Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0026764 (multiple myeloma)
 36,148 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Overexpression of the transmembrane protein-tyrosine phosphatase (PTPase) CD45 in nonhematopoietic cells results in decreased signaling through growth factor receptor tyrosine kinases. Consistent with these data, insulin receptor signaling is increased when the CD45-related PTPase LAR is reduced by antisense suppression in a rat hepatoma cell line. To test whether the hematopoietic cell-specific PTPase CD45 functions in a manner similar to LAR by negatively modulating insulin receptor signaling in hematopoietic cells, the insulin-responsive human multiple myeloma cell line U266 was isolated into two subpopulations that differed in CD45 expression. In CD45 nonexpressing (CD45-) cells, insulin receptor autophosphorylation was increased by 3-fold after insulin treatment when compared to CD45 expressing (CD45+) cells. This increase in receptor autophosphorylation was associated with similar increases in insulin-dependent tyrosine kinase activation. These receptor level effects were paralleled by postreceptor responses. Insulin-dependent tyrosine phosphorylation of insulin receptor substrate 1 (IRS-1) and Shc was 3-fold greater in CD45- cells. In addition, insulin-dependent IRS-1/phosphatidylinositol 3-kinase association and MAP kinase activation in CD45- cells were also 3-fold larger. While expression of CD45 was associated with a decrease in the responsiveness of early insulin receptor signaling, interleukin 6-dependent activation of mitogen-activated protein kinase kinase and mitogen-activated protein kinase was equivalent between CD45- and CD45+ cells. These observations indicate that CD45 can function as a negative modulator of growth factor receptor tyrosine kinases in addition to its well-established role as an activator of src family tyrosine kinases.
 ...
PMID:The transmembrane protein-tyrosine phosphatase CD45 is associated with decreased insulin receptor signaling. 855 83

Activation of early response genes by interferons (IFNs) requires tyrosine phosphorylation of the Stat transcription factors and is mediated by the Jak family of tyrosine kinases. Recent evidence suggests that ERK2 serine/threonine kinase modulates the IFN-stimulated Jak/Stat pathway. In this report we show that in the myeloma cell line U266 protein kinase A specifically interacts with the cytoplasmic domain of the IFNalpha/beta receptor. Treatment of cells with the adenylate cyclase activator forskolin inhibits IFNbeta-, IFNgamma-, and hydrogen peroxide/vanadate-induced formation of complexes that bind to enhancers known to stimulate the expression of IFN-regulated genes. Immunoprecipitations followed by anti-phosphotyrosine immunoblots indicate that tyrosine phosphorylation of the alpha chain of the IFNalpha/beta receptor, Jak1, Tyk2, as well as Stat1 and Stat2 is reduced as a consequence of incubation of cells with forskolin. In contrast, dideoxyforskolin, which fails to activate adenylate cyclase, has no effect on IFN induction of the Jak/Stat pathway. These results indicate a novel regulatory mechanism by which protein kinase A can modulate the Jak/Stat signaling cascade.
 ...
PMID:Activation of protein kinase A inhibits interferon induction of the Jak/Stat pathway in U266 cells. 861 15

Fas belongs to the family of type-1 membrane proteins that transduce apoptotic signals. In the present studies, we characterized signaling during Fas-induced apoptosis in RPMI-8226 and IM-9 multiple myeloma (MM) derived cell lines as well as patient plasma cell leukemia cells. Treatment with anti-Fas (7C11) monoclonal antibody (MoAb) induced apoptosis, evidenced by internucleosomal DNA fragmentation and propidium iodide staining, and was associated with increased expression of c-jun early response gene. We also show that anti-Fas MoAb treatment is associated with activation of stress-activated protein kinase (SAPK) and p38 mitogen-activated protein kinase (MAPK); however, no detectable increase in extracellular signal-regulated kinases (ERK1 and ERK2) activity was observed. Because interleukin-6 (IL-6) is a growth factor for MM cells and inhibits apoptosis induced by dexamethasone and serum starvation, we examined whether IL-6 affects anti-Fas MoAb-induced apoptosis and activation of SAPK or p38 MAPK in MM cells. Culture of MM cells with IL-6 before treatment with anti-Fas MoAb significantly reduced both DNA fragmentation and activation of SAPK, without altering induction of p38 MAPK activity. These results therefore suggest that anti-Fas MoAb-induced apoptosis in MM cells is associated with activation of SAPK, and that IL-6 may both inhibit apoptosis and modulate SAPK activity.
 ...
PMID:Interleukin-6 inhibits Fas-induced apoptosis and stress-activated protein kinase activation in multiple myeloma cells. 897 96

