Lung stem cell self-renewal relies on BMI1-dependent control of expression at imprinted loci

The transcription factor BMI1 increases hypoxic signaling in oral cavity epithelia

The tongue epithelium is maintained by a proliferative basal layer. This layer contains long-lived stem cells (SCs), which produce progeny cells that move up to the surface as they differentiate. B-lymphoma Mo-MLV insertion region 1 (BMI1), a protein in mammalian Polycomb Repressive Complex 1 (PRC1) and a biomarker of oral squamous cell carcinoma, is expressed in almost all basal epithelial SCs of the tongue, and single, Bmi1-labelled SCs give rise to cells in all epithelial layers. We previously developed a transgenic mouse model (KrTB) containing a doxycycline- (dox) controlled, Tet-responsive element system to selectively overexpress Bmi1 in the tongue basal epithelial SCs. Here, we used this model to assess BMI1 actions in tongue epithelia. Genome-wide transcriptomics revealed increased levels of transcripts involved in the cellular response to hypoxia in Bmi1-overexpressing (KrTB+DOX) oral epithelia even though these mice were not subjected to hypoxia conditions. Ectopic Bmi1 expression in tongue epithelia increased the levels of hypoxia inducible factor-1 alpha (HIF1α) and HIF1α targets linked to metabolic reprogramming during hypoxia. We used chromatin immunoprecipitation (ChIP) to demonstrate that Bmi1 associates with the promoters of HIF1A and HIF1A-activator RELA (p65) in tongue epithelia. We also detected increased SC proliferation and oxidative stress in Bmi1-overexpressing tongue epithelia. Finally, using a human oral keratinocyte line (OKF6-TERT1R), we showed that ectopic BMI1 overexpression decreases the oxygen consumption rate while increasing the extracellular acidification rate, indicative of elevated glycolysis. Thus, our data demonstrate that high BMI1 expression drives hypoxic signaling, including metabolic reprogramming, in normal oral cavity epithelia.

Age-associated H3K9me2 loss alters the regenerative equilibrium between murine lung alveolar and bronchiolar progenitors

The lung contains multiple progenitor cell types, but how their responses are choreographed during injury repair and whether this changes with age is poorly understood. We report that histone H3 lysine 9 di-methylation (H3K9me2), mediated by the methyltransferase G9a, regulates the dynamics of distal lung epithelial progenitor cells and that this regulation deteriorates with age. In aged mouse lungs, H3K9me2 loss coincided with fewer alveolar type 2 (AT2) cell progenitors and reduced alveolar regeneration but increased the frequency and activity of multipotent bronchioalveolar stem cells (BASCs) and bronchiolar progenitor club cells. H3K9me2 depletion in young mice decreased AT2 progenitor activity and impaired alveolar injury repair. Conversely, H3K9me2 depletion increased chromatin accessibility of bronchiolar cell genes, increased BASC frequency, and accelerated bronchiolar cell injury repair. These findings indicate that during aging, the epigenetic regulation that coordinates lung progenitor cells' regenerative responses becomes dysregulated, aiding our understanding of age-related susceptibility to lung disease.

BMI1 Silencing Liposomes Suppress Postradiotherapy Cancer Stemness against Radioresistant Hepatocellular Carcinoma

Radiotherapy causes DNA damage by direct ionization and indirect generation of reactive oxygen species (ROS) thereby destroying cancer cells. However, ionizing radiation (IR) unexpectedly elicits metastasis and invasion of cancer cells by inducing cancer stem cells' (CSCs) properties. As BMI1 is a crucial gene that causes radioresistance and an unfavorable prognosis of hepatocellular carcinoma (HCC), BMI1 inhibitor PTC-209 has been encapsulated in a ROS-responsive liposome (LP(PTC-209)) to be temporally and spatially delivered to radioresistant HCC tissue. The ROS generated during IR was not only considered to directly cause tumor cell death but also be used as a stimulator to trigger ROS-responsive drug release from LP(PTC-209). The PTC-209 released into resistant HCC tissue under radiotherapy further led to cancer stem cell (CSC) differentiation and then recovered radiosensitivity of HCC tumor. The suppression of the radioresistant performance of LP(PTC-209) has been proved on radiosensitive and radioresistant Hepa1-6 CSC tumor models, respectively. Our study clarified the relationship between radiotherapy and cancer stemness and provided insights to achieve complete suppression of radioresistant HCC tumor by inhibiting cancer stemness.

Human embryonic stem cell-derived mesenchymal stem cell secretome reverts silica-induced airway epithelial cell injury by regulating Bmi1 signaling

Silicosis is an irreversible chronic pulmonary disease caused by long-term inhalation and deposition of silica particles, which is currently incurable. The exhaustion of airway epithelial stem cells plays a pathogenetic role in silicosis. In present study, we investigated therapeutic effects and potential mechanism of human embryonic stem cell (hESC)-derived MSC-likes immune and matrix regulatory cells (IMRCs) (hESC-MSC-IMRCs), a type of manufacturable MSCs for clinical application in silicosis mice. Our results showed that the transplantation of hESC-MSC-IMRCs led the alleviation of silica-induced silicosis in mice, accompanied by inhibiting epithelia-mesenchymal transition (EMT), activating B-cell-specific Moloney murine leukemia virus integration site 1 (Bmi1) signaling and airway epithelial cell regeneration. In consistence, the secretome of hESC-MSC-IMRC exhibited abilities to restore the potency and plasticity of primary human bronchial epithelial cells (HBECs) proliferation and differentiation following the SiO2 -induced HBECs injury. Mechanistically, the secretome resolved the SiO2 -induced HBECs injury through the activation of BMI1 signaling and restoration of airway basal cell proliferation and differentiation. Moreover, the activation of BMI1 significantly enhanced the capacity of HBEC proliferation and differentiation to multiple airway epithelial cell types in organoids. Cytokine array revealed that DKK1, VEGF, uPAR, IL-8, Serpin E1, MCP-1 and Tsp-1 were the main factors in the hESC-MSC-IMRC secretome. These results demonstrated a potential therapeutic effect of hESC-MSC-IMRCs and their secretome for silicosis, in part through a mechanism by activating Bmi1 signaling to revert the exhaustion of airway epithelial stem cells, subsequentially enhance the potency and plasticity of lung epithelial stem cells.

MAST4 controls cell cycle in spermatogonial stem cells

Spermatogonial stem cell (SSC) self-renewal is regulated by reciprocal interactions between Sertoli cells and SSCs in the testis. In a previous study, microtubule-associated serine/threonine kinase 4 (MAST4) has been studied in Sertoli cells as a regulator of SSC self-renewal. The present study focused on the mechanism by which MAST4 in Sertoli cells transmits the signal and regulates SSCs, especially cell cycle regulation. The expression of PLZF, CDK2 and PLZF target genes was examined in WT and Mast4 KO testes by Immunohistochemistry, RT-qPCR and western blot. In addition, IdU and BrdU were injected into WT and Mast4 KO mice and cell cycle of SSCs was analysed. Finally, the testis tissues were cultured in vitro to examine the regulation of cell cycle by MAST4 pathway. Mast4 KO mice showed infertility with Sertoli cell-only syndrome and reduced sperm count. Furthermore, Mast4 deletion led to decreased PLZF expression and cell cycle progression in the testes. MAST4 also induced cyclin-dependent kinase 2 (CDK2) to phosphorylate PLZF and activated PLZF suppressed the transcriptional levels of genes related to cell cycle arrest, leading SSCs to remain stem cell state. MAST4 is essential for maintaining cell cycle in SSCs via the CDK2-PLZF interaction. These results demonstrate the pivotal role of MAST4 regulating cell cycle of SSCs and the significance of spermatogenesis.

