Maintenance Of Stemness Research Articles

Deubiquitinating enzyme MINDY1 is an independent risk factor for the maintenance of stemness and poor prognosis in liver cancer cells

Objective: To explore the key deubiquitinating enzymes that maintain the stemness of liver cancer stem cells and provide new ideas for targeted liver cancer therapy. Methods: The high-throughput CRISPR screening technology was used to screen the deubiquitinating enzymes that maintain the stemness of liver cancer stem cells. RT-qPCR and Western blot were used to analyze gene expression levels. Stemness of liver cancer cells was detected by spheroid-formation and soft agar colony formation assays. Tumor growth in nude mice was detected by subcutaneous tumor-bearing experiments. Bioinformatics and clinical samples were examined for the clinical significance of target genes. Results: MINDY1 was highly expressed in liver cancer stem cells. The expression of stem markers, the self-renewal ability of cells, and the growth of transplanted tumors were significantly reduced and inhibited after knocking out MINDY1, and its mechanism of action may be related to the regulation of the Wnt signaling pathway. The expression level of MINDY1 was higher in liver cancer tissues than that in adjacent tumors, which was closely related to tumor progression, and its high expression was an independent risk factor for a poor prognosis of liver cancer. Conclusion: The deubiquitinating enzyme MINDY1 promotes stemness in liver cancer cells and is one of the independent predictors of poor prognosis in liver cancer.

METTL3 promotes pancreatic cancer proliferation and stemness by increasing stability of ID2 mRNA in a m6A-dependent manner

In eukaryotes, N6-methyladenosine (m6A) is the most prevalent epigenetic alteration. Methyltransferase-like 3 (METTL3) is a key player in the control of m6A, although its function in pancreatic cancer is incompletely understood. In this study, we examined the role that METTL3 plays in pancreatic cancer cell proliferation and stemness. We discovered that in pancreatic cancer cells, METTL3-mediated m6A alterations regulate ID2 as a downstream target. The stability of ID2 mRNA was decreased and m6A modification was effectively eliminated by METTL3 knockdown in pancreatic cancer cells. We also demonstrate that m6a-YTHDF2 is necessary for the METTL3-mediated stabilization of ID2 mRNA. Additionally, we show that ID2 controls the stemness molecules NANOG and SOX2 via the PI3K-AKT pathway to support pancreatic cancer growth and stemness maintenance. Our data suggest that METTL3 may post-transcriptionally upregulate ID2 expression in an m6A-YTHDF2-dependent manner to further promote the stabilization of ID2 mRNA, which may be a new target for pancreatic cancer treatment.

Emerging Roles of YAP/TAZ in Tooth and Surrounding: from Development to Regeneration.

Yes associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are ubiquitous transcriptional co-activators that control organ development, homeostasis, and tissue regeneration. Current in vivo evidence suggests that YAP/TAZ regulates enamel knot formation during murine tooth development, and is indispensable for dental progenitor cell renewal to support constant incisor growth. Being a critical sensor for cellular mechano-transduction, YAP/TAZ lays at the center of the complex molecular network that integrates mechanical cues from the dental pulp chamber and surrounding periodontal tissue into biochemical signals, dictating in vitro cell proliferation, differentiation, stemness maintenance, and migration of dental stem cells. Moreover, YAP/TAZ-mediated cell-microenvironment interactions also display essential regulatory roles during biomaterial-guided dental tissue repair and engineering in some animal models. Here, we review recent advances in YAP/TAZ functions in tooth development, dental pulp, and periodontal physiology, as well as dental tissue regeneration. We also highlight several promising strategies that harness YAP/TAZ activation for promoting dental tissue regeneration.

Irbesartan overcomes gemcitabine resistance in pancreatic cancer by suppressing stemness and iron metabolism via inhibition of the Hippo/YAP1/c-Jun axis

