Project description:Abstract. Deregulated c-MYC is found in a variety of cancers where it promotes proliferation as well as apoptosis. In many hematological malignancies enhanced NF-kB exerts prosurvival functions. Here we investigated the role of NF-kB in mouse and human c-MYC-transformed lymphomas. The NF-kB-pathway is extinguished in murine lymphoma cells and extrinsic stimuli typically inducing NF-kB activity fail to activate this pathway. Genetic activation of the NF-kB pathway induces apoptosis in these cells, while inhibition of NF-kB by an IkBa superrepressor provides a selective advantage in vivo. Furthermore, in human Burkitt´s lymphoma cells we find that NF-kB activation induces apoptosis. NF-kB upregulates Fas and predisposes to Fas-induced cell death, which is caspase 8 mediated and can be prevented by CFLAR overexpression. We conclude that c-MYC overexpression sensitizes cells to NF-kB-induced apoptosis and persistent inacvtivity of NF-kB signaling is a prerequisite for MYC-mediated tumorigenesis. We could also show that low immunogenicity and Fas insensitivity of MYC driven lymphoma cells is reversed by activation of NF-kB. Our observations provide a molecular explanation for the described absence of the NF-kB signaling in Burkitt´s lymphoma and question the applicability of NF-kB inhibitors as candidates for treatment of this cancer.
Project description:Abstract. Deregulated c-MYC is found in a variety of cancers where it promotes proliferation as well as apoptosis. In many hematological malignancies enhanced NF-kB exerts prosurvival functions. Here we investigated the role of NF-kB in mouse and human c-MYC-transformed lymphomas. The NF-kB-pathway is extinguished in murine lymphoma cells and extrinsic stimuli typically inducing NF-kB activity fail to activate this pathway. Genetic activation of the NF-kB pathway induces apoptosis in these cells, while inhibition of NF-kB by an IkBa superrepressor provides a selective advantage in vivo. Furthermore, in human Burkitt´s lymphoma cells we find that NF-kB activation induces apoptosis. NF-kB upregulates Fas and predisposes to Fas-induced cell death, which is caspase 8 mediated and can be prevented by CFLAR overexpression. We conclude that c-MYC overexpression sensitizes cells to NF-kB-induced apoptosis and persistent inacvtivity of NF-kB signaling is a prerequisite for MYC-mediated tumorigenesis. We could also show that low immunogenicity and Fas insensitivity of MYC driven lymphoma cells is reversed by activation of NF-kB. Our observations provide a molecular explanation for the described absence of the NF-kB signaling in Burkitt´s lymphoma and question the applicability of NF-kB inhibitors as candidates for treatment of this cancer. Experiment Overall Design: Ramos cells were transfected in triplicates with pRTS-GFP (A+,C+,D+) or pRTS-CA-IKK2 (E+,F+,H+), selected with hygromycin and transgene expression was induced with doxycycline (0,5mg/ml) for 48hrs. RNA was isolated with RNeasy mini kit (Qiagen, Venlo, Netherlands) and Gene expression profiling (GEP) was performed using Affymetrix Human Genome U133 Plus 2.0 Array (Affymetrix, Santa Clara, CA, USA). 2 µg of total RNA were labeled using the GeneChip® One-Cycle Target Labeling assay kit (Affymetrix). After hybridization arrays were stained and washed in a FS 450 Fluidics station (Affymetrix) before imaging on an Affymetrix GeneChip (3000) scanner. Raw data were generated using the GCOS 1.4 software (Affymetrix). Probe level data were obtained using the Robust Multichip Average (RMA) normalization algorithm and CEL files were loaded into Genesifter (GeneSifter.Net, VizX Laboratories, Seattle, WA, USA). Genes were identified as differentially expressed among the two classes if a two-sample T-test revealed a nominal significance level of 0.05 and the ratio between the two classes was at least 2 fold. Calculation of false discovery rate was done according to the method of Benjamini and Hochberg. Biological significance was determined using Gene Ontolgy reports.
