Development Of Sporadic Colorectal Cancer Research Articles

Comparative genomic analysis to identify a signature of sporadic colorectal cancer development in young adults.

208 Background: Young-onset sporadic CRC is an important yet understudied heterogeneous group of aggressive cancers with distinct clinical and histopathological features. There is a steady increase in the incidence of cancer in this group of patients and currently, there are no screening guidelines to identify these patients due to a lack of understanding of the molecular mechanisms driving cancer in this patient group. Introduction: Despite screening guidelines and recent advances in cancer treatment, colorectal cancer (CRC) remains the second most diagnosed cancer and the second and third leading cause of cancer-related mortality in Canadian men and women, respectively [Canadian Cancer Statistics 2017.]. More striking is the rise in incidence of CRC in young adults in the United States [Siegel, R.L., et al, Bailey, C.E., et al., Dozois, E.J., et al., Deen, K.I., et al.], and the expectation that by the year 2030, the incidence rate will increase by 90% in this patient population. Data from the Surveillance and Cancer registry at Cancer Care Ontario shows a similar trend with increased rates in younger adults (ages 30 to 49) by 5.2 per cent per year between 2005 and 2012 [Ontario, C.C., Cancer Fact.]. Moreover, these younger patient groups are often diagnosed with aggressive forms and advanced stages of the disease [Ontario, C.C., Cancer Fact.]. Methods: In this study, using a total of 30 colorectal cancer patient samples from Windsor Regional Hospital Cancer Program, we performed comprehensive targeted gene sequencing to identify single nucleotide variants, small insertions/deletions, copy number variants in over 500 genes that are implicated in cancer. Mean age of the patients in this study was 44 years and only patients without any personal or family history of colon cancer /other malignancies or IBD were enrolled in the study. Results: While identifying previously known colorectal cancer associated genetic variants, our preliminary data shows distinct missense mutations in several genes potentially contributing to the development and progression of cancer in these patients. In addition to showing pathogenic mutations in colorectal cancers associated genes, such as PIK3CA (H1047R, E545K, E545G, R93W, V344A), KRAS (G12V, G12D, A146T) and APC, our study showed recurring missense mutations in several genes including AXIN2, ALK, CDKN1A, MAP3K1, ROS1, EPCAM, KDM5A and AURKA in over 50% of our samples. Conclusions: The genomic profiling performed using biopsies from young colorectal cancer patients through this study provides a unique ability to identify the potential “genomic triggers” for the development and progression of cancer in young sporadic colorectal cancer patients. This information can not only be used to develop targeted treatment options for these patients but also to design new screening protocols as well as optimal surveillance strategies.

Could Microplastics Be a Driver for Early Onset Colorectal Cancer?

Introduction: The incidence of colorectal cancer in those under 50 years of age (early onset colorectal cancer (EOCRC)) is increasing throughout the world. This has predominantly been an increase in distal colonic and rectal cancers, which are biologically similar to late onset colorectal cancer (LOCRC) but with higher rates of mucinous or signet ring histology, or poorly differentiated cancers. The epidemiology of this change suggests that it is a cohort effect since 1960, and is most likely driven by an environmental cause. We explore the possible role of microplastics as a driver for this change. Review: The development of sporadic colorectal cancer is likely facilitated by the interaction of gut bacteria and the intestinal wall. Normally, a complex layer of luminal mucus provides colonocytes with a level of protection from the effects of these bacteria and their toxins. Plastics were first developed in the early 1900s. After 1945 they became more widely used, with a resultant dramatic increase in plastic pollution and their breakdown to microplastics. Microplastics (MPs) are consumed by humans from an early age and in increasingly large quantities. As MPs pass through the gastrointestinal tract they interact with the normal physiological mechanism of the body, particularly in the colon and rectum, where they may interact with the protective colonic mucus layer. We describe several possible mechanisms of how microplastics may disrupt this mucus layer, thus reducing its protective effect and increasing the likelihood of colorectal cancer. Conclusions: The epidemiology of increase in EOCRC suggests an environmental driver. This increase in EOCRC matches the time sequence in which we could expect to see an effect of rapid increase of MPs in the environment and, as such, we have explored possible mechanisms for this effect. We suggest that it is possible that the MPs damage the barrier integrity of the colonic mucus layer, thus reducing its protective effect. MPs in CRC pathogenesis warrants further investigation. Future directions: Further clarification needs to be sought regarding the interaction between MPs, gut microbiota and the mucus layer. This will need to be modelled in long-term animal studies to better understand how chronic consumption of environmentally-acquired MPs may contribute to an increased risk of colorectal carcinogenesis.

