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Somatostatin receptor subtype 2 and 5 in human GH‐secreting pituitary adenomas: analysis of gene sequence and mRNA expression
Author(s) -
Corbetta S.,
Ballaré E.,
Mantovani G.,
Lania A.,
Losa M.,
Di Blasio A. M.,
Spada A.
Publication year - 2001
Publication title -
european journal of clinical investigation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.164
H-Index - 107
eISSN - 1365-2362
pISSN - 0014-2972
DOI - 10.1046/j.1365-2362.2001.00786.x
Subject(s) - somatostatin receptor 2 , somatostatin , somatostatin receptor , endocrinology , medicine , somatostatin receptor 1 , biology , messenger rna , microbiology and biotechnology , gene , genetics
The role of somatostatin receptor subtypes 2 and 5 (SSTR2 and SSTR5) in determining the secretory and proliferative phenotype as well as the sensitivity to somatostatin analogue treatment is not clearly established. We quantified the expression of SSTR2 and SSTR5 mRNA using a semiquantitative reverse transcription‐polymerase chain reaction (RT‐PCR) in 19 human growth hormone (GH) ‐secreting adenomas. Tumour characteristics and in vivo sensitivity to somatostatin analogues were assessed; tumours were screened for Gsα gene mutations. PCR products of SSTR2 and SSTR5 DNA from tumours resistant to somatostatin analogues were directly sequenced. All tumours expressed both SSTR2 and SSTR5 mRNA at variable levels. No significant correlation between SSTR2 and SSTR5 expression and the presence of Gsα mutation, GH levels, or tumour size and invasiveness was observed. A negative correlation between SSTR2 and SSTR5 mRNA levels was observed ( r = 0·5; P < 0·05). No significant correlation between the levels of SSTR2 and SSTR5 expression and the in vivo responsiveness to somatostatin analogues was observed, although a tendency to a low SSTR2 expression in resistant tumours was found. No mutations in the coding or bordering regions of either SSTR2 or SSTR5 adenomatous DNA from patients totally or partially resistant to somatostatin analogues were found. The study shows that the different expression of SSTR2 and SSTR5 in GH‐secreting adenomas is not significantly correlated with the secretory and proliferative phenotype, although the large, hypersecretory tumours and those with a poor sensitivity to somatostatin analogues seem to express low levels of SSTR2 mRNA. Moreover, both SSTR2 and SSTR5 DNA from tumours resistant to somatostatin analogues were found to possess intact coding sequences.