MiR-93-5p regulates tumorigenesis and tumor immunity by targeting PD-L1/CCND1 in breast cancer

BACKGROUND: Challenges in medical care posed by rapid tumor progression, individualized responses to therapy, and the heterogeneous characteristics of breast cancer (BRCA) highlight the urgent need for new treatment strategies, as well as therapeutic and prognostic markers. Accumulating evidence has revealed that microRNAs broadly participate in carcinogenesis, but our understanding of the role of miR-93-5p in BRCA remains limited. METHODS: The prognosis of miR-93-5p, programmed cell death-ligand 1 (PD-L1) and CCND1 were analyzed by datasets. Freshly excised breast cancer tissues (N=33) and adjacent noncancerous tissues (N=18) were collected to detect the expression of CCND1 and PD-L1 by immunohistochemistry (IHC). Quantitative real-time PCR (qRT-PCR) and Western blot were used to test the expression of miR-93-5p, PD-L1 and CCND1 after transfected mimics or inhibitors. Dual-luciferase reporter assay indicates the direct targeting between miR-93-5p and PD-L1. RESULTS: Bioinformatics analysis demonstrated that miR-93-5p plays differential roles in various tumors, and further verification using qRT-PCR revealed that the expression levels of miR-93-5p were lower in MDA-MB-231 cells than in noncancerous breast cells. In addition, we confirmed that PD-L1 and CCND1 generated mutual effects, and miR-93-5p directly targets the PD-L1/CCND1 signaling pathway to influence their accumulation and distribution in the cell membrane, nucleus, and cytoplasm, mediating tumor progression and immune regulation in BRCA. CONCLUSIONS: Taken together, miR-93-5p could regulate tumorigenesis and tumor immunity by targeting PD-L1/CCND1 in BRCA and our research provides a rationale for therapy with miR-93-5p to overcome immune escape and improve risk stratification.