To assess the impact of treatments on drug resistance mechanisms in U-87MG glioma cells, the expression levels of the key resistance markers P-glycoprotein (P-gp) and multidrug resistance-associated protein 1 (MRP1) were evaluated using immunoblotting (Figure 3D) and immunofluorescence analysis (Figure 3E). Here, ABCB1 is linked to central nervous system cancer.