Copy number analysis of plasma cells from AL amyloidosis patients

Immunoglobulin light chain (AL) amyloidosis is characterized by deposition of abnormal amyloid fibrils in multiple organs impairing their function. CD138-purified plasma cells producing these fibrils are investigated regarding chromosomal alterations by interphase fluorescence in situ hybridization (iFISH) using a multiple myeloma specific probe set for the IgH translocations as well as recurrent numerical aberrations. Aberrations genuine to AL amyloidosis cannot be detected due to the inherent limitation of this probe panel to known loci. We analyzed 118 AL amyloidosis patients by high-density copy number array to quantitatively detect genome-wide chromosomal imbalances. Most prevalent gains affected chromosomes 1q (37%), 9 (24%), 11q (24%), and 19 (16%). The most frequent deletion was monosomy 13 (28%) followed by partial deletions on 14q (21%), 16q (14%), and 13q (12%). The results were analyzed with respect to cytogenetic subgroups. In 88% of patients with translocation t(11;14) and concomitant gain of 11q22.3/11q23 detected by iFISH, the latter aberration was not due to trisomy of chromosome 11 but part of the unbalanced translocation der(14)t(11;14)(q13;q32) with breakpoint in the CCND1/MYEOV gene region. Partial loss of chromosomes 14q and 16q were significantly associated to patients with gain 1q. Our iFISH probe set is highly concordant with copy number results as it detects the most common cytogenetic aberrations present in AL amyloidosis. Beyond that, the probe panel is also the method of choice to detect translocations involving the IgH locus. In contrast to the results of our iFISH panel the frequency of hyperdiploidy detected by copy number array analysis is higher. Affymetrix CytoScanHD arrays were performed according to the manufacturer's directions on DNA extracted from FACS sorted CD138+ plasma cells from. 118 AL samples. Analyzed with ChAS 2.0 software using manufacturer's reference.