Metabolic liabilities of cancer cells to the tumor nutrient environment

 描述(由申请人提供)：最近有证据表明，癌细胞重新连接它们的新陈代谢以满足它们的增殖和生存需求。新陈代谢的变化在一定程度上是由肿瘤营养环境决定的，因为由于营养消耗增加和血管功能障碍，癌细胞经常缺乏营养，并暴露在有毒废物中。虽然大多数代谢途径的成分早已被描述，但对代谢产物如何在肿瘤的营养环境中重新连接仍知之甚少。我最近开发了两项技术，以便能够在类似肿瘤的营养环境中研究癌细胞：用于维持降低但稳定的营养浓度的连续流动细胞培养系统(Nutrostat)和用于同时测量在Nutrostat中培养的汇集癌细胞的生长的DNA条形码细胞竞争分析。专注于低糖，这些技术使我们能够系统地研究癌症代谢的依赖性，并发现大多数癌细胞在低糖条件下可逆地切换到更氧化的代谢。然而，一组具有异质功能缺失mtDNA突变的癌细胞在低糖条件下无法增加它们的氧气消耗。这种无法诱导氧化代谢的能力阻碍了细胞在缺乏葡萄糖的肿瘤环境中的生长，并表明存在更强的阳性选择来维持这种mtDNA突变。支持这一观点的是，mtDNA编码的OXPHOS成分截断突变的流行率据报道高达65%。然而，目前尚不清楚为什么有如此高比例的癌细胞积累mtDNA突变，以及这些突变如何被用作设计治疗方案的依据。在这项建议中，基于我之前的观察，我的目标是检验这一假设，即异质线粒体DNA突变在肿瘤发生中是否具有功能关键作用(AIM1)，并赋予可用于治疗的代谢倾向(AIM2)。此外，癌细胞对低糖的代谢脆弱性的存在要求对其他营养依赖进行更全面的检查。因此，作为这些目标的延伸，我将使用我们的DNA条形码细胞竞争分析(Aim3)绘制癌症营养依赖关系图。

 DESCRIPTION (provided by applicant): It has recently become evident that cancer cells rewire their metabolism to meet their demands of proliferation and survival. Metabolic changes are dictated in part by the tumor nutrient environment as cancer cells are frequently starved for nutrients and exposed to toxic waste products due to a combination of increased nutrient consumption and dysfunctional vasculature. While the components of most metabolic pathways have long been described, it remains poorly understood how the flow of metabolites is rewired in the nutrient environment of tumors. I have recently developed two technologies to enable study of cancer cells in a tumor-like nutrient environment: a continuous flow cell culture system for maintaining reduced but steady nutrient concentrations (nutrostat) and a DNA-barcoded cell competition assay for simultaneously measuring the growth of pooled cancer cell lines cultured in the nutrostats. Focused on low glucose, these technologies enabled us to systematically investigate the cancer metabolic dependencies and discovered that most cancer cells reversibly switch to a more oxidative metabolism under low glucose conditions. However, a subset of cancers cells with heteroplasmic loss-of-function mtDNA mutations are unable to increase their oxygen consumption in low glucose conditions. This inability to induce oxidative metabolism hampers cell growth in the glucose-poor tumor environment and suggests the existence of a stronger positive selection for persistence of such mtDNA mutations. Supporting this notion, the prevalence of truncating mutations in mtDNA-encoded OXPHOS components is reported to be as high as 65%. It is, however, unclear why such a high percentage of cancer cells accumulate mtDNA mutations and how these mutations can be exploited as a liability for designing therapies. In this proposal, building on my previous observations, I aim to test the hypothesis whether heteroplasmic mtDNA mutations have functionally critical roles in tumorigenesis (Aim1) and confer metabolic liabilities that can be exploited for therapy (Aim2). Additionally, existence of metabolic vulnerabilities of cancer cells to low glucose calls for a more comprehensive examination of other nutrient dependencies. Therefore, as an extension to these aims, I will map the cancer nutrient dependencies using our DNA-barcoded cell competition assay (Aim3).