Type I interferons (IFNs-alpha and IFN-beta) bind to a common receptor to exert strong antiproliferative activity on a broad range of cell types, including interleukin-6 (IL-6)-dependent myeloma cells. In this study, we investigated the effect of IFN-beta pretreatment on IL-6-stimulated mitogenic signaling in the human myeloma cell line U266. IL-6 induced transient tyrosine phosphorylation of the IL-6-receptor signal-transducing subunit gp130, the gp130-associated protein tyrosine kinases Jak1,Jak2, and Tyk2, the phosphotyrosine phosphatase PTP1D/Syp, the adaptor protein Shc and the mitogen-activated protein kinase Erk2, and accumulation of GTP-bound p21ras. Prior treatment of U266 cells with IFN-beta downregulated IL-6-induced tyrosine phosphorylation of gp130, Jak2, PTP1D/Syp, Shc, and Erk2, and GTP-loading of p21ras. Further analysis indicated that treatment with IFN-beta disrupted IL-6-induced binding of PTP1D/Syp to gp130 and the adaptor protein Grb2; IFN-beta pretreatment also interfered with IL-6-induced interaction of Shc with Grb2 and a 145-kD tyrosine-phosphorylated protein. These results suggest a novel mechanism whereby type I IFNs interrupt IL-6-promoted mitogenesis of myeloma cells in part by preventing the formation of essential signaling complexes leading to p21ras activation.
 ...
PMID:Interferon-beta interrupts interleukin-6-dependent signaling events in myeloma cells. 897

The stress-activated protein kinases (SAPKs), also known as c-Jun amino-terminal kinases (JNKs), are activated in response to diverse stimuli including DNA damage, heat shock, interleukin-1, tumor necrosis factor-alpha and Fas. Although all these inducers cause apoptosis, whether SAPK/JNK activation is required for apoptosis is controversial. In this study, we demonstrate that ionizing radiation (IR) and dexamethasone (Dex) induce apoptosis in multiple myeloma (MM) derived cell lines, as well as in patient cells. IR-induced apoptosis is associated with activation of SAPK/JNK and p38 kinase, in contrast to Dex-induced apoptosis, which is not associated with activation of stress kinases. Moreover, Dex-induced apoptosis is associated with a significant decrease in the activities of mitogen activated protein kinase (MAPK) and p70S6K, whereas IR-treatment does not alter the activity of these kinases. Both IR and Dex induce poly (ADP ribose) polymerase (PARP) cleavage, a signature event of apoptosis. Finally, interleukin-6 (IL-6) inhibits Dex-induced apoptosis, downregulation of MAP and p70S6K growth kinases and PARP cleavage; in contrast, IL-6 does not inhibit IR-induced apoptosis, activation of SAPK/JNK, and PARP cleavage. Taken together, our findings suggest that SAPK/JNK activation is not required for apoptosis in MM cells, and that there are at least two distinct apoptotic signaling pathways: (i) SAPK/JNK-associated, which is induced by IR and unaffected by IL-6; and (ii) SAPK/JNK-independent, which is induced by Dex, associated with downregulation of MAPK and p70S6K and inhibited by IL-6.
 ...
PMID:Dexamethasone induces apoptosis of multiple myeloma cells in a JNK/SAP kinase independent mechanism. 926 70

