A palmitate-rich metastatic niche enables metastasis growth via p65 acetylation resulting in pro-metastatic NF-κB signaling

Metabolic rewiring is often considered an adaptive pressure limiting metastasis formation; however, some nutrients available at distant organs may inherently promote metastatic growth. We find that the lung and liver are lipid-rich environments. Moreover, we observe that pre-metastatic niche formation increases palmitate availability only in the lung, whereas a high-fat diet increases it in both organs. In line with this, targeting palmitate processing inhibits breast cancer-derived lung metastasis formation. Mechanistically, breast cancer cells use palmitate to synthesize acetyl-CoA in a carnitine palmitoyltransferase 1a-dependent manner. Concomitantly, lysine acetyltransferase 2a expression is promoted by palmitate, linking the available acetyl-CoA to the acetylation of the nuclear factor-kappaB subunit p65. Deletion of lysine acetyltransferase 2a or carnitine palmitoyltransferase 1a reduces metastasis formation in lean and high-fat diet mice, and lung and liver metastases from patients with breast cancer show coexpression of both proteins. In conclusion, palmitate-rich environments foster metastases growth by increasing p65 acetylation, resulting in a pro-metastatic nuclear factor-kappaB signaling.

ZFTA Translocations Constitute Ependymoma Chromatin Remodeling and Transcription Factors

ZFTA (C11orf95)-a gene of unknown function-partners with a variety of transcriptional coactivators in translocations that drive supratentorial ependymoma, a frequently lethal brain tumor. Understanding the function of ZFTA is key to developing therapies that inhibit these fusion proteins. Here, using a combination of transcriptomics, chromatin immunoprecipitation sequencing, and proteomics, we interrogated a series of deletion-mutant genes to identify a tripartite transformation mechanism of ZFTA-containing fusions, including: spontaneous nuclear translocation, extensive chromatin binding, and SWI/SNF, SAGA, and NuA4/Tip60 HAT chromatin modifier complex recruitment. Thereby, ZFTA tethers fusion proteins across the genome, modifying chromatin to an active state and enabling its partner transcriptional coactivators to promote promiscuous expression of a transforming transcriptome. Using mouse models, we validate further those elements of ZFTA-fusion proteins that are critical for transformation-including ZFTA zinc fingers and partner gene transactivation domains-thereby unmasking vulnerabilities for therapeutic targeting. SIGNIFICANCE: Ependymomas are hard-to-treat brain tumors driven by translocations between ZFTA and a variety of transcriptional coactivators. We dissect the transforming mechanism of these fusion proteins and identify protein domains indispensable for tumorigenesis, thereby providing insights into the molecular basis of ependymoma tumorigenesis and vulnerabilities for therapeutic targeting.This article is highlighted in the In This Issue feature, p. 2113.

NF-κB pathways in hematological malignancies

The nuclear factor κB or NF-κB transcription factor family plays a key role in several cellular functions, i.e. inflammation, apoptosis, cell survival, proliferation, angiogenesis, and innate and acquired immunity. The constitutive activation of NF-κB is typical of most malignancies and plays a major role in tumorigenesis. In this review, we describe NF-κB and its two pathways: the canonical pathway (RelA/p50) and the non-canonical pathway (RelB/p50 or RelB/p52). We then consider the role of the NF-κB subunits in the development and functional activity of B cells, T cells, macrophages and dendritic cells, which are the targets of hematological malignancies. The relevance of the two pathways is described in normal B and T cells and in hematological malignancies, acute and chronic leukemias (ALL, AML, CLL, CML), B lymphomas (DLBCLs, Hodgkin's lymphoma), T lymphomas (ATLL, ALCL) and multiple myeloma. We describe the interaction of NF-κB with the apoptotic pathways induced by TRAIL and the transcription factor p53. Finally, we discuss therapeutic anti-tumoral approaches as mono-therapies or combination therapies aimed to block NF-κB activity and to induce apoptosis (PARAs and Nutlin-3).

Activation of nuclear factor-κB in acinar cells increases the severity of pancreatitis in mice

BACKGROUND & AIMS

Nuclear factor-κB (NF-κB) is activated during early stages of pancreatitis. This transcription factor regulates genes that control many cell activities, including inflammation and survival. There is evidence that activation of NF-κB protects against pancreatitis, and, in other cases, that it promotes this disease. We compared the effects of NF-κB in different mouse models of pancreatitis to understand these complications.

