ABCB1 and glioblastoma: Thus, to strengthen the relevance of ABCB1 for TMZ resistance on GBM cells, the silencing of ABCB1 was performed using four different siRNAs (Suppl Figure S10A) and the knock-down was further validated on U3017MG and U3031MG transfected with siRNA (A and D) targeting the ABCB1 transcripts (Fig. 5G and H, respectively).