Animal Models Of Colon Cancer Research Articles

751c Effectiveness of the Third Eye Retroscope for Detecting Polyps in the Right Colon

Background & Aims: Lysophosphatidic acid (LPA), a naturally produced phospholipid, mediates multiple effects that are vital to disease process, including cancer and inflammation. The expression of LPA receptor 2 (LPA2) is up-regulated in several types of cancer, including ovary and colon cancer (CC), but the importance of LPA and LPA2 in the development and progression of CC is unclear. Chronic inflammation is also a risk factor for CC. In this study, we sought to determine whether LPA and LPA2 regulate the progression of CC using animal models of CC. Methods: We examined the potential effects of LPA in CC progression by administering LPA to ApcMin/+ mice. We determined the role of LPA2 in colon tumorigenesis by examining the loss of LPA2 function. We treated LPA2-/mice with azoxymethane (AOM) and dextran sulfate sodium (DSS). Furthermore, we examined the role of LPA2 in modulating intestinal adenoma formation by crossing LPA2-/mice with ApcMin/+ mice. Results: We found that LPA treatment by gavage increased the number of adenomas in small intestine in Apcmin/+ mice. The difference in body weight and mortality suggested that the absence of LPA2 protected animals from the AOM/DSS treatment. LPA2-/mice treated with AOM/DSS showed significantly fewer and smaller tumors in the colon than wild-type (WT) mice. There was no difference in number and size of tumors between LPA2+/and WT mice. We observed reduced epithelial cell proliferation and decreases in β-catenin, Kruppel-like factor 5 (KLF5), and cyclooxygenase-2 (COX-2) expression in LPA2-/mice compared to WT. Compared to WT mice, induction of monocyte chemoattractant protein-1 (MCP-1) and macrophage migration inhibitory factor (MIF) was significantly abrogated in LPA2-/mice with reduced infiltration by macrophages. The absence of LPA2 expression in ApcMin/ + mice resulted in a significant decrease in adenomas. At 5 month, ApcMin/+/LPA2-/mice developed an average of 22 adenomas in the small intestine compared with 38 in ApcMin/ +/LPA2+/+ and 43 in ApcMin/+/LPA2+/mice. Consistently, the average number of adenomas in the colon was 2.67, 1.75, and 0.64 for ApcMin/+/LPA2+/+, ApcMin/+/LPA2+/-, and ApcMin/ +/LPA2-/respectively. Adenomas larger than 2 mm accounted for 18% for ApcMin/+/LPA2-/mice in contrast to 38% for ApcMin/+/LPA2+/+. Conclusion: The absence of LPA2 attenuates several effects that may contribute to tumorigenesis In Vivo. Hence, our studies identify LPA2 as a modulator of intestinal tumorigenesis.

751a Opt-80 Versus Vancomycin in Clostridium difficile Infection: Results of a Randomized Clinical Trial

