Sodium butyrate inhibits carcinoma development in a 1,2-dimethylhydrazine-induced rat colon cancer

Chitosan nanomedicines-engineered bifidobacteria complexes for effective colorectal tumor-targeted delivery of SN-38

The clinical application of 7-ethyl hydroxy-camptothecin (SN-38) maintains challenges not only due to its poor solubility and stability but also the lack of effective carriers to actively deliver SN-38 to deep tumor sites. Although SN-38-based nanomedicines could improve the solubility and stability from different aspects, the tumor targeting efficiency remains very low. Leveraging the hypoxic taxis of bifidobacteria bifidum (B. bifi) to the deep tumor area, we report SN-38-based nanomedicines-engineered bifidobacterial complexes for effective tumor-targeted delivery. Firstly, SN-38 was covalently coupled with poly-L-glutamic acid (L-PGA) and obtained soluble polymeric prodrug L-PGA-SN38 to improve its solubility and stability. To prolong the drug release, L-PGA-SN38 was mildly complexed with chitosan to form nanomedicines, and nanomedicines engineered B. bifi were further elaborated via electrostatic interaction of the excess of cationic chitosan shell from nanomedicines and anionic teichoic acid from B. bifi. The engineered B. bifi complexes inherited the bioactivity of native B. bifi and exhibited distinctly enhanced accumulation at the tumor site. More importantly, significantly elevated anti-tumor efficacy was achieved after the treatment of CS-L-PGA-SN38 NPs/B. bifi complexes, with favorable tumor suppression up to 80%. Such a B. bifi-mediated delivery system offers a promising platform for effective drug delivery and enhanced drug accumulation in the hypoxia deep tumor with superior anti-tumor efficacy.

Microbiome insights into pediatric familial adenomatous polyposis

BACKGROUND

Individuals with familial adenomatous polyposis (FAP) harbor numerous polyps with inevitable early progression to colon cancer. Complex microbiotic-tumor microenvironment perturbations suggest a dysbiotic relationship between polyp and microbiome. In this study, we performed comprehensive analyses of stool and tissue microbiome of pediatric FAP subjects and compared with unaffected cohabiting relatives through 16S V4 region amplicon sequencing and machine learning platforms.

RESULTS

Within our FAP and control patient population, Firmicutes and Bacteroidetes were the predominant phyla in the tissue and stool samples, while Proteobacteria dominated the polyp/non-polyp mucosa. A decline in Faecalibacterium in polyps contrasted with a decline in Bacteroides in the FAP stool. The alpha- and beta-diversity indices differed significantly within the polyp/non-polyp groups, with a concurrent shift towards lower diversity in polyps. In a limited 3-year longitudinal study, the relative abundance of Proteobacteria and Fusobacteria was higher in polyps compared to non-polyp and stool specimens over time. Through machine learning, we discovered that Archaeon_enrichment_culture_clone_A13, Micrococcus_luteus, and Eubacterium_hallii in stool and PL-11B10, S1-80, and Blastocatellaceae in tissues were significantly different between patients with and without polyps.

CONCLUSIONS

Detection of certain bacterial concentrations within stool or biopsied polyps could serve as adjuncts to current screening modalities to help identify higher-risk patients.

Biological Effects of Indole-3-Propionic Acid, a Gut Microbiota-Derived Metabolite, and Its Precursor Tryptophan in Mammals' Health and Disease

Actions of symbiotic gut microbiota are in dynamic balance with the host’s organism to maintain homeostasis. Many different factors have an impact on this relationship, including bacterial metabolites. Several substrates for their synthesis have been established, including tryptophan, an exogenous amino acid. Many biological processes are influenced by the action of tryptophan and its endogenous metabolites, serotonin, and melatonin. Recent research findings also provide evidence that gut bacteria-derived metabolites of tryptophan share the biological effects of their precursor. Thus, this review aims to investigate the biological actions of indole-3-propionic acid (IPA), a gut microbiota-derived metabolite of tryptophan. We searched PUBMED and Google Scholar databases to identify pre-clinical and clinical studies evaluating the impact of IPA on the health and pathophysiology of the immune, nervous, gastrointestinal and cardiovascular system in mammals. IPA exhibits a similar impact on the energetic balance and cardiovascular system to its precursor, tryptophan. Additionally, IPA has a positive impact on a cellular level, by preventing oxidative stress injury, lipoperoxidation and inhibiting synthesis of proinflammatory cytokines. Its synthesis can be diminished in the presence of different risk factors of atherosclerosis. On the other hand, protective factors, such as the introduction of a Mediterranean diet, tend to increase its plasma concentration. IPA seems to be a promising new target, linking gut health with the cardiovascular system.

Lactobacillus plantarum-derived metabolites sensitize the tumor-suppressive effects of butyrate by regulating the functional expression of SMCT1 in 5-FU-resistant colorectal cancer cells

A critical obstacle to the successful treatment of colorectal cancer (CRC) is chemoresistance. Chemoresistant CRC cells contribute to treatment failure by providing a mechanism of drug lethargy and modifying chemoresistance-associated molecules. The gut microbiota provide prophylactic and therapeutic effects by targeting CRC through anticancer mechanisms. Among them, Lactobacillus plantarum contributes to the health of the host and is clinically effective in treating CRC. This study confirmed that 5-fluorouracil (5-FU)-resistant CRC HCT116 (HCT116/5FUR) cells acquired butyrate-insensitive properties. To date, the relationship between 5-FU-resistant CRC and butyrate resistance has not been elucidated. Here, we demonstrated that the acquisition of butyrate resistance in HCT116/5FUR cells was strongly correlated with the inhibition of the expression and function of SMCT1, a major transporter of butyrate in colonocytes. L. plantarum-cultured cell-free supernatant (LP) restored the functional expression of SMCT1 in HCT116/5FUR cells, leading to butyrate-induced antiproliferative effect and apoptosis. These results suggest that LP has a synergistic effect on the SMCT1/butyrate-mediated tumor suppressor function and is a potential chemosensitizer to overcome dual 5-FU and butyrate resistance in HCT116 cells.

Fecal microbiota transplantation as a new treatment for canine inflammatory bowel disease

In human medicine, fecal microbiota transplantation (FMT) is an effective treatment for recurrent Clostridioides difficile infection. It has also been tested as a treatment for multiple gastrointestinal diseases, including inflammatory bowel disease (IBD). However, only a few studies have focused on the changes in the microbiome following FMT for canine IBD. Here, we performed FMT in nine dogs with IBD using the fecal matter of healthy dogs and investigated the subsequent changes in the fecal microbiome and clinical signs. In three dogs, the fecal microbiome was examined by 16S rRNA sequencing. Fusobacteria were observed at a low proportion in dogs with IBD. However, the post-FMT microbiome became diverse and showed a significant increase in Fusobacteria proportion. Fusobacterium was detected in the nine dogs by quantitative polymerase chain reaction. The proportion of Fusobacterium in the post-FMT fecal microbiome was significantly increased (p<0.05). The changes in clinical signs (e.g., vomiting, diarrhea, and weight loss) were evaluated according to the canine inflammatory bowel disease activity index. The score of this index significantly decreased in all dogs (p<0.05) with improvements in clinical signs. These improvements were related to the changes in the proportion of microbes, particularly the increase in Fusobacterium. The dogs with IBD showed a lower proportion of Fusobacterium than healthy dogs. This suggests that a low proportion of Fusobacterium is a characteristic feature of canine IBD and that Fusobacterium is involved in this disease. The results of this study may help elucidate the pathogenesis of this disease and its association with Fusobacterium.

A double-edged sword: Role of butyrate in the oral cavity and the gut

Butyrate, a four-carbon short-chain fatty acid (SCFA), is a metabolite of anaerobic bacteria. Butyrate has primarily been described as an energy substance in the studies on the digestive tract. The multiple mechanisms of its protective function in the gut and on underlying diseases (including metabolic diseases, diseases of the nervous system, and osteoporosis) via interaction with intestinal epithelial cells and immune cells have been well documented. There are many butyrogenic bacteria in the oral cavity as well. As essential components of the oral microbiome, periodontal pathogens are also able to generate butyrate when undergoing metabolism. Considerable evidence has indicated that butyrate plays an essential role in the initiation and perpetuation of periodontitis. However, butyrate is considered to participate in the pro-inflammatory activities in periodontal tissue and the reactivation of latent viruses. In this review, we focused on the production and biological impact of butyrate in both intestine and oral cavity and explained the possible pathway of various diseases that were engaged by butyrate. Finally, we suggested two hypotheses, which may give a better understanding of the significantly different functions of butyrate in different organs (i.e., the expanded butyrate paradox).

