Bmi1, stem cells, and senescence regulation

Rejuvenation of human mesenchymal stem cells using a nonintegrative and conditionally removable Sendai virus vector

Human mesenchymal stem cells (hMSCs) with extended lifespan and differentiation potential that can recapitulate in vivo characteristics could significantly contribute to basic research, drug development, and cell therapy. Specifically, they could ensure a stable supply of specific cellular resources, and possibly extracellular vesicles. Here, we established a technology for extending the lifespan while maintaining differentiation potential, termed "rejuvenation," of hMSCs (rej-hMSCs) using nonintegrative and conditionally removable temperature-sensitive Sendai virus (SeV) vectors. Various immortalizing factors (i.e., Bmi-1, hTERT, SV40T, and/or HPV E6/E7) were first introduced by the SeV vector into the cells. A combination of three SeVs with Bmi-1, hTERT, or SV40T conferred markedly improved cell proliferation and cloning ability while maintaining differentiation potential and a normal karyotype. An extended lifespan was also demonstrated in other cell types. The rejuvenation of long-passaged or aged hMSCs was also confirmed. SeV vectors were rapidly removed as a function of cell doubling by increasing the temperature from 35 °C to 37 °C or higher, while proliferative ability was maintained. Following FACS sorting, the complete removal of SeV vectors was confirmed by qPCR analyses. Therefore, our cell rejuvenation technology could contribute to research and clinical applications by enabling the supply of modified cells without damaging host chromosomes.

Role of mitochondria in endogenous renal repair

Renal tubules have potential to regenerate and repair after mild-to-moderate injury. Proliferation of tubular epithelial cells represents the initial step of this reparative process. Although for many years, it was believed that proliferating cells originated from a pre-existing intra-tubular stem cell population, there is now consensus that surviving tubular epithelial cells acquire progenitor properties to regenerate the damaged kidney. Scattered tubular-like cells (STCs) are dedifferentiated adult renal tubular epithelial cells that arise upon injury and contribute to renal self-healing and recovery by replacing lost neighboring tubular epithelial cells. These cells are characterized by the co-expression of the stem cell surface markers CD133 and CD24, as well as mesenchymal and kidney injury markers. Previous studies have shown that exogenous delivery of STCs ameliorates renal injury and dysfunction in murine models of acute kidney injury, underscoring the regenerative potential of this endogenous repair system. Although STCs contain fewer mitochondria than their surrounding terminally differentiated tubular epithelial cells, these organelles modulate several important cellular functions, and their integrity and function are critical to preserve the reparative capacity of STCs. Recent data suggest that the microenviroment induced by cardiovascular risk factors, such as obesity, hypertension, and renal ischemia may compromise STC mitochondrial integrity and function, limiting the capacity of these cells to repair injured renal tubules. This review summarizes current knowledge of the contribution of STCs to kidney repair and discusses recent insight into the key role of mitochondria in modulating STC function and their vulnerability in the setting of cardiovascular disease.

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.

Effect of Helichrysum italicum in Promoting Collagen Deposition and Skin Regeneration in a New Dynamic Model of Skin Wound Healing

Natural products have many healing effects on the skin with minimal or no adverse effects. In this study, we analyzed the regenerative properties of a waste product (hydrolate) derived from Helichrysum italicum (HH) on scratch-tested skin cell populations seeded on a fluidic culture system. Helichrysum italicum has always been recognized in the traditional medicine of Mediterranean countries for its wide pharmacological activities. We recreated skin physiology with a bioreactor that mimics skin stem cell (SSCs) and fibroblast (HFF1) communication as in vivo skin layers. Dynamic culture models represent an essential instrument for recreating and preserving the complex multicellular organization and interactions of the cellular microenvironment. Both cell types were exposed to two different concentrations of HH after the scratch assay and were compared to untreated control cells. Collagen is the constituent of many wound care products that act directly on the damaged wound environment. We analyzed the role played by HH in stimulating collagen production during tissue repair, both in static and dynamic culture conditions, by a confocal microscopic analysis. In addition, we performed a gene expression analysis that revealed the activation of a molecular program of stemness in treated skin stem cells. Altogether, our results indicate a future translational application of this natural extract to support skin regeneration and define a new protocol to recreate a dynamic process of healing.

Epigenetic modifier G9a is involved in regulation of mouse tongue development

OBJECTIVES

The tongue comprises multiple tissues of different embryonic origins, including pharyngeal arch, somite, and cranial neural crest (CNC). However, its developmental regulatory mechanisms, especially those involving epigenetic modifiers, remain poorly understood. This study examined the roles of the epigenetic modifier G9a in murine tongue development.

METHODS

We deleted G9a using Sox 9 (SRY-related HMG-box gene 9)-Cre recombinase, which acts in tongue progenitor cells, including CNC-derived cells, to generate G9a conditional knockout (cKO) mice. Histochemical and immunohistochemical analyses were conducted on sections prepared from tongue tissues of control and cKO mice.

RESULTS

Cre-dependent LacZ reporter mice, generated by crossing Rosa-LacZ mice with sox9-Cre mice, revealed Cre recombinase activity in the mucosal epithelium and tongue connective tissue of the embryonic tongue. Tongue volume was significantly reduced on embryonic day 17.5 (E17.5) and postnatal day 0 (P0) in cKO mice. Histological sections showed that the lingual mucosal epithelium was thinner in cKO mice. Reduced G9a levels were accompanied by decreased levels of a G9a substrate, dimethylated lysine 9 in histone H3, in the embryonic tongue. BrdU injection at E16.5 revealed reduced numbers of BrdU-positive cells in the mucosal epithelium and underlying connective tissue at E17.5 in cKO mice, indicating suppression of cell proliferation in both tissues. Investigation of keratin 5 and 8 protein localization showed significantly suppressed expression in the lingual mucosal epithelium in cKO mice.

CONCLUSIONS

G9a is required for proper proliferation and differentiation of sox9-expressing tongue progenitor cells and is thereby involved in tongue development.

Electrospun Nanofibers Encapsulated with Natural Products: A Novel Strategy to Counteract Skin Aging

The skin is the primary tissue affected by wounds and aging, significantly impacting its protective function. Natural products are widely used in cosmetics, representing a new approach to preventing age-related damage. Nanomedicine combines nanotechnology and traditional treatments to create innovative drugs. The main targets of nanotechnological approaches are wound healing, regeneration, and rejuvenation of skin tissue. The skin barrier is not easily permeable, and the creation of modern nanodevices is a way to improve the passive penetration of substances. In this study, Helichrysum italicum oil (HO) was combined with different types of electrospun nanofibers to study their protective activity on the skin and to evaluate their future application for topical treatments. In the present research, we used biodegradable polymers, including polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP), which were characterized by a scanning electron microscope (SEM). All results show a positive trend in cell proliferation and viability of human skin stem cells (SSCs) and BJ fibroblasts pre-treated with combined nanofibers and then exposed to UV stress. Gene expression analysis revealed the activation of a molecular rejuvenation program in SSCs treated with functionalized nanofibers before UV exposure. Understanding the mechanisms involved in skin changes during aging allows for the future application of nanomaterials combined with HO directly to the patients.

Peptidase inhibitor 16 promotes inflammatory arthritis by suppressing Foxp3 expression via regulating K48-linked ubiquitin degradation Bmi-1 in regulatory T cells

Abnormalities of regulatory T cells (Tregs) has been suggested in rheumatoid arthritis (RA), and Forkhead box P3 (Foxp3) is the key transcriptional factor of Tregs expression. However, the underlying molecular mechanism remains unclear. Here, we demonstrated peptidase inhibitor 16 (PI16) was significantly increased in the peripheral blood, synovial fluid, and synovial tissue from RA patients. PI16 transgenic mice (PI16Tg) aggravated arthritis severity partly through suppressing Foxp3 expression. Mechanistically, PI16 could interact with and stabilize Bmi-1 in Tregs via inhibiting K48-linked polyubiquitin of Bmi-1, which promotes the enrichment of repressive histone mark in Foxp3 promoter. Furthermore, Bmi-1 specific inhibitor PTC209 could restore Foxp3 expression and alleviate arthritis progression in PI16Tg mice, accompanied by increased recruitment of active histone mark in the promoter of Tregs. Our results suggest that PI16-Bmi-1 axis plays an important role in RA and other autoimmune diseases by suppressing Foxp3 expression in Tregs via Bmi-1-mediated histone modification.

