ANXA5 and neoplasm: The PSP1 peptide specifically targeted apoptotic cells in tumors following systemic administration to camptothecin-treated tumor-bearing (H460 cell) mice in comparison with a similar dose of annexin V. Our results suggest that PSP1 offers benefits for molecular imaging of tumor apoptosis compared with annexin V and could be effectively developed into a de novo small molecular probe for imaging of apoptosis in vivo.