Follicular thyroid carcinoma (FTC) is the second most common malignant tumor of the thyroid and is frequently diagnosed at advanced stages with distant metastasis. RAS mutations represent the predominant driver alterations in FTC. This study aimed to investigate the role of Carnosine dipeptidase 2 (CNDP2), identified through a proteomic analysis of FTC tissues, in the progression of RAS-mutant thyroid cancer.

Bottom-up proteomic profiling was performed on formalin-fixed paraffin-embedded (FFPE) thyroid tissues using LC-MS/MS, and differentially expressed proteins (DEPs) were identified using statistical and bioinformatics analyses. CNDP2 expression in thyroid cancer was further examined using The Cancer Genome Atlas (TCGA) dataset. To assess the functional role of CNDP2, shRNA-mediated knockdown was conducted in RAS-mutant Cal-62 thyroid cancer cells, followed by cell proliferation, colony formation, migration, and invasion assays. Alterations in signaling pathways were evaluated by Western blot analysis

Proteome profiling revealed a significant upregulation of CNDP2 in FTC compared with benign follicular nodular disease (FND). TCGA transcriptomic analysis demonstrated that high CNDP2 expression was associated with increased RAS signaling activity and activation of the AKT/mTOR pathway. CNDP2 knockdown markedly reduced cell proliferation, clonogenicity, migration, and invasion in Cal-62 cells, and suppressed AKT/mTOR pathway activation as well as the expression of cell cycle regulators including cyclin B1, D1, and E1.

This multi-layered analysis demonstrates that CNDP2 is upregulated in FTC, correlates with RAS-driven oncogenic signaling, and promotes cancer progression through activation of the AKT/mTOR pathway. These findings suggest that CNDP2 may serve as a potential diagnostic biomarker and therapeutic target for RAS-mutant thyroid cancer