Figure 2 depicts MRM used in the study by Ghantasala et al. The study showed how MRM, a targeted proteomics technique, was used to analyze peptides from proteins such as apolipoprotein A1 (APOA1), APOE, prostaglandin H2 D-isomerase (PTGDS), vitronectin, and complement C3 (C3) in CSF from meningioma patients [8]. Here, APOA1 is linked to meningioma.