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Frontiers in Immunology 2020The intestinal microbiota, composed of a large population of microorganisms, is often considered a "forgotten organ" in human health and diseases. Increasing evidence... (Review)
Review
The intestinal microbiota, composed of a large population of microorganisms, is often considered a "forgotten organ" in human health and diseases. Increasing evidence indicates that dysbiosis of the intestinal microbiota is closely related to colorectal cancer (CRC). The roles for intestinal microorganisms that initiated and facilitated the CRC process are becoming increasingly clear. Hypothesis models have been proposed to illustrate the complex relationship between the intestinal microbiota and CRC. Recent studies have identified , enterotoxigenic , , , , and as CRC candidate pathogens. In this review, we summarized the mechanisms involved in microbiota-related colorectal carcinogenesis, including inflammation, pathogenic bacteria, and their virulence factors, genotoxins, oxidative stress, bacterial metabolites, and biofilm. We also described the clinical values of intestinal microbiota and novel strategies for preventing and treating CRC.
Topics: Adenocarcinoma; Animals; Bacteria; Biodiversity; Biofilms; Carcinogenesis; Cell Transformation, Neoplastic; Colorectal Neoplasms; Diet; Gastrointestinal Microbiome; Genes, APC; Humans; Inflammation; Mice; Models, Biological; Mutagens; Neoplastic Syndromes, Hereditary; Oxidative Stress; Rats; Virulence
PubMed: 33329610
DOI: 10.3389/fimmu.2020.615056 -
Gastroenterology Jan 2022Dietary fat intake is associated with increased risk of colorectal cancer (CRC). We examined the role of high-fat diet (HFD) in driving CRC through modulating gut...
BACKGROUND AND AIMS
Dietary fat intake is associated with increased risk of colorectal cancer (CRC). We examined the role of high-fat diet (HFD) in driving CRC through modulating gut microbiota and metabolites.
METHODS
HFD or control diet was fed to mice littermates in CRC mouse models of an azoxymethane (AOM) model and Apc model, with or without antibiotics cocktail treatment. Germ-free mice for fecal microbiota transplantation were used for validation. Gut microbiota and metabolites were detected using metagenomic sequencing and high-performance liquid chromatography-mass spectrometry, respectively. Gut barrier function was determined using lipopolysaccharides level and transmission electron microscopy.
RESULTS
HFD promoted colorectal tumorigenesis in both AOM-treated mice and Apc mice compared with control diet-fed mice. Gut microbiota depletion using antibiotics attenuated colon tumor formation in HFD-fed mice. A significant shift of gut microbiota composition with increased pathogenic bacteria Alistipessp.Marseille-P5997 and Alistipessp.5CPEGH6, and depleted probiotic Parabacteroides distasonis, along with impaired gut barrier function was exhibited in HFD-fed mice. Moreover, HFD-modulated gut microbiota promotes colorectal tumorigenesis in AOM-treated germ-free mice, indicating gut microbiota was essential in HFD-associated colorectal tumorigenesis. Gut metabolites alteration, including elevated lysophosphatidic acid, which was confirmed to promote CRC cell proliferation and impair cell junction, was also observed in HFD-fed mice. Moreover, transfer of stools from HFD-fed mice to germ-free mice without interference increased colonic cell proliferation, impaired gut barrier function, and induced oncogenic genes expression.
CONCLUSIONS
HFD drives colorectal tumorigenesis through inducing gut microbial dysbiosis, metabolomic dysregulation with elevated lysophosphatidic acid, and gut barrier dysfunction in mice.
