辐射增敏药吉西他滨研究进展

近年来从化疗药中筛选辐射增敏药成为热点，新一代化疗药吉西他滨的辐射增敏作用研究初获成果。现就辐射增敏药的种类及应具备的条件、吉西他滨的作用及其增敏机制的研究作一综述。     

辐射增敏药吉西他滨研究进展

近年来从化疗药中筛选辐射增敏药成为热点,新一代化疗药吉西他滨的辐射增敏作用研究初获成果.现就辐射增敏药的种类及应具备的条件、吉西他滨的作用及其增敏机制的研究作一综述.     

核EGFR:潜在放疗增敏靶点研究进展

细胞核内EGFR在肿瘤发生发展、转移、治疗及预后等方面发挥重要的生物学作用。放疗作为治疗恶性肿瘤的主要手段之一,在治疗恶性肿瘤的同时可引起EGFR转移入核,从而降低放疗敏感性。深入了解核EGFR的生物学特性及其功能对提高放射敏感性有重要的参考价值,笔者从EGFR转运入核、核EGFR特性及其与放射敏感性和临床靶向治疗关系等几个方面做一综述。     

肿瘤放疗增敏药物新靶点

近期研究发现了一些对正常组织有保护作用而对病灶有放疗增敏作用的潜在有价值的药物靶点,包括氧自由基清除剂、针对DNA损伤修复和细胞周期的药物靶点、抑制细胞死亡新靶点、由生长因子介导的辐射防护、细胞信号通路的调节、血管紧张素转换酶抑制剂、辐射缓解剂等.     

DNA双链断裂修复抑制与放射增敏

全文着眼于近期以抑制肿瘤细胞DNA双链断裂(DSBs)修复为放射增敏策略的相关研究:加温、化疗、DSBs修复基因或蛋白抑制剂和表皮生长因子受体抑制剂,以进一步探讨放射增敏的生物学机制,并为临床综合治疗提供依据.     

放射增敏治疗的靶基因

对放、化疗的耐受是癌症治疗的主要障碍，基因治疗联合放疗代表了癌症治疗的一种新方式。采用基因治疗方式提高肿瘤细胞对射线的敏感性，然后联合放疗以提高治疗效果，在动物和临床试验中已取得显著效果。就放射增教治疗的靶基因及其实验和临床研究进展予以综述。     

piRNA—PIWI通路作为肿瘤治疗靶点研究进展

目的：总结piRNA—PIWI通路研究现状,归纳piRNA靶点和该通路的抑制方法。方法：在PubMed全文数据库检索系统中,以“piRNA、PIWI、合成、小分子药物和肿瘤干细胞（tumorstemcell,TSC）”作为关键词,检索2005—05—2013—06的相关文献97篇,其中,中文文献90篇,英文文献7篇。纳入标准：1）piRNA—PIWI的合成与工作机制;2）piR—NA-PIWI通路在TSC发生发展过程中的作用;3）已知的靶点piRNA与该通路的抑制方法。根据纳入标准符合分析的文献38篇。结果：piRNA-PIWI通路通过沉默转座子与调节基因表达而影响干细胞功能。piRNA-PIWI通路在TSC中高表达,在肿瘤发生发展中抑制凋亡通路、提高耐药性、扰乱miRNA系统、维持TSC的干性与过度甲基化。使用甲基化酶抑制剂与热休克蛋白90抑制剂可以抑制piRNA-PIWI通路。结论：piRNA-PIWI通路可以作为抗肿瘤治疗的新靶点。     

AG825对乳腺癌细胞的辐射增敏作用

目的：通过体外实验观察酪氨酸蛋白激酶抑制剂AG825对人类表皮生长因子受体2（ERBB-2）高表达乳腺癌细胞的生长抑制作用和辐射增敏作用，并从DNA双链断裂（Double strand break，DSB）损伤修复的角度初步探讨AG825辐射增敏机制。方法：首先通过MTT比色法观察了不同浓度AG825对ERBB-2高表达乳腺癌细胞系MDA—MB-453生长抑制作用。然后将细胞设为空白对照组，单纯放射组，AG825预处理组。通过克隆形成实验观察AG825预处理组和单纯辐射组乳腺癌细胞辐射后生存分数（Survivial fraction，SF）的差异。并且通过单细胞中性凝胶电泳分析了AG825预处理对辐射诱导的DSB的影响。同时用免疫印记法分析AG825预处理后MDA—MB-453细胞在辐射后不同时间DSB修复的关键激酶DNA依赖蛋白激酶催化亚单位（DNA dependent protein kinase catalytic subunit，DNA—PKcs）蛋白的表达情况。结果：MTT比色法显示AG825对MDA—MB-453生长抑制作用随AG825浓度增高而增加。辐射后单纯放射组MDA—MB-453细胞生存分数较空白对照组明显下降。AG825预处理组辐射后生存分数较单纯放射组进一步下降，同时DSB较单纯放射组增加。免疫印记显示单纯放射组DNA—PKcs蛋白表迭在辐射后较空白对照组增加，而AG825预处理组DNA—PKcs表达较单纯放射组下降。结论：AG825对ERBB2高表达乳腺癌细胞具有生长抑制作用一、并且其对ERBB2高表达乳腺癌细胞具有辐射增敏作用，其辐射增敏机制可能与AG825抑制DNA—PKes蛋白表达而减少辐射后DSB修复有关。但还需进一步的体内实验来评价AG825辐射增敏作用。     