Genetic heterogeneity of colorectal cancer and the microbiome

In 2020, the International Agency for Research on Cancer and the World Health Organization's GLOBOCAN database ranked colorectal cancer (CRC) as the third most common cancer in the world. Most cases of CRC (> 95%) are sporadic and develop from colorectal polyps that can progress to intramucosal carcinoma and CRC. Increasing evidence is accumulating that the gut microbiota can play a key role in the initiation and progression of CRC, as well as in the treatment of CRC, acting as an important metabolic and immunological regulator. Factors that may determine the microbiota role in CRC carcinogenesis include inflammation, changes in intestinal stem cell function, impact of bacterial metabolites on gut mucosa, accumulation of genetic mutations and other factors. In this review, I discuss the major mechanisms of the development of sporadic CRC, provide detailed characteristics of the bacteria that are most often associated with CRC, and analyze the role of the microbiome and microbial metabolites in inflammation initiation, activation of proliferative activity in intestinal epithelial and stem cells, and the development of genetic and epigenetic changes in CRC. I consider long-term studies in this direction to be very important, as they open up new opportunities for the treatment and prevention of CRC.

Abstract B023: Sox9 drives an aberrant transcriptional program impeding intestinal differentiation in colorectal cancer initiation

Abstract Despite the implementation of screening and preventative strategies, colorectal cancer (CRC) remains the second most deadly cancer worldwide and is responsible for an alarming trend of increasing prevalence among younger patients. Inappropriate WNT activation is the initiating step in sporadic CRC development, typically through deleterious mutations in the pathway negative regulator Adenomatous polyposis coli (APC). WNT pathway hinders whereas transforming growth factor (TGF-β)/bone morphogenetic protein (BMP) signaling supports differentiation of progenitors into mature enterocytes, establishing a crypt-villus gradient. Genomic alterations that dysregulate intestinal stem cell differentiation are central to CRC development. Impairment of differentiation and inappropriate Sox9 overexpression are conserved events in CRC initiation based on the evaluation of two genetically engineered mouse models, two carcinogen-induced mouse models, and a patient with familial adenomatous polyposis (FAP), a hereditary polyposis syndrome in which a mutant copy of APC is inherited. Single cell RNA-sequencing (scRNA-seq) of adenomas from an ApcKO mouse model and FAP sample implicates an aberrant stem cell-like program (herein referred to as AbSC) as a key aspect of CRC initiation. The AbSc program is characterized by selective intestinal stem cell activity, indiscriminate attenuation of differentiated lineages, and aberrant activation of genes associated with fetal intestinal development. Histopathology and scRNA-seq of adenomas and derivative organoids from a patient with FAP demonstrated a partial block in differentiation and confirmed reactivation of genes reserved for intestinal development. Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq) of APCKO epithelial cells revealed increased chromatin accessibility at fetal intestinal genes. Genetic inactivation of Sox9 prevented adenoma formation in ApcKO mice and induced differentiation of ApcKO organoids, obstructing the emergence of the ApcKO transcriptional state, including reactivation of a fetal-like intestinal program, restored multi-lineage differentiation, and markedly reduced the gained chromatin accessibility at developmental genes in neoplasia. These studies indicate that an aberrant transcriptional state hindering intestinal differentiation mediated by Sox9 is an early conserved event in CRC and carry important implications for developing therapeutics directed at inducing intestinal differentiation. Citation Format: Pratyusha Bala, Jonathan P. Rennhack, Clare Morris, Daulet Aitymbayev, Sydney M. Moyer, Gina Nicole Duronio, Paul Doan, William C. Hahn, Nilay S. Sethi. Sox9 drives an aberrant transcriptional program impeding intestinal differentiation in colorectal cancer initiation [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer; 2022 Oct 1-4; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_1):Abstract nr B023.

Colon Tumors in Enterotoxigenic Bacteroides fragilis (ETBF)-Colonized Mice Do Not Display a Unique Mutational Signature but Instead Possess Host-Dependent Alterations in the APC Gene.

