Association between STAT1 activity and BRAF mutations in papillary thyroid carcinomas

Abstract

Signal transducer and activator of transcription-1 (STAT1) plays a critical role in tumorigenesis by controlling several functions in both tumor cells and the immune system, and is considered to be a tumor suppressor. The present study evaluated the activity of STAT1 in human papillary thyroid carcinomas (PTC). STAT1 activity was measured in nuclear extracts of tumor tissues from 35 PTC patients using an ELISA-based kit. STAT1 activity was significantly lower in tumors than in the surrounding normal thyroid tissues (P < 0.01). The association between STAT1 activity and clinicopathologic factors was analyzed in PTC tissues. STAT1 activity was significantly lower in tumors that measured 2 cm or more than in tumors that measured 2 cm or less (P = 0.044). Moreover, tumor size was inversely correlated with STAT1 activity (Spearman's rank correlation coefficient (rho) = -0.34, P = 0.048). In addition, tumors with BRAF mutations showed lower STAT1 activity than wild-type BRAF tumors [0.064 (0.056-0.124) vs. 0.108 (0.073-0.153) arbitrary units, P = 0.048]. STAT1 activity is suppressed in PTCs (as measured by DNA-binding activities). The tumor with T1799A BRAF mutation and tumor sizes of 2 cm or more were clinicopathologic parameters associated with lower STAT1 activity. STAT1 activity of tumor might be one of potential biomarkers for PTC's.