Self-renewal and cancer of the gut: two sides of a coin

Wnt/β-catenin signaling within multiple cell types dependent upon kramer regulates Drosophila intestinal stem cell proliferation

The gut epithelium is subject to constant renewal, a process reliant upon intestinal stem cell (ISC) proliferation that is driven by Wnt/β-catenin signaling. Despite the importance of Wnt signaling within ISCs, the relevance of Wnt signaling within other gut cell types and the underlying mechanisms that modulate Wnt signaling in these contexts remain incompletely understood. Using challenge of the Drosophila midgut with a non-lethal enteric pathogen, we examine the cellular determinants of ISC proliferation, harnessing kramer, a recently identified regulator of Wnt signaling pathways, as a mechanistic tool. We find that Wnt signaling within Prospero-positive cells supports ISC proliferation and that kramer regulates Wnt signaling in this context by antagonizing kelch, a Cullin-3 E3 ligase adaptor that mediates Dishevelled polyubiquitination. This work establishes kramer as a physiological regulator of Wnt/β-catenin signaling in vivo and suggests enteroendocrine cells as a new cell type that regulates ISC proliferation via Wnt/β-catenin signaling.

Colonic crypt stem cell functions are controlled by tight junction protein claudin-7 through Notch/Hippo signaling

The tight junction protein claudin-7 is essential for tight junction function and intestinal homeostasis. Cldn7 deletion in mice leads to an inflammatory bowel disease-like phenotype exhibiting severe intestinal epithelial damage, weight loss, inflammation, mucosal ulcerations, and epithelial hyperplasia. Claudin-7 has also been shown to be involved in cancer metastasis and invasion. Here, we test our hypothesis that claudin-7 plays an important role in regulating colonic intestinal stem cell function. Conditional knockout of Cldn7 in the colon led to impaired epithelial cell differentiation, hyperproliferative epithelium, a decrease in active stem cells, and dramatically altered gene expression profiles. In 3D colonoid culture, claudin-7-deficient crypts were unable to survive and form spheroids, emphasizing the importance of claudin-7 in stem cell survival. Inhibition of the Hippo pathway or activation of Notch signaling partially rescued the defective stem cell behavior. Concurrent Notch activation and Hippo inhibition resulted in restored colonoid survival, growth, and differentiation to the level comparable to those of wild-type derived crypts. In this study, we highlight the essential role of claudin-7 in regulating Notch and Hippo signaling-dependent colonic stem cell functions, including survival, self-renewal, and differentiation. These new findings may shed light on potential avenues to explore for drug development in colorectal cancer.

The genomics of sporadic and hereditary colorectal cancer

Colorectal cancer (CRC) is a leading cause of cancer deaths worldwide. Over the past three decades, extensive efforts have sought to elucidate the genomic landscape of CRC. These studies reveal that CRC is highly heterogeneous at the molecular level, with different subtypes characterised by distinct somatic mutational profiles, epigenetic aberrations and transcriptomic signatures. This review summarises our current understanding of the genomic and epigenomic alterations implicated in CRC development and progression. Particular focus is given to how characterisation of CRC genomes is leading to more personalised approaches to diagnosis and treatment.

Human Intestinal Organoids and Microphysiological Systems for Modeling Radiotoxicity and Assessing Radioprotective Agents

Radiotherapy is a commonly employed treatment for colorectal cancer, yet its radiotoxicity-related impact on healthy tissues raises significant health concerns. This highlights the need to use radioprotective agents to mitigate these side effects. This review presents the current landscape of human translational radiobiology, outlining the limitations of existing models and proposing engineering solutions. We delve into radiotherapy principles, encompassing mechanisms of radiation-induced cell death and its influence on normal and cancerous colorectal cells. Furthermore, we explore the engineering aspects of microphysiological systems to represent radiotherapy-induced gastrointestinal toxicity and how to include the gut microbiota to study its role in treatment failure and success. This review ultimately highlights the main challenges and future pathways in translational research for pelvic radiotherapy-induced toxicity. This is achieved by developing a humanized in vitro model that mimics radiotherapy treatment conditions. An in vitro model should provide in-depth analyses of host-gut microbiota interactions and a deeper understanding of the underlying biological mechanisms of radioprotective food supplements. Additionally, it would be of great value if these models could produce high-throughput data using patient-derived samples to address the lack of human representability to complete clinical trials and improve patients' quality of life.

The E3 ubiquitin ligase RNF31 mediates the development of ulcerative colitis by regulating NLRP3 inflammasome activation

Ulcerative colitis (UC) is characterized by dysregulated inflammation and disruption of the intestinal barrier. The NLRP3 inflammasome, which is composed of NLRP3, ASC, and caspase-1, plays a crucial role in UC pathogenesis by triggering the production of proinflammatory cytokines. In this study, we investigated the regulatory role of RNF31 in NLRP3 inflammasome activation during UC development. Through comprehensive analysis of ulcerative colitis tissues using the GEO database and immunohistochemistry, we found that RNF31 expression was elevated in UC tissues, which prompted further investigation into its function. We constructed an RNF31 knockdown cell model and observed a significant reduction in NLRP3 inflammasome activation, indicating the involvement of RNF31 in regulating NLRP3. Mechanistically, RNF31 could interact with NLRP3 through the RBR structural domain, leading to increased K63-linked ubiquitination of NLRP3 and consequent stabilization. Coimmunoprecipitation experiments revealed a mutual interaction between RNF31 and NLRP3, substantiating their functional association. Finally, an in vivo mouse model with RNF31 knockdown showed a notable reduction in NLRP3 expression, which was accompanied by a decrease in the proinflammatory cytokines IL-18 and IL-1β. The successful attenuation of DSS-induced tissue inflammation by this treatment confirmed the physiological relevance of RNF31-mediated regulation of NLRP3. This study unveils a novel regulatory pathway by which RNF31 affects NLRP3 inflammasome activation, providing new insights into UC pathogenesis and potential therapeutic targets for UC treatment.

The cellular states and fates of shed intestinal cells

The intestinal epithelium is replaced every few days1. Enterocytes are shed into the gut lumen predominantly from the tips of villi2,3 and have been believed to rapidly die upon their dissociation from the tissue4,5. However, technical limitations prohibited studying the cellular states and fates of shed intestinal cells. Here we show that shed epithelial cells remain viable and upregulate distinct anti-microbial programmes upon shedding, using bulk and single-cell RNA sequencing of male mouse intestinal faecal washes. We further identify abundant shedding of immune cells, which is elevated in mice with dextran sulfate sodium-induced colitis. We find that faecal host transcriptomics reflect changes in the intestinal tissue following perturbations. Our study suggests potential functions of shed cells in the intestinal lumen and demonstrates that host cell transcriptomes in intestinal washes can be used to probe tissue states.