Topics: Animals; Anti-Bacterial Agents; Azoxymethane; Bacteria; Bacterial Translocation; Cell Proliferation; Cell Transformation, Neoplastic; Colon; Colorectal Neoplasms; Diet, High-Fat; Disease Models, Animal; Dysbiosis; Fecal Microbiota Transplantation; Feces; Gastrointestinal Microbiome; Genes, APC; Germ-Free Life; Humans; Lysophospholipids; Male; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Transgenic; Permeability; Tumor Cells, Cultured; Mice
PubMed: 34461052
DOI: 10.1053/j.gastro.2021.08.041 -
Cells Sep 2020The Wnt/β-catenin signaling pathway exerts integral roles in embryogenesis and adult homeostasis. Aberrant activation of the pathway is implicated in growth-associated... (Review)
Review
The Wnt/β-catenin signaling pathway exerts integral roles in embryogenesis and adult homeostasis. Aberrant activation of the pathway is implicated in growth-associated diseases and cancers, especially as a key driver in the initiation and progression of colorectal cancer (CRC). Loss or inactivation of Adenomatous polyposis coli (APC) results in constitutive activation of Wnt/β-catenin signaling, which is considered as an initiating event in the development of CRC. Increased Wnt/β-catenin signaling is observed in virtually all CRC patients, underscoring the importance of this pathway for therapeutic intervention. Prior studies have deciphered the regulatory networks required for the cytoplasmic stabilisation or degradation of the Wnt pathway effector, β-catenin. However, the mechanism whereby nuclear β-catenin drives or inhibits expression of Wnt target genes is more diverse and less well characterised. Here, we describe a brief synopsis of the core canonical Wnt pathway components, set the spotlight on nuclear mediators and highlight the emerging role of chromatin regulators as modulators of β-catenin-dependent transcription activity and oncogenic output.
Topics: Adenomatous Polyposis Coli Protein; Carcinogenesis; Chromatin; Colorectal Neoplasms; Disease Progression; Epigenesis, Genetic; Gene Expression Regulation, Neoplastic; Histones; Humans; Proteasome Endopeptidase Complex; Proteolysis; Signal Transduction; TCF Transcription Factors; Transcription, Genetic; Wnt Proteins; beta Catenin
PubMed: 32961708
DOI: 10.3390/cells9092125 -
Cell Stem Cell Mar 2020Forward genetic screens with genome-wide CRISPR libraries are powerful tools for resolving cellular circuits and signaling pathways. Applying this technology to...
Forward genetic screens with genome-wide CRISPR libraries are powerful tools for resolving cellular circuits and signaling pathways. Applying this technology to organoids, however, has been hampered by technical limitations. Here we report improved accuracy and robustness for pooled-library CRISPR screens by capturing sgRNA integrations in single organoids, substantially reducing required cell numbers for genome-scale screening. We applied our approach to wild-type and APC mutant human intestinal organoids to identify genes involved in resistance to TGF-β-mediated growth restriction, a key process during colorectal cancer progression, and validated hits including multiple subunits of the tumor-suppressive SWI/SNF chromatin remodeling complex. Mutations within these genes require concurrent inactivation of APC to promote TGF-β resistance and attenuate TGF-β target gene transcription. Our approach can be applied to a variety of assays and organoid types to facilitate biological discovery in primary 3D tissue models.
Topics: Clustered Regularly Interspaced Short Palindromic Repeats; Genetic Testing; Humans; Intestines; Organoids; Transforming Growth Factor beta
PubMed: 32142663
DOI: 10.1016/j.stem.2020.02.007 -
Gastroenterology Sep 2021Lipidomic changes were causally linked to metabolic diseases, but the scenario for colorectal cancer (CRC) is less clear. We investigated the CRC lipidome for putative...
OBJECTIVE
Lipidomic changes were causally linked to metabolic diseases, but the scenario for colorectal cancer (CRC) is less clear. We investigated the CRC lipidome for putative tumor-specific alterations through analysis of 3 independent retrospective patient cohorts from 2 clinical centers, to derive a clinically useful signature.
DESIGN
Quantitative comprehensive lipidomic analysis was performed using direct infusion electrospray ionization coupled with tandem mass spectrometry (ESI-MS/MS) and high-resolution mass spectrometry (HR-MS) on matched nondiseased mucosa and tumor tissue in a discovery cohort (n = 106). Results were validated in 2 independent cohorts (n = 28, and n = 20), associated with genomic and clinical data, and lipidomic data from a genetic mouse tumor model (Apc).
