Down-regulation of proliferating cell nuclear antigen gene expression occurs during cell cycle arrest induced by human fecal water in colonic HT-29 cells

Superior inhibitory efficacy of butyrate over propionate and acetate against human colon cancer cell proliferation via cell cycle arrest and apoptosis: linking dietary fiber to cancer prevention

Intake of dietary fiber may protect against colon cancer. The anticancer property is associated with an increased production of short chain fatty acids (SCFAs), including acetate, propionate and butyrate, during dietary fiber fermentation in the colon. However, the mechanisms remain to be determined. We hypothesized that butyrate exhibits a stronger inhibitory potential against colon cancer cell proliferation compared with acetate and propionate. We determined the half maximal inhibitory concentrations (IC₅₀) of SCFAs in HCT116 human colon cancer cell proliferation by examining cell growth curves. At 24- and 48-hour time points, IC₅₀ (mmol/L) concentrations of acetate, propionate, and butyrate were [66.0 and 29.0], [9.2 and 3.6], and [2.5 and 1.3], respectively. Consistent with the greater anti-proliferative effect, butyrate exhibits >3-fold stronger potential for inducing cell cycle arrest at the G2 phase with a drop in S-phase fraction (including c-Myc/p21 signaling) and apoptosis when compared with acetate and propionate. Subsequently, we focused on the effect of butyrate on apoptotic gene expression. Using a PCR array analysis, we identified 17 pro-apoptotic genes, 6 anti-apoptotic genes, and 4 cellular mediator genes with >1-fold increase or decrease in mRNA levels out of 93 apoptosis related genes in butyrate-treated HCT116 cells when compared with untreated HCT116 cells. These genes were mainly involved in the TNF, NFκB, CARD, and BCL-2 regulated pathways. Taken together, our data indicate a greater inhibitory efficacy of butyrate over propionate and acetate against human colon cancer cell proliferation via cell cycle arrest and apoptosis.

Butyrate Inhibits Deoxycholic-Acid-Resistant Colonic Cell Proliferation via Cell Cycle Arrest and Apoptosis: A Potential Pathway Linking Dietary Fiber to Cancer Prevention

SCOPE

Butyrate, an intestinal microbiota metabolite of dietary fiber, exhibits colon cancer preventive effects. In contrast, a high fat intake increases fecal secondary bile acids, such as deoxycholic acid (DCA, a potential cancer promoter), which selectively enrich mutant epithelial cells with an abnormally high resistance to DCA-induced apoptosis in the colon. This study is conducted to test the hypothesis that physiological concentrations of butyrate inhibit DCA-resistant colonic cell proliferation.

METHODS AND RESULTS

With human HCT-116 cells as parental colonic cells, a human DCA-resistant colonic cell line (DCA-RCL) is developed. DCA treatment increases apoptosis and intracellular reactive oxygen species (an apoptotic trigger) at a rate threefold greater in HCT-116 cells than in DCA-RCL cells. Subsequently, 41 apoptosis related genes (including signaling pathways) with greater than onefold (mRNA) change in DCA-RCL cells are identified compared with HCT-116 cells. Moreover, butyrate treatment inhibits DCA-RCL cell proliferation with similar efficacy when compared with HCT116 cells via cellular myelocytomatosis oncogene (c-Myc)/p38 mitogen-activated protein kinase pathway.

CONCLUSION

It is demonstrated that butyrate inhibits DCA-RCL cell proliferation at the cellular and molecular level. These data provide a proof of concept that butyrate can protect against colon carcinogenesis through a specific targeting of DCA-resistant colonic cells.