High-Throughput Quantitative Top-Down Proteomics: Histone H4

Proteins physiologically exist as "proteoforms" that arise from one gene and acquire additional function by post-translational modifications (PTM). When multiple PTMs coexist on single protein molecules, top-down proteomics becomes the only feasible method of characterization; however, most top-down methods have limited quantitative capacity and insufficient throughput to truly address proteoform biology. Here we demonstrate that top-down proteomics can be quantitative, reproducible, sensitive, and high throughput. The proteoforms of histone H4 are well studied both as a challenging proteoform identification problem and due to their essential role in the regulation of all eukaryotic DNA-templated processes. Much of histone H4's function is obfuscated from prevailing methods due to combinatorial mechanisms. Starting from cells or tissues, after an optimized protein purification process, the H4 proteoforms are physically separated by on-line C3 chromatography, narrowly isolated in MS1 and sequenced with ETD fragmentation. We achieve more than 30 replicates from a single 35-mm tissue culture dish by loading 55 ng of H4 on column. Parallelization and automation yield a sustained throughput of 12 replicates per day. We achieve reproducible quantitation (average biological Pearson correlations of 0.89) of hundreds of proteoforms (about 200-300) over almost six orders of magnitude and an estimated LLoQ of 0.001% abundance. We demonstrate the capacity of the method to precisely measure well-established changes with sodium butyrate treatment of SUM159 cells. We show that the data produced by a quantitative top-down method can be amenable to parametric statistical comparisons and is capable of delineating relevant biological changes at the full proteoform level.

Probiotic treatment during neonatal age provides optimal protection against experimental asthma through the modulation of microbiota and T cells

The incidence of allergic diseases, which increased to epidemic proportions in developed countries over the last few decades, has been correlated with altered gut microbiota colonization. Although probiotics may play a critical role in the restoration of gut homeostasis, their efficiency in the control of allergy is controversial. Here, we aimed to investigate the effects of probiotic treatment initiated at neonatal or adult ages on the suppression of experimental ovalbumin (OVA)-induced asthma. Neonatal or adult mice were orally treated with probiotic bacteria and subjected to OVA-induced allergy. Asthma-like symptoms, microbiota composition and frequencies of the total CD4+ T lymphocytes and CD4+Foxp3+ regulatory T (Treg) cells were evaluated in both groups. Probiotic administration to neonates, but not to adults, was necessary and sufficient for the absolute prevention of experimental allergen-induced sensitization. The neonatally acquired tolerance, transferrable to probiotic-untreated adult recipients by splenic cells from tolerant donors, was associated with modulation of gut bacterial composition, augmented levels of cecum butyrate and selective accumulation of Treg cells in the airways. Our findings reveal that a cross-talk between a healthy microbiota and qualitative features inherent to neonatal T cells, especially in the Treg cell subset, might support the beneficial effect of perinatal exposure to probiotic bacteria on the development of long-term tolerance to allergens.

Anti-proliferative, pro-apoptotic and anti-oxidative activity of Lactobacillus and Bifidobacterium strains: A review of mechanisms and therapeutic perspectives

Lactobacillus and Bifidobacterium strains, their isolated constituents and substances that they secrete exert various anti-cancer actions, resulting from their anti-proliferative, pro-apoptotic and anti-oxidant properties. They can express and secrete anti-oxidant enzymes, bind reactive oxygen species, release small molecular weight anti-oxidants and chelate transition metals, preventing detrimental actions of many carcinogens. Lactobacillus and Bifidobacterium can interact with proteins regulating the cell cycle inhibiting proliferation of cancer cells, which often are intrinsically resistant to apoptosis. Lactobacilli and bifidobacteria can break this resistance through activation of pro-caspases and downregulation of the anti-apoptotic Bcl-2 and upregulation of pro-apoptotic Bax proteins. Anti-cancer effects of these bacteria can be also associated with their multi-pathways action in the microbiota. However, exact mechanism of their anti-cancer action is poorly known and needs further studies, which are justified by the important role of these bacteria in cancer biology as well as their potential preventive and therapeutic use.

Role of short-chain fatty acids in colonic inflammation, carcinogenesis, and mucosal protection and healing

Short-chain fatty acids (SCFAs), mainly acetate, propionate, and butyrate, produced by microbial fermentation of undigested food substances are believed to play a beneficial role in human gut health. Short-chain fatty acids influence colonic health through various mechanisms. In vitro and ex vivo studies show that SCFAs have anti-inflammatory and anticarcinogenic effects, play an important role in maintaining metabolic homeostasis in colonocytes, and protect colonocytes from external harm. Animal studies have found substantial positive effects of SCFAs or dietary fiber on colonic disease, but convincing evidence in humans is lacking. Most human intervention trials have been conducted in the context of inflammatory bowel disease. Only a limited number of those trials are of high quality, showing little or no favorable effect of SCFA treatment over placebo. Opportunities for future research include exploring the use of combination therapies with anti-inflammatory drugs, prebiotics, or probiotics; the use of prodrugs in the setting of carcinogenesis; or the direct application of SCFAs to improve mucosal healing after colonic surgery.

N-(2-Hydroxypropyl)methacrylamide Copolymer-9-Aminocamptothecin Conjugate: Colon-Specific Drug Delivery in Rats

An N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer conjugate containing 9-aminocamptothecin (9-AC) boundvia a spacer containing an aromatic azo bond and leucylalanine (P-Azo-Leu-Ala-9-AC) was synthesized. The in vivo pharmacokinetic profile after oral administration was examined in rats and comparedto free 9-AC. The aromatic azo bond of P-Azo-Leu-Ala-9-AC was stable in stomach and small intestine; the delivery of a large amount of intact conjugate to the colon was achieved. In the colon, the azoreductase activity first cleaved the azo bond followed by peptidase catalyzed cleavage of the leucylalanyl drug derivative resulting in the release of free 9-AC. However, the release rate from the conjugate was not fast enough to achieve high colon concentrations of free 9-AC. The results of the study suggest design features for the second generation of conjugates, including the use of a side-chain with a higher cleavage rate in the colon, combined with the incorporation of bioadhesion technology, to increase colon transit time.

Regulation of colonic epithelial butyrate transport: Focus on colorectal cancer

Highlights

Fermentation of the dietary fiber by intestinal microflora results in production of butyrate.Butyrate possesses anticarcinogenic effect at the colonic level.Three transporters (MCT1, SMCT1 and BCRP) regulate the intracellular concentration of BT in colonic epithelial cells.Changes in the expression of these transporters occur in colorectal cancer.

Abstract

Colorectal cancer (CRC) is one of the most common solid tumors worldwide. Consumption of dietary fiber is associated with a low risk of developing CRC. The fermentation of the dietary fiber by intestinal microflora results in production of butyrate (BT). This short-chain fatty acid is an important metabolic substrate in normal colonic epithelial cells and has important homeostatic functions at the colonic level. Because the cellular effects of BT (e.g. inhibition of histone deacetylases) are dependent on its intracellular concentration, knowledge on the mechanisms involved in BT membrane transport and its regulation seems particularly relevant. In this review, we will present the carrier-mediated mechanisms involved in BT membrane transport at the colonic epithelial level and their regulation, with an emphasis on CRC. Several xenobiotics known to modulate the risk for developing CRC are able to interfere with BT transport at the intestinal level. Thus, interference with BT transport certainly contributes to the anticarcinogenic or procarcinogenic effect of these compounds and these compounds may interfere with the anticarcinogenic effect of BT. Finally, we suggest that differences in BT transport between normal colonocytes and tumoral cells contribute to the "BT paradox" (the apparent opposing effect of BT in CRC cells and normal colonocytes).

