Non-muscle myosin heavy chain 9 maintains intestinal homeostasis by preventing epithelium necroptosis and colitis adenoma formation

Non-muscle myosin IIA plays an important role in cell adhesion, cell migration, and tissue architecture. We previously showed that low activity of the heavy chain of non-muscle myosin II Myh9 is beneficial to LGR5+ intestinal stem cell maintenance. However, the function of Myh9 in adult mouse intestinal epithelium is largely unclear. In this study, we used the inducible Villin-creERT2 knockout approach to delete Myh9 in adult mouse intestinal epithelium and observed that homozygous deletion of Myh9 causes colitis-like morphologic changes in intestine, leads to a high sensitivity to dextran sulfate sodium and promotes colitis-related adenoma formation in the colon. Myh9 deletion disturbs cell junctions and impairs intestinal lumen barrier integrity, promoting the necroptosis of epithelial cells. Consistently, these changes can be partially rescued by Ripk3 knockout. Our results indicate that Myh9 is required for the maintenance of intestinal epithelium integrity and the prevention of cell necroptosis.

Targeting hyperactive TGFBR2 for treating MYOCD deficient lung cancer

Purpose: Clinical success of cancer therapy is severely limited by drug resistance, attributed in large part to the loss of function of tumor suppressor genes (TSGs). Developing effective strategies to treat those tumors is challenging, but urgently needed in clinic.

Experimental Design: MYOCD is a clinically relevant TSG in lung cancer patients. Our in vitro and in vivo data confirm its tumor suppressive function. Further analysis reveals that MYOCD potently inhibits stemness of lung cancer stem cells. Mechanistically, MYOCD localizes to TGFBR2 promoter region and thereby recruits PRMT5/MEP50 complex to epigenetically silence its transcription.

Conclusions: NSCLC cells deficient of MYOCD are particularly sensitive to TGFBR kinase inhibitor (TGFBRi). TGFBRi and stemness inhibitor synergize with existing drugs to treat MYOCD deficient lung cancers. Our current work shows that loss of function of MYOCD creates Achilles' heels in lung cancer cells, which might be exploited in clinic.

Noncanonical TGF-β signaling leads to FBXO3-mediated degradation of ΔNp63α promoting breast cancer metastasis and poor clinical prognosis

Transforming growth factor-β (TGF-β) signaling plays a critical role in promoting epithelial-to-mesenchymal transition (EMT), cell migration, invasion, and tumor metastasis. ΔNp63α, the major isoform of p63 protein expressed in epithelial cells, is a key transcriptional regulator of cell adhesion program and functions as a critical metastasis suppressor. It has been documented that the expression of ΔNp63α is tightly controlled by oncogenic signaling and is frequently reduced in advanced cancers. However, whether TGF-β signaling regulates ΔNp63α expression in promoting metastasis is largely unclear. In this study, we demonstrate that activation of TGF-β signaling leads to stabilization of E3 ubiquitin ligase FBXO3, which, in turn, targets ΔNp63α for proteasomal degradation in a Smad-independent but Erk-dependent manner. Knockdown of FBXO3 or restoration of ΔNp63α expression effectively rescues TGF-β-induced EMT, cell motility, and tumor metastasis in vitro and in vivo. Furthermore, clinical analyses reveal a significant correlation among TGF-β receptor I (TβRI), FBXO3, and p63 protein expression and that high expression of TβRI/FBXO3 and low expression of p63 are associated with poor recurrence-free survival (RFS). Together, these results demonstrate that FBXO3 facilitates ΔNp63α degradation to empower TGF-β signaling in promoting tumor metastasis and that the TβRI-FBXO3-ΔNp63α axis is critically important in breast cancer development and clinical prognosis. This study suggests that FBXO3 may be a potential therapeutic target for advanced breast cancer treatment.

