Regulation of Sox2 by STAT3 initiates commitment to the neural precursor cell fate

Super-Enhancer Driven LIF/LIFR-STAT3-SOX2 Regulatory Feedback Loop Promotes Cancer Stemness in Head and Neck Squamous Cell Carcinoma

Super-enhancers (SEs) have been recognized as key epigenetic regulators underlying cancer stemness and malignant traits by aberrant transcriptional control and promising therapeutic targets against human cancers. However, the SE landscape and their roles during head and neck squamous cell carcinoma (HNSCC) development especially in cancer stem cells (CSCs) maintenance remain underexplored yet. Here, we identify leukemia inhibitory factor (LIF)-SE as a representative oncogenic SE to activate LIF transcription in HNSCC. LIF secreted from cancer cells and cancer-associated fibroblasts promotes cancer stemness by driving SOX2 transcription in an autocrine/paracrine manner, respectively. Mechanistically, enhancer elements E1, 2, 4 within LIF-SE recruit SOX2/SMAD3/BRD4/EP300 to facilitate LIF transcription; LIF activates downstream LIFR-STAT3 signaling to drive SOX2 transcription, thus forming a previously unknown regulatory feedback loop (LIF-SE-LIF/LIFR-STAT3-SOX2) to maintain LIF overexpression and CSCs stemness. Clinically, increased LIF abundance in clinical samples correlate with malignant clinicopathological features and patient prognosis; higher LIF concentrations in presurgical plasma dramatically diminish following cancer eradication. Therapeutically, pharmacological targeting LIF-SE-LIF/LIFR-STAT3 significantly impairs tumor growth and reduces CSC subpopulations in xenograft and PDX models. Our findings reveal a hitherto uncharacterized LIF-SE-mediated auto-regulatory loop in regulating HNSCC stemness and highlight LIF as a novel noninvasive biomarker and potential therapeutic target for HNSCC.

Hesperidin ameliorates impairment in hippocampal neural stem cells related to apoptosis induced by methotrexate in adult rats

Neurogenesis is a process of generating neural stem cells (NSCs) as functional neurons can be decreased after chemotherapy treatments. Methotrexate (MTX) is a folate antagonist that is used for cancer treatment but has negative effects, including oxidative stress, neuronal apoptosis and cognitive impairments. Hesperidin (Hsd), a flavonoid found in citrus fruits, has antioxidant and neuroprotection properties. This study investigated whether Hsd could attenuate impairments of hippocampal neural stem cells related to apoptosis induced by MTX. Spraque-Dawley rats (n = 24) were divided into 4 groups: (1) Vehicle group received propylene glycol (21 days) and 0.9% normal saline (day 8 and 15), (2) Hsd group received 100 mg/kg (21 days), (3) MTX group received 75 mg/kg (days 8 and 15) and (4) MTX+Hsd group received MTX, 75 mg/kg (day 8 and 15) and Hsd 100 mg/kg (21 days). Our results showed that MTX decreased hippocampal neural stem cells including SRY (sex determining region Y)-box 2 (SOX2) and nestin. MTX diminished vascular related (VR) Ki-67 positive cells in the hippocampus but not non-vascular related (NVR) Ki-67. Additionally, MTX reduced SOX2, nestin, postsynaptic density protein 95 (PSD-95) and B-cell lymphoma-2 family of proteins (Bcl-2), whereas Bax and caspase-3 were enhanced in the hippocampal tissues. Interestingly, co-treatment with Hsd and MTX revealed upregulation of SOX2, nestin and VR Ki-67 positive cells as well as elevated SOX2, nestin, PSD-95 and Bcl-2 proteins. Moreover, receiving both Hsd and MTX significantly suppressed increased Bax and caspase-3. These results confirm that Hsd can ameliorate MTX-induced impairments of hippocampal NSC proliferation and neuronal apoptosis.

Therapeutic potential of pentamidine for glioma-initiating cells and glioma cells through multimodal antitumor effects

Glioma-initiating cells, which comprise a heterogeneous population of glioblastomas, contribute to resistance against aggressive chemoradiotherapy. Using drug reposition, we investigated a therapeutic drug for glioma-initiating cells. Drug screening was undertaken to select candidate agents that inhibit proliferation of two different glioma-initiating cells lines. The alteration of proliferation and stemness of the two glioma-initiating cell lines, and proliferation, migration, cell cycle, and survival of these two differentiated glioma-initiating cell lines and three different glioblastoma cell lines treated with the candidate agent were evaluated. We also used a xenograft glioma mouse model to evaluate anticancer effects of treated glioma cell lines. Among the 1301 agents, pentamidine-an antibiotic for Pneumocystis jirovecii-emerged as a successful antiglioma agent. Pentamidine treatment suppressed proliferation and stemness in glioma-initiating cell lines. Proliferation and migration were inhibited in all differentiated glioma-initiating cells and glioblastoma cell lines, with cell cycle arrest and caspase-dependent apoptosis induction. The in vivo study reproduced the same findings as the in vitro studies. Pentamidine showed a stronger antiproliferative effect on glioma-initiating cells than on differentiated cells. Western blot analysis revealed pentamidine inhibited phosphorylation of signal transducer and activator of transcription 3 in all cell lines, whereas Akt expression was suppressed in glioma-initiating cells but not in differentiated lines. In the present study, we identified pentamidine as a potential therapeutic drug for glioma. Pentamidine could be promising for the treatment of glioblastomas by targeting both glioma-initiating cells and differentiated cells through its multifaceted antiglioma effects.

Molecular Mechanisms Involved in the Regulation of Neurodevelopment by miR-124

miR-124 is a miRNA predominantly expressed in the nervous system and accounts for more than a quarter of the total miRNAs in the brain. It regulates neurogenesis, neuronal differentiation, neuronal maturation, and synapse formation and is the most important miRNA in the brain. Furthermore, emerging evidence has suggested miR-124 may be associated with the pathogenesis of various neurodevelopmental and neuropsychiatric disorders. Here, we provide an overview of the role of miR-124 in neurodevelopment and the underling mechanisms, and finally, we prospect the significance of miR-124 research to the field of neuroscience.

Cardiac inducing colonies halt fibroblast activation and induce cardiac/endothelial cells to move and expand via paracrine signaling

Myocardial fibrosis (MF), a common event that develops after myocardial infarction, initially is a reparative process but eventually leads to heart failure and sudden cardiac arrest. In MF, the infarct area is replaced by a collagenous-based scar induced by "excessive" collagen deposition from activated cardiac fibroblasts. The scar prevents ventricular wall thinning; however, over time it expands to noninfarcted myocardium. Therapies to prevent fibrosis include reperfusion, anti-fibrotic agents, and ACE inhibitors. Paracrine factor (PF)/stem cell research has recently gained significance as a therapy. We consistently find that cardiac inducing colonies (CiCs) (derived from human germline pluripotent stem cells) secrete PFs at physiologically relevant concentrations that suppress cardiac fibroblast activation and excessive extracellular matrix protein secretion. These factors also affect human cardiomyocytes and endothelial cells by inducing migration/proliferation of both populations into a myocardial wound model. Finally, CiC factors modulate matrix turnover and proinflammation. Taking the results together, we show that CiCs could help tip the balance from fibrosis toward repair.

Neuropilin-2 promotes lineage plasticity and progression to neuroendocrine prostate cancer

Neuroendocrine prostate cancer (NEPC), a lethal subset of prostate cancer, is characterized by loss of AR signaling and resulting resistance to AR-targeted therapy during neuroendocrine transdifferentiation, for which the molecular mechanisms remain unclear. Here, we report that neuropilin 2 (NRP2) is upregulated in both de novo and therapy-induced NEPC, which induces neuroendocrine markers, neuroendocrine cell morphology, and NEPC cell aggressive behavior. NRP2 silencing restricted NEPC tumor xenograft growth. Mechanistically, NRP2 engages in reciprocal crosstalk with AR, where NRP2 is transcriptionally inhibited by AR, and in turn suppresses AR signaling by downregulating the AR transcriptional program and confers resistance to enzalutamide. Moreover, NRP2 physically interacts with VEGFR2 through the intracellular SEA domain to activate STAT3 phosphorylation and subsequently SOX2, thus driving NEPC differentiation and growth. Collectively, these results characterize NRP2 as a driver of NEPC and suggest NRP2 as a potential therapeutic target in NEPC.