Dietary manipulation of oncogenic microRNA expression in human rectal mucosa: a randomized trial

High red meat (HRM) intake is associated with increased colorectal cancer risk, while resistant starch is probably protective. Resistant starch fermentation produces butyrate, which can alter microRNA (miRNA) levels in colorectal cancer cells in vitro; effects of red meat and resistant starch on miRNA expression in vivo were unknown. This study examined whether a HRM diet altered miRNA expression in rectal mucosa tissue of healthy volunteers, and if supplementation with butyrylated resistant starch (HRM+HAMSB) modified this response. In a randomized cross-over design, 23 volunteers undertook four 4-week dietary interventions; an HRM diet (300 g/day lean red meat) and an HRM+HAMSB diet (HRM with 40 g/day butyrylated high amylose maize starch), preceded by an entry diet and separated by a washout. Fecal butyrate increased with the HRM+HAMSB diet. Levels of oncogenic mature miRNAs, including miR17-92 cluster miRNAs and miR21, increased in the rectal mucosa with the HRM diet, whereas the HRM+HAMSB diet restored miR17-92 miRNAs, but not miR21, to baseline levels. Elevated miR17-92 and miR21 in the HRM diet corresponded with increased cell proliferation, and a decrease in miR17-92 target gene transcript levels, including CDKN1A. The oncogenic miR17-92 cluster is differentially regulated by dietary factors that increase or decrease risk for colorectal cancer, and this may explain, at least in part, the respective risk profiles of HRM and resistant starch. These findings support increased resistant starch consumption as a means of reducing risk associated with an HRM diet.

Impact of whole grains on the gut microbiota: the next frontier for oats?

The gut microbiota plays important roles in proper gut function and can contribute to or help prevent disease. Whole grains, including oats, constitute important sources of nutrients for the gut microbiota and contribute to a healthy gut microbiome. In particular, whole grains provide NSP and resistant starch, unsaturated TAG and complex lipids, and phenolics. The composition of these constituents is unique in oats compared with other whole grains. Therefore, oats may contribute distinctive effects on gut health relative to other grains. Studies designed to determine these effects may uncover new human-health benefits of oat consumption.

Sodium butyrate induces growth inhibition and apoptosis in human prostate cancer DU145 cells by up-regulation of the expression of annexin A1

Background

Sodium butyrate, a histone deacetylase inhibitor, has emerged as a promising anticancer drug for multiple cancers. Recent studies have indicated that sodium butyrate could inhibit the progression of prostate cancer; however, the exact mechanism is still unclear. The aim of this study was to investigate the mechanism of sodium butyrate action in prostate cancer DU145 cells.

Methods

The inhibitory effects of NaB on cell growth were detected by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrrazolium bromide assay. Cell apoptosis was determined by flow cytometric analysis of DU145 cells stained with annexin V and PI. Hoechst 33258 and fluorescence microscopes were used to observe the nuclear morphology of DU145 cells after treatment with NaB. ANXA1 knockdown cells were established through transfection with ANXA1 siRNA. ANXA1 mRNA levels were measured by qRT-PCR. Bcl-2, Bax, ANXA1, ERK1/2 and pERK1/2 were detected by western blot.

Results

NaB significantly inhibited the growth and induction apoptosis of DU145 and PC3 cells in a dose-dependent manner. Expression of the anti-apoptosis gene Bcl-xl and Bcl-2 in DU145 cells are decreased and expression of the pro-apoptosis gene Bax and Bak increased after NaB treatment. Further studies have demonstrated that NaB up-regulated the expression of ANXA1 and that the tumor inhibition action of NaB was reduced markedly through knockdown of the ANXA1 gene in DU145 cells. Moreover, the siANXA1 cells showed that cell proliferation increased and cell apoptosis was induced by the inactivation of extracellular regulated kinase (ERK).

Conclusion

Our results support a significant correlation between NaB functions and ANXA1 expression in prostate cancer, and pave the way for further studying the molecular mechanism of NaB actions in cancers.

Intestinal health functions of colonic microbial metabolites: a review

This review tries to find a scientific answer on the following two questions: (1) to what extent do we understand the specific role of colonic microbial metabolites, especially short-chain fatty acids (SCFA), in maintaining the health status and prevention of diseases of the colon and the host; (2) to what extent can we influence or even control the formation of colonic microbial metabolites which are beneficial for the health status. The review focuses on the following topics: energy source, intestinal motility, defence barrier, oxidative stress with special attention for antiinflammatory and anti-carcinogen functions, and satiety. Also the risk of overproduction of SCFA is discussed. Reviewing the literature as present today, it can be concluded that physiological levels of SCFA are vital for the health and well-being of the host and that the presence of carbohydrates (dietary fibre, prebiotics) is essential to favour the metabolic activity in the direction of carbohydrate fermentation. For optimal motor activity of the ileum and colon, to regulate the physiological intestinal mobility, steadily fermentable dietary fibres or prebiotics are crucial. The formation of SCFA, especially propionate and butyrate, up to high physiological levels in the colon, much likely also contributes to the defence mechanisms of the intestinal wall. No final answer can be given yet about the role of SCFA in anti-inflammation and anti-carcinogenicity, but recently published research shows possible mechanisms in this field. The intake of prebiotics or specific dietary fibres promotes the formation of SCFA within the physiological range, and more or less specifically increases the levels of propionate and butyrate. In this way, they provide benefit to the host, especially the natural regulation of the digestive system.

Effect of sodium butyrate on DMH-induced small intestinal and large intestinal tumors in rats

AIM: To investigate whether 1,2-dimethylhydrazine (DMH) can induce small intestinal tumors in rats and to examine the effect of sodium butyrate on DMH-induced small intestinal and large intestinal tumors.

METHODS: Eighty male Wistar rats were randomly divided into four groups: DMH group, DMH + NaBt group, NaBt group, and control group. After 30-32 weeks, rats were euthanized with an overdose of intravenous pentobarbital (200 mg/kg). After laparotomy, the small intestine and large intestine were dissected. The location, number, shape and size of intestinal tumors were examined and recorded. All tissues were subjected to hematoxylin and eosin (H&E) staining to observe histological changes.

RESULTS: The mortality rate of rats was 60.00% (18/30) in the DMH group and 48.00% (12/25) in the DMH + NaBt group. The intestinal tumor incidence was 66. 67% (8/12) in the DMH group with four small intestinal tumors and twelve large intestinal tumors observed. Four rats beared a single tumor while other four rats had multiple tumors. The mean number of beared tumors was 1.33. The intestinal tumor incidence was 84.62% (11/13) in the DMH + NaBt group with three small intestinal tumors and sixty large intestinal tumors observed. Six rats beared a single tumor while other five rats had multiple tumors. The mean number of beared tumors was 1.46. There were no significant differences in tumor incidence and mean tumor number between te DMH + NaBt group and DMH group. The large intestinal tumor incidence was significantly higher than the small intestinal tumor incidence in both the DMH group and DMH + NaBt group (75.00% vs 25.00%, P < 0.05; 84.21% vs 15.79%, P < 0.01). There were significant differences in average tumor volume (37.50% vs 73.68%, P < 0.05) and tumor infiltration depth (43.75% vs 10.53%, P < 0.05) between the DMH group and DMH + NaBt group.

CONCLUSION: These results suggest that small intestinal tumors can also be induced by DMH. Sodium butyrate can increase tumor malignancy by increasing tumor volume and infiltration depth.

Histone deacetylase inhibition in colorectal cancer cells reveals competing roles for members of the oncogenic miR-17-92 cluster

Diet-derived butyrate, a histone deacetylase inhibitor (HDI), decreases proliferation and increases apoptosis in colorectal cancer (CRC) cells via epigenetic changes in gene expression. Other HDIs such as suberoylanilide hydroxamic acid (SAHA) and trichostatin A (TSA) have similar effects. This study examined the role of microRNAs (miRNAs) in mediating the chemo-protective effects of HDIs, and explored functions of the oncogenic miR-17-92 cluster. The dysregulated miRNA expression observed in HT29 and HCT116 CRC cells could be epigenetically altered by butyrate, SAHA and TSA. These HDIs decreased expression of miR-17-92 cluster miRNAs (P < 0.05), with a corresponding increase in miR-17-92 target genes, including PTEN, BCL2L11, and CDKN1A (P < 0.05). The decrease in miR-17-92 expression may be partly responsible for the anti-proliferative effects of HDIs, with introduction of miR-17-92 cluster miRNA mimics reversing this effect and decreasing levels of PTEN, BCL2L11, and CDKN1A (P < 0.05). The growth effects of HDIs may be mediated by changes in miRNA activity, with down-regulation of the miR-17-92 cluster a plausible mechanism to explain some of the chemo-protective effects of HDIs. Of the miR-17-92 cluster miRNAs, miR-19a and miR-19b were primarily responsible for promoting proliferation, while miR-18a acted in opposition to other cluster members to decrease growth. NEDD9 and CDK19 were identified as novel miR-18a targets and were shown to be pro-proliferative genes, with RNA interference of their transcripts decreasing proliferation in CRC cells. This is the first study to identify competing roles for miR-17-92 cluster members, in the context of HDI-induced changes in CRC cells.

