MicroRNA-146b-5p/EPHA7 axis regulates cell invasion, metastasis, proliferation, and temozolomide-induced chemoresistance via regulation of IRAK4/TRAF6/NF-κB signaling pathway in aggressive pituitary adenoma

Abstract

Background. Aggressive pituitary adenoma (APA) is a huge challenge for neurosurgeons. Temozolomide (TMZ) is conventionally used in chemotherapy against APA, but acquired resistance developed during long-term therapy limits its benefits. MiRNA-146b-5p has been confirmed to inhibit tumor metastasis. This study aimed to explore the underlying biological functions of miRNA-146b-5p in APA. Methods. Sixty confirmed APA tissues and corresponding adjacent normal tissues were collected. We established a TMZ-resistant cell line (GH3/TMZ) by exposing GH3 cells to gradually increasing doses of TMZ for 5 months. Cell Counting Kit-8 assay, flow cytometric analysis, RNA pull-down assay, 5-ethynyl20-deoxyuridine assay, dual-luciferase reporter gene assay, wound healing assay, and invasion assay were used to explore the malignant biological characteristics of cells. Immunohistochemistry (IHC), western blotting analysis, and real-time quantitative PCR (qRT-PCR) were used to analyze the expression level of related proteins and nucleic acids. Results. The expression of miRNA-146b-5p was down-regulated not only in APA tissues but also in PA cell lines compared with the matched adjacent nontumor tissues or normal human astrocyte (NHA) cells. Low expression of miRNA-146b-5p was notably associated with poorer disease-free survival rate (P=0.032), overall survival rate (P=0.039), larger tumor size (P=0.028), poorer Knosp grade (P=0.020), and poorer Hardy grade (P=0.006) in APA patients. MiRNA146b-5p negatively regulated cell proliferation, invasion, migration, and induced apoptosis in GH3 cells. Overexpression of miRNA-146b-5p suppressed IRAK4 and TRAF6 protein expression and negatively regulated NF-κB phosphorylation. The restoration of EPHA7 expression in GH3 cells notably reversed the inhibitory effects of miRNA-146b-5p. MiRNA-146b-5p expression was significantly down-regulated and EPHA7 gene expression was significantly up-regulated in GH3/TMZ cells, compared to the parental cell line. Similarly, EPHA7 was up-regulated, while the miRNA-146b-5p level was down-regulated in chemoresistance tissues more than in chemosensitive tissues. The autophagic activity was decreased markedly with increasing miRNA-146b-5p expression, while it was enhanced after Lv-EPHA7 treatment in GH3/TMZ cells. Conclusions. MiRNA-146b-5p can inhibit EPHA7 expression, suppress the IRAK4/TRAF6/NF-κB signaling pathway, and weaken PA cell invasion, metastasis, proliferation, and TMZ-induced chemoresistance in vitro.