Project description:Targeting protein kinase C (PKC) isoforms by the small molecule inhibitor enzastaurin has shown promising pre-clinical activity in a wide range of tumor cells. In this study, we further delineated its mechanism of action in multiple myeloma (MM) cells and found a novel role of b-catenin in regulating growth and survival of tumor cells. Specifically, inhibition of PKC leads to rapid accumulation of b-catenin by preventing the phosphorylation required for its proteasomal degradation. Microarray analysis and siRNA-mediated gene silencing in MM cells revealed that accumulated b-catenin activates early ER stress signaling via eIF2a, CHOP and p21, leading to immediate growth inhibition. Furthermore, accumulated b-catenin contributes to enzastaurin-induced cell death. Both sequential knock-down of b-catenin, c-Jun, and p73, as well as overexpression of b-catenin or p73 confirmed that accumulated b-catenin triggers c-Jun-dependent induction of p73, thereby conferring MM cell apoptosis. In summary, our data reveal a novel role of b-catenin in ER stress-mediated growth inhibition, and a new pro-apoptotic mechanism triggered by b-catenin upon inhibition of PKC isoforms. Moreover, we identify p73 as a potential novel therapeutic target in MM. Based on these and previous data, enzastaurin is currently under clinical investigation in a variety of hematologic malignancies including MM. Keywords: time course
Project description:Aberrant activation of β-catenin is a common event in Acute Myeloid Leukemia (AML), and is recognized as an independent predictor of poor prognosis. Although increased β-catenin signaling in AML has been associated with AML1-ETO and PML-RARα translocation products, and activating mutations in the FLT3 receptor, it remains unclear which mechanisms activate β-catenin in AML more broadly. Here, we describe a novel link between interleukin-3 (IL-3) signaling and the regulation of β-catenin in myeloid transformation and AML. Using a murine model of HoxB8 and IL-3 cooperation we show that IL-3 modulates β-catenin protein levels, and Cre-induced deletion of β-catenin abolishes IL-3 dependent growth and colony formation. In the erythroleukemic cell line TF-1.8, we observed increased β-catenin protein levels and nuclear localization in response to IL-3, which correlated with transcriptional induction of β-catenin target genes. Furthermore, IL-3 promoted β-catenin accumulation in a subset of AML patient samples, and microarray gene expression analysis of these cells revealed induction of WNT/β-catenin and TCF4 transcriptional gene signatures in an IL-3 dependent manner. This study is the first to link β-catenin activation to IL-3 and suggests that targeting IL-3 signaling may be an effective approach for the inhibition of β-catenin activity in some patients with AML. AML patient samples (AML1-4) were cultured in the presence or absence of hIL-3 for 6 or 16h.
Project description:Bronchopulmonary dysplasia (BPD), a chronic lung disease of prematurity, has been linked to endoplasmic reticulum (ER) stress. To investigate a causal role for ER stress in BPD pathogenesis, we generated mice (cGrp78f/f) with lung epithelial cell-specific knockout (KO) of Grp78, a gene encoding the ER chaperone 78-kDa glucose-regulated protein (GRP78), a master regulator of ER homeostasis and the unfolded protein response (UPR). Lung epithelial-specific Grp78 KO disrupted lung morphogenesis, causing developmental arrest, increased alveolar epithelial type II cell apoptosis and decreased surfactant protein and type I cell marker expression in perinatal lungs. cGrp78f/f pups died immediately after birth, likely due to respiratory distress. Importantly, Grp78 KO triggered UPR activation with marked induction of pro-apoptotic transcription factor C/EBP homologous protein (CHOP). Increased expression of genes involved in oxidative stress and cell death and decreased expression of genes encoding antioxidant enzymes suggest a role for oxidative stress in alveolar epithelial cell (AEC) apoptosis. Increased Smad3 phosphorylation and expression of transforming growth factor-β (TGF-β)/Smad3 targets Cdkn1a (encoding p21) and Gadd45a suggest that interactions among the apoptotic arm of the UPR, oxidative stress and TGF-β/Smad signaling pathways contribute to Grp78 KO-induced AEC apoptosis and developmental arrest. Chemical chaperone taursodeoxycholic acid reduced UPR activation and apoptosis in cGrp78f/f lungs cultured ex vivo, confirming a role for ER stress in observed AEC abnormalities. These results demonstrate a key role for GRP78 in AEC survival and gene expression during lung development through modulation of ER stress and suggest the UPR as a potential therapeutic target in BPD.