放射增敏治疗的靶基因

对放、化疗的耐受是癌症治疗的主要障碍 ,基因治疗联合放疗代表了癌症治疗的一种新方式。采用基因治疗方式提高肿瘤细胞对射线的敏感性 ,然后联合放疗以提高治疗效果 ,在动物和临床试验中已取得显著效果。就放射增敏治疗的靶基因及其实验和临床研究进展予以综述。     

mTOR抑制剂放疗增敏的研究进展

放疗是肿瘤的重要治疗手段之一,仍有部分患者在接受放疗后存在复发或抗拒。哺乳动物雷帕霉素靶蛋白（mammalian target of rapamycin,mTOR）是PI3K/AKT信号通路的主要效应分子,分为mTORC1和mTORC2,对细胞生长及增殖、细胞周期进展及蛋白翻译等均有重要调节作用。mTOR异常表达与肿瘤发生及治疗反应密切相关。肿瘤的放疗敏感性与“4R”效应有关。mTOR抑制剂可通过影响细胞周期进展、DNA损伤修复及抗血管形成等多种途径发挥放疗增敏作用。初期研究证实依维莫司具有放疗增敏作用并且毒性可耐受。应用mTOR抑制剂后不同细胞及个体反应不同,可能与基因表达状态有关,需进一步研究证实。      

GLUT-1和DNA-PK在卵巢浆液性肿瘤中的表达及临床意义

[目的]探讨葡萄糖转运蛋白1(GLUT-1)和DNA依赖蛋白激酶(DNA-PK)在卵巢浆液性肿瘤中的表达及意义。[方法]采用RT-PCR法检测分析正常卵巢及卵巢良、恶性浆液性肿瘤组织中的GLUT-1、DNA-PK的表达水平。[结果]正常卵巢组织中GLUT-1低表达;在良性肿瘤组织、交界性肿瘤组织、恶性浆液性肿瘤组织中表达水平逐渐增高,而DNA-PK在正常卵巢组织中高表达;在良性肿瘤组织、交界性肿瘤组织、恶性浆液性肿瘤组织中表达水平逐渐降低。[结论]GLUT-1和DNA-PK的基因表达可能促进卵巢肿瘤细胞的恶性增殖和侵袭转移,与卵巢癌的发生、发展密切相关。     

胶质瘤DNA依赖性蛋白激酶活性与化疗药物敏感性的关系

目的 研究DNA依赖性蛋白激酶（DNA-PK）活性和脑胶质瘤化疗敏感性的关系。方法原代培养胶质瘤细胞,用MTT法检测其对6种不同抗癌药物的敏感性,以血药峰浓度（PPC）下的抑制率（IR）表示。提取同一胶质瘤组织标本中核蛋白质,用p53蛋白为特异底物的磷酸化反应检测其中的DNA-PK活性。结果不同胶质瘤组织标本中DNA-PK活性差别较大,36例组织标本中,16例的DNA-PK活性较高（相对活性≥0．40）,20例的DNA-PK活性较低（相对活性〈0．40）。对DDP、VCR敏感（IR≥50％）的肿瘤组织,DNA-PK活性低;对DDP、VCR不敏感（IR〈50％）的肿瘤组织,DNA-PK活性高（t=-3．445,P〈0．01）。同时,DNA-PK活性高的肿瘤组织,DDP、VCR体外抑制肿瘤细胞的IR值低;而DNA-PK活性低的肿瘤组织,相应的IR值高（t=-2．145,P〈0．05）。结论胶质瘤标本的DNA-PK活性与其对DDP、VCR敏感性显著相关,DNA-PK活性的高低可能是胶质瘤化疗敏感性的一个新的标记物。     