ABSTRACTEnterotoxigenic Bacteroides fragilis (ETBF) is consistently found at higher frequency in individuals with sporadic and hereditary colorectal cancer (CRC) and induces tumorigenesis in several mouse models of CRC. However, whether specific mutations induced by ETBF lead to colon tumor formation has not been investigated. To determine if ETBF-induced mutations impact the Apc gene, and other tumor suppressors or proto-oncogenes, we performed whole-exome sequencing and whole-genome sequencing on tumors isolated after ETBF and sham colonization of Apcmin/+ and Apcmin/+Msh2fl/flVC mice, as well as whole-genome sequencing of organoids cocultured with ETBF. Our results indicate that ETBF-induced tumor formation results from loss of heterozygosity (LOH) of Apc, unless the mismatch repair system is disrupted, in which case, tumor formation results from new acquisition of protein-truncating mutations in Apc. In contrast to polyketide synthase-positive Escherichia coli (pks+ E. coli), ETBF does not produce a unique mutational signature; instead, ETBF-induced tumors arise from errors in DNA mismatch repair and homologous recombination DNA damage repair, established pathways of tumor formation in the colon, and the same genetic mechanism accounting for sham tumors in these mouse models. Our analysis informs how this procarcinogenic bacterium may promote tumor formation in individuals with inherited predispositions to CRC, such as Lynch syndrome or familial adenomatous polyposis (FAP).IMPORTANCE Many studies have shown that microbiome composition in both the mucosa and the stool differs in individuals with sporadic and hereditary colorectal cancer (CRC). Both human and mouse models have established a strong association between particular microbes and colon tumor induction. However, the genetic mechanisms underlying putative microbe-induced colon tumor formation are not well established. In this paper, we applied whole-exome sequencing and whole-genome sequencing to investigate the impact of ETBF-induced genetic changes on tumor formation. Additionally, we performed whole-genome sequencing of human colon organoids exposed to ETBF to validate the mutational patterns seen in our mouse models and begin to understand their relevance in human colon epithelial cells. The results of this study highlight the importance of ETBF colonization in the development of sporadic CRC and in individuals with hereditary tumor conditions, such as Lynch syndrome and familial adenomatous polyposis (FAP).

Genetic variation at the catalytic subunit of glutamate cysteine ligase contributes to the susceptibility to sporadic colorectal cancer: a pilot study.

Glutathione is a tripeptide detoxifying a variety of exogenous and endogenous free radicals and carcinogens, and a deficiency of glutathione is associated with an increased host susceptibility to oxidative stress, a pathological condition implicated in the development and progression of cancer. The catalytic subunit of glutamate-cysteine ligase (GCLC) is an enzyme responsible for the initial and rate-limiting step of glutathione biosynthesis. The aim of this pilot study was to investigate whether genetic variation at the GCLC gene contributes to the risk of colorectal cancer (CRC). DNA samples from 681 unrelated Russian individuals (283 patients with CRC and 398 age- and sex-matched healthy controls) were genotyped for six common functional SNPs of the GCLC gene (SNPs) such as rs12524494, rs17883901, rs606548, rs636933, rs648595 and rs761142 of the GCLC gene using the MassARRAY-4 system. We found that genotype rs606548-C/T is significantly associated with increased risk of CRC regardless of sex and age (OR 2.24; 95% CI 1.24-4.03; P = 0.007, FDR = 0.04). Moreover, ten GCLC genotype combinations showed association with the risk of CRC (P < 0.05). Functional SNP annotation enabled establishing the CRC-associated polymorphisms are associated with a decreased GCLC expression that may be attributed to epigenetic effects of histone modifications operating in a colon-specific manner. The present study was the first to show that genetic variation at the catalytic subunit of glutamate-cysteine ligase may contribute to the risk of colorectal cancer risk. However, further genetic association studies with a larger sample size are required to substantiate the role of GCLC gene polymorphisms in the development of sporadic colorectal cancer.

A Comprehensive View on the Quercetin Impact on Colorectal Cancer.

