Reconstitution of the destruction complex defines roles of AXIN polymers and APC in ß-catenin capture, phosphorylation, and ubiquitylation.

The Wnt/ß-catenin pathway is a highly conserved, frequently mutated developmental and cancer pathway. Its output is defined mainly by ß-catenin's phosphorylation- and ubiquitylation-dependent proteasomal degradation, initiated by the multi-protein ß-catenin destruction complex. The precise mechanisms underlying destruction complex function have remained unknown, largely because of the lack of suitable in vitro systems. Here we describe the in vitro reconstitution of an active human ß-catenin destruction complex from purified components, recapitulating complex assembly, ß-catenin modification, and degradation. We reveal that AXIN1 polymerization and APC promote ß-catenin capture, phosphorylation, and ubiquitylation. APC facilitates ß-catenin's flux through the complex by limiting ubiquitylation processivity and directly interacts with the SCFß-TrCP E3 ligase complex in a ß-TrCP-dependent manner. Oncogenic APC truncation variants, although part of the complex, are functionally impaired. Nonetheless, even the most severely truncated APC variant promotes ß-catenin recruitment. These findings exemplify the power of biochemical reconstitution to interrogate the molecular mechanisms of Wnt/ß-catenin signaling.

Gene-specific ACMG/AMP classification criteria for germline APC variants: Recommendations from the ClinGen InSiGHT Hereditary Colorectal Cancer/Polyposis Variant Curation Expert Panel.

PURPOSE: The Hereditary Colorectal Cancer/Polyposis Variant Curation Expert Panel (VCEP) was established by the International Society for Gastrointestinal Hereditary Tumours and the Clinical Genome Resource, who set out to develop recommendations for the interpretation of germline APC variants underlying Familial Adenomatous Polyposis, the most frequent hereditary polyposis syndrome. METHODS: Through a rigorous process of database analysis, literature review, and expert elicitation, the APC VCEP derived gene-specific modifications to the ACMG/AMP (American College of Medical Genetics and Genomics and Association for Molecular Pathology) variant classification guidelines and validated such criteria through the pilot classification of 58 variants. RESULTS: The APC-specific criteria represented gene- and disease-informed specifications, including a quantitative approach to allele frequency thresholds, a stepwise decision tool for truncating variants, and semiquantitative evaluations of experimental and clinical data. Using the APC-specific criteria, 47% (27/58) of pilot variants were reclassified including 14 previous variants of uncertain significance (VUS). CONCLUSION: The APC-specific ACMG/AMP criteria preserved the classification of well-characterized variants on ClinVar while substantially reducing the number of VUS by 56% (14/25). Moving forward, the APC VCEP will continue to interpret prioritized lists of VUS, the results of which will represent the most authoritative variant classification for widespread clinical use.

Mutational inactivation of Apc in the intestinal epithelia compromises cellular organisation.

The adenomatous polyposis coli (Apc) protein regulates diverse effector pathways essential for tissue homeostasis. Truncating oncogenic mutations in Apc removing its Wnt pathway and microtubule regulatory domains drives intestinal epithelia tumorigenesis. Exuberant cell proliferation is one well-established consequence of oncogenic Wnt pathway activity; however, the contribution of other deregulated molecular circuits to tumorigenesis has not been fully examined. Using in vivo and organoid models of intestinal epithelial tumorigenesis we found that Wnt pathway activity controls intestinal epithelial villi and crypt structure, morphological features lost upon Apc inactivation. Although the Wnt pathway target gene c-Myc (also known as Myc) has critical roles in regulating cell proliferation and tumorigenesis, Apc specification of intestinal epithelial morphology is independent of the Wnt-responsive Myc-335 (also known as Rr21) regulatory element. We further demonstrate that Apc inactivation disrupts the microtubule cytoskeleton and consequently localisation of organelles without affecting the distribution of the actin cytoskeleton and associated components. Our data indicates the direct control over microtubule dynamics by Apc through an independent molecular circuit. Our study stratifies three independent Apc effector pathways in the intestinal epithelial controlling: (1) proliferation, (2) microtubule dynamics and (3) epithelial morphology.This article has an associated First Person interview with the first author of the paper.

A novel mutation of adenomatous polyposis coli (APC) gene results in the formation of supernumerary teeth.

