Resistance to ABT-737 correlates with NF-κB–mediated up-regulation of BCL2A1 and BCL-X_L. (A) Expression of BCL2 proteins was assessed by Western blotting after 0 to 24 hours of culture on CD154-expressing cells. (B) Expression of BCL2A1 was assessed by immunohistochemistry on lymph node sections from CLL patients. (C) CLL cells were cultured on CD154-expressing cells for 24 hours and simultaneously exposed to different concentrations of cycloheximide (CHX). Apoptosis was assessed by PS externalization and annexin V/FITC binding (top panel, n = 3). Expression of BCL2 proteins was assessed by Western blotting (bottom panel). (D,E) CLL cells were cultured on CD154-expressing cells for 24 hours and simultaneously exposed to different concentrations of DHMEQ (D) or BMS-34451 (E). Apoptosis was assessed by PS externalization and AnnexinV/FITC binding (top panel, n = 3). Expression of BCL2A1 was assessed by Western blotting (bottom panel).