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Crosstalk between the STAT3, NF-kB and Notch signaling pathways in glioblastoma stem cells

ABSTRACT: In this study, we describe a novel relationship between glioblastoma CSCs and the Notch pathway, which involves the constitutive activation of STAT3 and NF-κB signaling. We demonstrate that adherent glioma CSCs exhibit characteristics previously described for CSCs grown in suspension culture. The expression of CD133, Sox2 and Nestin increased when compared to glioma cells grown in monolayer, and the adherent CSCs were ~100 times more tumorigenic in vivo than monolayer cultured glioma cells. We also found that while the STAT3 and NF-κB signaling pathways are constitutively activated in glioma lines, these pathways are dramatically activated in glioma CSCs. Treatment with STAT3 inhibitors led to a loss of nuclear activation of STAT3 signaling and suppression of growth in both monolayer and CSC conditions. There was a markedly greater growth suppressive effect on glioma CSCs, suggesting that targeted therapy of these key pathways in glioma CSCs may be possible. To further investigate potential biomarkers in glioma CSCs, microarray analysis was performed and revealed deregulation of the Notch signaling pathway. This constitutive activation of STAT3, NF-κB, and Notch pathways in glioma CSCs helps identify novel therapeutic targets for the treatment of glioma. GBM6 cells were continuously maintained as subcutaneous xenografts in NSG mice, and monolayer and CSC cultures were derived from freshly harvested tumor tissue. A total of 6 samples were subjected to microarray analysis, with three biological replicates for each experimental condition.

ORGANISM(S): Homo sapiens

SUBMITTER: Garner Jo

PROVIDER: S-ECPF-GEOD-48079 | biostudies-other |

REPOSITORIES: biostudies-other

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Project description:The activated B cell-like (ABC) subgroup of diffuse large B cell lymphoma (DLBCL) is characterized by constitutive activation of the NF-ÃªB pathway. Here we show that the NF- ÃªB pathway induces the expression of the cytokines IL-6 and IL-10 in ABC DLBCL cell lines, which also have high levels of total and phosphorylated STAT3 protein, suggesting autocrine signaling. Using RNA interference for STAT3, we defined a gene expression signature of IL-6 and IL-10 signaling through STAT3. Based on this signature, we constructed a molecular predictor of STAT3 signaling that defined a subset of ABC DLBCL tumors with high expression of STAT3, IL-6 and/or IL-10, and their downstream targets. Although the STAT3-high and STAT3-low subsets had equivalent expression of genes that distinguish ABC DLBCL from GCB DLBCL, STAT3-high ABC DLBCLs had higher expression of signatures that reflected NF-kB activity, proliferation, and glycolysis. A smallmolecule inhibitor of JAK signaling, which blocked STAT3 signature expression, was toxic only for ABC DLBCL lines, and synergized with an inhibitor of NF-kB signaling. These findings suggest that the biological interplay between the STAT3 and NF-kB pathways may be exploited for the treatments of a subset of ABC DLBCLs. Activated B cell-like (ABC) subgroup of diffuse large B cell lymphoma (DLBCL) cell lines were used as model systems to study the cytokine pathways in these cells. We expressed inducible IkB super-repressor for 1 to 24 hours to identify NF-kB target genes in OCI-Ly3 and OCI-Ly10 cells for a total of 13 arrays with replicates of each time point. We treated OCI-Ly3 cells with IL-10 for 1 to 96 hours for a total of 10 arrays with replicates of each time point. We treated OCI-Ly10 cells with IL-6 for 30 minutes to 24 hours for a total of 8 arrays with replicates of each time point. OCI-Ly10 cells transfected with no siRNA versus STAT3-siRNA for 8, 24, or 48 hours for a total of 5 arrays with replicates for 24 and 48 hours. We treated OCI-Ly10 cells with JAK inhibitor I for 3 and 6 hours for a total of 4 arrays with replicates of each time point.

Project description:BackgroundMyc is a well known driver of lymphomagenesis, and Myc-activating chromosomal translocation is the recognized hallmark of Burkitt lymphoma, an aggressive form of non-Hodgkin's lymphoma. We developed a model that mimics this translocation event by inserting a mouse Myc cDNA gene into the immunoglobulin heavy chain locus, just upstream of the intronic Emu enhancer. These mice, designated iMyc E mu, readily develop B-cell lymphoma. To study the mechanism of Myc-induced lymphoma, we analyzed signaling pathways in lymphoblastic B-cell lymphomas (LBLs) from iMyc E mu mice, and an LBL-derived cell line, iMyc E mu-1.ResultsNuclear factor-kappaB (NF-kappaB) and signal transducer and activator of transcription 3 (STAT3) were constitutively activated in iMyc E mu mice, not only in LBLs but also in the splenic B-lymphocytes of young animals months before tumors developed. Moreover, inhibition of either transcription factor in iMyc E mu-1 cells suppressed growth and caused apoptosis, and the abrogation of NF-kappaB activity reduced DNA binding by both STAT3 and Myc, as well as Myc expression. Inhibition of STAT3 signaling eliminated the activity of both NF-kappaB and Myc, and resulted in a corresponding decrease in the level of Myc. Thus, in iMyc E mu-1 cells NF-kappaB and STAT3 are co-dependent and can both regulate Myc. Consistent with this, NF-kappaB and phosphorylated STAT3 were physically associated with one another. In addition, LBLs and iMyc E mu-1 cells also showed constitutive AKT phosphorylation. Blocking AKT activation by inhibiting PI3K reduced iMyc E mu-1 cell proliferation and caused apoptosis, via downregulation of NF-kappaB and STAT3 activity and a reduction of Myc levels. Co-treatment with NF-kappaB, STAT3 or/and PI3K inhibitors led to additive inhibition of iMyc E mu-1 cell proliferation, suggesting that these signaling pathways converge.ConclusionsOur findings support the notion that constitutive activation of NF-kappaB and STAT3 depends on upstream signaling through PI3K, and that this activation is important for cell survival and proliferation, as well as for maintaining the level of Myc. Together, these data implicate crosstalk among NF-kappaB, STAT3 and PI3K in the development of iMyc E mu B-cell lymphomas.

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Crosstalk between the STAT3, NF-kB and Notch signaling pathways in glioblastoma stem cells

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