Diagnosis of Gastroenteropancreatic Neuroendocrine Tumors
Diagnosis of Gastroenteropancreatic Neuroendocrine Tumors
Objectives: To elucidate the role of epithelial-mesenchymal transition markers in gastroenteropancreatic neuroendocrine tumors (GEP NETs) and the potential usefulness in their clinical management.
Methods: One hundred ten GEP NET paraffin-embedded samples were immunohistochemically analyzed for E-cadherin, N-cadherin, β-catenin, vimentin, Snail1, Snail2, Twist, and Foxc2 protein expression.
Results: The 5-year survival rate was reduced for those patients showing high Snail1 protein levels, a cytoplasmic E-cadherin pattern, reduced N-cadherin expression, and loss of E-cadherin/β-catenin adhesion complex integrity at the cell membrane. Interestingly, high β-catenin expression was useful in identifying a grade 1 NET subgroup with a favorable clinical course. Importantly, it also helped to discriminate small-cell vs large-cell grade 3 neuroendocrine carcinomas.
Conclusions: β-Catenin and N-cadherin immunohistochemical detection might be a useful tool in the differential diagnosis of small-cell vs large-cell G3 neuroendocrine carcinomas. High Snail1 and Foxc2 expression is associated with the invasion and metastatic spread of GEP NETs.
Gastroenteropancreatic neuroendocrine tumors (GEP NETs) are a poorly understood heterogeneous group of lesions derived from the neuroendocrine cells in the gastrointestinal mucosa and the pancreas. The overall incidence of GEP NETs is about 2.5 to 5 cases per 100,000 and has increased significantly over the past 3 decades.
These tumors are diagnosed by light microscopy based on their growth pattern and neuroendocrine differentiation. According to the recent World Health Organization (WHO) classification, they are classified as grade 1 neuroendocrine tumors (G1 NETs), grade 2 neuroendocrine tumors (G2 NETs), and grade 3 neuroendocrine carcinoma, large cell (G3 NEC-LC) or small cell (G3 NEC-SC) subtype. Immunohistochemically, these tumors stain for neuroendocrine markers chromogranin A and synaptophysin. Some features, such as the mitotic index, Ki-67 labeling index, tumor size, and the presence of necrosis or blood vessel invasion, are required for tumor classification.
The GEP NETs show a variable biologic aggressiveness and a clinical course that is poorly predicted by the clinical prognostic factors currently available in the clinical setting. Some patients showing low-risk pathologic features develop metastasis unexpectedly, compromising their life expectancy. The molecular basis underlying GEP NET development is poorly understood, and few studies have been reported to date.
The epithelial-mesenchymal transition (EMT) is a biologic process whereby epithelial cells express proteins (eg, vimentin) and show morphologic features of a mesenchymal phenotype. Epithelial cells are characterized by a cuboidal morphology and maintenance of cell polarity. Cells tightly interact with each other through homotypic adhesion complexes mediated by cell-cell junction proteins (composed mainly of the cadherin family). In EMT, the cells lose their polarity and cell-cell adhesion and gain motility and invasive capacities.
Epithelial-mesenchymal transitions have recently been classified into 3 general subgroups: type 1 EMT involves transitions during embryonic development (gastrulation, development of the neural crest, etc), type 2 EMT during tissue fibrosis, and type 3 EMT in the carcinogenic process.
In the carcinogenic setting, EMT takes place in the first phase of the metastatic cascade, prior to the local invasion. Once a distant organ is colonized, tumor cells must return to the epithelial phenotype by the reverse process known as the mesenchymal-epithelial transition.
At the molecular level, EMT transcriptional reprogramming occurs through transcription factors, such as Snail1, Snail2, Foxc2, and Twist, and the subsequent repression of adhesion molecules expression, such as E-cadherin. Another event triggered in EMT is the so-called cadherin switch, defined as an increase in N-cadherin expression with or without a decrease in E-cadherin expression. In addition, Twist has recently been shown to be involved in the cadherin switch as an inducer of N-cadherin expression.
Additional markers are urgently needed for the correct handling of these patients and clinical decision making regarding treatment options and patient follow-up. Our study analyzes EMT regulator expression involved in E-cadherin/β-catenin complex alteration in the whole spectrum of GEP NETs and patients' prognosis.
