[Synergistic anti-tumor effect of obatoclax and MG-132 in esophageal cancer cell line CaES-17].
OBJECTIVE
To explore whether MG-132 could enhance the anti-tumor activity of obatoclax against esophageal cancer cell line CaES-17.


METHODS
MTT assay was used to determine the cytotoxicity of obatoclax and MG-132 in CaES-17 cells. The IC(50) of obatoclax and MG-132 were used to determine the molar ratio (1:2.4) of the two drugs for combined treatment of the cells. The concentrations of obatoclax and MG-132 ranged from 1/8 IC(50) to 4 IC(50) after serial dilution, and their combination index (CI) was calculated using CompuSyn software. The expression of ubiquitin and the cleavage of PARP, caspase-9, phospho-histone H3 and phospho-aurora A/B/C in the exposed cells were examined with Western blotting; the cell apoptosis was measured by flow cytometry with Annexin V staining, and the percentage of cells in each cell cycle phase was also determined by flow cytometry.


RESULTS
The CI of obatoclax and MG-132 was 0.296 for a 50% inhibition of Caes-17 cells and was 0.104 for a 95% inhibition. The cells treated with obatoclax or MG-132 alone showed increased expression of ubiquitin and cleavage of PARP and caspase-9. Compared with the cells treated with obatoclax or MG-132 alone, the cells with a combined treatment exhibited significantly increased expression of ubiquitin, cleavage of PARP and caspase-9, and expression of phospho-Histone H3 (P<0.05). The combined treatment of the cells also resulted in significantly increased expression of phospho-Aurora A/B/C compared with obatoclax treatment alone. The cells with the combined treatment showed significantly higher percentages of apoptotic cells and cells in sub-G(1) and G(2)/M phases compared with the cells treated with either of the drugs (P<0.05).


CONCLUSIONS
Obatoclax combined with MG-132 shows a significant synergistic anti-tumor effect against esophageal cancer CaES-17 cells by inducing apoptosis and cell cycle arrest.
School of Pharmaceutical Sciences, Southern Medical University, Guangzhou 510515, China. E-mail: 984623086@qq.com.
Xu-Yan
XY
Zhao
Qing-Huan
QH
Lin
Fu-Chang
FC
Que
Chun-Ping
CP
Gu
Le
L
Yu
Shu-Wen
SW
Liu
D017209:Apoptosis; D053453:Caspase 9 / Q000378:metabolism; D059447:Cell Cycle Checkpoints; D045744:Cell Line, Tumor / Q000187:drug effects; D004938:Esophageal Neoplasms / Q000473:pathology*; D006657:Histones / Q000378:metabolism; D006801:Humans; D007211:Indoles; D007976:Leupeptins / Q000494:pharmacology*; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011758:Pyrroles / Q000494:pharmacology*
D006657:Histones; D007211:Indoles; D007976:Leupeptins; D011758:Pyrroles; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; C506433:CASP9 protein, human; D053453:Caspase 9; C520962:obatoclax; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde