Survivin expressions in human hepatoma HepG2 cells exposed to ionizing radiation of different LET.
Survivin is a member of the inhibitors of apoptosis (IAP) protein family that interferes with post-mitochondrial events including activation of caspases. To examine the regulation of survivin expression in response to irradiation with different linear energy transfer (LET), human hepatoma HepG2 cells were irradiated in vitro with X-rays and carbon ions. Cellular sensitivities to low- and high-LET radiation were determined by colony formation. Survivin expression at mRNA and protein level were measured with RT-PCR and Western blot analyses, respectively. Radiation-induced cell cycle arrest and apoptosis were investigated with flow cytometry. We found that low-LET X-rays induced dose-dependent increases in survivin expression. After exposure to high-LET carbon ions, survivin expression gradually increased from 0 to 4 Gy, and then declined at 6 Gy. More pronounced survivin expression, stronger G(2)/M phase arrest was observed after exposure to carbon ions in comparison with X-rays at doses from 0 to 4 Gy. These observations indicate that there is a differential survivin expression in response to different LET radiations and the cycle arrest mechanism may be associated with it. In addition, our data on induction of apoptosis are compatible with the assumption that survivin expression induced by low-LET X-rays radiation may play a critical role in inhibiting apoptosis. However, after irradiation with ions, an anti-apoptotic function of survivin is not evident, possibly because of the serious damage produced by densely ionizing radiation.
Jin
Xiao-Dong
XD
Institute of Modern Physics, Chinese Academy of Sciences, 509 Nanchang Road, 730000, Lanzhou, People's Republic of China.
Gong
Li
L
Guo
Chuan-Ling
CL
Hao
Ji-Fang
JF
Wei
Wei
W
Dai
Zhong-Ying
ZY
Li
Qiang
Q
D017209:Apoptosis / Q000528:radiation effects; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000532:radiotherapy*; D002453:Cell Cycle / Q000528:radiation effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000528:radiation effects; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D018499:Linear Energy Transfer; D008113:Liver Neoplasms / Q000378:metabolism / Q000532:radiotherapy*; D008869:Microtubule-Associated Proteins / Q000032:analysis / Q000235:genetics*; D009363:Neoplasm Proteins / Q000032:analysis / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D000077022:Survivin
C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D000077022:Survivin