Abstract
Exposure to ionizing radiation in childhood has been recognized as a risk factor for thyroid cancer. We previously demonstrated that neonatal X-irradiation induced specific deformation of the thyroid follicles. Here, we further analyzed this model to understand the possible relationship with thyroid carcinogenesis. Wistar rats were subjected to cervical X-irradiation at different ages of 1–8 weeks old and at different doses of 1.5–12 Gy. For tumor promotion, rats were fed with an iodine-deficient diet (IDD). In cervically X-irradiated neonatal rats, the size of thyroid follicles decreased, accompanied by an increase in the number of TUNEL-positive cells. Fas and Lgals3 mRNA levels increased, while Mct8 and Lat4 expressions decreased. The co-administration of IDD induced the proliferation and the upregulation in Lgals3 expression, resulting in thyroid adenoma development at 28 weeks post-exposure. Our data demonstrated that single neonatal X-irradiation induced continuous apoptotic activity in the thyroid with the long-term alternation in Fas, Mct8, Lat4, and Lgals3 mRNA expressions. Some of these changes were similar to those induced by IDD, suggesting that neonatal X-irradiation may partially act as a thyroid tumor promoter. These radiation-induced thyroidal changes may be enhanced by the combined treatment with IDD, resulting in the early development of thyroid adenoma.
Highlights
Exposure to ionizing radiation in childhood has been recognized as a risk factor for thyroid cancer
Similar changes in RET and BRAF were found in the post-Chernobyl thyroid cancer cases, they are not associated with the radiation exposure but strongly related to the patient’s age at o peration[3]
Lat[4], Met, and Lgals[3], were determined. We examined these parameters in the thyroid tumors induced by neonatal irradiation plus feeding an iodine-deficient diet (IDD)
Summary
Exposure to ionizing radiation in childhood has been recognized as a risk factor for thyroid cancer. Our data demonstrated that single neonatal X-irradiation induced continuous apoptotic activity in the thyroid with the long-term alternation in Fas, Mct[8], Lat[4], and Lgals[3] mRNA expressions Some of these changes were similar to those induced by IDD, suggesting that neonatal X-irradiation may partially act as a thyroid tumor promoter. Since the thyroid doses among the children in the Chernobyl accident were mainly less than 3 Gy16, the effects of 1.5 and 3 Gy of X-irradiation were investigated in addition to previously examined 6 and 12 Gy. In order to find the possible relationship between the initial thyroidal changes caused by neonatalirradiation and thyroid tumor development, mRNA expressions of thyroid cancer-related marker genes, Mct[8], Scientific Reports | (2021) 11:23620. ShamX at 5–6 days old 1.5 Gy at 5–6 days old 3 Gy at 5–6 days old 6 Gy at 5–6 days old 12 Gy at 5–6 days old
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