title: Screening for differentially methylated genes among human colorectal cancer tissues and normal mucosa by microarray chip.
abstract: High density DNA methylation microarrays were used to study the differences of gene methylation level in six pairs of colorectal cancer (CRC) and adjacent normal mucosa. We analyzed the profile of methylated genes by NimbleGen Microarray and the biologic functions by NIH-NAVID. In addition, preliminary validation studies were done in six pairs of samples by MSP (methylation-specific PCR). A total of 4,644 genes had a difference in methylation levels. Among them 2,296 were hypermethylated (log2ratio > 1), 2,348 genes were hypomethylated (log2ratio < -1), in which 293 hypermethylated and 313 hypomethylated genes were unmapped according to the NIH-NAVID. All these genes were randomly distributed on all the chromosomes. However, chromosome 1 contained the most of the hypermethylated genes (232 genes), followed by chromosome 19 (149 genes), chromosome 11 (144 genes), chromosome 2 (141 genes), chromosomes 3 (127 genes). Through the analysis of the statistics, There were 2 hypermethylated/3 hypomethylated genes involved in six pairs of samples simultaneously, followed by 10/14 in five samples, 34/37 in four samples, 101/113 in three samples, 341/377 in two samples, 1,808/1,804 in one sample. According to gene ontology analysis, some physiological processes play important roles in the cell division and the development of tumor, such as apoptosis, DNA repair, immune, cell cycle, cell cycle checkpoint, cell adhesion and invasion etc. Through Preliminary validation, there were two genes (St3gal6, Opcml) in thirty top-ranking genes shown hypermethylated in six pairs of CRC and adjacent normal mucosa.
  
  
  CONCLUSIONS
  High density DNA methylation microarrays is an effective method for screening aberrantly methylated genes in CRC. The methylated genes should be further studied for diagnostic or prognostic markers for CRC.
authors.affiliation: Department of Colorectal Surgery, The Sixth Affiliated Hospital, Sun Yat-sen University, 26 Yuancunerheng Rd, Guangzhou, Guangdong 510655, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.forename: Jun
authors.initials: J
authors.lastname: Xiang
authors.forename: De-Feng
authors.initials: DF
authors.lastname: Chen
authors.forename: Bei-Bei
authors.initials: BB
authors.lastname: Ni
authors.forename: Hao
authors.initials: H
authors.lastname: Chen
authors.forename: Xin-Juan
authors.initials: XJ
authors.lastname: Fan
authors.forename: Pu-Ning
authors.initials: PN
authors.lastname: Wang
authors.forename: Shun-Xin
authors.initials: SX
authors.lastname: Song
authors.forename: Le-Kun
authors.initials: LK
authors.lastname: Fang
authors.forename: Huan-Yu
authors.initials: HY
authors.lastname: Xiao
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Jian-Ping
authors.initials: JP
authors.lastname: Wang
mesh_terms: D002874:Chromosome Mapping; D016000:Cluster Analysis; D003106:Colon / Q000378:metabolism*; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000235:genetics*; D019175:DNA Methylation; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D058977:Molecular Sequence Annotation; D015203:Reproducibility of Results