单次、分次照射与125I 粒子低剂量率照射对人喉鳞癌 Hep2细胞的抑制作用

目的：探讨125I 粒子持续低剂量率照射与分次照射、单次照射对人喉鳞癌细胞 Hep2的抑制作用及其作用机制。方法实验分为无照射对照组（Ctrl 组）、单次照射组（SDR 组）、分次照射组（FDR 组）和125I 粒子持续低剂量率照射组（125I-CLDR 组）四组。采用细胞克隆形成实验法检测 Hep2细胞在不同照射条件下细胞克隆的形成能力;用流式细胞仪检测细胞凋亡和细胞周期阻滞情况;用蛋白印迹法检测不同照射条件后 Hep2细胞总γ-H2AX、CyclinB1、Caspase3蛋白表达的变化。结果经2 Gy、4 Gy、6 Gy 的剂量照射,125I-CLDR 组 Hep2细胞克隆形成率均低于 SDR 组和 FDR 组。经4 Gy 的剂量照射后,125I-CLDR 组 Hep2细胞出现 G2/M 期阻滞,且阻滞效应较 SDR 组及 FDR 组的细胞强;125I-CLDR 组 Hep2细胞的凋亡比例明显高于 SDR 组及 FDR 组;三个照射组γ-H2AX、CyclinB1、Caspase3、NF-κB、P21和 Cdk1的表达水平上调,125I-CLDR 组 p-Cdc25c 蛋白表达水平低于 SDR 组和 FDR 组。结论在本实验条件下,125I 粒子持续低剂量率照射较单次照射、分次照射能够诱发更多 Hep2细胞出现 DNA 损伤、引起持续的 G2/M 期阻滞、诱导细胞凋亡并抑制细胞的再增殖。     

Trastuzumab aggravates radiation induced cardiotoxicity in mice

Some breast cancer patients with overexpression of human epidermal growth factor receptor 2 need both chest radiotherapy and targeted therapy with trastuzumab (TRZ). The cardiotoxicity associated with combined treatment potentially restricts the clinical benefits of antitumor therapy. There is no consensus on whether and how chest radiotherapy can be given in concurrent with TRZ at present, considering the cardiotoxicity. This study intends to establish an in vitro and in vivo heart injury model by irradiation and TRZ, analyze whether there is a synergistic effect in heart, and to explore the molecular changes. First, an in vitro irradiation model of H9C2 cardiomyocytes was established. The effects of TRZ and radiation on cardiomyocyte injury were observed by cell flow cytometry, CCK-8 test, Western blot, γ-H2AX fluorescence focus formation and cell Reactive Oxygen Species (ROS) content test. Second, the mouse heart injury model was set up by X-ray cardiac irradiation combined with TRZ. Six months later, the cardiac function was analyzed by small animal ultrasound and ¹⁸FDG-micro PET/CT. The morphological changes of heart tissue were assessed by histological section. We found that concurrent TRZ aggravates the injury effect of irradiation on cardiomyocytes in vitro. The influence of TRZ might be consequence of inhibiting Akt phosphorylation, promoting the excessive accumulation of ROS in cells and promoting intracellular DNA damage. In animal experiments, the dysfunction of diastolic and myocardial ischemia of mouse heart was observed by echocardiography and ¹⁸FDG-micro PET/CT, respectively; myocardial fibrosis and cardiomyocyte apoptosis were also observed. Therefore, our in vitro and in vivo experiments have revealed that TRZ combined irradiation caused more cardiotoxicity than irradiation or TRZ alone. These results suggested that the concurrent management of TRZ and radiotherapy should be carefully made in clinical practice, and more attention is needed on cardiac safety.     

