Assessment of circulating proteins in thyroid cancer: Proteome-wide Mendelian randomization and colocalization analysis

The causality between circulating proteins and thyroid cancer (TC) remains unclear. We employed five large-scale circulating proteomic genome-wide association studies (GWASs) with up to 100,000 participants and a TC Meta-GWAS (nCase=3418, nControl=292703) to conduct Proteome-wide Mendelian randomization (MR) and Bayesian colocalization analysis. Protein and gene expression were validated in thyroid tissue. Through MR analysis, we identified 26 circulating proteins with a putative causal relationship with TCs, among which NANS protein passed multiple corrections (PBH=3.28e-5, 0.05/1525). These proteins were involved in amino acids and organic acid synthesis pathways. Colocalization analysis further identified six proteins (PP.H4 > 0.5) associated with TCs (VCAM1, LGMN, NPTX1, PLEKHA7, TNFAIP3, and BMP1). Tissue validation confirmed BMP1, LGMN, and PLEKHA7's differential expression between normal and TC tissues. We found limited evidence for linking circulating proteins and the risk of TCs. Our study highlighted the contribution of proteins, particularly those involved in amino acid metabolism, to TCs.