miR‐185‐3p regulates nasopharyngeal carcinoma radioresistance by targeting WNT2B in vitro

Aberrant microRNA (miRNA) expression contributes to a series of malignant cancer behaviors, including radioresistance. Our previous study showed differential expression of miR‐185‐3p in post‐radiation nasopharyngeal carcinoma (NPC) cells. To investigate the role of miR‐185‐3p in NPC radioresistance, CNE‐2 and 5‐8F cells were transfected with miR‐185‐3p mimic and miR‐185‐3p inhibitor, respectively. CCK‐8 assay and colony formation experiment confirmed that the expression of miR‐185‐3p affected the radioresistance of NPC cells. A negative correlation between miR‐185‐3p and WNT2B expression was observed in NPC cells and tissues. Luciferase reporter assays confirmed that miR‐185‐3p directly targeted the coding region of WNT2B. Furthermore, we found radioresistance decreased in WNT2B‐silenced NPC cells. Activation of the WNT2B/β‐catenin pathway was accompanied by epithelial–mesenchymal transition biomarker changes in NPC. We concluded that miR‐185‐3p contributed to the radioresistance of NPC via modulation of WNT2B expression in vitro.     

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.     

MiR-1204 sensitizes nasopharyngeal carcinoma cells to paclitaxel both in vitro and in vivo

Nasopharyngeal carcinoma (NPC) is an endemic tumor with a relatively high incidence in Southern China and Southeast Asia. Paclitaxel combination chemotherapy has been used for treatment of advanced NPC. However, treatment failure often occurs due to development of acquired paclitaxel resistance. In this study, we first established a paclitaxel-resistant CNE-1/Taxol, HNE-2/Taxol and 5–8F/Taxol cell sublines by treating the parental CNE-1, HNE-2 and 5–8F cells with increasing doses of paclitaxel for about 5 months, respectively. Then, microRNA arrays were used to screen differentially expressed miRNAs between the CNE-1/Taxol cells and the parental CNE-1 cells. We found 13 differentially expressed miRNAs, of which miR-1204 was significantly downregulated in the paclitaxel-resistant CNE-1/Taxol cells. We restored miR-1204 expression in the CNE-1/Taxol, HNE-2/Taxol and 5–8F/Taxol cells and found that restoration of miR-1204 re-sensitized the paclitaxel-resistant CNE-1/Taxol, HNE-2/Taxol and 5–8F/Taxol cells to paclitaxel both in vitro. Finally, we demonstrated that restoration of miR-1204 in significantly inhibits tumor growth in vivo. Thus, our study provides important information for the development of targeted gene therapy for reversing paclitaxel resistance in NPC.     

Inhibiting ERp29 expression enhances radiosensitivity in human nasopharyngeal carcinoma cell lines

ERp29 is an endoplasmic reticulum (ER) stress-inducible protein. It was found that ERp29 was highly expressed in several cancers and associated with resistance to oxidative and radiation stress, which may serve as a novel target for nasopharyngeal carcinoma (NPC) anticancer approach. In this study, we used immunohistochemistry to detect ERp29 expression in radioresistant and radiosensitive NPC tissues. As a result, ERp29 was up-regulated in radioresistant NPC tissues compared to radiosensitive NPC tissues. We also found that ERp29 knockdown attenuated radioresistance of NPC CNE-1 cells and ERp29 overexpression enhanced radioresistance of NPC CNE-2 cells. When exposed to radiation, ERp29 knockdown CNE-1 cells increased radiation-induced cell apoptosis and ERp29 overexpression CNE-2 cells reduced radiation-induced cell apoptosis. Further, we demonstrated that ERp29 up-regulated the expression of Hsp27. In conclusion, our study supports ERp29 could potentiate resistance to radiation in NPC cells, targeting of ERp29 is a rational strategy in treating radioresistant NPC.     

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.     

