Early Stages Of Colorectal Carcinogenesis Research Articles

Cyclooxygenase Inhibitors and Cancer: The Missing Pieces.

At 125, aspirin still represents the cornerstone of anti-platelet therapy for the acute treatment and long-term prevention of atherothrombosis. The development of a selective regimen of low-dose aspirin for the inhibition of platelet thromboxane production was key to maximizing its antithrombotic efficacy and minimizing its gastrointestinal toxicity. Based on about 50 observational studies, published over the past 30 years, aspirin and other cyclooxygenase inhibitors have been associated with a reduced risk of colorectal cancer, and possibly other digestive tract cancers. The apparent chemopreventive effect of aspirin has been confirmed in post-hoc analyses of randomized cardiovascular trials and their meta-analyses. Moreover, prevention of sporadic colorectal adenoma recurrence was demonstrated by randomized controlled trials of low-dose aspirin and selective cyclooxygenase-2 inhibitors. A single placebo-controlled randomized trial of aspirin has shown long-term colorectal cancer prevention in patients with the Lynch syndrome. The sequential involvement of thromboxane-dependent platelet activation and cyclooxygenase-2-driven inflammatory response in the early stages of colorectal carcinogenesis may explain these clinical benefits. The aim of this mini-review is to analyze the existing evidence for a chemopreventive effect of aspirin and other cyclooxygenase inhibitors and discuss the missing pieces of this mechanistic and clinical puzzle. SIGNIFICANCE STATEMENT: Low-dose aspirin and other cyclooxygenase inhibitors have been associated with a reduced risk of colorectal cancer, and possibly other digestive tract cancers. The sequential involvement of thromboxane-dependent platelet activation and cyclooxygenase-2-driven inflammatory response in the early stages of colorectal carcinogenesis may explain these clinical benefits. The aim of this mini-review is to analyze the evidence for a chemopreventive effect of aspirin and other cyclooxygenase inhibitors and discuss the missing pieces of this mechanistic and clinical puzzle.

Four methylation-driven genes detected by linear discriminant analysis model from early-stage colorectal cancer and their methylation levels in cell-free DNA.

The process of colorectal cancer (CRC) formation is considered a typical model of multistage carcinogenesis in which aberrant DNA methylation plays an important role. In this study, 752 methylation-driven genes (MDGs) were identified by the MethylMix package based on methylation and gene expression data of CRC in The Cancer Genome Atlas (TCGA). Iterative recursive feature elimination (iRFE) based on linear discriminant analysis (LDA) was used to determine the minimum MDGs (iRFE MDGs), which could distinguish between cancer and cancer-adjacent tissues. Further analysis indicated that the changes in methylation levels of the four iRFE MDGs, ADHFE1-Cluster1, CNRIP1-Cluster1, MAFB, and TNS4, occurred in adenoma tissues, while changes did not occur until stage IV in cell-free DNA. Furthermore, the methylation levels of iRFE MDGs were correlated with the genes involved in the reprogramming process of somatic cells to pluripotent stem cells, which is considered the common signature of cancer cells and embryonic stem cells. The above results indicated that the four iRFE MDGs may play roles in the early stage of colorectal carcinogenesis and highlighted the complicated relationship between tissue DNA and cell-free DNA (cfDNA).

Plasma metabolomic profiles for colorectal cancer precursors in women.

How metabolome changes influence the early process of colorectal cancer (CRC) development remains unknown. We conducted a 1:2 matched nested case-control study to examine the associations of pre-diagnostic plasma metabolome (profiled using LC-MS) with risk of CRC precursors, including conventional adenomas (n = 586 vs. 1141) and serrated polyps (n = 509 vs. 993), in the Nurses' Health Study (NHS) and NHSII. Conditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI). We used the permutation-based Westfall and Young approach to account for multiple testing. Subgroup analyses were performed for advanced conventional adenomas (defined as at least one adenoma of ≥ 10mm or with high-grade dysplasia, or tubulovillous or villous histology) and high-risk serrated polyps that were located in the proximal colon or with size of ≥ 10mm. After multiple testing correction, among 207 metabolites, higher levels of C36:3 phosphatidylcholine (PC) plasmalogen were associated with lower risk of conventional adenomas, with the OR (95% CI) comparing the 90th to the 10th percentile of 0.62 (0.48-0.81); C54:8 triglyceride (TAG) was associated with higher risk of serrated polyps (OR = 1.79, 95% CI: 1.31-2.43), and phenylacetylglutamine (PAG) was associated with lower risk (OR = 0.57, 95% CI:0.43-0.77). PAG was also inversely associated with advanced adenomas (OR = 0.57, 95% CI: 0.36-0.89) and high-risk serrated polyps (OR = 0.54, 95% CI: 0.32-0.89), although the multiple testing-corrected p value was > 0.05. Our findings suggest potential roles of lipid metabolism and phenylacetylglutamine, a microbial metabolite, in the early stage of colorectal carcinogenesis, particularly for the serrated pathway.