Background & Aims: Lysophosphatidic acid (LPA), a naturally produced phospholipid, mediates multiple effects that are vital to disease process, including cancer and inflammation. The expression of LPA receptor 2 (LPA2) is up-regulated in several types of cancer, including ovary and colon cancer (CC), but the importance of LPA and LPA2 in the development and progression of CC is unclear. Chronic inflammation is also a risk factor for CC. In this study, we sought to determine whether LPA and LPA2 regulate the progression of CC using animal models of CC. Methods: We examined the potential effects of LPA in CC progression by administering LPA to ApcMin/+ mice. We determined the role of LPA2 in colon tumorigenesis by examining the loss of LPA2 function. We treated LPA2-/mice with azoxymethane (AOM) and dextran sulfate sodium (DSS). Furthermore, we examined the role of LPA2 in modulating intestinal adenoma formation by crossing LPA2-/mice with ApcMin/+ mice. Results: We found that LPA treatment by gavage increased the number of adenomas in small intestine in Apcmin/+ mice. The difference in body weight and mortality suggested that the absence of LPA2 protected animals from the AOM/DSS treatment. LPA2-/mice treated with AOM/DSS showed significantly fewer and smaller tumors in the colon than wild-type (WT) mice. There was no difference in number and size of tumors between LPA2+/and WT mice. We observed reduced epithelial cell proliferation and decreases in β-catenin, Kruppel-like factor 5 (KLF5), and cyclooxygenase-2 (COX-2) expression in LPA2-/mice compared to WT. Compared to WT mice, induction of monocyte chemoattractant protein-1 (MCP-1) and macrophage migration inhibitory factor (MIF) was significantly abrogated in LPA2-/mice with reduced infiltration by macrophages. The absence of LPA2 expression in ApcMin/ + mice resulted in a significant decrease in adenomas. At 5 month, ApcMin/+/LPA2-/mice developed an average of 22 adenomas in the small intestine compared with 38 in ApcMin/ +/LPA2+/+ and 43 in ApcMin/+/LPA2+/mice. Consistently, the average number of adenomas in the colon was 2.67, 1.75, and 0.64 for ApcMin/+/LPA2+/+, ApcMin/+/LPA2+/-, and ApcMin/ +/LPA2-/respectively. Adenomas larger than 2 mm accounted for 18% for ApcMin/+/LPA2-/mice in contrast to 38% for ApcMin/+/LPA2+/+. Conclusion: The absence of LPA2 attenuates several effects that may contribute to tumorigenesis In Vivo. Hence, our studies identify LPA2 as a modulator of intestinal tumorigenesis.

Trefoil factor-3 expression in human colon cancer liver metastasis

Deaths from colorectal cancer are often due to liver metastasis. Trefoil factor-3 (TFF3) is expressed by normal intestinal epithelial cells and its expression is maintained throughout the colon adenoma-carcinoma sequence. Our previous work demonstrated a correlation between TFF3 expression and metastatic potential in an animal model of colon cancer. The aim of this study was to determine whether TFF3 is expressed in human colon cancer liver metastasis (CCLM) and whether inhibiting TFF3 expression in colon cancer cells would alter their invasive potential in vitro. Human CCLMs were analyzed at the mRNA and protein level for TFF3 expression. Two highly metastatic rat colon cancer cell lines that either natively express TFF3 (LN cells) or were transfected with TFF3 (LPCRI-2 cells), were treated with two rat TFF3 siRNA constructs (si78 and si365), and analyzed in an in vitro invasion assay. At the mRNA and protein level, TFF3 was expressed in 17/17 (100%) CCLMs and 10/11 (91%) primary colon cancers, but not in normal liver tissue. By real time PCR, TFF3 expression was markedly inhibited by both siRNA constructs in LN and LPCRI-2 cells. The si365 and si78 constructs inhibited invasion by 44% and 53%, respectively, in LN cells, and by 74% and 50%, respectively, in LPCRI-2 cells. These results provide further evidence that TFF3 contributes to the malignant behavior of colon cancer cells. These observations may have relevance for designing new diagnostic and treatment approaches to colorectal cancer.

UDCA targets S-phase and suppresses CDK2 and cyclin A expression: effects on colon cancer cell proliferation

Introduction: Ursodeoxycholic acid (UDCA) treatment of patients with primary sclerosing cholangitis appears to reduce the risk of colon cancer. UDCA prevents colon cancer in animal models; the mechanism of the chemopreventive action is still unknown. We investigated the effects of UDCA on proliferation of colon cancer cells in vitro.

