Sulfasalazine suppresses thyroid cancer cell proliferation and metastasis through T-cell originated protein kinase

Thyroid cancer patients with radioactive iodine-refractory or rapidly progressing presentation require effective treatment. T-cell originated protein kinase (TOPK) is highly expressed in a number of different tumor types, where it promotes proliferation and metastasis. However, the expression of TOPK in thyroid cancer is poorly documented. Therefore, immunohistochemistry was used to detect the expression of TOPK in thyroid cancer tissues, and its clinical significance in this disease was investigated. Sulfasalazine, a targeted inhibitor of TOPK that directly binds the protein with a dissociation constant (Kd) of 228 µM, was also investigated using microscale thermophoresis. Sulfasalazine inhibited TOPK activity, as determined by an in vitro pull-down assay. Furthermore, sulfasalazine inhibited the proliferation and metastasis of thyroid cancer cells. The results indicated that TOPK may be a potential therapeutic target and diagnostic biomarker for thyroid cancer and may be used as an index to evaluate malignant thyroid nodules. Therefore, sulfasalazine is a potential novel compound for the targeted treatment of thyroid cancer.