金纳米颗粒放射增敏机制研究进展

摘 要：金纳米颗粒（gold nanoparticles,GNPs）以其独特的理化特点而广泛应用于肿瘤诊疗研究。GNPs生物相容性好,原子序数高,对kV级射线的光电效应截面比软组织高,能提高肿瘤组织的局部能量沉积,是一种有良好应用前景的放射增敏剂。MV级射线通过康普顿散射与GNPs相互作用,但其截面远远低于kV级射线与GNPs作用的截面,因此GNPs对其增敏效应不如kV级射线显著。GNP诱导细胞内活性氧簇（reactive oxygen species,ROS）增加,引起DNA损伤,诱导细胞凋亡。GNPs通过调控细胞周期进程,使细胞阻滞在G2/M期,增强细胞的放射敏感性。此外,GNPs还能引起细胞内自噬体增多和溶酶体降解能力减弱并最终引起细胞死亡。GNPs也可以抑制缺氧诱导因子1α（hypoxia inducible factor-1α,HIF-1α）和血管内皮生长因子（vascular endothelial growth factor,VEGF）mRNA表达,使裸鼠肝癌血管形态趋于正常。     

肿瘤放射增敏剂及增敏机制研究进展

放射增敏剂是指能增强射线对肿瘤内乏氧细胞的杀灭作用而对有氧的正常组织一般损伤较小的一些化学物质。本文主要介绍了放射增敏剂的研究进展。从影响肿瘤放射敏感性因素入手,详细叙述了放射增敏剂的种类、主要作用机制和发展趋势。     

三氧化二砷对纤维肉瘤细胞放射增敏作用的研究

目的 研究和探讨三氧化二砷（As2O3）是否对纤维肉瘤细胞有放射增敏作用。方法以人纤维肉瘤细胞HTl080为实验对象，首先检测As2O3的单药毒性，确定IC10、IC50和IC90。放射增敏作用的实验分为空白对照组、单纯给药组、单纯照射组（包括1、2、4、6、8、10Gy剂量）、照射前加药组（于照射前24h加入设定浓度的As2O3，药物作用24h后进行照射）和照射后加药组（于照射后即刻加入设定浓度的As2O3，药物作用24h）。所有实验均重复3次。采用克隆形成分析法观察单纯照射和照射联合As2O3对细胞的杀伤作用。计算细胞的存活分数，用多靶单击模型进行拟合并做图。结果 HT1080细胞的IC10、IC50和IC90剂量分别为0．57、3．67和12．0μmol／L。无毒剂量的As2O3照射前给药增敏比（SER）为0．86（Do值比）、0．98（SF2值比），照射后给药SER为0．99（Do值比）、1．09（SF2值比）。IC50剂量的As2O3照射前给药SER为0．90（Do值比）、0．87（SF2值比），照射后给药SER为1．14（Do值比）、1．08（SF2值比）。IC90剂量的As2O3照射前给药和照射后给药的SER均为1．14（Do值比）、3．20（SF2值比），As2O3对低剂量照射的放射增敏作用好于高剂量照射（SERSF2〉SERDo）。结论 As2O3对HT1080纤维肉瘤细胞具有一定的放射增敏作用，为临床放疗和As2O3联合应用提供了实验依据。     

三氧化二砷对人宫颈癌Hela细胞系的放射增敏作用

目的 探讨三氧化二砷（As2O3）对人宫颈癌Hela细胞系的放射增敏作用。方法 MTT法确定As2O3对Hela细胞的半数致死浓度（LD30），采用集落形成法观察20％该浓度的As2O3对Hela细胞的放射增敏作用。结果（1）细胞生长抑制随As2O3浓度的增加而增强；（2）As2O3＋照射组的细胞存活率低于单纯照射组，耽值小于单纯照射组（1．58Gy、2．11Gy），Dq值也小于单纯照射组（0．27Gv、0．64Gv），存活曲线肩区（Dq）变小，放射增敏比（SER）1．34。结论 As2O3对宫颈癌细胞有明显的放射增敏作用，其作用机理有待进一步研究。     

