Inhibition of Lon blocks cell proliferation, enhances chemosensitivity by promoting apoptosis and decreases cellular bioenergetics of bladder cancer: potential roles of Lon as a prognostic marker and therapeutic target in baldder cancer
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Yongzhang Liu1,*, Linhua Lan1,*, Kate Huang2,*, Rongrong Wang2, Cuicui Xu1, Yang Shi1, Xiaoyi Wu1, Zhi Wu1, Jiliang Zhang1, Lin Chen1, Lu Wang1, Xiaomin Yu1, Haibo Zhu3 and Bin Lu1
1 Protein Quality Control and Diseases Laboratory, Attardi Institute of Mitochondrial Biomedicine, School of Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
2 Department of Pathology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
3 Department of Urology, The Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
* These authors contributed equally to this work.
Bin Lu, email:
Haibo Zhu, email:
Keywords: mitochondria, protein quality control, Lon protease, bladder cancer, chemosensitivity, cellular bioenergetics
Received: March 24, 2014 Accepted: May 27, 2014 Published: May 28, 2014
ATP-dependent Lon protease within mitochondrial matrix contributes to the degradation of abnormal proteins. The oxidative or hypoxic stress which represents the stress phenotype of cancer leads to up-regulation of Lon. However, the role of Lon in bladder cancer remains undefined. Here, we found that Lon expression in bladder cancer tissues was significantly higher than those in noncancerous tissues; down-regulation of Lon in bladder cancer cells significantly blocked cancer cell proliferation via suppression c-Jun N-terminal kinase (JNK) phosphorylation due to decreased reactive oxygen species (ROS) production and enhanced the sensitivity of bladder cancer cells to chemotherapeutic agents by promoting apoptosis. We further found that Lon down-regulation in bladder cancer cells decreased cellular bioenergetics as determined by measuring aerobic respiration and glycolysis using extracellular flux analyzer. The tissue microarray (TMA) results showed that high expression of Lon was related to the T and TNM stage, as well as histological grade of bladder cancer patients. We also demonstrated that Lon was an independent prognostic factor for overall survival of bladder cancer. Taken together, our data suggest that Lon could serve as a potential diagnostic biomarker and therapeutic target for treatment of bladder cancer, as well as for prediction of the effectiveness of chemotherapy.
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