Proteomic analysis of neuroblastoma-derived exosomes LC-MS

Neuroblastoma (NB) is the most common extracranial pediatric solid tumor. At diagnosis, around 70% of patients with metastatic disease present bone-marrow (BM) infiltration; however, the mechanism underlying this specific tropism has to be elucidated. Tumor-derived exosomes may support metastatic progression in several tumors by interacting with the microenvironment, and may serve as tumor biomarkers. The main objective of this study was to identify an exosomal signature associated with NB metastatic BM dissemination. Therefore, we characterized the proteomic cargo of exosomes isolated from NB cell lines derived from primary tumor (PT) and BM metastasis. The comparison among all exosomal proteins showed 15 proteins exclusively present in PT, mainly involved in neuronal development, and 6 proteins in BM metastasis-derived exosomes related to cancer progression. Significant proteins obtained with t-test analysis, performed between the 2 groups (PT and BM metastasis), revealed that PT exosomes contain a higher level of proteins involved in extra-cellular matrix (ECM) assembly and adhesion, as well as in neuronal development. Exosomes isolated from BM metastasis showed proteins involved in ameboidal cell migration and mitochondrial activity. This work shows that proteomic profiling of NB-derived exosomes reflects the advanced tumor stage and may be considered as potential tumor biomarker