Cancer cells undergo diverse metabolic adaptations to meet the energetic demands imposed by dysregulated growth and proliferation. Assessing metabolism in intact tumors allows the investigator to observe the combined metabolic effects of numerous cancer cell-intrinsic and -extrinsic factors that cannot be fully captured in culture models. We have developed methods to use stable isotope-labeled nutrients (e.g., [¹³C]glucose) to probe metabolic activity within intact tumors in vivo, in mice and humans. In these methods, the labeled nutrient is introduced to the circulation through an intravenous catheter prior to surgical resection of the tumor and adjacent nonmalignant tissue. Metabolism within these tissues during the infusion transfers the isotope label into metabolic intermediates from pathways supplied by the infused nutrient. Extracting metabolites from surgical specimens and analyzing their isotope labeling patterns provides information about metabolism in the tissue. We provide detailed information about this technique, from introduction of the labeled tracer through data analysis and interpretation, including streamlined approaches to quantify isotope labeling in informative metabolites extracted from tissue samples. We focus on infusions with [¹³C]glucose and the application of mass spectrometry to assess isotope labeling in intermediates from central metabolic pathways, including glycolysis, the tricarboxylic acid cycle and nonessential amino acid synthesis. We outline practical considerations to apply these methods to human subjects undergoing surgical resections of solid tumors. We also discuss the method’s versatility and consider the relative advantages and limitations of alternative approaches to introduce the tracer, harvest the tissue and analyze the data.

癌细胞经历多种代谢适应，以满足生长和增殖失调所带来的能量需求。评估完整肿瘤的代谢使研究人员能够观察许多癌细胞内在和外在因素的综合代谢影响，而这些因素在培养模型中无法完全捕获。我们开发了使用稳定同位素标记的营养物质（例如[ ¹³ C]葡萄糖）来探测小鼠和人类体内完整肿瘤内的代谢活性的方法。在这些方法中，在手术切除肿瘤和邻近的非恶性组织之前，通过静脉导管将标记的营养物引入循环中。输注过程中这些组织内的代谢将同位素标记从输注营养物质提供的途径转移到代谢中间体中。从手术标本中提取代谢物并分析其同位素标记模式可以提供有关组织代谢的信息。我们提供有关该技术的详细信息，从标记示踪剂的介绍到数据分析和解释，包括量化从组织样本中提取的信息代谢物中同位素标记的简化方法。我们专注于[ ¹³ C]葡萄糖的输注和应用质谱法来评估中央代谢途径中间体的同位素标记，包括糖酵解、三羧酸循环和非必需氨基酸合成。我们概述了将这些方法应用于接受实体瘤手术切除的人类受试者的实际考虑因素。 我们还讨论了该方法的多功能性，并考虑了引入示踪剂、收获组织和分析数据的替代方法的相对优势和局限性。