Cathepsin-facilitated invasion of BMI1-high hepatocellular carcinoma cells drives bile duct tumor thrombi formation

Bile duct tumor thrombosis (BDTT) is a complication mostly observed in patients with advanced hepatocellular carcinoma (HCC), causing jaundice and associated with poor clinical outcome. However, its underlying molecular mechanism is unclear. Here, we develop spontaneous preclinical HCC animal models with BDTT to identify the role of BMI1 expressing tumor initiating cells (BMI1high TICs) in inducing BDTT. BMI1 overexpression transforms liver progenitor cells into BMI1high TICs, which possess strong tumorigenicity and increased trans-intrahepatic biliary epithelial migration ability by secreting lysosomal cathepsin B (CTSB). Orthotopic liver implantation of BMI1high TICs into mice generates tumors and triggers CTSB mediated bile duct invasion to form tumor thrombus, while CTSB inhibitor treatment prohibits BDTT and extends mouse survival. Clinically, the elevated serum CTSB level determines BDTT incidence in HCC patients. Mechanistically, BMI1 epigenetically up-regulates CTSB secretion in TICs by repressing miR-218-1-3p expression. These findings identify a potential diagnostic and therapeutic target for HCC patients with BDTT.

Targeting BMI-1 to deplete antibody-secreting cells in autoimmunity

Objectives

B cells drive the production of autoreactive antibody-secreting cells (ASCs) in autoimmune diseases such as Systemic Lupus Erythematosus (SLE) and Sjögren's syndrome, causing long-term organ damage. Current treatments for antibody-mediated autoimmune diseases target B cells or broadly suppress the immune system. However, pre-existing long-lived ASCs are often refractory to treatment, leaving a reservoir of autoreactive cells that continue to produce antibodies. Therefore, the development of novel treatment methods targeting ASCs is vital to improve patient outcomes. Our objective was to test whether targeting the epigenetic regulator BMI-1 could deplete ASCs in autoimmune conditions in vivo and in vitro.

Methods

Use of a BMI-1 inhibitor in both mouse and human autoimmune settings was investigated. Lyn -/- mice, a model of SLE, were treated with the BMI-1 small molecule inhibitor PTC-028, before assessment of ASCs, serum antibody and immune complexes. To examine human ASC survival, a novel human fibroblast-based assay was established, and the impact of PTC-028 on ASCs derived from Sjögren's syndrome patients was evaluated.

Results

BMI-1 inhibition significantly decreased splenic and bone marrow ASCs in Lyn -/- mice. The decline in ASCs was linked to aberrant cell cycle gene expression and led to a significant decrease in serum IgG3, immune complexes and anti-DNA IgG. PTC-028 was also efficacious in reducing ex vivo plasma cell survival from both Sjögren's syndrome patients and age-matched healthy donors.

Conclusion

These data provide evidence that inhibiting BMI-1 can deplete ASC in a variety of contexts and thus BMI-1 is a viable therapeutic target for antibody-mediated autoimmune diseases.

LRRC15 expression indicates high level of stemness regulated by TWIST1 in mesenchymal stem cells

Mesenchymal stem cells (MSCs) are used as a major source for cell therapy, and its application is expanding in various diseases. On the other hand, reliable method to evaluate quality and therapeutic properties of MSC is limited. In this study, we focused on TWIST1 that is a transcription factor regulating stemness of MSCs and found that the transmembrane protein LRRC15 tightly correlated with the expression of TWIST1 and useful to expect TWIST1-regulated stemness of MSCs. The LRRC15-positive MSC populations in human and mouse bone marrow tissues highly expressed stemness-associated transcription factors and therapeutic cytokines, and showed better therapeutic effect in bleomycin-induced pulmonary fibrosis model mice. This study provides evidence for the important role of TWIST1 in the MSC stemness, and for the utility of the LRRC15 protein as a marker to estimate stem cell quality in MSCs before cell transplantation.

Immortalization Reversibility in the Context of Cell Therapy Biosafety

Immortalization (genetically induced prevention of replicative senescence) is a promising approach to obtain cellular material for cell therapy or for bio-artificial organs aimed at overcoming the problem of donor material shortage. Immortalization is reversed before cells are used in vivo to allow cell differentiation into the mature phenotype and avoid tumorigenic effects of unlimited cell proliferation. However, there is no certainty that the process of de-immortalization is 100% effective and that it does not cause unwanted changes in the cell. In this review, we discuss various approaches to reversible immortalization, emphasizing their advantages and disadvantages in terms of biosafety. We describe the most promising approaches in improving the biosafety of reversibly immortalized cells: CRISPR/Cas9-mediated immortogene insertion, tamoxifen-mediated self-recombination, tools for selection of successfully immortalized cells, using a decellularized extracellular matrix, and ensuring post-transplant safety with the use of suicide genes. The last process may be used as an add-on for previously existing reversible immortalized cell lines.

The role of BMI1 in endometrial cancer and other cancers

Endometrial cancer (EC) is the third leading gynecological malignancy, and its treatment remains challenging. B cell-specific Moloney murine leukemia virus integration site-1 (BMI1) is one of the core members of the polycomb group (PcG) family, which plays a promoting role in the occurrence and development of various tumors. Notably, BMI1 has been found to be frequently upregulated in endometrial cancer (EC) and promote the occurrence of EC through promoting epithelial-mesenchymal transition (EMT) and AKT/PI3K pathways. This review summarizes the structure and upstream regulatory mechanisms of BMI1 and its role in EC. In addition, we focused on the role of BMI1 in chemoradiotherapy resistance and summarized the current drugs that target BMI1.

Aging and Mesenchymal Stem Cells: Basic Concepts, Challenges and Strategies

Aging and frailty are complex processes implicating multifactorial mechanisms, such as replicative senescence, oxidative stress, mitochondrial dysfunction, or autophagy disorder. All of these mechanisms drive dramatic changes in the tissue environment, such as senescence-associated secretory phenotype factors and inflamm-aging. Thus, there is a demand for new therapeutic strategies against the devastating effects of the aging and associated diseases. Mesenchymal stem cells (MSC) participate in a "galaxy" of tissue signals (proliferative, anti-inflammatory, and antioxidative stress, and proangiogenic, antitumor, antifibrotic, and antimicrobial effects) contributing to tissue homeostasis. However, MSC are also not immune to aging. Three strategies based on MSC have been proposed: remove, rejuvenate, or replace the senescent MSC. These strategies include the use of senolytic drugs, antioxidant agents and genetic engineering, or transplantation of younger MSC. Nevertheless, these strategies may have the drawback of the adverse effects of prolonged use of the different drugs used or, where appropriate, those of cell therapy. In this review, we propose the new strategy of "Exogenous Restitution of Intercellular Signalling of Stem Cells" (ERISSC). This concept is based on the potential use of secretome from MSC, which are composed of molecules such as growth factors, cytokines, and extracellular vesicles and have the same biological effects as their parent cells. To face this cell-free regenerative therapy challenge, we have to clarify key strategy aspects, such as establishing tools that allow us a more precise diagnosis of aging frailty in order to identify the therapeutic requirements adapted to each case, identify the ideal type of MSC in the context of the functional heterogeneity of these cellular populations, to optimize the mass production and standardization of the primary materials (cells) and their secretome-derived products, to establish the appropriate methods to validate the anti-aging effects and to determine the most appropriate route of administration for each case.

