Abstract

Multiple myeloma (MM) is characterized by the accumulation within the bone marrow of malignant plasma cells with an enhanced survival capacity. Myeloma cells often develop drug resistance leading to treatment failure in patients. Survivin is a member of the inhibitor of apoptosis (IAP) gene family that has been implicated in both cell viability and regulation of mitosis in cancer cells. In this study, we have evaluated survivin expression and its biological involvement in viability, proliferation, cell cycle and drug resistance in myeloma cells. First by western blotting we detected survivin expression in 17 human myeloma cell lines (HMCL) from moderate level in the HMCL XG6 to strong level in the HMCL U266. Survivin was also detectable in primary myeloma cells purified from blood or bone marrow samples of 20 patients in contrast to purified B lymphocytes from tonsil samples or autologous EBV infected B lymphocytes. Survivin expression peaked at G2/M phase as obtained by drug-induced cell-cycle arrest. Second, we demonstrated that both major myeloma growth factors, IL-6 and IGF-1, induced upregulation of survivin expression through JAK/STAT and PI3K/AKT signalling pathways. In order to elucidate survivin role in myeloma cells, we established XG6 stable transfectants overexpressing survivin and extinguished survivin expression by siRNA in U266. Preliminary data suggest that survivin may participate in spontaneous cell death regulation, cell proliferation and drug sensitivity in those HMCL. In summary, our findings tend to show that survivin may be playing an important role in the pathogenesis of MM. A more defined understanding of survivin biology should enhance the rational development of drugs to inhibit its function in myeloma cells.

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