Introduction: The mechanism underlying the development of follicular thyroid carcinoma (FTC), the second commonest thyroid tumor, is still unknown. An interesting hypothesis is that changes in the expression of multiple regulatory RNA (miR) genes may be a major mechanism in thyroid carcinogenesis. For example, several studies suggested that SNP rs2910164 in the pre-miR146a, a precursor of miR146a, might be correlated to papillary carcinoma. The aim of this study was the evaluation of the role of SNP rs2910164 in FTC tumorigenesis. Here for the first time we analysed the genotype frequencies of rs2910164 in both genomic and somatic DNA of patients affected by FTC.
Materials and methods: The region of pre-miR146a containing SNP rs2910164 was sequenced in both genomic and somatic DNA of patients affected by FTC (n=39). Somatic DNA was extracted from formalin-fixed-paraffin-embedded tissue, while genomic DNA was from peripheral blood. We compared the SNP distribution between patients genomic and somatic DNA (both unaffected and tumor tissue). In addition, patients genomic DNA was compared to 208 controls with negative thyroid sonography. SNP distribution was correlated to the clinical data.
Results: SNP rs2910164 undergoes mutations in the transition from genomic to somatic DNA in 37% of cases and from unaffected to tumor tissue in 31% of cases resulting in an increase of allele G frequency in tumor tissue (P<0,05, χ2 test), in which CC genotype was completely absent. The SNP distribution in the patients genomic DNA was the same as in negative controls (P=0.9106; χ2 test). No correlation between this SNP and clinical features was found.
Conclusion: Our data suggest that somatic GG and GC genotypes are associated with FTC, while CC homozygous state might have a protective role. This could result in modifications of target genes, the expression of which is affected by the SNP status.