A Cicada Antimicrobial Peptide, Cryptonin, Exhibits Potent Antitumor Activity by Necrosis on Human Melanoma Cells

Antimicrobial peptides are the first defense molecules against various organisms such as bacteria, fungi and are produced by different organisms. In this study, we aimed to investigate the anticancer effects of an insect antimicrobial peptide, cryptonin isolated from the hemolymph of cicada, Cryptotympana dubia on malignant melanoma cells. Cryptonin decreased the cell viability in a dose and time-dependent manner and these effects are more in metastatic cells than in other cell lines. The release of LDH from damaged cells and the detection of HMGB1 in cell culture media after peptide treatment indicated that cryptonin could induce cell necrosis and this cell death may activate an immune response. The peptide also increased the necrotic cell nucleus stained with ethidium bromide. According to reactive oxygen species production and mitochondrial membrane depolarization results, the apoptotic effect of the peptide was low in melanoma cells. Although the peptide killed the keratinocytes in vitro, cryptonin or cryptonin- derived peptide may have potential use in the treatment of malignant melanoma.