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/EBPalpha 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 beta-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.     

Inhibitory effect of baicalein on IL‐6‐mediated signaling cascades in human myeloma cells

Interleukin‐6 (IL‐6) is an important growth factor for myeloma cells. IL‐6 promotes the survival and proliferation of multiple myeloma (MM) cells through the phosphorylated proteins, including STAT3, MAPK, and Akt. Chemical components that suppress the signaling proteins’ phosphorylation have a potential role for MM therapy. We recently identified that baicalein, a component of Scutellaria radix, suppressed proliferation and induced apoptosis of myeloma cells by blocking IκB‐α degradation followed by down‐regulating IL‐6 and XIAP gene expression. In the present study of four myeloma cell lines, namely U266, NOP2, AMO1, and ILKM2, we demonstrated that baicalein not only inhibited IL‐6‐mediated phosphorylation of signaling proteins, such as Jak, STAT3, MAPK, and Akt, but also inhibited the expression of their target genes, such as bcl‐xl. Finally, baicalein facilitated myeloma cell proliferation inhibited by dexamethasone. In contrast, baicalin, another major flavonoid derived from Scutellaria radix, had no significant effect on IL‐6‐mediated protein phosphorylation. Baicalein had no effect on Akt phosphorylation induced by the insulin‐like growth factor‐1 (IGF‐1) in NOP2 cells. Compared with PD98059, an MAPK inhibitor, baicalein exhibited a stronger inhibitory effect on Erk_1/2 phosphorylation. Our results demonstrate that baicalein is a potent inhibitor of protein phosphorylation induced by IL‐6, and thus may be a useful agent for the treatment of MM.     

CD9 expression enhances the susceptibility of myeloma cell lines to cell-mediated cytolysis

Myeloma tumor cells, both freshly excised and cultured, are extremely resistant to cell-mediated cytolysis. As evidence suggests that B-cell susceptibility to lysis is dependent upon its state of differentiation and activation, we tested the ability of a variety of B-cell proliferation and differentiation agents, including pokeweed mitogen (PWM), to enhance the sensitivity of myeloma cells to cell-mediated lysis. PWM was found to significantly enhance the susceptibility of myeloma cell lines and freshly isolated myeloma cells to interleukin-2 (IL-2)-activated cell-mediated cytolysis. This effect was seen with the use of both IL-2-stimulated natural killer (NK) cells and T cells as effectors. The enhanced sensitivity of myeloma cells to cytolysis correlated with an increase in their cell surface expression of CD9, a pre-B cell marker and member of the transmembrane 4 superfamily. Incubation of PWM-stimulated myeloma cells with either monoclonal antibodies or antisense oligonucleotides directed against CD9 abrogated the effect of PWM. In order to determine whether there was a direct relationship between the expression of CD9 and enhanced sensitivity to cytolysis, myeloma cell lines that lacked CD9 expression were transfected with the CD9 gene. The level of cell surface CD9 expression correlates with enhanced susceptibility to lysis. Therefore, CD9 appears to be an important component in enhancing the sensitivity of myeloma cells to lysis mediated by IL-2-activated T cells and NK cells.     

High expression of BCL3 in human myeloma cells is associated with increased proliferation and inferior prognosis

Background: BCL3 is a putative oncogene encoding for a protein belonging to the inhibitory κB-family. We experienced that this putative oncogene was a common target gene for growth-promoting cytokines in myeloma cell lines. Methods: Gene expression of BCL3 was studied in 351 newly diagnosed myeloma patients, 12 patients with smouldering myeloma, 44 patients with monoclonal gammopathy of undetermined significance and 22 healthy individuals. Smaller material of samples was included for mRNA detection by RT-PCR, protein detection by Western blot and immunohistochemistry, and for cytogenetic studies. A total of eight different myeloma cell lines were studied. Results: Bcl-3 was induced in myeloma cell lines by interleukin (IL)-6, IL-21, IL-15, tumor necrosis factor-α and IGF-1, and its upregulation was associated with increased proliferation of the cells. In a population of 351 patients, expression levels of BCL3 above 75th percentile were associated with shorter 5-yr survival. When this patient population was divided into subgroups based on molecular classification, BCL3 was significantly increased in a poor risk subgroup characterized by overexpression of cell cycle and proliferation related genes. Intracellular localization of Bcl-3 was dependent on type of stimulus given to the cell. Conclusion: BCL3 is a common target gene for several growth-promoting cytokines in myeloma cells and high expression of BCL3 at the time of diagnosis is associated with poor prognosis of patients with multiple myeloma (MM). These data may indicate a potential oncogenic role for Bcl-3 in MM.     

