title: 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.
abstract: 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.
authors.affiliation: Department of Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263, USA. myron.czuczman@roswellpark.org
authors.forename: Myron S
authors.initials: MS
authors.lastname: Czuczman
authors.forename: Scott
authors.initials: S
authors.lastname: Olejniczak
authors.forename: Aruna
authors.initials: A
authors.lastname: Gowda
authors.forename: Adam
authors.initials: A
authors.lastname: Kotowski
authors.forename: Arvinder
authors.initials: A
authors.lastname: Binder
authors.forename: Harman
authors.initials: H
authors.lastname: Kaur
authors.forename: Joy
authors.initials: J
authors.lastname: Knight
authors.forename: Petr
authors.initials: P
authors.lastname: Starostik
authors.forename: Julie
authors.initials: J
authors.lastname: Deans
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Hernandez-Ilizaliturri
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D058846:Antibodies, Monoclonal, Murine-Derived; D000920:Antibody-Dependent Cell Cytotoxicity; D018951:Antigens, CD20 / Q000235:genetics* / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D015152:Blotting, Northern; D015153:Blotting, Western; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D002118:Calcium / Q000378:metabolism; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D005434:Flow Cytometry; D020869:Gene Expression Profiling; D006801:Humans; D007136:Immunoglobulins / Q000378:metabolism; D016393:Lymphoma, B-Cell / Q000188:drug therapy* / Q000276:immunology / Q000378:metabolism; D021962:Membrane Microdomains / Q000187:drug effects; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D011480:Protease Inhibitors / Q000494:pharmacology; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000069283:Rituximab; D014158:Transcription, Genetic / Q000187:drug effects*; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D001897:Boronic Acids; D007136:Immunoglobulins; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D011719:Pyrazines; D012333:RNA, Messenger; D000069283:Rituximab; D000069286:Bortezomib; D002118:Calcium