system can be useful to track past and currently due preventive services for each patient and can also serve as a follow-up system for test results. Well-trained paramedical personnel can perform appropriate patient counseling and education. The goal of counseling and education is to change patient behavior. The first step in this difficult process is once again to ascertain health risks and then to determine the patient's stage of readiness--defined as precontemplation, contemplation, preparation, action, and maintenance. The counselor assists in identification of target behavior, advocates and commends behavior change, reinforces health benefits of behavior change, offers resources, strategies, and support, and creates a plan of action and monitoring mechanisms. Improved implementation of preventive services in primary care could have a major impact on the health of the population.

PPARdelta is an APC-regulated target of nonsteroidal anti-inflammatory drugs

PPARB was identified as a target of APC through the analysis of global gene expression profiles in human colorectal cancer (CRC) cells. PPARdelta expression was elevated in CRCs and repressed by APC in CRC cells. This repression was mediated by beta-catenin/Tcf-4-responsive elements in the PPARdelta promotor. The ability of PPARs to bind eicosanoids suggested that PPARdelta might be a target of chemopreventive non-steroidal anti-inflammatory drugs (NSAIDs). Reporters containing PPARdelta-responsive elements were repressed by the NSAID sulindac. Furthermore, sulindac was able to disrupt the ability of PPARdelta to bind its recognition sequences. These findings suggest that NSAIDs inhibit tumorigenesis through inhibition of PPARdelta, the gene for which is normally regulated by APC.