The CRCbiome study: a large prospective cohort study examining the role of lifestyle and the gut microbiome in colorectal cancer screening participants

BackgroundColorectal cancer (CRC) screening reduces CRC incidence and mortality. However, current screening methods are either hampered by invasiveness or suboptimal performance, limiting their effectiveness as primary screening methods. To aid in the development of a non-invasive screening test with improved sensitivity and specificity, we have initiated a prospective biomarker study (CRCbiome), nested within a large randomized CRC screening trial in Norway. We aim to develop a microbiome-based classification algorithm to identify advanced colorectal lesions in screening participants testing positive for an immunochemical fecal occult blood test (FIT). We will also examine interactions with host factors, diet, lifestyle and prescription drugs. The prospective nature of the study also enables the analysis of changes in the gut microbiome following the removal of precancerous lesions.MethodsThe CRCbiome study recruits participants enrolled in the Bowel Cancer Screening in Norway (BCSN) study, a randomized trial initiated in 2012 comparing once-only sigmoidoscopy to repeated biennial FIT, where women and men aged 50–74 years at study entry are invited to participate. Since 2017, participants randomized to FIT screening with a positive test result have been invited to join the CRCbiome study. Self-reported diet, lifestyle and demographic data are collected prior to colonoscopy after the positive FIT-test (baseline). Screening data, including colonoscopy findings are obtained from the BCSN database. Fecal samples for gut microbiome analyses are collected both before and 2 and 12 months after colonoscopy. Samples are analyzed using metagenome sequencing, with taxonomy profiles, and gene and pathway content as primary measures. CRCbiome data will also be linked to national registries to obtain information on prescription histories and cancer relevant outcomes occurring during the 10 year follow-up period.DiscussionThe CRCbiome study will increase our understanding of how the gut microbiome, in combination with lifestyle and environmental factors, influences the early stages of colorectal carcinogenesis. This knowledge will be crucial to develop microbiome-based screening tools for CRC. By evaluating biomarker performance in a screening setting, using samples from the target population, the generalizability of the findings to future screening cohorts is likely to be high.Trial registrationClinicalTrials.gov Identifier: NCT01538550.

Association of folate intake and colorectal cancer risk in the postfortification era in US women

Folate may play a preventive role in the early stages of colorectal carcinogenesis, but long latencies may be needed to observe a reduction in colorectal cancer (CRC) incidence. In addition, concerns have been raised about the potential for cancer promotion with excessive folate intake, especially after the mandatory folic acid fortification in the United States in 1998. We aimed to examine the association between folate intake in different chemical forms and CRC risk, especially in the postfortification era in the United States. We prospectively followed 86,320 women from the Nurses' Health Study (1980-2016). Folate intake was collected by validated food frequency questionnaires. CRC was self reported and confirmed by review of medical records. The association between the folate intake and CRC risk was assessed using Cox proportional hazards regression. We documented 1988 incident CRC cases during follow-up. Analyzing folate intake as a continuous variable, greater total folate intake 12-24 y before diagnosis was associated with lower risk of CRC (per increment of 400 dietary folate equivalents (DFE)/d, HR: 0.93, 95% CI: 0.85, 1.01 for 12-16 y; HR: 0.83, 95% CI: 0.75, 0.92 for 16-20 y; and HR: 0.87, 95% CI: 0.77, 0.99 for 20-24 y); and greater synthetic folic acid intake 16-24 y before diagnosis was also associated with a lower CRC risk (per increment of 400 DFE/d, HR: 0.91, 95% CI: 0.84, 0.99 for 16-20 y and HR: 0.91, 95% CI: 0.83-1.01 for 20-24 y). In the postfortification period (1998-2016), intake of total or specific forms of folate was not associated with CRC risk, even among multivitamin users. Folate intake, both total and from synthetic forms, was associated with a lower risk of overall CRC after long latency periods. There was no evidence that high folate intake in the postfortification period was related to increased CRC risk in this US female population.