Targeting cancer stemness mediated by BMI1 and MCL1 for non-small cell lung cancer treatment

Lung cancer is the leading cause of cancer‐associated death, with a global 5‐year survival rate <20%. Early metastasis and recurrence remain major challenges for lung cancer treatment. The stemness property of cancer cells has been suggested to play a key role in cancer plasticity, metastasis and drug‐resistance, and is a potential target for drug development. In this study, we found that in non‐small cell lung cancer (NSCLC), BMI1 and MCL1 play crucial roles of cancer stemness including invasion, chemo‐resistance and tumour initiation. JNK signalling serves as a link between oncogenic pathway or genotoxicity to cancer stemness. The activation of JNK, either by mutant EGFR or chemotherapy agent, stabilized BMI1 and MCL1 proteins through suppressing the expression of E3‐ubiquitin ligase HUWE1. In lung cancer patient samples, high level of BMI1 is correlated with poor survival, and the expression of BMI1 is positively correlated with MCL1. A novel small‐molecule, BI‐44, was developed, which effectively suppressed BMI1/MCL1 expressions and inhibited tumour formation and progression in preclinical models. Targeting cancer stemness mediated by BMI1/MCL1 with BI‐44 provides the basis for a new therapeutic approach in NSCLC treatment.

Neonatal lung-derived SSEA-1+ cells exhibited distinct stem/progenitor characteristics and organoid developmental potential

Stem/progenitor cells, because of their self-renewal and multiple cell type differentiation abilities, have good potential in regenerative medicine. We previously reported a lung epithelial cell population that expressed the stem cell marker SSEA-1 was abundant in neonatal but scarce in adult mice. In the current study, neonatal and adult mouse-derived pulmonary SSEA-1⁺ cells were isolated for further characterization. The results showed that neonatal-derived pulmonary SSEA-1⁺ cells highly expressed lung development-associated genes and had enhanced organoid generation ability compared with the adult cells. Neonatal pulmonary SSEA-1⁺ cells generated airway-like and alveolar-like organoids, suggesting multilineage cell differentiation ability. Organoid generation of neonatal but not adult pulmonary SSEA-1⁺ cells was enhanced by fibroblast growth factor 7 (FGF 7). Furthermore, neonatal pulmonary SSEA-1⁺ cells colonized and developed in decellularized and injured lungs. These results suggest the potential of lung-derived neonatal-stage SSEA-1⁺ cells with enhanced stem/progenitor activity and shed light on future lung engineering applications.

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Pulmonary SSEA-1⁺ cells are abundant in neonatal and scarce in adult stages

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The stem/progenitor activity of pulmonary SSEA-1⁺ cells is enhanced in neonatal stage

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Neonatal pulmonary SSEA-1⁺ cells developed into airway- and alveolar-like organoids

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FGF7 regulates alveolar epithelium development of neonatal pulmonary SSEA-1⁺ cells

p57 Suppresses the Pluripotency and Proliferation of Mouse Embryonic Stem Cells by Positively Regulating p53 Activation

Embryonic stem cells (ESCs) are pluripotent stem cells that have indefinite self-renewal capacities under appropriate culture conditions in vitro. The pluripotency maintenance and proliferation of these cells are delicately governed by the concert effect of a complex transcriptional regulatory network. Herein, we discovered that p57^Kip2 (p57), a cyclin-dependent kinase inhibitor canonically inhibiting cell proliferation, played a role in suppressing the pluripotency state of mouse ESCs (mESCs). p57 knockdown significantly stimulated the expressions of core pluripotency factors NANOG, OCT4, and SOX2, while p57 overexpression inhibited the expressions of these factors in mESCs. In addition, consistent with its function in somatic cells, p57 suppressed mESC proliferation. Further analysis showed that p57 could interact with and contribute to the activation of p53 in mESCs. In conclusion, the present study showed that p57 could antagonize the pluripotency state and the proliferation process of mESCs. This finding uncovers a novel function of p57 and provides new evidence for elucidating the complex regulatory of network of mESC fate.

Zinc-finger E-box-binding homeobox 1 (ZEB1) plays a crucial role in the maintenance of lung cancer stem cells resistant to gefitinib

Background

Zinc‐finger E‐box‐binding homeobox 1 (ZEB1) is an important regulator of epithelial‐mesenchymal transition (EMT) and is involved in the maintenance of cancer stem cells (CSCs) via miR‐200c and BMI1 pathway. Recent studies revealed that ZEB1 contributes to the EMT‐mediated acquired resistance to gefitinib in EGFR‐mutant non‐small cell lung cancer (NSCLC). However, the precise role of ZEB1 in the maintenance of lung CSCs that lead to acquired resistance to gefitinib remains unclear.

Methods

PC9 and HCC827 NSCLC cell lines were treated with high concentrations of gefitinib, and surviving cells were referred to as “gefitinib‐resistant persisters” (GRPs). ZEB1 knockdown or overexpression was performed to determine the biological significance of ZEB1 in the CSC features of GRPs, and animal models were studied for in vivo validation. Expression of ZEB1, BMI1, and ALDH1A1 was analyzed by immunohistochemistry in tumor specimens from NSCLC patients with acquired resistance to gefitinib.

Results

GRPs had characteristic features of mesenchymal and CSC phenotypes with high expression of ZEB1 and BMI1, and decreased miR‐200c, in vitro and in vivo. ZEB1 silencing attenuated the suppression of miR‐200c, resulting in the reduction in BMI1 and reversed the mesenchymal and CSC features of GRPs. Furthermore, ZEB1 overexpression induced EMT and increased the levels of CD133‐ and BMI1‐positive GRPs in vitro and gefitinib resistance in vivo. Finally, ZEB1, BMI1, and ALDH1A1 were highly expressed in tumor specimens from EGFR‐mutant NSCLC patients with gefitinib resistance.

Conclusions

ZEB1 plays an important role in gefitinib‐resistant lung CSCs with EMT features via regulation of miR‐200c and BMI1.

BMI1 enables extensive expansion of functional erythroblasts from human peripheral blood mononuclear cells

Transfusion of red blood cells (RBCs) from ABO-matched but genetically unrelated donors is commonly used for treating anemia and acute blood loss. Increasing demand and insufficient supply for donor RBCs, especially those of universal blood types or free of known and unknown pathogens, has called for ex vivo generation of functional RBCs by large-scale cell culture. However, generating physiological numbers of transfusable cultured RBCs (cRBCs) ex vivo remains challenging, due to our inability to either extensively expand primary RBC precursors (erythroblasts) or achieve efficient enucleation once erythroblasts have been expanded and induced to differentiation and maturation. Here, we report that ectopic expression of the human BMI1 gene confers extensive expansion of human erythroblasts, which can be derived readily from adult peripheral blood mononuclear cells of either healthy donors or sickle cell patients. These extensively expanded erythroblasts (E3s) are able to proliferate exponentially (>1 trillion-fold in 2 months) in a defined culture medium. Expanded E3 cells are karyotypically normal and capable of terminal maturation with approximately 50% enucleation. Additionally, E3-derived cRBCs can circulate in a mouse model following transfusion similar to primary human RBCs. Therefore, we provide a facile approach of generating physiological numbers of human functional erythroblasts ex vivo.

Pharmacokinetics and Safety of PTC596, a Novel Tubulin-Binding Agent, in Subjects With Advanced Solid Tumors

PTC596 is a novel, orally bioavailable, small-molecule tubulin-binding agent that reduces B-cell-specific Moloney murine leukemia virus insertion site 1 activity and is being developed for the treatment of solid tumors. A phase 1, open-label, multiple-ascending-dose study was conducted to evaluate the pharmacokinetics and safety of the drug in subjects with advanced solid tumors. PTC596 was administered orally biweekly based on body weight. Dose escalation followed a modified 3 + 3 scheme using doses of 0.65, 1.3, 2.6, 5.2, 7.0, and 10.4 mg/kg. Following oral administration, PTC596 was rapidly absorbed, and between 0.65 and 7.0 mg/kg reached a maximum plasma concentration 2 to 4 hours after dosing. Area under the plasma concentration-time curve increased proportionally with body weight-adjusted doses. Maximum plasma concentration increased with dose, although the increase was less than dose proportional at dose levels >2.6 mg/kg. No accumulation occurred after multiple administrations up to 7.0 mg/kg. PTC596 had a terminal half-life ranging 12 to 15 hours at all doses except for the highest dose of 10.4 mg/kg, where the half-life was approximately 20 hours. Overall, PTC596 was well tolerated. The most frequently reported PTC596-related treatment-emergent adverse events were mild to moderate gastrointestinal symptoms, including diarrhea (54.8%), nausea (45.2%), vomiting (35.5%), and fatigue (35.5%). Only 1 patient treated with 10.4 mg/kg experienced dose-limiting toxicity of neutropenia and thrombocytopenia, both of which were reversible. Stable disease as best overall response was observed among 7 patients, with 2 patients receiving the study drug up to 16 weeks. These results support the further development of PTC596 for the treatment of solid tumors.

