Identification of key genes in HER2-positive breast cancer with brain metastasis via bioinformatics methods.

Background: Brain metastasis (BM) represents one of the most common advanced disease states in breast cancer (BC), especially in human epidermal growth factor receptor 2 (HER2)-positive BC, and is associated with poor survival outcomes. Methods: In this study, in-depth analysis of the microarray data from the GSE43837 dataset with 19 BM samples of HER2-positive BC patients and 19 HER2-positive nonmetastatic primary BC samples was conducted. The differentially expressed genes (DEGs) between BM and primary BC samples were identified and function enrichment analysis of the DEGs was conducted to identify potential biological functions. The hub genes were identified by constructing the protein-protein interaction (PPI) network using STRING and Cytoscape. UALCAN and Kaplan-Meier plotter online tools were used to verify the clinical roles of the hub DEGs in HER2-positive BC with BM (BCBM). Results: A total of 1,056 DEGs including 767 downregulated and 289 upregulated genes were identified by comparing the microarray data of the HER2-positive BM and primary BC samples. Functional enrichment analysis demonstrated that the DEGs were mainly enriched in pathways related to extracellular matrix (ECM) organization, cell adhesion, and collagen fibril organization. PPI network analysis identified 14 hub genes. Among these, CD44, COL1A2, MMP14, POSTN, and SOX9 were associated with the survival outcomes of HER2-positive patients. Conclusions: In summary, 5 BM-specific hub genes were identified in the study; those are potential prognostic biomarkers and therapeutic targets for HER2-positive BCBM patients. However, further investigations are necessary to unravel the mechanisms by which these 5 hub genes regulate BM in HER2-positive BC.

miR-27-3p Enhances the Sensitivity of Triple-Negative Breast Cancer Cells to the Antitumor Agent Olaparib by Targeting PSEN-1, the Catalytic Subunit of Γ-Secretase.

Olaparib has been used in the treatment of triple-negative breast cancer (TNBC) with BRCA mutations. In the present study, we demonstrated the effect of miR-27-3p on the γ-secretase pathway by regulating the sensitivity of TNBC cells to olaparib. miR-27-3p, a microRNA with the potential to target PSEN-1, the catalytic subunit of γ-secretase mediating the second step of the cleavage of the Notch protein, was identified by the online tool miRDB and found to inhibit the expression of PSEN-1 by directly targeting the 3'-untranslated region (3'-UTR) of PSEN-1. The overexpression of miR-27-3p inhibited the activation of the Notch pathway via the inhibition of the cleavage of the Notch protein, mediated by γ-secretase, and, in turn, enhanced the sensitivity of TNBC cells to the antitumor agent olaparib. Transfection with PSEN-1 containing mutated targeting sites for miR-27-3p or the expression vector of the Notch protein intracellular domain (NICD) almost completely blocked the effect of miR-27-3p on the Notch pathway or the sensitivity of TNBC cells to olaparib, respectively. Therefore, our results suggest that the miR-27-3p/γ-secretase axis participates in the regulation of TNBC and that the overexpression of miR-27-3p represents a potential approach to enhancing the sensitivity of TNBC to olaparib.

MiRNA-96-5p impacts the progression of breast cancer through targeting FOXO3.

BACKGROUND: Breast cancer is the most common malignant tumor in women worldwide, with a high mortality rate. MicroRNAs are small non-coding RNAs that negatively regulate the expression of target genes by interacting with the target gene 3'-UTR, and participate in cell differentiation, proliferation, apoptosis and metabolism. The function of miRNA-96-5p in the progression of breast cancer has not been reported. METHODS: We used the StarBase database to investigate the expression of miRNA-96-5p in breast cancer and adjacent normal tissues. FOXO3 3'-UTR construct and luciferase reporter assays was performed for the target gene. Expression levels of miRNAs including its target were analyzed by qRT-PCR and western blot. Cell proliferation was detected by CCK8 and colony formation, EdU assay. RESULTS: Luciferase reporter assays showed miRNA-96-5p directly targeted FOXO3. Abrogation of miRNA-96-5p by transfection with its inhibitors in breast cancer cells significantly suppressed miRNA-96-5p expression and breast cancer cells proliferation. Western blot revealed that overexpression of miRNA-96-5p substantially reduced FOXO3 protein expression. We used the GEPIA, UALCAN and KM-plotter databases to investigate the expression of FOXO3 in human breast cancer and adjacent normal tissues, and its correlation with survival. In addition, we found that FOXO3 spoiled miR-96-5p induced breast cancer cell proliferation block effecting. CONCLUSIONS: miRNA-96-5p may exert a tumor promotion role through negatively regulating tumor suppressor gene FOXO3 and promoting cell proliferation.