Ken-ichiro Otsuyama

Complete Genome Sequence of NBRC 3288, a Unique Cellulose-Nonproducing Strain of Gluconacetobacter xylinus Isolated from Vinegar

Gluconacetobacter xylinus is involved in the industrial production of cellulose. We have determined the genome sequence of G. xylinus NBRC 3288, a cellulose-nonproducing strain. Comparative analysis of genomes of G. xylinus NBRC 3288 with those of the cellulose-producing strains clarified the genes important for cellulose production in Gluconacetobacter.

Accelerated proliferation of myeloma cells by interleukin-6 cooperating with fibroblast growth factor receptor 3-mediated signals.

Interleukin-6 (IL-6) is a cytokine that regulates the proliferation of some tumor cells including multiple myeloma (MM). Ectopic expression of fibroblast growth factor receptor 3 (FGFR3) associated with the chromosomal translocation, t(4;14)(p16.3;q32), is frequently found in MM, and therefore, has been implicated in the neoplastic transformation of this disease. Here, we show that IL-6 together with FGF enhanced proliferation of a myeloma cell line, KMS-11 carrying t(4;14)(p16.3;q32) and the FGFR3-transfected U266 myeloma cell line which ectopically expressed FGFR3 but responded to neither IL-6 nor FGF alone. In KMS-11, IL-6 activated signal transducer and activator of transcription 3 (STAT3) while FGF activated extracellular signal-regulated kinase 1/2 (ERK1/2) and phosphatidylinositol (PI)-3 kinase. As both MEK inhibitors and a PI 3-kinase inhibitor abolished the effect of IL-6 and FGF, the activation of both the ERK1/2 and PI 3-kinase signaling cascades is essential for the proliferation of KMS-11 enhanced by IL-6 and FGF. Furthermore, the FGF-induced activation of ERK1/2 contributed to the serine phosphorylation of STAT3, suggesting that the signaling crosstalk between the cytokine receptor, IL-6 receptor α/gp130 and the growth factor receptor tyrosine kinase, FGFR3. These results indicate that FGFR3 plays a crucial role in the accelerated proliferation of MM carrying t(4;14)(p16.3;q32).

Interleukin-6, CD45 and the Src-Kinases in Myeloma Cell Proliferation

Abstract Multiple myeloma (MM) is a proliferative disorder of monoclonal plasma cells which accumulate in human bone marrow, and myeloma cells proliferate in response to a cytokine, interleukin-6 (IL-6). We recently found that MPC-1−CD49e− immature myeloma cells expressing CD45 form a proliferating population in MM. IL-6 activates at least two intracellular pathways including signal transducer and activator of transcription 3 (STAT3) and extracellular signal-regulated kinase 1/2 (ERK1/2) following the activation of Janus kinases (JAKs) via its receptor complexes composed of the IL-6 receptor α chain and gp130. Although the roles of CD45 have been extensively studied for antigen receptors in B and T cells, its physiological consequences in other hematopoietic cells remain largely unknown. Myeloma cells expressing CD45 antigens which contain the activation of src family protein-tyrosine kinases (PTKs) independent of IL-6 stimulation proliferate in response to IL-6, whereas the proliferation of CD45 cells which lack a considerable activity of the src family PTKs is not promoted by IL-6. The STAT3 and ERK1/2 pathways are similarly activated by IL-6 in both cells either expressing or not expressing CD45. In this review, we argue a novel mechanism of proliferation of myeloma cells, in that the activation of both STAT3 and ERK1/2 is not sufficient for IL-6-induced proliferation which further requires IL-6-independent activation of the src family kinases associated with CD45 phosphatase. We propose that the cellular context, such as CD45 expression and src family kinase activation, is crucial for myeloma cells to proliferate in response to IL-6.

