Multiple Myeloma - Rafael Fonseca

Program Project (PPG)

Monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) are pre-malignant stages of the plasma cell (PC) neoplasm multiple myeloma (MM). Multiple chromosomal and genetic abnormalities have been described in MGUS, SMM and MM, and are thought to be important for disease pathogenesis and progression. The systematic study of genetic aberrations of the clonal cells of the PC neoplasms is the most rational and promising way to search for key therapeutic targets. Because of the cytogenetic complexity of the PC neoplasms, the genetic makeup of this disease was believed to be largely chaotic with no discernible underlying order. The two most common abnormalities are translocations involving the immunoglobulin heavy chain locus (IgH) and aneuploidy, including monosomy of chromosome 13. We and others have recently found that specific cytogenetic abnormalities have specific association patterns in patients with MM allowing for the cytogenetic sub classification of the disease. For example there is a strong association between the lack of IgH translocations and a hyperdiploid karotype. This has allowed the paradigm change that states that MM is not one disease, but rather several, best discerned according to the underlying cytogenetic aberrations. Likewise we believe that similar association patterns are likely present in MGUS, but this stage of the disease has not yet been studied in this context. Despite these advances in knowledge of the genetics of MM, it remains unknown what abnormalities are primary and which ones are simply the consequences of underlying genomic instability. It is also unknown whether some individuals are at higher risk of acquiring the cytogenetic features capable of causing disease initiation. We thus question:

• Can we establish that IgH translocations are seminal events in the pathogenesis of some PC neoplasms?
• Can the study of MGUS and MM cytogenetics further elucidate pathogenic pathways for the disease?
• Can we better understand the transcriptional upregulation consequences of the IgH translocations?
• Do patients that develop MGUS and MM have an underlying susceptibility to acquire IgH translocations?

Specific Aim 1: “Validate the biologic importance of IgH translocations for the pathogenesis of some PC neoplasms.”

1. To further validate the seminal biologic importance of translocations in the pathogenesis of some PC neoplasms we propose to
   • Determine the actual proportion of PCs in MGUS that share a signature IgH translocation
     1. by cytoplasmic immunoglobulin restriction
     2. through the use of allele specific oligonucleotide (ASO) mRNA fluorescent in-situ (FISH) hybridization
   • Analyze the persistence, and potential expansion of PCs bearing IgH translocations in serial samples of patients with MGUS/MM and subclones of human MM cell lines.

Specific Aim 2: “Determine whether there are genetic subcategories of MGUS, i.e., hyperdiploid-not translocated and non-hyperdiploid/translocated MGUS.”

2. To explore the cytogenetic sub-classification of MGUS into hyperdiploid (with low prevalence of primary IgH translocations) and non-hyperdiploid (primary translocations nearly universal) subtypes, as has been recently shown in MM
   • By performing supervised clustering analysis of the gene expression profiles of MGUS and MM according to the following cytogenetic categories: primary IgH Translocations, secondary IgH translocations, and no IgH translocations

Specific Aim 3: “Determine baseline propensity for IgH translocations of patients with MGUS and MM.”

3. To use surrogate markers of DNA repair problems in patients at risk for MGUS and MM
   • By determination of peripheral blood copy number of IgH/bci-2 transcripts.