Mechanism of Oxymatrine-induced Human Esophageal Cancer Cell Apoptosis by the Endoplasmic Reticulum Stress Pathway

Abstract

Endoplasmic reticulum stress is one of the mechanisms of cell apoptosis. In this study, the mechanism of oxymatrine-induced human esophageal cancer Eca-109 cell apoptosis by the endoplasmic reticulum stress pathway was investigated. Eca-109 cells were cultured in vitro with different doses of oxymatrine (0.5, 1, 2 μg/mL) for 48 h. The cell viability and proliferation inhibition rate were examined by MTT assay and cell cycle assay. The apoptosis rate was examined by Annexin V-FITC/propidium iodide assay. The expression of endoplasmic reticulum stress markers, including binding immunoglobulin protein and CCAAT-enhancer-binding protein homologous protein, were determined by real-time quantitative polymerase chain reaction and western blotting, respectively. MTT data showed that oxymatrine significantly inhibited the proliferation of Eca-109 cells. The cell apoptosis rate was quantified by flow cytometry. The expression of binding immunoglobulin protein was markedly downregulated in oxymatrine-treated Eca-109 cells while that of CCAAT-enhancer-binding protein homologous protein was upregulated. Oxymatrine inhibited proliferation and induced apoptosis of human esophageal carcinoma Eca-109 cells. Thus, oxymatrine may be a potential agent for treating human esophageal cancer.

Keywords: Binding immunoglobulin protein; CCAAT-enhancer-binding protein homologous protein; Human esophageal carcinoma Eca-109 cells; Oxymatrine.

Figure 1

Effects of oxymatrine on apoptotic rate of esophageal cancer Eca-109 cells. After treatment with 0.5, 1, and 2 μg/mL oxymatrine and 2 mg/mL 5-FU for 48 h, the Eca-109 cell apoptosis rate were quantified by Annexin V-FITC and PI double staining. (a) The apoptotic rate was 0.32 ± 0.08% in controls. (b) The apoptotic rate was 16.22 ± 0.19%in the 5-FU group. (c) The apoptotic rate was 2.74 ± 0.29% in the 0.5 μg/ mL oxymatrine-treated group. (d) The apoptotic rate was 9.32 ± 0.18% in the 1 μg/mL oxymatrine-treated group. (e) The apoptotic rate was 12.98 ± 0.54% in the 2 μg/mL oxymatrine-treated group. (f) The apoptotic rate in all groups is shown in the histogram. Comparison with the control group: ^*P < 0.05.

Figure 2

Effects of oxymatrine on the expression of BIP and CHOP in esophageal cancer Eca-109 cells. After treatment with 0.5,1, and 2 μg/ mL oxymatrine and 2 μg/mL 5-FU for 48 h, Eca-109 cells were collected and the relative expression levels of BIP, CHOP, and β-actin were analyzed by real-time PCR. (a) Relative expression of BIP mRNA. (b) Relative expression of CHOP mRNA.

Figure 3

Effects of oxymatrine on the expressions of BIP and CHOP of esophageal cancer Eca-109 cells. After treatment with 0.5, 1, and 2 μg/mL oxymatrine and 2 μg/mL 5-FU for 48 h, Eca-109 cells were collected and the relative expression levels of BIP, CHOP, and β-actin were analyzed by western blotting.