Identification of ERp29 as a biomarker for predicting nasopharyngeal carcinoma response to radiotherapy

Radioresistance continues to be a major problem in the treatment of nasopharyngeal carcinoma (NPC). This study aimed to identify novel proteins associated with NPC radio-resistance. We used a mass spectrometry driven-proteomic strategy to identify novel proteins associated with NPC radio-resistance, and differential proteins were subsequently processed by bio-informatic analysis. As a result, twelve proteins were identified with aberrant expression in radioresistant (RR) NPC tissues compare to radiosensitive (RS) NPC tissues. Among these proteins, ERp29, Mn-SOD, HSP27 and GST ω1 were found to be significantly up-regulated in RR NPC tissues, and ERp29 was selected for further validation. Immunohistochemistry analysis confirmed that ERp29 was overexpressed in RR NPC tissues compared with RS NPC tissues. To prove the role of ERp29 in the induction of NPC radioresistance, ERp29 was down-regulated in the ERp29 enriched NPC cells CNE-1 and 6-10B by specific shRNA. Radiosensitivity was measured using cell proliferation assay and clonogenic survival assay, and cell apoptosis was measured using flow cytometric analysis. We found that ERp29 knockdown attenuated CNE-1 and 6-10B cell radioresistance and enhanced cell apoptosis. These results suggest that ERp29 associates with radioresistance in NPC, and ERp29 could be a potential biomarker for predicting NPC response to radiotherapy.     

miRNA-381表达及其与鼻咽癌放疗敏感性的关系

目的:观察人鼻咽癌细胞及组织中miRNA-381的表达变化,探讨其与放射敏感性的关系.方法:采用RT-PCR法测定正常鼻咽部上皮细胞株NP460,人鼻咽癌细胞株CNE-2,放疗抵抗细胞株CNE-2R及20例符合纳入标准的鼻咽癌组织中miRNA-381的表达.完成放疗后3个月接受影像学复查,分析患者的近期放疗疗效.所有病例都有2年或2年以上随访记录,根据随访记录制定放疗敏感性评估标准.采用克隆形成实验检测细胞的放疗敏感性.结果:入组患者根据放疗敏感性评估标准,分为放疗抵抗组(7例)和放疗敏感组(13例),放疗抵抗组的miRNA-381表达显著低于放疗敏感组(P＜0.01).克隆形成实验结果显示细胞的放疗敏感性为NP460＞ CNE-2＞CNE-2R,且有显著统计学差异(P＜0.01).RT-PCR结果显示正常鼻咽部上皮细胞株NP460中miRNA-381表达量高于鼻咽癌细胞株,放疗抵抗细胞株CNE-2R中miRNA-381表达量远低于其亲代细胞株CNE-2.近期疗效和鼻咽癌组织中miRNA-381相对表达量的相关性分析显示miRNA-381相对表达量与近期疗效呈正相关(r=0.77,P ＜0.000 1).结论:miRNA-381在放疗抵抗的鼻咽癌细胞及临床标本中的表达量显著低于放疗敏感的细胞及组织.miRNA-381相对表达量越高的鼻咽癌患者接受根治性放疗后的近期疗效越好.     

鼻咽癌细胞系CNE-2Z放射敏感性异质性与凋亡的关系

目的评估人鼻咽癌细胞系CNE-2Z放射敏感性异质性与凋亡敏感性的相关性。方法用流式细胞仪、荧光显微镜、电镜、Western-blot检测H5和S1凋亡能力的不同及凋亡相关蛋白表达的差异。结果H5、S1两种细胞的凋亡率均随着照射后时间的延长而增加,但H5比S1高且差异有显著性(P<0.05)。结论人鼻咽癌细胞系CNE-2Z放射敏感性的异质性,与细胞受射线照射后凋亡呈正相关,对射线敏感的亚细胞系凋亡率高。     

Radiotherapy diagnostic biomarkers in radioresistant human H460 lung cancer stem-like cells

