Twenty-two cases of fresh patient material and 3 malignant B-cell lines derived from various disease subtypes were studied by either Southern blot using the 3′ BCL9 probe X665 and/or the nonchimeric BCL9 YAC 882B3: cell lines were additionally studied by Northern blot. One case showed a der(14)t(1;14)(q21;q32) similar to that seen in CEMO-1: FISH with the BCL9 YAC showed a telomeric 1q21 breakpoint. Four cases showed an apparent variant translocation t(1;22)(q21;q11): direct involvement ofIGλ was shown in 2 cases by FISH using cosmids spanning the IGλ locus (I.W., unpublished observations). One of these cases exhibited a breakpoint within theBCL9 YAC, whereas the breakpoint was telomeric in 1 case and centromeric in another: the final case was untested due to insufficient material. One case with no cytogenetic abnormality of 1q21 and no abnormality of YAC 882B3 showed rearrangement with the probe X665 on southern blot (Fig 6): this was a case of mantle cell lymphoma. Also, 1 case with t(1;19)(q21;p13) showed amplification of the BCL9YAC. Otherwise, none of the other cases appeared to involve theBCL9 locus. These cases included 2 with t(1;3)(q21;q27) in which both breakpoints were telomeric of BCL9, 2 with t(1;12)(q21;q13) and 6 cases with dup(1)(q21qter) with a variable distal breakpoint cytogenetically: other partner chromosomes were unique. 1q21 breakpoints in these cases were heterogeneous, falling both centromeric and telomeric of the BCL9 gene.

Abbreviations: BCP-ALL, B-cell precursor ALL; FL, follicular lymphoma; MCL, mantle cell lymphoma; R, rearranged; G, germline; NT, not tested; ++, overexpression; −, no overexpression.