microRNAome expression in chronic lymphocytic leukemia : comparison with normal B cell subsets and correlations with prognostic and clinical parameters

Purpose: Despite its indolent nature, chronic lymphocytic leukemia (CLL) remains an incurable disease. To establish the potential pathogenic role of microRNAs (miRNAs), the identification of deregulated miRNAs in CLL is crucial. Experimental Design: We analyzed the expression of 723 mature miRNAs in 217 early stage CLL cases and in various different normal B-cell subpopulations from tonsils and peripheral blood. Results: Our analyses indicated that CLL cells exhibited a miRNA expression pattern that was most similar to the subsets of antigen-experienced and marginal zone-like B-cells. These normal subpopulations were used as reference to identify differentially expressed miRNAs in comparison with CLL. Differences related to the expression of 25 miRNAs were found to be independent from IGHV mutation status or cytogenetic aberrations. These differences, confirmed in an independent validation set, led to a novel comprehensive description of miRNAs potentially involved in CLL. We also identified miRNAs whose expression was distinctive of cases with mutated versus unmutated IGHV genes or cases with 13q, 11q, and 17p deletions and trisomy 12. Finally, analysis of clinical data in relation to miRNA expression revealed that miR-26a, miR-532-3p, miR-146-5p and miR-29c* were strongly associated with progression free survival. Conclusion: This study provides novel information on miRNAs expressed by CLL and normal B-cell subtypes, with implication on the cell of origin of CLL. In addition, our findings indicate a number of deregulated miRNAs in CLL which may play a pathogenic role and promote disease progression. Collectively, this information can be utilized for developing miRNA-based therapeutic strategies in CLL