We found that a decrease of BIRC5 and LASP1 mRNA in TNBC cells after treated (Figure 3B), so we believe that miRNA-203 regulates BIRC5 and LASP1 expression at both protein and mRNA levels. Moreover,

a potential miR-203 targeting site was predicted in the 3’-UTRs of BIRC5 and LASP1 by TargetScan 6.0 (Figure 3C). To investigate whether the 3’-UTRs of BIRC5 and LASP1 are functional targets of miR-203 in breast cancer cells, we co-transfected the INCB018424 miR-203 precursor (or control miRNA) and pMIR-BIRC5-3’-UTR plasmid (or mutant) or pMIR-LASP1-3’-UTR plasmid (or mutant) into cells. Co-transfection with the miR-203 precursor was found to decrease wild type BIRC5 and LASP1 3’-UTR reporter activity (P < 0.05) compared with co-transfection with control miRNA in both two cell lines. However, co-transfection with the miR-203 precursor did not significantly alter mutant BIRC5 or LASP1 3’-UTR reporter activity (Figure 3D). These results demonstrated that miR-203 targets the predicted site within the 3’-UTRs of BIRC5 and LASP1 mRNA in TNBC cell lines. Figure 3 BIRC5 and LASP1 were identified as miR-203 target genes. (A) Immunoblots of BIRC5 and LASP1 protein in TNBC cells after treated with miR-203

precursor or control miRNA. Selleckchem Venetoclax β-actin was used as a loading control. (B) Relative BIRC5 and LASP1 expression at mRNA level in TNBC cells transfected with miR-203 precursor or control miRNA. The mRNA expression was normalized to that of β-actin. (C) Sequence alignment of miR-203 and its putative conserved target site in BIRC5 and LASP1 3’-UTR (downloaded from TargetScan 6.0).

(D) Luciferase reporter assays of the interaction between miR-203 and the BIRC5 and LASP1 3’-UTRs. Assays were performed by co-transfection of miR-203 precursor with a luciferase reporter gene linked to the 3’-UTRs of BIRC5 and LASP1, containing either wild type or mutated miR-203 complementary Rucaparib manufacturer sites. *, P < 0.05. Repressing BIRC5 expression could inhibit the proliferation of MDA-MB-231 cells To investigate the effect of BIRC5 on the proliferation of TNBC cell, we employed MDA-MB-231 cells as the model system to perform the subsequent studies. We evaluated the cell proliferative capacity of MDA-MB-231 cells transfected with BIRC5 siRNA (or control siRNA). The expression of BIRC5 protein in the cells transfected with BIRC5 siRNA was significantly decreased in comparison with that of cells transfected with control siRNA (Figure 4A), indicating that the expression of BIRC5 was effectively inhibited by BIRC5 siRNA. Subsequent studies showed that the proliferative capacity of cells transfected with BIRC5 siRNA was significantly lower than that of cells treated with control siRNA (Figure 4B). Figure 4 Repressing BIRC5 expression could inhibit the proliferation of MDA-MB-231 cells. (A) Immunoblots of BIRC5 protein in MDA-MB-231 cells treated with control siRNA or BIRC5 siRNA.