OP177: Exosomes isolated from saliva of cancer patients differ from those of healthy individuals

Abstract

Purpose To characterize exosomes from the saliva of oral cancer (OC) patients isolated by different methods and to compare them to exosomes from the saliva of healthy individuals (HI). Material and methods Whole saliva (5–10 ml) from OC patients (before being treated for their tumor) and from HI was collected under standardized conditions. Saliva was kept at 4 °C until centrifuged (3000 g/15 min), the clear supernatant was collected and the samples were deep freezed (−70 °C) until further use. Exosomes were isolated by two methods: chemical – Exoquick® (EQ, System Biosciences, CA, USA), and physical – ultracentrifugation (UC, 120,000 g/3 h). Isolated exosomes were characterized by ELISA, NanoSight, electron microscopy (EM) and atomic force microscopy (AFM). Results ELISA performed on saliva of OC patients using the exosomal marker CD63 presented higher concentrations compared to HI saliva by both methods, EQ and UC. These results were confirmed in the examination of OC saliva with NanoSight, which revealed a higher concentration of exosomes that were of a larger size compared to Hi saliva. Furthermore, AFM revealed that OC exosomes were also of variable size and contained some remarkably large exosomes, while HI saliva contained exosomes of a more uniform size, predominantly of small-size. Examination of HI saliva with EM revealed bi-layered round-shaped structures within a range of 30–150 nm that corresponded to exosomes, while exosomes of OC patients were larger and presented in an aggregated pattern. Conclusions Exosomes isolated from the saliva of OC patients seem to differ from those of HI saliva in their concentration, distribution and size. These differences should be further explored for diagnostic and therapeutic purposes.