Combining MALDI-TOF and molecular imaging with principal component analysis for biomarker discovery and clinical diagnosis of cancer

Molecular imaging using matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI-TOF MS) is effective for determining the distribution of molecules of interest in specific tissues. It can determine the direct correlation between metabolite, lipid, and protein expression and histology. Principle component analysis (PCA) can reduce the dimensions of a data set while still retaining the information present in the original data set. Using PCA to process MALDI data, samples with different statuses and ion patterns on their MALDI mass spectra can be classified, grouped, and evaluated on the same score plot. The use of MALDI-TOF in combination with PCA to compare the lipid, peptide, and protein profiles of different biological specimens can then be used to diagnose disease. Because ions with significant differences between sampling regions in a tissue can be indicated using PCA, the imaging of these “interesting peaks” can be visualized by plotting the ion intensity across the tissue section.