Cell cycle defect in connection with oxygen and iron sensitivity in Fanconi anemia lymphoblastoid cells

Fanconi anemia (FA) is an autosomal recessive disorder involving progressive pancytopenia, skeletal malformations, and a predisposition to leukemia. The in vitro growth of FA fibroblasts is impaired, due to a defective G2 phase traverse of the cell cycle. Analyzing the cell cycle of lymphoid cell lines (LCLs) obtained from peripheral blood of FA patients by transformation with Epstein-Barr virus, we found a similar G2 phase defect, which was dependent upon the oxygen concentration. In addition, FA cells exhibited hypersensitivity toward cis-dichlorodiammineplatinum and mitomycin C, and moderate sensitivity toward trans-dichlorodiammineplatinum. FA cells, however, showed no elevated sensitivity toward paraquat, an intracellular generator of superoxide radicals, or cumene hydroperoxide, a model organic peroxide. Chelating iron with low concentrations of o-phenanthrolin improved cell proliferation and G2 phase transit of FA cells at 20% oxygen, but little at 5% oxygen. LCL cultures from healthy subjects were inhibited in their proliferation rate at all concentrations of o-phenanthrolin. Exposure to excess iron, on the other hand, was very toxic to FA cells at 20%, but less toxic at 5% oxygen. In conclusion, the FA mutation leads to a cell cycle defect, which is expressed in cultures of lymphoid cells from FA patients, and involves hypersensitivity toward bifunctional alkylating agents, oxygen, and iron.