title: Gambogic acid enhances the radiosensitivity of human esophageal cancer cells by inducing reactive oxygen species via targeting Akt/mTOR pathway.
abstract: Radiotherapy is a widespread treatment in human solid tumors. However, therapy resistance and poor prognosis are still problems. Gambogic acid (GA), extracted from the dried yellow resin of gamboges, has an anticancer effect against various types of cancer cells. To explore the radiosensitivity of GA on esophageal cancer cell line TE13, cell viability was tested by Cell Counting Kit-8 (CCK-8) assay, colony formation assay was used to assess the effects of GA on the radiosensitivity of TE13, and flow cytometry was performed to meter the percentage of apoptosis. The protein levels of microtubule-associated protein 1 light chain 3 (LC3), caspase3, caspase8, casepase9, pAkt, and p-mammalian target of rapamycin (p-mTOR) were tested using Western blot. The distribution of LC3 was detected by immunofluorescence. Additionally, we also examined reactive oxygen species (ROS) expression by laser scanning confocal microscope (LSCM). The cells were transfected with adenovial vector to monitor the autophagy through the expression of green fluorescent protein (GFP-red fluroscent protein (RFP)-LC3. The rates of apoptotic cells in combined-treated TE13 increased significantly compared with the control groups in accordance with the results of Western blot. The clonogenic survival assay showed that GA enhances radiosensitivity with a sensitizing enhancement ratio (SER) of 1.217 and 1.436 at different concentrations. The LC3-II protein level increased in the combined group indicating the increase of autophagy incidence, and the results of GFP-RFP-LC3 experiment showed that GA may block the process of autophagic flux in TE13 cells. Moreover, we successfully demonstrated that ROS is involved in the induction of autophagy. ROS-mediated autophagy depends on the inhibition of the Akt/mTOR pathway. Taken together, GA induced radiosensitivity involves autophagy and apoptosis which are regulated by ROS hypergeneration and Akt/mTOR inhibition.
authors: Department of Radiotherapy, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors: Yan
authors: Y
authors: Yang
authors: Department of Radiotherapy, The 81st Hospital of PLA, Nanjing, Jiangsu Province, China.
authors: Xiangdong
authors: X
authors: Sun
authors: Department of Radiotherapy, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors: Yuehua
authors: Y
authors: Yang
authors: Department of Radiotherapy, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors: Xi
authors: X
authors: Yang
authors: Department of Radiotherapy, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors: Hongcheng
authors: H
authors: Zhu
authors: Department of Oncology, People's Hospital of Taizhou, Taizhou, Jiangsu Province, China.
authors: Shengbin
authors: S
authors: Dai
authors: Department of Radiotherapy, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors: Xiaochen
authors: X
authors: Chen
authors: Department of Radiotherapy, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors: Hao
authors: H
authors: Zhang
authors: Department of Radiotherapy, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.|Department of Oncology, People's Hospital of Taizhou, Taizhou, Jiangsu Province, China.
authors: Qing
authors: Q
authors: Guo
authors: Department of Radiation Oncology, Huai'an First People's Hospital, Nanjing Medical University, Nanjing, Jiangsu, 223300, China.
authors: Yaqi
authors: Y
authors: Song
authors: Department of Radiation Oncology, Nantong Tumor Hospital, Affiliated Tumor Hospital of Nantong University, Nantong, 226321, China.
authors: Feng
authors: F
authors: Wang
authors: Department of Synthetic Internal Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors: Hongyan
authors: H
authors: Cheng
authors: Department of Radiotherapy, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China. sunxinchen2012@163.com.
authors: Xinchen
authors: X
authors: Sun
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D004938:Esophageal Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000532:radiotherapy*; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011836:Radiation Tolerance / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000528:radiation effects; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D044004:Xanthones / Q000494:pharmacology*
chemical_list: C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D017382:Reactive Oxygen Species; D044004:Xanthones; C052659:gambogic acid; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D020169:Caspases
keywords: Autophagy; Esophageal cancer; GFP–RFP; Gambogic acid; LC3; Radiosensitivity