Abstract: Objective: To investigate the effect of demethylation of Syk gene promoter by the methylation transferase inhibitor 5-aza-CdR on the invasion and metastasis of medulloblastoma cell line Daoy. Methods: Medulloblastoma cell line Daoy was treated with 5-aza-CdR in vitro. Methylation-specific PCR, real time-PCR and Western blot were used to detect Syk gene promoter methylation status, Syk mRNA and protein expression respectively. Transwell was employed to study the invasion and metastasis of medulloblastoma cell line Daoyby counting the cells that had invaded through Matrigel and migrated to the undersurface of the membrane before and after treatment of 5-aza-CdR. Results: In comparison to control group, Syk gene promoter of 5-aza-CdR-treated groups was demethylated and expression of Syk mRNA and protein was significantly up-regulated by 3.40±0.24 folds (P<0.01) and 3.23±0.19 folds (P<0.01) respectively. The invasiveness and metastasis of medulloblastoma cell line Daoy was decreased(P<0.05). Conclusion: Hypermethylation of Syk gene promoter is responsible for the down-regulation of Syk gene expression in medulloblastoma cell line Daoy, which may be one of the mechanisms that enhanced cell invasion and metastasis. While 5-aza-CdR can reverse the hypermethylation of Syk gene promoter and restore Syk gene expression and thus suppresses invasiveness and metastasis of tumor cells.

Key words: medulloblastoma, Syk gene, methylation, 5-aza-CdR, invasion and metastasis