Common Gene Expression Signature of B-Cells of Waldenström Macroglobulinemia (WM) and IgM Monoclonal Gammopathies of Undetermined Significance (IgM MGUS) Compared to Healthy Subjects

We performed a comparative gene expression profiling (GEP) study on B-cells and plasma cells of Waldenström Macroglobulinemia (WM), IgM monoclonal gammopathies of undetermined significance (IgMMGUS), and normal individuals (CTRLs) to identify GEP changes as reliable predictors of progression of IgMMGUS to WM. We analyzed bone marrow B-cells and plasma cells from 36 WM patients, 13 IgMMGUS subjects, and 7 CTRLs by Affymetrix microarray, respectively (Table 1). GEP experiments were performed on the CD19+ and CD138+ cells using GeneChip-HGU133 Plus 2.0. Data were preprocessed and normalized by Robust Multi-Array Average and ComBat. Selection of the different expressed genes was performed separately for CD19+ and CD138+ cells, using Significance Analysis of Microarrays (SAM) on the 3 groups and a false discovery rate threshold of 5%, followed, for significance comparisons, by a pair-wise SAM test corrected for multiple testing. We focused on the comparison of the CD19+ cells of WM vs. IgMMGUS vs. CTRLs which highlighted 2038 unique genes whereas the same comparison of the CD138+ cells determined 29 unique genes (Trojani et.al. Cancers 2021). Among the 2038 DEGs, 115 genes were grouped in KEGG pathways involved in Wnt-signaling, BCR-signaling, calcium signaling, hematopoietic cell antigens, cell adhesion, adherens junctions, coagulation cascade, platelet activation, cytokine receptor, and signaling pathways responsible for cell cycle, apoptosis, and survival. Interestingly, most of the 115 DEGs in B-cells were different expressed in WM vs. IgMMGUS and CTRLs. Only 9/115 DEGs were significantly different expressed in WM vs. CTRLs and in IgMMGUS vs. CTRLs, but no significant expression changes were noted between WM and IgMMGUS (Table 2). To further inspect the similarities and the differences among WM and IgMMGUS, we computed the Euclidean pair-wise distance between subjects and, using this distance as weight, constructed a minimum spanning tree (MST) (Figure 1). Considerably, four probesets identified ADRB2 (transmembrane Beta adrenergic receptor) which was up regulated in WM and IgMMGUS compared to CTRLs. The over expression of ADRB2 was also demonstrated in Mantle Cell Lymphoma cell lines and in Diffuse large B-cell lymphoma (DLBCL) lymphocytes compared to normal B-cells (doi10.1016/j.cellsig.2017.08.002), and in most malignancies (doi10.1007/s11033-021-06250-y) . As far as we know, ADAM23 (ADAM Metallopeptidase Domain23) has not been found in WM, whereas we su