Butyrate Inhibits Cancerous HCT116 Colon Cell Proliferation but to a Lesser Extent in Noncancerous NCM460 Colon Cells

Butyrate, an intestinal microbiota metabolite of dietary fiber, exhibits chemoprevention effects on colon cancer development. However, the mechanistic action of butyrate remains to be determined. We hypothesize that butyrate inhibits cancerous cell proliferation but to a lesser extent in noncancerous cells through regulating apoptosis and cellular-signaling pathways. We tested this hypothesis by exposing cancerous HCT116 or non-cancerous NCM460 colon cells to physiologically relevant doses of butyrate. Cellular responses to butyrate were characterized by Western analysis, fluorescent microscopy, acetylation, and DNA fragmentation analyses. Butyrate inhibited cell proliferation, and led to an induction of apoptosis, genomic DNA fragmentation in HCT116 cells, but to a lesser extent in NCM460 cells. Although butyrate increased H3 histone deacetylation and p21 tumor suppressor expression in both cell types, p21 protein level was greater with intense expression around the nuclei in HCT116 cells when compared with that in NCM460 cells. Furthermore, butyrate treatment increased the phosphorylation of extracellular-regulated kinase 1/2 (p-ERK1/2), a survival signal, in NCM460 cells while it decreased p-ERK1/2 in HCT116 cells. Taken together, the activation of survival signaling in NCM460 cells and apoptotic potential in HCT116 cells may confer the increased sensitivity of cancerous colon cells to butyrate in comparison with noncancerous colon cells.

Forkhead Box Transcription Factor (FOXO3a) mediates the cytotoxic effect of vernodalin in vitro and inhibits the breast tumor growth in vivo

Background

Natural compounds have been demonstrated to lower breast cancer risk and sensitize tumor cells to anticancer therapies. Recently, we demonstrated that vernodalin (the active constituent of the medicinal herb Centratherum anthelminticum seeds) induces apoptosis in breast cancer cell-lines. The aim of this work was to gain an insight into the underlying anticancer mechanism of vernodalin using in vitro and in vivo model.

Methods

Vernodalin was isolated through the bioassay guided fractionation from the seeds. The protein expression of p-Akt, PI3K, FOXO3a, Bim, p27kip1, cyclinD1, and cyclinE was examined by the Western blot analysis. Immunoprecipitation assays were performed to analyse Akt kinase activity. Small interfering RNA (siRNA) was used to study the role of FOXO3a upregulation and their targets during vernodalin treatment. Immunofluorescence, subcellular localisation of FOXO3a by Western blot was performed to analyse FOXO3a localisation in nucleus of breast cancer cells. Immunohistochemical analysis of PCNA, Ki67, p27kip1, FOXO3a and p-FOXO3a in the LA7-induced mammary gland tumor model was performed.

Results

Our results showed that vernodalin regulates cancer cell apoptosis through activation of FOXO transcription factors and its downstream targets (Bim, p27Kip1, p21Waf1/cip1, cyclin D1, cyclin E) as examined by Western blots. Furthermore, we showed that FOXO3a/PI3K-Akt played a significant role in vernodalin induced apoptosis in breast cancer cells. Immunoprecipitation assays showed Akt kinase activity was downregulated. Immunofluorescence, subcellular fractionation and Western blot showed FOXO3a accumulation in the nucleus of breast cancer cells after vernodalin treatment. Silencing of FOXO3a protected breast cancer cells against vernodalin induced apoptosis. The anti-tumor action of vernodalin was further confirmed by examining cell proliferative markers, PCNA and Ki67 in the LA7-induced mammary gland tumor model. We also corroborated our findings in vivo by showing upregulation of p27Kip1, FOXO3a and decrease in the p-FOXO3a level in vernodalin-treated breast tumor tissue.

Conclusions

Our results suggest that PI3K-Akt/FOXOa pathway is a critical mediator of vernodalin-induced cytotoxicity and this compound could be further developed as a potential chemopreventive or chemotherapeutic agent for breast cancer therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-015-0266-y) contains supplementary material, which is available to authorized users.