Positive feedback of SuFu negating protein 1 on Hedgehog signaling promotes colorectal tumor growth

Hedgehog (Hh) signaling plays a critical role in embryogenesis and tissue homeostasis, and its deregulation has been associated with tumor growth. The tumor suppressor SuFu inhibits Hh signaling by preventing the nuclear translocation of Gli and suppressing cell proliferation. Regulation of SuFu activity and stability is key to controlling Hh signaling. Here, we unveil SuFu Negating Protein 1 (SNEP1) as a novel Hh target, that enhances the ubiquitination and proteasomal degradation of SuFu and thus promotes Hh signaling. We further show that the E3 ubiquitin ligase LNX1 plays a critical role in the SNEP1-mediated degradation of SuFu. Accordingly, SNEP1 promotes colorectal cancer (CRC) cell proliferation and tumor growth. High levels of SNEP1 are detected in CRC tissues and are well correlated with poor prognosis in CRC patients. Moreover, SNEP1 overexpression reduces sensitivity to anti-Hh inhibitor in CRC cells. Altogether, our findings demonstrate that SNEP1 acts as a novel feedback regulator of Hh signaling by destabilizing SuFu and promoting tumor growth and anti-Hh resistance.

LGR5 constitutively activates NF-κB signaling to regulate the growth of intestinal crypts

Mammalian LGR5 and LGR4, markers of adult stem cells, are involved in many physiological functions by enhancing WNT signaling. However, whether LGR5 and LGR4 are coupled to other intracellular signaling pathways to regulate stem cell function remains unknown. Here, we show that LGR5 and LGR4 can constitutively activate NF-κB signaling in a ligand-independent manner, which is dependent on their C-termini, but independent of receptor endocytosis. Moreover, the C-termini of LGR5/4 interact with TROY, which is required for activating NF-κB signaling. In small intestinal crypt organoids, overexpression of a C-terminal deletion mutant of LGR5 inhibits the growth and bud formation of organoids, whereas overexpression of the R-spondin-binding mutant of LGR5 that is defective for WNT signaling can still promote organoid growth. Our study reveals that NF-κB signaling, regulated by LGR5 and LGR4, plays an important role in the survival of colon cancer cells and the growth of intestinal crypts. Our findings also suggest that LGR5/4-induced NF-κB signaling and WNT signaling may co-regulate the growth of LGR5⁺ adult stem cells and intestinal crypts.

Single-cell transcriptome analysis reveals differential nutrient absorption functions in human intestine

Single-cell transcriptome analysis of epithelial cells from human ileum, colon, and rectum reveals different nutrient-absorption preferences in the small and large intestine, providing a rich resource for further characterization of human intestine cell constitution and functions.

The intestine plays an important role in nutrient digestion and absorption, microbe defense, and hormone secretion. Although major cell types have been identified in the mouse intestinal epithelium, cell type–specific markers and functional assignments are largely unavailable for human intestine. Here, our single-cell RNA-seq analyses of 14,537 epithelial cells from human ileum, colon, and rectum reveal different nutrient absorption preferences in the small and large intestine, suggest the existence of Paneth-like cells in the large intestine, and identify potential new marker genes for human transient-amplifying cells and goblet cells. We have validated some of these insights by quantitative PCR, immunofluorescence, and functional analyses. Furthermore, we show both common and differential features of the cellular landscapes between the human and mouse ilea. Therefore, our data provide the basis for detailed characterization of human intestine cell constitution and functions, which would be helpful for a better understanding of human intestine disorders, such as inflammatory bowel disease and intestinal tumorigenesis.

Intestinal epithelial plasticity and regeneration via cell dedifferentiation

The intestinal epithelium possesses a great capacity of self-renewal under normal homeostatic conditions and of regeneration upon damages. The renewal and regenerative processes are driven by intestinal stem cells (ISCs), which reside at the base of crypts and are marked by Lgr5. As Lgr5⁺ ISCs undergo fast cycling and are vulnerable to damages, there must be other types of cells that can replenish the lost Lgr5⁺ ISCs and then regenerate the damage epithelium. In addition to Lgr5⁺ ISCs, quiescent ISCs at the + 4 position in the crypt have been proposed to convert to Lgr5⁺ ISCs during regeneration. However, this “reserve stem cell” model still remains controversial. Different from the traditional view of a hierarchical organization of the intestinal epithelium, recent works support the dynamic “dedifferentiation” model, in which various cell types within the epithelium can de-differentiate to revert to the stem cell state and then regenerate the epithelium upon tissue injury. Here, we provide an overview of the cell identity and features of two distinct models and discuss the possible mechanisms underlying the intestinal epithelial plasticity.

