Bcl-xL mediates TRAIL resistance in the metastatic colon carcinoma cells.

<p><b>A</b>. Silencing Bcl-xL and survivin expression by siRNAs. SW620 cells were transiently transfected with scramble or gene-specific siRNAs for approximately 20 h and analyzed for Bcl-xL and Survivin mRNA level by RT-PCR. <b>B</b>. Silencing Bcl-xL but not survivin expression significantly increased the tumor cell sensitivity to TRAIL-induced apoptosis. The scramble and gene-specific siRNA-transfected cells were cultured in the absence or presence of TRAIL protein for approximately 24 h and analyzed for apoptosis. ** <i>p</i><0.01. <b>C</b>. Overexpression of Bcl-xL and Survivin decreased the tumor cell sensitivity to TRAIL-induced apoptosis. SW620 cells were transiently transfected with Vector control (Vector), Bcl-xL-expressing (Bcl-xL) or Survivin-expressing (Survivin) plasmids for approximately 20 h. The cells were then analyzed for Bcl-xL and Survivin mRNA level by RT-PCR (left panel). The cells were also treated with IFN-γ and TNFα for 4 h, followed by incubation with TRAIL protein for approximately 24 h and analysis for apoptosis by PI staining and flow cytometry analysis (right panel). ** <i>p</i><0.01.