BackgroundChemoresistance is the main reason for the poor prognosis of pancreatic ductal adenocarcinoma (PDAC). Thus, there is an urgent need to screen out new targets and compounds to reverse chemotherapeutic resistance.MethodsWe established a bio-bank of human PDAC organoid models, covering a representative range of PDAC tumor subtypes. We screened a library of 1304 FDA-approved compounds to identify candidates efficiently overcoming chemotherapy resistance. The effects of the compounds were evaluated with a CellTiter-Glo-3D assay, organoid apoptosis assay and in vivo patient-derived xenograft (PDX), patient-derived organoid (PDO) and LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx1-Cre (KPC) genetically engineered mouse models. RNA-sequencing, genome editing, sphere formation assays, iron assays and luciferase assays were conducted to elucidate the mechanism.ResultsHigh-throughput drug screening of chemotherapy-resistant PDOs identified irbesartan, an angiotensin ‖ type 1 (AT1) receptor antagonist, which could synergistically enhance the ability of chemotherapy to kill PDAC cells. In vitro and in vivo validation using PDO, PDX and KPC mouse models showed that irbesartan efficiently sensitized PDAC tumors to chemotherapy. Mechanistically, we found that irbesartan decreased c-Jun expression by inhibiting the Hippo/YAP1 pathway and further overcame chemotherapy resistance in PDAC. We also explored c-Jun, a potential target of irbesartan, which can transcriptionally upregulate the expression of key genes involved in stemness maintenance (SOX9/SOX2/OCT4) and iron metabolism (FTH1/FTL/TFRC). More importantly, we observed that PDAC patients with high levels of c-Jun expression demonstrated poor responses to the current standard chemotherapy regimen (gemcitabine plus nab-paclitaxel). Moreover, patients with PDAC had significant survival benefits from treatment with irbesartan plus a standard chemotherapy regimen in two-center retrospective clinical cohorts and patients with high c-Jun expression exhibited a better response to combination chemotherapy.ConclusionsIrbesartan could be used in combination with chemotherapy to improve the therapeutic efficacy in PDAC patients with high levels of c-Jun expression. Irbesartan effectively inhibited chemotherapy resistance by suppressing the Hippo/YAP1/c-Jun/stemness/iron metabolism axis. Based on our findings, we are designing an investigator-initiated phase II clinical trial on the efficacy and safety of irbesartan plus a standard gemcitabine/nab-paclitaxel regimen in the treatment of patients with advanced III/IV staged PDAC and are hopeful that we will observe patient benefits.

Low temperature and mTOR inhibition favor stem cell maintenance in human keratinocyte cultures

Adult autologous human epidermal stem cells can be extensively expanded ex vivo for cell and gene therapy. Identifying the mechanisms involved in stem cell maintenance and defining culture conditions to maintain stemness is critical, because an inadequate environment can result in the rapid conversion of stem cells into progenitors/transient amplifying cells (clonal conversion), with deleterious consequences on the quality of the transplants and their ability to engraft. Here, we demonstrate that cultured human epidermal stem cells respond to a small drop in temperature through thermoTRP channels via mTOR signaling. Exposure of cells to rapamycin or a small drop in temperature induces the nuclear translocation of mTOR with an impact on gene expression. We also demonstrate by single‐cell analysis that long‐term inhibition of mTORC1 reduces clonal conversion and favors the maintenance of stemness. Taken together, our results demonstrate that human keratinocyte stem cells can adapt to environmental changes (e.g., small variations in temperature) through mTOR signaling and constant inhibition of mTORC1 favors stem cell maintenance, a finding of high importance for regenerative medicine applications.

Combined GSK-3β and MEK inhibitors modulate the stemness and radiotherapy sensitivity of cervical cancer stem cells through the Wnt signaling pathway

Cancer stem cells (CSCs) are the basis of cancer and lead to the recurrence and metastasis of cervical cancer. The aim of this study was to investigate the effects of antineoplastic agents on the stemness and radiotherapy sensitivity of cervical CSCs. Side population (SP) and non-side population (NSP) cells from the SiHa cervical cancer cell line were separated using flow cytometry. The cell spheroidization, proliferation, and subcutaneous tumor formation abilities of SP cells were stronger than those of NSP cells, and cervical CSC marker expressions increased in SP cells. The proliferation, anti-apoptosis and migration of SP cells under ionizing radiation were higher than those of SiHa cells. GSK-3β and/or MEK inhibitors can increase the proliferation, migration and anti-apoptosis of SP cells, and CSC marker expressions. The Wnt pathway inhibitor decreased CSC stemness maintenance by combination of GSK-3β and MEK inhibitors. Injection of GSK-3β and MEK inhibitors under ionizing radiation promoted tumor growth and activated downstream factor expressions in the Wnt signaling pathway in vivo. This study demonstrated that combining GSK-3β and MEK inhibitors can activate Wnt signaling pathway in cervical CSCs, thereby affecting their stemness maintenance and radiotherapy sensitivity.

Notch and Wnt Signaling Modulation to Enhance DPSC Stemness and Therapeutic Potential.

