Czuczman Myron S, Olejniczak Scott, Gowda Aruna, Kotowski Adam, Binder Arvinder, Kaur Harman, Knight Joy, Starostik Petr, Deans Julie, Hernandez-Ilizaliturri Francisco J
Department of Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263, USA.
Clin Cancer Res. 2008 Mar 1;14(5):1561-70. doi: 10.1158/1078-0432.CCR-07-1254.
Acquirement of resistance to rituximab has been observed in lymphoma patients. To define mechanisms associated with rituximab resistance, we developed various rituximab-resistant cell lines (RRCL) and studied changes in CD20 expression/structure, lipid raft domain (LRD) reorganization, calcium mobilization, antibody-dependent cellular cytotoxicity, and complement-mediated cytotoxicity (CMC) between parental and RRCL. Significant changes in surface CD20 antigen expression were shown in RRCL. Decreased calcium mobilization and redistribution of CD20 into LRD were found in RRCL. Western blotting identified a unique 35 kDa protein band in RRCL, which was not seen in parental cells and was secondary to an increase in surface and cytoplasmic expression of IgM light chains. CD20 gene expression was decreased in RRCL. In vitro exposure to PS341 increased CD20 expression in RRCL and minimally improved the sensitivity to rituximab-associated CMC. Our data strongly suggest that the acquisition of rituximab resistance is associated with global gene and protein down-regulation of the CD20 antigen affecting LRD organization and downstream signaling. CD20 expression seems to be regulated at the pretranscriptional and posttranscriptional levels. Proteasome inhibition partially reversed rituximab resistance, suggesting the existence of additional mediators of rituximab resistance. Future research is geared to identify drugs and/or biological agents that are effective against RRCL.
在淋巴瘤患者中已观察到对利妥昔单抗产生耐药性的情况。为了确定与利妥昔单抗耐药相关的机制，我们构建了多种利妥昔单抗耐药细胞系（RRCL），并研究了亲代细胞与RRCL之间CD20表达/结构、脂筏结构域（LRD）重组、钙动员、抗体依赖性细胞毒性以及补体介导的细胞毒性（CMC）的变化。RRCL中表面CD20抗原表达出现显著变化。在RRCL中发现钙动员减少以及CD20重新分布至LRD。蛋白质印迹法在RRCL中鉴定出一条独特的35 kDa蛋白条带，亲代细胞中未见此条带，其出现继发于IgM轻链表面和细胞质表达的增加。RRCL中CD20基因表达降低。体外暴露于PS341可增加RRCL中CD20的表达，并略微提高对利妥昔单抗相关CMC的敏感性。我们的数据强烈表明，利妥昔单抗耐药性的获得与CD20抗原的整体基因和蛋白下调有关，这会影响LRD组织和下游信号传导。CD20表达似乎在转录前和转录后水平受到调控。蛋白酶体抑制可部分逆转利妥昔单抗耐药性，提示存在利妥昔单抗耐药的其他介质。未来的研究旨在确定对RRCL有效的药物和/或生物制剂。
