Breast cancer (BC) is the first cancer in terms of frequency and mortality in women. The aim of this retrospective study is to identify the role of exosome microRNAs (Exo-miRNAs) as possible early biomarkers for identifying patients with higher risk of developing the disease and to personalize their screening programmes. For this purpose, Exo-miRNAs derived from cyst fluid of women affected by Gross Cyst Disease of the Breast (GCDB - a benign disease of the mammary gland associated with a 2-4-fold increase in the risk of developing BC) have been analysed.
Cyst fluids have been selected among samples from 600 patients diagnosed with GCDB between 1985 and 1993, some of whom developed BC during follow-up. Exo-miRNAs were extracted from 400 μl of cyst fluid using the exoRNeasy midi kit (Qiagen). Quality control was assessed by Bioanalyser (Agilent) and Qubit™ using the microRNA Assay Kit (Thermo Fisher Scientific). Exo-miRNome profiles were investigated by microarray on Agilent platform using an optimised protocol (labelling and hybridization on SurePrint Human miR Microarrays 8×60 K and image acquisition using the G2565CA scanner).
A total of 46 samples (23 cases and 23 controls, paired on the bases of clinical and pathological variables) have been analysed. The analysis allowed to identify 10 Exo-miRNAs slightly modulated between cases and controls, and 7 Exo-miRNAs in the Type 1 cyst, that are correlated with a higher risk of developing BC. A single variable logistic regression model on the most expressed Exo-miRNAs detected, pointed out 3 Exo-miRs (miR-6076, miR-3660, miR-6879-5p), whose expression was negatively associated to the development of BC (raw p-value <0.05). A risk score combining the 3 Exo-miRNAs by multivariable logistic regression modelling showed an optimal accuracy (AUC = 0.8, 95%, [CI] 0.6703-0.9282).
These data, to be validated in further 72 samples equally divided between cases and controls, show that Exo-miRNAs are promising minimally invasive biomarkers of BC risk. In order to transfer these data to the clinic, the Exo-miR signature will be tested on plasma of patients with BC enrolled in a prospective study.
Protocol EsomiR- Supported by Compagnia San Paolo ROL ID 32134.
Prof. Lucia Del Mastro.
Fondazione Compagnia di San Paolo, ID ROL: 32134.
All authors have declared no conflicts of interest.