The cytotoxic effect of the tetrameric peptide LfcinB (20–25)4 against breast cancer cell line ATCC® HTB-22™ (MCF-7) was evaluated.

The cytotoxic effect against the breast cancer cell line MDA-MB-468 of the palindromic peptide LfcinB (21–25)Pal: 1RWQWRWQWR9 and its analogous peptides, obtained via alanine scanning, was evaluated.

The effect on the cytotoxicity against breast cancer cell lines of the substitution of 26Met residue in the sequence of the Bovine Lactoferricin-derived dimeric peptide LfcinB (20-30)2: (20RRWQWRMKKLG30)2-K-Ahx with amino acids of different polarity was evaluated. The process of the synthesis of the LfcinB (20-30)2 analog peptides was similar to the original peptide. The cytotoxic assays showed that some analog peptides exhibited a significant cytotoxic effect against breast cancer cell lines HTB-132 and MCF-7, suggesting that the substitution of the Met with amino acids of a hydrophobic nature drastically enhances its cytotoxicity against HTB-132 and MCF-7 cells, reaching IC50 values up to 6 µM. In addition, these peptides have a selective effect, since they exhibit a lower cytotoxic effect on the non-tumorigenic cell line MCF-12. Interestingly, the cytotoxic effect is fast (90 min) and is maintained for up to 48 h. Additionally, through flow cytometry, it was found that the obtained dimeric peptides generate cell death through the apoptosis pathway and do not compromise the integrity of the cytoplasmic membrane, and there are intrinsic apoptotic events involved. These results show that the obtained peptides are extremely promising molecules for the future development of drugs for use against breast cancer.

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