藤黄酸下调蛋白C受体表达杀伤三阴性乳腺癌干细胞的作用机制

Action mechanism by which gambogic acid down-regulates expression of protein C receptor to kill triple negative breast cancer stem cells

背景:藤黄酸对乳腺癌具有很强的细胞毒性,可有效杀伤三阴性乳腺癌干细胞,但潜在的机制尚不清楚。目的:探讨藤黄酸对三阴性乳腺癌干细胞的杀伤作用及可能的机制。方法:使用PharmMapper数据库预测藤黄酸的靶点蛋白,使用String网站构建各药物靶点蛋白互作网络关系,使用Cytoscape软件构建活性成分-作用靶点网络,通过R语言软件对潜在靶点进行KEGG信号通路富集分析。采用CCK-8法检测不同浓度藤黄酸对人乳腺癌细胞株MDA-MB-231活力的影响,筛选适宜的作用浓度。采用细胞球培养法富集MDA-MB-231细胞干细胞,经过不同浓度(0,0.5,1.0,2.0μmol/L)藤黄酸作用24 h,TUNEL荧光染色与流式细胞仪检测干细胞凋亡,qPCR与Western blot检测蛋白C受体表达,Western blot检测p-PI3K、p-AKT、Caspase-3和Cleaved Caspase-3蛋白表达;将干细胞分4组培养:空白对照组(干细胞不做任何处理)、siRNA-NC组、siRNA-蛋白C受体组和siRNA-蛋白C受体+PI3K激动剂组,培养36 h后,采用Western blot法检测p-PI3K、p-AKT、Caspase-3和Cleaved Caspase-3蛋白表达。结果与结论:(1)网络药理学发现,三阴性乳腺癌干细胞标志物蛋白C受体是藤黄酸的作用靶点之一;KEGG富集分析涉及细胞凋亡、上皮生长因子受体、RAS和PI3K-AKT信号通路等;(2)CCK-8检测结果显示,藤黄酸可抑制MDA-MB-231细胞活力,半数抑制浓度IC50值为(1.18±0.34)μmol/L,因此后续实验选择浓度0.5,1.0,2.0μmol/L;(3)TUNEL荧光染色和流式细胞术检测证实,藤黄酸以剂量依赖的方式诱导三阴性乳腺癌干细胞凋亡(P <0.05);qPCR和Western blot检测证实,藤黄酸可下调蛋白C受体mRNA和蛋白表达,下调Caspase-3、p-PI3K和p-AKT蛋白表达,上调Cleaved Caspase-3蛋白表达(P <0.05);siRNA-蛋白C受体转染实验也进一步证实,敲低三阴性乳腺癌干细胞蛋白C受体表达可提升Cleaved Caspase-3蛋白表达(P <0.05)、下调PI3K/AKT信号通路磷酸化水平(P <0.05),而应用PI3K激动剂740 Y-P能够降低Cleaved Caspase-3蛋白表达(P <0.05)、提升p-PI3K和p-AKT的磷酸化水平(P <0.05),一定程度上改善细胞凋亡情况;(4)结果表明,藤黄酸可能通过下调蛋白C受体来发挥三阴性乳腺癌及干细胞杀伤及诱导凋亡作用,进一步的分子机制可能和PI3K/AKT信号通路抑制有关。

BACKGROUND:Gambogic acid is highly cytotoxic to breast cancer and can effectively kill triple negative breast cancer stem cells,but the underlying mechanism is still unclear.OBJECTIVE:To investigate the lethal effect of gambogic acid on triple negative breast cancer stem cells as well as the possible mechanisms.METHODS:PharmMapper database was used to predict the target protein of gambogic acid.String website was used to construct the protein interaction network of various drug targets.Active ingredient-target network was constructed by Cytoscape software.KEGG signal pathway enrichment analysis was performed on potential targets by R language software.The effect of different concentrations of gambogic acid on the activity of human breast cancer cell line MDA-MB-231 was detected by CCK-8 assay.The appropriate concentration was screened.MDA-MB-231 stem cells were enriched by cell ball culture method and treated with gambogic acid at different concentrations(0,0.5,1.0,and 2.0μmol/L)for 24 hours.TUNEL fluorescence staining and flow cytometry were used to detect apoptosis of stem cells.qPCR and western blot assay were used to detect protein C receptor expression.The expression levels of p-PI3K,p-AKT,Caspase-3,and cleaved Caspase-3 were detected by western blot assay.Stem cells were cultured in four groups:Blank control group(stem cells were not treated),siRNA-NC group,siRNA-protein C receptor group,and siRNA-protein C receptor+PI3K agonist group.After culture for 36 hours,the expression levels of p-PI3K,p-AKT,Caspase-3,and cleaved Caspase-3 were detected by western blot assay.RESULTS AND CONCLUSION:(1)Network pharmacology exhibited that the protein C receptor,a marker of triple negative breast cancer stem cells,was one of the targets of gambogic acid.KEGG enrichment analysis involved apoptosis,epithelial growth factor receptor,RAS,and PI3K-AKT signaling pathways.(2)CCK-8 assay results showed that gambogic acid could inhibit the viability of MDA-MB-231 cells,and the median inhibitory concentration IC50 value was(1.18±0.34)μmol/L,so the concentrations of 0.5,1.0,and 2.0μmol/L were selected for subsequent experiments.(3)TUNEL fluorescence staining and flow cytometry showed that gambogic acid induced apoptosis of triple negative breast cancer stem cells in a dose-dependent manner(P<0.05).qPCR and western blot assay confirmed that gambogic acid down-regulated mRNA and protein expression of protein C receptor,down-regulated Caspase-3,p-PI3K,and p-Akt protein expression,and up-regulated cleaved Caspase-3 protein expression(P<0.05).siRNA-protein C receptor transfection experiments further confirmed that knockdown of protein C receptor expression in triple negative breast cancer stem cells increased cleaved Caspase-3 protein expression(P<0.05),and down-regulated phosphorylation of PI3K/AKT signaling pathway(P<0.05).Application of PI3K agonist 740 Y-P decreased cleaved Caspase-3 protein expression(P<0.05),increased phosphorylation levels of p-PI3K and p-AKT(P<0.05),and improved apoptosis to a certain extent.(4)The results show that gambogic acid may play a role in killing and inducing apoptosis of triple negative breast cancer stem cells by down-regulating protein C receptor,and the further molecular mechanism may be related to the inhibition of PI3K/AKT signaling pathway.