Abstract A55: Exosome-associated microRNAs as plasma biomarkers for breast cancer

Abstract

Abstract Introduction: microRNAs are promising candidate biomarkers due to their cancer-specific expression profiles. However, efforts to develop circulating breast cancer biomarkers are challenged by the heterogeneity of microRNAs in the blood. To overcome this challenge, we aimed to develop a molecular profile of microRNAs specifically secreted from breast cancer cells. The key to identifying breast cancer-derived microRNAs relies on capturing and analyzing the contents of exosomes, which are small secretory vesicles that selectively encapsulate microRNAs indicative of their cell of origin. Methods: Exosomes were collected from the conditioned media of breast cancer cell lines, breast ductal fluids, mouse plasma from patient-derived breast tumor orthotopic xenograft models (PDX), and from human plasma samples. Exosomes were verified by electron microscopy and western blot analysis. Cellular and exosome microRNAs from breast cancer cell lines were profiled by next-generation small RNA sequencing. Plasma exosome populations were selected by immunoaffinity isolation utilizing antibodies against CD63 and MUC1. Exosome microRNA expression was measured by qRT-PCR. Results: Small RNA sequencing and qRT-PCR analysis showed that several microRNAs are selectively expressed in breast cancer exosomes. Importantly, human breast cancer specific microRNAs were detectable in PDX mouse plasma. The microRNA expression patterns in the MUC1-precipitated plasma exosomes differed between breast cancer patients and control subjects. These results provide a potential new strategy to selectively analyze plasma breast cancer microRNAs that may be indicative of the presence of breast cancer. Conclusions: Several microRNAs are selectively enriched in breast cancer exosomes, which can be detected in the plasma of PDX mice and breast cancer patients. MUC1 is a viable membrane protein candidate for selective capture of circulating breast cancer specific exosomes from the plasma. These results suggest that selective capture and molecular analysis of breast cancer specific circulating exosomes is a promising strategy for breast cancer biomarker development. Citation Format: Bethany N. Hannafon, Yvonne D. Trigoso, David H. Lum, Alana L. Welm, William C. Dooley, Wei-Qun Ding. Exosome-associated microRNAs as plasma biomarkers for breast cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr A55.