MALDI Imaging Mass Spectrometry for small molecule quantitation and evaluation for markers of drug response in Gliomas

Abstract

MALDI IMAGING MASS SPECTROMETRY FOR SMALL MOLECULE QUANTITATION AND EVALUATION FOR MARKERS OF DRUG RESPONSE IN GLIOMAS

SARA L. FRAPPIER

Dissertation under the direction of Professor Richard M. Caprioli

A protocol has been developed to implement small molecule quantitation with MALDI Imaging MS directly from tissue sections. This protocol allows for MALDI based imaging technologies to correlate absolute drug concentration with pharmacological response in tissues while still maintaining spatial information in rapid, high-throughput molecularly specific experiments. The quantitation protocol has been applied to the investigation of two therapies under investigation for the treatment of Glioblastomas (brain tumors of glial cell origin) to determine the quantities of compound that reach the brain and tumor areas in mouse models. Imaging experiments performed by MALDI were able to provide the individual, label-free temporal distributions of IMAT and CYC from brain tissue sections with high sensitivity and reproducibility. Highly-accurate absolute quantities of each compound were also obtained directly from tissue sections without the need for homogenization or extraction procedures. Using the calculated drug concentrations of IMAT and CYC in conjunction with standard MALDI TOF imaging, it was possible to study the proteome affects that the drug presence had on primary brain tumor xenografts in mice. MALDI Imaging MS proved to be an invaluable tool to rapidly and reproducibly relate the tissue distribution of the IMAT and CYC to the observed pharmacological response within the same tissue sample while maintaining spatial resolution. Altered proteins were identified and can contribute to an improved understanding of the IMAT and CYC mechanisms of action as well as help gain a deeper understanding of the mechanisms involved in primary brain tumor function.