Project description:Endoplasmic reticulum (ER) and inflammatory stress responses are two pathophysiologic factors contributing to islet dysfunction and failure in Type 2 Diabetes (T2D). However, how human islet cells respond to these stressors and whether T2D-associated genetic variants modulate these responses is unknown. To fill this knowledge gap, we profiled transcriptional (RNA-seq) and epigenetic (ATAC-seq) remodeling in human islets exposed to ex vivo ER (thapsigargin) or inflammatory (IL-1β+IFN-γ) stress. 5,427 genes (~32%) were associated with stress responses; most were stressor-specific, including upregulation of genes mediating unfolded protein response (e.g. DDIT3, ATF4) and NFKB signaling (e.g. NFKB1, NFKBIA) in ER stress and cytokine-induced inflammation respectively. Islet single-cell RNA-seq profiling revealed strong but heterogeneous beta cell ER stress responses, including a distinct beta cell subset that highly expressed apoptotic genes. Epigenetic profiling uncovered 14,968 stress-responsive cis-regulatory elements (CREs; ~14%), the majority of which were stressor-specific, and revealed increased accessibility at binding sites of transcription factors that were induced upon stress (e.g. ATF4 for ER stress, IRF8 for cytokine-induced inflammation). Eighty-six stress-responsive CREs overlapped known T2D-associated variants, including 20 residing within CREs that were more accessible upon ER stress. Among these, we linked the rs6917676 T2D risk allele (T) to increased in vivo accessibility of an islet ER stress-responsive CRE and allele-specific beta cell nuclear factor binding in vitro. We showed that MAP3K5, the only ER stress-responsive gene in this locus, promotes beta cell apoptosis. Consistent with its pro-apoptotic and putative diabetogenic roles, MAP3K5 expression inversely correlated with beta cell abundance in human islets and was induced in beta cells from T2D donors. Together, this study provides new genome-wide insights into human islet stress responses and putative mechanisms of T2D genetic variants.
Project description:Endoplasmic reticulum (ER) and inflammatory stress responses are two pathophysiologic factors contributing to islet dysfunction and failure in Type 2 Diabetes (T2D). However, how human islet cells respond to these stressors and whether T2D-associated genetic variants modulate these responses is unknown. To fill this knowledge gap, we profiled transcriptional (RNA-seq) and epigenetic (ATAC-seq) remodeling in human islets exposed to ex vivo ER (thapsigargin) or inflammatory (IL-1β+IFN-γ) stress. 5,427 genes (~32%) were associated with stress responses; most were stressor-specific, including upregulation of genes mediating unfolded protein response (e.g. DDIT3, ATF4) and NFKB signaling (e.g. NFKB1, NFKBIA) in ER stress and inflammation respectively. Islet single-cell RNA-seq profiling revealed strong but heterogeneous beta cell ER stress responses, including a distinct beta cell subset that highly expressed apoptotic genes. Epigenetic profiling uncovered 14,968 stress-responsive cis-regulatory elements (CREs; ~14%), the majority of which were stressor-specific, and revealed increased accessibility at binding sites of transcription factors that were induced upon stress (e.g. ATF4 for ER stress, IRF8 for inflammation). Seventy-six stress-responsive CREs overlapped known T2D-associated variants, including 20 residing within CREs that were more accessible upon ER stress. Among these, we linked the rs6917676 T2D risk allele (T) to increased in vivo accessibility of an islet ER stress-responsive CRE and allele-specific beta-cell nuclear factor binding in vitro. We showed that MAP3K5, the only ER stress-responsive gene in this locus, promotes beta cell apoptosis. Consistent with its pro-apoptotic and putative diabetogenic roles, MAP3K5 expression inversely correlated with beta cell abundance in human islets and was upregulated in beta cells from T2D donors. Together, this study provides new genome-wide insights into human islet stress responses and putative mechanisms of T2D genetic variants.
Project description:Endoplasmic reticulum (ER) and inflammatory stress responses are two pathophysiologic factors contributing to islet dysfunction and failure in Type 2 Diabetes (T2D). However, how human islet cells respond to these stressors and whether T2D-associated genetic variants modulate these responses is unknown. To fill this knowledge gap, we profiled transcriptional (RNA-seq) and epigenetic (ATAC-seq) remodeling in human islets exposed to ex vivo ER (thapsigargin) or inflammatory (IL-1β+IFN-γ) stress. 5,427 genes (~32%) were associated with stress responses; most were stressor-specific, including upregulation of genes mediating unfolded protein response (e.g. DDIT3, ATF4) and NFKB signaling (e.g. NFKB1, NFKBIA) in ER stress and inflammation respectively. Islet single-cell RNA-seq profiling revealed strong but heterogeneous beta cell ER stress responses, including a distinct beta cell subset that highly expressed apoptotic genes. Epigenetic profiling uncovered 14,968 stress-responsive cis-regulatory elements (CREs; ~14%), the majority of which were stressor-specific, and revealed increased accessibility at binding sites of transcription factors that were induced upon stress (e.g. ATF4 for ER stress, IRF8 for inflammation). Seventy-six stress-responsive CREs overlapped known T2D-associated variants, including 20 residing within CREs that were more accessible upon ER stress. Among these, we linked the rs6917676 T2D risk allele (T) to increased in vivo accessibility of an islet ER stress-responsive CRE and allele-specific beta-cell nuclear factor binding in vitro. We showed that MAP3K5, the only ER stress-responsive gene in this locus, promotes beta cell apoptosis. Consistent with its pro-apoptotic and putative diabetogenic roles, MAP3K5 expression inversely correlated with beta cell abundance in human islets and was upregulated in beta cells from T2D donors. Together, this study provides new genome-wide insights into human islet stress responses and putative mechanisms of T2D genetic variants.