Supernumerary teeth are teeth that are present in addition to normal teeth. Although several hypotheses and some molecular signalling pathways explain the formation of supernumerary teeth, but their exact disease pathogenesis is unknown. To study the molecular mechanisms of supernumerary tooth-related syndrome (Gardner syndrome), a deeper understanding of the aetiology of supernumerary teeth and the associated syndrome is needed, with the goal of inhibiting disease inheritance via prenatal diagnosis. We recruited a Chinese family with Gardner syndrome. Haematoxylin and eosin staining of supernumerary teeth and colonic polyp lesion biopsies revealed that these patients exhibited significant pathological characteristics. APC gene mutations were detected by PCR and direct sequencing. We revealed the pathological pathway involved in human supernumerary tooth development and the mouse tooth germ development expression profile by RNA sequencing (RNA-seq). Sequencing analysis revealed that an APC gene mutation in exon 15, namely 4292-4293-Del GA, caused Gardner syndrome in this family. This mutation not only initiated the various manifestations typical of Gardner syndrome but also resulted in odontoma and supernumerary teeth in this case. Furthermore, RNA-seq analysis of human supernumerary teeth suggests that the APC gene is the key gene involved in the development of supernumerary teeth in humans. The mouse tooth germ development expression profile shows that the APC gene plays an important role in tooth germ development. We identified a new mutation in the APC gene that results in supernumerary teeth in association with Gardner syndrome. This information may shed light on the molecular pathogenesis of supernumerary teeth. Gene-based diagnosis and gene therapy for supernumerary teeth may become available in the future, and our study provides a high-resolution reference for treating other syndromes associated with supernumerary teeth.

Germline APC mutations in hepatoblastoma.

BACKGROUND: Conflicting reports on the frequency of germline adenomatous polyposis coli (APC) gene mutations in patients with hepatoblastoma (HB) have called into question the clinical value of APC mutation testing on apparently sporadic HB. METHODS: An Institutional Review Board approved retrospective review of clinical data collected from patients with HB who received APC testing at our institution was conducted. All HB patients seen at Cincinnati Children's Hospital Medical Center were eligible for testing. Potential genotype/phenotype correlations were assessed. RESULTS: As of July 2015, 29 patients with HB had received constitutional APC testing. Four (14%) were found to have APC pathogenic truncations of the APC protein and in addition two (7%) had APC missense variants of unknown clinical significance. Two patients (7%) had family histories indicative of familial adenomatous polyposis (FAP). Response to chemotherapy tracked differently in APC pathogenic cases, with a slower imaging response despite an equivalent or slightly faster α-fetoprotein (AFP) response. CONCLUSION: The prevalence of pathogenic APC variants in apparently sporadic HB may be higher than previously detected. Differences in time to imaging response, despite similar AFP response, may impact surgical planning. All patients with HB warrant germline APC mutation testing for underlying FAP.

Pin1-mediated Modification Prolongs the Nuclear Retention of ß-Catenin in Wnt3a-induced Osteoblast Differentiation.

The canonical Wnt signaling pathway, in which ß-catenin nuclear localization is a crucial step, plays an important role in osteoblast differentiation. Pin1, a prolyl isomerase, is also known as a key enzyme in osteogenesis. However, the role of Pin1 in canonical Wnt signal-induced osteoblast differentiation is poorly understood. We found that Pin1 deficiency caused osteopenia and reduction of ß-catenin in bone lining cells. Similarly, Pin1 knockdown or treatment with Pin1 inhibitors strongly decreased the nuclear ß-catenin level, TOP flash activity, and expression of bone marker genes induced by canonical Wnt activation and vice versa in Pin1 overexpression. Pin1 interacts directly with and isomerizes ß-catenin in the nucleus. The isomerized ß-catenin could not bind to nuclear adenomatous polyposis coli, which drives ß-catenin out of the nucleus for proteasomal degradation, which consequently increases the retention of ß-catenin in the nucleus and might explain the decrease of ß-catenin ubiquitination. These results indicate that Pin1 could be a critical target to modulate ß-catenin-mediated osteogenesis.

Novel APC gene mutations associated with protein alteration in diffuse type gastric cancer.

