Human papillomavirus 16 E6 increases the radiosensitivity of p53-mutated cervical cancer cells,associated with up-regulation of aurora A

Purpose:?To examine the effect of the human papillomavirus (HPV) type 16-E6 (HPV ‘early’ gene) oncoprotein on in vitro radiosensitivity of HPV-negative/p53 mutant C33a cervical cancer cells.

Methods and materials:?The human cervical cancer cell line C33a was stably transfected with either the HPV16 E6 cDNA cloned into the vector pcDNA?3.0 (C33aE6) or the empty-vector control (C33aV). Radiosensitivity, DNA damage, and cell cycle measurements were made using standard clonogenic assays, immunofluorescent assessment of nuclear histone H2AX phosphorylated on serine-139 (γ-H2AX) foci, and flow cytometry. Western immunoblotting and fluorescence confocal microscopy were used to analyse the changes in cellular proteins. Real-time polymerase chain reaction (PCR) was used to compare levels of aurora A mRNA.

Results:?Compared to C33aV cells, C33aE6 cells showed enhanced radiation cell killing. This was associated with a large amount of polyploidy which was followed by late cell death in C33aE6 cells. Aurora A was highly expressed in C33aE6 cells at pre- and post-irradiation times compared to C33aV cells. Silencing aurora A resulted in a reduced amount of residual γ-H2AX foci in C33aE6 cells, and diminished the difference in radiosensitivity between the C33aE6 and C33aV cells.

Conclusion:?Our in vitro results indicate that genetic instability could be augmented in the HPV-infected cancer cells by up-regulation of aurora A, especially against a background of dysfunctional p53. Further studies are needed to examine whether aurora A could be a viable therapeutic target in HPV-related tumours.     

Dexamethasone-induced radioresistance occurring independent of human papilloma virus gene expression in cervical carcinoma cells

Background

Inactivation of p53 by binding to simian virus 40-T antigen (SV40-T) and human papilloma virus type 16 protein E6 (HPV 16 E6) in transfected human diploid fibroblasts causes enhanced radioresistance. The aim of this study was to investigate the role of HPV 18 E6 and E7 gene products with respect to radiosensitivity of two cervical carcinoma cell lines.

Materials and Methods

The two cervical carcinoma lines C4-1 and SW 756 were used in which treatment with dexamethasone allows to modulate expression levels of HPV 18 E6 and E7 genes: upregulation in C4-1, downregulation in SW 756. Effects of treatment with dexamethasone on plating efficiency and radiosensitivity were assessed using a clonogenic assay.

Results

Treatment with dexamethasone increased plating efficiency of the C4-1 cells, but did not affect plating efficiency of SW 756 cells. Treatment with dexamethasone induced enhanced radioresistance in both cell lines. Thus, in C4-1 cells the observed changes in radioresistance correlate to the enhancement in expression of HPV 18 genes E6/E7, whereas in SW 756, a reduced expression correlates negatively with the enhanced radioresistance.

Conclusions

In C4-1 and SW 756 cells, treatment with dexamethasone induces radioresistance, and changes in expression levels of HPV 18 genes E6 and E7 do not correlate with the changes in radiosensitivity. Dexamethasone-induced radioresistance has previously been observed in HeLa cells, another human cervical carcinoma cell line. This leads us to speculate that dexamethasone-induced radioresistance may be important in certain clinical situations, and that therefore, the phenomenon deserves further study.     

B细胞易位基因2的表达水平对肿瘤细胞放射敏感性的影响

目的 研究B细胞易位基因2（BTG2）表达水平的改变对肿瘤细胞放射敏感性的影响。 方法 通过pcDNA3-BTG2脂质体转染的方法提高细胞的BTG2的表达水平,利用噻唑蓝和细胞克隆形成实验研究细胞放射敏感性的改变,应用Western blot方法研究蛋白表达水平的变化。 结果 噻唑蓝和细胞克隆形成实验结果显示,在不同剂量的γ射线照射后,提高BTG2的表达水平可明显提高乳腺癌MCF-7和MDA-MB-231细胞的放射敏感性。免疫共沉淀-Western blot实验结果显示BTG2蛋白与DNA损伤修复和抗氧化蛋白乳腺癌易感基因1（BRCA1）相互作用,形成复合物。高表达的BRCA1明显地抑制了BTG2高表达对乳腺癌细胞放射敏感性的调节作用,而降低BRCA1的表达水平则提高了BTG2对乳腺癌细胞放射敏感性的调节作用。另外,肺癌细胞放射敏感性与其所含的BRCA1的表达水平成反比,而与BTG2的表达水平成正比。 结论 BTG2的高表达明显提高了肿瘤细胞的放射敏感性,其机制可能与其同BRCA1形成复合物有关。     