DNA依赖蛋白激酶与大肠癌淋巴结转移的相关性研究

目的：探讨大肠癌组织中DNA依赖蛋白激酶（DNA-PK）表达与大肠癌淋巴结转移的关系。方法：采用免疫组织化学方法（二步法）检测60例大肠癌组织标本中KU70、KU80和PKcs的表达,其中无淋巴结转移和有淋巴结转移各30例。结果：KU70和KU80的表达与淋巴结是否转移密切相关,淋巴结未转移组呈高表达,而转移组则呈低表达,即与淋巴结转移呈负相关（KU70,r=-0．57;KU80,r=-0．38）;PKes则与淋巴结是否转移无相关性（P〉0．05）。KU70、KU80、PKes表达与患者年龄、性别、肿瘤部位、肿瘤浸润深度无相关性（P〉0．05）。结论：DNA-PK可能与大肠癌的发生、转移呈负相关,检测大肠癌组织中KU70和KU80的表达有可能为大肠癌的预后和疗效判断提供依据。     

Preclinical pharmacokinetics and metabolism of a novel prototype DNA-PK inhibitor NU7026

In this study we investigated the in vitro time dependence of radiosensitisation, pharmacokinetics and metabolism of NU7026, a novel inhibitor of the DNA repair enzyme DNA-dependent protein kinase (DNA-PK). At a dose of 10 muM, which is nontoxic to cells per se, a minimum NU7026 exposure of 4 h in combination with 3 Gy radiation is required for a significant radiosensitisation effect in CH1 human ovarian cancer cells. Following intravenous administration to mice at 5 mg kg(-1), NU7026 underwent rapid plasma clearance (0.108 l h(-1)) and this was largely attributed to extensive metabolism. Bioavailability following interperitoneal (i.p.) and p.o. administration at 20 mg kg(-1) was 20 and 15%, respectively. Investigation of NU7026 metabolism profiles in plasma and urine indicated that the compound undergoes multiple hydroxylations. A glucuronide conjugate of a bis-hydroxylated metabolite represented the major excretion product in urine. Identification of the major oxidation site as C-2 of the morpholine ring was confirmed by the fact that the plasma clearance of NU7107 (an analogue of NU7026 methylated at C-2 and C-6 of the morpholine ring) was four-fold slower than that of NU7026. The pharmacokinetic simulations performed predict that NU7026 will have to be administered four times per day at 100 mg kg(-1) i.p. in order to obtain the drug exposure required for radiosensitisation.     

Doxycycline down-regulates DNA-PK and radiosensitizes tumor initiating cells: Implications for more effective radiation therapy

DNA-PK is an enzyme that is required for proper DNA-repair and is thought to confer radio-resistance in cancer cells. As a consequence, it is a high-profile validated target for new pharmaceutical development. However, no FDA-approved DNA-PK inhibitors have emerged, despite many years of drug discovery and lead optimization. This is largely because existing DNA-PK inhibitors suffer from poor pharmacokinetics. They are not well absorbed and/or are unstable, with a short plasma half-life. Here, we identified the first FDA-approved DNA-PK inhibitor by “chemical proteomics”. In an effort to understand how doxycycline targets cancer stem-like cells (CSCs), we serendipitously discovered that doxycycline reduces DNA-PK protein expression by nearly 15-fold (> 90%). In accordance with these observations, we show that doxycycline functionally radio-sensitizes breast CSCs, by up to 4.5-fold. Moreover, we demonstrate that DNA-PK is highly over-expressed in both MCF7- and T47D-derived mammospheres. Interestingly, genetic or pharmacological inhibition of DNA-PK in MCF7 cells is sufficient to functionally block mammosphere formation. Thus, it appears that active DNA-repair is required for the clonal expansion of CSCs. Mechanistically, doxycycline treatment dramatically reduced the oxidative mitochondrial capacity and the glycolytic activity of cancer cells, consistent with previous studies linking DNA-PK expression to the proper maintenance of mitochondrial DNA integrity and copy number. Using a luciferase-based assay, we observed that doxycycline treatment quantitatively reduces the anti-oxidant response (NRF1/2) and effectively blocks signaling along multiple independent pathways normally associated with stem cells, including STAT1/3, Sonic Hedgehog (Shh), Notch, WNT and TGF-beta signaling. In conclusion, we propose that the efficacy of doxycycline as a DNA-PK inhibitor should be tested in Phase-II clinical trials, in combination with radio-therapy. Doxycycline has excellent pharmacokinetics, with nearly 100% oral absorption and a long serum half-life (18–22 hours), at a standard dose of 200-mg per day. In further support of this idea, we show that doxycycline effectively inhibits the mammosphere-forming activity of primary breast cancer samples, derived from metastatic disease sites (pleural effusions or ascites fluid). Our results also have possible implications for the radio-therapy of brain tumors and/or brain metastases, as doxycycline is known to effectively cross the blood-brain barrier. Further studies will be needed to determine if other tetracycline family members also confer radio-sensitivity.     

