Stem Cell Renewal Research Articles

448 RSPO1-mutated keratinocytes from palmoplantar keratoderma display impaired differentiation, alteration of cell-cell adhesion, EMT-like phenotype and invasiveness properties

Secreted R-spondin (RSPO) proteins play a key role in reproductive organ development, epithelial stem cell renewal and cancer induction by reinforcing canonical Wnt signaling. We have previously reported that palmoplantar keratoderma (PPK), predisposition to cutaneous squamous cell carcinoma (SCC) development and sex reversal segregate as autosomal recessive trait in patients carrying RSPO1-mutations. Although our previous findings suggested that RSPO1 secreted from fibroblasts regulates keratinocyte growth or differentiation, the role of this protein in the epidermis remains largely unexplored.

Lithium Attenuates Graft-Versus-Host Disease Via Effects on the Intestinal Stem Cell Niche

Allogeneic hematopoietic stem cell transplantation (HCT) is a curative therapy for the majority of hematological malignancies but is limited by graft-versus-host disease (GVHD) and opportunistic infections. Severe acute GVHD in the gastrointestinal (GI) tract is a major determinant of mortality and causes progressive epithelial and crypt loss leading to denudation of intestinal mucosa. Since the current approaches to prevent severe GVHD to date focus on the immune suppression of T cells with calcineurin inhibitors, anti-metabolites or alkylating agents, therapeutic strategies that protect intestinal epithelium from immune injury represents an attractive alternative approach. The renewal of intestinal stem cells (ISC) and their progeny, intestinal epithelial cells (IEC), is critical for the maintenance of gut integrity after transplantation. Multiple signaling pathways including WNT-β-Catenin signaling regulate this process. Lithium inhibits glycogen synthase kinase-3 (GSK-3), a pluripotent kinase that antagonizes WNT signaling, resulting in cellular proliferation and epithelial regeneration. In a clinical pilot study conducted at Fred Hutchinson Cancer Research Center (FHCRC) and the University of Washington, twenty patients with steroid-refractory gut GVHD and mucosal denudation at endoscopy were treated with oral lithium carbonate in addition to second line therapy. Ten of the 20 patients (50 %) had a complete remission, and 7 (35 %) survived more than 2 years 1. These results were encouraging since only 10% of the patients with steroid-refractory stage 3-4 intestinal GVHD at FHCRC survived for more than 2-years historically1. We thus investigated the activity of lithium in gastrointestinal GVHD in preclinical models. The administration of oral lithium chloride (LiCl) from 2 days before HCT to day 7 after T cell-replete HCT (B6 donors → B6D2F1 recipients) significantly decreased the GVHD-related mucosal injury in the ileum (pathology score: 7.4 ± 0.6 in control vs 4.6 ± 0.6 in LiCl (mean ± sem), p = 0.0049) but not the colon (13.4 ± 0.5 in control vs 12.4 ± 0.9 in LiCl, p > 0.05). We undertook multispectral immunofluorescence analysis in a second BALB/c → B6 system where recipient ISC were marked by Lgr5-driven GFP. LiCl significantly increased the frequency of Paneth cells (6.14 ± 0.4 % in control vs 15.0 ± 1.5 % in LiCl (mean ± sem), p = 0.0031) and their antimicrobial lysozyme content (% cytoplasm occupancy: 61.1 ± 0.7 % in control vs 65.0 ± 0.8 % in LiCl (mean ± sem), p = 0.0055). Lgr5+ ISCs in the ileum were not quantitatively different at this early timepoint. Given that Paneth cells are primarily distributed in the small intestine rather than the colon, these data explain the protection from GVHD afforded by LiCl in the ileum but not the colon. Since ISC regeneration is ultimately essential to repair severe ulceration of the epithelium, we examined the renewal of ISC at later timepoints. Compared to the vehicle control, LiCl treatment significantly increased the percentage of Lgr5+ ISCs (2.33 ± 0.2 % in control vs 4.80 ± 0.6 % in LiCl (mean ± sem), p = 0.0129) in the ileum on day 10. LiCl did not alter the frequencies of CD4+ and CD8+ T cells infiltrating the ileum. These findings suggest that LiCl exerts a protective effect in GVHD by promoting Paneth cell function and subsequent ISC regeneration. Our findings provide further rationale for studies of GSK inhibition, direct WNT activation, and other agents such as IL-22 and IL-28 that provide support of the ISC niche during GVHD, as a complement to immune suppression. Reference:Steinbach G, Hockenbery DM, Huls G, et al. Pilot study of lithium to restore intestinal barrier function in severe graft-versus-host disease. PloS one. 2017;12(8):e0183284.

