Shotgun proteomics of thyroid carcinoma exosomes – Insight into the role of exosomal proteins in carcinogenesis and thyroid homeostasis

Background

Transport of molecules via exosomes is one of the factors involved in thyroid cancer development, and transported molecules may serve as cancer biomarkers. The aim of the study was to characterize protein content of thyroid-derived exosomes and their functional effect exerted on recipient cells.

Methods

LC-MS/MS proteomics of exosomes released by FTC and 8305C thyroid carcinoma cell lines, and Nthy-ori 3–1 normal thyroid follicular cells was performed, followed by bioinformatic analysis and functional tests (wound healing and Alamar Blue assays).

Results

Exosomes from Nthy-ori 3–1 cells had the highest number of 1504 proteins, while in exosomes from thyroid carcinoma FTC and 8305C cells 730 and 1304 proteins were identified, respectively. For proteins uniquely found in FTC- and 8305C-derived exosomes, enriched cancer-related gene ontology categories included cell adhesion, positive regulation of cell migration, N-glycosylation, drug resistance, and response to NK/T cell cytotoxicity. Furthermore, through label-free quantification (that identified differentially expressed proteins) and comparison with The Human Protein Atlas database several potential diagnostic and/or prognostic biomarkers were indicated. Finally, exosomes from FTC and 8305C cells displayed ability to stimulate migratory properties of recipient Nthy-ori 3–1 cells. Additionally, 8305C-derived exosomes increased recipient cell viability.

Conclusions

Multiple proteins identified in thyroid cancer-derived exosomes have a direct link to thyroid cancer progression. Also, in functional tests exosomes enhanced growth and dissemination of non-transformed thyroid cells.

General significance

The obtained results expands the knowledge concerning the role of exosomal proteins in thyroid cancer and indicate potential biomarkers for further evaluation in clinical settings.