Project description:Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease characterized by late diagnosis and treatment resistance. Recurrent genetic alterations in defined genes in association with perturbations of developmental cell signaling pathways have been associated with PDAC development and progression. Here, we show that GATA6 contributes to pancreatic carcinogenesis during the temporal progression of pancreatic intraepithelial neoplasia by virtue of Wnt pathway activation. GATA6 is recurrently amplified by both quantitative-PCR and fluorescent in-situ hybridization in human pancreatic intraepithelial neoplasia and in PDAC tissues, and GATA6 copy number is significantly correlated with overall patient survival. Forced overexpression of GATA6 in cancer cell lines enhanced cell proliferation and colony formation in soft agar in vitro and growth in vivo, as well as increased Wnt signaling. By contrast siRNA mediated knockdown of GATA6 led to corresponding decreases in these same parameters. The effects of GATA6 were found to be due to its ability to bind DNA, as forced overexpression of a DNA-binding mutant of GATA6 had no effects on cell growth in vitro or in vivo, nor did they affect Wnt signaling levels in these same cells. A microarray analysis revealed the Wnt antagonist Dickopf-1 (DKK1) as a dysregulated gene in association with GATA6 knockdown, and direct binding of GATA6 to the DKK1 promoter was confirmed by chromatin immunoprecipitation and electrophoretic mobility shift assays. Transient transfection of GATA6, but not mutant GATA6, into cancer cell lines led to decreased DKK1 mRNA expression and secretion of DKK1 protein into culture media. Forced overexpression of DKK1 antagonized the effects of GATA6 on Wnt signaling in pancreatic cancer cells. These findings illustrate that one mechanism by which GATA6 promotes pancreatic intraepithelial neoplasia is by virtue of its activation of canonical Wnt signaling via regulation of DKK1. AsPC1 and A13A cells were stably transfected with a lentivirus expressing mock shRNA or shRNA to GATA6. Each control/shRNA pair (total 4 samples) was analyzed by two-color microarray and the genes commonly dysregulated in both cell lines identified.
Project description:Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease characterized by late diagnosis and treatment resistance. Recurrent genetic alterations in defined genes in association with perturbations of developmental cell signaling pathways have been associated with PDAC development and progression. Here, we show that GATA6 contributes to pancreatic carcinogenesis during the temporal progression of pancreatic intraepithelial neoplasia by virtue of Wnt pathway activation. GATA6 is recurrently amplified by both quantitative-PCR and fluorescent in-situ hybridization in human pancreatic intraepithelial neoplasia and in PDAC tissues, and GATA6 copy number is significantly correlated with overall patient survival. Forced overexpression of GATA6 in cancer cell lines enhanced cell proliferation and colony formation in soft agar in vitro and growth in vivo, as well as increased Wnt signaling. By contrast siRNA mediated knockdown of GATA6 led to corresponding decreases in these same parameters. The effects of GATA6 were found to be due to its ability to bind DNA, as forced overexpression of a DNA-binding mutant of GATA6 had no effects on cell growth in vitro or in vivo, nor did they affect Wnt signaling levels in these same cells. A microarray analysis revealed the Wnt antagonist Dickopf-1 (DKK1) as a dysregulated gene in association with GATA6 knockdown, and direct binding of GATA6 to the DKK1 promoter was confirmed by chromatin immunoprecipitation and electrophoretic mobility shift assays. Transient transfection of GATA6, but not mutant GATA6, into cancer cell lines led to decreased DKK1 mRNA expression and secretion of DKK1 protein into culture media. Forced overexpression of DKK1 antagonized the effects of GATA6 on Wnt signaling in pancreatic cancer cells. These findings illustrate that one mechanism by which GATA6 promotes pancreatic intraepithelial neoplasia is by virtue of its activation of canonical Wnt signaling via regulation of DKK1.
Project description:RNF43-mutant pancreatic tumors are driven by Wnt signaling and sensitive to Wnt inhibition, e.g. PORCN inhibitors. However, some RNF43-mutant pancreatic cancers are intrinsically resistant to Wnt inhibition. We identified that EP300 mutations confer resistance to PORCN inhibitors in RNF43-mutant pancreatic cancers. We found that EP300 knockout down-regulated GATA6 expression and GATA6-regulated differentiation program, making the anti-differentiation roles of Wnt signaling dispensable.
