Novel face of microRNA-155

Abstract

In this issue of Blood, Jiang and Aguiar1 present a novel mechanism in diffuse large B-cell lymphoma (DLBCL) cell lines by which microRNA (miR)-155 deregulate the crucial retinoblastoma protein (RB)/E2F cascade by repressing SMAD5. The resulting hyperphosphorylated RB is inactive and mediates unrestricted cell-cycle progression. Conversely, they demonstrate in mature B lymphocytes from miR-155 knockout (KO) mice elevated SMAD5 levels accompanied by a hypophosphorylated RB state and a more pronounced cell-cycle arrest. This might contribute to the reduced numbers of germinal center B cells and impaired T cell-dependent antibody response found in these mice. © 2014 by The American Society of Hematology.