Effect Of Dietary Folate Restriction On Colon Carcinogenesis In Dna Polymerase β Haploinsufficient Mice

The data presented in this research is central to establishing the role that the base excision repair pathway (BER) plays in the development and progression of colon cancer when dietary folate is deficient. Both cellular folate restriction and BER deficiencies have been shown to result in the accumulation of endogenous damage and lesions that could eventually develop into carcinogenesis. In this study, a dietary folate deficiency (FD) resulted in a significant increase in aberrant crypt foci (ACF) formation and triggered liver tumorogenesis in wildtype (WT) animals, as did a BER deficiency in DNA polymerase Β haploinsufficient (Β-pol+/-) mice exposed to 1, 2-dimethylhydrazine (DMH), a known colon and liver carcinogen. We combined both folate restriction and a BER deficiency to determine the fate of colon tissue after exposure to DMH. Of interest, we show that this model supports a protection against colon carcinogenesis. FD attenuated onset and progression of ACF and prevented liver tumorigenesis in Β-pol haploinsufficient mice. Analysis of the data suggests that the mechanism by which this phenomenon occurs appears to be through an elevation in DNA damage that signals recruitment of PARP enzymes to the site of damage, however, with a deficiency in BER, PARP function in DNA repair is futile leading to a depletion of cellular energetic levels. This energetic stress is sensed by cell death machinery and as such apoptosis is invoked

Hydrophobic bile acids, genomic instability, Darwinian selection, and colon carcinogenesis

Sporadic colon cancer is caused predominantly by dietary factors. We have selected bile acids as a focus of this review since high levels of hydrophobic bile acids accompany a Western-style diet, and play a key role in colon carcinogenesis. We describe how bile acid-induced stresses cause cell death in susceptible cells, contribute to genomic instability in surviving cells, impose Darwinian selection on survivors and enhance initiation and progression to colon cancer. The most likely major mechanisms by which hydrophobic bile acids induce stresses on cells (DNA damage, endoplasmic reticulum stress, mitochondrial damage) are described. Persistent exposure of colon epithelial cells to hydrophobic bile acids can result in the activation of pro-survival stress-response pathways, and the modulation of numerous genes/proteins associated with chromosome maintenance and mitosis. The multiple mechanisms by which hydrophobic bile acids contribute to genomic instability are discussed, and include oxidative DNA damage, p53 and other mutations, micronuclei formation and aneuploidy. Since bile acids and oxidative stress decrease DNA repair proteins, an increase in DNA damage and increased genomic instability through this mechanism is also described. This review provides a mechanistic explanation for the important link between a Western-style diet and associated increased levels of colon cancer

The AOM/DSS murine model for the study of colon carcinogenesis: From pathways to diagnosis and therapy studies

Colorectal cancer (CRC) is a major health problem in industrialized countries. Although inflammation-linked carcinogenesis is a well accepted concept and is often observed within the gastrointestinal tract, the underlying mechanisms remain to be elucidated. Inflammation can indeed provide initiating and promoting stimuli and mediators, generating a tumour-prone microenvironment. Many murine models of sporadic and inflammation-related colon carcinogenesis have been developed in the last decade, including chemically induced CRC models, genetically engineered mouse models, and xenoplants. Among the chemically induced CRC models, the combination of a single hit of azoxymethane (AOM) with 1 week exposure to the inflammatory agent dextran sodium sulphate (DSS) in rodents has proven to dramatically shorten the latency time for induction of CRC and to rapidly recapitulate the aberrant crypt foci-adenoma-carcinoma sequence that occurs in human CRC. Because of its high reproducibility and potency, as well as the simple and affordable mode of application, the AOM/DSS has become an outstanding model for studying colon carcinogenesis and a powerful platform for chemopreventive intervention studies. In this article we highlight the histopathological and molecular features and describe the principal genetic and epigenetic alterations and inflammatory pathways involved in carcinogenesis in AOM/DSS-treated mice; we also present a general overview of recent experimental applications and preclinical testing of novel therapeutics in the AOM/DSS model

