Animal Models Of Colon Cancer Research Articles

Mesalamine in IBD: Multiple hats?

Mesalamine in IBD: Multiple hats?

Bcl-2 overexpression attenuates apoptosis induction by sulindac sulfide in SW480 human colon cancer cells

3195 Background: Sulindac sulfide is a NSAID and an inhibitor of cyclooxygenase enzymes that regulate prostaglandin synthesis. Sulindac is a potent chemopreventive agent in animal models of colon cancer and in patients with familial adenomatous polyposis. Sulindac sulfide induces apoptosis in colon cancer cells which may be an important mechanism of its anti-tumor effects. Previously, we found that sulindac sulfide can modulate both the caspase-8-depedent and cytochrome c-dependent apoptotic pathways. We determined whether Bcl-2 overexpression, an inhibitor of the latter apoptotic pathway, can inhibit apoptosis induction by sulindac sulfide. Materials and Methods: SW480 cells were stably transfected with the pC3-Bcl-2 plasmid (SW480/Bcl-2) or vector alone (SW480/neo). The level of Bcl-2 protein expression was then determined by immunoblotting (anti-Bcl-2 antibody, Upstate). Cells were incubated with sulindac sulfide (0–120 μM) for 72 hr and then floating and attached cells were harvested and assayed for Annexin V-FITC (BD PharMingen) labeling by flow cytometry. The effect of a caspase-9 inhibitor (Z-LEHD-FMK, R & D Systems) or a caspase-8 inhibitor (Z-IETD-FMK, R & D Systems) upon sulindac sulfide-induced apoptosis was also studied. Results: SW480/Bcl-2 cells showed overexpression of Bcl-2 proteins relative to SW480/neo cells. Bcl-2 overexpression produced an anti-apoptotic effect (>50% reduction) compared to SW480/neo control cells, as assayed by Annexin V binding after incubation with sulindac sulfide (72 hr). Furthermore, co-treatment with a caspase-9 inhibitor significantly reduced the Annexin V binding (>50%) triggered by sulindac sulfide treatment. A caspase-8 inhibitor was also found to significantly reduce Annexin V binding (>50%) in sulindac sulfide-treated parental cells. Conclusion: Sulindac sulfide engages both the caspase-8- and caspase-9-dependent apoptotic signaling pathways in SW480 cells. Bcl-2-mediated inhibition of apoptosis by sulindac sulfide indicates that Bcl-2 is an important modulator of the therapeutic efficacy of this agent used for the prevention or treatment of human colon cancer. No significant financial relationships to disclose.

Bcl-2 overexpression attenuates apoptosis induction by sulindac sulfide in SW480 human colon cancer cells

3195 Background: Sulindac sulfide is a NSAID and an inhibitor of cyclooxygenase enzymes that regulate prostaglandin synthesis. Sulindac is a potent chemopreventive agent in animal models of colon cancer and in patients with familial adenomatous polyposis. Sulindac sulfide induces apoptosis in colon cancer cells which may be an important mechanism of its anti-tumor effects. Previously, we found that sulindac sulfide can modulate both the caspase-8-depedent and cytochrome c-dependent apoptotic pathways. We determined whether Bcl-2 overexpression, an inhibitor of the latter apoptotic pathway, can inhibit apoptosis induction by sulindac sulfide. Materials and Methods: SW480 cells were stably transfected with the pC3-Bcl-2 plasmid (SW480/Bcl-2) or vector alone (SW480/neo). The level of Bcl-2 protein expression was then determined by immunoblotting (anti-Bcl-2 antibody, Upstate). Cells were incubated with sulindac sulfide (0–120 μM) for 72 hr and then floating and attached cells were harvested and assayed for Annexin V-FITC (BD PharMingen) labeling by flow cytometry. The effect of a caspase-9 inhibitor (Z-LEHD-FMK, R & D Systems) or a caspase-8 inhibitor (Z-IETD-FMK, R & D Systems) upon sulindac sulfide-induced apoptosis was also studied. Results: SW480/Bcl-2 cells showed overexpression of Bcl-2 proteins relative to SW480/neo cells. Bcl-2 overexpression produced an anti-apoptotic effect (>50% reduction) compared to SW480/neo control cells, as assayed by Annexin V binding after incubation with sulindac sulfide (72 hr). Furthermore, co-treatment with a caspase-9 inhibitor significantly reduced the Annexin V binding (>50%) triggered by sulindac sulfide treatment. A caspase-8 inhibitor was also found to significantly reduce Annexin V binding (>50%) in sulindac sulfide-treated parental cells. Conclusion: Sulindac sulfide engages both the caspase-8- and caspase-9-dependent apoptotic signaling pathways in SW480 cells. Bcl-2-mediated inhibition of apoptosis by sulindac sulfide indicates that Bcl-2 is an important modulator of the therapeutic efficacy of this agent used for the prevention or treatment of human colon cancer. No significant financial relationships to disclose.