Project description:Diffuse large B-cell lymphoma (DLBCL) is an aggressive cancer with two major biological subtypes, activated B-cell like (ABC) and germinal center B-cell-like (GCB) DLCBL. Self-antigen engagement of B-cell receptors (BCRs) in ABC tumors promotes their clustering in the plasma membrane, thereby initiating chronic active signaling and downstream activation of the pro-survival NF-kB and PI3 kinase pathways. The potential of therapeutics targeting chronic active BCR signaling in ABC DLBCL is highlighted by the frequent response of these tumors to inhibitors of BTK, a kinase that links BCR signaling to NF-kB activation. Here we used genome-wide CRISPR-Cas9 screens to identify regulators of the IRF4, a direct NF-kB target and essential transcription factor in ABC cells. Unexpectedly, inactivation of the oligosaccharyltransferase (OST) complex, which mediates N-linked protein glycosylation, reduced IRF4 expression and NF-kB activity in ABC cells, resulting in cell death. Using functional glycoproteogenomics we linked this phenomenon to defective BCR glycosylation. Pharmacologic inhibition of OST reduced the size and abundance of BCR microclusters in the plasma membrane and blocked their internalization. These reorganized BCRs associated with the inhibitory coreceptor CD22, which attenuated proximal BCR signaling, thereby reducing NF-kB and PI3 kinase activation. OST inhibition also blocked the trafficking of TLR9 to the endolysosomal compartment, preventing its association with the BCR in the My-T-BCR signaling complex that activates NF-kB in ABC cells. In GCB DLBCL, OST inhibition also attenuated constitutive BCR signaling, reducing PI3 kinase signaling and triggering cell death. Our data highlight the therapeutic potential of OST inhibitors for the treatment of diverse B cell malignancies in which constitutive BCR signaling is essential.
Project description:Macrophage death in advanced atherosclerotic lesions is a key event in the conversion of benign lesions to vulnerable plaques. One fundamental transcription factor that has been shown to play a pivotal role in cell death/survival is nuclear factor kB (NF-kB). Still, the relevance of this key transcription factor for macrophage-derived foam cell survival has not been unequivocally resolved at the molecular level. THP-1 monocytic cell lines were generated in which NF-kB activation is specifically inhibited by overexpression of a trans-dominant, non-degradable form of IkBa (IkBa (32A/36A)) under control of the macrophage-specific SR-A promoter. A diminished lipid loading during NF-κB inhibition during foam cell formation was accompanied by increased cell death. A genome-wide expression profile of NF-kB-dependent genes during foam cell formation was established showing a widespread effect on the macrophage transcriptome. The three largest functional gene clusters identified and validated by independent techniques, were those involved in lipid metabolism, apoptosis and oxidative stress. The net result of these complex gene expression changes invoked by inhibition of NF-κB activation during lipid loading is a reduction of foam cell survival through caspase-dependent apoptosis. Thus, the NF-kB-dependent gene repertoire seems essential for sustained macrophage survival during the process of pathological lipid loading. Keywords: genetic modification, lipid loading, timecourse THP-1 cells and two different THP-1 IkB mutants (A3 and A12) were exposed to PMA to induce macrophage differentiation and subsequently loaded with oxidized LDL or vehicle for 5 or 8 days. One replicate per array, a total of 15 arrays. A common reference pool, composed of an equimolar mixture of all samples, was labeled with Cy3 and hybridized against the Cy5-labeled experimental sample.
Project description:The cancer stem cells (CSCs) have important therapeutic implications for multi-resistant cancers including hepatocellular carcinoma (HCC). Among the key pathways frequently activated in liver CSCs is NF-kB signaling. Here we evaluated the CSCs-depleting potential of NF-kB inhibition in liver cancer achieved by IKK inhibitor curcumin and specific peptide SN50 . The effects on CSCs were assessed by analysis of Side Population (SP) and expression levels of CSC-related genes as determined by RT-qPCR, gene expression microarray, EMSA, and Western blotting. Curcumin caused anti-proliferative and pro-apoptotic responses directly related to the extent of NF-kB inhibition. In curcumin-sensitive tumor cells, the treatment led to a selective CSC depletion as evidenced by a reduced SP size, decreased sphere formation, down-regulation of CSC markers and suppressed tumorigenicity. Similarly, NF-kB inhibition by SN50 caused a general suppression of cell growth accompanied by a reduced SP fraction. In contrast, curcumin-resistant cells exhibited a paradoxical increase in proliferation and expression of CSC markers. Mechanistically, CSC-depleting activity of curcumin was exerted by the NF-kB-mediated HDAC inhibition causing down-regulation of c-MYC and other key oncogenic targets. Co-administration of the class I/II HDAC inhibitor trichostatine sensitized resistant cells to curcumin. Further, integration of a predictive signature of curcumin sensitity with our HCC database indicated that HCC patients with poor prognosis and progenitor features are most likely to benefit from NF-kB inhibition. These results demonstrate that NF-kB inhibition can specifically target CSC populations and suggest a potential for combined inhibition of NF-kB and HDAC signaling for treatment of liver cancer patients with poor prognosis. Five human hepatoma cell lines with and without curcumin