Intervention with cloudy apple juice results in altered biological activities of ileostomy samples collected from individual volunteers

Apple juice is considered to be an important component of the healthy diet, with anticancer activities in colon cancer animal models and key ingredients have numerous chemoprotective activities in human colon cells in vitro. Since only little is known on comparable activities in the human colon in vivo, here a pilot study was performed to assess related mechanisms caused by ileostomy samples from volunteers that had consumed apple juice. Ileostomy samples were collected after intervention (0-8 h) with cloudy apple juice (1 l). They were characterized analytically for major apple polyphenols and biologically in HT29 colon cells for their potential to cause genotoxic damage, protect from the genotoxic insult by hydrogen peroxide (H(2)O(2)) and modulate the expression of GSTT2, an enzyme related to antioxidative defence against different peroxides. The analytical determination of polyphenols in the ileostomy samples revealed that the majority of the compounds were recovered in the samples collected 2 h after intervention. The comparison of genotoxic effects of samples before intervention and 2 h after intervention revealed a considerable variation of genotoxic response, but there was a trend for reduced genotoxicity in three of eight persons (P) after intervention. Samples collected at 2 h protected HT29 cells from genotoxic damage by H(2)O(2) (for 4 of 8 persons), resulted in an increased GSTT2 expression (for 2 of 6 persons) and of GSTT2 promotor activity (2 of 6 persons). The intervention with apple juice results in bioavailable concentrations of related polyphenols in the gut lumen, which could contribute to reduced genotoxicity, enhanced antigenotoxicity and favorable modulation of GSTT2 gene expression in some individuals. The pilot study for the first time used this combination of faecal biomarkers which in larger cohorts may either reveal overall significant alterations of chemoprotection or may be used to identify individuals which could particularly benefit from a personalized nutrition.

Obesity-related promotion of aberrant crypt foci in DMH-treated obese Zucker rats correlates with dyslipidemia rather than hyperinsulinemia

Obesity and energy restriction modulate the development of precancerous aberrant crypt foci (ACF) in animal models of colon cancer. Investigation of the major obesity-associated determinants for ACF-development and underlying mechanisms leading to ACF-modulation, such as changes in DNA damage or colonocytes hyperproliferation. Lean and obese Zucker rats fed ad libitum (a.l.) or obese pair fed (p.f.) were induced with 1,2-dimethylhydrazine (DMH) for colon cancer. Multiple regression analyses were performed to identify major metabolic factors correlated with ACF number and size (aberrant crypts/ACF). DNA damage is analyzed by the comet-assay, epithelial proliferation by immunohistochemistry. Aberrant crypt foci number was significantly elevated in Zucker obese a.l. (205.7+/-65.4 vs. lean 9.5+/-6.3, P<0.05) and is reduced by pair feeding in Zucker obese rats (81.4+/-28.5 vs. obese a.l., P<0.05). Compared to lean the ACF size was higher in Zucker obese a.l. (2.1+/-0.3 vs. lean 1.3+/-0.2., P<0.05) but is not reduced by pair feeding (1.7+/-0.2; P>0.05). While ACF number and size were modulated by genotype and/or pair feeding the DMH-induced DNA damage and hyperproliferation in colonocytes did not differ significantly between groups. Regression analysis showed that plasma parameters associated with lipid-metabolism (triglycerides, cholesterol, malondialdehyde) significantly correlated with the ACF number and size while parameters linked to carbohydrate-metabolism (glucose, insulin) were weaker determinants. Obesity or pair feeding-associated modulation of ACF correlate with parameters related to lipid-metabolism but is not accompanied by changes in DNA damage and proliferation.

Role for epithelial dysregulation in early-onset colitis-associated colon cancer in Gi2-alpha−/− mice

Inflammatory bowel disease (IBD) is a risk factor for developing colorectal cancer but the mechanisms are poorly characterized. Mice lacking the G-protein alpha subunit Gi2-alpha spontaneously develop colitis and colon cancer with high penetrance. Compared to canonical Wnt/APC signaling-based animal models of colon cancer, the tumors in Gi2-alpha-/- mice more closely recapitulate the features of IBD-associated cancers seen in humans. They are predominantly right-sided, multifocal, mucinous, and arise from areas of flat dysplasia. In evaluating the potential contribution of epithelial Gi2-alpha signaling to this phenotype, we found that Gi2-alpha-/- colonic epithelium is hyperproliferative even before the onset of colitis, and resistant to the induction of apoptosis. We generated colon cancer cell lines overexpressing dominant-negative Gi2-alpha. Like other cells lacking Gi2-alpha, these cells release less arachidonic acid, an important antiinflammatory and epithelial growth regulator. They are also hyperproliferative and resistant to camptothecin-induced apoptosis and caspase-3 activation. The colitis-associated cancers in Gi2-alpha-/- mice appear very similar to those seen in human IBD patients, and Gi2-alpha is a direct negative regulator of colonic epithelial cell growth.