GROWTH MECHANISM OF HUMAN MYELOMA CELLS BY INTERLEUKIN-6

Human myeloma cells are heterogenous morphologically and phenotypically. Myeloma cells can be classified into at least 5 subpopulations; MPC-1-CD45+CD49e-, MPC-1-CD45-CD49e- immature myeloma cells, MPC-1+CD45-CD49e-, MPC-1+CD45+CD49e- intermediate myeloma cells and MPC-1+CD45+CD49e+ mature myeloma cells. Interleukin-6(IL-6) is a major growth factor for human myeloma cells, but only MPC-1-CD45+CD49e- immature myeloma cells can response directly to IL-6 to proliferate. In the U-266 cell lines, IL-6 can lead to the induction of CD45 expression and CD45+ U-266 cells can proliferate in response to IL-6. In primary myeloma cells, MPC-1-CD45-CD49e-immature myeloma cells sorted from bone marrow samples can be changed to CD45+ cells by addition of IL-6 in vitro. In both CD45- and CD45+ U-266 cells, STAT3 and MAPK(ERK1/2) can be activated in response to IL-6 equally between them, but src family kinases such as Lyn, Fyn can be activated only in CD45+ U-266 cells. Thus, the activation of the src family kinases associated with CD45 expression is a prerequisite for the proliferation of myeloma cells. In the bone marrow of myeloma patients, most myeloma cells do not express CD45, and CD45+ immature myeloma cells are only 1∼2%. In order to clarify the difference of cellular context between CD45- and CD45+ myeloma cells, PCR-based cDNA subtraction was performed from CD45+ U-266 cells to CD45-U-266 cells. The series of this subtraction selected several genes. Furthermore, sensitivity to stress stimuli between CD45+ and CD45- U-266 cells was also compared. CD45-U-266 cells were markedly more resistant to stress conditions such as serum-free condition. Therefore, we can speculate that in the bone marrow of human myelomas IL-6 can induce proliferation of CD45+ immature cells, but the amount of IL-6 is too low to support CD45+ myeloma cells and loss of CD45 results in no direct response to IL-6 to proliferate but confers resistance to stress condition leading to the longer survival at the limited amount of IL-6.

Increased susceptibility to apoptosis in CD45(+) myeloma cells accompanied by the increased expression of VDAC1.

Expression of CD45 is quite variable in human myeloma cells and cell lines, such as U266, and CD45+ U266 proliferates in response to a growth factor, interleukin-6. Here, we show that CD45+ myeloma cell lines were more sensitive to various apoptotic stimuli, such as oxidative stress and endoplasmic reticulum (ER)-stress, than CD45− cells. Reactive oxygen species and calcium ion seemed to be involved in the susceptibility to apoptosis of CD45+ U266. The activation of the src family kinases associated with CD45 phosphatase played an important role in the augmented apoptosis in CD45+ U266 by oxidative stress. These results indicate that the CD45-expression renders myeloma cells competent for not only mitogenic but also apoptotic stimuli, resulting in either proliferation or apoptosis of CD45+ myeloma cells dependently upon the circumstantial stimuli. Furthermore, voltage-dependent anion channel (VDAC) 1 was identified as a gene highly expressed in CD45+ U266 by cDNA subtraction. The increased expression of VDAC1 seemed to augment the sensitivity to the ER-stress because the VDAC1-transfected U266 was more susceptible to the thapsigargin-induced apoptosis. Thus, CD45 expression accompanied by the increased VDAC1 expression sensitizes myeloma cells to the various extracellular stimuli that trigger apoptosis via the mitochondrial pathways.

Galectin-1 supports the survival of CD45RA(-) primary myeloma cells in vitro.

The survival and proliferation of human myeloma cells are considered to be heavily dependent on the microenvironment of bone marrow (BM). This study confirmed that galectin‐1 (Gal‐1) and SDF‐1α were produced by bone marrow mononuclear cells of myeloma patients. The addition of Gal‐1 and SDF‐1α to a serum‐free synthetic medium, maintained the viability of primary myeloma cells for 2 weeks similar to that before culture. While Gal‐1 reduced the viable cell number in CD45RA(+) B cell lines, it maintained the viability of CD45(−) U266 and CD45RA(−)RO(+) ILKM3 myeloma cell lines in the synthetic medium. This was confirmed with the transfection of the PTPRC (CD45) RA, ‐RB, or ‐RO gene into CD45(−) U266 cells. The combination of Gal‐1 and SDF‐1α significantly induced phosphorylation of Akt and IkB, while the phosphorylation of ERK1/2 was significantly reduced in CD45RA(+) U266 and Raji cells but not CD45(−) or CD45RA(−) U266 cells. Furthermore, we confirmed that Gal‐1 bound to CD45RA in CD45RA(+) Raji cells, and also physically interacted with β1‐integrin by immunoprecipitation followed by Western blotting and confocal microscopy. The results suggest that Gal‐1 has two different actions depending on its binding partner, and supports the survival of CD45RA(−) myeloma cells.

