Re-induction of cell differentiation and 131I uptake in dedifferentiated FTC-133 cell line by TSHR gene transfection

Introduction: Radioiodine therapy is commonly used to treat differentiated thyroid cancer (DTC), but a major challenge is dedifferentiation of DTC with the loss of radioiodine uptake. TSHR is a key molecule regulating thyrocyte proliferation and function. This study aimed to test the therapeutic potential of TSHR in dedifferentiated DTC by gene transfection in order to restore cell differentiation and radioiodine uptake. Methods: Dedifferentiated FTC-133 (dFTC-133) cells were obtained by monoclonal culture of FTC-133 cell line after 131I radiation. Recombinant plasmid pcDNA3.1-hTSHR was transfected into dFTC-133 cells by using Lipofectamine 2000 reagent. Immunofluorescence analysis was carried out to confirm TSHR expression and its location. Radioiodine uptake assay was thereafter investigated. mRNAs and proteins of TSHR and other thyroid differentiated markers were detected by real-time PCR and western blot respectively. Results: Among the thyroid specific genes in dFTC-133 cells with stable low radioiodine uptake, TSHR was down-regulated most significantly compared with FTC-133. Then, after TSHR gene transfection, augmented expression of TSHR was observed in dFTC-133 cell surface and cytoplasm by immunofluorescence analysis. It was found that 125I uptake was 2.9 times higher (t = 28.63, P < .01) in cells with TSHR transfection than control. The mRNAs of TSHR, NIS, TPO and Tg were also significantly increased by 1.7 times (t = 13.8, P < .05), 4 times (t = 28.52, P < .05), 1.5 times (t = 14.43, P < .05) and 2.2 times (t = 19.83, P < .05) respectively compared with control group. Conclusion: Decreased TSHR expression correlated with FTC-133 ongoing dedifferentiation. TSHR transfection contributed to the re-differentiation of dedifferentiated thyroid follicular carcinoma cells.