Downregulation of survivin by siRNA diminishes radioresistance of pancreatic cancer cells.
BACKGROUND
Survivin is a member of the inhibitor of apoptosis protein family, which inhibits apoptosis and regulates cell division. Survivin is expressed by the majority of human cancers, including pancreatic adenocarcinoma. We have reported that its expression is correlated with shorter survival of pancreatic cancer patients, so regulation of this molecule could be a new strategy for fighting pancreatic cancer.


METHODS
In 3 pancreatic cancer cell lines (AsPC-1, SUIT-2, and Panc-1), survivin promoter activity was determined by the luciferase reporter assay, and survivin messenger RNA (mRNA) expression was examined by quantitative reverse transcriptase-polymerase chain reaction. The dose-dependent cytotoxity of radiation was also assessed, while caspase-3 activity and induction of DNA fragmentation were evaluated. Furthermore, the effect of silencing or nonsilencing short interfering RNA (siRNA) expression plasmids directed against the survivin gene on AsPC-1 cells, the most radioresistant cell line, was evaluated.


RESULTS
Pancreatic cancer cell lines expressed varying levels of survivin mRNA in association with transcriptional activity of the survivin promoter. Both survivin promoter activity and mRNA expression were correlated with tumor cell radiosensitivity. Radiation significantly increased survivin promoter activity and survivin mRNA expression in all cell lines. Radiation induced a significant increase in caspase-3 activity and DNA fragmentation in AsPC-1 cells. After silencing siRNA treatment of AsPC-1 cells (AS-S cells), there was a significant decrease in survivin mRNA expression and increase in caspase-3 activity, compared with the effect of nonsilencing scramble siRNA on AsPC-1 cells (AS-NS cells). AS-S cells were more radiosensitive than AS-NS cells. Radiation induced higher caspase-3 activity and more DNA fragmentation in AS-S cells, compared with AS-NS cells.


CONCLUSIONS
Survivin may play an important role as 1 of the radioresistance factors. Downregulation of survivin by siRNA can diminish the radioresistance of pancreatic cancer cells, so combined therapy with survivin inhibition and radiation may be useful for the treatment of pancreatic cancer.
Kami
Kazuhiro
K
Department of Surgery and Basic Surgical Science, Kyoto University, Sakyo, Japan.
Doi
Ryuichiro
R
Koizumi
Masayuki
M
Toyoda
Eiji
E
Mori
Tomohiko
T
Ito
Daisuke
D
Kawaguchi
Yoshiya
Y
Fujimoto
Koji
K
Wada
Michihiko
M
Miyatake
Shin-Ichi
S
Imamura
Masayuki
M
D045744:Cell Line, Tumor; D003131:Combined Modality Therapy; D004307:Dose-Response Relationship, Radiation; D015536:Down-Regulation / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D015316:Genetic Therapy / Q000379:methods*; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D008156:Luciferases / Q000235:genetics; D008869:Microtubule-Associated Proteins / Q000235:genetics*; D009363:Neoplasm Proteins / Q000235:genetics*; D010190:Pancreatic Neoplasms / Q000503:physiopathology* / Q000532:radiotherapy*; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology*; D000077022:Survivin; D014158:Transcription, Genetic
C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D000077022:Survivin; D008156:Luciferases