Cancer-associated adipocyte-derived G-CSF promotes breast cancer malignancy via Stat3 signaling

Adipocyte is the most predominant cell type in the tumor microenvironment of breast cancer and plays a pivotal role in cancer progression, yet the underlying mechanisms and functional mediators remain elusive. We isolated primary preadipocytes from mammary fat pads of human breast cancer patients and generated mature adipocytes and cancer-associated adipocytes (CAAs) in vitro. The CAAs exhibited significantly different gene expression profiles as assessed by transcriptome sequencing. One of the highly expressed genes in CAAs is granulocyte colony-stimulating factor (G-CSF). Treatment with recombinant human G-CSF protein or stable expression of human G-CSF in triple-negative breast cancer (TNBC) cell lines enhanced epithelial-mesenchymal transition, migration, and invasion of cancer cells, by activating Stat3. Accordantly, targeting G-CSF/Stat3 signaling with G-CSF-neutralizing antibody, a chemical inhibitor, or siRNAs for Stat3 could all abrogate CAA- or G-CSF-induced migration and invasion of breast cancer cells. The pro-invasive genes MMP2 and MMP9 were identified as target genes of G-CSF in TNBC cells. Furthermore, in human breast cancer tissues, elevated G-CSF expression in adipocytes is well correlated with activated Stat3 signal in cancer cells. Together, our results suggest a novel strategy to intervene with invasive breast cancers by targeting CAA-derived G-CSF.

DNA Damage Activates TGF-β Signaling via ATM-c-Cbl-Mediated Stabilization of the Type II Receptor TβRII

Activation of both the DNA damage response (DDR) and transforming growth factor β (TGF-β) signaling induces growth arrest of most cell types. However, it is unclear whether the DDR activates TGF-β signaling that in turn contributes to cell growth arrest. Here, we show that in response to DNA damage, ataxia telangiectasia mutated (ATM) stabilizes the TGF-β type II receptor (TβRII) and thus enhancement of TGF-β signaling. Mechanistically, ATM phosphorylates and stabilizes c-Cbl, which promotes TβRII neddylation and prevents its ubiquitination-dependent degradation. Consistently, DNA damage enhances the interaction among ATM, c-Cbl, and TβRII. The ATM-c-Cbl-TβRII axis plays a pivotal role in intestinal regeneration after X-ray-induced DNA damage in mouse models. Therefore, ATM not only mediates the canonical DDR pathway but also activates TGF-β signaling by stabilizing TβRII. The double brake system ensures full cell-cycle arrest, allowing efficient DNA damage repair and avoiding passage of the damaged genome to the daughter cells.

Generation of 3D human gastrointestinal organoids: principle and applications

The stomach and intestine are important organs for food digestion, nutrient absorption, immune protection and hormone production. Gastrointestinal diseases such as cancer and ulcer are big threats to human health. Appropriate disease models are in sore need for mechanistic understanding and drug discovery. Organoids are three-dimensional in vitro cultured structures derived from tissues and pluripotent stem cells with multiple types of cells and mimicking in vivo tissues in major aspects. They have a great potential in regenerative medicine and personalized medicine. Here, we review the major signaling pathways regulating gastrointestinal epithelial homeostasis, summarize different methods to generate human gastrointestinal organoids and highlight their applications in biological research and medical practice.

A PROTAC peptide induces durable β-catenin degradation and suppresses Wnt-dependent intestinal cancer

Aberrant activation of Wnt/β-catenin signaling has been associated with the onset and progression of many types of tumors and thus β-catenin represents one attractive intracellular target for cancer therapy. Based on the Axin-derived peptide that binds to β-catenin, two stapled peptides SAHPA1 and xStAx were reported to enhance or impair Wnt/β-catenin signaling, respectively. In this study, we designed PROTACs (proteolysis targeting chimeras) by coupling SAHPA1 or xStAx with the VHL ligand to achieve efficient β-catenin degradation. The obtained xStAx-VHLL sustained β-catenin degradation and manifested strong inhibition of Wnt signaling in cancer cells and in APC-/- organoids. Furthermore, xStAx-VHLL could effectively restrain tumor formation in BALB/C nude mice, and diminish the existing tumors in APCmin/+ mice. More importantly, xStAx-VHLL could potently inhibit the survival of colorectal cancer patient-derived organoids. These findings suggest that xStAx-VHLL exhibits the ability of cancer prevention and cure, highlighting the potential of β-catenin degrader PROTACs as a new class of promising anticancer agent.

