TLR3 correlated with cervical lymph node metastasis in patients with papillary thyroid cancer

Papillary thyroid cancer (PTC) is the most rapidly increasing endocrine malignancy worldwide. Although less aggressive than the majority malignancies, PTC exhibits extensive cervical lymph node metastasis in early stage of PTC. However, the underlying molecular mechanism of this early-metastasis remains unknown. Toll like receptors (TLRs) constitute a crucial component of the innate immune response to bacterial and viral pathogens. Emerging evidence suggests that TLRs play important roles in cancer progression, invasion and immune evasion, whereas whether TLRs have any role in PTC remains to be clarified. In this study, we found that TLR3 was present in both PTC specimen and various thyroid cancer cell lines. Further IHC analysis of 63 PTC patients revealed that TLR3 expression was associated with cervical metastasis, but not correlated with patients' TNM staging, extrathyroidal invasion. In addition, TLR3 promoted migration of K1 cells in vitro. Activation of TLR3 increased cancer stem cell marker and migration promoting CD44 expression in vitro, indicating that TLR3 might promote metastasis of PTC via modulating CD44 expression. Taken together, our data revealed that TLR3 is correlated with cervical metastasis of PTC and might be an essential prognostic indicator and target for PTC metastasis.