Project description:Epithelial organs including the lung are known to possess regenerative abilities through activation of endogenous stem cell populations but the molecular pathways regulating stem cell expansion and regeneration are not well understood. Here we show that Gata6 regulates the temporal appearance and number of bronchioalveolar stem cells (BASCs) in the lung leading to the precocious appearance of BASCs and concurrent loss in epithelial differentiation in Gata6 null lung epithelium. This expansion of BASCs is the result of a dramatic increase in canonical Wnt signaling in lung epithelium upon loss of Gata6. Expression of the non-canonical Wnt receptor Fzd2 is down-regulated in Gata6 mutants and increased Fzd2 or decreased β-catenin expression rescues, in part, the lung epithelial defects in Gata6 mutants. During lung epithelial regeneration, we show that canonical Wnt signaling is activated in the niche containing BASCs and forced activation of Wnt signaling leads to a dramatic increase in BASC numbers. Moreover, Gata6 is required for proper lung epithelial regeneration and postnatal loss of Gata6 leads to increased BASC expansion and decreased differentiation. Together, these data demonstrate that Gata6 regulated Wnt signaling controls the balance between stem/progenitor expansion and epithelial differentiation required for both lung development and regeneration. Experiment Overall Design: 3 replicates of each condition-wild-type and GATA6 null tissue. 6 total samples.
Project description:Mutations in APC or β-catenin that cause aberrant activation of Wnt signaling are responsible for the initiation of colorectal tumor development. LGR5 is specifically expressed in stem cells of the intestine, stomach and hair follicle, and plays essential roles in maintaining tissue homeostasis. LGR5-positive stem cells have been shown to be responsible for the intestinal adenoma initiated by some mutations in APC . Furthermore, it has recently been reported that Lgr5, which is associated with the Frizzled/Lrp Wnt receptor complex, interacts with R-spondins and thereby activates Wnt signaling. However, the function of LGR5 in colorectal tumorigenesis has been unclear. Here we show that LGR5 is required for the tumorigenicity of colorectal cancer cells. We also show that the transcription factor GATA6 directly enhances the expression of LGR5. DLD1 cells were infected with a lentivirus expressing an shRNA targeting GATA6 or LGR5.
Project description:Epithelial organs including the lung are known to possess regenerative abilities through activation of endogenous stem cell populations but the molecular pathways regulating stem cell expansion and regeneration are not well understood. Here we show that Gata6 regulates the temporal appearance and number of bronchioalveolar stem cells (BASCs) in the lung leading to the precocious appearance of BASCs and concurrent loss in epithelial differentiation in Gata6 null lung epithelium. This expansion of BASCs is the result of a dramatic increase in canonical Wnt signaling in lung epithelium upon loss of Gata6. Expression of the non-canonical Wnt receptor Fzd2 is down-regulated in Gata6 mutants and increased Fzd2 or decreased β-catenin expression rescues, in part, the lung epithelial defects in Gata6 mutants. During lung epithelial regeneration, we show that canonical Wnt signaling is activated in the niche containing BASCs and forced activation of Wnt signaling leads to a dramatic increase in BASC numbers. Moreover, Gata6 is required for proper lung epithelial regeneration and postnatal loss of Gata6 leads to increased BASC expansion and decreased differentiation. Together, these data demonstrate that Gata6 regulated Wnt signaling controls the balance between stem/progenitor expansion and epithelial differentiation required for both lung development and regeneration. Keywords: gene targets in knockout mouse model
Project description:Wnt/b-catenin pathway is a key modulator of intestinal homeostasis by regulating stem cell biology during gut organogenesis and in adult life. DICKKOPF (DKK)-1 is a secreted inhibitor of Wnt/b-catenin signaling from plasma membrane receptors. We found that in human intestine, DKK-1 locates within the nucleus of differentiated enterocytes and enteroendocrine cells but not of proliferating and stem cells at the bottom of the crypts. DKK-1 is also nuclear in colon cancer cells locating at sites of active gene transcription. ChIP-seq and transcriptomic analysis both confirmed that DKK-1 binds chromatin and regulates gene expression. Thus, we demonstrate that DKK-1 is a multifunctional protein that inhibits Wnt/b-catenin signaling at plasma membrane and controls specific genes in the nucleus, suggesting that these functions are relevant for intestinal homeostasis. Analysis of DKK-1 location and associated roles in human colon cancer cells and crypts of small and large bowel.
