MiR-1299 promotes the synthesis and secretion of prolactin by inhibiting FOXO1 expression in drug-resistant prolactinomas

Prolactinoma is a clinically common intracranial tumor. When serum prolactin levels are not controlled despite administration of a dopamine agonist, the condition is referred to as drug-resistant prolactinoma. The mechanism underlying persistent prolactin secretion in drug-resistant prolactinoma remains unclear. MicroRNAs play an important role in tumorigenesis and development as well as chemotherapeutic resistance. This study was conducted to investigate the mechanism by which miRNA regulates prolactin secretion in drug-resistant prolactinoma. We first found that miR-1299 was elevated in drug-resistant prolactinoma and inhibited FOXO1 in a targeted manner through miRNA sequencing and luciferase assays. We then confirmed that FOXO1 binds to the promoter of the prolactin gene to inhibit its expression through chromatin immunoprecipitation-quantitative PCR and cytological experiments. Finally, inhibition or overexpression of miR-1299 in primary tumor cells confirmed that drug-resistant prolactinoma promoted prolactin secretion by promoting miR-1299 expression and reducing intracellular FOXO1. These results indicate that FOXO1 and miR-1299 are potential therapeutic targets for drug-resistant prolactinoma as well as other pituitary diseases.

Discordance between mass spectrometry and immunometric IGF-1 assay in pituitary disease: a prospective study

PURPOSE

Measuring IGF-1, a biomarker for GH activity, is critical to evaluating disordered hypothalamic-pituitary GH axis. Inconsistent IGF-1 measurements among different immunoassays are well documented. We switched from Immulite 2000 immunoassay to narrow-mass-extraction, high-resolution liquid chromatography mass-spectrometry (LC-MS) compliant with recent consensus recommendations on assay standardization. Comparability of these two assays in patients with pituitary disease in a clinical practice setting is not known. We sought to compare IGF-1 levels on Immulite 2000 and LC-MS in samples from naïve and treated patients with secretory and non-secretory pituitary masses.

METHODS

We prospectively collected serum samples from 101 patients treated at the Cedars-Sinai Pituitary Center between February 2012 and March 2014. We intentionally recruited more patients with acromegaly or GH deficiency to ensure a clinically representative cohort. Samples were classified as in or out of the respective reference ranges. Bland-Altman analysis was used to assess agreement between assays.

RESULTS

Twenty-four percent of samples were classified differently as below, in, or above range. Agreement between the assays was poor overall, with a significant bias for immunoassay reporting higher values than LC-MS. This pattern was also observed in patients with acromegaly and those with ≥ 2 pituitary hormone deficiencies.

CONCLUSIONS

IGF-1 results may differ after switching from an older immunoassay to a consensus-compliant assay such as LC-MS. Clinicians should consider the potential impact of assay switching before altering treatment due to discrepant results, particularly in patients monitored over time, such as those with acromegaly and GH deficiency.