Constitutively active Stat3 in mouse embryonic fibroblasts (MEFs)

Signal Transducer and Activator of Transcription 3 (STAT3) is considered as an oncogene being constitutively activated in a wide variety of primary human tumours, which often become addicted to its activity. Using primary fibroblasts derived from a knock-in mouse expressing only the constitutively active form STAT3-C as well as STAT3-dependent tumor cell lines MDA-MB468, DU145 and SKBR3, we provide evidence that STAT3 can act as a central regulator of cell metabolism. STAT3C/C MEFs are resistant to apoptosis and senescence and they show reduced mitochondrial activity but activate aerobic glycolysis, as shown by enhanced expression of master regulators of glycolysis such as PDK-1 and HIF-1α, and by increased lactate production, glucose avidity and sensitivity to glycolysis inhibitors. HIF-1α is up-regulated in the STAT3C/C MEFs and is responsible for the glycolytic phenotype. Moreover, inhibition of STAT3 activity in STAT3-addicted tumour cell lines restores mitochondrial activity and down-regulates glycolytic metabolism, preceding the induction of massive apoptosis. Thus, the essential role observed for STAT3 in so many different cancer cell types may be partly explained by its ability to act as a molecular switch of cellular metabolism triggering abnormal cell survival/proliferation. Three biological replicates of MEFs from mice with constitutively active Stat3 are compared to three biological replicates of wild-type MEFs.

信号转导与转录激活因子3（Signal Transducer and Activator of Transcription 3，STAT3）被视为一类癌基因，在多种人类原发性肿瘤中呈组成性激活状态，且此类肿瘤通常对其活性产生依赖。本研究采用仅表达组成性激活型STAT3-C的敲入小鼠来源的原代成纤维细胞，以及依赖STAT3的肿瘤细胞系MDA-MB468、DU145与SKBR3，证实STAT3可作为细胞代谢的核心调控因子。STAT3C/C 小鼠胚胎成纤维细胞（MEFs）对细胞凋亡与细胞衰老具有抵抗性，其线粒体活性降低，但可激活有氧糖酵解：具体体现为糖酵解关键调控因子PDK-1与缺氧诱导因子1α（Hypoxia-inducible factor 1 alpha，HIF-1α）的表达上调，同时乳酸生成增加、葡萄糖摄取亲和力增强，且对糖酵解抑制剂的敏感性升高。HIF-1α在STAT3C/C MEFs中呈上调状态，是其糖酵解表型的关键驱动因素。此外，在依赖STAT3的肿瘤细胞系中抑制STAT3活性，可恢复线粒体活性并下调糖酵解代谢，该效应先于大量细胞凋亡的诱导发生。综上，在诸多不同癌症细胞类型中观察到的STAT3必需功能，可部分通过其作为细胞代谢分子开关、触发异常细胞存活与增殖的能力得到解释。本研究将3批来自组成性激活Stat3小鼠的MEFs生物学重复样本，与3批野生型MEFs生物学重复样本进行对照比较。