Abstract 14414: Embryonic Stem Cell Derived Exosomes Enhance Anti-Tumor Efficacy of Doxorubicin and Improve Cardiac Function in Triple-Negative Breast Cancer Xenograft Mice

Abstract

Background: Doxorubicin (Dox) is a potent chemotherapeutic drug widely used for the treatment of triple negative breast cancer (TNBC). However, Dox treatment results in inadvertent cardiotoxic effects which often require supplemental therapy. We previously showed that treatment with embryonic stem cells derived exosomes (ES-Exos) enhanced chemosensitivity of Dox in breast cancer cells. Here we tested the hypothesis whether adjuvant therapy with ES-Exos in mice with orthotopic TNBC xenograft can enhance the anti-tumor effect of Dox and improve cardiac function. Methods and Results: Athymic female nude mice (6-wk old) were injected with human MDA-MB-231-Luc cell line in mammary intraductal T4 region to generate orthotopic xenografts of TNBC. After 2 weeks of tumor growth, mice (n=10/group) were treated for 4 weeks with: Saline (Con); Dox (5 mg/kg/week); ES-Exos (50 μg, twice a week); Dox+ES-Exos; and MEF (50 μg/twice a week; non-stem cell exosomes derived from mouse fibroblasts). ES-Exos were labelled with ExoGlow-Vivo near-IR dye to track the localization of exosomes in the tumor. Treatment with Dox+ES-Exos and Es-Exos showed improved survival as compared to Dox (2 deaths) and Con (3 deaths) (Fig.A) . Tumor size was significantly reduced with Dox+ES-Exos and ES-Exos treatments as compared to Con and Dox treatment (Fig.B) . Cardiac function measured by echocardiography showed improved ejection fraction in Dox+ES-Exos and ES-Exos as compared to Con group (Fig.C) . Cell proliferation rate assessed by Ki-67 score with immunofluorescence showed significantly higher rate in Con as compared to Dox and Dox+ES-Exos groups. RNA seq analysis identified upregulation of unique antitumorigenic regulators such as Semaphorin 5 (Sema5) and FOXO15 in ES-Exos compared to MEF, which may contribute to the therapeutic effect. Conclusion: Treatment with ES-Exos may be a promising novel strategy to improve chemosensitivity with attenuation of its cardiotoxic effect in TNBC.