STAT3 in medulloblastoma: a key transcriptional regulator and potential therapeutic target

Medulloblastoma is the most common malignant brain tumor of childhood accounting for about 60% of all pediatric embryonal tumors. Despite improvements in the overall survival rate, this tumor still lacks an efficient, reliable, and less toxic therapeutic approach. Characterization of the molecular mechanisms involved in medulloblastoma initiation and progression is a crucial step for the development of effective therapies. Signal transducer and activator of transcription 3 is a convergence point for several signaling cascades that are implicated in medulloblastoma tumorigenesis. Accumulated evidence has revealed the pivotal role of signal transducer and activator of transcription 3 in medulloblastoma pathogenesis such as proliferation, survival, angiogenesis, and immunosuppression as well as maintenance, drug resistance, and recurrence. In this review, we focus on the role of signal transducer and activator of transcription 3 in medulloblastoma tumorigenesis and discuss the recent advances of signal transducer and activator of transcription 3 inhibition as a promising developed strategy for medulloblastoma therapy.

BRN2 as a key gene drives the early primate telencephalon development

Evolutionary mutations in primate-specific genes drove primate cortex expansion. However, whether conserved genes with previously unidentified functions also play a key role in primate brain expansion remains unknown. Here, we focus on BRN2 (POU3F2), a gene encoding a neural transcription factor commonly expressed in both primates and mice. Compared to the limited effects on mouse brain development, BRN2 biallelic knockout in cynomolgus monkeys (Macaca fascicularis) is lethal before midgestation. Histology analysis and single-cell transcriptome show that BRN2 deficiency decreases RGC expansion, induces precocious differentiation, and alters the trajectory of neurogenesis in the telencephalon. BRN2, serving as an upstream factor, controls specification and differentiation of ganglionic eminences. In addition, we identified the conserved function of BRN2 in cynomolgus monkeys to human RGCs. BRN2 may function by directly regulating SOX2 and STAT3 and maintaining HOPX. Our findings reveal a previously unknown mechanism that BRN2, a conserved gene, drives early primate telencephalon development by gaining novel mechanistic functions.

PIAS3 suppresses damage in an Alzheimer's disease cell model by inducing the STAT3-associated STAT3/Nestin/Nrf2/HO-1 pathway

BACKGROUND

Alzheimer's disease (AD), the most common form of dementia, is caused by the degeneration of the central nervous system (CNS). A previous study reported that signal transducer and activator of transcription 3 (STAT3) is activated during AD development; nonetheless, the related mechanism remains unknown. Thus, this study used a cell model to explore whether and how the protein inhibitor of activated STAT3 (PIAS3) is involved in AD development.

METHODS

Cerebrospinal fluid (CSF) specimens of 30 patients with AD and 10 normal participants were included in this study. SH-SY5Y cells were used to constructed AD model. Relevant indices were then detected and analyzed.

RESULTS

The results showed that compared with the control group, PIAS3 expression was substantially decreased in patients with AD and amyloid beta (Aβ)-treated SH-SY5Y cells. PIAS3 overexpression was able to reverse the detrimental effects of Aβ treatment on cell survival and growth. Further, it could also ameliorate apoptosis and oxidative stress in Aβ-treated SH-SY5Y cells. Additionally, PIAS3 was shown to reduce the activated form of STAT3 and increase the activity of the downstream Nestin/nuclear factor erythroid 2-related factor/heme oxygenase-1 pathway.

CONCLUSIONS

STAT3 reactivation by colivelin treatment negated the influence of PIAS3 on the survival, growth, apoptosis, and oxidative stress of Aβ-treated SH-SY5Y cells.

Nitro-Oleic Acid Inhibits Stemness Maintenance and Enhances Neural Differentiation of Mouse Embryonic Stem Cells via STAT3 Signaling

Nitro-oleic acid (NO₂-OA), pluripotent cell-signaling mediator, was recently described as a modulator of the signal transducer and activator of transcription 3 (STAT3) activity. In our study, we discovered new aspects of NO₂-OA involvement in the regulation of stem cell pluripotency and differentiation. Murine embryonic stem cells (mESC) or mESC-derived embryoid bodies (EBs) were exposed to NO₂-OA or oleic acid (OA) for selected time periods. Our results showed that NO₂-OA but not OA caused the loss of pluripotency of mESC cultivated in leukemia inhibitory factor (LIF) rich medium via the decrease of pluripotency markers (NANOG, sex-determining region Y-box 1 transcription factor (SOX2), and octamer-binding transcription factor 4 (OCT4)). The effects of NO₂-OA on mESC correlated with reduced phosphorylation of STAT3. Subsequent differentiation led to an increase of the ectodermal marker orthodenticle homolog 2 (Otx2). Similarly, treatment of mESC-derived EBs by NO₂-OA resulted in the up-regulation of both neural markers Nestin and β-Tubulin class III (Tubb3). Interestingly, the expression of cardiac-specific genes and beating of EBs were significantly decreased. In conclusion, NO₂-OA is able to modulate pluripotency of mESC via the regulation of STAT3 phosphorylation. Further, it attenuates cardiac differentiation on the one hand, and on the other hand, it directs mESC into neural fate.

Bazedoxifene inhibits sustained STAT3 activation and increases survival in GBM

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High STAT3 is correlated with poor prognosis in GBM.

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Bazedoxifene targets IL-6-mediated sustained STAT3 activation.

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STAT3 drives glioma stem cell maintenance, bazedoxifene targets this pathway.

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Bazedoxifene crosses the BBB and prolongs survival in GBM bearing mice.

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Bazedoxifene-treated tumors have less activated STAT3.

An important factor correlated with poor survival in glioblastoma (GBM) is the aberrant and persistent activation of STAT3, a critical transcription factor that regulates multiple genes with key roles in cell survival, proliferation, resistance to chemotherapy, and stem cell maintenance. The Interleukin-6 (IL6)-STAT3 signaling axis has been studied extensively in inflammation and cancer. However, it is not completely understood how high levels of activated STAT3 are sustained in tumors. Previously, we identified a novel mechanism of biphasic activation of STAT3 in response to gp130-linked cytokines, including IL6, in which activation of STAT3 is prolonged by circumventing the negative regulatory mechanisms induced by its initial activationTo target prolonged STAT3 activation, we used the small molecule inhibitor bazedoxifene (BZA), which blocks formation of the IL6 receptor-gp130 complex. Glioma stem-like cells (GSCs) are more tumorigenic and more resistant to therapy. STAT3 is a key driver of the expression of stem cell transcription factors, making it a therapeutically important target in GBM. We show that treating GSCs with BZA decreases their self-renewal capacity and the expression of GSC markers in vitro. Additionally, BZA crosses the blood-brain barrier and confers a survival advantage in an orthotopic syngeneic mouse model of GBM. Although IL6-STAT3 signaling is important for GSC survival, a therapeutic agent that inhibits this pathway without toxicity has yet to be identified. Our findings reveal a mechanism of sustained STAT3 signaling in GBM and reveal its role in GSC maintenance, and we identify BZA as a novel candidate for treating GBM.

Signal Transducer and Activator of Transcription 3 Activation in Hippocampal Neural Stem Cells and Cognitive Deficits in Mice Following Short-term Cuprizone Exposure

Recent studies have emphasized that adult hippocampal neurogenesis impairment may be associated with cognitive problems. Because cuprizone (CPZ), a copper-chelating reagent, was shown to decrease the production of new neurons, we aimed to further understand the involvement of adult hippocampal neurogenesis impairment in cognitive function by using a short-term (2-week) CPZ exposure paradigm. The CPZ-fed mice showed cognitive deficits, i.e., impaired sensorimotor gating and reduced social novelty preference, compared to normal-fed mice. Although a long-term (e.g., 5-week) CPZ exposure paradigm was found to cause demyelination, we encountered that the labeling for myelin in the hippocampus was unaffected by 2-week CPZ exposure. The densities of neuronal progenitor cells (NPCs) and newborn granule cells (NGCs) were lower in CPZ-fed mice than in normal-fed mice, while those of neural stem cells (NSCs) were comparable between groups. We then examined whether short-term CPZ exposure might induce activation of signal transducer and activator of transcription 3 (STAT3), which plays a major role in cytokine receptor signaling. The densities of phosphorylated STAT3-positive (pSTAT3⁺) NSCs were higher in CPZ-fed mice than in normal-fed mice, while those of pSTAT3⁺ NPCs/NGCs were very low in both groups. Interestingly, the densities of bromodeoxyuridine-positive (BrdU⁺) NSCs were higher in CPZ-fed mice than in normal-fed mice 2 weeks after BrdU injection, while those of BrdU⁺ NPCs/NGCs were lower in CPZ-fed mice than in normal-fed mice. These findings suggest that short-term CPZ exposure inhibits differentiation of NSCs into NPCs via activation of STAT3, which may in part underlie cognitive deficits.