Identification of proline-rich protein 11 as a major regulator in mouse spermatogonia maintenance via an increase in BMI1 protein stability

BACKGROUND

Spermatogenesis accompanied by self-renewal and differentiation of spermatogonia under complicated regulation is crucial for male fertility. Our previous study demonstrated that the loss of the B-lymphoma Mo-MLV insertion region 1 (BMI1) could cause male infertility and found a potential interaction between BMI1 and proline-rich protein 11 (PRR11); however, the specific co-regulatory effects of BMI1/PRR11 on spermatogonia maintenance remain unclear.

METHODS AND RESULTS

The expression of PRR11 was downregulated in a mouse spermatogonia cell line (GC-1) via transfection with PRR11-siRNAs, and PRR11 knockdown was verified by real-time reverse transcriptase polymerase chain reaction (RT-qPCR). The proliferative activity of GC-1 cells was determined using the cell counting kit (CCK-8), colony formation, and 5-ethynyl-2-deoxyuridine (EdU) incorporation assay. A Transwell assay was performed to evaluate the effects of PRR11 on GC-1 cell migration. A terminal deoxynucleotidyl transferase dUTP nick end labeling assay was used to measure GC-1 cell apoptosis. Furthermore, co-immunoprecipitation, RT-qPCR, and western blot analyses were used for investigating the regulatory mechanisms involved in this regulation. It was found that downregulation of PRR11 could cause a marked inhibition of proliferation and migration and induced apoptosis in GC-1 cells. Moreover, silencing of PRR11 obviously led to a reduction in the BMI1 protein level. PRR11 was found to interact with BMII at the endogenous protein level. PRR11 knockdown produced a decrease in BMI1 protein stability via an increase in BMI1 ubiquitination after which derepression in the transcription of protein tyrosine phosphatase receptor type M (Ptprm) occurred. Importantly, knockdown of Ptprm in PRR11-deficient GC-1 cells led to a reversal of proliferation and migration of GC-1 cells.

CONCLUSIONS

This study uncovered a novel mechanism by which PRR11 cooperated with BMI1 to facilitate GC-1 maintenance through targeting Ptprm. Our findings may provide a better understanding of the regulatory network in spermatogonia maintenance.

The Crucial Roles of Bmi-1 in Cancer: Implications in Pathogenesis, Metastasis, Drug Resistance, and Targeted Therapies

B-cell-specific Moloney murine leukemia virus integration region 1 (Bmi-1, also known as RNF51 or PCGF4) is one of the important members of the PcG gene family, and is involved in regulating cell proliferation, differentiation and senescence, and maintaining the self-renewal of stem cells. Many studies in recent years have emphasized the role of Bmi-1 in the occurrence and development of tumors. In fact, Bmi-1 has multiple functions in cancer biology and is closely related to many classical molecules, including Akt, c-MYC, Pten, etc. This review summarizes the regulatory mechanisms of Bmi-1 in multiple pathways, and the interaction of Bmi-1 with noncoding RNAs. In particular, we focus on the pathological processes of Bmi-1 in cancer, and explore the clinical relevance of Bmi-1 in cancer biomarkers and prognosis, as well as its implications for chemoresistance and radioresistance. In conclusion, we summarize the role of Bmi-1 in tumor progression, reveal the pathophysiological process and molecular mechanism of Bmi-1 in tumors, and provide useful information for tumor diagnosis, treatment, and prognosis.

Repair, regeneration and rejuvenation require un-entangling pluripotency from senescence

There is a notion that pluripotency and senescence, represent two extremes of life of cells. Pluripotent cells display epigenetic youth, unlimited proliferative capacity and pluripotent differentiating potential whereas cells that reach the Hayflick limit, transit to senescence, undergo permanent inhibition of cell replication and create an aging tissue landscape. However, pluripotency and senescence appear to be intimately linked and are jointly generated in many different contexts such as during embryogenesis or formation of tissue spheroids, in stem cell niches, cancer, or by induction of a pluripotent state (induced pluripotency). Tissue damage and senescence provide signals that are critical to generation of a pluripotent state and, in turn, pluripotency, induces senescence. Thus, it follows, that precisely timed control of senescence is required for harnessing the full benefits of both senescence and its associated pluripotency during tissue regeneration or rejuvenation.

Suppressed miR-128-3p combined with TERT overexpression predicts dismal outcomes for neuroblastoma

BACKGROUND

Molecular and clinical diversity of neuroblastomas is notorious. The activating TERT rearrangements have been associated with dismal prognosis. Suppression of miR-128-3p may complement and enhance the adverse effects of TERT overexpression.

OBJECTIVE

The study aimed at evaluation of prognostic significance of the miR-128-3p/TERT expression in patients with primary neuroblastoma.

METHODS

RNA samples isolated from fresh-frozen tumor specimens (n= 103) were reverse transcribed for evaluation of miR-128-3p and TERT expression by qPCR. The normalized expression levels were tested for correlations with the event-free survival (EFS). ROC-analysis was used to establish threshold expression levels (TLs) for the possible best prediction of the outcomes. The median follow-up was 57 months.

RESULTS

Both TERT overexpression and miR-128-3p downregulation were independently associated with superior rates of adverse events (p= 0.027, TL =-2.32 log10 and p= 0.080, TL =-1.33 log10, respectively). The MYCN single-copy patients were stratified into groups based on the character of alterations in expression of the studied transcripts. Five-year EFS in the groups of patients with elevated TERT/normal miR-128-3p expression and normal TERT/reduced miR-128-3p expression were 0.74 ± 0.08 and 0.60 ± 0.16, respectively. The patients with elevated TERT/reduced miR-128-3p expression had the worst outcomes, with 5-year EFS of 0.40 ± 0.16 compared with 0.91 ± 0.06 for the patients with unaltered levels of both transcripts (p< 0.001). Cumulative incidence of relapse/progression for the groups constituted 0.23 ± 0.08, 0.40 ± 0.16, 0.60 ± 0.16 and 0.09 ± 0.06, respectively. Moreover, the loss of miR-128-3p was qualified as independent adverse predictor which outperformed the conventional clinical and genetic risk factors in the multivariate Cox regression model of EFS.

CONCLUSIONS

Combined expression levels of miR-128-3p and TERT represent a novel prognostic biomarker for neuroblastoma.

Lung Adenocarcinoma Tumor Origin: A Guide for Personalized Medicine

Simple Summary

Lung cancer is the leading cause of cancer-related death worldwide, with an average 5-year survival rate of approximately 15%. Among the multiple histological type of lung cancer, adenocarcinoma is the most common. Adenocarcinoma is characterized by a high degree of heterogeneity at many levels, including histological, cellular, and molecular. Understanding the cell of origin of adenocarcinoma, and the molecular changes during tumor progression, will allow better therapeutic strategies.

Abstract

Lung adenocarcinoma, the major form of lung cancer, is the deadliest cancer worldwide, due to its late diagnosis and its high heterogeneity. Indeed, lung adenocarcinoma exhibits pronounced inter- and intra-tumor heterogeneity cofounding precision medicine. Tumor heterogeneity is a clinical challenge driving tumor progression and drug resistance. Several key pieces of evidence demonstrated that lung adenocarcinoma results from the transformation of progenitor cells that accumulate genetic abnormalities. Thus, a better understanding of the cell of origin of lung adenocarcinoma represents an opportunity to unveil new therapeutic alternatives and stratify patient tumors. While the lung is remarkably quiescent during homeostasis, it presents an extensive ability to respond to injury and regenerate lost or damaged cells. As the lung is constantly exposed to potential insult, its regenerative potential is assured by several stem and progenitor cells. These can be induced to proliferate in response to injury as well as differentiate into multiple cell types. A better understanding of how genetic alterations and perturbed microenvironments impact progenitor-mediated tumorigenesis and treatment response is of the utmost importance to develop new therapeutic opportunities.