The Frida Study: An Option for Mutated FLT3 Relapsed/Refractory Acute Myeloid Leukemia Patients with a Novel Iadademstat and Gilteritinib Combination Therapy

Background: Epigenetic dysregulation is a hallmark of acute myeloid leukemia (AML) and is caused by recurrent translocations and/or mutations in chromatin regulators and transcription factors, resulting in myeloid differentiation blockade and leukemic stem cell renewal. Accordingly, about 70% of recurring mutations in AML patients target regulators of gene expression, underscoring the potential of epigenetic therapies to change the natural history of the disease. Iadademstat (iada/ORY-1001) is a specific, oral, potent, covalent inhibitor of the epigenetic Lysine-Specific Demethylase 1 (LSD1/KDMA1) enzyme. Preclinical models demonstrate that exposure to iada decreases leukemic stem cell survival and preclinical and clinical studies shows iada's effect on inducing macrophage/monocytic differentiation of blast cells. Furthermore, a Phase 2 ongoing study of iada in combination with azacitidine (ALICE) shows high complete remission (CR)/ CR with incomplete count recovery (CRi) and durable responses in treatment naïve, unfit AML patients (pts) without exacerbating the toxicity profile of azacitidine (Salamero et al., Abstract P586 EHA 2022). Despite improvements in AML therapy, relapses remain a common challenge, contributing to the death of more than 50% of pts, particularly in those subpopulations with higher risk genetics, the largest of which (up to 30-40% of AML pts) harbor mutations in the fms-like tyrosine kinase 3 (FLT3) gene. Use of the FLT3 inhibitor (FLT3i) gilteritinib as monotherapy for relapsed/refractory (R/R) pts has resulted in improved outcomes but the duration of remission achieved is transient and often brief. The Phase 3 randomized ADMIRAL trial of gilteritinib revealed a CR rate of 20%; and an event-free-survival (EFS) of 2.8 months (Perl, et al., NEJM 2019). Preclinically, iada produces marked synergy with FLT3i, including gilteritinib, in FLT3 wild-type and mutated (FLT3 mut+) AML cells and in derived cell lines resistant to venetoclax, azacitidine and other FLT3is. The novel MOAs generating this synergy of the combination include activation of a pro-differentiative epigenetic and transcriptional program with simultaneous suppression of the activity of MYC target genes (Yashar, et al. 2022, https://doi.org/10.1101/2022.01.17.476469). The FRIDA clinical trial is designed to establish the safety, tolerability of the combination of iada plus gilteritinib and to identify the recommended phase 2 dose (RP2D) in FLT3 mut+ R/R AML specifically according to FDA's Project Optimus. Methods: Adult pts with body weight ≥50 Kg and ECOG 0-2, with FLT3 mut+ R/R AML, after 1 or 2 prior lines of therapy, will be enrolled. Up to 18 pts, in a 3+3 escalation phase, will receive iada at doses of 75 to 150 ug, orally, in 5 days ON - 2 days OFF schedule, with continuous gilteritinib, at 120 mg/day orally. In the expansion phase, up to 14 pts at the selected safe and pharmacologically active dose/s (determined based on all available data from escalation pts including PK, target engagement (TE), safety, tolerability, and emerging activity) will be enrolled. TE will be assessed with a proprietary validated chemo-probe assay for LSD1 occupancy in PBMCs. Primary endpoints of the study are safety and RP2D determination, based on the same 5 criteria outlined above. Bayesian posterior probability efficacy monitoring will be performed periodically for each dose cohort starting from the first 6 additional pts in the expansion phase (total of 12). Bayesian efficacy futility and early stopping boundary will be applied during the monitoring. Posterior probability criterion (Prob (θ>0.3) ≥ 0.60) at the end of the study will warrant additional development. The safety of the combination treatment will be also continuously evaluated during expansion following a Bayesian design stopping rule. Secondary endpoints include overall survival, EFS, CR, CR/CR with partial hematologic recovery (CRh), overall response rates, time to response, duration of response, and transfusion rate. Exploratory endpoints include measurable residual disease and gene mutational analysis. Pts who achieve a response can undergo hematopoietic stem cell transplant. The study plans to have 15 sites enrolling in the US. Additional sites will be added for a subsequent randomized controlled double-blinded FRIDA 2 study to assess the efficacy of the iada and gilteritinib combination in R/R FLT3 mut+ AML.

