Essi Päivärinta

Promotion of intestinal tumor formation by inulin is associated with an accumulation of cytosolic β‐catenin in Min mice

Inulin, polydisperse β (2‐1) fructan, has been suggested to protect against colon carcinogenesis and is currently used in a number of food applications. However, the data regarding the role of inulin in intestinal carcinogenesis remains controversial since the results of our previous study suggested that inulin promotes intestinal tumor formation in Min mice, an animal model for intestinal cancer with a mutation in the Apc tumor suppressor gene (Carcinogenesis 2000;21:1167–73). In our present study, we further examined the effects of inulin on intestinal tumor formation in Min mice by carefully analyzing β‐catenin expression and cellular localization at 3 different time points during the tumorigenic process. Min mice were fed a high‐fat inulin‐enriched (10% w/w) diet or the high‐fat diet without any added fiber from the age of 6 weeks to the ages of 9, 12 or 15 weeks. The results showed that inulin significantly increased the number (by 20%) and especially the size (by 44%) of adenomas in the small intestine. At week 15, the promotion of tumor development was accompanied by an accumulation of cytosolic β‐catenin in the adenoma tissue. In the normal appearing mucosa, levels of membrane β‐catenin and PCNA were reduced in the inulin‐fed mice, possibly indicating impaired enterocyte migration. These data do not support the earlier suggestions on the cancer preventive effects of inulin and emphasize the need for further research and evaluation where health claims for inulin are concerned.

Ellagic acid and natural sources of ellagitannins as possible chemopreventive agents against intestinal tumorigenesis in the Min mouse.

Abstract: Ellagic acid has been shown to have chemopreventive effects in various experimental cancer models. We wanted to see whether pure ellagic acid and natural ellagitannins from cloudberry (Rubus chamaemorus) seed and pulp have any effect on adenoma formation in Apc-mutated Min mice. From the age of 5 wk, the mice were fed either a control diet, a diet containing pure ellagic acid at 1,564 mg/kg, or diets containing 4.7% (wt/wt) cloudberry seeds or 5.3% cloudberry pulp. The concentrations of ellagitannins and free ellagic acid in the seed diet were 807 and 42 mg/kg and in the pulp diet 820 and 34 mg/kg, respectively. After the 10-wk feeding period, ellagic acid had no effect on the number or size of adenomas in the distal or total small intestine, but it increased adenoma size in the duodenum when compared with the control diet (1.50 ± 0.29 vs. 1.16 ± 0.31 mm; P = 0.029). Neither cloudberry seed nor pulp diets had any effect on the adenoma formation. Chemopreventive effects and mechanisms of whole cloudberry and other similar sources of phenolic compounds should, however, be studied, further taking into account food matrix and interactions with other dietary constituents that may be involved in the bioavailability and metabolism of ellagitannins.

Chemoprevention by white currant is mediated by the reduction of nuclear β-catenin and NF-κB levels in Min mice adenomas

BackgroundBerries are a good natural source of phenolic compounds and many berries or their compounds have been shown to be chemopreventive. White currant is an interesting berry, as it contains low levels of dominant berry phenolics such as ellagic acid, anthocyanins and other flavonoids.Aims of the studyTo study if white currant is chemopreventive in an experimental model for intestinal tumorigenesis and further study the effects on β-catenin and NF-κB signaling pathways.MethodsMultiple intestinal neoplasia (Min) mice were fed an AIN-93G based control diet or a diet containing 10% freeze dried white currant (Ribes x pallidum) for 10 weeks. Cell signaling parameters were analysed from intestinal adenomas and surrounding mucosa by Western blotting and immunohistochemistry.ResultsThe white currant diet reduced the number of adenomas from 81 (min–max 47–114) to 51 (36–84) in the total small intestine of Min mice (P < 0.02). Most of the adenomas develop in the distal part of the small intestine, and in this area white currant reduced the number from 49 to 29.5 (P < 0.01) and also the size of the adenomas from 0.88 mm to 0.70 mm (P < 0.02). In the colon white currant increased the number of adenomas (0.3 ± 0.6 vs. 0.8 ± 0.6, mean ± SD, P < 0.05), but did not affect the size. White currant reduced nuclear β-catenin and NF-κB protein levels in the adenomas (P < 0.05 and P < 0.02, respectively). They were correlated with the size of adenomas (P < 0.01).ConclusionsThis study shows that white currant is effective in preventing cancer initiation and progression in the Min mouse. Whether the positive effects are due to its special phenolic composition needs to be studied in more detail.

