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MicroRNAs (miRNAs) are small, short noncoding RNAs that modulate the expression of numerous genes by targeting their mRNA. Numerous abnormal miRNA expression patterns are observed in various human malignancies, and certain miRNAs can act as oncogenes or tumor suppressors. Astrocytoma, the most common neuroepithelial cancer, represents the majority of malignant brain tumors in humans. In our previous studies, we found that the downregulation of miR-181b-5p in astrocytomas is associated with a poor prognosis. The aim of the present study was to investigate the functional role of miR-181b-5p and its possible target genes. miR-181b-5p was significantly downregulated in astrocytoma specimens, and the reduced expression of miR-181b-5p was inversely correlated with the clinical stage. The ectopic expression of miR-181b-5p inhibited proliferation, migration and invasion and induced apoptosis in astrocytoma cancer cells in vitro. The NOVA1 (neuro-oncological ventral antigen 1) gene was further identified as a novel direct target of miR-181b-5p. Specifically, miR-181b-5p bound directly to the 3'-untranslated region (UTR) of NOVA1 and suppressed its expression. In clinical specimens, NOVA1 was overexpressed, and its protein levels were inversely correlated with miR-181b-5p expression. Furthermore, the changing level of NOVA1 was significantly associated with a poor survival outcome. Similar to restoring miR-181b-5p expression, downregulating NOVA1 inhibited cell growth, migration and invasion. Overexpression of NOVA1 reversed the inhibitory effects of miR-181b-5p. Our results indicate that miR-181b-5p is a tumor suppressor in astrocytoma that inhibits tumor progression by targeting NOVA1. These findings suggest that miR-181b-5p may serve as a novel therapeutic target for astrocytoma.

Fibulin-4, an extracellular glycoprotein, which plays significant roles in elastic fiber assembly, is correlated to the progression of some cancers. However, the role of fibulin-4 in endometrial cancer cell invasion and metastasis remains unexplored. In our study, fibulin-4 expression was assessed by immunohistochemistry (IHC) and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) in normal endometrial tissues and endometrial carcinoma tissues. Using single cell cloning, strongly, and weakly, invasive subclones were derived from KLE and Ishikawa endometrial carcinoma cell lines. RT-qPCR, western blotting, and immunocytochemistry (ICC) were used to assess mRNA and protein expressions of fibulin-4 in primary cultured endometrial cells, 4 types of endometrial cancer cell lines, and the different invasive subclones. Using lentivirus transfection, fibulin-4 shRNA and pLVX-fibulin-4 were constructed and used to infect the strongly and weakly invasive subclones. The effects of fibulin-4 on the biological characteristics of endometrial carcinoma cells were detected by cell functional assays in vitro and in vivo. Using Wnt signaling pathway inhibitor XAV-939 and activator LiCl, we detected the role of fibulin-4 in the Wnt/β-catenin pathway and the relationship with epithelial to mesenchymal transition (EMT). Fibulin-4 was decreased in endometrial carcinoma tissues, and loss of fibulin-4 expression was significantly related with poor differentiation, lymph node metastasis, and poor prognosis of endometrial carcinoma. Fibulin-4 significantly inhibited endometrial carcinoma cell proliferation, invasion, metastasis, and EMT through the Wnt/β-catenin pathway. Fibulin-4 has the ability to suppress endometrial cancer progression. These results can contribute to the development of a new potential therapeutic target for patients with endometrial carcinoma.

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