[Apoptosis and re-expression of p16 gene in the myeloma cell line U266 induced by synergy of histone deacetylase inhibitor and demethylating agent].
OBJECTIVE
Histone deacetylation is associated with transcriptional activation controlled by DNA methylation. It is important to investigate changes of tumor cells treated with agent through two kinds of mechanisms. This study was designed to investigate the synergic effect of histone deacetylase inhibitor, sodium phenylbutyrate(SPB), and demethylating agent, 5-Aza-2'-deoxycytidine(5-Aza-CdR), on cell growth and explore the possibility of re-expression of the hypermethylated and silenced p16 gene in the myeloma cell line U266.


METHODS
The cell cycle was analyzed by flow cytometry. Apoptosis was observed by transmission electron microscopy, DNA ladder, fluorescence-activated cell sorter (FACS). The expression level of p16 was detected by RT-PCR and Western blot analysis.


RESULTS
The apoptotic rates of U266 cells induced by 5-Aza-CdR(1 mumol/L), SPB(1 mmol/L) alone and combination of 5-Aza-CdR and SPB were 15.09%, 89.19%, and 85.18%, respectively. The G1 phase was arrested and sub-G1 phase(50%) was induced by combination of 5-Aza-CdR and SPB. There was no G1 phase arrested when SPB or 5-Aza-CdR was used alone. The proportion of cells in G2 phase was increased with SPB alone. SPB was not able to induce the expression of p16. The expression level of p16 was induced with 5-Aza-CdR. The expression level of both mRNA and protein of p16 was increased significantly by synergy of SPB and 5-Aza-CdR.


CONCLUSIONS
p16 gene in U266 cell line could be reactivated markedly with synergy of 5-Aza-CdR and SPB with cell cycle arresting in G1 phase. Meanwhile, the cell cycle phase occurring apoptosis that induced by combination of 5-Aza-CdR with SPB is different from that induced by each alone.
Du
Hong-ling
HL
Department of Hematology, 2. Central Lab, First Hospital, Peking University, Beijing 100034, P. R. China.
Qi
Yu
Y
Shi
Yong-jin
YJ
Bu
Ding-fang
DF
Wu
Shu-lan
SL
D017304:Annexin A5 / Q000032:analysis; D017209:Apoptosis / Q000187:drug effects*; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors*; D004273:DNA, Neoplasm / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D000077209:Decitabine; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D010654:Phenylbutyrates / Q000494:pharmacology; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000648:ultrastructure
D017304:Annexin A5; D019941:Cyclin-Dependent Kinase Inhibitor p16; D004273:DNA, Neoplasm; D056572:Histone Deacetylase Inhibitors; D010654:Phenylbutyrates; D012333:RNA, Messenger; D000077209:Decitabine; D015254:DNA Modification Methylases; D001374:Azacitidine