Plant sterol feeding induces tumor formation and alters sterol metabolism in the intestine of Apc(Min) mice.

Dietary plant sterols reduce the absorption of cholesterol and therefore increase intraluminal cholesterol concentration. We examined how plant sterol esters from functional foods affect intestinal tumorigenesis in tumor-prone adenomatous polyposis coli (Apc) Minmice. Feeding plant sterols at 0.8% increased the number of intestinal adenomas, and the effect was significant in female mice. The concentration of mucosal free sitosterol increased by eightfold in plant sterol males and by threefold in plant sterol females when compared with respective controls. The concentration of mucosal free cholesterol was significantly lower in plant sterol males than in control males, and the decrease in free cholesterol was accompanied with a significant increase in nuclear sterol regulatory element binding protein-2. No difference was found in the levels of β-catenin, cyclin D1, epidermal growth factor receptor, extracellular signal-regulated kinase 1/2, or caveolin-1 in either gender after plant sterol feeding. Among all measured parameters, higher levels of estrogen receptor β and free cholesterol in the mucosa were among the strongest predictors of increased intestinal tumorigenesis. In addition, gene expression data showed significant enrichment of up-regulated genes of cell cycle control and cholesterol biosynthesis in plant sterol females. The results indicate that high intake of plant sterols accelerates intestinal tumorigenesis in female Apc Minmice; however, the mechanism behind the adverse effect remains to be discovered.

Cancer-Predicting Gene Expression Changes in Colonic Mucosa of Western Diet Fed Mlh1+/- Mice

Colorectal cancer (CRC) is the second most common cause of cancer-related deaths in the Western world and interactions between genetic and environmental factors, including diet, are suggested to play a critical role in its etiology. We conducted a long-term feeding experiment in the mouse to address gene expression and methylation changes arising in histologically normal colonic mucosa as putative cancer-predisposing events available for early detection. The expression of 94 growth-regulatory genes previously linked to human CRC was studied at two time points (5 weeks and 12 months of age) in the heterozygote Mlh1 +/- mice, an animal model for human Lynch syndrome (LS), and wild type Mlh1 +/+ littermates, fed by either Western-style (WD) or AIN-93G control diet. In mice fed with WD, proximal colon mucosa, the predominant site of cancer formation in LS, exhibited a significant expression decrease in tumor suppressor genes, Dkk1, Hoxd1, Slc5a8, and Socs1, the latter two only in the Mlh1 +/- mice. Reduced mRNA expression was accompanied by increased promoter methylation of the respective genes. The strongest expression decrease (7.3 fold) together with a significant increase in its promoter methylation was seen in Dkk1, an antagonist of the canonical Wnt signaling pathway. Furthermore, the inactivation of Dkk1 seems to predispose to neoplasias in the proximal colon. This and the fact that Mlh1 which showed only modest methylation was still expressed in both Mlh1 +/- and Mlh1 +/+ mice indicate that the expression decreases and the inactivation of Dkk1 in particular is a prominent early marker for colon oncogenesis.

Plant stanols induce intestinal tumor formation by up-regulating Wnt and EGFR signaling in ApcMin mice

The rate of APC mutations in the intestine increases in middle-age. At the same period of life, plant sterol and stanol enriched functional foods are introduced to diet to lower blood cholesterol. This study examined the effect of plant stanol enriched diet on intestinal adenoma formation in the Apc(Min) mouse. Apc(Min) mice were fed 0.8% plant stanol diet or control diet for nine weeks. Cholesterol, plant sterols and plant stanols were analyzed from the caecum content and the intestinal mucosa. Levels of β-catenin, cyclin D1, epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinase 1/2 (ERK1/2) were measured from the intestinal mucosa by Western blotting. Gene expression was determined from the intestinal mucosa using Affymetrix and the data were analyzed for enriched categories and pathways. Plant stanols induced adenoma formation in the small intestine, however, the adenoma size was not affected. We saw increased levels of nuclear β-catenin, phosphorylated β-catenin (Ser675 and Ser552), nuclear cyclin D1, total and phosphorylated EGFR and phosphorylated ERK1/2 in the intestinal mucosa after plant stanol feeding. The Affymetrix data demonstrate that several enzymes of cholesterol synthesis pathway were up-regulated, although the cholesterol level in the intestinal mucosa was not altered. We show that plant stanols induce adenoma formation by activating Wnt and EGFR signaling. EGFR signaling seems to have promoted β-catenin phosphorylation and its translocation into the nucleus, where the expression of cyclin D1 was increased. Up-regulated cholesterol synthesis may partly explain the increased EGFR signaling in the plant stanol-fed mice.

