Jazirehi Ali R, Gan Xiao-Hu, De Vos Sven, Emmanouilides Christos, Bonavida Benjamin
Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA 90095, USA.
Mol Cancer Ther. 2003 Nov;2(11):1183-93.
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.
抗CD20单克隆抗体利妥昔单抗（美罗华，IDEC-C2B8）已在一部分低级别或滤泡性非霍奇金淋巴瘤（NHL）患者的临床治疗中显示出有前景的结果。然而，对化疗和利妥昔单抗耐药的NHL患者可能会从一种以利妥昔单抗作为致敏剂的治疗方案中获益。本研究检测了利妥昔单抗在利妥昔单抗和紫杉醇耐药的CD20(+) NHL B细胞系（拉莫斯细胞、拉吉细胞、多奥迪细胞和2F7细胞）上介导的凋亡信号。用利妥昔单抗（20μg/ml）或紫杉醇（0.1 - 1000 nM）处理均抑制了NHL细胞系的活细胞恢复。利妥昔单抗和紫杉醇单独使用均未诱导显著凋亡，尽管联合治疗在凋亡方面产生了协同作用。利妥昔单抗选择性下调拉莫斯细胞中Bcl-xL的表达并诱导凋亡蛋白酶激活因子1（Apaf-1）的表达。紫杉醇下调Bcl-xL和凋亡抑制蛋白（c-IAP-1）的表达，并上调Bad和Apaf-1的表达。联合治疗导致截短的Bid形成、细胞色素c的胞质积累以及第二线粒体来源的半胱天冬酶激活剂/低PI凋亡直接抑制因子结合蛋白、半胱天冬酶-9、半胱天冬酶-7、半胱天冬酶-3的激活以及聚（ADP-核糖）聚合酶的裂解。这些发现确定了利妥昔单抗介导的信号在拉莫斯NHL细胞中的两个潜在新的细胞内靶点（即Bcl-xL和Apaf-1）。此外，这些发现表明利妥昔单抗和紫杉醇均选择性地改变参与凋亡信号转导途径的蛋白质的表达模式，并且通过功能互补，联合治疗在凋亡方面产生协同作用。讨论了这些发现的潜在治疗意义。
