Login to Access Video or Poster Abstract: MP60-07
Sources of Funding: Wilhelm Sander Foundation

Introduction

Bone metastasis has a great impact on the prognosis and clinical morbidity of patients with renal cell carcinoma (RCC). Overexpression of the Calcium-sensing receptor (CaSR) has been associated with the development of bone metastasis in several tumor entities. The goal of our study was to evaluate the impact of the CaSR in the development of bone metastasis in renal cancer.

Methods

The human clear cell RCC line 786-O was stably transfected with the CaSR gene. Cell adhesion to endothelial cells and the extracellular matrix compounds fibronectin, collagen I and IV and a BSA control was determined after calcium treatment of the cells.Chemotactical cell migration was assessed using a Boyden migration chamber with calcium as chemotaxin. Cell proliferation after calcium treatment was quantified via BrdU incorporation. Signalling pathway activation after calcium treatment of the CaSR overexpressing cells was determined by a human phospho-kinase array and Western blot. Development of bone metastasis was evaluated in vivo by an intracardiac injection mouse model.

Results

Calcium treated overexpressing CaSR 768-O cells show an increased adhesion to endothelial cells and the extracellular matrix components fibronectin and collagen I, but not to collagen IV. The chemotactical cell migration and proliferation was also induced by calcium treatment. The signalling mediators SHC, AKT, ERK, p38a JNK, p90RSK, CREB were enhanced, SRC reduced active after calcium treatment of CaSR overexpressing cells, but not of control cells. These effects were abolished by the CaSR inhibitor NPS2143. Intracardiac injection of CaSR overexpressing 768-O cells showed an increased rate of bone metastasis in vivo compared to control cells detected by MRI and bioluminescence.

Conclusions

CaSR is an important component in the mechanism of bone metastasis in RCC in vitro and in vivo. Therefore, targeting CaSR may be beneficial in patients with advanced RCC with high CaSR expression.

Funding

Wilhelm Sander Foundation