Stem Cell Signaling Research Articles

Disruption of Sonic Hedgehog Signaling Accelerates Age-Related Neurogenesis Decline and Abolishes Stroke-Induced Neurogenesis and Leads to Increased Anxiety Behavior in Stroke Mice.

Sonic Hedgehog (SHH) signaling has a critical role in mediating developmental neurogenesis and has been implicated in adult subventricular (SVZ) neurogenesis. However, the precise role of Smoothened (SMO) receptor-mediated SHH signaling in adult neurogenesis during aging especially in hippocampal subgranular zone (SGZ) neurogenesis remains undefined. Additionally, our previous study showed that stimulation of SHH signaling post-stroke leads to increased neurogenesis and improved behavioral functions after stroke. However, it is not clear whether SHH signaling in neural stem cells (NSCs) is required for stroke-induced neurogenesis and functional recovery post-stroke. In this study, using conditional knockout (cKO) of SHH signaling receptor Smo gene in NSCs, we show a decreased neurogenesis at both SVZ and SGZ in young-adult mice and an accelerated depletion of neurogenic cells in the process of aging suggesting that SHH signaling is critical in maintaining neurogenesis during aging. Behavior studies revealed that compromised neurogenesis in Smo cKO mice leads to increased anxiety/depression-like behaviors without affecting general locomotor function or spatial and fear-related learning. Importantly, we also show that NSCs with acKO of SHH signaling abolishes stroke-induced neurogenesis in Smo cKO mice. Compared to control mice, Smo cKO mice also show delayed motor function recovery and increased anxiety level after stroke. Our data highlights the essential role of Smo function in regulating adult neurogenesis and emotional behaviors during both aging and CNS injury such as stroke.

MUC1-C integrates type II interferon and chromatin remodeling pathways in immunosuppression of prostate cancer

ABSTRACT The oncogenic MUC1-C protein drives dedifferentiation of castrate resistant prostate cancer (CRPC) cells in association with chromatin remodeling. The present work demonstrates that MUC1-C is necessary for expression of IFNGR1 and activation of the type II interferon-gamma (IFN-γ) pathway. We show that MUC1-C→ARID1A/BAF signaling induces IFNGR1 transcription and that MUC1-C-induced activation of the NuRD complex suppresses FBXW7 in stabilizing the IFNGR1 protein. MUC1-C and NuRD were also necessary for expression of the downstream STAT1 and IRF1 transcription factors. We further demonstrate that MUC1-C and PBRM1/PBAF are necessary for IRF1-induced expression of (i) IDO1, WARS and PTGES, which metabolically suppress the immune tumor microenvironment (TME), and (ii) the ISG15 and SERPINB9 inhibitors of T cell function. Of translational relevance, we show that MUC1 associates with expression of IFNGR1, STAT1 and IRF1, as well as the downstream IDO1, WARS, PTGES, ISG15 and SERPINB9 immunosuppressive effectors in CRPC tumors. Analyses of scRNA-seq data further demonstrate that MUC1 correlates with cancer stem cell (CSC) and IFN gene signatures across CRPC cells. Consistent with these results, MUC1 associates with immune cell-depleted “cold” CRPC TMEs. These findings demonstrate that MUC1-C integrates chronic activation of the type II IFN-γ pathway and induction of chromatin remodeling complexes in linking the CSC state with immune evasion.

TRAF6 functions as a tumor suppressor in myeloid malignancies by directly targeting MYC oncogenic activity.

Clonal hematopoiesis (CH) is an aging-associated condition characterized by the clonal outgrowth of pre-leukemic cells that acquire specific mutations. Although individuals with CH are healthy, they are at an increased risk of developing myeloid malignancies, suggesting that additional alterations are needed for the transition from a pre-leukemia stage to frank leukemia. To identify signaling states that cooperate with pre-leukemic cells, we used an invivo RNAi screening approach. One of the most prominent genes identified was the ubiquitin ligase TRAF6. Loss of TRAF6 in pre-leukemic cells results in overt myeloid leukemia and is associated with MYC-dependent stem cell signatures. TRAF6 is repressed in a subset of patients with myeloid malignancies, suggesting that subversion of TRAF6 signaling can lead to acute leukemia. Mechanistically, TRAF6 ubiquitinates MYC, an event that does not affect its protein stability but rather represses its functional activity by antagonizing an acetylation modification.

