Iodine incorporation into thyroglobulin is dependent on the activities of both thyroperoxidase (TPO) and thyroid dual oxidase 2 (DuOx2). Although TPO expression is decreased in some thyroid nodular lesions, DuOx1 and 2 mRNA expressions are maintained, but DuOx H2O2-generating activity has never been evaluated in such tumors. Our goal was to determine DuOx activity in hypofunctioning lesions of the thyroid. We evaluated H2O2 generation by DuOx in 12 paranodular to cold nodule samples, 17 non-toxic multinodular goiters (MNG; 33 samples), 3 papillary carcinomas (PC; 4 samples), 3 follicular carcinomas (FC; 4 samples), and 10 follicular adenomas. DuOx activity was detected in all paranodular tissues (121±23 nmol H2O2/h per mg protein), but was undetectable (<1 nmol H2O2 generated) in all PC, two out of four FC samples and seven out of ten adenomas. In 11 MNG at least two different areas of the goiter have been evaluated, and in 5 of these goiters one of the samples had DuOx activity below the limit of detection. The coefficient of variation in MNG samples ranged from 11.3 to 57.2%. Interestingly, in all the adenomas studied, TPO activity (486±142 U/g protein, n=8) was well within the range found in paranodular tissues (414±116 U/g protein, n=3). We found a significant negative correlation between DuOx and TPO activities, suggesting that these enzymes are regulated in opposite directions, at least in thyroid tumors.
Maria Gloria P Ginabreda, Luciene C Cardoso, Flavia M Nobrega, Andrea C F Ferreira, Manuel Domingos C Gonçalves, Mário Vaisman and Denise P Carvalho
Giselle F Taboada, Raul M Luque, Wildebranham Bastos, Renata F C Guimarães, Jorge B Marcondes, Leila M C Chimelli, Rosita Fontes, Paulo J P Mata, Paulo Niemeyer Filho, Denise P Carvalho, Rhonda D Kineman and Mônica R Gadelha
Objective: It is believed that the variable effectiveness of somatostatin analogs in post-surgical management of somatotropinomas and non-functioning pituitary adenomas (NFPA) may be due in part to variable expression of somatostatin receptor isoforms (SSTR1–5), within and between pituitary tumor types.
Design and methods: Quantitative real-time RT-PCR was used to compare absolute mRNA copy numbers for all five SSTR isoforms in 23 somatotropinomas and 19 NFPA.
Results: Somatostatin receptor subtype 5 mRNA was present at the highest level in somatotropinomas, followed by SSTR2>SSTR3≫SSTR1⋙SSTR4. In contrast, SSTR3 mRNA was present at the highest level in NFPA, followed by SSTR2, while SSTR1, SSTR4, and SSTR5 transcripts were only detectable in select tumors. Among somatotropinomas, a positive correlation was found between SSTR2 mRNA levels and the percent decrease of GH (%GH) after 3 and 6 months of therapy with octreotide long acting repeatable (LAR) (r=0.51 and r=0.66; P=0.05 and P=0.008). Also the percent decrease of IGF-I (%IGF-I) after 3 months of octreotide LAR was negatively correlated with SSTR5 and %IGF-I after 6 months of octreotide LAR was positively correlated with SSTR2.
Conclusions: The present report is a large series examining SSTR mRNA levels in somatotropinomas and NFPA. These initial findings suggest that detailed knowledge of the SSTR mRNA expression profile in somatotropinomas can help to predict the hormonal response to therapy with LAR. Also, it appears that SSTR3 in NFPA may be a potential target for SSTR3 preferential or universal ligands such as pasireotide.
Giselle F Taboada, Raul M Luque, Leonardo Vieira Neto, Evelyn de O Machado, Bruna C Sbaffi, Romeu C Domingues, Jorge B Marcondes, Leila M C Chimelli, Rosita Fontes, Paulo Niemeyer, Denise P de Carvalho, Rhonda D Kineman and Mônica R Gadelha
To determine whether the somatostatin receptor subtype (SSTR) expression profile correlates with hormonal and tumor volume responses to postsurgical octreotide long acting repeatable (OCT LAR) treatment.
Design and methods
Quantitative real-time RT-PCR was used to evaluate the absolute mRNA copy numbers for all five SSTR subtypes in 22 somatotropinomas. Response to OCT LAR was studied by hormone levels (GH and IGF-I) and tumor volume (sella turcica magnetic resonance imaging).
SSTR5 was present at the highest level followed by SSTR2, SSTR3, SSTR1, and SSTR4 (2327 (1046–5555), 2098 (194–23 954), 97 (0–460), 14 (0–29 480), and 0 (0–652) copies respectively). Positive correlations were found between SSTR2 levels and the percentage decrease of GH and IGF-I after 3 (r=0.49, P<0.027 and r=0.49, P<0.029 respectively) and 6 (r=0.59, P<0.006 and r=0.58, P<0.008 respectively) months of OCT LAR. A negative correlation was found between SSTR5 mRNA levels and the percentage decrease of GH after 3 months of OCT LAR (r=−0.52, P=0.016, n=21). A higher SSTR2/SSTR5 ratio was observed among patients who obtained hormonal control with OCT LAR, when compared with those uncontrolled (2.4 (0.7–10) vs 0.3 (0.1–7.7), P=0.001). A ROC curve analysis showed a SSTR2/SSTR5 ratio of 1.3 as the best predictor of disease control, with a sensitivity of 88% and a specificity of 92% – area under curve, 0.9. A positive correlation was also found between SSTR2 mRNA levels and the percentage decrease in tumor volume after 6 months of OCT LAR (r=0.79, P=0.002, n=12).
Somatostatin receptor subtype 2 mRNA expression levels in somatotropinomas correlate positively with in vivo hormonal and tumor volume responses to OCT LAR.
Ana Paula Vidal, Bruno M Andrade, Fernanda Vaisman, Juliana Cazarin, Luis Felipe Ribeiro Pinto, Marisa Maria Dreyer Breitenbach, Rossana Corbo, Adriana Caroli-Bottino, Fernando Soares, Mario Vaisman and Denise P Carvalho
AMP-activated protein kinase (AMPK) is activated by the depletion in cellular energy levels and allows adaptive changes in cell metabolism and cell survival. Recently, our group described that AMPK plays an important role in the regulation of iodide and glucose uptake in thyroid cells. However, AMPK signaling pathway in human thyroid carcinomas has not been investigated so far.
To evaluate the expression and activity of AMPK in papillary thyroid carcinomas.
We examined total and phosphorylated AMPK (tAMPK and pAMPK) and phosphorylated acetyl-CoA-carboxylase (pACC) expressions through imunohistochemistry, using a tissue microarray block composed of 73 papillary thyroid carcinomas (PAP CA) or microcarcinomas (PAP MCA) and six adenoma (AD) samples from patients followed at the Federal University Hospital. The expression levels were compared with the non-neoplastic tissues from the same patient. Two different pathologists analyzed the samples and attributed scores of staining intensity and the proportion of stained cells. A total index was obtained by multiplying the values of intensity and the proportion of stained cells (INTxPROP).
tAMPK, pAMPK, and pACC showed a predominant cytoplasmic staining in papillary carcinomas, adenomas, and non-neoplastic thyroid tissues. However, the intensity and the proportion of stained cells were higher in carcinomas, so that a significant increase was found in the INTxPROP score both in PAP CA and PAP MCA, when compared with their respective controls.
Our results show unequivocally that AMPK pathway is highly activated in papillary thyroid carcinomas; however, more studies are necessary to understand the pathophysiological significance of AMPK activation in thyroid carcinogenesis.