PTEN-deficient intestinal stem cells initiate intestinal polyposis

LIM kinase 2 activates cardiac fibroblasts and exacerbates postinfarction left ventricular remodeling via crosstalk between the canonical and non-canonical Wnt pathways

Ischemic heart failure rates rise despite decreased acute myocardial infarction (MI) mortality. Excessive myofibroblast activation post-MI leads to adverse remodeling. LIM kinases (LIMK1 and LIMK2) regulate cytoskeleton homeostasis and are pro-fibrotic markers in atrial fibrillation. However, their roles and mechanisms in postinfarction fibrosis and ventricular remodeling remain unclear. This study found that the expression of LIMKs elevated in the border zone (BZ) in mice MI models. LIMK1/2 double knockout (DKO) restrained pathological remodeling and reduced mortality by suppressing myofibroblast activation. By using adeno-associated virus (AAV) with a periostin promoter to overexpress LIMK1 or LIMK2, this study found that myofibroblast-specific LIMK2 overexpression diminished these effects in DKO mice, while LIMK1 did not. LIMK2 kinase activity was critical for myofibroblast proliferation by using AAV overexpressing mutant LIMK2 lack of kinase activity. According to phosphoproteome analysis, functional rescue experiments, co-immunoprecipitation, and protein-protein docking, LIMK2 led to the phosphorylation of β-catenin at Ser 552. LIMK2 nuclear translocation also played a role in myofibroblast proliferation after MI with the help of AAV overexpressing mutant LIMK2 without nuclear location signal. Chromatin immunoprecipitation sequencing identified that LIMK2 bound to Lrp6 promoter region in TGF-β treated cardiac fibroblasts, positively regulating Wnt signaling via Wnt receptor internalization. This study demonstrated that LIMK2 promoted myofibroblast proliferation and adverse cardiac remodeling after MI, by enhancing phospho-β-catenin (Ser552) and Lrp6 signaling. This suggested that LIMK2 could be a target for the treatment of postinfarction injury.

A Novel CRISPR/Cas9-mediated Mouse Model of Colon Carcinogenesis

BACKGROUND & AIMS

Human sporadic colorectal cancer (CRC) results from a multistep pathway with sequential acquisition of specific genetic mutations in the colorectal epithelium. Modeling CRC in vivo is critical for understanding the tumor microenvironment. To accurately recapitulate human CRC pathogenesis, mouse models must include these multi-step genetic abnormalities. The aim of this study was to generate a sporadic CRC model that more closely mimics this multi-step process and to use this model to study the role of a novel Let7 target PLAGL2 in CRC pathogenesis.

METHODS

We generated a CRISPR/Cas9 somatic mutagenesis mouse model that is inducible and multiplexed for simultaneous inactivation of multiple genes involved in CRC pathogenesis. We used both a doxycycline-inducible transcriptional activator and a doxycycline-inactivated transcriptional repressor to achieve tight, non-leaky expression of the Cas9 nickase. This mouse has transgenic expression of multiple guide RNAs to induce sporadic inactivation in the gut epithelium of 4 tumor suppressor genes commonly mutated in CRC, Apc, Pten, Smad4, and Trp53. These were crossed to Vil-LCL-PLAGL2 mice, which have Cre-inducible overexpression of PLAGL2 in the gut epithelium.

RESULTS

These mice exhibited random somatic mutations in all 4 targeted tumor suppressor genes, resulting in multiple adenomas and adenocarcinomas in the small bowel and colon. Crosses with Vil-LCL-PLAGL2 mice demonstrated that gut-specific PLAGL2 overexpression increased colon tumor growth.

CONCLUSIONS

This conditional model represents a new CRISPR/Cas9-mediated mouse model of colorectal carcinogenesis. These mice can be used to investigate the role of novel, previously uncharacterized genes in CRC, in the context of multiple commonly mutated tumor suppressor genes and thus more closely mimic human CRC pathogenesis.

RHOF activation of AKT/β-catenin signaling pathway drives acute myeloid leukemia progression and chemotherapy resistance

Acute myeloid leukemia (AML) is a clonal malignancy originating from leukemia stem cells, characterized by a poor prognosis, underscoring the necessity for novel therapeutic targets and treatment methodologies. This study focuses on Ras homolog family member F, filopodia associated (RHOF), a Rho guanosine triphosphatase (GTPase) family member. We found that RHOF is overexpressed in AML, correlating with an adverse prognosis. Our gain- and loss-of-function experiments revealed that RHOF overexpression enhances proliferation and impedes apoptosis in AML cells in vitro. Conversely, genetic suppression of RHOF markedly reduced the leukemia burden in a human AML xenograft mouse model. Furthermore, we investigated the synergistic effect of RHOF downregulation and chemotherapy, demonstrating significant therapeutic efficacy in vivo. Mechanistically, RHOF activates the AKT/β-catenin signaling pathway, thereby accelerating the progression of AML. Our findings elucidate the pivotal role of RHOF in AML pathogenesis and propose RHOF inhibition as a promising therapeutic approach for AML management.

Akt-driven TGF-β and DKK1 Secretion Impairs F508del Cystic Fibrosis Airway Epithelium Polarity

Epithelial polarity is fundamental in maintaining barrier integrity and tissue protection. In cystic fibrosis (CF), apicobasal polarity of the airway epithelium is altered, resulting in increased apical fibronectin deposition and enhanced susceptibility to bacterial infections. Here, we evaluated the effect of highly effective modulator treatment (HEMT) on fibronectin apical deposition and investigated the intracellular mechanisms triggering the defect in polarity of the CF airway epithelium. To this end, primary cultures of CF (F508del variant) human airway epithelial cells (HAECs) and a HAEC line, Calu-3, knocked down for CFTR (CF transmembrane conductance regulator) were compared with control counterparts. We show that CFTR mutation in primary HAECs and CFTR knockdown cells promote the overexpression and oversecretion of TGF-β1 and DKK1 when cultured at an air-liquid interface. These dynamic changes result in hyperactivation of the TGF-β pathway and inhibition of the Wnt pathway through degradation of β-catenin leading to imbalanced proliferation and polarization. The abnormal interplay between TGF-β and Wnt signaling pathways is reinforced by aberrant Akt signaling. Pharmacological manipulation of TGF-β, Wnt, and Akt pathways restored polarization of the F508del CF epithelium, a correction that was not achieved by HEMT. Our data shed new insights into the signaling pathways that fine-tune apicobasal polarization in primary airway epithelial cells and may provide an explanation to the mitigated efficacy of HEMT on lung infection in people with CF.

Cbl and Cbl-b ubiquitin ligases are essential for intestinal epithelial stem cell maintenance

Receptor tyrosine kinases (RTKs) control stem cell maintenance vs. differentiation decisions. Casitas B-lineage lymphoma (CBL) family ubiquitin ligases are negative regulators of RTKs, but their stem cell regulatory roles remain unclear. Here, we show that Lgr5+ intestinal stem cell (ISC)-specific inducible Cbl-knockout (KO) on a Cblb null mouse background (iDKO) induced rapid loss of the Lgr5 Hi ISCs with transient expansion of the Lgr5 Lo transit-amplifying population. LacZ-based lineage tracing revealed increased ISC commitment toward enterocyte and goblet cell fate at the expense of Paneth cells. Functionally, Cbl/Cblb iDKO impaired the recovery from radiation-induced intestinal epithelial injury. In vitro, Cbl/Cblb iDKO led to inability to maintain intestinal organoids. Single-cell RNA sequencing in organoids identified Akt-mTOR (mammalian target of rapamycin) pathway hyperactivation upon iDKO, and pharmacological Akt-mTOR axis inhibition rescued the iDKO defects. Our results demonstrate a requirement for Cbl/Cblb in the maintenance of ISCs by fine-tuning the Akt-mTOR axis to balance stem cell maintenance vs. commitment to differentiation.

The role of the microscopic world: Exploring the role and potential of intratumoral microbiota in cancer immunotherapy

Microorganisms, including bacteria, viruses, and fungi, coexist in the human body, forming a symbiotic microbiota that plays a vital role in human health and disease. Intratumoral microbial components have been discovered in various tumor tissues and are closely linked to the occurrence, progression, and treatment results of cancer. The intratumoral microbiota can enhance antitumor immunity through mechanisms such as activating the stimulator of interferon genes signaling pathway, stimulating T and NK cells, promoting the formation of TLS, and facilitating antigen presentation. Conversely, the intratumoral microbiota might suppress antitumor immune responses by increasing reactive oxygen species levels, creating an anti-inflammatory environment, inducing T cell inactivation, and enhancing immune suppression, thereby promoting cancer progression. The impact of intratumoral microbiota on antitumor immunity varies based on microbial composition, interactions with cancer cells, and the cancer's current state. A deep understanding of the complex interactions between intratumoral microbiota and antitumor immunity holds the potential to bring new therapeutic strategies and targets to cancer immunotherapy.

