Expression of epithelial-mesenchymal transition regulators TWIST, SLUG and SNAIL in follicular thyroid tumours may relate to widely invasive, poorly differentiated and distant metastasis

AIMS

To assess the expression of epithelial-mesenchymal transition (EMT) regulators in follicular thyroid tumours.

METHODS AND RESULTS

The expression of E-cadherin (E-CAD) and transcription factors TWIST, SLUG and SNAIL in follicular thyroid tumours was examined by immunohistochemistry in tissue samples, including 18 follicular adenomas (FA), 12 minimally invasive follicular thyroid carcinomas (MI-FTC), 16 widely invasive follicular thyroid carcinomas (WI-FTC), 10 poorly differentiated follicular thyroid carcinomas (PDTC) and six anaplastic thyroid carcinomas (ATC). Metastatic tumour tissues from six of these cases were also examined. The results showed an increasing expression trend of EMT regulators in a panel of follicular tumour cases with a spectrum of morphological subtypes from low- to high-risk malignancy. The expression of EMT regulators was higher in the WI-FTC, PDTC and ATC groups but focal and lower in the FA and MI-FTC groups. Different expression intensity of E-CAD and EMT regulators at the tumour centre part and the invasive front (IF) was observed. The loss of E-CAD and expression of EMT regulators was significantly correlated with distant metastasis and vascular invasion (VI) in the well-differentiated follicular carcinoma (WD-FTC), and six tumours of metastatic sites also showed variables positive for EMT regulators. The disease-free survival analysis showed an apparent relationship between the expression of EMT regulators and the tumour disease-free outcomes in WD-FTC.

CONCLUSIONS

Our study supported the role of EMT in the development of follicular thyroid carcinoma and indicated that EMT regulatory proteins may play an important role in WD-FTC that are widely invasive and exhibit distant metastasis.

TERT aberrancies: a screening tool for malignancy in follicular thyroid tumours

Telomerase reverse transcriptase (TERT) promoter mutations have been linked to adverse clinical parameters in thyroid cancer, but TERT-expressing tumours are not always mutated. Little is known regarding other TERT-related genetic aberrations. To delineate the role of TERT gene aberrancies in follicular thyroid tumours, 95 follicular carcinomas (FTCs), 43 follicular adenomas (FTAs) and 33 follicular tumours of uncertain malignant potential (FT-UMPs) were collected. The tumours were assayed for TERT expression, TERT promoter mutations, TERT promoter hypermethylation and TERT gene copy number (CN) alterations and the results were compared to clinical parameters. Cases with mutation, detectable mRNA expression, CN gain or hypermethylation were classified as TERT aberrant, and these aberrancies were regularly found in FTC and FT-UMP but uncommonly found in FTA. In total, 59% FTCs and 63% FT-UMPs exhibited one or more of these TERT gene aberrancies. Moreover, 24 out of 28 FTCs (86%) with TERT expression displayed an evident TERT gene aberration, and statistics showed an increased risk for relapse in FTCs with TERT expression, CN gain or hypermethylation. We conclude that TERT expression in follicular thyroid tumours is coupled to promoter mutations, CN gain and increased promoter methylation. The molecular similarities regarding TERT aberrations between the FTC and FT-UMP groups indicate that a significant subset of FT-UMP cases may display future recurrences. TERT aberrancies are thus promising as future additional markers for determining malignant potential of follicular thyroid tumours.