Dermatan sulphate promotes neuronal differentiation in mouse and human stem cells

Dermatan sulphate (DS), a glycosaminoglycan, is present in the extracellular matrix and on the cell surface. Previously, we showed that heparan sulphate plays a key role in the maintenance of the undifferentiated state in mouse embryonic stem cells (mESCs) and in the regulation of their differentiation. Chondroitin sulphate has also been to be important for pluripotency and differentiation of mESCs. Keratan sulphate is a marker of human pluripotent stem cells. To date, however, the function of DS in mESCs has not been clarified. Dermatan 4 sulfotransferase 1, which transfers sulphate to the C-4 hydroxyl group of N-acetylgalactosamine of DS, contributes to neuronal differentiation of mouse neural progenitor cells. Therefore, we anticipated that neuronal differentiation would be induced in mESCs in culture by the addition of DS. To test this expectation, we investigated neuronal differentiation in mESCs and human neural stem cells (hNSCs) cultures containing DS. In mESCs, DS promoted neuronal differentiation by activation of extracellular signal-regulated kinase 1/2 and also accelerated neurite outgrowth. In hNSCs, DS promoted neuronal differentiation and neuronal migration, but not neurite outgrowth. Thus, DS promotes neuronal differentiation in both mouse and human stem cells, suggesting that it offers a novel method for efficiently inducing neuronal differentiation.

Role of IL-6 in the regulation of neuronal development, survival and function

The pleiotropic cytokine interleukin-6 (IL-6) is emerging as a molecule with both beneficial and destructive potentials. It can exert opposing actions triggering either neuron survival after injury or causing neurodegeneration and cell death in neurodegenerative or neuropathic disorders. Importantly, neurons respond differently to IL-6 and this critically depends on their environment and whether they are located in the peripheral or the central nervous system. In addition to its hub regulator role in inflammation, IL-6 is recently emerging as an important regulator of neuron function in health and disease, offering exciting possibilities for more mechanistic insight into the pathogenesis of mental, neurodegenerative and pain disorders and for developing novel therapies for diseases with neuroimmune and neurogenic pathogenic components.

TrkA Interacts with and Phosphorylates STAT3 to Enhance Gene Transcription and Promote Breast Cancer Stem Cells in Triple-Negative and HER2-Enriched Breast Cancers

Simple Summary

Breast cancer is the leading cancer in American women. Due to the inherent aggressiveness of triple-negative and HER2-enriched breast cancers, it is imperative to identify novel molecular targets for therapeutic intervention. Due to their abnormal activities in metastatic breast cancers, JAK2–STAT3 and TrkA pathways have been individually implicated in aggressive breast tumors. However, their co-activation and signaling interactions have not been thoroughly investigated. Therefore, our study aimed to elucidate the extent of crosstalk between JAK2–STAT3 and TrkA signaling pathways and its impact on breast cancer. Our data revealed a novel interaction between TrkA and STAT3, and that this interaction results in STAT3 phosphorylation and activation by TrkA, leading to enhanced stemness gene expression and stem cell renewal. We further found that the co-activation of JAK2–STAT3 and TrkA pathways is correlated with shorter time to develop overall and organ-specific metastasis, suggesting that this signaling crosstalk underlies the aggressiveness of triple-negative and HER2-enriched breast cancers.

Abstract

JAK2–STAT3 and TrkA signaling pathways have been separately implicated in aggressive breast cancers; however, whether they are co-activated or undergo functional interaction has not been thoroughly investigated. Herein we report, for the first time that STAT3 and TrkA are significantly co-overexpressed and co-activated in triple-negative breast cancer (TNBC) and HER2-enriched breast cancer, as shown by immunohistochemical staining and data mining. Through immunofluorescence staining–confocal microscopy and immunoprecipitation–Western blotting, we found that TrkA and STAT3 co-localize and physically interact in the cytoplasm, and the interaction is dependent on STAT3-Y705 phosphorylation. TrkA–STAT3 interaction leads to STAT3 phosphorylation at Y705 by TrkA in breast cancer cells and cell-free kinase assays, indicating that STAT3 is a novel substrate of TrkA. β-NGF-mediated TrkA activation induces TrkA–STAT3 interaction, STAT3 nuclear transport and transcriptional activity, and the expression of STAT3 target genes, SOX2 and MYC. The co-activation of both pathways promotes breast cancer stem cells. Finally, we found that TNBC and HER2-enriched breast cancer with JAK2–STAT3 and TrkA co-activation are positively associated with poor overall metastasis-free and organ-specific metastasis-free survival. Collectively, our study uncovered that TrkA is a novel activating kinase of STAT3, and their co-activation enhances gene transcription and promotes breast cancer stem cells in TNBC and HER2-enriched breast cancer.

Hearing Loss Caused by HCMV Infection through Regulating the Wnt and Notch Signaling Pathways

Hearing loss is one of the most prevalent sensory disabilities worldwide with huge social and economic burdens. The leading cause of sensorineural hearing loss (SNHL) in children is congenital cytomegalovirus (CMV) infection. Though the implementation of universal screening and early intervention such as antiviral or anti-inflammatory ameliorate the severity of CMV-associated diseases, direct and targeted therapeutics is still seriously lacking. The major hurdle for it is that the mechanism of CMV induced SNHL has not yet been well understood. In this review, we focus on the impact of CMV infection on the key players in inner ear development including the Wnt and Notch signaling pathways. Investigations on these interactions may gain new insights into viral pathogenesis and reveal novel targets for therapy.

Embryonic periventricular endothelial cells demonstrate a unique pro-neurodevelopment and anti-inflammatory gene signature

Brain embryonic periventricular endothelial cells (PVEC) crosstalk with neural progenitor cells (NPC) promoting mutual proliferation, formation of tubular-like structures in the former and maintenance of stemness in the latter. To better characterize this interaction, we conducted a comparative transcriptome analysis of mouse PVEC vs. adult brain endothelial cells (ABEC) in mono-culture or NPC co-culture. We identified > 6000 differentially expressed genes (DEG), regardless of culture condition. PVEC exhibited a 30-fold greater response to NPC than ABEC (411 vs. 13 DEG). Gene Ontology (GO) analysis of DEG that were higher or lower in PVEC vs. ABEC identified "Nervous system development" and "Response to Stress" as the top significantly different biological process, respectively. Enrichment in canonical pathways included HIF1A, FGF/stemness, WNT signaling, interferon signaling and complement. Solute carriers (SLC) and ABC transporters represented an important subset of DEG, underscoring PVEC's implication in blood-brain barrier formation and maintenance of nutrient-rich/non-toxic environment. Our work characterizes the gene signature of PVEC and their important partnership with NPC, underpinning their unique role in maintaining a healthy neurovascular niche, and in supporting brain development. This information may pave the way for additional studies to explore their therapeutic potential in neuro-degenerative diseases, such as Alzheimer's and Parkinson's disease.

