Non-steroidal anti-inflammatory drugs conjugated to a synthetic peptide exhibit <i>in vitro</i> cytotoxic activity against cervical cancer and melanoma cells

Previous studies have shown that the palindromic peptide RWQWRWQWR derived from bovine lactoferricin (LfcinB) has exhibited selective <i>in vitro</i> cytotoxic effects against multiple cancer cells such as cervical, breast, and prostate cancer. We designed and synthesized peptides based on this palindromic sequence conjugated with non-steroidal anti-inflammatory drugs (NSAIDs) such as naproxen and ibuprofen to obtain novel hybrid peptides that could trigger inflammatory processes within cancer cells. Incorporating the non-natural amino acid ornithine as a spacer was done to improve the aqueous solubility of the NSAID-peptide conjugates. The antibacterial activity of the conjugated peptides was evaluated, and these peptides showed significant activity against <i>E. coli</i> strain ATCC 25922, with MIC values of 12 μM. Cytotoxicity was assessed in human cervical cancer cells (HeLa) and human melanoma cells (A375), showing that the NSAID-conjugated peptides retained and even exhibited better anticancer activity compared to the palindromic peptide from which they were derived. The NSAID-LfcinB conjugates showed good selectivity towards cancer cells in the concentration ranges evaluated, being non-hemolytic. The cytotoxic effect of the IBU-Orn₃-1 and NAP-Orn₃-1 peptides was rapid and selective, inducing severe morphological changes, including rounding, shrinkage, and vacuole formation, which are associated with apoptosis. Flow cytometry assays revealed that the ibuprofen-conjugated palindromic sequence induced apoptosis independently of peptide concentration and treatment duration. These results suggest that the palindromic peptide RWQWRWQWR could be used for new applications in cancer research, such as delivering small molecules with anti-inflammatory activity in tumoral environments. The conjugation of NSAIDs to anticancer peptide sequences is a novel, viable, and rapid strategy that facilitates the synthesis of hybrid peptides with enhanced anticancer activity, thereby expanding the pool of promising molecules for preclinical and clinical studies in cancer therapy development.