Analyzing tumor metabolism in vivo

Altered metabolism is a clinically actionable hallmark of cancer. Some reprogrammed activities in cancer cells have predictive value and others are associated with therapeutic liabilities. Recent years have brought increased exploration of metabolism in intact tumors, complementing a large literature on cancer cell lines. We review the expanding tool kit available for studying the metabolic features of tumors in vivo. These techniques include metabolomics, positron emission tomography, magnetic resonance spectroscopy, and multiparametric magnetic resonance imaging, and they vary according to their invasiveness and breadth of metabolic assessment. Special attention is given to the emerging role of intraoperative infusions of stable, isotope-labeled nutrients, which have provided the first view of true metabolic flux in human tumors. These studies also demonstrate markedly different metabolic phenotypes from those observed in culture, indicating the potential for this approach to provide a disease-relevant view of cancer metabolism and to nominate new therapeutic targets from reprogrammed pathways.