Glucocorticoid-regulated microRNAs and mirtrons in acute lymphoblastic leukemia

Glucocorticoids (GC) have a major impact on the biology of normal and malignant cells of the lymphoid lineage. This includes induction of apoptosis which is exploited in the therapy of acute lymphoblastic leukemia (ALL) and related lymphoid malignancies. MicroRNAs (miRNAs) and the related mirtrons are ~22 nucleotide RNA molecules implicated in the control of essential biological functions including proliferation, differentiation and apoptosis. They derive from polymerase-II transcripts but whether GCs regulate miRNA-encoding transcription units is not known. We investigated miRNA/mirtron expression and GC regulation in 8 ALL in vitro models and 13 ALL children undergoing systemic GC monotherapy using a combination of expression profiling techniques, real time RT-PCR and northern blotting to detect mature miRNAs and/or their precursors. We identified a number of GC-regulated miRNAs/mirtrons, including the myeloid-specific miR-223 and the apoptosis and cell cycle arrest-inducing mir15~16 cluster. Thus, the observed complex changes in miRNA/mirtron expression during GC treatment might contribute to the anti-leukemic GC effects in a cell context dependent manner.

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Rainer J, Ploner C, Jesacher S, Ploner A, Eduardoff M, Mansha M, Wasim M, Panzer-Grümayer R, Trajanoski Z, Niederegger H, Kofler R