Fig. 9.

Knockdown of Bim or Noxa or enforced the expression of Mcl-1 renders cells less susceptible to GST-MDA-7/IL-24 lethality. U937 cells in which Bim (A, inset) or Noxa (B, inset) was stably knocked down with shRNA, and their control counterpart shGFP-transfected cells were lysed, and protein lysates were subjected to Western blot analysis to monitor down-regulation of Bim and Noxa. Cells were then exposed to GST-MDA-7/IL-24 (150 or 200 nM) for 48 h, after which the extent of cell death was determined using the Annexin V/PI staining assay (A and B). C, U937 cells ectopically expressing Mcl-1 or the empty vector (pCEP4) were exposed to GST-MDA-7/IL-24 for 48 h, after which the extent of cell death was monitored as above. Protein lysates were also prepared from cells before treatment and Mcl-1 protein levels were monitored by Western blot analysis (C, inset). *, significantly less than values obtained for pCEP4 cells (P < 0.01). D, U937 cells in which Bak or Bax was stably knocked down with shRNA or their control counterpart cells transfected with GFP-shRNA (shGFP) were exposed to GST-MDA-7/IL-24 for 48 h, after which the extent of cell death was monitored using the Annexin V/PI staining assay. For all studies, values represent the means for three separate experiments ± S.D. For A, B, and D, *, significantly lower than values obtained for shGFP-transfected cells (P < 0.05).