Neutralization Of Vascular Endothelial Growth Factor-A Induced CD138-Expression In Bone Marrow Cells From Multiple Myeloma Patients

We previously reported that when adult human dermal fibroblasts were cultured with interleukin (IL)-1-b, vascular endothelial growth factor (VEGF)-A was produced significantly (54^th ASH). And, when antihuman VEGF-A neutralizing antibody (VEGF-A Ab) was added to the cultures, CD138 (Syndecan-1) expressed significantly. CD138 is a member of cell-surface transmembrane haparan sulfate proteoglycans, and expresses in plasma cells from multiple myeloma (MM) cases. Membrane-anchoring CD138 shows a better prognosis in an immunodeficiency murine transplantation model in vivo; however, when extra-domain of CD138 is digested by heparanase to be shed from the cell-surface, MM cells invade to various kinds of tissues, and the patients show poor prognosis.

To validate a biological implication of inhibition of VEGF-A-signaling in MM cells, we observed effects of VEGF-A Ab to bone marrow cells from MM patients. Cell-proliferations as well as morphological changes were also observed time-dependently.

Institutional ethical committee approved our study, and bone marrow cells were obtained from the informed MM patients as well as normal individuals. Cells were separated with gravity-sedimentation method, and the prepared mononuclear cells were cultured with or without VEGF-A Ab, and the expression of specific genes was analyzed.

Twenty MM patients were eligible, in which three showed significant poor prognosis, and worsened after underwent intensive chemotherapy or allogeneic hematopoietic stem cells transplantation. Thirteen out of twenty expressed CD138, and when cells were cultured with VEGF-A Ab for four days, CD138-expression increased significantly in all cases. Four did not express CD138; however, CD138-expression was observed after 4 day’s culture with VEGF-A Ab. In three progressed cases CD138-expression decreased in accordance with the disease-progression; however, when VEGF-A Ab was added to the cell-cultures, CD138 was induced to express. Heparanase-expression was observed in 10 cases out of 20, which were down-regulated when VEGF-A Ab was added to the cultures. In contrast, in bone marrow cells from seven normal individuals CD138-expression was very low, which was down-regulated with the addition of VEGF-A Ab. Heparanase-expression was not observed in these normal cells, and were induced to be observed in four out of seven when VEGF-A Ab was added to the cultures.

Expression of CD138 is induced in fibroblast by the addition of fibroblast growth factor-2, and in keratinocytes by epidermal growth factor and keratinocyte growth factor; however, an induction of CD138 by the VEGF-A Ab has not been reported. Several cytokines including VEGF-A influence plasma cell-proliferation; however, little is reported on cytokine-suppression therapy. Inhibition of the signaling of VEGF receptors by the chemicals including solafenib is not specific for VEGF-A. Currently we validate the efficacy of the inhibition of VEGF-A-signaling to MM cells and their environmental cells using RNA interference.

No relevant conflicts of interest to declare.