Journal
BREAST CANCER RESEARCH
Volume 18, Issue -, Pages -Publisher
BMC
DOI: 10.1186/s13058-016-0753-x
Keywords
Exosomes; Breast cancer; microRNA; Biomarker; Patient-derived xenograft
Categories
Funding
- National Institute of General Medical Sciences of the National Institutes of Health [U54GM104938]
- American Cancer Society [CNE-117557]
- NIH OK-INBRE program [3P20RR016478-09S2]
- Oklahoma Center for the Advancement of Science and Technology [HR14-147]
- Functional Genomics Core facility at the Peggy and Charles Stephenson Cancer Center
- DNA Sequencing and Genomics facility in the Laboratory for Molecular Biology and Cytometry Research at the University of Oklahoma Health Sciences Center
- PDX-PCT Core (Patient-Derived Xenograft and Preclinical Therapeutics Core) Facility at the Oklahoma Medical Research Foundation
- Imaging Core Facility at the Oklahoma Medical Research Foundation
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Background: microRNAs are promising candidate breast cancer 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. Our first step towards this direction relates to capturing and analyzing the contents of exosomes, which are small secretory vesicles that selectively encapsulate microRNAs indicative of their cell of origin. To our knowledge, circulating exosome microRNAs have not been well-evaluated as biomarkers for breast cancer diagnosis or monitoring. Methods: Exosomes were collected from the conditioned media of human breast cancer cell lines, mouse plasma of patient-derived orthotopic xenograft models (PDX), and human plasma samples. Exosomes were verified by electron microscopy, nanoparticle tracking analysis, and western blot. Cellular and exosome microRNAs from breast cancer cell lines were profiled by next-generation small RNA sequencing. Plasma exosome microRNA expression was analyzed by qRT-PCR analysis. Results: Small RNA sequencing and qRT-PCR analysis showed that several microRNAs are selectively encapsulated or highly enriched in breast cancer exosomes. Importantly, the selectively enriched exosome microRNA, human miR-1246, was detected at significantly higher levels in exosomes isolated from PDX mouse plasma, indicating that tumor exosome microRNAs are released into the circulation and can serve as plasma biomarkers for breast cancer. This observation was extended to human plasma samples where miR-1246 and miR-21 were detected at significantly higher levels in the plasma exosomes of 16 patients with breast cancer as compared to the plasma exosomes of healthy control subjects. Receiver operating characteristic curve analysis indicated that the combination of plasma exosome miR-1246 and miR-21 is a better indicator of breast cancer than their individual levels. Conclusions: Our results demonstrate that certain microRNA species, such as miR-21 and miR-1246, are selectively enriched in human breast cancer exosomes and significantly elevated in the plasma of patients with breast cancer. These findings indicate a potential new strategy to selectively analyze plasma breast cancer microRNAs indicative of the presence of breast cancer.
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