However, most radiosensitizers used in clinic, including nitroimidazoles, fluorouracil, cisplatin and Taxol, do not match this criterion due to high toxicity to normal tissues. therapy of celecoxib and radiation in the prevention of radioresistance. Introduction Lung cancer, Gemcabene calcium particularly non-small-cell lung cancer (NSCLC), is one of the most common cancers worldwide [1]. Radiotherapy is a promising treatment strategy for enhancing the survival time of patients and promoting quality of life [2]. However, the development of radioresistance and severe side effects on normal tissues frequently result in Gemcabene calcium failure to apply radiotherapy. Therefore, it is critical to PRKCD develop an improved strategy to overcome radioresistance in lung cancer. An ideal radiosensitizer is expected to have low or absent toxicity to normal cells. However, most radiosensitizers used in clinic, including nitroimidazoles, fluorouracil, cisplatin and Taxol, do not match this criterion due to high toxicity to normal tissues. Therefore, various approaches have been explored to develop potent radiosensitizers to establish more suitable treatment strategies. Growing evidence indicates that inflammation serves an important role in modulating radiation responsiveness of cells [3]. Inflammation suppresses the effectiveness of radiotherapy [4] and substantially contributes to the development and progression Gemcabene calcium of cancer [5]. The goal of novel therapeutic approaches is to disrupt proinflammatory cytokines and to stimulate receptors and signaling cascades. The aim of the current study was to develop a new strategy to increase sensitivity to radiation. Nonsteroidal anti-inflammatory drugs (NSAIDs) are used worldwide for the treatment of pain, inflammation and fever. Cyclooxygenase-2 (COX-2) is an important rate-limiting enzyme in prostaglandin synthesis and interferes with angiogenesis and metastasis [6C8]. Previous studies have reported that the inhibition of COX-2 is beneficial for chemotherapy [8, 9]. Notably, COX-2 overexpression is frequently observed in human premalignant, malignant and metastatic epithelial tumors, including lung, breast, colorectal and prostate cancer [10, 11]. Suppression of COX-2 has been proposed to be associated with chemopreventive effects of NSAIDs. However, whether NSAIDs serve a role in the resistance of radiotherapy is currently unknown. Celecoxib belongs to the NSAIDs family and is a potent and COX-2-specific inhibitor. NSAIDs are commonly linked to side effects, including bleeding and perforation in the gastrointestinal system in chronic NSAID users [12]. Celecoxib has been demonstrated to be less toxic compared with traditional NSAIDs [13]. Preclinical studies have reveled that COX-2 inhibitors lower the proliferation of human lung cancer cells in combination with chemotherapy [14]; however, whether the combination of COX-2 inhibitors with radiotherapy has a better effect in NSCLC has not been investigated Gemcabene calcium in clinical trials or laboratory studies. A previous study suggested that anticancer effects of celecoxib are independent of COX-2 inhibition [15]. Later mechanistic studies indicated that celecoxib exhibits proapoptotic effects by inhibiting 3-phosphoinositide-dependent kinase-1 (PDK-1) and the downstream protein kinase B (Akt) signaling pathway in human colon cancer cells [16]. A recent study demonstrated that celecoxib downregulates specificity protein 1 by inhibiting c-Jun N-terminal kinase, thus enhancing the radiation sensitivity and inhibiting the migration and invasion of cancer cells [17]. To confirm this assumption, the current study evaluated effects of celecoxib on radiation response of NSCLC cells. In addition, possible underlying cellular mechanisms were investigated. The current study suggested the therapeutic potential of combination therapy of celecoxib and radiation in the prevention of radioresistance. Materials and methods Chemicals and reagents Celecoxib was purchased from Dalian Meilun Biology Technology Co., Ltd. (Dalian, China), dissolved in dimethyl sulfoxide (DMSO; 10 mM) and diluted with ddH2O immediately prior to each experiment. The final concentration of DMSO was <0.2%. Procedures of celecoxib preparation were previously described [18]. The Cell counting kit-8 (CCK-8) and the terminal transferase-mediated dUTP-biotin nick end labeling (TUNEL) assay kit were purchased from Beyotime Institute of Biotechnology (Nanjing, China). L-glutamine, penicillin and streptomycin were purchased from Aladdin Reagent Co., Ltd. (Shanghai, China). All antibodies details are reported in Table 1. All chemicals used were of the highest commercial grade. Table 1 Antibody details. experiments combined with radiotherapy was decreased compared with current clinical standards and may have potential beneficial implications for patients with lung cancer. Abbreviations COX-2cyclooxygenase-2-H2AXphosphorylated histone H2AXmTORmammalian target of rapamycinAktprotein kinase BNSAIDnonsteroidal anti-inflammatory drugNSCLCnon-small-cell lung cancerTUNELterminal deoxynucleotidyl transferase dUTP Gemcabene calcium nick-end labeling Funding Statement M.J. and Y.S. received support by the Chongqing Health and Family Planning Commission (grant no. 2017ZDXM030). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Data Availability All relevant data are within the paper..