miR-29b suppressed leukemic cell proliferation in SP1/p21–dependent manner. (A) 2A2-miR-29b-ILP (29b) downregulated SP1 and increased p21 expression in the human OSU-CLL cell line (lanes 1 and 2). The siRNA-mediated knockdown of SP1 resulted in increased p21 expression (lanes 3 and 4). (B) Transfection of p21-directed siRNA decreased control (SCR) as well as 2A2-miR29b-ILP (29b) induced p21 protein. (C-D) Accumulation of cells in G0/G1 with concomitant decrease in S/G2/M by miR-29b that is reversed upon SP1 and p21 knockdown in OSU-CLL cells. Panel C shows results from a representative experiment. Panel D presents compiled data from 4 independent experiments.