Project description:Although the oncogenic signalings driven by amplification and mutations of EGF receptor (EGFR) gene play a major role in glioblastoma pathogenesis, the responsible downstream mechanisms remain less clear. Here we demonstrate that tripartite motif-containing protein 59 (TRIM59), acting as a new downstream effector of EGFR signaling, regulates STAT3 activation in glioblastoma. EGFR signaling leads to TRIM59 upregulation through SOX9 that results in enhancing TRIM59 interaction with STAT3 in nucleus, and inhibiting STAT3 association with TC45 (the nuclear form of T cell protein tyrosine phosphatase TC-PTP), thereby maintaining STAT3 phosphorylation and activation and promoting tumorigenesis. Silencing TRIM59 suppresses cell proliferation, migration, and orthotopic xenograft brain tumorigenesis of GBM cells. Moreover, evaluation of GBM patient samples reveals an association among EGFR activation, TRIM59 expression, STAT3 phosphorylation, and poor prognoses. Our study identifies TRIM59 as a new regulator of oncogenic EGFR-STAT3 signaling and a potential therapeutic target for GBM patients with EGFR activation.
Project description:We identified a novel mechanism by which IL-6/STAT3 signaling up-regulates CD133 expression and promotes HCC progression. STAT3 activation upregulates the expression of CD133 during liver carcinogenesis. Targeting STAT3-mediated CD133 overexpression may represent a promising therapeutic strategy for HCC patients via eradicating the liver tumor microenviornment. To develop novel cancer therapeutic strategies by identification of signaling pathways or biomarkers and understanding their functions on cancer stem cell biology, we determined CD133 expression and STAT3 activation with tumor microenvironment in HCC patient tissues. The relation of STAT3 activation and CD133 expression was investigated by luciferase assay, shRNA knock-down, and chromatin immunoprecipitation assay in HCC cells, and in vivo xenograft model.
Project description:We identified a novel mechanism by which IL-6/STAT3 signaling up-regulates CD133 expression and promotes HCC progression. STAT3 activation upregulates the expression of CD133 during liver carcinogenesis. Targeting STAT3-mediated CD133 overexpression may represent a promising therapeutic strategy for HCC patients via eradicating the liver tumor microenviornment.
Project description:In the related study, to determine whether DUSP2 definitively served as a phosphatase for STAT3, an in vitro phosphatase assay was used. Using S-tag beads, p-STAT3 was pulled down from IL-6 stimulated HEK293T cells transfected with STAT3-S-Tag. DUSP2 or control protein, which was purified from HEK293T cells transfected with DUSP2-FLAG or empty vector through extraction with anti-FLAG beads and elution with FLAG peptides, were incubated with p-STAT3-S-Tag-beads in phosphatase buffer. Then bound proteins were eluted and subjected to MS analysis. When compared with the control, incubation of STAT3 and DUSP2 led to dephosphorylation of two STAT3 residues that have been reported to promote its activity, namely tyrosine 705 and serine 727.
Project description:This study is to identify downstream genes regulated by STAT3 in response cytosolic acidification. Dysregulated intracellular pH is emerging as a hallmark of cancer. In spite of their acidic environment, cancer cells maintain alkaline intracellular pH (≥7.4) that promotes cancer progression by inhibiting apoptosis and increasing glycolysis, cell growth, migration and invasion. Here, we identify signal transducer and activator of transcription 3 (STAT3) as a key player in the maintenance of alkaline cytosolic pH. STAT3 associates with the vacuolar H+-ATPase on lysosomal membranes in a coiled coil domain-dependent manner and increases its activity in living cells and in vitro. Accordingly, STAT3 depletion disrupts intracellular proton equilibrium by decreasing and increasing cytosolic and lysosomal pH, respectively. This dysregulation can be reverted by reconstitution with wild type STAT3 as well as STAT3 mutants unable to activate target genes (Tyr-705-Phe and DNA binding mutant) or to regulate mitochondrial respiration (Ser-727-Ala). Upon cytosolic acidification, phospho-Tyr-705-STAT3 is rapidly dephosphorylated, transcriptionally inactivated and further recruited to lysosomal membranes to reestablish intracellular proton equilibrium and to enhance cell survival. These data reveal STAT3 as a regulator of intracellular pH, and vice versa intracellular pH as a regulator of STAT3 localization and activity.
Project description:Oncogenic STAT3 functions are known in various malignancies. We found that STAT3 plays an unexpected tumor suppressive role in KRAS-mutant non-small-cell-lung cancer (NSCLC). In mice, tissue-specific inactivation of Stat3 resulted in increased Kras (G12D)-driven NSCLC initiation and malignant progression leading to markedly reduced survival. Clinically, low STAT3 expression levels correlate with poor survival in human lung adenocarcinoma patients with smoking history. Consistently, KRAS-mutant lung tumors showed reduced STAT3 levels. Mechanistically, we show that STAT3 controls NFκB-induced IL-8-expression by sequestering NFκB in the cytoplasm while IL-8 in turn regulates myeloid tumor infiltration and tumor vascularization thereby promoting tumor progression. These results identify a novel STAT3-NFκB-IL-8 axis in KRAS-mutant NSCLC with therapeutic and prognostic relevance WT: Control lung; KRAS: Lung tumors expressing KRAS G12D; KRAS STAT3 KO: Lung tumors expressing KRAS G12D- STAT3 deficient; tumors of four mice pooled per sample