BMI1 promotes osteosarcoma proliferation and metastasis by repressing the transcription of SIK1

Background

Osteosarcoma (OS) is the most common malignant tumor of bone, and the clinical efficacy of current treatments and associated survival rates need to be further improved by employing novel therapeutic strategies. Although various studies have shown that BMI1 protein is universally upregulated in OS cells and tissues, its specific role and underlying mechanism have not yet been fully explored.

Methods

Expression of BMI1 protein in OS cells was detected by western blot. The effect of BMI1 on proliferation and migration of OS cells (143B and U-2OS cell lines) was investigated in vitro using CCK-8, colony formation and transwell assays, and in vivo using subcutaneous tumorigenesis and lung metastasis assays in xenograft nude mice. Expression of epithelial–mesenchymal transition (EMT)-associated proteins was detected by immunofluorescence imaging. Bioinformatic analysis was performed using ENCODE databases to predict downstream targets of BMI1. SIK1 mRNA expression in osteosarcoma cells was detected by quantitative real-time reverse transcription PCR (qPCR). Chromatin immunoprecipitation-qPCR (ChIP-qPCR) was used to investigate expression of BMI1-associated, RING1B-associated, H2AK119ub-associated and H3K4me3-associated DNA at the putative binding region of BMI1 on the SIK1 promoter in OS cells.

Results

Using both in vitro and in vivo experimental approaches, we found that BMI1 promotes OS cell proliferation and metastasis. The tumor suppressor SIK1 was identified as the direct target gene of BMI1 in OS cells. In vitro experiments demonstrated that SIK1 could inhibit proliferation and migration of OS cells. Inhibition of SIK1 largely rescued the altered phenotypes of BMI1-deficient OS cells. Mechanistically, we demonstrated that BMI1 directly binds to the promoter region of SIK1 in a complex with RING1B to promote monoubiquitination of histone H2A at lysine 119 (H2AK119ub) and inhibit H3K4 trimethylation (H3K4me3), resulting in inhibition of SIK1 transcription. We therefore suggest that BMI1 promotes OS cell proliferation and metastasis by inhibiting SIK1.

Conclusions

Our results reveal a novel molecular mechanism of OS development promoted by BMI1 and provides a new potential target for OS treatment.

Evaluation of correlation between CD44, radiotherapy response, and survival rate in patients with advanced stage of head and neck squamous cell carcinoma (HNSCC)

Purpose

Cancer stem cells (CSCs) constitute a distinctive subpopulation of cancer cells that are competent in tumor initiation, invasion, recurrence, and resistance to chemoradiotherapy. CD44, a hyaluronic acid (HA) receptor has been considered as a potential CSC marker in head and neck cancer. The purpose of this study is to evaluate the correlation between CD44 and clinicopathological parameters, treatment response, survival, and recurrence.

Methods

The CD44 expression was examined by immunohistochemistry (IHC) in 90 samples of head and neck squamous cell carcinoma (HNSCC) confirmed patients. The expression of CD44 and its association with clinicopathological parameters, treatment response, and survival was determined.

Results

In all HNSCC patient samples, CD44 was expressed consistently at different intensities. Tumor size (p < 0.001), stage (p < 0.001), and treatment response (p < 0.001) showed statistically significant association with CD44 expression. Alcohol and CD44 were observed as independent predictors of response to radiotherapy using multivariate ordinal logistic regression analysis. Analysis of 2‐year overall survival (OS) showed that CD44 expression (p = 0.02), tumor size (p = 0.001), lymph node status (p < 0.001), stage (p < 0.001), and grade (p = 0.007) were significantly associated with OS. Using Cox regression analysis, lymph node status (p = 0.001), grade (p < 0.001), recurrence (p < 0.001), and CD44 expression (p = 0.003) were found to be potential independent predictors of OS.

Conclusion

Our findings suggest that CD44 contributes to resistance to radiotherapy and poor OS. The results also suggest that except for CD44 there could be other factors such as lymph node metastasis, grade, and alcohol which should be investigated as potential targets for therapy.

MicroRNAs, Long Non-Coding RNAs, and Circular RNAs in the Redox Control of Cell Senescence

Cell senescence is critical in diverse aspects of organism life. It is involved in tissue development and homeostasis, as well as in tumor suppression. Consequently, it is tightly integrated with basic physiological processes during life. On the other hand, senescence is gradually being considered as a major contributor of organismal aging and age-related diseases. Increased oxidative stress is one of the main risk factors for cellular damages, and thus a driver of senescence. In fact, there is an intimate link between cell senescence and response to different types of cellular stress. Oxidative stress occurs when the production of reactive oxygen species/reactive nitrogen species (ROS/RNS) is not adequately detoxified by the antioxidant defense systems. Non-coding RNAs are endogenous transcripts that govern gene regulatory networks, thus impacting both physiological and pathological events. Among these molecules, microRNAs, long non-coding RNAs, and more recently circular RNAs are considered crucial mediators of almost all cellular processes, including those implicated in oxidative stress responses. Here, we will describe recent data on the link between ROS/RNS-induced senescence and the current knowledge on the role of non-coding RNAs in the senescence program.

Repression of the Antioxidant Pyrroloquinoline Quinone in Skin Aging Induced by Bmi-1 Deficiency

It is uncertain whether Bmi-1 deficiency could lead to skin aging by redox imbalance and DNA damage. In this study, we first confirmed that Bmi-1 had a relatively high expression level in the skin and Bmi-1 expression levels gradually decreased with age. Then, we studied the role of Bmi-1 in the skin using a Bmi-1^−/− mouse model. Bmi-1^−/− mice were supplemented with or without pyrroloquinoline quinone (PQQ) for 5 weeks, and their skin phenotypes were compared with Bmi1^−/− and wild-type littermates. Our results showed that Bmi-1^−/− mice displayed decreased vertical thickness of skin, sparse hair follicles, and thinner and more irregular collagen bundles. Mechanistically, increased oxidative stress with reducing antioxidant capacity and induced DNA damage occurred in Bmi-1^−/− mice. Subsequently, this would lead to reduced cell proliferation, increased cell senescence and matrix metalloproteinases (MMPs), and the degradation of fibroblast function and further reduce collagen synthesis. All pathological alterations in the skin of Bmi-1^−/− mice were alleviated by PQQ supplementation. These results demonstrated that Bmi-1 might play a key role in protection from skin aging by maintaining redox balance and inhibiting DNA damage response and will be a novel and potential target for preventing skin aging.

Sex-related differential susceptibility to ponatinib cardiotoxicity and differential modulation of the Notch1 signalling pathway in a murine model

Ponatinib (PON), a tyrosine kinase inhibitor approved in chronic myeloid leukaemia, has proven cardiovascular toxicity. We assessed mechanisms of sex‐related PON‐induced cardiotoxicity and identified rescue strategies in a murine model. PON+scrambled siRNA‐treated male mice had a higher number of TUNEL‐positive cells (%TdT+6.12 ± 0.17), higher percentage of SA‐β‐gal‐positive senescent cardiac area (%SA‐β‐gal 1.41 ± 0.59) and a lower reactivity degree (RD) for the survival marker Bmi1 [Abs (OD) 5000 ± 703] compared to female (%TdT+3.75 ± 0.35; %SA‐β‐gal 0.77 ± 0.02; Bmi1 [Abs (OD) 8567 ± 2173]. Proteomics analysis of cardiac tissue showed downstream activation of cell death in PON+siRNA scrambled compared to vehicle or PON+siRNA‐Notch1‐treated male mice. Upstream analysis showed beta‐oestradiol activation, and downstream analysis showed activation of cell survival and inhibition of cell death in PON+scrambled siRNA compared to vehicle or PON+siRNA‐Notch1‐treated female mice. PON+scrambled siRNA‐treated mice also had a downregulation of cardiac actin—more marked in males—and vessel density—more marked in females. Female hearts showed greater cardiac fibrosis than their male counterparts at baseline, with no significant change after PON treatment. PON+siRNA‐scrambled mice had less fibrosis than vehicle or PON+siRNA‐Notch1‐treated mice. The left ventricular systolic dysfunction showed by PON+scrambled siRNA‐treated mice (male %EF 28 ± 9; female %EF 36 ± 7) was reversed in both PON+siRNA‐Notch1‐treated male (%EF 53 ± 9) and female mice (%EF 52 ± 8). We report sex‐related differential susceptibility and Notch1 modulation in PON‐induced cardiotoxicity. This can help to identify biomarkers and potential mechanisms underlying sex‐related differences in PON‐induced cardiotoxicity.

