Defective Drosha Processing Contributes to Downregulation of MiR-15/-16 in Chronic Lymphocytic Leukemia.. Homo sapiens

MIR15A and MIR16-1, located in chromosomal band 13q14, are tumor suppressor miRNAs often deleted and downregulated in chronic lymphocytic leukemia (CLL). This downregulation is not only due to loss of 13q, as it occurs also in 13q+/+ CLL patients. We found that a subgroup of CLL patients has a dysregulation of miR-15 /-16 processing intermediates due to defective processing by Drosha. These patients have reduced levels of miR-15a, miR-16 and miR-15b (another member of the miR-15 family), but not of most other miRNAs. Thus, we show that modulation of miRNA maturation leads to specific downregulation of a family of tumor suppressor miRNAs in leukemic cells. Overall design: 11 normal processing CLL sample; 12 processing defective CLL patients