Experimental Models to Study Drug Distributions in Tissue Using MALDI Mass Spectrometry Imaging A ́ kos Ve ́ gva ́ ri,* ,†,‡ Thomas E. Fehniger, ‡,§ Melinda Rezeli, † Thomas Laurell, † Bala ́ zs Dö me, ∥,⊥ Bo Jansson, # Charlotte Welinder, ▽ and Gyö rgy Marko-Varga †,○ † Clinical Protein Science & Imaging, Biomedical Center, Department of Measurement Technology and Industrial Electrical Engineering, Lund University, BMC C13, SE-221 84 Lund, Sweden ‡ CREATE Health, Lund University, Biomedical Centre D13, Tornavä gen 10, SE-221 84 Lund, Sweden § Institute of Clinical Medicine, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia ∥ Department of Thoracic Surgery, Medical University of Vienna, Spitalgasse 23, 1090 Vienna, Austria ⊥ Department of Tumor Biology, National Kora ́ nyi Institute of Pulmonology, Budapest, Hungary # BioInvent Int. AB, Sö lvegatan 41, SE-223 70 Lund, Sweden ▽ Department of Oncology, Clinical Sciences, Lund University, Barngatan 2B, SE-221 85 Lund, Sweden ○ Department of Surgery, Tokyo Medical University, 6-7-1 Nishishinjiku Shinjuku-ku Tokyo, 160-0023 Japan ABSTRACT: Requirements for patient safety and improved efficacy are steadily increasing in modern healthcare and are key drivers in modern drug development. New drug characterization assays are central in providing evidence of the specificity and selectivity of drugs. Meeting this need, matrix-assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI) is used to study drug localization within microenvironmental tissue compartments. Thin sections of human lung tumor and rat xenograft tissues were exposed to pharmaceutical drugs by either spotting or submerging. These drugs, the epidermal growth factor receptor antagonists, erlotinib (Tarceva) and gefitinib (Iressa), and the acetylcholine receptor antagonist, tiotropium, were characterized by microenvironment localization. Intact tissue blocks were also immersed in drug solution, followed by sectioning. MALDI-MSI was then performed using a Thermo MALDI LTQ Orbitrap XL instrument to localize drug-distribution patterns. We propose three MALDI-MSI models measuring drug disposition that have been used to map the selected compounds within tissue compartments of tumors isolated from lung cancer patients. KEYWORDS: lung cancer, adenocarcinoma, MALDI-mass spectrometry imaging, erlotinib, gefitinib, tiotropium 1. INTRODUCTION Today, mass spectrometry imaging (MSI) plays an important role in the pharmaceutical industry in the evaluation of candidate drugs in experimental models. Because MSI is not dependent on supplementary labels to detect administered compounds, the chemical structure of drugs is not modified and the detection of compounds within tissue is consistent with de novo uptake and dispersal. Despite its lower resolving power relative to autoradiography in whole tissue studies, MSI has the unique advantage of delivering the absolute mass identity of whole compounds, compound fragments, and compound metabolites not seen in other imaging technologies. 1 However, such assays do not necessarily utilize the entire potential of MSI. 2,3 New directions and experimental human models, which are dynamic in nature, for example, combinatorial cancer therapies, are areas of intense research. 4−6 A key event in the drug development process involves the linking of specific disease mechanisms to targets, which is interconnected to the target- drug binding properties and directly related to the pharmaco- kinetics and the pharmacodynamic properties of any given drug compound. Clearly, the physicochemical properties of a compound and its behavior in a tissue microenvironment would govern the selectivity and specificity of drug binding to the targeted protein. Translational research is vital in addressing and optimizing these properties; underlining the step going from animal disease models to man is probably the most crucial in the drug development process. Analyzing tissues by a direct measurement using matrix-assisted laser desorption ionization- mass spectrometry imaging (MALDI-MSI) is a technology that is developing rapidly. MALDI-MSI provides an accurate Received: June 19, 2013 Published: October 17, 2013 Article pubs.acs.org/jpr © 2013 American Chemical Society 5626 dx.doi.org/10.1021/pr400581b | J. Proteome Res. 2013, 12, 5626−5633