Quantitative miR analysis in chronic lymphocytic leukaemia/small lymphocytic lymphoma - proliferation centres are characterized by high miR-92a and miR-155 and low miR-150 expression.

Proliferation centres (PCs) are histological hallmarks of lymph nodes in chronic lymphocytic leukaemia/small lymphocytic lymphoma (CLL/SLL). Chromosomal abnormalities have already been described to accumulate preferably in the PCs as opposed to the intervening small cell areas. To further characterize the pathogenic role of PCs, the expression levels of 17 selected miRs known to be involved in the development of CLL/SLL were compared in the PCs and the intervening small cell areas in lymph nodes of 15 patients with CLL/SLL. The miR expression levels were also compared to the cytogenetic alterations defined by FISH analysis. Our results show that two known oncomiRs, miR-155 and -92a were upregulated and the tumour suppressor miR-150 was downregulated in the PCs. Low expression of miR-150 was also associated with loss of 11q. In summary we found significantly higher expression of oncomiRs and lower expression of a tumour suppressor miR in PCs of CLL/SLL lymph nodes, which support the hypothesis that the PCs may drive the disease and play a role in progression.