阿帕替尼对胃癌HGC-27细胞放射敏感性的影响及其作用机制

目的 探讨阿帕替尼对胃癌HGC-27细胞放射敏感性的影响及可能的作用机制。方法 以不同浓度阿帕替尼（5 μmol/L、10 μmol/L、15 μmol/L、20 μmol/L）以及不同照射剂量（2 Gy、4 Gy、6 Gy、10 Gy、20 Gy）分别处理HGC-27细胞,再选取2 Gy和6 Gy单独照射或联合10 μmol/L阿帕替尼处理HGC-27细胞;采用ELISA法检测细胞中血管内皮生长因子（vascular endothelial growth factor,VEGF）的表达情况,CCK-8法检测细胞增殖能力,流式细胞术检测细胞凋亡和细胞周期,免疫荧光染色技术检测γ-H2AX的表达情况。结果 阿帕替尼呈浓度及时间依赖性抑制胃癌HGC-27细胞增殖（均P<0.05）;不同剂量照射可促进细胞VEGF表达释放,且呈时间及剂量依赖性（均P<0.01）。10 μmol/L阿帕替尼分别联合2 Gy和6 Gy照射后,HGC-27细胞增殖抑制作用、细胞凋亡率及G2/M期的细胞比例均较单照组升高（均P<0.01）,且6 Gy联合组的作用强度大于2 Gy联合组（均P<0.01）。6 Gy联合组细胞核内γ-H2AX焦点淬灭较6 Gy单照组延迟。结论 阿帕替尼通过抑制细胞增殖,促进细胞凋亡并诱导细胞周期再分布增强胃癌HGC-27细胞放射敏感性,其作用机制可能与延迟γ-H2AX表达而干扰DNA双链断裂修复有关。     

r-H2AX在不同食管癌株系中的剂量时间效应特点

目的   通过检测不同食管癌株系的r-H2AX时间剂量效应关系,了解r-H2AX的动力学特点。 方法   将食管癌ECA109和TE13两种细胞株分别给予1、2、4和8Gy 的6MV-X线照射,并分别于0.5、1、2、4、8、12、24 h收集细胞提取蛋白,检测r-H2AX时间及剂量效应特点。 结果   (1) ECA109细胞和TE13细胞随着放疗剂量的增加,r-H2AX表达量第一次最高点出现的时间逐渐提前。(2) ECA109细胞接受低剂量照射后,r-H2AX在24 h内能够恢复到放疗前的水平,且剂量越低恢复越快;TE13细胞接受1、2、4和8Gy照射后24 h内r-H2AX均不能恢复到放疗前水平。(3)在0.5、1、2 h这3个时间点,随着放疗剂量的增加,r-H2AX的表达量并不都是逐渐增加。 结论   TE13细胞较ECA109细胞敏感,照射后r-H2AX更难恢复到正常水平。     

EGFR和TGF-α在肺癌细胞放疗增敏中的作用

目的 研究表皮生长因子受体（EGFR）、转化生长因子-α（TGF-α）与肺癌细胞不同放疗分割剂量的关系及可能作用机制。方法 对A549细胞采用常规分割（2 Gy／天）和大分割（4、8 Gy／天）照射，DT=8 Gy，采用实时荧光定量 PCR （QPCR）、酶联免疫吸附测定（ELISA）法、Western blotting分别检测A549细胞中EGFR、TGF-α基因和蛋白表达，另采用免疫荧光法测定γ-H2AX表达。结果 4 Gy／天和 8 Gy／天分割组A549细胞中EGFR、TGF-α mRNA表达水平均显著低于2 Gy／天组（P＜0.05）；4 Gy／天和 8 Gy／天分割组A549细胞中EGFR、TGF-α 蛋白表达均显著低于2 Gy／天组（P＜0.05）。免疫荧光法结果显示，4 Gy／天和 8 Gy／天分割组A549细胞中γ-H2AX表达明显高于对照组和2 Gy／天分割组。结论  大剂量分割放疗后EGFR、TGF-α 表达明显下调，增加A549细胞对放射线的敏感性，其机制可能与DNA损伤修复组蛋白γ-H2AX表达上调有关。     

