Interleukin-6-resistant melanoma cells exhibit reduced activation of STAT3 and lack of inhibition of cyclin E-associated kinase activity

J Invest Dermatol. 2001 Jul;117(1):132-40. doi: 10.1046/j.0022-202x.2001.01372.x.


Development of cytokine resistance is an important feature of melanoma cells during tumor progression. To study the mechanisms of interleukin-6 resistance, we examined an interleukin-6 sensitive (WM35) and an interleukin-6 unresponsive cell line (WM9). Interleukin-6 treatment resulted in rapid inhibition of cyclin-dependent kinase 2/cyclin E activity and accumulation of the hypophosphorylated retinoblastoma protein in WM35 but not in WM9 cells. In contrast to previous reports, no differences in the expression of the cyclin-dependent kinase 2 inhibitor p21Cip1/WAF1 upon interleukin-6 treatment were found in both cell lines. Interleukin-6-induced inhibition of cyclin-dependent kinase 2 was also not due to changes in protein expression of cyclin-dependent kinase 2, cyclin E, p27Kip1 and cdc25A, a phosphatase positively regulating cyclin-dependent kinase 2 activity. As it is established that interleukin-6 resistance of WM9 cells is not caused by differential interleukin-6 receptor expression, we studied whether this is due to defective interleukin-6 signaling in which activation of signal transducer and activator of transcription 3 is a critical step. WM9 cells showed reduced tyrosine phosphorylation, DNA binding, and delayed nuclear translocation of signal transducer and activator of transcription 3 as compared with WM35 cells. The kinase upstream of signal transducer and activator of transcription 3, Janus kinase 1, was constitutively tyrosine-phosphorylated in WM9 cells and did not respond to interleukin-6 with increased phosphorylation. As compared with WM35 cells, interleukin-6 treatment of WM9 cells was not paralleled by reduced activity of the mitogen-activated protein kinase kinase-1, which suppresses activation of signal transducer and activator of transcription 3. Our data suggest that resistance of advanced melanoma cells to interleukin-6 is associated with reduced inhibition of cyclin-dependent kinase 2, which appears to be a consequence of a complex alteration in interleukin-6 signal transduction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • CDC2-CDC28 Kinases*
  • Cell Cycle Proteins / metabolism
  • Cyclin E / metabolism
  • Cyclin-Dependent Kinase 2
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclin-Dependent Kinase Inhibitor p27
  • Cyclin-Dependent Kinases / antagonists & inhibitors
  • Cyclin-Dependent Kinases / metabolism*
  • Cyclins / metabolism
  • DNA-Binding Proteins / analysis
  • DNA-Binding Proteins / metabolism*
  • G1 Phase / drug effects
  • G1 Phase / physiology
  • Humans
  • Interleukin-6 / pharmacology*
  • Janus Kinase 1
  • MAP Kinase Kinase 1
  • Melanoma*
  • Mitogen-Activated Protein Kinase Kinases / metabolism
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / metabolism
  • Protein-Tyrosine Kinases / metabolism
  • Retinoblastoma Protein / metabolism
  • STAT3 Transcription Factor
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • Skin Neoplasms*
  • Trans-Activators / analysis
  • Trans-Activators / metabolism*
  • Tumor Cells, Cultured / chemistry
  • Tumor Cells, Cultured / drug effects
  • Tumor Cells, Cultured / enzymology
  • Tumor Suppressor Proteins*
  • Tyrosine / metabolism
  • cdc25 Phosphatases / metabolism


  • CDKN1A protein, human
  • Cell Cycle Proteins
  • Cyclin E
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclins
  • DNA-Binding Proteins
  • Interleukin-6
  • Retinoblastoma Protein
  • STAT3 Transcription Factor
  • STAT3 protein, human
  • Trans-Activators
  • Tumor Suppressor Proteins
  • Cyclin-Dependent Kinase Inhibitor p27
  • Tyrosine
  • Protein-Tyrosine Kinases
  • JAK1 protein, human
  • Janus Kinase 1
  • Protein-Serine-Threonine Kinases
  • CDC2-CDC28 Kinases
  • CDK2 protein, human
  • Cyclin-Dependent Kinase 2
  • Cyclin-Dependent Kinases
  • MAP Kinase Kinase 1
  • MAP2K1 protein, human
  • Mitogen-Activated Protein Kinase Kinases
  • CDC25A protein, human
  • cdc25 Phosphatases