miR-885-3p靶向AKT1对结直肠癌细胞HT-29放射敏感性的影响

目的 探究miR-885-3p对结直肠癌细胞HT-29放射敏感性的影响以及作用机制。方法 荧光定量PCR检测经不同剂量（0、2、4、6、8 Gy）X射线照射后HT-29细胞中miR-885-3p的表达量;建立过表达miR-885-3p细胞株,功能试验探讨其对HT-29细胞放射敏感性的影响;生物信息学预测miR-885-3p下游调控的靶基因,双荧光素酶报告基因法进一步验证;上调和下调miR-885-3p表达量探讨miR-885-3p与靶基因丝苏氨酸蛋白激酶1（AKT1）表达量的调控关系;慢病毒转染敲减AKT1表达量,观察其对HT-29细胞放射敏感性的影响;共转染miR-885-3p模拟物,探讨过表达AKT1对miR-885-3p诱导的HT-29细胞放射敏感性的影响。结果 miR-885-3p在放射诱导的HT-29细胞中表达上调（F=46.64,P<0.05）;过表达miR-885-3p和敲减AKT1可通过抑制HT-29细胞存活、促进其凋亡,从而增强HT-29细胞放射敏感性（t=12.33、12.95,P<0.05）,放射增敏比（SER）分别为1.602和1.946;抑制miR-885-3p可通过促进HT-29细胞存活、抑制其凋亡从而促进HT-29细胞放射抵抗（t=11.94,P<0.05）,SER为0.839;AKT1是miR-885-3p下游靶基因;过表达AKT1反转miR-885-3p增强HT-29放射敏感性的作用,SER为0.680。结论 miR-885-3p通过直接靶向AKT1增加结直肠癌HT-29细胞放射敏感性,为提高临床结直肠癌放疗敏感性提供一个靶点。     

肺癌乳头状瘤病毒感染与P53基因突变的研究

应用PCR与原位杂交技术检测了40例原发性肺癌乳头状瘤病毒（HPV）的感染率及与肺癌不同组织类型的关系；应用PCR-RFLP技术分析P53基因第七外显子的扩增与突变，结果显示；肺癌HPV阳性率为55%（22/40例），其中SCLC9/9例，鳞癌8/16例，腺癌5/12例阳性，P53基因第七外显子在HPV阳性的标本中有5/22例扩增，RFLP分析2/5例（SCLC，鳞癌各一例）突变，探讨HPV感染，P53基因与肺癌的关系。     

Expression of the DNA-PK binding protein E4-34K fails to confer radiation sensitivity to mammalian cells

PURPOSE: The adenovirus E4orf6 34 kDa protein (E4-34k) is known to disrupt V(D)J recombination as a result of its interaction with the catalytic subunit of cellular DNA-dependent protein kinase (DNA-PK(cs)), a major participant in the repair of DNA double-strand breaks (DSB). Previous studies have shown that cells with disrupted DSB repair and V(D)J recombination due to attenuation of DNA-PK(cs) activity exhibit a radiation-sensitive phenotype. It is not known at present whether the E4-34k protein can also modify cellular response to ionizing radiation. In an attempt to develop a novel gene therapy strategy to modify cellular radiation response, we sought to determine if expression of the adenovirus E4-34k protein resulted in sensitization to clinically relevant doses of ionizing radiation. MATERIALS AND METHODS: In order to minimize potential bias resulting from selection procedures, we performed clonogenic survival assays on DU 145 prostate cancer cells, RKO colorectal cancer cells and 293 kidney cells following transient transfection of E4-34k- and/or E1B-55k-expressing plasmids. Western blots and immunohistochemical analyses were used to demonstrate E4-34k expression within transfected cells. FACS sorting was carried out to enrich cells transfected with a plasmid that expresses both E4-34k and enhanced green fluorescent protein. RESULTS: It is shown that E4-34k expression does not affect cellular radiosensitivity of transiently transfected populations of either DU 145 prostate or RKO colon cancer cell lines. Similarly, the radiosensitivity of human embryonic kidney 293 cells, which constitutively express the E1B-55k protein, was also unaffected. The radiosensitivity of DU 145 cells co-transfected with E4-34k- and E1-55K-expressing plasmids was unchanged, suggesting that the adenovirus E1B-55k protein does not augment any effects E4-34k might have on DNA-PK(cs) activity. CONCLUSIONS: The lack of radiosensitization by E4-34k expression is quite intriguing as it is known that E4-34k interaction with DNA-PK(cs) causes disruption of V(D)J recombination, a process dependent on DSB rejoining. These data suggest that for future studies, preferential targeting of DNA-PK(cs) DSB activity will be required to influence cellular radiosensitivity.     

