Figure 2
IDH genotype determination using high-throughput DESI-MS. In IDH-mutant (IDH-mut) gliomas, an alteration in the function of the IDH enzyme leads to the accumulation of 2HG (a), an oncometabolite that can be monitored easily by MS/MS in the negative ion mode. In a single MS/MS scan, using a 3 m/z unit window, both 2HG and Glu can be isolated and fragmented through CID allowing their [M–H–H2O]− fragments to be monitored. Representative spectra for IDH-wildtype (IDH-wt; b) and IDH-mut (c) are both shown. Perfect classification of the samples in both TMAs (d) is achieved using the IDH mutation score (i.e. MS/MS ion ratio corrected for the 13C-Glu isotopic contribution) calculated from 6 s of MS/MS acquisition per sample. In all cases boxes show the 25th–75th percentile with the median, while whiskers correspond to 1.5 interquartile range (IQR); averages and outliers (outside 1.5 IQR) as white and black symbols, respectively. NCB: non-cancerous brain samples.
