Expression level is a key determinant of E2F1-mediated cell fate
Expression level is a key determinant of E2F1-mediated cell fate
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DOI：
10.1038/cdd.2017.12
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发表时间：
2017-04-01
影响因子：
12.4
通讯作者：
You, Lingchong
中科院分区：
文献类型：
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作者：
Shats, Igor;Deng, Michael;You, Lingchong
Rb/E2 F网络在调节细胞周期进程和细胞命运决定中具有关键作用。它在几乎所有的人类癌症中都是功能失调的，因为遗传病变会导致激活因子的过度表达、抑制因子的失活或两者兼而有之。奇怪的是，该网络的下游靶点E2 F1很少在癌症中强烈过表达。E2 F1可以诱导细胞增殖和凋亡，但决定这些关键细胞命运的因素仍不清楚。以前的研究集中在定性机制，如差异辅因子，翻译后修饰或其他信号通路的状态作为修饰剂的细胞命运决定下游的E2 F1激活。相比之下，E2 F1本身的表达水平在决定下游表型的重要性尚未得到严格的研究，部分原因是传统的群体水平测量的分辨率有限。在这里，通过单细胞定量分析，我们证明了E2 F1表达水平在决定单个细胞的命运中具有关键作用。低水平的外源性E2 F1促进增殖，中等水平诱导G1，G2和有丝分裂细胞周期停滞，非常高的水平促进凋亡。这些多种抗增殖机制导致强大的选择压力，导致从群体中快速消除E2 F1过表达细胞。RNA测序和RT-PCR显示，低水平的E2 F1足以诱导许多细胞周期促进基因，中等水平的E2 F1诱导生长停滞基因（即，p18、p19和p27），而更高水平是诱导关键凋亡E2 F1靶点APAF 1、APAF A、HRK和BIM所必需的。最后，用蛋白酶体抑制剂MLN 2238处理肺癌细胞系导致E2 F1依赖性有丝分裂阻滞和细胞凋亡，证实了内源性E2 F1水平在这些表型中的作用。中度过表达的E2 F1在多种癌症类型中的强抗增殖活性表明，靶向E2 F1上调可能代表癌症中有吸引力的治疗策略。
The Rb/E2F network has a critical role in regulating cell cycle progression and cell fate decisions. It is dysfunctional in virtually all human cancers, because of genetic lesions that cause overexpression of activators, inactivation of repressors, or both. Paradoxically, the downstream target of this network, E2F1, is rarely strongly overexpressed in cancer. E2F1 can induce both proliferation and apoptosis but the factors governing these critical cell fate decisions remain unclear. Previous studies have focused on qualitative mechanisms such as differential cofactors, posttranslational modification or state of other signaling pathways as modifiers of the cell fate decisions downstream of E2F1 activation. In contrast, the importance of the expression levels of E2F1 itself in dictating the downstream phenotypes has not been rigorously studied, partly due to the limited resolution of traditional population-level measurements. Here, through single-cell quantitative analysis, we demonstrate that E2F1 expression levels have a critical role in determining the fate of individual cells. Low levels of exogenous E2F1 promote proliferation, moderate levels induce G1, G2 and mitotic cell cycle arrest, and very high levels promote apoptosis. These multiple anti-proliferative mechanisms result in a strong selection pressure leading to rapid elimination of E2F1-overexpressing cells from the population. RNA-sequencing and RT-PCR revealed that low levels of E2F1 are sufficient to induce numerous cell cycle-promoting genes, intermediate levels induce growth arrest genes (i.e., p18, p19 and p27), whereas higher levels are necessary to induce key apoptotic E2F1 targets APAF1, PUMA, HRK and BIM. Finally, treatment of a lung cancer cell line with a proteasome inhibitor, MLN2238, resulted in an E2F1-dependent mitotic arrest and apoptosis, confirming the role of endogenous E2F1 levels in these phenotypes. The strong anti-proliferative activity of moderately overexpressed E2F1 in multiple cancer types suggests that targeting E2F1 for upregulation may represent an attractive therapeutic strategy in cancer.