Preliminary study pointing out a significant alteration in the biochemical composition of MUC2 in colorectal mucinous carcinoma

Generating an In Vitro Gut Model with Physiologically Relevant Biophysical Mucus Properties

Introduction

Gastrointestinal (GI) in vitro models have received lasting attention as an effective tool to model drug and nutrient absorption, study GI diseases, and design new drug delivery vehicles. A complete model of the GI epithelium should at a minimum include the two key functional components of the GI tract: mucus and the underlying epithelium. Mucus plays a key role in protecting and lubricating the GI tract, poses a barrier to orally administered therapies and pathogens, and serves as the microenvironment for the GI microbiome. These functions are reliant on the biophysical material properties of the mucus produced, including viscosity and pore size.

Methods

In this study, we generated in vitro models containing Caco-2 enterocyte-like cells and HT29-MTX goblet-like cells and determined the effects of coculture and mucus layer on epithelial permeability and biophysical properties of mucus using multiple particle tracking (MPT).

Results

We found that mucus height increased as the amount of HT29-MTX goblet-like cells increased. Additionally, we found that increasing the amount of HT29-MTX goblet-like cells within culture corresponded to an increase in mucus pore size and mucus microviscosity, measured using MPT. When compared to ex vivo mucus samples from mice and pigs, we found that a 90:10 ratio of Caco-2:HT29-MTX coculture displayed similar mucus pore size to porcine jejunum and that the mucus produced from 90:10 and 80:20 ratios of cells shared mechanical properties to porcine jejunum and ileum mucus.

Conclusions

GI coculture models are valuable tools in simulating the mucus barrier and can be utilized for a variety of applications including the study of GI diseases, food absorption, or therapeutic development.

MUC2 and MUC5AC Expression in Colon Cancer: A Preliminary Report from South India

Background: There is scanty data from India regarding MUC protein expression from colorectal cancers (CRC) among Indian patients. Aim of the Study: The aim of this study is to assess the alterations in the expression of MUC2 and MUC5AC in 25 patients with CRC by site of the tumor location and differentiation at histology. Materials and Methods: Patients with proven adenocarcinoma of the colon alone were included for the study. Biopsy specimens obtained from tumorous lesions in the colon were classified based on histopathology as well differentiated, moderately, and poorly differentiated adenocarcinoma. Immunohistochemistry was done in the 4 μm thick sections to identify the expression of MUC2 and MUC5AC mucins. Results: MUC2 was uniformly expressed with near similar intensity while MUC5 was moderately (56%) to highly expressed (36%) in mucinous tumors. In nonmucinous tumors, MUC2 was least expressed (68%) with a significant expression on MUC5AC (88%). Except for rectosigmoid growth which had greater expression of MUC5AC (31%), both proximal and distal carcinomas had significant MUC2 and MUC5AC expression. Conclusion: MUC2 and MUC5AC are expressed in colonic cancers, the former showing mildtomoderate expression and the latter moderatetointense expression. The expression is more in mucinous adenocarcinoma.

Asiatic acid abridges pre-neoplastic lesions, inflammation, cell proliferation and induces apoptosis in a rat model of colon carcinogenesis

The utmost aim of this present study was to investigate the anti-inflammatory, antiproliferative and proapoptotic potential of Asiatic acid (AA) on 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis in experimental rats. Rats were divided into six groups and received modified pellet diet for 32 weeks. Group 1 served as control rats. Group 2 received AA (4 mg/kg b.w. p.o.). Group 3-6 rats received 15 DMH (20 mg/kg b.w., s.c.) injections once a week starting from the 4th week. Besides DMH, rats received AA (4 mg/kg b.w. p.o.) in group 4 starting 2 weeks before carcinogen treatment till the end of the last DMH; group 5 starting 2 days after last DMH till the end of the experiment; and group 6 throughout the experiment. Pre-neoplastic lesions, xenobiotic metabolizing enzymes, inflammation, cell proliferation and apoptotic markers were analysed in our study. Our results ascertained AA supplementation to DMH-exposed rats significantly decreased the incidence of aberrant crypt foci (ACF) and phase I xenobiotic enzymes; and increased the phase II xenobiotic enzymes and mucin content as compared to DMH-alone-exposed rats. Moreover the increased expressions of mast cells, argyrophilic nucleolar organizer regions (AgNORs), proliferating cell nuclear antigen (PCNA) and cyclin D1 observed in the DMH-alone-exposed rats were reverted and were comparable with those of the control rats, when treated with AA. Concordantly AA also induced apoptosis by downregulating the expression of Bcl-2 and upregulating Bax, cytochrome c, caspase-3 and -9 in the DMH-alone-exposed rats. Thus AA was able to inhibit DMH-induced colon carcinogenesis by detoxifying the carcinogen, decreasing the preneoplastic lesions by virtue of its anti-inflammatory, antiproliferative and proapoptotic effects. Therefore our findings suggest that AA could be used as an effective chemopreventive agent against DMH induced colon carcinogenesis.

