SOMATOSTATIN RECEPTOR SUBTYPES SST(1), SST(2), SST(3) AND SST(5) EXPRESSION IN HUMAN PITUITARY, GASTROENTERO-PANCREATIC AND MAMMARY-TUMORS - COMPARISON OF MESSENGER-RNA ANALYSIS WITH RECEPTOR AUTORADIOGRAPHY

Using in situ hybridization techniques with selective oligoprobes, the gene expression of sst(1), sst(2), sst(3) and sst(5) was studied in a series of 32 human pituitary adenomas, 28 breast tumors and 21 endocr ine gastroentero-pancreatic tumors, shown to express somatostatin rece ptors to variable extents. In most of these tumors the sst(2) receptor subtype was abundantly expressed, even though a significant number of pituitary adenomas, breast and gastroentero-pancreatic tumors express ed sst(1) and/or sst(3) as well. A very high incidence of the sst(5) s ubtype was found in growth hormone-producing pituitary adenomas and, t o a lesser extent, in inactive pituitary adenomas, whereas breast tumo rs seldom expressed sst(5); gastroentero-pancreatic tumors showed all possible combinations of sst expression, with, however, a predominance of sst(2) and sst(1). Overall, the presence of sst(2) mRNA and/or sst (5) mRNA generally correlated with the presence of octreotide binding sites. A lack of octreotide binding sites corresponded with a lack of sst(2) mRNA. Several tumors exhibiting a low number of octreotide bind ing sites had no measurable sst(2) mRNA, despite abundance of beta-act in mRNA, suggesting in these cases a very low abundance of sst mRNAs o r a too low sensitivity of the in situ hybridization methodology. In a ll other cases, the method allowed precise localization of the respect ive mRNAs on the tumor tissue, notably in breast tumors with non-homog eneous receptor distribution. Tumors without measurable amounts of som atostatin receptors had no detectable sst mRNA. Our results indicate a highly variable abundance of the various sst mRNAs in individual soma tostatin receptor-containing tumors. (C) 1997 Wiley-Liss, Inc.