CSIG-07. GAIN-OF-FUNCTION MUTANT P53 REGULATES LONG-NONCODING RNAS IN GLIOBLASTOMA

Abstract P53 is frequently mutated in most human cancers, including glioblastoma (GBM). Many p53 mutants acquire gain-of-function oncogenic effects through only partially understood mechanisms. To investigate the role of gain-of-function mutant p53 (MUT-p53) in GBM, we performed ChIP-seq of wildtype p53 (WT-p53) and MUT-p53 GBM cell lines. Among 2834 unique peaks reads in MUT-p53 cells, we found 242 long non-coding RNAs (lncRNAs) with up to 145 fold enrichment relative to WT-p53. LncRNAs regulate many molecular and cellular functions, including gene expression, cell proliferation, death, cancer stem cell renewal and differentiation. We selected lncRNAs SOX21-AS1 and LINC00643 with highly enriched binding by MUT-p53 and investigated their expressions and functions in the p53 pathway. We performed ChIP confirmation of MUT-p53 binding to the promoters of these lncRNAs. We found that these lncRNAs are deregulated in GBM and correlated with GBM patient survival in the TCGA database. To investigate the functions of these LncRNAs, we knocked down their expressions by siRNA, and found significant cell death induced by si-SOX21-AS1, but not by si-LINC00643. Overexpression of LINC00643 in GBM cells led to inhibition of GBM cell proliferation, migration, invasion and in vivo xenograft growth. LINC00643 mediated the effects of MUT-p53. Co-expression of human LINC00643 and its mouse homologous in a RCAS transgenic mouse model of GBM reduced tumor growth and improved animal survival. To elucidate the mechanisms of action of the lncRNA, we performed Chromatin Isolation by RNA purification high-throughput sequencing (CHIRP-seq) to identify its binding targets. We found that LINC00643 binds to HIF1a 5’ promoter/enhancer region. Overexpression of LINC00643 in GBM cells at hypoxia growth condition reduced HIF1a mRNA and protein expression. Our study shows for the first time that gain-of-function mutant p53 regulates a subset of lncRNAs and that the lncRNAs mediate the oncogenic effects of the MUT-p53 in GBM.

Mechano-regulation of Wnt/β-Catenin signaling to control paraxial versus lateral mesoderm lineage bifurcation.