急性期放射性心肌损伤病理学表现及损伤机制研究

目的 建立实验动物模型观察急性期放射性心肌损伤的病理学表现,探索损伤机制。方法 12只成年雄性SD大鼠按完全随机法均分为对照组和照射组。照射组采用6 MV X线单次20 Gy经心前区照射构建放射性心脏损伤模型,照后第14天HE染色观察心肌细胞及细胞间质形态学改变,Masson染色观察胶原纤维分布情况。以心肌胶原容积分数(CVF)半定量分析。ELISA法检测总超氧化物歧化酶(T-SOD)活力和丙二醛(MDA)浓度。蛋白印迹法检测纤维化标志性蛋白Ⅰ型胶原(COL-1)和内质网应激相关蛋白GRP78和CHOP的表达水平。组间比较采用t、t’或非参数秩和检验。结果 大鼠心脏局部照射后第14天,照射组较对照组心肌细胞排列紊乱,明显水肿,部分心肌细胞断裂,心肌细胞核轻度固缩,心肌间质炎性细胞渗出。心肌组织胶原纤维主要分布于小血管周围及心肌细胞间质。照射组CVF明显高于对照组(11.35%、5.23%,P=0.000),COL-1表达水平升高(P=0.000)。放射线引起心肌组织T-SOD活力增高(156.61、137.06 U/mgprot,P=0.042),同时伴MDA浓度上升(2.36、1.31 nmol/mgprot,P=0.007)。放射线引起心肌组织内质网应激蛋白GRP78和CHOP表达水平均升高(GRP78,P=0.037,CHOP,P=0.009)。结论 急性期放射性心肌损伤的病理学表现主要为心肌细胞变性,间质炎性渗出,小血管周围和心肌间质胶原沉积。放射性心脏损伤急性期内即可发生心肌组织纤维化,机制可能与放射线引起的氧化应激、内质网应激有关。     

γ-H2AX promotes hepatocellular carcinoma angiogenesis via EGFR/HIF-1α/VEGF pathways under hypoxic condition

Hepatocellular carcinoma (HCC) is one of the most deadly cancers. Using mRNA microarray analysis, we found that H2AX decreased under hypoxic conditions. Hypoxia is an important physiological and pathological stress that induces H2AX phosphorylation (γ-H2AX), but the regulatory mechanism of γ-H2AX remains elusive in the progress of HCC. We report here that increased γ-H2AX expression in HCC is associated with tumor size, vascular invasion, TNM stage and reduced survival rate after liver transplantation (LT). γ-H2AX knockdown was able to effectively inhibit VEGF expression in vitro and tumorigenicity and angiogenesis of HCC in vivo. The mechanism of γ-H2AX on the angiogenic activity of HCC might go through EGFR/HIF-1α/VEGF pathways under hypoxic conditions. Combined γ-H2AX, HIF-1α and EGFR has better prognostic value for HCC after LT. This study suggests that γ-H2AX is associated with angiogenesis of HCC and γ-H2AX or a combination of γ-H2AX/EGFR/HIF-1α is a novel marker in the prognosis of HCC after LT and a potential therapeutic target.     

阿魏酸对人脐静脉血管内皮细胞辐射损伤的保护作用及其机制

目的：研究阿魏酸对电离辐射所致人脐静脉血管内皮细胞（HUVEC）损伤的保护作用,及其对辐射敏感蛋白Thbd和γH2AX的影响,探讨阿魏酸的抗辐射作用与机制。方法：以4~16 Gy的⁶⁰Co γ射线照射HUVEC细胞,照后48 h以MTS法检测细胞活力,探索适宜照射剂量。以10 Gy γ射线照射HUVEC细胞,分别于照射后1、3、6、12、24和48 h提取细胞总蛋白,蛋白质印迹法检测蛋白Thbd和γH2AX的表达水平。并于照射前2 h,预防性给予细胞0.001~1 μmol/L的阿魏酸,照后48 h检测细胞活力、Thbd和γH2AX蛋白表达水平的改变。结果：与未照射组（0 Gy）比较,HUVEC受到10 Gy γ射线照射后48 h,细胞活力约降低30%（P < 0.05）。以此剂量照射,照后1 h Thbd约降至正常水平的0.6（P < 0.05）,照射后48 h γH2AX约升高至正常水平的5倍（P < 0.05）。与照射对照组比较,0.1和1 μmol/L 的阿魏酸作用后,受照HUVEC的细胞活力提高（P < 0.05）,Thbd蛋白表达升高（P < 0.05）,γH2AX蛋白表达降低（P < 0.05）。结论：0.1~1 μmol/L的阿魏酸可调节10 Gy γ射线照射后HUVEC的Thbd和γH2AX蛋白的表达水平,从而促进HUVEC增殖,提高其细胞活力,发挥抗辐射作用。     

