Human chronic lymphocytic leukemia B cells can escape DNA damage-induced apoptosis through the nonhomologous end-joining DNA repair pathway.
Nonhomologous end-joining (NHEJ) DNA factors maintain genomic stability through their DNA double-strand break (DSB) repair and telomere-associated activities. Unrepaired or misrepaired DSBs can lead to apoptotic death or chromosomal damage. The B cells of some B-chronic lymphocytic leukemia (B-CLL) patients are resistant to radiation-induced apoptosis in vitro. We show here that the novel DNA-dependent protein kinase (DNA-PK) inhibitor, NU7026 (2-(morpholin-4-yl)-benzo[h]chomen-4-one), and the phosphatidylinositol 3 (PI-3) kinase inhibitor, wortmannin, restored sensitivity to DNA damage-induced apoptosis of otherwise resistant cells. These resistant malignant B cells also escaped DSB-induced apoptosis following exposure to etoposide or neocarzinostatin. We found that at 15 minutes after irradiation, the levels of NHEJ (as measured by an in vitro DSB end-ligation assay) and DNA-PK catalytic subunit (DNA-PKcs) activity were, respectively, 2-fold and 4-fold higher in radio-resistant than in radio-sensitive B-CLL cells or Epstein-Barr virus (EBV)-transformed B cells. Ku70/Ku80 heterodimer DNA end-binding activity was also 2- to 3-fold higher in the resistant B-CLL cell subset compared with the sensitive B-CLL cell subset. Our results provide the first evidence that overactivating the NHEJ DNA repair pathway impairs DNA damage-induced apoptosis in malignant B cells and that this may contribute to their resistance to current chemotherapy.
Deriano
Ludovic
L
Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Enegie Atomique, Fontenay-aux-Roses, France.
Guipaud
Olivier
O
Merle-Béral
Hélène
H
Binet
Jacques-Louis
JL
Ricoul
Michelle
M
Potocki-Veronese
Gaby
G
Favaudon
Vincent
V
Maciorowski
Zofia
Z
Muller
Catherine
C
Salles
Bernard
B
Sabatier
Laure
L
Delic
Jozo
J
D000730:Androstadienes / Q000494:pharmacology; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D034961:Antigens, Nuclear / Q000378:metabolism; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis; D001402:B-Lymphocytes / Q000473:pathology; D015153:Blotting, Western; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D002474:Cell-Free System; D002867:Chromones / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D005720:Gamma Rays; D006801:Humans; D000072200:Ku Autoantigen; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy* / Q000473:pathology*; D009025:Morpholines / Q000494:pharmacology; D019319:Okadaic Acid / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000494:pharmacology; D011485:Protein Binding; D016615:Telomere / Q000648:ultrastructure; D013997:Time Factors; D000077191:Wortmannin; D009353:Zinostatin / Q000494:pharmacology
C479235:2-(morpholin-4-yl)benzo(h)chromen-4-one; D000730:Androstadienes; D000903:Antibiotics, Antineoplastic; D034961:Antigens, Nuclear; D000972:Antineoplastic Agents, Phytogenic; D002867:Chromones; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D009025:Morpholines; D019319:Okadaic Acid; D005047:Etoposide; D004247:DNA; D009353:Zinostatin; D019869:Phosphatidylinositol 3-Kinases; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen; D000077191:Wortmannin