Mechanical cues are involved in many biological processes, including embryonic development and patterning. For example, external mechanical forces (shear stress), lateral cell-cell interactions, and mechanical properties (stiffness and composition) of the extracellular matrix are thought to modulate Wnt signaling, which is a highly conserved pathway involved in regulating stem cell renewal, proliferation, and differentiation. In this work, we employed a customized higher-throughput shear stress induction device for the controlled application of mechanical stress to study the effects of shear stress on the differentiation of human induced pluripotent stem cells (hiPSCs) toward the three germ layers. We found that mechanical stress alters lineage commitment during ectoderm and mesoderm differentiation. We show that this effect correlates with reduced Wnt signaling, evaluated in terms of the promoter activity of an established TCF3-responsive promoter. Whole transcriptome sequencing and pathway enrichment analysis of the differentially expressed genes between hiPSC-derived mesoderm cells differentiated in the presence or absence of piston-induced shear stress confirmed that Wnt/β-catenin signaling is among the most affected developmental pathways. Furthermore, our results suggest that suitably programmed shear stress application could be used to selectively promote differentiation of hiPSCs to either lateral or paraxial mesoderm in commercially available media.

Biological roles of adenine methylation in RNA.

N6-Methyladenosine (m6A) is one of the most abundant modifications of the epitranscriptome and is found in cellular RNAs across all kingdoms of life. Advances in detection and mapping methods have improved our understanding of the effects of m6A on mRNA fate and ribosomal RNA function, and have uncovered novel functional roles in virtually every species of RNA. In this Review, we explore the latest studies revealing roles for m6A-modified RNAs in chromatin architecture, transcriptional regulation and genome stability. We also summarize m6A functions in biological processes such as stem-cell renewal and differentiation, brain function, immunity and cancer progression.

Localization and characterization of SSCs from pre-pubertal bovine testes

Self renewal and proliferation ability of spermatogonial stem cells (SSCs) support spermatogenesis during adult life. Theoretically, these stem cells can be utilized for transmission of genetic information to descendants via testicular transplantation. However, lack of knowledge in methodologies for identification of SSCs limits the application of SSCs transplantation in domestic animals. Accumulated studies have shown that SSCs specific markers (DBA, UCHL1) and stem cell marker (Sox2, Oct4) are useful to screen SSCs that able to be used for transplantation. However, in cattle, less information is available on the expression status of these markers till date. Therefore, a study was carried out in 2019 at Tsukuba University, Japan where testes from 3, 5 and 7 months old calves were utilized to examine testicular localization and in vitro propogation of stem cell markers. SSCs were isolated by enzymatic digestion combined with centrifugal separation on discontinuous Percoll density gradient. Cell propagation and SSCs marker expression were determined at 5, 10 and 15 days post-culture. Immunostaining in conjunction with Western Blot analysis of cultured cells showed that stem cell markers (UCHL1, Oct4 and Sox2) were expressed in SSCs suggesting that differentiation of gonocyte started by 3 months and SSCs differentiation begins after 5 months of age. Taken together, these results demonstrated marker expression and localization of bull SSCs and showed that in vitro culturing of bull SSCs is implementable.

LYL1 facilitates AETFC assembly and gene activation by recruiting CARM1 in t(8;21) AML

Transcription factors (TFs) play critical roles in hematopoiesis, and their aberrant expression can lead to various types of leukemia. The t(8;21) leukemogenic fusion protein AML1-ETO (AE) is the most common fusion protein in acute myeloid leukemia and can enhance hematopoietic stem cell renewal while blocking differentiation. A key question in understanding AE-mediated leukemia is what determines the choice of AE to activate self-renewal genes or repress differentiation genes. Toward the resolution of this problem, we earlier showed that AE resides in the stable AETFC complex and that its components colocalize on up- or down-regulated target genes and are essential for leukemogenesis. In the current study, using biochemical and genomic approaches, we show that AE-containing complexes are heterogeneous, and that assembly of the larger AETFC (containing AE, CBFβ, HEB, E2A, LYL1, LMO2, and LDB1) requires LYL1. Furthermore, we provide strong evidence that the LYL1-containing AETFC preferentially binds to active enhancers and promotes AE-dependent gene activation. Moreover, we show that coactivator CARM1 interacts with AETFC and facilitates gene activation by AETFC. Collectively, this study describes a role of oncoprotein LYL1 in AETFC assembly and gene activation by recruiting CARM1 to chromatin for AML cell survival.

