Figure 1A shows a significantly higher expression of GDF15 in GBM and GSCs compared with normal tissue, while no significant difference was observed between GBM and GSCs. We then analyzed the secretion of GDF15 in the conditioned media of GSCs derived from two different patients using the R&D Human XL Cytokine Array kit, which targets human cytokines and growth factors. Figure 1B,C shows that among the 105 cytokines and factors analyzed, GDF15 is well secreted by GSCs into the medium. The gene discussed is GDF15; the disease is glioblastoma.