Control of Paneth cell function by HuR regulates gut mucosal growth by altering stem cell activity

Rapid self-renewal of the intestinal epithelium requires the activity of intestinal stem cells (ISCs) that are intermingled with Paneth cells (PCs) at the crypt base. PCs provide multiple secreted and surface-bound niche signals and play an important role in the regulation of ISC proliferation. Here, we show that control of PC function by RNA-binding protein HuR via mitochondria affects intestinal mucosal growth by altering ISC activity. Targeted deletion of HuR in mice disrupted PC gene expression profiles, reduced PC-derived niche factors, and impaired ISC function, leading to inhibited renewal of the intestinal epithelium. Human intestinal mucosa from patients with critical surgical disorders exhibited decreased levels of tissue HuR and PC/ISC niche dysfunction, along with disrupted mucosal growth. HuR deletion led to mitochondrial impairment by decreasing the levels of several mitochondrial-associated proteins including prohibitin 1 (PHB1) in the intestinal epithelium, whereas HuR enhanced PHB1 expression by preventing microRNA-195 binding to the Phb1 mRNA. These results indicate that HuR is essential for maintaining the integrity of the PC/ISC niche and highlight a novel role for a defective PC/ISC niche in the pathogenesis of intestinal mucosa atrophy.

Effect of aging on the formation and growth of colonic epithelial organoids by changes in cell cycle arrest through TGF-β-Smad3 signaling

BACKGROUND

This study aimed to investigate how aging alters the homeostasis of the colonic intestinal epithelium and regeneration after tissue injury using organoid models and to identify its underlying molecular mechanism.

METHODS

To investigate aging-related changes in the colonic intestinal epithelium, we conducted organoid cultures from old (older than 80 weeks) and young (6-10 weeks) mice and compared the number and size of organoids at day 5 of passage 0 and the growth rate of organoids between the two groups.

RESULTS

The number and size of organoids from old mice was significantly lower than that from young mice (p < 0.0001) at day 5 of passage 0. The growth rate of old-mouse organoids from day 4 to 5 of passage 0 was significantly slower than that of young-mouse organoids (2.21 times vs. 1.16 times, p < 0.001). RNA sequencing showed that TGF-β- and cell cycle-associated genes were associated with the aging effect. With regard to mRNA and protein levels, Smad3 and p-Smad3 in the old-mouse organoids were markedly increased compared with those in the young-mouse organoids. Decreased expression of ID1, increased expression of p16^INK4a, and increased cell cycle arrest were observed in the old mouse-organoids. Treatment with SB431542, a type I TGF-β receptor inhibitor, significantly increased the formation and growth of old-mouse organoids, and TGF-β1 treatment markedly suppressed the formation of young-mouse organoids. In the acute dextran sulfate sodium-colitis model and its organoid experiments, the colonic epithelial regeneration after tissue injury in old mice was significantly decreased compared with young mice.

CONCLUSIONS

Aging reduced the formation ability and growth rate of colonic epithelial organoids by increasing cell cycle arrest through TGF-β-Smad3-p16^INK4a signaling.

Research progress and application of the CRISPR/Cas9 gene-editing technology based on hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is now a common cause of cancer death, with no obvious change in patient survival over the past few years. Although the traditional therapeutic modalities for HCC patients mainly involved in surgery, chemotherapy, and radiotherapy, which have achieved admirable achievements, challenges are still existed, such as drug resistance and toxicity. The emerging gene therapy of clustered regularly interspaced short palindromic repeat/CRISPR-associated nuclease 9-based (CRISPR/Cas9), as an alternative to traditional treatment methods, has attracted considerable attention for eradicating resistant malignant tumors and regulating multiple crucial events of target gene-editing. Recently, advances in CRISPR/Cas9-based anti-drugs are presented at the intersection of science, such as chemistry, materials science, tumor biology, and genetics. In this review, the principle as well as statues of CRISPR/Cas9 technique were introduced first to show its feasibility. Additionally, the emphasis was placed on the applications of CRISPR/Cas9 technology in therapeutic HCC. Further, a broad overview of non-viral delivery systems for the CRISPR/Cas9-based anti-drugs in HCC treatment was summarized to delineate their design, action mechanisms, and anticancer applications. Finally, the limitations and prospects of current studies were also discussed, and we hope to provide comprehensively theoretical basis for the designing of anti-drugs.

COPS3 inhibition promotes cell proliferation blockage and anoikis via regulating PFKFB3 in osteosarcoma cancer cells

As a key component of the COP9 signalosome complex, which participates in a variety of physiological processes, COPS3 is intimately related to multiple cancers. It promotes cell proliferation, progression and metastasis in several cancer cells. However, whether COPS3 participates in regulating anoikis, a specific kind of apoptosis and functions as an essential modulator of cell metastasis, has not yet been studied. Here, we found COPS3 is highly expressed in several cancers especially in osteosarcoma (OS). Overexpression of COPS3 promoted cell proliferation, cell viability and migration/invasion in both control cells and oxaliplatin (Oxa) treated cells. On the contrary, knockdown of COPS3 further enhanced the cytotoxicity of Oxa. Utilizing bioinformatics analysis, we found that COPS3 was higher expressed in the metastatic group, and associated with the extra-cellular matrix (ECM) receptor interaction pathway, which involve in regulating anoikis. In an anoikis model, COPS3 expression varied and genetic modification of COPS3 influenced the cell death enhanced by Oxa. PFKFB3, an essential modulator of glycolysis, was found to interact with COPS3. Inhibition of PFKFB3 promoted apoptosis and anoikis enhanced by Oxa, and COPS3 overexpression failed to rescue this cell death. On the contrary, in the COPS3 knockdown cells, overexpression of PFKFB3 recovered the anoikis resistance, indicating COPS3 function upstream of PFKFB3. In summary, our results elucidated that COPS3 modulated anoikis via affecting PFKFB3 in OS cancer cells.

Fusobacterium & Co. at the Stem of Cancer: Microbe-Cancer Stem Cell Interactions in Colorectal Carcinogenesis

Adult stem cells lie at the crossroads of tissue repair, inflammation, and malignancy. Intestinal microbiota and microbe-host interactions are pivotal to maintaining gut homeostasis and response to injury, and participate in colorectal carcinogenesis. Yet, limited knowledge is available on whether and how bacteria directly crosstalk with intestinal stem cells (ISC), particularly cancerous stem-like cells (CR-CSC), as engines for colorectal cancer initiation, maintenance, and metastatic dissemination. Among several bacterial species alleged to initiate or promote colorectal cancer (CRC), the pathobiont Fusobacterium Nucleatum has recently drawn significant attention for its epidemiologic association and mechanistic linkage with the disease. We will therefore focus on current evidence for an F. nucleatum-CRCSC axis in tumor development, highlighting the commonalities and differences between F. nucleatum-associated colorectal carcinogenesis and gastric cancer driven by Helicobacter Pylori. We will explore the diverse facets of the bacteria-CSC interaction, analyzing the signals and pathways whereby bacteria either confer "stemness" properties to tumor cells or primarily target stem-like elements within the heterogeneous tumor cell populations. We will also discuss the extent to which CR-CSC cells are competent for innate immune responses and participate in establishing a tumor-promoting microenvironment. Finally, by capitalizing on the expanding knowledge of how the microbiota and ISC crosstalk in intestinal homeostasis and response to injury, we will speculate on the possibility that CRC arises as an aberrant repair response promoted by pathogenic bacteria upon direct stimulation of intestinal stem cells.

