The effect of SLC5A5 gene expression in tumor tissues on refractoriness to radioactive iodine treatment of differentiated thyroid carcinomas.

Background and objective: The majority of thyroid cancer patients have a good prognosis. Even in advanced disease, the radioactive iodine (RAI) response improves the prognosis. However, RAI refractoriness poses a significant challenge for these patients. The objective of the study was to assess the expression of SCL5A5 as a potential marker for predicting future resistance to radioiodine treatment.

Materials and methods: Radioactive iodine-refractory papillary thyroid carcinoma (RAIR-PTC) and iodine-sensitive papillary thyroid carcinoma (PTC) were included in the study. Demographic and clinicopathological data were retrospectively analyzed. RNA samples were converted to cDNA. Gene expression reactions were performed using synthesized solute carrier family 5 member 5 (SLC5A5) and glyceraldehyde-3-phosphate dehydrogenase (GADPH) primer samples.

Results: Of the patients, 51 (61.4%) had iodine-sensitive PTC and 32 (38.5%) were RAIR-PTC. Patients were followed up for 8 ± 6.4 years. The mean age at diagnosis was higher in the RAIR-PTC group (56.56 ± 15.22 years vs. 46.82 ± 12.43 years, p = 0.002). The PTC group had higher SLC5A5 gene expression than RAIR-PTC. In addition, no statistically significant correlation was observed between basal thyroglobulin levels and tumor standardized uptake value-maximum (SUV-max) on fluorodeoxyglucose positron emission tomography (p = 0.304).

Conclusion: SLC5A5 gene expression is reduced in radioactive iodine-refractory thyroid carcinoma. Furthermore, the decreased expression status of the SLC5A5 gene before preablative iodine treatment may serve as a predictive indicator of future resistance to RAI therapy.