Tumor cell radioresistance is a major contributor to radiotherapy failure, highlighting the importance of identifying predictive biomarkers for radioresistance. In this work, we established a radioresistant H460 (RR-H460) cell line from parental radiosensitive H460 lung cancer cells by exposure to fractionated radiation. The radiation-resistant, anti-apoptotic phenotype of RR-H460 cell lines was confirmed by their enhanced clonogenic survival and increased expression of the radioresistance genes Hsp90 and Her-3. RR-H460 cells displayed characteristics of cancer stem-like cells (CSCs), including induction of the surface marker CD44 and stem cell markers Nanog, Oct4, and Sox2. RR-H460 cells also exhibited sphere formation and malignant behavior, further supporting a CSC phenotype. Using proteomic analyses, we identified 8 proteins that were up-regulated in RR-H460 CSC lines and therefore potentially involved in radioresistance and CSC-related biological processes. Notably, 4 of these—PAI-2, NOMO2, KLC4, and PLOD3—have not been previously linked to radioresistance. Depletion of these individual genes sensitized RR-H460 cells to radiotoxicity and additively enhancing radiation-induced apoptosis. Our findings suggest the possibility of integrating molecular targeted therapy with radiotherapy as a strategy for resolving the radioresistance of lung tumors.     

Deubiquitinase USP9x Confers Radioresistance through Stabilization of Mcl-1

Myeloid cell leukemia sequence 1 (Mcl-1), an antiapoptotic member of the Bcl-2 family, is often overexpressed in tumor cells limiting the therapeutic success. Mcl-1 differs from other Bcl-2 members by its high turnover rate. Its expression level is tightly regulated by ubiquitylating and deubiquitylating enzymes. Interaction of Mcl-1 with certain Bcl-2 homology domain 3 (BH3)-only members of the Bcl-2 family can limit the access to Mcl-1 ubiquitin ligase E3 and stabilizes the antiapoptotic protein. In addition, the overexpression of the deubiquitinase ubiquitin-specific protease 9x (USP9x) can result in the accumulation of Mcl-1 by removing poly-ubiquitin chains from Mcl-1 preventing its proteasomal degradation. Analyzing radiation-induced apoptosis in Jurkat cells, we found that Mcl-1 was downregulated more efficiently in sensitive parental cells than in a resistant subclone. The decline of Mcl-1 correlated with cell death induction and clonogenic survival. Knockdown of BH3-only proteins Bim, Puma, and Noxa did not affect Mcl-1 level or radiation-induced apoptosis. However, ionizing radiation resulted in activation of USP9x and enhanced deubiquitination of Mcl-1 in the radioresistant cells preventing fast Mcl-1 degradation. USP9x knockdown enhanced radiation-induced decrease of Mcl-1 and sensitized the radioresistant cells to apoptosis induction, whereas USP9x knockdown alone did not change Mcl-1 level in unirradiated cells. Together, our results indicate that radiation-induced activation of USP9x inhibits Mcl-1 degradation and apoptosis resulting in increased radioresistance.     

Heat shock protein 90 inhibitor 17-allylamino-17-demethoxygeldanamycin potentiates the radiation response of tumor cells grown as monolayer cultures and spheroids by inducing apoptosis