Colorectal cancer (CRC) represents the third type of cancer in incidence and second in mortality worldwide, with the newly diagnosed case number on the rise. Among the diagnosed patients, approximately 70% have no hereditary germ-line mutations or family history of pathology, thus being termed sporadic CRC. Diet and environmental factors are to date considered solely responsible for the development of sporadic CRC; therefore; attention should be directed towards the discovery of preventative actions to combat the CRC initiation, promotion, and progression. Quercetin is a polyphenolic flavonoid plant secondary metabolite with a well-characterized antioxidant activity. It has been extensively reported as an anti-carcinogenic agent in the scientific literature, and the modulated targets of quercetin have been also characterized in the context of CRC, mainly in original research publications. In this fairly comprehensive review, we summarize the molecular targets of quercetin reported to date in in vivo and in vitro CRC models, while also giving background information about the signal transduction pathways that it up- and downregulates. Among the most relevant modulated pathways, the Wnt/β-catenin, PI3K/AKT, MAPK/Erk, JNK, or p38, p53, and NF-κB have been described. With this work, we hope to encourage further quests in the elucidation of quercetin anti-carcinogenic activity as single agent, as dietary component, or as pharmaconutrient delivered in the form of plant extracts.

Single-cell transcriptomic profiling unravels the adenoma-initiation role of protein tyrosine kinases during colorectal tumorigenesis

The adenoma-carcinoma sequence is a well-accepted roadmap for the development of sporadic colorectal cancer. However, cellular heterogeneity in aberrant epithelial cells limits our understanding of carcinogenesis in colorectal tissues. Here, we performed a single-cell RNA sequencing survey of 54,788 cells from patient-matched tissue samples, including blood, normal tissue, para-cancer, polyp, and colorectal cancer. At each stage of carcinogenesis, we characterized cell types, transcriptional signatures, and differentially expressed genes of distinct cell populations. The molecular signatures of epithelial cells at normal, benign, and malignant stages were defined at the single-cell scale. Adenoma and carcinoma precursor cell populations were identified and characterized followed by validation with large cohort biopsies. Protein tyrosine kinases (PTKs) BMX and HCK were identified as potential drivers of adenoma initiation. Specific BMX and HCK upregulations were observed in adenoma precursor cell populations from normal and adenoma biopsies. Overexpression of BMX and HCK significantly promoted colorectal epithelial cell proliferation. Importantly, in the organoid culture system, BMX and HCK upregulations resulted in the formation of multilayered polyp-like buds protruding towards the organoid lumen, mimicking the pathological polyp morphology often observed in colorectal cancer. Molecular mechanism analysis revealed that upregulation of BMX or HCK activated the JAK-STAT pathway. In conclusion, our work improved the current knowledge regarding colorectal epithelial evolution during carcinogenesis at the single-cell resolution. These findings may lead to improvements in colorectal cancer diagnosis and treatment.

Pro-mutagenic effects of the gut microbiota in a Lynch syndrome mouse model

ABSTRACT The gut microbiota strongly impacts the development of sporadic colorectal cancer (CRC), but it is largely unknown how the microbiota affects the pathogenesis of mismatch-repair-deficient CRC in the context of Lynch syndrome. In a mouse model for Lynch syndrome, we found a nearly complete loss of intestinal tumor development when animals were transferred from a conventional “open” animal facility to specific-pathogen-free (SPF) conditions. Using 16S sequencing we detected large changes in microbiota composition between the two facilities. Transcriptomic analyses of tumor-free intestinal tissues showed signs of strong intestinal inflammation in conventional mice. Whole exome sequencing of tumors developing in Msh2-Lynch mice revealed a much lower mutational load in the single SPF tumor than in tumors developing in conventional mice, suggesting reduced epithelial proliferation in SPF mice. Fecal microbiota transplantations with conventional feces altered the immune landscape and gut homeostasis, illustrated by increased gut length and elevated epithelial proliferation and migration. This was associated with drastic changes in microbiota composition, in particular increased relative abundances of different mucus-degrading taxa such as Desulfovibrio and Akkermansia, and increased bacterial-epithelial contact. Strikingly, transplantation of conventional microbiota increased microsatellite instability in untransformed intestinal epithelium of Msh2-Lynch mice, indicating that the composition of the microbiota influences the rate of mutagenesis in MSH2-deficient crypts.

