Association of EGFR and HER2 polymorphisms with risk and clinical features of thyroid cancer.

The epidermal growth factor receptor family plays a critical role in the control of many physiological processes. Genetic alterations and/or variations in the gene encoding these receptors have been implicated in a variety of human cancers. In this study we evaluate the association of two single-nucleotide polymorphisms (SNP), R497K and I655V, of the EGFR and HER2 genes, respectively, with thyroid cancer risk. The analysis was performed with 302 healthy individuals and 106 thyroid cancer patients. No significant difference was found in the allelic and genotypic frequency distribution of the SNP R497K between the control and patient groups. While for the SNP I655V, the allele G is more frequent in patients than in controls and was associated with an increased risk of thyroid cancer (odds ratio = 1.88; 95% confidence intervals: 1.18-3.01; p = 0.007). We have also investigated the relationship between these two polymorphic sites and clinicopathological characteristics such as thyroid-stimulating hormone level, off-thyroxin, serum thyroglobulin, tumor histology, metastasis, tumor status, tumor stage, and survival. No significant association was observed. Tumor status was found significantly associated with HER2 I655V as well as with two previously studied markers in the thyroid hormone receptor A and estrogen receptor 1 (ESR1) genes (D17S2189 and D6S440, respectively). We also report a correlation between thyroglobulin level and genotypes for SNP rs2228480 in exon 8 of the ESR1 gene. In conclusion, our results suggest that the SNP HER2 I655V, but not the EGFR R497K, was associated with thyroid cancer risk.