Activation of the PI3K-Akt pathway is known to induce tumor radioresistance. In the current study, we examined the ability of 17AAG, which decreases the levels of Hsp90 client proteins including components of the PI3K-Akt pathway, to sensitize radioresistant human squamous cell carcinoma cells to X-irradiation. Human squamous cell carcinoma cell lines (SQ20B, SCC61 and SCC13) were incubated for 16 h at 37 degrees C in medium containing 17AAG. Radiation sensitivity was determined by clonogenic assays, and protein levels were examined by western blotting. Apoptosis was determined in monolayer cells by AO/EB double staining and in spheroids using the TdT-mediated dUTP nick end labeling assay. 17AAG (0.2 microM) enhanced the radiosensitivity more effectively in radioresistant SQ20B and SCC13 cells than in radiosensitive SCC61 cells. However, in all three cell lines, 17AAG increased radiation-induced apoptosis by reducing the expression of EGFR and ErbB-2 and inhibiting the phosphorylation of Akt. Furthermore, 17AAG (1 microM) sensitized SQ20B spheroids to radiation, and inhibition of Akt activation by 17AAG increased radiation-induced apoptosis in spheroids. The findings suggest that 17AAG effectively sensitizes radioresistant cells to radiation by inhibiting the PI3K-Akt pathway. Targeting the PI3K-Akt pathway with 17AAG could be a useful strategy for radiosensitization of carcinomas.     

Overexpression of Bcl-2 in squamous cell carcinoma of the larynx: a marker of radioresistance

Squamous cell carcinoma of the larynx can be treated using radiotherapy or surgery, either alone or in combination. Radiotherapy is preferred for early-stage tumours, as it spares the larynx and therefore preserves speech and swallowing. Unfortunately, approximately 15% of tumours treated this way will prove to be radioresistant, as manifest by tumour recurrence within the original radiotherapy field over the ensuing 12 months. By causing extensive DNA damage, radiotherapy aims to induce apoptosis and tumour regression. Our hypothesis was that defects in the mechanisms that recognise DNA damage, induce cell cycle arrest or control apoptosis, either alone or in combination, may be responsible for radioresistance. We therefore undertook an immunohistochemic analysis of pretreatment biopsies of radioresistant (n = 8) and radiosensitive (n = 13) laryngeal tumours. To minimise the impact of confounding factors, strict inclusion criteria were observed; all tumours were of the glottic subsite and all recurrences developed within 12 months of radiotherapy at the site of the original tumour. The expression of key proteins involved in DNA damage recognition (p53), cell cycle arrest (ATM, p16 and p21/WAF1) and apoptosis (Bcl-2 and BAX) were studied. Ki-67 was also assessed as a marker of cell proliferation to exclude low mitotic rate as a cause of radioresistance. A statistically significant correlation was observed between overexpression of Bcl-2 and radioresistance (p = 0.003, Fisher's exact test). We hypothesise that overexpression of the anti-apoptotic protein Bcl-2 allows tumour cells with extensive radiation-induced DNA damage to continue proliferating; the absence of an appropriate apoptotic response manifests clinically as radioresistance.     

Downregulation of lncRNA ANRIL inhibits proliferation,induces apoptosis,and enhances radiosensitivity in nasopharyngeal carcinoma cells through regulating miR-125a

Increasing evidence demonstrated that long non-coding RNA ANRIL serves as a fatal oncogene in many cancers, including nasopharyngeal carcinoma (NPC). However, little is known whether ANRIL regulated NPC cell radioresistance. Quantitative real-time PCR (qRT-PCR) was performed to examine the expression of lncRNA ANRIL and miR-125a in NPC tissues and cell lines. MTT assay was conducted to measure the cell viability of CNE2 and HONE1 cells. The apoptotic rate of CNE2 and HONE1 cells was determined by flow cytometry analysis. Colony survival was determined by clonogenic assay. Luciferase reporter assay was performed to verity the direct target of miR-125a. LncRNA ANRIL was evidently elevated in NPC tissues and cell lines. ANRIL inhibition suppressed proliferation, induced apoptosis, and enhanced radiosensitivity in NPC. Moreover, ANRIL could negatively modulate miR-125a expression. Furethermore, ANRIL upregulation reserved the inhibited proliferation, induced apoptosis, and enhanced radiosensitivity triggered by miR-125a overexpression. The expression of lncRNA ANRIL was upregulated in NPC tissues and cells. Moreover, knockdown of ANRIL repressed proliferation, promoted apoptosis, and improved radiosensitivity in NPC via functioning as a miR-125a sponge.     