阻断血管内皮生长因子表达对食管癌细胞放射敏感性的影响

目的 观察转染反义VEGF cDNA质粒和反义寡核苷酸后,TE-1食管癌细胞在体外的生长状况、VEGF表达水平及其放射敏感性的变化。方法 分别用反义VEGF cDNA质粒及空载体质粒和反义VEGF寡核苷酸经Lipofectamine^TM2000介导转染TE-1细胞,然后经γ射线照射。采用RT-PCR、Western blotting、流式细胞术、MTT法和克隆形成实验分别检测4组细胞照射前后VEGF基因的表达、凋亡率和细胞周期变化、细胞增殖情况以及转染细胞放射敏感性的变化。结果 将反义VEGF cDNA和反义寡核苷酸成功转入食管癌TE-1细胞后,VEGF表达水平明显降低,细胞增殖反应、细胞周期无明显变化,亦未见明显凋亡发生。照射后4组细胞增殖情况未见明显差异;反义组细胞凋亡率略有上升, 放射敏感性增加。结论 转染反义VEGF cDNA质粒和反义寡核苷酸可抑制食管癌TE-1细胞VEGF表达,联合放射线作用,对TE-1细胞的增殖无明显影响,而对其放射敏感性有增强作用。     

HBXIP蛋白表达对宫颈癌细胞的增殖能力及放射敏感性的影响

目的探讨用siRNA敲降乙肝病毒X蛋白结合蛋白（HBXIP）的表达对宫颈癌ME-180细胞的增殖能力及放射敏感性的影响。方法根据不同的处理方法,分别按两种分组方式进行分组。（1）把宫颈癌ME-180细胞分为4组:空白对照组、4 Gy γ射线照射组、HBXIP-siRNA转染组以及HBXIP-siRNA+γ射线照射联合组。采用MTT和克隆形成实验法来检测细胞增殖;采用qRTPCR检测凋亡相关蛋白Bcl-2及Bid的表达;Western blot检测蛋白激酶AKT的磷酸化水平。（2）把宫颈癌ME-180细胞分为3组:空白对照组、HBXIP-siRNA单独处理组、HBXIP-siRNA和AKT共转染组。对3组细胞进行不同剂量的γ射线照射,并采用克隆形成实验方法检测细胞生长。采用Student t-test对数据进行统计学分析,P < 0.05表示差异有统计学意义。结果 MTT实验和克隆形成实验结果显示,与γ射线照射组相比,HBXIP-siRNA转染+γ射线照射联合组的宫颈癌ME-180细胞增殖率明显降低（t=11.63、12.17,均P < 0.01）,并伴随抑凋亡蛋白Bcl-2表达的降低（t=10.88,P < 0.01）和促凋亡蛋白Bid表达的增高（t=9.31,P < 0.01）。γ射线照射明显上调了HBXIP蛋白的表达水平和AKT蛋白的磷酸化水平,而转染HBXIP-siRNA则抑制了γ射线照射导致的AKT磷酸化水平的升高。另外,与HBXIP-siRNA单独处理组相比,HBXIP-siRNA和AKT共转染组中HBXIP-siRNA对宫颈癌ME-180细胞增殖的影响显著降低（t=8.96,P < 0.01）。结论降低HBXIP蛋白表达可以抑制辐照诱导的AKT磷酸化水平,进而降低宫颈癌ME-180细胞的增殖能力,同时增强其放射敏感性。     

