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Genomic characterisation of MGUS

ABSTRACT: he hematological malignancy multiple myeloma (MM), also called KahlerÃ¢Â€Â™s disease or plasma cell (PC) myeloma, is characterized by a clonal expansion of PCs originating in the bone marrow (BM). The expansion of these cells leads to an overproduction of antibodies and results in typical symptoms such as anemia, renal failure and bone lesions. All cases of MM are preceded by the asymptomatic, non-malignant pre-stage monoclonal gammopathy of undetermined significance (MGUS). Of all MGUS patients, only 1% per year will progress to MM. Despite efforts to elucidate the molecular mechanisms underlying the MGUS-to-MM progression, its pathogenesis still remains largely unknown. Additionally, the genetic profiles of MGUS patients have only been limitedly investigated due to the only incidental finding of MGUS, the difficulties in BM sampling and isolating a sufficient number of aberrant PCs from the BM aspirates of MGUS patients. Consequently, reliable biomarkers to individually predict which MGUS patients will progress to MM and which will not, are lacking. Therefore, it is highly required to study the molecular pathogenesis of MGUS and the role of genetic events in relation to the malignant transformation to MM.

PROVIDER: EGAS00001004124 | EGA |

REPOSITORIES: EGA

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Project description:Smoldering myeloma (SMM) is a pre-malignant monoclonal gammopathy with a 10% annual risk to progress to active multiple myeloma (MM). SMM diagnostic criteria, as well of those of others monoclonal gammopathies, have been updated by the International Myeloma Working Group (IMWG) in 2014. In particular, the previously defined “ultra high-risk” SMM (characterized by the presence of specific biomarkers associated with a ≥ 80% risk of progression to symptomatic MM within 2 years) has been included among patients with active MM. SMM is biologically heterogeneous, including a subset of patients with biological pre-malignancy and a subset with biological malignancy who have not yet developed organ damage, defined as onset of the classical CRAB criteria or Myeloma Defining Events (MDE). Thus, SMM encompassed patients with a very low rate of progression to symptomatic MM, similar to patients with monoclonal gammopathy of uncertain significance (MGUS), as well as patients who acquired organ damage and progress to active MM within the first year from diagnosis. The molecular mechanisms involved in the SMM to MM progression are still far to be fully understood. Genomic studies indicate that the genetic alterations that characterize MM patients are already present in SMM ones, who present similar mutational and copy number alteration load. However, few data are available on the transcriptional profiles of SMM patients in relationship to the progression to active MM, overall indicating minimal differential expression either in coding or non-coding RNA fraction. To date, robust data are still lacking which describe the transcriptional profiles of plasma cells (PCs) from paired samples obtained at the time of SMM and at MM onset. Herein, we compared the transcriptome of purified CD138+ PCs from paired samples of SMM patients progressed to active MM (P-SMM), aimed at describing any possible common transcriptional discrepancy that may help to understand the intra-patient disease evolution; at the same time, we investigated the transcriptional differences between P-SMM and a subset of non-progressed SMM (NP-SMM) at a minimum of 36 months.

Project description:Multiple myeloma (MM) is a malignant disorder characterized by the clonal proliferation of plasma cells (PCs) in the bone marrow (BM). The genetic background and clinical course of the disease are largely heterogeneous, and MM pathophysiology ranges from the premalignant condition of monoclonal gammopathy of undetermined significance (MGUS) to smoldering MM, symptomatic MM, and extramedullary MM/plasma cell leukemia (PCL). Recent genome-wide sequencing efforts have provided the rationale for molecularly aimed treatment approaches, identifying mutations that can be specifically targeted, such as those in the mitogen-activated protein kinase (MAPK) pathway, which represent the most prevalent mutations in MM. Among these, mutations affecting BRAF gene, detected in 4-15% of patients, are of potential immediate clinical relevance due to the availability of effective inhibitors of this serine-threonine kinase which are in fact being explored also in myeloma. In this study, we screened by next generation sequencing (NGS) a large and representative series of intramedullary and extramedullary MM patients, including primary and secondary plasma cell leukemia (pPCL and sPCL, respectively), for mutations in BRAF, NRAS and KRAS genes. We evaluated the relationship of identified variants with other clinical and biological features and determined the transcriptional signature associated with MAPK pathway activation in MM. To identify transcriptomic profiles possibly related to BRAF, NRAS and KRAS mutations found in our study, we investigated by Affymetrix microarray technology a large fraction (n=142) of the samples analyzed by NGS, including wild-type patients for all the three genes and cases carrying mutations in at least one of them. Assuming that alterations present in a very limited number of malignant PCs might not appreciably affect gene expression, we chose to arbitrarily establish 20% as the lower variant allele frequency cut-off to perform supervised analyses.

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Genomic characterisation of MGUS

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