Fhit-deficient hematopoietic stem cells survive hydroquinone exposure carrying precancerous changes.
The fragile FHIT gene is among the first targets of DNA damage in preneoplastic lesions, and recent studies have shown that Fhit protein is involved in surveillance of genome integrity and checkpoint response after genotoxin exposure. We now find that Fhit-deficient hematopoietic cells, exposed to the genotoxin hydroquinone, are resistant to the suppression of stem cell in vitro colony formation observed with wild-type (Wt) hematopoietic cells. In vivo-transplanted, hydroquinone-exposed, Fhit-deficient bone marrow cells also escaped the bone marrow suppression exhibited by Wt-transplanted bone marrow. Comparative immunohistochemical analyses of bone marrow transplants showed relative absence of Bax in Fhit-deficient bone marrow, suggesting insensitivity to apoptosis; assessment of DNA damage showed that occurrence of the oxidized base 8-hydroxyguanosine, a marker of DNA damage, was also reduced in Fhit-deficient bone marrow, as was production of intracellular reactive oxygen species. Treatment with the antioxidant N-acetyl-l-cysteine relieved hydroquinone-induced suppression of colony formation by Wt hematopoietic cells, suggesting that the decreased oxidative damage to Fhit-deficient cells, relative to Wt hematopoietic cells, accounts for the survival advantage of Fhit-deficient bone marrow. Homology-dependent recombination repair predominated in Fhit-deficient cells, although not error-free repair, as indicated by a higher incidence of 6-thioguanine-resistant colonies. Tissues of hydroquinone-exposed Fhit-deficient bone marrow-transplanted mice exhibited preneoplastic alterations, including accumulation of histone H2AX-positive DNA damage. The results indicate that reduced oxidative stress, coupled with efficient but not error-free DNA damage repair, allows unscheduled long-term survival of genotoxin-exposed Fhit-deficient hematopoietic stem cells carrying deleterious mutations.
Ishii
Hideshi
H
Center for Molecular Medicine, Jichi Medical University, Tochigi, Japan.
Mimori
Koshi
K
Ishikawa
Kazuhiro
K
Okumura
Hiroshi
H
Pichiorri
Flavia
F
Druck
Teresa
T
Inoue
Hiroshi
H
Vecchione
Andrea
A
Saito
Toshiyuki
T
Mori
Masaki
M
Huebner
Kay
K
D000111:Acetylcysteine / Q000737:chemistry; D017766:Acid Anhydride Hydrolases / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D004249:DNA Damage; D004260:DNA Repair; D006151:Guanosine / Q000031:analogs & derivatives / Q000737:chemistry; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D006657:Histones / Q000378:metabolism; D006873:Hydroquinones / Q000494:pharmacology*; D051379:Mice; D009153:Mutagens; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D009368:Neoplasm Transplantation; D018384:Oxidative Stress; D011230:Precancerous Conditions / Q000378:metabolism; D000099170:Bis(5'-adenosyl)triphosphatase
D000111:Acetylcysteine; D017766:Acid Anhydride Hydrolases; D006151:Guanosine; D006657:Histones; D006873:Hydroquinones; D009153:Mutagens; D009363:Neoplasm Proteins; D000099170:Bis(5'-adenosyl)triphosphatase; C046215:8-hydroxyguanosine; C031927:hydroquinone; C475961:gamma-H2AX protein, mouse