Targeting NF-κB Signaling in Cancer Stem Cells: A Narrative Review.

Among the cell populations existing within a tumor, cancer stem cells are responsible for metastasis formation and chemotherapeutic resistance. In the present review, we focus on the transcription factor NF-κB, which is present in every cell type including cancer stem cells. NF-κB is involved in pro-tumor inflammation by its target gene interleukin 1 (IL1) and can be activated by a feed-forward loop in an IL1-dependent manner. Here, we summarize current strategies targeting NF-κB by chemicals and biologicals within an integrated cancer therapy. Specifically, we start with a tyrosine kinase inhibitor targeting epidermal growth factor (EGF)-receptor-mediated phosphorylation. Furthermore, we summarize current strategies of multiple myeloma treatment involving lenalidomide, bortezomib, and dexamethasone as potential NF-κB inhibitors. Finally, we discuss programmed death-ligand 1 (PD-L1) as an NF-κB target gene and its role in checkpoint therapy. We conclude, that NF-κB inhibition by specific inhibitors of IκB kinase was of no clinical use but inhibition of upstream and downstream targets with drugs or biologicals might be a fruitful way to treat cancer stem cells.

Neuropilin-1 is over-expressed in claudin-low breast cancer and promotes tumor progression through acquisition of stem cell characteristics and RAS/MAPK pathway activation

BackgroundTriple-negative breast cancers (TNBC) have a relatively poor prognosis and responses to targeted therapies. Between 25 and 39% of TNBCs are claudin-low, a poorly differentiated subtype enriched for mesenchymal, stem cell and mitogen-activated signaling pathways. We investigated the role of the cell-surface co-receptor NRP1 in the biology of claudin-low TNBC.MethodsThe clinical prognostic value of NRP1 was determined by Kaplan–Meier analysis. GSVA analysis of METABRIC and Oslo2 transcriptomics datasets was used to correlate NRP1 expression with claudin-low gene signature scores. NRP1 siRNA knockdown was performed in MDA-MB-231, BT-549, SUM159 and Hs578T claudin-low cells and proliferation and viability measured by live cell imaging and DNA quantification. In SUM159 orthotopic xenograft models using NSG mice, NRP1 was suppressed by shRNA knockdown or systemic treatment with the NRP1-targeted monoclonal antibody Vesencumab. NRP1-mediated signaling pathways were interrogated by protein array and Western blotting.ResultsHigh NRP1 expression was associated with shorter relapse- and metastasis-free survival specifically in ER-negative BrCa cohorts. NRP1 was over-expressed specifically in claudin-low clinical samples and cell lines, and NRP1 knockdown reduced proliferation of claudin-low cells and prolonged survival in a claudin-low orthotopic xenograft model. NRP1 inhibition suppressed expression of the mesenchymal and stem cell markers ZEB1 and ITGA6, respectively, compromised spheroid-initiating capacity and exerted potent anti-tumor effects on claudin-low orthotopic xenografts (12.8-fold reduction in endpoint tumor volume). NRP1 was required to maintain maximal RAS/MAPK signaling via EGFR and PDGFR, a hallmark of claudin-low tumors.ConclusionsThese data implicate NRP1 in the aggressive phenotype of claudin-low breast cancer and offer a novel targeted therapeutic approach to this poor prognosis subtype.

The acidic domain of Hmga2 and the domain's linker region are critical for driving self-renewal of hematopoietic stem cell.

