[Difference in methylation of genomic DNA between gastric primary cancer and lymph nodes with metastatic gastric cancer].
OBJECTIVE
To investigate the difference in methylation of genomic DNA between gastric primary cancer and lymph nodes with metastatic gastric cancer.


METHODS
Methylation CpG island amplification (MCA) was used to enrich the methylated DNA sequences in the cancer tissues and lymph nodes with metastatic gastric cancer resected during operation from 5 patients. Representational difference analysis (RDA) was conducted with the MCA products from the lymph nodes with metastatic gastric cancer as testers and the MCA products of the gastric primary cancer as drivers. The differentially methylated DNA fragments were cloned and sequenced, and underwent similarity analysis by BLAST system. The relationship between the clone sequence and related gene was analyzed by GenBank. Hybridization analysis was performed, using the No 1-3 round RDA products and the MCA products of the tissues of gastric primary cancer and lymph nodes with metastatic gastric cancer with digoxin-labeled KL22 fragment as probe.


RESULTS
Nineteen differentially methylated DNA sequences were obtained, distributed at the 5'-end, exon, intron, and 3'-end. KL59 fragment was located in the 9q21, the first exon of p16 gene. KL12 fragment was located in the promoter region of phosphotyrosine phosphatase receptor G (PTPRG) gene. Hybridization signals were obtained for all No 1-3 round RDA products and all testers, but not for the drivers.


CONCLUSIONS
There is a difference in DNA methylation between the tissues of primary cancer and lymph nodes with metastatic gastric cancer. MCA-RNA is an effective method to study the gene methylation. PTPRG gene may be a candidate gene for metastasis of gastric cancer.
Wang
Jian-feng
JF
Department of Surgical Oncology, First Hospital Affiliated Hospital, China Medical University, Shenyang 110001, China.
Dai
Dong-qiu
DQ