Regulation of CD20 in rituximab-resistant cell lines and B-cell non-Hodgkin lymphoma Journal Article
| Authors: | Tsai, P. C.; Hernandez-Ilizaliturri, F. J.; Bangia, N.; Olejniczak, S. H.; Czuczman, M. S. |
| Article Title: | Regulation of CD20 in rituximab-resistant cell lines and B-cell non-Hodgkin lymphoma |
| Abstract: | Purpose: The aim of this research was to further investigate the contribution of CD20 antigen expression to rituximab activity and define the mechanisms responsible for CD20 downregulation in rituximabresistant cell lines (RRCL). Experimental Design: Rituximab-sensitive cell lines, RRCL, and primary neoplastic B cells were evaluated by chromium-51 release assays, ImageStream image analysis, immunohistochemical staining, flow cytometric analysis, CD20 knockdown, promoter activity, chromatin immunoprecipitation (ChIP) analysis of CD20 promoter, and CD20 plasmid transfection experiments to identify mechanisms associated with CD20 regulation in RRCL. Results: RRCL exhibited a gradual loss of CD20 surface expression with repeated exposure to rituximab. We identified a CD20 antigen surface threshold level required for effective rituximab-associated complement-mediated cytotoxicity (CMC). However, a direct correlation between CD20 surface expression and rituximab-CMC was observed only in rituximab-sensitive cell lines. CD20 promoter activity was decreased in RRCL. Detailed analysis of various CD20 promoter fragments suggested a lack of positive regulatory factors in RRCL. ChIP analysis showed reduced binding of several key positive regulatory proteins on CD20 promoter in RRCL. Interleukin-4 (IL-4) induced higher CD20 promoter activity and CD20 expression but modestly improved rituximab activity in RRCL and in primary B-cell lymphoma cells. Forced CD20 expression restored cytoplasmic but not surface CD20, suggesting the existence of a defect in CD20 protein transport in RRCL. Conclusions: We identified several mechanisms that alter CD20 expression in RRCL and showed that, whereas CD20 expression is important for rituximab activity, additional factors likely contribute to rituximab sensitivity in B-cell lymphoma. ©2012 AACR. |
| Keywords: | immunohistochemistry; controlled study; human tissue; human cell; rituximab; flow cytometry; antigen expression; multiple cycle treatment; interleukin 4; antineoplastic activity; b lymphocyte; drug dose escalation; b cell lymphoma; cd20 antigen; correlation analysis; drug mechanism; chromatin immunoprecipitation; lymphoma cell; protein transport; cytoplasm; down regulation; antigen binding; drug sensitivity; complement dependent cytotoxicity |
| Journal Title: | Clinical Cancer Research |
| Volume: | 18 |
| Issue: | 4 |
| ISSN: | 1078-0432 |
| Publisher: | American Association for Cancer Research |
| Date Published: | 2012-02-15 |
| Start Page: | 1039 |
| End Page: | 1050 |
| Language: | English |
| DOI: | 10.1158/1078-0432.ccr-11-1429 |
| PROVIDER: | scopus |
| PMCID: | PMC3288324 |
| PUBMED: | 22228637 |
| DOI/URL: | |
| Notes: | --- - "Export Date: 2 April 2012" - "CODEN: CCREF" - "Source: Scopus" |
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