Altered Interactions between the Gut Microbiome and Colonic Mucosa Precede Polyposis in APCMin/+ Mice

Mutation of the adenomatous polyposis coli (APC gene), an early event in the adenoma-carcinoma sequence, is present in 70-80% of sporadic human colorectal adenomas and carcinomas. To test the hypothesis that mutation of the APC gene alters microbial interactions with host intestinal mucosa prior to the development of polyposis, culture-independent methods (targeted qPCR assays and Illumina sequencing of the 16S rRNA gene V1V2 hypervariable region) were used to compare the intestinal microbial composition of 30 six-week old C57BL/6 APC^Min/+ and 30 congenic wild type (WT) mice. The results demonstrate that similar to 12-14 week old APC^Min/+ mice with intestinal neoplasia, 6 week old APC^Min/+ mice with no detectable neoplasia, exhibit an increased relative abundance of Bacteroidetes spp in the colon. Parallel mouse RNA sequence analysis, conducted on a subset of proximal colonic RNA samples (6 APC^Min/+, 6 WT) revealed 130 differentially expressed genes (DEGs, fold change ≥ 2, FDR <0.05). Hierarchical clustering of the DEGs was carried out by using 1-r dissimilarity measurement, where r stands for the Pearson correlation, and Ward minimum variance linkage, in order to reduce the number of input variables. When the cluster centroids (medians) were included along with APC genotype as input variables in a negative binomial (NB) regression model, four of seven mouse gene clusters, in addition to APC genotype, were significantly associated with the increased relative abundance of Bacteroidetes spp. Three of the four clusters include several downregulated genes encoding immunoglobulin variable regions and non-protein coding RNAs. These results support the concept that mutation of the APC gene alters colonic-microbial interactions prior to polyposis. It remains to be determined whether interventions directed at ameliorating dysbiosis in APC^Min/+mice, such as through probiotics, prebiotics or antibiotics, could reduce tumor formation.     

Cyclin D1 genetic heterozygosity regulates colonic epithelial cell differentiation and tumor number in ApcMin mice

Constitutive β-catenin/Tcf activity, the primary transforming events in colorectal carcinoma, occurs through induction of the Wnt pathway or APC gene mutations that cause familial adenomatous polyposis. Mice carrying Apc mutations in their germ line (Apc^Min) develop intestinal adenomas. Here, the crossing of Apc^Min with cyclin D1^−/− mice reduced the intestinal tumor number in animals genetically heterozygous or nullizygous for cyclin D1. Decreased tumor number in the duodenum, intestines, and colons of Apc^Min/cyclin D1^+/− mice correlated with reduced cellular proliferation and increased differentiation. Cyclin D1 deficiency reduced DNA synthesis and induced differentiation of colonic epithelial cells harboring mutant APC but not wild-type APC cells in vivo. In previous studies, the complete loss of cyclin D1 through homozygous genetic deletion conveyed breast tumor resistance. The protection of mice, genetically predisposed to intestinal tumorigenesis, through cyclin D1 heterozygosity suggests that modalities that reduce cyclin D1 abundance could provide chemoprotection.     

Synthesis and in vivo evaluation of N-ethylamino-2-oxo-1,2-dihydro-quinoline-3-carboxamide for inhibition of intestinal tumorigenesis in APCMin/+ mice

A selective KGFR tyrosine kinase inhibitor, N-ethylamino-2-oxo-1,2-dihydro-quinoline-3-carboxamide, was synthesized and its possible inhibitory effects on the development of colon polyps and colorectal tumors was examined in APC^Min/+ mice, a mouse model of human intestinal familial adenomatous polyposis. The present study shows for the first time that a dietary administration of a selective KGFR tyrosine kinase inhibitor lacks the overt-toxicities and significantly reduced the growth of small intestinal polyps in both male and female APC^Min/+ mice. This inhibition of polyp growth appears to occur at a greater extent in female mice.     

LC–MS/MS-based metabolome analysis detected changes in the metabolic profiles of small and large intestinal adenomatous polyps in <Emphasis Type="Italic">Apc</Emphasis><Superscript><Emphasis Type="Italic">Min</Emphasis>/+</Superscript> mice

Introduction

The adenomatous polyposis coli (APC) gene is a tumor suppressor gene that is inactivated in the initiation of colorectal neoplasia. Apc ^Min/+ mice, which possess a heterozygous APC mutation, develop numerous adenomatous polyps, which are similar to those observed in familial adenomatous polyposis (FAP) in humans. However, unlike FAP patients, Apc ^Min/+ mice predominantly develop adenomatous polyps in the small intestine. The metabolic changes associated with the development of polyps in the small and large intestine remain to be investigated.