METHODS

To model constitutive activation of NF-κB, we expressed a transgene that encodes its p65 subunit or the inhibitor of κB kinase (IKK)2 in pancreatic acinar cells of mice. We analyzed effects on pancreatic tissues and levels of NF-κB target genes in these mice and compared them with mice that did not express transgenic p65 or IKK2 (controls).

RESULTS

Transgenic expression of p65 led to compensatory expression of the inhibitory subunit IKB-α and, therefore, no clear phenotype. However, p65 transgenic mice given injections of cerulein, to induce acute pancreatitis, had higher levels of NF-κB activity in acinar cells, greater levels of inflammation, and more severe outcomes than control mice. In contrast, constitutive expression of IKK2 directly increased the activity of NF-κB in acinar cells and induced pancreatitis. Prolonged activity of IKK2 (3 months) resulted in activation of stellate cells, loss of acinar cells, and fibrosis, which are characteristics of chronic pancreatitis. Co-expression of IKK2 and p65 greatly increased the expression of inflammatory mediators and the severity of pancreatitis, compared with control mice.

CONCLUSIONS

The level of NF-κB activation correlates with the severity of acute pancreatitis in mice. Longer periods of activation (3 months) lead to chronic pancreatitis. These findings indicate that strategies to inactivate NF-κB might be used to treat patients with acute or chronic pancreatitis.

EGFR-induced and PKCε monoubiquitylation-dependent NF-κB activation upregulates PKM2 expression and promotes tumorigenesis

Many types of human tumor cells have overexpressed pyruvate kinase M2 (PKM2). However, the mechanism underlying this increased PKM2 expression remains to be defined. We demonstrate here that EGFR activation induces PLCγ1-dependent PKCε monoubiquitylation at Lys321 mediated by RINCK1 ubiquitin ligase. Monoubiquitylated PKCε interacts with a ubiquitin-binding domain in NEMO zinc finger and recruits the cytosolic IKK complex to the plasma membrane, where PKCε phosphorylates IKKβ at Ser177 and activates IKKβ. Activated RelA interacts with HIF1α, which is required for RelA to bind the PKM promoter. PKCε- and NF-κB-dependent PKM2 upregulation is required for EGFR-promoted glycolysis and tumorigenesis. In addition, PKM2 expression correlates with EGFR and IKKβ activity in human glioblastoma specimens and with grade of glioma malignancy. These findings highlight the distinct regulation of NF-κB by EGF, in contrast to TNF-α, and the importance of the metabolic cooperation between the EGFR and NF-κB pathways in PKM2 upregulation and tumorigenesis.

Variants of the RELA gene are associated with schizophrenia and their startle responses

The pathogenesis of schizophrenia is thought to involve aberrant immune and inflammatory responses. Nuclear factor kappa B (NF-κB) has important roles in the immune and inflammatory responses. The v-rel avian reticuloendotheliosis viral oncogene homolog A (RELA) gene encodes the major component of the NF-κB complex. We genotyped four single-nucleotide polymorphisms (SNPs) in the RELA gene and performed a gene-based association analysis using 1224 patients with schizophrenia and 1663 controls. We found significant associations of three SNPs (rs11820062: p=0.00011, rs2306365: p=0.0031, and rs7119750: p=0.0080) with schizophrenia and stronger evidence for association in a multi-marker sliding window haplotype analysis (the lowest p=0.00006). The association between this gene and schizophrenia was evident in male subjects but not in female subjects, when separately analyzed by gender. In silico genotype-gene expression analysis using web database and the WGAViewer software revealed that these three schizophrenia-associated SNPs might be related to RELA mRNA expression in immortalized B-lymphocytes. In silico analysis also suggested the putative promoter SNP, rs11820062, might disrupt the consensus transcription factor binding sequence of the androgen receptor. The impact of four RELA polymorphisms on pre-pulse inhibition (PPI) was investigated in 53 patients with schizophrenia. We provided evidence that at risk genotypes of three SNPs were associated with deficits in PPI; however, there was no effect of the one non-risk SNP on PPI. These findings suggest that variants of the RELA gene are associated with risk for schizophrenia and PPI deficits in a Japanese population.