Linking inflammation to cell cycle progression.

Risk of gastrointestinal cancers is closely related to increased levels of oxidants in the balance between oxidant and anti-oxidant agents. A possible explanation of this epidemiological observation is the local loss of the epithelial barrier function with a focal inflammatory response. Accordingly, chronic inflammatory diseases represent well-known risk factors for cancer and, on the other hand, it is known that anti-inflammatory agents, demulcents and antioxidants markedly inhibit the development of colon cancer in animal models as well in humans. At molecular level a key role in the process that link inflammation to cellular transformation seems to be played by activation of Cyclooxygenase-2 (COX-2) together with production of Reactive Oxygen Intermediate (ROI). Both these events have been strictly linked with cell proliferation and transformation, although the intracellular pathways involved in these processes are still not completely understood. The uncontrolled proliferation, which is a landmark of cellular transformation, is accompanied by the deregulation of proteins involved in the control of cell cycle checkpoints. Altered expression and function of cyclooxygenase and nitric oxide synthase seem to influence, among others, the expression of proteins involved in the regulation of cell cycle progression. Similarly, anti-inflammatory and antioxidant agents may also act on the expression and function of several cell cycle regulating proteins. Understanding the mechanisms by which chronic inflammation contributes to genetic and epigenetic changes involved in the regulation of critical cell cycle checkpoints may help to develop more and more specific treatment strategies for reducing malignant transformation of these inflammatory diseases.

The potential role of aprotinin in the perioperative management of malignant tumors

Aprotinin (Trasylol, Bayer Corporation, West Haven, CT), a nonspecific serine proteinase inhibitor, has been in clinical use since the early 1960s. It inhibits contact activation and fibrinolysis while preserving platelet function. In the United States aprotinin is used in cardiothoracic surgery for its beneficial effect on perioperative blood loss and transfusion requirements, reduction in explorative operations for bleeding, and inhibition of the systemic inflammatory response. In addition, aprotinin is effective in reducing intraoperative bleeding and reducing blood transfusion requirements in patients undergoing resections for meningioma, bladder carcinoma, and hepatic tumors, and in liver transplantation, orthopaedic procedures, and lumbar spine fusion. Less well known are reports that aprotinin may interfere with tumor growth and development of metastasis and may increase survival time after tumor resections. The role of aprotinin in tumor and metastasis inhibition is estimated to be three-fold. First, it is established that aprotinin reduces intraoperative blood loss and transfusion requirements. Second, its known antiinflammatory effect during the systemic inflammatory response syndrome is to prevent the sequestration of leukocytes within organs, and it suppresses the capacity of leukocytes to transmigrate through the vascular endothelium by interfering with expression of various adhesion molecules. The same integrin adhesion molecules used by normal leukocytes for traffic and localization in inflammation sites may be used by malignant cells for dissemination, so aprotinin is likely to interfere with tumor endothelial adhesion and transendothelial migration as well. Third, the ability of aprotinin to neutralize, to varying degrees, the action of several serine proteases, such as trypsin, chymotrypsin, and particularly the urokinase-type plasminogen activator (uPA) and kallikreins is important, because these proteases have been implicated in tumor progression and development of metastasis. In the pathogenesis of human malignancy, uPA mediates tumor cell growth, invasion, and metastatic dissemination. Evidence suggests a role for this system in several major human tumor types; tumor types in which the plasminogen activator-plasmin system has been implicated as a mechanism for tumor progression include breast, uterine cervix, endometrium, and ovary; stomach, colon, and rectum; bladder, kidney, liver, and pancreas; brain (glioma); nonsmall cell lung; and melanoma. Also, uPA facilitates the provisional matrix needed to promote endothelial cell adhesion, migration, proliferation, and survival in the formation of new blood vessels. Animal-model systems collectively point to the causal involvement of uPA in the metastatic process. This relationship between tumor cell uPA expression and tumor progression has been studied in animal models of breast, colon, lung, prostate, and ovarian cancer, and in human tumor cells in vitro. The kallikreins, a group of serine proteases, are associated with many disease processes, including cancer, inflammation, hypertension, renal disease, and pancreatitis. The association between kallikrein genes and human disease is summarized in Table 1. All members of the human kallikrein gene family encode for serine proteases and are involved in contact activation of the coagulation pathway. Manipulation of kallikreins may be a possible means of interfering with tumor progression. Prostate-specific antigen (PSA; human kallikrein 3) is the best-studied kallikrein, with a focus on its implication in prostate cancer. Serum PSA is generally elevated in patients with prostate cancer, although other published data suggest that PSA may be a tumor suppressor. Patients with breast tumors that produce PSA have a worse prognosis than patients whose tumors do not proNo competing interests declared.