The Dental Pulp of permanent human teeth is home to stem cells with remarkable multilineage differentiation ability: human Dental Pulp Stem Cells (DPSCs). These cells display a very notorious expression of pluripotency core factors, and the ability to give rise to mature cell lineages belonging to the three embryonic layers. For these reasons, several researchers in the field have long considered human DPSCs as pluripotent-like cells. Notably, some signaling pathways such as Notch and Wnt contribute to maintaining the stemness of these cells through a complex network involving metabolic and epigenetic regulatory mechanisms. The use of recombinant proteins and selective pharmacological modulators of Notch and Wnt pathways, together with serum-free media and appropriate scaffolds that allow the maintenance of the non-differentiated state of hDPSC cultures could be an interesting approach to optimize the potency of these stem cells, without a need for genetic modification. In this review, we describe and integrate findings that shed light on the mechanisms responsible for stemness maintenance of hDPSCs, and how these are regulated by Notch/Wnt activation, drawing some interesting parallelisms with pluripotent stem cells. We summarize previous work on the stem cell field that includes interactions between epigenetics, metabolic regulations, and pluripotency core factor expression in hDPSCs and other stem cell types.

Bromodomain and Extraterminal Domain (BET) Protein Inhibition Hinders Glioblastoma Progression by Inducing Autophagy-Dependent Differentiation.

Glioblastoma multiforme (GBM) is the most common and aggressive type of malignant primary brain tumor, and it is characterized by a high recurrence incidence and poor prognosis due to the presence of a highly heterogeneous mass of stem cells with self-renewal capacity and stemness maintenance ability. In recent years, the epigenetic landscape of GBM has been explored and many epigenetic alterations have been investigated. Among the investigated epigenetic abnormalities, the bromodomain and extra-terminal domain (BET) chromatin readers have been found to be significantly overexpressed in GBM. In this work, we investigated the effects of BET protein inhibition on GBM cell reprogramming. We found that the pan-BET pharmacological inhibitor JQ1 was able to promote a differentiation program in GBM cells, thus impairing cell proliferation and enhancing the toxicity of the drug Temozolomide (TMZ). Notably, the pro-differentiation capability of JQ1 was prevented in autophagy-defective models, suggesting that autophagy activation is necessary for BET protein activity in regulating glioma cell fate. Given the growing interest in epigenetic therapy, our results further support the possibility of introducing a BET-based approach in GBM clinical management.

Spontaneous spheroids from alveolar bone-derived mesenchymal stromal cells maintain pluripotency of stem cells by regulating hypoxia-inducible factors

BackgroundSpontaneous spheroid culture is a novel three-dimensional (3D) culture strategy for the rapid and efficient selection of progenitor cells. The objectives of this study are to investigate the pluripotency and differentiation capability of spontaneous spheroids from alveolar bone-derived mesenchymal stromal cells (AB-MSCs); compare the advantages of spontaneous spheroids to those of mechanical spheroids; and explore the mechanisms of stemness enhancement during spheroid formation from two-dimensional (2D) cultured cells.MethodsAB-MSCs were isolated from the alveolar bones of C57BL/6 J mice. Spontaneous spheroids formed in low-adherence specific culture plates. The stemness, proliferation, and multi-differentiation capacities of spheroids and monolayer cultures were investigated by reverse transcription quantitative polymerase chain reaction (RT-qPCR), immunofluorescence, alkaline phosphatase (ALP) activity, and oil-red O staining. The pluripotency difference between the spontaneous and mechanical spheroids was analyzed using RT-qPCR. Hypoxia-inducible factor (HIFs) inhibition experiments were performed to explore the mechanisms of stemness maintenance in AB-MSC spheroids.ResultsAB-MSCs successfully formed spontaneous spheroids after 24 h. AB-MSC spheroids were positive for MSC markers and pluripotency markers (Oct4, KLF4, Sox2, and cMyc). Spheroids showed higher Ki67 expression and lower Caspase3 expression at 24 h. Under the corresponding conditions, the spheroids were successfully differentiated into osteogenic and adipogenic lineages. AB-MSC spheroids can induce neural-like cells after neurogenic differentiation. Higher expression of osteogenic markers, adipogenic markers, and neurogenic markers (NF-M, NeuN, and GFAP) was found in spheroids than in the monolayer. Spontaneous spheroids exhibited higher stemness than mechanical spheroids did. HIF-1α and HIF-2α were remarkably upregulated in spheroids. After HIF-1/2α-specific inhibition, spheroid formation was significantly reduced. Moreover, the expression of the pluripotency genes was suppressed.ConclusionsSpontaneous spheroids from AB-MSCs enhance stemness and pluripotency. HIF-1/2α plays an important role in the stemness regulation of spheroids. AB-MSC spheroids exhibit excellent multi-differentiation capability, which may be a potent therapy for craniomaxillofacial tissue regeneration.

