CXCL16 positively correlated with M2-macrophage infiltration, enhanced angiogenesis, and poor prognosis in thyroid cancer.

Although various chemokines have pro-tumorigenic actions in cancers, the effects of CXCL16 remain controversial. The aim of this study was to investigate the molecular characteristics of CXCL16-expressing papillary thyroid cancers (PTCs). CXCL16 expressions were significantly higher in PTCs than benign or normal thyroid tissues. In the TCGA dataset for PTCs, a higher CXCL16 expression was associated with M2 macrophage- and angiogenesis-related genes and poor prognostic factors including a higher TNM staging and the BRAFV600E mutation. PTCs with a higher expression of 3-gene panel including CXCL16, AHNAK2, and THBS2 showed poor recurrence-free survivals than that of the lower expression group. Next, shCXCL16 was introduced into BHP10-3SCp cells to deplete the endogenous CXCL16, and then, the cells were subcutaneously injected to athymic mice. Tumors from the BHP10-3SCpshCXCL16 exhibited a delayed tumor growth with decreased numbers of ERG+ endothelial cells and F4/80+ macrophages than those from the BHP10-3SCpcontrol. CXCL16-related genes including AHNAK2 and THBS2 were downregulated in the tumors from the BHP10-3SCpshCXCL16 compared with that from the BHP10-3SCpcontrol. In conclusion, a higher CXCL16 expression was associated with macrophage- and angiogenesis-related genes and aggressive phenotypes in PTC. Targeting CXCL16 may be a good therapeutic strategy for advanced thyroid cancer.