Erythropoietin requires NF-kappaB and its nuclear translocation to prevent early and late apoptotic neuronal injury during beta-amyloid toxicity

No longer considered exclusive for the function of the hematopoietic system, erythropoietin (EPO) is now considered as a viable agent to address central nervous system injury in a variety of cellular systems that involve neuronal, vascular, and inflammatory cells. Yet, it remains unclear whether the protective capacity of EPO may be effective for chronic neurodegenerative disorders such as Alzheimer's disease (AD) that involve beta-amyloid (Abeta) apoptotic injury to hippocampal neurons. We therefore investigated whether EPO could prevent both early and late apoptotic injury during Abeta exposure in primary hippocampal neurons and assessed potential cellular pathways responsible for this protection. Primary hippocampal neuronal injury was evaluated by trypan blue dye exclusion, DNA fragmentation, membrane phosphatidylserine (PS) exposure, and nuclear factor-kappaB (NF-kappaB) expression with subcellular translocation. We show that EPO, in a concentration specific manner, is able to prevent the loss of both apoptotic genomic DNA integrity and cellular membrane asymmetry during Abeta exposure. This blockade of Abeta generated neuronal apoptosis by EPO is both necessary and sufficient, since protection by EPO is completely abolished by co-treatment with an anti-EPO neutralizing antibody. Furthermore, neuroprotection by EPO is closely linked to the expression of NF-kappaB p65 by preventing the degradation of this protein by Abeta and fostering the subcellular translocation of NF-kappaB p65 from the cytoplasm to the nucleus to allow the initiation of an anti-apoptotic program. In addition, EPO intimately relies upon NF-kappaB p65 to promote neuronal survival, since gene silencing of NF-kappaB p65 by RNA interference removes the protective capacity of EPO during Abeta exposure. Our work illustrates that EPO is an effective entity at the neuronal cellular level against Abeta toxicity and requires the close modulation of the NF-kappaB p65 pathway, suggesting that either EPO or NF-kappaB may be used as future potential therapeutic strategies for the management of chronic neurodegenerative disorders, such as AD.

Changes in chromatin accessibility across the GM-CSF promoter upon T cell activation are dependent on nuclear factor kappaB proteins

Granulocyte/macrophage colony-stimulating factor (GM-CSF) is a key cytokine in myelopoiesis and aberrant expression is associated with chronic inflammatory disease and myeloid leukemias. This aberrant expression is often associated with constitutive nuclear factor (NF)-kappaB activation. To investigate the relationship between NF-kappaB and GM-CSF transcription in a chromatin context, we analyzed the chromatin structure of the GM-CSF gene in T cells and the role of NF-kappaB proteins in chromatin remodeling. We show here that chromatin remodeling occurs across a region of the GM-CSF gene between -174 and +24 upon T cell activation, suggesting that remodeling is limited to a single nucleosome encompassing the proximal promoter. Nuclear NF-kappaB levels appear to play a critical role in this process. In addition, using an immobilized template assay we found that the ATPase component of the SWI/SNF chromatin remodeling complex, brg1, is recruited to the GM-CSF proximal promoter in an NF-kappaB-dependent manner in vitro. These results suggest that chromatin remodeling across the GM-CSF promoter in T cells is a result of recruitment of SWI/SNF type remodeling complexes by NF-kappaB proteins binding to the CD28 response region of the promoter.

Constitutive nuclear factor-kappa B activity is required for central neuron survival

The function of nuclear factor (NF)-kappaB within the developing and mature CNS is controversial. We have generated transgenic mice to reveal NF-kappaB transcriptional activity in vivo. As expected, constitutive NF-kappaB activity was observed within immune organs, and tumor necrosis factor-inducible NF-kappaB activity was present in mesenchymal cells. Intriguingly, NF-kappaB activity was also prominent in the CNS throughout development, especially within neocortex, olfactory bulbs, amygdala, and hippocampus. NF-kappaB in the CNS was restricted to neurons and blocked by overexpression of dominant-negative NF-kappaB-inducible kinase or the IkappaBalphaM super repressor. Blocking endogenous neuronal NF-kappaB activity in cortical neurons using recombinant adenovirus induced neuronal death, whereas induction of NF-kappaB activity increased levels of anti-apoptotic proteins and was strongly neuroprotective. Together, these data demonstrate a physiological role for NF-kappaB in maintaining survival of central neurons.