Roles of BMI1 in the Initiation, Progression, and Treatment of Hepatocellular Carcinoma

Liver cancer has high rates of morbidity and mortality, and its treatment is a global health challenge. Hepatocellular carcinoma (HCC) accounts for 90% of all primary liver cancer cases. B-lymphoma Mo-MLV insertion region 1 (BMI1) has been identified as a proto-oncogene, which contributes to the initiation and progression of many malignant tumors. BMI1 expression is upregulated in HCC, and it influences the occurrence and development of HCC by various mechanisms, such as the INK4a/ARF locus, NF-κB signaling pathway, and PTEN/PI3K/AKT signaling pathway. In addition, the expression of BMI1 is related to prognosis and recurrence of HCC. Hence, there is clear evidence that BMI1 is a novel and valid therapeutic target for HCC. Accordingly, the development of therapeutic strategies targeting BMI1 has been a focus of recent research, providing new directions for HCC treatment. This review summarizes the role of BMI1 in the occurrence and treatment of HCC, which will provide a basis for using BMI1 as a potential target for the development of therapeutic strategies for HCC.

Sorafenib, rapamycin, and venetoclax attenuate doxorubicin-induced senescence and promote apoptosis in HCT116 cells

Emerging evidence has shown that the therapy-induced senescent growth arrest in cancer cells is of durable nature whereby a subset of cells can reinstate proliferative capacity. Promising new drugs named senolytics selectively target senescent cells and commit them into apoptosis. Accordingly, senolytics have been proposed as adjuvant cancer treatment to cull senescent tumor cells, and thus, screening for agents that exhibit senolytic properties is highly warranted. Our study aimed to investigate three agents, sorafenib, rapamycin, and venetoclax for their senolytic potential in doxorubicin-induced senescence in HCT116 cells. HCT116 cells were treated with one of the three agents, sorafenib (5 µM), rapamycin (100 nM), or venetoclax (10 µM), in the absence or presence of doxorubicin (1 µM). Senescence was evaluated using microscopy-based and flow cytometry-based Senescence-associated-β-galactosidase staining (SA-β-gal), while apoptosis was assessed using annexin V-FITC/PI, and Muse caspase-3/-7 activity assays. We screened for potential genes through which the three drugs exerted senolytic-like action using the Human Cancer Pathway Finder PCR array. The three agents reduced doxorubicin-induced senescent cell subpopulations and significantly enhanced the apoptotic effect of doxorubicin compared with those treated only with doxorubicin. The senescence genes IGFBP5 and BMI1 and the apoptosis genes CASP7 and CASP9 emerged as candidate genes through which the three drugs exhibited senolytic-like properties. These results suggest that the attenuation of doxorubicin-induced senescence might have shifted HCT116 cells to apoptosis by exposure to the tested pharmacological agents. Our work argues for the use of senolytics to reduce senescence-mediated resistance in tumor cells and to enhance chemotherapy efficacy.

Advances in pathogenesis and precision medicine for nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a squamous carcinoma with apparent geographical and racial distribution, mostly prevalent in East and Southeast Asia, particularly concentrated in southern China. The epidemiological trend over the past decades has suggested a substantial reduction in the incidence rate and mortality rate due to NPC. These results may reflect changes in lifestyle and environment, and more importantly, a deeper comprehension of the pathogenic mechanism of NPC, leading to much progress in the preventing, screening, and treating for this cancer. Herein, we present the recent advances on the key signal pathways involved in pathogenesis of NPC, the mechanism of Epstein‐Barr virus (EBV) entry into the cell, and the progress of EBV vaccine and screening biomarkers. We will also discuss in depth the development of various therapeutic approaches including radiotherapy, chemotherapy, surgery, targeted therapy, and immunotherapy. These research advancements have led to a new era of precision medicine in NPC.

BMI1 promotes spermatogonia proliferation through epigenetic repression of Ptprm

Spermatogonia are accountable for spermatogenesis and male fertility, but the underlying mechanisms involved in spermatogonia maintenance are not clear. B lymphoma Mo-MLV insertion region 1 (BMI1) is a key component of epigenetic silencers. BMI1 is essential for stem-cell maintenance. Here, we attempted to uncover the role of BMI1 in spermatogonia maintenance using a mouse spermatogonia cell line (GC-1) and Bmi1-knockout (KO) mouse model. We showed that BMI1 promoted the proliferation and inhibited apoptosis of GC-1 cells. Mechanistically, we present in vitro and in vivo evidence to show that BMI1 binds to the promoter region of the Protein tyrosine phosphatase receptor type M (PTPRM) gene, thereby driving chromatin remodeling and gene silencing. Knockdown of Ptprm expression significantly improved spermatogonia proliferation in BMI1-deficient GC-1 cells. Collectively, our data show, for the first time, an epigenetic mechanism involving in BMI1-mediated gene silencing in spermatogonia maintenance, and provide potential targets for the treatment of male infertility.

Oral Cancer: Genetics and the Role of Precision Medicine

Oral squamous cell carcinoma (OSCC) is one of the leading cancers in the world. OSCC patients are managed with surgery and/or chemoradiation. Prognoses and survival rates are dismal, however, and have not improved for more than 20 years. Recently, the concept of precision medicine was introduced, and the introduction of targeted therapeutics demonstrated promising outcomes. This article reviews the current understanding of initiation, progression, and metastasis of OSCC from both genetic and epigenetic perspectives. In addition, the applications and integration of omics technologies in biomarker discovery and drug development for treating OSCC are reviewed.

Necdin: A purposive integrator of molecular interaction networks for mammalian neuron vitality

Necdin was originally found in 1991 as a hypothetical protein encoded by a neural differentiation‐specific gene transcript in murine embryonal carcinoma cells. Virtually all postmitotic neurons and their precursor cells express the necdin gene (Ndn) during neuronal development. Necdin mRNA is expressed only from the paternal allele through genomic imprinting, a placental mammal‐specific epigenetic mechanism. Necdin and its homologous MAGE (melanoma antigen) family, which have evolved presumedly from a subcomplex component of the SMC5/6 complex, are expressed exclusively in placental mammals. Paternal Ndn‐mutated mice totally lack necdin expression and exhibit various types of neuronal abnormalities throughout the nervous system. Ndn‐null neurons are vulnerable to detrimental stresses such as DNA damage. Necdin also suppresses both proliferation and apoptosis of neural stem/progenitor cells. Functional analyses using Ndn‐manipulated cells reveal that necdin consistently exerts antimitotic, anti‐apoptotic and prosurvival effects. Necdin interacts directly with a number of regulatory proteins including E2F1, p53, neurotrophin receptors, Sirt1 and PGC‐1α, which serve as major hubs of protein–protein interaction networks for mitosis, apoptosis, differentiation, neuroprotection and energy homeostasis. This review focuses on necdin as a pleiotropic protein that integrates molecular interaction networks to promote neuronal vitality in modern placental mammals.

