Centre for Research in Biomolecular Interactions presents Dr. Arash Zarrine-Afsar, Department of Medical Biophysics & Department of Surgery, University of Toronto

Talk Title: “Mass spectrometry imaging of cancer and cancer site heterogeneity; Challenges and solutions”

Abstract:

Mass spectrometry (MS) is a sensitive analytic technique that can provide a chemical fingerprint of a biological tissue on the basis of the mass-to-charge (m/z) ratios of its molecular constituents. Mass Spectrometry Imaging (MSI) combines the multiplexed (m/z) measurement capability of MS with a surface sampling process to deliver a spatially resolved chemical content map of the target tissue. MSI can provide a molecular image of the (m/z) space characteristic of the disease state, from which an image of the disease site that includes boundary and infiltrating regions can be created. Current MSI methods are thus limited in applicability to diseases for which characteristic (m/z) values are known and catalogued. In addition, while MS devices can detect chemical signatures within milliseconds of data acquisition time to allow rapid cancer typification, the non-targeted nature of current MSI methods necessitates probing the entire surface of the excised tissue sample to reveal molecular composition even if the information is only sought from a sample subsection. This leads to long analysis times. My laboratory’s recent efforts have focused on the potential of MSI to increase the speed and accuracy of cancer pathology assessments for improved tumour resection or rapid intraoperative cancer typing. We have shown that exogenous, broad specificity tumour labels can facilitate rapid cancer site mapping with MSI without the need for cancer specific (m/z) values. Furthermore, tumour subregion-specific adductization of these labels allows additional mapping of tumour heterogeneity such as margin and vasculature. We recently developed techniques for targeted, localized MS profiling of tissues for accelerated tumour margin assessment from ex vivo tissue slices by incorporating feedback from other imaging modalities in planning MS data acquisition, allowing efficient guiding MS probe to areas of interest such as the cancer site and the suspected cancer border, reducing the effective sample size to be analyzed and the overall process and analysis time. We are currently pursing in vivo MSI of biological tissues using Cold Laser Ablation Technology, a laser scalpel that desorbs tissue content in the absence of significant thermal damage to the tissue. Further engineering work will lead to full integration of cold ablation laser with mass spectrometry for real-time intraoperative surgical guidance on the basis of Simultaneous Mapping of Ablated Residues from Tissues (SMART Laser Scalpel).

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