RESUMEN
OBJECTIVE: To investigate the difference in methylation of PTPRG gene between gastric primary cancer and its lymph node metastases, and its regulation by 5-Aza-2'-deoxycytidin in a gastric cancer cell line SGC7901. METHODS: Methylation-specific polymerase chain reaction (MSP) and RT-PCR were applied to identify the difference between gastric primary cancer and lymph node metastases and assess the changes of methylation in gastric cancer cell line SGC7901 treated by 5-Aza-2'-deoxycytidin. RESULTS: There were significant differences of PTPRG gene methylation and PTPRG mRNA expression between gastric primary cancer and lymph node metastases: a linear regression analysis revealed a significant association between the quantity of metastatic lymph nodes and their methylation rate. A statistied relationship between methylation of PTPRG gene and loss of PTPRG mRNA expression was detected. PTPRG gene methylation in the gastric cancer cell line changed into negative and PTPRG mRNA expression in the cell line was recovered after 5-Aza-2'-deoxycytidin treatment. CONCLUSION: There is a difference of PTPRG gene methylation in gastric primary cancer and metastatic lymph nodes. 5-Aza-2'-deoxycytidin, an inhibitor of DNA methylation, can recovery the expression of PTPRG gene.