东部马脑炎病毒E2基因的表达及DNA免疫的初步研究

目的：构建东部马脑炎病毒E2基因的重组真核表达载体，对其DNA免疫原性进行观察。方法：采用RT-PCR扩增东部马脑炎病毒全长E2基因，构建真核表达载体pcDNA-E2，以脂质体法转染COS7细胞，经蛋白印迹法和免疫荧光法证明E2基因可以表达后，用庐重组质粒DNA免疫Balb/c小鼠，并用免疫荧光法检测鼠血清中病毒的特异抗体。结果：免疫印迹法、免疫荧光法检测表明E2基因在COS7细胞中获得瞬时表达，pcDNA-E2基因免疫小鼠可产生抗东部脑炎病毒的特异抗体。结论：东部马脑炎病毒E2基因的重组质粒DNA可刺激小鼠产生特异性的抗东部马脑炎病毒体液免疫应答，为基因疫苗的研制奠定了基础。     

转录因子Sp1对肺癌细胞LKB1-VEGF通路调控作用研究

目的:通过构建LKB1基因获得性肺癌细胞模型,了解转录因子Sp1对LKB1-血管内皮生长因子(VEGF)通路的调控作用.方法:应用巢式PCR(nPCR)方法扩增LKB1基因编码区,构建LKB1真核表达载体;Western 印迹检测LKB1在A549细胞中的表达;siRNA技术干扰Sp1的表达;RT-PCR联合ELISA方法检测VEGF的变化;SEAP检测系统检测Sp1的转录活性.结果:成功构建LKB1基因稳定表达细胞模型;LKB1蛋白下调VEGF表达和Sp1转录活性;siRNA介导的Sp1沉默伴随VEGF表达下调.结论:转录因子Sp1参与LKB1基因对VEGF的表达调控.     

反义表皮生长因子受体对人肺癌细胞放射敏感性的影响

目的 观察反义表皮生长因子受体(EGFR)对人肺腺癌细胞系放射敏感性的影响。方法在脂质体介导下用质粒pcDNA3-反义EGFR(pcDNA3-antiEGFR)转染spc-a-1细胞,并以未转染(对照组)和空质粒pcDNA3转染(pcDNA3组)细胞作对照。用G418筛选稳定表达的细胞克隆,以RT-PCR和Western blot检测转染后EGFR的mRNA及蛋白表达抑制情况,流式细胞仪检测转染后细胞周期及单次照射8 Gy后各组细胞凋亡比例。3组细胞分别给予6 MV X射线照射0、2、4、6和8 Gy,计算克隆形成率,拟合生长曲线。结果pcDNA3-antiEGFR组与对照组、pcDNA3组比较,EGFR mRNA和蛋白表达量明显减少,G₂/M期比例分别为(29.53±1.91)％、(13.7±1.30)%和(12.40±1.34)％,单次照射8Gy后,3个组细胞的凋亡率分别为(39.24±1.57)%、(13.79±0.63)%和(15.02±0.85)%。与对照组相比较,pcDNA3-antiEGFR组细胞的D₀、D_q、SF₂值分别由2.11、2.49和0.84降至1.19、0.15和0.32,提示抑制EGFR表达,可降低spc-a-1细胞对射线所致亚致死性损伤的修复能力。结论反义EGFR可以降低人肺癌spc-a-1细胞中EGFR的表达,改变细胞周期分布,促进凋亡,降低亚致死性损伤的修复能力,增加肺癌细胞系spc-a-1的放射敏感性。     

pcDNA3.1+Ape1质粒转染对人脐静脉内皮细胞辐射敏感性的影响

目的 探讨pcDNA3.1+Ape1质粒转染对血管内皮细胞电离辐射敏感性的影响。方法 以pcDNA3.1+空载体转染、未转染细胞作对照,在细胞转染pcDNA3.1+Ape1质粒后48 h,给予3组细胞2、4、6和8 Gy高能X线照射,采用碱性单细胞凝胶电泳和克隆形成实验,分析在不同辐射剂量条件下pcDNA3.1+Ape1质粒转染对人脐静脉内皮细胞辐射敏感性的影响。结果 与未转染细胞相比,3 μg pcDNA3.1+Ape1质粒转染细胞的初始OTM和残存OTM值在2 Gy照射时显著降低(P<0.01),但8Gy照射时差异无统计学意义(P>0.05);SF₂显著增高(P<0.05),但SF₄、SF₆及SF₈的差异均无统计学意义(P>0.05)。结论 pcDNA3.1+Ape1质粒转染可增加内皮细胞对低剂量电离辐射的抵抗能力。     

