Glucose-dependent insulinotropic peptide receptor overexpression in adrenocortical hyperplasia in MEN1 syndrome without loss of heterozygosity at the 11q13 locus

Abstract

BACKGROUND: The molecular mechanisms involved in the genesis of the adrenocortical lesions seen in MEN1 syndrome (ACL-MEN1) remain poorly understood; loss of heterozygosity at 11q13 and somatic mutations of MEN1 are not usually found in these lesions. Thus, additional genes must be involved in MEN1 adrenocortical disorders. Overexpression of the glucose-dependent insulinotropic peptide receptor has been shown to promote adrenocortical tumorigenesis in a mice model and has also been associated with ACTH-independent Cushing syndrome in humans. However, to our knowledge, the status of glucose-dependent insulinotropic peptide receptor expression in adrenocortical lesions in MEN1 has not been previously investigated. OBJECTIVE: To evaluate glucose-dependent insulinotropic peptide receptor expression in adrenocortical hyperplasia associated with MEN1 syndrome. MATERIALS/METHODS: Three adrenocortical tissue samples were obtained from patients with previously known MEN1 germline mutations and in whom the presence of a second molecular event (a new MEN1 somatic mutation or an 11q13 loss of heterozygosity) had been excluded. The expression of the glucose-dependent insulinotropic peptide receptor was quantified by qPCR using the DDCT method, and b-actin was used as an endogenous control. RESULTS: The median of glucose-dependent insulinotropic peptide receptor expression in the adrenocortical lesions associated with MEN1 syndrome was 2.6-fold (range 1.2 to 4.8) higher than the normal adrenal controls (p = 0.02). CONCLUSION: The current study represents the first investigation of glucose-dependent insulinotropic peptide receptor expression in adrenocortical lesions without 11q13 loss of heterozygosity in MEN1 syndrome patients. Although we studied a limited number of cases of MEN1 adrenocortical lesions retrospectively, our preliminary data suggest an involvement of glucose-dependent insulinotropic peptide receptor overexpression in the etiology of adrenocortical hyperplasia. New prospective studies will be able to clarify the exact role of the glucose-dependent insulinotropic peptide receptor in the molecular pathogenesis of MEN1 adrenocortical lesions.