Looking at the functions reported for the known players, highly expressed MMP9 in GBM contributes to cancer proliferation and progression41,42; CD163 is involved in the regulation of glioma cell stemness and proliferation43; and co-overexpression of CD163 and MMP9 may indicate the polarization of macrophages associated with tumor cells44, supporting their potential to serve as GBM blood markers together. Here, MMP9 is linked to central nervous system cancer.