Cyr61 (CCN1) is a novel target for Zometa (zoledronic acid) in breast cancer bone metastasis.

Abstract

Abstract Abstract #3074 Background: Cyr61, currently known as CCN1, is a pro-angiogenic factor highly expressed in triple negative breast carcinomas. CCN1 binds, among others, to αvβ3 integrin receptor, which is concomitantly expressed with CCN1 in triple negative carcinomas. It has clinically established that a greater part of the tumor initially diagnose as triple negative eventually metastasize to the bone. Women with advanced breast cancer often develop bone metastases. Currently, many patients receive bisphosphonate treatment as a support treatment to maintain bone density. Zometa (Zoledronic acid=ZOL), a third generation amino-bisphosphonate, inhibits bone resorption and it might prevent development of new osteolytic lesions; lesions induced by tumor metastases. Provided that: 1) ZOL has a direct anti-tumor activity on breast cancer cells in vitro, 2) CCN1:αvβ3 is an autocrine loop shown to be involved in breast cancer cells which metastasize to the bone, 3) ZOL inhibits αvβ3 expression in the cell surface of endothelial cells, and CCN1 induces the expression of αvβ3 expression.
 Material and Methods: Using MTT assay we analyzed the effect of ZOL in the viability of cells overexpressing CCN1:αvβ3. The study whether the effect of ZOL was at the transcriptional level of CCN1 a Luciferase reporter assay was performed. To study whether FOXO3a binding site on CCN1 promoter was an important site for ZOL effect on CCN1 we used a CCN1-promoter containing a deletion in the FOXO3a binding site and we performed the Luciferase reporter assay. We also analyze the effect of ZOL in the anchorage-independent growth by soft agar assay and in the branching and morphogenesis in 3D Matrigel culture.
 Results: We found that: a) ZOL regulates the expression of CCN1 expression in triple negative breast cancer cell lines; b) the IC50 for Zometa for CCN1:αvβ3 expressing cells is lower (about 12μM) than the IC50 for cells that express low to undetectable levels of CCN1:αvβ3 cells; c) ZOL specifically inhibited CCN1 at a protein and transcription expression levels in a concentration-dependent manner; d) FOXO3a is the site by which ZOL induces transcriptional activation of CCN1; e) ZOL induced specific inhibition of anchorage independent growth of CCN1:αvβ3 cells in a dose dependent manner, and f) ZOL induces Mesenchimal-Epithelial Transition (MET) of CCN1:αvβ3 expressing cells and inhibited the generation of branching and morphogenesis in 3D in Matrigel culture of CCN1:αvβ3 expressing cells.
 Discusion: Collectively, these data demonstrated for first time a specific effect of ZOL on a pro-angiogenic factor involved in triple negative carcinomas; providing a new model for the development of a therapeutic strategy for ZOL. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3074.