title: Screening and identification of down-regulated genes in colorectal carcinoma by subtractive hybridization: a method to identify putative tumor suppressor genes.
abstract: OBJECTIVE
  To search for new putative tumor suppressor genes in colorectal carcinoma.
  
  
  METHODS
  Subtractive hybridization technologies were applied to screen and select genes, the expression of which was down-regulated in colorectal carcinoma. mRNAs uniquely expressed in normal cells but not in colorectal carcinoma were recovered as cDNA (sub-cDNA) after two rounds of subtractive hybridization with mRNA prepared from colorectal carcinoma. The sub-cDNAs were then used as probes to screen a normal human colon cDNA library constructed in lambda-Zap II phage. The DNAs of positive clones were in vivo excised, and partial DNA sequences were analyzed and compared with DNA sequence database Genbank.
  
  
  RESULTS
  A total of 46 different clones with an average of about 1 kilobases in transcript size was recovered. Among these 46 down-regulated genes in colorectal carcinoma were genes encoding immunoglobulin (n = 32), 40-kDa keratin intermediate filamentous protein or IFP (n = 1), major histocompatibility complex-related protein (n = 1), unrelated structural proteins (n = 10) and gene products yet to be identified (n = 2). RNA dotblot hybridizations confirmed that all 46 clones contained genes that were down-regulated and have not been reported before in colorectal carcinoma.
  
  
  CONCLUSIONS
  The results of this study suggested that the 46 clones were down-regulated in colorectal carcinoma, they should be further studied as new putative tumor suppressor genes and could be used as new tumor markers of colorectal carcinoma.
authors.affiliation: Cancer Institute, Zhejiang Medical University, Hangzhou, China.
authors.forename: S
authors.initials: S
authors.lastname: Zheng
authors.forename: X
authors.initials: X
authors.lastname: Cai
authors.forename: J
authors.initials: J
authors.lastname: Cao
authors.forename: L
authors.initials: L
authors.lastname: Zheng
authors.forename: L
authors.initials: L
authors.lastname: Geng
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: J
authors.initials: J
authors.lastname: Gu
authors.forename: Z
authors.initials: Z
authors.lastname: Shi
mesh_terms: D015179:Colorectal Neoplasms / Q000235:genetics*; D015536:Down-Regulation; D016147:Genes, Tumor Suppressor / Q000235:genetics*; D006801:Humans; D009693:Nucleic Acid Hybridization; D017422:Sequence Analysis, DNA