Abstract and Introduction
Abstract
Objectives: To elucidate the role of epithelial-mesenchymal transition markers in gastroenteropancreatic neuroendocrine tumors (GEP NETs) and the potential usefulness in their clinical management.
Methods: One hundred ten GEP NET paraffin-embedded samples were immunohistochemically analyzed for E-cadherin, N-cadherin, β-catenin, vimentin, Snail1, Snail2, Twist, and Foxc2 protein expression.
Results: The 5-year survival rate was reduced for those patients showing high Snail1 protein levels, a cytoplasmic E-cadherin pattern, reduced N-cadherin expression, and loss of E-cadherin/β-catenin adhesion complex integrity at the cell membrane. Interestingly, high β-catenin expression was useful in identifying a grade 1 NET subgroup with a favorable clinical course. Importantly, it also helped to discriminate small-cell vs large-cell grade 3 neuroendocrine carcinomas.
Conclusions: β-Catenin and N-cadherin immunohistochemical detection might be a useful tool in the differential diagnosis of small-cell vs large-cell G3 neuroendocrine carcinomas. High Snail1 and Foxc2 expression is associated with the invasion and metastatic spread of GEP NETs.
Introduction
Gastroenteropancreatic neuroendocrine tumors (GEP NETs) are a poorly understood heterogeneous group of lesions derived from the neuroendocrine cells in the gastrointestinal mucosa and the pancreas. The overall incidence of GEP NETs is about 2.5 to 5 cases per 100,000 and has increased significantly over the past 3 decades.
These tumors are diagnosed by light microscopy based on their growth pattern and neuroendocrine differentiation. According to the recent World Health Organization (WHO) classification, they are classified as grade 1 neuroendocrine tumors (G1 NETs), grade 2 neuroendocrine tumors (G2 NETs), and grade 3 neuroendocrine carcinoma, large cell (G3 NEC-LC) or small cell (G3 NEC-SC) subtype. Immunohistochemically, these tumors stain for neuroendocrine markers chromogranin A and synaptophysin. Some features, such as the mitotic index, Ki-67 labeling index, tumor size, and the presence of necrosis or blood vessel invasion, are required for tumor classification.
The GEP NETs show a variable biologic aggressiveness and a clinical course that is poorly predicted by the clinical prognostic factors currently available in the clinical setting. Some patients showing low-risk pathologic features develop metastasis unexpectedly, compromising their life expectancy. The molecular basis underlying GEP NET development is poorly understood, and few studies have been reported to date.
The epithelial-mesenchymal transition (EMT) is a biologic process whereby epithelial cells express proteins (eg, vimentin) and show morphologic features of a mesenchymal phenotype. Epithelial cells are characterized by a cuboidal morphology and maintenance of cell polarity. Cells tightly interact with each other through homotypic adhesion complexes mediated by cell-cell junction proteins (composed mainly of the cadherin family). In EMT, the cells lose their polarity and cell-cell adhesion and gain motility and invasive capacities.
Epithelial-mesenchymal transitions have recently been classified into 3 general subgroups: type 1 EMT involves transitions during embryonic development (gastrulation, development of the neural crest, etc), type 2 EMT during tissue fibrosis, and type 3 EMT in the carcinogenic process.
In the carcinogenic setting, EMT takes place in the first phase of the metastatic cascade, prior to the local invasion. Once a distant organ is colonized, tumor cells must return to the epithelial phenotype by the reverse process known as the mesenchymal-epithelial transition.
At the molecular level, EMT transcriptional reprogramming occurs through transcription factors, such as Snail1, Snail2, Foxc2, and Twist, and the subsequent repression of adhesion molecules expression, such as E-cadherin. Another event triggered in EMT is the so-called cadherin switch, defined as an increase in N-cadherin expression with or without a decrease in E-cadherin expression. In addition, Twist has recently been shown to be involved in the cadherin switch as an inducer of N-cadherin expression.
Additional markers are urgently needed for the correct handling of these patients and clinical decision making regarding treatment options and patient follow-up. Our study analyzes EMT regulator expression involved in E-cadherin/β-catenin complex alteration in the whole spectrum of GEP NETs and patients' prognosis.