Elucidation of the BMI1 interactome identifies novel regulatory roles in glioblastoma

Glioblastoma (GBM) is the most common and aggressive intrinsic brain tumour in adults. Epigenetic mechanisms controlling normal brain development are often dysregulated in GBM. Among these, BMI1, a structural component of the Polycomb Repressive Complex 1 (PRC1), which promotes the H2AK119ub catalytic activity of Ring1B, is upregulated in GBM and its tumorigenic role has been shown in vitro and in vivo. Here, we have used protein and chromatin immunoprecipitation followed by mass spectrometry (MS) analysis to elucidate the protein composition of PRC1 in GBM and transcriptional silencing of defining interactors in primary patient-derived GIC lines to assess their functional impact on GBM biology. We identify novel regulatory functions in mRNA splicing and cholesterol transport which could represent novel targetable mechanisms in GBM.

Bmi1 Augments Proliferation and Survival of Cortical Bone-Derived Stem Cells after Injury through Novel Epigenetic Signaling via Histone 3 Regulation

Ischemic heart disease can lead to myocardial infarction (MI), a major cause of morbidity and mortality worldwide. Multiple stem cell types have been safely transferred into failing human hearts, but the overall clinical cardiovascular benefits have been modest. Therefore, there is a dire need to understand the basic biology of stem cells to enhance therapeutic effects. Bmi1 is part of the polycomb repressive complex 1 (PRC1) that is involved in different processes including proliferation, survival and differentiation of stem cells. We isolated cortical bones stem cells (CBSCs) from bone stroma, and they express significantly high levels of Bmi1 compared to mesenchymal stem cells (MSCs) and cardiac-derived stem cells (CDCs). Using lentiviral transduction, Bmi1 was knocked down in the CBSCs to determine the effect of loss of Bmi1 on proliferation and survival potential with or without Bmi1 in CBSCs. Our data show that with the loss of Bmi1, there is a decrease in CBSC ability to proliferate and survive during stress. This loss of functionality is attributed to changes in histone modification, specifically histone 3 lysine 27 (H3K27). Without the proper epigenetic regulation, due to the loss of the polycomb protein in CBSCs, there is a significant decrease in cell cycle proteins, including Cyclin B, E2F, and WEE as well as an increase in DNA damage genes, including ataxia-telangiectasia mutated (ATM) and ATM and Rad3-related (ATR). In conclusion, in the absence of Bmi1, CBSCs lose their proliferative potential, have increased DNA damage and apoptosis, and more cell cycle arrest due to changes in epigenetic modifications. Consequently, Bmi1 plays a critical role in stem cell proliferation and survival through cell cycle regulation, specifically in the CBSCs. This regulation is associated with the histone modification and regulation of Bmi1, therefore indicating a novel mechanism of Bmi1 and the epigenetic regulation of stem cells.

Cytomegalovirus subverts macrophage identity

Cytomegaloviruses (CMVs) have co-evolved with their mammalian hosts for millions of years, leading to remarkable host specificity and high infection prevalence. Macrophages, which already populate barrier tissues in the embryo, are the predominant immune cells at potential CMV entry sites. Here we show that, upon CMV infection, macrophages undergo a morphological, immunophenotypic, and metabolic transformation process with features of stemness, altered migration, enhanced invasiveness, and provision of the cell cycle machinery for viral proliferation. This complex process depends on Wnt signaling and the transcription factor ZEB1. In pulmonary infection, mouse CMV primarily targets and reprograms alveolar macrophages, which alters lung physiology and facilitates primary CMV and secondary bacterial infection by attenuating the inflammatory response. Thus, CMV profoundly perturbs macrophage identity beyond established limits of plasticity and rewires specific differentiation processes, allowing viral spread and impairing innate tissue immunity.

BMI1 regulates multiple myeloma-associated macrophage's pro-myeloma functions

Multiple myeloma (MM) is an aggressive malignancy characterized by terminally differentiated plasma cells accumulation in the bone marrow (BM). MM BM exhibits elevated MΦs (macrophages) numbers relative to healthy BM. Current evidence indicates that MM-MΦs (MM-associated macrophages) have pro-myeloma functions, and BM MM-MΦs numbers negatively correlate with patient survival. Here, we found that BMI1, a polycomb-group protein, modulates the pro-myeloma functions of MM-MΦs, which expressed higher BMI1 levels relative to normal MΦs. In the MM tumor microenvironment, hedgehog signaling in MΦs was activated by MM-derived sonic hedgehog, and BMI1 transcription subsequently activated by c-Myc. Relative to wild-type MM-MΦs, BMI1-KO (BMI1 knockout) MM-MΦs from BM cells of BMI1-KO mice exhibited reduced proliferation and suppressed expression of angiogenic factors. Additionally, BMI1-KO MM-MΦs lost their ability to protect MM cells from chemotherapy-induced cell death. In vivo analysis showed that relative to wild-type MM-MΦs, BMI1-KO MM-MΦs lost their pro-myeloma effects. Together, our data show that BMI1 mediates the pro-myeloma functions of MM-MΦs.

Correlation between the expression of cancer stem cell marker BMI1 and glioma prognosis

B-cell-specific Moloney murine leukemia virus integration site 1 (BMI1) appears to be essential for promoting certain types of cancer, and its inhibition effectively reduced the stemness of cancer cells. Therefore, this study aimed to investigate the potential role of BMI1 in glioma. To this end, we first investigated BMI1 expression in brain tumors using microarray datasets in ONCOMINE, which indicated that BMI1 levels were not commonly increased in clinical brain tumors. Moreover, survival plots in PROGgeneV2 also showed that BMI1 expression was not significantly associated with reduced survival in glioma patients. Interestingly, stressful serum deprivation and anchorage independence growth conditions led to an increased BMI1 expression in glioma cells. A stress-responsive pathway, HDAC/Sp1, was further identified to regulate BMI1 expression. The HDAC inhibitor vorinostat (SAHA) prevented Sp1 binding to the BMI1 promoter, leading to a decreased expression of BMI1 and attenuating tumor growth of TMZ-resistant glioma xenografts. Importantly, we further performed survival analysis using PROGgeneV2 and found that an elevated expression of HDAC1,3/Sp1/BMI1 but not BMI1 alone showed an increased risk of death in both high- and low-grade glioma patients. Thus, HDAC-mediated Sp1 deacetylation is critical for BMI1 regulation to attenuate stress- and therapy-induced death in glioma cells, and the HDAC/Sp1 axis is more important than BMI1 and appears as a therapeutic target to prevent recurrence of malignant glioma cells persisting after primary therapy.

MicroRNAs as the critical regulators of Doxorubicin resistance in breast tumor cells

BACKGROUND

Chemotherapy is one of the most common treatment options for breast cancer (BC) patients. However, about half of the BC patients are chemotherapeutic resistant. Doxorubicin (DOX) is considered as one of the first line drugs in the treatment of BC patients whose function is negatively affected by multi drug resistance. Due to the severe side effects of DOX, it is very important to diagnose the DOX resistant BC patients. Therefore, assessment of molecular mechanisms involved in DOX resistance can improve the clinical outcomes in BC patients by introducing the novel therapeutic and diagnostic molecular markers. MicroRNAs (miRNAs) as members of the non-coding RNAs family have pivotal roles in various cellular processes including cell proliferation and apoptosis. Therefore, aberrant miRNAs functions and expressions can be associated with tumor progression, metastasis, and drug resistance. Moreover, due to miRNAs stability in body fluids, they can be considered as non-invasive diagnostic markers for the DOX response in BC patients.

MAIN BODY

In the present review, we have summarized all of the miRNAs that have been reported to be associated with DOX resistance in BC for the first time in the world.

CONCLUSIONS

Since, DOX has severe side effects; it is required to distinguish the non DOX-responders from responders to improve the clinical outcomes of BC patients. This review highlights the miRNAs as pivotal regulators of DOX resistance in breast tumor cells. Moreover, the present review paves the way of introducing a non-invasive panel of prediction markers for DOX response among BC patients.

