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  • Title: Gp130 and ras mediated signaling in human plasma cell line INA-6: a cytokine-regulated tumor model for plasmacytoma.
    Author: Burger R, Guenther A, Bakker F, Schmalzing M, Bernand S, Baum W, Duerr B, Hocke GM, Steininger H, Gebhart E, Gramatzki M.
    Journal: Hematol J; 2001; 2(1):42-53. PubMed ID: 11920233.
    Abstract:
    INTRODUCTION: Cytokines of the gp130-family, particularly interleukin(IL)-6, play a crucial role in the propagation of malignant plasma cells. MATERIALS AND METHODS: The role of IL-6 and other gp130-cytokines was studied in the human plasma cell line INA-6 in vitro and in INA-6 xenografts. The proliferative response to gp130-cytokines was evaluated and activated components of gp130-signaling pathways were identified by Western blotting and DNA binding studies. Specifically, expression of IL-6 and receptors for IL-6 and leukemia inhibitory factor were analysed by RT-PCR and ELISA. RESULTS: The plasma cell line INA-6 was cultured for several years remaining strictly dependent on exogenous IL-6. Other gp130-cytokines had no significant effect on INA-6 cell proliferation in vitro. Due to an activating mutation in the N-ras gene, mitogen-activated protein kinases (MAPK) were constitutively phosphorylated. In contrast, signal transducer and activator of transcription(STAT)-3 activation was dependent on stimulation with IL-6. Blocking of either one of these pathways resulted in a significant decrease of INA-6 cell proliferation. Remarkably, INA-6 xenografts did not require exogeneous IL-6 for proliferation in vivo. Instead, an autocrine IL-6 loop and, in certain tumor sublines, responsiveness to additional gp130-cytokines was induced during in vivo growth. CONCLUSION: Activation of the gp130 signal transducer is mandatory for INA-6 cell growth in vitro and in vivo. Both the MAPK and the Jak/STAT pathway are operative in malignant plasma cells and either one is essential for plasma cell growth. The INA-6 cell line provides a preclinical model to study growth regulation of human plasmacytoma cells and to evaluate novel therapeutic strategies.
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