Molecular and Transcriptional Characterization of the Novel 17p11.2-p12 Chromosome Amplification in Multiple Myeloma.

Multiple myeloma (MM) is a fatal malignancy of clonal bone marrow plasma cells characterized by a high genomic instability increasing with disease progression. We describe here a genomic amplification at 17p11.2–p12, an unstable chromosomal region characterized by a large number of low copy repeats which have been proven to mediate deletion and duplication in several genomic disorders and amplifications in solid tumors. An approximately 5 Mb 17p11.2–p12 amplified region was detected in KMS-26 myeloma cell line by SNP microarray analysis. Further FISH mapping showed two unidentified amplified chromosomes as well as a complex pattern of rearranged chromosomes 17. The analysis of transcriptional profiles in a proprietary data base of myeloma cell lines, identified 12 significantly overexpressed genes in KMS–26 amplified region, including TNFRSF13B/TACI, COPS3, and NCOR1. The evaluation of their expression levels in a data base including 11 monoclonal gammopathy of uncertain significance, 121 MM and 9 plasma cell leukaemia, showed a significant overexpression of at least one gene in 13 patients. FISH analyses of these patients identified one MM carrying a 3.8 Mb amplified region and two MMs with gains specifically involving the TACI locus. Interestingly, the complete inactivation of TP53 at 17p13.1 was found in KMS–26 whereas a monoallelic loss was identifiable in two of the three patients carrying gain/amplification. Our data suggest that, as in the case of solid tumors, amplification/gain of the 17p11.2–p12 in MM could be mediated by the presence of repeats located in this region and may provide insights for defining novel candidate myeloma-associated genes.