In vitro fermentation of sugar beet arabino-oligosaccharides by fecal microbiota obtained from patients with ulcerative colitis to selectively stimulate the growth of Bifidobacterium spp. and Lactobacillus spp

The potential prebiotic properties of arabino-oligosaccharides (AOS) derived from sugar beet pulp was studied using mixed cultures of human fecal bacteria from patients with ulcerative colitis (UC), in remission or with active disease, and in healthy controls. These results were compared to those for fructo-oligosaccharides (FOS), which are known to have a prebiotic effect. Fermentation studies were carried out using a small-scale static batch system, and changes in the fecal microbial communities and metabolites were monitored after 24 h by quantitative real-time PCR and short-chain fatty acid analysis. With a few minor exceptions, AOS affected the communities similarly to what was seen for FOS. Quantitative real-time PCR revealed that Bifidobacterium spp. and Lactobacillus spp. were selectively increased after fermentation of AOS or FOS by fecal microbiota derived from UC patients. The stimulation of growth of Lactobacillus spp. and Bifidobacterium spp. was accompanied by a high production of acetate and hence a decrease of pH. The fermentation of AOS may help improve the inflammatory conditions in UC patients through stimulation of bacteria eliciting anti-inflammatory responses and through production of acetate. AOS may therefore represent a new prebiotic candidate for reduction of the risk of flare-ups in UC patients. However, human trials are needed to confirm a health-promoting effect.

Intrinsic mitochondrial membrane potential and associated tumor phenotype are independent of MUC1 over-expression

We have established previously that minor subpopulations of cells with stable differences in their intrinsic mitochondrial membrane potential (Δψm) exist within populations of mammary and colonic carcinoma cells and that these differences in Δψm are linked to tumorigenic phenotypes consistent with increased probability of participating in tumor progression. However, the mechanism(s) involved in generating and maintaining stable differences in intrinsic Δψm and how they are linked to phenotype are unclear. Because the mucin 1 (MUC1) oncoprotein is over-expressed in many cancers, with the cytoplasmic C-terminal fragment (MUC1 C-ter) and its integration into the outer mitochondrial membrane linked to tumorigenic phenotypes similar to those of cells with elevated intrinsic Δψm, we investigated whether endogenous differences in MUC1 levels were linked to stable differences in intrinsic Δψm and/or to the tumor phenotypes associated with the intrinsic Δψm. We report that levels of MUC1 are significantly higher in subpopulations of cells with elevated intrinsic Δψm derived from both mammary and colonic carcinoma cell lines. However, using siRNA we found that down-regulation of MUC1 failed to significantly affect either the intrinsic Δψm or the tumor phenotypes associated with increased intrinsic Δψm. Moreover, whereas pharmacologically mediated disruption of the Δψm was accompanied by attenuation of tumor phenotype, it had no impact on MUC1 levels. Therefore, while MUC1 over-expression is associated with subpopulations of cells with elevated intrinsic Δψm, it is not directly linked to the generation or maintenance of stable alterations in intrinsic Δψm, or to intrinsic Δψm associated tumor phenotypes. Since the Δψm is the focus of chemotherapeutic strategies, these data have important clinical implications in regard to effectively targeting those cells within a tumor cell population that exhibit stable elevations in intrinsic Δψm and are most likely to contribute to tumor progression.

Stable differences in intrinsic mitochondrial membrane potential of tumor cell subpopulations reflect phenotypic heterogeneity

Heterogeneity among cells that constitute a solid tumor is important in determining disease progression. Our previous work established that, within a population of metastatic colonic tumor cells, there are minor subpopulations of cells with stable differences in their intrinsic mitochondrial membrane potential (ΔΨm), and that these differences in ΔΨm are linked to tumorigenic phenotype. Here we expanded this work to investigate primary mammary, as well as colonic, tumor cell lines. We show that within a primary mammary tumor cell population, and in both primary and metastatic colonic tumor cell populations, there are subpopulations of cells with significant stable variations in intrinsic ΔΨm. In each of these 3 tumor cell populations, cells with relatively higher intrinsic ΔΨm exhibit phenotypic properties consistent with promotion of tumor cell survival and expansion. However, additional properties associated with invasive potential appear in cells with higher intrinsic ΔΨm only from the metastatic colonic tumor cell line. Thus, it is likely that differences in the intrinsic ΔΨm among cells that constitute primary mammary tumor populations, as well as primary and metastatic colonic tumor populations, are markers of an acquired tumor phenotype which, within the context of the tumor, influence the probability that particular cells will contribute to disease progression.

Butyrate-rich colonic microenvironment is a relevant selection factor for metabolically adapted tumor cells

The short chain fatty acid (SCFA) butyrate is a product of colonic fermentation of dietary fibers. It is the main source of energy for normal colonocytes, but cannot be metabolized by most tumor cells. Butyrate also functions as a histone deacetylase (HDAC) inhibitor to control cell proliferation and apoptosis. In consequence, butyrate and its derived drugs are used in cancer therapy. Here we show that aggressive tumor cells that retain the capacity of metabolizing butyrate are positively selected in their microenvironment. In the mouse xenograft model, butyrate-preselected human colon cancer cells gave rise to subcutaneous tumors that grew faster and were more angiogenic than those derived from untreated cells. Similarly, butyrate-preselected cells demonstrated a significant increase in rates of homing to the lung after intravenous injection. Our data showed that butyrate regulates the expression of VEGF and its receptor KDR at the transcriptional level potentially through FoxM1, resulting in the generation of a functional VEGF:KDR autocrine growth loop. Cells selected by chronic exposure to butyrate express higher levels of MMP2, MMP9, α2 and α3 integrins, and lower levels of E-cadherin, a marker for epithelial to mesenchymal transition. The orthotopic model of colon cancer showed that cells preselected by butyrate are able to colonize the animals locally and at distant organs, whereas control cells can only generate a local tumor in the cecum. Together our data shows that a butyrate-rich microenvironment may select for tumor cells that are able to metabolize butyrate, which are also phenotypically more aggressive.

Unveiling an abundant core microbiota in the human adult colon by a phylogroup-independent searching approach

The potential presence of widespread and stable bacterial core phylogroups in the human colon has promoted considerable attention. Despite major efforts, no such phylogroups have yet been identified. Therefore, using a novel phylogroup- and tree-independent approach, we present a reanalysis of 1,114,722 V2 region and 71,550 near full-length 16S rRNA sequences from a total of 210 human beings, with widespread geographic origin, ethnic background and diet, in addition to a wide range of other mammals. We found two highly prevalent core phylogroups (cores 1 and 2), belonging to the clostridial family Lachnospiraceae. These core phylogroups showed a log-normal distribution among human individuals, while non-core phylogroups showed more skewed distributions towards individuals with low levels compared with the log-normal distribution. Molecular clock analyses suggest that core 2 co-evolved with the radiation of vertebrates, while core 1 co-evolved with the mammals. Taken together, the stability, prevalence and potential functionality support the fact that the identified core phylogroups are pivotal in maintaining gut homeostasis and health.

Blueberry husks, rye bran and multi-strain probiotics affect the severity of colitis induced by dextran sulphate sodium

OBJECTIVE

The enteric microbiota is a pivotal factor in the development of intestinal inflammation in humans but probiotics, dietary fibres and phytochemicals can have anti-inflammatory effects. The aim of this study was to evaluate the therapeutic effect of multi-strain probiotics and two conceivable prebiotics in an experimental colitis model.

