Knock-down of XIAP by RNA interference sensitizes HL B-cell lines for cytostatic agents. (A) cIAP2, XIAP, caspase-3, Smac, cIAP1, and actin were detected in total cell extracts of L428, L428-scr-shRNA, L428-XIAP-shRNA, L591, L591-scr-shRNA, and L591-XIAP-shRNA by Western blot analysis using specific antibodies. (B) Quantitative analysis of panel A. Graphs of mean band intensity of XIAP from Western blot images were acquired on an Alpha Innotech documentation station. All values were normalized to actin expression levels and are presented as percentage of the mean levels in untreated cells (100%). The SD values were calculated from 3 individual experiments. (C-D) HL B-cell lines L428, L428-scr-shRNA, L428-XIAP-shRNA, L591, L591-scr-shRNA, and L591-XIAP-shRNA were left untreated or treated for 24 hours with STS (0.5 μM), etoposide (50 μM), doxorubicin (1 μM), vinblastine (0.2 μM), or cisplatin (200 μM). Viable cell number was determined using an XTT assay (C). PARP cleavage was detected in nuclear extracts by mouse anti-PARP antibody (D).