Immunomagnetic enrichment of CD138 positive cells from weakly infiltrated myeloma patients samples enables the determination of the tumor clone specific IgH rearrangement

In multiple myeloma, the polymerase chain reaction (PCR) of the Ig heavy ch ain with allele-specific oligonucleotide (ASO) primers is a common and well -described method of identifying the tumor clone in peripheral blood (PB), bone marrow (BM) or leukapheresis products (LA). A factor which is crucial to the detection of clonal Ig rearrangements lies in the 'purity' of the tu mor tissue used for the consensus PCR. We describe the application of a met hod to enrich CD138 positive myeloma cells derived from weakly infiltrated PB-, BM- and LA-samples. These are subjected to immunomagnetic enrichment w ith the MACS system, using an CD138 antibody directly conjugated to magneti c beads to obtain an enriched tumor cell population and the subsequent ampl ification of tumor specific IgH rearrangements. We investigated 29 samples (ten PB, ten BM, nine LA) with a median myeloma cell content of 0.5%. The a pproach led to a median enrichment factor of 118. Tumor-specific rearrangem ents could be amplified reproducibly from samples containing less than 0.1% myeloma cells.