Effect of Iodine Intake on p14ARF and p16INK4a Expression in Thyroid Papillary Carcinoma in Rats

BACKGROUND Iodine intake is related to thyroid disease. This study investigated the effect of the amount of iodine intake on p14ARF and p16INK4a expression of thyroid papillary carcinoma in rats. MATERIAL AND METHODS A cohort of 240 SD rats were randomly divided into control group, low iodine, normal iodine, and high iodine groups (n=60 per group). We inoculated 2 × 10(5) papillary thyroid carcinoma (PTC) cells on the left side of the thyroid gland. After 6 and 12 weeks, serum thyroid hormone level and urine iodine level were measured in addition to morphological observations of tumor tissues. Expression of p14ARF, p16INK4a was detected by immunohistochemical staining. RESULTS The expression of p14ARF, p16INK4a, FT3, and FT4 levels in all iodine-treated animals were significantly lower than in the control group, while TSH level was significantly higher (P<0.05). Compared to the normal iodine group, the low and high groups had lower p14ARF and p16INK4a expression, lower FT3 and FT4 levels, higher TSH levels, and heavier tumors (P<0.05). In a further between-group comparison, p14ARF and p16INK4a expression and FT3 and FT4 levels at 12 weeks were lower than at 6 weeks. Expression of p14ARF and p16INK4a were positively correlated with FT3 and FT4, and negatively correlated with TSH and tumor weight. CONCLUSIONS Low and high iodine diet intake could reduce p14ARF and p16INK4a expressions and promote tumor development.