Serine-threonine Kinase Receptor-Associated Protein is a Critical Mediator of APC Mutation–Induced Intestinal Tumorigenesis Through a Feed-Forward Mechanism

Inactivation of the Apc gene is a critical early event in the development of sporadic colorectal cancer (CRC). Expression of serine-threonine kinase receptor-associated protein (STRAP) is elevated in CRCs and is associated with poor outcomes. We investigated the role of STRAP in Apc mutation-induced intestinal tumor initiation and progression. We generated Strap intestinal epithelial knockout mice (StrapΔIEC) by crossing mice containing floxed alleles of Strap (Strapfl/fl) with Villin-Cre mice. Then we generated ApcMin/+;Strapfl/fl;Vill-Cre (ApcMin/+;StrapΔIEC) mice for RNA-sequencing analyses to determine the mechanism of function of STRAP. We used human colon cancer cell lines (DLD1, SW480, and HT29) and human and mouse colon tumor-derived organoids for STRAP knockdown and knockout and overexpression experiments. Strap deficiency extended the average survival of ApcMin/+ mice by 80 days and decreased the formation of intestinal adenomas. Expression profiling revealed that the intestinal stem cell signature, the Wnt/β-catenin signaling, and the MEK/ERK pathway are down-regulated in Strap-deficient adenomas and intestinal organoids. Correlation studies suggest that these STRAP-associated oncogenic signatures are conserved across murine and human colon cancer. STRAP associates with MEK1/2, promotes binding between MEK1/2 and ERK1/2, and subsequently induces the phosphorylation of ERK1/2. STRAP activated Wnt/β-catenin signaling through MEK/ERK-induced phosphorylation of LRP6. STRAP was identified as a target of mutated Apc and Wnt/β-catenin signaling as chromatin immunoprecipitation and luciferase assays revealed putative binding sites of the β-catenin/TCF4 complex on the Strap promoter. STRAP is a target of, and is required in, Apc mutation/deletion-induced intestinal tumorigenesis through a novel feed-forward STRAP/MEK-ERK/Wnt-β-catenin/STRAP regulatory axis.

Molecular Mechanisms of Alcohol-Induced Colorectal Carcinogenesis.

Simple SummaryAlcohol consumption is a leading cause of lifestyle-induced morbidity and mortality worldwide. It is well-established that there is an association between alcohol consumption and an increased risk of colorectal cancer. Long-term alcohol consumption causes a spectrum of liver diseases, including steatosis, hepatitis, and liver cancer, and is detrimental to many other organs. In the body, alcohol can be metabolized to chemicals that exhibit biological activity, such as acetaldehyde. The intracellular accumulation of these compounds can result in suppression of antioxidant defense systems, and alterations in DNA. In addition, they can elicit changes at the tissue level, leading to reductions in nutrient absorption, inflammation, and impairment of the immune system. Together, these effects may increase the risk of cancer in a variety of organs. This review discusses the mechanisms by which alcohol may promote colorectal cancer. It is anticipated that a clearer understanding of the mechanisms by which alcohol induces cancer will facilitate the development of more effective therapeutic interventions.The etiology of colorectal cancer (CRC) is complex. Approximately, 10% of individuals with CRC have predisposing germline mutations that lead to familial cancer syndromes, whereas most CRC patients have sporadic cancer resulting from a combination of environmental and genetic risk factors. It has become increasingly clear that chronic alcohol consumption is associated with the development of sporadic CRC; however, the exact mechanisms by which alcohol contributes to colorectal carcinogenesis are largely unknown. Several proposed mechanisms from studies in CRC models suggest that alcohol metabolites and/or enzymes associated with alcohol metabolism alter cellular redox balance, cause DNA damage, and epigenetic dysregulation. In addition, alcohol metabolites can cause a dysbiotic colorectal microbiome and intestinal permeability, resulting in bacterial translocation, inflammation, and immunosuppression. All of these effects can increase the risk of developing CRC. This review aims to outline some of the most significant and recent findings on the mechanisms of alcohol in colorectal carcinogenesis. We examine the effect of alcohol on the generation of reactive oxygen species, the development of genotoxic stress, modulation of one-carbon metabolism, disruption of the microbiome, and immunosuppression.

A case-control study examining the association of smad7 and TLR single nucleotide polymorphisms on the risk of colorectal cancer in ulcerative colitis.

