title: Gene expression differences between colon and rectum tumors.
abstract: OBJECTIVE
  Colorectal cancer studies typically include both colon and rectum tumors as a common entity, though this assumption is controversial and only minor differences have been reported at the molecular and epidemiologic level. We conducted a molecular study based on gene expression data of tumors from colon and rectum to assess the degree of similarity between these cancer sites at transcriptomic level.
  
  
  METHODS
  A pooled analysis of 460 colon tumors and 100 rectum tumors from four data sets belonging to three independent studies was conducted. Microsatellite instable tumors were excluded as these are known to have a different expression profile and have a preferential proximal colon location. Expression differences were assessed with linear models, and significant genes were identified using adjustment for multiple comparisons.
  
  
  RESULTS
  Minor differences at a gene expression level were found between tumors arising in the proximal colon, distal colon, or rectum. Only several HOX genes were found to be associated with tumor location. More differences were found between proximal and distal colon than between distal colon and rectum.
  
  
  CONCLUSIONS
  Microsatellite stable colorectal cancers do not show major transcriptomic differences for tumors arising in the colon or rectum. The small but consistent differences observed are largely driven by the HOX genes. These results may have important implications in the design and interpretation of studies in colorectal cancer.
authors: Unit of Biomarkers and Susceptibility, Catalan Institute of Oncology, IDIBELL, and CIBERESP, Barcelona, Spain.
authors: Rebeca
authors: R
authors: Sanz-Pamplona
authors: David
authors: D
authors: Cordero
authors: Antonio
authors: A
authors: Berenguer
authors: Flavio
authors: F
authors: Lejbkowicz
authors: Hedy
authors: H
authors: Rennert
authors: Ramon
authors: R
authors: Salazar
authors: Sebastiano
authors: S
authors: Biondo
authors: Xavier
authors: X
authors: Sanjuan
authors: Miguel A
authors: MA
authors: Pujana
authors: Laura
authors: L
authors: Rozek
authors: Thomas J
authors: TJ
authors: Giordano
authors: Ofer
authors: O
authors: Ben-Izhak
authors: Hector I
authors: HI
authors: Cohen
authors: Philip
authors: P
authors: Trougouboff
authors: Jacob
authors: J
authors: Bejhar
authors: Yanina
authors: Y
authors: Sova
authors: Gad
authors: G
authors: Rennert
authors: Stephen B
authors: SB
authors: Gruber
authors: Victor
authors: V
authors: Moreno
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003106:Colon / Q000473:pathology; D003110:Colonic Neoplasms / Q000145:classification / Q000235:genetics* / Q000473:pathology; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D012004:Rectal Neoplasms / Q000145:classification / Q000235:genetics* / Q000473:pathology; D012007:Rectum / Q000473:pathology; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism
chemical_list: D014157:Transcription Factors