Cells are exposed to various concentrations of MG-132 for 24, and 48 hours. Supernatant and monolayer cells are harvested by centrifugation and fixed in 70% ethanol in PBS for staining with acridine orange. Equal volumes of cells and acridine orange (5 mg/mL in PBS) are mixed on a microscope slide and examined by fluorescence microscopy. For annexin V analysis, cells are harvested by centrifugation and stained with annexin V and propidium iodide. For cell cycle analysis, cells are rehydrated in PBS at room temperature for 10 minutes, followed by staining with propidium iodide (5 mg/mL). All samples are analyzed using a Coulter Epics XL flow cytometer.