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Abstract No.: ThP-136
Session: Instrumentation and Methodologies for Imaging MS
Presentation date: Thu, Aug 31, 2006
Presentation time: 14:30 – 16:00

Examining the Distribution of the Bioreductive Drug AQ4N and Its Metabolites in Treated Tumours by Imaging MALDI-MS

Sally J. Atkinson1, Malcolm R. Clench1, Laurence H. Patterson2, Paul M. Loadman2

1 Sheffield Hallam University, Sheffield, United Kingdom
2 Institute of Cancer Therapeutics, Bradford, United Kingdom

Correspondence address: Sally J. Atkinson, Sheffield Hallam University, Biomedical Research Centre, 1 Howard Street, sheffield, S1 1WB United Kingdom.

Keywords: Drug; Imaging; Ionization, Matrix-Assisted Laser Desorption; MALDI.

Novel aspect: Parallel imaging of in situ metabolism of anti-cancer drugs for distribution studies.

 

Introduction
AQ4N is an innovative chemotherapeutic agent, designed specifically for treatment of solid tumours. The drug is targeted toward hypoxic tumour regions, which are resistant to conventional treatment by chemotherapy and radiotherapy. The highly reductive conditions found in hypoxic tissues function to activate AQ4N to the persistent anticancer agent AQ4. AQ4 is a DNA-affinic compound that has been found to sensitize tumours to existing chemo- and radiotherapy treatments.

Methods
Imaging MALDI-MS has been used in determining spatial distribution of both AQ4N and AQ4 in tumour samples. Direct analysis of AQ4N treated H460 human tumour xenographs has been carried out to examine the spatial distribution of AQ4N and AQ4 with respect to hypoxic tumour regions. Tumour bearing mice were treated with AQ4N (100mg/kg, i.p.) and tumours excised following 24h treatment. Tumours were flash frozen and tumour cryosections (12µm) were placed directly onto stainless steel MALDI targets and spray-coated with organic acid matrix (α-CHCA, 25mg/mL in acetone, 0.1% TFA). All images were obtained using an Applied Biosystems/MDS Sciex QStar Pulsar i, fitted with an orthogonal MALDI ion source and Nd:YaG laser (laser power 3.2 µJ, repetition rate 1000Hz).

Preliminary results
Due to the DNA affinic properties of AQ4 it was necessary to focus the method development on using matrices with varied levels of TFA (0-2%) in order to investigate the effects of pH on dissociation of AQ4 from DNA. Analysis of both AQ4N and its active metabolite AQ4 in tumour sections, was successful when using the appropriate matrix composition. Image analysis of both AQ4 and AQ4N from direct tissue samples has been successful. The addition of increased levels of matrix TFA has also proven to allow analysis of AQ4 through promoting dissociation of the compound from DNA. The success of this technique will enable further studies on the distribution and in situ metabolism of anticancer agents within solid tumours and other tissues.