紫杉醇对骨肉瘤细胞放射增敏作用的研究

目的观察体外环境下紫杉醇对骨肉瘤（osteosarcoma,OS）细胞的放射增敏效果及其与药物作用时间的关系。方法以MG-63细胞为实验对象,采用MTT法检测不同浓度紫杉醇（6、0.6、0.06、0.006和0.000 6μg/mL）对MG-63细胞的抑制作用,确定IC10作为后续实验的药物浓度;采用克隆形成分析法分别测定MG-63细胞在紫杉醇作用24h后照射以及单纯照射的存活分数（SF）,拟合细胞生存曲线并计算放射增敏比,分析紫杉醇对MG-63细胞的放射增敏作用;采用克隆形成分析法测定紫杉醇作用于MG-63细胞12、24和36h后细胞生存率的变化,确定最佳照射时间。组间比较采用单因素方差分析。结果 MTT实验结果显示,当紫杉醇浓度分别为0.000 6、0.006、0.06、0.6和6μg/mL时,其细胞抑制率分别为（3.25±2.58）%、（9.98±3.83）%、（20.35±3.91）%、（21.55±3.70）%和（55.36±4.67）%。提示,紫杉醇对MG-63细胞的生长抑制作用呈浓度依赖性,F=83.70,P〈0.01,IC10为0.01μg/mL;IC10浓度紫杉醇増敏比分别为1.14（D0比）、1.20（Dq比）和1.08（SF2比）;MG-63细胞α/β值为2.23,IC10浓度紫杉醇作用后α/β值为2.32。紫杉醇作用于MG-63细胞12、24和36h后再进行照射,细胞存活分数分别为（9.21±0.81）%、（5.39±0.75）%和（0.38±0.13）%,显著低于对照组的（12.86±1.07）%,差异有统计学意义,F=144.11,P〈0.01。结论紫杉醇对MG-63细胞有放射增敏作用,增敏作用呈时间依赖性,有一定的临床应用前景。     

肿瘤放射增敏剂及增敏机制研究进展

放射增敏剂是指能增强射线对肿瘤内乏氧细胞的杀灭作用而对有氧的正常组织一般损伤较小的一些化学物质.本文主要介绍了放射增敏剂的研究进展.从影响肿瘤放射敏感性因素入手,详细叙述了放射增敏剂的种类、主要作用机制和发展趋势.     

纳米金颗粒的基本特性及其对肿瘤放射增敏作用的研究进展

纳米金颗粒以其独特的理化性质在医学领域越来越受到重视。近年许多研究证实了纳米金在肿瘤治疗中可以减少组织受照剂量,减轻放射治疗对正常组织的伤害,在放射增敏方面有重要作用,本文从纳米金的基本特性、生物学毒性、放射增敏机制、在细胞和动物模型中增敏实验以及在临床前应用等几方面进行综述。     

放射增敏剂的研究进展

放射增敏剂可提高放射线对肿瘤细胞的杀伤作用。增加放疗效果。理想的放射增敏剂可以显著增加放疗疗效。对正常组织没有或很少有毒副反应。国内外学者进行了大量研究，在合成药物、分子靶向药物和天然药物等方面取得了新的进展，显示了放射增敏剂的发展趋势。文章主要对此进行综述。     

三氧化二砷对人肺腺癌A549细胞的放射增敏作用

[目的]探讨三氧化二砷(As2O3)对人肺腺癌A549细胞的放射增敏作用.[方法]MTT法确定As2O3对A549细胞的半数致死浓度(LD50),采用集落形成法观察20％LD50的As2O3对A549细胞的放射增敏作用.[结果]细胞生长抑制随As2O3浓度的增加而增强.As2O3+照射组的细胞存活率低于单纯照射组,D0值小于单纯照射组(1.46Gy vs 2.03 Gy),Dq值也小于单纯照射组(0.49 Gy vs 1.35Gy),存活曲线肩区(Dq)变小,放射增敏比(SER)为1.39.[结论]As2O3对肺腺癌A549细胞有明显的放射增敏作用,抑制A549细胞的修复能力使照射后细胞存活分数降低是其放射增敏的可能机制.     