BACKGROUND: The role of adenomatous polyposis coli (APC) gene in mitosis might be critical for regulation of genomic stability and chromosome segregation. APC gene mutations have been associated to have a role in colon cancer and since gastric and colon tumors share some common genetic lesions, it is relevant to investigate the role of APC tumor suppressor gene in gastric cancer. METHODS: We investigated for somatic mutations in the Exons 14 and 15 of APC gene from 40 diffuse type gastric cancersamples. Rabbit polyclonal anti-APC antibody was used, which detects the wild-type APC protein and was recommended for detection of the respective protein in human tissues. Cell cycle analysis was done from tumor and adjacent normal tissue. RESULTS: APC immunoreactivity showed positive expression of the protein in stages I, II, III and negative expression in Stages III and IV. Two novel deleterious variations (g.127576C > A, g.127583C > T) in exon 14 sequence were found to generate stop codon (Y622* and Q625*)in the tumor samples. Due to the generation of stop codon, the APC protein might be truncated and all the regulatory features could be lost which has led to the down-regulation of protein expression. Our results indicate that aneuploidy might occurdue to the codon 622 and 625 APC-driven gastric tumorigenesis, in agreement with our cell cycle analysis. The APC gene function in mitosis and chromosomal stability might be lost and G1 might be arrested with high quantity of DNA in the S phase. Six missense somatic mutations in tumor samples were detected in exon 15 A-B, twoof which showed pathological and disease causing effects based on SIFT, Polyphen2 and SNPs & GO score and were not previously reported in the literature or the public mutation databases. CONCLUSION: The two novel pathological somatic mutations (g.127576C > A, g.127583C > T) in exon 14 might be altering the protein expression leading to development of gastric cancer in the study population. Our study showed that mutations in the APC gene alter the protein expression and cell cycle regulation in diffuse type gastric adenocarcinoma.

Whole-exome sequencing of duodenal adenocarcinoma identifies recurrent Wnt/ß-catenin signaling pathway mutations.

BACKGROUND: Genomic alterations of small bowel cancers remain poorly understood due to the rarity of these diseases. In the current study, the authors report the identification of somatic mutations from patients with duodenal adenocarcinoma by whole-exome sequencing. METHODS: Whole-exome sequencing and follow-up analysis were conducted in 12 matched tumor-normal tissue duodenal adenocarcinoma tissue pairs to examine the genetic characteristics of this disease. Somatic mutations (single-nucleotide variants and short insertion/deletions) were obtained and filtered and then searched for recurrently mutated genes and pathways. RESULTS: An excess of C-to-T transitions at the CpG dinucleotide was observed in the substitution of bases. The authors identified recurrent mutations in tumor protein p53 (TP53), KRAS, catenin (cadherin-associated protein) ß-1 (CTNNB1), AT-rich interactive domain 2 (ARID2), adenomatous polyposis coli (APC), erb-b2 receptor tyrosine kinase 2 (ERBB2), ARID1A, cadherin-related family member 1 (CDHR1), NRAS, Bcl-2-related ovarian killer (BOK), radial spoke head 14 homolog (chlamydomonas) (RTDR1), cell division cycle 27 (CDC27), catalytic subunit of phosphoinositide-3-kinase (PIK3CA), and SMAD family member 4 (SMAD4). Pathway scan indicated that the Wnt signaling pathway, regulation of the actin cytoskeleton pathway, ErbB signaling pathway, and the pathway of focal adhesion were the most extensively affected pathways. CONCLUSIONS: This genomic characterization of duodenal adenocarcinoma provides researchers with insight into its somatic landscape and highlights the vital role of the Wnt/ß-catenin signaling pathway. The study data also indicate that duodenal adenocarcinomas have a genetic resemblance to gastric and colorectal cancers. These discoveries may benefit the future development of molecular diagnosis and personalized therapies. Cancer 2016;122:1689-96. © 2016 American Cancer Society.

The effect of a germline mutation in the APC gene on ß-catenin in human embryonic stem cells.