Carcinoma-Associated Fibroblasts Promote Growth of Sox2-Expressing Breast Cancer Cells

Simple Summary

The tumor microenvironment has a strong impact on the behavior of tumor cells. One major cell type residing in the tumor microenvironment is the carcinoma-associated fibroblast (CAF). We were interested in the effect of CAFs on Sox2 (sex determining region Y (SRY)-box 2), which not only is an essential embryonal stem cell transcription factor, but also plays a role in cancer stem cell activity. We found that long-term exposure of ERα-positive breast cancer cells to the cocktail of CAF-secreted factors strongly increased Sox2 expression involving tumor-related proteins and signaling pathways. However, Sox2 was not only present in those tumor cells that express stem cell markers, but was equally abundant in other tumor cells. By being widely expressed, Sox2 may have functions in non-stem cells. In fact, Sox2 was found to regulate ERα expression, to act anti-apoptotically, to promote cellular growth and to protect cells against the anti-estrogen fulvestrant.

Abstract

CAFs (Carcinoma-associated fibroblasts) play an important role in cancer progression. For instance, they promote resistance to anti-estrogens, such as fulvestrant. Here, we show that, in ERα-positive breast cancer cell lines, the cocktail of factors secreted by CAFs (CAF-CM) induce the expression of the embryonal stem cell transcription factor Sox2 (sex determining region Y (SRY)-box 2). Long-term exposure to CAF-CM was able to give rise to very high Sox2 levels both in the absence and presence of fulvestrant. IL-6 (interleukin-6), a major component of CAF-CM, failed to raise Sox2 expression. In MCF-7 sublines established in the presence of CAF-CM, almost all cells showed Sox2 expression, whereas long-term treatment of T47D cells with CAF-CM resulted in a ~60-fold increase in the proportions of two distinct populations of Sox2 high and low expresser cells. Exposure of BT474 cells to CAF-CM raised the fraction of Sox2 high expresser cells by ~3-fold. Cell sorting based on CD44 and CD24 expression or ALDH (aldehyde dehydrogenase) activity revealed that most Sox2 high expresser cells were not CD44^hi/CD24^lo- or ALDH-positive cells suggesting that they were not CSCs (cancer stem cells), though CD44 played a role in Sox2 expression. Functionally, Sox2 was found to protect CAF-CM-treated cells against apoptosis and to allow higher growth activity in the presence of fulvestrant. Mechanistically, the key drivers of Sox2 expression was found to be STAT3 (Signal transducer and activator of transcription 3), Bcl-3 (B-cell lymphoma 3) and the PI3K (Phosphoinositide 3-kinase)/AKT pathway, whose activities/expression can all be upregulated by CAF-CM. These data suggest that CAF-CM induces Sox2 expression in non-CSCs by activating proteins involved in growth control and drug resistance, leading to higher protection against apoptosis.

Combined inhibition of JAK2-STAT3 and SMO-GLI1/tGLI1 pathways suppresses breast cancer stem cells, tumor growth, and metastasis

Triple-negative breast cancer (TNBC) and HER2-positive breast cancer are particularly aggressive and associated with unfavorable prognosis. TNBC lacks effective treatments. HER2-positive tumors have treatment options but often acquire resistance to HER2-targeted therapy after initial response. To address these challenges, we determined whether novel combinations of JAK2-STAT3 and SMO-GLI1/tGLI1 inhibitors synergistically target TNBC and HER2 breast cancer since these two pathways are concurrently activated in both tumor types and enriched in metastatic tumors. Herein, we show that novel combinations of JAK2 inhibitors (ruxolitinib and pacritinib) with SMO inhibitors (vismodegib and sonidegib) synergistically inhibited in vitro growth of TNBC and HER2-positive trastuzumab-resistant BT474-TtzmR cells. Synergy was also observed against breast cancer stem cells. To determine if the combination is efficacious in inhibiting metastasis, we treated mice with intracardially inoculated TNBC cells and found the combination to inhibit lung and liver metastases, and prolong host survival without toxicity. The combination inhibited orthotopic growth, VEGF-A expression, and tumor vasculature of both TNBC and HER2-positive trastuzumab-refractory breast cancer. Lung metastasis of orthotopic BT474-TtzmR xenografts was suppressed by the combination. Together, our results indicated that dual targeting of JAK2 and SMO resulted in synergistic suppression of breast cancer growth and metastasis, thereby supporting future clinical testing.

Zinc Promotes Patient-Derived Induced Pluripotent Stem Cell Neural Differentiation via ERK-STAT Signaling

Nerve regeneration remains a challenge. Patient-derived induced pluripotent stem cell (iPSC)-differentiated neural stem cells (NSCs) provide a promising hope. Zinc is closely involved in central nervous system development and metabolism, but its role on iPSC neural differentiation is elusive and zinc detection methods in live cells are limited. In this study, intracellular zinc was detected in real time by a zinc fluorescent chemosensor and was shown to be increased during the iPSC neural induction process. iPSC neural differentiation was promoted with the addition of zinc chloride (ZnCl₂) and inhibited with the addition of zinc chelator N,N,N0,N0-tetrakis(2-pyridylmethyl)-ethylenediamine, indicated by western blot and enzyme-linked immunosorbent assay analysis of NSC marker Nestin expression and measurement of neurite-like structures. Mechanistically, the phosphorylation level of ERK1/2 and STAT3 was changed with the zinc level, suggesting that zinc may affect the neural differentiation of iPSCs through ERK-STAT signaling. In conclusion, our study shows the important role of zinc in iPSC neural differentiation and suggests a new idea for iPSC-derived NSC application in nerve regeneration.

Betavulgarin Isolated from Sugar Beet (Beta vulgaris) Suppresses Breast Cancer Stem Cells through Stat3 Signaling

Breast cancer is a major health problem that affects lives worldwide. Breast cancer stem cells (BCSCs) are small subpopulations of cells with capacities for drug resistance, self-renewal, recurrence, metastasis, and differentiation. Herein, powder extracts of beetroot were subjected to silica gel, gel filtration, thin layer chromatography (TLC), and preparatory high-pressure liquid chromatography (HPLC) for isolation of one compound, based on activity-guided purification using tumorsphere formation assays. The purified compound was identified as betavulgarin, using nuclear magnetic resonance spectroscopy and electrospray ionization (ESI) mass spectrometry. Betavulgarin suppressed the proliferation, migration, colony formation, and mammosphere formation of breast cancer cells and reduced the size of the CD44⁺/CD24⁻ subpopulation and the expression of the self-renewal-related genes, C-Myc, Nanog, and Oct4. This compound decreased the total level and phosphorylated nuclear level of signal transducer and activator of transcription 3 (Stat3) and reduced the mRNA and protein levels of sex determining region Y (SRY)-box 2 (SOX2), in mammospheres. These data suggest that betavulgarin inhibit the Stat3/Sox2 signaling pathway and induces BCSC death, indicating betavulgarin might be an anticancer agent against breast cancer cells and BCSCs.

JMJD3 and UTX determine fidelity and lineage specification of human neural progenitor cells

Neurogenesis, a highly orchestrated process, entails the transition from a pluripotent to neural state and involves neural progenitor cells (NPCs) and neuronal/glial subtypes. However, the precise epigenetic mechanisms underlying fate decision remain poorly understood. Here, we delete KDM6s (JMJD3 and/or UTX), the H3K27me3 demethylases, in human embryonic stem cells (hESCs) and show that their deletion does not impede NPC generation from hESCs. However, KDM6-deficient NPCs exhibit poor proliferation and a failure to differentiate into neurons and glia. Mechanistically, both JMJD3 and UTX are found to be enriched in gene loci essential for neural development in hNPCs, and KDM6 impairment leads to H3K27me3 accumulation and blockade of DNA accessibility at these genes. Interestingly, forced expression of neuron-specific chromatin remodelling BAF (nBAF) rescues the neuron/glia defect in KDM6-deficient NPCs despite H3K27me3 accumulation. Our findings uncover the differential requirement of KDM6s in specifying NPCs and neurons/glia and highlight the contribution of individual epigenetic regulators in fate decisions in a human development model.

Neurogenesis is an ordered transition from pluriptotent cells to neural precursor cells (NPCs) to neurons. Here the authors show that loss of the lysine demethylases JMJD3 and UTX leads reduced DNA accessibility at neurogenesis loci in human NPCs, and that the chromatin remodeller BAF can rescue differentiation defects.

Does in vitro fertilization affect the expression of miRNAs and their biogenesis pathway in preimplantation mouse embryos?