Abstract 2557: 15-lipoxygenase-1 suppresses linoleic acid promotion of colorectal tumorigenesis through oxidative metabolism of PI3P_linoleic acid to inhibit membranous LRP5 recycling and WNT/β-catenin signaling activation

Abstract Western-type diets have been increasingly enriched with linoleic acid (LA). The impact of excess dietary LA on cancer risk remains poorly understood although some studies suggest that high LA diets promote chemically-induced colorectal carcinogenesis (CRC) in rodent models. 15-lipoxygenase-1 (15-LOX-1), the main metabolizing enzyme of LA, is transcriptionally silenced during the early stages of CRC. Whether 15-LOX-1 impacts the effects of excess LA on CRC is unknown. Herein, we report that high dietary LA promoted CRC in intestinally targeted APC mutation (ApcΔ580) and azoxymethane-induced CRC mouse models by upregulating expression of LRP5, a Wnt receptor, and aberrant β-catenin activation. These effects were negatively regulated by 15-LOX-1 when this enzyme was transgenically expressed in intestinal epithelial cells. Complementary genetic deletion studies of 15-LOX-1 in mice further supported 15-LOX-1's suppressive effects on these events. Mechanistic studies showed that 15-LOX-1 peroxidation of LA in phosphatidylinositol-3-phosphates (PI3P_LA) into PI3P_13-HODE decreased PI3P binding to SNX17 and LRP5, which inhibited LRP5 recycling from endosomes to the plasma membrane, thereby leading to an increase of LRP5 lysosomal degradation. Our findings demonstrate for the first time the importance of linoleic acid metabolism by 15-LOX-1 within complex lipids such as PI3P in regulating LRP5 membranous abundance and subsequently Wnt/β-catenin aberrant signaling activation and CRC risk. These results strongly support the need to carefully consider the potential of increasing CRC risk by enriching the diets with LA especially for individuals with low 15-LOX-1 expression. Citation Format: Fuyao Liu, Xiangsheng Zuo, Yi Liu, Yasunori Deguchi, Micheline J. Moussalli, Weidong Chen, Peiying Yang, Bo Wei, Lin Tan, Philip L. Lorenzi, Shen Gao, Jonathan C. Jaoude, Amir Mehdizadeh, Lovie A. Valentin, Daoyan Wei, Imad Shureiqi. 15-lipoxygenase-1 suppresses linoleic acid promotion of colorectal tumorigenesis through oxidative metabolism of PI3P_linoleic acid to inhibit membranous LRP5 recycling and WNT/β-catenin signaling activation [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2557.

NAP1L1: A Novel Human Colorectal Cancer Biomarker Derived From Animal Models of Apc Inactivation.

IntroductionColorectal cancer (CRC) is the second leading cause of cancer death worldwide and most deaths result from metastases. We have analyzed animal models in which Apc, a gene that is frequently mutated during the early stages of colorectal carcinogenesis, was inactivated and human samples to try to identify novel potential biomarkers for CRC.Materials and MethodsWe initially compared the proteomic and transcriptomic profiles of the small intestinal epithelium of transgenic mice in which Apc and/or Myc had been inactivated. We then studied the mRNA and immunohistochemical expression of one protein that we identified to show altered expression following Apc inactivation, nucleosome assembly protein 1–like 1 (NAP1L1) in human CRC samples and performed a prognostic correlation between biomarker expression and survival in CRC patients.ResultsNap1l1 mRNA expression was increased in mouse small intestine following Apc deletion in a Myc dependant manner and was also increased in human CRC samples. Immunohistochemical NAP1L1 expression was decreased in human CRC samples relative to matched adjacent normal colonic tissue. In a separate cohort of 75 CRC patients, we found a strong correlation between NAP1L1 nuclear expression and overall survival in those patients who had stage III and IV cancers.ConclusionNAP1L1 expression is increased in the mouse small intestine following Apc inactivation and its expression is also altered in human CRC. Immunohistochemical NAP1L1 nuclear expression correlated with overall survival in a cohort of CRC patients. Further studies are now required to clarify the role of this protein in CRC.

Antibiotic Use Associated With Risk of Colorectal Polyps in a Nationwide Study

Use of antibiotics affects the composition of the microbiome and might affect development of colorectal polyps, which are precursors to colorectal cancer. We performed a nested case-control study in Sweden of 45,744 patients with a colorectal polyp (cases) in the nationwide gastrointestinal ESPRESSO histopathology cohort, using unaffected full siblings as controls (n= 93,307). Polyps were classified by morphology SnoMed codes into conventional adenomas and serrated polyps. Through linkage to the Prescribed Drug Register, we assessed use and cumulative dispensations of antibiotic until 1 year prior to polyp diagnosis for cases and their sibling controls. During a median study period of 6.9 years, compared with non-users, users of antibiotics (including 28,884 cases [63.1%] and 53,222 sibling controls [57.0%]) had a higher risk of colorectal polyps (odds ratio [OR], 1.08; 95% CI, 1.04-1.13). Risk increased with higher number of dispensations (OR for ≥ 6 dispensations, 1.33; 95% CI, 1.25-1.43) (Ptrend < .0001). We observed a stronger association with polyps for broad-spectrum antibiotics (OR comparing users to non-users, 1.23; 95% CI, 1.18-1.29) than for narrow-spectrum antibiotics (OR, 1.05; 95% CI, 1.01-1.10), and for tetracyclines and quinolones (OR, 1.21) than penicillin and other classes (ORs ranged from 1.04 to 1.16). The findings remained robust with several sensitivity analyses, including use of a 2-year lead-in period for antibiotic assessment and correction for misclassification in controls. Use of broad-spectrum antibiotics was more strongly associated with risk of serrated polyps (OR, 1.29; 95% CI, 1.21-1.38) compared with risk of conventional adenomas (OR, 1.17; 95% CI, 1.11-1.24). We found no differences in risk of colon vs rectal polyps with antibiotic use (Pheterogeneity > .10). We found stronger associations for younger (<50 years) vs older adults (≥50 years) for users of quinolones, sulfonamides, trimethoprim, and cephalosporins (Pinteraction < .001). In a nationwide case-control study in Sweden, after accounting for hereditary and early life environmental factors, antibiotic use was associated with increased risk of colorectal polyps. Our findings indicate a role for intestinal dysbiosis in early stages of colorectal carcinogenesis.

Serotonin synthesis protects the mouse colonic crypt from DNA damage and colorectal tumorigenesis.

Serotonin (5-HT) signaling pathways are thought to be involved in colorectal tumorigenesis (CRT), but the role of 5-HT synthesis in the early steps of this process is presently unknown. In this study, we used carcinogen treatment in the tryptophan hydroxylase 1 knockout (Tph1KO) and transgenic (Tph1fl/fl VillinCre ) mouse models defective in 5-HT synthesis to investigate the early mutagenic events associated with CRT. Our observations of the colonic crypt post-treatment followed a timeline designed to understand how disruption of 5-HT synthesis affects the initial steps leading to CRT. We found Tph1KO mice had decreased development of both allograft tumors and colitis-related CRT. Interestingly, carcinogenic exposure alone induced multiple colon tumors and increased cyclooxygenase-2 (Ptgs2) expression in Tph1KO mice. Deletion of interleukin 6 (Il6) in Tph1KO mice confirmed that inflammation was a part of the process. 5-HT deficiency increased colonic DNA damage but inhibited genetic repair of specific carcinogen-related damage, leading to CRT-related inflammatory reactions and dysplasia. To validate a secondary effect of 5-HT deficiency on another DNA repair pathway, we exposed Tph1KO mice to ionizing radiation and found an increase in DNA damage associated with reduced levels of ataxia telangiectasia and Rad3 related (Atr) gene expression in colonocytes. Restoring 5-HT levels with 5-hydroxytryptophan treatment decreased levels of DNA damage and increased Atr expression. Analysis of Tph1fl/fl VillinCre mice with intestine-specific loss of 5-HT synthesis confirmed that DNA repair was tissue specific. In this study, we report a novel protective role for 5-HT synthesis that promotes DNA repair activity during the early stages of colorectal carcinogenesis. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Epigenetic silencing of the synthesis of immunosuppressive Siglec ligand glycans by NF-κB/EZH2/YY1 axis in early-stage colon cancers

Normal colonic epithelial cells express sialyl 6-sulfo Lewisx and disialyl Lewisa on their cell surface, which are ligands for the immunosuppressive molecule Siglec-7. Expression of these normal glycans is frequently lost upon malignant transformation by silencing DTDST and ST6GalNAc6 at the early stage of colorectal carcinogenesis, and leads to production of inflammatory mediators that facilitate carcinogenesis.Indeed, by querying The Cancer Genome Atlas datasets, we confirmed that the level of DTDST or ST6GalNAc6 mRNA is substantially decreased at the early stage of colorectal carcinogenesis. Cultured colon cancer cell lines were used in this study including DLD-1, HT-29, LS174T and SW620. Their promoter regions were strongly marked by repressive mark H3K27me3, catalyzed by EZH2 that was markedly upregulated in early stage of colorectal carcinogenesis. Suppression of EZH2 substantially downregulated H3K27me3 mark and upregulated DTDST and ST6GalNAc6 as well as expression of normal glycans and Siglec-binding activities.Transcription factor YY1 was vital for the recruitment of PRC2-containing EZH2 to both promoters. Inhibition of NF-κB substantially reduced EZH2 transcription and restored their mRNAs as well as the production of normal Siglec ligand glycans in the results obtained from in vitro studies on cultured colon cancer cell lines.These findings provide a putative mechanism for promotion of carcinogenesis by loss of immunosuppressive molecules by epigenetic silencing through NF-κB-mediated EZH2/YY1 axis.

The association between fecal microbiota and different types of colorectal polyp as precursors of colorectal cancer

BackgroundColon cancer (CRC) is a heterogeneous disorder, arising from precursors-adenoma and serrated polyp. Previous studies have demonstrated the relationship between the human gut microbiota and CRC; however, its correlation to the different early precursors of CRC is not properly understood. Here, we studied the relationship between targeted gut bacteria and different colorectal polyp types, location, size and grade of dysplasia. Material and methodsIn the present case-control descriptive study, selected fecal bacteria were assessed in 118 patients, referred for standard screening colonoscopy, including 31 normal controls, 21 hyperplastic polyp (HP), 16 sessile serrated polyp (SSA), 29 tubular adenoma (TA) and 21 villous/tubuvillous polyp (VP/TVP) cases, between 2015 and 2017, by absolute quantitative real time PCR technique (q PCR) in different ethnicity of Iranian population. The panel of bacteria was including Streptococcus bovis/gallolyticus, Enterococcus faecalis, Enterotoxigenic Bacteroides fragilis (ETBF), Fusobacterium nucleatum, Porphyromonas spp., Lactobacillus spp., Roseburia spp., and Bifidobacterium spp. ResultsHigher numbers of F. nucleatum, E. feacalis, S. bovis, ETBF and Porphyromonas spp. were detected in AP cases, consisting TA and especially VP/TVP, in contrast to samples from the normal, HP and SSA groups (P < 0.001). On the contrary, lower number of Lactobacillus spp., Roseburia spp. and Bifidobacterium spp. were detected in AP, compared to the normal, HP and SSA. Surprisingly, a significant correlation was found among selected gut bacterial quantity, the size, location and grade of dysplasia of polyp cases. DiscussionThese findings suggest that gut bacteria might contribute in early stages of colorectal carcinogenesis through the development of AP, but not SSA. In fact, AP and SSA are also different in terms of molecular pathways and tendencies to present in specific colorectal location. Overall, these findings may lead to development of CRC prevention therapies, targeting early protagonist bacteria of colorectal carcinogenesis from AP.

Paracrine cyclooxygenase-2 activity by macrophages drives colorectal adenoma progression in the ApcMin/+ mouse model of intestinal tumorigenesis

Genetic deletion or pharmacological inhibition of cyclooxygenase (COX)-2 abrogates intestinal adenoma development at early stages of colorectal carcinogenesis. COX-2 is localised to stromal cells (predominantly macrophages) in human and mouse intestinal adenomas. Therefore, we tested the hypothesis that paracrine Cox-2-mediated signalling from macrophages drives adenoma growth and progression in vivo in the ApcMin/+ mouse model of intestinal tumorigenesis. Using a transgenic C57Bl/6 mouse model of Cox-2 over-expression driven by the chicken lysozyme locus (cLys-Cox-2), which directs integration site-independent, copy number-dependent transgene expression restricted to macrophages, we demonstrated that stromal macrophage Cox-2 in colorectal (but not small intestinal) adenomas from cLys-Cox-2 x ApcMin/+ mice was associated with significantly increased tumour size (P = 0.025) and multiplicity (P = 0.025), compared with control ApcMin/+ mice. Transgenic macrophage Cox-2 expression was associated with increased dysplasia, epithelial cell Cox-2 expression and submucosal tumour invasion, as well as increased nuclear β-catenin translocation in dysplastic epithelial cells. In vitro studies confirmed that paracrine macrophage Cox-2 signalling drives catenin-related transcription in intestinal epithelial cells. Paracrine macrophage Cox-2 activity drives growth and progression of ApcMin/+ mouse colonic adenomas, linked to increased epithelial cell β-catenin dysregulation. Stromal cell (macrophage) gene regulation and signalling represent valid targets for chemoprevention of colorectal cancer.

Association of plasma C-reactive protein level with the prevalence of colorectal adenoma: the Colorectal Adenoma Study in Tokyo

Epidemiologic studies have identified a positive association between obesity and colorectal neoplasia. Adiposity induces systemic low-grade inflammation, which is commonly assessed with a sensitive biomarker, C-reactive protein (CRP). To understand the molecular mechanisms of obesity in the etiology of colorectal neoplasia, the present study was conducted in 782 adenoma cases and 738 controls who underwent total colonoscopy, and their plasma CRP level was evaluated in relation to colorectal adenoma prevalence. A logistic regression model was used to compute odds ratios (OR) and 95% confidence intervals (CI) of adenoma according to quartile of plasma CRP. Plasma CRP level was positively associated with higher adenoma prevalence in all subjects (OR 1.30; 95% CI 0.94–1.79 for the highest versus lowest quartile; P trend = 0.031). Further analysis by adenoma size and number revealed a pronounced association with a larger size (≥5 mm) and multiple numbers (≥2). These positive associations were reduced to non-significance following further adjustment for body mass index, and OR for the highest versus lowest quartile of plasma CRP became 1.12 (95% CI 0.80–1.56; P trend = 0.25) in all subjects. In conclusion, this study suggests that obesity-related systemic low-grade inflammation may play an important role in the early stages of colorectal carcinogenesis.

