Plasma exosome microRNAs are indicative of breast cancer

Abstract

BackgroundmicroRNAs 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.MethodsExosomes 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.ResultsSmall 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.ConclusionsOur 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-016-0753-x) contains supplementary material, which is available to authorized users.

Novel determinants of mammalian primary microRNA processing revealed by systematic evaluation of hairpin-containing transcripts and human genetic variation

“…HepG2) published by the Mendell laboratory (Chang et al 2015), as well as publicly available mature miRNA sequencing data from other laboratories (Bogerd et al 2014;Cao et al 2016;Hannafon et al 2016). By examining miRNAs with a higher mature-to-primiRNA ratio versus those with a lower ratio, we observed significant enrichment for optimal stem length or CNNC, and a stronger enrichment when both features were present (Supplemental Fig.…”

Exosomal MicroRNA MiR-1246 Promotes Cell Proliferation, Invasion and Drug Resistance by Targeting CCNG2 in Breast Cancer

“…2B). Since miR-1246 has significantly high expression at the extracellular level in MDA-MB-231 cells compared to HMLE cells and has been shown to play a vital role in breast cancer invasion and metastasis [13], we focused on miR-1246 in the following experiments. Furthermore, we analyzed the expression levels of miR-1246 in breast cancer and normal breast tissues by qRT–PCR.…”

Cell‐to‐cell communication: microRNAs as hormones

“…showed that miR‐1246 was upregulated in exosomes from breast cancer cells compared to normal mammary epithelial cells and mouse plasma. When they analyzed human plasma samples, miR‐1246 and miR‐21 were detected at significantly higher levels in the plasma exosomes of 16 breast cancer patients as compared to the plasma exosomes of healthy control samples (Hannafon et al ., 2016). In another example, Zhang et al .…”