The Role of MARCKS in Metastasis and Treatment Resistance of Solid Tumors.

Simple SummaryCancer metastasis is a critical event in the progression of solid tumors and is invariably associated with adverse outcomes and mortality. Understanding novel mechanisms or molecules that promote cancer metastasis will facilitate the development of new strategies for cancer treatment. Recently, MARCKS has been studied extensively in several cancers and has been implicated in tumor progression and metastasis. This review summarizes recent advances in the understanding of MARCKS on cancer metastasis, stemness, and therapeutic resistance and provides prospects on targeting MARCKS therapeutically. Specifically, we review the molecular mechanisms and multiple signaling pathways by which MARCKS contributes to the progression and metastasis in solid tumors.The myristoylated alanine-rich C-kinase substrate (MARCKS) is a membrane-associated protein kinase C (PKC) substrate ubiquitously expressed in eukaryotic cells. MARCKS plays important roles in multiple cellular processes, including cell adhesion and motility, mucin secretion, exocytosis, and inflammatory response. Aberrant MARCKS signaling has been observed in the development and progression of multiple cancer types. In addition, MARCKS facilitates cancer metastasis through modulating cancer cell migration and invasion. Moreover, MARCKS contributes to treatment resistance, likely by promoting cancer stem cell renewal as well as immunosuppression. In this review, we describe MARCKS protein structure, cellular localization, and biological functions. We then discuss the role of MARCKS in cancer metastasis as well as its mechanisms of action in solid tumors. Finally, we review recent advances in targeting MARCKS as a new therapeutic strategy in cancer management.

The Musashi proteins direct post-transcriptional control of protein expression and alternate exon splicing in vertebrate photoreceptors

The Musashi proteins, MSI1 and MSI2, are conserved RNA binding proteins with a role in the maintenance and renewal of stem cells. Contrasting with this role, terminally differentiated photoreceptor cells express high levels of MSI1 and MSI2, pointing to a role for the two proteins in vision. Combined knockout of Msi1 and Msi2 in mature photoreceptor cells abrogated the retinal response to light and caused photoreceptor cell death. In photoreceptor cells the Musashi proteins perform distinct nuclear and cytoplasmic functions. In the nucleus, the Musashi proteins promote splicing of photoreceptor-specific alternative exons. Surprisingly, conserved photoreceptor-specific alternative exons in genes critical for vision proved to be dispensable, raising questions about the selective pressures that lead to their conservation. In the cytoplasm MSI1 and MSI2 activate protein expression. Loss of Msi1 and Msi2 lead to reduction in the levels of multiple proteins including proteins required for vision and photoreceptor survival. The requirement for MSI1 and MSI2 in terminally differentiated photoreceptors alongside their role in stem cells shows that, depending on cellular context, these two proteins can control processes ranging from cell proliferation to sensory perception.

Expression of extracellular matrix components in the meibomian gland.

PurposeExtracellular matrix (ECM) is a key component of the stem cell local microenvironment. Our study aims to explore the periglandular distribution of major components of ECM in the Meibomian gland (MG).MethodsHuman eyelids and mouse eyelids were collected and processed for immunofluorescence staining.ResultsHuman MG tissues stained positive for collagen IV α1, collagen IV α2, collagen IV α5, and collagen IV α6 around the acini and duct, but negative for collagen IV α3 and collagen IV α4. The mouse MG were stained positive for the same collagen IV subunits as early as postnatal day 15. Laminin α2, laminin β1 and perlecan stained the regions surrounding the acini and the acinar/ductal junction in the human MG, but not the region around the duct. Tenascin-C was found specifically located at the junctions between the acini and the central ducts. Neither agrin nor endostatin was found in the human MG tissues.ConclusionThe ECM expresses specific components in different regions around the MG, which may play a role in MG stem cell regulation, renewal, and regeneration.

