Fibroblast growth factor-2 up-regulates the expression of nestin through the Ras-Raf-ERK-Sp1 signaling axis in C6 glioma cells

XCHD Inhibits C6 Cell Growth Primarily via the p53/Caspase Pathway

The effects of XCHD on the proliferation of C6 cells and on factors associated with the microRNA-34a (miR-34a)/p53/caspase-3 signaling pathway in vitro were investigated. Methods. XCHD was purchased too much to complete the study. CCK-8 assay was used to measure the XCHD concentration, and qPCR was used to quantify miR-34a expression at the mRNA level. Apoptosis was assessed using TUNEL. Western blots were used to determine the p53, caspase-3, caspase-8, and Bcl-2 expression levels. Results. The optimal XCHD concentration and time effect for C6 cells were observed after 36 h of exposure to a concentration of 100 µg/ml XCHD. miR-34a expression increased 8 and 12 h after the addition of XCHD. The presence of XCHD decreased Bcl-2 expression but increased p53, cleaved caspase-3, Bax, and caspase-8 expression. When p53 was inhibited, miR-34a expression was unaffected by the addition of XCHD, Bcl-2 expression was low, and cleaved caspase-3, Bax, and caspase-8 expression increased. The inhibition of p53 promoted C6 cell growth when compared with C6 cells exposed to XCHD and with no inhibition of p53. Conclusions. XCHD inhibits C6 cell growth which was influenced by the p53/caspase pathway.

GPR50 Promotes Hepatocellular Carcinoma Progression via the Notch Signaling Pathway through Direct Interaction with ADAM17

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death worldwide, and it is thus critical to identify novel molecular biomarkers of HCC prognosis and elucidate the molecular mechanisms underlying HCC progression. Here, we show that G-protein-coupled receptor 50 (GPR50) in HCC is overexpressed and that GPR50 knockdown may downregulate cancer cell progression through attenuation of the Notch signaling pathway. GPR50 knockdown was found to reduce HCC progression by inactivating Notch signaling in a ligand-independent manner through a disintegrin and metalloproteinase metallopeptidase domain 17 (ADAM17), a proteolytic enzyme that cleaves the Notch receptor, which was corroborated by GPR50 overexpression in hepatocytes. GPR50 silencing also downregulated transcription and translation of ADAM17 through the AKT/specificity protein-1 (SP1) signaling axis. Notably, GPR50 was found to directly interact with ADAM17. Overall, we demonstrate a novel GPR50-mediated regulation of the ADAM17-Notch signaling pathway, which can provide insights into HCC progression and prognosis and development of Notch-based HCC treatment strategies.

The reciprocal interaction between tumor cells and activated fibroblasts mediated by TNF-α/IL-33/ST2L signaling promotes gastric cancer metastasis

Gastric cancer (GC) is characterized by extensive local invasion, distant metastasis and poor prognosis. In most cases, GC progression is associated with aberrant expression of cytokines or activation of signaling cascades mediated by tumor–stroma interactions. However, the mechanisms by which these interactions contribute to GC progression are poorly understood. In this study, we find that IL-33 and its receptor ST2L are upregulated in the human GC and served as prognostic markers for poor survival of GC patients. In a co-culture model with GC cells and cancer-associated fibroblasts (CAFs), we further demonstrate that CAFs-derived IL-33 enhances the migration and invasion of GC cells by inducing the epithelial–mesenchymal transition (EMT) through activation of the ERK1/2-SP1-ZEB2 pathway in a ST2L-dependent manner. Furthermore, the secretion of IL-33 by CAFs can be induced by the proinflammatory cytokines TNF-α that is released by GC cells via TNFR2-NF-κB-IRF-1 pathway. Additionally, silencing of IL-33 expression in CAFs or ST2L expression in GC cells inhibits the peritoneal dissemination and metastatic potential of GC cells in nude mice. Taken together, these results characterize a critical role of the interaction between epithelial-stroma mediated by the TNF-α/IL-33/ST2L signaling in GC progression, and provide a rationale for targeting this pathway to treat GC metastasis.