Identification of genes involved in radioresistance of nasopharyngeal carcinoma by integrating gene ontology and protein-protein interaction networks

Radioresistance remains one of the important factors in relapse and metastasis of nasopharyngeal carcinoma. Thus, it is imperative to identify genes involved in radioresistance and explore the underlying biological processes in the development of radioresistance. In this study, we used cDNA microarrays to select differential genes between radioresistant CNE-2R and parental CNE-2 cell lines. One hundred and eighty-three significantly differentially expressed genes (p<0.05) were identified, of which 138 genes were upregulated and 45 genes were downregulated in CNE-2R. We further employed publicly available bioinformatics related software, such as GOEAST and STRING to examine the relationship among differentially expressed genes. The results show that these genes were involved in type I interferon-mediated signaling pathway biological processes; the nodes tended to have high connectivity with the EGFR pathway, IFN-related pathways, NF-κB. The node STAT1 has high connectivity with other nodes in the protein-protein interaction (PPI) networks. Finally, the reliability of microarray data was validated for selected genes by semi-quantitative RT-PCR and Western blotting. The results were consistent with the microarray data. Our study suggests that microarrays combined with gene ontology and protein interaction networks have great value in the identification of genes of radioresistance in nasopharyngeal carcinoma; genes involved in several biological processes and protein interaction networks may be relevant to NPC radioresistance; in particular, the verified genes CCL5, STAT1-α, STAT2 and GSTP1 may become potential biomarkers for predicting NPC response to radiotherapy.     

MicroRNA-381 increases radiosensitivity in esophageal squamous cell carcinoma

Background: Radiation resistance poses a major clinical challenge in treatment of esophageal squamous cell carcinoma (ESCC). However, the mechanisms of radioresistance has not been fully elucidated. Since accumulating evidence demonstrates that aberrant expression of microRNAs (miRNAs) contributes to cancer sensitivity to radiation, we aimed to identify miRNAs associated with radioresistance of ESCC. Methods: In this study, we used GeneChip miRNA Array to perform an comparison of miRNAs expression in tissues from primary ESCC and recurrent ESCC in situ after radiotherapy. Differential expressions of miRNAs were comfirmed by quantitative Real-Time PCR in tissues and six ESCC cell lines. Cell radiosensitivity were determined by colony formation assay. Functional analyses of miRNA-381 in ESCC cells growth and metastasis were performed by MTT and Transwell Assays. In vivo assays of the functions of miRNA-381 were performed in tumor xenografts. Results: One miRNA candidate, miRNA-381, was found to be downregulated in radiation resistance tissues and cells. Enforced expression of miRNA-381 increased radiosensitivity of ESCC cells and promoted nonaggressive phenotype including decreased cellular proliferation and migration. In contrast, inhibition of miRNA-381 in ESCC cells promoted radiation resistance and development of an aggressive phenotype. In vivo assays extended the significance of these results, showing that miRNA-381 overexpression decreased the tumor growth and the resistance to radiation treatment in tumor xenografts. Conclusions: Together, our work reveals miRNA-381 expression as a critical determinant of radiosensitivity in esophageal cancer cells.     

MicroRNA-19b-3p regulates nasopharyngeal carcinoma radiosensitivity by targeting TNFAIP3/NF-κB axis

Background

Nasopharyngeal carcinoma (NPC) is among the most common squamous cell carcinoma in South China and Southeast Asia. Radiotherapy is the primary treatment for NPC. However, radioresistance acts as a significant factor that limits the efficacy of radiotherapy for NPC patients. Growing evidence supports that microRNAs (miRNAs) play an important role in radiation response.

Methods

Real-time quantitative PCR was used to analyze the expression of miR-19b-3p in NPC cell lines and NP69. miR-19b-3p expression profiles in NPC tissues were obtained from the Gene Expression Omnibus database. The effect of miR-19b-3p on radiosensitivity was evaluated by cell viability assays, colony formation assays and in vivo experiment. Apoptosis and cell cycle were examined by flow cytometry. Luciferase reporter assay was used to assess the target genes of miR-19b-3p. Expression of target proteins and downstream molecules were analyzed by Western blot.

Results

miR-19b-3p was upregulated in NPC and served as an independent predictor for reduced patient survival. Radioresponse assays showed that miR-19b-3p overexpression resulted in decreased sensitivity to irradiation, whereas miR-19b-3p downregulation resulted in increased sensitivity to irradiation in vitro. Moreover, miR-19b-3p decreased the sensitivity of NPC cells to irradiation in vivo. Luciferase reporter assay confirmed that TNFAIP3 was a direct target gene of miR-19b-3p. Knockdown of TNFAIP3 reduced sensitivity to irradiation, whereas upregulation of TNFAIP3 expression reversed the inhibitory effects of miR-19b-3p on NPC cell radiosensitivity. Mechanistically, we found that miR-19b-3p increased NPC cell radioresistance by activating the TNFAIP3/ NF-κB axis.