Sulindac suppresses β-catenin expression in human cancer cells

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.

Pharmacological doses of dietary curcumin increase colon epithelial cell proliferation in vivo in rats

Although curcumin has preventive actions in animal models of colon cancer, whether the mechanism of action is through anti-proliferation in normal environment is not clearly understood. Here, we studied the effects of chemopreventive doses of curcumin on the proliferation rate of colon epithelial cells (CEC), using a recently developed stable isotope-mass spectrometric method for measuring DNA synthesis rate. Adult male F344 rats were given diets containing 0, 2 and 4% curcumin for 5 weeks. 4% (2)H(2)O was given in drinking water to label DNA, after a priming bolus, for 4 days prior to sacrifice. The isotopic enrichment of the deoxyribose moiety of deoxyadenosine from DNA was measured by gas chromatography - mass spectrometry. Cell cycle analysis was performed after propidium iodide staining of CECs. Curcumin administration did not reduce but instead resulted in dose-dependent increases in CEC proliferation rate (p < 0.05) for 2% and 4% curcumin vs 0%). The length of the colon crypts and the fraction of cells in S-phase were also increased in the 2% and 4% curcumin groups (p < 0.05). Thus, pharmacological doses of curcumin increase CEC proliferation rate and pool size in normal rats. Reduction of CEC proliferation therefore cannot explain the proposed chemopreventive actions of curcumin in colon cancer.

Novel mucilage fraction of Sinapis alba L. (mustard) reduces azoxymethane-induced colonic aberrant crypt foci formation in F344 and Zucker obese rats

Seeds of Sinapis alba Linn. (commonly called yellow or white mustard) and their components have been reported to possess anticancer properties. In this study, we evaluated the efficacy of a novel mucilaginous fraction of mustard seeds in inhibiting colonic preneoplastic changes in animal models of sporadic and obesity-associated colon cancer. In two separate studies, male Sprague-Dawley or female Zucker obese rats, injected with azoxymethane (15 or 10 mg/kg body wt. once a week for 2 weeks, respectively), were fed AIN-93G diets with or without 5% mustard mucilage (MM) (w/w) for 8 weeks. Our aim was to measure the ability to modulate the number of aberrant crypt foci (ACF), putative preneoplastic lesions of the colon. The data were classified into total numbers of ACF and large ACF (crypt multiplicity of 4 or more). We report here that 5% MM significantly (p<0.05) decreased the number of total (approximately 21% inhibition) and large (approximately 50% inhibition) ACF in the colons of Sprague-Dawley rats compared to that in untreated controls. In addition, 5% MM supplemented diet significantly lowered (p<0.05) the number of total (approximately 63% inhibition) and large (approximately 60% inhibition) colonic ACF in Zucker obese rats compared to untreated obese rats, and had no effect on fasting plasma cholesterol or triglyceride levels. These results demonstrate the possible role of MM as a functional food against sporadic and obesity-associated colon cancer, and provide impetus to conduct research to understand the underlying mechanism(s) of action.

