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、蛋白质和脂质。这 对于快速增殖的癌细胞尤其重要，癌细胞重新编程代谢以满足增加的 增殖的生物合成需求。然而，生物合成的需求在不同的癌症类型和 生理环境。癌细胞如何改变代谢以响应特定的生物合成需求， 尚未得到很好的表征，更好地了解这些变化将揭示可能存在的代谢负债 靶向抑制肿瘤生长。 为了合成生物量，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，例如用于蛋白质合成的氨基酸和用于脂肪酸合成的柠檬酸盐。一 必需的电子受体是氧化还原辅因子NAD+。氧化的NAD+与还原的NADH的比率 (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，必须维持充分氧化的NAD+/NADH比率以使得能够合成氧化的NAD+/NADH。 生物量并且可以限制癌细胞增殖。我们发现，对氨基酸丝氨酸的需求增加， 和脂质前体柠檬酸盐升高NAD+需求，但癌细胞令人惊讶地保持类似的 NAD+/NADH比率，表明细胞保持NAD+/NADH稳态，尽管对NAD+/NADH的需求增加。 氧化生物质合成这项研究的目的是确定癌细胞是如何维持 NAD+/NADH稳态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的比例。 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， 研究癌细胞和肿瘤如何在脂质耗尽的条件下维持NAD+/NADH稳态， 营养环境，增加细胞NAD+对柠檬酸盐生产的需求，是一种生理条件 癌细胞所面临的问题。在目标1中，我将研究癌细胞是否会增加三种机制， NAD+再生以维持脂质合成和肿瘤生长的氧化还原稳态：发酵， 线粒体呼吸，以及从ATP合成中解偶联线粒体呼吸。在目标2中，我将 研究通过选择NAD+消耗氧化还原反应减少的通量是否增加NAD+可用性 用于脂质合成。在目标3中，我将研究烟酰胺的NAD+补救合成是否有助于维持 充分氧化的NAD+/NADH比率，以增加脂质合成和肿瘤生长。本研究结果 将有助于更好地了解癌细胞如何适应不同的营养和组织环境， 提供了一个基本的过程，其中癌细胞必须从事维持氧化还原稳态， 增殖这将改善靶向癌症代谢的治疗方法， 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.