IL-6 mediates growth of some human multiple myeloma (MM) cells and IL-6-dependent cell lines. Although three IL-6 signaling pathways (STAT1, STAT3, and Ras-dependent MAPK cascade) have been reported, cascades mediating IL-6-triggered growth of MM cells and cell lines are not defined. In this study, we therefore characterized IL-6 signaling cascades in MM cell lines, MM patient cells, and IL-6-dependent B9 cells to determine which pathway mediates IL-6-dependent growth. IL-6 induced phosphorylation of JAK kinases and gp130, regardless of the proliferative response of MM cells to this growth factor. Accordingly, we next examined downstream IL-6 signaling via the STAT3, STAT1, and Ras-dependent mitogen-activated protein kinase (MAPK) cascades. IL-6 triggered phosphorylation of STAT1 and/or STAT3 in MM cells independent of their proliferative response to IL-6. In contrast, IL-6 induced phosphorylation of Shc and its association with Sos1, as well as phosphorylation of MAPK, only in MM cells and B9 cells that proliferated in response to IL-6. Moreover, MAPK antisense, but not sense, oligonucleotide inhibited IL-6-induced proliferation of these cells. These data suggest that STAT1 and/or STAT3 activation may occur independently of the proliferative response to IL-6, and that activation of the MAPK cascade is an important distal pathway for IL-6-mediated growth.
 ...
PMID:IL-6 triggers cell growth via the Ras-dependent mitogen-activated protein kinase cascade. 927 9

Newer therapeutic strategies for the treatment of multiple myeloma have focused on antagonizing the growth-promoting functions of interleukin 6 (IL-6). In this study, we examined the antitumor effects of two mechanistically different microtubule poisons, Taxol and vinblastine, in U266 human myeloma cells and determined whether IL-6 altered these effects. Taxol and vinblastine led to a dose-dependent inhibition of [3H]thymidine incorporation and altered the DNA distribution pattern of U266 cells. Both drugs led to an increase in the proportion of cells in the sub-G1 fraction (<2N DNA). However, at the IC50 concentration, vinblastine, but not Taxol, increased the percentage of cells in the G2-M phase of the cell cycle. In the presence of IL-6, the DNA distribution pattern induced by Taxol or vinblastine was altered. Whereas IL-6 augmented the sub-G1 fraction and G2-M phase for Taxol-treated cells, only the G2-M phase was increased for vinblastine-treated cells. Furthermore, IL-6 enhanced the cytotoxicity of both drugs, which became evident only during recovery in cytokine-free and drug-free medium. However, the cytotoxicity of Taxol was augmented to a significantly greater extent than that of vinblastine (P < 0.001). Immunostaining with antibodies to alpha-tubulin and mitogen-activated protein kinase revealed colocalization of these two proteins within microtubule asters. In the presence of IL-6, the number of cells containing microtubule asters increased for Taxol treatment, but not for vinblastine treatment. These data indicate that IL-6 leads to differential modulation of the cytotoxicity of Taxol and vinblastine in U266 cells. Whereas recruitment of cells in the S phase of the cell cycle represents a major mechanism by which IL-6 potentiates the cytotoxicity of vinblastine, augmentation of the cytotoxicity of Taxol involves additional mechanisms. Furthermore, our data suggest that the microtubule-associated form of mitogen-activated protein kinase may play a role in IL-6-mediated enhancement of the cytotoxicity of Taxol. The clinical implications of these findings are discussed.
 ...
PMID:Interleukin 6 differentially potentiates the antitumor effects of taxol and vinblastine in U266 human myeloma cells. 956

It has been shown that granulocyte/macrophage colony stimulating factor (GM-CSF) is able to support myeloma cell propagation in cooperation with interleukin (IL)-6, the major growth factor for malignant plasma cells, although the biological mechanisms involved remain unknown. Therefore we investigated (i) the expression levels of the GM-CSF receptor (GM-CSFR) constituents in three malignant plasma cell lines and in native malignant plasma cells, (ii) the ability of the receptor to mediate common signalling pathways regulating proliferation and cell survival in malignant plasma cell lines, and (iii) the effects of GM-CSF on tumour cell biology. The GM-CSFRalpha subunit was detected in the malignant plasma cell lines RPMI-8226, MC/CAR, IM-9 as well as 6/6 native myeloma cell samples derived from the bone marrow of patients with overt disease. Furthermore, GM-CSFR expression was also detected in the CD19+ fraction from 2/3 bone marrow samples and 5/8 peripheral blood samples derived from patients with malignant plasma cell disorders, but not in the CD19+ fraction of peripheral blood from healthy donors. The expressed cytokine receptor alpha-subunit was able to constitute a functional signalling complex with the ubiquitously expressed GM-CSFRbeta subunit, as demonstrated by the fact that GM-CSF induced the p21-ras/mitogen-activated protein kinase (MAPK) signalling cascade in malignant plasma cell lines. Since this signalling cascade plays an essential role in the mediation of both proliferation and cell survival, we investigated the impact of GM-CSF on these two events. Application of GM-CSF led to an increase of DNA-synthesis in MC/CAR, IM-9 and RPMI-8226 cells. Furthermore, it increased longevity of these malignant plasma cell lines by reducing the rates of spontaneous apoptosis. We conclude that (i) the functional GM-CSFR is commonly expressed on malignant plasma cells and that (ii) GM-CSF promotes the clonal expansion of myeloma cells by inhibiting spontaneous apoptosis and promoting DNA synthesis.
 ...
PMID:Functional granulocyte/macrophage colony stimulating factor receptor is constitutively expressed on neoplastic plasma cells and mediates tumour cell longevity. 973 60

