Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q06643 (non-Hodgkin's lymphoma)
 11,307 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rituximab (Rituxan, IDEC-C2B8) has been shown to sensitize non-Hodgkin's lymphoma (NHL) cell lines to chemotherapeutic drug-induced apoptosis. Rituximab treatment of Bcl-2-deficient Ramos cells and Bcl-2-expressing Daudi cells selectively decreases Bcl-(xL) expression and sensitizes the cells to paclitaxel-induced apoptosis. This study delineates the signaling pathway involved in rituximab-mediated Bcl-(xL) down-regulation in Ramos and Daudi NHL B cells. We hypothesized that rituximab may interfere with the extracellular signal-regulated kinase (ERK) 1/2 pathway, leading to decreased Bcl-(xL) expression. Rituximab (20 microg/mL) inhibited the kinase activity of mitogen-activated protein kinase kinase (MEK) 1/2 and reduced the phosphorylation of the components of the ERK1/2 pathway (Raf-1, MEK1/2, and ERK1/2) and decreased activator protein-1 DNA binding activity and Bcl-(xL) gene expression. These events occurred with similar kinetics and were observed 3 to 6 hours after rituximab treatment. Rituximab-mediated effects were corroborated by using specific inhibitors of the ERK1/2 pathway, which also reduced Bcl-(xL) levels and sensitized the NHL B cells to paclitaxel-induced apoptosis. Previous findings implicated a negative regulatory role of the Raf-1 kinase inhibitor protein (RKIP) on the ERK1/2 pathway. Rituximab treatment of NHL B cells significantly up-regulated RKIP expression, thus interrupting the ERK1/2 signaling pathway through the physical association between Raf-1 and RKIP, which was concomitant with Bcl-(xL) down-regulation. These novel findings reveal a signaling pathway triggered by rituximab, whereby rituximab-mediated up-regulation of RKIP adversely regulates the activity of the ERK1/2 pathway, Bcl-(xL) expression, and subsequent chemosensitization of drug-refractory NHL B cells. The significance of these findings is discussed.
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PMID:Inhibition of the Raf-MEK1/2-ERK1/2 signaling pathway, Bcl-xL down-regulation, and chemosensitization of non-Hodgkin's lymphoma B cells by Rituximab. 1546 8

Immunotherapy with rituximab (a chimeric anti-CD20 monoclonal antibody), alone or in combination with chemotherapy, has improved the treatment outcome of patients with non-Hodgkin's lymphoma (NHL), but the in vivo mechanisms by which rituximab exerts its effects have not been elucidated. The mechanisms underlying resistance are not known. In addition to the proposed actions mediated by rituximab (such as complement-dependent cytotoxicity, antibody-dependent cellular cytotoxicity, and apoptosis), rituximab may signal the tumor cells and inhibit constitutively activated survival signaling pathways (Raf-1-MEK1/2-ERK1/2, p38 MAPK, NF-kappaB, and Akt), resulting in inhibition of cell growth and of selectively anti-apoptotic gene products such as Bcl-2 and Bcl-(xL). The inhibition of these anti-apoptotic gene products by rituximab sensitizes drug-resistant tumor cells to apoptosis induced by a variety of cytotoxic chemotherapeutic drugs. Also, rituximab sensitizes NHL cells to apoptosis resulting from upregulation of death receptors, implicating a novel in vivo role of host involvement in rituximab-mediated effects. We have developed rituximab-resistant clones that do not respond to rituximab-mediated cell signaling. The clones exhibited hyperactivated cell survival pathways and overexpression of anti-apoptotic gene products and could not be chemosensitized by rituximab. Inhibitors of the survival signaling pathways reverse drug resistance in both wildtype cells and resistant clones. These findings identify several novel intracellular pathways modifyed by rituximab that sensitize NHL cells to both chemotherapy and immunotherapy, as well as several therapeutic targets whose modifications reverse resistance. These findings have clinical relevance for both prognosis and novel treatment strategies for patients with NHL.
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PMID:What signals are generated by anti-CD20 antibody therapy? 2042 15