Novel Application of Ion Mobility Mass Spectrometry Reveals Complex Ganglioside Landscape in Diffuse Astrocytoma Peritumoral Regions

Diffuse astrocytoma is a primary brain tumor characterized by an insidious infiltration of tumor cells into surrounding brain tissue. Considering this trait, investigation of the peritumoral region is of major biological and clinical importance. In this study, ion mobility mass spectrometry (IMS MS) was optimized and introduced for the first time in the analysis of gangliosides expressed in the peritumoral tissue of diffuse astrocytoma. Profiling and structural analysis of ganglioside species were performed by high-resolution nanoelectrospray ionization (nanoESI) IMS MS and tandem MS (MS/MS) by collision induced dissociation at low energies tuned in the negative ion mode. Through IMS MS separation and screening, we discovered that the diversity of gangliosides in peritumoral tissue is significantly larger than previously reported. We observed the high expression of GT1(d18:1/18:0), GT1(d18:1/20:0), GM2(d18:1/16:2), GD1(d18:1/16:0), GD2(d18:1/20:0), Fuc-GT3(d18:1/24:4), and Fuc-GD1(d18:1/18:2), which suggest that these species: a) are potential biomarkers; b) create a microenvironment favorable to the infiltration of the tumor cells; c) promote the invasion of diffuse astrocytoma cells; d) uphold cellular interactions and possibly influence immune responses.In the second phase, IMS MS, tandem MS, and fragmentation data confirmed the structure of GT1(d18:1/20:0), identifying GT1b as the only isomer present in peritumoral regions.