RBBP6 increases radioresistance and serves as a therapeutic target for preoperative radiotherapy in colorectal cancer

Radiotherapy (RT) can be used as preoperative treatment to downstage initially unresectable locally rectal carcinoma, but radioresistance and recurrence remain significant problems. Retinoblastoma binding protein 6 (RBBP6) has been implicated in the regulation of cell cycle, apoptosis and chemoresistance both in vitro and in vivo. The present study investigated whether the inhibition of RBBP6 expression would improve radiosensitivity in human colorectal cancer cells. After SW620 and HT29 cells were exposed to radiation, the levels of RBBP6 mRNA and protein increased over time in both cells. Moreover, a significant reduction in clonogenic survival and a decrease in cell viability in parallel with an obvious increase in cell apoptosis were demonstrated in irradiated RBBP6‐knockdown cells. Transfection with RBBP6 shRNA improved the levels of G2‐M phase arrest, which blocked the cells in a more radiosensitive period of the cell cycle. These observations indicated that cell cycle and apoptosis mechanisms may be connected with tumor cell survival following radiotherapy. In vivo, the tumor growth rate of nude mice in the RBBP6‐knockdown group was significantly slower than that in other groups. These results indicated that RBBP6 overexpression could resist colorectal cancer cells against radiation by regulating cell cycle and apoptosis pathways, and inhibition of RBBP6 could enhance radiosensitivity of human colorectal cancer.     

Identification of inositol polyphosphate 4-phosphatase type II as a novel tumor resistance biomarker in human laryngeal cancer HEp-2 cells

Although tumor resistance remains a significant impediment to successful radiotherapy, associated regulatory markers and detailed molecular mechanisms underlying this phenomenon are not well defined. In this study, we identified inositol polyphosphate 4-phosphatase type II (INPP4B) as a novel marker of radioresistance by systematically analyzing Unigene libraries of laryngeal cancer. INPP4B was highly expressed in radioresistant laryngeal cancer cells and was induced by treatment with either radiation or anticancer drugs in various types of cancer cells. Ectopic INPP4B overexpression increased radioresistance and anticancer drug resistance by suppressing apoptosis in HEp-2 cells. Conversely, INPP4B depletion with small interfering RNA resensitized HEp-2 as well as A549 and H1299 cells to radiation- and anticancer drug-induced apoptosis. Furthermore, radiation-induced INPP4B expression was blocked by inhibition of extracellular signal-regulated kinase (ERK). INPP4B depletion significantly attenuated radiation-induced increases in Akt phosphorylation, indicating an association of INPP4B-mediated radioresistance with Akt survival signaling. Taken together, our data suggest that ERK-dependent induction of INPP4B triggers the development of a tumor-resistance phenotype via Akt signaling and identify INPP4B as a potentially important target molecule for resolving the radioresistance of cancer cells.     

Nuclear accumulation of KPNA2 impacts radioresistance through positive regulation of the PLSCR1‐STAT1 loop in lung adenocarcinoma

Lung adenocarcinoma (ADC) is the predominant histological type of lung cancer, and radiotherapy is one of the current therapeutic strategies for lung cancer treatment. Unfortunately, biological complexity and cancer heterogeneity contribute to radioresistance development. Karyopherin α2 (KPNA2) is a member of the importin α family that mediates the nucleocytoplasmic transport of cargo proteins. KPNA2 overexpression is observed across cancer tissues of diverse origins. However, the role of KPNA2 in lung cancer radioresistance is unclear. Herein, we demonstrated that high expression of KPNA2 is positively correlated with radioresistance and cancer stem cell (CSC) properties in lung ADC cells. Radioresistant cells exhibited nuclear accumulation of KPNA2 and its cargos (OCT4 and c‐MYC). Additionally, KPNA2 knockdown regulated CSC‐related gene expression in radioresistant cells. Next‐generation sequencing and bioinformatic analysis revealed that STAT1 activation and nuclear phospholipid scramblase 1 (PLSCR1) are involved in KPNA2‐mediated radioresistance. Endogenous PLSCR1 interacting with KPNA2 and PLSCR1 knockdown suppressed the radioresistance induced by KPNA2 expression. Both STAT1 and PLSCR1 were found to be positively correlated with dysregulated KPNA2 in radioresistant cells and ADC tissues. We further demonstrated a potential positive feedback loop between PLSCR1 and STAT1 in radioresistant cells, and this PLSCR1‐STAT1 loop modulates CSC characteristics. In addition, AKT1 knockdown attenuated the nuclear accumulation of KPNA2 in radioresistant lung cancer cells. Our results collectively support a mechanistic understanding of a novel role for KPNA2 in promoting radioresistance in lung ADC cells.     

