To better define the molecular basis of multiple myeloma (MM), we performed unsupervised hierarchic clustering of mRNA expression profiles in CD138-enriched plasma cells from 414 newly diagnosed patients who went on to receive high-dose therapy and tandem stem cell transplants. Seven disease subtypes were validated that were strongly influenced by known genetic lesions, such as c-MAF-and MAFB-, CCND1-and CCND3-, and MMSET-activating translocations and hyperdiploidy. Indicative of the deregulation of common pathways by gene orthologs, common gene signatures were observed in cases with c-MAF and MAFB activation and CCND1 and CCND3 activation, the latter consisting of 2 subgroups, one characterized by expression of the early B-cell markers CD20 and PAX5. A low incidence of focal bone disease distinguished one and increased expression of proliferation-associated genes of another novel subgroup. Comprising varying fractions of each of the other 6 subgroups, the proliferation subgroup dominated at relapse, suggesting that this signature is linked to disease progression. Proliferation and MMSET-spike groups were characterized by significant overexpression of genes mapping to chromosome 1q, and both exhibited a poor prognosis relative to the other groups. A subset of cases with a predominating myeloid gene expression signature, excluded from the profiling analyses, had more favorable baseline characteristics and superior prognosis to those lacking this signature. IntroductionMultiple myeloma (MM) is a malignancy of antibody-secreting, terminally differentiated B cells that home to and expand in the bone marrow, with symptoms related to anemia, immunosuppression, bone destruction, and renal failure. 1,2 Bone lesions developing adjacent to plasma cell foci result from the activation of osteoclasts and inactivation of osteoblasts. [3][4][5] Many of the pathogenetic mechanisms of this clinically heterogeneous malignancy have been unraveled by application of molecular genetics. [6][7][8] While sharing most of the genetic lesions seen in MM, 9-11 monoclonal gammopathy of undetermined significance (MGUS) rarely progresses to overt MM. 12 The universal activation of 1 of the 3 cyclin D genes is consistent with this being an initiating event in MM. 13 Nonhyperdiploid MM, present in 40%, is characterized by transcriptional activation of CCND1, CCND3, MAF, MAFB, or FGFR3/MMSET genes (resulting from translocations involving the immunoglobulin heavy chain locus). 8 While hyperdiploidy and CCND1 activation confer a favorable prognosis, MAF, MAFB, or FGFR3/MMSET activation and deletion of chromosomes 13 and 17 are associated with poor prognosis. [14][15][16][17][18][19][20][21][22][23][24][25] Although high-dose therapy has markedly improved MM prognosis, 26-28 individual patients' survival remains variable 29,30 and cannot be accurately predicted with current prognostic models. 31,32 In lymphoma and leukemia, microarray profiling has helped establish clinically relevant disease subclassifications. [33][34][35][36][37][38][39][40][41...

The production of DKK1, an inhibitor of osteoblast differentiation, by myeloma cells is associated with the presence of lytic bone lesions in patients with multiple myeloma.

Mechanisms of constitutive NF-kappaB signaling in multiple myeloma are unknown. An inhibitor of IkappaB kinase beta (IKKbeta) targeting the classical NF-kappaB pathway was lethal to many myeloma cell lines. Several cell lines had elevated expression of NIK due to genomic alterations or protein stabilization, while others had inactivating mutations of TRAF3; both kinds of abnormality triggered the classical and alternative NF-kappaB pathways. A majority of primary myeloma patient samples and cell lines had elevated NF-kappaB target gene expression, often associated with genetic or epigenetic alteration of NIK, TRAF3, CYLD, BIRC2/BIRC3, CD40, NFKB1, or NFKB2. These data demonstrate that addiction to the NF-kappaB pathway is frequent in myeloma and suggest that IKKbeta inhibitors hold promise for the treatment of this disease.

To molecularly define high-risk disease, we performed microarray analysis on tumor cells from 532 newly diagnosed patients with multiple myeloma (MM) treated on 2 separate protocols. Using log-rank tests of expression quartiles, 70 genes, 30% mapping to chromosome 1 (P < .001), were linked to early disease-related death. Importantly, most up-regulated genes mapped to chromosome 1q, and downregulated genes mapped to chromosome 1p. The ratio of mean expression levels of up-regulated to down-regulated genes defined a high-risk score present in 13% of patients with shorter durations of complete remission, event-free survival, and overall survival (training set: hazard ratio [HR], 5.16; P < .001; test cohort: HR, 4.75; P < .001). The high-risk score also was an independent predictor of outcome endpoints in multivariate analysis (P < .001) that included the International Staging System and high-risk translocations. In a comparison of paired baseline and relapse samples, the high-risk score frequency rose to 76% at relapse and predicted short postrelapse survival (P < .05). Multivariate discriminant analysis revealed that a 17-gene subset could predict outcome as well as the 70-gene model. Our data suggest that altered transcriptional regulation of genes mapping to chromosome 1 may contribute to disease progression, and that expression profiling can be used to identify high-risk disease and guide therapeutic interventions. (Blood.

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