High mobility group AT-hook 2 (Hmga2) is a chromatin modifier protein that plays a critical role in fetal development and leukemia propagation by binding to chromatin and DNA via its AT-hook domains. However, the molecular mechanisms by which Hmga2 activates the expression of target genes to drive the self-renewal of hematopoietic stem cells (HSCs) remain unclear. We generated Rosa26 locus Hmga2 conditional knock-in mice and found that overexpression of Hmga2 promoted self-renewal of normal HSCs, but maintained their fitness in bone marrow, and consequently was not sufficient to initiate malignancy. This result is consistent with previous findings showing that Hmga2 is a proto-oncogene. We also assessed the cellular functions of Hmga2 mutants lacking functional domains and demonstrated that the C-terminus acidic domain of Hmga2 and the domain's linker region were critical for activating genes involved in stem cell signatures, such as the Igf2bp2 gene, to drive proliferation of HSCs. In contrast, overexpression of Hmga1, a member of the Hmga family with a different linker region, did not drive proliferation of HSCs. Our results reveal a critical role for the acidic domain of Hmga2 and the domain's linker region in modulating the transcription and self-renewal functions of HSCs.

Canonical WNT pathway inhibition reduces ATP synthesis rates in glioblastoma stem cells.

The conserved stem cell signaling network canonical Wingless (WNT) plays important roles in development and disease. Aberrant activation of this pathway has been linked to tumor progression and resistance to therapy. Industry and academia have substantially invested in developing substances, which can efficiently and specifically block the WNT signaling pathway. However, a clear clinical proof of the efficacy of this approach is still missing. Studies on the metabolomics dysregulation of cancer cells have led to innovations in oncological diagnostics. In addition, modulation of cancer cell metabolome is at the base of promising clinical oncology trials currently underway. While onco-protein activation can have profound metabolic outcomes, the involvement of stem cell signals, such as the WNT pathway, in tumor cell metabolomics is yet insufficiently characterized. We determined live cell metabolism and bioenergetics in pathophysiological relevant, WNT-dependent glioblastoma stem cell (GSC) models. We quantified those parameters in cells with canonical WNT activity and in isogenic cells where WNT activity had been inhibited by short hairpin RNA against β-catenin. Furthermore, we applied computational analysis of RNA sequencing to verify our functional findings in independent GSCs cohorts. The investigated collection of disease models allows the separation in tumors with low, moderate and high base line metabolic activity. Suppression of canonical WNT signaling led to significant reduction of total, mitochondrial, and glycolytic ATP production rates. Elevated canonical WNT transcription signature in GSCs positively correlated with transcription levels of mitochondrial ATP synthesis, whereas non-canonical WNT gene expression signature did not. The applied disease modeling technology allows the recapitulation of inter-tumoral heterogeneous metabolic properties of glioblastoma. Our data show for the first time that inhibition of canonical WNT signaling in alive GSCs functionally correlates with energy inhibition and glucose homeostasis. As this correlation occurs in GSCs from different transcriptional or epigenetic transcriptional subtypes, our results suggest that developing therapies directed against glycolysis/ATP-synthesis may be a promising strategy to overcome therapy resistance due to inter-tumoral heterogeneity and offers starting point to impair downstream signal WNT.

The scaffolding protein DLG5 promotes glioblastoma growth by controlling Sonic Hedgehog signaling in tumor stem cells.

Tumor invasion, a hallmark of malignant gliomas, involves reorganization of cell polarity and changes in the expression and distribution of scaffolding proteins associated with polarity complexes. The scaffolding proteins of the DLG family are usually downregulated in invasive tumors and regarded as tumor suppressors. Despite their important role in regulating neurodevelopmental signaling, the expression and functions of DLG proteins have remained almost entirely unexplored in malignant gliomas. Western blot, immunohistochemistry, and analysis of gene expression were used to quantify DLG members in glioma specimens and cancer datasets. Over-expression and knockdown of DLG5, the highest-expressed DLG member in glioblastoma, were used to investigate its effects on tumor stem cells and tumor growth. qRT-PCR, Western blotting, and co-precipitation assays were used to investigate DLG5 signaling mechanisms. DLG5 was upregulated in malignant gliomas compared to other solid tumors, being the predominant DLG member in all glioblastoma molecular subtypes. DLG5 promoted glioblastoma stem cell invasion, viability, and self-renewal. Knockdown of this protein in vivo disrupted tumor formation and extended survival. At the molecular level, DLG5 regulated Sonic Hedgehog (Shh) signaling, making DLG5-deficient cells insensitive to Shh ligand. Loss of DLG5 increased the proteasomal degradation of Gli1, underlying the loss of Shh signaling and tumor stem cell sensitization. The high expression and pro-tumoral functions of DLG5 in glioblastoma, including its dominant regulation of Shh signaling in tumor stem cells, reveal a novel role for this protein that is strikingly different from its proposed tumor-suppressor role in other solid tumors.