Ursodeoxycholic acid modulates histone acetylation and induces differentiation and senescence

Agents that can modulate colonic environment and control dysregulated signaling are being evaluated for their chemopreventive potential in colon cancer. Ursodeoxycholate (UDCA) has shown chemopreventive potential in preclinical and animal models of colon cancer, but the mechanism behind it remains unknown. Here biological effects of UDCA were examined to understand mechanism behind its chemoprevention in colon cancer. Our data suggests that UDCA can suppress growth in a wide variety of cancer cell lines and can induce low level of apoptosis in colon cancer cells. We also found that UDCA treatment induces alteration in morphology, increased cell size, upregulation of cytokeratin 8, 18 and 19 and E-cadherin, cytokeratin remodeling and accumulation of lipid droplets, suggesting that UDCA induces differentiation in colon carcinoma cells. Our results also suggest significant differences in UDCA and sodium butyrate induced functional differentiation. We also report for the first time that UDCA can induce senescence in colon cancer cells as assessed by flattened, spread out and vacuolated morphology as well as by senescence marker beta-galactosidase staining. We also found that UDCA inhibits the telomerase activity. Surprisingly, we found that UDCA is not a histone deacytylase inhibitor but instead induces hypoacetylation of histones unlike hyperacetylation induced by sodium butyrate. Our results also suggest that, although UDCA induced senescence is p53, p21 and Rb independent, HDAC6 appears to be important in UDCA induced senescence. In summary, our data shows that UDCA modulates chromatin by inducing histone hypoacetylation and induces differentiation and senescence in colon cancer cells.

Bioproduction of Conjugated Linoleic Acid by Probiotic Bacteria Occurs In Vitro and In Vivo in Mice

Probiotics have been shown to reduce the incidence of colon cancer in animal models. The mechanisms responsible for this activity are poorly defined. Conjugated linoleic acids (CLA) are a group of isomers of linoleic acid (LA) possessing anti-inflammatory and anticarcinogenic properties, which can be produced from LA by certain bacterial strains. In this study, the ability of probiotic bacteria to exert anticarcinogenic effects through the production of CLA was assessed. Incubation of probiotic bacteria (VSL3, Lactobacillus acidophilus, L. bulgaricus, L. casei, L. plantarum, Bifidobacterium breve, B. infantis, B. longum, and Streptococcus thermophilus) in the presence of LA yielded CLA production as measured by gas chromatography. Conditioned medium, containing probiotic-produced CLA, reduced viability and induced apoptosis of HT-29 and Caco-2 cells, as assessed by MTT assay and DNA laddering, respectively. Western blotting demonstrated an increased expression of PPARgamma in cells treated with conditioned medium compared with LA alone. Incubation of murine feces with LA after administering VSL3 yielded 100-fold more CLA than feces collected prior to VSL3 feeding. This study supports a role for supplemental probiotics as a strategy both for attenuating inflammation and for preventing colon cancer.

An orthotopic colon cancer model for studying the B7-H3 antitumor effect in vivo

We established an orthotopic animal model of colon cancer in mice and applied this model to study the antitumor effects of B7-H3, the newest member of the B7 family of costimulatory molecules. Colon-26 murine colon adenocarcinoma cells were inoculated into the cecal subserosum of mice to induce colon tumor growth. The tumor growth rate and the survival time of the mice were observed. A stable B7-H3 transfected Colon-26 cell line was established and the immunogenic effect was investigated. All mice implanted with wild-type tumor cells had tumor growth in the colon and died. The mean survival rate was 23 days. Mice implanted with C26-B7-H3 had a significantly prolonged survival time of 38 days. Our data suggest that B7-H3 exerts an antitumor effect on adenocarcinoma of the colon and may be considered as an adjuvant immunotherapy in the treatment of colon cancers. Our orthotopic animal model of colon cancer in mice could be applied to in vivo experimental studies of colon cancer.