Optimizing the in vitro colony-forming assay for more efficient delineation of the interaction between lung epithelial stem cells and their niche

The use of in vitro 3D organoid/colony forming assay (CFA); which mimics the in vivo environment have provided insight into the mechanisms by which lung stem cells maintain and repair the lung. In recent years, the use of CFA has markedly expanded. However, variations among laboratories in lung cell isolation methods, media used, type, origin, and processing methods of mesenchymal cells used as feeders for the epithelial colonies, and terms utilized to describe and quantify the growing colonies, have caused difficulty in reproducing results among different labs. In this study, we compared several previously described methods for lung cell isolation and culture media, to identify their influence on retrieved cells and growing colonies. We also characterized the effect of freeze/thaw, and propagation of fibroblasts on their ability to support epithelial colonies. Importantly, we suggested markers to identify fibroblast subtypes that offer the best support to alveolar stem cell proliferation. Then, we used our optimized assay to confirm the in vitro identity of recently described epithelial progenitors. We also tested the effect of hyperoxia on lung stem cells, and examined the expression of the receptors for the SARS-COV-2 virus's entry into epithelial cells, on our organoids. In summary, our findings facilitate CFA standardization, help understand how niche cell variations influence growing colonies, and confirm some of the recently described lung stem cells.

Molecular Mechanisms of Renal Progenitor Regulation: How Many Pieces in the Puzzle?

Kidneys of mice, rats and humans possess progenitors that maintain daily homeostasis and take part in endogenous regenerative processes following injury, owing to their capacity to proliferate and differentiate. In the glomerular and tubular compartments of the nephron, consistent studies demonstrated that well-characterized, distinct populations of progenitor cells, localized in the parietal epithelium of Bowman capsule and scattered in the proximal and distal tubules, could generate segment-specific cells in physiological conditions and following tissue injury. However, defective or abnormal regenerative responses of these progenitors can contribute to pathologic conditions. The molecular characteristics of renal progenitors have been extensively studied, revealing that numerous classical and evolutionarily conserved pathways, such as Notch or Wnt/β-catenin, play a major role in cell regulation. Others, such as retinoic acid, renin-angiotensin-aldosterone system, TLR2 (Toll-like receptor 2) and leptin, are also important in this process. In this review, we summarize the plethora of molecular mechanisms directing renal progenitor responses during homeostasis and following kidney injury. Finally, we will explore how single-cell RNA sequencing could bring the characterization of renal progenitors to the next level, while knowing their molecular signature is gaining relevance in the clinic.

Functional Versatility of the CDK Inhibitor p57Kip2

The cyclin/CDK inhibitor p57^Kip2 belongs to the Cip/Kip family, with p21^Cip1 and p27^Kip1, and is the least studied member of the family. Unlike the other family members, p57^Kip2 has a unique role during embryogenesis and is the only CDK inhibitor required for embryonic development. p57^Kip2 is encoded by the imprinted gene CDKN1C, which is the gene most frequently silenced or mutated in the genetic disorder Beckwith-Wiedemann syndrome (BWS), characterized by multiple developmental anomalies. Although initially identified as a cell cycle inhibitor based on its homology to other Cip/Kip family proteins, multiple novel functions have been ascribed to p57^Kip2 in recent years that participate in the control of various cellular processes, including apoptosis, migration and transcription. Here, we will review our current knowledge on p57^Kip2 structure, regulation, and its diverse functions during development and homeostasis, as well as its potential implication in the development of various pathologies, including cancer.

Bronchioalveolar stem cells derived from mouse-induced pluripotent stem cells promote airway epithelium regeneration

Background

Bronchioalveolar stem cells (BASCs) located at the bronchioalveolar-duct junction (BADJ) are stem cells residing in alveoli and terminal bronchioles that can self-renew and differentiate into alveolar type (AT)-1 cells, AT-2 cells, club cells, and ciliated cells. Following terminal-bronchiole injury, BASCs increase in number and promote repair. However, whether BASCs can be differentiated from mouse-induced pluripotent stem cells (iPSCs) remains unreported, and the therapeutic potential of such cells is unclear. We therefore sought to differentiate BASCs from iPSCs and examine their potential for use in the treatment of epithelial injury in terminal bronchioles.

Methods

BASCs were induced using a modified protocol for differentiating mouse iPSCs into AT-2 cells. Differentiated iPSCs were intratracheally transplanted into naphthalene-treated mice. The engraftment of BASCs into the BADJ and their subsequent ability to promote repair of injury to the airway epithelium were evaluated.

Results

Flow cytometric analysis revealed that BASCs represented ~ 7% of the cells obtained. Additionally, ultrastructural analysis of these iPSC-derived BASCs via transmission electron microscopy showed that the cells containing secretory granules harboured microvilli, as well as small and immature lamellar body-like structures. When the differentiated iPSCs were intratracheally transplanted in naphthalene-induced airway epithelium injury, transplanted BASCs were found to be engrafted in the BADJ epithelium and alveolar spaces for 14 days after transplantation and to maintain the BASC phenotype. Notably, repair of the terminal-bronchiole epithelium was markedly promoted after transplantation of the differentiated iPSCs.

Conclusions

Mouse iPSCs could be differentiated in vitro into cells that display a similar phenotype to BASCs. Given that the differentiated iPSCs promoted epithelial repair in the mouse model of naphthalene-induced airway epithelium injury, this method may serve as a basis for the development of treatments for terminal-bronchiole/alveolar-region disorders.

Bronchioalveolar stem cells in lung repair, regeneration and disease

Bronchioalveolar stem cells (BASCs) are a lung resident stem cell population located at bronchioalveolar duct junctions that contribute to the maintenance of bronchiolar club cells and alveolar epithelial cells of the distal lung. Their transformed counterparts are considered to be likely progenitors of lung adenocarcinomas, which has been a major area of research in relation to BASCs. A critical limitation in addressing the function of BASCs in vivo has been the lack of a unique BASC marker, which has prevented specific targeting of BASCs in animal models of respiratory conditions. Recently, there have been several studies describing genetically modified mice that allow in vivo quantification, tracing, and functional analysis of BASCs to address this long-standing issue. These cutting-edge experimental tools will likely have significant implications for future experimental studies involving BASCs and the elucidation of their role in various lung diseases. To date, this has been largely explored in models of lung injury including naphthalene-induced airway injury, bleomycin-induced alveolar injury, hyperoxia-induced models of bronchopulmonary dysplasia, and influenza virus infection. These novel experimental mouse tools will facilitate the assessment of the impact of BASC loss on additional respiratory conditions including infection-induced severe asthma and chronic obstructive pulmonary disease, as well as respiratory bacterial infections, both in early life and adulthood. These future studies may shed light on the potential broad applicability of targeting BASCs for a diverse range of respiratory conditions during lung development and in promoting effective regeneration and repair of the lung in respiratory diseases. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

BRG1 Loss Predisposes Lung Cancers to Replicative Stress and ATR Dependency

Inactivation of SMARCA4/BRG1, the core ATPase subunit of mammalian SWI/SNF complexes, occurs at very high frequencies in non-small cell lung cancers (NSCLC). There are no targeted therapies for this subset of lung cancers, nor is it known how mutations in BRG1 contribute to lung cancer progression. Using a combination of gain- and loss-of-function approaches, we demonstrate that deletion of BRG1 in lung cancer leads to activation of replication stress responses. Single-molecule assessment of replication fork dynamics in BRG1-deficient cells revealed increased origin firing mediated by the prelicensing protein, CDC6. Quantitative mass spectrometry and coimmunoprecipitation assays showed that BRG1-containing SWI/SNF complexes interact with RPA complexes. Finally, BRG1-deficient lung cancers were sensitive to pharmacologic inhibition of ATR. These findings provide novel mechanistic insight into BRG1-mutant lung cancers and suggest that their dependency on ATR can be leveraged therapeutically and potentially expanded to BRG1-mutant cancers in other tissues. SIGNIFICANCE: These findings indicate that inhibition of ATR is a promising therapy for the 10% of non-small cell lung cancer patients harboring mutations in SMARCA4/BRG1. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/18/3841/F1.large.jpg.

