Role of VEGF-A and its receptors in sporadic and MEN2-associated pheochromocytoma.

Pheochromocytoma (PHEO), a rare catecholamine producing tumor arising from the chromaffin cells, may occurs sporadically (76%-80%) or as part of inherited syndromes (20%-24%). Angiogenesis is a fundamental step in tumor proliferation and vascular endothelial growth factor (VEGF-A) is the most well-characterized angiogenic factor. The role of angiogenic markers in PHEO is not fully understood; investigations were therefore made to evaluate the expression of VEGF-A and its receptors in PHEO and correlate to clinical parameters. Twenty-nine samples of PHEO were evaluated for VEGF-A, VEGF receptor-1 (VEGFR-1) VEGFR-2 expression and microvessel density (MVD) by immunohistochemistry. Clinical data were reviewed in medical records. The mean age of patients was 38±14 years, and 69% were woman. VEGF-A, VEGFR-1 and VEGFR-2 staining were detected in nearly all PHEO samples. No significant correlation was observed between VEGF-A, VEGFR-1, VEGFR-2 expression or MVD and age at diagnosis, tumor size or sporadic and hereditary PHEO. However, the levels of expression of these molecules were significantly higher in malignant PHEO samples (p=0.027, p=0.003 and p=0.026, respectively).VEGF-A and its receptors were shown to be up-regulated in malignant PHEO, suggesting that these molecules might be considered as therapeutic targets for unresectable or metastatic tumors.

Reduced tissue inhibitor of metalloproteinase-2 expression is associated with advanced medullary thyroid carcinoma.

Matrix metalloproteinases (MMPs) are enzymes for extracellular matrix remodeling that are involved in tumor growth, progression and metastasis. Among them, MMP-9 has been implicated in tumor angiogenesis. Tissue inhibitor of matrix metalloproteinase (TIMP)-2, a member of the family of MMP inhibitors, induces apoptosis and inhibits various stages of angiogenesis. Previous studies analyzing the expression of MMP-9 and TIMP-2 in medullary thyroid carcinoma (MTC) are scarce. The aims of the current study were to evaluate MMP-9 and TIMP-2 expression in MTC samples and correlate the results with clinical parameters. Paraffin-embedded samples from 77 MTC patients were evaluated for expression by immunohistochemistry. The clinical data in medical records were retrospectively reviewed. In total, 77 patients aged 35.6±17.1 years were enrolled. Of these patients, 36 had hereditary disease (46.8%). Immunohistochemical staining for MMP-9 and TIMP-2 was detected in 89.6 and 93.5% of the samples, respectively. The expression of MMP-9 was not found to correlate with clinical parameters, although, a trend toward a correlation between MMP-9 and distant metastasis was observed (P=0.053). By contrast, TIMP-2 staining was found to correlate with age at diagnosis (P=0.026) and negatively correlate with tumor size and tumoral stage (P=0.002 and P=0.001, respectively). Notably, the highest levels of TIMP-2 expression were observed in patients with intrathyroidal disease. The MMP-9 enzyme involved in extracellular matrix remodeling is overexpressed in MTC lesions and may contribute to tumor vascularization and growth. Reduced levels of TIMP-2 expression may be implicated in tumor progression and spread of disease.

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.

Papel do fator de crescimento endotelial vascular nos carcinomas de tireóide / The role of vascular endothelial growth factor in tumor

O crescimento tumoral está diretamente relacionado com a neovascularização, a qual decorre do desequilíbrio entre os fatores pró-angiogênicos e antiangiogênicos, secretados pelas células neoplásicas. O fator de crescimento endotelial vascular (VEGF) desempenha papel chave na angiogênese tumoral, estimulando a proliferação, migração e sobrevivência das células endoteliais. Atua através da ligação a receptores tirosina quinase específicos: VEGFR-1/Flt-1, VEGFR-2/KDR e VEGFR-3. O aumento da expressão do VEGF e de seus receptores tem sido associado à progressão, metastatização e pior prognóstico em diversos tumores malignos. A compreensão das vias moleculares que envolvem o mecanismo de indução da angiogênese tumoral por fatores de crescimento como o VEGF aumentam as possibilidades de novas terapêuticas a serem utilizadas no tratamento de tumores malignos humanos. Evidências indicam um importante papel do VEGF nas neoplasias da tireóide e a utilização de inibidores do VEGF ou de seus receptores pode constituir um importante recurso terapêutico, já tendo sido utilizado em determinados tipos de tumores humanos. O presente artigo tem como objetivo fazer uma revisão da atuação do VEGF no crescimento tumoral com enfoque nas neoplasias malignas da tireóide.