黄芪、党参提取物抑制肺癌细胞诱导血管内皮细胞迁移的实验研究

 目的 观察黄芪、党参提取物对肺癌细胞诱导的血管内皮细胞迁移的影响,探讨扶正中药抗肿瘤生长的机制.方法 采用免疫组化和图像分析技术,观察不同浓度的黄芪、党参提取物对人小细胞肺癌细胞(NCI-H446)VEGF蛋白表达的影响.采用Matrigel invasion chamber共培养法,观察黄芪、党参提取物对NCI-H446诱导人血管内皮细胞(ECV - 304) 迁移的抑制作用.结果 黄芪、党参提取物浓度达到40%(V/V)能够抑制NCI-H446诱导的ECV-304细胞迁移,并且具有显著的剂量-效应关系(r=-0.73,P=0.01).浓度达到50%(V/V)时可以明显抑制NCI-H446细胞VEGF表达(P=0.02).结论 高浓度的黄芪、党参提取物能够抑制肺癌细胞诱导的血管内皮细胞迁移,这种抑制作用可能与其抑制肺癌细胞VEGF表达有关.     

融合His标签的HCV包膜糖蛋白E2的真核表达及意义

目的 构建HCV包膜糖蛋白E2与His标签融合的真核表达载体并在CHO细胞中表达,为研究HCV包膜糖蛋白的功能奠定基础。方法 利用PCR技术从HCV基因组序列中扩增出编码HCV包膜糖蛋白E2的基因,将其插入原核表达载体pET28(a)载体中,构建pET28(a)-HCVE2,从pET28(a)-HCVE2上获得His-HCVE2融合基因,插入pcDNA3．1,构建表达HCV包膜糖蛋白E2与His标签融合蛋白的真核表达载体pcDNA3．1-His-E2。用脂质体介导法将pcDNA3．1-His-E2转染CHO细胞,通过间接免疫荧光、Western blot检测融合蛋白在CHO细胞内的表达。结果 转染HCVE2与His融合基因的真核表达载体的CHO细胞内声融合蛋白的表达。结论 与His标签融合的HCV包膜糖蛋白E2能够在CHO细胞内表达。     

Induction by carbon-ion irradiation of the expression of vascular endothelial growth factor in lung carcinoma cells

Purpose : To investigate the induction by carbon- ion irradiation of vascular endothelial growth factor (VEGF) mRNA and protein. Materials and methods : RERF-LC-AI lung squamous carcinoma cells were irradiated with carbon ions of either 13.3, 50 or 90keV/mum. Colony formation was used to determine cell survival. VEGF mRNA and protein of the irradiated cells were quantified by Northern blot analysis and ELISA assay, respectively. Genistein, Src tyrosine kinase inhibitor and H7, protein kinase C inhibitor, were used to inhibit VEGF mRNA expression. Results : The relative biological effectiveness (RBE) of carbon ions (13.3, 50 and 90 keV/mum) was 1.10, 1.97 and 2.30, respectively, in terms of D10 values. Single doses of 15 Gy with either X-rays or carbon ions significantly induced VEGF mRNA expression at 16-24 h after irradiation with a maximum induction of 2.81-fold. A significant increase was also observed in VEGF protein levels, detected in culture supernatant 24 h after irradiation with 50 and 90keV/ μ m carbon ions. Neither mRNA nor protein induction showed a dependence on LET. The induction of VEGF mRNA by carbon-ion irradiation was completely inhibited by pretreating cells with genistein and H7, indicating that Src tyrosine kinase and protein kinase C on cell surface membranes is involved in the induction. Conclusion : Irradiation of lung carcinoma cells with carbon ions induced VEGF mRNA expression and increased protein levels. The induction was dose-dependent. Radiation-induced DNA damage and/or its repair may not be a prerequisite for the induction of VEGF mRNA.     

