Abstract 3241: Peptide Power: A PSMA-targeted CT20 Nanoparticle to Fight Prostate Cancer

Abstract Chemotherapeutic agents within targeted nanoparticles typically trigger cell death not only in tumors cells but also in normal cells that non-specifically uptake these nanoparticles. An alternative approach would be to target the delivery of a therapeutic agent that is toxic to cancer cells while less toxic to non-tumor cells. To accomplish this, a Bax-derived peptide (CT20) was developed as a selective cancer-targeting agent, and a folate-decorated hyperbranched polyester (HBPE) nanoparticle was employed to deliver the peptide to prostate-specific membrane antigen (PSMA) (+) prostate cancer cells. The receptor-targeting capability of folic acid towards PSMA (+) in prostate cancer was examined using a fluorescence activatable probe, folate-S-S-doxorubicin, and the PSMA inhibitor 2-PMPA. Additionally, a folate-decorated HBPE nanoparticle was utilized to targeted-deliver the CT20 peptide to prostate cancer cells in vitro as well as in athymic mice. CT20-encapsulated folate (folate-CT20) nanoparticles were used to determine cell cytotoxicity against PSMA-positive and -negative cells using flow cytometry. Furthermore, cytotoxicity of folate-CT20 nanoparticles towards murine macrophages was evaluated to determine the consequences of non-specific uptake; the FDA-approved doxorubicin was used for comparison. Cell death associated with CT20 was determined through a violet ratiometric membrane asymmetry probe combined with SYTOX AADvanced dead cell stain to evaluate membrane asymmetry and membrane permeability. Folate-CT20 nanoparticles’ tumor-targeting and tumor-killing efficacy was evaluated in athymic mice bearing PSMA (+) tumors and PSMA (-) tumors. Nanoparticles were delivered intravenously through the tail vein and the tumor size was assessed with calipers and ultrasound. Folate-S-S-Doxorubicin was uptaken specifically by PSMA (+) prostate cancer cells showing fluorescence within 12 hours and cell death within 24 hours. Cells that were preincubated with 2-PMPA followed by folate-S-S-Doxorubicin demonstrated no cell-associated fluorescence or cytotoxicity. Similarly, folate-decorated nanoparticles were only internalized by PSMA (+) cells. Cytotoxicity of folate-CT20 nanoparticles towards PSMA (+) cancer cells occurred within 48 hours, while no changes occurred in PSMA (-) cells. When murine macrophages were treated with PSMA-targeting nanocarriers and doxorubicin individually, significant cytotoxicity only occurred in doxorubicin-exposed cells. In vivo, folate-CT20 nanoparticles were capable of preventing further PSMA (+) tumor growth and caused PSMA (+) tumor regression in some cases. Moreover, minimal liver and spleen damage was observed. Herein, we demonstrate that the CT20 peptide is capable of displaying specific lethality towards PSMA (+) prostate cancer cells and that folate-CT20 nanoparticles are promising vehicles to deliver CT20 in vitro and in vivo. Citation Format: Orielyz Flores, Daniel Nierenberg, Ana C. Carr, Rania Bassiouni, Arati Limaye, Santimukul Santra, Charalambos Kaittanis, Annette Khaled, Jesus Manuel Perez. Peptide power: A PSMA-targeted CT20 nanoparticle to fight prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3241. doi:10.1158/1538-7445.AM2017-3241