MMP-1 shRNAs specifically inhibit MMP-1 expression in BR3 and BR cells. A, real-time PCR quantification of MMP-1 mRNA levels. Compared with MDA-MB-231 parental cells and variants LC3 (selected from experimental lung metastases), the brain metastasis-derived BR3 and BR cells showed high levels of MMP-1 expression. This data shown are representative of 3 independent experiments. B, MMP-1 shRNAs knocked down MMP-1 mRNA level in BR3 and BR cell lines, compared with shCtr and shNTC cells expressing control shRNA. This experiment was performed in triplicate. C, ELISA assays and D, western blotting showed that MMP-1 protein levels in conditioned media were significantly reduced in BR3 and BR expressing MMP-1 targeting shRNA. These experiments were performed in triplicate. E, MMP-1 shRNA did not affect the expression of MMP-2, TIMP-1, TIMP-2 and VEGF in sh1 cells. This data shown are representative of 3 independent experiments.