Dehydroepiandrosterone can inhibit the proliferation of myeloma cells and the interleukin-6 production of bone marrow mononuclear cells from patients with myeloma.

The serum levels of an adrenal sex hormone, dehydroepiandrosterone sulfate (DHEA-S), are significantly more decreased in human myelomas compared with the reduction brought by physiologic decline with age. In order to clarify the effect of DHEA on myeloma cells, we investigated whether DHEA and DHEA-S could inhibit interleukin-6 (IL-6) production of bone marrow mononuclear cells and the proliferation of myeloma cells from patients with myeloma. DHEA-S and DHEA suppressed IL-6 production from a bone marrow stromal cell line, KM-102, as well as in bone marrow mononuclear cells from patients with myeloma. Furthermore, DHEA inhibited in vitro growth of the U-266 cell line and primary myeloma cells from the patients, as well as the in vivo growth of U-266 cells implanted i.p. in severe combined immunodeficiency-hIL6 transgenic mice. DHEA up-regulated the expression of peroxisome proliferator-activated receptor (PPAR), PPAR beta, but not PPARgamma or PPARalpha, and the expression of IkappaBalpha gene in myeloma cells and bone marrow stromal cells, which could explain the suppressive effect of DHEA on IL-6 production through the down-regulation of NF-kappaB activity. Therefore, these data revealed that DHEA-S, as well as DHEA, had a direct effect on myeloma and bone marrow stromal cells to inhibit their proliferation and IL-6 production, respectively.

Induction of Multilineage Markers in Human Myeloma Cells and Their Down-Regulation by Interleukin 6

Human primary myeloma cells are well known to be heterogeneous with regard to morphology and surface phenotype. We confirmed the heterogeneous expression of such multilineage markers as CD33, CD7, CD56, CD4, and CD86 in primary myeloma cells from 20 patients with multiple myeloma and in 8 human myeloma cell lines. CD33 expression in the Liu01 cell line, a subclone of U266 cells, and in vitamin D3-treated ILKM3 cells, correlated with a monocytoid morphology featuring convoluted nuclei and with increased C/EBPα expression. CD56+ myeloma cells from some myeloma patients and the CD56+ (but not the CD56-) myeloma cell lines expressed neuronal cell markers, such as neuron-specific enolase and β-tubulin III. CD7 expression in Liu01 cells and forskolin-stimulated U266 cells coincided with the presence of large cytoplasmic granules, and these cells featured increased expression of perforin messenger RNA and significant natural killer cell activity. Interleukin 6 (IL-6), a growth factor for myeloma cells, down-regulated CD33, CD7, or CD56 expression in primary myeloma cells, as well as in Liu01 cells. Therefore, these data suggest that human myeloma cells are capable of inducing the expression of multilineage markers and that IL-6 can down-regulate such expression.

Constitutively lower expressions of CD54 on primary myeloma cells and their different localizations in bone marrow

To evaluate nuclear factor‐κB (NF‐κB) activity in primary myeloma cells from myeloma patients, we confirmed that the expression levels of CD54 showed a good correlation with the levels of DNA binding activity for NF‐κB in human myeloma cell lines, and thus analyzed the expression levels of CD54 on CD38(++) plasma cell fractions as one of NF‐κB activity. Primary myeloma cells unexpectedly showed constitutively lower expressions of CD54 than normal bone marrow (BM) plasma cells. Furthermore, the expression levels of CD54 on these plasma cells showed a significant correlation with the plasma levels of CXCL12 stromal cell‐derived factor‐1α (SDF‐1α) in their BM aspirates, and the expressions of CXCR4, the receptor for CXCL12, decreased on primary myeloma cells compared with normal BM plasma cells. It was also confirmed that the addition of CXCL12 to the in vitro culture significantly induced the up‐regulation of CD54 expression in primary myeloma cells. In addition, myeloma cells with lower expressions of CD54 were more unstable in the in vitro culture, resulting in a marked reduction of the viable cell number. In the immunohistochemical analysis of BM aspirates, myeloma cells with lower CD54 expression resided in the perivascular regions. Therefore, these data suggest that primary myeloma cells exhibit constitutively lower CD54 that might be partially regulated by CXCL12, and their localizations in the BM may be associated with the expression levels of CD54.

PPARβ-mediated growth suppression of baicalein and dexamethasone in human myeloma cells

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