Visualizing Energy Charge in Breast Carcinoma Tissues by MALDI Mass-spectrometry Imaging Profiles of Low-molecular-weight Metabolites

Metabolomics is widely used for biomarker discovery, but conventional mass-spectrometry extraction procedures lose the spatial localization of metabolites. In this study, we directly analyzed breast carcinoma tissues embedded in frozen tissue microarrays (fTMAs) using MALDI mass-spectrometry imaging (MALDI-MSI). A total of 119 breast tissues (84 carcinoma and 35 normal) were used. MSI data were extracted from each tissue. Overall, 185 of 1,915 peaks which were commonly detected in 60% of target areas were subjected to further analysis. One hundred and fifty-two peaks of carcinoma showed significantly higher intensity than normal. Comparing metabolite profiles from carcinoma and normal tissues, energy charge (EC) and the sum of adenosine phosphate compound (AXP) indicated significantly higher intensities in cancerous tissues than normal. But comparisons of EC and AXP among lymph node metastasis, tumor size and tumor subtypes indicated no significant differences. Breast carcinoma tissues had higher EC and AXP values than normal. MALDI-MSI could be a tool for characterizing breast carcinoma.