Induction by carbon-ion irradiation of the expression of vascular endothelial growth factor in lung carcinoma cells

PURPOSE: To investigate the induction by carbon- ion irradiation of vascular endothelial growth factor (VEGF) mRNA and protein. MATERIALS AND METHODS: RERF-LC-AI lung squamous carcinoma cells were irradiated with carbon ions of either 13.3, 50 or 90keV/microm. Colony formation was used to determine cell survival. VEGF mRNA and protein of the irradiated cells were quantified by Northern blot analysis and ELISA assay, respectively. Genistein, Src tyrosine kinase inhibitor and H7, protein kinase C inhibitor, were used to inhibit VEGF mRNA expression. RESULTS: The relative biological effectiveness (RBE) of carbon ions (13.3, 50 and 90keV/microm) was 1.10, 1.97 and 2.30, respectively, in terms of D10 values. Single doses of 15 Gy with either X-rays or carbon ions significantly induced VEGF mRNA expression at 16-24h after irradiation with a maximum induction of 2.81-fold. A significant increase was also observed in VEGF protein levels, detected in culture supernatant 24h after irradiation with 50 and 90keV/microm carbon ions. Neither mRNA nor protein induction showed a dependence on LET. The induction of VEGF mRNA by carbon-ion irradiation was completely inhibited by pretreating cells with genistein and H7, indicating that Src tyrosine kinase and protein kinase C on cell surface membranes is involved in the induction. CONCLUSION: Irradiation of lung carcinoma cells with carbon ions induced VEGF mRNA expression and increased protein levels. The induction was dose-dependent. Radiation-induced DNA damage and/or its repair may not be a prerequisite for the induction of VEGF mRNA.     

Inhibition of the extracellular signal-regulated kinase (ERK) pathway and the induction of radioresistance in rat 3Y1 cells

PURPOSE: Activation of the extracellular signal-regulated kinase (ERK) pathway generally results in stimulation of cell growth and confers a survival advantage. However, the potential involvement of this pathway in cellular radiosensitivity remains unclear. The study was designed to examine whether the ERK pathway affects intrinsic radiosensitivity in mammalian cells. MATERIALS AND METHODS: Exponentially growing rat 3Y1 cells were used. A specific inhibitor of mitogen-activated ERK kinase (MEK), PD98059, was used to inhibit the ERK pathway. In addition, kinase-deficient MEK was expressed in cells to inhibit the pathway in a dominant-negative manner. Activation of ERK was visualized by Western blot using an antibody that recognizes the phosphorylated form of ERK. Radiosensitivity was evaluated by a colony-forming assay. RESULTS: 3Y1 cells treated with PD98059 exhibited a significant inhibition of cell proliferation and radiation-induced transient activation of ERK. Unexpectedly, it was found that the inhibitor enhanced clonogenic radioresistance. This effect on radioresistance was confirmed by expression of kinase-deficient MEK. Apoptotic activities following irradiation were significantly inhibited in PD98059-treated cells as determined by caspase-3-like activities. CONCLUSION: Activation of the MEK/ERK pathway increases clonogenic radiosensitivity in rat 3Y1 cells. These findings, together with a variety of other data, suggest that there might be clinical implications in targeting the MEK/ERK pathway in radiotherapy.     

高效表达的NO对肺腺癌细胞A549放射敏感性的影响

目的 研究同步、高效表达的一氧化氮（NO）对肺腺癌细胞A549放射敏感性的影响,探寻增强肿瘤放射敏感性的新途径.方法 利用前期构建的可调控目的 基因高效表达的载体pfos-iNOS/GFP转染肺腺癌细胞A549,将阳性转染细胞和未转染细胞给予2 Gy X线照射后,检测细胞照射前后不同时相点NO的产量;给予不同剂量的X线照射后,检测照射后各组细胞的存活率,根据细胞存活率分别绘制各组细胞的辐射剂量-存活曲线,并进一步通过计算Do值及放射增敏比（SER）分析各组细胞放疗敏感性的变化.结果 转染载体pfos-iNOS/GFP的细胞照射后,NO浓度较照射前明显增高,其中照射后16 h较照射前增强10倍.转染治疗载体组Do值（1.16 Gy）明显低于未转染组（3.93 Gy）,治疗载体组的放疗敏感性是对照组的3.5倍.结论 高效表达的NO使体外肺腺癌细胞的放射敏感性明显增强,为肿瘤放疗增敏提供了新的模式.