Neurogenesis-on-Chip: Electric field modulated transdifferentiation of human mesenchymal stem cell and mouse muscle precursor cell coculture

A number of bioengineering strategies, using biophysical stimulation, are being explored to guide the human mesenchymal stem cells (hMScs) into different lineages. In this context, we have limited understanding on the transdifferentiation of matured cells to another functional-cell type, when grown with stem cells, in a constrained cellular microenvironment under biophysical stimulation. While addressing such aspects, the present work reports the influence of the electric field (EF) stimulation on the phenotypic and functionality modulation of the coculture of murine myoblasts (C2C12) with hMScs [hMSc:C2C12=1:10] in a custom designed polymethylmethacrylate (PMMA) based microfluidic device with in-built metal electrodes. The quantitative and qualitative analysis of the immunofluorescence study confirms that the cocultured cells in the conditioned medium with astrocytic feed, exhibit differentiation towards neural-committed cells under biophysical stimulation in the range of the endogenous physiological electric field strength (8 ± 0.06  mV/mm). The control experiments using similar culture protocols revealed that while C2C12 monoculture exhibited myotube-like fused structures, the hMScs exhibited the neurosphere-like clusters with SOX2, nestin, βIII-tubulin expression. The electrophysiological study indicates the significant role of intercellular calcium signalling among the differentiated cells towards transdifferentiation. Furthermore, the depolarization induced calcium influx strongly supports neural-like behaviour for the electric field stimulated cells in coculture. The intriguing results are explained in terms of the paracrine signalling among the transdifferentiated cells in the electric field stimulated cellular microenvironment. In summary, the present study establishes the potential for neurogenesis on-chip for the coculture of hMSc and C2C12 cells under tailored electric field stimulation, in vitro.

Alpha6-Integrin Regulates FGFR1 Expression through the ZEB1/YAP1 Transcription Complex in Glioblastoma Stem Cells Resulting in Enhanced Proliferation and Stemness

Glioblastoma (GBM) is the most lethal primary brain tumor in adults and is known to be particularly aggressive and resistant to anti-cancer therapies, mainly due to the presence of GBM stem cells (GBMSC). By in vitro approaches supported by analysis from patients' databases, we determined how α6-integrin and Fibroblast Growth Factor Receptor 1 (FGFR1) work in concert to regulate proliferation and stemness of GBMSC. We showed that α6-integrin regulates the expression of FGFR1 and its target gene Fokhead Box M1 (FOXM1) via the ZEB1/YAP1 transcription complex. These results were in accordance with the positive correlation observed in GBM between α6-integrin expression and its target genes ZEB1/YAP1, FGFR1, and FOXM1 in the databases, TCGA and Rembrandt. In addition, the clinical data demonstrate that GBM patients with high levels of the five genes signature, including α6-integrin, ZEB1/YAP1, FGFR1 and FOXM1, have a significantly shorter overall survival. In vitro, we observed a similar decrease in the expression of stemness-related factors, neurospheres forming capacity, as well as spheroids growth when α6-integrin or FGFR1 was blocked individually with specific siRNA, whereas the combination of both siRNA led to a significantly higher inhibition of spheres formation. These data suggest that co-administration of anti-FGFR1 and anti-α6-integrin could provide an improved therapeutic response in GBMSC.

Endothelial cells are a source of Nestin expression in Pulmonary Arterial Hypertension

Uncontrolled proliferation of endothelial cells is essential to the pathogenesis of pulmonary arterial hypertension (PAH). Both proliferation and cytoskeleton reorganization are associated with upregulation of the intermediate filament protein Nestin. Recently, accumulation of Nestin-expressing cells was found in pulmonary vascular lesions of PAH patients. The goal of this study is to determine if Nestin expression contributes to endothelial proliferation in pulmonary arterial hypertension, using both lung tissues and endothelial cells. Here we found that endothelial cells from complex and plexiform lesions of PAH patients expressed Nestin. These Nestin+ cells further stained positive for the angiogenic factors CXC chemokine ligand 12 and Wnt1. Likewise, in the chronic hypoxia/SU5416 animal model of pulmonary hypertension, Nestin+ endothelial cells were found in occlusive pulmonary vascular lesions. In vitro, both growing rat and human lung endothelial cells expressed Nestin protein. When Nestin was overexpressed in endothelial cells (both rat and human), Nestin overexpression promoted proliferation and expression of CXC chemokine ligand 12. Nestin overexpression further increased angiogenic tube formation in vitro. Conclusions: We found increased Nestin expression from endothelial cells of occlusive lung vascular lesions in severe pulmonary hypertension. Elevated Nestin expression likely contributes to unchecked pulmonary vascular proliferation and angiogenesis, possibly via induction of CXC chemokine ligand 12. Additional studies are required to determine whether targeting Nestin would be beneficial to treat PAH.

Metabolic regulation of glioma stem-like cells in the tumor micro-environment

Cancer metabolism has emerged as one of the most interesting old ideas being revisited from a new perspective. In the early 20th century Otto Warburg declared metabolism the prime cause in a disease of many secondary causes, and this statement seems more prescient in view of modern expositions into the true nature of tumor evolution. As the complexity of tumor heterogeneity becomes more clear from a genetic perspective, it is important to consider the inevitably heterogeneous metabolic components of the tumor and the tumor microenvironment. High grade gliomas remain one of the most difficult to treat solid tumors, due in part to the highly vascularized nature of the tumor and the maintenance of more resistant stem-like subpopulations within the tumor. Maintenance of glioma stem cells (GSCs) requires specific alterations within the cells and the greater tumor microenvironment with regards to signaling and metabolism. Specific niches within gliomas help foster the survival of stem-like sub-populations of cells with high tumorigenicity and high metabolic plasticity. Understanding these maintenance pathways and the metabolic dependencies within the niche may highlight potential avenues of addressing tumor resistance and recurrence in glioma patients.