RESULTS
Significant differences were found between tumor and normal tissue for glycero-, glycerophospho-, and sphingolipids in the discovery cohort. Comparison to the validation collectives unveiled that glycerophospholipids showed high interpatient variation and were strongly affected by preanalytical conditions, whereas glycero- and sphingolipids appeared more robust. Signatures of sphingomyelin and triacylglycerol (TG) species significantly differentiated cancerous from nondiseased tissue in both validation studies. Moreover, lipogenic enzymes were significantly up-regulated in CRC, and FASN gene expression was prognostically detrimental. The TG profile was significantly associated with postoperative disease-free survival and lymphovascular invasion, and was essentially conserved in murine digestive cancer, but not associated with microsatellite status, KRAS or BRAF mutations, or T-cell infiltration.
CONCLUSION
Analysis of the CRC lipidome revealed a robust TG-species signature with prognostic potential. A better understanding of the cancer-associated glycerolipid and sphingolipid metabolism may lead to novel therapeutic strategies.
Topics: Adult; Aged; Aged, 80 and over; Animals; Biomarkers, Tumor; Ceramides; Colectomy; Colorectal Neoplasms; Disease-Free Survival; Female; Genes, APC; Germany; Humans; Lipidomics; Lipids; Male; Metabolome; Mice, Inbred C57BL; Mice, Transgenic; Middle Aged; Neoplasm Invasiveness; Reproducibility of Results; Retrospective Studies; Spectrometry, Mass, Electrospray Ionization; Sphingolipids; Tandem Mass Spectrometry; Triglycerides; Mice
PubMed: 34000281
DOI: 10.1053/j.gastro.2021.05.009 -
Nature Jun 2021The tumour suppressor APC is the most commonly mutated gene in colorectal cancer. Loss of Apc in intestinal stem cells drives the formation of adenomas in mice via...
The tumour suppressor APC is the most commonly mutated gene in colorectal cancer. Loss of Apc in intestinal stem cells drives the formation of adenomas in mice via increased WNT signalling, but reduced secretion of WNT ligands increases the ability of Apc-mutant intestinal stem cells to colonize a crypt (known as fixation). Here we investigated how Apc-mutant cells gain a clonal advantage over wild-type counterparts to achieve fixation. We found that Apc-mutant cells are enriched for transcripts that encode several secreted WNT antagonists, with Notum being the most highly expressed. Conditioned medium from Apc-mutant cells suppressed the growth of wild-type organoids in a NOTUM-dependent manner. Furthermore, NOTUM-secreting Apc-mutant clones actively inhibited the proliferation of surrounding wild-type crypt cells and drove their differentiation, thereby outcompeting crypt cells from the niche. Genetic or pharmacological inhibition of NOTUM abrogated the ability of Apc-mutant cells to expand and form intestinal adenomas. We identify NOTUM as a key mediator during the early stages of mutation fixation that can be targeted to restore wild-type cell competitiveness and provide preventative strategies for people at a high risk of developing colorectal cancer.
Topics: Adenoma; Adenomatous Polyposis Coli Protein; Animals; Cell Competition; Cell Differentiation; Cell Proliferation; Cell Transformation, Neoplastic; Colorectal Neoplasms; Culture Media, Conditioned; Disease Progression; Esterases; Female; Genes, APC; Humans; Ligands; Male; Mice; Mice, Inbred C57BL; Mutation; Organoids; Stem Cells; Wnt Proteins; Wnt Signaling Pathway
PubMed: 34079124
DOI: 10.1038/s41586-021-03525-z -
A molecular framework underlying low-nitrogen-induced early leaf senescence in Arabidopsis thaliana.Molecular Plant Apr 2023Nitrogen (N) deficiency causes early leaf senescence, resulting in accelerated whole-plant maturation and severely reduced crop yield. However, the molecular mechanisms...