Tamoxifen-induced enhancement of calcium signaling in glioma and MCF-7 breast cancer cells

The antiestrogen tamoxifen is commonly used to treat breast cancer, but it also has therapeutic activity in several other types of cancer. Many of these tumors, including malignant gliomas, are estrogen receptor negative. Nonetheless, high concentrations of tamoxifen can directly reduce cell proliferation in some of these tumors and induce apoptosis. In this study, the role of tamoxifen in calcium signaling and calcium-induced cell death was studied in both malignant glioma cell lines and MCF-7 breast cancer cells. Tamoxifen potently increased the spatial expansion of calcium waves by 30-150% while significantly enhancing and prolonging agonist-induced calcium elevations. Furthermore, tamoxifen pretreatment accelerated calcium ionophore-induced death by more than 20 min, suggesting that tamoxifen lowered cellular resistance to calcium loads. In contrast to its potentiating of calcium signaling in tumors, tamoxifen had no significant effect on calcium signaling in cultures of primary astrocytes from either human or rat brain. This study demonstrates the existence of calcium signaling in breast cancer and glioma cells and identifies tamoxifen as a potential modulator of tumor-associated calcium signaling.     

EZH2过表达在MCF-7获得性耐药中的作用

目的 探讨EZH2过表达在MCF-7/ADR获得性耐药中的作用。方法 应用荧光定量PCR技术和Western blot技术分别检测EZH2在MCF-7和MCF-7/ADR中的mRNA和蛋白的相对表达量。将带有报告基因eGFP的EZH2 shRNA、EZH2 shRNA-scramble质粒分别转染MCF-7/ADR细胞后,用G418筛选获得稳转细胞株,应用荧光定量PCR技术验证EZH2 shRNA组EZH2 mRNA表达是否被抑制。采用WST-1方法检测EZH2 shRNA、EZH2 shRNA-scramble和阴性对照组细胞对阿霉素敏感性的变化情况。结果 MCF-7/ADR中EZH2 mRNA相对表达量约为MCF-7的2.52±1.523倍,MCF-7/ADR中EZH2蛋白相对表达量约为MCF-7的1.58±0.58倍,差异均有统计学意义(P＜0.05)。EZH2 shRNA组稳转的细胞株EZH2 mRNA的抑制率约为84%(P＜0.05),加入阿霉素后细胞增殖能力约下降25%(P＜0.05),而EZH2 shRNA-scramble组和阴性对照组加入阿霉素后细胞增殖能力无明显变化。结论 在MCF-7/ADR细胞中EZH2 mRNA和蛋白的相对表达量较MCF-7细胞高。沉默EZH2的表达有可能逆转MCF-7/ADR细胞对阿霉素的耐药性。     

DHEA-induced antiproliferative effect in MCF-7 cells is androgen- and estrogen receptor-independent

Dehydroepiandrosterone, an adrenal hormone derived from cholesterol, can be metabolized to estrogens (estradiol) and androgens (testosterone). In this study, we evaluated whether the antiproliferative effect induced by dehydroepiandrosterone in MCF-7 cells (an estrogen-dependent breast cancer cell line) is direct, or indirect, through its conversion to estradiol or testosterone. Although dehydroepiandrosterone had an antiproliferative effect at supraphysiologic concentrations, when it was used at physiologic concentrations, it increased the proliferation of MCF-7 cells. 17Beta-estradiol induced an increase in MCF-7 cell proliferation at physiologic concentrations, whereas testosterone had a weak inhibitory effect at 100 microM. Dehydroepiandrosterone sulfate (its inactive sulfate ester) had no effect upon the cell cycle. Dehydroepiandrosterone-induced antiproliferative and proliferative effects were not blocked by inhibitors of androgen or estrogen receptors, thus indicating that its effect is secondary to a direct interaction with a "putative" receptor rather than a conversion into steroid hormones. These results suggest that dehydroepiandrosterone could be used at supraphysiologic concentrations in the treatment of breast cancer.     

