ANXA5 and neoplasm: Importantly, the PC-3 tumor cells did not present any fluorescence signals of both Annexin V-FITCand PI at 6 h post-treatment of TRAIL, indicating that Apo-S-Ac3ManNAz can visualize the early stage of apoptosis, compared to that of Annexin V-FITC- and PI-treated PC-3 tumor cells.