Epigenetic silencing of LRRC3B in colorectal cancer.
OBJECTIVE
Tumor suppressor gene silencing via promoter hypermethylation is an important event in the pathogenesis of colorectal cancer (CRC). Some aberrant DNA hypermethylation has high tumor specificity, so it may contribute to early diagnosis of CRC. The objective of this study was to establish novel therapeutic and diagnostic strategies against CRC by identifying the novel methylation-related genes.


METHODS
Two microarray-based approaches were used to identify novel methylation-related genes in CRC. We identified methylation-sensitive genes in colon cancer cell line SW1116 by comparing differential expression genes after treatment with the methylation inhibiting drug, 5-aza-2'-deoxycytidine (5-aza-dC) using gene expression microarray. Promoter microarray analysis was performed to identify cancer-specific, methylation-related genes in two patients with CRC. Gene promoter methylation was identified by methylation-specific polymerase chain reaction (PCR) (MSP) in primary CRC. Gene expression level was assessed using real-time PCR analysis.


RESULTS
By using gene expression microarray, up-regulation of 253 genes was detected in the CRC cell line, SW1116, after treatment with 5-aza-dC. Of the 253 genes identified by gene expression microarray analysis, LRRC3B (leucine-rich repeat containing 3B) was isolated as a potential methylation-specific gene by promoter microarray analysis. MSP analysis showed frequent methylation of LRRC3B in primary CRC (24/31 cases, 77%). In addition, the LRRC3B methylation intensity was significantly higher in cancer tissues than in the corresponding non-cancerous tissues. Decreased LRRC3B expression (17/31, 55%) was observed in the cancer tissues by real-time PCR.


CONCLUSIONS
LRRC3B may be a novel methylation-sensitive tumor suppressor gene in CRC. LRRC3B methylation has significant tumor specificity and may be a biomarker of CRC.
Tian
Xiao Qing
XQ
Shanghai Jiao-Tong University School of Medicine Renji Hospital, Shanghai Institute of Digestive Disease, Shanghai, PR China.
Zhang
Yanjie
Y
Sun
Danfeng
D
Zhao
Shuliang
S
Xiong
Hua
H
Fang
Jingyuan
J
D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology; D019175:DNA Methylation; D000077209:Decitabine; D004791:Enzyme Inhibitors / Q000494:pharmacology; D044127:Epigenesis, Genetic; D020868:Gene Silencing; D016147:Genes, Tumor Suppressor; D005819:Genetic Markers / Q000235:genetics; D006801:Humans; D066298:In Vitro Techniques; D046228:Microarray Analysis; D009363:Neoplasm Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction
D004791:Enzyme Inhibitors; D005819:Genetic Markers; C477813:LRRC3B protein, human; D009363:Neoplasm Proteins; D000077209:Decitabine; D001374:Azacitidine