Detection of recombinations between c-myc and immunoglobulin switch a in murine plasma cell tumors and preneoplastic lesions by polymerase chain reaction

Abstract

Virtually all murine plasmacytomas carry chromosomal translocations that activate c-myc. The predominant (≈90%) c-myc-activating chromosomal translocation in pristane (2,6,10,14-tetramethylpentadecane)-induced plasmacytomas in BALB/c mice is a reciprocal translocation t(12;15) in which an immunoglobulin heavy-chain switch sequence is joined to the 5′ region of c-myc. The most common switch region involved is Sα. We developed a direct PCR method to screen for recombinations between c-myc and Sα. The critical step in establishing the method was the cloning and sequencing of the 5′ flank of Cα, a region with a reduced number of switch repeats that is much more favorable for designing specific PCR primers than the highly repetitive Sα region. In applying this PCR method, we detected translocation-specific junction fragments in transplanted (10/16, 63%) and primary (5/15, 33%) plasmacytomas. Moreover, the sensitivity of a nested version of that technique allowed us to discern rare t(12;15)s in BALB/c mice in the preneoplastic stage of plasmacytomagenesis (8/20 mice, 40%) as early as 30 days after administration of pristane. We conclude that t(12;15) is the probable primary, if not initiating, oncogenic step in plasmacytomagenesis.