Abstract 1486: The regulatory mechanism of LncRNA CCAT1 via three-dimensional genome structure in colorectal cancer cells

Abstract Kruppel-like factor 5 (KLF5) belongs to zinc finger transcription factors and its expression is up-regulated in specific cancer types, such as gastrointestinal cancer and squamous carcinoma. It is reported that KLF5 is associated with the maintenance of stemness and essential for the integrity of intestinal epithelium and oncogenesis. Colon Cancer Associated Transcript 1 (CCAT1) is a long noncoding RNA that was initially found to be up-regulated in colorectal cancer (CRC), and studies have reported that high CCAT1 expression is associated with poor prognosis in CRC patients. In this study, we performed in vitro enChIP (engineered DNA-binding molecule-mediated chromatin immunoprecipitation)-sequencing to identify the KLF5 enhancer region which interacts with KLF5 promoter region. We successfully identified the KLF5 enhancer region in colorectal cancer cells and further found that KLF5 promoter region interacted with the transcription start site (TSS) region of CCAT1 gene, which is located at the different chromosome. Our results indicated that KLF5 protein participated in the core regulatory circuitry together with co-factors (BRD4, MED1, and RAD21), which contributes to construction of the three-dimensional genome structures consisting of KLF5 promoter, enhancer and CCAT1 TSS region. We also found that CCAT1 expression was highly correlated with KLF5 expression in CRC clinical samples and that KLF5 regulated CCAT1 expression. In conclusion, our data propose the mechanistic insight that KLF5 protein constructs the core regulatory circuitry with co-factors in the three-dimensional genome structure and coordinately regulates KLF5 and CCAT1 expression in CRC. Citation Format: Yuhki Yokoyama, Hirofumi Yamamoto. The regulatory mechanism of LncRNA CCAT1 via three-dimensional genome structure in colorectal cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1486.

HIGH ANTIOXIDATION-CAPACITY STEM CELLS ENHANCE CARTILAGE REGENERATION

Stem cells are known to have low levels of intracellular reactive oxygen species (ROS) and high levels of glutathione. ROS are thought to interact with several pathways that affect the transcription machinery required for stem cell differentiation, and are critical for maintaining stem cell function. In this study, we are developing a new fluorescent probe that rapidly and reversibly reacts with glutathione (GSH), the most abundant non-protein thiol in living cells that acts as an antioxidant and redox regulator.Multipotent perivascular progenitor cells derived from human ESCs (hESC-PVPCs): Differentiated ESCs as embryoid bodies in the presence of BMP4 to induce mesoderm differentiation followed by a simple cell selection strategy using attachment of single cells onto collagen-coated dishes. Differential gene expression profiling was performed among H9 hESCs, EBs induced by BMP4 and naturally selected CD140B+CD44+ population at Day 7 (PVPCs). Colony-forming assay: GSHhigh and GSHlow PVPCs were plated on 10-cm tissue culture-treated polystyrene dishes in triplicate in growth medium and cultured for 14 days. Transwell migration assay: GSHhigh and GSHlow PVPCs at passage 4 were resuspended at 1 × 106/mL in the migration medium and seeded in the upper chamber. The following human recombinant SDF-1 and PDGF-AA proteins were used as chemoattractants in the lower compartment.Probe-GSH conjugate shows shifts in fluorescence excitation and emission spectra that enables ratiometric measurement of GSH levels. Using these properties, stem cells can be purified by FACS-based technology according to intracellular GSH level. We are developing a protocol both for comparing GSH level in stem cell from different culture conditions and for preparing stem cells with high-GSH level . Our results reveal that GSHhigh PVPC purified by FACS show increased colony forming ability compared with that GSHlow PVPC, indicating that intracellular GSH contributes to the maintenance of stemness. Moreover, transplantation of GSHlow PVPC is more effective than that of GSHlow PVPC for cartilage regeneration in osteochondral defect.This technique enable FACS-based sorting of stem cells according to intracellular GSH levels and thus investigation of functional role of GSH (high antioxidant capacity) in the stem cell maintenance and chondrogenic differentiation.