BACKGROUND: Most cases of colorectal cancer (CRC) are initiated by inactivation mutations in the APC gene, which is a negative regulator of the Wnt-ß-catenin pathway. Patients with familial adenomatous polyposis (FAP) inherit a germline mutation in one APC allele, and loss of the second allele leads to the development of polyps that will turn malignant if not removed. It is not fully understood which molecular mechanisms are activated by APC loss and when the loss of the second APC allele occurs. METHODS: Two FAP human embryonic stem cell (hESCs) lines were derived from APC mutated embryos following pre-implantation genetic diagnosis (PGD) for FAP. These FAP-hESCs were cultured in vitro and following extended culture: 1) ß-catenin expression was analyzed by Western blot analysis; 2) Wnt-ß-catenin/TCF-mediated transcription luciferase assay was performed; 3) cellular localization of ß-catenin was evaluated by immunoflorecence confocal microscopy; and 4) DNA sequencing of the APC gene was performed. RESULTS: We have established a novel human in-vitro model for studying malignant transformation, using hESCs that carry a germline mutation in the APC gene following PGD for FAP. Extended culturing of FAP1 hESCs led to activation of the Wnt signaling pathway, as demonstrated by enhanced ß-catenin/TCF-mediated activity. Additionally, ß-catenin showed a distinct perinuclear distribution in most (91 %) of the FAP1 hESCs high passage colonies. DNA sequencing of the whole gene detected several polymorphisms in FAP1 hESCs, however, no somatic mutations were discovered in the APC gene. On the other hand, no changes in ß-catenin were detected in the FAP2 hESCs, demonstrating the natural diversity of the human FAP population. CONCLUSIONS: Our results describe the establishment of novel hESC lines from FAP patients with a predisposition for cancer mutation. These cells can be maintained in culture for long periods of time and may serve as a platform for studying the initial molecular and cellular changes that occur during early stages of malignant transformation.

Differences in neuropsychological and behavioral parameters and brain structure in patients with familial adenomatous polyposis: a sibling-paired study.

BACKGROUND: Familial adenomatous polyposis (FAP) is an autosomal dominant hereditary colon cancer syndrome caused by mutations in adenomatous polyposis coli (APC) with both colonic and extra-colonic manifestations. Case reports have noted an association with FAP and intellectual disability and animal studies have shown that APC is implicated in neural development and function, but no studies have investigated neuropsychological, behavioral, or structural brain characteristics of patients with FAP. METHODS: We undertook a pilot, sibling-pair study comparing three patients with FAP to their sex-matched siblings without FAP. Each sibling pair underwent neuropsychological testing by a blinded examiner, high resolution brain MRI scans, and the mother of each pair rated her children's adaptive life skills and behavioral and emotional characteristics. Given the small number of study participants in this pilot study, quantitative comparisons of results were made by subtracting the score of the non-FAP sibling from the FAP patient on the various neuropsychological tests and parent rating questionnaires to calculate a difference, which was then divided by the standard deviation for each individual test to determine the difference, corrected for the standard deviation. Diffusion numbers in multiple regions of the brain as assessed by MRI were calculated for each study participant. RESULTS: We found similarity between siblings in all three pairs on a wide range of neuropsychological measures (general intelligence, executive function, and basic academic skills) as tested by the psychologist as well as in descriptions of adaptive life skills as rated by mothers. However, mothers' ratings of behavioral and emotional characteristics of two of the three pairs showed differences between the siblings, specifically that the patients with FAP were found to have more behavioral and emotional problems compared to their siblings. No differences in brain structure were identified by MRI. CONCLUSION: We report the first study exploring neuropsychological, behavioral, emotional, and structural brain characteristics of patients with FAP and found subjective differences as assessed by maternal perception in behavioral and emotional characteristics in patients with FAP compared to their siblings. Larger studies are needed to elucidate the relationship, if any, between FAP and brain function.

Clinicopathological and genetic differences between low-grade and high-grade colorectal mucinous adenocarcinomas.

BACKGROUND: Although colorectal mucinous adenocarcinomas (MCs) are conventionally regarded as exhibiting high-grade differentiation, they can be divided by differentiation into 2 groups according to the glandular appearance: low-grade mucinous adenocarcinoma (low-MC) and high-grade mucinous adenocarcinoma (high-MC). METHODS: Patients with colorectal cancer (CRC) who underwent surgical resection between 2000 and 2012 were enrolled in this study. Among the cases with MC, the clinicopathological and genetic differences between low-MC and high-MC were investigated with next-generation sequencing. RESULTS: A total of 1373 patients with CRC were analyzed. Forty patients (2.9%) had MC, and 13 patients had high-MC. Patients with MC had significantly shorter disease-free survival (DFS) and overall survival (OS) periods than those with nonmucinous carcinoma. When low-MC patients and high-MC patients were compared, those with high-MC had significantly shorter DFS and OS periods than those with low-MC. Multivariate analyses revealed that high-MC was significantly associated with both shorter DFS and shorter OS, but low-MC was not. A genome analysis revealed that low-MC had a considerably larger number of mutations than high-MC, and Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations and adenomatous polyposis coli mutations were particularly frequently found in low-MC. In contrast, SMAD family member 4 (SMAD4) mutations were frequently found in high-MC. CONCLUSIONS: High-MC is an independent prognostic factor in CRC (but low-MC is not), and it is genetically different from other CRCs, including low-MC. Both the clinicopathological differences and the genetic differences suggest that low-MC and high-MC should be distinguished in clinical settings.

