Inhibition of STAT-3 results in radiosensitization of human squamous cell carcinoma.
BACKGROUND
Signal transducer and activator of transcription-3 (STAT-3) is a downstream component of the Epidermal Growth Factor Receptor (EGFr) signaling process that may facilitate the resistance of tumor cells to conventional cancer treatments. Studies were performed to determine if inhibition of this downstream protein produces radiosensitization.


RESULTS
A431 cells (human squamous cell carcinoma cells with EGFr overexpression) were found to be sensitized to radiation after treatment with STAT-3 small interfering RNA (siRNA). Therefore, a short hairpin RNA (shRNA) against STAT-3 was designed and cloned into a pBABE vector system modified for shRNA expression. Following transfection, clone 2.1 was selected for further study as it showed a dramatic reduction of STAT-3 protein (and mRNA) when compared to A431 parental cells or a negative control shRNA cell line (transfected with STAT-3 shRNA with 2 base pairs mutated). A431 2.1 showed doubling times of 25-31h as compared to 18-24h for the parental cell line. The A431 shRNA knockdown STAT-3 cells A431 were more sensitive to radiation than A431 parental or negative STAT-3 control cells.


CONCLUSIONS
A431 cells stably transfected with shRNA against STAT-3 resulted in enhanced radiosensitivity. Further work will be necessary to determine whether the inhibition of STAT-3 phosphorylation is a necessary step for the radiosensitization that is induced by the inhibition of EGFr.
Bonner
James A
JA
Department of Radiation Oncology, The University of Alabama at Birmingham, AL 35233, USA. gesims@uabmc.edu
Trummell
Hoa Q
HQ
Willey
Christopher D
CD
Plants
Brian A
BA
Raisch
Kevin P
KP
D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy*; D045744:Cell Line, Tumor / Q000378:metabolism / Q000528:radiation effects; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011836:Radiation Tolerance / Q000235:genetics*; D012016:Reference Values; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D012680:Sensitivity and Specificity; D015398:Signal Transduction; D012878:Skin Neoplasms / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy*; D014162:Transfection
D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; D066246:ErbB Receptors