Resveratrol inhibits proliferation, induces apoptosis, and overcomes chemoresistance through down-regulation of STAT3 and nuclear factor-kappaB-regulated antiapoptotic and cell survival gene products in human multiple myeloma cells

Whether resveratrol, a component of red grapes, berries, and peanuts, could suppress the proliferation of multiple myeloma (MM) cells by interfering with NF-kappaB and STAT3 pathways, was investigated. Resveratrol inhibited the proliferation of human multiple myeloma cell lines regardless of whether they were sensitive or resistant to the conventional chemotherapy agents. This stilbene also potentiated the apoptotic effects of bortezomib and thalidomide. Resveratrol induced apoptosis as indicated by accumulation of sub-G(1) population, increase in Bax release, and activation of caspase-3. This correlated with down-regulation of various proliferative and antiapoptotic gene products, including cyclin D1, cIAP-2, XIAP, survivin, Bcl-2, Bcl-xL, Bfl-1/A1, and TRAF2. In addition, resveratrol down-regulated the constitutive activation of AKT. These effects of resveratrol are mediated through suppression of constitutively active NF-kappaB through inhibition of IkappaBalpha kinase and the phosphorylation of IkappaBalpha and of p65. Resveratrol inhibited both the constitutive and the interleukin 6-induced activation of STAT3. When we examined CD138(+) plasma cells from patients with MM, resveratrol inhibited constitutive activation of both NF-kappaB and STAT3, leading to down-regulation of cell proliferation and potentiation of apoptosis induced by bortezomib and thalidomide. These mechanistic findings suggest that resveratrol may have a potential in the treatment of multiple myeloma.     

Effects of baicalin in CD4 + CD29 + T cell subsets of ulcerative colitis patients

AIM: To evaluate the role of baicalin in ulcerative colitis (UC) with regard to the CD4⁺CD29⁺ T helper cell, its surface markers and serum inflammatory cytokines.METHODS: Flow cytometry was used to detect the percentage of CD4⁺CD29⁺ cells in patients with UC. Real time polymerase chain reaction was used to detect expression of GATA-3, forkhead box P3, T-box expressed in T cells (T-bet), and retinoic acid-related orphan nuclear hormone receptor C (RORC). Western blotting was used to analyze expression of nuclear factor-κB (NF-κB) p65, phosphorylation of NF-κB (p-NF-κB) p65, STAT4, p-STAT4, STAT6 and p-STAT6. The concentrations of interferon-γ (IFN-γ), interleukin (IL)-4, IL-5, IL-6, IL-10 and TGF-β in serum were determined by ELISA assay.RESULTS: The percentages of CD4⁺CD29⁺ T cells were lower in treatment with 40 and 20 μmol/L baicalin than in the treatment of no baicalin. Treatment with 40 or 20 μmol/L baicalin significantly upregulated expression of IL-4, TGF-β1 and IL-10, increased p-STAT6/STAT6 ratio, but downregulated expression of IFN-γ, IL-5, IL-6, RORC, Foxp3 and T-bet, and decreased ratios of T-bet/GATA-3, p-STAT4/STAT4 and p-NF-κB/NF-κB compared to the treatment of no baicalin.CONCLUSION: The results indicate that baicalin regulates immune balance and relieves the ulcerative colitis-induced inflammation reaction by promoting proliferation of CD4⁺CD29⁺ cells and modulating immunosuppressive pathways.     

Role for interleukin-6 and insulin-like growth factor-I via PI3-K/Akt pathway in the proliferation of CD56- and CD56+ multiple myeloma cells

OBJECTIVES: Several studies including ours have suggested that lack of CD56 in multiple myeloma (MM) defines a unique patient subset with poorer prognosis. However, the mechanism underlying this aggressive behavior of CD56(-) MM has not been well elucidated. Interleukin-6 (IL-6) or insulin-like growth factor I (IGF-I) induce proliferation of MM cells. In this study, we report about the relationship between CD56 expression and responsiveness to these cytokines. METHODS: We sorted out both CD56(-) and CD56(+) fractions from MM cell lines such as KMS-21-BM and U-266, and investigated their different responsiveness to IL-6 or IGF-I. Furthermore, we compared the effects of these cytokines on the regulation of cell-cycle distribution between CD56(-) and CD56(+) cells. RESULTS: Although CD56(-) cells in both KMS-21-BM and U-266 cells responded significantly to IL-6, CD56(+) cells did not. Ki-67(+) cells in the CD56(-) cells were significantly increased by IL-6. Western blotting showed that IL-6 phosphorylated Akt, and upregulated and downregulated the level of cyclin D1 and p27 protein in the CD56(-) KMS-21-BM cells, respectively. LY-294002 completely blocked these effects of IL-6. On the other hand, Ki-67(+) cells in the CD56(+) cells did not respond to IL-6. Anti-IGF-I mAb significantly reduced Ki-67(+) cells only in the CD56(+) cells. IGF-I phosphorylated Akt and upregulated cyclin D1 in the CD56(+) KMS-21-BM cells, which was completely blocked by LY294002. CONCLUSIONS: These results suggest that CD56(-) and CD56(+) MM cells could be stimulated by IL-6 and IGF-I, respectively, via PI3-K/Akt pathway, and provide useful information for anticytokine therapies.     

