Isolation and characterisation of recombination events involving immunoglobulin heavy chain switch regions in multiple myeloma using long distance vectorette PCR (LDV-PCR)

Immunoglobulin class switching occurs as a result of recombination between pairs of switch region sequences located 5' to each constant heavy chain ge ne except C delta. In the B cell neoplasm multiple myeloma, tumour cells ha ve generally undergone class switching and often contain oncogenic sequence s translocated into switch regions, presumably as a result of aberrant swit ch recombination. We have developed a method (LDV-PCR) which combines long distance PCR with one-sided vectorette PCR that is capable of detecting and isolating both normal and aberrant switch recombination breakpoints from m ultiple myeloma cell lines and primary multiple myeloma tumour material. Us ing LDV-PCR we have directly cloned the translocation breakpoints present i n two multiple myeloma cell lines and isolated a normal productive switch r ecombination event from a primary tumour: Furthermore, we have isolated a n ovel translocation t(14;22)(q32;q12) from a primary tumour sample and have demonstrated that internal deletions within switch regions can occur In mul tiple myeloma cells. Compared to a Southern blotting approach, LDV-PCR is s impler and more rapid to perform, allows the simultaneous detection and iso lation of recombination events, and can also be applied to amounts of DNA w hich are too low to permit the conventional cloning of recombination breakp oints.