Consumption of a multi-deficient diet causes dynamic changes in the intestinal morphofunctional barrier, body composition and impaired physical development in post-weaning mice

Few studies have focused on nutrient-deficient diets and associated pathobiological dynamics of body composition and intestinal barrier function. This study evaluated the impact of a nutrient-deficient diet on physical development and intestinal morphofunctional barrier in mice. C57BL/6 (21 days of age) mice were fed a Northeastern Brazil regional basic diet (RBD) or a control diet for 21 d. The animals were subjected to bioimpedance analysis, lactulose test, morphometric analysis and quantitative reverse transcription-PCR to evaluate tight junctions and intestinal transporters. RBD feeding significantly reduced weight (P < 0·05) from day 5, weight gain from day 3 and tail length from day 14. The intake of RBD reduced total body water, extracellular fluid, fat mass and fat-free mass from day 7 (P < 0·05). RBD induced changes in the jejunum, with an increase in the villus:crypt ratio on day 7, followed by reduction on days 14 and 21 (P < 0·05). Lactulose:mannitol ratio increased on day 14 (P < 0·05). Changes in intestinal barrier function on day 14 were associated with reductions in claudin-1 and occludin, and on day 21, there was a reduction in the levels of claudin-2 and occludin. SGLT-1 levels decreased on day 21. RBD compromises body composition and physical development with dynamic changes in intestinal barrier morphofunctional. RBD is associated with damage to intestinal permeability, reduced levels of claudin-1 and occludin transcripts and return of bowel function in a chronic period.

Wnt/β-catenin signaling within multiple cell types dependent upon kramer regulates Drosophila intestinal stem cell proliferation

The gut epithelium is subject to constant renewal, a process reliant upon intestinal stem cell (ISC) proliferation that is driven by Wnt/β-catenin signaling. Despite the importance of Wnt signaling within ISCs, the relevance of Wnt signaling within other gut cell types and the underlying mechanisms that modulate Wnt signaling in these contexts remain incompletely understood. Using challenge of the Drosophila midgut with a non-lethal enteric pathogen, we examine the cellular determinants of ISC proliferation, harnessing kramer, a recently identified regulator of Wnt signaling pathways, as a mechanistic tool. We find that Wnt signaling within Prospero-positive cells supports ISC proliferation and that kramer regulates Wnt signaling in this context by antagonizing kelch, a Cullin-3 E3 ligase adaptor that mediates Dishevelled polyubiquitination. This work establishes kramer as a physiological regulator of Wnt/β-catenin signaling in vivo and suggests enteroendocrine cells as a new cell type that regulates ISC proliferation via Wnt/β-catenin signaling.

Cellular mechanisms of reverse epithelial curvature in tissue morphogenesis

Epithelial bending plays an essential role during the multiple stages of organogenesis and can be classified into two types: invagination and evagination. The early stages of invaginating and evaginating organs are often depicted as simple concave and convex curves respectively, but in fact majority of the epithelial organs develop through a more complex pattern of curvature: concave flanked by convex and vice versa respectively. At the cellular level, this is far from a geometrical truism: locally cells must passively adapt to, or actively create such an epithelial structure that is typically composed of opposite and connected folds that form at least one s-shaped curve that we here, based on its appearance, term as "reverse curves." In recent years, invagination and evagination have been studied in increasing cellular detail. A diversity of mechanisms, including apical/basal constriction, vertical telescoping and extrinsic factors, all orchestrate epithelial bending to give different organs their final shape. However, how cells behave collectively to generate reverse curves remains less well-known. Here we review experimental models that characteristically form reverse curves during organogenesis. These include the circumvallate papillae in the tongue, crypt-villus structure in the intestine, and early tooth germ and describe how, in each case, reverse curves form to connect an invaginated or evaginated placode or opposite epithelial folds. Furthermore, by referring to the multicellular system that occur in the invagination and evagination, we attempt to provide a summary of mechanisms thought to be involved in reverse curvature consisting of apical/basal constriction, and extrinsic factors. Finally, we describe the emerging techniques in the current investigations, such as organoid culture, computational modelling and live imaging technologies that have been utilized to improve our understanding of the cellular mechanisms in early tissue morphogenesis.

The role of NLRP3 inflammasome in colorectal cancer: potential therapeutic target

All phases of carcinogenesis are affected by inflammation. Activation of the inflammasome is a crucial signaling mechanism that leads to acute and chronic inflammation. When specific nucleotide-binding domains, leucine-rich repeat-containing proteins (NLRs) are activated, inflammasomes are formed. The NLRP3 is one of the NLR family members with the most functional characterization. NLRP3 can modulate the immune systems, apoptosis, growth, and/or the gut microbiome to impact cancer development. Colorectal cancer (CRC) is one of the most common cancers, and it begins as a tissue overgrowth on the internal part of the rectum or colon. In vivo and in vitro studies showed that the NLRP3 inflammasome has a role in CRC development due to its broad activity in shaping immune responses. Here, onwards, we focus on the NLRP3 inflammasome role in CRC development, as well as the therapeutic prospective of modifying NLRP3 inflammasome in the context of anti-cancer therapy.

The emerging era of personalized medicine in advanced colorectal cancer

Colorectal cancer (CRC) is a genetically heterogeneous disease with its pathogenesis often driven by varying genetic or epigenetic alterations. This has led to a substantial number of patients developing chemoresistance and treatment failure, resulting in a high mortality rate for advanced disease. Deep molecular analysis has allowed for the discovery of key intestinal signaling pathways which impacts colonic epithelial cell fate, and the integral role of the tumor microenvironment on cancer growth and dissemination. Through transitioning pre-clinical knowledge in research into clinical practice, many potential druggable targets within these pathways have been discovered in the hopes of overcoming the roadblocks encountered by conventional therapies. A personalized approach tailoring treatment according to the histopathological and molecular features of individual tumors can hopefully translate to better patient outcomes, and reduce the rate of recurrence in patients with advanced CRC. Herein, the latest understanding on the molecular science behind CRC tumorigenesis, and the potential treatment targets currently at the forefront of research are summarized.

TLR/WNT: A Novel Relationship in Immunomodulation of Lung Cancer

The most frequent cause of death by cancer worldwide is lung cancer, and the 5-year survival rate is still very poor for patients with advanced stage. Understanding the crosstalk between the signaling pathways that are involved in disease, especially in metastasis, is crucial to developing new targeted therapies. Toll-like receptors (TLRs) are master regulators of the immune responses, and their dysregulation in lung cancer is linked to immune escape and promotes tumor malignancy by facilitating angiogenesis and proliferation. On the other hand, over-activation of the WNT signaling pathway has been reported in lung cancer and is also associated with tumor metastasis via induction of Epithelial-to-mesenchymal-transition (EMT)-like processes. An interaction between both TLRs and the WNT pathway was discovered recently as it was found that the TLR pathway can be activated by WNT ligands in the tumor microenvironment; however, the implications of such interactions in the context of lung cancer have not been discussed yet. Here, we offer an overview of the interaction of TLR-WNT in the lung and its potential implications and role in the oncogenic process.

Proteobacteria and Firmicutes Secreted Factors Exert Distinct Effects on Pseudomonas aeruginosa Infection under Normoxia or Mild Hypoxia

Microbiota may alter a pathogen's virulence potential at polymicrobial infection sites. Here, we developed a multi-modal Drosophila assay, amenable to the assessment of human bacterial interactions using fly survival or midgut regeneration as a readout, under normoxia or mild hypoxia. Deploying a matrix of 12 by 33 one-to-one Drosophila co-infections via feeding, we classified bacterial interactions as neutral, synergistic, or antagonistic, based on fly survival. Twenty six percent of these interactions were antagonistic, mainly occurring between Proteobacteria. Specifically, Pseudomonas aeruginosa infection was antagonized by various Klebsiella strains, Acinetobacter baumannii, and Escherichia coli. We validated these interactions in a second screen of 7 by 34 one-to-one Drosophila co-infections based on assessments of midgut regeneration, and in bacterial co-culture test tube assays, where antagonistic interactions depended on secreted factors produced upon high sugar availability. Moreover, Enterococci interacted synergistically with P. aeruginosa in flies and in test tubes, enhancing the virulence and pyocyanin production by P. aeruginosa. However, neither lactic acid bacteria nor their severely hypoxic culture supernatants provided a survival benefit upon P. aeruginosa infection of flies or mice, respectively. We propose that at normoxic or mildly hypoxic sites, Firmicutes may exacerbate, whereas Proteobacteria secreted factors may ameliorate, P. aeruginosa infections.

