The anticancer activity of
cationic antimicrobial peptides (AMPs) has become more interesting because some AMPs have selective recognition against
cancer cells. However, their antitumor properties and underlying mechanisms in
cancer cells have not been clearly understood. In this study, we evaluated the effects of KT2 (
lysine/
tryptophan-rich
AMP) on the cellular uptake and internalization mechanism, cell viability, surface charge of the cell membrane, membrane integrity, apoptotic cell death, and autophagy in human HCT 116
colon cancer cells. We found that KT2 interacted with the cell membrane of HCT 116 cells and was internalized into HCT 116 cells via
clathrin-mediated and caveolae-mediated endocytosis mechanisms. The interaction of KT2 with cells caused cell membrane structure change, elevated membrane permeability, and KT2 also affected the
lipid component. The results of atomic force microscopy showed cellular membrane defects of KT2-treated cells. The internalized KT2 induced nuclear condensation and apoptotic cell death. It elevated the apoptotic factor levels including those of
cytochrome c and
apoptosis-inducing factor. Furthermore, KT2 inhibited autophagy by the suppression of autophagy-related 5, autophagy-related 7, autophagy-related 16 like 1, and
Beclin-1 proteins. In conclusion, these results revealed the cytotoxicity of cationic KT2 against HCT 116 cells and may help to clarify the interactions between cationic AMPs and
cancer cells.