Nitrogen (N) deficiency causes early leaf senescence, resulting in accelerated whole-plant maturation and severely reduced crop yield. However, the molecular mechanisms underlying N-deficiency-induced early leaf senescence remain unclear, even in the model species Arabidopsis thaliana. In this study, we identified Growth, Development and Splicing 1 (GDS1), a previously reported transcription factor, as a new regulator of nitrate (NO) signaling by a yeast-one-hybrid screen using a NO enhancer fragment from the promoter of NRT2.1. We showed that GDS1 promotes NO signaling, absorption and assimilation by affecting the expression of multiple NO regulatory genes, including Nitrate Regulatory Gene2 (NRG2). Interestingly, we observed that gds1 mutants show early leaf senescence as well as reduced NO content and N uptake under N-deficient conditions. Further analyses indicated that GDS1 binds to the promoters of several senescence-related genes, including Phytochrome-Interacting Transcription Factors 4 and 5 (PIF4 and PIF5) and represses their expression. Interestingly, we found that N deficiency decreases GDS1 protein accumulation, and GDS1 could interact with Anaphase Promoting Complex Subunit 10 (APC10). Genetic and biochemical experiments demonstrated that Anaphase Promoting Complex or Cyclosome (APC/C) promotes the ubiquitination and degradation of GDS1 under N deficiency, resulting in loss of PIF4 and PIF5 repression and consequent early leaf senescence. Furthermore, we discovered that overexpression of GDS1 could delay leaf senescence and improve seed yield and N-use efficiency (NUE) in Arabidopsis. In summary, our study uncovers a molecular framework illustrating a new mechanism underlying low-N-induced early leaf senescence and provides potential targets for genetic improvement of crop varieties with increased yield and NUE.
Topics: Arabidopsis; Arabidopsis Proteins; Plant Senescence; Nitrates; Plant Leaves; Gene Expression Regulation, Plant
PubMed: 36906802
DOI: 10.1016/j.molp.2023.03.006 -
Gastroenterology Jan 2022Genomic alterations that encourage stem cell activity and hinder proper maturation are central to the development of colorectal cancer (CRC). Key molecular mediators...
BACKGROUND AND AIMS
Genomic alterations that encourage stem cell activity and hinder proper maturation are central to the development of colorectal cancer (CRC). Key molecular mediators that promote these malignant properties require further elucidation to galvanize translational advances. We therefore aimed to characterize a key factor that blocks intestinal differentiation, define its transcriptional and epigenetic program, and provide preclinical evidence for therapeutic targeting in CRC.
METHODS
Intestinal tissue from transgenic mice and patients were analyzed by means of histopathology and immunostaining. Human CRC cells and neoplastic murine organoids were genetically manipulated for functional studies. Gene expression profiling was obtained through RNA sequencing. Histone modifications and transcription factor binding were determined with the use of chromatin immunoprecipitation sequencing.
RESULTS
We demonstrate that SRY-box transcription factor 9 (SOX9) promotes CRC by activating a stem cell-like program that hinders intestinal differentiation. Intestinal adenomas and colorectal adenocarcinomas from mouse models and patients demonstrate ectopic and elevated expression of SOX9. Functional experiments indicate a requirement for SOX9 in human CRC cell lines and engineered neoplastic organoids. Disrupting SOX9 activity impairs primary CRC tumor growth by inducing intestinal differentiation. By binding to genome wide enhancers, SOX9 directly activates genes associated with Paneth and stem cell activity, including prominin 1 (PROM1). SOX9 up-regulates PROM1 via a Wnt-responsive intronic enhancer. A pentaspan transmembrane protein, PROM1 uses its first intracellular domain to support stem cell signaling, at least in part through SOX9, reinforcing a PROM1-SOX9 positive feedback loop.
CONCLUSIONS
These studies establish SOX9 as a central regulator of an enhancer-driven stem cell-like program and carry important implications for developing therapeutics directed at overcoming differentiation defects in CRC.
Topics: AC133 Antigen; Animals; Cell Differentiation; Cell Proliferation; Colorectal Neoplasms; Enhancer Elements, Genetic; Gene Expression Regulation, Neoplastic; Genes, APC; HT29 Cells; Humans; Mice, Transgenic; Neoplastic Stem Cells; SOX9 Transcription Factor; Tumor Burden; Tumor Cells, Cultured; Wnt Signaling Pathway
PubMed: 34571027
DOI: 10.1053/j.gastro.2021.09.044