Colon cancer prevention by NSAIDs: what is the mechanism of action?

Colorectal cancer is second to lung cancer as the most common cause of cancer death in the United States; both environmental (diet, physical activity) and genetic (family history, mutations, polymorphisms) factors are related to colon cancer risk. Epidemiologic, animal model, and clinical studies all suggest that nonsteroidal anti-inflammatory drugs (NSAIDs) are potent preventive agents for colon cancer. Most epidemiologic studies (case control, and cohort) are consistent with a protective effect of regular, long-term use of aspirin use, although the prospective Physicians Health Study failed to find a significant protective effect. The entire class of NSAIDs appear to be effective in preventing carcinogen induced colon cancer in animal models. Clinical trials using the NSAID sulindac have shown dramatic regression of colonic adenomas in patients with Familial Polyposis. The biologic and biochemical mechanisms of the putative chemopreventive activity of the NSAIDs is under intense investigation. These drugs can induce cell cycle arrest and apoptosis in colon cancer cell lines through a mechanism that is fundamentally different from the apoptosis caused by cancer chemotherapeutic agents. Sulindac and its metabolites also appear to induce apoptosis in colonic adenomas in vivo. The clinically used NSAIDs are anti-inflammatory due to their ability to decrease prostaglandin synthesis by inhibiting the cyclooxygenase (COX) enzymes. Cyclooxygenase inhibition, particularly COX 2 inhibition, is one putative biochemical target of the chemopreventive activity of NSAIDs. However, recent reports of chemopreventive activity of NSAID derivatives that no longer have COX inhibitory activity suggest that there are other biochemical targets as well.

COX-2 and colorectal cancer.

Metabolites of arachidonic acid participate in normal growth responses and in aberrant cellular growth and proliferation, including carcinogenesis. The key step in the conversion of free arachidonic acid to prostaglandins is catalyzed by the cyclooxygenase enzyme (COX). There are two COX enzymes, COX-1 and COX-2. COX-1 is expressed constitutively and is part of normal cell metabolic functions. COX-2, on the other hand, is induced and expressed in neoplastic growths. The connection between COX expression and carcinogenesis was first implicated in studies that demonstrated the efficacy of aspirin and non-steroidal anti-inflammatory drugs to reduce the relative risk of colon cancer and also promote tumor regression in both humans and animal models of colon cancer. Investigation of the molecular basis of these observations showed that high levels of COX-2 protein were present in both human and animal colorectal tumors. A variety of evidence gathered from epidemiological, whole animal, and cellular studies indicate that unregulated COX-2 expression is a rate-limiting step in tumorigenesis and also that the loss of regulation occurs early in carcinogenesis. The interest in the COX-2 enzyme is that specific inhibition of COX-2 could theoretically avoid the gastrointestinal and other complications observed with the use of nonspecific COX inhibitors (most NSAIDs) or COX-1 inhibitors. The mechanisms by which COX-2 inhibitors lead to decreased colon carcinogenesis are not fully understood but they involve an increase not only in COX-2 dependent but also in COX-2 independent mechanisms.

