JW. Hong*a (Prof), YJ. Leeb (Dr), J. Leec (Prof), EJ. Leeb (Prof), CR. Kub (Prof)

a Inje University College of Medicine, Goyang, KOREA, REPUBLIC OF ; b Yonsei University College of Medicine, Seoul, KOREA, REPUBLIC OF ; c Hanyang University Myongji Hospital, Goyang, KOREA, REPUBLIC OF

* hjwcarrot@paik.ac.kr

The objective of this study was to identify circulating microRNAs (miRNAs) as a potential biomarker predicting responsiveness of dopamine agonist (DA) for differential diagnosis of pituitary tumors with hyperprolactinemia.
The Nanostring nCounter assay for circulating miRNA are conducted in plasma of patients with hyperprolactinemia combined with pituitary adenoma. To achieve the solid screening result and obtain the powerful candidate miRNAs, we arrayed the blood samples according to three groups; 1)cabergoline responsive group (clinically diagnosed as prolactinoma) vs. non-responsive group (clinically diagnosed as nonfunctioning pituitary adenoma (NFPA),) (n=12 vs. 12), 2)postoperative confirmed prolactioma vs. NFPA (n=6 vs. 6), and 3)before and after cabergoline treatment (n=12 vs. 12). Three out of 8 candidate miRNAs presented the identical tendency between nCounter assay and qRT-PCR, which included miRNA 2X-5p, miRNA 42X-5p, and miRNA 51X-5p. Three miRNAs were revalidated in 284 patients.
In our investigation, circulating miRNA 2X-5p, miRNA 42X-5p and miRNA 51X-5p were all increased in hyperprolactinemic patients about 3 to 10 times more compared to normoprolactine subjects. Circulating miRNA 2X-5p and 42X-5p were significantly overexpressed in pathologically diagnosed as prolactinoma compared to NFPA. Circulating miRNA 51X-5p was differentially expressed between clinically diagnosed as prolactinoma and NFPA in hyperprolactinemic patients. All the circulating miRNAs returned to normal levels with normalization of blood prolactin level after cabergoline treatment or surgical resection. Among the three miRNAs, only miRNA 2X-5p was increased significantly in prolactinoma tissues.
In vitro, mimic and inhibitors for circulating miRNA 2X-5p, miRNA 42X-5p, and miRNA 51X-5p were transfected into MMQ4 cell line. Mimic of miRNA 2X-5p increased cell proliferation. Mimic of miRNA 42X-5p increased prolactin synthesis and secretion. Inhibition of miRNA 42X-5p and 2X-5p decreased prolactin secretion. Mimic of miRNA 2X-5p decreased the mRNA expression of MAPK1 and RAPGEF4, which also affected the reduction of prolactin secretion by cabergoline. Mimic of miRNA 42X-5p and 51X-5p increased prolactin reduction by cabergoline.
In conclusion, circulating miRNAs could be the potential biomarker for predicting response to DA therapy for pituitary tumors with hyperprolactinemia.

The author has declared no conflict of interest.