Débora Rodrigues Siqueira

Increased Expression of Vascular Endothelial Growth Factor and Its Receptors, VEGFR-1 and VEGFR-2, in Medullary Thyroid Carcinoma

BACKGROUND Vascular endothelial growth factor (VEGF-A) expression is upregulated in the majority of human tumors, where it stimulates proliferation, migration, and survival of endothelial cells. Studies have suggested that VEGF inhibitors can be used as an alternative therapy in medullary thyroid carcinoma (MTC), but data about expression of VEGF-A and its receptor in this tumor are scarce. The aims of this study were to evaluate VEGF-A, VEGF receptor (VEGFR)-1, VEGFR-2, and microvessel density (MVD) expression in MTC samples and correlate it with clinical parameters. METHODS Paraffin-embedded samples from 38 MTC patients were evaluated for VEGF-A, VEGFR-1, VEGFR-2, and MVD expression by immunohistochemistry. Clinical data were retrospectively reviewed in medical records. RESULTS Thirty-eight patients aged 31.8 +/- 17.1 years were enrolled. Twenty-seven patients had hereditary disease (71.1%). Twenty-five of them were found to have multiple endocrine neoplasia (MEN) 2A and two were found to have MEN 2B. VEGF-A immunohistochemical staining was detected in 95% (36/38), VEGFR-1 in 96% (36/37), and VEGFR-2 in 91% (31/34) of MTC samples. Age at surgery was positively correlated with VEGFR-2 (p = 0.003). There was no correlation between VEGF-A, VEGFR-2, and tumor stage (tumor node metastasis). Nevertheless, VEGFR-1 was found to be inversely correlated with tumor node metastasis (p = 0.034). We also observed a trend toward an association between VEGFR-1 signal intensity and cure of disease, although this did not reach statistical significance (p = 0.054). Neither VEGF-A nor VEGFR-2 was associated with disease outcome after a median follow-up period of 5 years (p = 0.882 and p = 0.236, respectively). As expected, MVD was correlated with age at surgery (p = 0.005) and tumor size (p = 0.03). Patients with the hereditary form of the disease had a stronger intensity for VEGFR-1 (p = 0.039), whereas patients with sporadic disease displayed higher MVD counts (44 [27-63] vs. 21 [9-49], p = 0.018). CONCLUSION The VEGF-A, VEGFR-1, and VEGFR-2 immunoreactive proteins are overexpressed in MTC lesions and might be implicated in tumor progression. It is not clear, however, if expression of these molecules provides prognostic information regarding the spread or outcome of MTC.

The RET polymorphic allele S836S is associated with early metastatic disease in patients with hereditary or sporadic medullary thyroid carcinoma

The possible role of RET variants in modifying the natural course of medullary thyroid carcinoma (MTC) is still a matter of debate. Here, we investigate whether the RET variants L769L, S836S, and G691S/S904S influence disease presentation in hereditary or sporadic MTC patients. One hundred and two patients with hereditary MTC and 81 patients with sporadic MTC attending our institution were evaluated. The frequencies of RET polymorphisms in hereditary MTC were as follows: L769L, 17.3%; S836S, 7.95%; and S904S/G691S, 18.2%. No associations were observed between these polymorphisms and pheochromocytoma, hyperparathyroidism, lymph node, or distant metastasis. However, patients harboring the S836S variant were younger than those without this allele (17±8.2 vs 28.6±14.4 years, P=0.01), suggesting that these patients had metastases at a young age. Accordingly, the cumulative frequency of local and/or distant metastases as estimated by Kaplan-Meier curves showed that lymph node and distant metastases occurred earlier in patients harboring the S836S variant (P=0.003 and P=0.026 respectively). The S836S allele frequency was higher in sporadic MTC patients than in controls (10.5 vs 3.1%, P=0.01). Individuals harboring the S836S variant were younger (38.6±13.3 vs 48.5±16.7 years, P=0.02) and showed a higher percentage of lymph node and distant metastases (P=0.02 and P=0.04 respectively). Kaplan-Meier estimates of lymph node and distant metastases yielded distinct curves for patients with or without the S836S allele (P=0.002 and P=0.001 respectively). Additional analyses using a COX regression model showed that the S836S variant was independently associated with metastatic disease (hazard ratio 2.82 (95% confidence interval 1.51-5.26), P=0.001). In conclusion, the RET S836S variant is associated with early onset and increased risk for metastatic disease in patients with hereditary or sporadic MTC.

