Establishment of B-lymphoid cell lines retaining cytogenetic characteristics of Bloom syndrome

The present study describes the establishment of and chromosomal changes in B-lymphoid cell lines from cells of Bloom syndrome (BS) patients using Epstein-Barr virus (EBV). Even though PHA-stimulated BS lymphocytes from all five patients studied showed high levels of sister chromatid exchange (SCE), three EBV-transformed BS-B-lymphoid cell lines had normal levels of SCE and two yielded two types of cell populations, i.e., one with increased SCE and chromosome instability (including breaks and quadriradials) and another with normal levels of SCE and without structural aberrations. The karyotypic abnormalities, as observed in the BS lines have not been seen in the cells of any established normal B-lymphoid lines transformed by EBV and strongly suggest that the chromosome abnormalities in the BS--B-cell lines with abnormal karyotypes originated in vivo and not through an in vitro effect of EBV. Furthermore, in the EBV-transformed B-cell lines, we found quadriradial formation between sister chromosomes during endomitoses instead of between homologous chromosomes, strongly suggesting that quadriradial formation may be closely related to SCE. The coexistence in BS subjects of abnormal and normal populations of cells with respect to the number of SCE awaits explanation.