Modulation of ionizing radiation-induced apoptosis and cell cycle arrest by all-trans retinoic acid in promyelocytic leukemia cells (HL-60).
Acute promyelocytic leukemia is characterized by a block of myeloid differentiation. The incubation of cells with 1 micromol/l all-trans retinoic acid (ATRA) for 72 h induced differentiation of HL-60 cells and increased the number of CD11b positive cells. Morphological and functional changes were accompanied by a loss of proliferative capacity. Differentiation caused by preincubation of leukemic cells HL-60 with ATRA is accompanied by loss of clonogenicity (control cells: 870 colonies/10(3) cells, cells preincubated with ATRA: 150 colonies/10(3) cells). D0 for undifferentiated cells was 2.35 Gy, for ATRA differentiated cells 2.46 Gy. Statistical comparison of clonogenity curves indicated that in the whole range 0.5-10 Gy the curves are not significantly different, however, in the range 0.5-3 Gy ATRA differentiated cells were significantly more radioresistant than non-differentiated cells. When HL-60 cells preincubated with 1 micromol/l ATRA were irradiated by a sublethal dose of 6 Gy, more marked increase of apoptotic cells number was observed 24 h after irradiation and the surviving cells were mainly in the G1 phase of the cell cycle, while only irradiated cells were accumulated in G(2) phase. Our results imply that preincubation of cells with ATRA accelerates apoptosis occurrence (24 h) after irradiation by high sublethal dose of 6 Gy. Forty-eight hours after 6 Gy irradiation, late apoptotic cells were found in the group of ATRA pretreated cells, as determined by APO2.7 positivity. This test showed an increased effect (considering cell death induction) in comparison to ATRA or irradiation itself.
Mareková
M
M
Dept. of Medical Biochemistry, Faculty of Medicine Hradec Králové, Charles University Prague, Simkova 870, 500 01 Hradec Králové, Czech Republic. marekova@lfhk.cuni.cz
Vávrová
J
J
Vokurková
D
D
Psutka
J
J
D017209:Apoptosis / Q000187:drug effects* / Q000528:radiation effects; D039481:CD11b Antigen / Q000032:analysis; D002452:Cell Count; D002453:Cell Cycle / Q000187:drug effects* / Q000528:radiation effects; D016923:Cell Death / Q000187:drug effects / Q000528:radiation effects; D002454:Cell Differentiation / Q000187:drug effects / Q000276:immunology / Q000528:radiation effects; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D004247:DNA / Q000032:analysis; D004307:Dose-Response Relationship, Radiation; D005434:Flow Cytometry; D016195:G2 Phase / Q000187:drug effects / Q000528:radiation effects; D005720:Gamma Rays; D018922:HL-60 Cells; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology*; D014410:Tumor Stem Cell Assay
D039481:CD11b Antigen; D008565:Membrane Proteins; C102086:antigen 7A6; D014212:Tretinoin; D004247:DNA