Altered BMP2/4 Signaling in Stem Cells and Their Niche: Different Cancers but Similar Mechanisms, the Example of Myeloid Leukemia and Breast Cancer.

Understanding mechanisms of cancer development is mandatory for disease prevention and management. In healthy tissue, the microenvironment or niche governs stem cell fate by regulating the availability of soluble molecules, cell-cell contacts, cell-matrix interactions, and physical constraints. Gaining insight into the biology of the stem cell microenvironment is of utmost importance, since it plays a role at all stages of tumorigenesis, from (stem) cell transformation to tumor escape. In this context, BMPs (Bone Morphogenetic Proteins), are key mediators of stem cell regulation in both embryonic and adult organs such as hematopoietic, neural and epithelial tissues. BMPs directly regulate the niche and stem cells residing within. Among them, BMP2 and BMP4 emerged as master regulators of normal and tumorigenic processes. Recently, a number of studies unraveled important mechanisms that sustain cell transformation related to dysregulations of the BMP pathway in stem cells and their niche (including exposure to pollutants such as bisphenols). Furthermore, a direct link between BMP2/BMP4 binding to BMP type 1 receptors and the emergence and expansion of cancer stem cells was unveiled. In addition, a chronic exposure of normal stem cells to abnormal BMP signals contributes to the emergence of cancer stem cells, or to disease progression independently of the initial transforming event. In this review, we will illustrate how the regulation of stem cells and their microenvironment becomes dysfunctional in cancer via the hijacking of BMP signaling with main examples in myeloid leukemia and breast cancers.

Integrative analysis of the 3D genome structure reveals that CTCF maintains the properties of mouse female germline stem cells

The three-dimensional configuration of the genome ensures cell type-specific gene expression profiles by placing genes and regulatory elements in close spatial proximity. Here, we used in situ high-throughput chromosome conformation (in situ Hi-C), RNA sequencing (RNA-seq) and chromatin immunoprecipitation sequencing (ChIP-seq) to characterize the high-order chromatin structure signature of female germline stem cells (FGSCs) and identify its regulating key factor based on the data-driven of multiple omics data. By comparison with pluripotent stem cells (PSCs), adult stem cells (ASCs), and somatic cells at three major levels of chromatin architecture, A/B compartments, topologically associating domains, and chromatin loops, the chromatin architecture of FGSCs was most similar to that of other ASCs and largely different from that of PSCs and somatic cells. After integrative analysis of the three-dimensional chromatin structure, active compartment-associating loops (aCALs) were identified as a signature of high-order chromatin organization in FGSCs, which revealed that CCCTC-binding factor was a major factor to maintain the properties of FGSCs through regulation of aCALs. We found FGSCs belong to ASCs at chromatin structure level and characterized aCALs as the high-order chromatin structure signature of FGSCs. Furthermore, CTCF was identified to play a key role in regulating aCALS to maintain the biological functions of FGSCs. These data provide a valuable resource for future studies of the features of chromatin organization in mammalian stem cells and further understanding of the fundamental characteristics of FGSCs.

Wif1 Mediates Coordination of Bone Morphogenetic Protein and Wnt Signaling in Neural and Glioma Stem Cells

