HGF potentiates TRAIL induced apoptosis in DAOY cells. A. HGF enhances TRAIL induced cell death in a dose-dependent manner as measured by MTT assay. TRAIL at 10 ng/ml induced 50% cell loss. Pre-incubation with HGF (100 ng/ml) for 72 h resulted in 18% more cell death compare to TRAIL alone. B. HGF alone induces DAOY cell growth. Cells were counted every two days after plating with or without HGF in medium containing 10% FBS. HGF promoted cell growth in a dose-dependent manner. C. HGF sensitizes TRAIL (3 ng/ml) induced cell death in a time-dependent manner. Pre-incubation with HGF for at least 24 h was required to enhance TRAIL-induced cell death. D. FACscan analysis of DAOY cell apoptosis using Annexin V-FITC and propidium iodide (PI) staining. Annexin V-positive cells were found to be 6%, 32% and 44% in the presence of HGF (100 ng/ml), TRAIL (10 ng/ml) and HGF+TRAIL, respectively. Experiments were repeated three times. Data represents mean ± SE (N = 9, * P < 0.001).