ISG12a promotes immunotherapy of HBV-associated hepatocellular carcinoma through blocking TRIM21/AKT/β-catenin/PD-L1 axis

Hepatitis B virus (HBV) infection generally elicits weak type-I interferon (IFN) immune response in hepatocytes, covering the regulatory effect of IFN-stimulated genes. In this study, low level of IFN-stimulated gene 12a (ISG12a) predicted malignant transformation and poor prognosis of HBV-associated hepatocellular carcinoma (HCC), whereas high level of ISG12a indicated active NK cell phenotypes. ISG12a interacts with TRIM21 to inhibit the phosphorylation activation of protein kinase B (PKB, also known as AKT) and β-catenin, suppressing PD-L1 expression to block PD-1/PD-L1 signaling, thereby enhancing the anticancer effect of NK cells. The suppression of PD-1-deficient NK-92 cells on HBV-associated tumors was independent of ISG12a expression, whereas the anticancer effect of PD-1-expressed NK-92 cells on HBV-associated tumors was enhanced by ISG12a and treatments of atezolizumab and nivolumab. Thus, tumor intrinsic ISG12a promotes the anticancer effect of NK cells by regulating PD-1/PD-L1 signaling, presenting the significant role of innate immunity in defending against HBV-associated HCC.

Therapeutic role of PTEN in tissue regeneration for management of neurological disorders: stem cell behaviors to an in-depth review

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) represents the initial tumor suppressor gene identified to possess phosphatase activity, governing various cellular processes including cell cycle regulation, migration, metabolic pathways, autophagy, oxidative stress response, and cellular senescence. Current evidence suggests that PTEN is critical for stem cell maintenance, self-renewal, migration, lineage commitment, and differentiation. Based on the latest available evidence, we provide a comprehensive overview of the mechanisms by which PTEN regulates activities of different stem cell populations and influences neurological disorders, encompassing autism, stroke, spinal cord injury, traumatic brain injury, Alzheimer's disease and Parkinson's disease. This review aims to elucidate the therapeutic impacts and mechanisms of PTEN in relation to neurogenesis or the stem cell niche across a range of neurological disorders, offering a foundation for innovative therapeutic approaches aimed at tissue repair and regeneration in neurological disorders. This review unravels novel therapeutic strategies for tissue restoration and regeneration in neurological disorders based on the regulatory mechanisms of PTEN on neurogenesis and the stem cell niche.

SHP-1 inhibition targets leukaemia stem cells to restore immunosurveillance and enhance chemosensitivity by metabolic reprogramming

Leukaemia stem cells (LSCs) in acute myeloid leukaemia present a considerable treatment challenge due to their resistance to chemotherapy and immunosurveillance. The connection between these properties in LSCs remains poorly understood. Here we demonstrate that inhibition of tyrosine phosphatase SHP-1 in LSCs increases their glycolysis and oxidative phosphorylation, enhancing their sensitivity to chemotherapy and vulnerability to immunosurveillance. Mechanistically, SHP-1 inhibition leads to the upregulation of phosphofructokinase platelet (PFKP) through the AKT-β-catenin pathway. The increase in PFKP elevates energy metabolic activities and, as a consequence, enhances the sensitivity of LSCs to chemotherapeutic agents. Moreover, the upregulation of PFKP promotes MYC degradation and, consequently, reduces the immune evasion abilities of LSCs. Overall, our study demonstrates that targeting SHP-1 disrupts the metabolic balance in LSCs, thereby increasing their vulnerability to chemotherapy and immunosurveillance. This approach offers a promising strategy to overcome LSC resistance in acute myeloid leukaemia.

Monogenic deficiency in murine intestinal Cdc42 leads to mucosal inflammation that induces crypt dysplasia

CDC42 controls intestinal epithelial (IEC) stem cell (IESC) division. How aberrant CDC42 initiates intestinal inflammation or neoplasia is unclear. We utilized models of inflammatory bowel diseases (IBD), colorectal cancer, aging, and IESC injury to determine the loss of intestinal Cdc42 upon inflammation and neoplasia. Intestinal specimens were collected to determine the levels of CDC42 in IBD or colorectal cancer. Cdc42 floxed mice were crossed with Villin-Cre, Villin-CreERT2 and/or Lgr5-eGFP-IRES-CreERT2, or Bmi1-CreERT2 mice to generate Cdc42 deficient mice. Irradiation, colitis, aging, and intestinal organoid were used to evaluate CDC42 upon mucosal inflammation, IESC/progenitor regenerative capacity, and IEC repair. Our studies revealed that increased CDC42 in colorectal cancer correlated with lower survival; in contrast, lower levels of CDC42 were found in the inflamed IBD colon. Colonic Cdc42 depletion significantly reduced Lgr5+ IESCs, increased progenitors' hyperplasia, and induced mucosal inflammation, which led to crypt dysplasia. Colonic Cdc42 depletion markedly enhanced irradiation- or chemical-induced colitis. Depletion or inhibition of Cdc42 reduced colonic Lgr5+ IESC regeneration. In conclusion, depletion of Cdc42 reduces the IESC regeneration and IEC repair, leading to prolonged mucosal inflammation. Constitutive monogenic loss of Cdc42 induces mucosal inflammation, which could result in intestinal neoplasia in the context of aging.

The mechanisms of class 1A PI3K and Wnt/β-catenin coupled signaling in breast cancer

The class IA PI3K signaling pathway is activated by growth factor stimulation and regulates a signaling cascade that promotes diverse events including cell growth, proliferation, migration and metabolism. PI3K signaling is one of the most commonly hyperactivated pathways in breast cancer, leading to increased tumor growth and progression. PI3K hyperactivation occurs via a number of genetic and epigenetic mechanisms including mutation or amplification of PIK3CA, the gene encoding the p110α subunit of PI3Kα, as well as via dysregulation of the upstream growth factor receptors or downstream signaling effectors. Over the past decade, extensive efforts to develop therapeutics that suppress oncogenic PI3K signaling have been undertaken. Although FDA-approved PI3K inhibitors are now emerging, their clinical success remains limited due to adverse effects and negative feedback mechanisms which contribute to their reduced efficacy. There is an emerging body of evidence demonstrating crosstalk between the PI3K and Wnt/β-catenin pathways in breast cancer. However, PI3K exhibits opposing effects on Wnt/β-catenin signaling in distinct tumor subsets, whereby PI3K promotes Wnt/β-catenin activation in ER+ cancers, but paradoxically suppresses this pathway in ER- breast cancers. This review discusses the molecular mechanisms for PI3K-Wnt crosstalk in breast cancer, and how Wnt-targeted therapies have the potential to contribute to treatment regimens for breast cancers with PI3K dysregulation.

Cbl and Cbl-b Ubiquitin Ligases are Essential for Intestinal Epithelial Stem Cell Maintenance

Among the signaling pathways that control the stem cell self-renewal and maintenance vs. acquisition of differentiated cell fates, those mediated by receptor tyrosine kinase (RTK) activation are well established as key players. CBL family ubiquitin ligases are negative regulators of RTKs but their physiological roles in regulating stem cell behaviors are unclear. While hematopoietic Cbl/Cblb knockout (KO) leads to a myeloproliferative disease due to expansion and reduced quiescence of hematopoietic stem cells, mammary epithelial KO led to stunted mammary gland development due to mammary stem cell depletion. Here, we examined the impact of inducible Cbl/Cblb double-KO (iDKO) selectively in the Lgr5-defined intestinal stem cell (ISC) compartment. Cbl/Cblb iDKO led to rapid loss of the Lgr5 Hi ISC pool with a concomitant transient expansion of the Lgr5 Lo transit amplifying population. LacZ reporter-based lineage tracing showed increased ISC commitment to differentiation, with propensity towards enterocyte and goblet cell fate at the expense of Paneth cells. Functionally, Cbl/Cblb iDKO impaired the recovery from radiation-induced intestinal epithelial injury. In vitro , Cbl/Cblb iDKO led to inability to maintain intestinal organoids. Single cell RNAseq analysis of organoids revealed Akt-mTOR pathway hyperactivation in iDKO ISCs and progeny cells, and pharmacological inhibition of the Akt-mTOR axis rescued the organoid maintenance and propagation defects. Our results demonstrate a requirement for Cbl/Cblb in the maintenance of ISCs by fine tuning the Akt-mTOR axis to balance stem cell maintenance vs. commitment to differentiation.

Diet suppresses glioblastoma initiation in mice by maintaining quiescence of mutation-bearing neural stem cells

Glioblastoma is thought to originate from neural stem cells (NSCs) of the subventricular zone that acquire genetic alterations. In the adult brain, NSCs are largely quiescent, suggesting that deregulation of quiescence maintenance may be a prerequisite for tumor initiation. Although inactivation of the tumor suppressor p53 is a frequent event in gliomagenesis, whether or how it affects quiescent NSCs (qNSCs) remains unclear. Here, we show that p53 maintains quiescence by inducing fatty-acid oxidation (FAO) and that acute p53 deletion in qNSCs results in their premature activation to a proliferative state. Mechanistically, this occurs through direct transcriptional induction of PPARGC1a, which in turn activates PPARα to upregulate FAO genes. Dietary supplementation with fish oil containing omega-3 fatty acids, natural PPARα ligands, fully restores quiescence of p53-deficient NSCs and delays tumor initiation in a glioblastoma mouse model. Thus, diet can silence glioblastoma driver mutations, with important implications for cancer prevention.

