Abstract
Triple negative breast cancer presents higher mortality and poorer survival rates than other breast cancer (BC) types, due to the proneness to brain metastases formation, which are usually diagnosed at advanced stages. Therefore, the discovery of BC brain metastases (BCBM) biomarkers appears pivotal for a timely intervention. With this work, we aimed to disclose microRNAs (miRNAs) and extracellular vesicles (EVs) in the circulation as biomarkers of BCBM formation. Using a BCBM animal model, we analyzed EVs in plasma by nanoparticle tracking analysis and ascertained their blood-brain barrier (BBB) origin by flow cytometry. We further evaluated circulating miRNAs by RT-qPCR and their brain expression by in situ hybridization. In parallel, a cellular model of BCBM formation, combining triple negative BC cells and BBB endothelial cells, was used to differentiate the origin of biomarkers. Established metastases were associated with an increased content of circulating EVs, particularly of BBB origin. Interestingly, deregulated miRNAs in the circulation were observed prior to BCBM detection, and their brain origin was suggested by matching alterations in brain parenchyma. In vitro studies indicated that miR-194-5p and miR-205-5p are expressed and released by BC cells, endothelial cells and during their interaction. These results highlight miRNAs and EVs as biomarkers of BCBM in early and advanced stages, respectively.
Highlights
In 2020, more than two million new cases of breast cancer (BC) were diagnosed worldwide, comprising the most frequent malignancy among women and being responsible for 684,996 deaths [1]
We observed that plasma Extracellular vesicles (EVs) and non-vesicular particles from the different time points essentially displayed a similar size distribution profile, with most of them presenting a size below 150 nm (Figure 1A), a feature described to correspond to exosome dimensions [10]
Concerning the vesicles mean size, no major differences were observed during the time of metastases development, apart from those at 5 days, which presented on average a higher diameter than at 7 days (p < 0.05, Figure 1B) and that can be explained by the appearance of a small peak of circa 150 nm in the size distribution profile (Figure 1A)
Summary
In 2020, more than two million new cases of breast cancer (BC) were diagnosed worldwide, comprising the most frequent malignancy among women and being responsible for 684,996 deaths [1]. Metastatic brain tumors from BC affect approximately 15% of patients [2], with a propensity of circa 50% in triple negative BC (TNBC) [3] and a poor prognosis, with reports of 1-year survival of only 20% [4] For this dramatic scenario contributes the lack of reliable peripheral biomarkers of BC brain metastases (BCBM) during disease progression, culminating with the disease only being diagnosed at advanced stages. Extracellular vesicles (EVs) and/or small, non-coding regulatory micro RNAs (miRNAs or miR) found in the circulation encompass new candidate disease biomarkers worth exploring Both can be detected in body fluids, holding a role as potential tumor markers and prognostic factors, and providing a powerful minimally-invasive approach for tumor progression assessment [6,7,8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
