Abstract 2079: IONP-LPrA2 and PEG-LPrA2 therapies for triple negative breast cancer

Background: Breast cancer (BC) is an epidemic in the US. It is estimated that there will be over 230,000 new BC diagnoses in 2016. Triple Negative Breast Cancer (TNBC) comprises ∼15% of BC cases and lacks targeted therapeutic options. Obesity and high leptin levels are associated with higher TNBC incidence and poorer patient outcomes. Overexpression of leptin and its receptor, Ob-R, induce BC cell growth and angiogenesis; therefore leptin/Ob-R may serve as a TNBC therapeutic target. We have developed a Leptin Peptide Receptor Antagonist, LPrA2, which effectively inhibits leptin signaling. To increase its efficacy LPrA2 was coupled to iron oxide nanoparticles (IONPs) and polyethylene glycol (PEG), and subsequently tested in vitro and in vivo in obese mice hosting syngeneic TNBC-like mammary tumors. Methods: The conjugation of LPrA2 to IONPs and PEG was confirmed by immunoblotting analysis. E0771, mouse BC cells, which are progesterone receptor and HER2 negative were made insensitive to estrogen stimuli by long-term treatment with Tamoxifen (TAM). Cell cycle and MTT assays were performed to determine the effectiveness of leptin signaling inhibition by conjugated LPrA2 in vitro. C57BL/6 female mice were fed a 60% fat diet to induce obesity. The obese mice were injected with E0771-TAM cells in the mammary fat pad and treated with IONP-LPrA2 and PEG-LPrA2 after tumor development. Obese mice treated with IONP-LPrA2 Scramble (Sc) and PEG-LPrA2 Sc served as negative controls. Results and Conclusion: IONP-LPrA2 and PEG-LPrA2 attenuated leptin signaling in vitro and decreased tumor growth and progression in vivo in comparison to the controls. These findings indicate that conjugated LPrA2 may serve as a targeted therapy for TNBC. IONP-LPrA2 may be especially useful in treating this more aggressive form of BC due to its ability to capture multiple LPrA2 peptides as well as its small and uniform particle size. Citation Format: Tia L. Harmon, Adriana Harbuzariu, Antonio Rampoldi, Courtney Dill, Viola Lanier, Danielle Daley-Brown, Crystal Lipsey, Cynthia Tchio, Lily Yang, Ruben Rene Gonzalez-Perez. IONP-LPrA2 and PEG-LPrA2 therapies for triple negative breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2079.