Co-delivery of Bmi1 small interfering RNA with ursolic acid by folate receptor-targeted cationic liposomes enhances anti-tumor activity of ursolic acid in vitro and in vivo

Overexpression of Bmi1 gene is an important feature of cancer stem cell in various human tumors. Therefore, Bmi1 gene can be a potential target for small interfering RNA (siRNA) mediated cancer therapy. Ursolic acid (UA) as a natural product plays a pivotal role in anti-tumor field, although its performance is limited by low bioavailability and poor hydrophilicity. A folate receptor-targeted cationic liposome system was designed for the purpose of investigating the relationship between Bmil siRNA and UA. The folate receptor-targeted cationic liposomes co-delivering UA and Bmi1 siRNA (FA-UA/siRNA-L) were fabricated by electrostatic interaction between folate UA liposome (FA-UA-L) and Bmi1 siRNA. Tumor growth is inhibited by FA-UA/siRNA-L in vitro and in vivo and this inhibition is contributed by a synergistic anti-tumor effect of UA and Bmi1 siRNA. The western blot measurement of apoptosis-protein and cancer stem cell (CSC) marked-protein demonstrated that UA led to activation-induced tumor cell death and Bmi1 siRNA resulted in inhibition of cancer stem cells. Overall, these results indicate that Bmi1 as a regulating gene for cancer stem cell is an effective target for cancer treatment using siRNA and co-delivery of UA and Bmi1 siRNA using folate-targeted liposomes is a promising strategy for improved anti-tumor effect.

The Central Contributions of Breast Cancer Stem Cells in Developing Resistance to Endocrine Therapy in Estrogen Receptor (ER)-Positive Breast Cancer

Breast cancer stem cells (BCSC) play critical roles in the acquisition of resistance to endocrine therapy in estrogen receptor (ER)-positive (ER + ve) breast cancer (BC). The resistance results from complex alterations involving ER, growth factor receptors, NOTCH, Wnt/β-catenin, hedgehog, YAP/TAZ, and the tumor microenvironment. These mechanisms are likely converged on regulating BCSCs, which then drive the development of endocrine therapy resistance. In this regard, hormone therapies enrich BCSCs in ER + ve BCs under both pre-clinical and clinical settings along with upregulation of the core components of “stemness” transcriptional factors including SOX2, NANOG, and OCT4. SOX2 initiates a set of reactions involving SOX9, Wnt, FXY3D, and Src tyrosine kinase; these reactions stimulate BCSCs and contribute to endocrine resistance. The central contributions of BCSCs to endocrine resistance regulated by complex mechanisms offer a unified strategy to counter the resistance. ER + ve BCs constitute approximately 75% of BCs to which hormone therapy is the major therapeutic approach. Likewise, resistance to endocrine therapy remains the major challenge in the management of patients with ER + ve BC. In this review we will discuss evidence supporting a central role of BCSCs in developing endocrine resistance and outline the strategy of targeting BCSCs to reduce hormone therapy resistance.

Genome imprinting in stem cells: A mini-review

Genomic imprinting is an epigenetic process result in silencing of one of the two alleles (maternal or paternal) based on the parent of origin. Dysregulation of imprinted genes results in detectable developmental and differential abnormalities. Epigenetics erasure is required for resetting the cell identity to a ground state during the production of induced pluripotent stem (iPS) cells from somatic cells. There are some contradictory reports regarding the status of the imprinting marks in the genome of iPS cells. Additionally, many studies highlighted the existence of subtle differences in the imprinting loci between different types of iPS cells and embryonic stem (ES) cells. These observations could ultimately undermine the use of patient-derived iPS cells for regenerative medicine.

HRI coordinates translation necessary for protein homeostasis and mitochondrial function in erythropoiesis

Iron and heme play central roles in the production of red blood cells, but the underlying mechanisms remain incompletely understood. Heme-regulated eIF2α kinase (HRI) controls translation by phosphorylating eIF2α. Here, we investigate the global impact of iron, heme, and HRI on protein translation in vivo in murine primary erythroblasts using ribosome profiling. We validate the known role of HRI-mediated translational stimulation of integratedstressresponse mRNAs during iron deficiency in vivo. Moreover, we find that the translation of mRNAs encoding cytosolic and mitochondrial ribosomal proteins is substantially repressed by HRI during iron deficiency, causing a decrease in cytosolic and mitochondrial protein synthesis. The absence of HRI during iron deficiency elicits a prominent cytoplasmic unfolded protein response and impairs mitochondrial respiration. Importantly, ATF4 target genes are activated during iron deficiency to maintain mitochondrial function and to enable erythroid differentiation. We further identify GRB10 as a previously unappreciated regulator of terminal erythropoiesis.

Red blood cells use a molecule called hemoglobin to transport oxygen around the body. To make hemoglobin, cells require iron to build a component called heme. If an individual does not get enough iron in their diet, the body cannot produce enough red blood cells, or the cells lack hemoglobin. This condition is known as iron deficiency anemia, and it affects around one-third of the world’s population.

Researchers did not know exactly how iron levels control red blood cell production, though several proteins had been identified to play important roles. Heme forms in the cell's mitochondria: the compartments in the cell that supply it with energy. When heme levels in a developing red blood cell are low, a protein called HRI reduces the production of many proteins, most importantly the proteins that make up hemoglobin. HRI also boosts the production of a protein called ATF4, which switches on a set of genes that help both the cell and its mitochondria to adapt to the lack of heme. In turn, HRI and ATF4 reduce the activity of a signaling pathway called mTORC1, which controls the production of proteins that help cells to grow and divide.

To understand in more detail how iron and heme regulate the production of new red blood cells, Zhang et al. looked at immature red blood cells from the livers of developing mice. Some of the mice lacked the gene that produces HRI, and some experienced iron deficiency. Comparing gene activity in the different mice revealed that in the developing blood cells of iron-deficient mice, HRI largely reduces the rate of protein production in both the mitochondria and the wider cell. At the same time, the increased activity of ATF4 allows the mitochondria to carry on releasing energy and the cells to continue developing. Zhang et al. also found that a protein that inhibits the mTORC1 signaling pathway needs to be active for the new red blood cells to mature.

Overall, the results suggest that drugs that activate HRI or block the activity of the mTORC1 pathway could help to treat anemia. The next step is to test the effects that such drugs have in anemic mice and cells from anemic people.

RNA-seq of Isolated Chromaffin Cells Highlights the Role of Sex-Linked and Imprinted Genes in Adrenal Medulla Development

Adrenal chromaffin cells and sympathetic neurons synthesize and release catecholamines, and both cell types are derived from neural crest precursors. However, they have different developmental histories, with sympathetic neurons derived directly from neural crest precursors while adrenal chromaffin cells arise from neural crest-derived cells that express Schwann cell markers. We have sought to identify the genes, including imprinted genes, which regulate the development of the two cell types in mice. We developed a method of separating the two cell types as early as E12.5, using differences in expression of enhanced yellow fluorescent protein driven from the tyrosine hydroxylase gene, and then used RNA sequencing to confirm the characteristic molecular signatures of the two cell types. We identified genes differentially expressed by adrenal chromaffin cells and sympathetic neurons. Deletion of a gene highly expressed by adrenal chromaffin cells, NIK-related kinase, a gene on the X-chromosome, results in reduced expression of adrenaline-synthesizing enzyme, phenyl-N-methyl transferase, by adrenal chromaffin cells and changes in cell cycle dynamics. Finally, many imprinted genes are up-regulated in chromaffin cells and may play key roles in their development.

Recent Developments in mRNA-Based Protein Supplementation Therapy to Target Lung Diseases

Protein supplementation therapy using in vitro-transcribed (IVT) mRNA for genetic diseases contains huge potential as a new class of therapy. From the early ages of synthetic mRNA discovery, a great number of studies showed the versatile use of IVT mRNA as a novel approach to supplement faulty or absent protein and also as a vaccine. Many modifications have been made to produce high expressions of mRNA causing less immunogenicity and more stability. Recent advancements in the in vivo lung delivery of mRNA complexed with various carriers encouraged the whole mRNA community to tackle various genetic lung diseases. This review gives a comprehensive overview of cells associated with various lung diseases and recent advancements in mRNA-based protein replacement therapy. This review also covers a brief summary of developments in mRNA modifications and nanocarriers toward clinical translation.

