Pattern of Mir-155 and PU.1 Expression in CLL/SLL and Aggressive Lymphomas

Abstract 4600 MicroRNA miR-155 represents a candidate pathogenic factor in chronic lymphocytic leukemia (CLL) and lymphomas (Eis PS, et al. 2005, Fulci V, et al. 2007, Calin GA, et al. 2005, Kluiver J, et al. 2005, Metzler M, et al. 2004, van den Berg A, et al. 2003., Vargova K. et al 2011). In diffuse large B-cell lymphoma (DLBCL) expression of miR-155 was associated with NFkB pathway (Rai et al., 2008). In addition, increased miR-155 levels were associated with more aggressive (Activated B-cell like) DLBCL (Eis et al. 2005). The targets of up-regulated miR-155 apparently include a key hematopoietic transcription factor PU.1. Down-regulation of PU.1 represents an important and critical step for both myeloid as well as lymphoid tumorigenesis. We herein found the increased levels of miR-155 coupled with downregulation of its target PU.1 are frequent events in B cells of a vast majority of CLL patients (N=169). To advance understanding of miR-155 and PU.1 in lymphoid malignancies we studied lymph node biopsies derived from patients with lymphomas. We show that increased miR-155 levels are also found in DLBCL (N=31, P Disclosures: No relevant conflicts of interest to declare.