Phosphorylation of Yun is required for stem cell proliferation and tumorigenesis

Stem cells maintain adult tissue homeostasis under physiological conditions. Uncontrolled stem cell proliferation will lead to tumorigenesis. How stem cell proliferation is precisely controlled is still not fully understood. Phosphorylation of Yun is essential for ISC proliferation. Yun is essential for the proliferation of normal and transformed intestinal stem cells. Our mass spectrometry and biochemical data suggest that Yun can be phosphorylated at multiple residues in vivo. Interestingly, we show that the phosphorylation among these residues is likely interdependent. Furthermore, phosphorylation of each residue in Yun is important for its function in ISC proliferation regulation. Thus, our study unveils the important role of post-translational modification of Yun in stem cell proliferation.

Alterations of mucosa-attached microbiome and epithelial cell numbers in the cystic fibrosis small intestine with implications for intestinal disease

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Defective CFTR leads to accumulation of dehydrated viscous mucus within the small intestine, luminal acidification and altered intestinal motility, resulting in blockage. These changes promote gut microbial dysbiosis, adversely influencing the normal proliferation and differentiation of intestinal epithelial cells. Using Illumina 16S rRNA gene sequencing and immunohistochemistry, we assessed changes in mucosa-attached microbiome and epithelial cell profile in the small intestine of CF mice and a CF patient compared to wild-type mice and non-CF humans. We found increased abundance of pro-inflammatory Escherichia and depletion of beneficial secondary bile-acid producing bacteria in the ileal mucosa-attached microbiome of CFTR-null mice. The ileal mucosa in a CF patient was dominated by a non-aeruginosa Pseudomonas species and lacked numerous beneficial anti-inflammatory and short-chain fatty acid-producing bacteria. In the ileum of both CF mice and a CF patient, the number of absorptive enterocytes, Paneth and glucagon-like peptide 1 and 2 secreting L-type enteroendocrine cells were decreased, whereas stem and goblet cell numbers were increased. These changes in mucosa-attached microbiome and epithelial cell profile suggest that microbiota-host interactions may contribute to intestinal CF disease development with implications for therapy.

Auxilin regulates intestinal stem cell proliferation through EGFR

Adult tissue homeostasis is maintained by residential stem cells. The proliferation and differentiation of adult stem cells must be tightly balanced to avoid excessive proliferation or premature differentiation. However, how stem cell proliferation is properly controlled remains elusive. Here, we find that auxilin (Aux) restricts intestinal stem cell (ISC) proliferation mainly through EGFR signaling. aux depletion leads to excessive ISC proliferation and midgut homeostasis disruption, which is unlikely caused by defective Notch signaling. Aux is expressed in multiple types of intestinal cells. Interestingly, aux depletion causes a dramatic increase in EGFR signaling, with a strong accumulation of EGFR at the plasma membrane and an increased expression of EGFR ligands in response to tissue stress. Furthermore, Aux co-localizes and associates with EGFR. Finally, blocking EGFR signaling completely suppresses the defects caused by aux depletion. Together, these data demonstrate that Aux mainly safeguards EGFR activation to keep a proper ISC proliferation rate to maintain midgut homeostasis.

Microbes affect gut epithelial cell composition through immune-dependent regulation of intestinal stem cell differentiation

Gut microbes play important roles in host physiology; however, the mechanisms underlying their impact remain poorly characterized. Here, we demonstrate that microbes not only influence gut physiology but also alter its epithelial composition. The microbiota and pathogens both influence intestinal stem cell (ISC) differentiation. Intriguingly, while the microbiota promotes ISC differentiation into enterocytes (EC), pathogens stimulate enteroendocrine cell (EE) fate and long-term accumulation of EEs in the midgut epithelium. Importantly, the evolutionarily conserved Drosophila NFKB (Relish) pushes stem cell lineage specification toward ECs by directly regulating differentiation factors. Conversely, the JAK-STAT pathway promotes EE fate in response to infectious damage. We propose a model in which the balance of microbial pattern recognition pathways, such as Imd-Relish, and damage response pathways, such as JAK-STAT, influence ISC differentiation, epithelial composition, and gut physiology.

Ursolic Acid Protects Sodium Dodecyl Sulfate-Induced Drosophila Ulcerative Colitis Model by Inhibiting the JNK Signaling

Ursolic acid (UA) is a bioactive molecule widely distributed in various fruits and vegetables, which was reported to play a therapeutic role in ulcerative colitis (UC) induced by toxic chemicals. However, the underlying mechanism has not been well clarified in vivo. Here, using a Drosophila UC model induced by sodium dodecyl sulfate (SDS), we investigated the defensive effect of UA on intestinal damage. The results showed that UA could significantly protect Drosophila from the damage caused by SDS exposure. Further, UA alleviated the accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA) induced by SDS and upregulated the activities of total superoxide dismutase (T-SOD) and catalase (CAT). Moreover, the proliferation and differentiation of intestine stem cells (ISCs) as well as the excessive activation of the c-Jun N-terminal kinase (JNK)-dependent JAK/STAT signaling pathway induced by SDS were restored by UA. In conclusion, UA prevents intestine injury from toxic compounds by reducing the JNK/JAK/STAT signaling pathway. UA may provide a theoretical basis for functional food or natural medicine development.

The Yun/Prohibitin complex regulates adult Drosophila intestinal stem cell proliferation through the transcription factor E2F1

Stem cells maintain tissue homeostasis. We identified a factor, Yun, required for proliferation of normal and transformed intestinal stem cells in adult Drosophila. Yun acts as a scaffold to stabilize the Prohibitin (PHB) complex previously implicated in various cellular and developmental processes and diseases. The Yun/PHB complex acts downstream of EGFR/MAPK signaling and affects the levels of E2F1 to regulate intestinal stem cell proliferation. The role of the PHB complex in cell proliferation is evolutionarily conserved. Our results provide insight into the underlying mechanisms of how stem cell proliferation is properly controlled during tissue homeostasis and tumorigenesis.

Stem cells constantly divide and differentiate to maintain adult tissue homeostasis, and uncontrolled stem cell proliferation leads to severe diseases such as cancer. How stem cell proliferation is precisely controlled remains poorly understood. Here, from an RNA interference (RNAi) screen in adult Drosophila intestinal stem cells (ISCs), we identify a factor, Yun, required for proliferation of normal and transformed ISCs. Yun is mainly expressed in progenitors; our genetic and biochemical evidence suggest that it acts as a scaffold to stabilize the Prohibitin (PHB) complex previously implicated in various cellular and developmental processes and diseases. We demonstrate that the Yun/PHB complex is regulated by and acts downstream of EGFR/MAPK signaling. Importantly, the Yun/PHB complex interacts with and positively affects the levels of the transcription factor E2F1 to regulate ISC proliferation. In addition, we find that the role of the PHB complex in cell proliferation is evolutionarily conserved. Thus, our study uncovers a Yun/PHB-E2F1 regulatory axis in stem cell proliferation.

