1. ¹Clinical Cooperation Group Gene Therapy, GSF – National Research Center for Environment and Health, Munich, Germany
2. ²SIREEN AG, Am Klopferspitz, Martinsried, Germany
3. ³CRELUX GmbH, Am Klopferspitz, Martinsried, Germany
4. ⁴Institute of Molecular Immunology, GSF – National Research Center for Environment and Health, Munich, Germany
5. ⁵Clinic I for Internal Medicine, University Hospital Cologne, Cologne, Germany

Correspondence: Dr G Krause, University Hospital Cologne, Clinic I for Internal Medicine, Kerpener Str. 62, D-50923 Cologne, Germany. E-mail: guenter.krause@uk-koeln.de

Received 19 May 2006; Revised 21 December 2006; Accepted 29 December 2006; Published online 19 February 2007.

Abstract

An acidic domain (AD) of gp130 was previously found to interact with the Src family kinase (SFK) Hck. Here, the influence of myristoylated peptides derived from this AD was assessed in the mouse myeloma cell line, 7TD1. The IL-6-dependent growth of 7TD1 cells was reduced by 75%, if 100 M of myristoylated 18mer peptide (18AD) was included in the growth medium, but was unaffected by a control peptide with scrambled sequence (18sc). A similar differential inhibition by peptides 18AD and 18sc was observed for the erythropoietin-dependent growth of BaF-EH cells expressing chimeric erythropoietin receptor-gp130 and human Hck and for the human myeloma cell line INA-6. While the peptide 18AD concentration inhibiting 50% was 30 M in 7TD1 and BaF-EH cells, peptide 18AD did not significantly inhibit growth of IL-6-independent MM1.S myeloma and OKT1 hybridoma cells or of BaF-EH cells supplied with IL-3. Treatment with 100 M peptide 18AD caused the same degree or 60% of apoptosis induction as IL-6 deprivation in 7TD1 or INA-6 cells, respectively. Co-immunoprecipitation experiments revealed that peptide 18AD interfered with the association of Hck and gp130 in 7TD1 lysates in a concentration-dependent manner. IL-6-treatment of INA-6 cells induced the kinase activities of Fyn, Lyn and Hck, but not Src, and the IL-6-induced SFK activities were inhibited by peptide 18AD. Expression in 7TD1 cells of a kinase-inactive Hck mutant (K269R) elicited a dominant-negative effect on cell number increases providing further evidence that SFKs are required for gp130 signalling in myeloma cells.