Bmi-1 high-expressing cells enrich cardiac stem/progenitor cells and respond to heart injury

Bmi‐1 gene is well recognized as an oncogene, but has been recently demonstrated to play a role in the self‐renewal of tissue‐specific stem cells. By using Bmi‐1^GFP/+ mice, we investigated the role of Bmi‐1 in cardiac stem/progenitor cells and myocardial repair. RT‐PCR and flow cytometry analysis indicated that the expression of Bmi‐1 was significantly higher in cardiac side population than the main population from CD45⁻Ter119⁻CD31⁻ heart cells. More Sca‐1⁺ cardiac stem/progenitor cells were found in Bmi‐1 GFP^hi subpopulation, and these Bmi‐1 GFP^hi heart cells showed the potential of differentiation into SMM⁺ smooth muscle‐like cells and TnT⁺ cardiomyocyte‐like cells in vitro. The silencing of Bmi‐1 significantly inhibited the proliferation and differentiation of heart cells. Otherwise, myocardial infarction induced a significantly increase (2.7‐folds) of Bmi‐1 GFP^hi population, mainly within the infarction and border zones. These preliminary data suggest that Bmi‐1^hi heart cells are enriched in cardiac stem/progenitor cells and may play a role in myocardial repair.

Overexpression of Sirt1 in mesenchymal stem cells protects against bone loss in mice by FOXO3a deacetylation and oxidative stress inhibition

OBJECTIVE

B cell-specific Moloney murine leukemia virus integration site 1 (Bmi-1) deficiency (Bmi-1^-/-) leads to an osteoporotic phenotype with a significant downregulation of Sirt1 protein expression. Sirtuin 1 (Sirt1) haploinsufficiency results in a bone loss by decreased bone formation; however, it is unclear whether Sirt1 overexpression in mesenchymal stem cells (MSCs) plays an anti-osteoporotic role. The aim of the study is to identify whether the overexpression of Sirt1 in MSCs could restore skeletal growth retardation and osteoporosis in Bmi-1 deficient mice.

METHODS

We used our new generated transgenic mouse model that overexpresses Sirt1 in its MSCs (Sirt1^TG) to cross with Bmi-1^-/- mice to generate Bmi-1^-/- mice with Sirt1 overexpression in MSCs, and compared their skeletal metabolism with those of their Bmi-1^-/- and wild-type (WT) littermates (6 mice for each genotype) at 4 weeks of age using imaging, histopathological, immunohistochemical, histomorphometric, cellular, and molecular methods.

RESULTS

The levels of expression for Sirt1 were noticeably higher in the skeletal tissue of Sirt1^TG mice than in those of WT mice. In Comparison to WT mice, the body weight and size, skeletal size, bone volume, osteoblast number, alkaline phosphatase and type I collagen positive areas, osteogenic related gene expression levels were all significantly increased in the Sirt1^TG mice. Overexpression of Sirt1 in Bmi-1^-/- mouse MSCs resulted in a longer lifespan, improved skeletal growth and significantly increased bone mass by stimulating osteoblastic bone formation and inhibiting osteoclastic bone resorption in the Bmi-1^-/- mice, although the defects were not completely restored. Furthermore, Sirt1 overexpression in MSCs reduced the acetylation level of FOXO3a (Forkhead box O3a), increasing levels of expression for FOXO3a and SOD2 (Superoxide dismutase 2) in bony tissue, enhanced osteogenesis and reduced osteogenic cell senescence. We also demonstrated that nicotinamide, a Sirt1 inhibitor, blocks the effect of overexpression of Sirt1 in MSCs on osteogenesis and osteogenic cell senescence.

CONCLUSIONS

Taken together, these results demonstrate that Sirt1 overexpression in MSCs increased the osteoblastic bone formation and partially restores the defects in skeletal growth and osteogenesis in Bmi-1^-/- mice by FOXO3a deacetylation and oxidative stress inhibition. Our data support the proposal that Sirt1 is a target for promoting bone formation as an anabolic approach for the treatment of osteoporosis.

Cellular localization of the cell cycle inhibitor Cdkn1c controls growth arrest of adult skeletal muscle stem cells

Adult skeletal muscle maintenance and regeneration depend on efficient muscle stem cell (MuSC) functions. The mechanisms coordinating cell cycle with activation, renewal, and differentiation of MuSCs remain poorly understood. Here, we investigated how adult MuSCs are regulated by CDKN1c (p57^kip2), a cyclin-dependent kinase inhibitor, using mouse molecular genetics. In the absence of CDKN1c, skeletal muscle repair is severely impaired after injury. We show that CDKN1c is not expressed in quiescent MuSCs, while being induced in activated and proliferating myoblasts and maintained in differentiating myogenic cells. In agreement, isolated Cdkn1c-deficient primary myoblasts display differentiation defects and increased proliferation. We further show that the subcellular localization of CDKN1c is dynamic; while CDKN1c is initially localized to the cytoplasm of activated/proliferating myoblasts, progressive nuclear translocation leads to growth arrest during differentiation. We propose that CDKN1c activity is restricted to differentiating myoblasts by regulated cyto-nuclear relocalization, coordinating the balance between proliferation and growth arrest.

The imprinted gene Pw1/Peg3 regulates skeletal muscle growth, satellite cell metabolic state, and self-renewal

Pw1/Peg3 is an imprinted gene expressed from the paternally inherited allele. Several imprinted genes, including Pw1/Peg3, have been shown to regulate overall body size and play a role in adult stem cells. Pw1/Peg3 is expressed in muscle stem cells (satellite cells) as well as a progenitor subset of muscle interstitial cells (PICs) in adult skeletal muscle. We therefore examined the impact of loss-of-function of Pw1/Peg3 during skeletal muscle growth and in muscle stem cell behavior. We found that constitutive loss of Pw1/Peg3 function leads to a reduced muscle mass and myofiber number. In newborn mice, the reduction in fiber number is increased in homozygous mutants as compared to the deletion of only the paternal Pw1/Peg3 allele, indicating that the maternal allele is developmentally functional. Constitutive and a satellite cell-specific deletion of Pw1/Peg3, revealed impaired muscle regeneration and a reduced capacity of satellite cells for self-renewal. RNA sequencing analyses revealed a deregulation of genes that control mitochondrial function. Consistent with these observations, Pw1/Peg3 mutant satellite cells displayed increased mitochondrial activity coupled with accelerated proliferation and differentiation. Our data show that Pw1/Peg3 regulates muscle fiber number determination during fetal development in a gene-dosage manner and regulates satellite cell metabolism in the adult.

Overexpressed Sirt1 in MSCs Promotes Dentin Formation in Bmi1-Deficient Mice

Sirt1 promotes odontoblastic gene expression in human dental pulp cells, whereas the inhibition of Sirt1 downregulates the expression of those genes. To investigate whether the overexpression of Sirt1 in mesenchymal stem cells (MSCs) driven by Prx1 promoter could rescue the dentin formation defects in Bmi1-deficient (Bmi1^-/-) mice, we established the MSCs overexpressing Sirt1 in Bmi1 knockout mice (Sirt1^TGBmi1^-/-). First, we used Prx1-Cre/ROSA^nTnG mice to demonstrate that Prx1 linage cells exist mainly in the pulp horns at 4 wk of age. Second, we found that 4-wk-old Sirt1^TG mice had increased tooth volume as compared with wild-type (WT) littermates. The expression level of Sirt1 was significantly higher in dental papilla mesenchymal cells of Sirt1^TG mice than WT mice. Furthermore, we demonstrated that the tooth mineralization, dental volume, dentin sialoprotein-immunopositive areas, odontoblastic gene expression, and percentage of proliferating BrdU-positive cells were significantly elevated in the Sirt1^TG mice and dramatically reduced in the Bmi1^-/- mice versus the WT littermates at 4 wk of age. However, the areas of predentin and the percentage of TUNEL-positive apoptotic cells were significantly reduced in the Sirt1^TG mice but dramatically increased in the Bmi1^-/- mice as compared with the WT littermates. All these parameters were rescued in the Sirt1^TGBmi1^-/- mice versus the Bmi1^-/- mice. Finally, by using dental papilla mesenchymal cells, we found that the overexpression of Sirt1 rescued the reduced cell proliferation and differentiation and increased the cell apoptosis caused by Bmi1 deficiency, which was associated with increased p53 deacetylation. Therefore, this study indicates that Sirt1 is a potential therapeutic target for promoting dentin formation in an anabolic approach to the treatment of dental developmental defects.

