MiR-139 Modulates Cancer Stem Cell Function of Human Breast Cancer through Targeting CXCR4

SIMPLE SUMMARY: The C-X-C motif chemokine receptor 4 (CXCR4) is overexpressed in various cancer stem/progenitor cells via activation of the epithelial-mesenchymal transition (EMT) program to facilitate tumor cell aggressiveness in the premetastatic niche. Through miRNAs microarray and bioinformatics analysis, we confirmed that miR-139 directly interacted with the 3′-untranslated region (3′-UTR) of CXCR4. Overexpression of miR-139 down-modulated CXCR4/p-Akt axis to attenuate invasion and migration of human breast cancer stem cells both in vitro and in vivo. Furthermore, miR-139 expression assessed by quantitative real-time PCR (qRT-PCR) in laser capture microdissected tumor samples significantly correlated with more advanced tumors in patients with breast cancer. Our findings provide support to account for the preferential role of miR-139 in interrupting breast cancer progression, identifying miR-139 as a potential biomarker in prediction of breast cancer invasiveness. ABSTRACT: Elevated expression of C-X-C motif chemokine receptor 4 (CXCR4) correlates with chemotaxis, invasion, and cancer stem cell (CSC) properties within several solid-tumor malignancies. Recent studies reported that microRNA (miRNA) modulates the stemness of embryonic stem cells. We aimed to investigate the role of miRNA, via CXCR4-modulation, on CSC properties in breast cancer using cell lines and xenotransplantation mouse model and evaluated miR-193 levels in 191 patients with invasive ductal carcinoma. We validated miR-139 directly targets the 3′-untranslated region of CXCR4. Hoechst 33342 fluorescence-activated cell sorting (FACS) and sphere-forming assay were used to identify CSCs. MiR-139 suppressed breast CSCs with mesenchymal traits; led to decreased migration and invasion abilities through down-regulating CXCR4/p-Akt signaling. In lung cancer xenograft model of nude mice transplanted with human miR-139-carrying MDA-MB-231 cells, metastatic lung nodules were suppressed. Clinically, microdissected breast tumor tissues showed miR-139 reduction, compared to adjacent non-tumor tissues, that was significantly associated with worse clinicopathological features, including larger tumor size, advanced tumor stage and lymph node metastasis; moreover, reduced miR-139 level was predominately occurred in late-stage HER2-overexpression tumors. Collectively, our findings highlight miR-139-mediated suppression of CXCR4/p-Akt signaling and thereby affected mesenchymal stem-cell genesis, indicating its potential as a therapeutic target for invasive breast cancer.