Poster Presentation 23rd Annual Lorne Proteomics Symposium 2018

An investigation into MALDI imaging sample preparation compared to DESI imaging for multimodal MSI in Pre-clinical Breast Cancer Research (#126)

Heather Patsiouras 1 , Emmanuelle Claude 2 , Jonathan Sleeman 3 , Mark Towers 2 , Phillipa Hart 2 , Kirill A Veselkov 4
  1. Waters Australia, Rydalmere, NSW, Australia
  2. Waters Organisation, Wilmslow
  3. Centre for Biomedicine and Medical Technology Mannheim, Karlsruhe Institute of Technology (KIT), , Karlsruhe, Germany
  4. Department of Surgery and Cancer, Imperial College, London, U.K

Breast cancer is a complex and heterogeneous disease that has distinct biological features and clinical characteristics. The understanding of breast cancer, which is the most frequently diagnosed form of cancer and the second leading cause of death in Western women, has greatly profited from research using genetically modified mouse models1.

Mass spectrometry imaging (MSI) is an established analytical tool for biomolecular research which can accurately determine the spatial location of molecules in a tissue section.

In this study, we present data comparing several sample preparation protocols for MALDI MSI and contrasting with DESI MSI using mouse breast normal and tumour samples.

Experiments were conducted on normal and tumour samples from the polyoma middle T oncoprotein (PyMT) mouse model of breast cancer, which were sectioned using a cryotome and deposited onto  standard microscope slides preserved at -80C degrees until analysis by mass spectrometry.

The tissue sections were analyzed firstly by MALDI MSI using a SYNAPT G2-Si mass spectrometer with a MALDI source operating with a solid-state diode-pumped ND:YAG laser using a repetition rate of 1 KHz. Consecutive tissues were then analyzed by DESI MSI, using a modified Prosolia source, directly mounted onto the SYNAPT G2-Si.

With DESI control tissue datasets, the highest signals were generated by the triglyceride molecules directly from the tissue sections. However, molecular profiles changed considerably in the breast tumor samples, with an increase in intensity of signal for  the detection of phosphatidylcholine . This was not observed with the datasets generated by MALDI MSI. Indeed, with MALDI triglyceride molecules were clearly shown in both normal or cancerous tissue under the sample preparation conditions used. The observed difference in lipid profiles using MALDI between the tissue types were more subtle and were found to be related to differences in phospholipids.