Application of MALDI-mass spectrometry imaging for assessment of anti-neoplastic compounds in tissue.

Lalowski, M. (Handledare)

Aktivitet: ExaminationstyperHandledning av annat kunskapsprov (pro gradu, licentiatavhandling)


The practical work described in this thesis was performed at the Meilahti Clinical Prote-omics Core Facility; Medicum, Faculty of Medicine, University of Helsinki, Finland.
The overall aim of the thesis was to define precise conditions for optimal drug penetration and detection sensitivity using MALDI mass spectrometry imaging (MSI) approaches. For this purpose, eight anti-neoplastic compounds under development or in clinical use were obtained via a Pfizer Compound Transfer program and utilized in this thesis. The project was carried out by investigating the spectral properties of the xenobiotic com-pounds utilizing three MALDI matrices, namely alpha-cyano-4-hydroxycinnamic acid (CHCA), sinapinic acid (SA) and 2, 5-dihydroxybenzoic acid (DHB).
As the presence of biological tissue interferes with the ionization efficiency of MALDI ions (due to background signals, lipid concentration and quenching effects) a strategy employing the spiking of compounds on tissue material was utilized to mimic the interference of tissues on the compound spectral properties. Known concentrations of the eight compounds were spiked into known amounts of tissue material ground at liquid N2 temperature utilizing a Retsch Cryomill.
MSI was utilized to assess the spectral properties of the compounds in tissue backgrounds. For this purpose, the blocks of “spiked tissues” were cut on a cryostat at 12 µm thickness and thaw-mounted onto indium tin oxide (ITO)-coated MALDI target slides. CHCA matrix was sprayed onto the samples using an iMatrixSpray instrument and analyzed with an UltrafleXtreme MALDI mass spectrometer. Measurements were performed in Reflectron MS and LIFT MS/MS modes to determine the spectral properties of the intact compound and its fragments. Of the eight starting compounds three were selected on the basis of their optimal ionization properties to be employed in a perfusion paradigm able to deliver known amounts of compounds in the liver of perfused animals.
Utilizing this experimental pipeline a concentration of 2.5 µM of Sunitinib and its specific fragments (in MS and LIFT MS/MS modes) perfused into rat liver was clearly visible. These results serves as a basis for future studies investigating the penetration of anti-neoplastic compounds in tumors analyzing the spatial localization of the intact compound and its metabolites in order to better investigate the compound efficacy and possible side effects.
Period1 mar 201930 aug 2019