Suppression of bcl-2 gene by RNA interference increases chemosensitivity to cisplatin in nasopharyngeal carcinoma cell line CNE1

To explore the effect of suppressing BCL-2 expression using RNA interference (RNAi) technique in nasopharyngeal carcinoma cell line CNE1. CNE1 cell lines stably expressing shRNAs targeted bcl-2 and GL3 gene were established and gene expression inhibition was assessed by Western blotting analysis. The effect of suppressing bcl-2 by RNAi on cell growth was studied, the apoptosis induction and the sensitization of CNE1 cells to cisplatin were quantified by MTT assay and flow cytometry. The results showed that: stable transfection of CNE1     

Polymorphism analyses of hepatitis B virus X gene in hepatocellular carcinoma patients from southern China

Chronic hepatitis B virus(HBV)infection is one of the major causes of hepatocellularcarcinoma(HCC),and the HBV X(HBx)gene plays a critical role in the molecular pathogenesis ofHBV-related HCC.We have investigated whether there are particular HBx gene mutations associated withHCC in patients from southern China.The HBx gene was examined in 51 paraffin-embedded tumor tissuesamples from patients with HCC and 25 serum samples from the HBV carrier by nested polymerase chainreaction(PCR),single-stranded conformational polymorphism and heteroduplex analysis.The HBx geneswith potentially important mutations from tumor tissue samples were cloned,sequenced and aligned withthe published HBx gene sequence.HBV genotypes in tumor tissue samples were analyzed by nested PCR.Analyses of HBx gene polymorphism showed that 31.3% of HBx gene fragments in tumor tissue sampleshad a special pattern.A common deletion at nt 382-400 of the HBx gene accompanied by 29 point mutationswas detected in four randomly selected tumor tissue samples with this pattern which caused a frame-shiftin the HBx open reading frame with a new stop codon at nt 1818,resulting in an HBx polypeptide chaintruncated at the C end in these cases.Among the four randomly selected samples,three were HBV genotypeB,and one was not detected by our present assay.In another tumor tissue sample,amplification of thefull-length HBx gene yielded a shorter fragment.Sequencing of this fragment revealed a 264 bp deletionbetween nt 1577 and 1840 of the HBV gene.These results suggest that HBx gene mutation occurs frequentlyin HCC samples,and the deletion at nt 382-400 of the HBx gene might play a role in carcinogenesis of HCCin southern China.     

Computational screening of disease associated mutations on NPC1 gene and its structural consequence in Niemann-Pick type-C1

Niemann-Pick disease type C1 （NPC1）, caused by mutations of NPC1 gene, is an inherited lysosomal lipid storage disorder. Loss of functional NPC1 causes the accumulation of free cholesterol （FC） in endocytic organelles that comprised the characteristics of late endosomes and/or lysosomes. In this study we analyzed the pathogenic effect of 103 nsSNPs reported in NPC1 using computational methods. Rl186C, S940L, R958Q and I1061T mutations were predicted as most deleterious and disease associated with NPC1 using SIFT, Polyphen 2.0, PANTHER, PhD-SNP, Pmut and MUTPred tools which were also endorsed with previous in vivo experimental studies. To understand the atomic arrangement in 3D space, the native and disease associated mutant （Rl186C, S940L, R958Q and I1061T） structures were modeled. Quantitative structural and flexibility analysis was conceded to observe the structural consequence of prioritized disease associated mutations （R1186C, S940L, R958Q and I1061T）. Accessible surface area （ASA）, free folding energy （FFE） and hydrogen bond （NH bond） showed more flexibility in 3D space in mutant structures. Based on the quantitative assessment and flexibility analysis of NPC1 variants, I1061T showed the most deleterious effect. Our analysis provides a clear clue to wet laboratory scientists to understand the structural and functional effect of NPCI gene upon mutation.     

mad—overexpression down regulates the malignant growth and p53 mediated apoptosis in human hepatocellular carcinoma BEL—7404 cells

