Acquirement of Rituximab Resistance in Lymphoma Cell Lines Is Associated with Both Global CD20 Gene and Protein Down-Regulation Regulated at the Pretranscriptional and Posttranscriptional Levels

• Published in: Clinical cancer research 2008-03, Vol.14 (5), p.1561-1570
• Main Authors: CZUCZMAN, Myron S, OLEJNICZAK, Scott, GOWDA, Aruna, KOTOWSKI, Adam, BINDER, Arvinder, KAUR, Harman, KNIGHT, Joy, STAROSTIK, Petr, DEANS, Julie, HERNANDEZ-LLIZALITURRI, Francisco J
• Format: Article
• Language: English
• Subjects: Antibodies, Monoclonal - pharmacology; Antibodies, Monoclonal, Murine-Derived; Antibody-Dependent Cell Cytotoxicity; Antigens, CD20 - genetics; Antigens, CD20 - metabolism; Antineoplastic agents; Antineoplastic Agents - pharmacology; Apoptosis - drug effects; Biological and medical sciences; Biomarkers, Tumor - genetics; Biomarkers, Tumor - metabolism; Blotting, Northern; Blotting, Western; Boronic Acids - pharmacology; Bortezomib; Calcium - metabolism; CD20-antigen; Down-Regulation; Drug Resistance, Neoplasm; Flow Cytometry; Gene Expression Profiling; Hematologic and hematopoietic diseases; Humans; Immunoglobulins - metabolism; Leukemias. Malignant lymphomas. Malignant reticulosis. Myelofibrosis; Lymphoma, B-Cell - drug therapy; Lymphoma, B-Cell - immunology; Lymphoma, B-Cell - metabolism; Medical sciences; Membrane Microdomains - drug effects; non–Hodgkin's lymphoma; Oligonucleotide Array Sequence Analysis; Pharmacology. Drug treatments; Phenotype; Protease Inhibitors - pharmacology; Proteasome Inhibitors; Pyrazines - pharmacology; Resistance; Reverse Transcriptase Polymerase Chain Reaction; Rituximab; RNA, Messenger - genetics; RNA, Messenger - metabolism; Transcription, Genetic - drug effects; Tumor Cells, Cultured
• ISSN: 1078-0432; 1557-3265
• 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.