Ulcerative colitis (UC) is characterized by chronic mucosal inflammation and an increased risk of colorectal cancer. smad7, TLR2 and TLR4 modulate intestinal inflammation and their polymorphisms affect the risk of development of sporadic colorectal cancer. The aim of the current study was to examine the association between single nucleotide polymorphisms (SNPs) in smad7, TLR2 and TLR4 and the development of colorectal cancer in patients with UC. DNA was extracted from formalin-fixed, paraffin-embedded tissue from 90 patients with UC who had undergone panproctocolectomy between 1985 and 2013 (30 with UC-associated colorectal cancer and 60 control UC patients). Control cases were matched 2:1 for age at diagnosis of colitis, duration of disease and gender. Genotyping was performed for the smad7 rs4464148, rs11874392, rs12953717 and rs4939827 SNPs, the TLR2 rs5743704 and rs5743708 SNPs and the TLR4 rs4986790 and rs4986791 SNPs. Sixty three of the 90 patients (70%) were men and the mean age at diagnosis of UC was 38.6±1.6years. The mean time to the diagnosis of UC-associated colorectal cancer was 13.5±1.9years. The 5-year recurrence-free and cancer-specific survival rates were 76% and 88%, respectively. All eight SNPs were in Hardy-Weinberg equilibrium. None of the eight SNPs assessed in smad7, TLR2 or TLR4 were associated with the development of UC-associated colorectal cancer at an allelic or genotypic level. These data do not support an association between polymorphisms in smad7, TLR2 or TLR4 and the development of UC-associated colorectal cancer.

Transcriptome and Gene Fusion Analysis of Synchronous Lesions Reveals lncMRPS31P5 as a Novel Transcript Involved in Colorectal Cancer

Fusion genes and epigenetic regulators (i.e., miRNAs and long non-coding RNAs) constitute essential pieces of the puzzle of the tumor genomic landscape, in particular in mechanisms behind the adenoma-to-carcinoma progression of colorectal cancer (CRC). In this work, we aimed to identify molecular signatures of the different steps of sporadic CRC development in eleven patients, of which synchronous samples of adenomas, tumors, and normal tissues were analyzed by RNA-Seq. At a functional level, tumors and adenomas were all characterized by increased activity of the cell cycle, cell development, cell growth, and biological proliferation functions. In contrast, organic survival and apoptosis-related functions were inhibited both in tumors and adenomas at different levels. At a molecular level, we found that three individuals shared a tumor-specific fusion named MRPS31-SUGT1, generated through an intra-chromosomal translocation on chromosome 13, whose sequence resulted in being 100% identical to the long non-coding RNA (lncRNA) MRPS31P5. Our analyses suggest that MRPS31P5 could take part to a competitive endogenous (ce)RNA network by acting as a miRNA sponge or/and as an interactor of other mRNAs, and thus it may be an important gene expression regulatory factor and could be used as a potential biomarker for the detection of early CRC events.

Soy Metabolism by Gut Microbiota from Patients with Precancerous Intestinal Lesions.

Background: Colorectal cancer (CRC) requires the presence of a variety of factors predisposing a tumorigenic milieu. Excluding familial clustering and hereditary CRC syndromes, the development of sporadic CRC from precancerous lesions is influenced by tissue inflammation, modulation of intestinal immunity, hormones, dietary habits and gut microbiota composition. As concerning the last two aspects, the intestinal presence of equol, the most biologically active metabolite of the soy isoflavone daidzein and the presence of a genetic determinant of gut microbiota able to metabolize daidzein, seem to lower the CRC risk. It has been hypothesized that the anaerobic microorganisms of the Bacteroides genus play a role in equol production. Aim: To evaluate the presence of (i) anaerobic gut microbiota and (ii) the urinary levels of soy isoflavones (daidzein, genistein and equol) in patients with and without precancerous lesions, challenged with a daidzein-rich soy extract. Methods: Consecutive subjects undergoing colonoscopy participated to the study. Feces were collected from all patients one week before colonoscopy for gut microbiota studies. After the endoscopy examination and the histological evaluation, 40 subjects, 20 with sporadic colorectal adenomas (SCA/P group) and 20 without proliferative lesions (control group) were enrolled for the study. Urine levels of soy isoflavones daidzein, genistein and their metabolite equol, were determined by high performance liquid chromatographic (HPLC) analysis and gut microbiota analysis was performed by Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS) procedure. Results: Seventeen different bacterial species were identified in the fecal samples of the forty subjects participating to the study. Ten bacterial species resulted anaerobic Gram-negative bacteria, all belonging to the Bacteroides genus. A significant difference of bacteria species was evidenced in the fecal samples of the two groups of subjects. Particularly important was the evidence of Parabacteroides distasonis, Clostridium clostridioforme and Pediococcus pentasaceus only in control fecal samples, such as the presence of Bacteroides fragilis and Prevotella melaningenica only in SCA/P fecal samples. Concerning the soy isoflavones levels, no statistically significant differences were revealed in the genistein and daidzein urinary levels between the two groups of subjects. On the contrary, urinary equol levels were undetectable in ten SCA/P subjects and in two controls; moreover, when present, the levels of urinary equol were significantly lower in SCA/P subjects compared to controls (0.24 ± 0.27 mg/24 hrs vs. 21.25 ± 4.3 mg/24 hrs, respectively, p = 1.12 × 10−6). Conclusions: Our results suggest that the presence of anaerobic Bacteroides in the colon, and the production of equol from soy, could determine a milieu able to contrast the development of colonic mucosa proliferative lesions.

