Iodine-131 treatment of thyroid cancer cells leads to suppression of cell proliferation followed by induction of cell apoptosis and cell cycle arrest by regulation of B-cell translocation gene 2-mediated JNK/NF-κB pathways

Iodine-131 ((131)I) is widely used for the treatment of thyroid-related diseases. This study aimed to investigate the expression of p53 and BTG2 genes following (131)I therapy in thyroid cancer cell line SW579 and the possible underlying mechanism. SW579 human thyroid squamous carcinoma cells were cultured and treated with (131)I. They were then assessed for (131)I uptake, cell viability, apoptosis, cell cycle arrest, p53 expression, and BTG2 gene expression. SW579 cells were transfected with BTG2 siRNA, p53 siRNA and siNC and were then examined for the same aforementioned parameters. When treated with a JNK inhibitor of SP600125 and (131)I or with a NF-κB inhibitor of BMS-345541 and (131)I, non-transfected SW579 cells were assessed in JNK/NFκB pathways. It was observed that (131)I significantly inhibited cell proliferation, promoted cell apoptosis and cell cycle arrest. Both BTG2 and p53 expression were enhanced in a dose-dependent manner. An increase in cell viability by up-regulation in Bcl2 gene, a decrease in apoptosis by enhanced CDK2 gene expression and a decrease in cell cycle arrest at G(0)/G(1) phase were also observed in SW579 cell lines transfected with silenced BTG2 gene. When treated with SP600125 and (131)I, the non-transfected SW579 cell lines significantly inhibited JNK pathway, NF-κB pathway and the expression of BTG2. However, when treated with BMS-345541 and (131)I, only the NF-κB pathway was suppressed. (131)I suppressed cell proliferation, induced cell apoptosis, and promoted cell cycle arrest of thyroid cancer cells by up-regulating B-cell translocation gene 2-mediated activation of JNK/NF-κB pathways.