title: Epigenetic inactivation of calcium-sensing receptor in colorectal carcinogenesis.
abstract: Ca2+ 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 protein-coupled 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'-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 Ca2+ 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 β-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.
authors.affiliation: First Department of Internal Medicine, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Hizaki
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Taniguchi
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Adachi
authors.forename: Mayumi
authors.initials: M
authors.lastname: Nakazawa
authors.forename: Tokuma
authors.initials: T
authors.lastname: Tanuma
authors.forename: Norihiro
authors.initials: N
authors.lastname: Kato
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Sukawa
authors.forename: Jose V
authors.initials: JV
authors.lastname: Sanchez
authors.forename: Hiromu
authors.initials: H
authors.lastname: Suzuki
authors.forename: Shigeru
authors.initials: S
authors.lastname: Sasaki
authors.forename: Kohzoh
authors.initials: K
authors.lastname: Imai
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Shinomura
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D000236:Adenoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D018938:Caco-2 Cells; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D018899:CpG Islands; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000032:analysis; D000077209:Decitabine; D015870:Gene Expression / Q000187:drug effects; D020868:Gene Silencing; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D044169:Receptors, Calcium-Sensing / Q000235:genetics* / Q000378:metabolism; D046888:Tissue Array Analysis
chemical_list: D018906:Antineoplastic Agents, Alkylating; C095550:CASR protein, human; D004273:DNA, Neoplasm; D006877:Hydroxamic Acids; D012333:RNA, Messenger; D044169:Receptors, Calcium-Sensing; C012589:trichostatin A; D000077209:Decitabine; D001374:Azacitidine