[New insight into the mechanism of p53 inducing leukemia cell apoptosis].
OBJECTIVE
To investigate the expression changes of intrinsic cytokines TGF-beta(1) and TNF-alpha, telomerase activity and bcl-2 during ongoing apoptosis of HL-60 and K562 cells induced by p53.


METHODS
pN53cG (Val135), a temperature sensitive p53 mutant, which behaved like wild type p53 (wt-p53) at 32.5 degrees C, were introduced into p53-null HL-60 and K562 cells respectively by lipofectin. In the presence of G418, HL-60-pN53cG and K562 pN53cG clones expressing p53 protein were selected. The ongoing expression of intrinsic cytokines (TGF-beta(1) and TNF-alpha), bcl-2 oncogene and hTERT mRNA during the apoptosis of HL-60 and K562 cells induced by p53 and the effects of exogenous p53 gene, TGF-beta(1) and TNF-alpha antisense PS-ODNS on the apoptosis of HL-60 and K562 cells and the expression of bcl-2 were studied by RT-PCR, quantitative RT-PCR, DNA fragmentation, TdT-mediated dUTP nick end labeling (TUNEL) and flow cytometery. The levels of secreted TGF-beta(1) and telomerase activity were detected by ELISA and PCR-ELISA, respectively.


RESULTS
(1) The expressions of intrinsic TGF-beta(1) and TNF-alpha mRNA were up-regulated, while that of bcl-2 and hTERT down-regulated. The levels of TGF-beta(1) in the supernatant of HL-60 and K562 cells were increased, and the level of telomerase activity decreased. (2) Antisense PS-ODNS of TGF-beta(1) and TNF-alpha could obviously inhibit the p53 inducing cell apoptosis, and restore bcl-2 mRNA and protein to pre-treated level.


CONCLUSIONS
Exogenous p53 induces leukemia cell apoptosis via up-regulating the expression of intrinsic TGF-beta(1) and TNF-alpha and down-regulating the expression of hTERT and bcl-2.
Chen
Yuan-zhong
YZ
Fujian Institute of Hematology, Union Hospital, Fujian Medical University, Fuzhou 350001, China.
Wu
Yong
Y
Liang
Min
M
Li
Nai-nong
NN
Zhang
Zhao-xiu
ZX
Lu
Lian-huang
LH
D017209:Apoptosis / Q000187:drug effects / Q000235:genetics*; D016373:DNA, Antisense / Q000494:pharmacology; D004268:DNA-Binding Proteins; D015972:Gene Expression Regulation, Neoplastic; D018922:HL-60 Cells; D006801:Humans; D020014:K562 Cells; D007938:Leukemia / Q000235:genetics / Q000473:pathology; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019098:Telomerase / Q000235:genetics; D014162:Transfection / Q000379:methods; D016212:Transforming Growth Factor beta / Q000235:genetics; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000502:physiology*
D016373:DNA, Antisense; D004268:DNA-Binding Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; C508960:TGFB1 protein, human; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha; D016159:Tumor Suppressor Protein p53; D019098:Telomerase