Wnts, bone morphogenetic protein (BMP), and fibroblast growth factor (FGF) are paracrine signaling pathways implicated in the niche control of stem cell fate decisions. BMP-on and Wnt-off are the dominant quiescent niche signaling pathways in many cell types, including neural stem cells (NSCs). However, among the multiple inhibitory family members of the Wnt pathway, those with direct action after BMP4 stimulation in NSCs remain unclear. We examined 11 Wnt inhibitors in NSCs after BMP4 treatment. Wnt inhibitory factor 1 (Wif1) has been identified as the main factor reacting to BMP4 stimuli. RNA sequencing confirmed that Wif1 was markedly upregulated after BMP4 treatment in different gene expression analyses. Similar to the functional role of BMP4, Wif1 significantly decreased the cell cycle of NSCs and significantly inhibited cell proliferation (P < 0.05). Combined treatment with BMP4 and Wif1 significantly enhanced the inhibition of cell growth compared with the single treatment (P < 0.05). Wif1 expression was clearly lower in glioblastoma and low-grade glioma samples than in normal samples (P < 0.05). A functional analysis revealed that both BMP4 and Wif1 could decrease glioma cell growth. These effects were abrogated by the BMP inhibitor Noggin. The collective findings demonstrate that Wif1 plays a key role in quiescent NSC homeostasis and glioma cell growth downstream of BMP-on signaling. The functional roles of Wif1/BMP4 in glioma cells may provide a technical basis for regenerative medicine, drug discovery, and personal molecular therapy in future clinical treatments.

Advances in the Regulation of Osteogenic Differentiation of Periodontal Stem Cells by Signalling Pathways

Periodontal ligament stem cells (PDLSCs) are mesenchymal stem cells derived from periodontal tissues with self-renewal and multidirectional differentiation potential, and are an important cell population for periodontal tissue repair. At present, studies have shown that various signaling pathways play a crucial role in the osteogenic differentiation of periodontal stem cells, but the mechanisms involved in the regulation of osteogenic differentiation of periodontal stem cells are still in the early stage of research. Therefore, it is necessary to investigate the interrelationship and regulation of these pathways in the osteogenic differentiation of periodontal stem cells, cell signaling and new bone formation, in order to further reveal their molecular biological mechanisms. In this paper, we review the research on the regulation of osteogenic differentiation of periodontal stem cells by Notch signaling pathway, Wnt signaling pathway, NF-κB (nuclear factor-kappa B) signaling pathway and MARK signaling pathway, and provide a theoretical basis for the clinical treatment of periodontal bone defects by targeting the signaling pathways.

Alignment of single-cell trajectories by tuMap enables high-resolution quantitative comparison of cancer samples.

Single-cell technologies allow characterization of cancer samples as continuous developmental trajectories. Yet, the obtained temporal resolution cannot be leveraged for a comparative analysis due to the large phenotypic heterogeneity existing between patients. Here, we present the tuMap algorithm that exploits high-dimensional single-cell data of cancer samples exhibiting an underlying developmental structure to align them with the healthy development, yielding the tuMap pseudotime axis that allows their systematic, meaningful comparison. We applied tuMap on single-cell mass cytometry data of acute lymphoblastic and myeloid leukemia to reveal associations between the tuMap pseudotime axis and clinics that outperform cellular assignment into developmental populations. Application of the tuMap algorithm on single-cell RNA sequencing data further identified gene signatures of stem cells residing at the very-early parts of the cancer trajectories. The quantitative framework provided by tuMap allows generation of metrics for cancer patients evaluation.

Role of the store-operated Ca2+ channel in ATP-induced Ca2+ signalling in mesenchymal stem cells and regulation of cell functions.

It is well-known that extracellular ATP acts as an autocrine/paracrine signal to regulate cell functions by inducing intracellular Ca2+ signalling through its cognate receptors, namely, the ligand-gated ion channel P2X receptors that mediate Ca2+ influx and/or the Gq/11-coupled P2Y receptors that link to Ca2+ release from the ER. The reduction in ER Ca2+ can trigger further extracellular Ca2+ entry by activating the store-operated Ca2+ (SOC) channel. Mesenchymal stem cells (MSC) play an important role in the homeostasis of residing tissues and have promising applications in regenerative medicines. MSC can release ATP spontaneously or in response to diverse stimuli, and express multiple P2X and Gq/11-coupled P2Y receptors that participate in ATP-induced Ca2+ signalling and regulate cell function. There is increasing evidence to show the contribution of the SOC channel in ATP-induced Ca2+ signalling in MSC. In this mini-review, we discuss the current understanding of the expression of the SOC channel in MSC and its potential role in mediating ATP-induced Ca2+ signalling and regulation of MSC differentiation, proliferation and migration.