Dedifferentiation: the return road to repair the intestinal epithelium

In the March 5 issue of Cell Stem Cell, (Murata K et al. Cell Stem Cell. 26(377–390):e376 2020) reported that intestinal stem cell recovery after injury is principally through Ascl2-dependent dedifferentiation of absorptive and secretory precursors in mice. This study provides evidence for robust regenerative capability of the intestinal epithelium via dedifferentiation of absorptive and secretory progenitors in the crypt.

DDB1 promotes the proliferation and hypertrophy of chondrocytes during mouse skeleton development

The proliferation and hypertrophy of chondrocytes play important roles in endochondral ossification, which is tightly regulated during skeleton development. However, the regulation mechanism remains largely unknown. Here we show that DDB1 (Damaged DNA Binding Protein 1) has a critical function in the development of growth plates. Using chondrocyte-specific DDB1 knockout mice, we found that DDB1 deletion in chondrocytes results in dwarfism due to the aberrant skeleton development. The structure of growth plate in tibia becomes disordered at P21, not in femur. But at P70, the changes are severer in femur than tibia. Chondrocyte proliferation and differentiation are attenuated and asynchronous in both tibia and femur at P7 and P21. Furthermore, DDB1 deficiency induces p27 upregulation and subsequent cell cycle arrest in primary chondrocytes. Therefore, our data reveal that DDB1 is essential for the skeleton development by controlling chondrocyte proliferation and differentiation.

Investigation on gas permeability of compacted GMZ bentonite with consideration of variations in liquid saturation, dry density and confining pressure

During the long term operation of a disposal repository, gas will be inevitably generated. Determination of gas permeability of compacted bentonite is of great importance for the safety assessment of the engineered barrier system. In the present work, the steady-state and residual pressure methods were employed to determine the gas permeability of GaoMiaoZi (GMZ) bentonite with consideration of variations in liquid saturation, dry density and confining pressure. Results show that, gas migration in saturated GMZ bentonite was mainly controlled by diffusion with an effective gas permeability of 1E-23 m² - 1E-25 m². While in unsaturated GMZ bentonite, significant gas flow rates could be observed, which increased stably with the increase of gas injection pressure. Klinkenberg effect was significant when gas flow through GMZ bentonite. The Klinkenberg corrected gas permeability decreased by 3.5-5.5 orders of magnitude as the liquid saturation increased from 10% to 70%. A decreasing magnitude of 1-2 orders in Klinkenberg corrected gas permeability was presented with the dry density increased from 1.5 Mg/m³ and 1.7 Mg/m³. The Klinkenberg corrected gas permeability decreased by 0-1 orders of magnitude as the confining pressure increased from 3 MPa to 7 MPa. By using the accessible porosity, gas measured intrinsic permeability could be determined with values ranged between 1E-15 m² to 4E-15 m², which was higher than the water measured one by 5 orders of magnitude. Additionally, a generalized power law was successfully adopted in this study to describe the evolution of gas relative permeability with the liquid saturation. Overall, the effective gas permeability, Klinkenberg corrected gas permeability, intrinsic and relative permeability determined in this study provided a comprehensive perspective to assess the buffering property of GMZ bentonite in multi-physical field coupling environment. The parameters obtained can be adopted in further simulation works for long-term safety analysis of the disposal repository from the viewpoint of gas migration.

