Valproic acid decreases the reparation capacity of irradiated MOLT-4 cells.
The aim of our work was to evaluate mechanisms leading to radiosensitization of MOLT-4 leukemia cells following valproic acid (VA) treatment. Cells were pretreated with 2 mM VA for 24 h followed by irradiation with a dose of 0.5 or 1 Gy. The effect of both noxae, alone and combined, was detected 1 and 24 hours after the irradiation. Induction of apoptosis was evaluated by a flow cytometry. The extent of DNA damage was further determined by phosphorylation of histone H2AX using confocal microscopy. Changes in protein expression were identified by SDS-PAGE/immunoblotting. Two-millimolar VA increased apoptosis induction after irradiation as well as phosphorylation of H2AX and provokes an increase in the level of p53 and its phosphorylation at Ser392 in 4 h post-irradiation. Likewise, p21 protein reached its maximal expression in 4 h after the irradiation of VA-treated cells. Twenty four hours later, only the p53 phosphorylated at Ser15 was detected. At the same time, the protein mdm2 (negative regulator of p53) was maximally activated. The 24-hour treatment of MOLT-4 leukemia cells with 2 mM VA results in radiosensitizing, increases apoptosis induction, H2AX phosphorylation, and also p53 and p21 activation.
Department of Medical Biochemistry, Faculty of Medicine in Hradec Kralove, Charles University in Prague, Czech Republic.
D
D
Muthna
J
J
Vavrova
E
E
Lukasova
A
A
Tichy
J
J
Knizek
R
R
Kohlerova
N
N
Mazankova
M
M
Rezacova
D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D004249:DNA Damage / Q000187:drug effects / Q000528:radiation effects; D004260:DNA Repair / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005720:Gamma Rays; D005786:Gene Expression Regulation / Q000187:drug effects / Q000528:radiation effects; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007938:Leukemia / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D014635:Valproic Acid / Q000494:pharmacology*; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
D004791:Enzyme Inhibitors; C468783:H2AX protein, human; D006657:Histones; D011838:Radiation-Sensitizing Agents; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D014635:Valproic Acid; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D020741:rho GTP-Binding Proteins