Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.22.62 (caspase-9)
 7,507 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rituximab is a chimeric monoclonal antibody directed at CD20 with significant activity in non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL). A variety of pathways of tumor cytotoxicity different from cytotoxic chemotherapy have been proposed for this therapeutic antibody including antibody-dependent cellular cytotoxicity and complement-mediated cell lysis. This report describes that a proportion of patients with CLL receiving rituximab treatment have in vivo activation of caspase-9, caspase-3, and poly(ADP-ribose) polymerase (PARP) cleavage in blood leukemia cells immediately following infusion of rituximab. This suggests that apoptosis using a pathway similar to fludarabine and other chemotherapeutic agents is intricately involved in the blood elimination of tumor cells after rituximab treatment. Patients having caspase-3 activation and PARP cleavage in vivo had a significantly lower blood leukemia cell count after treatment as compared to those without caspase activation. Significant down-modulation of the antiapoptotic proteins XIAP and Mcl-1 was also noted, possibly explaining in part how rituximab sensitizes CLL cells to the cytotoxic effect of chemotherapy in vivo. These findings suggest that the therapeutic benefit of antibody-based therapy in vivo for patients with CLL depends in part on induction of apoptosis and provides another area of focus for studying mechanisms of antibody-resistance in neoplastic cells.
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PMID:The mechanism of tumor cell clearance by rituximab in vivo in patients with B-cell chronic lymphocytic leukemia: evidence of caspase activation and apoptosis induction. 1180 10

The anti-CD20 monoclonal antibody rituximab (Rituxan, IDEC-C2B8) has shown promising results in the clinical treatment of a subset of patients with low grade or follicular non-Hodgkin's lymphoma (NHL). However, chemotherapy- and rituximab-refractory NHL patients may benefit from a regimen in which rituximab acts as a sensitizing agent. This study examined the apoptotic signaling mediated by rituximab on rituximab- and paclitaxel-resistant CD20(+) NHL B cell lines (Ramos, Raji, Daudi, and 2F7). Treatment with either rituximab (20 micro g/ml) or paclitaxel (0.1-1000 nM) inhibited viable cell recovery of NHL lines. Neither rituximab nor paclitaxel induced significant apoptosis, although the combination treatment resulted in synergy in apoptosis. Rituximab selectively down-regulated Bcl-xL and induced apoptosis protease activating factor 1 (Apaf-1) expressions in Ramos cells. Paclitaxel down-regulated the expression of Bcl-xL and inhibitor of apoptosis proteins (c-IAP-1) and up-regulated the expression of Bad and Apaf-1. The combination treatment resulted in the formation of truncated Bid, cytosolic accumulation of cytochrome c and second mitochondria-derived activator of caspase/direct inhibitor of apoptosis-binding protein with low PI, activation of caspase-9, caspase-7, caspase-3, and cleavage of poly(ADP-ribose) polymerase. The findings identify two potential novel intracellular targets of rituximab-mediated signaling in Ramos NHL cells (i.e., Bcl-xL and Apaf-1). Further, the findings show that both rituximab and paclitaxel selectively modify the expression pattern of proteins involved in the apoptosis signal transduction pathway and, through functional complementation, the combination results in synergy in apoptosis. The potential therapeutic significance of these findings is discussed.
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PMID:Rituximab (anti-CD20) selectively modifies Bcl-xL and apoptosis protease activating factor-1 (Apaf-1) expression and sensitizes human non-Hodgkin's lymphoma B cell lines to paclitaxel-induced apoptosis. 1461 92

Rituximab maintenance therapy provides a significant benefit in patients with indolent B-cell non-Hodgkin lymphoma (NHL). Based on its efficacy in improving response to chemotherapy, the anti-CD20 antibody is currently under evaluation as maintenance therapy also in patients with B-CLL. We evaluated rituximab-mediated cytotoxicity in 10 B-CLL cases pretreated in vitro with non-cytotoxic concentrations of fludarabine. This combination induced a synergic cytotoxic effect in 8 out of 10 patients at a mean level of 26.15 +/- 13.9%, compared to 8.05 +/- 5.3% cytotoxicity observed with rituximab alone. Consistent with the viability assay, we found an increased caspase-3 activity together with activation of caspase-9 in B-CLL cells sensitive to sequential non-cytotoxic fludarabine and rituximab exposure. Non-cytotoxic fludarabine concentrations may sensitize B-CLL cells to rituximab-mediated cytotoxicity via caspase-3 activation.
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PMID:Low-dose fludarabine increases rituximab cytotoxicity in B-CLL cells by triggering caspases activation in vitro. 2000 Dec 34

Rituximab is the first line drug to treat non Hodgkin's lymphoma (B-NHL) alone or in combination with chemotherapy. However, 30-40% of B-NHL patients are unresponsive to rituximab or resistant after therapy. Human phosphatidylethanolamine-binding protein 4 (hPEBP4) is a novel member of PEBP family and functions as an anti-apoptotic molecule. In this study, we found hPEBP4 to be expressed in up to 90% of B-cell lymphoma patients, but in only 16.7% of normal lymph nodes. Interestingly, hPEBP4 overexpression inhibited rituximab-mediated complement dependent cytotoxicity (R-CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC) in B-NHL cells while downregulation of hPEBP4 augmented the therapeutic efficacy of rituximab both in vitro and in vivo. Furthermore, hPEBP4 silencing sensitized the primary B-acute lymphocytic leukemia (B-ALL) cells to R-CDC. During rituximab-mediated complement dependent cytotoxicity, hPEBP4 was recruited to the cell membrane in a PE-binding domain dependent manner and inhibited R-CDC induced calcium flux and reactive oxygen species (ROS) generation. These events contributed to the decrease of cell death induced by R-CDC in B-cell lymphomas. Meanwhile, hPEBP4 knockdown potentiated the chemosensitization of the rituximab in B-cell lymphoma cells by regulating the expression of Bcl-xl, Cycline E, p21(waf/cip1) and p53 and the activation of caspase-3 and caspase-9. Considering that hPEBP4 conferred cellular resistance to rituximab treatment and was preferentially expressed in lymphoma tissue, it could be a potential valuable target for adjuvant therapy for B-cell lymphoma.
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PMID:Silencing of human phosphatidylethanolamine-binding protein 4 enhances rituximab-induced death and chemosensitization in B-cell lymphoma. 2345 Oct 95