Loss of PI3k activity of inositol polyphosphate multikinase impairs PDK1-mediated AKT activation, cell migration, and intestinal homeostasis

Protein kinase B (AKT) is essential for cell survival, proliferation, and migration and has been associated with several diseases. Here, we demonstrate that inositol polyphosphate multikinase (IPMK's) lipid kinase property drives AKT activation via increasing membrane localization and activation of PDK1 (3-Phosphoinositide-dependent kinase 1), largely independent of class I PI3k (cPI3K). Deletion of IPMK impairs cell migration, which is partially associated with the abolition of PDK1-mediated ROCK1 disinhibition and subsequent myosin light chain (MLC) phosphorylation. IPMK is highly expressed in intestinal epithelial cells (IEC). Deleting IPMK in IEC reduced AKT phosphorylation and diminished the number of Paneth cells. Ablation of IPMK impaired IEC regeneration both basally and after chemotherapy-induced damage, suggesting a broad role for IPMK in activating AKT and intestinal tissue regeneration. In conclusion, the PI3k activity of IPMK is necessary for PDK1-mediated AKT activation and intestinal homeostasis.

mTOR inhibition suppresses Myc-driven polyposis by inducing immunogenic cell death

Myc is a key driver of colorectal cancer initiation and progression, but remains a difficult drug target. In this study, we show that mTOR inhibition potently suppresses intestinal polyp formation, regresses established polyps, and prolongs lifespan of APC^Min/+ mice. Everolimus in diet strongly reduces p-4EBP1, p-S6, and Myc levels, and induces apoptosis of cells with activated β-catenin (p-S552) in the polyps on day 3. The cell death is accompanied by ER stress, activation of the extrinsic apoptotic pathway, innate immune cell recruitment, and followed by T-cell infiltration on day 14 persisting for months thereafter. These effects are absent in normal intestinal crypts with physiologic levels of Myc and a high rate of proliferation. Using normal human colonic epithelial cells, EIF4E S209A knockin and BID knockout mice, we found that local inflammation and antitumor efficacy of Everolimus requires Myc-dependent induction of ER stress and apoptosis. These findings demonstrate mTOR and deregulated Myc as a selective vulnerability of mutant APC-driven intestinal tumorigenesis, whose inhibition disrupts metabolic and immune adaptation and reactivates immune surveillance necessary for long-term tumor control.

State-of-the-art therapeutic strategies for targeting cancer stem cells in prostate cancer

The development of new therapeutic strategies is on the increase for prostate cancer stem cells, owing to current standardized therapies for prostate cancer, including chemotherapy, androgen deprivation therapy (ADT), radiotherapy, and surgery, often failing because of tumor relapse ability. Ultimately, tumor relapse develops into advanced castration-resistant prostate cancer (CRPC), which becomes an irreversible and systemic disease. Hence, early identification of the intracellular components and molecular networks that promote prostate cancer is crucial for disease management and therapeutic intervention. One of the potential therapeutic methods for aggressive prostate cancer is to target prostate cancer stem cells (PCSCs), which appear to be a primary focal point of cancer metastasis and recurrence and are resistant to standardized therapies. PCSCs have also been documented to play a major role in regulating tumorigenesis, sphere formation, and the metastasis ability of prostate cancer with their stemness features. Therefore, the current review highlights the origin and identification of PCSCs and their role in anti-androgen resistance, as well as stemness-related signaling pathways. In addition, the review focuses on the current advanced therapeutic strategies for targeting PCSCs that are helping to prevent prostate cancer initiation and progression, such as microRNAs (miRNAs), nanotechnology, chemotherapy, immunotherapy, the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) gene-editing system, and photothermal ablation (PTA) therapy.

MiR-181a-5p promotes neural stem cell proliferation and enhances the learning and memory of aged mice

Hippocampal neural stem cell (NSC) proliferation is known to decline with age, which is closely linked to learning and memory impairments. In the current study, we found that the expression level of miR-181a-5p was decreased in the hippocampal NSCs of aged mice and that exogenous overexpression of miR-181a-5p promoted NSC proliferation without affecting NSC differentiation into neurons and astrocytes. The mechanistic study revealed that phosphatase and tensin homolog (PTEN), a negative regulator of the AKT signaling pathway, was the target of miR-181a-5p and knockdown of PTEN could rescue the impairment of NSC proliferation caused by low miR-181a-5p levels. Moreover, overexpression of miR-181a-5p in the dentate gyrus enhanced the proliferation of NSCs and ameliorated learning and memory impairments in aged mice. Taken together, our findings indicated that miR-181a-5p played a functional role in NSC proliferation and aging-related, hippocampus-dependent learning and memory impairments.

Clinical Spectrum and Science Behind the Hamartomatous Polyposis Syndromes

The hamartomatous polyposis syndromes are a set of clinically distinct disorders characterized by the occurrence of hamartomatous polyps in the gastrointestinal tract. These syndromes include juvenile polyposis syndrome, Peutz-Jeghers syndrome, and PTEN hamartoma tumor syndrome. Although each of the syndromes has distinct phenotypes, the hamartomatous polyps can be challenging to differentiate histologically. Additionally, each of these syndromes is associated with increased lifetime risks of gene-specific and organ-specific cancers, including those outside of the gastrointestinal tract. Germline pathogenic variants can be identified in a subset of individuals with these syndromes, which facilitates molecular diagnosis and subsequent gene-enabled management in the setting of genetic counseling. Although the malignant potential of hamartomatous polyps remains elusive, timely recognition of these syndromes is important and enables presymptomatic cancer surveillance and management before symptom exacerbation. Presently, there are no standard agents to prevent the development of polyps and cancers in the hamartomatous polyposis syndromes.

Intratumoral microbiota: roles in cancer initiation, development and therapeutic efficacy

Microorganisms, including bacteria, viruses, fungi, and other eukaryotes, play critical roles in human health. An altered microbiome can be associated with complex diseases. Intratumoral microbial components are found in multiple tumor tissues and are closely correlated with cancer initiation and development and therapy efficacy. The intratumoral microbiota may contribute to promotion of the initiation and progression of cancers by DNA mutations, activating carcinogenic pathways, promoting chronic inflammation, complement system, and initiating metastasis. Moreover, the intratumoral microbiota may not only enhance antitumor immunity via mechanisms including STING signaling activation, T and NK cell activation, TLS production, and intratumoral microbiota-derived antigen presenting, but also decrease antitumor immune responses and promote cancer progression through pathways including upregulation of ROS, promoting an anti-inflammatory environment, T cell inactivation, and immunosuppression. The effect of intratumoral microbiota on antitumor immunity is dependent on microbiota composition, crosstalk between microbiota and the cancer, and status of cancers. The intratumoral microbiota may regulate cancer cell physiology and the immune response by different signaling pathways, including ROS, β-catenin, TLR, ERK, NF-κB, and STING, among others. These viewpoints may help identify the microbiota as diagnosis or prognosis evaluation of cancers, and as new therapeutic strategy and potential therapeutic targets for cancer therapy.

Embryonic organizer formation disorder leads to multiorgan dysplasia in Down syndrome

Despite the high prevalence of Down syndrome (DS) and early identification of the cause (trisomy 21), its molecular pathogenesis has been poorly understood and specific treatments have consequently been practically unavailable. A number of medical conditions throughout the body associated with DS have prompted us to investigate its molecular etiology from the viewpoint of the embryonic organizer, which can steer the development of surrounding cells into specific organs and tissues. We established a DS zebrafish model by overexpressing the human DYRK1A gene, a highly haploinsufficient gene located at the "critical region" within 21q22. We found that both embryonic organizer and body axis were significantly impaired during early embryogenesis, producing abnormalities of the nervous, heart, visceral, and blood systems, similar to those observed with DS. Quantitative phosphoproteome analysis and related assays demonstrated that the DYRK1A-overexpressed zebrafish embryos had anomalous phosphorylation of β-catenin and Hsp90ab1, resulting in Wnt signaling enhancement and TGF-β inhibition. We found an uncovered ectopic molecular mechanism present in amniocytes from fetuses diagnosed with DS and isolated hematopoietic stem cells (HSCs) of DS patients. Importantly, the abnormal proliferation of DS HSCs could be recovered by switching the balance between Wnt and TGF-β signaling in vitro. Our findings provide a novel molecular pathogenic mechanism in which ectopic Wnt and TGF-β lead to DS physical dysplasia, suggesting potential targeted therapies for DS.