Effect of Bmi1 over-expression on gene expression in adult and embryonic murine neural stem cells

The ability of isolated neural stem cells (NSCs) to proliferate as neurospheres is indicative of their competence as stem cells, and depends critically on the polycomb group (PcG) member Bmi1: knockdown of Bmi1 results in defective proliferation and self-renewal of isolated NSCs, whereas overexpression of Bmi1 enhances these properties. Here we report genome-wide changes in gene expression in embryonic and adult NSCs (eNSCs and aNSCs) caused by overexpression of Bmi1. We find that genes whose expression is altered by perturbations in Bmi1 levels in NSCs are mostly distinct from those affected in other multipotent stem/progenitor cells, such as those from liver and lung, aside from a small core of common targets that is enriched for genes associated with cell migration and mobility. We also show that genes differing in expression between prospectively isolated quiescent and activated NSCs are not affected by Bmi1 overexpression. In contrast, a comparison of genes showing altered expression upon Bmi1 overexpression in eNSCs and in aNSCs reveals considerable overlap, in spite of their different provenances in the brain and their differing developmental programs.

The putative tumor suppressor gene EphA7 is a novel BMI-1 target

Bmi1 was originally identified as a gene that contributes to the development of mouse lymphoma by inhibiting MYC-induced apoptosis through repression of Ink4a and Arf. It codes for the Polycomb group protein BMI-1 and acts primarily as a transcriptional repressor via chromatin modifications. Although it binds to a large number of genomic regions, the direct BMI-1 target genes described so far do not explain the full spectrum of BMI-1-mediated effects. Here we identify the putative tumor suppressor gene EphA7 as a novel direct BMI-1 target in neural cells and lymphocytes. EphA7 silencing has been reported in several different human tumor types including lymphomas, and our data suggest BMI1 overexpression as a novel mechanism leading to EphA7 inactivation via H3K27 trimethylation and DNA methylation.

Visualizing Changes in Cdkn1c Expression Links Early-Life Adversity to Imprint Mis-regulation in Adults

Imprinted genes are regulated according to parental origin and can influence embryonic growth and metabolism and confer disease susceptibility. Here, we designed sensitive allele-specific reporters to non-invasively monitor imprinted Cdkn1c expression in mice and showed that expression was modulated by environmental factors encountered in utero. Acute exposure to chromatin-modifying drugs resulted in de-repression of paternally inherited (silent) Cdkn1c alleles in embryos that was temporary and resolved after birth. In contrast, deprivation of maternal dietary protein in utero provoked permanent de-repression of imprinted Cdkn1c expression that was sustained into adulthood and occurred through a folate-dependent mechanism of DNA methylation loss. Given the function of imprinted genes in regulating behavior and metabolic processes in adults, these results establish imprinting deregulation as a credible mechanism linking early-life adversity to later-life outcomes. Furthermore, Cdkn1c-luciferase mice offer non-invasive tools to identify factors that disrupt epigenetic processes and strategies to limit their long-term impact.

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Allele-specific expression of imprinted Cdkn1c imaged in vivo using bioluminescence

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Chromatin-modifying drugs applied in utero transiently de-repress Cdkn1c imprinting

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In utero exposure to low-protein diet permanently disrupts the Cdkn1c imprint

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Folate supplements during gestation protect against loss of Cdkn1c imprinting

Deletion of the Imprinted Gene Grb10 Promotes Hematopoietic Stem Cell Self-Renewal and Regeneration

Imprinted genes are differentially expressed by adult stem cells, but their functions in regulating adult stem cell fate are incompletely understood. Here we show that growth factor receptor-bound protein 10 (Grb10), an imprinted gene, regulates hematopoietic stem cell (HSC) self-renewal and regeneration. Deletion of the maternal allele of Grb10 in mice (Grb10^m/+ mice) substantially increased HSC long-term repopulating capacity, as compared to that of Grb10^+/+ mice. After total body irradiation (TBI), Grb10^m/+ mice demonstrated accelerated HSC regeneration and hematopoietic reconstitution, as compared to Grb10^+/+ mice. Grb10-deficient HSCs displayed increased proliferation after competitive transplantation or TBI, commensurate with upregulation of CDK4 and Cyclin E. Furthermore, the enhanced HSC regeneration observed in Grb10-deficient mice was dependent on activation of the Akt/mTORC1 pathway. This study reveals a function for the imprinted gene Grb10 in regulating HSC self-renewal and regeneration and suggests that the inhibition of Grb10 can promote hematopoietic regeneration in vivo.

Expression of polycomb protein BMI-1 maintains the plasticity of basal bronchial epithelial cells

The airway epithelium is altered in respiratory disease and is thought to contribute to disease etiology. A caveat to disease research is that the technique of isolation of bronchial epithelial cells from patients is invasive and cells have a limited lifespan. The aim of this study was to extensively characterize the plasticity of primary human bronchial epithelial cells that have been engineered to delay cell senescence including the ability of these cells to differentiate. Cells were engineered to express BMI‐1 or hTERT using viral vector systems. Cells were characterized at passage (p) early (p5), mid (p10), and late (p15) stage for: BMI‐1, p16, and CK14 protein expression, viability and the ability to differentiate at air–liquid interface (ALI), using a range of techniques including immunohistochemistry (IHC), immunofluorescence (IF), transepithelial electrical resistance (TEER), scanning electron microscopy (SEM), MUC5AC and beta tubulin (BTUB) staining. BMI‐1‐expressing cells maintained elevated levels of the BMI‐1 protein and the epithelial marker CK14 and showed a suppression of p16. BMI‐1‐expressing cells had a viability advantage, differentiated at ALI, and had a normal karyotype. In contrast, hTERT‐expressing cells had a reduced viability, showed limited differentiation, and had an abnormal karyotype. We therefore provide extensive characterization of the plasticity of BMI‐1 expressing cells in the context of the ALI model. These cells retain properties of wild‐type cells and may be useful to characterize respiratory disease mechanisms in vitro over sustained periods.

Intersections of lung progenitor cells, lung disease and lung cancer

The use of stem cell biology approaches to study adult lung progenitor cells and lung cancer has brought a variety of new techniques to the field of lung biology and has elucidated new pathways that may be therapeutic targets in lung cancer. Recent results have begun to identify the ways in which different cell populations interact to regulate progenitor activity, and this has implications for the interventions that are possible in cancer and in a variety of lung diseases. Today's better understanding of the mechanisms that regulate lung progenitor cell self-renewal and differentiation, including understanding how multiple epigenetic factors affect lung injury repair, holds the promise for future better treatments for lung cancer and for optimising the response to therapy in lung cancer. Working between platforms in sophisticated organoid culture techniques, genetically engineered mouse models of injury and cancer, and human cell lines and specimens, lung progenitor cell studies can begin with basic biology, progress to translational research and finally lead to the beginnings of clinical trials.

Stem cell biology has brought new techniques to the lung field and has elucidated possible therapeutic pathwayshttp://ow.ly/h74x30cA6Lo

Lkb1 inactivation drives lung cancer lineage switching governed by Polycomb Repressive Complex 2

Adenosquamous lung tumours, which are extremely poor prognosis, may result from cellular plasticity. Here, we demonstrate lineage switching of KRAS+ lung adenocarcinomas (ADC) to squamous cell carcinoma (SCC) through deletion of Lkb1 (Stk11) in autochthonous and transplant models. Chromatin analysis reveals loss of H3K27me3 and gain of H3K27ac and H3K4me3 at squamous lineage genes, including Sox2, ΔNp63 and Ngfr. SCC lesions have higher levels of the H3K27 methyltransferase EZH2 than the ADC lesions, but there is a clear lack of the essential Polycomb Repressive Complex 2 (PRC2) subunit EED in the SCC lesions. The pattern of high EZH2, but low H3K27me3 mark, is also prevalent in human lung SCC and SCC regions within ADSCC tumours. Using FACS-isolated populations, we demonstrate that bronchioalveolar stem cells and club cells are the likely cells-of-origin for SCC transitioned tumours. These findings shed light on the epigenetics and cellular origins of lineage-specific lung tumours.