HER-3基因表达对HER-2阳性型乳腺癌细胞放射敏感性的影响及作用机制

目的:探讨人表皮生长因子受体-3（human epidermal growth factor receptor-3,HER-3）表达对HER-2阳性型乳腺癌细胞放射敏感性的影响。方法:使用慢病毒颗粒感染HER-2阳性型乳腺癌细胞系（AU-565、SKBR-3）构建HER-3基因敲低细胞系模型,蛋白质印迹法（Western blot）及实时定量PCR(RT-qPCR)技术检测感染的效率。克隆形成实验测定不同组别乳腺癌细胞放射增敏效果。将HER-3敲低组与对照组细胞分别给予X线照射（6 Gy,6 MV,源皮距100 cm）,流式细胞术测定不同组别细胞凋亡率以及细胞周期分布的变化。免疫荧光法检测细胞辐射后不同时间段的γH2AX焦点数,评估辐射后DNA损伤情况,蛋白质印迹法检测细胞周期调控相关蛋白CyclinB1的表达。结果:克隆形成实验结果显示,HER-3敲低组乳腺癌细胞放射敏感性增强。流式细胞术结果显示,HER-3敲低后,HER-2阳性型乳腺癌细胞辐射后凋亡率明显增加,细胞周期G2期分布比例提高。免疫荧光结果显示,HER-3敲低后,HER-2阳性型乳腺癌细胞γH2AX焦点数目在辐射后先增加后降低,较对照组峰值更高,降低时趋势更慢,提示HER-3敲低可增强辐射诱导的DNA损伤,减少DNA修复。蛋白质印迹法结果显示,细胞周期相关驱动蛋白CyclinB1表达降低。结论:HER-3基因敲低后一方面增加了HER-2阳性型乳腺癌细胞辐射后DNA的损伤并减缓其修复能力,促进细胞凋亡;另一方面通过下调细胞周期蛋白CyclinB1的表达,增加G2期细胞分布,提升了放射敏感性。     

X射线诱导γH2AX焦点形成的定量分析及其致DNA双链断裂的动态变化

目的 比较DNA依赖蛋白激酶催化亚基(DNA-PKcs^+/+)和DNA-PKcs^-/-小鼠胚胎成纤维细胞(MEF) X射线诱导γH2AX焦点形成的定量分析,并对鼻咽癌SUNE-1细胞进行X射线致DNA DSB动态变化。方法 采用蛋白印迹检测DNA-PKcs蛋白表达情况,细胞免疫荧光检测X射线5 Gy诱导的γH2AX焦点形成,通过ImageJ软件分析γH2AX焦点形成数量的差异。结果 DNA-PKcs在DNA-PKcs^-/-和DNA-PKcs^+/+ MEF细胞中分别表达缺失和正常。应用γH2AX焦点/细胞和γH2AX焦点/mm²分析方法动态分析X射线诱导的DNA-PKcs^+/+、DNA-PKcs^-/-MEF细胞和SUNE-1细胞DSB形成的总体趋势一致;照后 0.5~1.0 h大量γH2AX焦点形成,DNA-PKcs^+/+ MEF细胞于照后6.0 h完成修复,DNA-PKcs^-/-MEF和SUNE-1细胞X射线后于照后24.0 h完成修复。γH2AX焦点/细胞的峰值出现在照后1.0 h,γH2AX焦点/mm²的峰值则出现在照后0.5 h。对于DNA-PKcs^+/+和DNA-PKcs^-/-MEF细胞,γH2AX焦点/细胞在照后0.5、1.0、3.0、6.0、12.0 h的不同,而γH2AX焦点/mm²在照后3.0、6.0、12.0 h不同。结论 利用细胞免疫荧光动态检测照后致γH2AX焦点/细胞或γH2AX焦点/mm²的分析方法为动态定量研究DSB损伤及修复提供了新的思路。     

Survivin inhibition and DNA double-strand break repair: A molecular mechanism to overcome radioresistance in glioblastoma

Background and purpose

Gliomas display prime examples of ionizing radiation (IR) resistant tumors. The IAP Survivin is reported to be critically involved in radiation resistance by anti-apoptotic and by caspase-independent mechanisms. The present study aimed to elucidate an interrelationship between Survivin’s cellular localization and DNA damage repair in glioma cells.

