全硫代反义寡核苷酸对骨肉瘤细胞生长及端粒酶活性的影响

目的采用针对人端粒酶hTR基因的反义寡聚脱氧核苷酸,探讨端粒酶反义寡聚脱氧核苷酸（ASODN）对骨肉瘤细胞HOS细胞端粒酶活性及细胞增殖的影响。方法脂质体介导的细胞转染后,PS-ASODN和PS-SODN分别作用于骨肉瘤细胞HOS细胞后并培养24、48、72h,分别采用酶联免疫吸附法（ELISA）、吖啶橙染色法检测骨肉瘤细胞HOS细胞的端粒酶活性、细胞形态改变。结果端粒酶PS-ASODN作用骨肉瘤细胞HOS细胞72h后端粒酶活性表达为阴性。PS-ASODN作用的骨肉瘤细胞HOS细胞有明显凋亡现象,凋亡细胞体积缩小,染色质浓缩。结论 PS-ASODN对端粒酶活性的抑制率与PS-ASODN的浓度和作用时间呈依赖关系,即抑制率随着反义寡核苷酸的浓度和作用时间的增加而增大。     

氨基酸酯基二硫代甲酸酯类化合物的合成及体外生物活性评价

目的 合成18种氨基酸酯基二硫代甲酸酯类化合物(化合物1～18),并进行体外抗肿瘤活性以及抗乙肝病毒(HBV)活性评价.方法 以L-苯丙氨酸、L-丙氨酸、L-亮氨酸、L-异亮氨酸、L-谷氨酸及L-甘氨酸的甲酸酯为原料,通过碱催化,与CS2和卤代烷缩合反应,合成18种氨基酸酯基二硫代甲酸酯类化合物.化合物的结构及组成经过质谱、1H-NMR和熔点仪测试技术进行了表征.利用MTT法测定目标化合物1～18对子宫颈癌HeLa、肝癌HepG2、胃癌BGC-823、乳腺癌MCF-7、结肠癌SW-480细胞株的增殖抑制作用;ELISA法测定对HBsAg和HBeAg的抑制效果;实时荧光定量PCR法检测上清液中HBV DNA的表达量.结果 化合物11、12、17和18对上述5种肿瘤细胞株增殖有较好的抑制作用;相对于阳性对照拉米呋啶,化合物14和15能够较好的抑制HBV抗原的分泌和病毒DNA的复制.化合物14抑制HBV DNA、HBsAg和HBeAg的IC50值分别是0.43、0.28和0.1 mmol·L-1;化合物15的IC50值分别为0.24、0.02、0.03mmol·L-1.结论 这些二硫代甲酸酯类衍生物中,化合物11、12、17和18在体外具有抑制肿瘤细胞增殖的活性;化合物14和15在体外对HBV有较好的抑制作用.该研究为进一步开发二硫酯在抗肿瘤及抗病毒方面奠定了很好的基础.     

The mechanism of thrombocytopenia caused by cholesterol-conjugated antisense oligonucleotides

In this study, we investigated thrombocytopenia caused by cholesterol-conjugated antisense oligonucleotides (Chol-ASO). First, we evaluated platelet activation induced by Chol-ASO in mice by flow cytometry after administration of platelet-rich plasma (PRP). An increase in the number of large particle-size events with platelet activation was detected in the Chol-ASO-treated group. In a smear study, numerous platelets were observed to attach to nucleic acid-containing aggregates. A competition binding assay showed that the conjugation of cholesterol to ASOs increased their affinity for glycoprotein VI. Platelet-free plasma was then mixed with Chol-ASO to form aggregates. The assembly of Chol-ASO was confirmed by dynamic light scattering measurements in the concentration range in which the formation of aggregates with plasma components was observed. In conclusion, the mechanism by which Chol-ASOs causes thrombocytopenia is proposed to be as follows: (1) Chol-ASOs form polymers, (2) the nucleic acid portion of the polymers interacts with plasma proteins and platelets, which cross-links them to form aggregates, and (3) platelets bound to aggregates become activated, resulting in platelet aggregation, leading to a decrease in platelet count in vivo. The details of the mechanism revealed in this study could contribute to creating safer oligonucleotide therapies without the risk of thrombocytopenia.     