Abstract 2428: Cancer stem cells maintain stemness via autocrine activation of the IFN/JAK/STAT signaling pathway

Abstract Interferons (IFNs) and Janus Kinase/Signal Transducer and Activator of Transcription (JAK/STAT) signaling are best known for their roles in immunity. However, recent work has suggested that both IFNs and the JAK/STAT pathways are associated with tumor growth and progression, as well as the maintenance of cancer stem cell (CSC) populations. To better understand the regulation of the CSC population maintenance by the IFN/JAK/STAT signaling pathway, we enriched CSCs from a panel of non-small cell lung cancer (NSCLC) cell lines by using spheroid culture and determined the phosphorylation of STAT1. We found that sphere cells exhibit increased level of pSTAT1-Y701 compared to their corresponding bulk cells. We further determined the expression level of a few interferon-stimulated genes (ISGs) and found that sphere cells possess enhanced expression of ISG54 and ISG56 genes, which are normally induced by type I IFN (IFN-I), as well as IFNA and IFNB. These results indicate that the IFN-I/STAT1 signaling is highly activated in CSCs, which produce and secrete increased amount of IFN-I. To directly show the effect of IFN-I on the stemness of NSCLC cells, we treated NSCLC cells with IFNβ, and found that IFNβ can significantly enhance the expression of SOX2, a stem cell-specific transcription factor; Inhibition of the JAK signaling blocked both basal and IFNβ-induced SOX2 expression. In addition, knockdown of STAT1 also reduced SOX2 expression, indicating that STAT1 activation plays an important role in mediating IFN-induced enhancement of stemness. Finally, the ChIP assay demonstrated that STAT1 protein can bind to the promoter region of the SOX2 gene to serve as a transcription factor. In summary, our results indicate that CSCs produce and secrete IFN-I via their enhanced JAK/STAT1 signaling. The secreted IFN-I can bind to the receptor on the CSCs, further activate their JAK/STAT1 signaling, promoting the expression of SOX2 and maintenance of stemness of CSCs via an autocrine manner. Citation Format: Aidan Li, Xuetao Bai, Na Li, Shurui Cai, Ananya Banerjee, Kousalya Lavudi, Linzhou Wang, Qianyun Ge, Yajing Yang, Qi-En Wang. Cancer stem cells maintain stemness via autocrine activation of the IFN/JAK/STAT signaling pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2428.

Abstract 3661: Extracellular vesicle derived from neural stem cells as potential vehicles of genetic information to modulate glioblastoma biology

Abstract Glioblastoma (GBM) is a deadly brain tumor and its high aggressiveness is partly due to a subpopulation of tumor stem cells known as glioblastoma stem-like cells (GSCs). GBM establishes crosstalk with non-tumoral cells, mediated mainly by extracellular vesicles (EVs) and the interaction between GSCs and neural stem cells (NSCs) from the subventricular zone may influence GBM biology. Literature data suggests that cellular communication is an important process for GSCs stemness maintenance, and some authors consider NSCs as a possible cell of origin for GSCs. However, the specific effects that neural stem cells-derived extracellular vesicles (NSCs-EVs) promote in GSCs are still uncertain. Previous data from our group demonstrated specific groups of microRNAs (hsa-miR -137, -216a-5p, -216b-5p, 217), enriched in NSCs-EVs in contrast to intracellular compartments, suggesting these molecules are being produced for secretion. Our study aims to evaluate the role of the miRs contained in NSCs-EVs in GSCs biology. Human induced pluripotent stem cells (hiPSC) were differentiated into NSCs. NSCs were characterized by western blotting and immunofluorescence by the expression of neural commitment markers, such as nestin and β-III-tubulin. NSCs-EVs were isolated from NSCs’ culture media with a commercial kit and analyzed by NTA (nanosight) for EVs size profiling and western blotting to detect specific markers, such as Alix, CD63, and HSP90. In a first approach, we analyzed the effects played by those miRs through predictive online tools. We identified target genes related to stemness (NANOG, SOX2, KLF4), oncogenesis (KRAS, CDC42, CDK6) and metabolism (CAMK2A), besides the Wnt and Notch signaling pathways. The online predictions also identified transcriptional factors related to vasculogenesis and self-renewal, key processes for GSCs activity. We will expose GSCs to NSCs-EVs and evaluate the expression of neural and stemness markers. In a future step, the GSCs previously exposed to NSCs-EVs will be treated with temozolomide, and viability assays will be performed. Additionally, we intend to modulate the four miRs identified and evaluate if they act as effector molecules of NSCs-EVs. Our data corroborate with our initial hypothesis that NSCs-EVs may act as important signalling modes in GSCs activity and consequently in GBM biology. Supported by FAPESP:22/08106-1. Citation Format: João Pedro Alves de Araújo, Lilian Cruz, Maria Clara da Silva Souza, Mariana Brandão Prado, Rodrigo Nunes Alves, Bárbara Paranhos Coelho, Samuel Ribeiro Soares, Camila Félix Fernandes, Marilene Hohmuth Lopes. Extracellular vesicle derived from neural stem cells as potential vehicles of genetic information to modulate glioblastoma biology. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3661.

