Breast cancer (BrCa) is the most frequent cancer type in women and a leading cause of cancer related deaths in the world. Despite the decrease in mortality due to better diagnostics and palliative care, there is a lack of prognostic markers of metastasis. Recently, the exploitation of liquid biopsies and in particular of the extracellular vesicles has shown promise in the identification of such prognostic markers.
In this study researchers from the Karolinska Institutet compared the proteomic content of exosomes derived from metastatic and non-metastatic human (MCF7 and MDA-MB-231) and mouse (67NR and 4T1) cell lines. They found significant differences not only in the amount of secreted exosomes but most importantly in the protein content of exosomes secreted from metastatic versus non-metastatic ones. The researchers identified periostin as a protein that is enriched in exosomes secreted by metastatic cells and validated its presence in a pilot cohort of breast cancer patient samples with localized disease or lymph node (LN) metastasis.
Characterization and validation of exosomes isolated from patients
with non-metastatic or metastatic breast cancer
A. Nanoparticle Tracking Analysis (NTA) of particles isolated from patients’ plasma with early or late metastatic breast cancer (means +/- SD, 3 patients with early disease and 3 patients with lymph node metastasis, n=1). B. Immuno-EM of exosomes isolated from patient samples, for the indicated proteins. (Scale bar: 100nm) C. Western blot analysis of exosomes (15 μg) secreted from patients with non- or lymph node metastasis, probed for the indicated proteins (n=3).