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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 -
Nature Oct 2020Somatic mutations in p53, which inactivate the tumour-suppressor function of p53 and often confer oncogenic gain-of-function properties, are very common in cancer. Here...
Somatic mutations in p53, which inactivate the tumour-suppressor function of p53 and often confer oncogenic gain-of-function properties, are very common in cancer. Here we studied the effects of hotspot gain-of-function mutations in Trp53 (the gene that encodes p53 in mice) in mouse models of WNT-driven intestinal cancer caused by Csnk1a1 deletion or Apc mutation. Cancer in these models is known to be facilitated by loss of p53. We found that mutant versions of p53 had contrasting effects in different segments of the gut: in the distal gut, mutant p53 had the expected oncogenic effect; however, in the proximal gut and in tumour organoids it had a pronounced tumour-suppressive effect. In the tumour-suppressive mode, mutant p53 eliminated dysplasia and tumorigenesis in Csnk1a1-deficient and Apc mice, and promoted normal growth and differentiation of tumour organoids derived from these mice. In these settings, mutant p53 was more effective than wild-type p53 at inhibiting tumour formation. Mechanistically, the tumour-suppressive effects of mutant p53 were driven by disruption of the WNT pathway, through preventing the binding of TCF4 to chromatin. Notably, this tumour-suppressive effect was completely abolished by the gut microbiome. Moreover, a single metabolite derived from the gut microbiota-gallic acid-could reproduce the entire effect of the microbiome. Supplementing gut-sterilized p53-mutant mice and p53-mutant organoids with gallic acid reinstated the TCF4-chromatin interaction and the hyperactivation of WNT, thus conferring a malignant phenotype to the organoids and throughout the gut. Our study demonstrates the substantial plasticity of a cancer mutation and highlights the role of the microenvironment in determining its functional outcome.
Topics: Animals; Anti-Bacterial Agents; Carcinogenesis; Female; Gallic Acid; Gastrointestinal Microbiome; Genes, Tumor Suppressor; Humans; Male; Mice; Mutation; Oncogenes; Organoids; Transcription, Genetic; Tumor Suppressor Protein p53; Wnt Signaling Pathway
PubMed: 32728212
DOI: 10.1038/s41586-020-2541-0 -
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 -
Acta Pharmaceutica Sinica. B Jan 2022Colorectal cancer (CRC), a malignant tumor worldwide consists of microsatellite instability (MSI) and stable (MSS) phenotypes. Although SHP2 is a hopeful target for...
Colorectal cancer (CRC), a malignant tumor worldwide consists of microsatellite instability (MSI) and stable (MSS) phenotypes. Although SHP2 is a hopeful target for cancer therapy, its relationship with innate immunosuppression remains elusive. To address that, single-cell RNA sequencing was performed to explore the role of SHP2 in all cell types of tumor microenvironment (TME) from murine MC38 xenografts. Intratumoral cells were found to be functionally heterogeneous and responded significantly to SHP099, a SHP2 allosteric inhibitor. The malignant evolution of tumor cells was remarkably arrested by SHP099. Mechanistically, STING-TBK1-IRF3-mediated type I interferon signaling was highly activated by SHP099 in infiltrated myeloid cells. Notably, CRC patients with MSS phenotype exhibited greater macrophage infiltration and more potent SHP2 phosphorylation in CD68 macrophages than MSI-high phenotypes, suggesting the potential role of macrophagic SHP2 in TME. Collectively, our data reveals a mechanism of innate immunosuppression mediated by SHP2, suggesting that SHP2 is a promising target for colon cancer immunotherapy.
PubMed: 35127377
DOI: 10.1016/j.apsb.2021.08.006 -
Journal of Experimental & Clinical... Sep 2023FAT4 (FAT Atypical Cadherin 4) is a member of the cadherin-associated protein family, which has been shown to function as a tumor suppressor by inhibiting proliferation...
BACKGROUND
FAT4 (FAT Atypical Cadherin 4) is a member of the cadherin-associated protein family, which has been shown to function as a tumor suppressor by inhibiting proliferation and metastasis. The Wnt/β-catenin pathway activation is highly associated with PD-L1-associated tumor immune escape. Here, we report the mechanism by which FAT4 overexpression regulates anti-tumor immunity in cervical cancer by inhibiting PD-L1 N-glycosylation and cell membrane localization in a β-catenin-dependent manner.