Conclusions

miR-19b-3p contributes to the radioresistance of NPC by activating the TNFAIP3/ NF-κB axis. miR-19b-3p is a determinant of NPC radioresponse and may serve as a potential therapeutic target in NPC treatment.

     

Minicircle-IFNgamma induces antiproliferative and antitumoral effects in human nasopharyngeal carcinoma.

PURPOSE: The aims of this work were to investigate the antitumor effect of IFNgamma gene transfer on human nasopharyngeal carcinoma (NPC) and to assess the potential of minicircle vector for antitumor gene therapy. EXPERIMENTAL DESIGN: We developed a recombinant minicircle vector carrying the human IFNgamma gene and evaluated the effects of minicircle-mediated IFNgamma gene transfer on NPC cell lines in vitro and on xenografts in vivo. RESULTS: Relative to p2PhiC31-IFNgamma, minicircle-mediated IFNgamma gene transfer in vitro resulted in 19- to 102-fold greater IFNgamma expression levels in transfected cells (293, NIH 3T3, CNE-1, CNE-2, and C666-1) and inhibited the growth of CNE-1, CNE-2, and C666-1 cells more efficiently, reducing relative growth rates to 7.1 +/- 1.6%, 2.7 +/- 1.0%, and 6.1 +/- 1.6%, respectively. Flow cytometry and caspase-3 activity assays suggested that the antiproliferative effects of IFNgamma gene transfer on NPC cell lines could be attributed to G(0)-G(1) arrest and apoptosis. Minicircle-mediated intratumoral IFNgamma expression in vivo was 11 to 14 times higher than p2PhiC31-IFNgamma in CNE-2- and C666-1-xenografted mice and lasted for 21 days. Compared with p2PhiC31-IFNgamma treatment, minicircle-IFNgamma treatment significantly increased survival and achieved inhibition rates of 77.5% and 83%, respectively. CONCLUSIONS: Our data indicate that IFNgamma gene transfer exerts antiproliferative effects on NPC cells in vitro and leads to a profound antitumor effect in vivo. Minicircle-IFNgamma is more efficient than corresponding conventional plasmids due to its capability of mediating long-lasting high levels of IFNgamma gene expression. Therefore, minicircle-mediated IFNgamma gene transfer is a promising novel approach in the treatment of NPC.     

AMIGO2通过激活PI3K/AKT/mTOR信号通路促进鼻咽癌细胞的增殖

目的：探讨Ig 样结构域 2 黏附分子（adhesion molecule with Ig like domain 2,AMIGO2）在鼻咽癌（nasopharyngeal carcinoma,NPC）细胞增殖中的作用及其机制。方法: 选用2017年9月至11月福建省肿瘤医院收集的10例NPC组织和10例正常鼻 咽黏膜上皮组织标本,以及NPC细胞系CNE-1、CNE-2、SUNE-1、 6-10B、 C666-1和人永生化鼻咽黏膜上皮细胞株NP69, 用qPCR法 检测NPC组织和细胞中AMIGO2 mRNA的表达。构建慢病毒载体干扰AMIGO2表达, 用qPCR法验证其干扰效率; 用CCK-8 法、克隆形成及流式细胞术检测干扰AMIGO2表达对NPC细胞增殖、克隆形成和凋亡的影响, 用 Western blotting 检测干扰 AMIGO2 表达对 NPC 细胞增殖及 PI3K/AKT/mTOR 信号通路相关标志蛋白表达的影响。结果: AMIGO2在NPC组织和 CNE-2和SUNE-1细胞中高表达（均P<0.01）。慢病毒AMIGO2感染后,CNE-2和SUNE-1细胞的AMIGO2干扰效率均达50%以 上。干扰AMIGO2表达,显著降低CNE-2和SUNE-1细胞增殖及克隆形成能力（均P<0.01）、明显提高细胞的凋亡率（均P<0.01）; 降低 SUNE-1 细胞中PI3K、AKT和mTOR磷酸化蛋白的表达水平 （均P<0.01）、下调survivin 和 PCNA 蛋白的表达水平（均P<0.01）。 结论：AMIGO2通过激活PI3K/AKT/mTOR信号通路促进NPC细胞增殖并抑制其凋亡,提示AMIGO2可能是NPC治疗的潜 在靶点。     

