[Mechanism of G2/M cell cycle arrest before apoptosis in leukemia cell line HL-60 induced by proteasome inhibitor MG132].
OBJECTIVE
Proteasome inhibitor is a kind of potential anti-tumor drug,it can induce apoptosis in various tumor cells. This study was designed to investigate the molecular mechanism of apoptosis and G(2)/M arrest in leukemia cell line HL-60 induced by proteasome inhibitor MG132 (Z-Leu-Leu-Leu-CHO).


METHODS
Apoptosis in HL-60 cells was observed under fluorescent microscope, flow cytometry and immunoblot were used to analyze cell apoptosis, cell cycle arrest, and the mechanisms.


RESULTS
MG132 (2 micromol/L)induced apoptosis in HL-60 cells after 24-h treatment. Meanwhile, HL-60 cells were arrested at G(2)/M phase before apoptosis after induced by MG132. The percentage of G(2)/M phase in MG132-treated HL-60 cells at 12 h was 63.42+/-2.02,while that in untreated cells was 7.29+/-3.01 (P< 0.01). The percentage of apoptosis in MG132-treated HL-60 cells at 24 h was 16.67+/-1.48, while untreated cells had no death (P< 0.01). Compared to the treatment with MG132 only, caffeine (2 mmol/L) exposure can reduce G(2)/M arrest and apoptosis in MG132-treated HL-60 cells. Expression of cyclin-dependent kinase inhibitor p21waf/cip1 up-regulated after treated with MG132 for 3 h, but no p53 or p27 detected.


CONCLUSIONS
Proteasome inhibitor MG132 can induce G2/M arrest before the apoptosis appeared in HL-60 cells. The obvious up-regulation of p21 indicated that it is p21(waf/cip1), but not p53 or p53-related proteins,that involved in the regulation of G(2)/M arrest and subsequent apoptosis induced by MG132 in HL-60 cells.
Institute of Radiation Medicine, Academy of Military Medical Sciences, Beijing, 100850, P.R.China.
Guo-Jing
GJ
Sun
Jun-Jie
JJ
Qian
Xiang-Bing
XB
Meng
Yi
Y
Song
Feng
F
Zhang
Zhu-Zhong
ZZ
Mei
Yan
Y
Dong
Zhi-Xian
ZX
Sun
D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D016195:G2 Phase / Q000187:drug effects*; D018922:HL-60 Cells; D006801:Humans; D020014:K562 Cells; D015458:Leukemia, T-Cell / Q000473:pathology; D007976:Leupeptins / Q000494:pharmacology*; D015854:Up-Regulation
D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde