Analysis of apoptosis by nuclear staining with Hoechst 33258 (Invitrogen) was performed as previously described (18 (link)). Annexin V/propidium iodide (PI) staining was performed using annexin Alexa 488 (Invitrogen) and PI as described (14 (link)). For analysis of cytochrome c release, mitochondrial and cytosolic fractions were isolated by the differential centrifugation method previously described (19 (link)), and probed by Western blotting for cytochrome c. For colony formation assays, the treated cells were plated in 12-well plates at appropriate dilutions, and allowed to grow for 10–14 days before staining with crystal violet (Sigma). For detection of mitochondrial membrane potential change, the treated cells were stained by MitoTracker Red CMXRos (Invitrogen) for 15 min at room temperature, and then analyzed by flow cytometry.