Bone morphogenetic protein 4 induced miRNA expression in breast cancer cell lines

Bone morphogenetic protein 4 (BMP4) is a remarkably powerful inhibitor of breast cancer cell proliferation, but is also able to induce breast cancer cell migration in certain cellular contexts. Previous data demonstrate that BMP4 controls the transcription of a variety of protein coding genes, but not much is known about microRNAs (miRNA) regulated by BMP4. In this study, miRNA expression patterns following BMP4 treatment were determined in one mammary epithelial and seven breast cancer cell lines using microarrays. The analysis identified 20 to 128 differentially expressed miRNAs in individual cell lines with emphasis on upregulation over downregulation. Four miRNAs (miR-16-5p, miR-106b-5p, miR-23a-3p and miR-23b-3p) were commonly induced in a subset of breast cancer cells upon BMP4 treatment and inhibition of their expression resulted in an increase in BT-474 cell number, indicating that they possess tumor suppressive properties. Yet no major change was detected when the cells were simultaneously treated with BMP4, and thus these miRNAs do not act as the main mediators of BMP4-induced growth reduction. MiR-16-5p and miR-106b-5p were elevated in MDA-MB-231 cells that respond to BMP4 with increased migration. Their inhibition, in combination with BMP4 treatment, resulted in enhanced MDA-MB-231 cell migration, suggesting that miR-16-5p and miR-106b-5p are engaged in BMP4-induced motility. Taken together, we have shown for the first time that in breast cancer cells BMP4 induces variable miRNA expression patterns. Seven breast cancer cell lines and one mammary epithelial cell line were treated with 100 ng/ml BMP4 or vehicle control for four hours. Total of 16 labeled samples were hybridized to Agilent microarrays.