Modulation of Ionizing
Radiation-Induced Apoptosis and Cell Cycle Arrest by All-Trans
Retinoic Acid in Promyelocytic Leukemia Cells (HL-60)
M. MAREKOVÁ1, J. VÁVROVÁ2,
D. VOKURKOVÁ3, J. PSUTKA4
1Department of Medical Biochemistry, Faculty of
Medicine Hradec Králové, Charles University, Prague, 2Institute
of Radiobiology and Immunology, Purkyně Military Medical Academy
Hradec Králové, 3Institute of Clinical Immunology and
Allergology, University Hospital, Hradec Králové, and 4Department
of Military Medical Service Organization, Purkyně Military
Medical Academy Hradec Králové, Czech Republic
Received April 15, 2002
Accepted October 16, 2002
Summary
Acute promyelocytic leukemia is characterized by a block of
myeloid differentiation. The incubation of cells with 1 μmol/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/103 cells,
cells preincubated with ATRA: 150 colonies/103 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
μmol/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 G2 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.
Key words
Apoptosis • All-trans retinoic acid • Ionizing radiation • HL-60
cells
Reprint requests
MUDr. Martina Mareková, Ph.D.,
Dept. of Medical Biochemistry, Faculty of Medicine Hradec
Králové, Charles University Prague, Šimkova 870, 500 01 Hradec
Králové, Czech Republic, e-mail:
marekova@lfhk.cuni.cz
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