Epigenetic regulator BMI1 promotes alveolar rhabdomyosarcoma proliferation and constitutes a novel therapeutic target

Rhabdomyosarcoma (RMS) is an aggressive pediatric soft tissue sarcoma. There are two main subtypes of RMS, alveolar rhabdomyosarcoma (ARMS) and embryonal rhabdomyosarcoma. ARMS typically encompasses fusion‐positive rhabdomyosarcoma, which expresses either PAX3‐FOXO1 or PAX7‐FOXO1 fusion proteins. There are no targeted therapies for ARMS; however, recent studies have begun to illustrate the cooperation between epigenetic proteins and the PAX3‐FOXO1 fusion, indicating that epigenetic proteins may serve as targets in ARMS. Here, we investigate the contribution of BMI1, given the established role of this epigenetic regulator in sustaining aggression in cancer. We determined that BMI1 is expressed across ARMS tumors, patient‐derived xenografts, and cell lines. We depleted BMI1 using RNAi and inhibitors (PTC‐209 and PTC‐028) and found that this leads to a decrease in cell growth/increase in apoptosis in vitro, and delays tumor growth in vivo. Our data suggest that BMI1 inhibition activates the Hippo pathway via phosphorylation of LATS1/2 and subsequent reduction in YAP levels and YAP/TAZ target genes. These results identify BMI1 as a potential therapeutic vulnerability in ARMS and warrant further investigation of BMI1 in ARMS and other sarcomas.

Bmi1 regulate tooth and mandible development by inhibiting p16 signal pathway

To determine whether the deletion of p16 can correct tooth and mandible growth retardation caused by Bmi1 deficiency, we compared the tooth and mandible phenotypes of homozygous p16‐deficient (p16^−/−) mice, homozygous Bmi1‐deficient (Bmi1^−/−) mice, double homozygous Bmi1 and p16‐deficient (Bmi1^−/−p16^−/−) mice to those of their wild‐type littermates at 4 weeks of age by radiograph, histochemistry and immunohistochemistry. Results showed that compared to Bmi1^−/− mice, the dental mineral density, dental volume and dentin sialoprotein immunopositive areas were increased, whereas the ratio of the predentin area to total dentin area and that of biglycan immunopositive area to dentin area were decreased in Bmi1^−/−p16^−/− mice. These results indicate that the deletion of p16 can improve tooth development in Bmi1 knockout mice. Compared to Bmi1^−/− mice, the mandible mineral density, cortical thickness, alveolar bone volume, osteoblast number and activity, alkaline phosphatase positive area were all increased significantly in Bmi1^−/−p16^−/− mice. These results indicate that the deletion of p16 can improve mandible growth in Bmi1 knockout mice. Furthermore, the protein expression levels of cyclin D, CDK4 and p53 were increased significantly in p16^−/− mice compared with those from wild‐type mice; the protein expression levels of cyclin D and CDK4 were decreased significantly, whereas those of p27 and p53 were increased significantly in Bmi1^−/− mice; these parameters were partly rescued in Bmi1^−/−p16^−/− mice compared with those from Bmi1^−/− mice. Therefore, our results indicate that Bmi1 plays roles in regulating tooth and mandible development by inhibiting p16 signal pathway which initiated entry into cell cycle.

Understanding stem cells and its pivotal role in regenerative medicine

Stem cells (SCs) are clonogenic cells that develop into the specialized cells which later responsible for making up various types of tissue in the human body. SCs are not only the appropriate source of information for cell division, molecular and cellular processes, and tissue homeostasis but also one of the major putative biological aids to diagnose and cure various degenerative diseases. This study emphasises on various research outputs that occurred in the past two decades. This will give brief information on classification, differentiation, detection, and various isolation techniques of SCs. Here, the various signalling pathways which includes WNT, Sonic hedgehog, Notch, BMI1 and C-met pathways and how does it effect on the regeneration of various classes of SCs and factors that regulates the potency of the SCs are also been discussed. We also focused on the application of SCs in the area of regenerative medicine along with the cellular markers that are useful as salient diagnostic or curative tools or in both, by the process of reprogramming, which includes diabetes, cancer, cardiovascular disorders and neurological disorders. The biomarkers that are mentioned in various literatures and experiments include PDX1, FOXA2, HNF6, and NKX6-1 (for diabetes); CD33, CD24, CD133 (for cancer); c-Kit, SCA-1, Wilm's tumor 1 (for cardiovascular disorders); and OCT4, SOX2, c-MYC, EN1, DAT and VMAT2 (for neurological disorders). In this review, we come to know the advancements and scopes of potential SC-based therapies, its diverse applications in clinical fields that can be helpful in the near future.

The inhibitory effect of human DEFA5 in growth of gastric cancer by targeting BMI1

Defensins, a class of small cysteine‐rich cationic polypeptides across cellular life, are identified as antimicrobial compounds that display direct antimicrobial and immune signaling activities that are involved in the host defense. In addition to their roles in the innate immune system, accumulating studies have reported that some members of defensins are expressed and involved in some cancer cells, such as colon cancer, colorectal cancer, lung cancer and renal cell carcinomas. However, the roles of α‐Defensin 5 (DEFA5) in tumorigenesis and development remain unknown. In the present study, bioinformatics analysis and quantitative PCR results showed that the expression level of DEFA5 was dramatically downregulated in human gastric cancer. Overexpression of human DEFA5 in gastric cancer cell lines SGC7901 and BGC823 effectively diminished cell proliferation and reduced the colony forming ability. Moreover, DEFA5 overexpression induced cell cycle arrest by significantly increasing the number of G1‐phase cells. Consistently, in vivo tumor formation experiments in nude mice showed the suppression of the tumor growth by DEFA5 overexpression, suggesting an inhibitory effect of DEFA5 in gastric cancer. Mechanistically, DEFA5 directly binds to BMI1, which subsequently decreased its binding at the CDKN2a locus and upregulated the expression of 2 cyclin‐dependent kinase inhibitors, p16 and p19. Taken together, we concluded that DEFA5 showed an inhibitory effect in gastric cancer cell growth and may serve as a potential tumor suppressor in gastric cancer.

Bmi1 drives the formation and development of intrahepatic cholangiocarcinoma independent of Ink4A/Arf repression

Hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC) are the most prevalent types of primary liver cancer. Compared with HCC, for which several drugs have been approved, ICC is associated with shorter survival, and no drug has been approved for this type. Previously, we reported that Bmi1 drives HCC and is required for HCC development and growth. However, whether Bmi1 plays a critical role in ICC is not clear, although it reportedly is highly expressed in ICC. Therefore, we investigated its role in ICC. Here, we report that Bmi1 promotes ICC initiation and progression independent of the Ink4A/Arf pathway, a canonical downstream pathway of Bmi1. We found that Bmi1 is overexpressed in human ICC. Co-expression of Bmi1 and NRas induced ICC formation in mice. Knockdown or inactivation of Bmi1 inhibited ICC growth in vitro. Liver-specific knockout or inactivation of Bmi1 remarkably suppressed ICC tumor formation and development in vivo. Mechanistically, no correlation between Bmi1 and Ink4A/Arf levels was found in mouse and human ICC tissues. Together, our data indicate that Bmi1 functions as an oncogene independent of repression of the Ink4A/Arf locus in ICC and that it can serve as a target for ICC treatment.