EBV-miR-BART10-3p facilitates epithelial-mesenchymal transition and promotes metastasis of nasopharyngeal carcinoma by targeting BTRC

Epstein-Barr virus (EBV) infection is closely associated with tumorigenesis and development of nasopharyngeal carcinoma (NPC), but the underlying molecular mechanisms remain poorly understood. It has been recently reported that EBV encodes 44 mature miRNAs, some of which were found to promote tumor development by targeting virus-infected host genes or self-viral genes. However, few targets of EBV encoded-miRNAs that are related to NPC development have been identified to date. In this study, we revealed that in NPC cells, EBV-miR-BART10-3p directly targets BTRC gene that encodes βTrCP (beta-transducin repeat containing E3 ubiquitin protein ligase). We found that EBV-miR-BART10-3p expression in clinical samples from a cohort of 106 NPC patients negatively correlated with BTRC expression levels. Over-expression of EBV-miR-BART10-3p and down-regulation of BTRC were associated with poor prognosis in NPC patients. EBV-miR-BART10-3p promoted the invasion and migration cabilities of NPC cells through the targeting of BTRC and regulation of the expression of the downstream substrates β-catenin and Snail. As a result, EBV-miR-BART10-3p facilitated epithelial-mesenchymal transition of NPC. Our study presents an unreported mechanism underlying EBV infection in NPC carcinogenesis, and provides a potential novel biomarker for NPC diagnosis, treatment and prognosis.     

Down-regulation of GnT-V inhibits nasopharyngeal carcinoma cell CNE-2 malignancy in vitro and in vivo

To investigate the role of N-acetylglucosaminyltransferases V (GnT-V) in the development of human nasopharyngeal carcinoma (NPC) both in vitro and in vivo, the GnT-V stably suppressed cell line CNE-2 GnT-V/2224 was constructed from CNE-2. The studies indicated that down-regulation of GnT-V inhibited the proliferation, migration and invasion abilities of the NPC cell line CNE-2. The radio sensitivity of CNE-2 was enhanced after down-regulation of GnT-V, which may be associated with the decreased expression of bcl-2.     

微小RNA hsa-miR-93靶向STAT3提高鼻咽癌对放疗敏感性的机制研究

目的 研究hsa-miR-93在鼻咽癌放疗抗拒过程中的作用及分子机制。方法 以人鼻咽癌细胞株CNE-1、CNE-2、CNE-2R、HONE1、C666.1以及鼻咽上皮永生细胞NP460为研究对象,采用实时荧光定量PCR(qRT-PCR)法检测各组细胞经放疗后hsa-miR-93的表达;采用Western blot法检测各组细胞经放疗后STAT3蛋白的表达;通过miRWalk软件和RNAHybrid软件预测hsa-miR-93和STAT3的结合作用及结合位点;通过双荧光素酶报告基因法检测hsa-miR-93对STAT3靶向结合情况;瞬时转染小分子模拟物或抑制剂调控hsa-miR-93的表达后,采用qRT-PCR和Western blot法检测STAT3的表达;转染siSTAT3沉默STAT3的表达后,通过细胞集落形成实验检测鼻咽癌细胞经放疗后的集落形成能力。结果 与CNE-1、CNE-2细胞(相对放疗敏感)相比,hsa-miR-93在HONE1、CNE-2R细胞(相对放疗抗拒)中表达降低(P＜0.001),且各组鼻咽癌细胞经放疗后hsa-miR-93的表达呈剂量及时间依赖性降低(P＜0.05);与CNE-1、CNE-2细胞相比,STAT3在HONE1、CNE-2R细胞中表达升高,且各组鼻咽癌细胞经放疗后表达呈剂量及时间依赖性升高;经预测,hsa-miR-93可直接靶向结合STAT3。过表达hsa-miR-93可以在mRNA以及蛋白水平上显著抑制STAT3的表达(P＜0.05),而抑制hsa-miR-93的表达可以显著上调STAT3的表达(P＜0.05);过表达hsa-miR-93或沉默STAT3均使鼻咽癌细胞的集落形成显著减少(P＜0.001);抑制hsa-miR-93减弱了鼻咽癌对放疗的敏感性,而同时抑制hsa-miR-93和STAT3后,可提高鼻咽癌对放疗的敏感性。结论 hsa-miR-93可能通过靶向STAT3提高鼻咽癌对放疗的敏感性。     