Targeted gene knock-in by homology-directed genome editing using Cas9 ribonucleoprotein and AAV donor delivery

Realizing the full potential of genome editing requires the development of efficient and broadly applicable methods for delivering programmable nucleases and donor templates for homology-directed repair (HDR). The RNA-guided Cas9 endonuclease can be introduced into cells as a purified protein in complex with a single guide RNA (sgRNA). Such ribonucleoproteins (RNPs) can facilitate the high-fidelity introduction of single-base substitutions via HDR following co-delivery with a single-stranded DNA oligonucleotide. However, combining RNPs with transgene-containing donor templates for targeted gene addition has proven challenging, which in turn has limited the capabilities of the RNP-mediated genome editing toolbox. Here, we demonstrate that combining RNP delivery with naturally recombinogenic adeno-associated virus (AAV) donor vectors enables site-specific gene insertion by homology-directed genome editing. Compared to conventional plasmid-based expression vectors and donor templates, we show that combining RNP and AAV donor delivery increases the efficiency of gene addition by up to 12-fold, enabling the creation of lineage reporters that can be used to track the conversion of striatal neurons from human fibroblasts in real time. These results thus illustrate the potential for unifying nuclease protein delivery with AAV donor vectors for homology-directed genome editing.

Acidic pH with coordinated reduction of basic fibroblast growth factor maintains the glioblastoma stem cell-like phenotype in vitro

Glioblastoma stem cells (GSCs) are a unique subpopulation of cells within glioblastoma multiforme (GBM) brain tumors that possess the ability to self-renew and differentiate into bulk tumor cells. GSCs are resistant to currently available treatments and are the likely culprit behind tumor relapse in GBM patients. However, GSCs are currently inaccessible to the larger scientific community because obtaining a sufficient number of GSCs remains technically challenging and cost-prohibitive. Thus, the objective of this study was to develop a more efficient GSC culture strategy that results in a higher cell yield of GSCs at a lower cost. We observed that the basic fibroblast growth factor (bFGF) is indispensable in allowing GSCs to retain an optimal stem cell-like phenotype in vitro, but little change was seen in their stemness when grown with lower concentrations of bFGF than the established protocol. Interestingly, a dynamic fluctuation of GSC protein marker expression was observed that corresponded to the changes in the bFGF concentration during the culture period. This suggested that bFGF alone did not control stem cell-like phenotype; rather, it was linked to the fluctuations of both bFGF and media pH. We demonstrated that a high level of stem cell-like phenotype could be retained even when lowering bFGF to 8 ng/mL when the media pH was simultaneously lowered to 6.8. These results provide the proof-of-concept that GSC expansion costs could be lowered to a more economical level and warrant the use of pH- and bFGF-controlled bioprocessing methodologies to more optimally expand GSCs in the future.

Glioma Stem Cells and Their Microenvironments: Providers of Challenging Therapeutic Targets

Malignant gliomas are aggressive brain tumors with limited therapeutic options, possibly because of highly tumorigenic subpopulations of glioma stem cells. These cells require specific microenvironments to maintain their “stemness,” described as perivascular and hypoxic niches. Each of those niches induces particular signatures in glioma stem cells (e.g., activation of Notch signaling, secretion of VEGF, bFGF, SDF1 for the vascular niche, activation of HIF2α, and metabolic reprogramming for hypoxic niche). Recently, accumulated knowledge on tumor-associated macrophages, possibly delineating a third niche, has underlined the role of immune cells in glioma progression, via specific chemoattractant factors and cytokines, such as macrophage-colony stimulation factor (M-CSF). The local or myeloid origin of this new component of glioma stem cells niche is yet to be determined. Such niches are being increasingly recognized as key regulators involved in multiple stages of disease progression, therapy resistance, immune-escaping, and distant metastasis, thereby substantially impacting the future development of frontline interventions in clinical oncology. This review focuses on the microenvironment impact on the glioma stem cell biology, emphasizing GSCs cross talk with hypoxic, perivascular, and immune niches and their potential use as targeted therapy.

