Defective repair of DNA double-strand breaks and chromosome damage in fibroblasts from a radiosensitive leukemia patient.

A radiation-sensitive fibroblast culture (180BR) established from an acute lymphoblastic leukemia patient who died following radiotherapy is defective in the repair of radiation-induced DNA double-strand breaks. The cells also show a reduced capacity to repair interphase chromosome damage visualized by means of premature chromosome condensation and metaphase chromosome aberrations measured by fluorescence in situ hybridization on chromosome 4. This case represents the first example in humans where hypersensitivity to ionizing radiation can be ascribed directly to a defect in DNA and chromosome repair, and the defect may underlie the cancerous phenotype observed.