Global Screening of Methylated Genes in Gastric Cancer by Differential Methylation Hybridization and CpG DNA Microarray and Identification of Low Density Lipoprotein Receptor-Related Protein 1B as a Potential Tumor Suppressor Gene in Gastric Cancer

• Main Authors: Yen-Jung Lu, 陸燕榮
• Other Authors: Yu-Sun Chang
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/93497197014267446088

博士 === 國立陽明大學 === 微生物及免疫學研究所 === 98 === Gastric cancer is the second most common cancer worldwide, while in Taiwan it is the fifth leading cause of cancer-related death. Several factors have been implicated in the development of gastric cancer, including chromosomal instability, genetic and epigenetic alterations, Helicobacter pylori infection, and environmental factors such as diet and smoking. Among them, the aberrant methylation of CpG dinucleotides has been reported during tumorigenesis in gastric cancer. In this study, we used CpG island microarray and differential methylation hybridization (DMH) to identify novel epigenetic targets in gastric cancer. We identified 107 genes that were differentially hypermethylated in the four gastric cancer cell lines (AGS, AZ521, KATOIII and TMC1) but not in the two adult normal stomach tissue samples. Several tumor suppressor genes previously identified as being regulated by DNA methylation in gastric cancer were identified by our approach. One of the candidate genes, LRP1B, was hypermethylated in four gastric cancer cell lines and clinical samples (45 out of 74, 60.8%), and low LRP1B mRNA expression was associated with high methylation levels in gastric cancer cell lines. Addition of DNA methylation inhibitor (5-Aza-dC) can restore the mRNA expression of LRP1B in these cell lines, indicating that DNA methylation is involved in regulating LRP1B expression. In 15 out of 19 (78.9%) gastric tumor tissues, LRP1B mRNA expression was significantly lower than in adjacent normal tissues. In addition, ectopic expression of mLRP1B4 in gastric cancer cell lines suppressed cell growth, colony formation and tumor formation in nude mice. These results collectively indicate that LRP1B is a functional tumor suppressor gene in gastric cancer, and that is regulated by DNA methylation.