Project description:In many human cancers the transcription factor STAT3 is constitutively active and contributes to oncogenesis, tumour growth and progression. Recently, gain-of-function mutations of STAT3 have been identified in patients suffering from various haematopoietic malignancies and are postulated to enhance the transcriptional activity of STAT3. We investigated the gene expression and binding profile of the most common STAT3 mutant Y640F compared to wild-type STAT3, describing it's mechanism of action and pinpointing to novel therapeutic intervention sites.
Project description:The marsupial Tasmanian devil (Sarcophilus harrisii) faces extinction due to transmissible devil facial tumor disease (DFTD). To unveil the culprit molecular underpinnings, we designed an approach that combines sensitivity to drugs with an integrated systems-biology characterization. Sensitivity to inhibitors of the ERBB family of receptor tyrosine kinases correlated with their overexpression, suggesting a causative link. Proteomic and DNA methylation analyses revealed tumor-specific signatures linked to oncogenic signaling hubs including evolutionary conserved STAT3. Indeed, inhibition of ERBB blocked phosphorylation of STAT3 and arrested cancer cells. Blockade of ERBB signaling prevented tumor growth in a xenograft model and resulted in recovery of MHC-I gene expression. This link between the hyperactive ERBB-STAT3 axis and decreased MHC-I mediated tumor immunosurveillance provides mechanistic insights into horizontal transmissibility and lets us propose a dual chemo-immunotherapeutic strategy to save Tasmanian devils from DFTD.
Project description:Signal transducer and activator of transcription 3 (STAT3) is a critical transcription factor in cancer. However, while the protein-coding target genes of STAT3 have been extensively studied, the microRNA target genes of STAT3 are less understood. MicroRNAs are short, non-coding RNAs that regulate messenger RNAs through translational inhibition and transcript degradation. They have been found to be involved in all aspects of cancer biology. Given the roles of both STAT3 and miRNAs in cancer, the function of STAT3 as a transcription factor, and the dearth of known STAT3 miRNA targets, our goal was to identify novel STAT3 miRNA targets relevant to cancer. To do so, we engineered MCF-10A cells with doxycycline-inducible expression of STAT3C. STAT3C is a constitutively-active mutant version of STAT3. Although STAT3 can be activated by various growth factors and kinases, other pathways can be activated as well, which would confound analysis of the results. Thus, the advantage of STAT3C is that it allowed specific and focused activation of STAT3 alone, and this screen represents the first genome-wide survey of miRNA expression changes associated specifically with STAT3 activity. MCF-10A, a non-transformed breast epithelial cell line, was chosen because STAT3C has been reported to be sufficient to cause their neoplastic transformation. Therefore, we reasoned that analysis of STAT3C’s effects in MCF-10A cells would be especially informative for STAT3-regulated miRNAs relevant to cancer. As a result of our study, we identified previously-known as well as novel miRNA targets of STAT3. Doxycycline-inducible MCF-10A cells were seeded, and then untreated (grown in standard growth media alone) or treated with 2?g/ml doxycycline for 48hr. Each condition was performed in biological triplicate (labeled A, B, and C), for a total of 6 samples. Total RNA was harvested and submitted to the Dana-Farber Cancer Institute Molecular Diagnostics Laboratory. MicroRNA expression profiling was performed using TaqMan Low-Density Arrays (TLDA), human miRNA version 2.0A and version 3.0B cards (Applied Biosystems).
Project description:Purpose: Recently discovered activating Interleukin-6 receptor subunit beta (IL6ST, encoding glycoprotein 130 (gp130)) mutations, as well as germline Signal transducer and activator of transcription 3 (STAT3) gain-of-function mutations are associated with multi-organ autoimmunity, severe morbidity, and adverse prognosis, resulting in an unmet medical need. Methods: To decipher the crucial cellular subsets and disease biology associated with STAT3 gain-of-function mutations, we examined the gene expression profile of STAT3 gain-of-function and loss-of-function mutations in unstimulated, IL10- or IL21-stimulated CD4 T cells and compared them to healthy donor cells. Results: Activating gp130 signaling in vivo resulted in fatal early-onset multi-organ autoimmunity, resembling numerous clinical features of human STAT3 gain-of-function disease. We observed strong T-cell activation and effector differentiation, accompanied by TH17 expansion and interferon-gamma production. Transcriptome profiling of murine CD4+ and CD8+ T-cells revealed commonly dysregulated genes and a STAT3 gain-of-function signature that was used to discriminate between STAT3 gain-of-function and healthy control patients. Conclusions: Hyperactive gp130/STAT3 signaling leads to strong TH17-mediated autoimmunity phenotypically resembling human STAT3 gain-of-function disease and identify TH17-cells as a key cellular subset for initiation and maintenance of autoimmunity
Project description:STAT3 signaling is fundamental to T cells, where it underlies basic cellular processes like metabolism and apoptosis, and specialized processes like differentiation and cytokine production. However, mutations of STAT3 are strikingly prevalent in T cell cancers and aberrant or excessive STAT3 signaling is thought to mobilize cellular pathways that encourage malignancy. To better understand how STAT3 mutations drive T cell cancers, we compared two frequent cancer-associated variants, Y640F and N647I, at cellular and molecular levels. Using a retrogenic system, we demonstrate that they are qualitatively similar yet quantitatively distinct; each bears a gain-of-function phenotype but Y640F has greater transcriptome-wide effects. We also discovered that these and other common STAT3 mutants invoke a T regulatory 1 (Tr1) gene program characterized by expression of IL-10 and other factors that dampen T cell responses, most notably LAG3 and CD39. Importantly, Tr1 ’skewing’ is evident in both mouse T cells expressing cancer-associated STAT3 variants and humans afflicted with T cell malignancies. These studies advance current understanding of how cancer-associated mutations impact STAT3 function and reveal anti-inflammatory properties that may help transformed T cells persist, expand and/or avoid eradication.