Tetramethylpyrazine induces SH-SY5Y cell differentiation toward the neuronal phenotype through activation of the PI3K/Akt/Sp1/TopoIIβ pathway

Tetramethylpyrazine (TMP) is an active compound extracted from the traditional Chinese medicinal herb Chuanxiong. Previously, we have shown that TMP induces human SH-SY5Y neuroblastoma cell differentiation toward the neuronal phenotype by targeting topoisomeraseIIβ (TopoIIβ), a protein implicated in neural development. In the present study, we aimed to elucidate whether the transcriptional factors specificity protein 1 (Sp1) and nuclear factor Y (NF-Y), in addition to the upstream signaling pathways ERK1/2 and PI3K/Akt, are involved in modulating TopoIIβ expression in the neuronal differentiation process. We demonstrated that SH-SY5Y cells treated with TMP (80μM) terminally differentiated into neurons, characterized by increased neuronal markers, tubulin βIII and microtubule associated protein 2 (MAP2), and increased neurite outgrowth, with no negative effect on cell survival. TMP also increased the expression of TopoIIβ, which was accompanied by increased expression of Sp1 in the differentiated neuron-like cells, whereas NF-Y protein levels remained unchanged following the differentiation progression. We also found that the phosphorylation level of Akt, but not ERK1/2, was significantly increased as a result of TMP stimulation. Furthermore, as established by chromatin immunoprecipitation (ChIP) assay, activation of the PI3K/Akt pathway increased Sp1 binding to the promoter of the TopoIIβ gene. Blockage of PI3K/Akt was shown to lead to subsequent inhibition of TopoIIβ expression and neuronal differentiation. Collectively, the results indicate that the PI3K/Akt/Sp1/TopoIIβ signaling pathway is necessary for TMP-induced neuronal differentiation. Our findings offer mechanistic insights into understanding the upstream regulation of TopoIIβ in neuronal differentiation, and suggest potential applications of TMP both in neuroscience research and clinical practice to treat relevant diseases of the nervous system.

Roles and potential clinical applications of intermediate filament proteins in brain tumors

Intermediate filament (IF) proteins are cytoplasmic and nuclear cytoskeletal proteins. Of the ~70 IF proteins, nearly 12 are found in the nervous system, where their expression is largely cell-type specific. Astrocytes express glial fibrillary acidic protein (GFAP), whereas different neuron types contain neurofilament proteins, α-internexin, or peripherin. These proteins are often downregulated in brain cancer. In addition, brain cancer cells may also contain vimentin, nestin, and synemin, which are the IF proteins found in neural progenitor cells. In different brain tumor types, the expression of nestin, vimentin, and α-internexin appears to correlate with the clinical outcome. Experimental investigations have also demonstrated that IF proteins have distinct roles in specific brain tumor cell behaviors: nestin, for instance, is important for the proliferation of glioma cells, whereas synemin also affect their mobility. The mechanisms responsible for these effects involve the interaction of IF proteins with specific signaling pathways. Synemin, for instance, positively regulates glioma cell proliferation by antagonizing protein phosphatase 2A. Further evidence for the potential of IF proteins as therapeutic targets derives from animal models showing the influence of IF proteins on tumor growth. Nestin downregulation, for instance, dramatically reduced intracerebral glioma growth. Selective targeted therapies of IFs to date primarily include gene therapy approaches using nestin or GFAP gene promoters to drive transgene expression into glioma cells. Although attempts to identify small molecules specifically antagonizing IF proteins have been unsuccessful to date, it is anticipated that the identification of such compounds will be instrumental in expanding therapeutic approaches for brain tumors.

Melanoma spheroid formation involves laminin-associated vasculogenic mimicry

Melanoma is a tumor where virulence is conferred on transition from flat (radial) to three-dimensional (tumorigenic) growth. Virulence of tumorigenic growth is governed by numerous attributes, including presence of self-renewing stem-like cells and related formation of patterned networks associated with the melanoma mitogen, laminin, a phenomenon known as vasculogenic mimicry. Vasculogenic mimicry is posited to contribute to melanoma perfusion and nutrition in vivo; we hypothesized that it may also play a role in stem cell-driven spheroid formation in vitro. Using a model of melanoma in vitro tumorigenesis, laminin-associated networks developed in association with three-dimensional melanoma spheroids. Real-time PCR analysis of laminin subunits showed that spheroids formed from anchorage-independent melanoma cells expressed increased α4 and β1 laminin chains and α4 laminin expression was confirmed by in situ hybridization. Association of laminin networks with melanoma stem cell-associated nestin and vascular endothelial growth factor receptor-1 also was documented. Moreover, knockdown of nestin gene expression impaired laminin expression and network formation within spheroids. Laminin networks were remarkably similar to those observed in melanoma xenografts in mice and to those seen in patient melanomas. These data indicate that vasculogenic mimicry-like laminin networks, in addition to their genesis in vivo, are integral to the extracellular architecture of melanoma spheroids in vitro, where they may serve as stimulatory scaffolds to support three-dimensional growth.