Several observations have suggested that NF-kappa B transcription factors could be involved in carcinogenesis. To investigate the possibility that members of the NF-kappa B family participate in the ...molecular control of the transformed phenotype, we examined the expression of these proteins in human breast cancer cell lines as well as in primary tumors. Western Immunoblots demonstrated high expression of the p52 precursor p100 (NFKB2) in several breast cancer cell lines while human mammary epithelial cells express this protein only faintly. Eighteen primary breast tumors out of 24 displayed significant expression of the p100/p52 protein. In MDA-MB-435 cells, overexpressed p100 and p52 are predominantly cytoplasmic and coimmunoprecipitation experiments demonstrated that p100 sequesters the heterodimer p50/p65 in the cytoplasm. We demonstrate that most p65 protein is complexed with p100 in these cells while it is complexed predominantly with I kappa B-alpha in cell lines expressing less p100. Our data strengthen the hypothesis that NF-kappa B could be involved in carcinogenesis and suggest that the p100/p52 NF-kappa B subunit could play a role in the development of human breast cancers, possibly by sequestering other NF-kappa B-related proteins in the cytoplasm.
Since the beginning, the scientific research was an integral part of the
mission of the European Oncology Institute (IEO). Its position is at the intersection
between Surgical Units, the Department ...of Pathology and Research Units. This
organization makes the IEO Biobank for Translational Medicine (B4MED) a critical
resource that reflects the mission of IEO to perform "Research for Care".
The B4MED collects, catalogues and stores biological samples that are non-essential
for diagnostic purposes from patients who provide informed consent for the use of their
tissues for research purposes. A direct pipeline with the operating theatres for the
collection of tissue samples ensures negligible sample degradation. Surgically-excised
pathological and non-pathological tissue samples, plasma/serum, total blood, DNA and
RNA are collected and stored according to specific protocols and standard operating
procedures. All biobanked samples are managed and tracked through a software
package that is fully integrated with the hospital medical records database, pathology
database and central registry of patient demographic information. This ensures that
each sample is linked to a full complement of anonymous or anonymized (according to
patient choice) patient information that is accessible solely by authorized Biobank
personnel.
The high quality biospecimens collected by the B4MED are used for biomarker and
drug discovery experiments, both for basic research and for clinical research, with the
ultimate aim of providing excellence in patient care through excellence in research.
Expression of B cell-activating factor (BAFF), a critical B cell survival factor, is elevated in autoimmune and lymphoproliferative disorders. Mice overproducing BAFF develop systemic lupus ...erythematosus (SLE)-like disease and exhibit B cell activation of classical and alternative NF-κB-signaling pathways. We used a genetic approach and found that both NF-κB-signaling pathways contributed to disease development but act through distinct mechanisms. Whereas BAFF enhanced long-term B cell survival primarily through the alternative, but not the classical, NF-κB pathway, it promoted immunoglobulin class switching and generation of pathogenic antibodies through the classical pathway. Activation of the alternative NF-κB pathway resulted in integrin upregulation, thereby retaining autoreactive B cells in the splenic marginal zone, a compartment that contributes to their survival. Thus, both classical and alternative NF-κB signaling are important for development of lupus-like disease associated with BAFF overproduction. The same mechanisms may be involved in the pathogenesis of human SLE.
It has previously been reported that distinct signaling pathways can lead to nuclear factor (NF)-κB activation following stimulation of different cell types with inflammatory cytokines. As the role ...of atypical protein kinase C (PKC) isoforms in NF-κB activation remains a matter of controversy, we investigated whether this role might be cell type-dependent. Immunoblots detected atypical PKC expression in all the analyzed cell lines. The PKC inhibitor calphostin C inhibited NF-κB activation by tumor necrosis factor (TNF)-α or interleukin (IL)-1β in Jurkat or NIH3T3 cells but not in MCF7 A/Z cells. Cell transfections with a PKC λ/ι dominant negative mutant abolished TNF-α-induced NF-κB-dependent transcription in NIH3T3 and Jurkat cells but not in MCF7 A/Z cells. Similarly, the same mutant blocked NF-κB-dependent transactivation after IL-1β stimulation of NIH3T3 cells, but was ineffective after IL-1β treatment of MCF7 A/Z cells. In MCF7 A/Z cells, however, the PKC λ/ι dominant negative mutant could abolish transactivation of an AP-1-dependent reporter plasmid after stimulation with TNF-α but not with IL-1β. These data thus confirm that transduction pathways for NF-κB activation after cell stimulation with TNF-α or IL-1β are cell-type specific and that atypical PKC isoforms participate in this pathway in NIH3T3 and Jurkat cells.
IkappaB Kinase (IKK)alpha is required for activation of an alternative NF-kappaB signaling pathway based on processing of the NF-kappaB2/p100 precursor protein, which associates with RelB in the ...cytoplasm. This pathway, which activates RelB:p52 dimers, is required for induction of several chemokine genes needed for organization of secondary lymphoid organs. We investigated the basis for the IKKalpha dependence of the induction of these genes in response to engagement of the lymphotoxin beta receptor (LTbetaR). Using chromatin immunoprecipitation, we found that the promoters of organogenic chemokine genes are recognized by RelB:p52 dimers and not by RelA:p50 dimers, the ubiquitous target for the classical NF-kappaB signaling pathway. We identified in the IKKalpha-dependent promoters a novel type of NF-kappaB-binding site that is preferentially recognized by RelB:p52 dimers. This site links induction of organogenic chemokines and other important regulatory molecules to activation of the alternative pathway.
IkappaB Kinase (IKK)alpha is required for activation of an alternative NF-kappaB signaling pathway based on processing of the NF-kappaB2/p100 precursor protein, which associates with RelB in the ...cytoplasm. This pathway, which activates RelB:p52 dimers, is required for induction of several chemokine genes needed for organization of secondary lymphoid organs. We investigated the basis for the IKKalpha dependence of the induction of these genes in response to engagement of the lymphotoxin beta receptor (LTbetaR). Using chromatin immunoprecipitation, we found that the promoters of organogenic chemokine genes are recognized by RelB:p52 dimers and not by RelA:p50 dimers, the ubiquitous target for the classical NF-kappaB signaling pathway. We identified in the IKKalpha-dependent promoters a novel type of NF-kappaB-binding site that is preferentially recognized by RelB:p52 dimers. This site links induction of organogenic chemokines and other important regulatory molecules to activation of the alternative pathway.
In mammals, the canonical nuclear factor kappaB (NF-kappaB) signaling pathway activated in response to infections is based on degradation of IkappaB inhibitors. Senftleben et al show that IKKalpha is ...required for B cell maturation, formation of secondary lymphoid organs, increased expression of certain NF-kappaB target genes, and processing of the NF-kappaB2 (p100) precursor.
PDF
![Activation by IKK[Alpha] of...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0036-8075/small "Activation by IKK[Alpha] of a Second, Evolutionary Conserved, NF-ΚB Signaling Pathway")