Antioxidant Activity of Tea Polyphenols In Vivo: Evidence from Animal Studies

Tea is particularly rich in polyphenols, including catechins, theaflavins and thearubigins, which are thought to contribute to the health benefits of tea. Tea polyphenols act as antioxidants in vitro by scavenging reactive oxygen and nitrogen species and chelating redox-active transition metal ions. They may also function indirectly as antioxidants through 1) inhibition of the redox-sensitive transcription factors, nuclear factor-kappaB and activator protein-1; 2) inhibition of "pro-oxidant" enzymes, such as inducible nitric oxide synthase, lipoxygenases, cyclooxygenases and xanthine oxidase; and 3) induction of phase II and antioxidant enzymes, such as glutathione S-transferases and superoxide dismutases. The fact that catechins are rapidly and extensively metabolized emphasizes the importance of demonstrating their antioxidant activity in vivo. Animal studies offer a unique opportunity to assess the contribution of the antioxidant properties of tea and tea polyphenols to the physiological effects of tea administration in different models of oxidative stress. Most promising are the consistent findings in animal models of skin, lung, colon, liver and pancreatic cancer that tea and tea polyphenol administration inhibit carcinogen-induced increases in the oxidized DNA base, 8-hydroxy-2'-deoxyguanosine. In animal models of atherosclerosis, green and black tea administration has resulted in modest improvements in the resistance of lipoproteins to ex vivo oxidation, although limited data suggest that green tea or green tea catechins inhibit atherogenesis. To determine whether tea polyphenols act as effective antioxidants in vivo, future studies in animals and humans should employ sensitive and specific biomarkers of oxidative damage to lipids, proteins and DNA.

Cytotoxic effect of replication-competent adenoviral vectors carrying L-plastin promoter regulated E1A and cytosine deaminase genes in cancers of the breast, ovary and colon.

Prodrug activating transcription unit gene therapy is one of several promising approaches to cancer gene therapy. Combining that approach with conditionally replication-competent viral vectors that are truly tumor specific has been an important objective of recent work. In this study, we report the construction of a new conditionally replication-competent bicistronic adenoviral vector in which the cytosine deaminase (CD) gene and the E1a gene are driven by the L-plastin tumor-specific promoter (AdLpCDIRESE1a). A similar vector driven by the CMV promoter has also been constructed (AdCMVCDIRESE1a) as a control. We have carried out in vitro cytotoxicity in carcinomas of the breast, ovary and colon, and in vivo efficacy studies with these vectors in an animal model of colon cancer. While the addition of the AdLpCDIRESE1a vector to established cancer cell lines showed significant cytotoxicity in tumor cells derived from carcinomas of the breast (MCF-7), colon (HTB-38) and ovary (Ovcar 5), no significant toxicity was seen in explant cultures of normal human mammary epithelial cells (HMEC) exposed to this vector. The addition of 5-fluorocytosine (5FC) significantly increased the cytotoxicity in an additive fashion of both the AdLpCDIRESE1a and AdCMVCDIRESE1a vectors as well as that of the AdLpCD replication incompetent vector to established tumor cell lines. However, no significant cytotoxicity was observed with the addition of 5FC to explant cultures of normal human mammary epithelial cells that had been exposed to the L-plastin-driven vectors. Studies with mixtures of infected and uninfected tumor cell lines showed that the established cancer cell lines infected with the AdLpCDIRESE1a vector generated significant toxicity to surrounding uninfected cells (the "bystander effect") even at a ratio of 0.25 of infected cells to infected + uninfected cells in the presence of 5FC. The injection of the AdLpCDIRESE1a vector into subcutaneous deposits of human tumor nodules in the nude mice was potentiated by administering 5-FC by intraperitoneal injection. This treatment resulted in a decreased tumor size and a decreased tumor cell growth rate. The mice treated with a combination of the AdLpCDIRESE1a vector intratumoral injection and intraperitoneal 5FC injections lived much longer than the other experimental groups exposed to the viral vector alone or to the combination of the intratumoral AdLpCD replication incompetent vector injections plus intraperitoneal 5-FC injections. These encouraging results with our newly constructed AdLpCDIRESE1a vector suggest a need for further study of its utility in a preclinical model of intracavitary therapy of pleural or peritoneal carcinomatosis.

Chemically programmed monoclonal antibodies for cancer therapy: adaptor immunotherapy based on a covalent antibody catalyst.

Proposing that a blend of the chemical diversity of small synthetic molecules with the immunological characteristics of the antibody molecule will lead to therapeutic agents with superior properties, we here present a device that equips small synthetic molecules with both effector function and long serum half-life of a generic antibody molecule. As a prototype, we developed a targeting device that is based on the formation of a covalent bond of defined stoichiometry between a 1,3-diketone derivative of an integrin alpha(v)beta(3) and alpha(v)beta(5) targeting Arg-Gly-Asp peptidomimetic and the reactive lysine of aldolase antibody 38C2. The resulting complex was shown to (i) spontaneously assemble in vitro and in vivo, (ii) selectively retarget antibody 38C2 to the surface of cells expressing integrins alpha(v)beta(3) and alpha(v)beta(5), (iii) dramatically increase the circulatory half-life of the Arg-Gly-Asp peptidomimetic, and (iv) effectively reduce tumor growth in animal models of human Kaposi's sarcoma and colon cancer. This immunotherapeutic has the potential to target a variety of human cancers, acting on both the vasculature that supports tumor growth as well as the tumor cells themselves. Further, by use of a generic antibody molecule that forms a covalent bond with a 1,3-diketone functionality, essentially any compound can be turned into an immunotherapeutic agent thereby not only increasing the diversity space that can be accessed but also multiplying the therapeutic effect.

