Translational Research Laboratory, Catalan Institute of Oncology, Girona, Catalonia, Spain.
Cell Cycle. 2012 Mar 15;11(6):1235-46. doi: 10.4161/cc.11.6.19665.
We have tested the hypothesis that the antidiabetic biguanide metformin can be used to manipulate the threshold for stress-induced senescence (SIS), thus accelerating the onset of cancer-protective cellular senescence in response to oncogenic stimuli. Using senescence-prone murine embryonic fibroblasts (MEFs), we assessed whether metformin treatment modified the senescence phenotype that is activated in response to DNA damaging inducers. Metformin significantly enhanced the number of MEFs entering a senescent stage in response to doxorubicin, an anthracycline that induces cell senescence by activating DNA damage signaling pathways (e.g., ATM/ATR) in a reactive oxygen species (ROS)-dependent manner. Using WI-38 and BJ-1 human diploid fibroblasts (HDFs), we explored whether metformin supplementation throughout their entire replicative lifespan may promote the early appearance of the biomarkers of replicative senescence. Chronic metformin significantly reduced HDFs' lifespan by accelerating both the loss of replicative potential and the acquisition of replicative senescence-related biomarkers (e.g., enlarged and flattened cell shapes, loss of arrayed arrangement, accumulation of intracellular and extracellular debris and SA-β-gal-positive staining). Metformin functioned as a bona fide stressful agent, inducing monotonic, dose-dependent, SIS-like responses in BJ-1 HDFs, which are highly resistant to ROS-induced premature senescence. Metformin-induced SIS in BJ-1 fibroblasts was accompanied by the striking activation of several microRNAs belonging to the miR-200s family (miR-200a, miR-141 and miR429) and miR-205, thus mimicking a recently described ability of ROS to chemosensitize cancer cells by specifically upregulating anti-EMT (epithelial-to-mesenchymal transition) miR-200s. Because the unlimited proliferative potential of stem cells results from their metabolic refractoriness to SIS, we finally tested if metformin treatment could circumvent the stress (e.g., ROS)-resistant phenotype of induced pluripotent stem cells (iPSCs). Metformin treatment drastically reduced both the number and the size of iPSC colonies and notably diminished the staining of the pluripotency marker alkaline phosphatase. Our current findings, altogether, reveal for the first time that metformin can efficiently lower the threshold for SIS to generate an "stressed" cell phenotype that becomes pre-sensitized to oncogenic-like stimuli, including DNA damaging, proliferative and/or stemness inducers.
我们已经验证了这样一个假设，即抗糖尿病药物二甲双胍可以用于控制应激诱导衰老（SIS）的阈值，从而加速对致癌刺激的保护性细胞衰老的发生。使用易发生衰老的鼠胚胎成纤维细胞（MEF），我们评估了二甲双胍治疗是否改变了对 DNA 损伤诱导剂反应时激活的衰老表型。二甲双胍显著增加了对多柔比星（一种通过 ROS 依赖性方式激活 DNA 损伤信号通路（例如 ATM/ATR）诱导细胞衰老的蒽环类药物）反应进入衰老阶段的 MEF 的数量。使用 WI-38 和 BJ-1 人二倍体成纤维细胞（HDF），我们探索了在整个复制寿命中补充二甲双胍是否可以促进复制衰老生物标志物的早期出现。慢性二甲双胍通过加速复制潜力的丧失和获得与复制衰老相关的生物标志物（例如，细胞形状增大和平坦化、排列排列丧失、细胞内和细胞外碎片的积累以及 SA-β-半乳糖阳性染色），显著缩短了 HDF 的寿命。二甲双胍作为一种真正的应激剂，在对 ROS 诱导的过早衰老具有高度抗性的 BJ-1 HDF 中诱导单调的、剂量依赖性的 SIS 样反应。在 BJ-1 成纤维细胞中，二甲双胍诱导的 SIS 伴随着几种属于 miR-200 家族（miR-200a、miR-141 和 miR429）和 miR-205 的 microRNA 的显著激活，从而模拟了最近描述的 ROS 通过特异性上调抗 EMT（上皮-间质转化）miR-200s 使癌细胞对化疗敏感的能力。由于干细胞的无限增殖潜力源于它们对 SIS 的代谢抗性，因此我们最后测试了二甲双胍治疗是否可以避免诱导多能干细胞（iPSC）的应激（例如，ROS）抗性表型。二甲双胍处理大大减少了 iPSC 集落的数量和大小，并显著降低了多能性标志物碱性磷酸酶的染色。我们目前的发现首次揭示，二甲双胍可以有效地降低 SIS 的阈值，产生一种“应激”细胞表型，使细胞对致癌样刺激（包括 DNA 损伤、增殖和/或干性诱导剂）预先敏感。
