Pro-apoptotic cationic host defense peptides rich in lysine or arginine to reverse drug resistance by disrupting tumor cell membrane.

Host defense peptides have been demonstrated to exhibit prominent advantages in cancer therapy with selective binding ability toward tumor cells via electrostatic attractions, which can overcome the limitations of traditional chemotherapy drugs, such as toxicity on non-malignant cells and the emergence of drug resistance. In this work, we redesigned and constructed a series of cationic peptides by inserting hydrophobic residues into hydrophilic surface or replacing lysine (K) with arginine (R), based on the experience from the preliminary work of host defense peptide B1. In-depth studies demonstrated that the engineered peptides exhibited more potent anti-cancer activity against various cancer cell lines and much lower toxicity to normal cells compared with B1. Further investigation revealed that compounds I-3 and I-7 could act on cancer cell membranes and subsequently alter the permeability, which facilitated obvious pro-apoptotic activity in paclitaxel-resistant cell line (MCF-7/Taxol). The result of mitochondrial membrane potential assay (ΔΨm) demonstrated that the peptides induced ΔΨm dissipation and mitochondrial depolarization. The caspase-3 cellular activity assay showed that the anti-cancer activity of peptides functioned via caspase-3-dependent apoptosis. The study yielded compound I-7 with superior properties for antineoplastic activity in comparison to B1, which makes it a promising potential candidate for cancer therapy.