Abstract 325: The cellular prion protein is involved in the modulation of Wnt signaling in glioblastoma

Abstract Glioblastoma (GBM) is an aggressive, invasive and therapy resistant brain tumor. Our research group has been unraveling the role of the cellular prion protein (PrPC) on GBM biology. PrPC is a scaffold protein that interacts with a plethora of partners, and it is important for proliferation and stemness maintenance of glioblastoma stem-like cells (GSCs), that are responsible for the aggressiveness and resistance to therapy of GBM. GSCs have aberrant activation of several signaling pathways that control self-renewal and differentiation, such as the Notch, Hedgehog (Hh) and Wnt pathways. Additionally, PrPC was proposed as a modulator of the Wnt signaling pathway on proliferating intestinal epithelial cells due to its binding to beta-catenin and upregulation of the transcriptional activity of the beta-catenin/TCF7L2 complex. Therefore, we aim to further explore this connection between Wnt signaling and PrPC in GBM. We generated U87 and U251 GBM PrPC knockout cells (PrPC-KO) by CRISPR-Cas9. RNA sequencing analysis comparing PrPC-KO GBM cells with wild-type controls resulted in 28 differentially expressed genes (DEGs) for U87 cells and 10 DEGs for U251 cells that are components of pathways related to Wnt signaling. We chose to analyze the expression of the upregulated DEGs CAMK2A, NFATC4, WISP1, PPP2R2B, SFRP2; and the downregulated DEGs RAC3 and SHH by qPCR. Our results indicate that the Wnt-Ca2+ pathway may be activated in U87 PrPC -KO cells, due to increased expression of NFATC4 and CAMK2A. Regarding the canonical Wnt signaling, it appears to be a balance in the expression of genes that activate or inhibit these pathways in U87 PrPC-KO cells, since WISP1 and PPP2R2B were upregulated and SFRP2 was downregulated. When analyzing the expression of the same genes in U251 PrPC-KO cells, however, we observed a different expression profile than what was found for U87 cells. Apart from RAC3, the expression of all genes analyzed were downregulated. Importantly, expression of SHH was downregulated in both U87 and U251 PrPC-KO cells. When we analyzed protein levels of Wnt signaling components, we found a decrease of beta-catenin and Wnt5a/b in U87 PrPC-KO, demonstrating a downregulation of the canonical signaling. Moreover, we found by immunofluorescence that beta-catenin distribution on the cellular membrane was altered in U87 PrPC-KO cells. Our results demonstrate, therefore, a potential involvement of PrPC in modulating Wnt signaling in GBM. As a scaffolding protein, PrPC may be contributing to GBM biology by increasing the effectiveness of Wnt signaling, by localizing beta-catenin on important regions of the tumor cell membrane, or by insulating beta-catenin from degradation. Altogether, PrPC may be a promising target for the development of novel therapy strategies against GBM. Supported by FAPESP (2019/14952-0) Citation Format: Barbara Paranhos Coelho, Mariana B. Prado, Frederico M. Ferreira, Tiago G. dos Santos, Helder I. Nakaya, Marilene H. Lopes. The cellular prion protein is involved in the modulation of Wnt signaling in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 325.

