PARP-1 promotes autophagy via the AMPK/mTOR pathway in CNE-2 human nasopharyngeal carcinoma cells following ionizing radiation, while inhibition of autophagy contributes to the radiation sensitization of CNE-2 cells

Chen,Ze‑Tan; Zhao,Wei; Qu,Song; Li,Ling; Lu,Xiao-Di; Su,Fang; Liang,Zhong-Guo; Guo,Si-Yan; Zhu,Xiao-Dong

doi:10.3892/mmr.2015.3604

PARP-1 promotes autophagy via the AMPK/mTOR pathway in CNE-2 human nasopharyngeal carcinoma cells following ionizing radiation, while inhibition of autophagy contributes to the radiation sensitization of CNE-2 cells

Authors:
- Ze‑Tan Chen
- Wei Zhao
- Song Qu
- Ling Li
- Xiao-Di Lu
- Fang Su
- Zhong-Guo Liang
- Si-Yan Guo
- Xiao-Dong Zhu
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Affiliations: Department of Radiation Oncology, Affiliated Cancer Hospital of Guangxi Medical University, Cancer Institute of Guangxi Zhuang Autonomous Region, Nanning, Guangxi 530021, P.R. China
Published online on: April 9, 2015 https://doi.org/10.3892/mmr.2015.3604
Pages: 1868-1876
Copyright: © Chen et al. This is an open access article distributed under the terms of Creative Commons Attribution License [CC BY_NC 3.0].

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Abstract

It was previously reported that poly‑(adenosine diphosphate‑ribose) polymerase‑1 (PARP‑1) regulated ionizing radiation (IR)‑induced autophagy in CNE‑2 human nasopharyngeal carcinoma cells. The present study aimed to investigate whether PARP‑1‑mediated IR‑induced autophagy occurred via activation of the liver kinase B1 (LKB1)/adenosine monophosphate‑activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling pathway in CNE‑2 cells. In addition, the effect of PARP‑1 and AMPK inhibition on the radiation sensitization of CNE‑2 cells was investigated. CNE‑2 cells were treated with 10 Gy IR in the presence or absence of the AMPK activator 5‑amino‑1‑β‑D‑ribofuranosyl‑1H‑imid‑azole‑4‑carboxamide (AICAR). In addition, IR‑treated CNE‑2 cells were transfected with lentivirus‑delivered small‑hairpin RNA or treated with the AMPK inhibitor Compound C. Western blot analysis was used to assess the protein expression of PARP‑1, phosphorylated (p)‑AMPK, microtubule‑associated protein 1 light chain 3 (LC3)‑Ⅱ and p‑P70S6K. Cell viability and clone formation assays were performed to determine the effect of PARP‑1 silencing and AMPK inhibition on the radiation sensitization of CNE‑2 cells. The results showed that IR promoted PARP‑1, p‑AMPK and LC3‑Ⅱ protein expression as well as decreased p‑P70S6K expression compared with that of the untreated cells. In addition, AICAR increased the expression of p‑AMPK and LC3‑Ⅱ as well as decreased p‑P70S6K expression compared with that of the IR‑only group; however, AICAR did not increase PARP‑1 expression. Furthermore, PARP‑1 gene silencing decreased the expression of PARP‑1, p‑AMPK and LC3‑Ⅱ as well as increased p‑P70S6K expression. Compound C decreased p‑AMPK and LC3‑Ⅱ expression as well as increased p‑P70S6K expression; however, Compound C did not increase PARP‑1 expression. Western blot analysis detected limited expression of p‑LKB1 in all treatment groups. Cell viability and clone formation assays revealed that PARP‑1 or AMPK inhibition reduced the proliferation of CNE‑2 cells following IR. In conclusion, the present study demonstrated that PARP‑1 promoted autophagy via the AMPK/mTOR pathway; in addition, PARP‑1 or AMPK inhibition contributed to the radiation sensitization of CNE‑2 cells following IR. However, it remains to be elucidated whether PARP‑1 is an upstream mediator of the LKB1 pathway in CNE‑2 cells following IR.

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