新型LL-37 杂合肽对乳腺癌MCF-7 细胞的抗肿瘤活性的研究

目的：探究新型LL-37 杂合肽对乳腺癌MCF-7 细胞的抗肿瘤活性及其作用机制。方法:利用抗菌肽数据库（http://aps.unmc.edu/AP/main.php）筛选出人源的抗肿瘤抗菌肽，即LL-37 和中性粒细胞防御素-1（human neutrophil peptide 1，HNP-1），经生物信息学软件分析提取有效肽片段，改造整合成新型LL-37 杂合肽；采用CCK-8 法检测0~70 μmol/L 的新型LL-37 杂合肽对MCF-7 细胞和人正常乳腺细胞MCF10A增殖的影响，激光扫描共聚焦显微镜观察分析新型LL-37 杂合肽与肿瘤细胞的亲和能力，流式细胞仪检测新型LL-37 杂合肽和caspase 抑制剂对MCF-7 细胞凋亡和周期的影响。结果:经软件分析得出新型LL-37 杂合肽为水脂两亲性的阳离子多肽，可靶向性地抑制乳腺癌MCF-7 细胞的增殖（P<0.05），其IC50值为58.34 μmol/L，而对正常乳腺MCF10A细胞无明显抑制作用；新型LL-37 杂合肽与MCF-7 细胞具有较高的亲和力，可引起细胞周期阻滞于S期及显著增加细胞早期凋亡率（P<0.01）；但在加入caspase 抑制剂后，细胞周期阻滞及凋亡情况明显缓解（P<0.01）。结论:新型LL-37 杂合肽对乳腺癌MCF-7 细胞具有抗肿瘤活性，可能通过caspase依赖的信号通路阻滞细胞周期和诱导细胞凋亡。     

The regulatory effect of tamoxifen on fibronectin expression in estrogen-dependent MCF-7 breast carcinoma cells

We investigated the regulatory effect of tamoxifen (TAM) on fibronectin (FN) expression in estrogen-dependent MCF-7 breast carcinoma cells both in vitro and in vivo. in vitro, MCF-7 cells were cultured with 17beta-estradiol (E2) and/or TAM. In the animal experiment in vivo, MCF-7 tumors were grown in ovariectomized athymic mice by implanting a sustained release E2 pellet. The E2 pellets were removed after 3 weeks of E2 treatment. Animals were then divided into four groups: 1) an E2 (0.72 mg/pellet) pellet [E2(+)]; 2) an E2 and a TAM (5 mg/pellet) pellet [E2(+)TAM]; 3) no treatment [E2(-)] and 4) a TAM pellet [E2(-)TAM]. Following each treatment for 4 weeks, all animals were sacrificed and tumors were removed. Specimens, cells (in vitro) or tumors (in vivo), were homogenized and assayed for FN by Western blots. In the in vitro experiment, FN expression in MCF-7 cells decreased by incubating with 10(-9) M E2 and increased with 10(-6) M TAM. The effect of TAM increasing FN expression was inhibited by incubation accompanied with 10(-9) M E2 or 1 microg/ml transforming growth factor-beta (TGF-beta) neutralizing antibody. In the in vivo animal experiment FN expression in the tumors of E2(+) mice was lower than that of E2(-) mice. However, TAM increased FN expression in the tumors regardless of E2 pellet. These results suggest that TAM increases FN expression of MCF-7 breast carcinoma cells and that these regulatory effects of TAM on FN expression are partly mediated by TAM-induced TGF-beta.     

