Abstract 7252: Characterization of targeting peptide sequences for peptide-mediated delivery of siRNA in HER2+ breast cancer
Authors: Miserendino Audreanna , Tekle Sevrina , Kalogeros James , Alexander-Bryant Angela 
Published: March 2024

Abstract
Introduction: This work presents the characterization of two novel HER2 targeting peptides to measure which has the most compatible properties to be used as a siRNA carrier to knock down the CD44 gene in HER2+ breast cancer.
Procedures: Targeting peptides were electrostatically complexed with non-targeting siRNAs at different N:P ratios to determine the minimum binding ratios needed to form nanoparticles. Different ratios of peptide-siRNA complexes were tested to determine the minimum molar ratio at which the peptides would protect siRNA from degradation. Cytotoxicity assays were performed to determine cytotoxicity levels at different peptide concentrations. Dynamic light scattering assay was performed to determine peptide-siRNA nanoparticle size and zeta potential. Immunofluorescent microscopy was used to determine the targeting of the peptide to HER2+ cells compared to cells not expressing HER2.
Summary of Results: Peptide-siRNA complexes for the P51 and P25 peptides formed at a minimum 20:1 N:P ratio. P25 and P51 peptides both successfully protects the siRNA at N:P ratios from 20:1 to 60:1 for both degradation agents. Cytotoxicity assays show that in the SKBR3 cell line, the P25 and P51 peptides both showed above 80% viability until the 70:1 ratio; however, in the BT474 cell line, the P25 showed above 80% viability to the 50:1 ratio, but the P51 was only viable in the 20:1 ratio. The results of these studies illustrate how both peptides protect siRNA but that the P51 peptide is toxic to some HER2+ breast cancer cell lines.
Conclusions: Results show that both peptides target HER2+ breast cancer and are compatible carriers of siRNA, protecting the siRNA well within a cell-like environment. However, from MTS studies, P25 appears less cytotoxic to the cell lines than P51, which shows higher cytotoxicity at high molar ratios. We observed that the P25 protects siRNA from degradation, is cytocompatibility, and promotes efficient internalization into HER2+ cell lines. Future work will include the development of a tandem peptide, including a targeting peptide fused with a fusogenic peptide to increase cancer targeting and efficacy of this targeted treatment.
Acknowledgments: This research was supported in part by the Dabo Swinney All-In Foundation as well as Materials Assembly and Design Excellence in South Carolina (MADE in SC) under the National Science Foundation EPSCoR Program under NSF Award #OIA-1655740. Data presented in this material was partially collected using SC BioCRAFT facilities supported by the National Institute of General Medical Sciences (NIGMS) of the National Institutes of Health under award number P30 GM131959.
Citation Format: Audreanna Miserendino, Sevrina Tekle, James Kalogeros, Angela Alexander-Bryant. Characterization of targeting peptide sequences for peptide-mediated delivery of siRNA in HER2+ breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7252.