Material and methods

Cellular distribution and nuclear complex formation were assayed by immunoblotting, immunofluorescence staining and co-immunoprecipitation of Survivin bound proteins in LN229 glioblastoma cells. Apoptosis induction, survival and DNA repair following IR were assayed by means of caspase3/7 activity, clonogenic assay, γ-H2AX/53BP1 foci formation, single cell gel electrophoresis assay, and DNA-PKcs kinase assay in the presence of Survivin siRNA or over expression of Survivin-GFP.

Results

Following irradiation, we observed a nuclear accumulation and a direct interrelationship between Survivin, MDC1, γ-H2AX, 53BP1 and DNA-PKcs, which was confirmed by immunofluorescence co-localization. Survivin downregulation by siRNA resulted in an increased apoptotic fraction, decreased clonogenic survival and increased DNA-damage, as demonstrated by higher amount of DNA breaks and an increased amount of γ-H2AX/53BP1 foci post irradiation. Furthermore, we detected in Survivin-depleted LN229 cells a hampered S2056 (auto)phosphorylation and a significantly decreased DNA-PKcs kinase activity.

Conclusion

Nuclear accumulation of Survivin and interaction with components of the DNA-double-strand break (DSB) repair machinery indicates Survivin to regulate DSB damage repair that leads to a significant improvement of survival of LN229 glioblastoma cells.     

吉非替尼对肺癌细胞株A549和H1975放射敏感度的影响及其机制

目的 本研究旨在探讨小分子表皮生长因子受体（epidermal growth factor receptor, EGFR）酪氨酸激酶抑制剂吉非替尼是否能增加肺癌细胞株A549和H1975的放疗敏感度及其机制。方法 选取两种非小细胞肺癌细胞株A549和H1975,分为单纯X线组和X线+吉非替尼组。单纯X线组采用单纯X线照射,X线+吉非替尼组经10 μmol/L吉非替尼作用24 h后行X线照射。两株细胞不同分组细胞,采用克隆形成实验检测放射敏感度,免疫荧光激光共聚焦显微镜观察X线照射后不同时间点细胞核中磷酸化H2AX（γ-H2AX）亮点在细胞中的定位情况,Western blot法检测放疗后胞质胞核蛋白中EGFR的表达。结果 克隆形成实验中,A549细胞X线+吉非替尼组在各放疗剂量点的SF2值（0.3475）低于单纯X线组（0.4833）;H1975细胞X线+吉非替尼组与单纯X线组在各放疗剂量点的SF2值分别为0.3094和0.3207,无明显差异。免疫荧光结果显示,照射4 Gy后各时间点X线+吉非替尼组A549细胞核中γ-H2AX亮点相比单纯X线多;单纯X线组和X线+吉非替尼组H1975细胞γ-H2AX亮点在各时间点无明显差异; Western blot结果显示,A549细胞经4Gy照射后EGFR有入核现象,而预先经吉非替尼处理再接受4Gy照射,EGFR蛋白绝大部分位于细胞质内;H1975细胞,单纯X线组和X线+吉非替尼组EGFR蛋白均在细胞质中表达,胞核中几乎没有,且两组无明显差异。结论 吉非替尼能增加肺癌细胞株A549的放射敏感度,可能与阻止放疗后EGFR入核进行双链断裂（double strand break,DSB）修复有关;对H1975细胞无影响,与其放疗后EGFR不入核相关。     

