Relationships of BRAF mutation and HMGB1 to papillary thyroid carcinoma.

A poor papillary thyroid cancer (PTC) prognosis is strongly associated with the BRAF V600E mutation. During tumor progression, levels of the high mobility group box 1 (HMGB1) protein are often dysregulated. Results herein demonstrate that HMGB1 protein levels differ between tumor and adjacent non-tumor tissue and that HMGB1 mRNA levels were higher in wild-type BRAF PTC tissues than in BRAF V600E PTC tissues (2-△Ct 0.31 ± 0.25 vs. 0.16 ± 0.12; P < 0.05). HMGB1 protein levels also differed in the same manner (wild-type BRAF PTC tissues 0.11 ± 0.04 vs. BRAF V600E PTC tissues 0.03 ± 0.03; P < 0.001). Although not detected in peripheral blood, low levels of HMGB1 were significantly related to PTC cell lymph node metastasis and extra-glandular infiltration (P = 0.045 and P = 0.002). Experimental results at the cellular level were consistent with tissues and further verified the relationship of BRAF V600E and HMGB1. These findings demonstrate that the BRAF V600E mutation down-regulates levels of HMGB1, likely through activation of the mitogen-activated protein kinase (MAPK) signaling pathways.