Nuclear factor-κB (NF-κB) is involved in proliferation, angiogenesis, and metastasis in various malignancies; however, the role of NF-κB in papillary thyroid carcinoma (PTC) has not been fully elucidated. The purpose of this study was to elucidate the role and clinicopathological significance of the NF-κB signaling pathway in PTC. We investigated NF-κB RelA expression in 122 patients with conventional PTC by immunohistochemistry, and evaluated the correlation between RelA expression and clinicopathological parameters, including BRAF(V600E) mutation. Nuclear expression of NF-κB RelA, regardless of cytoplasmic expression, was identified in 91 of 122 PTCs (74.6%), and was more frequent in PTCs larger than 1cm (overt PTC) (P=0.001). There were significant differences in clinicopathological parameters, such as extrathyroidal extension (P=0.031), nodal metastasis (P=0.021) and BRAF(V600E) mutation (P=0.039), between NF-κB-positive and negative PTCs. Proliferation index was strongly associated with NF-κB activation (P=0.045) but not with BRAF(V600E) mutation (P=0.141). Taken together, our results suggest that NF-κB RelA activation contributes, at least in part, to tumor growth and aggressiveness of PTC after tumor transformation. The expression pattern of NF-κB may serve as a prognostic marker and a potential therapeutic target.
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