Selective cancer cell cytotoxicity of enantiomeric 9-mer peptides derived from beetle defensins depends on negatively charged phosphatidylserine on the cell surface

Four enantiomeric 9-mer peptides named D-peptide A, B, C and D were designed and synthesized on the basis of 43-mer insect defensins from two beetles. The D-9-mer peptides maintained bacterial membrane disruptive activity similar to the original peptides and also showed various extents of growth inhibitory activity against different cancer cell lines. Of these peptides, D-peptide B exhibited the highest selective cancer cell cytotoxicity against the mouse myeloma cell line, P3-X63-Ag8.653. Flow cytometric and scanning electron microscopic analysis revealed D-peptide B disrupts mouse myeloma membrane construction, whereas no cytotoxic effect on normal leukocytes was observed. Moreover, a strong correlation between negatively charged phosphatidylserine (PS) density in cancer cell membrane surface and sensitivity to D-9-mer peptides were observed in various cancer cell lines. These results suggest that D-9-mer peptides have negative charge-dependent selective cancer cell cytotoxicity targeting PS in the cancer cell membrane. In addition, synergic growth inhibitory activity against mouse myeloma was observed in combinations of D-peptide B and dexamethasone. These results suggest D-9-mer peptides are promising candidates for novel anticancer drugs. Crown Copyright (c) 2008 Published by Elsevier Inc. All rights reserved.