ANPEP and acute myeloid leukemia: The AML cell lines (U937, HL-60, NB4 and THP-1) rapidly underwent death after CNGRC-GG-D(KLAKLAK)2 (NGR-peptide-1) treatment (as evidenced by PS externalization and cell shrinkage), whereas CNGRC-G, D(KLAKLAK)2 (free peptide-1) and CNGRC-GG-LVTT did not affect cell viability, thus indicating that the lethal action of NGR-peptide-1 is both dependent on CD13 targeting and D(KLAKLAK)2.