Loss of repairability of DNA interstrand crosslinks in Fanconi's anemia cells with culture age.

Some published reports have suggested a possible repair deficiency for DNA interstrand crosslinks in cells derived from patients with Fanconi's anemia (F.A.), that others, using different F.A. cell lines, were unable to confirm. A reinvestigation of the cell lines used in the original report might resolve this controversy. The purpose of this study, then, was to compare 2 F.A. fibroblast cell lines, FA9 and FA18 (previously reported to be repair-deficient), with a normal human line, Detroit 550, in their ability to repair nitrogen mustard (NM)- and mitomycin C (MMC)-induced crosslinks. The alkaline elution technique was used in the analysis of repairability. Prelabeled cells in quiescent phase were treated with NM or MMC for 1 h and crosslinks were assayed immediately after treatment and at 24 h after drug removal. Early passage F.A. cells repaired crosslinks to the same extent as normal, early passage cells. However, with increasing passage number, the F.A. cells demonstrated a corresponding decrease in their ability to repair NM-induced crosslinks. In contrast, the normal cells did not show any age-related decrease in their ability to repair NM-induced crosslinks. Approximately equivalent repair rates were observed in quiescent 550 and F.A. fibroblasts after MMC treatment. Exponential and quiescent Detroit 550 cell populations showed no difference in the repair rate of MMC-induced crosslinks. These results indicate that F.A. cells can repair crosslinks early in cell culture but this ability is nearly eliminated with increasing passage.