MATERIAL AND METHODS

Sprague-Dawley rats were fed a fibre-free diet alone or in combination with Lactobacillus crispatus DSM 16743, L. gasseri DSM 16737 and Bifidobacterium infantis DSM 15158 and/or rye bran and blueberry husks. Colitis was induced by 5% dextran sulphate sodium (DSS) given by oro-gastric tube. Colitis severity, inflammatory markers, gut-load of lactobacilli and Enterobacteriaceae, bacterial translocation and formation of carboxylic acids (CAs) were analysed.

RESULTS

The disease activity index (DAI) was lower in all treatment groups. Viable counts of Enterobacteriaceae were reduced and correlated positively with colitis severity, while DAI was negatively correlated with several CAs, e.g. butyric acid. The addition of probiotics to blueberry husks lowered the level of caecal acetic acid and increased that of propionic acid, while rye bran in combination with probiotics increased caecal CA levels and decreased distal colonic levels. Blueberry husks with probiotics reduced the incidence of bacterial translocation to the liver, colonic levels of myeloperoxidase, malondialdehyde and serum interleukin-12. Acetic and butyric acids in colonic content correlated negatively to malondialdehyde.

CONCLUSIONS

A combination of probiotics and blueberry husks or rye bran enhanced the anti-inflammatory effects compared with probiotics or dietary fibres alone. These combinations can be used as a preventive or therapeutic approach to dietary amelioration of intestinal inflammation.

In vitro studies on the inhibition of colon cancer by butyrate and carnitine

OBJECTIVE

Epidemiologic studies support an association between diet and the incidence of colorectal cancer. Butyrate, a short-chain fatty acid present in dietary fiber and dairy products, is a potential anticarcinogenic compound. We previously showed that carnitine can enhance the bioavailability of butyrate in vivo. In the present study, we evaluated the effects of butyrate alone and in combination with carnitine on colon cancer cells in vitro, examining proliferation and apoptosis and the molecular mechanisms by which these nutrients may inhibit colon cancer.

METHODS

Caco-2 cells, a well-established cell model, were incubated with butyrate (2.5-20mM) with or without carnitine (10mM) for various incubation periods. Proliferation was measured by incorporation of (3)H-thymidine, and apoptosis was detected using flow cytometry, and then confirmed by analyzing the presence of single-strand DNA breaks typical of apoptotic cells. Prostaglandin E(2) production was assayed and Bcl-2 and cyclo-oxygenase-2 expressions were examined by western blotting.

RESULTS

Butyrate and carnitine inhibited Caco-2 cell proliferation (P<0.05) and induced apoptosis (P<0.05). Prostaglandin E(2) production was decreased in treated Caco-2 cells. At the molecular level, the expression of proapoptotic Bax and Bak proteins were increased in cells incubated with butyrate and carnitine, whereas expression of antiapoptotic Bcl-x(L) was decreased. Cyclo-oxygenase-2 expression was decreased in cells incubated with butyrate and carnitine.

CONCLUSIONS

Butyrate and carnitine inhibit human colon carcinoma cell proliferation and induce apoptosis in human colon carcinoma cells. This is accompanied by an appreciable alteration of the Bax-to-Bcl-x(L) and Bak-to-Bcl-x(L) ratios in favor of apoptosis. This study provides a scientific rationale to study the effects of carnitine and butyrate in colon cancer in vivo.

HDAC inhibitors in models of inflammation-related tumorigenesis

Histone deacetylase (HDAC) inhibitors have been described in detail for their anti-proliferative potency. Recently, an anti-inflammatory property was characterized in vitro and in vivo. This dual efficacy of HDAC inhibitors is highly attractive, since chronic inflammations such as ulcerative colitis are associated with an increased risk of developing carcinomas. Additionally, in models of colitis and inflammation-induced tumorigenesis inflammation as well as tumor development was significantly inhibited by HDAC inhibitor treatment. The mechanisms involved reach beyond the simple regulation of histone acetylation and deacetylation. The currently known key target structures and mechanisms mediating this dual effect will be discussed in this review.

Nitric oxide as a target of complementary and alternative medicines to prevent and treat inflammation and cancer

Nitric oxide (NO) and associated reactive nitrogen species (RNS) are involved in many physiological functions. There has been an ongoing debate to whether RNS can inhibit or perpetuate chronic inflammation and associated carcinogenesis. Although the final outcome depends on the genetic make-up of its target, the surrounding microenvironment, the activity and localization of nitric oxide synthase (NOS) isoforms, and overall levels of NO/RNS, evidence is accumulating that in general, RNS drive inflammation and cancers associated with inflammation. To this end, many complementary and alternative medicines (CAMs) that work in chemoprevention associated with chronic inflammation, are inhibitors of excessive NO observed in inflammatory conditions. Here, we review recent literature outlining a role of NO/RNS in chronic inflammation and cancer, and point toward NO as one of several targets for the success of CAMs in treating chronic inflammation and cancer associated with this inflammation.

Review article: the role of butyrate on colonic function

BACKGROUND

Butyrate, a short-chain fatty acid, is a main end-product of intestinal microbial fermentation of mainly dietary fibre. Butyrate is an important energy source for intestinal epithelial cells and plays a role in the maintenance of colonic homeostasis.

AIM

To provide an overview on the present knowledge of the bioactivity of butyrate, emphasizing effects and possible mechanisms of action in relation to human colonic function.

METHODS

A PubMed search was performed to select relevant publications using the search terms: 'butyrate, short-chain fatty acid, fibre, colon, inflammation, carcinogenesis, barrier, oxidative stress, permeability and satiety'.

RESULTS

Butyrate exerts potent effects on a variety of colonic mucosal functions such as inhibition of inflammation and carcinogenesis, reinforcing various components of the colonic defence barrier and decreasing oxidative stress. In addition, butyrate may promote satiety. Two important mechanisms include the inhibition of nuclear factor kappa B activation and histone deacetylation. However, the observed effects of butyrate largely depend on concentrations and models used and human data are still limited.

CONCLUSION

Although most studies point towards beneficial effects of butyrate, more human in vivo studies are needed to contribute to our current understanding of butyrate-mediated effects on colonic function in health and disease.

ATM phosphorylates ZBP-89 at Ser202 to potentiate p21waf1 induction by butyrate

Histone deacetylase inhibitors (HDACi) induce growth arrest and differentiation, particularly in the colon where they are potential chemotherapeutic agents. A key mediator of HDACi action is the cyclin dependent kinase (CDK) inhibitor p21(waf1). HDACi treatment of colonic cells promotes the formation of an ATM/ZBP-89/p300 complex on p21(waf1) proximal promoter, and this multi-molecular complex plays an important role in HDACi induction of p21(waf1) expression in vitro and mucosal protection in vivo. Here we found that ZBP-89 is phosphorylated by ATM kinase in vitro and in vivo. Disruption of the ATM phosphorylation motif (202)SQ within the zinc finger domain of ZBP-89 attenuated its ability to enhance p21(waf1) activation by butyrate. Moreover, disruption of the ATM phosphorylation site abrogated the ability of ZBP-89 to potentiate butyrate induction of endogenous p21(waf1) expression. These results demonstrate that ATM phosphorylation of ZBP-89 contributes to HDACi induction of p21(waf1) gene expression.

A novel cell type-specific role of p38alpha in the control of autophagy and cell death in colorectal cancer cells

Cancer develops when molecular pathways that control the fine balance between proliferation, differentiation, autophagy and cell death undergo genetic deregulation. The prospects for further substantial advances in the management of colorectal cancer reside in a systematic genetic and functional dissection of these pathways in tumor cells. In an effort to evaluate the impact of p38 signaling on colorectal cancer cell fate, we treated HT29, Caco2, Hct116, LS174T and SW480 cell lines with the inhibitor SB202190 specific for p38alpha/beta kinases. We report that p38alpha is required for colorectal cancer cell homeostasis as the inhibition of its kinase function by pharmacological blockade or genetic inactivation causes cell cycle arrest, autophagy and cell death in a cell type-specific manner. Deficiency of p38alpha activity induces a tissue-restricted upregulation of the GABARAP gene, an essential component of autophagic vacuoles and autophagosomes, whereas simultaneous inhibition of autophagy significantly increases cell death by triggering apoptosis. These data identify p38alpha as a central mediator of colorectal cancer cell homeostasis and establish a rationale for the evaluation of the pharmacological manipulation of the p38alpha pathway in the treatment of colorectal cancer.