Spatiotemporal Effects of Dietary Bioactives on Lgr5+ Stem Cells during Colon Tumorigenesis

To better understand how the stem cells respond to environmental factors such as diet and carcinogen, we investigated the chemo-protective effects of dietary agents (n-3 PUFA and curcumin) on DNA damage response in colonic stem cells isolated from Lgr5-EGFP-IRES-CreER^T2 knock in mice injected with AOM. We demonstrated that n-3 PUFA and curcumin synergize to promote targeted apoptosis of damaged Lgr5⁺ stem cells in part by enhancing p53 signaling in Lgr5⁺ stem cells at the tumor initiation stage. In addition, at the pre-tumor stage of tumorigenesis in colon cancer, we demonstrated n-3 PUFA and curcumin combination synergistically reduces nuclear -catenin levels in aberrant crypt foci, a surrogate marker of colon cancer. In order to assess the dose-dependency of n-3 PUFA and curcumin action, we also calculated the median effective concentration and the Human equivalent dose of n-3 PUFA + curcumin required to remove DNA damaged Lgr5⁺ stem cells by targeted apoptosis. In order to further elucidate the effects of oncogenesis on the biophysical properties of the colonocyte plasma membrane at the pre tumor stage, we generated CDX2P-CreER^T2 –Apc^580S/+; KrasLSL-^G12D/+ (ACK) transgenic mice. Our findings demonstrate for the first time that oncogenic Apc and Kras increase plasma membrane order by perturbing cholesterol homeostasis and promoting cell proliferation. Genes associated with cholesterol uptake and de novo synthesis of cholesterol are enhanced in ACK mice. This process is associated with the upregulation of Myc signaling, a well-known upstream mediator of cholesterol homeostasis. Our preliminary findings also indicate that the addition of exogenous cholesterol can dose-dependently promote cell proliferation in colonic cell lines and mouse colonic organoids. In complementary experiments, we also investigated the chemo-protective effects of dietary agents on cholesterol homeostasis and plasma membrane order in ACK mice. Our findings indicate that perturbed plasma membrane order and cholesterol homeostasis is ameliorated by n-3 PUFA + curcumin feeding. In summary, our results indicate for the first time that fish oil plus curcumin synergistically reduce colon cancer risk in part by modulating (i) p53 signaling in Lgr5+ stem cells, and (ii) plasma membrane properties implicated in the regulation of the colon cancer cells and tumor development

Red Meats and Processed Meat as the Carcinogenic Foods and Phytochemical-chemoprevention

BACKGROUND: Along with its increased prevalence, in the past decade, cancer had joined the list of chronic debilitating diseases. Nutrition become substantial aspects, due to its time-dependent effect to modulate inflammation thus trigger carcinogenic effects by altering the immune check point. Thus, nutrition contributes to the progression and therapeutic response of cancer, both in human or animal models.CONTENT: Meat is well favored food with appreciable appealing. Due to its high nutritional values it plays a central role in human development. Meat or meat derivate are important sources of proteins, minerals and vitamins. Their nutritional importance is worth compare to their economic impact but recent publication of WHO has set the social alarm about the relationship between red and/or processed meat consumption and cancer. On the other side, some natural or biologic agents may inhibit or reverse tumor growth. Some phytochemical agents including curcumin, resveratrol, lycopene, folates and tea polyphenols clinically proved to tune the signaling pathways regulating cell proliferation and apoptosis in transformed cells, enhance the host immune system and sensitize malignant cells to cytotoxic agents.SUMMARY: Recent studies on chemopreventive agents involves a wide range of molecules, natural (plants, fruits and vegetables) or synthetic will provide better insights for cancer early pathogenesis, important end-point biomarker, and finally potential for reducing the burden of cancer.KEYWORDS: blocking agents, suppressing agents, red meat, processed meat, chemoprevention, phytochemical