Evolution of the membrane/particulate guanylyl cyclase: From physicochemical sensors to hormone receptors

Guanylyl cyclase (GC) is an enzyme that produces 3',5'-cyclic guanosine monophosphate (cGMP), one of the two canonical cyclic nucleotides used as a second messenger for intracellular signal transduction. The GCs are classified into two groups, particulate/membrane GCs (pGC) and soluble/cytosolic GCs (sGC). In relation to the endocrine system, pGCs include hormone receptors for natriuretic peptides (GC-A and GC-B) and guanylin peptides (GC-C), while sGC is a receptor for nitric oxide and carbon monoxide. Comparing the functions of pGCs in eukaryotes, it is apparent that pGCs perceive various environmental factors such as light, temperature, and various external chemical signals in addition to endocrine hormones, and transmit the information into the cell using the intracellular signaling cascade initiated by cGMP, e.g., cGMP-dependent protein kinases, cGMP-sensitive cyclic nucleotide-gated ion channels and cGMP-regulated phosphodiesterases. Among vertebrate pGCs, GC-E and GC-F are localized on retinal epithelia and are involved in modifying signal transduction from the photoreceptor, rhodopsin. GC-D and GC-G are localized in olfactory epithelia and serve as sensors at the extracellular domain for external chemical signals such as odorants and pheromones. GC-G also responds to guanylin peptides in the urine, which alters sensitivity to other chemicals. In addition, guanylin peptides that are secreted into the intestinal lumen, a pseudo-external environment, act on the GC-C on the apical membrane for regulation of epithelial transport. In this context, GC-C and GC-G appear to be in transition from exocrine pheromone receptor to endocrine hormone receptor. The pGCs also exist in various deuterostome and protostome invertebrates, and act as receptors for environmental, exocrine and endocrine factors including hormones. Tracing the evolutionary history of pGCs, it appears that pGCs first appeared as a sensor for physicochemical signals in the environment, and then evolved to function as hormone receptors. In this review, the author proposes an evolutionary history of pGCs that highlights the emerging role of the GC/cGMP system for signal transduction in hormone action.

Platform for the Delivery of Unformulated RNA In Vivo

The successful delivery of RNA therapeutics is the gating hurdle to greater clinical translation and utility of this novel class of therapeutics. Delivery strategies today are limited and predominantly rely on lipid nanoparticles or conjugates, which can facilitate hepatic delivery but are poor for achieving uptake outside the liver. The ability to deliver RNA to other organs outside the liver in a formulation-agnostic approach could serve to unlock the broader potential of these therapies and enable their use in a broader set of disease. Here we demonstrate this formulation-agnostic delivery of two model siRNAs using low-frequency ultrasound to the gastrointestinal (GI) tract. Unformulated siRNAs targeting β-catenin (Ctnnb 1) and Sjögren syndrome antigen B (SSB) genes were successfully delivered to colonic mucosa in mice, achieving robust knockdown of the target mRNA from whole-colon tissue samples. Indeed, the capacity to target and successfully suppress expression from genes underscores the power of this platform to rapidly deliver unformulated and unoptimized sequences against a range of targets in the GI tract.

Identification of a new allele of O-fucosyltransferase 1 involved in Drosophila intestinal stem cell regulation

Adult stem cells are critical for the maintenance of tissue homeostasis. However, how the proliferation and differentiation of intestinal stem cells (ISCs) are regulated remains not fully understood. Here, we find a mutant, stum 9-3, affecting the proliferation and differentiation of Drosophila adult ISCs in a forward genetic screen for factors regulating the proliferation and differentiation ISCs. stum 9-3 acts through the conserved Notch signaling pathway, upstream of the S2 cleavage of the Notch receptor. Interestingly, the phenotype of stum 9-3 mutant is not caused by disruption of stumble (stum), where the p-element is inserted. Detailed mapping, rescue experiments and mutant characterization show that stum 9-3 is a new allele of O-fucosyltransferase 1 (O-fut1). Our results indicate that unexpected mutants with interesting phenotype could be recovered in forward genetic screens using known p-element insertion stocks.

Summary: A mutant, stum 9-3, affecting the proliferation and differentiation of Drosophila adult intestinal stem cells (ISCs) was identified in a forward genetic screen for factors regulating the proliferation and differentiation ISCs. stum 9-3 acts through the Notch signaling pathway. Detailed mapping, rescue experiments and characterization show that stum 9-3 is not a stumble mutant where the p-element is inserted, but a new allele of O-fucosyltransferase 1 (O-fut1).

Derlin-1 and TER94/VCP/p97 are required for intestinal homeostasis

Adult stem cells are critical for the maintenance of residential tissue homeostasis and functions. However, the roles of cellular protein homeostasis maintenance in stem cell proliferation and tissue homeostasis are not fully understood. Here, we find that Derlin-1 and TER94/VCP/p97, components of the ER-associated degradation (ERAD) pathway, restrain intestinal stem cell proliferation to maintain intestinal homeostasis in adult Drosophila. Depleting any of them results in increased stem cell proliferation and midgut homeostasis disruption. Derlin-1 is specifically expressed in the ER of progenitors and its C-terminus is required for its function. Interestingly, we find that increased stem cell proliferation is resulted from elevated ROS levels and activated JNK signaling in Derlin-1- or TER94-deficient progenitors. Further removal of ROS or inhibition of JNK signaling almost completely suppressed increased stem cell proliferation. Together, these data demonstrate that the ERAD pathway is critical for stem cell proliferation and tissue homeostasis. Thus we provide insights into our understanding of the mechanisms underlying cellular protein homeostasis maintenance (ER protein quality control) in tissue homeostasis and tumor development.

Inflammasomes and Colorectal Cancer

Inflammasomes are important intracellular multiprotein signaling complexes that modulate the activation of caspase-1 and induce levels of the proinflammatory cytokines interleukin-1β (IL-1β) and IL-18 in response to pathogenic microorganisms and molecules that originated from host proteins. Inflammasomes play contradictory roles in the development of inflammation-induced cancers. Based on several findings, inflammasomes can initiate and promote carcinogenesis. On the contrary, inflammasomes also exhibit anticancer effects by triggering pyroptosis and immunoregulatory functions. Herein, we review extant studies delving into different functions of inflammasomes in colorectal cancer development.

The Promising Effect of Peucedanum chenur Chloroformic Extract on Prevention of Human Colorectal Cancer Progression by Modulating miR-135b, miR-21, and APC Genes

PURPOSE

The therapeutic use of herbal medicines for the diseases, including cancer, is increasing due to their lower side effects. The present research evaluated the effect of Peucedanum chenur chloroformic extract (PCCE) on cell proliferation against HCT-116 human colorectal cancer cell line.

METHODS

The cytotoxic effect of PCCE was evaluated by MTT assay. The activity of the Wnt/B-catenin pathway was assayed through measuring the expression of miR-135b, miR-21, and APC genes by real-time PCR. The flow cytometry and scratch tests were used to study the cell cycle and cell migration, respectively. Also, the antioxidant activity of PCCE was measured by DPPH and iron-chelating tests.