Ehrlichia chaffeensis TRP120 ubiquitinates tumor suppressor APC to modulate Hippo and Wnt signaling.

Ehrlichia chaffeensis: TRP120 is a multifunctional effector that acts as a ligand mimic to activate evolutionary conserved eukaryotic signaling pathways Notch, Wnt, Hedgehog and Hippo. In addition, TRP120 is also a HECT E3 ubiquitin ligase known to ubiquitinate several host cell regulatory proteins (FBW7, PCGF5 and ENO-1) for degradation. We previously determined that TRP120 ubiquitinates the Notch negative regulator, FBW7, to maintain Notch signaling and promote infection. In this study, we investigated a potential mechanism used by Ehrlichia chaffeensis to maintain Hippo and Wnt signaling by ubiquitinating the tumor suppressor, adenomatous polyposis coli (APC), a negative regulator of Wnt and Hippo signaling. We determined that APC was rapidly degraded during E. chaffeensis infection despite increased APC transcription. Moreover, RNAi knockdown of APC significantly increased E. chaffeensis infection and coincided with increased active Yap and ß-catenin in the nucleus. We observed strong nuclear colocalization between TRP120 and APC in E. chaffeensis-infected THP-1 cells and after ectopic expression of TRP120 in HeLa cells. Additionally, TRP120 interacted with both APC full length and truncated isoforms via co-immunoprecipitation. Further, TRP120 ubiquitination of APC was demonstrated in vitro and confirmed by ectopic expression of a TRP120 HECT Ub ligase catalytic site mutant. This study identifies APC as a TRP120 HECT E3 Ub ligase substrate and demonstrates that TRP120 ligase activity promotes ehrlichial infection by degrading tumor suppressor APC to positively regulate Hippo and Wnt signaling.

Enhanced ApcMin/+ adenoma formation after epithelial CUL4B deletion by recruitment of myeloid-derived suppressor cells.

Colorectal cancer (CRC) stands as a prevalent malignancy globally. A pivotal event in CRC pathogenesis involves the loss-of-function mutation in the APC gene, leading to the formation of benign polyps. Despite the well-established role of APC, the contribution of CUL4B to CRC initiation in the pre-tumorous stage remains poorly understood. In this investigation, we generated a murine model by crossing ApcMin/+ mice with Cul4bΔIEC mice to achieve specific deletion of Cul4b in the gut epithelium against an ApcMin/+ background. By employing histological methods, RNA-sequencing (RNA-seq), and flow cytometry, we assessed alterations and characterized the immune microenvironment. Our results unveiled that CUL4B deficiency in gut epithelium expedited ApcMin/+ adenoma formation. Notably, CUL4B in adenomas restrained the accumulation of tumor-infiltrating myeloid-derived suppressor cells (MDSCs). In vivo inhibition of MDSCs significantly delayed the growth of CUL4B deleted ApcMin/+ adenomas. Furthermore, the addition of MDSCs to in vitro cultured ApcMin/+; Cul4bΔIEC adenoma organoids mitigated their alterations. Mechanistically, CUL4B directly interacted with the promoter of Csf3, the gene encoding granulocyte-colony stimulating factor (G-CSF) by coordinating with PRC2. Inhibiting CUL4B epigenetically activated the expression of G-CSF, promoting the recruitment of MDSCs. These findings offer novel insights into the tumor suppressor-like roles of CUL4B in regulating ApcMin/+ adenomas, suggesting a potential therapeutic strategy for CRC initiation and progression in the context of activated Wnt signaling.

When You Come to a Fork in the Road, Take It: Wnt Signaling Activates Multiple Pathways through the APC/Axin/GSK-3 Complex.