Aberrant Wnt Signaling Induces Comedo-Like Changes in the Murine Upper Hair Follicle

Stem cell proliferation and differentiation must be carefully balanced to support tissue maintenance and growth. Defective stem cell regulation may underpin diseases in many organs, including the skin. LRIG1-expressing stem cells residing in the hair follicle junction zone (JZ) support sebaceous gland homeostasis. An emerging hypothesis from observations in both mice and human holds that imbalances in key stem cell regulatory pathways such as Wnt signaling may lead to abnormal fate determination of these LRIG1+ve cells. They accumulate and form cystic structures in the JZ that are similar to the comedones found in human acne. To test the possible involvement of Wnt signals in this scenario, we used the Lrig1-CreERT2 mouse line to modulate Wnt signaling in JZ stem cells. We observed that persistent activation of Wnt signaling leads to JZ cyst formation, with associated sebaceous gland atrophy. The cysts strongly express stem cell markers and can be partially reduced by all-trans retinoic acid treatment as well as by Hedgehog signaling inhibition. Conversely, loss of Wnt signaling leads to enlargement of JZ, infundibulum, and sebaceous glands. These data implicate abnormal Wnt signaling in the generation of mouse pathologies that resemble human acne and respond to acne treatments.

Olfactomedin 4 Is Not a Precise Marker for Human Intestinal Stem Cells, But Is Involved in Intestinal Carcinogenesis

Olfactomedin 4 Is Not a Precise Marker for Human Intestinal Stem Cells, But Is Involved in Intestinal Carcinogenesis

Non-canonical Wnt signaling promotes directed migration of intestinal stem cells to sites of injury

Tissue regeneration after injury requires coordinated regulation of stem cell activation, division, and daughter cell differentiation, processes that are increasingly well understood in many regenerating tissues. How accurate stem cell positioning and localized integration of new cells into the damaged epithelium are achieved, however, remains unclear. Here, we show that enteroendocrine cells coordinate stem cell migration towards a wound in the Drosophila intestinal epithelium. In response to injury, enteroendocrine cells release the N-terminal domain of the PTK7 orthologue, Otk, which activates non-canonical Wnt signaling in intestinal stem cells, promoting actin-based protrusion formation and stem cell migration towards a wound. We find that this migratory behavior is closely linked to proliferation, and that it is required for efficient tissue repair during injury. Our findings highlight the role of non-canonical Wnt signaling in regeneration of the intestinal epithelium, and identify enteroendocrine cell-released ligands as critical coordinators of intestinal stem cell migration.

Abstract P145: The RNA helicase EIF4A is a therapeutic vulnerability in triple-negative breast cancer

Abstract Background: Translational control of oncoprotein expression has been implicated in the pathogenesis of multiple solid tumors. The eukaryotic translation initiation factor 4A (eIF4A) is an RNA helicase that catalyzes the unwinding of secondary structure in the 5′-untranslated region (5′-UTR) of mRNAs to facilitate translation initiation. eIF4A is an essential gene in many cancer cell lines and multiple oncogenes or anti-apoptotic proteins that contain structured 5’-UTRs have been shown to require enhanced eIF4A activity for translation. Zotatifin (eFT226) is a selective eIF4A inhibitor that has been shown previously to inhibit tumor growth in several immunocompromised mouse models and is currently in Phase I clinical trials as a single agent (NCT04092673). In this study we investigated the effects of Zotatifin both as a single agent and in combination with standard-of-care chemotherapy on tumor progression in several syngeneic triple-negative breast cancer (TNBC) mouse models. Methods: The activity of Zotatifin was assessed as single agent in eight different syngeneic p53-null mouse TNBC models across several intrinsic molecular subtypes. Synergism of Zotatifin with chemotherapy was evaluated in three responsive models. In addition, a Zotatifin-resistant model was developed following prolonged drug treatment. Drug response mechanisms and the effect on the tumor immune microenvironment were determined by tandem mass tag mass spectrometry, reverse phase protein array (RPPA) and mass cytometry. Results: Zotatifin treatment slowed tumor growth in six out of eight syngeneic TNBC models without obvious toxicity. Mass spectrometry of acutely treated tumors revealed that Zotatifin inhibited proliferative and stem cell signaling pathways including E2F targets, G2/M checkpoints, and NOTCH signaling, and induced proteins involved in Interferon-α and Interferon-γ responses. Mass cytometry analyses showed that Zotatifin suppressed the infiltration of M2 macrophages and neutrophils and promoted the infiltration of conventional dendritic cells to the tumor microenvironment. Interestingly, combination therapy of Zotatifin with chemotherapy significantly slowed tumor growth and improved survival. However, drug resistance emerged after prolonged treatment. The resistant tumors strikingly displayed a mesenchymal histology and an increased activity of the PI3K-AKT-mTOR pathway as determined by RPPA analysis. Combination treatment of Zotatifin with the mTOR inhibitor Everolimus prolonged survival. Conclusions: eIF4A is a therapeutic vulnerability in TNBC. Zotatifin inhibits tumor progression both through tumor-intrinsic mechanisms and by targeting the tumor immune microenvironment. Synergism between Zotatifin and chemotherapy supports the clinical potential of combination therapies. Citation Format: Na Zhao, Jeffrey Mark Rosen. The RNA helicase EIF4A is a therapeutic vulnerability in triple-negative breast cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P145.