Objectives

The objective of this study was to elucidate the metabolic changes associated with intestinal polyp formation.

Methods

We compared the metabolite levels of pairs of polyp and non-polyp tissues obtained from the small intestines (n = 12) or large intestines (n = 7) of Apc ^Min/+ mice. To do this, we analyzed the tissue samples using two methods, liquid chromatography-tandem mass spectrometry (1) with a pentafluorophenylpropyl column for cation analysis, and (2) with a C18 reversed phase column coupled to an ion-pair reagent for anion analysis.

Results

Pathway mapping of the metabolites whose levels were significantly altered revealed that the polyp tissue of the small intestine contained significantly higher levels of intermediates involved in glycolysis, the pentose phosphate pathway, nucleotide metabolism, or glutathione biosynthesis than in the equivalent non-polyp tissue. In addition, significantly higher levels of methionine cycle intermediates were detected in the polyp tissues of both the large and small intestines. Organ-dependent (small vs. large intestine) differences were also detected in the levels of most amino acids and urea cycle intermediates.

Conclusion

Our results indicate that various metabolic changes are associated with polyp development, and understanding these alterations could make it possible to evaluate the treatment response of colorectal cancer earlier.

     

CCR6, the Sole Receptor for the Chemokine CCL20, Promotes Spontaneous Intestinal Tumorigenesis

Interactions between the inflammatory chemokine CCL20 and its receptor CCR6 have been associated with colorectal cancer growth and metastasis, however, a causal role for CCL20 signaling through CCR6 in promoting intestinal carcinogenesis has not been demonstrated in vivo. In this study, we aimed to determine the role of CCL20-CCR6 interactions in spontaneous intestinal tumorigenesis. CCR6-deficient mice were crossed with mice heterozygous for a mutation in the adenomatous polyposis coli (APC) gene (APC^MIN/+ mice) to generate APC^MIN/+ mice with CCR6 knocked out (CCR6KO-APC^MIN/+ mice). CCR6KO-APC^MIN/+ mice had diminished spontaneous intestinal tumorigenesis. CCR6KO-APC^MIN/+ also had normal sized spleens as compared to the enlarged spleens found in APC^MIN/+ mice. Decreased macrophage infiltration into intestinal adenomas and non-tumor epithelium was observed in CCR6KO-APC^MIN/+ as compared to APC^MIN/+ mice. CCL20 signaling through CCR6 caused increased production of CCL20 by colorectal cancer cell lines. Furthermore, CCL20 had a direct mitogenic effect on colorectal cancer cells. Thus, interactions between CCL20 and CCR6 promote intestinal carcinogenesis. Our results suggest that the intestinal tumorigenesis driven by CCL20-CCR6 interactions may be driven by macrophage recruitment into the intestine as well as proliferation of neoplastic epithelial cells. This interaction could be targeted for the treatment or prevention of malignancy.     

Acarbose improved survival for Apc+/Min mice

Acarbose blocks the digestion of complex carbohydrates, and the NIA Intervention Testing Program (ITP) found that it improved survival when fed to mice. Yet, we do not know if lifespan extension was caused by its effect on metabolism with regard to the soma or cancer suppression. Cancer caused death for ~80% of ITP mice. The ITP found rapamycin, an inhibitor to the pro‐growth mTORC1 (mechanistic target of rapamycin complex 1) pathway, improved survival and it suppressed tumors in Apc^+/Min mice providing a plausible rationale to ask if acarbose had a similar effect. Apc^+/Min is a mouse model prone to intestinal polyposis and a mimic of familial adenomatous polyposis in people. Polyp‐associated anemia contributed to their death. To address this knowledge gap, we fed two doses of acarbose to Apc^+/Min mice. Acarbose improved median survival at both doses. A cross‐sectional analysis was performed next. At both doses, ACA fed mice exhibited reduced intestinal crypt depth, weight loss despite increased food consumption and reduced postprandial blood glucose and plasma insulin, indicative of improved insulin sensitivity. Dose‐independent and dose‐dependent compensatory liver responses were observed for AMPK and mTORC1 activities, respectively. Only mice fed the high dose diet exhibited reductions in tumor number with higher hematocrits. Because low‐dose acarbose improved lifespan but failed to reduced tumors, its effects seem to be independent of cancer. These data implicate the importance of improved carbohydrate metabolism on survival.     

