miR-155 impairs TGF-β1–mediated RB activation in DLBCL miR-155 impairs TGF-β1–mediated RB activation in DLBCL. Western blot analysis of hypo-pRB (left panels) or phospho-Ser780 residue (right panels) was performed in the DLBCL cell lines Ly7 (A), Ly18 (B), and DHL5 (C), genetically modified to express an empty ... miR-155 impairs TGF-β1–mediated RB activation in DLBCL. Western blot analysis of hypo-pRB (left panels) or phospho-Ser780 residue (right panels) was performed in the DLBCL cell lines Ly7 (A), Ly18 (B), and DHL5 (C), genetically modified to express an empty vector (MSCV) or miR-155. Upon TGF-β1 exposure (5 ng/mL), an increase in the abundance of hypo-pRB (active RB) is detected in the MSCV-expressing cell lines and, to a much lesser degree, in their isogenic counterparts expressing miR-155 (left panels). In agreement with this observation, the phosphorylation levels of RB’s Ser780 residue was markedly suppressed by TGF-β1 in MSCV-expressing cells, but not in their isogenic miR-155 counterparts (right panels). Immunoblotting for total RB confirms that miR-155 does not modify its expression level, and equal loading is also verified with β-actin or tubulin. The data shown in this figure were confirmed in 2 to 4 biological replicates. Daifeng Jiang, and Ricardo C. T. Aguiar Blood 2014;123:86-93 ©2014 by American Society of Hematology