BACKGROUND

In vitro fertilization (IVF) is a well-accepted procedure which has been utilized for the treatment of infertile patients. As embryos at early stages of development are very vulnerable, the IVF conditions may influence genetic and epigenetic regulation of preimplantation mouse embryo.

METHODS

We assessed the effect of IVF on the expression of developmental and implantation related miRNAs (miR-21, miR-93, miR-24, and let-7a), their common presumptive target (Stat3), and miRNA biogenesis pathway genes (Drosha, Dgcr8, Exportin-5, Dicer, and Ago2). in vivo 8-cell and blastocysts were compared to IVF embryos. Expression levels of miRNAs, Stat3, and miRNA biogenesis pathway genes were evaluated by qRT-PCR in in vivo (n = 8) and IVF (n = 4) embryos.

RESULTS

The expression levels of let-7a and Stat3 were significantly reduced in IVF blastocyst when compared with in vivo (p = .004 and p = .009, respectively). Nevertheless, the IVF procedure did not influence the expression levels of miRNA biogenesis pathway components in 8-cell and blastocyst embryos.

CONCLUSIONS

Downregulation of let-7a and developmental related transcription factor, Stat3, in IVF mouse blastocysts may affect preimplantation development and implantation of embryos. Moreover, the genes of the miRNA biogenesis pathway were not changed in preimplantation mouse embryos through the IVF procedure.

Sox2: A Regulatory Factor in Tumorigenesis and Metastasis

The transcription factor Sox2 plays an important role in various phases of embryonic development, including cell fate and differentiation. These key regulatory functions are facilitated by binding to specific DNA sequences in combination with partner proteins to exert their effects. Recently, overexpression and gene amplification of Sox2 has been associated with tumor aggression and metastasis in various cancer types, including breast, prostate, lung, ovarian and colon cancer. All the different roles for Sox2 involve complicated regulatory networks consisting of protein-protein and protein-nucleic acid interactions. Their involvement in the EMT modulation is possibly enabled by Wnt/ β-catenin and other signaling pathways. There are number of in vivo models which show Sox2 association with increased cancer aggressiveness, resistance to chemo-radiation therapy and decreased survival rate suggesting Sox2 as a therapeutic target. This review will focus on the different roles for Sox2 in metastasis and tumorigenesis. We will also review the mechanism of action underlying the cooperative Sox2- DNA/partner factors binding where Sox2 can be potentially explored for a therapeutic opportunity to treat cancers.

Therapeutic Implication of SOCS1 Modulation in the Treatment of Autoimmunity and Cancer

The suppressor of cytokine signaling (SOCS) family of intracellular proteins has a vital role in the regulation of the immune system and resolution of inflammatory cascades. SOCS1, also called STAT-induced STAT inhibitor (SSI) or JAK-binding protein (JAB), is a member of the SOCS family with actions ranging from immune modulation to cell cycle regulation. Knockout of SOCS1 leads to perinatal lethality in mice and increased vulnerability to cancer, while several SNPs associated with the SOCS1 gene have been implicated in human inflammation-mediated diseases. In this review, we describe the mechanism of action of SOCS1 and its potential therapeutic role in the prevention and treatment of autoimmunity and cancer. We also provide a brief outline of the other JAK inhibitors, both FDA-approved and under investigation.

SOX2-mediated upregulation of CD24 promotes adaptive resistance toward targeted therapy in melanoma

Melanoma is often characterized by a constitutively active RAS-RAF-MEK-ERK pathway. For targeted therapy, BRAF inhibitors are available that are powerful in the beginning but resistance occurs rather fast. A better understanding of the mechanisms of resistance is urgently needed to increase the success of the treatment. Here, we observed that SOX2 and CD24 are upregulated upon BRAF inhibitor treatment. A similar upregulation was seen in targeted therapy-resistant, melanoma-derived induced pluripotent cancer cells (iPCCs). SOX2 and CD24 are known to promote an undifferentiated and cancer stem cell-like phenotype associated with resistance. We, therefore, elucidated the role of SOX2 and CD24 in targeted therapy resistance in more detail. We found that the upregulation of SOX2 and CD24 required activation of STAT3 and that SOX2 induced the expression of CD24 by binding to its promoter. We find that the overexpression of SOX2 or CD24 significantly increases the resistance toward BRAF inhibitors, while SOX2 knock-down rendered cells more sensitivity toward treatment. The overexpression of CD24 or SOX2 induced Src and STAT3 activity. Importantly, by either CD24 knock-down or Src/STAT3 inhibition in resistant SOX2-overexpressing cells, the sensitivity toward BRAF inhibitors was re-established. Hence, we suggest a novel mechanism of adaptive resistance whereby BRAF inhibition is circumvented via the activation of STAT3, SOX2 and CD24. Thus, to prevent adaptive resistance, it might be beneficial to combine Src/STAT3 inhibitors together with MAPK pathway inhibitors.

STAT3-Inducible Mouse ESCs: A Model to Study the Role of STAT3 in ESC Maintenance and Lineage Differentiation

Studies have demonstrated that STAT3 is essential in maintaining self-renewal of embryonic stem cells (ESCs) and modulates ESC differentiation. However, there is still lack of direct evidence on STAT3 functions in ESCs and embryogenesis because constitutive STAT3 knockout (KO) mouse is embryonic lethal at E6.5-E7.5, prior to potential functional role in early development can be assessed. Therefore, in this study, two inducible STAT3 ESC lines were established, including the STAT3 knockout (InSTAT3 KO) and pSTAT3 overexpressed (InSTAT3 CA) using Tet-on inducible system in which STAT3 expression can be strictly controlled by doxycycline (Dox) stimulation. Through genotyping, deletion of STAT3 alleles was detected in InSTAT3 KO ESCs following 24 hours Dox stimulation. Western blot also showed that pSTAT3 and STAT3 protein levels were significantly reduced in InSTAT3 KO ESCs while dominantly elevated in InSTAT3 CA ECSs upon Dox stimulation. Likewise, it was found that STAT3-null ESCs would affect the differentiation of ESCs into mesoderm and cardiac lineage. Taken together, the findings of this study indicated that InSTAT3 KO and InSTAT3 CA ESCs could provide a new tool to clarify the direct targets of STAT3 and its role in ESC maintenance, which will facilitate the elaboration of the mechanisms whereby STAT3 maintains ESC pluripotency and regulates ESC differentiation during mammalian embryogenesis.

Human Cytomegalovirus Immediate Early 1 Protein Causes Loss of SOX2 from Neural Progenitor Cells by Trapping Unphosphorylated STAT3 in the Nucleus

The mechanisms underlying neurodevelopmental damage caused by virus infections remain poorly defined. Congenital human cytomegalovirus (HCMV) infection is the leading cause of fetal brain development disorders. Previous work has linked HCMV infection to perturbations of neural cell fate, including premature differentiation of neural progenitor cells (NPCs). Here, we show that HCMV infection of NPCs results in loss of the SOX2 protein, a key pluripotency-associated transcription factor. SOX2 depletion maps to the HCMV major immediate early (IE) transcription unit and is individually mediated by the IE1 and IE2 proteins. IE1 causes SOX2 downregulation by promoting the nuclear accumulation and inhibiting the phosphorylation of STAT3, a transcriptional activator of SOX2 expression. Deranged signaling resulting in depletion of a critical stem cell protein is an unanticipated mechanism by which the viral major IE proteins may contribute to brain development disorders caused by congenital HCMV infection.IMPORTANCE Human cytomegalovirus (HCMV) infections are a leading cause of brain damage, hearing loss, and other neurological disabilities in children. We report that the HCMV proteins known as IE1 and IE2 target expression of human SOX2, a central pluripotency-associated transcription factor that governs neural progenitor cell (NPC) fate and is required for normal brain development. Both during HCMV infection and when expressed alone, IE1 causes the loss of SOX2 from NPCs. IE1 mediates SOX2 depletion by targeting STAT3, a critical upstream regulator of SOX2 expression. Our findings reveal an unanticipated mechanism by which a common virus may cause damage to the developing nervous system and suggest novel targets for medical intervention.