The mechanisms that govern the transdifferentiation of lung adenocarcinomas (ADC) to squamous cell carcinoma (SCC) are not fully understood. Here, the authors show that EZH2 loss exacerbates the transdifferentiation of ADCs to SCCs as a result of chromatin changes that lead to expression of squamous differentiation genes.

[Advances in Classification and Research Methods of Lung Epithelial Stem and Progenitor Cells]

分离和鉴定肺上皮干/祖细胞，深入了解他们在肺脏生理病理条件下的具体作用机理，对于防治包括肺癌在内的肺脏疾病有重要意义。本综述介绍了已鉴定的肺上皮干/祖细胞种类和肺上皮干/祖细胞研究方法的最新进展，前者具有区域特异性，主要包括位近端气道的基底细胞和导管细胞，位细支气管的Clara细胞、变异Clara细胞、细支气管肺泡干细胞和诱导出的krt5⁺细胞及位肺泡的Ⅱ型肺泡上皮细胞和Ⅱ型肺泡上皮祖细胞；后者主要包括肺损伤模型、谱系示踪技术、三维培养技术、移植、慢性标记细胞法及单细胞转录组学分析等。最后简述了肺上皮干/祖细胞与肺癌的关系以及肺癌干细胞靶向药物治疗进展。

Regulatory links between imprinted genes: evolutionary predictions and consequences

Genomic imprinting is essential for development and growth and plays diverse roles in physiology and behaviour. Imprinted genes have traditionally been studied in isolation or in clusters with respect to cis-acting modes of gene regulation, both from a mechanistic and evolutionary point of view. Recent studies in mammals, however, reveal that imprinted genes are often co-regulated and are part of a gene network involved in the control of cellular proliferation and differentiation. Moreover, a subset of imprinted genes acts in trans on the expression of other imprinted genes. Numerous studies have modulated levels of imprinted gene expression to explore phenotypic and gene regulatory consequences. Increasingly, the applied genome-wide approaches highlight how perturbation of one imprinted gene may affect other maternally or paternally expressed genes. Here, we discuss these novel findings and consider evolutionary theories that offer a rationale for such intricate interactions among imprinted genes. An evolutionary view of these trans-regulatory effects provides a novel interpretation of the logic of gene networks within species and has implications for the origin of reproductive isolation between species.

Paternal Insulin-like Growth Factor 2 (Igf2) Regulates Stem Cell Activity During Adulthood

Insulin-like Growth Factor 2 (IGF2) belongs to the IGF/Insulin pathway, a highly conserved evolutionarily network that regulates growth, aging and lifespan. Igf2 is highly expressed in the embryo and in cancer cells. During mouse development, Igf2 is expressed in all sites where hematopoietic stem cells (HSC) successively expand, then its expression drops at weaning and becomes undetectable when adult HSC have reached their niches in bones and start to self-renew. In the present study, we aim to discover the role of IGF2 during adulthood. We show that Igf2 is specifically expressed in adult HSC and we analyze HSC from adult mice deficient in Igf2 transcripts. We demonstrate that Igf2 deficiency avoids the age-related attrition of the HSC pool and that Igf2 is necessary for tissue homeostasis and regeneration. Our study reveals that the expression level of Igf2 is critical to maintain the balance between stem cell self-renewal and differentiation, presumably by regulating the interaction between HSC and their niche. Our data have major clinical interest for transplantation: understanding the changes in adult stem cells and their environments will improve the efficacy of regenerative medicine and impact health- and life-span.

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The imprinted gene Igf2 is expressed in adult tissue stem cells.

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Igf2 deficiency increases HSC (hematopoietic stem cells) self-renewal and avoids age-related attrition of the HSC pool.

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Igf2 deficiency decreases HSC differentiation and mobilization.

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Igf2 deficiency modifies the interaction between HSC and their environment.

IGF2 belongs to the IGF/Insulin family that regulates growth, aging and lifespan. This role is evolutionarily conserved from worms to mammals. IGF2 favors cell proliferation during embryonic development but its role in adulthood is unknown. To decipher its function we undertook a lifelong analysis of the consequences of Igf2 deficiency on hematopoiesis, in steady-state conditions and during bone marrow transplantation. We demonstrate that lowering Igf2 levels increases the pool of stem cells, without uncontrolled proliferation and migration of immature cells that would lead to cancer. This is a promising way to enhance the stem cells pool during aging that has major interest for transplantation.

Ezh2 restricts the smooth muscle lineage during mouse lung mesothelial development

During development, the lung mesoderm generates a variety of cell lineages, including airway and vascular smooth muscle. Epigenetic changes in adult lung mesodermal lineages are thought to contribute towards diseases such as idiopathic pulmonary fibrosis and chronic obstructive pulmonary disease, although the factors that regulate early lung mesoderm development are unknown. We show in mouse that the PRC2 component Ezh2 is required to restrict smooth muscle differentiation in the developing lung mesothelium. Mesodermal loss of Ezh2 leads to the formation of ectopic smooth muscle in the submesothelial region of the developing lung mesoderm. Loss of Ezh2 specifically in the developing mesothelium reveals a mesothelial cell-autonomous role for Ezh2 in repression of the smooth muscle differentiation program. Loss of Ezh2 derepresses expression of myocardin and Tbx18, which are important regulators of smooth muscle differentiation from the mesothelium and related cell lineages. Together, these findings uncover an Ezh2-dependent mechanism to restrict the smooth muscle gene expression program in the developing mesothelium and allow appropriate cell fate decisions to occur in this multipotent mesoderm lineage.

B-cell-specific Moloney murine leukemia virus integration site 1: potential stratification factor and therapeutic target for epithelial ovarian cancer

Epithelial ovarian cancer, a vexing challenge for clinical management, still lacks biomarkers for early diagnosis, precise stratification, and prognostic evaluation of patients. B-cell-specific Moloney murine leukemia virus integration site 1 (BMI1), a member of the polycomb group of proteins, engages in diverse cellular processes, including proliferation, differentiation, senescence, and stem cell renewal. In addition, BMI1, as a cancer stem-cell marker, participates in tumorigenesis through various pathways. Rewardingly, recent studies have also revealed a relationship between BMI1 expression and the clinical grade/stage, therapy response, and survival outcome in a majority of human malignancies, including epithelial ovarian cancer. Therefore, BMI1 might serve as a potential stratification factor and treatment target for epithelial ovarian cancer, pending evidence from further investigations.

Lung cancer stem cells-characteristics, phenotype

Lung cancer remains a major cause of cancer-related deaths worldwide with unfavourable prognosis mainly due to the late stage of disease at presentation. High incidence and disease recurrence rates are a fact despite advances in treatment. Ongoing experimental and clinical observations suggest that the malignant phenotype in lung cancer is sustained by lung cancer stem cells (CSCs) which are putative stem cells situated throughout the airways that have the potential of initiating lung cancer formation. These cells share the common characteristic of increased proliferation and differentiation, long life span and resistance to chemotherapy and radiation therapy. This review summarises the current knowledge on their characteristics and phenotype.

Maternal-fetal conflict, genomic imprinting and mammalian vulnerabilities to cancer

Antagonistic coevolution between maternal and fetal genes, and between maternally and paternally derived genes may have increased mammalian vulnerability to cancer. Placental trophoblast has evolved to invade maternal tissues and evade structural and immunological constraints on its invasion. These adaptations can be co-opted by cancer in intrasomatic selection. Imprinted genes of maternal and paternal origin favour different degrees of proliferation of particular cell types in which they reside. As a result, the set of genes favouring greater proliferation will be selected to evade controls on cell-cycle progression imposed by the set of genes favouring lesser proliferation. The dynamics of stem cell populations will be a particular focus of this intragenomic conflict. Gene networks that are battlegrounds of intragenomic conflict are expected to be less robust than networks that evolve in the absence of conflict. By these processes, maternal-fetal and intragenomic conflicts may undermine evolved defences against cancer.