Wnt Signaling Modulator DKK4 Inhibits Colorectal Cancer Metastasis through an AKT/Wnt/β-catenin Negative Feedback Pathway

Aberrant activation of the Wnt/β-catenin signaling pathway is implicated in most malignant cancers, especially in the initiation and progression of colorectal cancer (CRC). DKK4 is a classical inhibitory molecule of the Wnt/β-catenin pathway, but its role in CRC is ambiguous, and the molecular mechanism remains unclear. Here, we determined DKK4 expression was significantly upregulated in 23 CRC cell lines and 229 CRC tissues when analyzed by quantitative PCR and immunohistochemistry, respectively. Our analysis of tissue samples indicated the survival time of CRC patients with high DKK4 expression was longer than that of patients with medium-low DKK4 expression. We examined the effects of DKK4 on cell proliferation and metastasis by cell counting kit-8 assays, Transwell assays, and subcutaneous and metastatic mouse tumor models, and we discovered that DKK4 silencing promoted the metastasis of CRC cells both in vitro and in vivo. Our RNA-seq analysis revealed that AKT2, FZD6, and JUN, which play important roles in AKT and Wnt signaling, were significantly increased after DKK4 knockdown. DKK4 represses Wnt/β-catenin signaling by repressing FZD6 and AKT2/s552 β-catenin in CRC. Further experiments revealed recombinant Wnt3a and LiCl could induce DKK4 expression. Moreover, our bioinformatics analysis and luciferase reporter assays identified posttranscriptional regulators of DKK4 in CRC cells. In summary, DKK4 is elevated in CRC and inhibits cell metastasis by a novel negative feedback mechanism of the Wnt3a/DKK4/AKT/s552 β-catenin regulatory axis to restrict overactivation of Wnt activity in CRC. Therefore, DKK4 restoration may be applied as a potential CRC therapeutic strategy.

Combinatorial treatment with statins and niclosamide prevents CRC dissemination by unhinging the MACC1-β-catenin-S100A4 axis of metastasis

Colorectal cancer (CRC) is the second-most common malignant disease worldwide, and metastasis is the main culprit of CRC-related death. Metachronous metastases remain to be an unpredictable, unpreventable, and fatal complication, and tracing the molecular chain of events that lead to metastasis would provide mechanistically linked biomarkers for the maintenance of remission in CRC patients after curative treatment. We hypothesized, that Metastasis-associated in colorectal cancer-1 (MACC1) induces a secretory phenotype to enforce metastasis in a paracrine manner, and found, that the cell-free culture medium of MACC1-expressing CRC cells induces migration. Stable isotope labeling by amino acids in cell culture mass spectrometry (SILAC-MS) of the medium revealed, that S100A4 is significantly enriched in the MACC1-specific secretome. Remarkably, both biomarkers correlate in expression data of independent cohorts as well as within CRC tumor sections. Furthermore, combined elevated transcript levels of the metastasis genes MACC1 and S100A4 in primary tumors and in blood plasma robustly identifies CRC patients at high risk for poor metastasis-free (MFS) and overall survival (OS). Mechanistically, MACC1 strengthens the interaction of β-catenin with TCF4, thus inducing S100A4 synthesis transcriptionally, resulting in elevated secretion to enforce cell motility and metastasis. In cell motility assays, S100A4 was indispensable for MACC1-induced migration, as shown via knock-out and pharmacological inhibition of S100A4. The direct transcriptional and functional relationship of MACC1 and S100A4 was probed by combined targeting with repositioned drugs. In fact, the MACC1-β-catenin-S100A4 axis by statins (MACC1) and niclosamide (S100A4) synergized in inhibiting cancer cell motility in vitro and metastasis in vivo. The MACC1-β-catenin-S100A4 signaling axis is causal for CRC metastasis. Selectively repositioned drugs synergize in restricting MACC1/S100A4-driven metastasis with cross-entity potential.

Tumor-associated macrophages promote epithelial-mesenchymal transition and the cancer stem cell properties in triple-negative breast cancer through CCL2/AKT/β-catenin signaling

BACKGROUND

Triple-negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer with poor prognosis and limited treatment. As a major component of the tumor microenvironment, tumor-associated macrophages (TAMs) play an important role in facilitating the aggressive behavior of TNBC. This study aimed to explore the novel mechanism of TAMs in the regulation of epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC) properties in TNBC.

METHODS

Expression of the M2-like macrophage marker CD163 was evaluated by immunohistochemistry in human breast cancer tissues. The phenotype of M2 macrophages polarized from Tohoku-Hospital-Pediatrics-1 (THP1) cells was verified by flow cytometry. Transwell assays, wound healing assays, western blotting, flow cytometry, ELISA, quantitative polymerase chain reaction (qPCR), luciferase reporter gene assays, and immunofluorescence assays were conducted to investigate the mechanism by which TAMs regulate EMT and CSC properties in BT549 and HCC1937 cells.

RESULTS

Clinically, we observed a high infiltration of M2-like tumor-associated macrophages in TNBC tissues and confirmed that TAMs were associated with unfavorable prognosis in TNBC patients. Moreover, we found that conditioned medium from M2 macrophages (M2-CM) markedly promoted EMT and CSC properties in BT549 and HCC1937 cells. Mechanistically, we demonstrated that chemokine (C-C motif) ligand 2 (CCL2) secretion by TAMs activated Akt signaling, which in turn increased the expression and nuclear localization of β-catenin. Furthermore, β-catenin knockdown reversed TAM-induced EMT and CSC properties.

CONCLUSIONS

This study provides a novel mechanism by which TAMs promote EMT and enhance CSC properties in TNBC via activation of CCL2/AKT/β-catenin signaling, which may offer new strategies for the diagnosis and treatment of TNBC. Video Abstract.

Phosphorylation-Dependent Regulation of WNT/Beta-Catenin Signaling

WNT/β-catenin signaling is a highly complex pathway that plays diverse roles in various cellular processes. While WNT ligands usually signal through their dedicated Frizzled receptors, the decision to signal in a β-catenin-dependent or -independent manner rests upon the type of co-receptors used. Canonical WNT signaling is β-catenin-dependent, whereas non-canonical WNT signaling is β-catenin-independent according to the classical definition. This still holds true, albeit with some added complexity, as both the pathways seem to cross-talk with intertwined networks that involve the use of different ligands, receptors, and co-receptors. β-catenin can be directly phosphorylated by various kinases governing its participation in either canonical or non-canonical pathways. Moreover, the co-activators that associate with β-catenin determine the output of the pathway in terms of induction of genes promoting proliferation or differentiation. In this review, we provide an overview of how protein phosphorylation controls WNT/β-catenin signaling, particularly in human cancer.

Overexpression of IGF-1 During Early Development Expands the Number of Mammary Stem Cells and Primes them for Transformation

Insulin-like growth factor I (IGF-1) has been implicated in breast cancer due to its mitogenic and anti-apoptotic effects. Despite substantial research on the role of IGF-1 in tumor progression, the relationship of IGF-1 to tissue stem cells, particularly in mammary tissue, and the resulting tumor susceptibility has not been elucidated. Previous studies with the BK5.IGF-1 transgenic (Tg) mouse model reveals that IGF-1 does not act as a classical, post-carcinogen tumor promoter in the mammary gland. Pre-pubertal Tg mammary glands display increased numbers and enlarged sizes of terminal end buds, a niche for mammary stem cells (MaSCs). Here we show that MaSCs from both wild type (WT) and Tg mice expressed IGF-1R and that overexpression of Tg IGF-1 increased numbers of MaSCs by undergoing symmetric division, resulting in an expansion of the MaSC and luminal progenitor (LP) compartments in pre-pubertal female mice. This expansion was maintained post-pubertally and validated by mammosphere assays in vitro and transplantation assays in vivo. The addition of recombinant IGF-1 promoted, and IGF-1R downstream inhibitors decreased mammosphere formation. Single-cell transcriptomic profiles generated from two related platforms reveal that IGF-1 stimulated quiescent MaSCs to enter the cell cycle and increased their expression of genes involved in proliferation, plasticity, tumorigenesis, invasion, and metastasis. This study identifies a novel, pro-tumorigenic mechanism, where IGF-1 increases the number of transformation-susceptible carcinogen targets during the early stages of mammary tissue development, and “primes” their gene expression profiles for transformation.

Nucleoporin 93 mediates β-catenin nuclear import to promote hepatocellular carcinoma progression and metastasis

Nuclear pore complex (NPC) embedded in the nuclear envelope, is the only channel for macromolecule nucleocytoplasmic transportation and has important biological functions. However, the deregulation of specific nucleoporins (Nups) and NPC-Nup-based mechanisms and their function in tumour progression remain poorly understood. Here, we aimed to identify the Nups that contribute to HCC progression and metastasis in 729 primary hepatocellular carcinoma (HCC) cases using molecular, cytological, and biochemical techniques. Our results revealed elevated Nup93 expression in HCC tissues, especially in cases with metastasis, and was linked to worse prognosis. Furthermore, Nup93 knockdown suppressed HCC cell metastasis and proliferation, while Nup93 overexpression promoted these activities. We observed that Nup93 promotes HCC metastasis and proliferation by regulating β-catenin translocation. In addition, we found that Nup93 interacted with β-catenin directly, independent of importin. Furthermore, LEF1 and β-catenin facilitated the Nup93-mediated metastasis and proliferation in HCC via a positive feedback loop. Thus, our findings provide novel insights into the mechanisms underlying the Nup93-induced promotion of HCC metastasis and suggest potential therapeutic targets in the LEF1-Nup93-β-catenin pathway for HCC therapeutics.