METHODS
FAT4 expression was first detected in cervical cancer tissues and cell lines. Cell proliferation, clone formation, and immunofluorescence were used to determine the tumor suppressive impact of FAT4 overexpression in vitro, and the findings were confirmed in immunodeficient and immunocomplete mice xenografts. Through functional and mechanistic experiments in vivo and in vitro, we investigated how FAT4 overexpression affects the antitumor immunity via the β-catenin/STT3/PD-L1 axis.
RESULTS
FAT4 is downregulated in cervical cancer tissues and cell lines. We determined that FAT4 binds to β-catenin and antagonizes its nuclear localization, promotes phosphorylation and degradation of β-catenin by the degradation complexes (AXIN1, APC, GSK3β, CK1). FAT4 overexpression decreases programmed death-ligand 1 (PD-L1) mRNA expression at the transcriptional level, and causes aberrant glycosylation of PD-L1 via STT3A at the post-translational modifications (PTMs) level, leading to its endoplasmic reticulum (ER) accumulation and polyubiquitination-dependent degradation. We found that FAT4 overexpression promotes aberrant PD-L1 glycosylation and degradation in a β-catenin-dependent manner, thereby increasing cytotoxic T lymphocyte (CTL) activity in immunoreactive mouse models.
CONCLUSIONS
These findings address the basis of Wnt/β-catenin pathway activation in cervical cancer and provide combination immunotherapy options for targeting the FAT4/β-catenin/STT3/PD-L1 axis. Schematic cartoons showing the antitumor immunity mechanism of FAT4. (left) when Wnts bind to their receptors, which are made up of Frizzled proteins and LRP5/6, the cytoplasmic protein DVL is activated, inducing the aggregation of degradation complexes (AXIN, GSK3β, CK1, APC) to the receptor. Subsequently, stable β-catenin translocates into the nucleus and binds to TCF/LEF and TCF7L2 transcription factors, leading to target genes transcription. The catalytically active subunit of oligosaccharyltransferase, STT3A, enhances PD-L1 glycosylation, and N-glycosylated PD-L1 translocates to the cell membrane via the ER-to-Golgi pathway, resulting in immune evasion. (Right) FAT4 exerts antitumor immunity mainly through following mechanisms: (i) FAT4 binds to β-catenin and antagonizes its nuclear localization, promotes phosphorylation and degradation of β-catenin by the degradation complexes (AXIN1, APC, GSK3β, CK1); (ii) FAT4 inhibits PD-L1 and STT3A transcription in a β-catenin-dependent manner and induces aberrant PD-L1 glycosylation and ubiquitination-dependent degradation; (iii) Promotes activation of cytotoxic T lymphocytes (CTL) and infiltration into the tumor microenvironment.
Topics: Animals; Female; Humans; Mice; B7-H1 Antigen; beta Catenin; Cadherins; Glycogen Synthase Kinase 3 beta; Tumor Microenvironment; Tumor Suppressor Proteins; Uterine Cervical Neoplasms
PubMed: 37658376
DOI: 10.1186/s13046-023-02758-2 -
Frontiers in Oncology 2021The adenomatous polyposis coli () gene, known as tumor suppressor gene, has the two promoters 1A and 1B. Researches on have usually focused on its loss-of-function... (Review)
Review
The adenomatous polyposis coli () gene, known as tumor suppressor gene, has the two promoters 1A and 1B. Researches on have usually focused on its loss-of-function variants causing familial adenomatous polyposis. Hypermethylation, however, which is one of the key epigenetic alterations of the CpG sequence, is also associated with carcinogenesis in various cancers. Accumulating studies have successively explored the role of hypermethylation in gastrointestinal (GI) tumors, such as in esophageal, colorectal, gastric, pancreatic, and hepatic cancer. In sporadic colorectal cancer, the hypermethylation of CpG island in is even considered as one of the primary causative factors. In this review, we systematically summarized the distribution of gene methylation in various GI tumors, and attempted to provide an improved general understanding of DNA methylation in GI tumors. In addition, we included a robust overview of demethylating agents available for both basic and clinical researches. Finally, we elaborated our findings and perspectives on the overall situation of gene methylation in GI tumors, aiming to explore the potential research directions and clinical values.
