Regulation of the nuclear proteasome activity in myelomonocytic human leukemia cells after adriamycin treatment

Treatment of different human leukemia cell variants with the anthracycline adriamycin was associated with a rapid activation of the proteasome.Thus, p roliferating U937, TUR, and retrodifferentiated U937 cells exhibited a 4.3- fold, 5.8-fold, end 4.3-fold proteasome activation within 15 minutes after adriamycin treatment, respectively. In contrast, little if any proteasome a ctivation was detectable in a growth-arrested differentiated U937 populatio n following adriamycin treatment. Further analysis of this mechanism reveal ed a significant reduction of adriamycin-induced proteasome activity after inhibition of poly(ADP-ribose) polymerase (PARP) by 3-aminobenzamide (3-ABA ) in the proliferating leukemic cell types. These findings suggested that P ARP is involved in the regulation of drug-induced proteasome activation. In deed, anti-PARP immunoprecipitation experiments of adriamycin-treated cells revealed increasing levels of coprecipitated, enzymatically active proteas ome particularly in the proliferating cell variants in contrast to the diff erentiated U937 cells, with a maximum after 15 minutes, and sensitivity to PARP inhibition by 3-ABA. The specific role of the PARP was investigated in U937 and TUR cell crones stably transfected with a constitutively active a ntisense PARP (asPARP) vector. Thus, asPARP-TUR cells developed a 25-fold i ncreased sensitivity to adriamycin treatment. Furthermore, we investigated leukemic blasts isolated from acute myelogenous leukemia patients and obtai ned a similarly enhanced proteasome activity after adriamycin treatment, wh ich was dependent on the PARP and thus could be coprecipitated with anti-PA RP antibodies. Transient transfection of leukemic blasts with the asPARP ve ctor significantly reduced the adriamycin-induced proteasome activation. Th ese data suggest that the PARP-associated nuclear proteasome activation rep resents a potential target within chemotherapeutic defense mechanisms devel oped by leukemia cells. (Blood, 2001;97: 2830-2838) (C) 2001 by The America n Society of Hematology.