Effects of high-fat diet and intestinal aryl hydrocarbon receptor deletion on colon carcinogenesis.

Consumption of a high-fat diet has been associated with an increased risk of developing colorectal cancer (CRC). However, the effects of the interaction between dietary fat content and the aryl hydrocarbon receptor (AhR) on colorectal carcinogenesis remain unclear. Mainly known for its role in xenobiotic metabolism, AhR has been identified as an important regulator for maintaining intestinal epithelial homeostasis. Although previous research using whole body AhR knockout mice has revealed an increased incidence of colon and cecal tumors, the unique role of AhR activity in intestinal epithelial cells (IECs) and modifying effects of fat content in the diet at different stages of sporadic CRC development are yet to be elucidated. In the present study, we have examined the effects of a high-fat diet on IEC-specific AhR knockout mice in a model of sporadic CRC. Although loss of AhR activity in IECs significantly induced the development of premalignant lesions, in a separate experiment, no significant changes in colon mass incidence were observed. Moreover, consumption of a high-fat diet promoted cell proliferation in crypts at the premalignant colon cancer lesion stage and colon mass multiplicity as well as β-catenin expression and nuclear localization in actively proliferating cells in colon masses. Our data demonstrate the modifying effects of high-fat diet and AhR deletion in IECs on tumor initiation and progression.NEW & NOTEWORTHY Through the use of an intestinal-specific aryl hydrocarbon receptor (AhR) knockout mouse model, this study demonstrates that the expression of AhR in intestinal epithelial cells is required to reduce the formation of premalignant colon cancer lesions. Furthermore, consumption of a high-fat diet and the loss of AhR in intestinal epithelial cells influences the development of colorectal cancer at various stages.

Influence of the Gut Microbiome, Diet, and Environment on Risk of Colorectal Cancer

Researchers have discovered associations between elements of the intestinal microbiome (including specific microbes, signaling pathways, and microbiota-related metabolites) and risk of colorectal cancer (CRC). However, it is unclear whether changes in the intestinal microbiome contribute to the development of sporadic CRC or result from it. Changes in the intestinal microbiome can mediate or modify the effects of environmental factors on risk of CRC. Factors that affect risk of CRC also affect the intestinal microbiome, including overweight and obesity; physical activity; and dietary intake of fiber, whole grains, and red and processed meat. These factors alter microbiome structure and function, along with the metabolic and immune pathways that mediate CRC development. We review epidemiologic and laboratory evidence for the influence of the microbiome, diet, and environmental factors on CRC incidence and outcomes. Based on these data, features of the intestinal microbiome might be used for CRC screening and modified for chemoprevention and treatment. Integrated prospective studies are urgently needed to investigate these strategies.

Effect of physical fitness on colorectal tumor development in patients with familial adenomatous polyposis.

Although accumulated epidemiological evidence indicates that a good physical fitness level may prevent the development of sporadic colorectal cancer (CRC), few studies have examined the effect of physical fitness level on familial adenomatous polyposis (FAP). This cross-sectional study aimed to examine the relationship between physical fitness and CRC development in patients with FAP.A total of 119 patients (54 male; 65 female) with FAP, aged 17 to 73 years, underwent a step test to induce exercise stress. Predicted maximal oxygen uptake (VO2max) was calculated for each patient by using heart rate as an index of physical fitness. The association of VO2max with the presence or absence of CRC and polyp diameter was examined. Patients with FAP were divided into 3 categories according to their VO2max (high, medium, and low). The association between maximum polyp size and VO2max among the patients with FAP without a history of colectomy was examined.The risk of CRC was significantly higher in the low VO2max group than in the high VO2max group (odds ratio = 4.07; 95% confidence interval, 1.02-16.26). The maximum polyp diameter was significantly negatively correlated with the VO2max among the patients with FAP without a history of colectomy (r = -.44, P = .01). In the multiple linear regression analysis, maximum polyp diameter was independently correlated with VO2max.Our results suggest a preventive association between physical fitness and CRC development or colorectal adenoma growth exists in patients with FAP.

