Interferon-gamma-mediated growth regulation of melanoma cells: involvement of STAT1-dependent and STAT1-independent signals.
Interferon-gamma, a known inhibitor of tumor cell growth, has been used in several protocols for the treatment of melanoma. We have studied the molecular events underlying interferon-gamma-induced G0/G1 arrest in four metastatic melanoma cell lines with different responsiveness to interferon-gamma. The growth arrest did not result from enhanced expression of cyclin-dependent kinase inhibitors p21 and p27. Instead, it correlated with downregulation of cyclin E and cyclin A and inhibition of their associated kinase activities. We show that interferon-gamma-induced growth inhibition could be abrogated by overexpression of dominant negative STAT1 (signal transducer and activator of transcription 1) in the melanoma cell line A375, suggesting that STAT1 plays a crucial part for the anti-proliferative effect. Erythropoietin stimulation of a chimeric receptor led to a concentration-dependent STAT1 activation and concomitant growth arrest when it contained the STAT recruitment motif Y440 of the interferon-gamma receptor 1. In contrast, dose-response studies for interferon-gamma revealed a discrepancy between levels of STAT1 activation and the extent of growth inhibition; whereas STAT1 was activated by low doses of interferon-gamma (10 U per mL), growth inhibitory effects were only visible with 100-fold higher concentrations. Our results suggest the presence of additional signals emanating from the interferon-gamma receptor, which may counteract the anti-proliferative function of STAT1.
Institut für Biochemie, Aachen, Germany.
Marcin
M
Kortylewski
Waraporn
W
Komyod
Maria-Elisabeth
ME
Kauffmann
Anja
A
Bosserhoff
Peter C
PC
Heinrich
Iris
I
Behrmann
D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D016193:G1 Phase / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D008545:Melanoma; D016192:Resting Phase, Cell Cycle / Q000187:drug effects; D050794:STAT1 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects; D012878:Skin Neoplasms; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
D000970:Antineoplastic Agents; D016213:Cyclins; D004268:DNA-Binding Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D015534:Trans-Activators; D007371:Interferon-gamma; D018844:Cyclin-Dependent Kinases