Objective To detect hypermethylation status of the CpG island locating in the promoter region of PNRC gene and the regulation of hypermethylation on expression of PNRC gene in breast cancer cells.   Methods The expression of PNRC gene in normal mammary gland cell and breast cancer cell line was analyzed by RTPCR. After prediction of CpG island in promoter of PNRC gene using “MethPrimer” software

the status of methylation of CpG island in promoter of PNRC gene was analyzed using methylation-specific PCR (MSP). The expressions of mRNA and protein of PNRC were analyzed by RT-PCR

Northern hybridization and Western blot after treatment with methyltransferase inhibitor 5-aza-2’-deoxycytidine (5-Aza-dc). MCF-7 cells transfected with the luciferase report plasmid that contains the promoter sequence of PNRC were treated with 5-Aza-dc and the promoter activity of PNRC was detected by luciferase assay.   Results The expression level of PNRC gene in breast cancer cells was much lower than that in normal mammary gland cells

MCF-10A. The CpG island in promoter of PNRC was found to be methylated only in breast cancer MCF-7 cells but not in normal breast MCF-10A cells. In addition

the levels of mRNA and protein of PNRC in MCF-7 cells were increased dramatically in response to the treatment of 5-Aza-dc. The promoter activity of PNRC in MCF-7 cells was found to be elevated upon the treatment of 5-Aza-dc.   Conclusion The hypermethylation of CpG island in promoter of PNRC is probably responsible for low PNRC expression in breast cancer cells.