FLOW CYTOMETRY IN THE DEVELOPMENT AND CHARACTERIZATION OF PRECLINICAL TUMOR MODELS BASED ON THE ANALYSIS OF EXTRACELLULAR VESICLES AS CANDIDATE LIQUID BIOMARKERS

I. D’Agnano | Institute of Biomedical Technologies, CNR, Segrate, Milan, Italy

The precise causes of most brain tumours in adults remain largely unknown. Glioblastoma (GBM) is characterized as the most aggressive form of brain tumour, with a 5-year survival rate from diagnosis of less than 5%. Brain metastases from different organ tumors account for more than one-half of all intracranial tumours in adults. Therefore, the identification of new biomarkers remains a major challenge to integrate prognosis and improve diagnosis for brain tumours. The molecular profiling of brain tumors has become an integral component of routine neuro-oncologic care. Currently, it is mainly achieved through invasive procedures such as tissue biopsy and surgical resection, often associated with complications and especially challenging. Due to these reasons, liquid biopsy is an attractive option providing the opportunity to capture the complex global heterogeneity of the whole brain tumour. Regardless of the tumour type, liquid biopsy is a minimally invasive technique performed on samples of blood or other human biological fluids to detect and quantify circulating tumor cells (CTCs) or other tumor-derived elements, such as cell-free tumor DNA (ctDNA) and, more recently, extracellular vesicles (EVs), which are released in the bloodstream or other fluids by cancer cells. Tumor cells produce large amounts of EVs and can select the EV cargo, which is constituted by proteins, nucleic acids and lipids, thus safeguarding them from degradation and conveying to nearby or distant cells. miRNAs packed into tumour-released EVs have been shown to contribute to tumour establishment and metastatic spread, suggesting not only diagnostic/prognostic but also therapeutic target potential. To identify miRNAs to be used as biomarkers for brain tumour diseases, we analysed the expression profiles of circulating small EV-enriched miRNAs in preclinical models of intracranial human metastatic melanoma and GBM in nude mice. Thus, extracellular miRNAs have been studied in the small EVs (sEVs) purified from culture cell supernatants and from the plasma of mice bearing tumour to brain by next generation sequencing.