AbstractsBiology & Animal Science

B-cell receptor signaling- and p53-dependent non-coding RNA expression in chronic lymphocytic leukemia

by Carolin J. Blume

Institution: Universität Heidelberg
Department: The Faculty of Bio Sciences
Degree: PhD
Year: 2015
Record ID: 1109612
Full text PDF: http://www.ub.uni-heidelberg.de/archiv/18024


Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in adults of the Western world. It is a malignancy characterized by an accumulation of CD5 positive B-cells in blood and lymphoid organs. CLL is a very heterogeneous disease, where molecular subgroups display striking differences in treatment response and prognosis. A greater BCR signaling capacity and a loss of p53 signaling activity confer a poor prognosis. While the higher BCR signaling activity seen in CLL with unmutated IGHV genes supports tumor cell survival, p53 aberrations mediate resistance towards standard therapy. The aim of this work was to characterize the involvement of non-coding RNA in these two key signaling pathways of CLL cell survival and resistance. Small RNA sequencing was applied to comprehensively assess microRNA (miRNA) and other non-coding RNA expression in peripheral blood mononuclear cells of 35 CLL patients. miRNAs were identified that display IGHV mutation status dependent expression, and the transcript levels of 15 miRNAs predicted IGHV mutation status with 82% accuracy. By abrogation of BCR signaling in vitro using the small-molecule inhibitor ibrutinib, the expression of miR-320c, miR-1246, miR-484, miR-17-5p, miR-155-3p and miR-27a-5p was found to be BCR signaling dependent, suggesting a role in mediating CLL cell survival. The basal expression of 10 miRNAs was associated with ibrutinib sensitivity in vitro, implicating an involvement of these miRNAs in the regulation of BCR signaling. It was hypothesized that p53-dependent ncRNAs could be identified by comparison of CLL samples with or without TP53 mutation/deletion for their ncRNA expression changes upon DNA damage-triggered p53 induction. In addition to miR-34a, a set of further miRNAs was found to be TP53 status dependently induced (particularly miR-182-5p, miR-7-5p and miR-320d/c). Beyond miRNAs, the present data demonstrate p53-dependent expression of the long non-coding RNAs lincRNA-p21 (long intergenic non-coding RNA p21) and NEAT1 (nuclear enriched abundant transcript 1) upon DNA damage and direct p53 activation with nutlin-3. p53-dependent induction of expression was further proven in a panel of Burkitt’s lymphoma (BL) cell lines including cell lines with genetically engineered knockout or knockdown of p53. p53 ChIP demonstrated direct binding of p53 to the NEAT1 promoter. This provides first evidence of p53-dependent regulation of long non-coding RNAs in CLL and BL. The discovery of p53-dependent NEAT1 induction, which is an integral part of nuclear paraspeckles, paves the way for further research on the role of paraspeckles in tumor cell apoptosis and resistence. The current work identifies additional components of the p53-dependent DNA damage response in lymphoma. The results of these studies provide new insight into the involvement of miRNAs and lncRNAs in two key signaling pathways regulating cell survival and treatment resistance in CLL and lymphoma. Die chronisch lymphatische Leukämie (CLL) ist die häufigste Form der Leukämie in…