Signal transducer and activator of transcription 1 regulates both cytotoxic and prosurvival functions in tumor cells.
Elsewhere, we reported that multiple serial in vivo passage of a squamous cell carcinoma cells (SCC61) concurrent with ionizing radiation (IR) treatment resulted in the selection of radioresistant tumor (nu61) that overexpresses the signal transducer and activator of transcription 1 (Stat1)/IFN-dependent pathway. Here, we report that (a) the Stat1 pathway is induced by IR, (b) constitutive overexpression of Stat1 is linked with failure to transmit a cytotoxic signal by radiation or IFNs, (c) selection of parental cell line SCC61 against IFN-alpha and IFN-gamma leads to the same IR- and IFN-resistant phenotype as was obtained by IR selection, and (d) suppression of Stat1 by short hairpin RNA renders the IR-resistant nu61 cells radiosensitive to IR. We propose a model that transient induction of Stat1 by IFN, IR, or other stress signals activates cytotoxic genes and cytotoxic response. Constitutive overexpression of Stat1 on the other hand leads to the suppression of the cytotoxic response and induces prosurvival genes that, at high levels of Stat1, render the cells resistant to IR or other inducers of cell death.
Khodarev
Nikolai N
NN
Department of Radiation and Cellular Oncology, The University of Chicago, Chicago, Illinois 60637, USA.
Minn
Andy J
AJ
Efimova
Elena V
EV
Darga
Thomas E
TE
Labay
Edwardine
E
Beckett
Michael
M
Mauceri
Helena J
HJ
Roizman
Bernard
B
Weichselbaum
Ralph R
RR
D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000532:radiotherapy; D019008:Drug Resistance, Neoplasm; D005260:Female; D015870:Gene Expression / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology; D007371:Interferon-gamma / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D034741:RNA, Small Interfering / Q000235:genetics; D011836:Radiation Tolerance; D050794:STAT1 Transcription Factor / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D014183:Transplantation, Heterologous
D016898:Interferon-alpha; D034741:RNA, Small Interfering; D050794:STAT1 Transcription Factor; D007371:Interferon-gamma