Tumor suppressor functions of miRNA-375 in nasopharyngeal carcinoma through inhibition of ubiquitin-specific protease 1 expression

Background: Nasopharyngeal carcinoma (NPC) development involves many genetic alterations. This study profiled differentially expressed MicroRNAs (DE-miRNAs) and selected miR-375 for further study.

Methods: DE-miRNAs were screened using online databases and subjected to various analyzes. miR-375 mimics with negative control (NC) cDNA, and a Ubiquitin-Specific Protease 1 (USP1) as well as a NC group were transfected into NPC cells for analysis by quantitative PCR, western blotting, wound healing, Transwell, flow cytometry, cell counting kit-8 (CCK-8), and luciferase gene reporter assays.

Results: Among these DE-miRNAs, miR-375 was downregulated and miR-21 was upregulated in NPC cells. Bioinformatical analysis identified USP1 as a potential target gene of miR-375. Increased USP1 expression was associated with poor survival of head and neck Cancer patients. The luciferase assay confirmed miR-375 binding to the USP1 3'-untranslated region (UTR), while the transfection experiment confirmed miR-375 expression reduced USP1 expression. USP1 overexpression reversed the anti-tumor activity of miR-375 in NPC cells as determined by tumor cell migration, invasion, Apoptosis, and viability assays. In addition, USP1 overexpression activated phosphoinositide 3-kinase (PI3K) signaling, whereas a selective PI3K Inhibitor (S2739) could reverse the effects of USP1 on NPC cells in vitro.

Conclusions: miR-375 and miR-21 are both related to NPC and miR-375 can target USP1. Further experiments revealed that up-regulated miR-375 expression led to USP1 down-regulation, and miR-375 overexpression suppressed PI3K/Akt signaling and inhibited NPC cell migration and invasion, but promoted NPC cell Apoptosis.