Methylation of NOTCH genes in normal and at-risk colorectal epithelium

PhD ThesisIntroduction Colorectal cancer (CRC) arises from genetic defects in stem cells. NOTCH signalling plays a key role in stem cell replication control. NOTCH-related genes are overexpressed in CRC. The mechanism for this is not known but could include epigenetic activation of NOTCH oncogenes via promoter hypomethylation. Methylation can be modulated by environmental stimuli including dietary factors such as butyrate, produced by bacterial fermentation of non-digestible carbohydrates in the colon. Butyrate exerts potent anti-oncogenic effects in the colorectal mucosa. Methods Participants were recruited at endoscopy and included those at normal risk of CRC (n=75), or higher risk of CRC because of previous adenomatous polyps (n=28) or ulcerative colitis (n=12). Participants provided 9 rectal biopsies. Normal risk participants were randomised to resistant starch (Hi-maize 260) or polydextrose supplementation in a 2x2 factorial placebo controlled trial for 50 days. Methylation of several CpG sites in the promoters of JAG1 (NOTCH pathway ligand) and RBP-J (NOTCH intracellular activator) was quantified using pyrosequencing. Results For JAG1 there was trend towards lower methylation at all CpG sites in those at higher CRC risk. Methylation at RBP-J CpG 11 was lower in polyp patients than in controls (18.0(1.5) vs. 23.6% (0.8), p=0.011). At JAG1 CpG 4, methylation increased following polydextrose supplementation compared to placebo (3.1(0.4) vs. 1.7%(0.4), p=0.009). A similar, but non-significant, trend was observed at other CpG sites for JAG1. Conclusions DNA methylation of NOTCH signalling genes is altered in macroscopically normal colorectal mucosa of patients at higher CRC risk. The observed changes in JAG1 methylation after polydextrose supplementation are consistent with a protective effect against carcinogenesis.Northumbria Healthcare NHS Foundation Trust: The BBSRC (grant reference BH090948)

Chemistry meets biology in colitis-associated carcinogenesis

The intestine comprises an exceptional venue for a dynamic and complex interplay of numerous chemical and biological processes. Here, multiple chemical and biological systems, including the intestinal tissue itself, its associated immune system, the gut microbiota, xenobiotics, and metabolites meet and interact to form a sophisticated and tightly regulated state of tissue homoeostasis. Disturbance of this homeostasis can cause inflammatory bowel disease (IBD)—a chronic disease of multifactorial etiology that is strongly associated with increased risk for cancer development. This review addresses recent developments in research into chemical and biological mechanisms underlying the etiology of inflammation-induced colon cancer. Beginning with a general overview of reactive chemical species generated during colonic inflammation, the mechanistic interplay between chemical and biological mediators of inflammation, the role of genetic toxicology, and microbial pathogenesis in disease development are discussed. When possible, we systematically compare evidence from studies utilizing human IBD patients with experimental investigations in mice. The comparison reveals that many strong pathological and mechanistic correlates exist between mouse models of colitis-associated cancer, and the clinically relevant situation in humans. We also summarize several emerging issues in the field, such as the carcinogenic potential of novel inflammation-related DNA adducts and genotoxic microbial factors, the systemic dimension of inflammation-induced genotoxicity, and the complex role of genome maintenance mechanisms during these processes. Taken together, current evidence points to the induction of genetic and epigenetic alterations by chemical and biological inflammatory stimuli ultimately leading to cancer formation.Massachusetts Institute of Technology. Center for Environmental Health Sciences (ES002109)National Institutes of Health (U.S.) (NIH (CA26731)

CYP2W1 in colorectal cancer : aspects of risk, prognosis and future treatment options

