Objective    To investigate the methylation status of promoter CpG islands of the estrogen receptors (ERs) in leukemia cell lines

including 3 promoters of ERα (ERα-A

-B and -C) and one promoter of ERβ

and explore the possible relationship between the mRNA expressions of the promoters and the CpG methylation.     Methods    With RT-PCR and methylation specific PCR (MSP)

the mRNA expressions of above promoters and their status of methylation in leukemia cell lines HL-60

K562

Jurkat

THP-1

U937 and MOLT-410

and health controls with or without treatment of 5-AzA-2′-Deoxycitidine (5-Aza-DC).     Results    Promoters of ER were all methylated or semi-methylated in the 6 strains of leukemia cells. Only the ERα-A was inactivated in these leukemia cell lines and was unmethylated in all 10 health controls

and the expression was recovered after the treatment of 5′-Aza-DC.     Conclusion    The CpG islands of ER promoter are hypermethylated in 6 strains of leukemia cells

and this inactivate the expression of ERα-A

which can be activated by the treatment of 5′-Aza-DC.