Poster 10
Presenter: Michael Johnson
Thursday, 4:00 – 6:00pm
M.G. Johnson, J. Kristianto, A. Gustavson, K. Koenicke, J. Wu and R.D Blank University of Wisconsin-Madison Department of Endrocrinology
Endothelin (ET1) promotes the growth of osteoblastic breast and prostate cancer metastases, previously shown to be due in part to derepression of WNT signaling. Conversion of big ET1 to mature ET1, catalyzed by endothelin converting enzyme 1 (ECE1), is necessary for ET1 activity. We exposed TMOb osteoblasts to 25 ng/ml big ET1 for 6 days in growth medium and for and additional 15 days in mineralization medium. Cells and conditioned media were harvested every three days. TMOb cells exposed to big ET showed greater mineralization than control cells (N 6, p 0.008). The difference was specific to ET1 signaling, as it was blocked by inhibition of ECE1 or endothelin receptor A. Ece1 mRNA expression showed no change over the course of mineralization, ET1 was repressed and endothelin receptor A was induced. Addition of big ET1 repressed expression of all three genes. We measured mRNA levels of genes involved in the ET1 signaling axis, production of paracrine factors involved in osteogenesis, and miRNA expression. IGF-1 levels were significantly (1.3-1.8X) higher over time in the presence of big ET (p<0.001). Big ET1 repressed anti-osteogenic miRNAs, while miRNAs that target proteins involved in bone catabolism were induced by big ET1 exposure. Modulation of WNT signaling could not fully account for ET1’s osteogenic effects, as big ET1 produced a greater mineralization than treatment with LiCl. Moreover, our data suggest that ET1’s osteogenic effects are mediated by changes in the miRNA environment and IGF-1 induction, previously unrecognized ET1 osteogenic mechanisms.