STAT3 is a master regulator of epithelial identity and KRAS-driven tumorigenesis

A dichotomy exists regarding the role of signal transducer and activator of transcription 3 (STAT3) in cancer. Functional and genetic studies demonstrate either an intrinsic requirement for STAT3 or a suppressive effect on common types of cancer. These contrasting actions of STAT3 imply context dependency. To examine mechanisms that underlie STAT3 function in cancer, we evaluated the impact of STAT3 activity in KRAS-driven lung and pancreatic cancer. Our study defines a fundamental and previously unrecognized function of STAT3 in the maintenance of epithelial cell identity and differentiation. Loss of STAT3 preferentially associates with the acquisition of mesenchymal-like phenotypes and more aggressive tumor behavior. In contrast, persistent STAT3 activation through Tyr705 phosphorylation confers a differentiated epithelial morphology that impacts tumorigenic potential. Our results imply a mechanism in which quantitative differences of STAT3 Tyr705 phosphorylation, as compared with other activation modes, direct discrete outcomes in tumor progression.

miRNA-125b-5p Suppresses Hypothyroidism Development by Targeting Signal Transducer and Activator of Transcription 3

Background

A deficiency of maternal thyroid hormones (THs) during pregnancy has severe impacts on fetal brain development. Neural stem cells (NSCs) are major targets of THs and provided a powerful model to explore the underlying mechanism of THs during brain development. Although miRNA-125 might be associated with the NSCs differentiation, the relationship between miR-125 and hypothyroidism (HypoT) development remains unclear.

Material/Methods

In our study, we screened a differentially expressed gene miR-125b-5p from brain between euthyroid (EuT) and HypoT rats. In vitro, we employed anion exchange resin to remove THs to stimulate HypoT. QRT-PCR and Western blot were used to examine the expression of signal transducer and activator of transcription 3 (Stat3). The relationship between miR-125b-5p and Stat3 was detected via a dual-luciferase assay.

Results

QRT-PCR results showed that the level of miR-125b-5p in HypoT rat brains was significantly suppressed, suggesting some relationship between miR-125b-5p and HypoT. In C17.2, miR-125b-5p promoted cell differentiation into neurons by regulating the expression of tubulin beta chain 3 (TUBB3) and glial fibrillary acid protein (GFAP). QRT-PCR and Western blot results revealed that miR-125b-5p mimic modulated the contents of total Stat3 and p-Stat3. A dual-luciferase assay showed that miR-125b-5p negatively regulated the expression of Stat3 by binding with the first site in 3′ UTR of Stat3.

Conclusions

These results revealed Stat3 is a new target of miR-125b-5p and revealed the mechanism of miR-125b-5p suppressing HypoT development. These findings provide a new target for HypoT therapy.

Re-Defining Stem Cell-Cardiomyocyte Interactions: Focusing on the Paracrine Effector Approach

Stem cell research for treating or curing ischemic heart disease has, till date, culminated in three basic approaches: the use of induced pluripotent stem cell (iPSC) technology; reprogramming cardiac fibroblasts; and cardiovascular progenitor cell regeneration. As each approach has been shown to have its advantages and disadvantages, exploiting the advantages while minimizing the disadvantages has been a challenge. Using human germline pluripotent stem cells (hgPSCs) along with a modified version of a relatively novel cell-expansion culture methodology to induce quick, indefinite expansion of normally slow growing hgPSCs, it was possible to emphasize the advantages of all three approaches. We consistently found that unipotent germline stem cells, when removed from their niche and cultured in the correct medium, expressed endogenously, pluripotency genes, which induced them to become hgPSCs. These cells are then capable of producing cell types from all three germ layers. Upon differentiation into cardiac lineages, our data consistently showed that they not only expressed cardiac genes, but also expressed cardiac-promoting paracrine factors. Taking these data a step further, we found that hgPSC-derived cardiac cells could integrate into cardiac tissue in vivo. Note, while the work presented here was based on testes-derived hgPSCs, data from other laboratories have shown that ovaries contain very similar types of stem cells that can give rise to hgPSCs. As a result, hgPSCs should be considered a viable option for eventual use in patients, male or female, with ischemic heart disease

SOX2 Is a Marker for Stem-like Tumor Cells in Bladder Cancer

It has been reported that functionally distinct cancer stem cells (CSCs) exist in human bladder cancer (BCa). Here, we found that Sox2, a transcription factor that is well characterized as a marker for stem cells, is upregulated in both mouse and human BCa. Sox2 expression is absent in normal urothelial cells, but it begins to be expressed in pre-neoplastic bladder tumors and continues to be expressed in invasive mouse BCa. Using s as a reporter of Sox2 transcriptional expression, we demonstrated that Sox2-expressing cells mark a subpopulation of tumor cells that fuel the growth of established BCa. SOX2-positive cells also expressed other previously reported BCa CSC markers, including Keratin14 (KRT14) and CD44v6. Ablation of Sox2-expressing cells within primary invasive BCa led to enhanced tumor regression, supporting the essential role of SOX2-positive cells in regulating BCa maintenance and progression. Our data show that Sox2 is a marker of bladder CSCs and indicate it as a potential clinical target for BCa therapy.

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Sox2 expression marks bladder cancer stem cells in vivo

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SOX2-positive cells are a subpopulation of KRT14-expressing cancer stem cells

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SOX2-positive cells are a subpopulation of CD44v6-expressing cancer stem cells

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Elimination of Sox2-expressing cells led to reduction of bladder cancer progression

CRISPR/CAS9 ablation of individual miRNAs from a miRNA family reveals their individual efficacies for regulating cardiac differentiation

Although it is well understood that genetic mutations, chromosomal abnormalities, and epigenetic miscues can cause congenital birth defects, many defects are still labeled idiopathic, meaning their origin is not yet understood. microRNAs are quickly entering the causal fray of developmental defects. miRNAs use a 7-8 base-pair seed sequence to target a corresponding sequence on one or multiple mRNAs resulting in rapid down-regulation of translation. miRNAs can also control protein 'amounts' in cells. As a result if miRNAs are over or under expressed during development protein homeostasis can be compromised resulting in defects in the development of organ systems. Here, we show that during differentiation of embryonic stem cells, individual miRNAs that reside in the miRNA17 family (composed of 14 miRNAs) do not share the same function even though they have the same seed sequence. The advent of CRISPR/CAS9 technology has not only yielded a true observation of individual miRNA function, it has also reconnected advanced molecular biology approaches to classical cell biology approaches such as gene rescue. We show that miRNA106a and to a lesser extent miR17 and 93 target the cardiac suppressor gene Fog2, which specifically suppress Gata-4 and Coup-TF2. However, when each miRNA is knocked out, we find that their targeting efficacies for Fog2 differ resulting in varying degrees of cardiac differentiation.

AKR1C1 Activates STAT3 to Promote the Metastasis of Non-Small Cell Lung Cancer

Metastasis is the leading cause of mortality for human non-small cell lung cancer (NSCLC). However, it is difficult to target tumor metastasis because the molecular mechanisms underlying NSCLC invasion and migration remain unclear. Methods: GEO data analyses and IHC analyses were performed to identify that the expression level of AKR1C1, a member of human aldo-keto reductase family, was highly elevated in patients with metastasis or metastatic foci of NSCLC patients. Functional analyses (in vitro and in vivo) and quantitative genomic analyses were preformed to confirm the pro-metastatic effects of AKR1C1 and the underlying mechanisms. The correlation of AKR1C1 with the prognosis of NSCLC patients was evaluated using Kaplan-Meier analyses. Results: in NSCLC patients, AKR1C1 expression was closely correlated with the metastatic potential of tumors. AKR1C1 overexpression in nonmetastatic cancer cells significantly promoted metastasis both in vitro and in vivo, whereas depletion of AKR1C1 in highly metastatic tumors potently alleviated these effects. Quantitative genomic and functional analyses revealed that AKR1C1 directly interacted with STAT3 and facilitated its phosphorylation-thus reinforcing the binding of STAT3 to the promoter regions of target genes-and then transactivated these genes, which ultimately promoted tumor metastasis. Further studies showed that AKR1C1 might facilitate the interaction of STAT3 with its upstream kinase JAK2. Intriguingly, AKR1C1 exerted these pro-metastatic effects in a catalytic-independent manner. In addition, a significant correlation between AKR1C1 and STAT3 pathway was observed in the metastatic foci of NSCLC patients, and the AKR1C1-STAT3 levels were highly correlated with a poor prognosis in NSCLC patients. Conclusions: taken together, we show that AKR1C1 is a potent inducer of NSCLC metastasis. Our study uncovers the active function of AKR1C1 as a key component of the STAT3 pathway, which promotes lung cancer metastasis, and highlights a candidate therapeutic target to potentially improve the survival of NSCLC patients with metastatic disease.