Project description:Macrophage death in advanced atherosclerotic lesions is a key event in the conversion of benign lesions to vulnerable plaques. One fundamental transcription factor that has been shown to play a pivotal role in cell death/survival is nuclear factor kB (NF-kB). Still, the relevance of this key transcription factor for macrophage-derived foam cell survival has not been unequivocally resolved at the molecular level. THP-1 monocytic cell lines were generated in which NF-kB activation is specifically inhibited by overexpression of a trans-dominant, non-degradable form of IkBa (IkBa (32A/36A)) under control of the macrophage-specific SR-A promoter. A diminished lipid loading during NF-κB inhibition during foam cell formation was accompanied by increased cell death. A genome-wide expression profile of NF-kB-dependent genes during foam cell formation was established showing a widespread effect on the macrophage transcriptome. The three largest functional gene clusters identified and validated by independent techniques, were those involved in lipid metabolism, apoptosis and oxidative stress. The net result of these complex gene expression changes invoked by inhibition of NF-κB activation during lipid loading is a reduction of foam cell survival through caspase-dependent apoptosis. Thus, the NF-kB-dependent gene repertoire seems essential for sustained macrophage survival during the process of pathological lipid loading. Keywords: genetic modification, lipid loading, timecourse
Project description:Mutations in KRAS occur in a variety of tumors of epithelial origin, driving the oncogenic phenotype.The NF-kB transcription factor pathway is important for oncogenic RAS to transform cells and to drive tumorigenesis in animal models. Recently TAK1, an upstream regulator of IKK which controls canonical NF-kB, was shown to be important for chemoresistance in pancreatic cancer and for regulating KRAS+ colorectal cancer cell growth and survival. Here we show that GSK-3alpha is upregulated by KRAS leading to interaction with TAK1 to stabilize the TAK1/TAB complex to promote IKK activity. Additionally, GSK-3alpha is required for promoting critical non-canonical NF-kB signaling in pancreatic cancer cells. Pharmacologic inhibition of GSK-3 suppresses growth of human pancreatic tumor explants, consistent with loss of expression of genes such as c-myc and TERT. These data identify GSK-3alpha as a key downstream effector of oncogenic RAS via its ability to coordinately regulate distinct NF-kB signaling pathways GSK-3 inhibition at 2 and 8 hours
Project description:Activation of NF-kB induces MES trans-differentiation and radio-resistance in glioma stem cells (GSCs), but molecular mechanisms for NF-kB activation in GSCs are currently unknown. Here we report that Mixed Lineage Kinase 4 (MLK4) is overexpressed in MES but not PN GSCs. Silencing MLK4 suppresses self-renewal, motility, tumorigenesis, and radio-resistance of MES GSCs via a loss of the MES signature. MLK4 binds and phosphorylates the NF-κB regulator IKKα, leading to activation of NF-κB signaling in GSCs. MLK4 expression is inversely correlated with patient prognosis in MES, but not PN high-grade gliomas. Collectively, our results uncover MLK4 as an upstream regulator of NF-kB signaling and a potential molecular target for the MES subtype of GBMs. We used microarrays to validate MLK4 target gene expression.
Project description:The cancer stem cells (CSCs) have important therapeutic implications for multi-resistant cancers including hepatocellular carcinoma (HCC). Among the key pathways frequently activated in liver CSCs is NF-kB signaling. Here we evaluated the CSCs-depleting potential of NF-kB inhibition in liver cancer achieved by IKK inhibitor curcumin and specific peptide SN50 . The effects on CSCs were assessed by analysis of Side Population (SP) and expression levels of CSC-related genes as determined by RT-qPCR, gene expression microarray, EMSA, and Western blotting. Curcumin caused anti-proliferative and pro-apoptotic responses directly related to the extent of NF-kB inhibition. In curcumin-sensitive tumor cells, the treatment led to a selective CSC depletion as evidenced by a reduced SP size, decreased sphere formation, down-regulation of CSC markers and suppressed tumorigenicity. Similarly, NF-kB inhibition by SN50 caused a general suppression of cell growth accompanied by a reduced SP fraction. In contrast, curcumin-resistant cells exhibited a paradoxical increase in proliferation and expression of CSC markers. Mechanistically, CSC-depleting activity of curcumin was exerted by the NF-kB-mediated HDAC inhibition causing down-regulation of c-MYC and other key oncogenic targets. Co-administration of the class I/II HDAC inhibitor trichostatine sensitized resistant cells to curcumin. Further, integration of a predictive signature of curcumin sensitity with our HCC database indicated that HCC patients with poor prognosis and progenitor features are most likely to benefit from NF-kB inhibition. These results demonstrate that NF-kB inhibition can specifically target CSC populations and suggest a potential for combined inhibition of NF-kB and HDAC signaling for treatment of liver cancer patients with poor prognosis.
Project description:MUC1-C subunit plays an essential role in regulating NEAT1 expression. MUC1-C activates the NEAT1 gene with induction of the NEAT1_1 and NEAT1_2 isoforms by NF-kB- and MYC-mediated mechanisms. MUC1-C/MYC signaling also induces expression of the SFPQ, NONO and FUS RNA binding proteins (RBPs) that associate with NEAT1_2 and are necessary for paraspeckle formation.