Tumor-initiating stem cell shapes its microenvironment into an immunosuppressive barrier and pro-tumorigenic niche

Tumor-initiating stem cells (TSCs) are critical for drug resistance and immune escape. However, the mutual regulations between TSC and tumor microenvironment (TME) remain unclear. Using DNA-label retaining, single-cell RNA sequencing (scRNA-seq), and other approaches, we investigated intestinal adenoma in response to chemoradiotherapy (CRT), thus identifying therapy-resistant TSCs (TrTSCs). We find bidirectional crosstalk between TSCs and TME using CellPhoneDB analysis. An intriguing finding is that TSCs shape TME into a landscape that favors TSCs for immunosuppression and propagation. Using adenoma-organoid co-cultures, niche-cell depletion, and lineaging tracing, we characterize a functional role of cyclooxygenase-2 (Cox-2)-dependent signaling, predominantly occurring between tumor-associated monocytes and macrophages (TAMMs) and TrTSCs. We show that TAMMs promote TrTSC proliferation through prostaglandin E2 (PGE2)-PTGER4(EP4) signaling, which enhances β-catenin activity via AKT phosphorylation. Thus, our study shows that the bidirectional crosstalk between TrTSC and TME results in a pro-tumorigenic and immunosuppressive contexture.

Kras activation in endometrial organoids drives cellular transformation and epithelial-mesenchymal transition

KRAS, an oncogene, is frequently activated by mutations in many cancers. Kras-driven adenocarcinoma development in the lung, pancreas, and biliary tract has been extensively studied using gene targeting in mice. By taking the organoid- and allograft-based genetic approach to these organs, essentially the same results as in vivo models were obtained in terms of tumor development. To verify the applicability of this approach to other organs, we investigated whether the combination of Kras activation and Pten inactivation, which gives rise to endometrial tumors in mice, could transform murine endometrial organoids in the subcutis of immunodeficient mice. We found that in KrasG12D-expressing endometrial organoids, Pten knockdown did not confer tumorigenicity, but Cdkn2a knockdown or Trp53 deletion led to the development of carcinosarcoma (CS), a rare, aggressive tumor comprising both carcinoma and sarcoma. Although they originated from epithelial cells, some CS cells expressed both epithelial and mesenchymal markers. Upon inoculation in immunodeficient mice, tumor-derived round organoids developed carcinoma or CS, whereas spindle-shaped organoids formed monophasic sarcoma only, suggesting an irreversible epithelial-mesenchymal transition during the transformation of endometrial cells and progression. As commonly observed in mutant Kras-driven tumors, the deletion of the wild-type Kras allele was identified in most induced tumors, whereas some epithelial cells in CS-derived organoids were unexpectedly negative for KrasG12D. Collectively, we showed that the oncogenic potential of KrasG12D and the histological features of derived tumors are context-dependent and varies according to the organ type and experimental settings. Our findings provide novel insights into the mechanisms underlying tissue-specific Kras-driven tumorigenesis.

Rictor/Mammalian Target of Rapamycin Complex 2 Signaling Protects Colonocytes from Apoptosis and Prevents Epithelial Barrier Breakdown

Epithelial barrier impairment is a hallmark of several pathologic processes in the gut, including inflammatory bowel diseases. Several intracellular signals prevent apoptosis in intestinal epithelial cells. Herein, we show that in colonocytes, rictor/mammalian target of rapamycin complex 2 (mTORC2) signaling is a prosurvival stimulus. Mechanistically, mTORC2 activates Akt, which, in turn, inhibits apoptosis by phosphorylating B-cell lymphoma 2 (BCL2) associated agonist of cell death (Bad) and preventing caspase-3 activation. Nevertheless, during inflammation, rictor/mTORC2 signaling declines and Akt activity is reduced. Consequently, active caspase-3 increases in surface colonocytes undergoing apoptosis/anoikis and causes epithelial barrier breakdown. Likewise, Rictor ablation in intestinal epithelial cells interrupts mTORC2/Akt signaling and increases apoptosis/anoikis of surface colonocytes without affecting the crypt architecture. The increase in epithelial permeability induced by Rictor ablation produces a mild inflammatory response in the colonic mucosa, but minimally affects the development/establishment of colitis. The data identify a previously unknown mechanism by which rictor/mTORC2 signaling regulates apoptosis/anoikis in intestinal epithelial cells during colitis and clarify its role in the maintenance of the intestinal epithelial barrier.

Transcription Factor β-Catenin Plays a Key Role in Fluid Flow Shear Stress-Mediated Glomerular Injury in Solitary Kidney

Increased fluid flow shear stress (FFSS) in solitary kidney alters podocyte function in vivo. FFSS-treated cultured podocytes show upregulated AKT-GSK3β-β-catenin signaling. The present study was undertaken to confirm (i) the activation of β-catenin signaling in podocytes in vivo using unilaterally nephrectomized (UNX) TOPGAL mice with the β-galactosidase reporter gene for β-catenin activation, (ii) β-catenin translocation in FFSS-treated mouse podocytes, and (iii) β-catenin signaling using publicly available data from UNX mice. The UNX of TOPGAL mice resulted in glomerular hypertrophy and increased the mesangial matrix consistent with hemodynamic adaptation. Uninephrectomized TOPGAL mice showed an increased β-galactosidase expression at 4 weeks but not at 12 weeks, as assessed using immunofluorescence microscopy (p < 0.001 at 4 weeks; p = 0.16 at 12 weeks) and X-gal staining (p = 0.008 at 4 weeks; p = 0.65 at 12 weeks). Immunofluorescence microscopy showed a significant increase in phospho-β-catenin (Ser552, p = 0.005) at 4 weeks but not at 12 weeks (p = 0.935) following UNX, and the levels of phospho-β-catenin (Ser675) did not change. In vitro FFSS caused a sustained increase in the nuclear translocation of phospho-β-catenin (Ser552) but not phospho-β-catenin (Ser675) in podocytes. The bioinformatic analysis of the GEO dataset, #GSE53996, also identified β-catenin as a key upstream regulator. We conclude that transcription factor β-catenin mediates FFSS-induced podocyte (glomerular) injury in solitary kidney.

How can we turn the PI3K/AKT/mTOR pathway down? Insights into inhibition and treatment of cancer

Introduction: The phosphatidylinositol 3-kinase/protein kinase-B/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway is a fundamental regulator of cell proliferation and survival. Dysregulation in this pathway leads to the development of cancer. Accumulating evidence indicates that dysregulation in this pathway is involved in cancer initiation, progression, and recurrence. However, the pathway consists of various signal transducing factors related with cellular events, such as transformation, tumorigenesis, cancer progression, and drug resistance. Therefore, it is very important to determine the targets in this pathway for cancer therapy. Although many drugs inhibiting this signaling pathway are in clinical trials or have been approved for treating solid tumors and hematologic malignancies, further understanding of the signaling mechanism is required to achieve better therapeutic efficacy.Areas covered: In this review, we have describe the PI3K/AKT/mTOR pathway in detail, along with its critical role in cancer stem cells, for identifying potential therapeutic targets. We also summarize the recent developments in different types of signaling inhibitors.Expert opinion: Downregulation of the PI3K/AKT/mTOR pathway is very important for treating all types of cancers. Thus, further studies are required to establish novel prognostic factors to support the current progress in cancer treatment with emphasis on this pathway.

Wnt/β-catenin Signaling Inhibitors suppress the Tumor-initiating properties of a CD44+CD133+ subpopulation of Caco-2 cells

Tumor-initiating cells or cancer stem cells are a subset of cancer cells that have tumorigenic potential in human cancer. Although several markers have been proposed to distinguish tumor-initiating cells from colorectal cancer cells, little is known about how this subpopulation contributes to tumorigenesis. Here, we characterized a tumor-initiating cell subpopulation from Caco-2 colorectal cancer cells. Based on the findings that Caco-2 cell subpopulations express different cell surface markers, we were able to discriminate three main fractions, CD44-CD133-, CD44-CD133+, and CD44+CD133+ subsets, and characterized their biochemical and tumorigenic properties. Our results show that CD44+CD133+ cells possessed an unusual capacity to proliferate and could form tumors when transplanted into NSG mice. Additionally, primary tumors grown from CD44+CD133+ Caco-2 cells contained mixed populations of CD44+CD133+ and non-CD44+CD133+ Caco-2 cells, indicating that the full phenotypic heterogeneity of the parental Caco-2 cells was re-created. Notably, only the CD44+CD133+ subset of Caco-2-derived primary tumors had tumorigenic potential in NSG mice, and the tumor growth of CD44+CD133+ cells was faster in secondary xenografts than in primary transplants. Gene expression analysis revealed that the Wnt/β-catenin pathway was over-activated in CD44+CD133+ cells, and the growth and tumorigenic potential of this subpopulation were significantly suppressed by small-molecule Wnt/β-catenin signaling inhibitors. Our findings suggest that the CD44+CD133+ subpopulation from Caco-2 cells was highly enriched in tumorigenic cells and will be useful for investigating the mechanisms leading to human colorectal cancer development.

