HL-60/MX1 is a mitoxantrone resistant derivative of the HL-60 cell line (see ATCC CCL-240) which was obtained from peripheral blood leukocytes obtained by leukopheresis from patient with acute promyelocytic leukemia. The cells were selected and subcloned in 1987 for resistance to 39 nM mitoxantrone, an anthracenedione antitumor agent. Subsequent exposure of the HL-60/MX1 cells to higher concentrations of mitoxantrone led to the emergence of cells capable of growth at 190 nM (see ATCC CRL-2257, HL-60/MX2). HL-60/MX1 cells display atypical multidrug resistance (MDR), altered topoisomerase II catalytic activity and reduced levels of topoisomerase II alpha and beta proteins. HL-60/MX1 cells are cross resistant to etoposide, teniposide, bisantrene. Dactinomycin, 4'-(9-acridinylamino)methane-sulfon-m-anisidide, and the anthracyclines daunorubicin and doxorubicin but retain sensitivity to the Vinca alkaloids vincristine and vinblastine, melphalan, mitomycin C and cisplatin. |