Towards microbial fermentation metabolites as markers for health benefits of prebiotics

Available evidence on the bioactive, nutritional and putative detrimental properties of gut microbial metabolites has been evaluated to support a more integrated view of how prebiotics might affect host health throughout life. The present literature inventory targeted evidence for the physiological and nutritional effects of metabolites, for example, SCFA, the potential toxicity of other metabolites and attempted to determine normal concentration ranges. Furthermore, the biological relevance of more holistic approaches like faecal water toxicity assays and metabolomics and the limitations of faecal measurements were addressed. Existing literature indicates that protein fermentation metabolites (phenol, p-cresol, indole, ammonia), typically considered as potentially harmful, occur at concentration ranges in the colon such that no toxic effects are expected either locally or following systemic absorption. The endproducts of saccharolytic fermentation, SCFA, may have effects on colonic health, host physiology, immunity, lipid and protein metabolism and appetite control. However, measuring SCFA concentrations in faeces is insufficient to assess the dynamic processes of their nutrikinetics. Existing literature on the usefulness of faecal water toxicity measures as indicators of cancer risk seems limited. In conclusion, at present there is insufficient evidence to use changes in faecal bacterial metabolite concentrations as markers of prebiotic effectiveness. Integration of results from metabolomics and metagenomics holds promise for understanding the health implications of prebiotic microbiome modulation but adequate tools for data integration and interpretation are currently lacking. Similarly, studies measuring metabolite fluxes in different body compartments to provide a more accurate picture of their nutrikinetics are needed.

Differentiation-inducing and anti-proliferative activities of lupeol on canine melanoma cells

Canine melanoma is the most common oral malignant tumor reported in the field of veterinary medicine. We found that lupeol, a lupine triterpene, inhibited mouse melanoma cell growth in vitro and in vivo by inducing cell differentiation. In the present study, we examined the differentiation-inducing activities of lupeol on 4 canine melanoma cells in vitro and in vivo.

The induction of canine melanoma cell differentiation by lupeol was confirmed by evaluating some differentiation markers such as tyrosinase with real-time RT-PCR. Furthermore, we transplanted canine melanoma cells into a severe combined immunodeficiency mouse, and studied the anti-progressive effects of lupeol on tumor tissue.

The gene expression of microphthalmia-associated transcription factor, tyrosinase, and tyrosinase-related protein-2, which are markers of pigment cell differentiation, was induced in 4 canine oral malignant melanoma cells by lupeol, and the agent markedly inhibited tumor progression in canine melanoma-bearing mice.

Thymoquinone inhibits cell proliferation through regulation of G1/S phase cell cycle transition in N-nitrosodiethylamine-induced experimental rat hepatocellular carcinoma

Dysregulated cell proliferation and tumorigenesis is frequently encountered in several cancers including hepatocellular carcinogenesis (HCC). Thus, agents that inhibit cell proliferation and restrain hepatic tumorigenesis through cell cycle regulation have a beneficial effect in the treatment of hepatocellular carcinogenesis. The present study was aimed to investigate the efficacy of thymoquinone (TQ), an active compound derived from the medicinal plant Nigella sativa, on N-nitrosodiethylamine (NDEA) [0.01% in drinking water for 16 weeks]-induced hepatocarcinogenesis in experimental rats. After experimental period, the hepatic nodules, liver injury markers and tumor markers levels were substantially increased in NDEA induced liver tumors in rats. However, TQ (20mg/kg body weight) treatment greatly reduced liver injury markers and decreased tumor markers and prevented hepatic nodule formation and reduced tumor multiplicity in NDEA induced hepatic cancer bearing rats and this was evident from argyrophilic nucleolar organizer region (AgNORs) staining. Moreover, the uncontrolled cell proliferation was assessed by specific cell proliferative markers [proliferating cell nuclear antigen (PCNA) and Ki67] by immunofluorescence, immunoblot and analysis of mRNA expression. Simultaneously, we assessed the activity of TQ on G1/S phase cell cycle regulation with specific cell cycle proteins (p21(WAF1/CIP1), CDK4, Cyclin D1 and Cyclin E) by immunoprecipitation in experimental rats. Treatment with TQ significantly reduced the detrimental alterations by abrogating cell proliferation, which strongly induced G1/S arrest in cell cycle transition. In conclusion, our results suggest that TQ has a potent anti proliferative activity by regulating the G1/S phase cell cycle transition and exhibit a beneficial role in the treatment of HCC.

