低氧环境对三阴性乳腺癌细胞糖代谢途径的重编程

代谢改变是癌细胞的特征之一。研究表明,低氧会使癌细胞的糖代谢发生改变,但是更详细的分子机制仍有待进一步研究。本研究利用转录物组测序技术(RNA-sequencing,RNA-seq)和生物信息学分析发现,低氧导致BT549细胞中334个基因和MDA-MB-231细胞中215个基因在转录水平的表达改变。这些表达变化的基因多与糖代谢相关。进一步分析RNA-seq数据并应用Western 印迹、酶活性检测和代谢产物定量测定的结果显示,低氧通过升高BT549细胞中葡萄糖转运蛋白1(GLUT1)和MDA-MB-231细胞中GLUT1和GLUT3的表达以增加葡萄糖的摄入;低氧使催化糖的无氧氧化途径几乎全部反应的酶都至少有一种同工酶或酶蛋白亚基,以及调节酶6-磷酸果糖-2-激酶/果糖-2,6-二磷酸酶3(PFKFB3)和4(PFKFB4)同工酶的表达增加来促进了糖的无氧氧化;低氧还通过增加调节丙酮酸脱氢酶激酶1(PDK1)和3(PDK3)同工酶基因的表达,以及降低关键酶异柠檬酸脱氢酶3(IDH3)同工酶、琥珀酸脱氢酶B亚基和D亚基的表达来减少糖的有氧氧化途径进行;低氧可能还增加磷酸戊糖途径的关键酶葡糖-6-磷酸脱氢酶、糖原合成途径的关键酶糖原合酶GYS1同工酶的表达以促进这2条途径的进行,而对糖异生和糖原分解代谢途径酶基因的表达影响较小。生物信息学分析乳腺癌组织样本在线数据库中糖代谢途径酶基因在转录水平表达结果与细胞研究结果基本一致。总之,该文系统分析了低氧对糖代谢6条代谢途径中全部酶以及2种重要调节酶的影响,可见低氧会通过改变这些酶的同工酶或亚基的基因表达使糖代谢途径进行重编程,这对进一步认识低氧环境下癌细胞糖代谢的分子机制具有一定的意义。

Reprogramming of Glucose Metabolism Pathways in Triple-negative Breast Cancer Cells under Hypoxia

Metabolic changes are recognized as one of the hallmarks of cancer cells. Previous studies have shown that hypoxia can change the glucose metabolism of cancer cells. However, the mechanisms still need to be studied in detail. In this study, by using RNA-Sequencing (RNA-seq) and bioinformatics analysis, we found that there is a significant change in the expression of 334 genes in BT549 cells and 215 genes in MDA-MB-231 cells induced by hypoxia at the mRNA level. Most of these genes were associated with glucose metabolism. RNA-seq data, Western blot, enzyme activity assays, and metabolite quantification experiments showed that the glucose uptake increased by elevating the expression of glucose transporter protein 1 (GLUT1) in BT549 cells and GLUT1 and GLUT3 in MDA-MB-231 cells induced by hypoxia. Hypoxia promotes glycolysis by increasing the expression of at least one isozyme or enzyme protein subunit of the enzymes that catalyze the each reaction in the glycolysis pathway, as well as the regulatory enzymes 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3(PFKFB3) and 4(PFKFB4) isozymes. Hypoxia increases the expression of pyruvate dehydrogenase kinase 1 (PDK1) and PDK3 andreduces the expression of isocitrate dehydrogenase 3(IDH3), succinate dehydrogenase subunitB(SDHB) and D(SDHD) to reduce the aerobic oxidation pathway. The expression of glucose-6-phosphate dehydrogenase (G6PD) and glycogen synthase was significantly increased to promote the pentose phosphate pathway and glycogen synthesis pathway. The mRNA levels of enzyme genes had no significant difference in gluconeogenesis and glycogenolysis. The breast cancer database suggests that the mRNA levels of the glucose metabolism enzymes were consistent in vivo and in vitro. Hypoxia regulates the reprogramming of glucose metabolism by altering the gene expression of isozymes or subunits of these enzymes. The study comprehensively analyzed the effects of hypoxia on the expression of all enzyme genes and major regulatory enzymes in six glucose metabolism pathways and provides an understanding of glucose metabolism in cancer cells under a hypoxia environment.