Evidence for a direct growth-stimulating effect of estradiol on human MCF-7 cells in vivo

The MCF-7 continuous line of human breast cancer cells requires that athymic nude mice receive supplemental estrogen so that inocula can produce progressively growing tumors. Although these cells contain a typical estrogen receptor complex, the lack of consistent growth stimulation induced by estrogens added to in vitro culture systems has raised the question as to whether this class of hormones acts directly upon the cells or induces a second message produced in other tissues. The present experiments were designed to test the effect of estradiol on the growth of these cells in vivo by exposing them directly to the hormone prior to its absorption into the hepatic portal circulation and subsequent metabolic inactivation. Tumor fragments that were placed next to an estradiol-containing pellet in the spleen grew to produce grossly evident tumor masses, whereas those in the subcutis of the same animals did not, although some minute residua did remain. In the splenic tumors, the mitotic index of the MCF-7 cells immediately adjacent to the estrogen pellets was 2.4 times that of cells on the other side of the same tumor and 3.5 times that of those in the minute s.c. residua. We interpret these data as indicating that in vivo estradiol is acting directly upon the MCF-7 cells to increase their rate of proliferation rather than to initiate the production of a second message to be released into the circulation. Additionally, it was found that s.c. tumors that were decreasing in volume subsequent to withdrawal of systemic estrogen still contained dividing neoplastic cells but with a lower frequency than that seen in progressively growting tumors stimulated with estradiol. This finding indicates that MCF-7 cells can proliferate in vivo in the absence of a substantial amount of estrogen but only at a rate insufficient to sustain progressive tumor growth.     

Invasive and metastatic properties of MCF-7 cells and rasH-transfected MCF-7 cell lines.

In vitro invasion and in vivo metastasis assays were performed with a panel of MCF-7 cells transfected with isogenic constructs of mutated rasH genes. Both increased levels of rasH expression and rasH oncogene activation increased activity of derivative cell lines in in vitro invasion assays. In vivo formation of spontaneous metastases was assessed after intradermal inoculation of MCF-7 cells in the vicinity of the mammary fat pads of ovariectomized nude mice. No metastases were seen in the absence of estradiol treatment of the mice. With estradiol supplementation of the mice both the rasH-transfected and control transfected cell lines gave a higher incidence of metastases than parental MCF-7 cells. Prolonged treatment of mice with exogenous estradiol (60 days vs. 21 days) resulted in more frequent metastases to liver and lung at the end of the 90-day observation period. In contrast to activated rasH-gene enhancement of metastatic capacity of rodent fibroblast and epithelial cell lines, there was no correlation of rasH expression with in vivo metastatic capacity of a human mammary carcinoma cell line.     

Anti-apoptotic effect of claudin-1 in tamoxifen-treated human breast cancer MCF-7 cells

Background  

Claudin-1 is a membrane protein of tight junctions, and is associated with the development of various cancers. However, the significance of claudin-1 expression in cancer cells is not well understood. Here, we showed for the first time the anti-apoptotic effect of claudin-1 in human breast cancer MCF-7 cells.     

Paclitaxel-induced apoptosis in MCF-7 breast-cancer cells

A study of MCF-7 human breast cancer cells was undertaken to ascertain the degree of apoptosis induction by paclitaxel and if the induction of apoptosis could be enhanced by caffeine. Paclitaxel (0–20 ng/ml) caused concentration-dependent increases in morphologically identifiable apoptotic cells (up to 43% of cell population) and cells with DNA strand breaks (up to 38%), a commonly cited marker of apoptosis. Maximal DNA strand breakage occurred after 16 hr of exposure to paclitaxel and maximal apoptotic-appearing cells occurred after 24 hr. The remaining non-apoptotic paclitaxel-exposed cells were growth arrested in G₂. A 4-hr exposure to caffeine concentration-dependently (0–20 mM) increased apoptosis to 88% of the cell population. Our results show induction of apoptosis in breast cancer cells by paclitaxel, and enhancement of this process by caffeine. Int. J. Cancer, 70:214–220, 1997. © 1997 Wiley-Liss Inc.