Tumor microenvironment-responsive conformational activation of apoA-I mimetic peptides for targeted cancer therapy

Apolipoprotein A-I (ApoA-I) mimetic peptides have garnered attention as potential anticancer agents owing to their role in cholesterol metabolism and ability to interact with the SR-BI receptor. However, their tendency to form lipid-bound structures in circulation limits their tumor-targeting therapeutic potential and raises the risk of off-target effects. In this study, we engineered a stimuli-responsive ApoA-I mimetic peptide by incorporating reactive oxygen species (ROS) -responsive amino acid derivatives into its sequence. Under normal physiological conditions, the peptide adopted a disordered conformation, minimizing nonspecific interactions. In contrast, the exposure to the tumor microenvironment, which is characterized by low pH and elevated ROS, could trigger a conformational transition to a structured <i>α</i>-helical state, thereby enhancing its membrane-disruptive and tumor-targeting capabilities. Molecular dynamics simulations predicted a rapid increase in <i>α</i>-helical content for the peptide candidate 5A under tumor-like conditions. These predictions were experimentally validated using circular dichroism spectroscopy, liposome leakage assays, and transmission electron microscopy, which demonstrated that peptide 5A effectively interacted with lipid membranes only upon activation in a tumor-like environment. <i>In vitro</i> cytotoxicity assays further confirmed the selective anticancer activity of peptide 5A under acidic conditions, while <i>in vivo</i> imaging and tumor inhibition studies in breast cancer models revealed significant tumor accumulation and a tumor growth inhibition rate of up to 71.43% at a 6 mg/kg dose. Our results demonstrated the potential of stimuli-responsive ApoA-I mimetic peptides for targeted cancer therapy, offering a promising strategy to enhance therapeutic efficacy while minimizing systemic toxicity.