Spatially resolved analysis of immune and cancer cell metabolism in vivo

Abstract

Mass spectrometry (MS) is an invaluable tool utilized in many research areas to identify and quantify molecules ranging from proteins to small molecules. Of all the various MS techniques, matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) has grown to be of significant import due to its ability to directly analyze tissue sections without disrupting sample integrity. However, measuring the concentration of metabolites does not yield complete information. Understanding pathway activity, or metabolic flux, for different cell types and cell state along with metabolomics is equally important. Here, by coupling isotope tracing to help determine metabolic activities in vivo to MALDI-MSI and histology, we provide spatial metabolic insight for both immune and cancer cells. We reveal for the first time the in vivo fuel sources for rapidly proliferating germinal center B cells by systematically infusing the top nine nutrients with highest flux, and reveal the metabolic rewiring in the context of malignant transformation. Next, we demonstrate methodological optimizations to maximize sensitivity for small analytes that have yet to be detected by MALDI-MSI. Finally, we deploy the MALDI-MSI optimizations to examine translational application in the clinic. In summary, the work described herein provides a novel and biologically relevant usage of MALDI-MSI to quantify relative and direct circulating sources of energy for cells of interest. In sum, this body of work in this thesis highlights the significant technological improvements made to further enhance the potential of MALDI-MSI for biomedical research.