Expression of Tumor Suppressor microRNAs in Diffuse Large B-Cell Lymphoma
Bowen Wang, Young A Kim, Philip Starshak, Zifen Gao, Jonathan W Said, Dinesh S Rao. UCLA, Los Angeles, CA; Health Science Center of Peking University, Beijing, China
Background: The most common subtype of B-cell lymphoma, diffuse large B-cell lymphoma, is a disease that arises from mature B-cells that are at various stages of antigenic activation and terminal differentiation into plasma cells. Recently, it has become clear that gene expression is significantly modified post-transcriptionally by microRNA (miRNA). Here, we focus on two miRNAs that are of importance in cancer. miR-34a is induced by the tumor suppressor protein p53 and has significant effects on B-cell development. miR-146a is induced by NF-kB and is a negative feedback regulator of signaling through this inflammatory pathway.
Design: To examine dysregulation of miRNAs in DLBCL, we have conducted a retrospective analysis of diffuse large B-cell lymphoma (DLBCL) for expression of miR-34a and miR-146a, with a final study size of 100 cases. We have completed analyses on 33 cases so far, including 25 cases of activated B-cell type DLBCL (ABC-DLBCL)and 8 cases of germinal center B-cell type DLBCL (GCB-DLBCL). RNA was isolated from paraffin embedded tissues using standard protocols and a commercially available kit. RT-qPCR for miR-34a, miR-146a was performed using ABI Taqman primers. We also analyzed levels of p53 as well as TRAF6 and IRAK1, two targets of miR-146a. To correlate the results with functional assays, we generated stably transduced DLBCL lines and analyzed changes in growth properties with MTT assays.
Results: miR-146a expression is higher in ABC-DLBCL than in GCB-DLBCL and is correlated with the expression of IRAK1 and TRAF6 in ABC-type DLBCL, but a subset of cases shows low miR-146a expression. miR-34a expression is highly correlated with RNA-level expression of p53. The expression of miR-34a and miR-146a is now being correlated with clinicopathologic parameters. miR-34a-transduced DLBCL lines demonstrated slower growth by MTT assay as compared to control cell lines.
Conclusions: The expression of miR-146a is correlated with the ABC-DLBCL subtype. Loss of miR-34a is also observed in DLBCL. Re-expression of miR-34a in DLBCL causes a decrease in cell growth in DLBCL cell lines. The findings demonstrate an important role for miR-34a in DLBCL pathogenesis and may indicate a role for miR-34a in future therapeutic strategies for DLBCL. miR-146a expression is also lost in a subset of DLBCL, indicating that it may play a role in the constitutive activation of NF-kB. Further work is required to understand whether these miRNAs may represent independent clinicopathologic indicators of disease or therapeutic avenues in DLBCL.
Tuesday, March 20, 2012 1:00 PM
Poster Session IV # 202, Tuesday Afternoon