Kappa deleting element as an alternative molecular target for minimal residual disease assessment by real-time quantitative PCR in patients with multiple myeloma.

Eur J Haematol 2012 Oct 25;89(4):328-35. Epub 2012 Aug 25.

Department of Hematology, University Hospital of Salamanca, Paseo de San Vicente, Salamanca, Spain.

Background And Objectives: Minimal residual disease (MRD) assessment by PCR in multiple myeloma (MM) has several shortcomings, including the lack of a suitable target. Kappa deleting element (KDE) rearrangements occur in virtually all Ig-lambda B-cell malignancies and in 1/3 of Ig-kappa are not affected by somatic hypermutation and, as in ALL, could be used as PCR targets.

Methods: We have first investigated the incidence, gene segment usage, and CDR3 composition of IGK-KDE rearrangements in 96 untreated myeloma patients. Second, we tested 16 KDE gene rearrangements as molecular targets for MRD assessment by RQ-PCR using a germline reverse primer and a germline Taqman probe in combination with allele-specific oligonucleotides (ASO) as forward primers.

Results: Monoclonal KDE rearrangements were amplified in 45% (43/96) of cases, monoallelic in 2/3 of them (29 cases), and biallellic in the remaining 14 cases. Overall, 88% of cases were successfully sequenced, KDE being equally frequently rearranged with VK and with intron-Recombination signal sequence (RSS). Median numbers of inserted and deleted nucleotides in the junctional region were one and five, respectively.

Conclusions: Using KDE rearrangements as additional PCR target for MRD assessment in MM improves the applicability of these studies in 9% of cases overall and in 20% of lambda cases. Its use in the latter subset could represent a significant advance.

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http://dx.doi.org/10.1111/ejh.12000DOI Listing
October 2012
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