RESUMO
Retinoblastoma (RB) protein inactivation during tumor progression is often associated with acquisition of immature phenotypes and resistance to therapy. Determination of an RB inactivation signature in a context of gaining undifferentiated phenotype in a p53-null sarcoma system revealed a critical role for interleukin (IL)-6. Using a Gene Set Enrichment Analysis (GSEA), we discovered that poorly differentiated breast cancers are enriched for this RB inactivation signature. Accelerated IL-6 secretion following RB inactivation in an RB-intact luminal-type breast cancer cell line MCF-7 promoted a positive feed forward loop between IL-6 and STAT3 driving tumor growth and endocrine therapy resistance. In addition, some of RB-intact basal-like type breast cancer cell lines exhibited a similar phenotype following RB depletion. The mechanism whereby RB inactivation increases IL-6 production in MCF-7 cells appeared to involve fatty acid oxidation (FAO)-dependent mitochondrial metabolism and c-Jun NH(2)-terminal kinase (JNK). In addition, IL-6, via STAT3-mediated feedback to mitochondria, autonomously adjusts mitochondrial superoxide to levels suitable to maintain stem cell-like activity. The gene expression profile of luminal-type breast cancer patients with low RB expression revealed high enrichment of genes involved in mitochondrial respiration and downstream targets of IL-6. These findings unveiled an unexpected strategy whereby RB suppresses malignant features of cancer cells through metabolic reprogramming and cell-autonomous inflammation.
Assuntos
Neoplasias da Mama/patologia , Autorrenovação Celular/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos , Interleucina-6/metabolismo , Mitocôndrias/patologia , Proteína do Retinoblastoma/metabolismo , Tamoxifeno/farmacologia , Animais , Antineoplásicos Hormonais/farmacologia , Apoptose/efeitos dos fármacos , Biomarcadores Tumorais/genética , Biomarcadores Tumorais/metabolismo , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/metabolismo , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Ácidos Graxos/química , Ácidos Graxos/metabolismo , Feminino , Humanos , Interleucina-6/genética , Metaboloma , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Proteína do Retinoblastoma/genética , Fator de Transcrição STAT3/genética , Fator de Transcrição STAT3/metabolismo , Células Tumorais Cultivadas , Proteína Supressora de Tumor p53/fisiologia , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Leukocyte antigen-related protein (LAR) is a prototype for a family of transmembrane protein tyrosine phosphatases whose extracellular domain is composed of three Ig and several fibronectin type III (FnIII) domains. Complex alternative splicing of the LAR-FnIII domains 4-8 has been observed. The extracellular matrix laminin-nidogen complex was identified as a ligand for the LAR-FnIII domain 5 (Fn5) using a series of GST-LAR-FnIII domain fusion proteins and testing them in in vitro ligand-binding assays. LAR- laminin-nidogen binding was regulated by alternative splicing of a small exon within the LAR-Fn5 so that inclusion of this exon sequence resulted in disruption of the laminin-nidogen-binding activity. Long cellular processes were observed when HeLa cells were plated on laminin-nidogen, but not when plated on a fibronectin surface. Indirect immunofluorescent antibody staining revealed high expression of LAR in a punctate pattern, throughout the length of these cellular processes observed on laminin-nidogen. Antibody-induced cross-linking of LAR inhibited formation of these cellular processes, and inhibition was correlated with changes in cellular actin cytoskeletal structure. Thus, LAR-laminin-nidogen binding may play a role in regulating cell signaling induced by laminin-nidogen, resulting in cell morphological changes.
Assuntos
Processamento Alternativo , Isoenzimas/metabolismo , Laminina/metabolismo , Glicoproteínas de Membrana/metabolismo , Proteínas Tirosina Fosfatases/metabolismo , Receptores de Superfície Celular/metabolismo , Sítios de Ligação , Fibronectinas/metabolismo , Células HeLa , Humanos , Ligantes , Proteínas de Membrana/metabolismo , Proteínas Tirosina Fosfatases Classe 4 Semelhantes a Receptores , Proteínas Recombinantes de Fusão/metabolismo , Células Tumorais CultivadasRESUMO
An osmosensing mechanism in the budding yeast (Saccharomyces cerevisiae) involves both a two-component signal transducer (Sln1p, Ypd1p and Ssk1p) and a MAP kinase cascade (Ssk2p/Ssk22p, Pbs2p, and Hog1p). The transmembrane protein Sln1p contains an extracellular sensor domain and cytoplasmic histidine kinase and receiver domains, whereas the cytoplasmic protein Ssk1p contains a receiver domain. Ypd1p binds to both Sln1p and Ssk1p and mediates the multistep phosphotransfer reaction (phosphorelay). This phosphorelay system is initiated by the autophosphorylation of Sln1p at His576. This phosphate is then sequentially transferred to Sln1p-Asp-1144, then to Ypd1p-His64, and finally to Ssk1p-Asp554. We propose that the multistep phosphorelay mechanism is a universal signal transduction apparatus utilized both in prokaryotes and eukaryotes.