Molecular Basis of Medullary Thyroid Carcinoma: The Role of RET Polymorphisms

Medullary thyroid carcinoma is a rare malignant tumor originating in parafollicular C cells. It accounts for 5 to 8% of all thyroid cancers. MTC develops in either sporadic (75%) or hereditary form (25%). Genetic and molecular studies have demonstrated the involvement of the RET proto-oncogene in hereditary MTC and, less often, in its sporadic form. Although a strong genotype-phenotype correlation has been described, wide clinical heterogeneity is observed among families with the same RET mutation or even in carriers of the same kindred. In recent years, several single nucleotide polymorphisms of the RET gene have been described in the general population as well as in patients with MTC. Some studies have reported associations between the presence of polymorphisms and development or progression of MTC. Nonetheless, other studies failed to demonstrate any effect of the RET variants. Differences in the genetic background of distinct populations or methodological approaches have been suggested as potential reasons for the conflicting results. Here, we review current knowledge concerning the molecular pathogenesis of sporadic and hereditary MTC. In particular, we analyze the role of RET polymorphisms in the clinical presentation and prognosis of MTC based on the current literature.

Signaling pathways in follicular cell-derived thyroid carcinomas (review).

Thyroid carcinoma is the most common malignant endocrine neoplasia. Differentiated thyroid carcinomas (DTCs) represent more than 90% of all thyroid carcinomas and comprise the papillary and follicular thyroid carcinoma subtypes. Anaplastic thyroid carcinomas correspond to less than 1% of all thyroid tumors and can arise de novo or by dedifferentiation of a differentiated tumor. The etiology of DTCs is not fully understood. Several genetic events have been implicated in thyroid tumorigenesis. Point mutations in the BRAF or RAS genes or rearranged in transformation (RET)/papillary thyroid carcinoma (PTC) gene rearrangements are observed in approximately 70% of papillary cancer cases. Follicular carcinomas commonly harbor RAS mutations and paired box gene 8 (PAX8)-peroxisome proliferator-activated receptor γ (PPARγ) rearrangements. Anaplastic carcinomas may have a wide set of genetic alterations, that include gene effectors in the mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K) and/or β-catenin signaling pathways. These distinct genetic alterations constitutively activate the MAPK, PI3K and β-catenin signaling pathways, which have been implicated in thyroid cancer development and progression. In this context, the evaluation of specific genes, as well as the knowledge of their effects on thyroid carcinogenesis may provide important information on disease presentation, prognosis and therapy, through the development of specific tyrosine kinase targets. In this review, we aimed to present an updated and comprehensive review of the recent advances in the understanding of the genetic basis of follicular cell-derived thyroid carcinomas, as well as the molecular mechanisms involved in tumor development and progression.

Toxic Cardiomyopathy leading to fatal acute cardiac failure related to vandetanib: a case report with histopathological analysis

CONTEXT Medullary thyroid carcinoma (MTC) accounts for 3-4% of all malignant thyroid neoplasias. Vandetanib, a tyrosine kinase inhibitor (TKI) targeting vascular endothelial growth factor receptor 2, epidermal growth factor receptor, and RET, has been approved by the FDA for the treatment of locally advanced or metastatic MTC. The heart seems to be particularly susceptible to adverse effects associated with TKI therapy, and virtually all TKIs have been associated with cardiovascular events. CLINICAL PRESENTATION We report the case of a patient with metastatic MTC who was enrolled in the Phase III clinical study (NCT00410761) and presented a favorable response to vandetanib therapy, displaying marked decrease in the level of serologic tumor markers and shrinkage of metastatic lesions. After 14 months of therapy, the patient developed a fatal cardiac failure. Myocardial infarction was excluded by serial measurements of specific cardiac markers (serial troponin-T measurements varied from 0.037 to 0.042 ng/ml) and serologic tests for Chagas disease were negative. Postmortem examination of the heart revealed cardiomyocyte hypertrophy and marked myocyte degeneration in the subendocardial zones and papillary muscles of the myocardium. These pathological changes are similar to those observed in TKI-treated rats and are suggestive of drug-induced cardiotoxicity. CONCLUSION This case illustrates a previously unreported serious vandetanib-related adverse effect and highlights the need for close monitoring of patients under TKI therapy in order to identify early signs of congestive heart failure or myocardium damage.

