Defining the Mechanistic Determinants of Response to Selective Electron Transport Chain Inhibition in Cancer

摘要：细胞利用两种主要的能量代谢方式：糖酵解和氧化磷酸化。 (OXPHOS)。针对癌症新陈代谢的努力主要集中在糖酵解上，因为观察到 癌细胞优先利用这种模式，称为华宝效应。然而，人们对以下方面重新产生了兴趣 通过其效应器电子传输链(ETC)靶向OXPHOS，主要是因为这一发现 被广泛使用的抗糖尿病药物二甲双胍降低了糖尿病患者的癌症发病率，并导致死亡 通过抑制ETC的复合体I在体内外对癌细胞产生抑制作用。 ETC由五个络合物组成，这些络合物在一系列氧化还原过程中依次转移电子 产生三磷酸腺苷的反应。由于在癌症中靶向ETC的努力相对较新， 基础知识，例如对ETC的依赖情况，更具体地说，是特定的ETC 跨越癌症的复合体仍是未知的。为了研究这些问题，我们的实验室定义了 依赖于一大批不同的癌细胞系中每个ETC复合体的抑制。有趣的是，细胞 不同品系对单个ETC复合体的抑制反应不同，而复合体I的抑制产生同质性 细胞死亡和复合II-V抑制导致异质性细胞死亡。我们天真地预料到了ETC情结 由于ETC的线性关系，相关性将相互关联；其他初步数据显示 在ETC抑制情况下，ATP水平保持不变。总而言之，这些结果表明ETC 复合体可能在维持细胞活性方面发挥重要作用，而不是依赖于它们在 氧磷酸盐。为此，我们进行了CRISPR/Cas9筛查和代谢组学分析，以确定非 规范的新陈代谢机制，调节等复杂的依赖。我们鉴定了各种生物合成的 调节和受个体ETC复合体抑制作用的代谢途径。 特别有趣的是，我们发现了一种新的合成致死组合，在化合物III的抑制作用之间 以及甲氧戊酸途径的缺失，该途径具有很好的翻译潜力。甲氧戊酸途径 合成各种异戊二烯类化合物，如胆固醇和泛醌，并与肿瘤的发生有关 此外，这一途径还被临床上常用的他汀类药物抑制，以降低 胆固醇水平。由于甲氧戊酸途径对复合体III的调节机制尚未见报道 然而，由于基本的和翻译的原因，这是一个值得研究的有趣的关系。 在这项提议中，我们将研究泛醌合成调节这一关系的假设。 甲氧丙戊酸途径和复合体III之间的关系。我们还将确定复合体III的抑制效果 在免疫活性和免疫缺陷的小鼠癌症模型中使用他汀类药物都可以增强这种作用。

Abstract: Cells utilize two major modes of energy metabolism: glycolysis and oxidative phosphorylation (OXPHOS). Efforts to target metabolism in cancer have mainly focused on glycolysis due to the observation that cancer cells preferentially utilize this mode, termed the Warburg effect. However, there is renewed interest in targeting OXPHOS through its effector, the electron transport chain (ETC), primarily because of the discovery that the widely used anti-diabetic drug, metformin, lowers risk of cancer incidence in diabetes patients and kills cancer cells in vitro and in vivo through inhibiting complex I of the ETC. The ETC is composed of five complexes that work to sequentially transfer electrons in a series of redox reactions that result in the generation of ATP. As the efforts to target the ETC in cancer are relatively recent, fundamental knowledge such as the landscape of dependence on the ETC and more specifically, particular ETC complexes, across cancers remains unknown. To investigate these questions, our lab has defined the dependence on inhibition of each ETC complex across a large panel of diverse cancer cell lines. Intriguingly, cell lines respond variably to inhibition of individual ETC complexes, with complex I inhibition yielding homogeneous cell death and complex II-V inhibition causing heterogeneous cell death. We naively expected that ETC complex dependencies would correlate with each other due to the linearity of the ETC; additional preliminary data show that ATP levels remain unchanged with ETC inhibition. Taken together, these results suggest that ETC complexes may play important roles in maintaining cell viability independently of their canonical roles in OXPHOS. To that end, we performed CRISPR/Cas9 screens and metabolomics analyses to determine the non- canonical metabolic mechanisms modulating ETC complex dependences. We identified various biosynthetic metabolic pathways that modulate, and are modulated by, individual ETC complex inhibition. Of particular interest, we identified a novel synthetic lethal combination between complex III inhibition and loss of the mevalonate pathway that has promising translational potential. The mevalonate pathway synthesizes various isoprenoids, such as cholesterol and ubiquinone, and has been implicated in tumor initiation and progression; additionally, this pathway is inhibited by statin drugs, commonly used in the clinic to lower cholesterol levels. As mechanisms describing the regulation of complex III by the mevalonate pathway have not yet been elucidated, this is an interesting relationship to investigate for both basic and translational reasons. In this proposal, we will investigate the hypothesis that ubiquinone synthesis regulates the relationship between the mevalonate pathway and complex III. We will also determine if the efficacy of complex III inhibition can be enhanced by using statins in both immune-competent and immune-deficient mouse models of cancer.