Abstract
Approximately 30–40% of growth hormone-secreting pituitary adenoma (GHPA) harbor somatic mutations in the GNAS (α subunit of the stimulatory G protein) gene. However, the latent functional role of the mutations and relative molecular mechanism in GHPA remain unknown. The GNAS gene mutations were detected in GHPAs using a standard PCR-sequencing procedure. The mutation-associated MEG3 expression was measured by RT-qPCR. MEG3 was manipulated in GH3 cells using a lentiviral expression system. Alterations in mRNA profiles in the MEG3-overexpressed cells were analyzed by RNA-seq. The cell invasion ability was measured using a Transwell assay, and the EMT-associated proteins were quantified by immunofluorescence and western blot. Finally, a tumor cell xenograft mouse model was applied to verify the effect of MEG3 on tumor growth and invasiveness. The percentage of invasive tumors was significantly declined in GNAS-mutated GHPA tumors with the GNAS mutations compared to those tumors with the wild-type of GNAS. Consistently, the GH3 cell invasion capacity was decreased by expressing the mutant GNAS. MEG3 is uniquely expressed at high levels in GHPA harboring the mutated GNAS gene. Accordingly, the upregulation of MEG3 resulted in inhibiting cell invasion; and vice versa, the downregulation of MEG3 led to enhancing cell invasion. Mechanistically, the high level of MEG3 in mutated GNAS cells prevented the cell invasion via inactivation of the Wnt/β-catenin signaling pathway, which was further validated in vivo. The GNAS mutations inhibit the invasiveness of GHPA cells via inactivation of the MEG3/Wnt/β-catenin signaling pathway.
Mutations in the GNAS Gene Prevent the Cell Invasion by Activating the MEG3/Wnt/β-catenin Axia in Growth Hormone-secreting Pituitary Adenoma
