Also, the expression of ALDH1 was upregulated in the RR and RTR GBM cells (1 ± 0 vs. 1.05 ± 0.04 and 1.10 ± 0.34, p = 0.0153 and 0.0017 for U87MG vs. 2GR4 and R4T3) (Figure 3C). Here, ALDH1A1 is linked to glioblastoma.