Different properties in lymphoblastoid cell lines from patients with Bloom syndrome

In 3 lymphoblastoid cell lines derived from 3 patients with Bloom syndrome (BS), the baseline frequency of sister chromatid exchanges (SCEs), chromosomal breakage, sensitivity to ethylmethane-sulfonate (EMS), and bromodeoxyuridine (BrdUrd) were examined. The SCE frequency of 2 BS lines (EB-BS-NoKi-2 and EB-BS-AkSak) was about 2 to 2.5 times those of the normal cell lines, while that of another BS line (EB-BS-2KA) was about 10 to 11 times. The net increase in the number of SCEs in EB-BS-NoKi-2 and EB-BS-AkSak lines induced by EMS was similar to that of normal cell lines, but it was high in the BS-2KA line. Sensitivity to BrdUrd was examined using SCE induction at different concentrations of BrdUrd and by cell cycle analysis. EB-BS-NoKi-2 and EB-BS-AkSak lines were no more sensitive than normal cell lines, while the EB-BS-2KA line was more sensitive than controls. High frequency of chromosomal breakage was found only in the EB-BS-2KA line. These results suggest that 2 types of cells exist in the B-lymphoblastoid cells of BS.