Clinical implications of extracellular vesicles in prostate and breast cancer

Extracellular vesicles (EVs) are small membrane-derived particles released in physiological and also pathological conditions. EVs can be found in different body fluids, such as blood, urine and saliva, but also into extracellular space of all cell types. EVs carry several biological and genetic information leading to recognition of them as important mediators for cellular communication from donor to recipient cells. Recent evidence has shown the clinical implication of EVs, in particular of small vesicles, called exosomes, as good candidates for investigation of biomarkers associated with cancer diagnosis, prognosis, monitoring and therapy decision. Prostate cancer (PCa) is the most frequently diagnosed cancer in the elderly population. The serum prostate-specific antigen (PSA) level is the gold standard biomarkers used for the PCa early diagnosis. However, PSA test alone results not sufficiently specific and, consequently, gives false positive samples who need an invasive useless bioptic evaluation, leading to the need of a more accurate biomarkers research. Breast cancer (BC) is the most frequently diagnosed female cancer. BC relapse occurs in the first 5 years after diagnosis in patients with hormone receptor-positive BC. Systemic recurrence is due to the presence of the minimal residual disease (MRD) after surgery or present at initial diagnosis, but undetectable by imaging or conventional blood tests. Putative biomarkers able to detect MRD using non-invasive approaches can allow the monitoring of tumor evolution, providing prognostic information and guiding therapeutic decisions. The analysis and the characterisation of prostate and breast tumor-related EVs was performed aiming at finding their potential clinical implications. Different isolation methods were tested to obtain a high quantity and quality EVs from several body fluids (serum and urinary supernatant). Prostate cancer EVs were investigated aiming to find an early diagnostic role. In particular, EVs isolated from sera and urine of 10 PCa patients, 10 BPH patients and 10 healthy individuals, were phenotypically and morphologically characterised using MACSPlex kit, which allows simultaneous analysis of 37 surface epitopes, and transmission electron microscopy (TEM), respectively. We found a different significant expressions of surface exosome-related proteins in EVs from serum (CD62P, CD41b, CD42a, CD29, CD31) and from urinary supernatant (CD9, CD63, CD24) of PCa patients, BPH patients and healthy donors. TEM analysis showed no difference in terms of shape and size of EVs among the various conditions. Breast cancer EVs were investigated for their miRNA cargo as potential monitoring MRD markers after surgery. In particular, EVs were isolated from sera of 12 BC patients, which were collected after 6 months from the surgery, and of 11 healthy individuals. Exosomal miRNAs were extracted and a small RNA Seq approach was performed. After raw data elaboration and normalization, 52 exosomal miRNAs were found to be significantly differentially expressed between BC and H, suggesting a putative role of this miRNA pattern as BC-related markers and for MRD detection. Several exosomal miRNA have been already shown as correlated with BC but also with other cancer types (i.e. miR-148a-3p, miR-221-3p, miR-16-5p, miR-15a-5p, miR-25-3p). Other miRNAs are involved in pathways, such as Wnt and mTOR/PI3K/Akt, in cell cycle, TNF, Ras, p53 signalling. In conclusion, our results suggest the potential clinical application of EVs analysis in prostate and breast cancer as good non-invasive and informative biomarkers.