Molecular Analysis of the t(2;8)/MYC-IGK Translocation in High-Grade Lymphoma/Leukemia by Long-Distance Inverse PCR

Burkitt lymphoma and a subset of diffuse large B-cell lymphomas are characterized by chromosomal alterations affecting the MYC oncogene on 8q24. In most cases MYC is found juxtaposed to the immunoglobulin heavy chain (IGH) gene locus. Translocations to the immunoglobulin kappa (IGK) gene locus on 2p11 are observed in around 10% of cases. Little data exist on the molecular mechanisms leading to this aberration. The chromosomal breakpoints on chromosome 8 have been found dispersed over a large area 3’ of MYC. Currently, molecular cytogenetics (FISH) and cytogenetics are the methods of choice to detect the t(2;8) translocation and until now there exists no PCR method to reliably detect it.

In order to obtain a better understanding of this chromosomal translocation we developed a long-distance inverse (LDI) PCR method for the identification of chromosomal translocations affecting the IGK locus. The LDI PCR method takes advantage of the fact that the chromosomal breaks occur on chromosome 2 in the vicinity of the IGK joining segments. Using this method we investigated a number of cytogenetically mostly uncharacterized high-grade lymphoma samples.

A MYC-IGK juxtaposition was identified in 7 patients and three t(2;8)-positive cell lines. The chromosomal breakpoints were molecularly characterized and analyzed. The linear distance of the breakpoints on chromosome 8 to MYC ranged from some 100 bp to more than 0.5 MB. The breakpoints appeared to be clustered in distinctive regions, however, the number is still to small to draw definitive conclusions. The reciprocal translocated allele could be characterized in the majority of cases and putative break mechanisms are proposed. No larger sequence homologies were detected at the break sites. A minority of breaks were located near putative recombination signal sequences (RSS).

This study represents the largest series of t(2;8)-positive cases analyzed so far and the LDI PCR developed therein is the first universally applicable PCR-based method to detect this aberration. This LDI PCR should furthermore in general be useful for the molecular analysis of chromosomal translocations affecting the IGK locus. These aberrations have been detected in various lymphoma entities but are currently largely unexplored.

No relevant conflicts of interest to declare.