Regulation of E-cadherin and β-catenin by Ca2+ in colon carcinoma is dependent on calcium-sensing receptor expression and function
✍ Scribed by Narasimharao Bhagavathula; Andrew W. Hanosh; Kamalakar C. Nerusu; Henry Appelman; Subhas Chakrabarty; James Varani
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- French
- Weight
- 854 KB
- Volume
- 121
- Category
- Article
- ISSN
- 0020-7136
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✦ Synopsis
Abstract
An siRNA directed against the extracellular calcium‐sensing receptor (CaSR) was used to down‐regulate this protein in CBS colon carcinoma cells. In additional studies, we utilized a variant of the parental CBS line that demonstrates CaSR expression but does not upregulate this protein in response to extracellular Ca^2+^. In neither the siRNA‐transfected cells nor the Ca^2+^‐nonresponsive variant cells did inclusion of Ca^2+^ in the culture medium inhibit proliferation or induce morphological alterations. Extracellular Ca^2+^ also failed to induce E‐cadherin production or a shift in β‐catenin from the cytoplasm to the cell membrane. In mock‐transfected cells and in a Ca^2+^‐responsive variant line derived from the same parental CBS cells, Ca^2+^ treatment resulted in growth‐reduction. This was accompanied by increased E‐cadherin production and a shift in β‐catenin distribution from the cytoplasm to the cell membrane. Additionally, down‐regulation of c‐myc and cyclin D1 expression was observed in mock‐transfected cells and in the Ca^2+^‐responsive variant line (along with reduced T cell factor transcriptional activation). Neither c‐myc nor cyclin D1 was significantly down‐regulated in the siRNA‐transfected cells or in the Ca^2+^‐nonresponsive variant cells upon Ca^2+^ stimulation. In histological sections of human colon carcinoma CaSR was significantly reduced as compared to the level in normal colonic crypt epithelial cells. Where CaSR expression was high, strong surface staining for E‐cadherin and β‐catenin was observed. Where CaSR expression was reduced, β‐catenin surface expression was likewise reduced. © 2007 Wiley‐Liss, Inc.