Investigation of BK virus, Epstein-Barr virus and human papillomavirus sequences in postoperative thyroid gland specimens.

BACKGROUND: Although recent evidence has implicated viruses in the regulation of epithelial-to-mesenchymal transition and tumor progression, little is known regarding viral infections in thyroid malignancies. Thus the aim of this study was to detect sequences of 3 potentially oncogenic viruses - BK virus (BKV), Epstein-Barr virus (EBV) and human papillomavirus (HPV) - in a series of postoperative thyroid gland specimens. METHODS: Thirty patients with thyroid nodules who underwent surgery for thyroid disease within a 3-year period were enrolled. Both nodular and adjacent normal thyroid tissue was surgically excised from each patient. Viral gene sequences of BKV (VP1), EBV (LMP1, EBNA2 and EBER1) and HPV were amplified by PCR. The PCR results were confirmed by direct sequencing analysis. RESULTS: VP1 gene sequences were detected in 60% (18/30) of thyroid cancer or multinodular hyperplasia lesions compared with in 43.3% (13/30) of adjacent normal thyroid tissue specimens. Fifteen of thirty (50%) of thyroid cancer or multinodular hyperplasia samples revealed LMP1 sequences compared with 46.7% (14/30) of corresponding normal thyroid tissues. EBNA2 gene sequences were detected in 90% (27/30) of thyroid cancer or multinodular hyperplasia samples, compared with 90% (27/30) of adjacent normal thyroid tissue specimens. All samples were negative for EBER1 sequences, while HPV DNA was not detected in either nodular or normal thyroid tissue. CONCLUSIONS: This study suggests that BKV and EBV "infection" is an early event, occurring within normal tissue. Our findings do not show a clear role for the viruses examined, instead they suggest an "endemicity" pattern rather than a causal effect.

Expression analysis of B-Raf oncogene in V600E-negative benign and malignant tumors of the thyroid gland: correlation with late disease onset.

B-Raf, a member of the Raf serine/threonine kinase family, is an intermediate molecule in the mitogen-activated protein kinase pathway, which relays extracellular signals from the cell membrane to the nucleus via a cascade of phosphorylation events, ultimately promoting cancer development. This pathway is usually activated in human neoplasias. The purpose of this study was to investigate the role of B-Raf in thyroid pathology. We scanned for the presence of mutations at codon 600 (V → E) of the B-Raf gene, using a PCR-RFLP assay. In tumors with no mutation (32 benign and malignant thyroid tumors) and in their adjacent normal tissue, we measured the expression levels of B-Raf gene, using a quantitative real-time PCR (qPCR) assay. B-Raf expression in V600E-negative tumors deviated from the normal pattern, since it was overexpressed in 42 % of benign samples and downregulated in 54 % of malignant specimens. Hashimoto's thyroiditis also seemed to play an important role, since benign specimens with Hashimoto's thyroiditis had a 2.2-fold higher B-Raf expression than samples without thyroiditis (1.71 ± 0.63 vs. 0.78 ± 0.13). Statistical analysis revealed that B-Raf deregulation postponed disease onset by more than 10 years in both benign and malignant thyroid (benign: 55.6 ± 3.9 vs. 45.3 ± 3.3, p = 0.049; malignant: 52.2 ± 3.5 vs. 33.0 ± 7.9, p = 0.020). From the above results, we deduce that in the absence of mutation activation, B-Raf overexpression or downregulation is a protective event, since it delays the development of both malignant and benign thyroid tumors.