Project description:Breast cancer is one of the most common types of cancer in women. One key signaling pathway known to regulate tumor growth, metabolic adaptation, and cellular stress response in breast cancer is Wnt signaling. Breast cancer patients, specifically triple negative breast cancer (TNBC), with upregulated Wnt signaling often have a poor clinical prognosis. However, the effects of Wnt/β-catenin signaling on the nucleolus and the resultant impact on cancer development and progression remain unclear. A notable reduction was observed in the number of nucleoli per nucleus in response to Wnt/β-catenin signaling inhibition in multiple TNBC cell lines. Our comparative proteomic analysis revealed several changes in the composition of the nucleolar proteome of TNBC cells upon inhibition of Wnt signaling. Overall, we demonstrate that Wnt/β-catenin signaling will affects nucleolar functionality and thus influences breast cancer progression. Understanding the role of Wnt signaling in the nucleolus and breast cancer is a critical step towards developing novel therapeutic options for the treatment of breast cancer.
Project description:In colorectal cancer, p53 is commonly inactivated, associated with chemo-resistance, and marks the transition from non-invasive to invasive disease. Cancers, including colorectal cancer, are thought to be diseases of aberrant stem cell populations, as stem cells are able to self-renew, making them long-lived enough to acquire mutations necessary to manifest the disease. We have shown that extracts from sweet sorghum stalk components eliminate colon cancer stem cells (CCSC) in a partial p53-dependent fashion. However, the underlying mechanisms are unknown. In the present study, CCSC were transfected with short hairpin-RNA against p53 (CCSC p53 shRNA) and treated with sweet sorghum phenolics extracted from different plant components (dermal layer, leaf, seed head and whole plant). While all components demonstrated anti-proliferative and pro-apoptotic effects in CCSC, phenolics extracted from the dermal layer and seed head were more potent in eliminating CCSC by elevating caspases 3/7 activity, PARP cleavage, and DNA fragmentation in a p53-dependent and p53-independent fashion, respectively. Further investigations revealed that the anti-proliferative and pro-apoptotic effects were associated with decreases in beta-catenin protein levels, and beta-catenin targets cyclin D1, cMyc, and survivin. These results suggest that the anti-proliferative and pro-apoptotic effects of sweet sorghum extracts against human colon cancer stem cells are via suppression of Wnt/beta-catenin pro-survival signaling in a p53-dependent (dermal layer) and partial p53-independent (seed head) fashion. LCMS used to identify phenolic compounds associated with extract activity
Project description:The Wnt signaling pathway is involved in many differentiation events during embryonic development and can lead to tumor formation after aberrant activation of its components. Β-catenin, a cytoplasmic component, plays a major role in the transduction of the canonical wnt/ β-catenin signaling. The aim of this study was to identify novel genes that are regulated by active β-catenin/TCF signaling in hepatocellular carcinoma. We selected and expanded isogenic clones from hepatocellular carcinoma-derived Huh7 cells with high and low β-catenin/TCF activities. We showed that, high TCF activity Huh7 cells lead to bigger and more aggressive tumors when xenografted into nude mice. We used SAGE (Serial Analysis of Gene Expression), genome-wide microarray and in silico promoter analysis in parallel, to compare gene expression between low (basal) and high (transfected) β-catenin/TCF activity clones, those had been xenografted into nude mice. We compared and contrasted SAGE and genome-wide microarray data, in parallel. Finally; after combined analysis, we identified BRI3 and HSF2 as novel targets of Wnt/β-catenin signaling in hepatocellular carcinoma. Experiment Overall Design: High TCF activity Huh7 cell line (Huh7-S33Y) was compared to control Huh7 cell line (Huh7-Vec) by using 10 ug of total RNA isolated from each sample (15 ug of labeled cRNA was hybridized to the arrays). Triplicates are coming from same total RNA extraction.
Project description:Secreted frizzled-related proteins (SFRPs) are mainly known for their role as extracellular modulators and tumor suppressors that down-regulate Wnt signaling. Using the established (CRISPR/Cas9 targeting promoters of SFRPs and targeting SFRPs transcript) system, we find that nuclear SFRPs interact with β-catenin and either promote or suppress TCF4 recruitment. SFRPs bind with β-catenin on both their N and C termini, which the repressive effects caused by SFRP-β-catenin-N-terminus binding overpower the promoting effects of their binding at the C terminus. By high Wnt activity, β-catenin and SFRPs only bind with their C termini, which results in the up-regulation of β-catenin transcriptional activity and cancer stem cell (CSC)-related genes. Furthermore, we identify disulfide bonds of the CRD domain and two threonine phosphorylation events of the NTR domain of SFRPs that are essential for their role as biphasic modulators, suggesting that SFRPs are biphasic modulators of Wnt signaling-elicited CSC properties beyond extracellular control.