MicroRNA-383-5p restrains the proliferation and migration of breast cancer cells and promotes apoptosis via inhibition of PD-L1

Aims: MicroRNAs (miRs) play pivotal roles in breast cancer development. The dysregulation of miRs has been associated with PD-L1 -mediated immune suppression. This study aimed to examine the effect of transfected miR-383-5p on breast cancer cells and T-cells and its association with clinicopathological features in affected patients. Main methods: Initially, miR-383-5p and PD-L1 expression levels were investigated in breast cancer tissues. Then, MDA-MB-231 cells were transfected with miR-383-5p mimics to perform analyses. Cell viability was investigated using the MTT assay, and the annexin V/PI staining assay was performed to examine apoptosis induction. Furthermore, the effect of miR-383-5p on cell migration and cell cycle progression was analyzed using the wound-healing assay and flow cytometry, respectively. Gene and protein expressions were studied using qRT-PCR and western blotting. Finally, the effect of miR-383-5p on T-cells, which were co-cultured with cancer cells, was investigated. Key findings: Compared to non-malignant tissues, PD-L1 was up-regulated, and miR-383-5p expression was downregulated in breast cancer tissues. Moreover, miR-383-5p reduced breast cancer cell viability via inducing apoptosis and modulating the expression of apoptosis-related genes. Besides, miR-383-5p could inhibit the migration of breast cancer cells via down-regulating metastasis-related genes. Besides, transfected miR-383-5p induced the secretion of pro-inflammatory cytokines from T-cells. Furthermore, the results showed that miR-383-5p might exert its tumor-suppressive effect via inhibiting the PI3K/AKT/mTOR pathway. The inhibitory effect of transfected miR-383-5p on the PI3K/AKT/mTOR pathway might be the underlying mechanism for inhibiting tumoral PD-Ll expression. Significance: Overall, miR-383-5p can be a promising therapeutic agent for treating breast cancer.