Translocation of bcl-2 gene in non-Hodgkin's lymphomas in Hong Kong Chinese.

The close association between translocation of the proto-oncogene bcl-2 and follicular lymphomas has been well established in Caucasian patients and the de-regulation of bcl-2 has been implicated in follicular lymphomagenesis. Similar molecular structural alterations have also been detected in diffuse lymphomas with a previous history of a follicular pattern as well as in a smaller proportion of de novo diffuse lymphomas. There is a lower incidence of follicular lymphomas in Chinese. In order to investigate further this phenomenon, we used bcl-2 translocation as a genetic marker of follicular lymphomas, to study 31 cases of B cell non-Hodgkin's lymphomas in Chinese patients by Southern blot analysis. Eight out of 16 cases of follicular lymphomas showed bcl-2 translocation with involvement of the major breakpoint region (MBR). Six of these cases utilized breakpoints within the 4.3 kb HindIII fragment, while in two cases the breakpoints were more dispersed, but still within the BamHI fragment. An additional case of follicular lymphoma showed translocation of bcl-2 gene with involvement of the minor cluster region (mcr), making a total of nine out of 16. None of the 15 cases of diffuse lymphomas showed similar molecular structural alterations. These data show that bcl-2 translocation is present in 57% of follicular lymphomas in Chinese patients, and support the notion that bcl-2 translocation is a consistent marker for follicular lymphomas irrespective of ethnic differences. As the translocation is not detected in the diffuse lymphomas, there is no evidence to suggest that the low incidence of follicular lymphomas in Chinese patients is due to a greater tendency for follicular tumours to progress rapidly and present as diffuse lymphomas.