AKT-dependent NOTCH3 activation drives tumor progression in a model of mesenchymal colorectal cancer

Recently, a transcriptome-based consensus molecular subtype (CMS) classification of colorectal cancer (CRC) has been established, which may ultimately help to individualize CRC therapy. However, the lack of animal models that faithfully recapitulate the different molecular subtypes impedes adequate preclinical testing of stratified therapeutic concepts. Here, we demonstrate that constitutive AKT activation in intestinal epithelial cells markedly enhances tumor invasion and metastasis in Trp53^ΔIEC mice (Trp53^ΔIECAkt^E17K) upon challenge with the carcinogen azoxymethane. Gene-expression profiling indicates that Trp53^ΔIECAkt^E17K tumors resemble the human mesenchymal colorectal cancer subtype (CMS4), which is characterized by the poorest survival rate among the four CMSs. Trp53^ΔIECAkt^E17K tumor cells are characterized by Notch3 up-regulation, and treatment of Trp53^ΔIECAkt^E17K mice with a NOTCH3-inhibiting antibody reduces invasion and metastasis. In CRC patients, NOTCH3 expression correlates positively with tumor grading and the presence of lymph node as well as distant metastases and is specifically up-regulated in CMS4 tumors. Therefore, we suggest NOTCH3 as a putative target for advanced CMS4 CRC patients.

Paneth Cell Alertness to Pathogens Maintained by Vitamin D Receptors

BACKGROUND AND AIMS

Vitamin D exerts a regulatory role over mucosal immunity via the vitamin D receptor (VDR). Although Paneth cells and their products are known to regulate the commensal and pathogenic microbiota, the role that VDRs in Paneth cells play in these responses is unknown.

METHODS

We identified the decreased intestinal VDR significantly correlated with reduction of an inflammatory bowel disease risk gene ATG16L1 and Paneth cell lysozymes in patients with Crohn's disease. We generated Paneth cell-specific VDR knockout (VDR^ΔPC) mice to investigate the molecular mechanisms.

RESULTS

Lysozymes in the Paneth cells were significantly decreased in the VDR^ΔPC mice. Isolated VDR^ΔPC Paneth cells exhibited weakened inhibition of pathogenic bacterial growth and displayed reduced autophagic responses. VDR^ΔPC mice had significantly higher inflammation after Salmonella infections. VDR^ΔPC mice also showed high susceptibility to small intestinal injury induced by indomethacin, a nonsteroidal anti-inflammatory drug. Co-housing of VDR^ΔPC and VDR^lox mice made the VDR^ΔPC less vulnerable to dextran sulfate sodium colitis, suggesting the transmission of protective bacterial from the VDR^lox mice. Thus, a lack of VDR in Paneth cells leads to impaired antibacterial activities and consequently increased inflammatory responses. Genetically and environmentally regulated VDRs in the Paneth cells may set the threshold for the development of chronic inflammation, as observed in inflammatory bowel diseases.

CONCLUSIONS

We provide new insights into the tissue-specific functions of VDRs in maintaining Paneth cell alertness to pathogens in intestinal disorders. Targeting the VDR affects multiple downstream events within Paneth cells that inhibit intestinal inflammation and establish host defense against enteropathogens.

Oxytocin signalling in dendritic cells regulates immune tolerance in the intestine and alleviates DSS-induced colitis

BACKGROUND

Ulcerative colitis (UC) is a type of inflammatory bowel disease (IBD) that is associated with immune dysfunction. Recent studies have indicated that the neurosecretory hormone oxytocin (OXT) has been proven to alleviate experimental colitis.

METHODS

We investigated the role of OXT/OXT receptor (OXTR) signalling in dendritic cells (DCs) using mice with specific OXTR deletion in CD11c+ cells (OXTRflox/flox×CD11c-cre mice) and a dextran sulfate sodium (DSS)-induced colitis model.

RESULTS

The level of OXT was abnormal in the serum or colon tissue of DSS-induced colitis mice or the plasma of UC patients. Both bone marrow-derived DCs (BMDCs) and lamina propria DCs (LPDCs) express OXTR. Knocking out OXTR in DCs exacerbated DSS-induced acute and chronic colitis in mice. In contrast, the injection of OXT-pretreated DCs significantly ameliorated colitis. Mechanistically, OXT prevented DC maturation through the phosphatidylinositol 4,5-bisphosphate 3-kinase (Pi3K)/AKT pathway and promoted phagocytosis, adhesion and cytokine modulation in DCs. Furthermore, OXT pre-treated DCs prevent CD4+ T cells differentiation to T helper 1 (Th1) and Th17.

CONCLUSIONS

Our results suggest that OXT-induced tolerogenic DCs efficiently protect against experimental colitis via Pi3K/AKT pathway. Our work provides evidence that the nervous system participates in the immune regulation of colitis by modulating DCs. Our findings suggest that generating ex vivo DCs pretreated with OXT opens new therapeutic perspectives for the treatment of UC in humans.

CMTM6 drives cisplatin resistance by regulating Wnt signaling through the ENO-1/AKT/GSK3β axis

Rewiring tumor cells to undergo drug-induced apoptosis is a promising way to overcome chemoresistance. Therefore, identifying causative factors for chemoresistance is of high importance. Unbiased global proteome profiling of sensitive, early, and late cisplatin-resistant oral squamous cell carcinoma (OSCC) lines identified CMTM6 as a top-ranked upregulated protein. Analyses of OSCC patient tumor samples demonstrated significantly higher CMTM6 expression in chemotherapy (CT) nonresponders as compared with CT responders. In addition, a significant association between higher CMTM6 expression and poorer relapse-free survival in esophageal squamous cell carcinoma, head and neck squamous cell carcinoma, and lung squamous cell carcinoma was observed from Kaplan-Meier plot analysis. Stable knockdown (KD) of CMTM6 restored cisplatin-mediated cell death in chemoresistant OSCC lines. Upon CMTM6 overexpression in CMTM6-KD lines, the cisplatin-resistant phenotype was rescued. The patient-derived cell xenograft model of chemoresistant OSCC displaying CMTM6 depletion restored the cisplatin-induced cell death and tumor burden substantially. The transcriptome analysis of CMTM6-KD and control chemoresistant cells depicted enrichment of the Wnt signaling pathway. We demonstrated that CMTM6 interaction with membrane-bound Enolase-1 stabilized its expression, leading to activation of Wnt signaling mediated by AKT–glycogen synthase kinase-3β. CMTM6 has been identified as a stabilizer of programmed cell death ligand 1. Therefore, as CMTM6 facilitates tumor cells for immune evasion and mediates cisplatin resistance, it could be a promising therapeutic target for treating therapy-resistant OSCC.

Nonmicrobial Activation of TLRs Controls Intestinal Growth, Wound Repair, and Radioprotection

TLRs, key components of the innate immune system, recognize microbial molecules. However, TLRs also recognize some nonmicrobial molecules. In particular, TLR2 and TLR4 recognize hyaluronic acid, a glycosaminoglycan in the extracellular matrix. In neonatal mice endogenous hyaluronic acid binding to TLR4 drives normal intestinal growth. Hyaluronic acid binding to TLR4 in pericryptal macrophages results in cyclooxygenase2- dependent PGE2 production, which transactivates EGFR in LGR5+ crypt epithelial stem cells leading to increased proliferation. The expanded population of LGR5+ stem cells leads to crypt fission and lengthening of the intestine and colon. Blocking this pathway at any point (TLR4 activation, PGE2 production, EGFR transactivation) results in diminished intestinal and colonic growth. A similar pathway leads to epithelial proliferation in wound repair. The repair phase of dextran sodium sulfate colitis is marked by increased epithelial proliferation. In this model, TLR2 and TLR4 in pericryptal macrophages are activated by microbial products or by host hyaluronic acid, resulting in production of CXCL12, a chemokine. CXCL12 induces the migration of cyclooxygenase2-expressing mesenchymal stem cells from the lamina propria of the upper colonic crypts to a site adjacent to LGR5+ epithelial stem cells. PGE2 released by these mesenchymal stem cells transactivates EGFR in LGR5+ epithelial stem cells leading to increased proliferation. Several TLR2 and TLR4 agonists, including hyaluronic acid, are radioprotective in the intestine through the inhibition of radiation-induced apoptosis in LGR5+ epithelial stem cells. Administration of exogenous TLR2 or TLR4 agonists activates TLR2/TLR4 on pericryptal macrophages inducing CXCL12 production with migration of cyclooxygenase2-expressing mesenchymal stem cells from the lamina propria of the villi to a site adjacent to LGR5+ epithelial stem cells. PGE2 produced by these mesenchymal stem cells, blocks radiation-induced apoptosis in LGR5+ epithelial stem cells by an EGFR mediated pathway.

Is There Such a Thing as a Genuine Cancer Stem Cell Marker? Perspectives from the Gut, the Brain and the Dental Pulp

The conversion of healthy stem cells into cancer stem cells (CSCs) is believed to underlie tumor relapse after surgical removal and fuel tumor growth and invasiveness. CSCs often arise from the malignant transformation of resident multipotent stem cells, which are present in most human tissues. Some organs, such as the gut and the brain, can give rise to very aggressive types of cancers, contrary to the dental pulp, which is a tissue with a very remarkable resistance to oncogenesis. In this review, we focus on the similarities and differences between gut, brain and dental pulp stem cells and their related CSCs, placing a particular emphasis on both their shared and distinctive cell markers, including the expression of pluripotency core factors. We discuss some of their similarities and differences with regard to oncogenic signaling, telomerase activity and their intrinsic propensity to degenerate to CSCs. We also explore the characteristics of the events and mutations leading to malignant transformation in each case. Importantly, healthy dental pulp stem cells (DPSCs) share a great deal of features with many of the so far reported CSC phenotypes found in malignant neoplasms. However, there exist literally no reports about the contribution of DPSCs to malignant tumors. This raises the question about the particularities of the dental pulp and what specific barriers to malignancy might be present in the case of this tissue. These notable differences warrant further research to decipher the singular properties of DPSCs that make them resistant to transformation, and to unravel new therapeutic targets to treat deadly tumors.

