Synergistic anti-tumor effect of obatoclax and MG-132 in esophageal cancer cell line CaES-17 / 南方医科大学学报

<p><b>OBJECTIVE</b>To explore whether MG-132 could enhance the anti-tumor activity of obatoclax against esophageal cancer cell line CaES-17.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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).</p><p><b>CONCLUSION</b>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.</p>

Cisplatin induces drug resistance in human esophageal squamous carcinoma cell line EC109 by decreasing CTR1 protein expression / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the mechanism of the development of cisplatin resistance in a human esophageal squamous carcinoma cell line.</p><p><b>METHODS</b>The cytotoxicity of cisplatin in the cisplatin-resistant resistant cell line EC109/CDDP and its parental cell line EC109 was measured by MTT assay. Whole-cell cisplatin accumulation and Pt-DNA adduct formation were determined by inductively coupled plasma mass spectrometry (ICP-MS). Western blotting was used to investigate the protein expression of full length PARP, cleaved PARP, and copper transporter 1 (CTR1).</p><p><b>RESULTS</b>EC109/CDDP cells was more resistant to cisplatin-induced cytotoxicity and apoptosis than EC109 cells. Compared with EC109 cells, EC109/CDDP cells exhibited less cisplatin accumulation and Pt-DNA adduct formation with also decreased CTR1 protein expression.</p><p><b>CONCLUSION</b>Cisplatin induces drug resistant phenotype by decreasing the protein level of CTR1, which controls cell accumulation and cytotoxic effect of cisplatin.</p>