Abstract A02: High-depth sequencing reveals the presence of multi-clonality in colorectal premalignancy

Abstract Clonality in carcinomas is thought to arise from the accumulation of mutations and changes in selective pressure during carcinogenesis and further stages of tumor development. However, the identification of clonality through different molecular and systems biology tools has challenged the current understanding of carcinogenesis and progression. Familial Adenomatous Polyposis (FAP) is a genetic condition secondary to germline mutations in APC and characterized by the development of hundreds of polyps in the colorectum. Therefore, FAP is an ideal model to study the presence of clonality during early stages of colorectal carcinogenesis in humans. Second hits in APC are a valuable and intuitive method to establish the presence of clonality in FAP, as additional somatic APC mutations will reflect the presence of additional clones. Here, we present a targeted high-depth sequencing analysis of APC and KRAS in conjunction with high density SNP array data in 37 colorectal adenomas and matched adjacent uninvolved mucosa samples. Ampliseq sequencing was performed using the next-generation sequencing platform IT Personal Genome Machine (PGM; Life Technologies) using the Ion PGM 200 Sequencing Kit on an Ion 318 Chip Kit (Life Technologies, average of 70% bases at 500x). Ion Torrent Variant Caller v4.2 was run in the somatic low stringency proton mode to detect variants in APC and KRAS against hg19. Then, normal variants were subtracted from matched adenoma variants to create a list of somatic candidates for each adenoma and normal pair. SNP array analysis was performed using the HumanOmniExpressExome-8 v1.2 BeadChip (Illumina, San Diego, CA). To validate the presence of double somatic hits in APC we performed a colony genotyping assay from one adenoma sample. First, we identified APC somatic mutations or loss of heterogeneity (LOH) in 5q (second hits) in 81% (30/37) and KRAS somatic mutations in 35% (16/37) of adenomas analyzed. Six adenomas (16%) presented double somatic APC mutations with different allelic frequencies with three of them showing a significant difference in allelic frequencies among the somatic APC hits (&amp;gt;30%); in addition, one adenoma presented two KRAS mutations. The APC clonality was validated in one adenoma using colony analysis. The region that contains the two somatic mutations (c.4348C&amp;gt;T and c.4267_4280del) and the germline mutation (c.2894delA) was amplified by Long-Range PCR and cloned into the pGEM-T plasmid. DNA from one hundred colonies was extracted and genotyped using Taqman assay probes. All samples were genotyped in triplicate and positive and negative controls for all mutations were included in every single plate. A total of 25% of the colonies harbored a wild-type allele, 36% the known germline APC mutation, 15% the APC somatic c.4348C&amp;gt;T mutation and 24% the APC somatic c.4267_4280del mutation. In conclusion, our analysis showed that there are multiple mutated APC subclones driving initiation of colorectal carcinogenesis, thus supporting experimentally a finding of multi-clonality in premalignant colonic lesions. These findings support a model of colorectal carcinogenesis that is based on polycryptal polyclonal adenomas and calls for revisiting the “Big-Bang” model based on the presence of multiple initiator clones. Further analyses aimed to understand the functional impact and the hierarchical relations among the different identified subclones are warranted. Citation Format: Ester Borras, Kyle Chang, Anthony San Lucas, Gita Masand, Axel Delgado Amador, Jerry Fowler, Gareth E. Davies, Erik A. Ehli, Y. Nancy You, Patrick M. Lynch, Ernest T. Hawk, Gabriel Capella, Paul A. Scheet, Eduardo Vilar. High-depth sequencing reveals the presence of multi-clonality in colorectal premalignancy. [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer: From Initiation to Outcomes; 2016 Sep 17-20; Tampa, FL. Philadelphia (PA): AACR; Cancer Res 2017;77(3 Suppl):Abstract nr A02.

Dietary Inflammatory Index and Risk of Colorectal Adenoma Recurrence: A Pooled Analysis

ABSTRACTNo studies have evaluated the association between the dietary inflammatory index (DII) and colorectal adenoma recurrence. DII scores were calculated from a baseline food frequency questionnaire. Participants (n = 1727) were 40–80 years of age, enrolled in two Phase III clinical trials, who had ≥1 colorectal adenoma(s) removed within 6 months of study registration, and a follow-up colonoscopy during the trial. Multiple logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs). No statistically significant associations were found between DII and odds of colorectal adenoma recurrence [ORs (95% CIs) = 0.93 (0.73, 1.18) and 0.95 (0.73, 1.22)] for subjects in the second and third DII tertiles, respectively, compared to those in the lowest tertile (Ptrend = 0.72). No associations were found for recurrent colorectal adenoma characteristics, including advanced recurrent adenomas, large size, villous histology, or anatomic location. While our study did not support an association between a proinflammatory diet and colorectal adenoma recurrence, future studies are warranted to elucidate the role of a proinflammatory diet on the early stages of colorectal carcinogenesis.

