GSE196062
miR-183-5p and miR-492 over-expression trigger loss of polarity and nuclear circularity and enhanced invasion and proliferation in nontumorigenic breast epithelium
microRNAs (miRNAs) are stable and abundant in body fluids and exhibit unique dysregulation signatures in cancers, making them attractive novel noninvasive cancer biomarkers. In an HMT-3522 S1 (S1) breast epithelial risk-progression 3D culture model, non-tumorigenic S1 cells form a fully polarized epithelium. Their pretumorigenic counterparts, silenced for gap junction and tumor suppressor Cx43, Cx43-KO-S1, lose epithelial polarity, multilayer, exhibit proliferative and invasion potential, and mimic tumor-initiated in vivo mammary epithelial morphology. To characterize the miRNA profile specific to Cx43 loss in the breast epithelia, miRNA-sequencing was performed and revealed 65 differentially expressed miRNAs in Cx43-KO-S1 as compared to S1 cells. A comparative analysis was conducted between the 65 differentially expressed miRNAs and 15 tumor-associated miRNAs from a young Lebanese patient validation cohort. miR-183-5p, downstream of Cx43 loss and commonly upregulated in the patient cohort and the breast epithelia and miR-492, not attributed to Cx43 loss, and only up-regulated in the young Lebanese patients were chosen for stable over-expression in the nontumorigenic S1 cells. Ectopic over-expression of miR-183 and miR-492 in S1 cells, through pLenti-III-miR-GPF tagged vectors, resulted in the formation of larger acini devoid of lumen assembly with cell multilayering, disrupted epithelial polarity and decreased nuclear circularity in 3D cultures, as well as in enhanced proliferation and invasion capacity and altered apical localization of Cx43 and apico-lateral localization of ß-catenin and Scrib. miR-183-5p and miR-492 over-expression in nontumorigenic S1 cells thus recapitulate pretumorigenic phenotypes similar to those reported upon Cx43 loss and act as oncomiRs and prognostic biomarkers. Overall design: miRNA-seq on control and Cx43 knock-down cells