Mutational analysis of patients with adenomatous polyposis: Identical inactivating mutations in unrelated individuals

Samples of constitutional DNA from 60 unrelated patients with adenomatous polyposis coli (APC) were examined for mutations in the APC gene. Five inactivating mutations were observed among 12 individuals with APC; all were different from the six inactivating mutations previously reported in this panel of patients. The newly discovered mutations included single-nucleotide substitutions leading to stop codons and small deletions leading to frameshifts. Two of the mutations were observed in multiple APC families and in sporadic cases of APC; allele-specific PCR primers were designed for detecting mutations at these common sites. No missense mutations that segregated with the disease were found.     

Infection with genotoxin‐producing Salmonella enterica synergises with loss of the tumour suppressor APC in promoting genomic instability via the PI3K pathway in colonic epithelial cells

Several commensal and pathogenic Gram‐negative bacteria produce DNA‐damaging toxins that are considered bona fide carcinogenic agents. The microbiota of colorectal cancer (CRC) patients is enriched in genotoxin‐producing bacteria, but their role in the pathogenesis of CRC is poorly understood. The adenomatous polyposis coli (APC) gene is mutated in familial adenomatous polyposis and in the majority of sporadic CRCs. We investigated whether the loss of APC alters the response of colonic epithelial cells to infection by Salmonella enterica, the only genotoxin‐producing bacterium associated with cancer in humans. Using 2D and organotypic 3D cultures, we found that APC deficiency was associated with sustained activation of the DNA damage response, reduced capacity to repair different types of damage, including DNA breaks and oxidative damage, and failure to induce cell cycle arrest. The reduced DNA repair capacity and inability to activate adequate checkpoint responses was associated with increased genomic instability in APC‐deficient cells exposed to the genotoxic bacterium. Inhibition of the checkpoint response was dependent on activation of the phosphatidylinositol 3‐kinase pathway. These findings highlight the synergistic effect of the loss of APC and infection with genotoxin‐producing bacteria in promoting a microenvironment conducive to malignant transformation.     

Role of nucleotide excision repair deficiency in intestinal tumorigenesis in multiple intestinal neoplasia (Min) mice

Mice deficient in the Xeroderma pigmentosum group A (Xpa) gene are defective in nucleotide excision repair (NER) and highly susceptible to skin carcinogenesis after dermal exposure to UV light or chemicals. Min (multiple intestinal neoplasia) mice, heterozygous for a germline nonsense mutation in the tumor suppressor gene adenomatous polyposis coli (Apc), develop intestinal tumors spontaneously and show additional intestinal tumors after exposure to the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). In this study, we investigated the impact of loss of XPA function on PhIP-induced intestinal tumorigenesis in F1 offspring of Min/+ (Apc^+/−) mice crossed with Xpa gene-deficient mice. Apc^+/− mice lacking both alleles of Xpa had higher susceptibility towards toxicity of PhIP, higher levels of PhIP–DNA adducts in the middle and distal small intestines, as well as in liver, and a higher number of small intestinal tumors at 11 weeks, compared with Apc^+/− mice with one or two intact Xpa alleles. Localization of tumors was not affected, being highest in middle and distal small intestines in all genotypes. At 11 weeks of age, the number of spontaneous intestinal tumors was not significantly increased by homozygous loss of Xpa, but untreated Apc^+/−/Xpa^−/− mice had significantly shorter life-spans than their XPA-proficient littermates. Heterozygous loss of Xpa did not affect any of the measured end points. In conclusion, the Xpa gene and the NER pathway are involved in repair of bulky PhIP–DNA adducts in the intestines and the liver, and most probably of DNA lesions leading to spontaneous intestinal tumors. These results confirm a role of the NER pathway also in protection against cancer in internal organs, additional to its well-known importance in protection against skin cancer. An effect of Apc^+/− on adduct levels, additional to that of Xpa^−/−, indicates that the truncated APC protein may affect a repair pathway other than NER.     

