Anti‐Tumor Effect of Embryonic Stem Cell Derived Exosomes in Triple Negative Breast Cancer: Potential Role of TCF7‐E‐Cadherin and VEGF

Abstract

BackgroundTriple Negative Breast Cancer (TNBC) is an aggressive form of cancer and accounts for 10‐20 % of all breast cancer types. TNBC patients are widely treated with chemotherapeutic drugs such as doxorubicin (Dox), which is a primary standard of care. Dox treatment results in unwanted side effects including cardiac dysfunction and skeletal muscle weakness. We previously demonstrated the anti‐tumor effects and cardioprotective effects of embryonic stem cell derived exosomes (Es‐Exos) in the xenograft model of TNBC. The purpose of this study was to identify the biomolecules present in Es‐Exos, which may be linked to the anti‐tumor effects in the xenograft model.Methods and ResultsOrthotopic xenograft model of TNBC was generated by injecting human MDA‐MB‐231‐Tom‐Luc cell line in mammary intraductal T4 region of nude mice. Non‐tumor bearing female mice were used as control (NT‐Con;n=6) as applicable. The animals (n=10/group) were randomized to receive Saline (Con); Dox (5 mg/kg/week); Es‐Exos (50 ug/animal/twice a week; Dox+Es‐Exos; Es‐Exos alone and MEF‐Exos‐(mouse embryonic fibroblast cell derived exosomes 50 ug/animal/twice a week) for up to 4 weeks. Skeletal muscle grip strength declined both in Con and upon treatment with Dox in tumor bearing mice as compared to NT‐Con, which was restored upon treatment with Es‐Exos. Cardiac function measured by echocardiography showed decline in ejection fraction (EF) in saline treated tumor bearing Con and in Dox group, when compared to NT‐Con. Treatment with Dox+Es‐Exos and Es‐Exos improved ejection fraction compared to Con and Dox cohort. Treatment with Es‐Exos significantly reduced the tumor size compared to Dox and saline treated Con groups (Con Vs Dox and Dox+Es‐Exos; p‐value <0.05). Picro Sirius red staining showed increased deposition of collagen in saline treated Con, which was reduced in Dox+Es‐Exos and Es‐Exos groups. RNA seq analysis of Es‐Exos identified several anti‐proliferative genes including a 6‐fold expression of Transcription Factor 7 (TCF7) and 6.5‐fold higher expression of E‐Cadherin (CDH1). Immunohistochemistry analysis of tumor tissue showed abundant expression of VEGF in untreated Con, which was reduced by combined treatment with Es‐Exos and Dox.ConclusionEmbryonic stem cells derived exosomes contain anti‐proliferative genes which may possibly lead to their anti‐tumor property in the TNBC tumor model.