Tat-SmacN7 induces radiosensitization in cancer cells through the activation of caspases and induction of apoptosis

Chen,Fenghua; Xu,Chang; Du,Liqing; Wang,Yan; Cao,Jia; Fu,Yue; Guo,Yanting; Liu,Qiang; Fan,Feiyue

doi:10.3892/ijo.2013.1785

Tat-SmacN7 induces radiosensitization in cancer cells through the activation of caspases and induction of apoptosis

Authors:
- Fenghua Chen
- Chang Xu
- Liqing Du
- Yan Wang
- Jia Cao
- Yue Fu
- Yanting Guo
- Qiang Liu
- Feiyue Fan
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Affiliations: Department of Radiation Hazard Evaluation, Institute of Radiation Medicine of Chinese Academy of Medical Science and Peking Union Medical College, Tianjin 300192, P.R. China
Published online on: January 22, 2013 https://doi.org/10.3892/ijo.2013.1785
Pages: 985-992

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Abstract

A major concern in cancer therapy is resistance of tumors such as human non-small cell lung cancer and esophageal cancer to radiotherapy. Intrinsic radioresistance of these cancer cells limits therapeutic efﬁciency. Here, we determined in two cancer cell lines the potential radiosensitizing activity of Tat-SmacN7, a small molecule compound, which mimics the activity of Smac, a mitochondrial protein released during apoptosis. We found that Tat-SmacN7 can enter the cells and promote RNA expression and the activity of caspase-3, -8 and -9 and sensitized the cancer cells to radiation with a sensitization enhancement ratio (SER) of 1.5-1.6. Tat-SmacN7 radiosensitization was mediated by both extrinsic and intrinsic apoptosis pathways through activation of caspases. Consistently, blockage of caspase activation, through treatment with a caspase inhibitor, z-VAD-fmk, inhibited apoptosis and abrogated Tat-SmacN7 radiosensitization. Our study demonstrates that Tat-SmacN7 also has radiosensitization effects in vivo, so it could be further developed as a novel class of radiosensitizers for the treatment of radioresistant human non-small cell lung cancer and esophageal cancer.

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