The neoplasic process is directly related to neovascularization, an imbalance between pro-angiogenic and antiangiogenic factors. The vascular endothelial growth factor (VEGF) plays a key role in tumor angiogenesis, stimulating proliferation, migration and survival of endothelial cells. VEGF acts through binding to specific tyrosine kinase receptor: VEGFR-1/Flt-1, VEGFR-2/KDR and VEGFR-3. Increased expression of VEGF and its receptors have been associated with progression, metastasis and worse prognosis in human malignant tumors. Understanding molecular pathways of tumor angiogenesis related to growth factors such as VEGF is a crucial step on developing new treatment options. Evidence indicates an important role of VEGF in thyroid cancer and inhibition of VEGF or its receptors may constitute an important therapeutic resource, particularly for those patients with metastatic diseases. This aim of this article is to review the role of VEGF in tumor growth, focusing on thyroid malignancies.

Normal perioperative serum calcitonin levels in patients with advanced medullary thyroid carcinoma: case report and review of the literature.

CONTEXT: Medullary thyroid carcinoma (MTC), a tumor of the parafollicular C cells of the gland, comprises 3-5% of all malignant thyroid neoplasms. Calcitonin, a polypeptidic hormone secreted by the neoplastic cells, is considered a very sensitive and specific MTC tumor marker. Patients with MTC usually present elevated serum calcitonin levels, which correlate with tumor burden and prognosis. OBJECTIVES: To describe a case of advanced MTC with normal serum calcitonin and review the literature on this subject. DESIGN: A case study was performed. INTERVENTION: There were no interventions. PATIENTS: A case of advanced MTC with normal serum calcitonin was studied. RESULTS: Serum calcitonin was measured by two distinct assays, a chemiluminescent immunometric and an in-house two-site monoclonal antibody-based immunofluorometric assay. To rule out a "hook effect," or posttranslational modifications of calcitonin molecule, serum dilutions and tumor immunohistochemistry for calcitonin with the same antibodies used for serum calcitonin measurements were performed. Serum calcitonin levels were within the normal range in both assays, whereas the tumor stained strongly positive for calcitonin. These findings suggest that the tumor was able to produce but not to secrete the calcitonin protein. Five other cases of advanced MTC with normal serum calcitonin levels had been previously reported. CONCLUSIONS: We present an unusual case of advanced MTC with normal serum calcitonin levels. Awareness of MTC cases presenting with normal serum calcitonin levels is important in clinical practice and is particularly relevant to centers that use this test for screening.

The fatty acid-binding protein-2 A54T polymorphism is associated with renal disease in patients with type 2 diabetes.

The intestinal fatty-acid binding protein-2 (FABP2) gene codes a protein responsible for the absorption of long-chain fatty acids. To test whether FABP2 is a candidate gene for renal disease in patients with type 2 diabetes, a functional A54T polymorphism was genotyped in 1,042 Brazilians with type 2 diabetes. Patients were classified as having normoalbuminuria (urinary albumin excretion [UAE] <20 microg/min; n = 529), microalbuminuria (UAE 20-199 microg/min; n = 217), or proteinuria (UAE >199 microg/min; n = 160). Patients with end-stage renal disease (ESRD) (n = 136) were also included. The prevalence of the TT genotype was higher in patients with renal involvement compared with those with normoalbuminuria (odds ratio [95% CI] 2.4 [1.1-5.4]) following adjustment for type 2 diabetes duration, BMI, hypertension, A1C, and cholesterol levels. The risk was similar considering different stages of renal involvement. In a second independent patient sample (483 type 2 diabetic Caucasians residing in Massachusetts), a significant association was also observed between the TT genotype and proteinuria or ESRD (2.7 [1.0-7.3]; P = 0.048). This study thus provides evidence that FABP2 confers susceptibility to renal disease in type 2 diabetic patients.

The type 2 deiodinase A/G (Thr92Ala) polymorphism is associated with decreased enzyme velocity and increased insulin resistance in patients with type 2 diabetes mellitus.

The single-nucleotide polymorphism A/G in the type 2 deiodinase (D2) gene predicts a threonine (Thr) to alanine (Ala) substitution at codon 92 (D2 Thr92Ala) and is associated with insulin resistance in obese patients. Here, this association was investigated in 183 patients with type 2 diabetes mellitus, using homeostasis model assessment. The median fasting plasma insulin in Ala/Ala individuals was significantly higher than in patients with Ala/Thr or Thr/Thr genotypes (19.6 vs. 12.0 vs. 14.8 mIU/ml, respectively; P = 0.004). Assuming a recessive model, the homeostasis model assessment index was higher in the Ala/Ala group when compared with Ala/Thr-Thr/Thr group (8.50 vs. 4.85, P = 0.003). Although this polymorphism has not been associated with changes in D2 kinetics as measured in HEK-293 cells transiently expressing D2 Thr92Ala, we investigated whether such association could be detected in human tissue samples. Remarkably, in thyroid and skeletal muscle samples from subjects homozygous for the Ala allele, D2 velocity was significantly lower than in subjects with Ala/Thr-Thr/Thr genotypes (P = 0.05 and 0.04, respectively). In conclusion, the A/G polymorphism is associated with greater insulin resistance in type 2 diabetes mellitus patients and with lower D2 velocity in tissue samples. These findings suggest that the D2-generated T(3) in skeletal muscle plays a role in insulin resistance.