[Promoter methylation status of PTEN gene and the effect of induced demethylation in leukemia cell lines].
OBJECTIVE
To explore the mechanism of PTEN gene expression silence in leukemia cells, and the effect of induced PTEN gene expression in leukemia cells.


METHODS
Methylation status of PTEN in leukemic cell lines, including HL-60, Nalm-6, NB4, U937, Raji, K562 and KG-1a was assessed by methylation specific PCR (MSP). The cell lines were then treated with different concentrations of methyltransferase inhibitor 5-Aza-2'-deoxycytidine (5-Aza-CdR). After that the changes in PTEN methylation status were detected by MSP, and PTEN mRNA expression level by reverse transcription PCR (RT-PCR). Growth inhibition and apoptosis of HL-60 and Nalm-6 cells induced by 5-Aza-CdR were observed by MTT assay, and Wright and Annexin V staining, respectively.


RESULTS
Hypermethylation of PTEN promoter was detected in HL-60, U937, Nalm-6, Raji and KG-1a, while hypomethylation was found in NB4 and K562 by MSP. After 5-Aza-CdR treatment, the hypermethylation status of PTEN promoter in HL-60 and Nalm-6 cells was reversed and their PTEN mRNA expression levels were up regulated in dose dependent manner with the 5-Aza-CdR concentrations, and the cell apoptosis was induced.


CONCLUSIONS
Hypermethylation in the promoter region is one of major mechanisms responsible for transcriptional suppression of PTEN. Methyltransferase inhibitor could induce the expression of PTEN gene and lead to the leukemia cells apoptosis.
Li
Min
M
State Key Laboratory of Experimental Hematology, Institute of Hematology and Blood Diseases Hospital, CAMS, Tianjin 300020, China.
Liu
Hang
H
Xu
Zhi-Fang
ZF
Liu
Xiang-Rong
XR
Wang
Yang
Y
Rao
Qing
Q
Wang
Jian-Xiang
JX
Wang
Min
M
D045744:Cell Line, Tumor; D019175:DNA Methylation; D006801:Humans; D007938:Leukemia / Q000235:genetics*; D051059:PTEN Phosphohydrolase / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics
D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human