p53和γ-H2AX作为乙醛引起DNA损伤早期生物标记物的实验研究

目的： 评价乙醛染毒p53野生型人类淋巴母细胞(TK6)后,细胞中DNA损伤标记物p53、γ-H2AX的表达变化,并与彗星试验中的DNA链断裂指标进行敏感性比较,探讨p53和γ-H2AX 作为乙醛引起DNA损伤的早期生物标记物的可能。方法：乙醛在0.5~20 mmol/L的浓度范围分别染毒TK6细胞20 min、2和12 h后,采用高通量的流式细胞术检测肿瘤抑制蛋白total-p53、磷酸化p53(p-p53)以及磷酸化组蛋白(γ-H2AX)的细胞表达率和表达强度(平均荧光强度);同时采用碱性彗星试验检测乙醛引起的DNA链断裂指标(细胞拖尾率、尾长、尾部DNA百分含量以及尾矩)的变化。结果：乙醛染毒TK6细胞12 h后,γ-H2AX的表达强度在15及20 mmol/L浓度下显著升高(P<0.05),p-p53的细胞表达率在0.5~7.5 mmol/L浓度范围内呈现剂量依赖的升高趋势,total-p53的细胞表达率趋势与p-p53相似,但与阴性对照组相比,差异无统计学意义。彗星试验中,细胞拖尾率、尾长、尾部DNA百分含量以及尾矩在5.0~12.5 mmol/L浓度范围内均增加,并呈现剂量依赖性。染毒2 h后,与阴性对照组相比,total-p53和p-p53的细胞表达率在15和20 mmol/L浓度下显著升高(P均<0.05),细胞拖尾率、尾部DNA百分含量以及尾矩在20 mmol/L浓度升高(P均<0.05)。染毒20 min后,3种生物标志物均未见清晰的变化趋势,4种DNA链断裂指标均未见显著变化(P均＞0.05)。结论：乙醛染毒TK6细胞12 h可诱导p-p53细胞表达率升高、γ-H2AX细胞表达强度升高、 total-p53细胞表达率轻微升高,以及细胞拖尾率、尾长、尾部DNA百分含量、尾矩的升高。p-p53比γ-H2AX和DNA链断裂指标在检测乙醛诱导的DNA损伤方面更加敏感。     

Radiation- and anthracycline-induced cardiac toxicity and the influence of ErbB2 blocking agents

In Her2-positive breast cancer patients, inhibition of epidermal growth factor receptor 2 (ErbB2)-signaling is often combined with chemotherapy and radiotherapy. The risk of cardiac toxicity after anthracyclines and radiotherapy is recognized, but little is known about increased risk when these treatments are combined with ErbB2 inhibition. This study investigated whether ErbB2 inhibition increased radiation or anthracycline-induced toxicity. In an in vitro study, human cardiomyocytes were treated with irradiation or doxorubicin, alone or in combination with trastuzumab, and evaluated for cell survival and growth. Groups of mice received 0 or 14 Gy to the heart, alone or in combination with lapatinib, or 3 × 4 mg/kg doxorubicin alone or in combination with lapatinib. Mice were evaluated 40 weeks after treatment for cardiac damage. Changes in cardiac function (^99mTc-Myoview gated SPECT) were related to histomorphology and microvascular damage. Radiation or doxorubicin-induced cardiomyocyte toxicity (in vitro) were not exacerbated by trastuzumab. Cardiac irradiation of mice decreased microvascular density (MVD) and increased endothelial damage in surviving capillaries (decrease alkaline phosphatase expression and increased von Willebrand factor), but these changes were not exacerbated by lapatinib. Inflammatory responses in the irradiated epicardium (CD45+ and F4/80+ cells) were significantly reduced in combination with lapatinib. Irradiation, doxorubicin, and lapatinib each induced cardiac fibrosis but this was not further enhanced when treatments were combined. At the ultra-structural level, both lapatinib and doxorubicin induced mitochondrial damage, which was enhanced in combined treatments. Lapatinib alone also induced mild changes in cardiac function but this was not enhanced in the combined treatments. Trastuzumab did not enhance direct radiation or anthracycline toxicity of cardiomyocytes in vitro. Lapatinib did not enhance the risk of radiation or anthracycline-induced cardiac toxicity in mice up to 40 weeks after treatment, but mitochondrial damage was more severe after doxorubicin combined with lapatinib.     