Probiotic mixture decreases DNA adduct formation in colonic epithelium induced by the food mutagen 2-amino-9H-pyrido[2,3-b]indole in a human-flora associated mouse model.

Consumption of probiotic bacteria such as bifidobacteria has been shown to reduce the risk of colon cancer in animal models. However, the composition and metabolic activities of the intestinal flora of experimental animals are significantly different from those of humans. The aim of the study was to examine whether the probiotic mixture, which consisted of Streptococcus faecalis, Clostridium butyricum and Bacillus mesentericus, could decrease DNA adduct formation induced by 2-amino-9H-pyrido[2,3-b]indole (2-amino-alpha-carboline; AAC) in the colonic epithelium of a human-flora-associated (HFA) mouse model. Ten HFA mice were divided into a control group (n=4) and a probiotic group (n=6). The control group was administered AAC for 3 days and sacrificed 24 h after the last dose. The probiotic group was administered the probiotic mixture for 2 weeks prior to the administration of AAC. Analysis of DNA adducts with the 32P-high-performance liquid chromatography method was performed on stomach, jejunum and colonic epithelium, representing direct exposure sites of AAC, and colon wall, liver and kidney, representing indirect exposure sites. The mean level of the DNA adducts in the colonic epithelium of the probiotic group was significantly lower than that of control group, while the mean levels at the other sites did not differ significantly between the groups. The results indicated that the probiotic mixture could decrease the DNA adduct formation in the colonic epithelium induced by AAC.

Antitumor Activity of Extract of Zingiber aromaticum and Its Bioactive Sesquiterpenoid Zerumbone

The anticancer properties of zerumbone (2,6,9 humulatriene-8-one, a sesquiterpenoid) from Zingiber aromaticum were compared with those of curcumin from Curcuma longa in an in vitro MTT tetrazolium salt assay using HT-29, CaCo-2, and MCF-7 cancer cells and in an azoxymethane (AOM)-induced animal model of colon cancer using aberrant crypt foci (ACFs) as a preneoplastic marker. The IC50 of zerumbone was approximately 10 μM and that of curcumin was 25 μM. Cell cycle arrest in HT-29 cells was observed at G0/G1 for 10 and 12.5 μMand G2/M for 25 μafter 24 h at concentrations of 10-25 μM of zerumbone, and a concentration-dependent increase in apoptosis (2-6% of viable cells) was observed after 48 h using the same concentration range. Male Sprague-Dawley rats were fed extracts in an AIN diet prepared from the equivalent of 4% by weight of dried rhizomes of Z. aromaticum and C. longa. ACFs were induced by two doses (15 mg/kg body weight) subcutaneously of AOM1 wk apart, the rats were killed 10 wk later, and the ACFs were assessed in the colon. Total ACFs were significantly reduced by Z. aromaticum extract (down 21%, P < 0.05) relative to control, the effect being most evident with large ACFs (≥3 aberrant crypts per focus). Similar reductions were observed with 4% C. longa extract in the diet (down 24%, P < 0.01) and with 2,000 ppm curcumin, the effect being particularly evident with large ACFs. The concentration of zerumbone in the Z. aromaticum extract diet was assayed at 300 ppm and of curcumin in the C. longa extract diet was also 300 ppm, i.e., the extract of C. longa was as effective at one-seventh the concentration of curcumin as the positive control. Zerumbone is effective as an anticancer agent, possibly by its apoptosis-inducing and antiproliferative influences. This latter possibility is currently being investigated.