A dual role of lola in Drosophila ovary development: regulating stem cell niche establishment and repressing apoptosis

In Drosophila ovary, niche is composed of somatic cells, including terminal filament cells (TFCs), cap cells (CCs) and escort cells (ECs), which provide extrinsic signals to maintain stem cell renewal or initiate cell differentiation. Niche establishment begins in larval stages when terminal filaments (TFs) are formed, but the underlying mechanism for the development of TFs remains largely unknown. Here we report that transcription factor longitudinals lacking (Lola) is essential for ovary morphogenesis. We showed that Lola protein was expressed abundantly in TFCs and CCs, although also in other cells, and lola was required for the establishment of niche during larval stage. Importantly, we found that knockdown expression of lola induced apoptosis in adult ovary, and that lola affected adult ovary morphogenesis by suppressing expression of Regulator of cullins 1b (Roc1b), an apoptosis-related gene that regulates caspase activation during spermatogenesis. These findings significantly expand our understanding of the mechanisms controlling niche establishment and adult oogenesis in Drosophila.

Hepatic cytochrome P450 8B1 and cholic acid potentiate intestinal epithelial injury in colitis by suppressing intestinal stem cell renewal.

Although disrupted bile acid (BA) homeostasis is implicated in inflammatory bowel disease (IBD), the role of hepatic BA metabolism in the pathogenesis of colitis is poorly understood. Here, we found that cholic acid (CA) levels were increased in patients and mice. Cytochrome P450 8B1 (CYP8B1), which synthesizes CA, was induced in livers of colitic mice. CA-treated or liver Cyp8b1-overexpressing mice developed more severe colitis with compromised repair of the mucosal barrier, whereas Cyp8b1-knockout mice were resistant to colitis. Mechanistically, CA inhibited peroxisome proliferator-activated receptor alpha (PPARα), resulting in impeded fatty acid oxidation (FAO) and impaired Lgr5+ intestinal stem cell (ISC) renewal. A PPARα agonist restored FAO and improved Lgr5+ ISC function. Activation of the farnesoid X receptor (FXR) suppressed liver CYP8B1 expression and ameliorated colitis in mice. This study reveals a connection between the hepatic CYP8B1-CA axis and colitis via regulating intestinal epithelial regeneration, suggesting that BA-based strategies might be beneficial in IBD treatment.

Genome Maintenance in Mammalian Stem Cells.

Various stem cells in the body are tasked with maintaining tissue homeostasis throughout the life of an organism and thus must be resilient to intrinsic and extrinsic challenges such as infection and injury. Crucial to these challenges is genome maintenance because a high mutational load and persistent DNA lesions impact the production of essential gene products at proper levels and compromise optimal stem cell renewal and differentiation. Genome maintenance requires a robust and well-regulated DNA damage response suited to maintaining specific niches and tissues. In this review, we explore the similarities and differences between diverse stem cell types derived from (or preceding) all germ layers, including extraembryonic tissues. These cells utilize different strategies, including implementation of robust repair mechanisms, modulation of cell cycle checkpoints best suited to eliminating compromised cells, minimization of cell divisions, and differentiation in response to excessive damage.

A reductionist approach to determine the effect of cell-cell contact on human epidermal stem cell differentiation