Additive effect of RET polymorphisms on sporadic medullary thyroid carcinoma susceptibility and tumor aggressiveness

OBJECTIVE RET single nucleotide polymorphisms (SNPs) have been implicated in the pathogenesis and progression of medullary thyroid carcinoma (MTC). Here, we investigated the influence of multiple RET variants (G691S, L769L, S836S, and S904S) on the risk of MTC and tumor behavior. DESIGN AND METHODS One hundred and seven MTC patients and 308 cancer-unaffected control individuals were included. SNPs were analyzed using Custom TaqMan Genotyping Assays. Haplotypes based on the combination of allelic variants were inferred using a Bayesian statistical method. RESULTS The minor allele frequencies in MTC patients were as follows: L769L: 28.0%, S836S: 8.9%, and G691S/S904S: 22.2%. The RET L769L and S836S SNPs were associated with increased risk of MTC (odds ratio (OR)=1.95, 95% CI: 1.2-3.1, P=0.005 and OR=2.29, 95% CI: 1.2-4.5, P=0.017 respectively). The adjusted OR for individuals harboring haplotypes with three or more polymorphic alleles was 3.79 (95% CI: 1.5-9.5; P=0.004), indicating an additive effect of these variants on the risk for MTC. Among MTC patients, no significant associations were observed between RET variants and age of diagnosis or tumor size but serum calcitonin levels increased according to the number of risk alleles (P=0.003). Remarkably, patients carrying haplotypes with three or four risk alleles had increased risk for lymph node and distant metastases at diagnosis (OR=5.84, 95% CI: 1.1-31.2, P=0.039). Further analysis using Kaplan-Meier model demonstrated that metastatic disease occurred earlier in individuals harboring multiple risk alleles. CONCLUSION Our results demonstrated an additive effect of RET polymorphic alleles on the estimated risk of developing aggressive MTC.

Diagnóstico, tratamento e seguimento do carcinoma medular de tireoide: recomendações do Departamento de Tireoide da Sociedade Brasileira de Endocrinologia e Metabologia

INTRODUCTION Medullary thyroid carcinoma (MTC) originates in the thyroid parafollicular cells and represents 3-4% of the malignant neoplasms that affect this gland. Approximately 25% of these cases are hereditary due to activating mutations in the REarranged during Transfection (RET) proto-oncogene. The course of MTC is indolent, and survival rates depend on the tumor stage at diagnosis. The present article describes clinical evidence-based guidelines for the diagnosis, treatment, and follow-up of MTC. OBJECTIVE The aim of the consensus described herein, which was elaborated by Brazilian experts and sponsored by the Thyroid Department of the Brazilian Society of Endocrinology and Metabolism, was to discuss the diagnosis, treatment, and follow-up of individuals with MTC in accordance with the latest evidence reported in the literature. MATERIALS AND METHODS After clinical questions were elaborated, the available literature was initially surveyed for evidence in the MedLine-PubMed database, followed by the Embase and Scientific Electronic Library Online/Latin American and Caribbean Health Science Literature (SciELO/Lilacs) databases. The strength of evidence was assessed according to the Oxford classification of evidence levels, which is based on study design, and the best evidence available for each question was selected. RESULTS Eleven questions corresponded to MTC diagnosis, 8 corresponded to its surgical treatment, and 13 corresponded to follow-up, for a total of 32 recommendations. The present article discusses the clinical and molecular diagnosis, initial surgical treatment, and postoperative management of MTC, as well as the therapeutic options for metastatic disease. CONCLUSIONS MTC should be suspected in individuals who present with thyroid nodules and family histories of MTC, associations with pheochromocytoma and hyperparathyroidism, and/or typical phenotypic characteristics such as ganglioneuromatosis and Marfanoid habitus. Fine-needle nodule aspiration, serum calcitonin measurements, and anatomical-pathological examinations are useful for diagnostic confirmation. Surgery represents the only curative therapeutic strategy. The therapeutic options for metastatic disease remain limited and are restricted to disease control. Judicious postoperative assessments that focus on the identification of residual or recurrent disease are of paramount importance when defining the follow-up and later therapeutic management strategies.