Gene therapy for human nasopharyngeal carcinoma by adenovirus-mediated transfer of human p53, GM-CSF, and B7-1 genes in a mouse xenograft tumor model

Incidence of nasopharyngeal carcinoma (NPC) remains high in endemic regions. Prevention of tumor recurrences and metastases is a crucial approach to improve therapeutic outcome in NPC patients. In this study, we investigated the effects of the cotransfer of the tumor suppressor gene, p53, in combination with the immunostimulatory genes, GM-CSF and B7-1, on tumor regression and subsequent tumor recurrence. We constructed a recombinant adenovirus carrying human wild-type p53, granulocyte-macrophage colony-stimulating factor (GM-CSF), and B7-1 genes (Ad-p53/GM-CSF/B7-1), which mediated high-level expression of these three genes in NPC CNE-1 cells. Ad-p53/GM-CSF/B7-1 infection inhibited the growth of CNE-1 cells and induced tumor-specific cytotoxic T-lymphocytes (CTLs) in vitro. In CNE-1 xenograft tumor models in huPBL-nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice, an intratumoral injection of Ad-p53/GM-CSF/B7-1 resulted in a reduced tumor burden, compared to normal saline (NS) and Ad-p53 controls. Tumors in the Ad-p53/GM-CSF/B7-1 group displayed diffuse necrosis and infiltration of human T-cells. Further, the tumor occurrence of CNE-1 cell rechallenge largely decreased after the primary tumor was intratumorally injected with Ad-p53/GM-CSF/B7-1 in the HuPBL-NOD/SCID mice model. Only 2 of 8 (25%) animals in the Ad-p53/GM-CSF/B7-1 group had developed measurable tumors, which demonstrated extensive necrosis and much more human T-cell infiltration, compared to 5 of 7 (71%) in the NS and Ad-p53 groups. Therefore, the adenovirus-mediated introduction of p53, GM-CSF, and B7-1 genes could improve local control and prevent the recurrence or metastases of NPC tumors, which suggests a potential therapeutic value in NPC treatment.     

抑制Polo样激酶1对鼻咽癌细胞辐射敏感性的影响

目的:探索抑制Polo样激酶1(Polo-like kinase 1,PLK1)对鼻咽癌(nasopharyngeal carcinoma,NPC)细胞CNE-1和CNE-2辐射敏感性的影响.方法:分别运用siRNA和小分子抑制剂BI2536抑制CNE-1和CNE-2细胞内PLK1的表达或磷酸化,通过MTT法检测抑制PLK1对NPC细胞增殖能力的影响,流式细胞技术检测对细胞周期和凋亡的影响,细胞免疫荧光检测对辐射后DNA损伤位点的影响,克隆形成实验及曲线拟合计算对辐射后细胞放射生物参数和放射增敏比(sensitizationenhancement ratio,SER)的影响.结果:与对照组相比,抑制PLK1可以明显抑制NPC细胞增殖,并诱导细胞发生G2-M期阻滞和有丝分裂灾难.抑制NPC细胞PLK1联合射线辐射后,NPC细胞克隆形成能力下降(CNE-1:P ＜0.05;CNE-2:P ＜0.05),且随着BI2536浓度的增大克隆形成能力下降更加明显(CNE-1:P ＜0.05;CNE-2:P ＜0.05);细胞生存分数明显降低(均P＜0.05);核中γ-H2AX位点数目明显增加(P＜0.05);细胞凋亡率显著升高(均P＜0.05);siR-PLK1转染CNE-1和CNE-2后SER分别为1.1988和1.3198,BI2536处理CNE-1和CNE-2后SER分别为1.5508和1.2028.结论:抑制PLK1可以抑制NPC细胞增殖,诱导发生细胞周期阻滞和有丝分裂灾难,并能显著提高NPC细胞辐射敏感性.     