Gut stem cell aging is driven by mTORC1 via a p38 MAPK-p53 pathway

Nutrients are absorbed solely by the intestinal villi. Aging of this organ causes malabsorption and associated illnesses, yet its aging mechanisms remain unclear. Here, we show that aging-caused intestinal villus structural and functional decline is regulated by mTORC1, a sensor of nutrients and growth factors, which is highly activated in intestinal stem and progenitor cells in geriatric mice. These aging phenotypes are recapitulated in intestinal stem cell-specific Tsc1 knockout mice. Mechanistically, mTORC1 activation increases protein synthesis of MKK6 and augments activation of the p38 MAPK-p53 pathway, leading to decreases in the number and activity of intestinal stem cells as well as villus size and density. Targeting p38 MAPK or p53 prevents or rescues ISC and villus aging and nutrient absorption defects. These findings reveal that mTORC1 drives aging by augmenting a prominent stress response pathway in gut stem cells and identify p38 MAPK as an anti-aging target downstream of mTORC1.

Intestinal aging is associated with declines in structure and absorption of nutrients. Here, the authors show that aging related intestinal decline is mediated by activation of the mTORC1-p38MAPK-p53 pathway in intestinal stem cells and can be ameliorated by abrogating mTORC1 or p38MAPK activity.

[Clinical study on topography-guided laser ablation combined with accelerated corneal collagen cross-linking for early keratoconus]

Objective: To study the safety and efficacy of topography-guided customized excimer laser subepithelial ablation combined with accelerated collagen cross-linking technique in treatment of early keratoconus. Methods: Ninteen patients(20 eyes) (13 males 14 eyes, and 6 females 6 eyes), aged 12 to 44 years (24.7±8.0) were diagnosed as keratoconus by three-dimensional corneal topography and tomography, clinical history and examinations, and classified as KC1~KC3. Based on the classical excimer laser subepithelial keratomileusis (LASEK) method, topography guided laser ablation was performed with an excimer laser system (WaveLight EX500). After laser ablation, the corneal stromal bed was immersed with 0.1% riboflavin for 10 minutes, and then was irradiated by ultraviolet light (Avedro KXL) at 30 mW/cm(2) for 4 minutes. All the patients were followed up for more than 12 months. The uncorrected visual acuity (UCVA), diopter, best corrected visual acuity (BSCVA), corneal topography, central corneal endothelial cell density (ECD), hexagonal cell percentage (HEX), coefficient of variation (CV) and other indicators were observed. For normal distribution variables, Dunnett-t test was used before and after operation, and Wilcoxon test was used for variables with abnormal distribution. And the complications were recorded. Results: There was no loss of BSCVA at 12 months postoperatively, 20% of the eyes had no change of BSCVA, and 15% of the eyes gained 1 line of BSCVA, 15% of the eyes gained 2 lines of BSCVA, 50% of the eyes gained 3 lines and more of BSCVA. There was no significant difference in UCVA, BSCVA, manifest refractive spherical equivalent (MRSE) and the cylinder at 3 months postoperatively (P>0.05). The BSCVA were significantly improved at 6 and 12 months postoperatively compared with those before operation (t=3.095, 3.079, <0.05). Although there was no significant difference in UCVA and MRSE, the cylinder was significantly reduced at 6 and 12 months postoperatively (t=-2.890, -2.435, P<0.05). Apex curvature (Kapex) and mean pupil power (MPP) within 4.5mm of central cornea decreased significantly (Z=-2.903, P<0.01; Z=-2.667, P<0.01). Even though the thinnest corneal thickness decreased from pre-operational (461.9±31.1) μm to post-operational (416.6±27.0) μm (Z=-3.059, P<0.01), the cornea became regular with keratometric asymmetry index of anterior corneal surface decreased (Z=-2.667, P<0.01). The corneal optical quality parameters were improved. There was no significant difference in ECD, HEX and CV at 12 months postoperatively (P>0.05). Twelve months after operation, grade 0, 0.5, 1 and 2 haze were seen on 20%, 55%, 20% and 5% corneas respectively. Conclusions: The topography guided excimer laser ablation combined with accelerated corneal collagen cross linking is safe and effective in treatment of early stage keratoconus. It can significantly improve corneal regularity while preventing keratoconus progression, so as to improve the best corrected visual acuity postoperatively. (Chin J Ophthalmol, 2019, 55: 904-910).