Recruitment of ataxia-telangiectasia mutated to the p21(waf1) promoter by ZBP-89 plays a role in mucosal protection

BACKGROUND & AIMS

Histone deacetylase inhibitors (HDACi) induce growth arrest, apoptosis, and differentiation, particularly in colon cancer cells where they are potential chemopreventive agents. HDACi induction of the cyclin-dependent kinase inhibitor p21(waf1) has been shown to require ataxia-telangiectasia mutated (ATM). Nevertheless, how ATM participates in p21(waf1) gene expression has not been defined.

METHODS

In vivo protein complexes forming in response to butyrate were studied using co-immunoprecipitation and mass spectroscopy. DNA elements in the p21(waf1) promoter were analyzed in vivo by chromatin immunoprecipitation and in vitro DNA affinity precipitation assays. The expression of p21(waf1) was analyzed by immunoblots and reporter assays.

RESULTS

Reduction of ZBP-89 or ATM with small interfering RNAs blocked HDACi-induced p21(waf1) expression. Chromatin immunoprecipitation and DNA affinity precipitation assays showed that both ZBP-89 and ATM are recruited to the GC-rich DNA elements of the p21(waf1) promoter with HDACi treatment. Co-immunoprecipitation revealed that ATM associates with ZBP-89 in an HDACi-dependent manner. Serial deletions revealed that ATM interacts with both the N-terminal and DNA binding domains of ZBP-89. Moreover, we found that immunodepletion of ZBP-89 prevented recruitment of ATM to the p21(waf1) promoter in vitro. Silencing of ZBP-89 expression blocked HDACi-induced phosphorylation of ATM(Ser1981) and p53(Ser15). ATM(Ser1981) phosphorylation in the colons of mutant mice expressing an N-terminally truncated form of ZBP-89 was not observed after ingestion of dextran sodium sulfate and correlated with exacerbation of the mucosal injury.

CONCLUSIONS

ZBP-89 interacts with ATM in a butyrate-dependent manner and is essential for colonic homeostasis in the setting of acute mucosal injury.

The effects of short-chain fatty acids on colon epithelial proliferation and survival depend on the cellular phenotype

PURPOSE

The short-chain fatty acids (SCFA) are produced via anaerobic bacterial fermentation of dietary fiber within the colonic lumen. Among them, butyrate is thought to protect against colon carcinogenesis. However, few studies analyze the effects of butyrate, and other SCFA, on normal epithelial cells and on epithelial regeneration during disease recovery. Since there are controversial in vitro studies, we have explored the effects of SCFA on different biological processes.

METHODS

We used both tumoral (HT-29) and normal (FHC) epithelial cells at different phenotypic states. In addition, we analyzed the in vivo activity of soluble dietary fiber and SCFA production in the proliferation rate and regeneration of intestinal epithelial cells.

RESULTS

The effect of butyrate on epithelial cells depends on the phenotypic cellular state. Thus, in nondifferentiated, high proliferative adenocarcinoma cells, butyrate significantly inhibited proliferation while increased differentiation and apoptosis, whereas other SCFA studied did not. However, in normal cells or in differentiated cultures as well as in in vivo studies, the normal proliferation and regeneration of damaged epithelium is not affected by butyrate or SCFA exposure.

CONCLUSION

Although butyrate could exert antiproliferative effects in tumor progression, its production is safe and without consequences for the normal epithelium growth.

Does butyrate protect from colorectal cancer?

Butyrate, the four-carbon fatty acid, is formed in the human colon by bacterial fermentation of carbohydrates (including dietary fiber), and putatively suppresses colorectal cancer (CRC). Butyrate has diverse and apparently paradoxical effects on cellular proliferation, apoptosis and differentiation that may be either pro-neoplastic or anti-neoplastic, depending upon factors such as the level of exposure, availability of other metabolic substrate and the intracellular milieu. In humans, the relationship between luminal butyrate exposure and CRC has been examined only indirectly in case-control studies, by measuring fecal butyrate concentrations, although this may not accurately reflect effective butyrate exposure during carcinogenesis. Perhaps not surprisingly, results of these investigations have been mutually contradictory. The direct effect of butyrate on tumorigenesis has been assessed in a number of in vivo animal models, which have also yielded conflicting results. In part, this may be explained by methodological differences in the amount and route of butyrate administration, which are likely to significantly influence delivery of butyrate to the distal colon. Nonetheless, there appears to be some evidence that delivery of an adequate amount of butyrate to the appropriate site protects against early tumorigenic events. Future study of the relationship between butyrate and CRC in humans needs to focus on risk stratification and the development of feasible strategies for butyrate delivery.

The intrinsic mitochondrial membrane potential of colonic carcinoma cells is linked to the probability of tumor progression

We subcloned cell lines from SW620 cells establishing that, despite the dynamic nature of the mitochondrial membrane potential (Deltapsim), there are significant and stable differences in the intrinsic Deltapsim among cells within an in vitro population of human colonic carcinoma cells. Whereas more dramatic differences in Deltapsim would likely perturb essential mitochondrial functions, the differences in Deltapsim of the subclones did not affect steady-state reactive oxygen species levels, electron transport activity, or cellular viability and growth rates. However, the differences in intrinsic Deltapsim had a significant effect on the tumorigenic behavior of the cells. Subcloned cell lines with higher Deltapsim were more likely to exhibit elevated steady-state levels of vascular endothelial growth factor and matrix metalloproteinase 7, and increased invasive behavior (properties associated with tumor progression), than cells with lower intrinsic Deltapsim, whereas cells with lower Deltapsim were more likely to respond to the chemopreventive activities of butyrate, including Deltapsim dissipation, growth arrest, and apoptosis, than cells with higher Deltapsim. Therefore, these data establish that the probability for tumor development and progression is linked to stable differences in the intrinsic Deltapsim of colonic epithelial cells.

The influence of specific luminal factors on the colonic epithelium: high-dose butyrate and physical changes suppress early carcinogenic events in rats

INTRODUCTION

Although luminal delivery of butyrate is one putative mechanism by which biology of the colonic epithelium might be influenced by changes in luminal contents, there is a paucity of supportive cause-effect evidence. This study aimed to directly establish whether distal colonic butyrate delivery is able to alter the response of the distal colonic epithelium to a carcinogen.

METHODS

Groups of male Sprague-Dawley rats with chronically intubated colons received infusions of 80 mM butyrate or 0.9 percent saline into distal colon two or five times daily. Three weeks after exposure to azoxymethane (15 mg/kg subcutaneously), the density of aberrant crypts was quantified in distal colon.

RESULTS

Infusions of 0.5 ml twice daily, whether containing saline or butyrate, decreased the number of aberrant crypt foci by 45 percent compared with rats receiving no infusions (P = 0.004, analysis of variance). Similar results were obtained when infusions were restricted to the post-initiation phase. When infusions were increased to 1 ml five times daily, saline infusions similarly suppressed aberrant crypt formation (38 percent), but butyrate infusions suppressed it to a greater degree (by 64 percent; P = 0.02 compared with saline infusion, t-test).

CONCLUSIONS

High levels of butyrate delivery to the distal colonic lumen alter the epithelial response to a carcinogen in otherwise healthy rats. This finding directly supports the notion that the effects of butyrate on cells in vitro do occur in vivo provided a sufficient dose is delivered. The effect of infusion of liquid per se on the epithelial response highlights the potential impact physical changes alone can have on the colonic epithelium.

Butyrate-induced differentiation of colon cancer cells is PKC and JNK dependent

Butyric acid, a short-chain fatty acid physiologically present in human large gut, is derived from bacterial fermentation of complex carbohydrates. It has been shown to reduce the growth and motility of colon cancer cell lines and to induce cell differentiation and apoptosis. Apoptosis is considered a result of normal colonocyte terminal differentiation in vivo. The aim of this study was to characterize the cellular mechanisms regulating differentiation of colon cancer cells stimulated with sodium butyrate (NaB). The two human colon cancer cell lines Caco-2 and HT-29 were treated with NaB at physiologically relevant concentrations. Alkaline phosphatase (ALP) activity, a marker of colonocyte differentiation, was increased 48 hr after treatment with 1 mM NaB. Higher doses of NaB (5 and 10 mM) induced apoptosis of the cells and failed to stimulate the colonocyte differentiation. Therefore, we assumed that butyrate augments cell differentiation and induces apoptosis, acting via various intracellular mechanisms, and butyrate-mediated programmed cell death cannot be considered a consequence of colonocyte terminal differentiation. The effect of NaB on ALP activity was significantly attenuated in the presence of inhibitors of protein kinase C and JNK. Inhibition of MEK-ERK signal transduction pathways augmented the impact of butyrate on colonocyte differentiation. These results suggest that butyrate could influence the colonocyte differentiation via modulation of the activity of cellular protein kinases and signal transduction.