Advanced medullary thyroid cancer : pathophysiology and management

Medullary thyroid carcinoma (MTC) is a rare malignant tumor originating from thyroid parafollicular C cells. This tumor accounts for 3%–4% of thyroid gland neoplasias. MTC may occur sporadically or be inherited. Hereditary MTC appears as part of the multiple endocrine neoplasia syndrome type 2A or 2B, or familial medullary thyroid cancer. Germ-line mutations of the RET proto-oncogene cause hereditary forms of cancer, whereas somatic mutations can be present in sporadic forms of the disease. The RET gene encodes a receptor tyrosine kinase involved in the activation of intracellular signaling pathways leading to proliferation, growth, differentiation, migration, and survival. Nowadays, early diagnosis of MTC followed by total thyroidectomy offers the only possibility of cure. Based on the knowledge of the pathogenic mechanisms of MTC, new drugs have been developed in an attempt to control metastatic disease. Of these, small-molecule tyrosine kinase inhibitors represent one of the most promising agents for MTC treatment, and clinical trials have shown encouraging results. Hopefully, the cumulative knowledge about the targets of action of these drugs and about the tyrosine kinase inhibitor-associated side effects will help in choosing the best therapeutic approach to enhance their benefits.

Role of RET genetic variants in MEN2-associated pheochromocytoma

BACKGROUND RET polymorphisms have been involved in the clinical presentation and prognosis of multiple endocrine neoplasia type 2 (MEN2)-associated medullary thyroid carcinoma. OBJECTIVE To investigate the effect of RET variants on the penetrance of pheochromocytoma (PHEO) in MEN2 patients. METHODS The RET variants L769L, S836S, and G691S/S904S were evaluated in a cohort of 153 MEN2 patients attending a tertiary teaching hospital. A comparison of RET variant frequencies between patients with and without PHEO was performed. Kaplan-Meier curves and Cox regression analysis were used to estimate the effect of RET variants on the age-dependent penetrance. RESULTS A total of 48 (31.4%) patients presented with MEN2-associated PHEOs. The mean age at diagnosis was 35.5±13.4 years, 60.4% of patients were women, and 92.8% had RET mutations at codon 634. The frequencies of RET polymorphisms were as follows: 20.1% L769L, 4.75% S836S, and 17.3% S904S/G691S. We did not observe any association between the frequencies of L769L, S836S, or S904S/G691S variants and PHEO development (all P>0.05). However, individuals carrying two RET polymorphic alleles had an increased estimated risk of PHEO (2.63; 95% CI, 1.4-5.0; P=0.004) and were younger at diagnosis when compared with those with one or no polymorphism (29.6±6.3 and 39.3±14.4 years respectively; P=0.006). Accordingly, additional analysis using Cox proportional hazard models demonstrated that the presence of two RET variants was associated with an increased risk for early PHEO development (hazard ratio, 5.99 (95% CI, 2.24-16.03); P<0.001). CONCLUSIONS RET polymorphic alleles have an additive effect on the estimated risk of age-related PHEO penetrance in MEN2 patients.

Hipertensão arterial pulmonar e doenças da tireoide

Recent studies have suggested an association between pulmonary arterial hypertension (PAH) and thyroid diseases (hypothyroidism and hyperthyroidism). This combination has a good prognosis, because the increase in the pulmonary artery pressure is usually slight and reverses after the treatment of the thyroid disease. Although the exact mechanism involved in the pathogenesis of this combination has not yet been established, it has been hypothesized that thyroid hormones and autoimmunity have a direct influence. Due to the high prevalence of thyroid disease in patients with PAH, thyroid function tests should be considered in the investigation of every patient with PAH. In this review, we describe the prevalence of PAH in patients with thyroid diseases and the prevalence of thyroid disease in patients with PAH, as well as addressing the principal effects that thyroid diseases have on the respiratory system. In addition, we report the treatment effects in patients with these diseases.