Modulation of SOCS protein expression influences the interferon responsiveness of human melanoma cells.
BACKGROUND
Endogenously produced interferons can regulate the growth of melanoma cells and are administered exogenously as therapeutic agents to patients with advanced cancer. We investigated the role of negative regulators of interferon signaling known as suppressors of cytokine signaling (SOCS) in mediating interferon-resistance in human melanoma cells.


METHODS
Basal and interferon-alpha (IFN-alpha) or interferon-gamma (IFN-gamma)-induced expression of SOCS1 and SOCS3 proteins was evaluated by immunoblot analysis in a panel of n = 10 metastatic human melanoma cell lines, in human embryonic melanocytes (HEM), and radial or vertical growth phase melanoma cells. Over-expression of SOCS1 and SOCS3 proteins in melanoma cells was achieved using the PINCO retroviral vector, while siRNA were used to inhibit SOCS1 and SOCS3 expression. Tyr701-phosphorylated STAT1 (P-STAT1) was measured by intracellular flow cytometry and IFN-stimulated gene expression was measured by Real Time PCR.


RESULTS
SOCS1 and SOCS3 proteins were expressed at basal levels in melanocytes and in all melanoma cell lines examined. Expression of the SOCS1 and SOCS3 proteins was also enhanced following stimulation of a subset of cell lines with IFN-alpha or IFN-gamma. Over-expression of SOCS proteins in melanoma cell lines led to significant inhibition of Tyr701-phosphorylated STAT1 (P-STAT1) and gene expression following stimulation with IFN-alpha (IFIT2, OAS-1, ISG-15) or IFN-gamma (IRF1). Conversely, siRNA inhibition of SOCS1 and SOCS3 expression in melanoma cells enhanced their responsiveness to interferon stimulation.


CONCLUSIONS
These data demonstrate that SOCS proteins are expressed in human melanoma cell lines and their modulation can influence the responsiveness of melanoma cells to IFN-alpha and IFN-gamma.
Lesinski
Gregory B
GB
Department of Surgery Arthur G, James Cancer Hospital and Richard J, Solove Research Institute, The Ohio State University, Columbus, OH 43210, USA.
Zimmerer
Jason M
JM
Kreiner
Melanie
M
Trefry
John
J
Bill
Matthew A
MA
Young
Gregory S
GS
Becknell
Brian
B
Carson
William E
WE
D006801:Humans; D000077190:Interferon alpha-2; D016898:Interferon-alpha / Q000494:pharmacology*; D007371:Interferon-gamma / Q000494:pharmacology*; D008545:Melanoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000235:genetics; D011994:Recombinant Proteins; D050794:STAT1 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction; D000071222:Suppressor of Cytokine Signaling 1 Protein; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D014162:Transfection
D000077190:Interferon alpha-2; D016898:Interferon-alpha; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; C108944:SOCS1 protein, human; C106644:SOCS3 protein, human; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D000071222:Suppressor of Cytokine Signaling 1 Protein; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D007371:Interferon-gamma
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