The mechanism of extract of ginkgo biloba inducing mitochondrial autophagy in breast cancer cells MCF-7 / 国际肿瘤学杂志

ABSTRACT

Objective:To investigate the mechanism of extract of ginkgo biloba (EGB) on mitochondrial autophagy in breast cancer cells MCF-7.Methods:Breast cancer MCF-7 cells were divided into four groups. EGB with mass concentrations of 40, 80, 120 mg/L was used to incubate breast cancer MCF-7 cells for 24 h or 48 h, as a low concentration group of EGB, a medium concentration group of EGB, and a high concentration group of EGB. Breast cancer MCF-7 cells without intervention were taken as control group. Cell proliferation was measured using MTT assay; Flow cytometry was used to detect cell apoptosis; Immunofluorescence assay was used to determine the contents of prostacyclin (P62), microtubule-associated protein light chain 3Ⅱ (LC3Ⅱ), and caspase-3; The levels of multidrug resistance-associated protein 1 (MRP1), multidrug resistance gene 1 (MDR1) and breast cancer resistance protein (BCRP) were identified by PCR; Western blotting was used to detect the expression of extracellular signal-regulated kinase (ERK), mitogen-activated protein kinase (MAPK), p-ERK, and p-MAPK proteins in cells.Results:The results of MTT assay for cell proliferation showed that cell proliferation at 24 h in control group, EGB low, medium and high concentration groups were 0.95±0.14, 0.65±0.09, 0.51±0.07, 0.37±0.04, respectively, with a statistically significant difference ( F=43.13, P<0.001), cell proliferation at 48 h were 1.32±0.19, 0.54±0.08, 0.32±0.05, 0.15±0.02, respectively, with a statistically significant difference ( F=141.30, P<0.001). Compared with 24 h, cell proliferation was decreased in EGB low, medium and high concentration groups at 48 h (all P<0.05). Pairwise comparison showed that EGB treatment significantly decreased MCF-7 cell viability and cell proliferation was decreased in turn at 24 and 48 h in control group, low, medium, high EGB groups (all P<0.05). Flow cytometry analysis revealed that the apoptosis rates of MCF-7 cells in control group, EGB low, medium and high concentration groups were 2.12%±0.23%, 9.28%±0.45%, 15.17%±1.28% and 22.21%±2.32%, respectively, with a statistically significant difference ( F=128.80, P<0.001). Pairwise comparison showed that the apoptosis rate of control group, EGB low, medium and high concentration groups were increased in turn (all P<0.05). The results of immunofluorescence assay showed that the protein relative expression levels of P62 protein in MCF-7 cells of control group, EGB low, medium and high concentration groups were 3.34±0.52, 2.85±0.47, 2.02±0.18 and 1.08±0.21, respectively, with a statistically significant difference ( F=41.55, P<0.001). LC3Ⅱ protein relative expression levels were 0.24±0.05, 1.02±0.14, 1.47±0.26, 1.95±0.21, respectively, with a statistically significant difference ( F=94.82, P<0.001). The relative expression levels of caspase-3 protein were 0.25±0.03, 0.68±0.21, 1.12±0.17 and 1.65±0.23, respectively, with a statistically significant difference ( F=68.09, P<0.001). Pairwise comparison showed that LC3Ⅱ and caspase-3 protein expression levels were increased in turn in control group, EGB low, medium and high concentration groups, while P62 protein expression levels were decreased in turn (all P<0.05). The PCR experiment results showed that the MRP1 mRNA level of MCF-7 cells in control group, EGB low, medium and high concentration groups were 1.06±0.14, 0.83±0.18, 0.71±0.11, 0.52±0.08, respectively, with a statistically significant difference ( F=17.41, P<0.001). The mRNA levels of MDR1 were 1.14±0.17, 0.75±0.13, 0.60±0.09, 0.48±0.06, respectively, with a statistically significant difference ( F=34.40, P<0.001). BCRP mRNA levels were 1.09±0.11, 0.88±0.13, 0.69±0.07, 0.57±0.05, respectively, with a statistically significant difference ( F=34.13, P<0.001). Pairwise comparison showed that the levels of MRP1, MDR1 and BCRP mRNA were decreased in turn in control group, EGB low, medium and high concentration groups (all P<0.05). The results of Western blotting showed that the expression of ERK in MCF-7 cells in control group, EGB low, medium and high concentration groups were 2.54±0.38, 1.89±0.25, 1.55±0.21, 1.12±0.16, respectively, with a statistically significant difference ( F=31.18, P<0.001). MAPK expression were 2.47±0.34, 1.96±0.29, 1.63±0.27, 1.20±0.24, respectively, with a statistically significant difference ( F=20.90, P<0.001). p-ERK expression were 2.03±0.29, 1.74±0.21, 1.45±0.11, 1.18±0.24, respectively, with a statistically significant difference ( F=16.31, P<0.001). p-MAPK expression were 2.26±0.47, 1.90±0.41, 1.61±0.33, 1.35±0.16, respectively, with a statistically significant difference ( F=7.01, P=0.002). Pairwise comparison showed that the expressions of ERK, MAPK, p-ERK and p-MAPK in control group, EGB low, medium and high concentration groups were decreased in turn (all P<0.05) . Conclusion:EGB can inhibit the proliferation of breast cancer MCF-7 cells, promote the apoptosis of MCF-7 cells, decrease the expression of P62 protein, increase the expression of LC3Ⅱ and caspase-3 protein, induce mitochondrial autophagy.