H3K18ac Primes Mesendodermal Differentiation upon Nodal Signaling

Cellular responses to transforming growth factor β (TGF-β) depend on cell context. Here, we explored how TGF-β/nodal signaling crosstalks with the epigenome to promote mesendodermal differentiation. We find that expression of a group of mesendodermal genes depends on both TRIM33 and nodal signaling in embryoid bodies (EBs) but not in embryonic stem cells (ESCs). Only in EBs, TRIM33 binds these genes in the presence of expanded H3K18ac marks. Furthermore, the H3K18ac landscape at mesendodermal genes promotes TRIM33 recruitment. We reveal that HDAC1 binds to active gene promoters and interferes with TRIM33 recruitment to mesendodermal gene promoters. However, the TRIM33-interacting protein p300 deposits H3K18ac and further enhances TRIM33 recruitment. ATAC-seq data demonstrate that TRIM33 primes mesendodermal genes for activation by maintaining chromatin accessibility at their regulatory regions. Altogether, our study suggests that HDAC1 and p300 are key factors linking the epigenome through TRIM33 to the cell context-dependent nodal response during mesendodermal differentiation.

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The H3K18ac landscape changes at gene promoters during mesendodermal differentiation

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Histone acetylation facilitates TRIM33 recruitment to the chromatin

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HDAC1 and p300 are the key factors for nodal signaling crosstalk with epigenome

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Chromatin accessibility at mesendodermal genes depends on TRIM33

Efficient Culture of Intestinal Organoids with Blebbistatin

The intestinal epithelium is one of the most rapidly self-renewing tissues throughout life in mammals. A small population of stem cells at the base of crypt in the epithelium can continually self-renew and give rise to differentiated epithelial cells. The self-renewal and differentiation of intestinal stem cells are under a tight control during homeostasis, and disruption of this balancing regulation leads to intestinal degeneration or tumorigenesis. Accordingly, exploration of the mechanism underlying the regulation of stem cells is essential for the understanding and treatment of intestinal disorders. As traditional methods using mice models are costly and time-consuming, the recently established ex vivo intestinal organoids model provides an ideal tool to investigate the mechanisms regulating the self-renewal and differentiation of intestinal stem cells. The intestinal organoids recapitulate major characteristics in both structure and function of intestinal epithelium in vivo. Here, we describe a new protocol to generate the intestinal organoids from both crypts and single stem cells with a higher efficiency using the small molecule blebbistatin and provide an approach to assess the self-renewal and differentiation of stem cells in intestinal organoids.

2D- and 3D-Based Intestinal Stem Cell Cultures for Personalized Medicine

Colorectal cancer (CRC) is one of the most common cancers that have high occurrence and death in both males and females. As various factors have been found to contribute to CRC development, personalized therapies are critical for efficient treatment. To achieve this purpose, the establishment of patient-derived tumor models is critical for diagnosis and drug test. The establishment of three-dimensional (3D) organoid cultures and two-dimensional (2D) monolayer cultures of patient-derived epithelial tissues is a breakthrough for expanding living materials for later use. This review provides an overview of the different types of 2D- and 3D-based intestinal stem cell cultures, their potential benefits, and the drawbacks in personalized medicine in treatment of the intestinal disorders.

Activin/Smad2 and Wnt/β-catenin up-regulate HAS2 and ALDH3A2 to facilitate mesendoderm differentiation of human embryonic stem cells

Activin and Wnt signaling are necessary and sufficient for mesendoderm (ME) differentiation of human embryonic stem cells (ESCs). In this study, we report that during ME differentiation induced by Activin and Wnt, Activin/Smad2 induces a decrease of the repressive histone modification of H3K27me3 by promoting the proteasome-dependent degradation of enhancer of zeste 2 polycomb (EZH2)-repressive complex 2 subunit. As a result, recruitment of the forkhead protein FOXH1 on open chromatin regions integrates the signals of Activin/Smad2 and Wnt/β-catenin to activate the expression of the ME genes including HAS2 and ALDH3A2 Consistently, H3K27me3 decrease is enriched on open chromatin around regulatory regions. Furthermore, knockdown of HAS2 or ALDH3A2 greatly attenuates ME differentiation. These findings unveil a pathway from extracellular signals to epigenetic modification-mediated gene activation during ME commitment.