Alterations of regulatory factors and DNA methylation pattern in thyroid cancer.

PURPOSE: DNA methylation plays an important role in thyroid oncogenesis. The aim of this study was to investigate the connection between global and local DNA methylation status and to establish the levels of important DNA methylation regulators (TET family and DNMT1) in thyroid tumours: follicular adenoma-FA, papillary thyroid carcinoma-PTC (classic papillary thyroid carcinoma-cPTC and papillary thyroid carcinoma follicular variant fvPTC). METHODS: Global DNA methylation profile in thyroid tumours tissue (41 paired samples) was assessed by 5-methylcytosine and 5-hydroxymethylcytosine levels evaluation (ELISA), along with TETs and DNMT1 genes expression quantification. Also, it was investigated for the first time TET1 and TET2 promoter's methylation in thyroid tumours. BRAF V600E mutation and RET/PTC translocation testing were performed on all investigated samples. In vitro studies upon DNA methylation in K1 thyroid cancer cells were performed with demethylating agents (5-AzaC and vitamin C). RESULTS: TET1 and TET2 displayed a significantly reduced gene expression level in PTC, while DNMT1 gene presented a high level of expression. PTC samples presented increased levels of 5-methylcytosine and low levels of 5-hydroxymethylcytosine. 5-methylcytosine levels were associated with TET1/TET2 expression levels. TET1 gene expression was significantly lower in patients positive for BRAF mutation and with RET/PTC rearrangement. TET2 gene was found hypermethylated in thyroid carcinoma patients overall, especially in PTC-follicular variant samples (p= 0.0002), where TET2 gene expression levels were significantly reduced (p= 0.0031). Furthermore, the data indicate for all thyroid cancer patients a good sensitivity (81.08%) and specificity (86.49%) regarding the use of TET1 (p< 0.0001), and TET2 (71.79%, 64.10%, p= 0.0001) hypermethylation as biomarkers for thyroid oncogenesis. CONCLUSIONS: These results suggest that TET1/TET2 gene expression and methylation may serve as potential diagnostic tools for thyroid neoplasia. Our study showed that the methylation of TET1 increases in malignant thyroid tumours. fvPTC patients presented lower methylation levels compared to cPTC and could be a discriminatory factor between two cancer types and benign lesions. TET2 is a poorer discriminator between FA and fvPTC, but it can be useful for cPTC identification. K1-cells treated with demethylating agents showed a demethylation effect, especially upon TET2 gene. The cumulative effect of L-AA and 5-AzaC proved to have a potent combined demethylating effect on genes promoter's activation and could open new perspectives for thyroid cancer therapy.

Cerebral arteriopathy with subcortical infarcts and leukoencephalopathy in acromegalic patient with severe headache.

A 68-year-old female patient was admitted in our clinic with severe frontal bilateral headache, dizziness, depression and cognitive decline in the context of a previously diagnosed acromegaly. She also had high blood pressure, dyslipidemia, secondary diabetes mellitus. Acromegaly was caused by a growth hormone (GH) secreting-pituitary macroadenoma, so a transsphenoidal surgery was performed. The postoperative magnetic resonance imaging (MRI) scan revealed a 20÷22÷25 mm pituitary mass remnant and medical therapy with somatostatin analogues (SSAs) was started. After nine months of treatment with SSAs, she continued having severe headache, the blood pressure was well controlled, but GH secretion was only partially controlled with insulin-like growth factor-1 (IGF-1) level still above the normal value. The MRI scan showed the same pituitary tumor remnant with supra- and parasellar right extension and also multiple fronto-temporo-parietal subcortical lesions that could suggest in the clinical context cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). According to a pregenetic screening tool, the Pescini Scale, the patient had a 19 points score, which is highly suggestive for CADASIL, an inherited cerebrovascular disease due to mutations of the Notch3 gene at the chromosome locus 19p13. In the absence of genetic testing, an alternate way to prove small vessels disease, the skin biopsy, was performed. Electron microscopy showed granular osmiophilic material (GOM) surrounding the vascular smooth muscle cells on that are pathognomonic for the disease. Our report underscores the importance of repeated investigations even in patients with apparently obvious explanations of their condition since they may have multiple diseases with the same presenting clinical signs.