Modulatory effect of troxerutin on biotransforming enzymes and preneoplasic lesions induced by 1,2-dimethylhydrazine in rat colon carcinogenesis

Colon cancer is the third most global oncologic problem faced by medical fraternity. Troxerutin, a flavonoid present in tea, coffee, cereal grains, and a variety of fruits and vegetables, exhibits various pharmacological and biological activities. This study was carried out to investigate the effect of troxerutin on xenobiotic metabolizing enzymes, colonic bacterial enzymes and the development of aberrant crypt foci (ACF) during 1,2-dimethylhydrazine (DMH) induced experimental rat colon carcinogenesis. Male albino Wistar rats were randomly divided into six groups. Group 1 served as control. Group 2 received troxerutin (50 mg/kg b.w., p.o. every day) for 16 weeks. Groups 3-6 received subcutaneous injections of DMH (20 mg/kg b.w.) once a week, for the first four weeks. In addition, groups 4-6 received different doses of troxerutin (12.5, 25, 50 mg/kg b.w., p.o. every day respectively) along with DMH injections. Our results reveal that DMH treated rats exhibited elevated activities of phase I enzymes such as cytochrome P450, cytochrome b5, cytochrome P4502E1, NADPH-cytochrome P450 reductase and NADH-cytochrome b5 reductase and reduced activities of phase II enzymes such as glutathione-S-transferase (GST), DT-diaphorase (DTD) and uridine diphospho glucuronyl transferase (UDPGT) in the liver and colonic mucosa of control and experimental rats. Furthermore, the activities of fecal and colonic mucosal bacterial enzymes, such as β-glucronidase, β-glucosidase, β-galactosidase and mucinase were found to be significantly higher in DMH alone treated rats than those of the control rats. On supplementation with troxerutin to DMH treated rats, the alterations in the activities of the biotransforming enzymes, bacterial enzymes and the pathological changes were significantly reversed, the effect being more pronounced when troxerutin was supplemented at the dose of 25 mg/kg b.w. Thus troxerutin could be considered as a good chemopreventive agent against the formation of preneoplastic lesions in a rat model of colon carcinogenesis.

Modulating effect of d-carvone on 1,2-dimethylhydrazine-induced pre-neoplastic lesions, oxidative stress and biotransforming enzymes, in an experimental model of rat colon carcinogenesis

OBJECTIVES

The present study has aimed to evaluate chemopreventive potential of d-carvone on oxidative stress markers, biotransforming enzymes, incidence of colonic polyps and aberrant crypt foci (ACF) in 1,2-dimethylhydrazine (DMH)-induced experimental colon carcinogenesis.

MATERIALS AND METHODS

Rats were randomly divided into six groups, with group I serving as control. Group II animals received d-carvone every day orally (20 mg/kg body weight) for 16 weeks; groups III-VI received subcutaneous injections of DMH (20 mg/kg body weight) once a week, for the first 4 weeks. In addition, groups IV-VI received different doses of d-carvone (5, 10 and 20 mg/kg body weight everyday orally) along with DMH injections.

RESULTS

Our results revealed that supplementation with d-carvone significantly reduced incidence of polyps/ACF and ACF multiplicity in DMH-exposed rats compared to DMH-alone-exposed rats. Moreover, our results showed reduced activities of liver and circulatory antioxidants and increased levels of lipid peroxidation by products in DMH-exposed animals, which were significantly reversed on supplementation with d-carvone. In addition, colonic antioxidants and lipid peroxidation were significantly diminished in DMH-exposed rats, which were significantly elevated on supplementation with d-carvone. Furthermore, we also determined activities of biotransforming enzymes, which were found to be altered in DMH-exposed rats, but reversed on d-carvone supplementation. All these observations of changes were supported by histochemical findings.

CONCLUSION

Overall, results obtained from this study suggest that d-carvone at 10 mg/kg body weight provided optimum protection and could be used as an effective chemopreventive agent against colon carcinogenesis induced by DMH.

Clinicopathological Significance of Mucin 2 Immuno-histochemical Expression in Colorectal Cancer: A Meta-Analysis

OBJECTIVE

To evaluate the association between mucin 2 (MUC2) expression and clinicopathological characters of colorectal cancer.