Expression profiling of CC531 colon carcinoma cells reveals similar regulation of beta-catenin target genes by both butyrate and aspirin

The CC531 cell line has been widely used to study different aspects of tumor growth and metastasis and provides an excellent experimental platform to develop novel antitumor strategies. To characterize the CC531 model at the molecular level, we screened for mutations in genes covering important signal-transduction pathways that are known to play major roles during colon carcinogenesis, the wnt and the ki-ras signaling pathways. We found both a prototypic beta-catenin (Ctnnb1) mutation (Thr(41)Ile) and a ki-ras (G12D) mutation, providing unambiguous evidence for the constitutive activation of these pathways in CC531 cells. We further established comprehensive gene expression profiles of CC531 cells and investigated the molecular response to 2 antitumor drugs, butyrate and aspirin. Using oligonucleotide microarrays, we screened the expression levels of 7,700 genes and identified a total of 398 genes whose expression was significantly changed upon treatment with butyrate. When using aspirin, 121 genes were significantly altered. Interestingly, 36 genes were regulated by both butyrate and aspirin and 35 of them were regulated in the same direction. We found 7 differentially expressed genes, cyclin D1, cyclin E, c-myc, Fosl1, c-fos, Cd44 and follistatin, which are known targets of the beta-catenin and/or the ras pathway. In all cases, butyrate and aspirin reversed the changes in expression normally found in response to active signaling of these oncogenic pathways. The microarray data are available (http://ncbi.nlm.nih.gov/geo/).

Sodium Butyrate Inhibits Cell Growth and Stimulates p21WAF1/CIP1 Protein in Human Colonic Adenocarcinoma Cells Independently of p53 Status

Butyric acid, one of the short-chain fatty acids produced by microbial fermentation in the colon, exhibits antiproliferative activities in various cancer cell lines. The initial objective of the study was to assess whether the effect of sodium butyrate (NaB) on cell growth differed by p53 status of the cells. Four human colorectal adenocarcinoma cell lines were used: HT29 (p53 point mutation), Caco2 (p53 truncation), LS513 (p53 wild type), and Lovo (p53 wild type). NaB significantly inhibited cell growth in all four cell lines. NaB arrested HT29 and LS513 cells in G0/G1 and Caco2 and Lovo in G2-phase. A second objective was to determine whether NaB similarly affected the cyclin-dependent kinase inhibitor, p21WAF1/CIP1. In all cell lines, p21 mRNA levels were immediately elevated after NaB exposure, and p21 protein levels were increased within 6 h. NaB increased p21 promoter activity in both Caco2 and Lovo, suggesting p53 independence. NaB did not influence p21 mRNA stability. Although three DNase I hypersensitivity sites were identified in the region of the p21 gene, induction of p21 mRNA by NaB was not accompanied by relaxation of the chromatin in the region of the p21 gene.

Differential modulation of enterocyte-like Caco-2 cells after exposure to short-chain fatty acids

The response of intestinal epithelial cells to short-chain fatty acids, which are increasingly used as food additives, was investigated. Human small intestinal epithelial cell model Caco-2 cells were exposed to formate, propionate and butyrate to assess their effect on cellular growth, metabolism, differentiation and protection against bacteria. The Caco-2 cells were entirely grown in the different short-chain fatty acids and respective growth patterns were determined. Differentiated cells were exposed to 0-20 mM short-chain fatty acids for 48 h and changes in DNA, RNA, (glyco)protein syntheses, sucrase isomaltase activity, transepithelial electrical resistance and protection against Salmonella enteritidis were measured. The short-chain fatty acids, altered linearly and differentially the growth pattern ranging from stimulation by formate to inhibition by butyrate. Formate inhibited cellular metabolism. Low concentrations of up to 5 mM propionate and 2 mM butyrate stimulated metabolism, while higher doses were inhibitory. Formate had no effect on sucrase isomaltase enzyme activity and transepithelial electrical resistance, whereas propionate and butyrate increased these markers of differentiation. Infection with S. enteritidis did not benefit from the short-chain fatty acid-induced transepithelial electrical resistance. It is concluded that formate, propionate and butyrate selectively and differentially modulate growth characteristics, cellular metabolism, sucrase isomaltase activity and transepithelial electrical resistance in a concentration- and carbon atom-related fashion. The short-chain fatty acid-induced transepithelial electrical resistance does not confer protection against S. enteritidis.

The effects of short-chain fatty acids on human colon cancer cell phenotype are associated with histone hyperacetylation

The short-chain fatty acid (SCFA) butyrate is produced via anaerobic bacterial fermentation within the colon and is thought to be protective in regard to colon carcinogenesis. Although butyrate (C4) is considered the most potent of the SCFA, a variety of other SCFA also exist in the colonic lumen. Butyrate is thought to exert its cellular effects through the induction of histone hyperacetylation. We sought to determine the effects of a variety of the SCFA on colon carcinoma cell growth, differentiation and apoptosis. HT-29 or HCT-116 (wild-type and p21-deleted) cells were treated with physiologically relevant concentrations of various SCFA, and histone acetylation state was assayed by acid-urea-triton-X gel electrophoresis and immunoblotting. Growth and apoptotic effects were studied by flow cytometry, and differentiation effects were assessed using transient transfections and Northern blotting. Propionate (C3) and valerate (C5) caused growth arrest and differentiation in human colon carcinoma cells. The magnitude of their effects was associated with a lesser degree of histone hyperacetylation compared with butyrate. Acetate (C2) and caproate (C6), in contrast, did not cause histone hyperacetylation and also had no appreciable effects on cell growth or differentiation. SCFA-induced transactivation of the differentiation marker gene, intestinal alkaline phosphatase (IAP), was blocked by histone deacetylase (HDAC), further supporting the critical link between SCFA and histones. Butyrate also significantly increased apoptosis, whereas the other SCFA studied did not. The growth arrest induced by the SCFA was characterized by an increase in the expression of the p21 cell-cycle inhibitor and down-regulation of cyclin B1 (CB1). In p21-deleted HCT-116 colon cancer cells, the SCFA did not alter the rate of proliferation. These data suggest that the antiproliferative, apoptotic and differentiating properties of the various SCFA are linked to the degree of induced histone hyperacetylation. Furthermore, SCFA-mediated growth arrest in colon carcinoma cells requires the p21 gene.

Molecular changes in the expression of human colonic nutrient transporters during the transition from normality to malignancy

Healthy colonocytes derive 60-70% of their energy supply from short-chain fatty acids, particularly butyrate. Butyrate has profound effects on differentiation, proliferation and apoptosis of colonic epithelial cells by regulating expression of various genes associated with these processes. We have previously shown that butyrate is transported across the luminal membrane of the colonic epithelium via a monocarboxylate transporter, MCT1. In this paper, using immunohistochemistry and in situ hybridisation histochemistry, we have determined the profile of MCT1 protein and mRNA expression along the crypt to surface axis of healthy human colonic tissue. There is a gradient of MCT1 protein expression in the apical membrane of the cells along the crypt-surface axis rising to a peak in the surface epithelial cells. MCT1 mRNA is expressed along the crypt-surface axis and is most abundant in cells lining the crypt. Analysis of healthy colonic tissues and carcinomas using immunohistochemistry and Western blotting revealed a significant decline in the expression of MCT1 protein during transition from normality to malignancy. This was reflected in a corresponding reduction in MCT1 mRNA expression, as measured by Northern analysis. Carcinoma samples displaying reduced levels of MCT1 were found to express the high affinity glucose transporter, GLUT1, suggesting that there is a switch from butyrate to glucose as an energy source in colonic epithelia during transition to malignancy. The expression levels of MCT1 in association with GLUT1 could potentially be used as determinants of the malignant state of colonic tissue.