Heat Shock Protein 70 Neutralization Exerts Potent Antitumor Effects in Animal Models of Colon Cancer and Melanoma

When overexpressed, the stress protein heat shock protein 70 (HSP70) increases the oncogenic potential of cancer cells in rodent models. HSP70 also prevents apoptosis, thereby increasing the survival of cells exposed to a wide range of otherwise lethal stimuli. These protective functions of HSP70 involve its interaction with and neutralization of the adaptor molecule apoptotic protease activation factor-1, implicated in caspase activation, and the flavoprotein apoptosis-inducing factor (AIF), involved in caspase-independent cell death. We have shown previously that a peptide containing the AIF sequence involved in its interaction with HSP70 (ADD70, amino acids 150-228) binds to and neutralizes HSP70 in the cytosol, thereby sensitizing cancer cells to apoptosis induced by a variety of death stimuli. Here, we show that expression of ADD70 in tumor cells decreases their tumorigenicity in syngeneic animals without affecting their growth in immunodeficient animals. ADD70 antitumorigenic effects are associated with an increase in tumor-infiltrating cytotoxic CD8+ T cells. In addition, ADD70 sensitizes rat colon cancer cells (PROb) and mouse melanoma cells (B16F10) to the chemotherapeutic agent cisplatin. ADD70 also shows an additive effect with HSP90 inhibition by 17-allylamino-17-demethoxygeldanamycin in vitro. Altogether, these data indicate the potential interest of targeting the HSP70 interaction with AIF for cancer therapy.

Galectin-3 Modulates MUC2 Mucin Expression in Human Colon Cancer Cells at the Level of Transcription via AP-1 Activation

Galectin-3 and MUC2 intestinal mucin each have been correlated with the malignant behavior of colon cancer cells. Galectin-3 modulates expression of MUC2 protein, but the specific regulatory mechanisms are unknown. This study sought to determine how galectin-3 increases MUC2 expression. Galectin-3 levels in human colon cancer cells of high and low metastatic ability were manipulated via expression of galectin-3 complementary DNA in sense or antisense orientation. Galectin-3 and MUC2 protein expression were determined by Western analysis and immunocytochemistry. Transient transfections of promoter reporter constructs were used to monitor MUC2 transcription and AP-1 activity. Electrophoretic mobility shift assays, site-directed mutagenesis, and chromatin immunoprecipitation were used to monitor the participation of AP-1 in MUC2 transcription. Alterations in galectin-3 levels correlated with both MUC2 protein expression and transcription. By using MUC2 promoter constructs of different lengths, galectin-3 responsiveness was found between 1500 and 2186 bp upstream of the translation start site, a region that contains 1 consensus AP-1 binding site. AP-1 activity paralleled MUC2 transcription in the different cell lines. Mutation in the AP-1 site markedly decreased MUC2 promoter activity, and MUC2 transcription was inhibited by cotransfection with a dominant-negative AP-1 vector. Electrophoretic mobility shift assays, co-immunoprecipitation, and chromatin immunoprecipitation analyses suggested an association between galectin-3, c-Jun, and Fra-1 in forming a complex at the AP-1 site on the MUC2 promoter. Galectin-3 up-regulation of MUC2 transcription occurs at the level of transcription through AP-1 activation. This may have important implications for understanding the role of galectin-3 and MUC2 in colon cancer metastasis.

Comparative uptakes and biodistributions of internalizing vs. noninternalizing copper-64 radioimmunoconjugates in cell and animal models of colon cancer

Copper-64-labeled monoclonal antibodies (mAbs) have previously demonstrated unexpectedly effective tumor control in rodent models of cancer at relatively low tumor-absorbed radiation doses. This property has been associated with delivery platforms resulting in cellular internalization. The purpose of the present studies was to evaluate the in vitro internalization and in vivo distribution of a two-antibody model of 64Cu radioimmunotherapy (RIT) in the same cell and animal models of cancer. Biodistributions of an internalizing antibody, cBR96, and a noninternalizing antibody, cT84.66, labeled with 64Cu, were obtained in nude mice bearing LS174T colon carcinoma xenografts from 15 min to 48 h. The 64Cu-DOTA-cBR96 conjugate demonstrated rapid tumor uptake, reaching 20.2% ID/g at 3 h and peaking at 35.4% ID/g by 24 h. Tumor accumulation of 64Cu-DOTA-cT84.66 was more gradual, 8.19% ID/g at 3 h and 43.8% ID/g by 24 h, but maximum uptake was not statistically different from 64Cu-DOTA-cBR96. Mouse xenograft dosimetry was estimated to be 1128 rad/mCi (304.9 mGy/MBq) for 64Cu-DOTA-cBR96 and 1409 rad/mCi (380.5 mGy/MBq) for 64Cu-DOTA-cT84.66. In LS174T cells, internalized radioactivity increased by a factor of 3.8 over 4 h for 64Cu-DOTA-cBR96, but remained unchanged 64Cu-DOTA-cT84.66. When normalized to uptake at 1 h, cellular efflux of 64Cu was essentially identical for both mAbs. The biodistributions and tumor dosimetry of these internalizing and noninternalizing radiolabeled mAbs were sufficiently similar for direct comparison of the therapeutic efficacies of low doses of 64Cu RIT agents in the same animal model of cancer.