METHODS

A literature search was performed on December 31, 2010 according to defined selection criteria. We evaluated the correlation between MUC2 (detected by immunohistochemistry) and clinicopathological characters of colorectal cancer. According to the tumor histological type, differentiation, location and TNM staging of colorectal carcinoma, we divided the clinicopathological characteristics into different subgroups. Fixed and random effects models were applied for estimation of the summarized risk ratios (RRs) and 95% confidence intervals (CIs) in different subgroups. Finally, forest plots and funnel plots were created to allow for visual comparison of the results or the effect of publication bias.

RESULTS

According with the inclusive criteria, fourteen studies (n=1,558) were eligible for the meta-analysis. We observed a trend towards a correlation of MUC2 higher positivity in mucinous than non-mucinous carcinoma (RR, 2.10; 95% CI, 1.30-3.40; P=0.002) and less positivity in distal than proximal colon (RR, 0.74; 95% CI, 0.64-0.85; P=0.000). There was no statistically significance for the association between MUC2 expression and differentiation or TNM staging of colorectal cancer, but MUC2 overexpression tended to be associated with the presence of T stage tumor (RR, 1.17; P=0.052).

CONCLUSION

MUC2 overexpression was associated with the mucinous and proximal colorectal cancer.

Suppression of mucin 2 enhances the proliferation and invasion of LS174T human colorectal cancer cells

Altered expression of MUC2 (mucin 2) is related to tumour development in colorectal cancer. Colorectal mucinous carcinomas are positive for MUC2 expression, whereas MUC2 is down-regulated in non-mucinous adenocarcinomas. In the present study, we down-regulated MUC2 expression by RNAi (RNA interference) and investigated the in vitro and in vivo effects on the proliferation and invasion/migration potential of the LS174T human colorectal cancer cells. The LS174T cell line is a goblet-cell-like colorectal cancer cell line that continuously produces high levels of MUC2. Inhibition of MUC2 expression in vitro by transfection of LS174T cells with the recombinant plasmid pcDNA6.2-GW/EmGFP-miR-MUC2 led to the production of a stably transfected MUC2-RNAi LS174T cell line. The proliferation and invasion/migration of MUC2-RNAi cells in vitro were significantly higher than those in control cells, as assessed by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide], colony formation and transwell assays. Subcutaneous injection of MUC2-RNAi LS174T cells into nude mice resulted in the development of subcutaneous tumours visible to the naked eye after 1 week. The growth rate of tumours derived from MUC2-RNAi LS174T cells was greater than that of tumours derived from control cells. Ki67 and matrix metalloproteinase-9 proteins were detected by immunohistochemistry in the xenografts. The expression levels of these proteins were higher in the MUC2-RNAi-derived xenografts than in xenografts derived from control cells. Although the role of MUC2 in colorectal tumorigenesis is not fully understood, these results strongly suggest a relationship between the proliferation and invasion of LS174T cells and the expression of MUC2.

Gut bacteria in health and disease: a survey on the interface between intestinal microbiology and colorectal cancer

A healthy human body contains at least tenfold more bacterial cells than human cells and the most abundant and diverse microbial community resides in the intestinal tract. Intestinal health is not only maintained by the human intestine itself and by dietary factors, but is also largely supported by this resident microbial community. Conversely, however, a large body of evidence supports a relationship between bacteria, bacterial activities and human colorectal cancer. Symbiosis in this multifaceted organ is thus crucial to maintain a healthy balance within the host-diet-microbiota triangle and accordingly, changes in any of these three factors may drive a healthy situation into a state of disease. In this review, the factors that sustain health or drive this complex intestinal system into dysbiosis are discussed. Emphasis is on the role of the intestinal microbiota and related mechanisms that can drive the initiation and progression of sporadic colorectal cancer (CRC). These mechanisms comprise the induction of pro-inflammatory and pro-carcinogenic pathways in epithelial cells as well as the production of (geno)toxins and the conversion of pro-carcinogenic dietary factors into carcinogens. A thorough understanding of these processes will provide leads for future research and may ultimately aid in development of new strategies for CRC diagnosis and prevention.

Caco-2 and LS174T cell lines provide different models for studying mucin expression in colon cancer

To compare the differences in MUC2 and MUC5AC mRNA among four colon cancer cell lines and to identify the best in vitro models for studying mucin expression, quantitative real-time polymerase chain reaction was used to measure the expression of MUC2 and MUC5AC mRNA in Caco-2, HT29, LoVo, and LS174T cell lines. The levels of MUC2 mRNA expression in the four colon cancer cell lines ranked in order of mRNA abundance were: LS174T>LoVo>HT-29>Caco-2. In contrast to MUC2, the abundances of MUC5AC mRNA were in the order: Caco-2>HT-29>LS174T>LoVo. Caco-2 (highest level of MUC5AC mRNA) and LS174T (highest level of MUC2 mRNA) were used to investigate the phenotypes. Morphologically, Caco-2 cells were larger with low electron density mucus-storing vacuoles, many cell surface microvilli, and no obvious intercellular spaces between cells, compared to LS174T cells. The proliferative and invasive capacities of LS174T cells were significantly higher than those of Caco-2 cells. Caco-2 and LS174T cells provide excellent in vitro models for studying mucin expression in colon cancer.

New developments in oestrogen signalling in colonic epithelium

Epidemiological studies show that oestrogen reduces the risk of colorectal cancer in postmenopausal women and ERβ (oestrogen receptor β)-selective ligands have been reported to be very effective treatment in animal models of inflammatory bowel disease. Several studies have shown that ERβ is the predominant ER in the colonic epithelium, but it is not clear whether the benefit of ERβ agonists in inflammatory bowel disease are due to their action on the colon epithelium itself, or on the immune system. In order to address this issue, we have compared colons of ERβ−/− and wild-type mice with regard to morphology, histology, proliferation and differentiation. We found that the number of proliferating cells was higher in ERβ−/− mice, and the migration of labelled cells from base to lumen of the crypts was faster. Additionally, immunohistochemical staining revealed fewer apoptotic cells (cleaved caspase 3-positive), a significant decrease in expression of the epithelial differentiation marker, cytokeratin CK20, the adherens junction protein, α-catenin, and the hemidesmosomal protein, plectin, in ERβ−/− mice. These findings suggest a role for ERβ in growth, organization and maintenance of the normal colonic crypt–villus architecture. The next step is to elucidate the molecular mechanisms that underlie the signalling of ERβ in normal cell growth and assess whether or not ERβ agonists will be useful drugs in the prevention or treatment of colorectal cancer. Dietary phyto-oestrogens are believed to play a role in protection against colorectal cancer. Lignans, such as enterolactone, an ER agonist, prevent cancer development in animal models. Since ERβ is the only ER in the colon, there is enough reason to speculate that phyto-oestrogens are acting through ERβ.

Role of estrogen receptor beta in colonic epithelium

Several papers report that the colon is one of the tissues regulated by estrogen receptor (ER)beta. To better understand the physiological role of ERbeta in colonic tissue, we have compared morphology, proliferation, and differentiation of colonic epithelium in ERbeta-/- mice and WT littermates. BrdUrd labeling revealed that the number of proliferating cells was higher in ERbeta-/- mice and that the migration of labeled cells toward the luminal surface was faster in ERbeta-/- mice than in WT littermates. Additionally, in the absence of ERbeta, there was a decrease in apoptosis, which was measured by immunohistochemical staining of cleaved caspase-3. The state of differentiation of the colonic epithelial cells was studied by using epithelial markers. In ERbeta-/- mice, there was a significant decrease in the expression of the differentiation marker cytokeratin (CK)20 and in the cellular adhesion molecules alpha-catenin (an adherens junction protein) and plectin (a hemidesmosomal protein). These changes were also evident by electron microscopy as abnormalities in tight junctions and in the number and shape of desmosomes in ERbeta-/- mice. These findings suggest a role for ERbeta in the organization and architectural maintenance of the colon. Furthermore, our results indicate that the rapidly proliferating cells of the colonic epithelium in ERbeta-/- mice are lost by increased shedding and not by increased apoptosis. In this way, hyperproliferative cells that lack ERbeta do not form hyperplastic lesions and do not accumulate in the superficial epithelium.

Differential expression of MUC genes in endometrial and cervical tissues and tumors

Background

Mucin glycoprotein's are major components of mucus and are considered an important class of tumor associated antigens. The objective of this study was to investigate the expression of human MUC genes (MUC1, MUC2, MUC5B, MUC5AC and MUC8) in human endometrium and cervix, and to compare and quantitate the expression of MUC genes in normal and cancerous tissues.

Methods

Slot blot techniques were used to study the MUC gene expression and quantitation.

Results

Of the five-mucin genes studied, MUC1, MUC5B and MUC8 showed high expression levels in the normal and cancerous endometrial and cervical tissues, MUC2 and MUC5AC showed considerably lower expression. Statistically, higher levels of MUC1, MUC5B and MUC8 were observed in endometrial adenocarcinomas compared to normal tissues. In contrast, only MUC1 levels increased with no significant changes in expression of MUC5B and MUC8 in cervical tumors over normal cervical tissues.

Conclusion

Endometrial tumors showed increased expression of MUC1, MUC5B and MUC8 over normal tissues. Only MUC1 appears to be increase, in cervical tumors. All the studied tissues showed high and consistent expression of MUC8 mRNA. Low to neglible levels of MUC2 and MUC5AC were observed in all studied endometrial and cervical tissues.