Title

Runx2 transcriptional activation of Indian Hedgehog and a downstream bone metastatic pathway in breast cancer cells

UMMS Affiliation

Department of Cell Biology; Department of Orthopedics and Physical Rehabilitation

Date

10-3-2008

Document Type

Article

Subjects

Animals; Bone Neoplasms; Breast Neoplasms; Core Binding Factor Alpha 1 Subunit; inhibitors; Gene Expression Regulation, Neoplastic; Genes, bcl-1; Hedgehog Proteins; Humans; Kruppel-Like Transcription Factors; Mice; Mice, SCID; Models, Biological; Nuclear Proteins; Osteoclasts; Parathyroid Hormone-Related Protein; RNA, Small Interfering; Signal Transduction; Tissue Distribution; *Transcriptional Activation; Transforming Growth Factor beta; Transplantation, Heterologous; Tumor Cells, Cultured

Abstract

Runx2, required for bone formation, is ectopically expressed in breast cancer cells. To address the mechanism by which Runx2 contributes to the osteolytic disease induced by MDA-MB-231 cells, we investigated the effect of Runx2 on key components of the "vicious cycle" of transforming growth factor beta (TGFbeta)-mediated tumor growth and osteolysis. We find that Runx2 directly up-regulates Indian Hedgehog (IHH) and colocalizes with Gli2, a Hedgehog signaling molecule. These events further activate parathyroid hormone-related protein (PTHrP). Furthermore, Runx2 directly regulates the TGFbeta-induced PTHrP levels. A subnuclear targeting deficient mutant Runx2, which disrupts TGFbeta-induced Runx2-Smad interactions, failed to induce IHH and downstream events. In addition, Runx2 knockdown in MDA-MB-231 inhibited IHH and PTHrP expression in the presence of TGFbeta. In vivo blockade of the Runx2-IHH pathway in MDA-MB-231 cells by Runx2 short hairpin RNA inhibition prevented the osteolytic disease. Thus, our studies define a novel role of Runx2 in up-regulating the vicious cycle of metastatic bone disease, in addition to Runx2 regulation of genes related to progression of tumor metastasis.

Rights and Permissions

Citation: Cancer Res. 2008 Oct 1;68(19):7795-802. Link to article on publisher's site

Related Resources

Link to Article in PubMed

Journal Title

Cancer research

PubMed ID

18829534