(A) Structures of HMBA and 4a1. (B) MCF7 were treated with vehicle (DMSO), HMBA, or 4a1 using indicated concentrations for 8 h. (C) MDA-MB-231, MDA-MB-468, or BT-474 cells were treated with vehicle (DMSO), 5 mM HMBA, or 50 uM 4a1 for 8 h. Cells were processed for Western blot analyses of HEXIM1 expression. The figures are representative of 3 experiments. * p < 0.01 relative to DMSO treated cells.