The role of upregulated miR-375 expression in breast cancer: An in vitro and in silico study

Breast cancer (BC) is the most common cancer worldwide. However, the expression and potential mechanism of miR-375 in BC are still controversial. We first collected microRNA chips and microRNA sequencing data from multiple databases for analyzing the expression level of miR-375, and further exploring the target genes and underlying molecular mechanism in BC. miR-375 in BC was predominantly overexpressed compared with that in normal breast tissues (pooled standard mean difference [SMD] = 0.49; 95 % confidence interval [CI]: 0.24-0.73, p < 0.0001). Meanwhile, the overall pooled area under the curve (AUC) in the summary receiver operating characteristic (SROC) of miR-375 was 0.83 (95 % CI = 0.79-0.86) based on 2928 cases of BC patients and 816 cases of controls, while the diagnostic positive likelihood ratio (DLR) positive and the DLR negative value were 3.90 (95 % CI = 2.46-6.19) and 0.39 (95 % CI = 0.28-0.54), respectively. The hazard ratios (HRs) were 1.29 (95 % CI = 1.04-1.6, P = 0.02) and 1.23 (95 % CI = 0.89-1.7, P = 0.22) for the cohorts of METABRIC and The Cancer Genome Atlas (TCGA). In vitro study demonstrated that miR-375 inhibitor could suppress the cell growth and induce apoptosis of BC cells. A total of 107 overlapping genes from microarrays after miR-375 transfection, the TCGA RNA sequencing, the microarrays of Affymetrix platform, and online predicting software were selected as the prospective targets of miR-375 in BC. Based on Gene Ontology (GO) enrichment analysis, the potential targets of miR-375 were notable for their somatic stem cell division, plasma membrane, and proline-rich region binding. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway examination demonstrated that the targets were associated with the pathways of prion diseases, proteoglycans in cancer, and focal adhesion. Then, 107 targets of miR-375 in BC were used to construct a protein-protein interaction (PPI) network. Finally, EGFR, PRKCA, PPARA, ADIPOQ, and ITSN1 were found to be the hub genes of miR-375. These targets showed negative correlations with miR-375 level. The upregulated miR-375 might play an essential part in the tumorigenesis and progression of BC.