Quantification of human intestinal gene expression profiles using exfoliated colonocytes: a pilot study

Early detection of colon cancer can result in a high cure rate; therefore, an accurate screening method is imperative. Adoption of non-invasive testing designed to reduce anxiety over colorectal cancer screening and improve early detection is highly desirable. Therefore, we have developed a novel non-invasive methodology utilizing exfoliated colonocytes in order to quantify colonic messenger RNAs (mRNAs). Previously we have demonstrated in the rat that intact eukaryotic mRNA can be isolated due to the presence of exfoliated colonocytes in the faecal stream. To assess use of this methodology in humans, this pilot study evaluated exfoliated colonocyte mRNA expression of 11 putative biomarkers using real-time reverse transcription-polymerase chain reaction (RT-PCR) in seven normal subjects, four subjects with inflammation, and 10 tumour-bearing subjects presenting for colonoscopy. Expression of the biomarkers was evaluated following normalization to TATA box binding protein mRNA levels. Tumour-bearing subjects diagnosed with adenoma had elevated levels of cyclin Dl (p = 0.041). In addition, subjects displaying inflammation of the colon exhibited higher mRNA levels of cyclooxygenase-2 (p = 0.007). These data suggest that mRNA isolated from exfoliated colonocytes could be used to detect early stages of colon cancer, and possibly chronic inflammation. To broaden the utility of non-invasive marker analysis, additional studies are needed to generate a multi-target assay panel of diagnostic markers. This will allow for the development of robust classifiers that can determine critical gene sets for the diagnosis and prediction of colon cancer in animal models and humans.

Notions récentes sur la cancérogenèse intestinale, leurs implications dans le dépistage du risque génétique et l’action préventive des anti-inflammatoires non stéroïdiens

Colorectal cancer is the most common malignant tumor in the french population. This tumor represents 45% of the cancers of the digestive tract in female and 60% in male. It is one of the main problem in the field of Public Health but recent progress for research, prophylaxis and treatment have been performed. There are two different pathogenic pathways for colorectal cancer. In chromosomal instability a sequence of rearrangements leads step by step from normal to adenoma and to carcinoma. It is the common pathway observed in 85% of colorectal cancers, mainly localized in left colon. In genic nucleotidic instability loss of tumor-suppresor genes and activation of cellular oncogenes are the consequence of DNA mismatch repair system, which is controlled by several genes. The defect of DNA mismatch repair leads to a hypermutable state in which simple repetitive DNA sequences are specially instable. This is the basis for a test to demonstrate nucleotidic instability. This pathway is found in the remaining 15% of colorectal cancers which are mainly localized on right colon. A mutational inactivation of both alleles of APC gene is considered as an initial gatekeeper event although some cancers begin with a mutation in beta-catenin gene which has the same functional impact. APC expression plays central role in regulating the rate of beta-catenin degradation. Destruction of beta-catenin prevents its translocation into the nucleus where it promotes cellular proliferation. About 5% of colorectal cancer are developed in a high risk population, Familial Adenomatous Polyposis coli (FAP) or Hereditary Non Polyposis Colon Cancer (HNPCC). FAP is caused by a germline mutation in APC gene. Every cell harbors a mutation of an APC allele which insures that a large number of adenomas will occur once an inactivating event occurs on the other wild-type APC allele. The demonstration of a constitutional mutation in a family allows to limit the survey only to the carriers. The phenotypic expression (attenuated, profuse, associated with extra-intestinal lesions) is correlated with the site of the APC mutation. Thus the determination of this site occurs in the choice of the treatment. HNPCC is suggested on clinical and genealogical criterions (young age of onset of cancer, multiple family members affected with cancer in multiple generations, the association of certain tumors in an individual of family, multiple tumors). A biological test may be useful to demonstrate the nucleotidic instability (MSI: microsatellite instability). Constitutional mutations on the mismatch repair genes, mainly MSH2 and MLH1, cause HNPCC syndrome. Endometrial and urethelial malignant tumors are frequent in an individual or in the family. The proven or suspected carriers of mutations undergo colonoscopic surveillance every 1 to 2 years, starting at age 25. An anti-tumoral action of the non steroidal antiinflammatory drugs (NSAID) is now recognized. Firstly observed in animal models of colon cancer the suppressive action was demonstrated in patient with Familial Adenomatous Polyposis. From the results of several epidemiological studies the suppressive action can be generalized to common intestinal tumors. This effect is in relation with the cyclooxygenase 2 inhibition. Other independent pathways intervene: NSAID interfere with beta-catenin, decreasing its action on cellular division. The indication of NSAID and more specifically of COX2 inhibitors in the prophylaxis of colo rectal cancer are yet questioned. The results of trials in progress are expected.

Cyclooxygenase-2: a molecular target for chemoprevention of epithelial tumors of skin and colon.

