Expression of growth hormone-releasing hormone receptor splicing variants in human primary adrenocortical tumours

Abstract

Objective: Several splice variants (SVs) of GHRH receptor (GHRH-R) have been identified in various human cancers through which GHRH antagonists may exert their IGF-II-mediated antiproliferative action. Because the overexpression of the IGF-II gene is a frequent feature of adrenal carcinoma, we searched for the presence of GHRH-R SVs in these tumours.

Methods and results: The expression of GHRH-R SVs was assessed by nested PCR in 45 human adrenocortical tumours. We have amplified 720-, 566- and 335-bp PCR products only in carcinomas. Their sequence revealed three open reading frames, corresponding to SV1, SV2 and SV4 of GHRH-R. SV2 was detected in five of 24 cancers examined, whereas the incidence of SV1 and SV4 was lower. Their simultaneous expression was observed in one carcinoma. No PCR products for SV3 or wild-type GHRH-R were found in carcinomas; mRNA for wild-type GHRH-R or SVs of GHRH-R were not observed either in adenomas or in normal adrenal or in NCI-H295R cells. Interestingly, all carcinomas which expressed SVs were also positive for the presence of GHRH mRNA.

Conclusion: This is the first time that the expression of splice variants of GHRH-R has been demonstrated in human adrenal carcinoma. This study raises the possibility that splice variants might play a role in adrenal carcinogenesis and might offer the possibility for new therapeutic strategies at least in a subgroup of adrenal carcinomas.