Changes in intestinal immunity, gut microbiota, and expression of energy metabolism-related genes explain adenoma growth in bilberry and cloudberry-fed ApcMin mice

We showed previously that ellagitannin-rich cloudberries and anthocyanin-rich bilberries reduce the number of intestinal adenomas in multiple intestinal neoplasia/+ (ApcMin) mice. We also found that cloudberries decreased the size of adenomas, whereas bilberries increased it. Here we hypothesized that the difference in adenoma growth could be explained by dissimilar effects of the berries on intestinal immune responses and gut microbiota, potentially driven by the distinct polyphenol compositions of the 2 berries. Our objectives were to investigate lymphocyte subtypes and the predominant cecal bacterial diversity in mice fed with bilberries and cloudberries, and to analyze global gene expression profiles in the intestinal mucosa. Immunostainings of CD3+ T lymphocytes, FoxP3+ regulatory T lymphocytes, and CD45R+ B lymphocytes revealed a smaller ratio of intraepithelial to all mucosal CD3+ T lymphocytes in the cloudberry-fed mice compared with controls, suggesting an attenuation of inflammation. Bilberry feeding induced no changes in the density of any of the lymphocyte subtypes. The predominant bacterial diversity in cecal contents, analyzed using polymerase chain reaction-denaturating gradient gel electrophoresis, was higher in the bilberry group than in the control or cloudberry groups. The microbial profiles of cloudberry-fed mice clustered together and were associated with small adenoma size. Pathway analyses of gene expression data showed that cloudberry down-regulated and bilberry up-regulated the expression of energy metabolism-related genes in the intestinal mucosa. In conclusion, attenuation of intestinal inflammation, changes in microbial profiles, and down-regulation of mucosal energy metabolism may account for the smaller adenoma size in cloudberry-fed mice in comparison to bilberry-fed mice.

Western diet enhances intestinal tumorigenesis in Min/+ mice, associating with mucosal metabolic and inflammatory stress and loss of Apc heterozygosity.

Western-type diet (WD) is a risk factor for colorectal cancer, but the underlying mechanisms are poorly understood. We investigated the interaction of WD and heterozygous mutation in the Apc gene on adenoma formation and metabolic and immunological changes in the histologically normal intestinal mucosa of ApcMin/+ (Min/+) mice. The diet used was high in saturated fat and low in calcium, vitamin D, fiber and folate. The number of adenomas was twofold higher in the WD mice compared to controls, but adenoma size, proliferation or apoptosis did not differ. The ratio of the Min to wild-type allele was higher in the WD mice, indicating accelerated loss of Apc heterozygosity (LOH). Densities of intraepithelial CD3ε+ T lymphocytes and of mucosal FoxP3+ regulatory T cells were higher in the WD mice, implying inflammatory changes. Western blot analyses from the mucosa of the WD mice showed suppressed activation of the ERK and AKT pathways and a tendency for reduced activation of the mTOR pathway as measured in phosphoS6/S6 levels. The expression of pyruvate dehydrogenase kinase 4 was up-regulated in both mRNA and protein levels. Gene expression analyses showed changes in oxidation/reduction, fatty acid and monosaccharide metabolic pathways, tissue organization, cell fate and regulation of apoptosis. Together, our results suggest that the high-risk Western diet primes the intestine to tumorigenesis through synergistic effects in energy metabolism, inflammation and oxidative stress, which culminate in the acceleration of LOH of the Apc gene.