Lipid profiling of mouse intestinal organoids for studying APC mutations

Inactivating mutations including both germline and somatic mutations in the adenomatous polyposis coli (APC) gene drives most familial and sporadic colorectal cancers. Understanding the metabolic implications of this mutation will aid to establish its wider impact on cellular behaviour and potentially inform clinical decisions. However, to date, alterations in lipid metabolism induced by APC mutations remain unclear. Intestinal organoids have gained widespread popularity in studying colorectal cancer and chemotherapies, because their 3D structure more accurately mimics an in vivo environment. Here, we aimed to investigate intra-cellular lipid disturbances induced by APC gene mutations in intestinal organoids using a reversed-phase ultra-high-performance liquid chromatography mass spectrometry (RP-UHPLC-MS)-based lipid profiling method. Lipids of the organoids grown from either wild-type (WT) or mice with APC mutations (Lgr5–EGFP-IRES-CreER^T2 Apc^fl/fl) were extracted and analysed using RP-UHPLC-MS. Levels of phospholipids (e.g. PC(16:0/16:0), PC(18:1/20:0), PC(38:0), PC(18:1/22:1)), ceramides (e.g. Cer(d18:0/22:0), Cer(d42:0), Cer(d18:1/24:1)) and hexosylceramides (e.g. HexCer(d18:1/16:0), HexCer(d18:1/22:0)) were higher in Apc^fl/fl organoids, whereas levels of sphingomyelins (e.g. SM(d18:1/14:0), SM(d18:1/16:0)) were lower compared with WT. These observations indicate that cellular metabolism of sphingomyelin was up-regulated, resulting in the cellular accumulation of ceramides and production of HexCer due to the absence of Apc^fl/fl in the organoids. Our observations demonstrated lipid profiling of organoids and provided an enhanced insight into the effects of the APC mutations on lipid metabolism, making for a valuable addition to screening options of the organoid lipidome.     

More than two decades of Apc modeling in rodents

Mutation of tumor suppressor gene adenomatous polyposis coli (APC) is an initiating step in most colon cancers. This review summarizes Apc models in mice and rats, with particular concentration on those most recently developed, phenotypic variation among different models, and genotype/phenotype correlations.     

Elevated expression of p53 in early colon polyps in a pig model of human familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is a hereditary predisposition to formation of colon polyps that can progress to colorectal cancer (CRC). The severity of polyposis varies substantially within families bearing the same germline mutation in the adenomatous polyposis coli (APC) tumour suppressor gene. The progressive step-wise accumulation of genetic events in tumour suppressor genes and oncogenes leads to oncogenic transformation, with driver alterations in the tumour protein p53 (TP53) gene playing a key role in advanced stage CRC. We analysed groups of pigs carrying a truncating mutation in APC (APC^1311/+; orthologous to human APC^1309/+) to study the influence of TP53 polymorphisms and expression on the frequency of polyp formation and polyp progression in early-stage FAP. Five generations of APC^1311/+ pigs were examined by colonoscopy for polyposis severity and development. A total of 19 polymorphisms were found in 5′-flanking, coding, and 3′ untranslated regions of TP53. The distribution of TP53 genotypes did not differ between APC^1311/+ pigs with low (LP) and high (HP) number of colon polyps. p53 mRNA expression was analysed in distally located normal mucosa samples of wild-type pigs, APC^1311/+ LP and HP pigs, and also in distally located polyp samples histologically classified as low-grade (LG-IEN) and high-grade intraepithelial dysplastic (HG-IEN) from APC^1311/+ pigs. p53 mRNA expression was found to be significantly elevated in HG-IEN compared to LG-IEN samples (p?= 0.012), suggesting a role for p53 in the early precancerous stages of polyp development.     