The gut microbiota in conventional and serrated precursors of colorectal cancer.

BackgroundColorectal cancer is a heterogeneous disease arising from at least two precursors—the conventional adenoma (CA) and the serrated polyp. We and others have previously shown a relationship between the human gut microbiota and colorectal cancer; however, its relationship to the different early precursors of colorectal cancer is understudied. We tested, for the first time, the relationship of the gut microbiota to specific colorectal polyp types.ResultsGut microbiota were assessed in 540 colonoscopy-screened adults by 16S rRNA gene sequencing of stool samples. Participants were categorized as CA cases (n = 144), serrated polyp cases (n = 73), or polyp-free controls (n = 323). CA cases were further classified as proximal (n = 87) or distal (n = 55) and as non-advanced (n = 121) or advanced (n = 22). Serrated polyp cases were further classified as hyperplastic polyp (HP; n = 40) or sessile serrated adenoma (SSA; n = 33). We compared gut microbiota diversity, overall composition, and normalized taxon abundance among these groups.CA cases had lower species richness in stool than controls (p = 0.03); in particular, this association was strongest for advanced CA cases (p = 0.004). In relation to overall microbiota composition, only distal or advanced CA cases differed significantly from controls (p = 0.02 and p = 0.002). In taxon-based analysis, stool of CA cases was depleted in a network of Clostridia operational taxonomic units from families Ruminococcaceae, Clostridiaceae, and Lachnospiraceae, and enriched in the classes Bacilli and Gammaproteobacteria, order Enterobacteriales, and genera Actinomyces and Streptococcus (all q < 0.10). SSA and HP cases did not differ in diversity or composition from controls, though sample size for these groups was small. Few taxa were differentially abundant between HP cases or SSA cases and controls; among them, class Erysipelotrichi was depleted in SSA cases.ConclusionsOur results indicate that gut microbes may play a role in the early stages of colorectal carcinogenesis through the development of CAs. Findings may have implications for developing colorectal cancer prevention therapies targeting early microbial drivers of colorectal carcinogenesis.Electronic supplementary materialThe online version of this article (doi:10.1186/s40168-016-0218-6) contains supplementary material, which is available to authorized users.

Thymoquinone subdues tumor growth and potentiates the chemopreventive effect of 5-fluorouracil on the early stages of colorectal carcinogenesis in rats.

Colorectal cancer (CRC) is one of the most prevalent cancers and has a high mortality rate. Insensitivity and the limited therapeutic efficacy of its standard chemotherapeutic drug, 5-fluorouracil (5-FU), represents an important challenge in CRC treatment. The robust antitumor properties of thymoquinone (TQ), the main bioactive constituent of Nigella sativa, have recently been demonstrated on different cancers. We investigated whether TQ could potentiate the chemopreventive effect of 5-FU to eradicate the early stages of CRC and elucidated its underlying mechanisms. An intermediate-term (15 weeks) model of colorectal tumorigenesis was induced in male Wistar rats by azoxymethane (AOM), and the animals were randomly and equally divided into five groups: control, AOM, AOM/5-FU, AOM/TQ, and AOM/5-FU/TQ. TQ (35 mg/kg/d; 3 d/wk) was given during the seventh and 15th weeks post-AOM injection, while 5-FU was given during the ninth and tenth weeks (12 mg/kg/d for 4 days; then 6 mg/kg every other day for another four doses). At week 15, the resected colons were subjected to macroscopic, histopathological, molecular, and immunohistochemical examinations. Interestingly, 5-FU/TQ combination therapy resulted in a more significant reduction on AOM-induced colorectal tumors and large aberrant crypts foci than treatment with the individual drugs. Mechanistically, 5-FU and TQ remarkably cooperated to repress the expression of procancerous Wnt, β-catenin, NF-κB, COX-2, iNOS, VEGF, and TBRAS and upregulate the expression of anti-tumorigenesis DKK-1, CDNK-1A, TGF-β1, TGF-βRII, Smad4, and GPx. Overall, our findings present the first report describing the in vivo enhancement effect of combined TQ and 5-FU against early stages of CRC; however, further studies are required to determine the value of this combination therapy in an advanced long-term model of CRC and also to realize its clinical potential.

TP53 mutation at early stage of colorectal cancer progression from two types of laterally spreading tumors.

