Background: H2AX, one of the variants of histone H2A with conserved sequence, plays a vital role in maintaining genomic stability. DNA double-strand break (DSB) induces H2AX phosphorylation (γH2AX). Growing evidence indicated γH2AX was linked to thyroid disease. However, the precise expression of γH2AX in papillary thyroid carcinoma (PTC) and nodular goiter was unknown. In this study, the yH2AX expression in PTC and nodular goiter and the significance of the aberrant expression were investigated.
Methods: The γH2AX expression level was evaluated by immunohistochemistry staining in 140 specimens with thyroid diseases (30 cases of nodular goiter, 30 cases of PTC, and 80 cases of PTC coexisting with nodular goiter). The possible relationships between γH2AX expression and patients' clinicopathological characteristics were analyzed.
Results: In the set of nodular goiter, 20.0% (6/30) of nodular goiter component and 10.0% (3/30) of normal adjacent tissues exhibited high expression of γH2AX (p > 0.05). In the set of PTC, 70.0% (21/30) of PTC component and 0.0% (0/30) of normal adjacent tissues showed high expression of γH2AX (p < 0.05). In the set of PTC coexisting with nodular goiter, 95.0% (76/80) of PTC component, 12.5% (10/80) of nodular goiter component, and 8.8% (7/80) of normal adjacent specimens showed high expression of γH2AX (p < 0.05). 85.5% (65/76) of PTC patients with lymph node metastasis were found to have a high expression level of γH2AX, and the proportion was lower than that in patients without lymph node metastasis (34/34, 100.0%) (p = 0.003). High γH2AX expression was also found in 76.2% (16/21) of stage IV patients and the proportion was lower than that in stage I - III patients (83/89, 93.3%) (p = 0.034). No statistically significant correlation was found between yH2AX expression level and other clinicopathological features, including age, gender, capsular invasion, tumor size, tumor focus number, distant metastasis, and T status.
Conclusions: γH2AX expression was increased in PTC patients, while nodular goiter and normal adjacent tissues exhibited no statistically significant difference in γH2AX expression. yH2AX expression had a negative correlation with TNM stage and lymph node metastasis. γH2AX seems to play a more critical role in early-stage PTC rather than late-stage PTC and might inhibit lymph node metastasis.