PubMed: 33968756
DOI: 10.3389/fonc.2021.653222 -
Gastroenterology Dec 2020Mutant KRAS promotes glutaminolysis, a process that uses steps from the tricarboxylic cycle to convert glutamine to α-ketoglutarate and other molecules via glutaminase... (Observational Study)
Observational Study
BACKGROUND & AIMS
Mutant KRAS promotes glutaminolysis, a process that uses steps from the tricarboxylic cycle to convert glutamine to α-ketoglutarate and other molecules via glutaminase and SLC25A22. This results in inhibition of demethylases and epigenetic alterations in cells that increase proliferation and stem cell features. We investigated whether mutant KRAS-mediated glutaminolysis affects the epigenomes and activities of colorectal cancer (CRC) cells.
METHODS
We created ApcKras mice with intestine-specific knockout of SLC25A22 (ApcKrasSLC25A22 mice). Intestine tissues were collected and analyzed by histology, immunohistochemistry, and DNA methylation assays; organoids were derived and studied for stem cell features, along with organoids derived from 2 human colorectal tumor specimens. Colon epithelial cells (1CT) and CRC cells (DLD1, DKS8, HKE3, and HCT116) that expressed mutant KRAS, with or without knockdown of SLC25A22 or other proteins, were deprived of glutamine or glucose and assayed for proliferation, colony formation, glucose or glutamine consumption, and apoptosis; gene expression patterns were analyzed by RNA sequencing, proteins by immunoblots, and metabolites by liquid chromatography-mass spectrometry, with [U-C]-glutamine as a tracer. Cells and organoids with knocked down, knocked out, or overexpressed proteins were analyzed for DNA methylation at CpG sites using arrays. We performed immunohistochemical analyses of colorectal tumor samples from 130 patients in Hong Kong (57 with KRAS mutations) and Kaplan-Meier analyses of survival. We analyzed gene expression levels of colorectal tumor samples in The Cancer Genome Atlas.
RESULTS
CRC cells that express activated KRAS required glutamine for survival, and rapidly incorporated it into the tricarboxylic cycle (glutaminolysis); this process required SLC25A22. Cells incubated with succinate and non-essential amino acids could proliferate under glutamine-free conditions. Mutant KRAS cells maintained a low ratio of α-ketoglutarate to succinate, resulting in reduced 5-hydroxymethylcytosine-a marker of DNA demethylation, and hypermethylation at CpG sites. Many of the hypermethylated genes were in the WNT signaling pathway and at the protocadherin gene cluster on chromosome 5q31. CRC cells without mutant KRAS, or with mutant KRAS and knockout of SLC25A22, expressed protocadherin genes (PCDHAC2, PCDHB7, PCDHB15, PCDHGA1, and PCDHGA6)-DNA was not methylated at these loci. Expression of the protocadherin genes reduced WNT signaling to β-catenin and expression of the stem cell marker LGR5. ApcKrasSLC25A22 mice developed fewer colon tumors than ApcKras mice (P < .01). Organoids from ApcKrasSLC25A22 mice had reduced expression of LGR5 and other markers of stemness compared with organoids derived from ApcKras mice. Knockdown of SLC25A22 in human colorectal tumor organoids reduced clonogenicity. Knockdown of lysine demethylases, or succinate supplementation, restored expression of LGR5 to SLC25A22-knockout CRC cells. Knockout of SLC25A22 in CRC cells that express mutant KRAS increased their sensitivity to 5-fluorouacil. Level of SLC25A22 correlated with levels of LGR5, nuclear β-catenin, and a stem cell-associated gene expression pattern in human colorectal tumors with mutations in KRAS and reduced survival times of patients.
CONCLUSIONS
In CRC cells that express activated KRAS, SLC25A22 promotes accumulation of succinate, resulting in increased DNA methylation, activation of WNT signaling to β-catenin, increased expression of LGR5, proliferation, stem cell features, and resistance to 5-fluorouacil. Strategies to disrupt this pathway might be developed for treatment of CRC.
Topics: Animals; Colon; Colorectal Neoplasms; DNA Demethylation; Drug Resistance, Neoplasm; Female; Fluorouracil; Follow-Up Studies; Gene Expression Regulation, Neoplastic; Gene Knockdown Techniques; Glutamine; Hong Kong; Humans; Intestinal Mucosa; Kaplan-Meier Estimate; Ketoglutaric Acids; Male; Mice, Knockout; Mitochondrial Membrane Transport Proteins; Neoplastic Stem Cells; Proto-Oncogene Proteins p21(ras); Wnt Signaling Pathway; Xenograft Model Antitumor Assays
PubMed: 32814111
DOI: 10.1053/j.gastro.2020.08.016