Abstract 146: MicroRNA-150 expression induces differentiation of myeloid leukemias

Abstract

Abstract Blocked myeloid differentiation is a major feature of chronic myeloid leukemia (CML) disease progression and acute myeloid leukemia (AML). Normal myeloid differentiation is a tightly controlled process involving the coordinated action of specific transcription factors, which are dysregulated by chromosomal translocations, DNA mutations, epigenetic changes, and aberrant gene and microRNA (miRNA) expression in leukemias. Previously, we identified decreased miR-150 expression in CML and AML cell lines and primary cells when compared to normal bone marrow, and determined miR-150 expression is decreased in CML by the Bcr-Abl fusion protein. Furthermore, lentiviral expression of miR-150 in AML cell lines and primary CML patient samples induced myeloid differentiation as detected by CD11b expression, morphologic differentiation, and colony forming ability in methylcellulose, both in the absence and presence of the differentiating agents. In this study, we elucidated the targets responsible for miR-150 induced differentiation. Expression of the validated miR-150 target MYB, a transcription factor involved in blocking differentiation in progenitor cells, was only decreased in miR-150 expressing cells in the presence of differentiating agent all-trans retinoic acid (ATRA). Furthermore, lentiviral overexpression of MYB lacking miR-150 binding sites in the 3′-UTR partially decreased the CD11b expression in the presence and absence of ATRA in both control and miR-150 expressing HL60 cells. These results suggest additional miR-150 targets are involved in differentiation besides MYB. To identify additional miRNA-150 targets, we profiled changes in mRNAs associated with the RNA-induced silencing complex (RISC) using RNA-immunoprecipitation of Ago2 followed by microarray gene expression profiling in miR-150 versus control HL60 cells. Furthermore, although almost all functional investigations have focused on the mature strand, we have found that miR-150 and its partner star strand miR-150* are expressed at almost equal levels in normal myeloid hematopoietic cells, and are investigating the individual contributions of their separate targets in induction of differentiation. In conclusion, miR-150 expression promotes myeloid differentiation through targeting transcription factor MYB and additional targets, while downregulation of miR-150 in myeloid leukemias contributes to the block in differentiation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 146. doi:1538-7445.AM2012-146