The balance between stem cell renewal and differentiation is determined by the interplay between intrinsic cellular controls and extrinsic factors presented by the microenvironment, or ‘niche’. Previous studies on cultured human epidermis have utilised suspension culture and restricted cell spreading to investigate regulation of differentiation in single keratinocytes. However, keratinocytes are typically adherent to neighbouring cells in vivo. We therefore developed experimental models to investigate the combined effects of cell-ECM adhesion and cell-cell contact. We utilized lipid-modified oligonucleotides to form clusters of keratinocytes which were subsequently placed in suspension to induce terminal differentiation. In this experimental model cell-cell contact had no effect on suspension-induced differentiation of keratinocytes. We next developed a high-throughput platform for robust geometrical confinement of keratinocytes to hexagonal ECM-coated islands permitting direct cell-cell contact between single cells. As in the case of circular islands, differentiation was stimulated on the smallest single hexagonal islands. However, the percentage of involucrin-positive cells on small bowtie islands was significantly lower than on single islands, demonstrating that cell-cell contact reduced differentiation in response to decreased substrate adhesion. None of the small bowtie islands contained two involucrin-positive cells. Rather, if one cell was involucrin-positive the other was involucrin-negative. This suggests that there is intrinsic asymmetry in the effect of cell-cell contact in decreasing differentiation. Thus, our reductionist approaches provide new insights into the effect of the niche on keratinocyte differentiation. Statement of significanceStem cell behaviour is regulated by a combination of external signals, including the nature of the adhesive substrate and cell-cell interactions. An understanding of how different signals are integrated creates the possibility of developing new biomaterials to promote tissue regeneration and broaden our understanding of skin diseases such as eczema and psoriasis, in which stem cell proliferation and differentiation are perturbed. In this study we have applied two methods to engineer intercellular adhesion of human epidermal stem cells, one involving lipid-modified DNA and the other involving hexagonal micropatterns. We show that the effect of cell-cell adhesion depends on cell-substrate adhesion and uncover evidence that two cells in equivalent environments can nevertheless behave differently.

Targeting the mRNA endonuclease CPSF73 inhibits breast cancer cell migration, invasion, and self-renewal

SummaryCleavage by the endonuclease CPSF73 and polyadenylation of nascent RNA is an essential step in co-transcriptional mRNA maturation. Recent work has surprisingly identified CPSF73 as a promising drug target for inhibiting the growth of specific cancers, triggering further studies on understanding CPSF73 regulation and functions in cells. Here, we report that a HECT-like E3 ligase, UBE3D, participates in stabilizing CPFS73 protein by preventing its ubiquitin-mediated degradation by the proteasome. Depletion of UBE3D leads to CPSF73 downregulation, a pre-mRNA cleavage defect, and dysregulated gene expression in cells. UBE3D dysfunction or chemical inactivation of CPSF73 inhibited migration and invasion as well as stem cell renewal phenotypes in vitro in triple-negative breast cancer cells. In addition, genetic overexpression of CPSF73 promoted breast cancer stemness and knocking down CPSF73 inhibited stem cell renewal properties. Together, our findings indicate that targeting the pre-mRNA processing nuclease CPSF73 has potential for breast cancer therapy.

PDGFD switches on stem cell endothelial commitment

The critical factors regulating stem cell endothelial commitment and renewal remain not well understood. Here, using loss- and gain-of-function assays together with bioinformatic analysis and multiple model systems, we show that PDGFD is an essential factor that switches on endothelial commitment of embryonic stem cells (ESCs). PDGFD genetic deletion or knockdown inhibits ESC differentiation into EC lineage and increases ESC self-renewal, and PDGFD overexpression activates ESC differentiation towards ECs. RNA sequencing reveals a critical requirement of PDGFD for the expression of vascular-differentiation related genes in ESCs. Importantly, PDGFD genetic deletion or knockdown increases ESC self-renewal and decreases blood vessel densities in both embryonic and neonatal mice and in teratomas. Mechanistically, we reveal that PDGFD fulfills this function via the MAPK/ERK pathway. Our findings provide new insight of PDGFD as a novel regulator of ESC fate determination, and suggest therapeutic implications of modulating PDGFD activity in stem cell therapy.