Mad protein has been shown as an antagonist of cMyc protein in some cell lines.The effect of Mad protein to the malignant phenotype of human hepatoma BEL-7404 cell line was investigated experimentally.An eukarryotic vector pCDNA Ⅲ containing full ORF fragment of mad cDNA was transfected into targeted cells.Under G418 selection,stable Mad-overexpressed cells were cloned.Studies on the effect of Mad over-expression in cell proliferation and cell cycle revealed that cell morphology of the Mad-overexpressed BEL-7404-M1 cells was significantly different from the parent and control vector transfected cells.DNA synthesis,cell proliferation and anchorage-independent growth in soft-agar of the madtransfected cells were partially inhibited in comparison to control cells.Flos cytometry analysis indicated that mad over-expression might block more transfectant cells at G0/G1 phase,resulting in the retardation of cell proliferation.RT-PCR detected a marked inhibition of the expression of cdc25A,an important regulator gene of G0/G1 to S phase in cell cycle.It was also found that Mad protein overexpression could greatly suppress p53-mediated apoptosis in BEL-74040M1 cells in the absence of serume.Thus,Mad proteins may function as a negative regulator antagonizing c-Myc activity in the control of cell growth and apoptosis in human hepatocellular carcinoma BEL-7404 cells.     

人癌细胞线粒体DNA控制区序列特征分析

为了探讨癌细胞mtDNA控制区序列的变化特征, 采用PCR产物限制性片段长度多态性(PCR-RFLP)分析与直接测序相结合的方法,对比分析6株人癌细胞系、 6例癌患者及4例健康成人白细胞mtDNA控制区序列。发现第16519位T→C、16 534位A→G、46位T→G和49位A→C突变, 在癌细胞系和癌患者白细胞mtDNA中分别占50%(3/6)和33.3%(2/6), 健康成人白细胞mtDNA中未见此类型突变;第16 278位C→T突变,在癌细胞系mtDNA中占50%(3/6),显著高于正常人群mtDNA中此位点的多态性变异。表明癌细胞和癌患者白细胞mtDNA重链复制起点及其 相邻D环区的特征性突变可能与细胞癌变/或癌的易感性有关。 Abstract：　To explore the sequence feature of mitochondrial DNA(mtDNA) control region in human carcinoma cells, polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP) and direct sequence techniques were used to analyze the sequence of mtDNA control region of 6 human carcinoma cell lines versus white blood cells which from 6 tumor patients and 4 normal adults. The T to C mutation at np 16 519, A to G mutation at np 16 534, T to G mutation at np 46, and A to C mutation at np 49 was found in 50% (3/6 cases) of carcinoma cell lines and in 33.3%(2/6 cases) of tumor patients, but it was not found in normal adults. The C to T mutation at np 16 278 was found in 50%(3/6 cases) of carcinoma cell lines, it was significantly higher than that of the polymorphism of normal population. These findings suggest that the typical mutation in the starting area of heavy-strand replication and the first half of D-loop region might probably be associated with carcinogenesis or susceptibility of carcinoma.     

Identification of the proteins related to p53-mediated radioresponse in nasopharyngeal carcinoma by proteomic analysis

Radiotherapy is the primary treatment for nasopharyngeal cancer (NPC), and p53 is closely associated with the radiosensitivity of cancer, but the molecular mechanisms of p53-mediated radioresponse in NPC remains unclear. We previously established NPC CNE2sip53 cell line with p53 knockdown and paired control cell line CNE2/pSUPER, which provides a cell model system to investigate mechanisms of p53-mediated radioresponse in NPC. In this study, we first compared the radiosensitivity of CNE2sip53 and CNE2/pSUPER by a clonogenic survival assay, cell growth assay, and Hoechst 33258 staining and flow cytometry analysis of apoptotic cells. The results showed that the radiosensitivity of CNE2sip53 was significantly lower than that of CNE2/pSUPER, indicating that p53 plays a role in mediating NPC radiosensitivity. To search for the proteins associated with the p53-mediated radioresponse in NPC, a proteomic approach was performed to identify the radioresponsive proteins in CNE2sip53 and CNE2p/SUPER, respectively, and then the difference of radioresponsive proteins in CNE2sip53 and CNE2p/SUPER was compared. As a result, 14 differential radioresponsive proteins were identified in the two cell lines, 4 proteins of which were conformed by Western blot. Among them, 9 and 5 proteins were identified solely from CNE2p/SUPER and CNE2sip53, respectively. Furthermore, protein-protein interaction analysis showed that 7 differential radioresponsive proteins identified only in CNE2p/SUPER were related to p53 protein. Our results suggest that the differential radioresponsive proteins unique to CNE2p/SUPER may be involved in p53-mediated radioresponse in NPC, which will be helpful for elucidating the mechanisms of p53-mediated NPC cellular response to radiotherapy.     