Interleukin 6 (IL-6) is a growth factor for multiple myeloma (MM) cells, yet not all MM cell lines or patient cells require IL-6 for their growth. It is well known that IL-6 activates the signal transducers and activators of transcription (stat) 1-stat3 heterodimer, stat3 homodimer, and Ras-dependent mitogen-activated protein kinase (MAPK) cascades in multiple cell systems. We have shown previously that the MAPK pathway is an important pathway for IL-6-mediated MM cell growth. In this study, we delineate the pattern of upstream MAPK cascade activation in IL-6-responsive B9 cells and in IL-6-nonresponsive U266, OCI-My5, and RPMI8226 MM cells to define sites of blockade of this pathway associated with loss of responsiveness to IL-6. In B9 cells, IL-6 triggered the following in sequence: gp130 phosphorylation, gp130-to-protein tyrosine phosphatase 1D (PTP1D) binding, PTP1D phosphorylation, PTP1D complex formation with Grb2-Son of sevenless 1 (Sos1), and Sos1 phosphorylation. gp130 phosphorylation, gp130-to-PTP1D binding, PTP1D phosphorylation, and PTP1D-to-Grb2 binding are also induced by IL-6 in all IL-6-independent MM cell lines studied. However, Grb2 is not associated with Sos1, and neither Grb2-to-Sos1 binding nor Sos1 phosphorylation is triggered by IL-6 in OCI-My5 MM cells. On the other hand, Grb2 and Sos1 are associated constitutively in U266 and RPMI8226 MM cells, but phosphorylation of Sos1 is not induced by IL-6. These data suggest that lack of Sos1 activation is associated with loss of IL-6 responsiveness in MM cell lines that grow independently of IL-6.
 ...
PMID:Blockade of mitogen-activated protein kinase cascade signaling in interleukin 6-independent multiple myeloma cells. 981 79

The ability of IFN-alpha to induce an anti-viral state in a wide variety of cell types as well as to inhibit cellular growth has long been appreciated. It is less clear, however, whether both these effects lie downstream of a common signaling pathway. In this study we have taken advantage of an atypical human myeloma cell line (KAS-6/1) displaying a dramatic proliferative response to IFN-alpha in an effort to resolve the signaling requirements for IFN-alpha-induced anti-viral and growth regulatory effects. Thus, we have analyzed the ability of IFN-alpha to induce a number of known receptor-initiated events in this cell line and have compared these responses with those exhibited by a cell lineage- and maturation stage-matched myeloma cell line (ANBL-6) that displays typical IFN-alpha responsiveness. Despite the widely contrasting effects of IFN-alpha on cellular proliferation, IFN-alpha was shown to be comparable in its ability to induce the expression of early response genes as well as induce resistance to viral infection in both cell lines. By contrast, the effects of IFN-alpha on the activation of mitogen-activated protein kinase (MAPK) were strikingly distinct. Finally, although inhibition of MEK and MAPK activation had no effect on the induction of the anti-viral response, it completely blocked IFN-alpha-stimulated proliferation of the KAS-6/1 cells. In summary, our analysis of the role of the MAPK and anti-viral signaling pathways using these two cell lines suggests that the anti-viral and growth regulatory effects of IFN-alpha display a differential requirement for activation of the MAPK pathway.
 ...
PMID:Dissociation between IFN-alpha-induced anti-viral and growth signaling pathways. 1009 81


1 2 3 4 5 6 7 8 9 10 Next >>