Theranostics 2019; 9(22):6380-6395. doi:10.7150/thno.34443

Research Paper

SDH5 Depletion Enhances Radiosensitivity by Regulating p53: A New Method for Noninvasive Prediction of Radiotherapy Response

Yan Zong1, Qianwen Li1, Furong Zhang1, Xunde Xian2, Sihua Wang1, Jiahong Xia3, Jie Li1, Zhan Tuo1, Guangqin Xiao1, Li Liu1, Guiling Li1, Sheng Zhang1, Gang Wu1✉, Jun Liu1✉

1. Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
2. Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, United States
3. Department of Cardiac Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China

Abstract

Radiotherapy is an effective treatment for lung cancer but lacks a reliable prediction method. Cell-free nucleic acids in plasma have been reported as a novel tumor marker. Here, we evaluate circulating succinate dehydrogenase 5 (SDH5) mRNA in plasma and SDH5 protein in tumors, assess their predictive value in lung cancer patients undergoing radiotherapy, and explore the underlying mechanisms.

Methods: SDH5 expression was measured in peripheral blood samples and fresh tumor specimens from 208 non-small cell lung cancer (NSCLC) patients and correlated with clinical outcomes. SDH5 knockout mice and human xenograft mice were used to evaluate radiosensitivity. Cell growth, apoptosis, and the DNA damage response were assessed. Relevant RNA and protein levels were analyzed by qRT-PCR and Western blotting. Immunoprecipitation and GST pulldown assays were performed to detect protein-protein interactions. Polyubiquitination of p53 was examined by an in vitro ubiquitination assay.

Results: Plasma and tumor SDH5 mRNA levels were positively correlated (rho=0.894, P<0.001). Patients with relatively low SDH5 levels in plasma (0.47, 0.12-0.89) and tumors (3.85, 0.96-7.23) had a better prognosis after radiotherapy (median PFS: 30.0 versus 15.0 months, hazard ratio: 0.276, 95% CI: 0.201-0.379, P<0.001). In SDH5 knockout mice, the lung epithelial cells exhibited increased DNA damage after radiation. In human lung xenograft mice, SDH5-deficient tumors had a smaller volume after radiotherapy. Furthermore, SDH5 depletion inhibits p53 degradation via the ubiquitin/proteasome pathway, which promotes apoptosis and enhances radiosensitivity in NSCLC.

Conclusion: Our findings provide a novel noninvasive method for prediction of response to radiotherapy and may have significant implications for cancer radiotherapy.

Keywords: SDH5, p53, Radiotherapy, Apoptosis, Lung cancer, Noninvasive, Prediction

This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/). See http://ivyspring.com/terms for full terms and conditions.
How to cite this article:
Zong Y, Li Q, Zhang F, Xian X, Wang S, Xia J, Li J, Tuo Z, Xiao G, Liu L, Li G, Zhang S, Wu G, Liu J. SDH5 Depletion Enhances Radiosensitivity by Regulating p53: A New Method for Noninvasive Prediction of Radiotherapy Response. Theranostics 2019; 9(22):6380-6395. doi:10.7150/thno.34443. Available from http://www.thno.org/v09p6380.htm