379 Human Endogenous Retrovirus-K (HML-2) Contributes to a Unique Stem-Cell Niche in Glioblastoma

INTRODUCTION: Human Endogenous Retrovirus (HERV) are ancestral viral relics that comprise nearly 8% of the human genome. Although silenced in normal tissues, the most recently integrated provirus HERV-K (HML-2) can be pathologically reactivated in certain cancers. METHODS: We utilized a combination approach using scRNA-seq, multiplex immunofluorescence, and TEM to characterize HERV-K expression in malignant gliomas. Using CRISPR engineering and CHIP-qPCR, we downregulated HML-2 in both patient-derived glioma neurospheres and intracranial orthotopic models and identified interactions between HERV-K and pluirpotency transcription factors. RESULTS: We identified pathological expression of HML-2 in human malignant gliomas in CSF (HERV-K DNA/RPP30 = 35.2 ± 8.8 vs 23.1 ± 6.7, n = 18, p = 0.02) and tumors (HERV-K RNA/HPRT mean = 1.15 ± 0.2 vs. 0.5 ± 0.2, p = 0.01, n = 20) compared to epilepsy controls. Aberrant HML-2 expression corresponded to a unique stem-cell niche using multivoxel automated segmentation. Using a tailored scRNA-seq sequencing pipeline, we identified glioblastoma cellular populations with elevated HML-2 transcripts in neural progenitor-like cells that can drive cellular plasticity (ANOVA, p < 0.001). Using CRISPR technology, we demonstrate that HML-2 is critical to maintenance of glioblastoma stemness and tumorigenesis in both glioblastoma neurospheres and intracranial orthotopic murine models (OS: 26 days vs. 18.6, p=0.0008, n=20). Downregulation of HERV-K using CRISPRi reduces the glioblastoma neurosphere formation (2-way ANOVA, p < 0.0001) and HERV-K env, Polymerase, OCT4 and Nestin transcripts (2-way ANOVA p < 0.001). Moreover, using Transmission Electron Microscopy, we discovered that some glioma stem-cells form immature retroviral virions in glioblastoma. Inhibiting HML-2 expression with nucleoside reverse transcriptase inhibitors reduces extracellular reverse transcriptase (One-way ANOVA, p < 0.05), tumor viability (IC50 = 75.8-123.1 uM), and pluripotency (1-way ANOVA, p < 0.01). CONCLUSIONS: Our results suggest that HML-2 is overexpressed in the glioblastoma stem-cell niche. Since persistence of glioblastoma stem-cells is considered responsible for treatment resistance/recurrence, HML-2 may serve as a unique therapeutic target in glioblastoma.

The dysregulation of leukemia inhibitory factor and its implications for endometriosis pathophysiology.

Endometriosis is an estrogen dominant, chronic inflammatory disease characterized by the growth of endometrial-like tissue outside of the uterus. The most common symptoms experienced by patients include manifestations of chronic pelvic pain- such as pain with urination, menstruation, or defecation, and infertility. Alterations to Leukemia Inhibitory Factor (LIF), a cytokine produced by the luminal and glandular epithelium of the endometrium that is imperative for successful pregnancy, have been postulated to contribute to infertility. Conditions such as recurrent implantation failure, unexplained infertility, and infertility associated diseases such as adenomyosis and endometriosis, have demonstrated reduced LIF production in the endometrium of infertile patients compared to fertile counterparts. While this highlights the potential involvement of LIF in infertility, LIF is a multifaceted cytokine which plays additional roles in the maintenance of cell stemness and immunomodulation. Thus, we sought to explore the implications of LIF production within ectopic lesions on endometriosis pathophysiology. Through immunohistochemistry of an endometrioma tissue microarray and ELISA of tissue protein extract and peritoneal fluid samples, we identify LIF protein expression in the ectopic lesion microenvironment. Targeted RT qPCR for LIF and associated signaling transcripts, identify LIF to be significantly downregulated in the ectopic tissue compared to eutopic and control while its receptor, LIFR, is upregulated, highlighting a discordance in ectopic protein and mRNA LIF expression. In vitro treatment of endometriosis representative cell lines (12Z and hESC) with LIF increased production of immune-recruiting cytokines (MCP-1, MCP-3) and the angiogenic factor, VEGF, as well as stimulated tube formation in human umbilical vein endothelial cells (HUVECs). Finally, LIF treatment in a syngeneic mouse model of endometriosis induced both local and peripheral alterations to immune cell phenotypes, ultimately reducing immunoregulatory CD206+ small peritoneal macrophages and T regulatory cells. These findings suggest that LIF is present in the ectopic lesions of endometriosis patients and could be contributing to lesion vascularization and immunomodulation.

Effect of HPSE and HPSE2 SNPs on the Risk of Developing Primary Paraskeletal Multiple Myeloma.

