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Long-distance PCRを用いた、非ホジキンリンパ腫におけるBCL6/免疫グロブリン融合遺伝子の構造解析：赤坂浩司¹、赤坂尚司¹、大野仁嗣¹、内山　卓¹ (¹京大・医・血液病態学)

Refinement of the BCL6/immunoglobulin fusion genes in non-Hodgkin's lymphoma by long-distance polymerase chain reaction : Hiroshi AKASAKA¹, Takashi AKASAKA¹, Hitoshi OHNO¹, Takashi UCHIYAMA¹ (¹Dept. of Hematology/Oncology, Kyoto Univ.)

Genomic structures of 3q27 translocations involving one of the three immunoglobulin gene (IG) loci have been described. t(2;3)(p12;q27) and t(3;22)(q27;q11) result in head-to-head recombination of the BCL6 gene on 3q27 with the downstream sequences of the IGκ and IGλ light chain gene. In contrast, 5' sequences of the BCL6 (5'-BCL6) in t(3;14)(q27;q32) are linked to 3' regions of the IGH on the der(14) in the same transcriptional orientation. To detect these junctional sequences, we applied long-distance (LD-) PCR technique using BCL6/Cκ, BCL6/Cλ, and 5'-BCL6/CH primer combinations. Of a total of 61 cases with non-Hodgkin's lymphoma carrying rearrangement of the BCL6, 1 had a BCL6/IGκ, 5 had a BCL6/IGλ, 4 had a 5'-BCL6/Cμ and 8 had a 5'-BCL6/Cγ fusion sequence. The LD-PCR products, ranging from 4.1 to 17 kb in size, were cloned into plasmids and restriction analysis as well as nucleotide sequencing were performed. The results showed that breakpoints on IGs were distributed in Vκ, Vλ, Jλ, 5' of Eμ, Sμ and Sγ regions; no breakpoints within the JH were found. Thus, considering the hierarchical order of the IG recombination process, it is likely that 3q27 translocations occur in a stage of B-cell maturation where VDJ assembly in IGH has been completed. Breakpoints on BCL6 were within the major translocation cluster including the exon 1, and we identified a 160 bp narrow hyper-cluster region immediately 3' of the exon 1. There were no signal-like sequences which have been observed at other oncogene/IG junctions.