Wnt/β-catenin signaling pathway inhibits porcine reproductive and respiratory syndrome virus replication by enhancing the nuclear factor-κB-dependent innate immune response

The Wnt/β-catenin signaling pathway is an evolutionarily highly conserved signaling pathway related to the replication of various viruses. However, the interaction between the Wnt/β-catenin pathway and porcine reproductive and respiratory syndrome virus (PRRSV) is unknown. In the present study, we showed that PRRSV-infected Marc-145 and PAM cells expressed high levels of c-myc and cyclinD1 mRNA and accumulation of β-catenin in the nucleus. PRRSV nonstructural proteins (Nsps) 1α, 1β, 3, 4, 7, 10, and 12, and proteins encoded by open reading frames (ORFs) 2b, 3, and 5 induced the activation of the Wnt pathway according to TOP/FOP luciferase reporter assay. But, Nsp5 inhibited the activation of the Wnt pathway. Pre-treatment with Wnt3a inhibited PRRSV replication in Marc-145 cells in a dose-dependent manner. Over-expression of β-catenin also inhibited PRRSV replication, while silencing of β-catenin by small hairpin RNA increased its replication in Marc-145 cells. Over-expression of β-catenin increased interferon regulatory factor (IRF)-3 expression and nuclear factor (NF)-κB phosphorylation, NF-κB and interferon-stimulated response element promoter activities, and interferon-β, DExD/H-box helicase 58 (DDX58), interferon-induced protein with tetratricopeptide repeats 1 (IFIT1), interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-8 mRNA expression. Conversely, silencing β-catenin decreased phosphorylated IRF-3 and NF-κB, NF-κB and IFIT1 promoter activities, and IFN-β, DDX58, IFIT1, IL-1β, TNF-α, and IL-8 mRNA levels in Marc-145 cells. Co-immunoprecipitation and immunofluorescence colocalization analyses confirmed that β-catenin interacted with NF-κB in Marc-145 cells. In conclusion, PRRSV infection activates the Wnt/β-catenin signaling pathway via Nsps 1α, 1β, 3, 4, 7, 10, and 12, and proteins encoded by ORFs 2b, 3, and 5. The Wnt/β-catenin pathway then inhibits PRRSV replication by enhancing the NF-κB-dependent innate immune response. These findings further our understanding of the role of the Wnt/β-catenin signaling pathway in regulating PRRSV replication and provide new insights into virus-host interactions.

Differentiated cancer cell-originated lactate promotes the self-renewal of cancer stem cells in patient-derived colorectal cancer organoids

Tumors harbor diverse compartments of cells with distinct metabolic properties and phenotypes, but the mechanism by which metabolic commensalism among distinct subsets of cancer cells affects tumor progression remains unclear. Colorectal cancer (CRC) has been reported to consist of cancer stem cells (CSCs) and differentiated cancer cells (non-CSCs). In the present study, organoid models were employed to show that CSCs and non-CSCs in CRC were characterized by distinct metabolic phenotypes. Treatment with either non-CSC-derived conditioned medium or exogenous lactate enhanced organoid-forming and tumor-initiating capacity of CSCs. In tumor regeneration assays with co-implanted CSCs and non-CSCs, the tumor-initiating activity was reduced when either monocarboxylate transporter (MCT)4 in non-CSCs or MCT1 in CSCs was silenced or inhibited. Mechanistically, oxiadative phosphorylation-derived reactive oxygen species in CSCs activated AKT-Wnt/β-catenin signaling, which could be induced by lactate from non-CSCs. Overall, these results suggest that CSCs and non-CSCs possess distinct metabolic profiles and, unexpectedly, non-CSC-originated lactate promotes self-renewal of CSCs and thus contributes to CRC progression. Our findings establish a rationale for developing novel therapies targeting the metabolic commensalism between different cell populations in CRC.

Activation of protein kinase B by WNT4 as a regulator of uterine leiomyoma stem cell function

OBJECTIVE

To investigate the functional interaction between the Wnt/β-catenin and protein kinase B (Akt) pathways in leiomyoma stem cells (LSC).

DESIGN

Laboratory study.

SETTING

Research laboratory.

PATIENT(S)

Premenopausal women (n = 36; age range: 28 to 49 years) undergoing hysterectomy or myomectomy for leiomyoma.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Gene expression, protein phosphorylation, and cell proliferation.

RESULT(S)

Cells from human leiomyoma tissues were sorted by fluorescence-activated cell sorting (FACS) into three populations: LSC, intermediate cells (LIC), and differentiated cells (LDC) with the function of the Wnt/β-catenin and Akt signaling pathways in leiomyoma cells evaluated using real-time quantitative polymerase chain reaction and immunoblot analyses. The Wnt/β-catenin signaling pathway components were differentially expressed in each leiomyoma cell population. WNT4 was distinctly overexpressed in LIC, and its receptor FZD6 was primarily expressed in LSC. WNT4 stimulated Akt phosphorylation, activated β-catenin, and increased primary leiomyoma cell proliferation. These stimulatory effects were abolished by cotreatment with the Akt inhibitor, MK-2206. WNT4 up-regulated the expression of pro-proliferative genes, c-Myc and cyclin D1, specifically in LSC; this was also abrogated by Akt inhibition.

CONCLUSION(S)

Our data suggest that WNT4 regulates LSC proliferation via Akt-dependent β-catenin activation, representing a key step toward a better understanding of LSC regulation and potentially novel therapeutic targets.

Erk and MAPK signaling is essential for intestinal development through Wnt pathway modulation

Homeostasis of intestinal stem cells (ISCs) is maintained by the orchestration of niche factors and intrinsic signaling networks. Here, we have found that deletion of Erk1 and Erk2 (Erk1/2) in intestinal epithelial cells at embryonic stages resulted in an unexpected increase in cell proliferation and migration, expansion of ISCs, and formation of polyp-like structures, leading to postnatal death. Deficiency of epithelial Erk1/2 results in defects in secretory cell differentiation as well as impaired mesenchymal cell proliferation and maturation. Deletion of Erk1/2 strongly activated Wnt signaling through both cell-autonomous and non-autonomous mechanisms. In epithelial cells, Erk1/2 depletion resulted in loss of feedback regulation, leading to Ras/Raf cascade activation that transactivated Akt activity to stimulate the mTor and Wnt/β-catenin pathways. Moreover, Erk1/2 deficiency reduced the levels of Indian hedgehog and the expression of downstream pathway components, including mesenchymal Bmp4 - a Wnt suppressor in intestines. Inhibition of mTor signaling by rapamycin partially rescued Erk1/2 depletion-induced intestinal defects and significantly prolonged the lifespan of mutant mice. These data demonstrate that Erk/Mapk signaling functions as a key modulator of Wnt signaling through coordination of epithelial-mesenchymal interactions during intestinal development.

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.

Dynamic Expression Profiles of β-Catenin during Murine Cardiac Valve Development

β-catenin has been widely studied in many animal and organ systems across evolution, and gain or loss of function has been linked to a number of human diseases. Yet fundamental knowledge regarding its protein expression and localization remains poorly described. Thus, we sought to define whether there was a temporal and cell-specific regulation of β-catenin activities that correlate with distinct cardiac morphological events. Our findings indicate that activated nuclear β-catenin is primarily evident early in gestation. As development proceeds, nuclear β-catenin is down-regulated and becomes restricted to the membrane in a subset of cardiac progenitor cells. After birth, little β-catenin is detected in the heart. The co-expression of β-catenin with its main transcriptional co-factor, Lef1, revealed that Lef1 and β-catenin expression domains do not extensively overlap in the cardiac valves. These data indicate mutually exclusive roles for Lef1 and β-catenin in most cardiac cell types during development. Additionally, these data indicate diverse functions for β-catenin within the nucleus and membrane depending on cell type and gestational timing. Cardiovascular studies should take into careful consideration both nuclear and membrane β-catenin functions and their potential contributions to cardiac development and disease.

Me6TREN targets β-catenin signaling to stimulate intestinal stem cell regeneration after radiation

Background: Acute gastrointestinal syndrome (AGS) is one of the most severe clinical manifestations after exposure to high doses of radiation, and is life-threatening in radiological emergency scenarios. However, an unmet challenge is lacking of an FDA-approved drug that can ameliorate the damage of radiation-exposed intestinal tissues and accelerate the regeneration of injured epithelia. In this study, we investigated whether the small molecule Me6TREN (Me6) can regulate intestinal stem cell (ISC) proliferation and promote crypt regeneration after irradiation.