Numerous epidemiological studies have found a reduced risk to develop colorectal cancer of persons with a regular intake of aspirin or other non-steroidal antiinflammatory drugs (NSAIDs). Clinical trials with NSAIDs in patients suffering from Familial Adenomatous Poliposis Coli (FAP) due to a germline mutation in the APC-tumor suppressor gene have clearly shown a regression of already existing colorectal adenomas`. Furthermore, animal models of colon and skin cancer have demonstrated a reduction in tumor multiplicity and incidence by a continuous application of NSAIDs, such as aspirin, sulindac3indomethacin4piroxicam5SC-581256Celecoxib’, (and our own unpublished observation), and MF-tricyclic8. Experimental colon carcinogenesis was studied in the azoxymethane-treated rat and in Min mice, which carry a heterozygous germline deletion in the APC-gene and spontaneously develop adenomas throughout the intestinal tract. Squamous cell carcinogenesis has been studied predominantly in mouse skin. Here, tumorigenesis is initiated by a single mutation of the cellular Ha-ras gene, induced by exposure to a low dose of the carcinogen dimethyl-7,12-benz(a)anthracene. Initiated epidermal keratinocytes grow into macroscopically visible tumors only upon repeated treatment with tumor promoters such as the phorbolester TPA. Most of the papillomas regress, but some of them progress into carcinomas in the absence of any further treatment.

Colon cancer: a role for cyclo-oxygenase-2-specific nonsteroidal anti-inflammatory drugs.

Large bowel cancer is not only the third most frequent cancer in the world but is one of the most common human malignancies in Western countries, including North America. In recent years, multidisciplinary research in epidemiology, molecular biology, and laboratory animal model studies have contributed much to our understanding of the aetiology of this cancer; more importantly, it has enabled us to devise preventive strategies. Several epidemiological studies have detected a 40 to 50% decrease in risk of colorectal cancer in individuals who regularly use aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs). Clinical trials with NSAIDs in patients with familial adenomatous polyposis have demonstrated that treatment with NSAIDs caused regression of pre-existing adenomas. Preclinical efficacy studies have provided scientifically sound evidence as to how NSAIDs act to retard, block, or reverse colonic carcinogenesis. Equally exciting are opportunities for effective chemoprevention with selective cyclo-oxygenase-2 inhibitors in a variety of animal models of colon cancer. Selective cyclo-oxygenase-2 inhibitors such as celecoxib have been proven to be effective chemopreventive agents against colonic carcinogenesis with minimal gastrointestinal toxicity. Our exploration of the multistep process of carcinogenesis has provided substantial insights into the mechanisms by which anti-inflammatory agents modulate these events. There is growing optimism for the view that realisation of preventive concepts in large bowel cancer will also serve as a model for preventing malignancies of the prostate and breast.

COX-2 and colon cancer: potential targets for chemoprevention.

Evidence derived from several lines of investigation suggest that prostaglandins, metabolites of arachidonic acid, play an important role in colon cancer development. Elevated prostaglandin levels are found in colon cancers and their precursor lesions, adenomatous polyps. Agents such as aspirin and NSAIDs, which inhibit the generation of these arachidonic acid metabolites, are associated with a decreased risk of developing or dying from colon cancer. Both the amount of the agent used and the duration of exposure seem to be important variables. In animals, NSAIDs are among the most potent agents discovered for the reduction of tumors in both genetic and carcinogen-induced models. Data from human trials also suggests that NSAIDs such as sulindac can reduce the size and number of polyps in individuals with familial adenomatous polyposis (FAP). In parallel with the above findings, it is now understood that at least two forms of the enzyme responsible for the metabolism of arachidonic acid exist. One of these forms, COX-1, is generally considered a constitutive form that is responsible for maintaining normal physiologic function. Inhibition of COX-1 leads to many of the clinically undesirable side effects associated with NSAID use. The other known form of the enzyme, COX-2, is an inducible form that is found in increased levels in inflammatory states and in many cancers and their associated pre-malignant lesions. Levels of COX-2 are increased by exposure to mitogens and growth factors. Agents that specifically inhibit COX-2 are now in clinical development and appear to be well-tolerated and effective for the treatment of osteoarthritis and rheumatoid arthritis. The potential for use of COX-2 specific NSAIDs in the prevention of colon cancer is suggested from the distribution of COX-2 in adenomatous polyps and colon cancer and the effectiveness of these agents in genetic and carcinogen-induced animal models of colon cancer. The development of these agents for the prevention of colon cancer will be discussed.