A comparison of the gene expression profiles of CRL-1807 colonocytes exposed to endogenous AAPH-generated peroxides and exogenous peroxides from heated oil

Oxidation of PUFAs in the diet has the potential to be genotoxic and hence carcinogenic. Such carcinogenic processes originate within stem cells of the colon. These cells appear to be predisposed to the carcinogenic process. In colon cells (CRL-1807) exposed to chemical reactions simulating exogenous and endogenous peroxidation reactions, we have observed that undifferentiated cells could mount an effective recombinational repair/TCR response to an endogenous peroxidative DNA damage insult, but not to an external exogenous peroxidative insult as one would encounter from a dietary source. This may suggest that defects in such specific DNA repair may play a role in tumour development in undifferentiated colonocytes exposed to a diet-derived lipid peroxides.

Gelsolin induces promonocytic leukemia differentiation accompanied by upregulation of p21CIP1

Tumor suppressor genes have received much attention for their roles in the development of human malignancies. Gelsolin has been found to be down-regulated in several types of human cancers, including leukemias. It is, however, expressed in macrophages, which are the final differentiation derivatives for the monocytic myeloid lineage, implicating this protein in the differentiation process of such cells. In order to investigate the role of gelsolin in leukaemic cell differentiation, stable clones over-expressing ectopic gelsolin, and a control clone were established from U937 leukaemia cells. Unlike the control cells, both gelsolin-overexpressing clones displayed retarded growth, improved monocytic morphology, increased NADPH and NSE activities, and enhanced surface expression of the β-integrin receptor, CD11b, when compared with the parental U937 cells. Interestingly, RT- PCR and western blot analysis also revealed that gelsolin enhanced p21CIP1 mRNA and protein expression in the overexpressing clones. Moreover, transient transfection with siRNA silencing P21CIP1, but not the control siRNA, resulted in a reduction in monocytic differentiation, accompanied by an increase in proliferation. In conclusion, our work demonstrates that gelsolin, by itself, is capable of inducing monocytic differentiation in U937 leukaemia cells, most probably through p21CIP1 activation.

An in vitro assay system for antihyperlipidemic agents by evaluating lipoprotein profiles from human intestinal epithelium-like cells

We developed an in vitro screening system for antihyperlipidemic activity by measuring lipoprotein profiles secreted from human intestinal epithelium-like cells from the colon cancer cell line, Caco-2. Sodium (Na) butyrate at 5 mM differentiated Caco-2 cells into intestinal epithelium-like cells and numerous microvilli on the apical side of cells were observed under transmission electron microscopy. Real-time RT-PCR analysis revealed that Na butyrate stimulated expression levels of intestinal differentiation markers in Caco-2 cells in a dose-dependent manner and 5 mM Na butyrate up-regulated intestinal alkaline phosphatase, sucrase–isomaltase complex, and microsomal triglyceride transfer protein by 8.1-, 1.9-, and 2.1-fold that of non-treated cells, respectively. Lipoprotein secretions from differentiated Caco-2 cells were promoted by lysophosphatidyl choline and Na oleate, which are a stimulator of lipoprotein secretion and a substrate of triglycerides, respectively. We examined the effects of Pluronic L-81, a lipoprotein secretion inhibitor, on lipoprotein profiles of differentiated Caco-2 cells. Pluronic L-81 at 1.0 μg/ml inhibited TG contents in lipoprotein fractions from cells by 25.6 % and secretion was completely suppressed by the agent at 10 μg/ml.

