Affects Of Egb761on The Cell Proliferation And Apoptosis Induced By Cisplatin And Etoposide In Human Gastric Cancer SGC-7901Cells

OBJECTIVE:To study the effect of Ginkgo biloba extract (EGb761) on the cell proliferation and apoptosis induced by cisplatin or etoposide in human gastric cancer SGC-7901cells and to explore the possible mechanisms involved.METHODS:Human gastric cancer SGC-7901cells were treated with EGb761, cisplatin, etoposide, EGb761combined with cisplatin or etoposide. The cells viability was measured by MTT assay, the cells apoptosis was measured by flow cytometry. The chemical colorimetric method was used to detect the activity of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) and the content of malondialdehyde (MDA) in cells. Moreover, the protein expressions of ERK1/2,p-ERK1/2and nuclear transcription factor-kappa B (NF-κB) p65were determined by western blotting. The protein expressions of p-ERK1/2and NF-KBp65also were assessed by the method of immunocytochemistry.RESULTS:Cisplatin and etoposide significantly inhibited the growth of SGC-7901cell. EGb761significantly enhanced the cell inhibitory efficiency of cisplatin and etoposide. The cancer cells treated with cisplatin+EGb761or etoposide+EGb761showed significantly higher level of apoptotic phenotype than those treated with cisplatin or etoposide only. When treating cells with EGb761, the activities of SOD, GSH-Px and CAT were notably elevated. The activities of SOD, GSH-Px and CAT in cisplatin group and cisplatin+EGb761group were as follows:the activity of SOD:17.36U/mgprot±3.13U/mgprot vs27.35U/mgprot±4.84U/mgprot, the activity of CAT:2.56U/mgprot±0.37U/mgprot vs3.91U/mgprot±0.59U/mgprot, the activity of GSH-PX:23.98μmol/(min·mgprot)±3.35μmol/(min·mgprot) vs35.78μmol/(min·mgprot)±6.56μmol/(min·mgprot), all P<0.05. The activities of SOD, GSH-PX and CAT in etoposide group and etoposide+EGb761group were as follows:the activity of SOD:16.23U/mgprot±2.79U/mgprot vs26.40U/mgprot±4.27U/mgprot, the activity of CAT:2.61U/mgprot±0.38U/mgprot vs3.84U/mgprot±0.62U/mgprot, the activity of GSH-PX:22.87μmol/(min·mgprot)±4.34μmol/(min·mgprot) vs35.33μmol/(min·mgprot)±5.90μmol/(min·mgprot), P<0.05. While the content of MDA was significantly decreased, the content of MDA for the cisplatin group and cisplatin+EGb761group were as follows:2.27nmol/mgprot±0.39nmol/mgprot vs1.39nmol/mgprot±0.25nmol/mgprot, the content of MDA in etoposide group and etoposide+EGb761group were as follows:2.33nmol/mgprot±0.45nmol/mgprot vs1.40nmol/mgprot±0.23nmol/mgprot, P<0.05. Results of western blotting showed that the expressions of ERK1/2, p-ERK1/2and NF-κBp65were significantly induced by cisplatin or etoposide, while EGb761suppressed the expression of ERK1/2, p-ERK1/2and NF-κBp65induced by cisplatin or etoposide. The relative expression levels of ERK1/2, p-ERK1/2and NF-κBp65in cisplatin group and cisplatin+EGb761group were as follows:the relative expression level of ERK1/2:0.726±0.125vs0.476±0.083, the relative expression level of p-ERK1/2:0.520±0.087vs0.276±0.049, the relative expression level of NF-κBp65:0.524±0.091vs 0.274±0.045, the relative expression levels of ERK1/2, p-ERK1/2and NF-KBp65in etoposide group and etoposide+EGb761group were as follows: the relative expression level of ERK1/2:0.734±0.126vs0.488±0.086, the relative expression level of p-ERK1/2:0.486±0.091vs0.298±0.053, the relative expression level of NF-KBp65:0.458±0.086vs0.256±0.042, P<0.05. Results of immunocytochemistry indicated that EGb761can suppress the expressions of p-ERK1/2and NF-KBp65induced by cisplatin or etoposide. The average optical density (AOD) of p-ERK1/2and NF-KBp65protein expressions in cisplatin group and cisplatin+EGb761group were as follows:cisplatin group and cisplatin+EGb761group, the AOD of p-ERK1/2protein expression:0.61±0.11vs0.32±0.05, the AOD of NF-KBp65protein expression:0.58±0.09vs0.35±0.06, The AOD of p-ERK1/2and NF-KBp65protein expressions in etoposide group and etoposide+EGb761group, the AOD of p-ERK1/2protein expression:0.68±0.13vs0.43±0.07, the AOD of NF-KBp65protein expression:0.72±0.13vs0.45±0.07, P<0.05.CONCLUSION: EGb761significantly enhances the cell inhibitory efficiency and the cell apoptosis level induced by cisplatin or etoposide and then improves the sensitivity of chemotherapy. EGb761enhancing cellular antioxidant capacity and suppressing the ERK and NF-κB signaling pathways may be it’s mechanism.