title: DNA-dependent protein kinase catalytic subunit inhibitor reverses acquired radioresistance in lung adenocarcinoma by suppressing DNA repair.
abstract: The mechanisms underlying lung cancer radioresistance remain to be fully elucidated. The DNA repair pathway is a predominant target of radiotherapy, which is considered to be involved in the acquired radioresistance of cancer cells. The present study aimed to establish a radioresistant cell model using the A549 human lung cancer cell line, and to further investigate the potential mechanisms underlying the radioresistance. The A549R radioresistant lung cancer cell variant was established by exposing the parental A549 cells to repeated γ-ray irradiation at a total dose of 60 Gy. Colony formation assays were then used to determine cell survival following γ-ray exposure. The established radioresistant cells were subsequently treated with or without the NU7026 DNA-PKcs inhibitor. The levels of DNA damage were determined by counting the number of fluorescent γ-H2AX foci in the cells. The cellular capacity for DNA repair was assessed using antibodies for the detection of various DNA repair pathway proteins. The radioresistant sub-clones exhibited significantly decreased survival following NU7026 treatment, compared with the parental cells, as determined by colony formation assays (P<0.05), and this finding was found to be dose-dependent. Treatment with the DNA-dependent protein kinase (DNA-PK) inhibitor significantly reduced γ-H2AX foci formation (P<0.05) following acute radiation exposure in the radioresistant sub-clones, compared with the parental control cells. The decreased levels of γ-H2AX were accompanied by an increase in the percentage of apoptotic cells in the radioresistant cell line following post-radiation treatment with the DNA-PKcs inhibitor. The expression levels of proteins associated with the DNA repair pathway were altered markedly in the cells treated with NU7026. The results of the present study suggested that radioresistance may be associated with enhanced DNA repair following exposure to radiation, resulting in reduced apoptosis. Therefore, the quantity of γ-H2AX determines the radioresistance of cells. The DNA repair pathway is important in mediating radioresistance, and treatment with the DNA-PKcs inhibitor, NU7026 restored the acquired radiation resistance.
authors: Department of Oncology, Guizhou Provincial People's Hospital, Guiyang, Guizhou 550002, P.R. China.
authors: Yong
authors: Y
authors: Li
authors: Department of Oncology, Guizhou Provincial People's Hospital, Guiyang, Guizhou 550002, P.R. China.
authors: Hang
authors: H
authors: Li
authors: Department of Oncology, Guizhou Provincial People's Hospital, Guiyang, Guizhou 550002, P.R. China.
authors: Wen
authors: W
authors: Peng
authors: Department of Oncology, Guizhou Provincial People's Hospital, Guiyang, Guizhou 550002, P.R. China.
authors: Xin-Yun
authors: XY
authors: He
authors: Department of Occupational and Environmental Health, School of Public Health, Ningxia Medical University, Ningxia 750004, P.R. China.
authors: Min
authors: M
authors: Huang
authors: Department of Oncology, Guizhou Provincial People's Hospital, Guiyang, Guizhou 550002, P.R. China.
authors: Dong
authors: D
authors: Qiu
authors: Department of Oncology, Guizhou Provincial People's Hospital, Guiyang, Guizhou 550002, P.R. China.
authors: Ying-Bo
authors: YB
authors: Xue
authors: Department of Oncology, Guizhou Provincial People's Hospital, Guiyang, Guizhou 550002, P.R. China.
authors: Liang
authors: L
authors: Lu
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy*; D000077192:Adenocarcinoma of Lung; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D002867:Chromones / Q000008:administration & dosage; D004249:DNA Damage / Q000187:drug effects / Q000528:radiation effects; D004260:DNA Repair / Q000187:drug effects / Q000528:radiation effects; D051747:DNA-Activated Protein Kinase / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D005720:Gamma Rays; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000528:radiation effects; D006657:Histones / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy*; D009025:Morpholines / Q000008:administration & dosage; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D010766:Phosphorylation / Q000235:genetics; D011836:Radiation Tolerance / Q000187:drug effects* / Q000235:genetics
chemical_list: C479235:2-(morpholin-4-yl)benzo(h)chromen-4-one; D002867:Chromones; C468783:H2AX protein, human; D006657:Histones; D009025:Morpholines; D009687:Nuclear Proteins; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human