EIF4A1 and B-cell chronic lymphocytic leukemia: Although silvestrol induces apoptosis in CLL cells with an IC50 of ~ 10 nM following 72 h of drug exposure [25], it seemed unlikely that the inhibitory effects of eIF4Ai on mRNA translation were a consequence of reduced viability since our experiments were performed at an earlier time point (24 h), in the presence of the caspase inhibitor, Q-VD-OPh, and the cells analyzed for OPP labeling were gated on the viable cell population according to their FFC/SSC.