Abstract
The pathogenesis of multiple myeloma (MM) is thought to involve at least two pathways, which generate hyperdiploid (HRD) or nonhyperdiploid (NHRD) tumors, respectively. Apart from chromosome content, the two pathways are distinguished by five primary immunoglobulin heavy chain (IGH) rearrangements (4p16, FGFR3, and MMSET; 6p21, CCND3; 11q13, CCND1; 16q23, MAF; 20q12, MAFB) that are present mainly in NHRD tumors. To determine the prevalence and structures of IGH, immunoglobulin (IG) light chain, and MYC genomic rearrangements in MM, we have done comprehensive metaphase fluorescent in situ hybridization analyses on 48 advanced MM tumors and 47 MM cell lines. As expected, the prevalence of the five primary IGH rearrangements was nearly 70% in NHRD tumors, but only 12% in HRD tumors. However, IGH rearrangements not involving one of the five primary partners, and IG light chain rearrangements, have a similar prevalence in HRD and NHRD tumors. In addition, MYC rearrangements, which are thought to be late progression events that sometimes do not involve an IG heavy or light chain locus, also have a similar prevalence in HRD and NHRD tumors. In contrast to the primary IGH rearrangements, which usually are simple balanced translocations, these other IG rearrangements usually have complex structures, as previously described for MYC rearrangements in MM. We conclude that IG light chain and MYC rearrangements, as well as secondary IGH rearrangements, make similar contributions to the progression of both HRD and NHRD MM tumors.