Source data for Primary and metastatic tumors exhibit systems-level differences in dependence on mitochondrial respiratory function

The Warburg effect, aerobic glycolysis, is a hallmark feature of cancer cells grown in culture. However, the relative roles of glycolysis and respiratory metabolism in supporting in vivo tumor growth and processes such as tumor dissemination and metastatic growth remain poorly understood, particularly on a systems level. Using a CRISPRi mini-library enriched for mitochondrial ribosomal protein and respiratory chain genes in multiple human lung cancer cell lines we analyzed in vivo metabolic requirements in xenograft tumors grown in distinct anatomic contexts. While knockdown of mitochondrial ribosomal protein and respiratory chain genes (mito-respiratory genes) has little impact on growth in vitro, tumor cells depend heavily on these genes when grown in vivo as either flank or primary orthotopic lung tumor xenografts. In contrast, respiratory function is comparatively dispensable for metastatic tumor growth. RNA-Seq and metabolomics analysis of tumor cells expressing individual sgRNAs against mito-respiratory genes indicate overexpression of glycolytic genes and increased sensitivity of glycolytic inhibition compared to control when grown in vitro, but when grown in vivo as primary tumors these cells downregulate glycolytic mechanisms. These studies demonstrate that discrete perturbations of mitochondrial respiratory chain function impact in vivo tumor growth in a context-specific manner with differential impacts on primary and metastatic tumors.

瓦博格效应（Warburg effect）即有氧糖酵解，是体外培养癌细胞的标志性特征。然而，糖酵解与呼吸代谢在支持体内肿瘤生长，以及肿瘤播散、转移生长等过程中的相对作用仍不甚明确，在系统层面的研究尤为匮乏。本研究借助在多株人肺癌细胞系中富集线粒体核糖体蛋白与呼吸链基因的CRISPR干扰（CRISPRi）微型文库，分析了不同解剖部位生长的异种移植瘤的体内代谢需求。尽管敲低线粒体核糖体蛋白与呼吸链基因（mito-respiratory genes）对体外肿瘤生长几乎无影响，但当肿瘤细胞以皮下异种移植瘤或原位肺异种移植瘤的形式在体内生长时，会强烈依赖此类基因。与之相反，呼吸功能对于转移瘤的生长则相对非必需。对表达靶向线粒体呼吸基因的单引导RNA（sgRNAs）的肿瘤细胞开展RNA测序（RNA-Seq）与代谢组学分析显示，体外培养时，此类细胞的糖酵解基因呈过表达状态，且与对照组相比对糖酵解抑制的敏感性升高；但在体内作为原位肿瘤生长时，这些细胞会下调糖酵解通路。本研究表明，线粒体呼吸链功能的特异性扰动会以情境特异性的方式影响体内肿瘤生长，且对原位肿瘤与转移瘤的影响存在差异。