Interleukin-6 upregulates SOX18 expression in osteosarcoma

Aim

SOX18 is a potential oncogene in osteosarcoma via controlling osteosarcoma cell proliferation and metastasis. Interleukin-6 (IL-6), a major activator of Janus kinase 2 (JAK2)/signal transducers and activators of transcription 3 (STAT3) signaling, plays an important role in the growth of carcinoma cells. The present study aims to investigate the correlation between IL-6 and SOX18 in osteosarcoma.

Materials and methods

Protein expression and mRNA expression were determined by Western blot and real-time polymerase chain reaction (PCR) analysis, respectively. Cell proliferation and apoptosis were identified by Cell Counting Kit-8 assay and flow cytometry analysis, respectively.

Results

We found that SOX18, IL-6 and p-STAT3 were elevated in osteosarcoma compared with bone cyst tissues. A positive correlation between the mRNA levels of IL-6 and SOX18 was observed in osteosarcoma tissues. IL-6 stimulation dose dependently induced the mRNA and protein levels of SOX18 in U-2OS and MG63 cells. Furthermore, IL-6 significantly rescued the inhibitory and induction effects of SOX18 knockdown on osteosarcoma cell proliferation and apoptosis, respectively. The changes in cell proliferation (PCNA) and apoptosis-related proteins (Bcl-2, Bax and Cleaved-Caspase 3) were in line with the results of cell proliferation and apoptosis assays.

Conclusion

Our data suggest that IL-6 is a possible upstream regulator for SOX18 in osteosarcoma.

3D modeling of cancer stem cell niche

Cancer stem cells reside in a distinct microenvironment called niche. The reciprocal interactions between cancer stem cells and niche contribute to the maintenance and enrichment of cancer stem cells. In order to simulate the interactions between cancer stem cells and niche, three-dimensional models have been developed. These in vitro culture systems recapitulate the spatial dimension, cellular heterogeneity, and the molecular networks of the tumor microenvironment and show great promise in elucidating the pathophysiology of cancer stem cells and designing more clinically relavant treatment modalites.

RBP4-STRA6 Pathway Drives Cancer Stem Cell Maintenance and Mediates High-Fat Diet-Induced Colon Carcinogenesis

The transmembrane protein, STRA6, functions as a vitamin A transporter and a cytokine receptor when activated by vitamin A-bound serum retinol binding protein 4 (RBP4). STRA6 activation transduces a JAK2-STAT3 signaling cascade and promotes tumorigenesis in a xenograft mouse model of colon cancer. We show here that RBP4 and STRA6 expression is associated with poor oncologic prognosis. Downregulating STRA6 or RBP4 in colon cancer cells decreased the fraction of cancer stem cells and their sphere and tumor initiation frequency. Furthermore, we show that high-fat diet (HFD) increases LGR5 expression and promotes tumor growth in a xenograft model independent of obesity. HFD increased STRA6 levels, and downregulation of STRA6 delays and impairs tumor initiation, tumor growth, and expression of stemness markers. Together, these data demonstrate a key role of STRA6 and RBP4 in the maintenance of colon cancer self-renewal and that this pathway is an important link through which consumption of HFD contributes to colon carcinogenesis.

Activation of tumor suppressor LKB1 by honokiol abrogates cancer stem-like phenotype in breast cancer via inhibition of oncogenic Stat3

Tumor suppressor and upstream master kinase Liver kinase B1 (LKB1) plays a significant role in suppressing cancer growth and metastatic progression. We show that low-LKB1 expression significantly correlates with poor survival outcome in breast cancer. In line with this observation, loss-of-LKB1 rendered breast cancer cells highly migratory and invasive, attaining cancer stem cell-like phenotype. Accordingly, LKB1-null breast cancer cells exhibited an increased ability to form mammospheres and elevated expression of pluripotency-factors (Oct4, Nanog and Sox2), properties also observed in spontaneous tumors in Lkb1^-/- mice. Conversely, LKB1-overexpression in LKB1-null cells abrogated invasion, migration and mammosphere-formation. Honokiol (HNK), a bioactive molecule from Magnolia grandiflora increased LKB1 expression, inhibited individual cell-motility and abrogated the stem-like phenotype of breast cancer cells by reducing the formation of mammosphere, expression of pluripotency-factors and aldehyde dehydrogenase activity. LKB1, and its substrate, AMP-dependent protein kinase (AMPK) are important for HNK-mediated inhibition of pluripotency factors since LKB1-silencing and AMPK-inhibition abrogated, while LKB1-overexpression and AMPK-activation potentiated HNK's effects. Mechanistic studies showed that HNK inhibited Stat3-phosphorylation/activation in an LKB1-dependent manner, preventing its recruitment to canonical binding-sites in the promoters of Nanog, Oct4 and Sox2. Thus, inhibition of the coactivation-function of Stat3 resulted in suppression of expression of pluripotency factors. Further, we showed that HNK inhibited breast tumorigenesis in mice in an LKB1-dependent manner. Molecular analyses of HNK-treated xenografts corroborated our in vitro mechanistic findings. Collectively, these results present the first in vitro and in vivo evidence to support crosstalk between LKB1, Stat3 and pluripotency factors in breast cancer and effective anticancer modulation of this axis with HNK treatment.

Sequential EMT-MET induces neuronal conversion through Sox2

Direct neuronal conversion can be achieved with combinations of small-molecule compounds and growth factors. Here, by studying the first or induction phase of the neuronal conversion induced by defined 5C medium, we show that the Sox2-mediated switch from early epithelial-mesenchymal transition (EMT) to late mesenchymal-epithelial transition (MET) within a high proliferation context is essential and sufficient for the conversion from mouse embryonic fibroblasts (MEFs) to TuJ⁺ cells. At the early stage, insulin and basic fibroblast growth factor (bFGF)-induced cell proliferation, early EMT, the up-regulation of Stat3 and Sox2, and the subsequent activation of neuron projection. Up-regulated Sox2 then induced MET and directed cells towards a neuronal fate at the late stage. Inhibiting either stage of this sequential EMT-MET impaired the conversion. In addition, Sox2 could replace sequential EMT-MET to induce a similar conversion within a high proliferation context, and its functions were confirmed with other neuronal conversion protocols and MEFs reprogramming. Therefore, the critical roles of the sequential EMT-MET were implicated in direct cell fate conversion in addition to reprogramming, embryonic development and cancer progression.

Interleukin-6-Mediated Induced Pluripotent Stem Cell (iPSC)-Derived Neural Differentiation

In an aging society with an increasing threat to higher brain cognitive functions due to dementia, it becomes imperative to identify new molecular remedies for supporting adult neurogenesis. Interleukin-6 (IL-6) is a promising cytokine that can support neurogenesis under conditions of neurodegeneration, and neuron replacement is eventually possible due to its agonistic acting soluble receptor sIL-6R. Here, we report that activation of the IL-6-signal transducer and activator of transcription 3 (STAT3) axis is neurogenic and has potential therapeutic applications for the treatment of neurodegenerative diseases such as Parkinson's disease (PD).

