In contrast to the combined effect of XIAP knockdown and TRAIL, no significant increase in cytotoxicity was observed when these agents were combined with XIAP knockdown, compared with the various control groups (Figure 6B and 6D; Table 2 Similar results were obtained with these same agents in the PC-3 prostate cancer cell line (Additional File 4) Table 2 To verify efficient knockdown in the HCT-116 and SW-620 cells, XIAP protein levels were determined in parallel cultures of both cell lines at 48 hr post electroporation (knockdown nadir). This evidence concerns the gene XIAP and prostate carcinoma.