title: Novel Insights into Gastric Cancer: Methylation of R-spondins and Regulation of LGR5 by SP1.
abstract: Recently, it was shown that leucine-rich repeat-containing receptor 5 (LGR5)-expressing stem cells are the cellular origin of intestinal-type gastric cancer. The aim of our study was to uncover regulatory mechanisms of LGR5 expression in gastric mucosa and their implications for cancer development. Reporter assays identified an LGR5 promoter fragment, which is highly relevant for active LGR5 expression. Chromatin immunoprecipitation verified that SP1 is bound within this region, and reporter activity increased in SP1 transfected cells. Subsequently, the expression of R-spondins (RSPO1 and RSPO2), ligands of LGR5, was explored in neoplastic and nonneoplastic gastric tissue and gastric cancer cell lines. Using IHC, distinct spatial expression patterns of LGR5, RSPO1, and RSPO2 were found in nonneoplastic stomach mucosa and gastric cancer. RSPO expression was lower in gastric cancer compared with nonneoplastic mucosa on both the transcriptional (P= 0.003 for RSPO1 andP= 0.000 for RSPO2;n= 50) and the translational level. Methylation-specific PCR showed higher methylation levels of RSPO1/2 and reexpression of RSPOs in the gastric cancer cell lines MKN45 and MKN74 were induced by demethylating 5-aza-C treatment. Finally, expression patterns of LGR5 and RSPO were similar in gastric cancer.Implications:This report identifies a regulatory mechanism of LGR5 expression in gastric carcinogenesis, with SP1 as an important component of the transcriptional complex and LGR5 activity, which is modulated by its ligands RSPO1 and RSPO2, whose expression is modulated by methylation.Visual Overview:http://mcr.aacrjournals.org/content/15/6/776/F1.large.jpg.Mol Cancer Res; 15(6); 776-85. ©2017 AACR.
authors.affiliation: Department of Pathology, Christian-Albrechts-University, Kiel, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Wilhelm
authors.affiliation: Department of Pathology, Christian-Albrechts-University, Kiel, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Simon
authors.affiliation: Department of Pathology, Christian-Albrechts-University, Kiel, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Böger
authors.affiliation: Department of Pathology, Christian-Albrechts-University, Kiel, Germany.
authors.forename: Hans-Michael
authors.initials: HM
authors.lastname: Behrens
authors.affiliation: Department of Pathology, Christian-Albrechts-University, Kiel, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Krüger
authors.affiliation: Department of Pathology, Christian-Albrechts-University, Kiel, Germany. christoph.roecken@uksh.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Röcken
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism; D045744:Cell Line, Tumor; D019175:DNA Methylation; D005753:Gastric Mucosa / Q000378:metabolism* / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D013274:Stomach Neoplasms / Q000378:metabolism* / Q000473:pathology; D019699:Thrombospondins / Q000235:genetics / Q000378:metabolism; D000098907:R-Spondins
chemical_list: D014408:Biomarkers, Tumor; D036341:Intercellular Signaling Peptides and Proteins; D043562:Receptors, G-Protein-Coupled; D016329:Sp1 Transcription Factor; D019699:Thrombospondins; C116884:LGR5 protein, human; C503243:RSPO1 protein, human; D000098907:R-Spondins; C557408:Rspo2 protein, human; C108209:SP1 protein, human