Project description:Signal transducer and activator of transcription 3 (STAT3) is a critical transcription factor in cancer. However, while the protein-coding target genes of STAT3 have been extensively studied, the microRNA target genes of STAT3 are less understood. MicroRNAs are short, non-coding RNAs that regulate messenger RNAs through translational inhibition and transcript degradation. They have been found to be involved in all aspects of cancer biology. Given the roles of both STAT3 and miRNAs in cancer, the function of STAT3 as a transcription factor, and the dearth of known STAT3 miRNA targets, our goal was to identify novel STAT3 miRNA targets relevant to cancer. To do so, we engineered MCF-10A cells with doxycycline-inducible expression of STAT3C. STAT3C is a constitutively-active mutant version of STAT3. Although STAT3 can be activated by various growth factors and kinases, other pathways can be activated as well, which would confound analysis of the results. Thus, the advantage of STAT3C is that it allowed specific and focused activation of STAT3 alone, and this screen represents the first genome-wide survey of miRNA expression changes associated specifically with STAT3 activity. MCF-10A, a non-transformed breast epithelial cell line, was chosen because STAT3C has been reported to be sufficient to cause their neoplastic transformation. Therefore, we reasoned that analysis of STAT3C’s effects in MCF-10A cells would be especially informative for STAT3-regulated miRNAs relevant to cancer. As a result of our study, we identified previously-known as well as novel miRNA targets of STAT3.
Project description:Purpose: Recently discovered activating Interleukin-6 receptor subunit beta (IL6ST, encoding glycoprotein 130 (gp130)) mutations, as well as germline Signal transducer and activator of transcription 3 (STAT3) gain-of-function mutations are associated with multi-organ autoimmunity, severe morbidity, and adverse prognosis, resulting in an unmet medical need. Methods: To dissect crucial cellular subsets and disease biology involved in activated gp130 signaling, in this study we constitutively activated the gp130/JAK/STAT3 axis by means of a transgene, L-gp130, specifically targeted to T-cells. Results: Activating gp130 signaling in vivo resulted in fatal early-onset multi-organ autoimmunity, resembling numerous clinical features of human STAT3 gain-of-function disease. We observed strong T-cell activation and effector differentiation, accompanied by TH17 expansion and interferon-gamma production. Transcriptome profiling of murine CD4+ and CD8+ T-cells revealed commonly dysregulated genes and a STAT3 gain-of-function signature that was used to discriminate between STAT3 gain-of-function and healthy control patients. Conclusions: Hyperactive gp130/STAT3 signaling leads to strong TH17-mediated autoimmunity phenotypically resembling human STAT3 gain-of-function disease and identify TH17-cells as a key cellular subset for initiation and maintenance of autoimmunity
Project description:The development of therapeutic strategies to combat immune-associated diseases requires the molecular mechanisms of human Th17 cell differentiation to be fully identified and understood. To investigate transcriptional control of Th17 cell differentiation we used primary human CD4+ T cells in siRNA-mediated gene silencing and chromatin-immunoprecipitation followed by massive parallel sequencing (ChIP-seq) to identify both the early direct and indirect targets of STAT3. The integrated data set presented in this study confirms that STAT3 is critical for transcriptional regulation of early human Th17 cell differentiation. Importantly, we found that a large number of SNPs from loci associated with immune mediated disorders were located at sites where STAT3 binds to induce Th17 cell specification. Introduction of such SNPs alters STAT3 binding in DNA Affinity Precipitation Assays. Overall, our study provides important new insights for modulating Th17-mediated pathogenic immune responses in humans.
Project description:Genome Wide Binding profile and transcriptome of STAT3 and STAT3 Mutant Y640F in STAT3 Wildtype and STAT3 Mutant Y640F hematopoietic progenitor cell lines
Project description:Germline gain-of-function (GOF) variants in STAT3 cause early-onset poly-autoimmunity and immune dysregulation. STAT3 is a pleiotropic transcription factor that affects the induction and regulation of immune responses, with diverse effects on the immune response. Using a mouse model of STAT3 GOF (p.G421R), we observed spontaneous and imiquimod (IMQ)-induced skin inflammation with increased cell-intrinsic local Th17 responses. CD4+ T cells were required and sufficient to drive skin inflammation, and upregulated Il22 expression in expanded clones. However, certain aspects of disease, including epidermal thickness, required the presence of STAT3 GOF in epithelial cells. Treatment with a JAK inhibitor improved skin disease, without affecting local Th17 recruitment and cytokine production. Collectively, these data support a role for a Th17 response and in the development of organ-specific immune dysregulation in STAT3 GOF, and also suggest that the presence of STAT3 GOF in tissues is important for disease and can be targeted with JAK inhibition.