The Wnt signaling pathway is a highly conserved regulator of metazoan development and stem cell maintenance. Activation of Wnt signaling is an early step in diverse malignancies. Work over the past four decades has defined a "canonical" Wnt pathway that is initiated by Wnt proteins, secreted glycoproteins that bind to a surface receptor complex and activate intracellular signal transduction by inhibiting a catalytic complex composed of the classical tumor suppressor Adenomatous Polyposis Coli (APC), Axin, and Glycogen Synthase Kinase-3 (GSK-3). The best characterized effector of this complex is ß-catenin, which is stabilized by inhibition of GSK-3, allowing ß-catenin entrance to the nucleus and activation of Wnt target gene transcription, leading to multiple cancers when inappropriately activated. However, canonical Wnt signaling through the APC/Axin/GSK-3 complex impinges on other effectors, independently of ß-catenin, including the mechanistic Target of Rapamycin (mTOR), regulators of protein stability, mitotic spindle orientation, and Hippo signaling. This review focuses on these alternative effectors of the canonical Wnt pathway and how they may contribute to cancers.

Exosomal miR-125b-5p derived from cancer-associated fibroblasts promotes the growth, migration, and invasion of pancreatic cancer cells by decreasing adenomatous polyposis coli (APC) expression.

Background: A significant desmoplastic response, particularly in the fibroblasts, is a characteristic of pancreatic ductal adenocarcinoma (PDAC). Increasing evidence has shown that cancer-associated fibroblasts (CAFs) assist tumor development, invasion, and metastasis in PDAC. However, CAFs-derived molecular determinants that regulate the molecular mechanisms of PDAC have not been fully characterized. Methods: The expression of microRNA 125b-5p (miR-125b-5p) in Pancreas Cancer (PC) tissue and para-cancerous normal tissue was examined using Polymerase Chain Reaction (PCR). Cell counting kit-8 (CCK8), wound healing, and transwell experiments were utilized to assess the effect of miR-125b-5p. Using a cell luciferase activity test and bioinformatics, it was demonstrated that miR-125b-5p may bind to the 3'-untranslated region (3'-UTR) of the adenomatous polyposis coli (APC), thereby limiting the progression of pancreatic cancer. Results: PDAC cells are prompted to proliferate, undergo the epithelial-mesenchymal transition (EMT), and spread. Importantly, CAFs release exosomes into PDAC cells, which significantly increase the level of miR-125b-5p in those cells. Meanwhile, pancreatic cancer cell lines and PDAC tissues have considerably higher miR-125b-5p expression. MiR-125b-5p's elevated expression mechanically suppresses the expression of APC and accelerates the spread of pancreatic cancer. Conclusions: Exosomes released by CAFs promote PDAC growth, invasion, and metastasis. Exosomal miR-125b-5p inhibition offers an alternate strategy for combating the basic malady of PDAC.

Improved Drug-Response Prediction Model of APC Mutant Colon Cancer Patient-Derived Organoids for Precision Medicine.

Colorectal cancer is the third most common cancer in the world, with an annual incidence of 2 million cases. The success of first-line chemotherapy plays a crucial role in determining the disease outcome. Therefore, there is an increasing demand for precision medicine to predict drug responses and optimize chemotherapy in order to increase patient survival and reduce the related side effects. Patient-derived organoids have become a popular in vitro screening model for drug-response prediction for precision medicine. However, there is no established correlation between oxaliplatin and drug-response prediction. Here, we suggest that organoid culture conditions can increase resistance to oxaliplatin during drug screening, and we developed a modified medium condition to address this issue. Notably, while previous studies have shown that survivin is a mechanism for drug resistance, our study observed consistent survivin expression irrespective of the culture conditions and oxaliplatin treatment. However, clusterin induced apoptosis inhibition and cell survival, demonstrating a significant correlation with drug resistance. This study's findings are expected to contribute to increasing the accuracy of drug-response prediction in patient-derived APC mutant colorectal cancer organoids, thereby providing reliable precision medicine and improving patient survival rates.

Bacterial translocation and barrier dysfunction enhance colonic tumorigenesis.

In the development of colon cancer, the intestinal dysbiosis and disruption of barrier function are common manifestations. In the current study, we hypothesized that host factors, e.g., vitamin D receptor deficiency or adenomatous polyposis coli (APC) mutation, contribute to the enhanced dysbiosis and disrupted barrier in the pathogenesis of colorectal cancer (CRC). Using the human CRC database, we found enhanced tumor-invading bacteria and reduced colonic VDR expression, which was correlated with a reduction of Claudin-10 mRNA and protein. In the colon of VDRΔIEC mice, deletion of intestinal epithelial VDR led to lower protein of tight junction protein Claudin-10. Lacking VDR and a reduction of Claudin-10 are associated with an increased number of tumors in the mice without myeloid VDR. Intestinal permeability was significantly increased in the mice with myeloid VDR conditional deletion. Further, mice with conditional colonic APC mutation showed reduced mucus layer, enhanced bacteria in tumors, and loss of Claudin-10. Our data from human samples and colon cancer models provided solid evidence- on the host factor regulation of bacterial translocation and dysfunction on barriers in colonic tumorigenesis. Studies on the host factor regulation of microbiome and barriers could be potentially applied to risk assessment, early detection, and prevention of colon cancer.

