Anticancer Activity and Mechanism of Action of kla-TAT Peptide

Conjugation of cell-penetrating peptides to anticancer peptides is an effective strategy to enhance tumor treatment. The hybrid peptide, kla-TAT, by attaching the TAT peptide to the C-terminus of the pro-apoptotic peptide kla exhibited strong anticancer activity when co-administration with other peptide, but the systematic mechanism was not clear. In this study, the mechanisms of action of kla-TAT including the uptake pathway, distribution in cytoplasm, apoptosis-inducing ability and micro-morphology were investigated. The results indicated that the hybrid peptide internalized into A549 cells through two transmembrane mechanisms: endocytosis mediated by the clathrin-mediated endocytosis route and the rapid membrane disruption mechanism. Peptides that were endocytosed could interact with the mitochondrial membrane, while peptides internalized by disrupting the cell membrane caused disruption of the mitochondrial membrane. Thus, the hybrid kla-TAT peptide transfers through the cell membrane, inducing apoptosis by destroying the mitochondrial membrane and causethe expression of cyclin-D1 down-regulation. Meanwhile, the changes of the micro-morphology of the cancer cells was detected using atomic force microscope (AFM) and scanning electron microscope (SEM), which provided the visualized evidence for the mechanism of the peptides.