A novel Rhein derivative: Activation of Rac1/NADPH pathway enhances sensitivity of nasopharyngeal carcinoma cells to radiotherapy

Radiation resistance and recurrent have become the major factors resulting in poor prognosis in the clinical treatment of patients with nasopharyngeal carcinoma (NPC). New strategies to enhance the efficacy of radiotherapy have been focused on the development of radiosensitizers and searching for directly targets that modulated tumor radiosensitivity. A novel potential radiosensitizer 1,8-Dihydroxy −3-(2′-(4″-methylpiperazin-1″-yl) ethyl-9,10-anthraquinone −3-carboxylate (RP-4) was designed and synthesized based on molecular docking technology, which was expected to regulate the radiosensitivity of tumor cells through targeting Rac1. In order to assess the radiosensitization activity of RP-4 on NPC cells, the highly differentiated CNE1 and poorly differentiated CNE2 cells NPC lines were employed. According to the results, RP-4 showed higher binding affinity toward the interaction with Rac1 than lead compounds. We found that RP-4 could inhibit cell viability and proliferation in CNE1 and CNE2 cells and significantly induced apoptosis after non-toxic concentration of RP-4 combined with 2Gy irradiation. RP-4 could effectively modulated the radiosensitivity both CNE1 cells and CNE2 cells through activating Rac1/NADPH signaling pathway and its downstream JNK/AP-1 pathway. What's more, Rac1/NADPH signaling pathway were significantly activated in Rac1-overexpressed CNE1 and CNE2 cells after treated with RP-4. Taken together, Rac1 and its downstream pathway may probably be the direct targets of RP-4 in regulating radiosensitivity of NPC cells, our finding provided a novel strategy for the development of therapeutic agents in response to tumorous radiation resistance.     

DNA-PK的活性与鼻咽癌细胞株CNE1/CNE2放射敏感性的关系

本文主要研究DNA依赖的蛋白激酶（DNA-dependent protein kinase,DNA-PK）与鼻咽癌细胞放射敏感性之间的关系。克隆形成实验分析鼻咽癌细胞CNEI／CNE2的剂量存活曲线,Signa TECT DNA-PK试剂盒检测DNA-PK活性,免疫荧光及激光显微共聚焦分析放疗前及放疗后15min、1h、6h、12h和24hCNE1／CNE2细胞中Kus及DNA-PKcs的亚细胞定位,Western blot分析两株细胞中Kus蛋白的表达。结果显示：CNE1细胞在每个剂量点的存活分数均高于CNE2细胞;同时发现放疗前后CNE1细胞中的DNA-PK活性也均高于CNE2细胞,但两株细胞中Ku70／Ku80蛋白表达无明显差异;放疗可使DNA-PK活性增加,且各个检测时间点CNE1细胞增加的幅度大于CNE2细胞;DNA-PK亚基可同时定位于胞浆和胞核,但主要位于胞核,细胞照射后Ku70、Ku80和DNA-PKcs从胞浆转运到胞核。结果表明：DNA-PK活性更高可能是CNE1细胞较CNE2细胞更能抵抗放射的原因之一;放疗所致DNA-PK活性增高可能与DNA-PK亚基从胞浆转运到胞核有关,而与Ku蛋白表达的总量无关。     

Dual Phosphoinositide 3-Kinase/Mammalian Target of Rapamycin Inhibitor NVP-BEZ235 Has a Therapeutic Potential and Sensitizes Cisplatin in Nasopharyngeal Carcinoma

Phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin inhibitor (mTOR) pathway is often constitutively activated in human tumor cells and thus has been considered as a promising drug target. To ascertain a therapeutical approach of nasopharyngeal carcinoma (NPC), we hypothesized NVP-BEZ235, a novel and potent imidazo[4,5-c] quinolone derivative, that dually inhibits both PI3K and mTOR kinases activities, had antitumor activity in NPC. Expectedly, we found that NVP-BEZ235 selectively inhibited proliferation of NPC cells rather than normal nasopharyngeal cells using MTT assay. In NPC cell lines, with the extended exposure, NVP-BEZ235 selectively inhibited proliferation of NPC cells harboring PIK3CA mutation, compared to cells with wild-type PIK3CA. Furthermore, exposure of NPC cells to NVP-BEZ235 resulted in G1 growth arrest by Propidium iodide uptake assay, reduction of cyclin D1and CDK4, and increased levels of P27 and P21 by Western blotting, but negligible apoptosis. Moreover, we found that cisplatin (CDDP) activated PI3K/AKT and mTORC1 pathways and NVP-BEZ235 alleviated the activation by CDDP through dually targeting PI3K and mTOR kinases. Also, NVP-BEZ235 combining with CDDP synergistically inhibited proliferation and induced apoptosis in NPC cells. In CNE2 and HONE1 nude mice xenograft models, orally NVP-BEZ235 efficiently attenuated tumor growth with no obvious toxicity. In combination with NVP-BEZ235 and CDDP, there was dramatic synergy in shrinking tumor volumes and inducing apoptosis through increasing Noxa, Bax and decreasing Mcl-1, Bcl-2. Based on the above results, NVP-BEZ235, which has entered phase I/II clinical trials in patients with advanced solid tumors, has a potential as a monotherapy or in combination with CDDP for NPC treatment.     

Identification of differential proteins in nasopharyngeal carcinoma cells with p53 silence by proteome analysis

Although mutation of p53 tumor-suppressor gene is rare in nasopharyngeal carcinoma (NPC), NPC has a high frequency of overexpression of p53 protein. There seem to be complex mechanisms of inactivation and stabilization of p53 in NPC. To detect proteins associated with the function of p53 in high throughout screening, we succeeded in establishing p53 knockdown human NPC CNE2 cell line (CNE2sip53) using stable RNA interference, and compared the proteomic changes between CNE2sip53 and control cell line CNE2/pSUPER using two-dimensional gel electrophoresis. Twenty-two differentially expressed proteins between the two cell lines were identified by both matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and electrospray ionization tandem mass spectrometry, some of which are known to be associated with the p53 function (HSP27, hnRNP K, 14-3-3sigma, etc.), and others may be novel proteins associated with p53 function (eIF4B, TPT1, hnRNP H3, SFRS1 etc.). Furthermore, several differential proteins including HSP27, HSP70, GRP75 and GRP78 were verified as p53 interacting proteins in NPC by immunoprecipitation and Western blot analysis, and the suppression of HSP27 expression by HSP27 antisense oligonucleotides could decrease the p53 protein level. Our data suggest that these differential proteins may be associated with the function of p53 in NPC, and provide new clues to elucidate the mechanisms of inactivation and stabilization of p53 in NPC.     

Tx基因与Igk基因的同源性研究及其在不同细胞株的表达

本文对以前报道的Ｔｘ基因２．８ｋｂ片段的核苷酸序列与人免疫球蛋白ｋａｐｐａ链Ｃ区基因的核苷酸序列及其编码产物的氨基酸序列进行了同源性比较。结果表明,Ｔｘ基因与ｋａｐｐａ链Ｃ区基因的同源性高达９９．５％以上,编码区的同源性高达１００％。从而提示Ｔｘ基因与ｋａｐｐａ链Ｃ区基因可能是同一种基因。限制性内切酶图谱及Ｓｏｕｔｈｅｒｎ印迹杂交分析,也进一步支持这一观点。本文还报道了ｋａｐｐａ链Ｃ区基因在不同细     