Multivalent Interaction of Beta-Catenin With its Intrinsically Disordered Binding Partner Adenomatous Polyposis Coli.

The Wnt signalling pathway plays key roles in cell proliferation, differentiation and fate decisions in embryonic development and maintenance of adult tissues, and the twelve Armadillo (ARM) repeat-containing protein ß-catenin acts as the signal transducer in this pathway. Here we investigate the interaction between ß-catenin's ARM repeat domain and the intrinsically disordered protein adenomatous polyposis coli (APC). APC is a giant multivalent scaffold that brings together the different components of the so-called "ß-catenin destruction complex", which drives ß-catenin degradation via the ubiquitin-proteasome pathway. Mutations and truncations in APC, resulting in loss of APC function and hence elevated ß-catenin levels and upregulation of Wnt signalling, are associated with numerous cancers including colorectal carcinomas. APC has a long intrinsically disordered region (IDR) that contains a series of 15-residue and 20-residue binding regions for ß-catenin. Here we explore the multivalent nature of the interaction of ß-catenin with the highest affinity APC repeat, both at equilibrium and under kinetic conditions. We use a combination of single-site substitutions, deletions and insertions to dissect the mechanism of molecular recognition and the roles of the three ß-catenin-binding subdomains of APC.

To Identify Adenomatous Polyposis Coli Gene Mutation as a Predictive Marker of Endometrial Cancer Immunotherapy.

The adenomatous polyposis coli (APC) gene is the chromatin-remodeling-related gene and a typical tumor suppressor. Patients with a high expression of programmed death-ligand 1 (PD-L1) or a high level of tumor mutational burden (TMB) may benefit from immunotherapy in endometrial cancer (EC). This study aimed to demonstrate the role of APC in the diagnosis and immunotherapy treatment of EC. We performed an integrative analysis of a commercial panel including 520 cancer-related genes on 99 tumors from an endometrial cancer cohort in China and DNA-seq data from The Cancer Genome Atlas (TCGA) to identify new gene mutations as endometrial cancer immunotherapy markers. We found that the significant mutant genes that correlated with the PD-L1 expression and TMB were related to the chromatin state and generated a discovery set having 12 mutated genes, including the APC gene, which was identified as a new marker for immunotherapy. Further analysis revealed that tumors with the APC mutation had high TMB, increased expression of PD-L1, and increased lymphocytic infiltration. Next, we verified that APC has an inactive mutation in EC, which may affect the immune response, including PD-L1 expression, microsatellite instability, and lymphocytic infiltrate. Furthermore, patients with the APC mutation had longer overall survival. Our study demonstrates that APC could play an important role in enhancing the response to endometrial cancer treatment, particularly immunotherapy.

Distinct phenotypic spectra of hepatocellular carcinoma in liver-specific tumor suppressor-deficient hepatitis B virus transgenic mice.

The hepatitis B virus (HBV) transgenic mouse model was used to interrogate the origins of HCC heterogeneity. HBV biosynthesis was used as a marker of liver tumor heterogeneity. Principal component and correlation analysis of HBV and cellular transcript levels demonstrated major differences within and between the gene expression profiles of Apc-deficient, Apc-deficient Pten-deficient, and Pten-deficient HCC. Hence, both oncogenic stimuli and zonal hepatocyte properties determine heterogeneous HCC phenotypes. Additionally, Apc-deficient HCC display decreased expression of Apob, Otc and Tet2 relative to Pten-deficient HCC and control liver tissue suggesting their gene products may represent markers of Apc-deficient HCC. A subset of human HCC with mutations in the ß-catenin gene (CTNNB1) displayed a gene expression profile similar to that observed in the mouse Apc-deficient HCC indicating this model of liver cancer may be useful for interrogating the molecular properties of these tumors and their potential therapeutic vulnerabilities.