relA over-expression reduces tumorigenicity and activates apoptosis in human cancer cells

We previously demonstrated that bcl-2 over-expression increases the malignant behaviour of the MCF7 ADR human breast cancer cell line and enhances nuclear factor-kappa B (NF-kappa B) transcriptional activity. Here, we investigated the direct effect of increased NF-kB activity on the tumorigenicity of MCF7 ADR cells by over-expressing the NF-kappa B subunit relA/p65. Surprisingly, our results demonstrated that over-expression of relA determines a considerable reduction of the tumorigenic ability in nude mice as indicated by the tumour take and the median time of tumour appearance. In vitro studies also evidenced a reduced cell proliferation and the activation of the apoptotic programme after relA over-expression. Apoptosis was associated with the production of reactive oxygen species, and the cleavage of the specific substrate Poly-ADP-ribose-polymerase. Our data indicate that there is no general role for NF-kappa B in the regulation of apoptosis and tumorigenicity. In fact, even though inhibiting NF-kappa B activity has been reported to be lethal to tumour cells, our findings clearly suggest that an over-induction of nuclear NF-kappa B activity may produce the same effect.

The glucocorticoid receptor inhibits NFkappaB by interfering with serine-2 phosphorylation of the RNA polymerase II carboxy-terminal domain

Glucocorticoids repress NFkappaB-mediated activation of proinflammatory genes such as interleukin-8 (IL-8) and ICAM-1. Our experiments suggest that the glucocorticoid receptor (GR) confers this effect by associating through protein-protein interactions with NFkappaB bound at each of these genes. That is, we show that the GR zinc binding region (ZBR), which includes the DNA binding and dimerization functions of the receptor, binds directly to the dimerization domain of the RelA subunit of NFkappaB in vitro and that the ZBR is sufficient to associate with RelA bound at NFkappaB response elements in vivo. Moreover, we demonstrate in vivo and in vitro that GR does not disrupt DNA binding by NFkappaB. In transient transfections, we found that the GR ligand binding domain is essential for repression of NFkappaB but not for association with it and that GR can repress an NFkappaB derivative bearing a heterologous activation domain. We used chromatin immunoprecipitation assays in untransfected A549 cells to infer the mechanism by which the tethered GR represses NFkappaB-activated transcription. As expected, we found that the inflammatory signal TNFalpha stimulated preinitiation complex (PIC) assembly at the IL-8 and ICAM-1 promoters and that the largest subunit of RNA polymerase II (pol II) in those complexes became phosphorylated at serines 2 and 5 in its carboxy-terminal domain (CTD) heptapeptide repeats (YSPTSPS); these modifications are required for transcription initiation. Remarkably, GR did not inhibit PIC assembly under repressing conditions, but rather interfered with phosphorylation of serine 2 of the pol II CTD.

The guanosine nucleotide (p)ppGpp initiates development and A-factor production in myxococcus xanthus

Guanosine 3'-di-5'-(tri)di-phosphate nucleotides [(p)ppGpp], synthesized in response to amino acid limitation, induce early gene expression leading to multicellular fruiting body formation in Myxococcus xanthus. A mutant (DK527) that fails to accumulate (p)ppGpp in response to starvation was found to be blocked in development prior to aggregation. By use of a series of developmentally regulated Tn5lac transcriptional fusion reporters, the time of developmental arrest in DK527 was narrowed to within the few hours of development, the period of starvation recognition. The mutant is also defective in the production of A-factor, an early extracellular cell-density signal. The relA gene from Escherichia coli, which encodes a ribosome-dependent (p)ppGpp synthetase, rescues this mutant. We also demonstrate that inactivation of the M. xanthus relA homolog blocks development and the accumulation of (p)ppGpp. Moreover, the wild-type allele of Myxococcus relA rescues DK527. These observations support a model in which accumulation of (p)ppGpp, in response to starvation, initiates the program of fruiting body development, including the production of A-factor.