Immunoglobulin Variable Light Chain Restriction, Cytokine Expression and Plasma Cell-Stromal Cell Interactions in POEMS Syndrome Patients

POEMS syndrome is defined by the presence of peripheral neuropathy (P), organomegaly (O), endocrinopathy (E), monoclonal protein expression (M), and skin changes (S). In addition, patients also have sclerotic bone lesions, papilledema, extravascular volume overload, thrombocytosis, and restrictive lung disease/pulmonary hypertension. A striking but inexplicable feature of the clonal plasma cells in patients with POEMS is that they are virtually always lambda restricted. More surprising is that of the 81 functional immunoglobulin light-chain variable-region genes (IgVL) available in the plasma cell/B cell repertoire, among the 13 cases in which variable gene light chain usage has been reported, all have been either IgVL1-40 or IgVL1-44. The molecular mechanisms triggering the initiation and the progression of POEMS syndrome or the clonal expansion of plasma cells marking this condition remain unclear. We have analyzed the immunoglobulin heavy and light chains sequences in the plasma cells of POEMS patients at the Mayo Clinic Rochester. We found that in 8 out of the 9 patients tested, we could document heavy chain clonality in any given patient; however, no restriction of gene usage among patients was observed in the variable regions of these chains. In the case of light chains, in 14 out of 17 patients we could document not only clonality but also restriction of light chain variable gene usage to IgVL1-40 or IgVL1-44. Our goal is to understand the relevance of this restricted expression of light chain variable region, and its effect on the communication between plasma cells and the neighboring stromal cells that might provide more insight into the disease pathology. To this end, we are generating viral vector constructs that will harbor the germline or mutant versions of IgVλ1-40 and IgVλ1-44 genes and introduced into pre-established malignant plasma cell lines (i.e. myeloma cell lines). We will assay the effects of this over expression in terms of alterations in the expression of cytokines such as VEGF and TNF, and on plasma cell-stromal cell interaction (in a co-culture system). Results from these assays will be discussed.