Selenium in bone health: roles in antioxidant protection and cell proliferation

Selenium (Se) is an essential trace element for humans and animals, and several findings suggest that dietary Se intake may be necessary for bone health. Such findings may relate to roles of Se in antioxidant protection, enhanced immune surveillance and modulation of cell proliferation. Elucidation of the mechanisms by which Se supports these cellular processes can lead to a better understanding of the role of this nutrient in normal bone metabolism. This article reviews the current knowledge concerning the molecular functions of Se relevant to bone health.

Differentiation- and apoptosis-inducing activities of rice bran extracts in a human colon cancer cell line

Rice bran water extract (RBWE) and ethanol extract (RBEE) at 1.0 mg/ml markedly inhibited the proliferation of LS174T human colon cancer cells. RBEE but not RBWE induced apoptosis. RBWE promoted the production of intestinal mucin (MUC2). Real-time RT-PCR demonstrated that RBWE up-regulated the expression of MUC2 and sucrase-isomaltase complex (a differentiation marker of colon cancer cells), and attenuated that of proliferating cell nuclear antigen at the mRNA level in a dose-dependent manner. These findings suggested that RBWE suppress the proliferation of colon cancer cells by inducting differentiation not apoptosis.

Antiproliferative and cytotoxic effects of sodium selenite in human colon cancer cells

Sodium selenite has been reported to interfere with cell growth and proliferation and to induce cell death. Despite of our current knowledge, details about its effects on growth and behavior of colonocytes with differing p53 status remain unknown. In our study, we evaluated the antiproliferative, cell cycle specific and proapoptotic potential of sodium selenite in HCT-116 colorectal cells with wild type p53 and its isogenic control HCT-116-p53KO cell line. Cell proliferation in selenite-treated cells was followed by computer-enhanced time-lapse videomicroscopy, by measuring protein content (Coomassie Brilliant Blue assay), metabolic activity (WST-1) and DNA synthesis (BrdU). Changes in cell cycle were determined by flow cytometry and Western blotting. Cell death was measured with the nuclear fragmentation assay and caspase-3 immunostaining. We show that sodium selenite inhibits the growth and proliferation of colon cancer cells in a time- and dose-dependent manner, with HCT-116 cells being more sensitive than HCT-116-p53KO cells. Moreover, upon sodium selenite treatment, there was a tendency for cells to accumulate at G2 phase which was accompanied by the increasing expression of cyclin B1, Cdc2 p34, p21 and the sub G1 fraction of the cell cycle. In addition, PARP and nuclear fragmentation and activation of caspase-3 were more profound in HCT-116 cells versus HCT-116-p53KO cells, thus indicating important role of p53 and dependent signaling in selenite-induced toxicity.

Selenium as an essential micronutrient: roles in cell cycle and apoptosis

Selenium is an essential trace element for humans and animals, and selenium deficiency is associated with several disease conditions such as immune impairment. In addition, selenium intakes that are greater than the recommended daily allowance (RDA) appear to protect against certain types of cancers. In humans and animals, cell proliferation and death must be regulated to maintain tissue homeostasis, and it has been well documented that numerous human diseases are directly related to the control of cell cycle progression and apoptosis. Thus, the elucidation of the mechanisms by which selenium regulates the cell cycle and apoptosis can lead to a better understanding of the nature of selenium's essentiality and its role in disease prevention. This article reviews the status of knowledge concerning the effect of selenium on cell cycle and apoptosis.

NMR metabolomic analysis of fecal water from subjects on a vegetarian diet

A vegetarian diet rich in phytochemicals may prevent colon carcinogenesis by affecting biochemical processes in the colonic mucosa. Compounds passing the digestive system reaching the colon could potentially be detected in fecal water. We previously reported that intact fecal water samples from human volunteers significantly decreased prostaglandin production and COX-2 protein expression in colonic cells. The aim with the present study was to further study the composition of the fecal waters, using NMR spectroscopy and multivariate data analysis, and to trace the COX-2 inhibiting activity. Intact fecal water samples and fractions thereof were analyzed for their ability to inhibit prostaglandin E2 production in the human colon cell line HT-29. The majority of the tested aqueous phases derived from intact fecal water showed ability to inhibit prostaglandin production in cells (13.8+/-1.34% inhibition, p=0.01). NMR analysis indicated the presence of significant quantities of amino acids and fatty acids. Major metabolites included; acetic acid, butanoic acid, propanoic acid, glutamic acid and alanine. Smaller amounts of glycine and fumaric acid, which are known to have anti-inflammatory and anti-tumorigenic properties, were also detected. This study describes for the first time NMR metabolomic analysis of fecal water from subjects on a vegetarian diet.

