Primary Effusion Lymphoma (PEL) is a lymphoproliferative disease of B cell origin associated with HHV-8 infection and characterized by migration of tumor cells to serous body cavities. PEL cells originate from post-germinal center B cells yet harbor a non-B, non-T phenotype, a characteristic that has not been fully explained. In the present study we demonstrate that PEL cells have an impaired expression of B cell-specific transcription factors and this results in a decreased activity of promoters regulating essential B cell genes. PEL cells lack PU.1 expression, although its transcription partner IRF-4 is highly upregulated, leading to decreased activity of the immunoglobulin lambda and kappa light chain ETS-IRF enhancers. Expression of the B cell specific transcription factor Oct-2 and the B cell specific co-activator of octamer factors (Bob-1), which are known to regulate PU.1 expression, was also impaired. Ectopic expression of Oct-2 was able to fully restore PU.1 promoter activity in the PEL cell line BCBL-1, while PU.1 expression also reconstituted the activation of the lambdaB Ets-IRF site. In addition, protein levels of BSAP/Pax-5 and IRF-8/ICSBP were undetectable in PEL cells. The pattern of transcription factor ablation observed in PEL was found to be comparable to that observed in classical Hodgkin's disease-derived cell lines, which also lack B cell specific surface markers. Comparative analysis of gene expression by cDNA microarray of BCBL-1 cells (PEL), L-428 (cHD) and BJAB cells revealed a subset of genes that were differentially expressed in PEL cells. Among these, four genes involved in cell migration and chemotaxis were strongly upregulated in PEL cells: LTA4H, IL-16, TSP-1, and selectin-P ligand. Upregulation of LTA4H was investigated at the transcriptional level. The LTA4H promoter exhibited 50% higher activity in BCBL-1 cells than in BJAB or L-428 cells. Deletion analysis of the LTA4H promoter revealed a positive cis regulatory element active only in BCBL-1 cells in the promoter proximal region located between -76 to -40 bp. Formation of a specific DNA-protein complex in this region was confirmed by Electromobility Shift Assay (EMSA). Co-culture of BCBL-1 cells with ionophore-stimulated primary neutrophils lead to an increased production of LTB4 by transcellular biosynthesis compared to L-428 cells, demonstrating the functional significance of LTA4H upregulation. BCBL-1 cells also demonstrated increased migration even in the absence of chemotactic stimulus compared to L-428 cells. These observations indicate that (1) disruption of the B-cell specific transcriptional program is likely to contribute to the incomplete B cell phenotype characteristic of PEL cells and (2) upregulation of factors involved in cell migration and chemotaxis constitute a unique characteristic of PEL cells that may contribute to the localization of this lymphoma to serous body cavities.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.103020 |
| Date | January 2006 |
| Creators | Arguello, Meztli. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Microbiology and Immunology.) |
| Rights | © Meztli Arguello, 2006 |
| Relation | alephsysno: 002584341, proquestno: AAINR32291, Theses scanned by UMI/ProQuest. |
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