KDM1A genotyping and expression in 146 sporadic somatotroph pituitary adenomas

Introduction: Paradoxical increase of GH following oral glucose load has been described in ∼30% of patients with acromegaly and has been related to the ectopic expression of the glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) in somatotropinomas. Recently, we identified germline pathogenic variants and somatic loss of heterozygosity of lysine demethylase 1A (KDM1A) in patients with GIP-dependent primary bilateral macronodular adrenal hyperplasia with Cushing's syndrome. The ectopic expression of GIPR in both adrenal and pituitary lesions suggests a common molecular mechanism. We aimed to analyze KDM1A gene sequence and KDM1A and GIPR expression in somatotroph pituitary adenomas. Methods: We conducted a cohort study at university hospitals in France and in Italy. We collected pituitary adenoma specimens from acromegalic patients who had undergone pituitary surgery. We performed targeted exome sequencing (gene panel analysis) and array-CGH on somatic DNA derived from adenomas and performed droplet digital PCR on adenoma samples to quantify KDM1A and GIPR expression. Results: 146 patients with sporadic acromegaly were studied; 72.6% presented unsuppressed classical GH response, whereas 27.4% displayed a paradoxical rise in GH after oral glucose load. We did not identify any pathogenic variant in the adenomas of these patients. However, we identified a recurrent 1p deletion encompassing the KDM1A locus in 29 adenomas and observed a higher prevalence of paradoxical GH rise (p = 0.0166), lower KDM1A expression (4.47 ± 2.49 vs 8.56 ± 5.62, p < 0.0001) and higher GIPR expression (1.09 ± 0.92 vs 0.43 ± 0.51, p = 0.0012) in adenomas from patients with KDM1A haploinsufficiency compared to those with two KDM1A copies. Discussion: Unlike in GIP-dependent primary bilateral macronodular adrenal hyperplasia, KDM1A genetic variations are not the cause of GIPR expression in somatotroph pituitary adenomas. Recurrent KDM1A haploinsufficiency, more frequently observed in GIPR-expressing adenomas, could be responsible for decreased KDM1A function resulting in transcriptional derepression on the GIPR locus.