Centre for Cancer Cell Reprogramming, Faculty of Medicine, Institute of Clinical Medicine, University of Oslo, Montebello, N-0379, Oslo, Norway.
Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, N-0379, Oslo, Norway.
BMC Biol. 2021 May 10;19(1):85. doi: 10.1186/s12915-021-01012-5.
Radioactive or stable isotopic labeling of metabolites is a strategy that is routinely used to map the cellular fate of a selected labeled metabolite after it is added to cell culture or to the circulation of an animal. However, a labeled metabolite can be enzymatically changed in cellular metabolism, complicating the use of this experimental strategy to understand how a labeled metabolite moves between organs. These methods are also technically demanding, expensive and potentially toxic. To allow quantification of the bulk movement of metabolites between organs, we have developed a novel application of stable isotope ratio mass spectrometry (IRMS).
We exploit natural differences in C/C ratios of plant nutrients for a low-cost and non-toxic carbon labeling, allowing a measurement of bulk carbon transfer between organs in vivo. IRMS measurements were found to be sufficiently sensitive to measure organs from individual Drosophila melanogaster larvae, giving robust measurements down to 2.5 μg per sample. We apply the method to determine if carbon incorporated into a growing solid tumor is ultimately derived from food or host tissues.
Measuring tumor growth in a D. melanogaster larvae tumor model reveals that these tumors derive a majority of carbon from host sources. We believe the low cost and non-toxic nature of this methodology gives it broad applicability to study carbon flows between organs also in other animals and for a range of other biological questions.
代谢物的放射性或稳定同位素标记是一种策略，通常用于在选定的标记代谢物添加到细胞培养物或动物循环后，追踪其在细胞中的命运。然而，标记的代谢物在细胞代谢中可能会发生酶促变化，这使得这种实验策略难以用于理解标记代谢物如何在器官之间移动。这些方法在技术上也具有挑战性、昂贵且潜在有毒。为了能够定量研究代谢物在器官之间的整体移动，我们开发了一种稳定同位素比质谱（IRMS）的新应用。
我们利用植物营养物中 C/C 比的天然差异进行低成本、无毒的碳标记，从而可以测量体内器官之间的碳整体转移。IRMS 测量结果足够灵敏，可以测量单个黑腹果蝇幼虫的器官，每个样本的测量下限低至 2.5μg。我们应用该方法来确定进入生长中的固体肿瘤的碳最终是来自食物还是宿主组织。
在黑腹果蝇幼虫肿瘤模型中测量肿瘤生长表明，这些肿瘤的大部分碳来自宿主来源。我们认为，这种方法的低成本和无毒性质使其具有广泛的适用性，可用于研究其他动物器官之间的碳流动，以及一系列其他生物学问题。
