FIGURE 6. Effect of treatment of Smac on levels of XIAP protein in IEC-6 cells exposed to Smac. A, Representative autoradiograms of Western immunoblots from IEC-6 cells exposed to 0.5 mmol/L TDCA for 6 days and Smac at the concentration of 1 μg/mL during the last 24 hours. Cells were grown in DMEM with 5% dialyzed FBS in the presence or absence of TDCA for 6 days. Whole cell lysates were harvested and applied to each lane equally (20 μg), and levels of XIAP (57 kDa) were identified by probing nitrocellulose with the specific anti-XIAP antibody. Actin immunoblotting was performed as an internal control for equal loading. B, Quantitative analysis of XIAP immunoblots by densitometry from cells described in A. Values are 3 separate experiments. *P < 0.05 versus TDCA alone.