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Somatostatin type 2A receptor immunoreactivity in human pancreatic adenocarcinomas
M Pilichowska1, N Kimura, M Schindler
1Department of Pathology, Tufts University School of Medicine, Boston, MA, USA. mpilichowska@lifespan.org
Abstract:
Somatostatin and its analogs have been included in experimental treatment protocols for advanced pancreatic adenocarcinoma based on their known antisecretory and antiproliferative properties. Somatostatin receptor type 2 (sstr2A) mediates antiproliferative actions of somatostatin and has the strongest affinity to the therapeutically used somatostatin analog--octreotide. We investigated localization of sstr2A in 27 pancreatic adenocarcinomas in relation to tumor histological features and neuroendocrine differentiation confirmed by immunoreactivity for chromogranin A (CgA), chromogranin B (CgB), or somatostatin. Immunoreactivity for sstr2A generally coincided with tumor neuroendocrine differentiation demonstrated by staining for CgA and was present on the cell membranes of pancreatic islet cells and endocrine cells occasionally present in the wall of normal pancreatic ducts. Thirteen pancreatic adenocarcinomas contained cells immunoreactive for sstr2A in numbers ranging from occasional single cells, cell clusters, or carcinoma duct segments. In two cases, cells immunoreactive for sstr2A and CgA represented more than 30 and 10% of the total tumor cell population (case 1 and 15, respectively). Case 1 fulfills the diagnostic criteria of mixed ductal endocrine carcinoma. We conclude that immunohistochemical staining for a generic neuroendocrine marker such as CgA would facilitate identification of a subgroup of pancreatic adenocarcinomas expressing sstr2A receptors. Future studies need to evaluate the responsiveness of these tumors to somatostatin analogue treatment.
Insights
This study found that somatostatin receptor type 2 (sstr2A) is present in pancreatic adenocarcinomas, often coinciding with neuroendocrine differentiation. Identifying sstr2A-expressing tumors may guide future somatostatin analog treatments.
Area of Science:
- Oncology
- Endocrinology
- Gastroenterology
Background:
- Somatostatin analogs are explored for advanced pancreatic adenocarcinoma due to antisecretory and antiproliferative effects.
- Somatostatin receptor type 2 (sstr2A) mediates somatostatin's antiproliferative actions and binds octreotide.
- Neuroendocrine differentiation is a feature in some pancreatic adenocarcinomas.
Purpose of the Study:
- To investigate the localization of somatostatin receptor type 2 (sstr2A) in pancreatic adenocarcinomas.
- To correlate sstr2A expression with histological features and neuroendocrine differentiation markers.
- To identify potential subgroups of pancreatic adenocarcinomas responsive to somatostatin analog therapy.
Main Methods:
- Immunohistochemical staining for sstr2A, chromogranin A (CgA), chromogranin B (CgB), and somatostatin.
- Analysis of 27 pancreatic adenocarcinoma samples.
- Correlation of sstr2A immunoreactivity with tumor histology and neuroendocrine markers.
Main Results:
- sstr2A immunoreactivity generally coincided with neuroendocrine differentiation markers like CgA.
- sstr2A was found on pancreatic islet cells and endocrine cells in normal ducts.
- Thirteen of 27 adenocarcinomas showed sstr2A-positive cells; two cases had significant percentages (>10-30%) of sstr2A and CgA positive cells.
- One case met criteria for mixed ductal-endocrine carcinoma.
Conclusions:
- Immunohistochemical staining for CgA can help identify pancreatic adenocarcinomas expressing sstr2A.
- These findings suggest a subgroup of pancreatic adenocarcinomas may benefit from somatostatin analog treatment.
- Further studies are needed to evaluate treatment responsiveness in sstr2A-expressing tumors.