Colorectal cancer (CRC) is a common disease and a major cause of cancer related death globally. Prognosis is rather good in early stages but worse in cases with disseminated disease. There is a constant need of developing all treatment modalities, which also has been done over the last decades. There are needs to find predictive markers in order to assess who will and who will not benefit of chemotherapy, just as there are needs to develop drugs targeting novel pathways and proteins prevalent in primary tumors and metastases. CYP2W1 is a member of the cytochrome P450 superfamily of enzymes with unknown physiological functions but found to have the capacity to metabolize both carcinogens and various other xenobiotic substances. It is expressed in fetal rat colonic tissue and in human colorectal tumors, but not to our knowledge in any adult normal human tissue. CYP2W1 expression, both mRNA and protein, has previously been studied in a material consisting of about 50 colorectal tumor samples. We wanted to investigate the extent of CYP2W1 expression in a larger tumor material using immunohistochemistry. We found it also interesting to see if CYP2W1 expression affects prognosis. Another aim of the thesis was to assess the association between polymorphism in the CYP2W1 gene and risk to develop CRC. A last aim was to evaluate the CYP2W1 expression in metastases. For the first aim, we used three different patient cohorts, two of which were derived from a randomized Nordic trial aiming to compare no adjuvant versus adjuvant treatment in patients with stage II and III CRC. These cohorts consisted of 162 and 235 patients respectively. The third patient cohort consisted of 96 patients being resected for liver metastases from CRC. All tumor manifestations in these patients were investigated with immunohistochemistry, addressing both the first and the last aim, and the findings indicate that CYP2W1 is expressed at high levels in between 26-36% of the primary tumors. It is expressed in about one third of lymph node metastases and almost half of the liver metastases. We performed two investigations regarding CYP2W1 as a prognostic factor using the two cohorts from the Nordic study (n=162 and n=235). In the first study, high CYP2W1 expression was of independent prognostic value for poor survival together with stage. In the second study aiming to reproduce this, the result was not as clear-cut, CYP2W1 was of prognostic value only in multivariate analysis but not in univariate analysis. In the subgroup of patients with stage III CRC (n=132), CYP2W1 expression was of independent prognostic value. The third aim was addressed using a material of DNA from individuals in a large casecontrol study aiming to investigate various polymorphisms and their relation to CRC risk. DNA from 1785 CRC patients and 1761 control subject was analyzed regarding three CYP2W1 variants. We also experimentally assessed enzymatic activity of the gene products of the variants studied. No difference was seen, neither in CRC risk between cases and controls, nor in enzymatic activity between the three variant proteins. In conclusion, CYP2W1 seems to be expressed in about one third of primary CRC and half of the liver metastases. The association with prognosis in CRC requires further studies to be elucidated. Genetic polymorphism in the CYP2W1 gene does not seem to have any impact on CRC risk. The tumor specific expression of a catalytic enzyme in CRC and metastases is interesting in the aspect of future targeted anti-cancer therapies

The use of mathematical and computational models to define the role of mutation and infection in colorectal cancer.

Research over the past twenty five years has led to the development of the hypothesis that colorectal cancer is caused by the accumulation of mutations in tumor suppressor genes and proto-oncogenes. The last ten years has also revealed that the common JC Virus (JCV) is frequently found in colorectal tumors. This has led to the hypothesis that the virus, which is known to cause tumors in the lab, may playa role in colorectal cancer. However, the presence of JCV in colorectal tumors does not necessarily indicate a cause-effect relationship. Unlike in vivo and in vitro studies, mathematical and computational modeling provides an opportunity to evaluate the roles that mutation and infection play in colorectal tumorigenesis. Three probability models are developed to assess whether colorectal cancer can occur by mutation alone or if infection is required. Two models find that JCV is required for tumorigenesis, and that mutation alone is unable to generate any tumors. The third probability model finds the opposite; mutation is able to generate realistic numbers of colorectal cancer patients, while infection is not. All three models do indicate that selection for a stem cell mutation rate that is 100 times lower than transit cells provides protection from cancer, confirming the findings of other research groups. An agent based model is also developed to simulate many of the complexities that cannot be modeled in the probability models. The results from the agent based model indicate that ICV exacerbates colorectal cancer and greatly increases the risk of developing cancer. It also finds that mutation alone is able to cause colorectal cancer, although not as frequently as IC virus associated cases. All together, these models indicate that both mutation and infection have the capacity to drive tumorigenesis, but that the presence of IC Virus increases the risk of developing colorectal cancer. This strongly suggests that the role of ICV in colorectal cancer deserves more attention. If future studies confirm these findings, it would indicate that the prevalence of colorectal cancer can be reduced by taking measures to prevent infection by IC Virus