RESULTS

The results showed the downregulation of miR-135b and miR-21 and overexpression of the APC gene. Furthermore, PCCE decreased the free radicals, cell migration, and cell proliferation. The antioxidant activity of PCCE was confirmed by standard tests.

CONCLUSION

Altogether, our findings suggest that purified compounds of PCCE could be developed as a potent chemo-preventive drug for the treatment of CRC.

Selective in vitro cytotoxicity effect of Drimia calcarata bulb extracts against p53 mutant HT-29 and p53 wild-type Caco-2 colorectal cancer cells through STAT5B regulation

Colorectal cancer is the fourth leading cause of oncological-related deaths and the third most diagnosed malignancy, worldwide. The emergence of chemoresistance is a fundamental drawback of colorectal cancer therapies and there is an urgent need for novel plant-derived therapeutics. In this regard, other compounds are needed to improve the efficacy of treatment against colorectal cancer. Medicinal plants have been effectively used by traditional doctors for decades to treat various ailments with little to no side effects. Drimia calcarata (D. calcarata) is one of the plants used by Pedi people in South Africa to treat a plethora of ailments. However, the anticancer therapeutic use of D. calcarata is less understood. Thus, this study was aimed at evaluating the potential anticancer activities of D. calcarata extracts against human colorectal cancer cells. The phytochemical analysis and antioxidant activity were analysed using LC-MS, DPPH, and FRAP. The inhibitory effects and IC50 values of D. calcarata extracts were determined using the MTT assay. Induction of cellular apoptosis was assessed using fluorescence microscopy, the Muse® Cell Analyser, and gene expression analysis by Polymerase Chain Reaction (PCR). Water extract (WE) demonstrated high phenolic, tannin, and flavonoid contents than the methanol extract (ME). LC-MS data demonstrated strong differences between the ME and WE. Moreover, WE showed the best antioxidant activity than ME. The MTT data showed that both ME and WE had no significant activity against human embryonic kidney Hek 293 cell line that served as non-cancer control cells. Caco-2 cells demonstrated high sensitivity to the ME and demonstrated resistance toward the WE, while HT-29 cells exhibited sensitivity to both D. calcarata extracts. The expression of apoptosis regulatory genes assessed by PCR revealed an upregulation of p53 by ME, accompanied by downregulation of Bcl-2 and high expression of Bax after treatment with curcumin. The Bax gene was undetected in HT-29 cells. The methanol extract induced mitochondrial-mediated apoptosis in colorectal Caco-2 and HT-29 cells and WE induced the extrinsic apoptotic pathway in HT-29 cells. ME downregulated STAT1, 3, and 5B in HT-29 cells. The D. calcarata bulb extracts, therefore, contain potential anticancer agents that can be further targeted for cancer therapeutics.

RAL GTPases mediate EGFR-driven intestinal stem cell proliferation and tumourigenesis

RAS-like (RAL) GTPases function in Wnt signalling-dependent intestinal stem cell proliferation and regeneration. Whether RAL proteins work as canonical RAS effectors in the intestine and the mechanisms of how they contribute to tumourigenesis remain unclear. Here, we show that RAL GTPases are necessary and sufficient to activate EGFR/MAPK signalling in the intestine, via induction of EGFR internalisation. Knocking down Drosophila RalA from intestinal stem and progenitor cells leads to increased levels of plasma membrane-associated EGFR and decreased MAPK pathway activation. Importantly, in addition to influencing stem cell proliferation during damage-induced intestinal regeneration, this role of RAL GTPases impacts on EGFR-dependent tumourigenic growth in the intestine and in human mammary epithelium. However, the effect of oncogenic RAS in the intestine is independent from RAL function. Altogether, our results reveal previously unrecognised cellular and molecular contexts where RAL GTPases become essential mediators of adult tissue homeostasis and malignant transformation.

Autophagy induction in tumor surrounding cells promotes tumor growth in adult Drosophila intestines

During tumorigenesis, tumor cells interact intimately with their surrounding cells (microenvironment) for their growth and progression. However, the roles of tumor microenvironment in tumor development and progression are not fully understood. Here, using an established benign tumor model in adult Drosophila intestines, we find that non-cell autonomous autophagy (NAA) is induced in tumor surrounding neighbor cells. Tumor growth can be significantly suppressed by genetic ablation of autophagy induction in tumor neighboring cells, indicating that tumor neighboring cells act as tumor microenvironment to promote tumor growth. Autophagy in tumor neighboring cells is induced downstream of elevated ROS and activated JNK signaling in tumor cells. Interestingly, we find that active transport of nutrients, such as amino acids, from tumor neighboring cells sustains tumor growth, and increasing nutrient availability could significantly restore tumor growth. Together, these data demonstrate that tumor cells take advantage of their surrounding normal neighbor cells as nutrient sources through NAA to meet their high metabolic demand for growth and progression. Thus we provide insights into our understanding of the mechanisms underlying the interaction between tumor cells and their microenvironment in tumor development.

Colon Fibroblasts and Inflammation: Sparring Partners in Colorectal Cancer Initiation?

Simple Summary

Colorectal cancer (CRC) is the third most common cause of cancer-related death. Patients suffering inflammatory bowel disease have an increased risk of CRC. It is admitted that CRC found its origin within crypts of the colon mucosa, which host the intestinal stem cells (ISCs) responsible of the tissue renewal. ISC behavior is controlled by the fibroblasts that surround the crypt. During inflammation, the signals delivered by fibroblasts are altered, leading to stem cells’ dysregulation, possibly turning them into cancer-initiating cells. Here, we reviewed the interplays between the fibroblast and the ISCs, possibly leading to the initiation of CRC due to chronic inflammation.

Abstract

Colorectal cancer (CRC) is the third most common cause of cancer-related death. Significant improvements in CRC treatment have been made for the last 20 years, on one hand thanks to a better detection, allowing surgical resection of the incriminated area, and on the other hand, thanks to a better knowledge of CRC’s development allowing the improvement of drug strategies. Despite this crucial progress, CRC remains a public health issue. The current model for CRC initiation and progression is based on accumulation of sequential known genetic mutations in the colon epithelial cells’ genome leading to a loss of control over proliferation and survival. However, increasing evidence reveals that CRC initiation is more complex. Indeed, chronic inflammatory contexts, such as inflammatory bowel diseases, have been shown to increase the risk for CRC development in mice and humans. In this manuscript, we review whether colon fibroblasts can go from the main regulators of the ISC homeostasis, regulating not only the renewal process but also the epithelial cells’ differentiation occurring along the colon crypt, to the main player in the initiation of the colorectal cancer process due to chronic inflammation.

Desacetyl-α-MSH and α-MSH have sex specific interactions with diet to influence mouse gut morphology, metabolites and microbiota

The melanocortin peptides have an important role in regulating body weight and appetite. Mice that lack the desacetyl-α-MSH and α-MSH peptides (Pomctm1/tm1) develop obesity. This effect is exacerbated by a high fat diet (HFD). However, development of obesity in female Pomctm1/tm1 mice during chronic HFD conditions is not fully accounted for by the increased energy intake. We hypothesized that the protection against chronic HFD-induced obesity imparted by MSH peptides in females is mediated by sex-specific alterations in the gut structure and gut microbiota. We determined that female WT mice had reduced jejunum villus length and increased crypt depth in response to chronic HFD. WT males and Pomctm1/tm1 mice lacked this adaptation to a chronic HFD. Both Pomctm1/tm1 genotype and chronic HFD were significantly associated with gut microbiota composition. Sex-specific associations between Pomctm1/tm1 genotype and gut microbiota were observed in the presence of a chronic HFD. Pomctm1/tm1 females had significantly reduced fecal acetate and propionate concentrations when compared to WT females. We conclude that MSH peptides influence jejunum villus length, crypt depth and the structure of the gut microbiota. These effects favor reduced nutrient absorption and occur in addition to the recognized roles of desacetyl-α-MSH and α-MSH peptides in appetite control.

