Mass Spectrometry Imaging (MSI) is typically used to determine the distribution of proteins, lipids or metabolites in fresh frozen tissue. Formalin-fixed paraffin embedded (FFPE) tissue can be analyzed after antigen retrieval and enzymatic digest with trypsin or PNGase F on tissue for imaging tryptic peptides and N-glycans. Imaging tryptic peptides and N-glycans in FFPE tissue has multiple advantages over imaging of intact proteins in fresh frozen tissue. These includes the identification of peptides and N-glycans by matching accurate m/z from the MSI experiment with in situ MS/MS on tissue and high quality LC-MS/MS data obtained through in solution digestion of relevant laser dissected tissue. A novel method for investigating tissue-specific N-linked glycans was recently developed by our group on FFPE tissue.
Here we present the latest developments within our group, including up-to-date methods for analysis of FFPE tissue (e.g. tryptic peptide and PNGase F released glycans) and the use of tissue micro arrays. We present that MSI can spatially profile glycoforms in tissue-specific regions, while through LC-ESI-MS/MS the corresponding glycol compositions are structurally characterized. These methods are applied to endometrial and ovarian cancer FFPE tissues to potentially make diagnostic decisions in order to improve treatment of cancer patients.
We also show the testing of cancer drugs (olaparib, CDK 4/6 and CDK 9 Inhibitors) using 3 dimensional ovarian cancer spheroids and show distribution of the drugs and their efficacy by using embedding, sectioning and MSI analysis.