Chromosome aberrations acquired in vitro by human B-cell lines. II. Distribution of break points

Among 165 human B-cell lines examined, 57 were found to have karyotypic abnormalities that involved chromosome breakage. The sites of breakage were identified with quinacrine-, Giemsa-, and reverse-banding techniques, and the distribution of 239 break points was plotted. A pronounced excess of telomeric and, to a lesser extent, centromeric breaks was observed. Chromosomes No. 7, 8, 9, 11, and 14 were involved in structural rearrangements more often and chromosomes No. 2, 5, 10, 20, and X less often than was predicted on the basis of their relative lengths. Lines derived from patients with different categories of disorders varied in the distribution of break points throughout the karyotype. In this sample of cell lines, No. 8q; 14q translocations were found only in cultures derived from patients with Burkitt's lymphoma and were never observed to arise among other Epstein-Barr virus-carrying lines even after several hundred cell generations in vitro. An additional feature, which was evidently restricted to lines derived from leukemia or lymphoma patients, was the presence of interstitial insertion, deletion, or reduplication, particularly involving the long arm of chromosome No. 1.