Hypersensitivity (collateral sensitivity) of MDA-MB-231-BCRP cells vs. MDA-MB-231-pcDNA cells (D.R. of 0.51), and U87.MGΔEGFR glioblastoma cells vs. U87.MG cells (D.R. of 0.69) to BAL was observed (Table 2). This evidence concerns the gene ABCG2 and glioblastoma.