||HT29, MKN-45, and MDA-MB-231 cells are seeded in black 96-well plates at 5 × 103 cells per well overnight in a medium with 10% FBS. The next day, cells are treated with increasing concentrations of ARQ-197 (0.03-10 μM) for 24, 32, and 48 hours at 37 °C. After ARQ-197 treatment, the drug-containing medium is removed and cells are incubated for at least 10 minutes in a labeling solution (10 mM HEPES, 140 mM NaCl, and 6 mM CaCl2) containing 2 μg/mL Hoescht 33342 (blue channel), 500-times diluted Annexin V-FITC (green channel), and 1 μg/mL propidium iodide (red channel). High-content image acquisition and analysis are carried out. The program is set to take four images per well. The exposure time is set at 16.7 ms/10% gain, 500 ms/35% gain, and 300 ms/30% gain for the 4,6-diamidino-2-phenylindole, FITC, and rhodamine channels, respectively. Images are processed and the numbers of positive cells for each channel and each condition are determined. In addition, HT29 cells are treated with increasing concentrations of ARQ-197 for 32 hours in the absence or the presence of 25, 50, and 100 μM ZvAD-FMK (irreversible general caspase inhibitor), and the same procedures are undertaken. All experiments are done in triplicate. To determine whether the apoptotic effect is due to c-Met inhibition, the effect of ARQ-197 when glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and c-Met are knocked down using siRNA is investigated. HT29, MKN-45, and MDA-MB-231 cells are transfected with a nontargeted control siRNA, a gapgh-targeted control siRNA, or a met-targeted siRNA. After 3 days, c-Met, GAPDH, and β-actin expression levels are determined using specific antibodies. To determine if the effect is caspase dependent, HT29, MKN-45, and MDA-MB-231 cells are transfected with a met-targeted siRNA for 2 days and incubated in the absence or the presence of increasing concentrations of ZvAD-FMK for 1 additional day. A nontargeted siRNA and a gapgh-targeted siRNA (siRNA GAPDH) are also transfected in parallel, as controls. Cells are then stained with Annexin V-FITC and propidium iodide, and the percentage of apoptotic cells is determined.