Defective DNA repair replication in xeroderma pigmentosum fibroblasts and DNA repair of somatic cell hybrids after UV irradiation.

Primary fibroblast cultures were obtained from 9 patients with xeroderma pigmentosum of various clinical types. Repair replication of the UV-damaged DNA in fibroblasts was studied by means of 3H-thymidine labeling and radioautography. A DNA repair replication was found to be decreased in all xeroderma pigmentosum fibroblasts as compared with the control cells obtained from normal donors. The repair activities in cells from patients ranged from nearly 0% in two infant cases and one case of De Sanctis-Cacchione syndrome to approximately 100% in adult moderate case. There was, however, no correlation between the level of repair replication and the severity of clinical symptoms. Since two cases which showed a lack of repair DNA replication were infant, it is assumed that these cases may develop De Sanctis-Cacchione syndrome in future. On xeroderma pigmentosum cells, a genetic analysis was performed with cell fusion methods using irradiated HVJ virus in order to determine the type of the complementation group. XP-1, XP-4 and XP-9 may be classified into the group D; XP-2, XP-7 and XP-8 into the group A; and XP-5 into the group E.