Properties of Adult Lung Stem and Progenitor Cells

The last decade has seen significant progress in understanding the organisation of regenerative cells in the adult lung. Cell-lineage tracing and in vitro clonogenic assays have enabled the identification and characterisation of endogenous lung epithelial stem and progenitor cells. Selective lung injury models, and genetically engineered mice have revealed highly conserved gene networks, factors, signalling pathways, and cellular interactions important in maintaining lung homeostasis and regulating lung regeneration and repair following injury. This review describes the current models of lung epithelial stem and progenitor cell organisation in adult mice, and the impediments encountered in translational studies aiming to identify and characterise their human homologs. J. Cell. Physiol. 231: 2582-2589, 2016. © 2016 Wiley Periodicals, Inc.

Cdkn1c Boosts the Development of Brown Adipose Tissue in a Murine Model of Silver Russell Syndrome

The accurate diagnosis and clinical management of the growth restriction disorder Silver Russell Syndrome (SRS) has confounded researchers and clinicians for many years due to the myriad of genetic and epigenetic alterations reported in these patients and the lack of suitable animal models to test the contribution of specific gene alterations. Some genetic alterations suggest a role for increased dosage of the imprinted CYCLIN DEPENDENT KINASE INHIBITOR 1C (CDKN1C) gene, often mutated in IMAGe Syndrome and Beckwith-Wiedemann Syndrome (BWS). Cdkn1c encodes a potent negative regulator of fetal growth that also regulates placental development, consistent with a proposed role for CDKN1C in these complex childhood growth disorders. Here, we report that a mouse modelling the rare microduplications present in some SRS patients exhibited phenotypes including low birth weight with relative head sparing, neonatal hypoglycemia, absence of catch-up growth and significantly reduced adiposity as adults, all defining features of SRS. Further investigation revealed the presence of substantially more brown adipose tissue in very young mice, of both the classical or canonical type exemplified by interscapular-type brown fat depot in mice (iBAT) and a second type of non-classic BAT that develops postnatally within white adipose tissue (WAT), genetically attributable to a double dose of Cdkn1c in vivo and ex-vivo. Conversely, loss-of-function of Cdkn1c resulted in the complete developmental failure of the brown adipocyte lineage with a loss of markers of both brown adipose fate and function. We further show that Cdkn1c is required for post-transcriptional accumulation of the brown fat determinant PR domain containing 16 (PRDM16) and that CDKN1C and PRDM16 co-localise to the nucleus of rare label-retaining cell within iBAT. This study reveals a key requirement for Cdkn1c in the early development of the brown adipose lineages. Importantly, active BAT consumes high amounts of energy to generate body heat, providing a valid explanation for the persistence of thinness in our model and supporting a major role for elevated CDKN1C in SRS.

Silver Russell syndrome is a severe developmental disorder characterised by low birth weight, sparing of the head and neonatal hypoglycemia. SRS adults are small and can be extremely thin, lacking body fat. Numerous genetic and epigenetic mutations have been linked to SRS primarily involving imprinted genes, but progress has been hampered by the lack of a suitable animal model. Here we describe a mouse model of the rare micro duplications reported in some SRS patients, which recapitulated many of the defining features of SRS, including extreme thinness. We showed that these mice possessed substantially more of the energy consuming brown adipose tissue (BAT), driven by a double dose of the imprinted Cdkn1c gene. We further show that Cdkn1c is required for the postranscriptional accumulation of the BAT determinant PRDM16 and that these proteins co-localise to the nucleus of in a rare label-retaining cell within BAT. These data suggest that Cdkn1c contributes to the development of BAT by modulating PRDM16 and supports a major role for this gene in SRS.

Polycomb Repressive Complex 2 Is a Barrier to KRAS-Driven Inflammation and Epithelial-Mesenchymal Transition in Non-Small-Cell Lung Cancer

Polycomb repressive complexes (PRC) are frequently implicated in human cancer, acting either as oncogenes or tumor suppressors. Here, we show that PRC2 is a critical regulator of KRAS-driven non-small cell lung cancer progression. Modulation of PRC2 by either Ezh2 overexpression or Eed deletion enhances KRAS-driven adenomagenesis and inflammation, respectively. Eed-loss-driven inflammation leads to massive macrophage recruitment and marked decline in tissue function. Additional Trp53 inactivation activates a cell-autonomous epithelial-to-mesenchymal transition program leading to an invasive mucinous adenocarcinoma. A switch between methylated/acetylated chromatin underlies the tumor phenotypic evolution, prominently involving genes controlled by Hippo/Wnt signaling. Our observations in the mouse models were conserved in human cells. Importantly, PRC2 inactivation results in context-dependent phenotypic alterations, with implications for its therapeutic application.

A Novel Aspect of Tumorigenesis-BMI1 Functions in Regulating DNA Damage Response

BMI1 plays critical roles in maintaining the self-renewal of hematopoietic, neural, intestinal stem cells, and cancer stem cells (CSCs) for a variety of cancer types. BMI1 promotes cell proliferative life span and epithelial to mesenchymal transition (EMT). Upregulation of BMI1 occurs in multiple cancer types and is associated with poor prognosis. Mechanistically, BMI1 is a subunit of the Polycomb repressive complex 1 (PRC1), and binds the catalytic RING2/RING1b subunit to form a functional E3 ubiquitin ligase. Through mono-ubiquitination of histone H2A at lysine 119 (H2A-K119Ub), BMI1 represses multiple gene loci; among these, the INK4A/ARF locus has been most thoroughly investigated. The locus encodes the p16INK4A and p14/p19ARF tumor suppressors that function in the pRb and p53 pathways, respectively. Its repression contributes to BMI1-derived tumorigenesis. BMI1 also possesses other oncogenic functions, specifically its regulative role in DNA damage response (DDR). In this process, BMI1 ubiquitinates histone H2A and γH2AX, thereby facilitating the repair of double-stranded DNA breaks (DSBs) through stimulating homologous recombination and non-homologous end joining. Additionally, BMI1 compromises DSB-induced checkpoint activation independent of its-associated E3 ubiquitin ligase activity. We review the emerging role of BMI1 in DDR regulation and discuss its impact on BMI1-derived tumorigenesis.

The Dlk1-Gtl2 Locus Preserves LT-HSC Function by Inhibiting the PI3K-mTOR Pathway to Restrict Mitochondrial Metabolism

The mammalian imprinted Dlk1-Gtl2 locus produces multiple non-coding RNAs (ncRNAs) from the maternally inherited allele, including the largest miRNA cluster in the mammalian genome. This locus has characterized functions in some types of stem cell, but its role in hematopoietic stem cells (HSCs) is unknown. Here, we show that the Dlk1-Gtl2 locus plays a critical role in preserving long-term repopulating HSCs (LT-HSCs). Through transcriptome profiling in 17 hematopoietic cell types, we found that ncRNAs expressed from the Dlk1-Gtl2 locus are predominantly enriched in fetal liver HSCs and the adult LT-HSC population and sustain long-term HSC functionality. Mechanistically, the miRNA mega-cluster within the Dlk1-Gtl2 locus suppresses the entire PI3K-mTOR pathway. This regulation in turn inhibits mitochondrial biogenesis and metabolic activity and protects LT-HSCs from excessive reactive oxygen species (ROS) production. Our data therefore show that the imprinted Dlk1-Gtl2 locus preserves LT-HSC function by restricting mitochondrial metabolism.

miR-300 mediates Bmi1 function and regulates differentiation in primitive cardiac progenitors

B lymphoma Mo-MLV insertion region 1 (Bmi1) is a polycomb-family transcriptional factor critical for self-renewal in many adult stem cells and human neoplasia. We sought to identify microRNAs regulated by Bmi1 that could play a role in multipotent cardiac progenitor cell (CPC) decisions. We found that miR-300, a poorly characterized microRNA mapping in the Dlk1-Dio3 microRNA cluster, was positively regulated by Bmi1 in CPCs. Forced expression of miR-300 in CPCs promoted an improved stemness signature with a significant increase in Oct4 levels, a reduction in senescence progression and an enhanced proliferative status via p19 activation and inhibition of p16 accumulation. Endothelial and cardiogenic differentiation were clearly compromised by sustained miR-300 expression. Additionally, RNA and protein analysis revealed a significant reduction in key cardiac transcription factors, including Nkx2.5 and Tbx5. Collectively, these results suggest that some functions attributed to Bmi1 are due to induction of miR-300, which decreases the cardiogenic differentiation potential of multipotent CPCs in vitro and promotes self-renewal.