Proteomics analysis reveals elevated RAB21 in serum‑derived extracellular vesicles from patients with follicular thyroid carcinoma

Follicular thyroid carcinoma (FTC) is a common thyroid malignancy that poses diagnostic challenges because of its cytological similarity to benign follicular thyroid adenoma (FTA). The present study aimed to identify characteristic protein signatures in serum-derived extracellular vesicles (EVs) of FTC and FTA for potential diagnostic and therapeutic applications. Serum EVs from patients with FTC and FTA were purified using the phosphatidylserine affinity method. Proteomics analysis via nano liquid chromatography-tandem mass spectrometry identified 18 significantly differentially expressed proteins between the two patient groups. RAB21, a small GTPase involved in cellular trafficking, was markedly elevated in serum EVs from patients with FTC. Furthermore, cell invasion and migration assays of a human FTC cell line revealed that RAB21 knockdown reduced cell migratory ability, suggesting its role in the malignant phenotype of FTC. The present findings indicated that RAB21 in serum EVs may be a candidate biomarker able to distinguish FTC from FTA, and that RAB21 could be a potential therapeutic target for FTC.