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- DOI: 10.1186/bcr3048
- PMID: 22032690
- UKPMCID: 22032690
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Metastatic breast cancer cells inhibit osteoblast differentiation through the Runx2/CBFβ-dependent expression of the Wnt antagonist, sclerostin
Mendoza-Villanueva, Daniel; Zeef, Leo; Shore, Paul
Breast cancer research : BCR. 2011;13(5):R106.
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Full-text held externally
- DOI: 10.1186/bcr3048
- PMID: 22032690
- UKPMCID: 22032690
Abstract
ABSTRACT: INTRODUCTION: Breast cancers frequently metastasise to the skeleton where they cause osteolytic bone destruction by stimulating osteoclasts to resorb bone and by preventing osteoblasts from producing new bone. The transcription factor, Runx2, is an important determinant of bone metastasis in breast cancer. Runx2 is known to mediate activation of osteoclast activity and inhibition of osteoblast differentiation by metastatic breast cancer cells. However, whilst Runx2-regulated genes that mediate osteoclast activation have been identified, how Runx2 determines inhibition of osteoblasts is unknown. METHODS: The aim of this study was to determine how Runx2 mediates the ability of metastatic breast cancer cells to modulate the activity of bone cells. We have previously demonstrated that Runx2 requires the co-activator CBFbeta to regulate gene expression in breast cancer cells. We therefore performed independent microarray analyses to identify target genes whose expression is dependent upon both Runx2 and CBFbeta. Common target genes, with a role in modulating bone-cell function, were confirmed using a combination of siRNA, q-RT-PCR, ELISA, promoter reporter analysis, EMSA and ChIP assays. The function of Runx2/CBFbeta-regulated genes in mediating the ability of MDA-MB-231 to inhibit osteoblast differentiation was subsequently establsihed in primary bone marrow stromal cell cultures and MC-3T3 osteoblast cells. RESULTS: We show that Runx2/CBFbeta mediates inhibition of osteoblast differentiation by MDA-MB-231 cells through induction of the Wnt signaling antagonist, sclerostin. We demonstrate that MDA-MB-231 cells secrete sclerostin and that sclerostin-expression is critically dependent on both Runx2 and CBFbeta. We also identified the osteoclast activators IL-11 and GM-CSF as new target genes of Runx2/CBFbeta in metastatic breast cancer cells. CONCLUSION: This study demonstrates that Runx2 and CBFbeta are required for the expression of genes that mediate the ability of metastatic breast cancer cells to directly modulate both osteoclast and osteoblast function. We also show that Runx2-dependent inhibition of osteoblast differentiation by breast cancer cells is mediated through the Wnt antagonist, sclerostin.