Interleukin-6-resistant melanoma cells exhibit reduced activation of STAT3 and lack of inhibition of cyclin E-associated kinase activity.
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.
Böhm
M
M
Ludwig Boltzmann Institute for Cell Biology and Immunobiology of the Skin, Department of Dermatology, University of Münster, Münster, Germany. bohmm@uni-muenster.de
Schulte
U
U
Funk
J O
JO
Raghunath
M
M
Behrmann
I
I
Kortylewski
M
M
Heinrich
P C
PC
Kues
T
T
Luger
T A
TA
Schwarz
T
T
D042846:CDC2-CDC28 Kinases; D018797:Cell Cycle Proteins / Q000378:metabolism; D019927:Cyclin E / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016213:Cyclins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000032:analysis / Q000378:metabolism*; D016193:G1 Phase / Q000187:drug effects / Q000502:physiology; D006801:Humans; D015850:Interleukin-6 / Q000494:pharmacology*; D053613:Janus Kinase 1; D048369:MAP Kinase Kinase 1; D008545:Melanoma; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D050796:STAT3 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D012878:Skin Neoplasms; D015534:Trans-Activators / Q000032:analysis / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology; D025521:Tumor Suppressor Proteins; D014443:Tyrosine / Q000378:metabolism; D020687:cdc25 Phosphatases / Q000378:metabolism
C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; D015850:Interleukin-6; D016160:Retinoblastoma Protein; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; C507904:JAK1 protein, human; D053613:Janus Kinase 1; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases; C517004:CDC25A protein, human; D020687:cdc25 Phosphatases