EXPRESSION AND SUBCELLULAR LOCALIZATION OF DNA-PK IN NASOPHARYNGEAL CARCINOMA CELL LINES CNE1 AND CNE2 WITH DIFFERENT RADIOSENSITIVITY

Exploring mechanism of radioresistance and searching for some suitable radiosensitized approaches isone of the ways to improve the curative rate of nasopharyngeal carcinoma. As we know, radiosensitivity is highly correlated with the number of DNA double strand breaks (DSBs) and the extent of it’s repair[1], and the ability of DSBs repair is one of the important factors influencing radiosensitivity. In mammalian cells, the nonhomologous end joining (NHEJ) is the predominan pathway of DSB…     

Impact of PARP-1 and DNA-PK expression on survival in patients with glioblastoma multiforme

Purpose

To analyze, whether higher tumor levels of DNA repair enzymes contribute to worse treatment results of glioblastoma multiforme (GBM) patients after postoperative radiotherapy.

Materials and methods

Thirty four patients with GBM received postoperative radiotherapy. Tumor sections were examined for poly-ADP ribose polymerase-1 (PARP-1) and DNA protein kinase (DNA-PK) expression. Immunohistochemical staining intensities of PARP-1 and DNA-PK were determined (score 0-3) and expression levels were correlated with patients overall survival.

Results

Median survival time of the whole study group was 10.0 months (95% CI 8.1-11.9). Median survival of patients with high and low (?median and <median) tumor PARP-1 levels were 10.0 months (95% CI 7.9-12.1) and 12.0 months (95% CI 8.3-15.7), respectively (p = 0.93). In contrast, median survival of patients with high and low tumor DNA-PK levels were 9.0 months (95% CI 7.2-10.8) and 13.0 months (95% CI 10.7-15.3), respectively (p = 0.02). In multivariate analysis, DNA-PK expression emerged as a significant independent predictor for overall survival (HR 3.9, 95% CI 1.5-10.7, p = 0.01).

Conclusion

This hypothesis generating study showed that high tumor levels of DNA-PK correlate with poor survival of GBM patients. Further studies are needed to confirm these results and to clarify whether DNA-PK inhibitors might have a potential to radiosensitize GBM and improve the treatment outcome of this devastating disease.     

白花丹醌通过增强凋亡提高肝癌细胞放疗敏感性的研究

目的:探究白花丹醌对肝癌细胞放疗敏感性的作用及其生物学机制。方法:用白花丹醌（Plumbagin,PLU）预处理肝癌细胞,并暴露于单一剂量的γ射线或碳离子束。随后检测细胞集落形成、细胞活力;用Hoechst 33342染色和流式细胞术检测细胞凋亡;DCFH-DA探针检测活性氧水平。用裸鼠异种移植肝癌模型检测白花丹醌对肝肿瘤体积的影响,并用免疫组化法观察其对Ki67和cleaved caspase 3表达水平的影响。结果:白花丹醌促进放疗在肝癌细胞中的细胞毒性;促进放疗后的肝癌细胞凋亡;诱导肝癌细胞的氧化应激水平;体内实验证明,白花丹醌可减小裸鼠的肿瘤体积,显著降低Ki67水平,升高cleaved caspase 3水平。结论:白花丹醌通过增强氧化应激和凋亡提高肝癌细胞放疗敏感性。     

Gene amplification as a target for cancer chemotherapy.

Facile gene amplification is one aspect of the genetic instability associated with transformed cells. Amplification of oncogenes and proto-oncogenes contributes to carcinogenesis and tumor progression. Gene amplification is also a common basis for resistance to anticancer drugs. The observation that low level cytotoxic stress can cause rapid loss of amplified genes from cultured cell populations suggests that gene amplification may be a potential target for cancer chemotherapy. Drug-induced loss of amplified genes is seen with a wide variety of extrachromosomally amplified genes, including drug resistance genes and proto-oncogenes. A number of drugs and differentiating agents have been reported to cause rapid loss of unstably amplified genes. An effect on amplified genes or cells carrying amplified genes may contribute to the selective action of drugs presently used for cancer chemotherapy. A better understanding of drug-induced amplified gene loss may lead to new strategies for cancer treatment.