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- Casar-Borota, Olivera, et al.
(author)
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Expression of SSTR2a, but not of SSTRs 1, 3, or 5 in Somatotroph Adenomas Assessed by Monoclonal Antibodies Was Reduced by Octreotide and Correlated With the Acute and Long-Term Effects of Octreotide
- 2013
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In: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 98:11, s. E1730-E1739
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Journal article (peer-reviewed)abstract
- Context: Reduced expression of somatostatin receptors (SSTRs) in somatotroph adenomas and their potential down-regulation after medical treatment may explain the unsatisfactory response to octreotide in particular acromegalic patients. The expression of SSTRs other than SSTR2a has not been studied in large, unselected cohorts using novel rabbit monoclonal antibodies. Objective: We aimed to determine the expression of SSTRs 1, 2a, 3, and 5 in somatotroph adenomas, to correlate expression with clinical characteristics and the response to octreotide, and to ascertain whether preoperative octreotide treatment affected SSTR expression. Design, Setting, Patients: The study included 78 adenomas from patients operated on consecutively during 2000 to 2010. After exclusion of 13 patients, immunohistochemical analysis with rabbit monoclonal antibodies against SSTRs 1, 2a, 3, and 5 (clones UMB-7, -1, -5, and -4) was performed on 65 adenomas. Intervention: Twenty-eight patients received preoperative octreotide, and 37 patients were operated on without pretreatment. Twenty-six patients were randomized to direct surgery (n = 13) or to octreotide pretreatment (n = 13). Main Outcome Measure: SSTR expression was evaluated using a 12-grade scoring system. The responses to the octreotide test dose (GH reduction) and to 6 months of octreotide (IGF-I reduction) were measured. Results: The majority of adenomas showed membranous expression of SSTRs 2a and 5. SSTR2a expression was reduced in the pretreated group and correlated with the acute octreotide test results and the effect of octreotide treatment. In a linear regression model with SSTR2 a expression as the determinant, the correlation with the acute test response improved after adjustment for medical pretreatment. Conclusion: Rabbit monoclonal antibodies are reliable markers of SSTRs in somatotroph adenomas. SSTR2a expression correlated with the response to octreotide and was reduced after octreotide treatment, indicating the need for adjustment when SSTR2a expression is correlated with baseline characteristics. Evaluation of SSTR subtypes may be an important aspect of improving the medical treatment for acromegaly.
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| 2. |
- Casar-Borota, Olivera, et al.
(author)
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KIT protein expression and mutational status of KIT gene in pituitary adenomas
- 2012
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In: Virchows Archiv. - New York : Springer-Verlag New York. - 0945-6317 .- 1432-2307. ; 460:2, s. 171-181
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Journal article (peer-reviewed)abstract
- KIT protein expression and mutational status of KIT gene in different types of tumours have been intensively studied since Imatinib Mesylate, KIT/PDGFRA tyrosine kinase inhibitor became available. However, only one immunohistochemical study on KIT expression in pituitary adenomas has been published. There are currently no reports on mutational status of KIT gene in pituitary adenomas. We have immunohistochemically investigated KIT expression in 252 pituitary adenomas and found cytoplasmic reactivity in 52.4% and membranous reactivity in 8.3% of all adenomas. There was statistically significant difference in KIT expression between clinically non-functioning, growth hormone- and adrenocorticotroph hormone-producing adenomas. The group with membranous expression was dominated by somatotropinomas and clinically non-functioning adenomas. KIT expression in a subset of adenomas was also confirmed by western blot analysis of 48 adenomas. Immunohistochemical KIT expression was correlated with basic clinical data and in a cohort of acromegalic patients with additional data (somatostatin receptor type 2A expression, response to somatostatin analogue treatment and mutational status of gsp oncogene). Exons 9, 11, 13 and 17 of KIT gene were searched for mutations in the tumours with membranous KIT expression and in a minority of tumours with cytoplasmic KIT expression using denaturing high-performance liquid chromatography and in suspected cases sequencing of one or more exons. No mutations in the examined exons were found. Our results may suggest a role of KIT in the pathogenesis of a subset of pituitary adenomas and point out the need for further research to find out if KIT-reactive adenomas could be sensitive to Imatinib Mesylate.
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