| P15 gene is a candidate as tumor suppressor gene. As cell cycle negative regulator, it is a inhibitor of cyclin-dependent kinase CDK4 and CDK6,whose expression is induced by transforming growth factor(TGF-β)which is a potent inhibitor of cell growth . Abberrant methylation of 5'-CpG islands of P15 gene promoter has been recently described as an alternative mechanism of gene inactivation besides gene deletion. 5'-Aza-2cdR, which can inhibit DNA methylation by covalently traping DNA methylases as their target site in DNA, plays a role in demethylation and reactivate growth-regulator gene inactivated by demethylation. Using a recently found method that methylation-specific ploymerose chain reaction (MSP) is preceded by bisulfite modification of DNA, we investigated the methylation status of 32 NHL cases and raji cell lines of non-Hodgkin's lymphoma (NHL) induced by 5-Aza-2cdR, and investigated the P15 gene reexpression of raji cell lines before and after induced by 5-Aza-2cdR by RT-PCR.The results have showed that 18.75% (6/32) in NHL is methylation in P15 gene,and methylation was much more frequently in high grade malignant NHL patients 31.6% than in low grade malignant patients 0%. P15 gene can be demethylated and reexpressed with 5-Aza-2cdR of 10-7-10-6 mollL concentration so that inhibited the growth of rajicell lines and resulted in about 2-fold increase in the proportion of cells in G1\G0.The results have also suggested that 5-Aza-2cdR can inhibit the raji cell growth by inducing the reexpression of P15 gene.The method of P15 gene of demethylation provides an experimental foundation for hematologic malignant clincal therapy.
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