Copy number abnormality, MYC activity and the genetic fingerprint of normal B-cells and the microRNA profile of DLBCL-21

A better understanding of the pathogenesis of diffuse large B-cell lymphoma (DLBCL) has clarified its relationship to normal B-cells, pointed to distinct mechanisms of cell transformation, and facilitated the design of novel treatments. However, these data derive from mRNA genes studies, whereas genome-wide integrative investigations of the role of microRNAs (miRNAs) in DLBCL are still unavailable. We used array-CGH and microarray-based expression analyses to map the abnormalities targeting miRNAs in DLBCLs (n=86). Using training and validation DLBCL cohorts, we defined a collection of miRNAs that robustly segregates these tumors in three unique subsets. This miRNA-driven substructure appears to influence disease outcome, is independent of other mRNA-based DLBCL classifications, and stems from copy number changes targeting the miRNA genome, MYC activity, and the miRNA fingerprints of mature normal B-cells. Our data have uncovered clinically relevant additional molecular complexity in DLBCL and have established a blueprint for the detailed characterizations of miRNAs that are pertinent to B-cell lymphoma biology. Total RNA was isolated from 21 frozen DLBCL samples using Trizol and hybridized (100ng, single channel, Cy3-labeled) to microarray slides (8 complete microarrays/slide) and washed following manufacturer’s guidelines. The arrays were subsequently scanned and the intensity of the hybridization signals obtained using the Feature Extraction software (Agilent Technologies).