Differential expression of proteins in radioresistant and radiosensitive human squamous carcinoma cells.

BACKGROUND: Previous studies support a genetic basis for cellular radioresistance. The associated biochemical and molecular events, however, are not fully understood. PURPOSE: We investigated the differential protein pattern as a molecular determinant of resistance or sensitivity of head and neck squamous carcinoma cells to ionizing radiation. METHODS: Using two-dimensional polyacrylamide gel electrophoresis followed by computer-assisted quantitative analysis, we compared the protein profiles of three relatively radioresistant and three relatively radiosensitive head and neck squamous carcinoma cell lines (previously characterized by in vitro and clinical parameters as radioresistant or radiosensitive) to determine which proteins were consistently expressed or enhanced in the radioresistant compared with the radiosensitive phenotype. RESULTS: Our analysis indicated that 14 proteins were preferentially expressed in the radio-resistant cell lines SQ-20B, JSQ-3, and SCC-35, with one protein (molecular mass of 92 kd and pI of 5.5) distinctly expressed in the radioresistant cell lines. Four proteins were enhanced by greater than 10-fold, three were enhanced fivefold to 10-fold, and six were enhanced twofold to fivefold in the radioresistant cell lines. In addition, we observed a second set of 15 proteins preferentially expressed in the radio-sensitive cell lines SQ-9G, SQ-38, and SCC-9. A 40-kd protein (pI 7.1) was distinctly expressed in the radiosensitive cell lines. The remaining radiosensitive cell-specific proteins were enhanced by greater than 10-fold (two proteins), fivefold to 10-fold (two proteins), or twofold to fivefold (10 proteins) compared with their counterparts in the radioresistant cell lysates. CONCLUSION: These results provide evidence for differential protein expression associated with phenotypic expression of cellular radioresistance or radiosensitivity. IMPLICATIONS: This study will facilitate the characterization of these proteins correlated with the radiation response-specific phenotype.     

Targeting polymerase θ impairs tumorigenesis and enhances radiosensitivity in lung adenocarcinoma

Radioresistance remains a major obstacle to efficacious radiotherapy in non–small-cell lung cancer (NSCLC). DNA replication proteins are novel targets for radiosensitizers. POLQ is a DNA polymerase involved in DNA damage response and repair. We found that POLQ is overexpressed in NSCLC and is clinically correlated with high tumor stage, poor prognosis, increased tumor mutational burden, and ALK and TP5 mutation status; POLQ inhibition impaired lung tumorigenesis. Notably, POLQ expression was higher in radioresistant lung cancer cells than in wild-type cancer cells. Moreover, POLQ expression was further increased in radioresistant cells after radiation. Enhanced radioresistance is through a prolonged G2/M phase and faster repair of DNA damage, leading to reduced radiation-induced apoptosis. Novobiocin (NVB), a POLQ inhibitor, specifically targeted cancer cells. Genetic knockdown of POLQ or pharmacological inhibition by NVB decreased radioresistance in lung adenocarcinoma while causing little toxicity to normal pulmonary epithelial cells. In conclusion, POLQ is a promising and practical cancer-specific target to impair tumorigenesis and enhance radiosensitivity in NSCLC.     

MiR-23a sensitizes nasopharyngeal carcinoma to irradiation by targeting IL-8/Stat3 pathway

Radioresistance poses a major challenge in nasopharyngeal carcinoma (NPC) treatment, but little is known about how miRNA regulates this phenomenon. In this study, we investigated the function and mechanism of miR-23a in NPC radioresistance, one of downregulated miRNAs in the radioresistant NPC cells identified by our previous microarray analysis. We observed that miR-23a was frequently downregulated in the radioresistant NPC tissues, and its decrement correlated with NPC radioresistance and poor patient survival, and was an independent predictor for reduced patient survival. In vitro radioresponse assays showed that restoration of miR-23a expression markedly increased NPC cell radiosensitivity. In a mouse model, therapeutic administration of miR-23a agomir dramatically sensitized NPC xenografts to irradiation. Mechanistically, we found that reduced miR-23a promoted NPC cell radioresistance by activating IL-8/Stat3 signaling. Moreover, the levels of IL-8 and phospho-Stat3 were increased in the radioresistance NPC tissues, and negatively associated with miR-23a level. Our data demonstrate that miR-23a is a critical determinant of NPC radioresponse and prognostic predictor for NPC patients, and its decrement enhances NPC radioresistance through activating IL-8/Stat3 signaling, highlighting the therapeutic potential of miR-23a/IL-8/Stat3 signaling axis in NPC radiosensitization.     

Transcriptional activation of TRADD mediates p53-independent radiation-induced apoptosis of glioma cells.

Survival of patients with Glioblastoma Multiforme (GM), a highly malignant brain tumor, remains poor despite concerted efforts to improve therapy. The median survival of patients with GM has remained approximately 1 year regardless of the therapeutic approach. Since radiation therapy is the most effective adjuvant therapy for GM and nearly half of GM tumors harbor p53 mutations, we sought to identify genes that mediate p53-independent apoptosis of GM cells in response to ionizing radiation. Using broad-scale gene expression analysis we found that following radiation treatment, TRADD expression was induced in a uniquely radiosensitive GM cell line but not in radioresistant GM cell lines. TRADD over-expression killed GM cells and activated NF-kappa B. We found that blocking the TRADD-mediated pathway using a dominant-negative mutant of FADD (FADD-DN) enhanced radiation resistance of GM cells, as reflected in both susceptibility to apoptosis and clonogenic survival following irradiation. Conversely, stable expression of exogenous TRADD enhanced radiation-induced apoptosis of GM cell lines, reflecting the biological significance of TRADD regulation in p53-independent apoptosis. These findings generate interest in utilizing TRADD in gene therapy for GM tumors, particularly in light of its dual function of directly inducing rapid apoptosis and sensitizing GM cells to standard anti-neoplastic therapy.     

LncRNA LINC00261下调miR-620表达调控鼻咽癌放射敏感性实验研究

目的:探讨LINC00261对鼻咽癌放射敏感性影响及其作用机制。方法:用qRT-PCR检测放射敏感、放射抵抗鼻咽癌组织中miR-620和LINC00261的相对表达水平。采用0、2、4、6、8 Gy 60Coγ射线照射鼻咽癌细胞系6-10B、HNE-3细胞后,qRT-PCR法检测miR-620和LINC0...     

