SOMATOSTATINE RECEPTORS EXPRESSION IN CLINICAL NON-FUNCTIONING ADENOMAS REGARDING THEIR IMUMUNOHISTOCHEMICAL PROFILE

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 167-198-Hypothalamus-Pituitary Development & Biology
Basic/Clinical
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-169
Filip Gabalec*1, Monika Drastikova1, Martin Beranek1, David Netuka2, Vaclav Masopust2, Tomas Cesak1, Josef Marek3 and Jan Cap1
1Charles University Hospital and Faculty of Medicine, Hradec Kralove, Czech Republic, 2Charles University in Prague, Central Military Hospital in Prague, 3Charles Univ/ Medical Sch, Prague 2, Czech Republic
Clinically non-functioning pituitary adenomas (CNFAs) represent about one-third of pituitary tumors. The majority of them are pathologically classified as gonadotropinomas or null-cell adenomas. The treatment of choice is transsphenoidal adenectomy. Conservative therapy with dopamine agonists and somatostatin analogues is effective only in some cases in dependence of somatostatin (SSTR) and dopamine receptors expression.

The aim of the study was quantitative analysis of somatostatin receptors (SSTR) in CNFAs using real-time RT-PCR and correlation with immunohistochemical profile.

Results: All 69 adenomas, 40 men and 29 women, aged 25–84 years (mean 61.4 +/-1.5, med 63) expressed SSTR1–4 and SSTR5 was expressed in 38 (55 %) of adenomas. High variability of expression for a particular type was present. SSTR1 mRNA was expressed from 909 to 242069, SSTR2 1413–148 681, SSTR3 63–46 914, SSTR4 568–99 227 and SSTR5 mRNA 0–43 777 (all in copies/5μl cDNA). Relative median quantity after normalization to housekeeping gene GUS was 0.65 SSTR1 > 0.54 SSTR2 > 0.26 SSTR4 >0.19 SSTR3 > 0.01 SSTR5. After immunohistochemical analysis, we had 56 gonadotroph, 3 null-cell adenomas, 6 silent corticotroph and 4 plurihormonal tumors. SSTR1-4 expression was not statistically different in regard to histological type of adenoma. SSTR5 was highly expressed in silent corticotroph adenomas (relative median quantity after normalization to housekeeping gene GUS 0.01) than in gonadotroph adenomas (0.14).

Conclusion: A very heterogeneous level of SSTR expression may explain low clinical effectiveness of somatostatin analogues in the majority of CNFAs. Immunohistochemical profile except for silent corticotroph adenomas is not helpful for predicting receptor expression. qRT-PCR could help to choose patients profiting from expensive medical treatment with somatostatin analogues and chimeric compounds and preventing residuum tumor growth.

Project is supported by Ministry of Health Project No. NT/11344-4/2010 and GAUK 723912

Nothing to Disclose: FG, MD, MB, DN, VM, TC, JM, JC

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm