Adaptable haemodynamic endothelial cells for organogenesis and tumorigenesis.

Endothelial cells adopt tissue-specific characteristics to instruct organ development and regeneration1,2. This adaptability is lost in cultured adult endothelial cells, which do not vascularize tissues in an organotypic manner. Here, we show that transient reactivation of the embryonic-restricted ETS variant transcription factor 2 (ETV2)3 in mature human endothelial cells cultured in a serum-free three-dimensional matrix composed of a mixture of laminin, entactin and type-IV collagen (LEC matrix) 'resets' these endothelial cells to adaptable, vasculogenic cells, which form perfusable and plastic vascular plexi. Through chromatin remodelling, ETV2 induces tubulogenic pathways, including the activation of RAP1, which promotes the formation of durable lumens4,5. In three-dimensional matrices-which do not have the constraints of bioprinted scaffolds-the 'reset' vascular endothelial cells (R-VECs) self-assemble into stable, multilayered and branching vascular networks within scalable microfluidic chambers, which are capable of transporting human blood. In vivo, R-VECs implanted subcutaneously in mice self-organize into durable pericyte-coated vessels that functionally anastomose to the host circulation and exhibit long-lasting patterning, with no evidence of malformations or angiomas. R-VECs directly interact with cells within three-dimensional co-cultured organoids, removing the need for the restrictive synthetic semipermeable membranes that are required for organ-on-chip systems, therefore providing a physiological platform for vascularization, which we call 'Organ-On-VascularNet'. R-VECs enable perfusion of glucose-responsive insulin-secreting human pancreatic islets, vascularize decellularized rat intestines and arborize healthy or cancerous human colon organoids. Using single-cell RNA sequencing and epigenetic profiling, we demonstrate that R-VECs establish an adaptive vascular niche that differentially adjusts and conforms to organoids and tumoroids in a tissue-specific manner. Our Organ-On-VascularNet model will permit metabolic, immunological and physiochemical studies and screens to decipher the crosstalk between organotypic endothelial cells and parenchymal cells for identification of determinants of endothelial cell heterogeneity, and could lead to advances in therapeutic organ repair and tumour targeting.

ETHE1 overexpression promotes SIRT1 and PGC1α mediated aerobic glycolysis, oxidative phosphorylation, mitochondrial biogenesis and colorectal cancer.

Ethylmalonic Encephalopathy Protein 1 (ETHE1) is a sulfur dioxygenase that regulates cellular H2S levels. We previously demonstrated a significant increase of ETHE1 expression in "single-hit" colon epithelial cells from crypts of patients with Familial Adenomatous Polyposis (FAP). Here, we report elevated levels of ETHE1 expression and increased mitochondrial density occurring in-situ in phenotypically normal FAP colorectal mucosa. We also found that constitutive expression of ETHE1 increased aerobic glycolysis ("Warburg effect"), oxidative phosphorylation, and mitochondrial biogenesis in colorectal cancer (CRC) cell lines, thereby depleting H2S which relieved the inhibition of phosphodiesterase (PDE), and increased adenosine monophosphate (AMP) levels. This led to activation of the energy sensing AMP-activated protein kinase (AMPKp), Sirtuin1 (SIRT1) and peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α), a master regulator of mitochondrial biogenesis. By contrast, shRNA silencing of ETHE1 reduced PDE activity, AMPKp/SIRT1/PGC1α levels and mitochondrial biogenesis. Constitutive expression of ETHE1 accelerated both CRC cell xenograft and orthotopic patient derived xenograft CRC cell growth in vivo. Overall, our data nominate elevated ETHE1 expression levels as a novel biomarker and potential therapeutic target for the prevention of CRC tumorigenesis.

Corrigendum: Colonic organoids derived from human induced pluripotent stem cells for modeling colorectal cancer and drug testing.

This corrects the article DOI: 10.1038/nm.4355.

Colonic organoids derived from human induced pluripotent stem cells for modeling colorectal cancer and drug testing.

