MicroRNAs （miRNAs）, which are small noncoding RNA molecules, play important roles in the post-transcriptional regulation process. The microRNA-21 gene （miR-21） has been reported to be highly expressed in various s...MicroRNAs （miRNAs）, which are small noncoding RNA molecules, play important roles in the post-transcriptional regulation process. The microRNA-21 gene （miR-21） has been reported to be highly expressed in various solid tumors, including breast cancer. Bone morphogenetic protein-6 （BMP-6） has been identified as an inhibitor of breast cancer epithelial-mesenchymal transition （EMT） through rescuing E-cadherin expression. We initiated experi- ments to identify the relationships between miR-21 and BMP-6 in breast cancer progression. Real-time PCR analysis showed that miR-21 expression was very high in MDA-MB-231 cells that expressed little BMP-6. A reverse correla- tion between BMP-6 and miR-21 was also determined in breast cancer tissue samples. Moreover, BMP-6 inhibited miR-21 transcription in MDA-MB-231 cells. In order to investigate how BMP-6 inhibited the miR-21 promoter （miPPR-21）, we constructed a series of miPPR-21 reporters. Luciferase assay results indicated that BMP-6 inhibited miPPR-21 activity through the E2-box and AP-l-binding sites. We also demonstrated that both δEF1 and TPA in- duced miR-21 expression. Using site-directed mutation and CHIP assay, we found that δEF1 induced miPPR-21 ac- tivity by binding to the E2-box on miPPR-21. Moreover, TPA triggered miPPR-21 activity through the AP-I binding sites. BMP-6 treatment significantly reduced the binding of these factors to miPPR-21 by decreasing the expression of δEF1 and c-Fos/c-Jun. We also demonstrated that BMP-6-induced downregulation of miR-21 modified the activ- ity of PDCD4 3＇UTR and inhibited MDA-MB-231 cell invasion. δEF1 overexpression and TPA induction blocked this inhibitory effect of BMP-6. In conclusion, BMP-6-induced inhibition of miR-21 suggests that BMP-6 may function as an anti-metastasis factor by a mechanism involving transcriptional repression of miR-21 in breast cancer.展开更多
文摘MicroRNAs （miRNAs）, which are small noncoding RNA molecules, play important roles in the post-transcriptional regulation process. The microRNA-21 gene （miR-21） has been reported to be highly expressed in various solid tumors, including breast cancer. Bone morphogenetic protein-6 （BMP-6） has been identified as an inhibitor of breast cancer epithelial-mesenchymal transition （EMT） through rescuing E-cadherin expression. We initiated experi- ments to identify the relationships between miR-21 and BMP-6 in breast cancer progression. Real-time PCR analysis showed that miR-21 expression was very high in MDA-MB-231 cells that expressed little BMP-6. A reverse correla- tion between BMP-6 and miR-21 was also determined in breast cancer tissue samples. Moreover, BMP-6 inhibited miR-21 transcription in MDA-MB-231 cells. In order to investigate how BMP-6 inhibited the miR-21 promoter （miPPR-21）, we constructed a series of miPPR-21 reporters. Luciferase assay results indicated that BMP-6 inhibited miPPR-21 activity through the E2-box and AP-l-binding sites. We also demonstrated that both δEF1 and TPA in- duced miR-21 expression. Using site-directed mutation and CHIP assay, we found that δEF1 induced miPPR-21 ac- tivity by binding to the E2-box on miPPR-21. Moreover, TPA triggered miPPR-21 activity through the AP-I binding sites. BMP-6 treatment significantly reduced the binding of these factors to miPPR-21 by decreasing the expression of δEF1 and c-Fos/c-Jun. We also demonstrated that BMP-6-induced downregulation of miR-21 modified the activ- ity of PDCD4 3＇UTR and inhibited MDA-MB-231 cell invasion. δEF1 overexpression and TPA induction blocked this inhibitory effect of BMP-6. In conclusion, BMP-6-induced inhibition of miR-21 suggests that BMP-6 may function as an anti-metastasis factor by a mechanism involving transcriptional repression of miR-21 in breast cancer.
