Two human B-cell lines carrying a 14;18 chromosome translocation [t(14;18)(q32;q21)], designated FL-218 and FL-318, were established from effusion cells of two Japanese patients manifesting the transformed histology of follicular lymphoma. The FL-218 and FL-318 cell lines were composed of cells in the hyperdiploid range, which had two and three or four 18q- chromosomes, respectively. These 18q- chromosomes were not distinguishable from an 18q- chromosome derived from t(14;18) since they exhibited the same banding pattern. Southern blot analysis revealed that in both cell lines, breakage of the bcl-2 gene occurred within the major breakpoint cluster region and the truncated gene juxtaposed to an immunoglobulin heavy chain gene locus. The autoradiographic intensity of the retained fragment each on 18q- chromosome was more enhanced than that of the translocated fragment on 14q+ chromosome. These findings suggest that the extra 18q- chromosome found in t(14;18)-positive cancer does not arise from de novo independent t(14;18) but from duplication of a preexisting 18q- chromosome.

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This work was supported by Grants-in-Aid from the Ministry of Education, Science, and Culture (63570572) and from the Ministry of Health and Welfare of Japan (61-2).

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