Probiotics and gastrointestinal health

Evidence for positive health benefits of Lactobacilli applies to only a few strains used for commercial applications. It is generally agreed that a probiotic must be capable of colonizing the intestinal tract to influence human health; this requirement disqualifies many of the strains currently used in fermented dairy products. Lactobacillus GG, a variant of L. casei sps rhamnosus, has been studied extensively in adults and children. When consumed as a dairy product or as a lyophilized powder, LGG colonizes the gastrointestinal tract for 1–3 days in most individuals and up to 7 days in about 30% of subjects. Traveler’s diarrhea, antibiotic-associated diarrhea, and relapsing Clostridium difficile colitis are improved with LGG. In infantile diarrhea, the severity and duration of the attack is reduced. LGG-fermented milk lessens the intestinal permeability defects caused by exposure to cows milk or rotavirus infection. LGG has proven beneficial effects on intestinal immunity. It increases the numbers of IgA and other immunoglobulin-secreting cells in the intestinal mucosa. LGG stimulates local release of interferon. It facilitates antigen transport to underlying lymphoid cells, which serves to increase antigen uptake in Peyer’s patches. LGG also acts as an immunoadjuvant for oral vaccines. In an animal model of colon cancer, LGG reduced the incidence of chemically induced tumors in the large bowel of rodents. Extensive safety testing has shown no pathogenic potential in humans or animals. Probiotic cultures of Lactobacilli have the potential to bring substantial health benefits to the consumer. The purported benefits for any probiotic must pass the highest standards of scientific scrutiny before the claims can be accepted.

Role of COX-2 in colon tumorigenesis

Sulindac has been reported to be effective in suppressing tumor growth through the induction of p21WAF1/cip1 in human, animal models of colon cancer and colon cancer cells. In this study, we treated human breast cancer cell line MCF-7 and lung cancer cell line A549 as well as colon cancer cell line SW620 with sulindac to observe the effects of sulindac in other tissue sites. In all cell lines, proliferation was significantly inhibited by sulindac after 24 and 72 h of treatment. Apoptosis was induced by sulindac in both lung cancer cells and colon cancer cells but was not induced in breast cancer cells. Western blots showed that p21 protein level were induced by sulindac in lung cancer cells and colon cancer cells, but not in breast cancer cells. However, the suppression of β-catenin, a key mediator of Wnt signaling pathway, was seen in all three cell lines with sulindac administration. Further studies revealed that transcriptional activities of β-catenin were significantly inhibited by sulindac and that the inhibition was sulindac dosage-dependent. The transcriptional targets of β-catenin, c-myc, cyclin D1 and cdk 4 were also dramatically downregulated. In conclusion, our data demonstrated that the efficacy of sulindac in the inhibition of cell proliferation (rather than the induction of apoptosis) might be through the suppression of β-catenin pathway in human cancer cells.

Inhibition of cyclo-oxygenase 2 expression in colon cells by the chemopreventive agent curcumin involves inhibition of NF-kappaB activation via the NIK/IKK signalling complex.

Colorectal cancer is a major cause of cancer deaths in Western countries, but epidemiological data suggest that dietary modification might reduce these by as much as 90%. Cyclo-oxygenase 2 (COX2), an inducible isoform of prostaglandin H synthase, which mediates prostaglandin synthesis during inflammation, and which is selectively overexpressed in colon tumours, is thought to play an important role in colon carcinogenesis. Curcumin, a constituent of turmeric, possesses potent anti-inflammatory activity and prevents colon cancer in animal models. However, its mechanism of action is not fully understood. We found that in human colon epithelial cells, curcumin inhibits COX2 induction by the colon tumour promoters, tumour necrosis factor alpha or fecapentaene-12. Induction of COX2 by inflammatory cytokines or hypoxia-induced oxidative stress can be mediated by nuclear factor kappa B (NF-kappaB). Since curcumin inhibits NF-kappaB activation, we examined whether its chemopreventive activity is related to modulation of the signalling pathway which regulates the stability of the NF-kappaB-sequestering protein, IkappaB. Recently components of this pathway, NF-kappaB-inducing kinase and IkappaB kinases, IKKalpha and beta, which phosphorylate IkappaB to release NF-kappaB, have been characterised. Curcumin prevents phosphorylation of IkappaB by inhibiting the activity of the IKKs. This property, together with a long history of consumption without adverse health effects, makes curcumin an important candidate for consideration in colon cancer prevention.