The armadillo repeat domain of Apc suppresses intestinal tumorigenesis

The adenomatous polyposis coli (APC) gene is known to act as a tumor suppressor gene in both sporadic and hereditary colorectal cancer by negatively regulating WNT signaling. Familial adenomatous polyposis (FAP) patients develop intestinal polyps due to the presence of a single germline mutation in APC. The severity of the FAP phenotype is a function of the position of the APC mutation, indicating a complex role for APC that extends beyond the canonical WNT pathway. APC encodes a large protein with multiple functional domains, including an armadillo repeat domain that has been linked to protein–protein interactions. To determine the effect of the armadillo repeat domain on intestinal tumorigenesis, we generated a congenic mouse line (Apc ^Δ242 ) carrying a gene trap cassette between exons 7 and 8 of the murine Apc gene. Apc ^Δ242/+ mice express a truncated Apc product lacking the armadillo repeat domain as part of a fusion protein with β-geo. Expression of the fusion product was confirmed by X-gal staining, ensuring that Apc ^Δ242 is not a null allele. In contrast, Apc ^Min/+ mice produce a truncated Apc product that contains an intact armadillo repeat domain. On the C57BL/6J background, Apc ^Δ242/+ mice develop more polyps than do Apc ^Min/+ mice along the entire length of the small intestine; however, polyps were significantly smaller in Apc ^Δ242/+ mice. In addition, polyp multiplicity in Apc ^Δ242/+ mice is affected by polymorphisms between inbred strains. These data suggest that the armadillo repeat domain of the Apc protein suppresses tumor initiation in the murine intestine while also promoting tumor growth.     

Germline mutations of the adenomatous polyposis coli (APC) gene in Algerian familial adenomatous polyposis cohort: first report

Background

Familial adenomatous polyposis (known also as classical or severe FAP) is a rare autosomal dominant colorectal cancer predisposition syndrome, characterized by the presence of hundreds to thousands of adenomatous polyps in the colon and rectum from an early age. In the absence of prophylactic surgery, colorectal cancer (CRC) is the inevitable consequence of FAP. The vast majority of FAP is caused by germline mutations in the adenomatous polyposis coli (APC) tumor suppressor gene (5q21). To date, most of the germline mutations in classical FAP result in truncation of the APC protein and 60% are mainly located within exon 15.

Material and methods

In this first nationwide study, we investigated the clinical and genetic features of 52 unrelated Algerian FAP families. We screened by PCR-direct sequencing the entire exon 15 of APC gene in 50 families and two families have been analyzed by NGS using a cancer panel of 30 hereditary cancer genes.

Results

Among 52 FAP index cases, 36 had 100 or more than 100 polyps, 37 had strong family history of FAP, 5 developed desmoids tumors, 15 had extra colonic manifestations and 21 had colorectal cancer. We detected 13 distinct germline mutations in 17 FAP families. Interestingly, 4 novel APC germline pathogenic variants never described before have been identified in our study.

Conclusions

The accumulating knowledge about the prevalence and nature of APC variants in Algerian population will contribute in the near future to the implementation of genetic testing and counseling for FAP patients.

     

The Somatic Mutation Hit on Top of Genetic APC mutations Cause Skin Tumor

Inactivation of the adenomatous polyposis coli (APC) gene is the initiating event in familial adenomatous polyposis (FAP) patients. Up to 90% of FAP patients show intestinal tumors and other extracolonic malignancies including hepatoblastomas, desmoid tumors, and brain cancer. APC mutation mice (Apc^Min/+ mice) develop benign polyps in the intestinal tract. It has been reported that small numbers of Apc^Min/+ mice develop breast carcinomas. Here, we found that approximately 1.6% of Apc^Min/+ mice suffered skin neoplasm. The results demonstrated that these skin tumors are not derived from intestinal adenomas. Sequencing of skin tumors of Apc^Min/+ mice and Apc^Min/+ mice skin. The data showed that somatic mutations and gene expression levels changed greatly in skin tumors compared to control. Similarly, APC mutation accounts for 27% in the patients of nonmelanoma skin carcinomas in cancer database, and two above genes mutation coexist was observed in all patients. Furthermore, using gene mutation reagent (DMBA)–treated Apc^Min/+ mice skin, the skin epithelium and glandular begin hyperplasia in Apc^Min/+ mice. These findings revealed that the somatic mutation hit on the germline mutation increase the tumor incidence, suggesting that the somatic mutation should be avoided if the germline mutation exists in one body.     