2-Chloroethyl-3-sarcosinamide-1-nitrosourea (SarCNU) exhibits p53-dependent and -independent antiproliferative activity in human nasopharyngeal carcinoma cells in vitro and in vivo

2-Chloroethyl-3-sarcosinamide-1-nitrosourea (SarCNU) has been used to treat patients with advanced solid tumours. However, the molecular mechanisms are not well understood. In the present study, we report that SarCNU inhibited proliferation of human HK-1 and CNE-2 nasopharyngeal carcinoma (NPC) in vivo and in vitro. In vitro study showed that wild-type p53 HK-1 cells were 3-fold more sensitive to SarCNU than p53 mutant CNE-2 cells. G2/M arrest, reduction in p21(Cip1/Waf1) and inactivation of cellular cdc-2 activity were seen in both SarCNU-treated HK-1 and CNE-2 cells. Upregulation of p53, phosphorylated p53 at Ser15 and biochemical markers for apoptosis, such as cleaved caspase-3, cleaved caspase-7 and cleaved PARP, were observed in SarCNU-treated HK-1 but not CNE-2 cells. The levels of cyclin B1, Wee1 and phosphorylated cdc-2 but not total cdc-2 in HK-1 cells were significantly reduced by SarCNU treatment. In contrast to HK-1 cells, decrease in total cdc-2 but increase in phosphorylated cdc-2 at Tyr15, cyclin B1 and Wee1 was observed in CNE-2 cells treated with SarCNU. Introduction of mutant p53 into HK-1 cells resulted in growth enhancement in vivo and increased resistance to SarCNU-induced apoptosis in vitro. Furthermore, CNE-2 cells transfected with wild-type p53 became susceptible to SarCNU-induced apoptosis in vitro but not their growth rate in vivo. The data indicate that in NPC cells SarCNU-induced apoptosis was p53-dependent while SarCNU-induced G2/M arrest was mediated by altering the levels of cyclin B1-cdc-2 complex and phosphorylation of cdc-2 at Tyr15 resulting in inactivation of cellular cdc-2 activity. Our data suggest a potential use of SarCNU in the treatment of NPC.     

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.     

Promoter hypermethylation contributes to the frequent suppression of the CDK10 gene in human nasopharyngeal carcinomas

Background

Previous studies have shown a down-regulation of the gene encoding cyclin-dependent kinase 10 (CDK10) in hepatocellular carcinomas. Here we provide evidence that down-regulation of the CDK10 gene is mediated by promoter hypermethylation in primary human nasopharyngeal carcinomas (NPC) and NPC-derived cell lines.

Methods

RT-PCR, Western blotting, methylation-specific PCR and bisulfite sequencing were performed to assess the expression and methylation status of the CDK10 gene in primary NPC samples, NPC-derived cell lines and patient-derived peripheral blood samples. The NPC-derived cell line CNE-2 was selected for treatment with a methylation inhibitor to restore CDK10 expression. In addition, cell proliferation, invasion and colony formation assays were performed to assess the inhibitory effects of ectopic CDK10 expression in CNE-2 cells.

Results

Down-regulation of CDK10 expression in primary NPC samples (23/40, 57.5 %) was found to be significantly correlated with the methylation status of its promoter CpG island (21/40, 52.5 %). Demethylation by 5-aza-dC treatment led to reactivation of the CDK10 gene in the CNE-2 cell line. Additionally, exogenous expression of CDK10 in CNE-2 cells strongly suppressed its growth, invasion and colony formation capacities. The high sensitivity (15/40, 37.5 %) and specificity (0 % false positives) of detecting CDK10 promoter hypermethylation in NPC patient-derived peripheral blood samples suggest that it could be employed as an epigenetic marker for noninvasive cancer diagnosis and recurrence screening.

Conclusion

Our findings implicate that aberrant methylation of the CDK10 gene promoter occurs frequently in NPC, and that reactivation of CDK10 might be utilized as a novel epigenetic strategy for the treatment of NPC patients.