Lineage tracing: technology tool for exploring the development, regeneration, and disease of the digestive system

Lineage tracing is the most widely used technique to track the migration, proliferation, and differentiation of specific cells in vivo. The currently available gene-targeting technologies have been developing for decades to study organogenesis, tissue injury repairing, and tumor progression by tracing the fates of individual cells. Recently, lineage tracing has expanded the platforms available for disease model establishment, drug screening, cell plasticity research, and personalized medicine development in a molecular and cellular biology perspective. Lineage tracing provides new views for exploring digestive organ development and regeneration and techniques for digestive disease causes and progression. This review focuses on the lineage tracing technology and its application in digestive diseases.

Notch in Head and Neck Cancer

Head and neck cancer is a group of neoplastic diseases affecting the facial, oral, and neck region. It is one of the most common cancers worldwide with an aggressive, invasive evolution. Due to the heterogeneity of the tissues affected, it is particularly challenging to study the molecular mechanisms at the basis of these tumors, and to date we are still lacking accurate targets for prevention and therapy. The Notch signaling is involved in a variety of tumorigenic mechanisms, such as regulation of the tumor microenvironment, aberrant intercellular communication, and altered metabolism. Here, we provide an up-to-date review of the role of Notch in head and neck cancer and draw parallels with other types of solid tumors where the Notch pathway plays a crucial role in emergence, maintenance, and progression of the disease. We therefore give a perspective view on the importance of the pathway in neoplastic development in order to define future lines of research and novel therapeutic approaches.

Gorlin Syndrome: Recent Advances in Genetic Testing and Molecular and Cellular Biological Research

Gorlin syndrome is a skeletal disorder caused by a gain of function mutation in Hedgehog (Hh) signaling. The Hh family comprises of many signaling mediators, which, through complex mechanisms, play several important roles in various stages of development. The Hh information pathway is essential for bone tissue development. It is also the major driver gene in the development of basal cell carcinoma and medulloblastoma. In this review, we first present the recent advances in Gorlin syndrome research, in particular, the signaling mediators of the Hh pathway and their functions at the genetic level. Then, we discuss the phenotypes of mutant mice and Hh signaling-related molecules in humans revealed by studies using induced pluripotent stem cells.

CRISPR/Cas: From Tumor Gene Editing to T Cell-Based Immunotherapy of Cancer

The clustered regularly interspaced short palindromic repeats system has demonstrated considerable advantages over other nuclease-based genome editing tools due to its high accuracy, efficiency, and strong specificity. Given that cancer is caused by an excessive accumulation of mutations that lead to the activation of oncogenes and inactivation of tumor suppressor genes, the CRISPR/Cas9 system is a therapy of choice for tumor genome editing and treatment. In defining its superior use, we have reviewed the novel applications of the CRISPR genome editing tool in discovering, sorting, and prioritizing targets for subsequent interventions, and passing different hurdles of cancer treatment such as epigenetic alterations and drug resistance. Moreover, we have reviewed the breakthroughs precipitated by the CRISPR system in the field of cancer immunotherapy, such as identification of immune system-tumor interplay, production of universal Chimeric Antigen Receptor T cells, inhibition of immune checkpoint inhibitors, and Oncolytic Virotherapy. The existing challenges and limitations, as well as the prospects of CRISPR based systems, are also discussed.

Constitutive Activation of Nrf2 in Mice Expands Enterogenesis in Small Intestine Through Negative Regulation of Math1

BACKGROUND & AIMS

Notch signaling coordinates cell differentiation processes in the intestinal epithelium. The transcription factor Nrf2 orchestrates defense mechanisms by regulating cellular redox homeostasis, which, as shown previously in murine liver, can be amplified through signaling crosstalk with the Notch pathway. However, interplay between these 2 signaling pathways in the gut is unknown.

METHODS

Mice modified genetically to amplify Nrf2 in the intestinal epithelium (Keap1^f/f::VilCre) were generated as well as pharmacological activation of Nrf2 and subjected to phenotypic and cell lineage analyses. Cell lines were used for reporter gene assays together with Nrf2 overexpression to study transcriptional regulation of the Notch downstream effector.

RESULTS

Constitutive activation of Nrf2 signaling caused increased intestinal length along with expanded cell number and thickness of enterocytes without any alterations of secretory lineage, outcomes abrogated by concomitant disruption of Nrf2. The Nrf2 and Notch pathways in epithelium showed inverse spatial profiles, where Nrf2 activity in crypts was lower than villi. In progenitor cells of Keap1^f/f::VilCre mice, Notch downstream effector Math1, which regulates a differentiation balance of cell lineage through lateral inhibition, showed suppressed expression. In vitro results demonstrated Nrf2 negatively regulated Math1, where 6 antioxidant response elements located in the regulatory regions contributed to this repression.

CONCLUSIONS

Activation of Nrf2 perturbed the dialog of the Notch cascade though negative regulation of Math1 in progenitor cells, leading to enhanced enterogenesis. The crosstalk between the Nrf2 and Notch pathways could be critical for fine-tuning intestinal homeostasis and point to new approaches for the pharmacological management of absorptive deficiencies.

Elevating EGFR-MAPK program by a nonconventional Cdc42 enhances intestinal epithelial survival and regeneration

The regulatory mechanisms enabling the intestinal epithelium to maintain a high degree of regenerative capacity during mucosal injury remain unclear. Ex vivo survival and clonogenicity of intestinal stem cells (ISCs) strictly required growth response mediated by cell division control 42 (Cdc42) and Cdc42-deficient enteroids to undergo rapid apoptosis. Mechanistically, Cdc42 engaging with EGFR was required for EGF-stimulated, receptor-mediated endocytosis and sufficient to promote MAPK signaling. Proteomics and kinase analysis revealed that a physiologically, but nonconventionally, spliced Cdc42 variant 2 (V2) exhibited stronger MAPK-activating capability. Human CDC42-V2 is transcriptionally elevated in some colon tumor tissues. Accordingly, mice engineered to overexpress Cdc42-V2 in intestinal epithelium showed elevated MAPK signaling, enhanced regeneration, and reduced mucosal damage in response to irradiation. Overproducing Cdc42-V2 specifically in mouse ISCs enhanced intestinal regeneration following injury. Thus, the intrinsic Cdc42-MAPK program is required for intestinal epithelial regeneration, and elevating this signaling cascade is capable of initiating protection from genotoxic injury.

