ABCB1 and breast cancer: We observed that NSC23925 reverses chemoresistance in a wide variety of tumor types where MDR1 is highly expressed; these tumor types include the ovarian cancer cell lines SKOV-3TR and OVCAR8TR, breast cancer cell line MCF-7TR, and sarcoma cell lines MESSA/Dx5, KHOS R2, and U-2OSDR (representative data from SKOV-3TR, OVCAR8TR, and KHOS R2 shown in Table 1).