Ellagitannin-rich cloudberry inhibits hepatocyte growth factor induced cell migration and phosphatidylinositol 3-kinase/AKT activation in colon carcinoma cells and tumors in Min mice

Berries have been found to inhibit colon carcinogenesis in animal models, and thus represent a potential source of compounds for prevention and treatment of colorectal cancer. The mechanistic basis for their effects is not well understood. We used human colon carcinoma cells and Min mice to investigate the effects of ellagitannin-rich cloudberry (Rubus chamaemorus) extract on cancer cell migration and underlying cell signaling. Intrinsic and hepatocyte growth factor (HGF) -induced cell motility in human HT29 and HCA7 colon carcinoma cells was assessed carrying out cell scattering and scratch wound healing assays using time-lapse microscopy. Activation of Met, AKT, and ERK in cell lines and tumors of cloudberry-fed Min mice were determined using immunoprecipitation, Western blot and immunohistochemical analyses. Cloudberry extract significantly inhibited particularly HGF-induced cancer cell migration in both cell lines. Cloudberry extract inhibited the Met receptor tyrosine phosphorylation by HGF and strongly suppressed HGF-induced AKT and ERK activation in both HT29 and HCA7 cells. Consistently, cloudberry feeding (10% w/w freeze-dried berries in diet for 10 weeks) reduced the level of active AKT and prevented phosphoMet localization at the edges in tumors of Min mice. These results indicate that cloudberry reduces tumor growth and cancer cell motility by inhibiting Met signaling and consequent activation of phosphatidylinositol 3-kinase/AKT in vitro and in tumors in vivo. As the Met receptor is recognized to be a major target in cancer treatment, our results suggest that dietary phytochemicals may have therapeutic value in reducing cancer progression and metastasis.

Abstract 4871: Berry feeding changes gut microbiota and immune function in association with adenoma formation in the Min mouse.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC In the gut, the interaction between the tumor tissue and its microenvironment including the microbiota and immune cells may play a significant role in the carcinogenic process. Here we studied whether the anti-carcinogenic effects of berry diets were mediated by changes in the gut microbiota and immune cells. Male and female Min mice were fed modified high-fat AIN93-G diets containing 10% (w/w) freeze-dried bilberry or cloudberry for 10 weeks. The control diet was similar but without any berries. Mucosal B and T lymphocytes were analysed using immunohistochemical staining. The microbial profile was determined carrying out PCR-DGGE analysis using bacterial genomic DNA extracted from caecal contents. Microbial PCR-DGGE profiles contained 10-19 amplicons, indicating that the microbiota in the mouse cecum contents is diverse. According to their PCR-DGGE patterns, samples of control and cloudberry-fed mice could be divided to well-defined subgroups both visually and using Molecular Analyst software. Instead, visual grouping of the samples of bilberry-fed mice was impossible and the samples were only grouped using the software. In the control mice, amplicons a-d were present in all samples but on the basis of their intensity, amplicons b-d represented the dominant species. In the cloudberry mice, amplicons a, c, d, e and f existed in all samples but some of them lacked a pronounced amplicon b. In the bilberry mice, the amplicons a-e existed in all samples. In addition, bilberry samples contained amplicon g that seemed to be more prevalent and intense than in the samples of the other two groups. The amplicon g was sequenced and found to belong to the Clostridiales order of the Clostridia class in the Firmicutes phylum and to represent an uncultured bacterium clone abc21b07.x1: AY667976. Cloudberry feeding resulted in a smaller density of mucosal CD3+ T lymphocytes (p=0.149) and a significantly smaller ratio of intraepithelial to total CD3+ T lymphocytes (p=0.034) when compared to the control group. Furthermore, there was a significant positive correlation (p=0.012) between the ratio of intraepithelial to total CD3+ T lymphocytes and adenoma burden in the small intestine of Min mice. Interestingly, no difference in the density of any lymphocytes was found between the bilberry and the control group. Berry feeding did not affect the density of B lymphocytes in the intestinal mucosa. Here we show that berry feeding changes the microbiota and the distribution of immune cells in the intestine of Min mice and these changes are associated with adenoma formation. Citation Format: Anne-Maria Pajari, Essi Paivarinta, Johanna Maukonen, Mikael Niku, Anu Heiman-Lindh, Maria Saarela, Marja Mutanen. Berry feeding changes gut microbiota and immune function in association with adenoma formation in the Min mouse. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4871. doi:10.1158/1538-7445.AM2013-4871