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

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 non-functioning 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.