Cationic lytic-type
peptides have been studied for clinical application in various
infections and
cancers, but their functional cellular mechanisms remain unclear. We generated anti-
cancer epithelial
growth factor receptor (
EGFR)-lytic hybrid peptide, a 32-amino-acid
peptide composed of an EGFR-binding sequence and lytic sequence. In this study, we investigated the distribution of
EGFR-lytic hybrid peptide in BxPC-3 human
pancreatic cancer cells by an immunocytochemical (ICC) method. Distribution of EGFR
protein expression was unchanged
after treatment with
EGFR-lytic peptide compared with non-treated cells. In confocal
laser scanning microscopy, immunostaining of
EGFR-lytic peptide was observed in the cytoplasm, mostly in the form of granules. Some staining was also localized on the mitochondrial membrane. At the ultrastructure level, cells treated with
EGFR-lytic peptide had a low electron density, disappearance of microvilli, and swollen mitochondria. Fragments of cell membrane were also observed in the proximity of the membrane. In immunoelectron microscopy,
EGFR-lytic peptide was observed in the cell membrane and cytoplasm. A number of granules were considered swollen mitochondria. Activation of the
caspase pathway as a result of
mitochondrial dysfunction was also examined to determine the cytotoxic activity of
EGFR-lytic peptide; however, no effect on cell death after EGFR-lytic treatment was observed, and moreover, apoptosis was not found to play a critical role in the cell death mechanism. These results suggest that
EGFR-lytic peptide is localized on cell and mitochondrial membranes, with disintegration of the cell membrane contributing mainly to cell death.