title: Differential roles of EPS8 in carcinogenesis: loss of protein expression in a subset of colorectal carcinoma and adenoma.
abstract: OBJECTIVE
  To analyze the epidermal growth factor receptor pathway substrate 8 (EPS8) expression status and role in colorectal carcinogenesis given that EPS8 has a conserved actin barbed-end capping function that is required for proper maturation in intestinal cells.
  
  
  METHODS
  We studied 8 colon cancer cell lines and 58 colorectal tumors (19 adenomas and 39 carcinomas). We performed expression microarray analysis of colon cancer cell lines followed by loss of heterozygosity (LOH) analysis and immunohistochemistry for EPS8 expression in colon tumors. Subsequently, we performed mutation analysis by direct sequencing and methylation analysis by bisulfite sequencing and methylation-specific polymerase chain reaction assays.
  
  
  RESULTS
  Expression microarray analysis of colon cancer cell lines showed overexpression of EPS8 transcript in all lines but RKO. Genome wide loss of heterozygosity (LOH) analysis of colon tumors, showed considerable LOH at the EPS8 gene locus. Immunohistochemically, EPS8 was constitutively expressed in normal colonic mucosa with a dot-like supranuclear localization with accentuation at the luminal surface supporting its proposed role in epithelial maturation. Nineteen colon tumors (4 adenoma, 15 carcinoma) out of 51 (37%) showed strikingly tumor specific EPS8 protein loss. Of the remaining tumors, 5/51 (2 adenoma, and 3 carcinoma, 10%) showed marked overexpression, while 27/51 tumors (53%) showed retained expression. Mutation analysis revealed a missense mutation (c.794C>T, p.R265C) in exon 8 in RKO. The EPS8 promoter was also methylated in RKO, but there was no significant methylation in other cell lines or carcinoma specimens.
  
  
  CONCLUSIONS
  The loss of EPS8 expression in colorectal adenomas and carcinomas suggests that down regulation of this gene contributes to the development of a subset of colorectal cancers, a finding which could have applications in diagnosis and treatment.
authors.affiliation: Department of Medical Laboratory Sciences, College of Health Sciences, University of Sharjah, Sharjah, United Arab Emirates. whassan@sharjah.ac.ae
authors.forename: Wael M
authors.initials: WM
authors.lastname: Abdel-Rahman
authors.forename: Salla
authors.initials: S
authors.lastname: Ruosaari
authors.forename: Sakari
authors.initials: S
authors.lastname: Knuutila
authors.forename: Päivi
authors.initials: P
authors.lastname: Peltomäki
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000378:metabolism*; D000236:Adenoma / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism*; D019175:DNA Methylation; D004252:DNA Mutational Analysis; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D019656:Loss of Heterozygosity; D053842:Microsatellite Instability; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C489989:EPS8 protein, human; D012333:RNA, Messenger; D012334:RNA, Neoplasm