Differential expression of somatostatin receptor subtype-related genes and proteins in non-functioning and functioning adrenal cortex adenomas

Abstract

Abstract. Adrenocortical adenomas display highly variable expressions of somatostatin receptor (SSTR) subtypes, whose expression is mandatory (although not always sufficient) to achieve the positive effects of somatostatin (SST) analog therapy. Immunohistochemistry (IHC) is the main method used to investigate receptor protein expression. The molecular biology method -polymerase chain reaction (PCR) -is also often used to investigate receptor expression. Nevertheless, the expression of receptor mRNA and the respective receptor protein is not always synchronized. The aim of this study was to investigate SSTR expression by IHC in adrenal adenomas, to compare the results to data obtained by real-time PCR and to determine whether hormonally functioning and nonfunctioning adenomas differ in this respect. Adrenocortical adenomas were removed surgically from 13 females and 2 males. The tissues were obtained from 9 non-functioning and 6 functioning adenomas. The intensity of IHC reaction was scored semiquantitatively by two independent observers. Real-time PCR was performed using pairs of primers in a reaction amplified along a gradient of temperatures. Amplified DNA was measured by monitoring SYBR-Green fluorescence. In non-functioning tumors, compatibility between IHC and PCR results was observed for SSTR 1 and 2 in 62.5% of the samples. Fifty percent of patients demonstrated compatibility for SSTR 4 and 5 and 37.5% for SSTR 3. In hormonally active adenomas, total compatibility of both methods was noted for SSTR 2 (100%). The compatibility obtained for SSTR 5 was 66.6%. We conclude that receptor gene and respective receptor protein expression are not always synchronized. Messenger RNA detection alone is not sufficient to predict the presence of the receptor protein acting as a target for SST and its analogs.

Molecular and functional properties of densely and sparsely granulated GH-producing pituitary adenomas

“…Detection of SSTR mRNA was compared with SSTR immunohistochemical protein staining, which revealed concordance rates between 57 and 89% comparable to published results from various other tissues (46,47,48) (Supplementary Table 3, see section on supplementary data given at the end of this article).…”

“…Overall SSTR mRNA expression profiles corresponded well but not perfectly to protein expression, probably because mRNA expression may not always lead to translation into detectable protein expression. (46,47,48). Therefore, determining protein expression by immunohistochemistry appears to be the preferable measure for defining the adenoma cell SSTR status.…”

An Immunohistochemical Investigation of the Expression of Somatostatin Receptor Subtypes – Should Therapeutic Trials be Performed to Determine the Efficacy of Somatostatin Analogs in Treating Advanced Thyroid Malignances?

“…The knowledge about SSTR expression is based on their detection in thyroid gland tumors by diagnostic methods such as immunohistochemistry, molecular biology methods (RT-PCR), applied "in vitro" conditions or imaging techniques applied "in vivo". Of these, IHC is arguably the most effective, as it can detect all SSTR-1-5 receptor proteins, including 2A and 2B in surgically isolated endocrine tumor tissues [30,31]. The mean scores of reactions ± SEM were calculated.…”

MicroRNA expression patterns associated with hyperfunctioning and non-hyperfunctioning phenotypes in adrenocortical adenomas

“…Despite several studies attempting to characterize the gene expression profiles of these benign tumors (12,13,14,15), the molecular basis of these tumors has not yet been fully understood. Previous miRNA-profiling studies in ACT focused mainly on differential miRNA expression associated with malignancy (8,11,16,17,18); their expression patterns in benign tumors remain unclear.…”