Local cell proliferation in rheumatoid synovial tissue: analysis by cyclin expression

The immunohistochemical staining of cyclins was done to evaluate the proliferating cells in synovial tissue of rheumatoid arthritis (RA). Synovial specimens obtained from 18 patients with RA, 12 with osteoarthritis (OA), and 8 with traumatic arthritis (TA) were used for immunostaining of cyclins A and B1 and proliferating cell nuclear antigen (PCNA). The positive cells in lining layer (synoviocytes) and sublining layer (lymphoid and nonlymphoid cells) were counted. Moreover, the relationship between the frequency of their positive cells and clinical data of RA patients was analyzed statistically. In general, cyclin-A-, cyclin-B1-, and PCNA-positive cells in RA were more frequently observed as compared with those in OA and TA. Significant differences were found between RA and OA or TA in cyclin-A-, cyclin-B1-, and PCNA-positive sublining lymphoid cells, between RA and OA or TA in cyclin-B1- and PCNA-positive sublining nonlymphoid cells, and between RA and OA in cyclin-B1-positive synoviocytes. The ratio of cyclin-A- or cyclin-B1-positive cells per PCNA-positive cells was significantly higher in sublining lymphoid cells in RA than TA and in sublining lymphoid and nonlymphoid cells of RA than OA or TA. Moreover, a better relationship was observed between the frequency of cyclin-A-positive synoviocytes and age and between cyclin-A-positive sublining nonlymphoid cells and duration of the disease in RA patients. Our data demonstrated clearly that synoviocytes, as well as sublining lymphoid and nonlymphoid cells, could divide in situ, and more frequent cell division and a higher ratio of cyclin-A- or cyclin-B1-positive/PCNA-positive sublining cells could occur in RA than OA and TA.

Prolonged butyrate treatment inhibits the migration and invasion potential of HT1080 tumor cells

Butyrate, a normal constituent of the colonic luminal contents, is produced by the bacterial fermentation of dietary fibers and resistant starches. It has been hypothesized that butyrate may inhibit the invasion of tumor cells. The purpose of the present study was to investigate the effects of butyrate treatment on the growth, migration, and invasion characteristics of tumor HT1080 cells. HT1080 cells cultured in the presence of 0.5 and 1 mmol/L butyrate for 14 d exhibited an increase in the G(1) and G(2) fractions with a concomitant drop in the S-phase, thus showing slower cell growth. Interestingly, 0.5 and 1 mmol/L butyrate inhibited the migration and invasion rate of the tumor cells compared with the untreated (control) cells. The protein and mRNA levels of the tissue inhibitors of metalloproteinase-1 (TIMP-1) and TIMP-2 were significantly increased in HT1080 cells cultured with 0.5 and 1 mmol/L butyrate. Enzymatic activities and the mRNA level of the latent forms of matrix metalloproteinase (MMP), pro-MMP-2 and pro-MMP-9, were also increased in HT1080 cells cultured with 0.5 and 1 mmol/L butyrate. In contrast, the active form of MMP-2 was detectable by zymographic analysis in control but not butyrate-conditioned media. Collectively, these results demonstrate that prolonged and low-dose butyrate treatment increases both prometastasis MMP-2, -9 and antimetastasis TIMP-1, -2 expression, and the net effect of these increases is the inhibition of pro-MMP-2 activation and of tumor cell migration/invasion potential.