Attenuation of breast tumor cell growth by conjugated linoleic acid via inhibition of 5-lipoxygenase activating protein

Conjugated linoleic acid (CLA) consists of a group of linoleic acid geometric isomers that have been shown to reduce tumor growth and metastasis in animal models of breast, prostate and colon cancer. To delineate a possible mechanism of action for CLA, we have recently shown that the 5-lipoxygenase product, 5-hydroxyeicosatetraenoic acid (5-HETE), could play a role in CLA alteration of mammary tumorigenesis. In this study, we determined how CLA could modulate 5-lipoxygenase activity. The t10, c12-CLA isomer reduced production of 5-HETE but not 12- and 15-HETE in MDA-MB-231 human breast tumor cells. That isomer and the c9, t11-CLA isomer decreased 5-HETE production by competition with the lipoxygenase substrate, arachidonic acid (AA). Interestingly, t10, c12-CLA reduced the expression of five-lipoxygenase activating protein (FLAP) but not the 5-lipoxygenase enzyme. Over-expression of FLAP abrogated t10, c12-CLA-reduced viability of MDA-MB-231 cells. These data suggest that the reduction of 5-HETE by t10, c12-CLA was due to competition with AA and the reduction of FLAP expression.

PTEN Up-Regulates the Tumor Metastasis Suppressor Gene Drg-1 in Prostate and Breast Cancer

PTEN (phosphatase and tensin homologue deleted on chromosome 10) has been shown to be inactivated in a wide variety of cancers, and the role of this gene as a tumor suppressor has been well established. On the other hand, results of recent animal studies as well as clinical evidence indicate that PTEN is also involved in tumor metastasis suppression. Although PTEN is known to play a key role in controlling cell growth and apoptosis, how PTEN exerts the metastasis suppressor function remains largely unknown. Recently, a microarray analysis identified the Drg-1 gene (differentiation related gene 1) as one of the potential targets of PTEN. The Drg-1 gene has been shown to suppress tumor metastasis in animal models of prostate and colon cancer, and the expression of this gene is significantly reduced with advancement of prostate and breast cancers in clinical setting. In this study, we explored the possibility that PTEN controls tumor metastasis by regulating the expression of the Drg-1 gene. Our results indicate that overexpression of PTEN significantly augments the endogenous expression of Drg-1 protein, whereas inhibition of PTEN by small interfering RNA decreases Drg-1 in a dose- and time-dependent manner. We also found that the control of the Drg-1 gene by PTEN seems to be at the transcriptional level, and that a phospho-Akt inhibitor restores the Drg-1 expression, indicating that PTEN controls Drg-1 by an Akt-dependent pathway. Consistent with these results, our immunohistochemical analysis revealed that PTEN expression correlates significantly with Drg-1 in both prostate and breast cancer cases. Furthermore, combination of the two markers, PTEN and Drg-1, emerged as a significantly better predictor of prostate and breast cancer patient survival than either marker alone.

634 poster A reproducible animal model of colon cancer with a solitary neoplastic growth

634 poster A reproducible animal model of colon cancer with a solitary neoplastic growth

Mesalamine in IBD: Multiple hats?

Mesalamine in IBD: Multiple hats?