Investigating how cancer cells maintain redox homeostasis to support biomass production

项目摘要 为了增殖，细胞必须合成足够的生物量，包括核苷酸、蛋白质和脂类。这 对于快速增殖的癌细胞来说尤其重要，癌细胞重新编程以满足增加的 生物合成的增殖需求。然而，对生物合成的需求因癌症类型和 生理环境。癌细胞如何改变新陈代谢以响应特定的生物合成需求 没有很好地表征，并且更好地理解这些变化将揭示可能是 靶向抑制肿瘤生长。 为了合成生物质，细胞需要电子受体来氧化葡萄糖和谷氨酰胺等营养物质。 转化为生物质前体，如用于蛋白质合成的氨基酸和用于合成脂肪酸的柠檬酸盐。一 必需的电子受体是氧化还原辅因子NAD。氧化态NAD与还原型NADH之比 (NAD/NADH)影响细胞氧化还原状态，并反映NAD对氧化生物合成的可用性 反应。因此，必须保持充分氧化的NAD/NADH的比率，以便能够合成氧化的 生物量和可以限制癌细胞的增殖。我们发现，对氨基酸丝氨酸的需求增加 而脂质前体柠檬酸盐提高了NAD的需求，但令人惊讶的是，癌细胞保持着类似的 NAD/NADH比率，表明细胞维持NAD/NADH动态平衡，尽管对 氧化生物质合成。这项拟议中的研究的目标是确定癌细胞如何维持 NAD/NADH动态平衡以支持增加的氧化生物合成需求和肿瘤生长。我假设 癌细胞通过调节NAD的再生、消耗和合成来维持NAD/NADH的比率 以支持生物质生产。为了验证这一假设，我将使用癌细胞系和小鼠模型来验证 研究在脂质耗竭条件下，癌细胞和肿瘤如何维持NAD/NADH动态平衡。 增加细胞对柠檬酸生产的NAD需求的营养环境，是一种生理状态 面对体内的癌细胞。在目标1中，我将研究癌细胞是否增加了三种机制 NAD再生以维持脂质合成和肿瘤生长的氧化还原动态平衡：发酵， 线粒体呼吸，以及线粒体呼吸与ATP合成的解偶联。在《目标2》中，我会 调查通过选择NAD消耗氧化还原反应而减少的通量是否提高了NAD的可用性 用于脂肪合成。在目标3中，我将研究从烟酰胺中合成NAD残留物是否有助于维持 充分氧化NAD/NADH比率，促进脂质合成和肿瘤生长。这项研究的结果 将有助于更好地理解癌细胞如何适应不同的营养和组织环境 洞察到癌细胞必须参与以维持氧化还原稳态的基本过程 扩散。这将改进针对癌症新陈代谢的治疗方法，并导致 开发更有效和更有选择性的癌症治疗方法。

Project Summary To proliferate, cells must synthesize sufficient biomass, including nucleotides, proteins, and lipids. This is particularly important for rapidly proliferating cancer cells, which reprogram metabolism to meet the increased biosynthetic demands of proliferation. However, biosynthetic demands differ across cancer types and physiological environments. How cancer cells alter metabolism in response to specific biosynthetic demands is not well characterized, and better understanding these alterations will reveal metabolic liabilities that can be targeted to inhibit tumor growth. To synthesize biomass, cells require electron acceptors to oxidize nutrients like glucose and glutamine into biomass precursors, such as amino acids for protein synthesis and citrate for fatty acid synthesis. One essential electron acceptor is the redox cofactor NAD+. The ratio of oxidized NAD+ to reduced NADH (NAD+/NADH) influences the cellular redox state and reflects NAD+ availability for oxidative biosynthetic reactions. Thus, a sufficiently oxidized NAD+/NADH ratio must be maintained to enable synthesis of oxidized biomass and can limit cancer cell proliferation. We have found that increased demands for the amino acid serine and the lipid precursor citrate elevate the NAD+ demand, yet cancer cells surprisingly maintain a similar NAD+/NADH ratio, indicating that cells preserve NAD+/NADH homeostasis despite increased demands for oxidized biomass synthesis. The goal of the proposed research is to determine how cancer cells maintain NAD+/NADH homeostasis to support increased oxidative biosynthetic demands and tumor growth. I hypothesize that cancer cells maintain the NAD+/NADH ratio by modulating NAD+ regeneration, consumption, and synthesis to support biomass production. To test this hypothesis, I will use both cancer cell lines and mouse models to investigate how cancer cells and tumors maintain NAD+/NADH homeostasis in lipid-depleted conditions, a nutrient environment that increases cellular NAD+ demand for citrate production and is a physiological condition faced by cancer cells in the body. In Aim 1, I will investigate whether cancer cells increase three mechanisms of NAD+ regeneration to maintain redox homeostasis for lipid synthesis and tumor growth: fermentation, mitochondrial respiration, and uncoupling mitochondrial respiration from ATP synthesis. In Aim 2, I will investigate whether decreased flux through select NAD+ consuming redox reactions increases NAD+ availability for lipid synthesis. In Aim 3, I will investigate if NAD+ salvage synthesis from nicotinamide helps maintain a sufficiently oxidized NAD+/NADH ratio for increased lipid synthesis and tumor growth. The results of this study will lead to a better understanding of how cancer cells adapt to different nutrient and tissue environments and provide insight into a fundamental process in which cancer cells must engage to maintain redox homeostasis for proliferation. This will improve therapeutic approaches that target cancer metabolism and lead to the development of more effective and selective cancer treatments.