Identification of Mom12 and Mom13, two novel modifier loci of ApcMin-mediated intestinal tumorigenesis

Colorectal cancer is a heterogeneous disease resulting from a combination of genetic and environmental factors. The C57BL/6J (B6) Apc^Min/+ mouse develops polyps throughout the gastrointestinal tract and has been a valuable model for understanding the genetic basis of intestinal tumorigenesis. Apc^Min/+ mice have been used to study known oncogenes and tumor suppressor genes on a controlled genetic background. These studies often utilize congenic knockout alleles, which can carry an unknown amount of residual donor DNA. The Apc^Min model has also been used to identify modifer loci, known as Modifier of Min (Mom) loci, which alter Apc^Min-mediated intestinal tumorigenesis. B6 mice carrying a knockout allele generated in WW6 embryonic stem cells were crossed to B6 Apc^Min/+ mice to determine the effect on polyp multiplicity. The newly generated colony developed significantly more intestinal polyps than Apc^Min/+ controls. Polyp multiplicity did not correlate with inheritance of the knockout allele, suggesting the presence of one or more modifier loci segregating in the colony. Genotyping of simple sequence length polymorphism (SSLP) markers revealed residual 129X1/SvJ genomic DNA within the congenic region of the parental knockout line. An analysis of polyp multiplicity data and SSLP genotyping indicated the presence of two Mom loci in the colony: (1) Mom12, a dominant modifier linked to the congenic region on chromosome 6 and (2) Mom13, which is unlinked to the congenic region and whose effect is masked by Mom12. The identification of Mom12 and Mom13 demonstrates the potential problems resulting from residual heterozygosity present in congenic lines.Key words: adenomatous polyposis coli, modifier of min, congenic mice, caveolin-1, cancer susceptibility     

Repurposing the FDA-Approved Pinworm Drug Pyrvinium as a Novel Chemotherapeutic Agent for Intestinal Polyposis

Mutations in the WNT-pathway regulator ADENOMATOUS POLYPOSIS COLI (APC) promote aberrant activation of the WNT pathway that is responsible for APC-associated diseases such as Familial Adenomatous Polyposis (FAP) and 85% of spontaneous colorectal cancers (CRC). FAP is characterized by multiple intestinal adenomas, which inexorably result in CRC. Surprisingly, given their common occurrence, there are few effective chemotherapeutic drugs for FAP. Here we show that the FDA-approved, anti-helminthic drug Pyrvinium attenuates the growth of WNT-dependent CRC cells and does so via activation of CK1α. Furthermore, we show that Pyrvinium can function as an in vivo inhibitor of WNT-signaling and polyposis in a mouse model of FAP: APC^min mice. Oral administration of Pyrvinium, a CK1α agonist, attenuated the levels of WNT-driven biomarkers and inhibited adenoma formation in APC^min mice. Considering its well-documented safe use for treating enterobiasis in humans, our findings suggest that Pyrvinium could be repurposed for the clinical treatment of APC-associated polyposes.     

Oncogenic mutations in adenomatous polyposis coli (Apc) activate mechanistic target of rapamycin complex 1 (mTORC1) in mice and zebrafish

Truncating mutations in adenomatous polyposis coli (APC) are strongly linked to colorectal cancers. APC is a negative regulator of the Wnt pathway and constitutive Wnt activation mediated by enhanced Wnt–β-catenin target gene activation is believed to be the predominant mechanism responsible for APC mutant phenotypes. However, recent evidence suggests that additional downstream effectors contribute to APC mutant phenotypes. We previously identified a mechanism in cultured human cells by which APC, acting through glycogen synthase kinase-3 (GSK-3), suppresses mTORC1, a nutrient sensor that regulates cell growth and proliferation. We hypothesized that truncating Apc mutations should activate mTORC1 in vivo and that mTORC1 plays an important role in Apc mutant phenotypes. We find that mTORC1 is strongly activated in apc mutant zebrafish and in intestinal polyps in Apc mutant mice. Furthermore, mTORC1 activation is essential downstream of APC as mTORC1 inhibition partially rescues Apc mutant phenotypes including early lethality, reduced circulation and liver hyperplasia. Importantly, combining mTORC1 and Wnt inhibition rescues defects in morphogenesis of the anterior-posterior axis that are not rescued by inhibition of either pathway alone. These data establish mTORC1 as a crucial, β-catenin independent effector of oncogenic Apc mutations and highlight the importance of mTORC1 regulation by APC during embryonic development. Our findings also suggest a new model of colorectal cancer pathogenesis in which mTORC1 is activated in parallel with Wnt/β-catenin signaling.KEY WORDS: APC, Wnt, mTOR, mTORC1, Zebrafish, Colon cancer, Polyposis, GSK-3