JAPANESE B-CELL CHRONIC LYMPHOCYTIC-LEUKEMIA - A CYTOGENETIC AND MOLECULAR BIOLOGICAL STUDY

Clinical, cytogenetic, and molecular genetic studies were performed to clarify the pathophysiology of Japanese B cell chronic lymphocytic le ukaemia (B-CLL), since the incidence of B-CLL in Japan is significantl y lower than in western countries. The clinical and laboratory feature s of 55 Japanese patients with B-CLL in this study did not differ from those of Americans or Europeans with B-CLL. In the chromosome analyse s, suitable metaphases with good band quality were obtained from 48 pa tients (87.2%), of whom 22 patients (45.8%) showed clonal chromosome a berrations and 14 (29.2%) had non-clonal aberrations. Trisomy 12 and a bnormalities of 14q and 13q were found in four (18.2%), two (9.1%) and six patients (27.2%), respectively. There were no particular chromoso me abnormalities or specific breakpoints in Japanese B-CLL. However, c omplex karyotype was found in higher incidence than in western countri es. In the Southern blot analyses, rearranged band patterns were obser ved in the major breakpoint region (mbr) of the bcl-2 gene in one case , in the 5'-breakpoint region (5'-bcl-2) in two, and bcl-3 in one. Of the two patients with 5'-bcl-2 rearrangements. one had a normal karyot ype and the other had t(2;18)(p12:q21). The incidence of rearrangement s of the bcl-1, bcl-2 and bcl-3 genes in Japanese B-CLL was similar to that in western countries. These findings suggest that the biological characteristics of B-CLL in Japan are almost the same as those in wes tern countries, although the incidence of B-CLL in Japan is quite diff erent; this may be related to racial differences, which seem to be an important factor in the development of B-CLL.