The effect of Apo2L/TRAIL on levels of procaspase 8, Bid, a marker of intact mitochondria, and procaspase 3 in Tumor #3 (Apo2L/TRAIL sensitive) and Tumor #4 (Apo2L/TRAIL resistant). Two tumors were removed from each group shown in Figure 5 on day 2 of treatment. The lanes are: (+) - positive control for each antibody; C- two tumors from the control group; T- two tumors from the Apo2L/TRAIL treated group; A. The Apo2L/TRAIL sensitive Tumor #3. By the second day of treatment with Apo2L/TRAIL, the levels of procaspase 8, Bid, the mitochondrial marker and procaspase 3 (outlined) in these tumors are greatly reduced. B. The Apo2L/TRAIL resistant Tumor #4. In the tumor that was resistant to Apo2L/TRAIL treatment, although there is a slightly diminished amount of procaspase 8 and Bid present in these tumors following 2 days of treatment with Apo2L/TRAIL, the levels of the mitochondrial marker and procaspase 3 (outlined) remain comparable to the controls. (In A and B a representative actin loading control is shown for each tumor).