Multiple myeloma (MM) is a plasma cell malignancy that is accompanied by hypercalcemia, renal failure, anemia, and lytic bone lesions. Heparanase (HPSE) plays an important role in supporting and promoting myeloma progression, maintenance of plasma cell stemness, and resistance to therapy. Previous studies identified functional single nucleotide polymorphisms (SNPs) located in the HPSE gene. In the present study, 5 functional HPSE SNPs and 11 novel HPSE2 SNPs were examined. A very significant association between two enhancer (rs4693608 and rs4693084), and two insulator (rs4364254 and rs4426765) HPSE SNPs and primary paraskeletal disease (PS) was observed. SNP rs657442, located in intron 9 of the HPSE2 gene, revealed a significant protective association with primary paraskeletal disease and lytic bone lesions. The present study demonstrates a promoting (HPSE gene) and protective (HPSE2 gene) role of gene regulatory elements in the development of paraskeletal disease and bone morbidity. The effect of signal discrepancy between myeloma cells and normal cells of the tumor microenvironment is proposed as a mechanism for the involvement of heparanase in primary PS. We suggest that an increase in heparanase-2 expression can lead to effective suppression of heparanase activity in multiple myeloma accompanied by extramedullary and osteolytic bone disease.

Transplantation of endothelial progenitor cells overexpressing mir-126-3p improves vascular repair in a diabetic rat model.

Transplantation of endothelial progenitor cells overexpressing mir-126-3p improves vascular repair in a diabetic rat model.

Ginsenoside Rg2 Promotes the Proliferation and Stemness Maintenance of Porcine Mesenchymal Stem Cells through Autophagy Induction

Mesenchymal stem cells (MSCs) can be used as a cell source for cultivated meat production due to their adipose differentiation potential, but MSCs lose their stemness and undergo replicative senescence during expansion in vitro. Autophagy is an important mechanism for senescent cells to remove toxic substances. However, the role of autophagy in the replicative senescence of MSCs is controversial. Here, we evaluated the changes in autophagy in porcine MSCs (pMSCs) during long-term culture in vitro and identified a natural phytochemical, ginsenoside Rg2, that could stimulate pMSC proliferation. First, some typical senescence characteristics were observed in aged pMSCs, including decreased EdU-positive cells, increased senescence-associated beta-galactosidase activity, declined stemness-associated marker OCT4 expression, and enhanced P53 expression. Importantly, autophagic flux was impaired in aged pMSCs, suggesting deficient substrate clearance in aged pMSCs. Rg2 was found to promote the proliferation of pMSCs using MTT assay and EdU staining. In addition, Rg2 inhibited D-galactose-induced senescence and oxidative stress in pMSCs. Rg2 increased autophagic activity via the AMPK signaling pathway. Furthermore, long-term culture with Rg2 promoted the proliferation, inhibited the replicative senescence, and maintained the stemness of pMSCs. These results provide a potential strategy for porcine MSC expansion in vitro.

MED27 plays a tumor-promoting role in breast cancer progression by targeting KLF4.

The mediator complex usually cooperates with transcription factors to be involved in RNA polymerase II-mediated gene transcription. As one component of this complex, MED27 has been reported in our previous studies to promote thyroid cancer and melanoma progression. However, the precise function of MED27 in breast cancer development remains poorly understood. Here, we found that MED27 was more highly expressed in breast cancer samples than in normal tissues, especially in triple-negative breast cancer, and its expression level was elevated with the increase in pathological stage. MED27 knockdown in triple-negative breast cancer cells inhibited cancer cell metastasis and stemness maintenance, which was accompanied by downregulation of the expression of EMT- and stem traits-associated proteins, and vice versa in non-triple-negative breast cancer. Furthermore, MED27 knockdown sensitized breast cancer cells to epirubicin treatment by inducing cellular apoptosis and reducing tumorsphere-forming ability. Based on RNA-seq, we identified KLF4 as the possible downstream target of MED27. KLF4 overexpression reversed the MED27 silencing-mediated arrest of cellular metastasis and stemness maintenance capacity in breast cancer in vitro and in vivo. Mechanistically, MED27 transcriptionally regulated KLF4 by binding to its promoter region at positions -156 to +177. Collectively, our study not only demonstrated the tumor-promoting role of MED27 in breast cancer progression by transcriptionally targeting KLF4, but also suggested the possibility of developing the MED27/KLF4 signaling axis as a potential therapeutic target in breast cancer.