RSPO1-mutated keratinocytes from palmoplantar keratoderma display impaired differentiation, alteration of cell–cell adhesion, EMT-like phenotype and invasiveness properties: implications for squamous cell carcinoma susceptibility in patients with 46XX disorder of sexual development

BackgroundSecreted R-spondin (RSPO) proteins play a key role in reproductive organ development, epithelial stem cell renewal and cancer induction by reinforcing canonical Wnt signaling. We have previously reported that palmoplantar keratoderma (PPK), predisposition to cutaneous squamous cell carcinoma (SCC) development and sex reversal segregate as autosomal recessive trait in patients carrying RSPO1-mutations.Although our previous findings suggested that RSPO1 secreted from fibroblasts regulates keratinocyte growth or differentiation, the role of this protein in the epidermis remains largely unexplored. Our study was aimed at expanding the phenotypic, molecular and functional characterization of RSPO1-mutated skin and keratinocytes.ResultsCultured primary keratinocytes from PPK skin of a RSPO1-mutated XX-sex reversed patient displayed highly impaired differentiation and epithelial-mesenchymal transition (EMT)-like phenotype. Interestingly, RSPO1-mutated PPK skin expressed markers of increased proliferation, dedifferentiation and altered cell–cell adhesion. Furthermore, all these signs were more evident in SCC specimens of the patient. Cultured PPK patient’s keratinocytes exhibited increased expression of cell‒matrix adhesion proteins and extracellular matrix remodeling enzymes. Moreover, they showed invasiveness properties in an organotypic skin model in presence of PPK fibroblasts, which behave like cancer-associated fibroblasts. However, the co-culture with normal fibroblasts or treatment with the recombinant RSPO1 protein did not revert or reduce the EMT-like phenotype and invasion capability of PPK keratinocytes. Notably, RSPO1-mutated PPK fibroblasts induced a hyperproliferative and dedifferentiated phenotype of age-matched normal control plantar keratinocytes. Wnt signaling has a key role in both PPK promotion and SCC development. Accordingly, Wnt mediators were differentially expressed in both PPK keratinocytes and skin specimens of RSPO1-mutated patient compared to control.ConclusionsAltogether our data indicate that the absence of RSPO1 in patients with 46XX disorder of sexual development affects the skin microenvironment and epidermal integrity, thus contributing to the risk of SCC tumorigenesis in palmoplantar regions exposed to major frictional stresses.

TGA factors promote plant root growth by modulating redox homeostasis or response.

To identify novel regulators of stem cell renewal, we mined an existing but little explored cell type-specific transcriptome dataset for the Arabidopsis root. A member of the TGA family of transcription factors, TGA8, was found to be specifically expressed in the quiescent center (QC). Mutation in TGA8 caused a subtle root growth phenotype, suggesting functional redundancy with other TGA members. Using a promoter::HGFP transgenic approach, we showed that all TGA factors were expressed in the root, albeit at different levels and with distinct spatial patterns. Mutant analyses revealed that all TGA factors examined contribute to root growth by promoting stem cell renewal, meristem activity, and cell elongation. Combining transcriptome analyses, histochemical assays, and physiological tests, we demonstrated that functional redundancy exists among members of clades II and V or those in clades I and III. These two groups of TGA factors act differently, however, as their mutants responded to oxidative stress differently and quantitative reverse transcription polymerase chain reaction assays showed they regulate different sets of genes that are involved in redox homeostasis. Our study has thus uncovered a previously unrecognized broad role and a mechanistic explanation for TGA factors in root growth and development.

Hedgehog signaling regulates the development and treatment of glioblastoma.

Glioblastoma (GBM) is the most common and fatal malignant tumor type of the central nervous system. GBM affects public health and it is important to identify biomarkers to improve diagnosis, reduce drug resistance and improve prognosis (e.g., personalized targeted therapies). Hedgehog (HH) signaling has an important role in embryonic development, tissue regeneration and stem cell renewal. A large amount of evidence indicates that both normative and non-normative HH signals have an important role in GBM. The present study reviewed the role of the HH signaling pathway in the occurrence and progression of GBM. Furthermore, the effectiveness of drugs that target different components of the HH pathway was also examined. The HH pathway has an important role in reversing drug resistance after GBM conventional treatment. The present review highlighted the relevance of HH signaling in GBM and outlined that this pathway has a key role in the occurrence, development and treatment of GBM.