Role of autocrine bone morphogenetic protein signaling in trophoblast stem cells†.

The Bone Morphogenetic Protein (BMP) pathway is involved in numerous developmental processes, including cell growth, apoptosis, and differentiation. In mouse embryogenesis, BMP signaling is a well-known morphogen for both mesoderm induction and germ cell development. Recent evidence points to a potential role in development of the extraembryonic compartment, including trophectoderm-derived tissues. In this study, we investigated the effect of BMP signaling in both mouse and human trophoblast stem cells (TSC) in vitro, evaluating the expression and activation of the BMP signaling response machinery, and the effect of BMP signaling manipulation during TSC maintenance and differentiation. Both mouse trophoblast stem cells (mTSC) and human trophoblast stem cells (hTSC) expressed various BMP ligands and the receptors BMPR1A and BMPR2, necessary for BMP response, and displayed maximal active BMP signaling when undifferentiated. We also observed a conserved modulatory role of BMP signaling during trophoblast differentiation, whereby maintenance of active BMP signaling blunted differentiation of TSC in both species. Conversely, the effect of BMP signaling on the undifferentiated state of TSC appeared to be species-specific, with SMAD-independent signaling important in maintenance of mTSC, and a more subtle role for both SMAD-dependent and -independent BMP signaling in hTSC. Altogether, these data establish an autocrine role for the BMP pathway in the trophoblast compartment. As specification and correct differentiation of the extraembryonic compartment are fundamental for implantation and early placental development, insights on the role of the BMP signaling in early development might prove useful in the setting of in vitro fertilization as well as targeting trophoblast-associated placental dysfunction.

TIFAB accelerates MLL-AF9−Induced acute myeloid leukemia through upregulation of HOXA9

SummaryWe previously showed stabilization of NIK−induced activation of NF-κB non-canonical signaling suppresses MLL-AF9−induced AML. In the current study, we demonstrate that deletion of NF-κB non-canonical RelB prevents the inhibitory effect of NIK stabilization in MLL-AF9 AML. Mechanistically, RelB suppresses its direct target, TIFAB, which is upregulated in human AML and correlates negatively with the survival of AML patients. Forced expression of TIFAB reverses NIK−induced impaired AML development through downregulation of RelB and upregulation of HOXA9. Consistent with upregulation of HOXA9, gene set enrichment analysis shows that forced expression of TIFAB blocks myeloid cell development, upregulates leukemia stem cell signature and induces similar gene expression patterns to those of HOXA9-MEIS1 and HOXA9-NUP98, and upregulates oxidative phosphorylation. Accordingly, forced expression of HOXA9 also largely releases the inhibitory impact of NIK stabilization via downregulation of RelB and upregulation of RelA. Our data suggest that NIK/RelB suppresses MLL-AF9−induced AML mainly through downregulation of TIFAB/HOXA9.