These data strongly suggest that: first, the CpG islands at the promoter region of CH25H are hypermethylated and the expression of CH25H is suppressed in MDS/leukemia cell lines; second, the promoter region of CH25H is hardly methylated and CH25H message is expressed to some extent in normal bone marrow CD34-positive cells; and third, DNMT inhibitors promote CH25H expression by altering the hypermethylated status of this gene and induce cell death. The gene discussed is CD34; the disease is leukemia.