Bleomycin-induced differentiation of bcl-2-transfected U937 leukemia cells.
In this study, the effect of bleomycin on myeloid leukemic U937 cells transfected with murine bcl-2 or vector alone (vector containing neomycin-resistant gene only; MNC) was investigated. Sublethal concentrations of bleomycin (1 microgram/ml) induced a decrease in cell growth in both vector-only and bcl-2-transfected U937 cells. In MNC-transfected U937 cells, loss of viable cells and colony-forming cells was observed following 4 days of bleomycin treatment. This was accompanied by accumulation of cells in the G0-G1 phase of the cell cycle and morphological changes as well as induced expression of markers associated with myeloid differentiation (i.e., increased granularity and CD11b expression). In contrast, bcl-2-transfected U937 cells maintained viable cell numbers and colony forming cells for up to 2 weeks in the presence of bleomycin. These cells did not show cell cycle accumulation in G0-G1 and in addition, displayed delayed expression of differentiation markers when compared with bleomycin-treated, vector-only transfected U937 cells. One day following a 5-day exposure to 1 microgram/ml bleomycin, a loss of differentiated cells by apoptosis, as demonstrated by dUTP and analyzed by flow cytometry, was observed in the MNC-transfected U937 cell population. In contrast, differentiated bcl-2-transfected U937 cells remained viable for 2 weeks following bleomycin treatment. The results of this study suggest that up-regulated Bcl-2 not only blocks apoptosis in proliferating myeloid cells but also delays or prevents apoptosis in differentiated myeloid cells.
Guedez
L
L
Department of Medicine, University of Florida, Gainesville 32610, USA.
Zucali
J
J
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001761:Bleomycin / Q000494:pharmacology*; D015153:Blotting, Western; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D053938:DNA Fragmentation; D005434:Flow Cytometry; D005609:Free Radicals / Q000378:metabolism; D006801:Humans; D007951:Leukemia, Myeloid; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D015854:Up-Regulation / Q000502:physiology
D000964:Antimetabolites, Antineoplastic; D005609:Free Radicals; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D001761:Bleomycin