Arsenic trioxide reverses hypermethylation of p16 and activates its transcription in malignant lymphoma cell line CA46 / 中国实验血液学杂志

This study was aimed to investigate the reversing effect of arsenic trioxide (As2O3) on methylation status and the regulatory effect on transcription of malignant lymphoma cell line CA46 p16 gene as well as their possibe mechanisms. The hypermethylated malignant lymphoma cell line CA46 was used as a subject of experiment for studying relation of gene methylation with expression. The effect of As2O3 on the proliferation and viability of CA46 was detected by SRB method, the change of p16 methylation status after exposure to As2O3 was determined by nMSP, the expressions of p16, DNMT1, DNMT3A, DNMT3B mRNA were assayed by RT-PCR, the influence of As2O3 on CA46 cell cycle was analyzed by flow cytometry using analytical method for DNA ploidy. The results showed that the methylation level of p16 gene was obviously reduced after treatment with As2O3 for 72 hours and the hypermethylation of p16 gene was successfully reversed; the expression of p16 gene in untreated (control) group was low while it was enhanced in treated groups; the gray scale ratios of p16 gene to beta-actin in groups treated with As2O3 of concentration 0.5, 1.0 and 2.0 micromol/L were 0.33+/-0.10, 0.57+/-0.11 and 0.67+/-0.09 respectively, exhibiting a significant difference in comparison with 0.73+/-0.13 of positive control (p<0.01); as compared with the untreated group, the expression of DNMT3A and DNMT3B in treated groups was obviously down-regulated in a concentration-dependent manner, while expression of DNMT1 was nearly unchanged; as compared with control, all the 3 different concentrations of As2O3 could inhibit the proliferation of CA46 cells and increase the cell number in G0/G1 phase. It is concluded that the As2O3 may up-regulate the expression of p16 gene, recover the activity of p16 gene, thereby promote the regulatory function on cell cycle resul-ting in arrest of cells in G0/G1 phase and inhibit growth of tumor cells through depressing the expression of DNMT3A and DNMT3B and/or directly reversing the methylation status of p16 gene.

Detection of promoter methylation of p16 gene in hematological malignant cell lines by nested methylation specific polymerase chain reaction / 中国实验血液学杂志

This study was aimed to investigate the efficiency of modified methylation-specific polymerase chain reaction i.e. nested methylation-specific polymerase chain reaction, used to detect the promoter methylation of p16 gene in six hematological malignant cell lines, and to explore the application in selection of hematological malignant cell lines with promoter hypermethylation, and make them to be an idel cell models for studying the relationship between gene methylation and expression. DNAs were denatured by NaOH and then were subjected to bisulfite modification and a nested-MSP was used to amplify the promoter region, nested MSP product of p16 gene promoter was analyzed and sequenced. The results showed that the hypermethylation of p16 gene was detected in CA46 and U266, however, Molt4, K562, HL-60 and Jurkat cell lines were unmethylated. In conclusion, p16 gene methylation in hematological malignant cell lines can be perfectly detected by nested-MSP method, which is simple, sensitive and specific for screening all kinds of hematological malignant cell lines with p16 gene methylated.