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Somatic mutation spectrum in monoclonal gammopathy of undetermined significance indicates a simpler genomic landscape compared to multiple myeloma

ABSTRACT: Monoclonal gammopathy of undetermined significance (MGUS) is a premalignant precursor of multiple myeloma (MM) with a 1% risk of progression per year. Although targeted analyses have shown the presence of specific genetic abnormalities such as IGH translocations, RB1 deletion, 1q gain, hyperdiploidy or RAS genes mutations, little is known about the molecular mechanism of malignant transformation. We have performed whole-exome sequencing together with CGH+SNP array analysis in 33 flow-cytometry separated abnormal plasma cell samples from MGUS patients to describe somatic gene mutations and chromosome changes at the genome-wide level. Non-synonymous mutations and copy-number alterations were present in 97.0% and in 60.6% of cases, respectively. Importantly, the number of somatic mutations was significantly lower in MGUS compared to MM (p<10-4) and we have identified six genes that are significantly mutated in MM (KRAS, NRAS, DIS3, HIST1H1E, EGR1 and LTB) in the MGUS dataset. We also found a positive correlation with increasing chromosome changes and somatic mutations. IGH translocations were present in 27.3% of cases comprising t(4;14), t(11;14), t(14;16) or t(14;20) and were in a similar frequency to MM, which corresponded with the primary lesion hypothesis. Data from this study showed MGUS is a genetically comprehensive disease, however, overall genetic instability is significantly lower compared to MM.

ORGANISM(S): Homo sapiens

PROVIDER: GSE77979 | GEO | 2016/02/18

SECONDARY ACCESSION(S): PRJNA312372

REPOSITORIES: GEO

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Project description:Fibroblasts are a key cellular component of tumour microenvironment, along with other stromal cells playing a critical role in disease initiation and progression (1). In this study, bone marrow fibroblasts deriving from patients with monoclonal gammopathy of undetermined significance (MGUS) or active multiple myeloma (MM) were subjected to global gene expression analysis, in order to identify progression-associated alterations of gene expression. Through immunoselection procedures, primary coltures of bone marrow fibroblasts were established from bone marrow aspirate of 18 patients fullfilling the International Myeloma Working Group diagnostic criteria for MM (n=10) and MGUS (n=8). Differentially expressed genes were investigated through cDNA microarray (21,329 70-mer oligonucleotides; dual-label competitive hybridization), using the reference design as experimental protocol and t-test statistics for identifying differentially expressed genes. A number of genes functionally involved in survival, proliferation, motility, inflammation and angiogenesis were found to be up-regulated in bone marrow fibroblasts from MM patients with respect to MGUS patients. In parallel, several genes were down-regulated in MM fibroblasts. Overall, bone marrow fibroblasts from MM patients show a distinct gene expression pattern that differentiates them from bone marrow fibroblasts of MGUS. The observation of differentially expressed genes indicates an activation state of fibroblasts in MM, which very likely concur to determine a microenvironment supporting disease progression. 1) 1. Kalluri R, Zeisberg M: Fibroblasts in cancer. Nat Rev Cancer 2006; 6: 392 â401. Bone marrow fibroblasts deriving from patients with monoclonal gammopathy of undetermined significance (MGUS) and active multiple myeloma (MM), were provided by A.Vacca, (Department of Biomedical Sciences and Human Oncology, UniversitÃ degli Studi di Bari Aldo Moro, Italy). Briefly, primary coltures of bone marrow fibroblasts were established through immunoselection procedures on aspirates of 18 patients fullfilling the IMWG diagnostic criteria for active MM (n=10) and MGUS (n=8). Total RNA was extracted from each primary culture (test samples), and 1 Î¼g-aliquots of RNA from MGUS samples were pooled to obtain the reference RNA. Linear amplification of mRNA and fluorescent labelling of cDNA targets (Cy5, MM and MGUS test samples; Cy3, reference RNA) were performed by using the Amino Allyl MessageAmp II aRNA Amplification Kit (Ambion), and examined on Micro-CRIBI Human Oligo Array (Operon V2.0) microarrays. Array scanning was carried out using a VersArray ChipReaderÂ® 5Î¼m dual confocal laser scanner with VersArray ChipReader v3.1 analysis software , while row scanner images were analyzed with VersArray Analyzer Software v4.5 (Bio-Rad Laboratories) using media pixel intensities for each spot. Global background was subtracted by biquadratic polynomial approximation, and cross-channel normalization was performed by local regression (LOESS); logarithmic transformation was then performed for each expression level.

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Somatic mutation spectrum in monoclonal gammopathy of undetermined significance indicates a simpler genomic landscape compared to multiple myeloma

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