Epigenetic inactivation of the metastasis suppressor RECK enhances invasion of human colon cancer cells

Down-regulation of RECK, an important metastasis suppressor gene, has been found in human colon cancer. However, the molecular mechanism for this down- regulation and its biological significance are still unclear. In the present study, we investigated whether down-regulation of RECK is caused by epigenetic inactivation via promoter methylation and tested the effect of DNA methyltransferase (DNMT) inhibitor on RECK expression and cell invasion. The mRNA and protein levels of RECK in colon tumor tissues and their normal counterparts were compared. We found that down-regulation of RECK was found in 48% of the twenty five tumors analyzed. MSP analysis demonstrated that methylation of RECK promoter was detected in 44% (11/25) of the tumor tissues and a strong correlation between down-regulation and promoter methylation was found (P = 0.028). Promoter methylation was also found in SW480 and SW620 human colon cancer cell lines. DNA methyltransferase (DNMT) inhibitor 5'-azacytidine reversed promoter methylation, restored RECK expression and suppressed invasion by these two cell lines. Restoration of RECK is critical for 5'-azacytidine-mediated suppression of cell invasion because inhibition of RECK by a specific antibody significantly attenuated the anti-invasive ability of 5'-azacytidine. Taken together, our results suggest that down-regulation of the metastasis suppressor RECK in colon cancer is associated with promoter methylation and that a DNMT inhibitor may restore RECK expression to inhibit cell invasion.