The Physiological microRNA Landscape in Nipple Aspirate Fluid: Differences and Similarities with Breast Tissue, Breast Milk, Plasma and Serum

Abstract

Background: MicroRNAs (miRNAs) target 60% of human messenger RNAs and can be detected in tissues and biofluids without loss of stability during sample processing, making them highly appraised upcoming biomarkers for evaluation of disease. However, reporting of the abundantly expressed miRNAs in healthy samples is often surpassed. Here, we characterized for the first time the physiological miRNA landscape in a biofluid of the healthy breast: nipple aspirate fluid (NAF), and compared NAF miRNA expression patterns with publically available miRNA expression profiles of healthy breast tissue, breast milk, plasma and serum. Methods: MiRNA RT-qPCR profiling of NAF (n=41) and serum (n=23) samples from two healthy female cohorts was performed using the TaqMan OpenArray Human Advanced MicroRNA 754-Panel. MiRNA quantification data based on non-targeted or multi-targeted profiling techniques for breast tissue, breast milk, plasma and serum was retrieved from literature by means of a systematic search. MiRNAs from each individual study were orderly ranked between 1-50, combined into an overall ranking per sample type and compared. Findings: NAF expressed 11 unique miRNAs and shared 21/50 miRNAs with breast tissue. Seven miRNAs were shared between the five sample types. Overlap between sample types varied between 42-62%. Highly ranked NAF miRNAs have established roles in breast carcinogenesis. Interpretation: This is the first study to characterize and compare the unique physiological NAF-derived miRNA landscape with the physiological expression pattern in breast tissue, breast milk, plasma and serum. Breast-specific sources did not mutually overlap more than with systemic sources. Given their established role in carcinogenesis, NAF miRNA assessment could be a valuable tool in breast tumor diagnostics. Funding: This work was supported by the Dutch Cancer Society (KWF) under grant number UU2016-8191. This was previously A Sister’s Hope grant with grant number 2012.WO38.C142. Declaration of Interests: The authors declare no potential conflicts of interest. Ethics Approval Statement: These studies were approved by the Institutional Review Boards of the UMC Utrecht and other participating hospitals and the UMC Utrecht Biobank Research Ethics Committee (TCBio). Informed consent was obtained from all participating women.