Mammalian target of rapamycin inhibitors, temsirolimus and torin 1, attenuate stemness-associated properties and expression of mesenchymal markers promoted by phorbol-myristate-acetate and oncostatin-M in glioblastoma cells

The phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin signaling pathway is crucial for tumor survival, proliferation, and progression, making it an attractive target for therapeutic intervention. In glioblastoma, activated mammalian target of rapamycin promotes invasive phenotype and correlates with poor patient survival. A wide range of mammalian target of rapamycin inhibitors are currently being evaluated for cytotoxicity and anti-proliferative activity in various tumor types but are not explored sufficiently for controlling tumor invasion and recurrence. We recently reported that mammalian target of rapamycin inhibitors-rapamycin, temsirolimus, torin 1, and PP242-suppressed invasion and migration promoted by tumor necrosis factor-alpha and phorbol-myristate-acetate in glioblastoma cells. As aggressive invasion and migration of tumors are associated with mesenchymal and stem-like cell properties, this study aimed to examine the effect of mammalian target of rapamycin inhibitors on these features in glioblastoma cells. We demonstrate that temsirolimus and torin 1 effectively reduced the constitutive as well as phorbol-myristate-acetate/oncostatin-M-induced expression of mesenchymal markers (fibronectin, vimentin, and YKL40) and neural stem cell markers (Sox2, Oct4, nestin, and mushashi1). The inhibitors significantly abrogated the neurosphere-forming capacity induced by phorbol-myristate-acetate and oncostatin-M. Furthermore, we demonstrate that the drugs dephosphorylated signal transducer and activator transcription factor 3, a major regulator of mesenchymal and neural stem cell markers implicating the role of signal transducer and activator transcription factor 3 in the inhibitory action of these drugs. The findings demonstrate the potential of mammalian target of rapamycin inhibitors as "stemness-inhibiting drugs" and a promising therapeutic approach to target glioma stem cells.

EpEX/EpCAM and Oct4 or Klf4 alone are sufficient to generate induced pluripotent stem cells through STAT3 and HIF2α

Epithelial cell adhesion molecule (EpCAM) was reported to be cleaved into extracellular domain of EpCAM (EpEX) and intracellular domain of EpCAM (EpICD). We previously reported that EpCAM serves as a potent stem cell marker which is highly and selectively expressed by undifferentiated rather than differentiated hESC. However, the functional role of EpCAM remains elusive. Here, we found that EpEX and EpCAM enhance the efficiency of OSKM reprogramming. Interestingly, Oct4 or Klf4 alone, but not Sox2, can successfully reprogram fibroblasts into iPSCs with EpEX and EpCAM. Moreover, EpEX and EpCAM trigger reprogramming via activation of STAT3, which leads to the nuclear-translocation of HIF2α. This study reveals the importance of a novel EpEX/EpCAM-STAT3-HIF2α signal in the reprogramming process, and uncovers a new means of triggering reprogramming by delivery of soluble and transmembrane proteins.

Mesoderm-specific Stat3 deletion affects expression of Sox9 yielding Sox9-dependent phenotypes

To date, mutations within the coding region and translocations around the SOX9 gene both constitute the majority of genetic lesions underpinning human campomelic dysplasia (CD). While pathological coding-region mutations typically result in a non-functional SOX9 protein, little is known about what mechanism(s) controls normal SOX9 expression, and subsequently, which signaling pathways may be interrupted by alterations occurring around the SOX9 gene. Here, we report the identification of Stat3 as a key modulator of Sox9 expression in nascent cartilage and developing chondrocytes. Stat3 expression is predominant in tissues of mesodermal origin, and its conditional ablation using mesoderm-specific TCre, in vivo, causes dwarfism and skeletal defects characteristic of CD. Specifically, Stat3 loss results in the expansion of growth plate hypertrophic chondrocytes and deregulation of normal endochondral ossification in all bones examined. Conditional deletion of Stat3 with a Sox9Cre driver produces palate and tracheal irregularities similar to those described in Sox9+/- mice. Furthermore, mesodermal deletion of Stat3 causes global embryonic down regulation of Sox9 expression and function in vivo. Mechanistic experiments ex vivo suggest Stat3 can directly activate the expression of Sox9 by binding to its proximal promoter following activation. These findings illuminate a novel role for Stat3 in chondrocytes during skeletal development through modulation of a critical factor, Sox9. Importantly, they further provide the first evidence for the modulation of a gene product other than Sox9 itself which is capable of modeling pathological aspects of CD and underscore a potentially valuable therapeutic target for patients with the disorder.

Nucleophosmin-anaplastic lymphoma kinase: the ultimate oncogene and therapeutic target

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase physiologically expressed by fetal neural cells. However, aberrantly expressed ALK is involved in the pathogenesis of diverse malignancies, including distinct types of lymphoma, lung carcinoma, and neuroblastoma. The aberrant ALK expression in nonneural cells results from chromosomal translocations that create novel fusion proteins. These protein hybrids compose the proximal part of a partner gene, including its promoter region, and the distal part of ALK, including the coding sequence for the entire kinase domain. ALK was first identified in a subset of T-cell lymphomas with anaplastic large cell lymphoma (ALCL) morphology (ALK+ ALCL), the vast majority of which harbor the well-characterized nucleophosmin (NPM)-ALK fusion protein. NPM-ALK co-opts several intracellular signal transduction pathways, foremost being the STAT3 pathway, normally activated by cytokines from the interleukin-2 (IL-2) family to promote cell proliferation and to inhibit apoptosis. Many genes and proteins modulated by NPM-ALK are also involved in evasion of antitumor immune response, protection from hypoxia, angiogenesis, DNA repair, cell migration and invasiveness, and cell metabolism. In addition, NPM-ALK uses epigenetic silencing mechanisms to downregulate tumor suppressor genes to maintain its own expression. Importantly, NPM-ALK is capable of transforming primary human CD4⁺ T cells into immortalized cell lines indistinguishable from patient-derived ALK+ ALCL. Preliminary clinical studies indicate that inhibition of NPM-ALK induces long-lasting complete remissions in a large subset of heavily pretreated adult patients and the vast majority of children with high-stage ALK+ ALCL. Combining ALK inhibition with other novel therapeutic modalities should prove even more effective.

SOX2, OCT3/4 and NANOG expression and cellular plasticity in rare human somatic cells requires CD73

Endogenous Plastic Somatic (ePS) cells isolated from adult human tissues exhibit extensive lineage plasticity in vitro and in vivo. Here we visualize these rare ePS cells in a latent state, i.e. lacking SOX2, OCT3/4 and NANOG (SON) expression, in non-diseased breast specimens through immunohistochemical analysis of previously identified ePS-specific biomarkers (CD73⁺, EpCAM⁺ and CD90^-). We also report a novel mechanism by which these latent ePS cells acquire SON expression and plasticity in vitro. Four extracellular factors are necessary for the acquisition of SON expression and lineage plasticity in ePS cells: adenosine (which is produced by the 5' ecto-nucleotidase CD73 and activates in turn the PKA-dependent IL6/STAT3 pathway through the adenosine receptor ADORA2b), IL6, FGF2 and ACTIVIN A. Blocking any pathway component renders ePS cells incapable of SON expression and lineage plasticity. Notably, hESCs do not use adenosine or IL6 nor they express CD73 or ADORA2b and inhibition of adenosine signaling does not ablate their plasticity. Therefore, the data presented here delineate novel circuitry and physiological signals for accessing SON expression in rare, undifferentiated human cells.

Down-Regulation of SOX2 Underlies the Inhibitory Effects of the Triphenylmethane Gentian Violet on Melanoma Cell Self-Renewal and Survival

Human melanomas contain a population of tumor-initiating cells that are able to maintain the growth of the tumor. We previously showed that the embryonic transcription factor SOX2 is essential for self-renewal and tumorigenicity of human melanoma-initiating cells. However, targeting a transcription factor is still challenging. Gentian violet (GV) is a cationic triphenylmethane dye with potent antifungal and antibacterial activity. Recently, a combination therapy of imiquimod and GV has shown an inhibitory effect against melanoma metastases. Whether and how GV affects melanoma cells remains unknown. Here we show that GV represses melanoma stem cell self-renewal through inhibition of SOX2. Mechanistically, GV hinders EGFR activation and inhibits the signal transducer and activator of transcription-3 [(STAT3)/SOX2] axis. Importantly, we show that GV treatment decreases STAT3 phosphorylation at residue tyrosine 705, thus preventing the translocation of STAT3 into the nucleus and its binding to SOX2 promoter. In addition, GV affects melanoma cell growth by promoting mitochondrial apoptosis and G2 cell cycle arrest. This study shows that in melanoma, GV affects both the stem cell and the tumor bulk compartments, suggesting the potential use of GV in treating human melanoma alone or in combination with targeted therapy and/or immunotherapy.