ShRNA-mediated silencing of the ubiquitin-specific protease 22 gene restrained cell progression and affected the Akt pathway in nasopharyngeal carcinoma

Ubiquitin-specific protease 22 (USP22) is closely related with poor prognosis of cancer patients. However, the role of USP22 expression in nasopharyngeal carcinoma (NPC) has not been determined. The main aim of this study was to determine the role of USP22 in the pathologic processes of NPC. Immunohistochemistry (IHC), western blot (WB), and real-time polymerase chain reaction (RT-PCR) were used to measure the expression of USP22 in cell lines and tissues of NPC in comparison with expression in non-cancerous cells and tissues. USP22-specific short hairpin RNA (shRNA) was used to knock down USP22 expression in the NPC cell line CNE-1 and CNE-2. Furthermore, the impact of USP22 in cellular proliferation, growth, and cell cycle were detected respectively. WB was used to determine the role of USP22 in the AKT/GSK-3/Cyclin signaling pathway. The expression levels of USP22 were remarkably higher in NPC cell lines and tissues. With cell counting and the MTS assay, cellular growth and proliferation progression of USP22 knockdown cell line was shown to be effectively restrained. The USP22 silencing both in CNE-1 and CNE-2 cells caused them to accumulate in the G0/G1 phase of the cell cycle. USP22 knockdown was also found to modulate the AKT/GSK-3/Cyclin pathway, resulting in downregulation of p-AKT, p-GSK-3β, and cyclinD1. This study suggests that USP22 plays a critical regulatory role in the pathologic processes of NPC, and that it may be a potential biological treatment target in the future.     

Studies with cytotoxic agents suggest that apoptosis is not a major determinant of clonogenic death in neuroblastoma cells

We have previously reported the selection of a radioresistant human neuroblastoma cell line, Clone F, from IMR32 cells. We have shown that clonogenic radioresistance in these cells is accompanied by a reduced level of radiation-induced apoptosis [Cancer Res 55 (1995) 4915]. Here, we measured the response of these lines to several cytotoxic agents, in terms of clonogenicity and apoptosis. In the clonogenic assay, the radioresistant line was also resistant to cisplatin, melphalan and doxorubicin, but not to perillyl alcohol. However, all these agents produced less apoptosis in the Clone F cells, except cisplatin, which failed to induce any apoptosis in either cell line. Reduced apoptosis cannot be the cause of the Clone F cells' resistance to cisplatin. By extension, the Clone F cells' resistance to radiation and other agents cannot be due to diminished apoptosis either. Based on these results, apoptosis may not be a useful surrogate for clonogenic outcome.     

Icotinib Enhanced Radiosensitization of Nasopharyngeal Carcinoma by Inhibiting the Expression of Epidermal Growth Factor Receptor

Epidermal growth factor receptor (EGFR) is frequently overexpressed in multiple malignancies. Icotinib (IH), a new EGFR tyrosine kinase inhibitor, enhances radiosensitivity in various types of cancer, but its effect on nasopharyngeal carcinoma (NPC) remains unclear. Total 115 NPC tissue sections and 30 nasopharyngitis tissue sections were enrolled. The correlation of EGFR expression and clinicopathologic features of NPC was analyzed. Survival analysis was calculated by using univariate and multivariate regression analysis. A radioresistant NPC cell line, CNE-2R, was established with a gradient irradiation schedule. Cell viability, colony formation and EGFR expression of CNE-2/2R cells were examined. Significant higher expression of EGFR was observed in NPC tissues than chronic nasopharyngitis lesions. EGFR expression was significantly correlated with both tumor stage (P < 0.001) and tumor-node-metastasis stage of NPC (P = 0.006). EGFR expression was an independent prognostic factor of disease-free survival (P = 0.047) and the overall survival of NPC (P = 0.016). Cell viability was higher in CNE-2R than CNE-2 on days 1, 2, 4, and 6 after radiation of 4 Gy. The colony number of CNE-2R was significantly higher than that of CNE-2 (P < 0.05), while IH enhanced the radiosensitizing effect of CNE-2R with lower survival fraction (P < 0.05). EGFR mRNA and protein expression levels were significantly higher in CNE-2R cells compared to CNE-2 cells, but significantly decreased after IH treatment (all P < 0.05). In conclusion, high EGFR expression is a poor prognostic factor for NPC patients. IH enhances the radiosensitivity of CNE-2R cells and reduce EGFR expression.