Comparing DESI-MSI and MALDI-MSI Mediated Spatial Metabolomics and Their Applications in Cancer Studies

Abstract

Metabolic heterogeneity of cancer contributes significantly to its poor treatment outcomes and prognosis. As a result, studies continue to focus on identifying new biomarkers and metabolic vulnerabilities, both of which depend on the understanding of altered metabolism in cancer. In the recent decades, the rise of mass spectrometry imaging (MSI) enables the in situ detection of large numbers of small molecules in tissues. Therefore, researchers look to using MSI-mediated spatial metabolomics to further study the altered metabolites in cancer patients. In this review, we examined the two most commonly used spatial metabolomics techniques, MALDI-MSI and DESI-MSI, and some recent highlights of their applications in cancer studies. We also described AFADESI-MSI as a recent variation from the DESI-MSI and compare it with the two major techniques. Specifically, we discussed spatial metabolomics results in four types of heterogeneous malignancies, including breast cancer, esophageal cancer, glioblastoma and lung cancer. Multiple studies have effectively classified cancer tissue subtypes using altered metabolites information. In addition, distribution trends of key metabolites such as fatty acids, high-energy phosphate compounds, and antioxidants were identified. Therefore, while the visualization of finer distribution details requires further improvement of MSI techniques, past studies have suggested spatial metabolomics to be a promising direction to study the complexity of cancer pathophysiology.

Keywords: DESI-MSI; MALDI-MSI; breast cancer; cancer heterogeneity; esophageal cancer; glioblastoma; lung cancer; spatial metabolomics.

Figure 1

Schematics of MALDI, DESI, and AFADESI. Overview of MALDI, DESI, and AFADESI processes prior to MSI. All three techniques accept frozen or FFPE tissues, and MALDI requires an additional matrix deposition step. Subsequently, MALDI technique uses a laser to ionize the sample before MS detection whereas DESI and AFADESI use high pressure solvent to directly ionize the sample. Additionally, AFADESI depends on air flow to carry the ions over long distances to be detected.