The genetic factors associated with Wnt signaling pathway in colorectal cancer

Colorectal cancer (CRC) is a common cancer with poor prognosis and high mortality. There is growing information about the factors involved in the pathogenesis of CRC. However, the knowledge of the predisposing factors is limited. The development of CRC is strongly associated with the Wingless/Integrated (Wnt) signaling pathway. This pathway comprises several major target proteins, including LRP5/6, GSK3β, adenomatous polyposis coli (APC), axis inhibition protein (Axin), and β-catenin. Genetic variations in these components of the Wnt signaling pathway may lead to the activation of β-catenin, potentially increasing the proliferation of colorectal cells. Because of the potentially important role of the Wnt signaling pathway in CRC, we aimed to review the involvement of different mutations in the main downstream proteins of this pathway, including LRP5/6, APC, GSK3β, Axin, and β-catenin. Determination of the genetic risk factors involved in the progression of CRC may lead to novel approaches for the early diagnosis of CRC and the identification of potential therapeutic targets in the treatment of CRC.

Genomic instability and cancer: lessons from Drosophila

Cancer is a genetic disease that involves the gradual accumulation of mutations. Human tumours are genetically unstable. However, the current knowledge about the origins and implications of genomic instability in this disease is limited. Understanding the biology of cancer requires the use of animal models. Here, we review relevant studies addressing the implications of genomic instability in cancer by using the fruit fly, Drosophila melanogaster, as a model system. We discuss how this invertebrate has helped us to expand the current knowledge about the mechanisms involved in genomic instability and how this hallmark of cancer influences disease progression.

Maternal Vitamin D Deficiency Increases Intestinal Permeability and Programs Wnt/β-Catenin Pathway in BALB/C Mice

BACKGROUND

Recent studies suggest that vitamin D deficiency is associated with intestinal dysfunctions, but the underlying mechanism remains unclear. This study aimed to investigate whether maternal vitamin D deficiency increases intestinal permeability in offspring and its related mechanism.

METHODS

Timed-pregnant mice were fed with either a standard chow diet (SC) or a vitamin D-deprived chow diet (VD-) 6 weeks prior to breeding and kept on the same diet until the end of gestation. All offspring were fed an SC for 3 weeks after weaning and then observed for effects associated with maternal vitamin D deficiency.

RESULTS

Maternal vitamin D deficiency increased intestinal permeability in offspring, which corresponded with the decreased expression of the tight junction protein claudin-1. Maternal vitamin D deficiency also repressed the messenger RNA expression of wingless/integrated family member 3a (Wnt3a) and the protein expression of nuclear β-catenin. The decreased Wnt3a gene expression in male was concurrent with the changes in histone H4 acetylation at either promoter or coding regions. The activation of the Wnt/β-catenin pathway protected against the impairment of intestinal permeability induced by maternal vitamin D deficiency.

CONCLUSIONS

Maternal vitamin D deficiency increased intestinal permeability and decreased tight junction protein expression in offspring. The suppression of the Wnt/β-catenin signaling pathway through histone modification might be involved in the underlying mechanism.

Frequent Activation of Notch Signaling Pathway in Colorectal Cancers and Its Implication in Patient Survival Outcome

Colorectal cancer is a major health concern as it ranks third in incidence and second major cause of cancer-related deaths worldwide. A leading cause of treatment failure has been attributed to cancer stem cells that can invariably resist existing chemotherapeutic regimens. Notch signaling pathway has been involved in the maintenance of stem cells besides being crucial in cell fate decision and embryonic development. This pathway has also been implicated in several human malignancies including colorectal cancer. We investigated mRNA expression of four Notch receptors (Notch1–4), five ligands (Jag1, Jag2, Dll1, Dll3, and Dll4), and four target genes (Hes1, Hes5, Hey1, and Hey2) using highly specific TaqMan gene expression assays in colorectal adenomas and cancers. Upregulated expression of Notch receptors ranged between 29 and 73% in colorectal cancers and between 11 and 56% in adenomas. Expression of Notch3 and Notch4 receptors was significantly higher in colorectal cancers compared to normal and adenoma tissues. The Jagged and Delta-like ligands were overexpressed between 25 and 52% in colorectal cancers, while in adenomas, it ranged between 0 and 33%. Combining the data for upregulation of receptors and ligands suggests that 86% colorectal cancers and 56% adenomas exhibited overexpression of Notch pathway genes in our cohort. Notch target genes were upregulated between 24 and 33% in colorectal cancers and between 11 and 22% in adenomas. Collating upregulation of Notch receptors and ligands with the target genes showed concordance in 58% colorectal tumors. Additionally, we evaluated expression of Notch receptors, ligands, and target genes with prognosis using the TCGA mRNA expression dataset. Patients overexpressing Notch3, Notch4, and Hey1 had significantly poorer overall survival relative to those having lower levels of these genes. Taken together, Notch signaling components are aberrantly overexpressed in colorectal tumors, and development of therapeutics targeting the Notch pathway may prove to be beneficial in the management of colorectal cancers.

Overview of Basic Mechanisms of Notch Signaling in Development and Disease

Notch signaling is an evolutionarily conserved pathway associated with the development and differentiation of all metazoans. It is needed for proper germ layer formation and segmentation of the embryo and controls the timing and duration of differentiation events in a dynamic manner. Perturbations of Notch signaling result in blockades of developmental cascades, developmental anomalies, and cancers. An in-depth understanding of Notch signaling is thus required to comprehend the basis of development and cancer, and can be further exploited to understand and direct the outcomes of targeted cellular differentiation into desired cell types and complex tissues from pluripotent or adult stem and progenitor cells. In this chapter, we briefly summarize the molecular, evolutionary, and developmental basis of Notch signaling. We will focus on understanding the basics of Notch signaling and its signaling control mechanisms, its developmental outcomes and perturbations leading to developmental defects, as well as have a brief look at mutations of the Notch signaling pathway causing human hereditary disorders or cancers.

Heparan sulfate maintains adult midgut homeostasis in Drosophila

Tissue homeostasis is controlled by the differentiated progeny of residential progenitors (stem cells). Adult stem cells constantly adjust their proliferation/differentiation rates to respond to tissue damage and stresses. However, how differentiated cells maintain tissue homeostasis remains unclear. Here, we find that heparan sulfate (HS), a class of glycosaminoglycan (GAG) chains, protects differentiated cells from loss to maintain intestinal homeostasis. HS depletion in enterocytes (ECs) leads to intestinal homeostasis disruption, with accumulation of intestinal stem cell (ISC)-like cells and mis-differentiated progeny. HS-deficient ECs are prone to cell death/stress and induced cytokine and epidermal growth factor (EGF) expression, which, in turn, promote ISC proliferation and differentiation. Interestingly, HS depletion in ECs results in the inactivation of decapentaplegic (Dpp) signaling. Moreover, ectopic Dpp signaling completely rescued the defects caused by HS depletion. Together, our data demonstrate that HS is required for Dpp signal activation in ECs, thereby protecting ECs from ablation to maintain midgut homeostasis. Our data shed light into the regulatory mechanisms of how differentiated cells contribute to tissue homeostasis maintenance.

Diet, Microbiota, and Colorectal Cancer

The intestinal epithelium is a very dynamic tissue under a high regenerative pressure, which makes it susceptible to malignant transformation. Proper integration of various cell signaling pathways and a balanced cross talk between different cell types composing the organ are required to maintain intestinal homeostasis. Dysregulation of this balance can lead to colorectal cancer (CRC). Here, we review important insights into molecular and cellular mechanisms of CRC. We discuss how perturbation in complex regulatory networks, including the Wnt, Notch, BMP, and Hedgehog pathways; and how variations in inflammatory signaling, nutrients, and microbiota can affect intestinal homeostasis contributing to the malignant transformation of intestinal cells.