Epigenetic inactivation of calcium-sensing receptor in colorectal carcinogenesis

Abstract

Ca 2 þ is a chemopreventive agent for colon cancer. Ion transport systems are often altered in human cancer. The aim of this study was to clarify the alterations of calcium-sensing receptor (CASR), a member of the G proteincoupled receptor family, in colorectal carcinogenesis. We analyzed the expression of CASR in colorectal cancer cell lines and in cancer and adenoma tissues by RT-PCR and immunostaining. In addition, we analyzed methylation of the CASR promoter by using bisulfite sequence analysis and methylation-specific PCR. CASR mRNA and protein expression was significantly downregulated in most of the cancer cell lines. CpG islands were densely methylated in cancer cell lines with reduced CASR mRNA expression. Treatment with a demethylating agent, 5-aza-2 0 -deoxycytidine, and/or a histone deacetylase inhibitor, trichostatin A, restored CASR expression in the cancer cell lines. Disruption of CASR expression in CASR-unmethylated HCT-8 cells blocked the enhancing effect of Ca 2 þ on the cytotoxic response to 5-fluorouracil. CASR expression was observed in normal colonic epithelial cells and was retained in most adenoma tissues. CASR mRNA and protein expression was significantly downregulated in cancer tissues. There was an inverse relationship between CASR expression and degree of differentiation. Immunohistochemical CASR staining was reduced more predominantly in less-differentiated cancer tissues and/or in cancer cells at the invasive front, where nuclear/ cytoplasmic b-catenin was often localized. CASR methylation was detected in 69% of colorectal cancer tissues and 90% of lymph node metastatic tissues and was significantly correlated with reduced CASR expression. CASR methylation was also detected in 32% of advanced adenoma tissues but was detected in only 9% of adenoma tissues and was not detected in hyperplastic polyp tissues. CASR methylation seems to occur at an early stage and progress in colorectal carcinogenesis. The results suggest that epigenetic inactivation of CASR has an important role in colorectal carcinogenesis.

Activation of the calcium-sensing receptor induces deposition of tight junction components to the epithelial cell plasma membrane

“…Such Ca 2+ signaling mediated by the CaSR is thought to stop cell division, initiate cell differentiation, and favor E-cadherin-based junction formation to connect cells to one another (Chakrabarty et al, 2003). In colorectal carcinoma, epigenetic silencing of the CASR gene promoter by methylation is detected in 69% of cases and in 90% of lymph node metastases, correlating strongly with reduced CaSR expression (Hizaki et al, 2011). Taken together, these findings indicate that changes in [Ca 2+ ] e sensed by the CaSR participate in the regulation of TJ assembly or maintenance.…”

Parathyroid Hormone Gene rs6256 and Calcium Sensing Receptor Gene rs1801725 Variants are not Associated with Susceptibility to Colorectal Cancer in Iran

“…In fact, loss of the CaSR expression in colonic epithelium is a key event in the pathogenesis of colon cancer (Rogers et al, 2012). Furthermore, epigenetic inactivation of CaSR (CaSR methylation) has an important role in colorectal carcinogenesis (Hizaki et al, 2011). CaSR is a very large gene and its variants appear to be involved in maintaining calcium homeostasis (Cole et al, 1999).…”

Synthetic biology-based cellular biomedical tattoo for detection of hypercalcemia associated with cancer

“…Its role as a second messenger in signal transduction, managing physiological functions associated with cell proliferation and apoptosis as well as differentiation, cell adhesion, and motility, has been extensively studied (11), but its role as a first messenger in the development of cancer has only recently been uncovered (12). In humans, calcium is stored in bone as mineralized hydroxyapatite and is present in blood, either as free Ca 2+ or bound to various carriers such as albumin (13).…”