Noxa is required for apoptosis induced by the combination of vinblastine plus ABT-737. (A, B) Freshly-isolated lymphocytes from CLL patients were incubated with 0–1 μM vinblastine for various times and then harvested for total RNA or protein. (A) Quantitative RT-PCR was performed for Noxa, using GAPDH as a control. (B) Immunoblotting was used to determine protein expression; lysates from THP-1 cells were used as a control. Data shown is a representative from three patients. (C) NB4 or (D) CLL cells were transfected with scrambled or Noxa siRNA, and incubated with drugs for 6 h prior to harvest. A representative of three separate Noxa-targeting experiments for each cell type is shown. Noxa siRNA significantly reduced the percentage of cleaved PARP induced by vinblastine + ABT-737; the reduction in NB4 cells averaged 54%, range 40–68% (p<0.005); the reduction in CLL cells averaged 24%, range 17–36% (p=0.05). The THP-1 control lanes were graphically pasted from a different section of the same western blot.