miR‐221/222 Facilitate Pituitary Adenoma Progression Via PHACTR4 Downregulation

Most of pituitary adenomas are biologically benign, but some grow local-invasively and can invade important adjacent tissues, resulting in clinical symptoms such as hormone secretion disorders and visual field defects. MicroRNA-221/222 (miR-221/222) is tandemly encoded on the X chromosome in humans, mice and rats, and is highly conserved in vertebrates with the same seed sequence. To date, miR-221/222 has been reported as either a tumor suppressor or a tumor promoter in different tumors, however, its role in pituitary tumors has not been elucidated. Our study aimed to investigate the effect and mechanism of miRNA-221/222 in pituitary tumor cells. Results of real-time quantitative PCR showed that the expression level of miRNA-221/222 in plasma exosomes from patients with pituitary tumor was significantly higher than that from healthy people. Results of cell function experiments indicated that miRNA-221/222 significantly promoted cell proliferation and migration, inhibited apoptosis and significantly inhibited the expression of Cleaved-Caspase3 and E-cadherin, while promoted the expression level of N-cadherin. With transcriptome sequencing and comprehensive bioinformatics analysis, PHACTR4 was identified as the potential target gene of miRNA-221/222 in regulating biological functions of pituitary adenoma cells. Dual luciferase reporter assay confirmed that PHACTR4 was the direct target gene of miRNA-221/222 and overexpression of PHACTR4 gene reversed the regulatory effects of miRNA-221/222. In vivo experiment of subcutaneous tumor formation in nude mice verified that miRNA-221/222 promoted tumor growth by targeting PHACTR4. In conclusion, miRNA-221/222 played the role of proto-oncogene in the occurrence and development of pituitary tumors by targeting PHACTR4, which provided a new target for the diagnosis and molecular treatment of pituitary adenomas.