Functional STAT3 deficiency compromises the generation of human T follicular helper cells

T follicular helper (Tfh) cells are critical for providing the necessary signals to induce differentiation of B cells into memory and Ab-secreting cells. Accordingly, it is important to identify the molecular requirements for Tfh cell development and function. We previously found that IL-12 mediates the differentiation of human CD4(+) T cells to the Tfh lineage, because IL-12 induces naive human CD4(+) T cells to acquire expression of IL-21, BCL6, ICOS, and CXCR5, which typify Tfh cells. We have now examined CD4(+) T cells from patients deficient in IL-12Rβ1, TYK2, STAT1, and STAT3 to further explore the pathways involved in human Tfh cell differentiation. Although STAT1 was dispensable, mutations in IL12RB1, TYK2, or STAT3 compromised IL-12-induced expression of IL-21 by human CD4(+) T cells. Defective expression of IL-21 by STAT3-deficient CD4(+) T cells resulted in diminished B-cell helper activity in vitro. Importantly, mutations in STAT3, but not IL12RB1 or TYK2, also reduced Tfh cell generation in vivo, evidenced by decreased circulating CD4(+)CXCR5(+) T cells. These results highlight the nonredundant role of STAT3 in human Tfh cell differentiation and suggest that defective Tfh cell development and/or function contributes to the humoral defects observed in STAT3-deficient patients.     

The Protein Tyrosine Phosphatase CD45 Is Required for Interleukin 6 Signaling in U266 Myeloma Cells

The objective of this study was to examine whether CD45 mediates interleukin 6 (IL-6) signaling in human multiple myeloma (MM) cells. We chose U266 MM cells as a study model and isolated cells into CD45+ and CD45- subpopulations. CD45+ and CD45- U266 cells were cocultured with bone marrow stromal cells (BMSCs). IL-6-induced proliferation in CD45+ U266 cells was inhibited by vanadate, a potent protein tyrosine phosphatase inhibitor. However, IL-6-independent CD45- U266 cell growth was not affected by vanadate. CD45+ U266 cells, but not CD45- U266 cells, have the capability of cell adhesion concomitant with actin filament polymerization at the adherent cells. Adhesion of CD45+ U266 cells to BMSCs was impaired by vanadate. We clarified the signaling differences between CD45+ and CD45- U266 cells in response to IL-6. In CD45+ U266 cells, IL-6 increased tyrosine phosphorylation of gp130 and STAT3 and stimulated the level of Mcl-1 protein expression. An association between CD45 and the Src-family protein tyrosine kinase, Lyn, was maintained in the presence of IL-6; the formation of the CD45/Lyn complex was impaired by vanadate. Additionally, IL-6-induced Lyn kinase activity in CD45+ U266 cells was increased by the cross-linking of CD45, and this increase was due to the dephosphorylation of Tyr507 at Lyn. In conclusion, IL-6-dependent MM cells require CD45 to initiate IL-6 signaling and to maintain Lyn kinase activity, both of which are essential for cell proliferation and cell adhesion.     

IL-2-independent generation of FOXP3(+)CD4(+)CD8(+)CD25(+) cytotoxic regulatory T cell lines from human umbilical cord blood

OBJECTIVE: Since the existence of mouse naturally occurring CD4(+)CD25(+) T regulatory (Treg) cells was demonstrated, a variety of human Treg subsets have been identified as distinct T cell populations. Here we show the establishment of novel Treg cell lines possessing unique characteristics. METHODS: Novel Treg cell lines, designated HOZOT, were generated by coculturing human umbilical cord blood cells with mouse stromal cell lines in the absence of exogenous IL-2 or other cytokines. HOZOT were characterized and compared with CD4(+)CD25(+) Treg cells in terms of the CD phenotype, FOXP3 expression, suppressor activity against allogeneic MLR, anergy property, and IL-10 production. RESULTS: HOZOT were generated and expanded as normal lymphoblastoid cells with cytotoxic activity against the cocultured stromal cells. HOZOT consisted of three subpopulations as defined by phenotype: CD4(+)CD8(+), CD4(+)CD8(dim), and CD4(-)CD8(+). All three subpopulations showed both suppressor and cytotoxic activities. While HOZOT's expression of FOXP3, CD25, GITR, and cytoplasmic CTLA-4 implied a similarity to naturally occurring CD4(+)CD25(+) Treg cells, these two Treg cells differed in IL-2 responsiveness and IL-10 production. CONCLUSIONS: Our studies introduce a new method of generating Treg cells in an IL-2-independent manner and highlight a unique Treg cell type with cytotoxic activity and a phenotype of FOXP3(+)CD4(+)CD8(+)CD25(+).     

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.