(A) NID1 and NID2 promoter methylation and gene expression in human cancer cell lines. With few exceptions, there is a clear correlation between gene expression and lack of promoter methylation. Each sample was checked and confirmed for quality and equal cDNA amount used by analyzing expression of GAPDH by RT PCR amplification (GAPDH experiment was identical for both genes). (B) NID1 and NID2 genes are reactivated by the DNA demethylating agent zebularine. The panels show the effect of zebularine (ZEB) and trichostatin (TSA) on DNA demethylation and gene expression in the human cell line MDA-MB-231. Zebularine, alone or in combination with TSA, induced expression of both genes, which was absent in the parental untreated cell line and in the treatment with TSA alone. PBL, peripheral blood leukocytes, and the cell line A204 were used as positive controls. 123 bp, Molecular weight marker 123 bp ladder.