Project description:Canonical Wnt signaling controls proliferation and differentiation of osteogenic progenitor cells, and tumor-derived secretion of the Wnt antagonist Dickkopf-1 (Dkk1) is correlated with osteolyses and metastasis in many bone malignancies. However, the role of Dkk1 in the oncogenesis of primary osteosarcoma (OS) remains unexplored. Here, we over-expressed Dkk1 in the OS cell line MOS-J. Contrary to expectations, Dkk1 had autocrine effects on MOSJ cells in that it increased proliferation and resistance to metabolic stress in vitro. In vivo, Dkk1 expressing MOS-J cells formed larger and more destructive tumors than controls. These effects were attributed in part to up-regulation of the stress response enzyme and cancer stem cell marker aldehyde-dehydrogenase-1 (ALDH1) through Jun-N-terminal kinase signaling. This is the first report linking Dkk1 to tumor stress resistance, further supporting the targeting of Dkk1 not only to prevent and treat osteolytic bone lesions but also to reduce numbers of stress-resistant tumor cells. Two samples were analyzed, one human DKK1 transfected MOS-J cell sample and one control vector transfected MOS-J cell sample.
Project description:Aberrant activation of WNT signaling and loss of BMP signals represent the two main alterations leading to the initiation of colorectal cancer (CRC). Here we screen for genes required for maintaining the tumor stem cell phenotype and identify the zinc-finger transcription factor GATA6 as key regulator of the WNT and BMP pathways in CRC. GATA6 directly drives the expression of LGR5 in adenoma stem cells while it restricts BMP signaling to differentiated tumor cells. Genetic deletion of Gata6 in mouse colon adenomas increases the levels of BMP factors, which signal to block self-renewal of tumor stem cells. In human tumors, GATA6 represses BMP4 gene expression through binding to a regulatory region that has been previously linked to increased susceptibility to develop CRC. Thus, GATA6 creates a permissive environment for tumor stem cell expansion by controlling the major signaling pathways that influence CRC initiation. Total RNA from biological replicates of VillinCreERT2Gata6+/+Apcfl/fl and VillinCreERT2Gata6fl/flApcfl/fl colon adenoma tumor organoids grown for one week in control media (see growth protocol).Total RNA was extracted using the TRIzolM-BM-. Plus RNA Purification Kit (Life Technologies).
Project description:Circulating tumour cells (CTCs) shed into blood from primary cancers include putative precursors that initiate distal metastases. While these cells are extraordinarily rare, they may identify cellular pathways contributing to the blood-borne dissemination of cancer. Here, we adapted a microfluidic device for efficient capture of CTCs from an endogenous mouse pancreatic cancer model and subjected CTCs to single-molecule RNA sequencing, identifying Wnt2 as enriched in CTCs. Expression of Wnt2 in pancreatic cancer cells suppresses anoikis, enhances anchorage-independent sphere formation, and increases metastatic propensity in vivo. The effect of Wnt2 is correlated with fibronectin upregulation, and it is mediated in part through non-canonical Wnt signaling and suppressed by inhibition of the Map3k7 (Tak1) kinase, an integrator of Wnt, BMP and TGF-beta signaling. In humans, formation of non-adherent tumour spheres by pancreatic cancer cells is associated with upregulation of multiple Wnt genes, and pancreatic CTCs revealed significant enrichment for non-canonical Wnt signaling in 5 of 11 cases. Thus, molecular analysis of CTCs may identify novel therapeutic targets to prevent the distal spread of cancer. Expression profiling of primary tumor, circulating tumor cells and ascites in a mouse model of pancreatic cancer suggested WNT signaling plays a role in pancreatic cancer metastasis. Induction of Wnt2 signaling in mouse pancreatic NB508 cells supported the hypothesis.