The use of P-gp inhibitors together with TMZ in U87MG and T98G GBM cells caused increased caspase-3 activity and induced apoptosis, while in an in vivo knockout model for ABCB1 (P-gp) the efficacy of TMZ treatment was higher than in control animals [18,19]. The gene discussed is ABCB1; the disease is glioblastoma.