MKI67 and glioblastoma: To further confirm the connection between GPNMB and GSC stemness, we performed validation assays using tumor and plasma samples from patients with GBM and found that GPNMB levels in tumors and plasma from patients with GBM positively correlated with their intratumoral SOX2 (Figure 7, F and G) and Ki67 (Figure 7H) expression, respectively.