With the goal of modeling human disease of the large intestine, we sought to develop an effective protocol for deriving colonic organoids (COs) from differentiated human embryonic stem cells (hESCs) or induced pluripotent stem cells (iPSCs). Extensive gene and immunohistochemical profiling confirmed that the derived COs represent colon rather than small intestine, containing stem cells, transit-amplifying cells, and the expected spectrum of differentiated cells, including goblet and endocrine cells. We applied this strategy to iPSCs derived from patients with familial adenomatous polyposis (FAP-iPSCs) harboring germline mutations in the WNT-signaling-pathway-regulator gene encoding APC, and we generated COs that exhibit enhanced WNT activity and increased epithelial cell proliferation, which we used as a platform for drug testing. Two potential compounds, XAV939 and rapamycin, decreased proliferation in FAP-COs, but also affected cell proliferation in wild-type COs, which thus limits their therapeutic application. By contrast, we found that geneticin, a ribosome-binding antibiotic with translational 'read-through' activity, efficiently targeted abnormal WNT activity and restored normal proliferation specifically in APC-mutant FAP-COs. These studies provide an efficient strategy for deriving human COs, which can be used in disease modeling and drug discovery for colorectal disease.

Unbiased metabolite profiling indicates that a diminished thymidine pool is the underlying mechanism of colon cancer chemoprevention by alpha-difluoromethylornithine.

UNLABELLED: The ornithine decarboxylase inhibitor α-difluoromethylornithine (DFMO) is a highly effective chemopreventive agent for colorectal cancer thought to act via polyamine depletion. However, in DFMO-treated patients, mucosal polyamine levels do not directly correlate with colorectal cancer risk. Untargeted metabolite profiling was used to broadly survey DFMO actions on colon cancer cell metabolism. We found that DFMO treatment of Apc(Min) intestinal tumors and human colorectal cancer cells is associated with reduced levels of folate-dependent metabolites, including S-adenosylmethionine (SAM), thymidine pools, and related pathway intermediates. We hypothesized that unrestrained SAM consumption/regeneration constitutes a futile DFMO-triggered cascade that can steal tetrahydrofolate from thymidylate synthase and thereby diminish thymidine pools. In accord with this hypothesis, DFMO treatment altered the folate cofactor balance and thymidine supplementation prevented DFMO-elicited cytostasis without restoring polyamine levels. These findings suggest that thymidine metabolite pool insufficiency is a fundamental mechanism of DFMO cytostatic activity. SIGNIFICANCE: A previously unappreciated metabolic linkage between polyamine and thymidine biosynthesis is revealed, based on the competing requirement of these pathways for a limited pool of tetrahydrofolate cofactor. This study identifies the fi rst shared mechanism for colorectal cancer chemoprevention and chemotherapy, suggesting a common metabolic target for both premalignant and malignant colon cells.

A microRNA miR-34a-regulated bimodal switch targets Notch in colon cancer stem cells.

microRNAs regulate developmental cell-fate decisions, tissue homeostasis, and oncogenesis in distinct ways relative to proteins. Here, we show that the tumor suppressor microRNA miR-34a is a cell-fate determinant in early-stage dividing colon cancer stem cells (CCSCs). In pair-cell assays, miR-34a distributes at high levels in differentiating progeny, whereas low levels of miR-34a demarcate self-renewing CCSCs. Moreover, miR-34a loss of function and gain of function alter the balance between self-renewal versus differentiation both in vitro and in vivo. Mechanistically, miR-34a sequesters Notch1 mRNA to generate a sharp threshold response where a bimodal Notch signal specifies the choice between self-renewal and differentiation. In contrast, the canonical cell-fate determinant Numb regulates Notch levels in a continuously graded manner. Altogether, our findings highlight a unique microRNA-regulated mechanism that converts noisy input into a toggle switch for robust cell-fate decisions in CCSCs.

Pharmacological inhibition of polycomb repressive complex-2 activity induces apoptosis in human colon cancer stem cells.

Colorectal cancer is among the leading causes of cancer death in the USA. The polycomb repressive complex 2 (PRC2), including core components SUZ12 and EZH2, represents a key epigenetic regulator of digestive epithelial cell physiology and was previously shown to promote deleterious effects in a number of human cancers, including colon. Using colon cancer stem cells (CCSC) isolated from human primary colorectal tumors, we demonstrate that SUZ12 knockdown and treatment with DZNep, one of the most potent EZH2 inhibitors, increase apoptosis levels, marked by decreased Akt phosphorylation, in CCSCs, while embryonic stem (ES) cell survival is not affected. Moreover, DZNep treatments lead to increased PTEN expression in these highly tumorigenic cells. Taken together, our findings suggest that pharmacological inhibition of PRC2 histone methyltransferase activity may constitute a new, epigenetic therapeutic strategy to target highly tumorigenic and metastatic colon cancer stem cells.

