However, co-treatments with verapamil (a known blocker of the drug-pumping-out activity of P-glycoprotein [32]), while it sensitized MCF-7/MDR1 cells to 17AAG and geldanamycin, did not exert analogous effects toward HBL-100, FRO and B16 cancer cells (not shown). Here, ABCB1 is linked to cancer.