Micro RNA-155 influences B-cell receptor signaling and associates with aggressive disease in chronic lymphocytic leukemia

Abstract

High-level leukemia cell expression of micro-RNA 155 (miR-155) is associated with more aggressive disease in patients with chronic lymphocytic leukemia (CLL), including those cases with a low-level expression of ζ-chain-associated protein of 70 kD. CLL with highlevel miR-155 expressed lower levels of Src homology-2 domain-containing inositol 5-phosphatase 1 and were more responsive to B-cell receptor (BCR) ligation than CLL with low-level miR-155. Transfection with miR-155 enhanced responsiveness to BCR ligation, whereas transfection with a miR-155 inhibitor had the opposite effect. CLL in lymphoid tissue expressed higher levels of miR155HG than CLL in the blood of the same patient. Also, isolated CD5brightCXCR4dim cells, representing CLL that had been newly released from the microenvironment, expressed higher levels of miR-155 and were more responsive to BCR ligation than isolated CD5dimCXCR4bright cells of the same patient. Treatment of CLL or normal B cell swith CD40-ligandor B-cell-activating factor upregulated miR-155 and enhanced sensitivity to BCR ligation, effects that could be blocked by inhibitors tomiR-155. This study demonstrates that the sensitivity to BCR ligation can be enhanced by high-level expression of miR-155, which in turn can be induced by crosstalk within the tissue microenvironment, potentially contributing to its association with adverse clinical outcome in patients with CLL. © 2014 by The American Society of Hematology.