Cyclin D1 overexpression is not a specific grouping marker, but may collaborate with CDC37 in myeloma cells.

Cyclin D1 is a positive-regulator of the cell cycle and is overexpressed in myeloma cells with t(11;14)(q13;q32). First, we analyzed whether there was a correlation between cyclin D1 overexpression and the presence of Ki67-positive myeloma cells in multiple myeloma (MM). Cyclin D1 overexpression was examined by competitive RT-PCR. Then we found these two markers were present independently in a given case. FISH analysis revealed that cyclin D1 over-expression was caused by t(11;14)(q13;q32) or extra copies of B-cell leukemia/lymphoma-1 (BCL-1/CCND1), and unknown mechanism without them. We compared the gene expression between myeloma cells with cyclin D1 overexpression and those without it using cDNA microarray analysis. Analysis of the expression profiles showed that the significantly up-regulated genes included cyclin D1, cell division cycle 37 (CDC37) and B-cell leukemia/lymphoma-2 (BCL-2), while the down-regulated genes included cyclin D2 and CD9 antigen (p24) in MM cases with cyclin D1 overexpression. However, hierarchical clustering analysis of the data showed that myeloma cells of MM cases with cyclin D1 overexpression could not be distinguished clearly from those without it. Real-time RT-PCR showed that the expression of CDC37 gene was significantly up-regulated in MM patients with cyclin D1 overexpression compared with those without it (p=0.0418). However, there was no significant difference in BCL-2 gene (p=0.5748). These results suggested that MM cases with cyclin D1 overexpression do not constitute a specific group, and cyclin D1 overexpression may not be caused only by abnormality of the BCL-1/CCND1 gene. The CDC37 may collaborate with cyclin D1 in progression of MM.

Initial expression of interferon alpha receptor 2 (IFNAR2) on CD34-positive cells and its down-regulation correlate with clinical response to interferon therapy in chronic myelogenous leukemia.

In order to investigate the mechanism of interferon-alpha (IFNalpha) action in the treatment of chronic myelogenous leukemia (CML), we examined surface expressions of both type I interferon receptor 1 (IFNAR1) and 2 (IFNAR2) subunits on CD34-positive cells in bone marrow (BM) in a total of 57 CML patients. Initial cell-surface IFNAR2 expression at diagnosis assessed by flow cytometry widely distributed but showed overall significantly higher expression in CML patients when compared with normal controls. In 15 fresh patients who subsequently received IFNalpha therapy, IFNAR2 expression at diagnosis was significantly higher in cytogenetic good responders than in poor responders. Down-regulation of IFNAR2 expression during IFNalpha therapy was observed only in good responders but not in poor responders. In addition to protein level, both initial high IFNAR2c mRNA expression level and its down-regulation during IFNalpha therapy, in purified CD34-positive cells, were also observed only in good responders. In contrast to IFNAR2, cell-surface IFNAR1 expression was generally lower than IFNAR2, and correlation between either the pretreatment level or down-regulation of IFNAR1 and clinical response was not evident. With in vitro IFNalpha stimulation, CD34-positive cells showed down-regulations of cell-surface IFNAR2, and IFNAR1 to a lesser extent, in one good-responder patient, but not in one poor-responder patient. Serum soluble interferon receptor (sIFNR) was higher in untreated CML patients than in normal controls, without any correlation with clinical response to IFNalpha. Thus, the pretreatment protein and mRNA expression levels of IFNAR2 and their down-regulations during IFNalpha therapy correlate well with IFNalpha response in CML patients.

A possible role for the loss of CD27-CD70 interaction in myelomagenesis.

CD27 is a marker of memory B cells and its interaction with its ligand, CD70, is very important for differentiation into plasma cells. Although CD27 is detected on normal plasma cells, its expression is significantly reduced with the progression of multiple myeloma (MM), including monoclonal gammopathy of undetermined significance (MGUS). CD27+ myeloma cells are thought to represent an early phase of myeloma, as CD27+ plasma cells from MM patients were found to be composed of normal plasma cells (CD19+/CD38++) and myeloma cells (CD19-/CD38++), and monoclonality was detected in the CD27+/CD38++ fraction. Given that the lack of CD27 on plasma cells is related to myelomagenesis and that the pro-apoptotic protein Siva is thought to bind to the cytoplasmic tail of CD27, we analysed alterations of cell growth and genes caused by co-culturing CD27-transfected myeloma cell lines (U266, KMS-5) with CD70-transfected NIH3T3 cells. CD27-CD70 interaction could not induce apoptosis in either type of myeloma transfectant, and binding between Siva and CD27 was not detected. cDNA microarray (human apoptosis CHIP) analysis showed a significant upregulation of expression of the ectodermal neural cortex 1 (ENC1) gene by CD27-CD70 interaction compared with CD27 transfection alone. These findings show that the relationship between the loss of CD27 and oncogenesis of plasma cells is not simple. It remains unclear whether the lack of CD27 leads to evasion of apoptosis.