Modulation of HMG-N2 binding to chromatin by butyrate-induced acetylation in human colon adenocarcinoma cells

Butyrate, a short chain fatty acid (SCFA), is generated by anaerobic fermentation of undigested carbohydrates within the colon. Butyrate enhances acetylation of core histones, a process directly linked to the formation of active chromatin and gene expression. However, additional chromatin components also contribute to the formation of transcriptionally active chromatin. The high mobility group protein N2 (HMG-N2), a nonhistone protein, is involved in chromatin structure modulation. We examined the effects of butyrate on HMG-N2 expression, hyperacetylation and chromatin binding. HT29 human adenocarcinoma cells were incubated with butyrate. Levels of HMG-N2 mRNA and of total or acetylated HMG-N2 protein were analyzed. Protein dynamics were investigated with transfected cells expressing HMG-N2-EGFP fusion proteins. Treatment of HT29 cells with butyrate led to significant hyperacetylation of HMG-N2. Levels of HMG-N2 protein remained unchanged. Northern blot analysis revealed a significant reduction in HMG-N2 mRNA levels after treatment with butyrate. Analysis of HMG-N2-EGFP transfected HT29 cells demonstrated that butyrate treatment changes the binding properties of HMG-N2-EGFP to chromatin. In addition, butyrate treatment resulted in solubilization of endogenous acetylated HMG-N2 into the supernatant of permeabilized cells. We demonstrate that butyrate treatment is associated with hyperacetylation of HMG-N2 protein in HT29 cells. The modulation of this nonhistone chromatin protein resulted in altered binding properties to chromatin. This may represent an additional step in changing chromatin structure and composition with subsequent consequences for transcription and gene expression. Modulation of nonhistone chromatin proteins, like the ubiquitous HMG-N2 proteins, may be partly responsible for the wide range of butyrate-associated effects.

Dietary fiber and colorectal neoplasia

PURPOSE

Dietary fiber has been implicated in colorectal neoplasia, despite conflicting evidence. This is a review of the currently available data on the role of dietary fiber in colorectal carcinogenesis.

METHODS

A literature search was conducted using the MEDLINE database. All case-control, longitudinal, and randomized, controlled studies published in English between 1988 and 2000 were identified, as were animal model studies in the period 1986 to 2000. Data from the various studies were tabulated and systematically analyzed, with particular emphasis on the effect of dietary fiber on tumor incidence and luminal parameters such as short chain fatty acids.

RESULTS

Epidemiologic correlation studies show a high intake of dietary fiber to be associated with a lower risk of colorectal neoplasia. Thirteen of the 24 case-control studies reviewed demonstrated a protective effect of dietary fiber against colorectal neoplasia, and 16 showed a protective effect of vegetables or vegetable fiber. On the other hand, of 13 longitudinal studies in various cohorts, only 3 demonstrated a protective effect of fiber and 4 a protective effect of vegetables or vegetable fiber. The five published randomized, controlled trials all investigated the effect of increased fiber intake on short-term adenoma recurrence; however, none showed any significant protective effect. Among 19 experimental studies in animal models, 15 showed a protective effect of fiber against tumor induction compared with controls. Animal studies also showed that poorly fermentable fibers (e.g., wheat bran and cellulose) were more protective than soluble fibers (e.g., guar gum and oat bran), which sometimes enhanced carcinogenesis. No clear correlation was found between luminal pH or short chain fatty acids and tumor induction.

CONCLUSIONS

On the basis of current data, there is little evidence to support the use of dietary fiber supplements to reduce the risk of colorectal neoplasia. Lifelong and early exposure may be important but are difficult to study. Other risk factors interact with the effects of dietary fiber.

Are dietary fiber-induced alterations in colonic epithelial cell proliferation predictive of fiber's effect on colon cancer?

Alterations in cell proliferation of the colon have been observed as a result of changes in amount and type of dietary fiber and in relation to risk of developing colon cancer. Although some human observational and intervention studies contribute to the database, most information results from experiments on rodents. Because of numerous contradictory reports linking dietary fiber, cell proliferation, and colon cancer, we undertook a critical review of existing methods in an attempt to explain the inconsistencies. Although there may be some individual types of dietary fiber that protect against chemically induced colon cancer, dietary fiber as a single entity does not appear to afford any consistent protection. Because of significant differences in experimental protocols among laboratories, it is not yet possible to state with certainty that increases in cell proliferation, induced by fiber consumption, are predictive of increased tumorigenesis. Much of what has been observed and interpreted as elevation of risk may simply be normal homeostatic changes in cell proliferation. Even though fermentation to short-chain fatty acids is a mechanistically attractive hypothesis to explain why fiber modulates cytokinetics, data do not consistently support short-chain fatty acids as biological intermediates in risk of colon cancer. The state of the art in this field has not yet progressed to the point where a clear effect of dietary fiber on cytokinetics and colon carcinogenesis can be assessed with any degree of certainty. Additional markers of apoptosis, differentiation, and cell-cell communication may be required for a more accurate analysis of the relation among fiber, cytokinetics, and colon cancer.

Transient vs. prolonged histone hyperacetylation: effects on colon cancer cell growth, differentiation, and apoptosis

The role of histone hyperacetylation in regard to growth, differentiation, and apoptosis in colon cancer cells was assessed in an in vitro model system. HT-29 cells were grown in +/-10% fetal bovine serum with either 5 mM sodium butyrate or 0.3 microM trichostatin A [single dose (T) or 3 doses 8 h apart (TR)] for 24 h. Serum-starved HT-29 cells were further treated with epidermal growth factor or insulin-like growth factor I for an additional 24 h. Apoptosis was quantified with propidium iodide and characterized by electron microscopy. Northern blot analyses were performed with cDNA probes specific for intestinal alkaline phosphatase, Na-K-2Cl cotransporter, the cell cycle inhibitor p21, and the actin control. Flow cytometric analysis revealed a time-dependent growth suppression along with early induction of p21 mRNA in the butyrate, T, and TR groups. Histone hyperacetylation, assessed by acid-urea-triton gel electrophoresis, was transient in the T group but persisted for up to 24 h in the butyrate and TR groups. Induction of apoptosis, growth factor unresponsiveness, and differentiation occurred in the butyrate- and TR-treated cells but not those treated with a single dose of trichostatin A. Thus transient hyperacetylation of histones is sufficient to induce p21 expression and produce cellular growth arrest, but prolonged histone hyperacetylation is required for induction of the programs of differentiation, apoptosis, and growth factor unresponsiveness.

Wheat aleurone flour increases cecal beta-glucuronidase activity and butyrate concentration and reduces colon adenoma burden in azoxymethane-treated rats

Processed wheat aleurone flour (WAF) is a source of insoluble fermentable dietary fiber that comes from the outer layers of the wheat kernel. A study was designed to evaluate WAF, wheat bran (WB) and alpha-cellulose as the source of dietary fiber (5 g/100 g of diet) in a semipurified high fat (20 g/100 g of as 1:1 lard/sunflower seed oil) diet fed to male Sprague-Dawley rats in which intestinal tumors were induced using azoxymethane (AOM). WAF at 33 g/100 g of diet (WAF33) and WB at 16 g/100 g of diet (WB16) increased the weight of feces and produced significantly higher concentrations in the cecum of the short-chain fatty acid butyrate (P < 0.001) than did no fiber (NF) and WAF added at only 10 g/100 g (1.5 g of dietary fiber) (WAF10). Cecal and fecal pH were both significantly lower in the WAF33 and WB16 treatments relative to control and no fiber treatments (P < 0.001). The intestinal tumors in the rats were assessed at 6 mo after the study began, and the WAF33- or WB16-fed rats showed a trend (P = 0.06) with 43% fewer colon adenomas relative to control. There was a significant inverse relationship between ss-glucuronidase activity and colon adenomas in the rat colon (r2 = 0.37, P = 0.001). WAF fiber influenced some metabolic markers of fermentation in the colon in a manner similar to that of WB, which, independent of the bulking effect, was associated with a trend to reduced colon adenomas. Significantly increased cecal ss-glucuronidase activity and/or butyrate concentrations may have protective influences in this context by mechanisms not yet fully elucidated.