The
lipid compositions of different
breast tumor microenvironments are largely unknown due to limitations in
lipid imaging techniques. Imaging
lipid distributions would enhance our understanding of processes occurring inside growing
tumors, such as
cancer cell proliferation, invasion, and
metastasis. Recent developments in MALDI mass spectrometry imaging (MSI) enable rapid and specific detection of
lipids directly from thin tissue sections. In this study, we performed multimodal imaging of acylcarnitines,
phosphatidylcholines (PC), a
lysophosphatidylcholine (LPC), and a
sphingomyelin (SM) from different microenvironments of
breast tumor xenograft models, which carried
tdTomato red fluorescent protein as a
hypoxia-response element-driven reporter gene. The MSI molecular
lipid images revealed spatially heterogeneous
lipid distributions within
tumor tissue. Four of the most-abundant
lipid species, namely
PC(16:0/16:0),
PC(16:0/18:1), PC(18:1/18:1), and PC(18:0/18:1), were localized in viable
tumor regions, whereas LPC(16:0/0:0) was detected in necrotic
tumor regions. We identified a heterogeneous distribution of
palmitoylcarnitine, stearoylcarnitine,
PC(16:0/22:1), and SM(d18:1/16:0)
sodium adduct, which colocalized primarily with hypoxic
tumor regions. For the first time, we have applied a multimodal imaging approach that has combined optical imaging and MALDI-MSI with ion mobility separation to spatially localize and structurally identify acylcarnitines and a variety of
lipid species present in
breast tumor xenograft models.