Inhibition of PRC2 histone methyltransferase activity increases TRAIL-mediated apoptosis sensitivity in human colon cancer cells.

Colorectal cancer is ranked among the top leading causes of cancer death in industrialized populations. Polycomb group proteins, including Suz12 and Ezh2, are epigenetic regulatory proteins that act as transcriptional repressors of many differentiation-associated genes and are overexpressed in a large subset of colorectal cancers. Retinoic acid (RA) acts as a negative regulator of PcG actions in stem cells, but has shown limited therapeutic potential in some solid tumors, including colorectal cancer, in part because of retinoic acid receptor ß silencing. Through treatment with RA, Suz12 shRNA knockdown, or Ezh2 pharmacological inhibition with 3-deazaneplanocin A (DZNep), we increased TRAIL-mediated apoptosis in human colorectal cancer cell lines. This increased apoptosis in human colon cancer cells after RA or DZNep treatment was associated with a ~2.5-fold increase in TNFRSF10B (DR5) transcript levels and a 42% reduction in the H3K27me3 epigenetic mark at the TNFRSF10B promoter after DZNep addition. Taken together, our findings indicate that pharmacological inhibition of Polycomb repressive complex 2 histone methyltransferase activity may constitute a new epigenetic therapeutic strategy to overcome RA non-responsiveness in a subset of colorectal tumors by increasing TRAIL-mediated apoptosis sensitivity.

Epigenetic repression of DNA mismatch repair by inflammation and hypoxia in inflammatory bowel disease-associated colorectal cancer.

Sporadic human mismatch repair (MMR)-deficient colorectal cancers account for approximately 12.5% of all cases of colorectal cancer. MMR-deficient colorectal cancers are classically characterized by right-sided location, multifocality, mucinous histology, and lymphocytic infiltration. However, tumors in germ-line MMR-deficient mouse models lack these histopathologic features. Mice lacking the heterotrimeric G protein alpha subunit Gialpha2 develop chronic colitis and multifocal, right-sided cancers with mucinous histopathology, similar to human MMR-deficient colorectal cancer. Young Gialpha2-/- colonic epithelium has normal MMR expression but selectively loses MLH1 and consequently PMS2 expression following inflammation. Gialpha2-/- cancers have microsatellite instability. Mlh1 is epigenetically silenced not by promoter hypermethylation but by decreased histone acetylation. Chronically inflamed Gialpha2-/- colonic mucosa contains patchy hypoxia, with increased crypt expression of the hypoxia markers DEC-1 and BNIP3. Chromatin immunoprecipitation identified increased binding of the transcriptional repressor DEC-1 to the proximal Mlh1 promoter in hypoxic YAMC cells and colitic Gialpha2-/- crypts. Treating Gialpha2-/- mice with the histone deacetylase inhibitor suberoylanilide hydroxamic acid significantly decreased colitis activity and rescued MLH1 expression in crypt epithelial cells, which was associated with increased acetyl histone H3 levels and decreased DEC-1 binding at the proximal Mlh1 promoter, consistent with a histone deacetylase-dependent mechanism. These data link chronic hypoxic inflammation, epigenetic MMR protein down-regulation, development of MMR-deficient colorectal cancer, and the firstmouse model of somatically acquired MMR-deficient colorectal cancer.

Accurate classification of MLH1/MSH2 missense variants with multivariate analysis of protein polymorphisms-mismatch repair (MAPP-MMR).

Lynch syndrome, also known as hereditary nonpolyposis colon cancer (HNPCC), is the most common known genetic syndrome for colorectal cancer (CRC). MLH1/MSH2 mutations underlie approximately 90% of Lynch syndrome families. A total of 24% of these mutations are missense. Interpreting missense variation is extremely challenging. We have therefore developed multivariate analysis of protein polymorphisms-mismatch repair (MAPP-MMR), a bioinformatic algorithm that effectively classifies MLH1/MSH2 deleterious and neutral missense variants. We compiled a large database (n>300) of MLH1/MSH2 missense variants with associated clinical and molecular characteristics. We divided this database into nonoverlapping training and validation sets and tested MAPP-MMR. MAPP-MMR significantly outperformed other missense variant classification algorithms (sensitivity, 94%; specificity, 96%; positive predictive value [PPV] 98%; negative predictive value [NPV], 89%), such as SIFT and PolyPhen. MAPP-MMR is an effective bioinformatic tool for missense variant interpretation that accurately distinguishes MLH1/MSH2 deleterious variants from neutral variants.