The Role of miRNAs, miRNA Clusters, and isomiRs in Development of Cancer Stem Cell Populations in Colorectal Cancer

MicroRNAs (miRNAs or miRs) have a critical role in regulating stem cells (SCs) during development and altered expression can cause developmental defects and/or disease. Indeed, aberrant miRNA expression leads to wide-spread transcriptional dysregulation which has been linked to many cancers. Mounting evidence also indicates a role for miRNAs in the development of the cancer SC (CSC) phenotype. Our goal herein is to provide a review of: (i) current research on miRNAs and their targets in colorectal cancer (CRC), and (ii) miRNAs that are differentially expressed in colon CSCs. MicroRNAs can work in clusters or alone when targeting different SC genes to influence CSC phenotype. Accordingly, we discuss the specific miRNA cluster classifications and isomiRs that are predicted to target the ALDH1, CD166, BMI1, LRIG1, and LGR5 SC genes. miR-23b and miR-92A are of particular interest because our previously reported studies on miRNA expression in isolated normal versus malignant human colonic SCs showed that miR-23b and miR-92a are regulators of the LGR5 and LRIG1 SC genes, respectively. We also identify additional miRNAs whose expression inversely correlated with mRNA levels of their target genes and associated with CRC patient survival. Altogether, our deliberation on miRNAs, their clusters, and isomiRs in regulation of SC genes could provide insight into how dysregulation of miRNAs leads to the emergence of different CSC populations and SC overpopulation in CRC.

MicroRNA regulation of cancer stem cells in the pathogenesis of breast cancer

Breast cancer is the most common cancer among women and accounts for 30% of all female malignancies worldwide. Breast cancer stem cells (BCSCs) are a small population of breast cancer cells that exhibit multiple characteristics including differentiation capacity, self-renewal and therapeutic resistance. Recently, BCSCs have attracted attention due to their modulation of breast tumor behaviors and drug resistance. miRNAs are small noncoding mRNAs involved in virtually all biological processes, including stem cell development, maintenance and differentiation. In breast cancer, miRNAs appear to be multi-faceted since they can act as either suppressors or oncogenes to regulate breast cancer progression. This review summarizes the critical roles of miRNAs in regulating multiple signaling pathways such as Wnt/β-catenin, Notch, PI3K/AKT/mTOR, BMI-1 and STAT3 that are important for the BCSC maintenance.

BMI1 in the heart: Novel functions beyond tumorigenesis

The BMI1 protein, a member of the PRC1 family, is a well recognised transcriptional suppressor and has the capability of maintaining the self-renewal and proliferation of tissue-specific stem cells. Numerous studies have established that BMI1 is highly expressed in a variety of malignant cancers and serves as a key regulator in the tumorigenesis process. However, our understanding of BMI1 in terminally differentiated organs, such as the heart, is relatively nascent. Importantly, emerging data support that, beyond the tumor, BMI1 is also expressed in the heart tissue and indeed exerts profound effects in various cardiac pathological conditions. This review gives a summary of the novel functions of BMI1 in the heart, including BMI1-positive cardiac stem cells and BMI1-mediated signaling pathways, which are involved in the response to various cardiac pathological stimuli. Besides, we summarize the recent progress of BMI1 in some novel and rapidly developing cardiovascular therapies. Furtherly, we highlight the properties of BMI1, a therapeutic target proved effective in cancer treatment, as a promising target to alleviate cardiovascular diseases.

MicroRNAs are critical regulators of senescence and aging in mesenchymal stem cells

MicroRNAs (miRNAs) have recently come under scrutiny for their role in various age-related diseases. Similarly, cellular senescence has been linked to disease and aging. MicroRNAs and senescence likely play an intertwined role in driving these pathologic states. In this review, we present the connection between these two drivers of age-related disease concerning mesenchymal stem cells (MSCs). First, we summarize key miRNAs that are differentially expressed in MSCs and other musculoskeletal lineage cells during senescence and aging. Additionally, we also reviewed miRNAs that are regulated via traditional senescence-associated secretory phenotype (SASP) cytokines in MSC. Lastly, we summarize miRNAs that have been found to target components of the cell cycle arrest pathways inherently activated in senescence. This review attempts to highlight potential miRNA targets for regenerative medicine applications in age-related musculoskeletal disease.

Smart Nanofibers with Natural Extracts Prevent Senescence Patterning in a Dynamic Cell Culture Model of Human Skin

Natural cosmetic products have recently re-emerged as a novel tool able to counteract skin aging and skin related damages. In addition, recently achieved progress in nanomedicine opens a novel approach yielding from combination of modern nanotechnology with traditional treatment for innovative pharmacotherapeutics. In the present study, we investigated the antiaging effect of a pretreatment with Myrtus communis natural extract combined with a polycaprolactone nanofibrous scaffold (NanoPCL-M) on skin cell populations exposed to UV. We set up a novel model of skin on a bioreactor mimicking a crosstalk between keratinocytes, stem cells and fibroblasts, as in skin. Beta-galactosidase assay, indicating the amount of senescent cells, and viability assay, revealed that fibroblasts and stem cells pretreated with NanoPCL-M and then exposed to UV are superimposable to control cells, untreated and unexposed to UV damage. On the other hand, cells only exposed to UV stress, without NanoPCL-M pretreatment, exhibited a significantly higher yield of senescent elements. Keratinocyte-based 3D structures appeared disjointed after UV-stress, as compared to NanoPCL-M pretreated samples. Gene expression analysis performed on different senescence associated genes, revealed the activation of a molecular program of rejuvenation in stem cells pretreated with NanoPCL-M and then exposed to UV. Altogether, our results highlight a future translational application of NanoPCL-M to prevent skin aging.

Senescence Induced by BMI1 Inhibition Is a Therapeutic Vulnerability in H3K27M-Mutant DIPG

Diffuse intrinsic pontine glioma (DIPG) is an incurable brain tumor of childhood characterized by histone mutations at lysine 27, which results in epigenomic dysregulation. There has been a failure to develop effective treatment for this tumor. Using a combined RNAi and chemical screen targeting epigenomic regulators, we identify the polycomb repressive complex 1 (PRC1) component BMI1 as a critical factor for DIPG tumor maintenance in vivo. BMI1 chromatin occupancy is enriched at genes associated with differentiation and tumor suppressors in DIPG cells. Inhibition of BMI1 decreases cell self-renewal and attenuates tumor growth due to induction of senescence. Prolonged BMI1 inhibition induces a senescence-associated secretory phenotype, which promotes tumor recurrence. Clearance of senescent cells using BH3 protein mimetics co-operates with BMI1 inhibition to enhance tumor cell killing in vivo.

Increased activation of HDAC1/2/6 and Sp1 underlies therapeutic resistance and tumor growth in glioblastoma

BACKGROUND

Glioblastoma is associated with poor prognosis and high mortality. Although the use of first-line temozolomide can reduce tumor growth, therapy-induced stress drives stem cells out of quiescence, leading to chemoresistance and glioblastoma recurrence. The specificity protein 1 (Sp1) transcription factor is known to protect glioblastoma cells against temozolomide; however, how tumor cells hijack this factor to gain resistance to therapy is not known.

METHODS

Sp1 acetylation in temozolomide-resistant cells and stemlike tumorspheres was analyzed by immunoprecipitation and immunoblotting experiments. Effects of the histone deacetylase (HDAC)/Sp1 axis on malignant growth were examined using cell proliferation-related assays and in vivo experiments. Furthermore, integrative analysis of gene expression with chromatin immunoprecipitation sequencing and the recurrent glioblastoma omics data were also used to further determine the target genes of the HDAC/Sp1 axis.

RESULTS

We identified Sp1 as a novel substrate of HDAC6, and observed that the HDAC1/2/6/Sp1 pathway promotes self-renewal of malignancy by upregulating B cell-specific Mo-MLV integration site 1 (BMI1) and human telomerase reverse transcriptase (hTERT), as well as by regulating G2/M progression and DNA repair via alteration of the transcription of various genes. Importantly, HDAC1/2/6/Sp1 activation is associated with poor clinical outcome in both glioblastoma and low-grade gliomas. However, treatment with azaindolyl sulfonamide, a potent HDAC6 inhibitor with partial efficacy against HDAC1/2, induced G2/M arrest and senescence in both temozolomide-resistant cells and stemlike tumorspheres.

CONCLUSION

Our study uncovers a previously unknown regulatory mechanism in which the HDAC6/Sp1 axis induces cell division and maintains the stem cell population to fuel tumor growth and therapeutic resistance.