Methods: Lethally irradiated mice were administered with Me6 or PBS to study the survival rate, and sections of their small intestine were subjected to immunostaining to evaluate epithelial regeneration. An intestinal organoid culture system was employed to detect the role of Me6 in organoid growth and ISC proliferation. We further investigated the key signaling pathways associated with Me6 using microarray, western blotting, and RNA interference techniques.

Results: We identified the small molecule Me6 as a potent intestinal radiation countermeasure. Systemic administration of Me6 significantly improved ISC and crypt cell regeneration and enhanced the survival of mice after high doses of radiation. Using an in vitro intestinal organoid culture system, we found that Me6 not only induced ISC proliferation but also increased the budding rate of intestinal organoids under unirradiated and irradiated conditions. Me6 remarkably activated the expression of ISC-associated and proliferation-promoting genes, such as Ascl2, Lgr5, Myc, and CyclinD1. Mechanistically, Me6 strongly stimulated the phosphorylation of β-catenin at the S552 site and increased the transcriptional activity of β-catenin, a key signaling pathway for ISC self-renewal and proliferation. This is further evidenced by the fact that knockdown of β-catenin abolished the effect of Me6 on intestinal organoid growth in vitro and crypt regeneration in irradiated mice.

Conclusion: The small molecule Me6TREN induced ISC proliferation, enhanced intestinal organoid growth in vitro, and promoted intestinal tissue regeneration after radiation injury by activating β-catenin signaling.

The Role of Tricellulin in Epithelial Jamming and Unjamming via Segmentation of Tricellular Junctions

Collective cellular behavior in confluent monolayers supports physiological and pathological processes of epithelial development, regeneration, and carcinogenesis. Here, the attainment of a mature and static tissue configuration or the local reactivation of cell motility involve a dynamic regulation of the junctions established between neighboring cells. Tricellular junctions (tTJs), established at vertexes where three cells meet, are ideally located to control cellular shape and coordinate multicellular movements. However, their function in epithelial tissue dynamic remains poorly defined. To investigate the role of tTJs establishment and maturation in the jamming and unjamming transitions of epithelial monolayers, a semi-automatic image-processing pipeline is developed and validated enabling the unbiased and spatially resolved determination of the tTJ maturity state based on the localization of fluorescent reporters. The software resolves the variation of tTJ maturity accompanying collective transitions during tissue maturation, wound healing, and upon the adaptation to osmolarity changes. Altogether, this work establishes junctional maturity at tricellular contacts as a novel biological descriptor of collective responses in epithelial monolayers.

Notch Signaling Mediates Differentiation in Barrett's Esophagus and Promotes Progression to Adenocarcinoma

BACKGROUND & AIMS

Studies are needed to determine the mechanism by which Barrett's esophagus (BE) progresses to esophageal adenocarcinoma (EAC). Notch signaling maintains stem cells in the gastrointestinal tract and is dysregulated during carcinogenesis. We explored the relationship between Notch signaling and goblet cell maturation, a feature of BE, during EAC pathogenesis.

METHODS

We measured goblet cell density and levels of Notch messenger RNAs in BE tissues from 164 patients, with and without dysplasia or EAC, enrolled in a multicenter study. We analyzed the effects of conditional expression of an activated form of NOTCH2 (pL2.Lgr5.N2IC), conditional deletion of NOTCH2 (pL2.Lgr5.N2fl/fl), or loss of nuclear factor κB (NF-κB) (pL2.Lgr5.p65fl/fl), in Lgr5+ (progenitor) cells in L2-IL1B mice (which overexpress interleukin 1 beta in esophagus and squamous forestomach and are used as a model of BE). We collected esophageal and stomach tissues and performed histology, immunohistochemistry, flow cytometry, transcriptome, and real-time polymerase chain reaction analyses. Cardia and forestomach tissues from mice were cultured as organoids and incubated with inhibitors of Notch or NF-kB.

RESULTS

Progression of BE to EAC was associated with a significant reduction in goblet cell density comparing nondysplastic regions of tissues from patients; there was an inverse correlation between goblet cell density and levels of NOTCH3 and JAG2 messenger RNA. In mice, expression of the activated intracellular form of NOTCH2 in Lgr5+ cells reduced goblet-like cell maturation, increased crypt fission, and accelerated the development of tumors in the squamocolumnar junction. Mice with deletion of NOTCH2 from Lgr5+ cells had increased maturation of goblet-like cells, reduced crypt fission, and developed fewer tumors. Esophageal tissues from in pL2.Lgr5.N2IC mice had increased levels of RelA (which encodes the p65 unit of NF-κB) compared to tissues from L2-IL1B mice, and we found evidence of increased NF-κB activity in Lgr5+ cells. Esophageal tissues from pL2.Lgr5.p65fl/fl mice had lower inflammation and metaplasia scores than pL2.Lgr5.N2IC mice. In organoids derived from pL2-IL1B mice, the NF-κB inhibitor JSH-23 reduced cell survival and proliferation.

CONCLUSIONS

Notch signaling contributes to activation of NF-κB and regulates differentiation of gastric cardia progenitor cells in a mouse model of BE. In human esophageal tissues, progression of BE to EAC was associated with reduced goblet cell density and increased levels of Notch expression. Strategies to block this pathway might be developed to prevent EAC in patients with BE.

Wnt Signaling Mediates the Aging-Induced Differentiation Impairment of Intestinal Stem Cells

Stem cell aging underlies aging-associated disorders, such as steeply increased incidences of tumors and impaired regeneration capacity upon stress. However, whether and how the intestinal stem cells age remains largely unknown. Here we show that intestinal stem cells derived from 24-month-old mice hardly form typical organoids with crypt-villus structures, but rather mainly form big, rounded cysts devoid of differentiated cell types, which mimics the culturing of heterozygous APC-deficient cells from the APC^min mouse line. Further analysis showed that cultured crypts derived from aged mice exhibited reduced expression levels of differentiation genes and higher expression of Wnt target genes. Lowering the concentration of R-spondin-1 in the culture system significantly reduced formation of rounded cysts, accompanied by an increased formation of organoids from crypts derived from old mice. We are the first to uncover that intestinal stem cells derived from old mice harbor significant deficiency in differentiation that can be partially rescued through a reduction in R-spondin-1 exposure. This could be highly relevant to intestinal tumor development and the reduced regeneration potential observed in the aged population. Our study provides the first experimental evidence that an over-responsiveness to Wnt/beta-catenin signaling of aged intestinal stem cells mediates the aging-induced deficiency in differentiation, and could serve as a potential target to ameliorate aging-associated intestinal pathologies.

Hyaluronic acid promotes Lgr5+ stem cell proliferation and crypt fission through TLR4 and PGE2 transactivation of EGFR

Hyaluronic acid (HA), a glycosaminoglycan in the extracellular matrix, binds to CD44 and Toll-like receptor 4 (TLR4). We previously demonstrated that both CD44 and TLR4, but predominately TLR4, mediated HA stimulation of Lgr5⁺ stem cell proliferation, crypt fission, and intestinal growth in postnatal mice. Here we address the questions of which cell type expresses the relevant TLR4 in driving intestinal growth and what are the downstream events from TLR4 activation. Studies were done in 14-day-old mice: wild type (WT), mice deficient in cyclooxygenase 2 (COX2), mice deficient in myeloid cell TLR4, and mice deficient in epithelial cell epidermal growth factor receptor (EGFR). Biological end points included crypt fission and Lgr5 cell proliferation. In WT mice, treatment with NS-398 (a COX2 inhibitor), clodronate (a macrophage-depleting agent), or tyrphostin (an EGFR inhibitor) resulted in 30% reductions in crypt fission and Lgr5⁺ stem cell proliferation compared with control mice. Mice deficient in COX2 or myeloid TLR4 or epithelial cell EGFR all had 30% reductions in crypt fission and Lgr5⁺ stem cell proliferation compared with WT mice. Administration of dimethyl PGE₂, a stable PGE₂ analog, increased crypt fission and Lgr5⁺ stem cell proliferation. Administration of dimethyl PGE₂ reversed the effects of NS-398, clodronate, COX2 deficiency, and myeloid TLR4 deficiency but had no effect on mice treated with tyrphostin or mice deficient in epithelial cell EGFR. We conclude that, in postnatal mice, ~30% of intestinal growth as manifested by crypt fission and Lgr5⁺ stem cell proliferation is driven by a novel pathway: Extracellular HA binds TLR4 on pericryptal macrophages, inducing the production of PGE₂ through COX2. PGE₂ transactivates EGFR in Lgr5⁺ epithelial stem cells, resulting in Lgr5⁺ stem cell proliferation and crypt fission.NEW & NOTEWORTHY This study, in newborn mice, describes a novel molecular pathway regulating Lgr5⁺ epithelial stem cell proliferation and normal intestinal elongation, as assessed by crypt fission. In this pathway, endogenous extracellular hyaluronic acid binds to Toll-like receptor 4 on pericryptal macrophages releasing PGE₂ which binds to epidermal growth factor receptor on Lgr5⁺ stem cells resulting in proliferation. Lgr5⁺ stem cell proliferation leads to crypt fission and intestinal elongation. The demonstration that normal growth requires microbial-independent Toll-like receptor activation is novel.