Although most sporadic colorectal cancers (CRC) are thought to develop from protruded adenomas through the adenoma–carcinoma sequence, some CRC develop through flat lesions, so‐called laterally spreading tumors (LST). We previously analyzed epigenetic aberrations in LST and found that LST are clearly classified into two molecular subtypes: intermediate‐methylation with KRAS mutation and low‐methylation with absence of oncogene mutation. Intermediate‐methylation LST were mostly granular type LST (LST‐G) and low‐methylation LST were mostly non‐granular LST (LST‐NG). In the present study, we conducted a targeted exon sequencing study including 38 candidate CRC driver genes to gain insight into how these genes modulate the development of LST. We identified a mean of 11.5 suspected nonpolymorphic variants per sample, including indels and non‐synonymous mutations, although there was no significant difference in the frequency of total mutations between LST‐G and LST‐NG. Genes associated with RTK/RAS signaling pathway were mutated more frequently in LST‐G than LST‐NG (P = 0.004), especially KRAS mutation occurring at 70% (30/43) of LST‐G but 26% (13/50) of LST‐NG (P < 0.0001). Both LST showed high frequency of APC mutation, even at adenoma stage, suggesting its involvement in the initiation stage of LST, as it is involved at early stage of colorectal carcinogenesis via adenoma‐carcinoma sequence. TP53 mutation was never observed in adenomas, but was specifically detected in cancer samples. TP53 mutation occurred during development of intramucosal cancer in LST‐NG, but during development of cancer with submucosal invasion in LST‐G. It is suggested that TP53 mutation occurs in the early stages of cancer development from adenoma in both LST‐G and LST‐NG, but is involved at an earlier stage in LST‐NG.

Depletion of enteroendocrine and mucus-secreting cells is associated with colorectal carcinogenesis severity and impaired intestinal motility in rats.

This study investigated the relationship between enteroendocrine and mucus-secreting cells distribution, the severity of colonic mucosal injury and intestinal motility in experimental colorectal carcinogenesis. Using a standardized murine model of colorectal carcinogenesis, eight-weeks-old female Wistar rats weighting 147.30 ± 29.15g were randomized into two groups receiving a subcutaneous injection of 0.9% saline (control) or the chemical carcinogen 1,2-dimethylhydrazine (DMH) at 20 mg/kg per week during 10 weeks. Aberrant crypt foci (ACF) were more frequent in DMH group compared to control group (P < 0.001). The number of enteroendocrine and mucus-secreting cells, and intestinal motility was reduced in DMH animals (P < 0.05). The distribution of enteric neurons was similar in both groups. In DMH animals there was a direct correlation between colonic motility and distribution of enteroendocrine (R(2) = 0.68, P < 0.05) and mucus-secreting cells (R(2) = 0.77, P < 0.05). Inverse correlation between the number of ACF, mucus-secreting cells (R(2) = -0.57, P < 0.05), and enteroendocrine cells (R(2) = -0.74, P < 0.05) was also observed. There was inverse correlation between the severity of the mucosal lesion, the number of mucus-secreting cells (R(2) = -0.83, P < 0.05) and enteroendocrine cells (R(2) = -0.96, P < 0.05). There was a direct correlation between nucleolar organizer regions (AgNOR) and ACF number (R(2) = 0.62; P < 0.01). Inverse correlation was also found between AgNOR, the number of mucus-secreting cells (R(2) = -0.76; P < 0.001), and enteroendocrine cells (R(2) = -0.86; P < 0.001). Taken together, the results indicated that colonic malignant transformation is related to depletion of mucus-secreting and enteroendocrine cells, which was a useful indicator of the evolutionary status of intestinal neoplasm, partially explaining the intestinal motility disorders in the early stages of colorectal carcinogenesis.

Aspects of dietary carbohydrate intake are not related to risk of colorectal polyps in the Tennessee Colorectal Polyp Study.

High digestible carbohydrate intakes can induce hyperglycemia and hyperinsulinemia and collectively have been implicated in colorectal tumor development. Our aim was to explore the association between aspects of dietary carbohydrate intake and risk of colorectal adenomas and hyperplastic polyps in a large case-control study. Colorectal polyp cases (n=1,315 adenomas only, n=566 hyperplastic polyps only and n=394 both) and controls (n=3,184) undergoing colonoscopy were recruited between 2003 and 2010 in Nashville, Tennessee, USA. Dietary intakes were estimated by a 108-item food frequency questionnaire. Unconditional logistic regression analysis was applied to determine odds ratios (OR) and corresponding 95% confidence intervals (CI) for colorectal polyps according to dietary carbohydrate intakes, after adjustment for potential confounders. No significant associations were detected for risk of colorectal adenomas when comparing the highest versus lowest quartiles of intake for total sugars (OR 1.03; 95% CI 0.84-1.26), starch (OR 1.01; 95% CI 0.81-1.26), total or available carbohydrate intakes. Similar null associations were observed between dietary carbohydrate intakes and risk of hyperplastic polyps, or concurrent adenomas and hyperplastic polyps. In this US population, digestible carbohydrate intakes were not associated with risk of colorectal polyps, suggesting that dietary carbohydrate does not have an etiological role in the early stages of colorectal carcinogenesis.