EBV-related alteration of gene expression is often reversed by treatment with a demethylating agent. Bar graphs show substantial dysregulation of 11 genes upon EBV infection, as tested by rtPCR, with zero representing baseline expression levels in parental AGS cells. Treatment of uninfected cells with 5-aza-2'-deoxycytidine (5aza) reveals induction of ID2, ID4, CCND1, CDKN2A (p16) and IGFBP3, suggesting pre-existing promoter methylation. Treatment of infected cells reveals that demethylation can overcome the effect of EBV infection on virus-induced gene dysregulation, at least in part. The most marked drug effect was seen in ID2, CCND1 and COX2 where demethylation virtually completely reversed the impact of viral infection.