High calcium concentration in bones promotes bone metastasis in renal cell carcinomas expressing calcium-sensing receptor

Mol Cancer. 2014 Feb 28;13:42. doi: 10.1186/1476-4598-13-42.

Abstract

Background: The prognosis for renal cell carcinoma (RCC) is related to a high rate of metastasis, including 30% of bone metastasis. Characteristic for bone tissue is a high concentration of calcium ions. In this study, we show a promoting effect of an enhanced extracellular calcium concentration on mechanisms of bone metastasis via the calcium-sensing receptor (CaSR) and its downstream signaling molecules.

Methods: Our analyses were performed using 33 (11/category) matched specimens of normal and tumor tissue and 9 (3/category) primary cells derived from RCC patients of the 3 categories: non-metastasized, metastasized into the lung and metastasized into bones during a five-year period after nephrectomy. Expression of CaSR was determined by RT-PCR, Western blot analyses and flow cytometry, respectively. Cells were treated by calcium and the CaSR inhibitor NPS 2143. Cell migration was measured in a Boyden chamber with calcium (10 μM) as chemotaxin and proliferation by BrdU incorporation. The activity of intracellular signaling mediators was quantified by a phospho-kinase array and Western blot.

Results: The expression of CaSR was highest in specimens and cells of patients with bone metastases. Calcium treatment induced an increased migration (19-fold) and proliferation (2.3-fold) exclusively in RCC cells from patients with bone metastases. The CaSR inhibitor NPS 2143 elucidated the role of CaSR on the calcium-dependent effects. After treatment with calcium, the activity of AKT, PLCγ-1, p38α and JNK was clearly enhanced and PTEN expression was almost completely abolished in bone metastasizing RCC cells.

Conclusions: Our results indicate a promoting effect of extracellular calcium on cell migration and proliferation of bone metastasizing RCC cells via highly expressed CaSR and its downstream signaling pathways. Consequently, CaSR may be regarded as a new prognostic marker predicting RCC bone metastasis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Western
  • Bone Neoplasms / secondary*
  • Bone and Bones / chemistry*
  • Calcium / metabolism*
  • Carcinoma, Renal Cell / metabolism*
  • Carcinoma, Renal Cell / secondary
  • Flow Cytometry
  • Humans
  • Immunohistochemistry
  • Kidney Neoplasms / metabolism*
  • Kidney Neoplasms / pathology
  • Receptors, Calcium-Sensing / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction

Substances

  • Receptors, Calcium-Sensing
  • Calcium