Nuclear factor (erythroid‐derived 2)‐like 2 antioxidative response mitigates cytoplasmic radiation‐induced DNA double‐strand breaks

It has been reported that DNA double‐strand breaks (DSB) can be induced by cytoplasm irradiation, and that both reactive free radicals and mitochondria are involved in DSB formation. However, the cellular antioxidative responses that are stimulated and the biological consequences of cytoplasmic irradiation remain unknown. Using the Single Particle Irradiation system to Cell (SPICE) proton microbeam facility at the National Institute of Radiological Sciences ([NIRS] Japan), the response of nuclear factor (erythroid‐derived 2)‐like 2 (NRF2) antioxidative signaling to cytoplasmic irradiation was studied in normal human lung fibroblast WI‐38 cells. Cytoplasmic irradiation stimulated the localization of NRF2 to the nucleus and the expression of its target protein, heme oxygenase 1. Activation of NRF2 by tert‐butylhydroquinone mitigated the levels of DSB induced by cytoplasmic irradiation. Mitochondrial fragmentation was also promoted by cytoplasmic irradiation, and treatment with mitochondrial division inhibitor 1 (Mdivi‐1) suppressed cytoplasmic irradiation‐induced NRF2 activation and aggravated DSB formation. Furthermore, p53 contributed to the induction of mitochondrial fragmentation and activation of NRF2, although the expression of p53 was significantly downregulated by cytoplasmic irradiation. Finally, mitochondrial superoxide (MitoSOX) production was enhanced under cytoplasmic irradiation, and use of the MitoSOX scavenger mitoTEMPOL indicated that MitoSOX caused alterations in p53 expression, mitochondrial dynamics, and NRF2 activation. Overall, NRF2 antioxidative response is suggested to play a key role against genomic DNA damage under cytoplasmic irradiation. Additionally, the upstream regulators of NRF2 provide new clues on cytoplasmic irradiation‐induced biological processes and prevention of radiation risks.     

High-mobility group box 2 (HMGB2) modulates radioresponse and is downregulated by p53 in colorectal cancer cell

Overexpression of high-mobility group box 2 (HMGB2) is recently reported in several malignant cancers and was correlated with poor response to preoperative chemoradiotherapy of colorectal cancer patients. To enhance the chemoradiotherapy efficacy, the biological function of HMGB2 was investigated with respect to radiation response. HMGB2 gene knockdown cells were constructed by infecting shRNA expressing lentivirus and clonogenic assay was performed to count the radiosensitivity. HMGB2 knockdown sensitized HCT-116 and HT-29 colorectal cancer cells to ionizing radiation. This could be due to an increased DNA damage and an inefficient DNA damage repair in HMGB2 knockdown cells. In addition, an exposure to radiation downregulated HMGB2 expression in colorectal cancer cells with an intact TP53 gene. HMGB2 gene expression of TP53-mutant cell was not affected by irradiation. p53-mediated downregulation of HMGB2 was confirmed by direct activation of p53 using Nutlin-3 or by inducing p53 expression using Tet-On system. Luciferase reporter assay showed that HMGB2 promoter activity was inversely correlated with the amount p53 cotransfected. Our study revealed that HMGB2 is necessary to protect colorectal cancer cells from DNA damage and efficient DNA repair and p53-mediated downregulation is a critical mechanism of modulating HMGB2 expression.     

Downregulation of a novel human gene,ROGDI, increases radiosensitivity in cervical cancer cells

ROGDI is a protein that contains a leucine zipper domain and may be involved in cell proliferation. In addition, ROGDI is associated with genome stability by regulating the activity of a DNA damage marker, γ-H2AX. The role of ROGDI in tumor radiosensitization has not been investigated. Previous studies have indicated that radiosensitivity is associated with DNA repair and the cell cycle. In general, the G2/M DNA damage checkpoint is more sensitive to radiation, whereas the G1/S phase transition is more resistant to radiation. Inhibition of cyclin-dependent kinases (CDKs) can lead to a halt of cell cycle progression and a stay at different phases or checkpoints. Our data show that the downregulation of ROGDI led to a decreased expression of CDK 1, 2, cyclin A, B and resulted in a G2/M phase transition block. In addition, the downregulation of ROGDI increased cell accumulation at the G2 phase as detected using flow cytometry and decreased cell survival as revealed by clonogenic assay in HeLa and C33A cells following irradiation. These findings suggest that the downregulation of ROGDI can mediate radiosensitivity by blocking cells at G2/M, the most radiosensitive phase of the cell cycle, as well as exerting deleterious effects in the form of DNA damage, as shown by increased γ-H2AX activation.     