NFY结合位点缺失下调NPCEDRG基因启动子转录活性和效率

NPCEDRG基因是一个鼻咽癌(nasopharyngeal carcinoma, NPC)相关基因. NPCEDRG基因启动子为TATA-less启动子,其核心启动子区域位于-146 ～-8 bp区,该区域包含NFY、STAT1和cMYB等转录因子结合位点. 前期研究结果提示,转录因子NFY可能参与NPCEDRG基因的转录调控. 为明确NFY转录因子在NPCEDRG基因转录中的作用,本研究应用报告基因载体系统分析方法对NPCEDRG基因核心启动子区进行NFY结合位点（或CCAAT-box）缺失突变及其功能分析,分别构建NPCEDRG基因核心启动子区NFY结合位点缺失突变的Luc和EGFP报告基因表达载体. 比较核心启动子和NFY结合位点缺失突变体报告基因载体的转录活性和效率. 结果表明,在MCF7和CNE2细胞中,NFY结合位点缺失突变体的转录活性分别约为其核心启动子转录活性66.94%和75.72%,即NFY结合位点缺失致使该启动子转录效率在MCF7和CNE2细胞中分别降低了33.06%和24.28%;EGFP报告基因表达载体系统研究结果与Luc报告基因载体系统结果基本吻合. 本研究再次证实,转录因子NFY通过结合NPCEDRG基因启动子的核心元件NFY结合位点参与NPCEDRG基因的转录调控,并提高其基因转录活性和效率.     

Identification Keratin 1 as a cDDP-resistant protein in nasopharyngeal carcinoma cell lines

Multidrug resistance (MDR) to anticancer drugs is a major obstacle to successful chemotherapy of tumors. Understanding the molecular basis to chemoresistance is likely to provide better treatment. Cell lines resistant to cis-diamminedichloroplatinum (CNE2/cDDP) were established from human nasopharyngeal carcinoma (NPC) cell lines CNE2. Comparative proteomics involving 2-dimensional gel electrophoresis (2-DE) and ESI-Q-TOF-MS were performed on protein extracted from CNE2 and CNE2/cDDP cell lines to screen drug resistance-related proteins. Keratin 1 (KRT1), cathepsin D (CTSD) and annexin a5 (ANXA5) were identified as three proteins showing higher expression in CNE2/cDDP compared to CNE2. Furthermore, suppression of KRT1 expression by siRNA resulted in decreased MDR in siRNA-CNE2/cDDP cells. And upregulation of KRT1 could result in increased of drug resistance in NPC cell lines. Taken together, KRT1 protein and its activity levels were higher in cDDP-resistant NPC cell lines compared to their parental cell lines. These data clearly linked KRT1 and cDDP resistance mechanisms. KRT1 could serve as a biomarker for chemotherapy sensitivity of NPC.     

5-Azacytidine Enhances the Radiosensitivity of CNE2 and SUNE1 Cells In Vitro and In Vivo Possibly by Altering DNA Methylation

The radioresistance of tumor cells remains a major cause of treatment failure in nasopharyngeal carcinoma (NPC). Recently, several reports have highlighted the importance of epigenetic changes in radiation-induced responses. Here, we investigated whether the demethylating agent 5-azacytidine (5-azaC) enhances the radiosensitivity of NPC cells. The NPC cell lines CNE2 and SUNE1 were treated with 1 μmol/L 5-azaC for 24 h before irradiation (IR); clonogenic survival was then assessed. Tumor growth was investigated in a mouse xenograft model in vivo. The apoptosis, cell cycle progression and DNA damage repair were examined using flow cytometry, immunofluorescent staining and western blotting. Promoter methylation and the expression of four genes epigenetically silenced during the development of NPC were evaluated by pyrosequencing and real-time PCR. We found that pretreatment with 5-azaC significantly decreased clonogenic survival after IR compared to IR alone; the sensitivity-enhancement ratio of 5-azaC was 1.4 and 1.2 for CNE2 and SUNE1 cells, respectively. The combined administration of 5-azaC and IR significantly inhibited tumor growth in the mouse xenograft model, and enhanced radiation-induced apoptosis in vitro compared to 5-azaC alone or IR alone. 5-AzaC also decreased promoter methylation and upregulated the expression of genes which are epigenetically silenced both in vitro and in vivo in NPC. Thus, 5-azaC enhance the radiosensitivity of both the CNE2 and SUNE1 cell lines, possibly by altering DNA methylation levels and increasing the ability of irradiated cells to undergo apoptosis. The use of 5-azaC combined with IR maybe represent an attractive strategy for the treatment of NPC.