Dedifferentiation of differentiated thyroid carcinoma cell line FTC-133 is enhanced by 131I pretreatment

IntroductionDifferentiated thyroid carcinoma (DTC) usually has a high iodine uptake. However, dedifferentiation of DTC with decreased or no radioiodine (131I) uptake is observed in clinical practice, with poor prognosis. The aim of this study was to investigate the effects of 131I radiation on radioiodine uptake (RAIU) and the expression of thyroid-specific molecules.MethodsFTC-133 cells were treated with 131I, the dosage dictated by methylthiazol tetrazolium test results and preliminary experiments. The experimental cell group was incubated with 131I for 48 h and then cultured for 3 months in 131I-free medium. The control group was set without 131I. Primary cells were defined as the blank group. Following treatment, RAIU was measured with a gamma counter as the counts/cell number. Na+/I− symporter (NIS), thyroid-stimulating hormone receptor (TSHR), thyroid peroxidase (TPO) and thyroglobulin (Tg) levels were detected by Western blotting and radioimmunoassay, and their mRNAs were detected by real-time polymerase chain reaction.ResultsRAIU of FTC-133 cells decreased gradually after coincubation with 131I and did not recover even if 131I was removed. The relative RAIU of the control and experimental groups was 0.567 and 0.182, respectively, a statistically significant difference (P<.01). Expression of NIS, TSHR, TPO and Tg decreased in the experimental group to a statistically significant degree compared to that of controls (P<.05).ConclusionChanges in the mRNA levels were in accordance with the expression of thyroid-specific proteins. Thus, FTC-133 cells undergo dedifferentiation during long-term culture in vitro, and 131I may promote this progress.