吉非替尼对肺癌细胞株HCC827和H358放射敏感性的影响及其机制研究

背景与目的表皮生长因子受体(epidermal growth factor receptor,EGFR)是决定放疗效应的一个重要因素,其过表达或是下游通路的激活与包括非小细胞肺癌在内的肿瘤的放疗抵抗相关,因而阻断EGFR的信号通路可能会增强放疗敏感性。本研究旨在探讨小分子EGFR酪氨酸激酶抑制剂吉非替尼能否增加肺癌细胞株HCC827和H358的放疗敏感性及其可能的机制。方法选取HCC827和H358这两个非小细胞肺癌细胞株,分为单纯X线组和X线+吉非替尼两组。单纯X线组采用单纯X线照射,X线+吉非替尼组经1μmol/L吉非替尼作用24h后再行X线照射。克隆形成实验比较两株细胞中不同分组细胞放射敏感性,免疫荧光激光共聚焦显微镜观察X线照射后各时间点细胞核中的磷酸化H2AX(γ-H2AX)及EGFR焦点在细胞中的定位情况,Western blot法检测放疗后胞质胞核蛋白中EGFR的表达。结果克隆形成实验中,H358细胞实验组与对照组在各放疗剂量点的SF2值分别为0.355和0.433;HCC827细胞实验组与对照组在各放疗剂量点的SF2值分别为0.223和0.242,差别不明显。激光共聚焦显微镜观察照射4Gy后各时间段实验组H358细胞核中g-H2AX斑点相比对照组要多,且持续时间更长。而对照组和实验组的HCC827细胞g-H2AX斑点在各时间段并无明显差异;激光共聚焦显微镜观察照射4Gy后对照组H358的EGFR蛋白在1h内入核,而经吉非替尼处理后EGFR蛋白几乎不入核;实验组及对照组HCC827细胞的EGFR表达位置均在细胞质中,胞核中很少或者没有,可以认为并无入核现象;Western blot结果显示,H358细胞在经4Gy放射处理后有入核现象,而预先经吉非替尼处理后,EGFR蛋白几乎不在核内表达而仍位于细胞浆内。对于HCC827细胞,实验组及对照组的EGFR蛋白均在细胞质中表达,胞核中很少或没有,且两组并无明显差异。结论吉非替尼可增加肺癌细胞株H358的放射敏感性,这可能与其阻止放疗后EGFR入核、影响放疗后双链断裂(double strand break,DSB)修复有关;而对HCC827细胞无影响,可能与其放疗后EGFR不入核相关。     

Relationship between p53 status and radiosensitivity in human tumour cell lines.

We examined the relationship between p53 levels before and after irradiation, radiation-induced cell cycle delays, apoptotic cell death and radiosensitivity in a panel of eight human tumour cell lines. The cell lines differed widely in their clonogenic survival after radiation, (surviving fraction at 2 Gy: SF2=0.18-0.82). Constitutive p53 protein levels varied from 2.2 +/- 0.4 to 6.3 +/- 0.3 optical density units (OD) per 10(6) cells. p53 after irradiation (6 Gy) also varied between the cell lines, ranging from no induction to a 1.6-fold increase in p53 levels 4 h after treatment. p53 function was also assessed by G1 cell cycle arrest after irradiation. The cellular response to radiation, measured as G0/G1 arrest, and the induction of apoptosis were in good agreement. However, a trace amount of DNA ladder formation was found in two cell lines lacking G1 arrest. Overall cellular radiosensitivity correlated well with the level of radiation-induced G1 arrest (correlation coefficient r=0.856; P=0.0067), with p53 constitutive levels (r=0.874, P=0.0046), and with p53 protein fold induction (r=-0.882, P=0.0038). Our data suggest that (1) the constitutive p53 level, (2) G1 arrest after irradiation, or (3) the p53 protein response to radiation may be good predictive tests for radiosensitivity in some cell types.