Abstract 3446: STRAP is involved in mutated Apc-induced stemness and tumorigenesis in colon cancer

Abstract Inactivation of the Apc gene is a critical early event in the development of sporadic colorectal cancer (CRC). Loss of its normal function leads to constitutive activation of β-catenin/T-cell factor 4 signaling and hence transcription of Wnt target genes. The signaling scaffold protein STRAP is upregulated in several cancers, where it promotes tumorigenicity and stemness. Here, we tested the effect of conditional deletion of Strap on intestinal tumor formation and growth by crossing ApcMin/+ mice with mice that are null for Strap in the intestinal epithelium, Strapfl/fl;Vil-Cre mice (StrapIEKO). We observed a dramatic decrease in the number of intestinal polyps in the ApcMin/+;Strapfl/fl;Vil-Cre mice (called StrapIEKO;ApcMin/+) compared to mice with intact Strap (Strapfl/fl;ApcMin/+). In an attempt to understand the mechanism of function of STRAP, we have observed that colon tumors from StrapIEKO;ApcMin/+ mice displayed a decrease in β-catenin nuclear localization and downregulation of Wnt targets such as c-Myc, AXIN2, and CCND1. Enteroids prepared from StrapIEKO;ApcMin/+ mice exhibited more budding compared to the ApcMin/+ enteroids, indicating the role of STRAP in stemness. STRAP knockdown in human CRC cells significantly diminished β-catenin/TCF4 transcriptional activity. Specifically, STRAP knockdown impaired the assembly of β-catenin/TCF4 complex and recruitment of the complex to the promoters of β-catenin target genes. Functional proteomic analyses of crypt cells from different genetic mice suggested that the MEK/ERK signaling pathway is suppressed in StrapIEKO;ApcMin/+ mice that is required for the effect of STRAP on Wnt/β-catenin signaling. We have shown that STRAP associates with MEK1/2 and promotes binding between MEK1/2 and ERK1/2 and subsequently induces the phosphorylation of ERK1/2. Given that MEK/ERK signaling is found to promote Wnt/β-catenin signaling, our results suggest that STRAP indirectly induce Wnt/β-catenin signaling through activating MEK/ERK pathway. Importantly, STRAP is found to be a novel target of Wnt/β-catenin signaling as ChIP assays determined putative binding sites of β-catenin/TCF4 complex on Strap promoter. Finally, we showed that forced expression of STRAP in colon cancer organoids derived from patients with colon cancer can induce the growth of colon tumor organoids through promoting Wnt/β-catenin signaling. Altogether, these results suggest that STRAP is involved in mutated APC-induced tumor initiation through a novel feed-forward STRAP/MEK-ERK/β-catenin/STRAP regulatory axis. Citation Format: Trung Vu. STRAP is involved in mutated Apc-induced stemness and tumorigenesis in colon cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3446.

Metformin inhibits β-catenin phosphorylation on Ser-552 through an AMPK/PI3K/Akt pathway in colorectal cancer cells.

Several epidemiologic studies have revealed strong inverse associations between metformin use and risk of colorectal cancer development. Nevertheless, the underlying mechanisms are still uncertain. The Wnt/β-catenin pathway, which plays a central role in intestinal homeostasis and sporadic colorectal cancer development, is regulated by phosphorylation cascades that are dependent and independent of Wnt. Here we report that a non-canonical Ser552 phosphorylation in β-catenin, which promotes its nuclear accumulation and transcriptional activity, is blocked by metformin via AMPK-mediated PI3K/Akt signaling inhibition.

Candida albicans from a rectal swab is associated with newly diagnosed colorectal cancer - observational single centre study

Background: The role of gut microbiota in the development of sporadic colorectal cancer (CRC) is supported by a number of studies. However, the conclusiveness of metagenomic studies is questioned by technical pitfalls and limited by small cohort sizes. Therefore, culture techniques should be considered as a viable alternative, particularly when MALDI-TOF MS has brought about a breakthrough in pure culture examination by reducing labor, time and costs needed for identification.