端粒酶反义寡核苷酸对宫颈癌HeLa细胞端粒酶活性的影响

目的　探讨端粒酶反义寡核苷酸 (ASON)对宫颈癌HeLa细胞体外生长抑制的作用机制。方法　针对端粒酶RNA的ASON作用于HeLa细胞 ,台盼蓝排斥法测定细胞存活力 ,以PCR为基础的TRAP法测定端粒酶的活性 ,流式细胞仪 (FCM)检测细胞凋亡及细胞周期。结果　ASON连续治疗 5d ,HeLa细胞的存活力无明显下降 ;在FuGENE6的介导下 ,ASON对端粒酶活性的抑制与ASON的浓度和治疗时间呈正相关。FCM未检测到特征性的亚G1 峰 ,ASON组中G2 /M期的DNA含量显著增多。结论　针对端粒酶RNA的ASON能抑制HeLa细胞的端粒酶活性 ,并将细胞阻滞在分裂期达到抑制细胞生长的目的     

Targeting human telomerase by antisense oligonucleotides and ribozymes

Human telomerase is a ribonucleoprotein enzyme complex that enables cells to maintain telomere length, allowing indefinite replicative capacity. The notion that telomerase is reactivated in 80-90% of human cancers has led to the proposal of telomerase as a promising therapeutic target for novel anticancer interventions. Due to its inherent accessibility to nucleic acids, telomerase appears an ideal target for strategies based on the use of antisense oligonucleotides and ribozymes that target its RNA template. In this review a summary of the different antisense- and ribozyme-based approaches used thus far to inhibit telomerase activity in human cancer cells is provided. All these strategies significantly inhibited the enzyme's catalytic activity in in vitro and in vivo tumor models. However, while in some studies tumor cell growth arrest was observed as a consequence of telomere shortening after prolonged telomerase inhibition, other studies have shown that antisense- and ribozyme-based treatments targeting telomerase induced rapid loss (i.e. within a few days) of tumor cell viability with concomitant apoptosis. In the latter case it is unlikely that cell death was related to telomere erosion since the cells would not have undergone enough divisions to significantly shorten their telomeres. A possible explanation is that telomerase inhibitors may induce apoptosis in cancer cells directly by interfering with the capping function of the enzyme. Overall, the available results indicate antisense oligonucleotides and ribozymes as good tools to inhibit telomerase and suggest that abrogation of telomerase activity may affect tumor cell proliferation also through pathways that are not dependent on telomere erosion.     

Chemosensitization by antisense oligonucleotides targeting MDM2

The MDM2 oncogene is overexpressed in many human cancers, including sarcomas, certain hematologic malignancies, and breast, colon and prostate cancers. The p53-MDM2 interaction pathway has been suggested as a novel target for cancer therapy. To that end, several strategies have been explored, including the use of small polypeptides targeted to the MDM2-p53 binding domain, anti-MDM2 antisense oligonucleotides, and natural agents. Different generations of anti-human-MDM2 oligonucleotides have been tested in in vitro and in vivo human cancer models, revealing specific inhibition of MDM2 expression and significant antitumor activity. Use of antisense oligos potentiated the effects of growth inhibition, p53 activation and p21 induction by several chemotherapeutic agents. Increased therapeutic effectiveness of chemotherapeutic drugs in human cancer cell lines carrying p53 mutations or deletions have shown the ability of MDM2 inhibitors to act as chemosensitizers in various types of tumors through both p53-dependent and p53-independent mechanisms. Inhibiting MDM2 appears to also have a role in radiation therapy for human cancer, regardless of p53 status, providing a rationale for the development of a new class of radiosensitizers. Moreover, MDM2 antisense oligonucleotides potentiate the effect of epidermal growth factor receptor (EGFR) inhibitors by affecting in vitro and in vivo proliferation, apoptosis and protein expression in hormone-refractory and hormone-dependent human prostate cancer cells. These data support the development, among other MDM2 inhibitors, of anti-MDM2 antisense oligonucleotides as a novel class of anticancer agents, and suggest a potentially relevant role for the oligonucleotides when integrated with conventional treatments and/or other signaling inhibitors in novel therapeutic strategies.     

Efficient inhibition of human telomerase activity by antisense oligonucleotides sensitizes cancer cells to radiotherapy

AIM: To investigate the effect of the antisense oligonucleotides (ASODN) specific for human telomerase RNA (hTR) on radio sensitization and proliferation inhibition in human neurogliocytoma cells (U251). METHODS: U251 cells were transfected with hTR ASODN or nonspecific oligonucleotides (NSODN). Before and after irradiation of (60)Co- gamma ray, telomerase activity was assayed by telomeric repeat amplification protocol ( TRAP-PCR-ELISA), and DNA damage and repair were examined by the comet assay. The classical colony assay was used to plot the cell-survival curve, to detect the D(0 )value. RESULTS: hTR antisense oligonucleotides could downregulate the telomerase activity, increase radiation induced DNA damage and reduce the subsequent repair. Furthermore, it could inhibit the proliferation and decrease the D(0 ) value which demonstrates rising radiosensitivity. However, telomere length was unchanged over a short period of time. CONCLUSION: These findings suggest that an ASODN-based strategy may be used to develop telomerase inhibitors, which can efficiently sensitize radiotherapy.     

Cationic lipids enhance cellular uptake and activity of phosphorothioate antisense oligonucleotides.

We have investigated the use of a cationic lipid preparation to enhance antisense oligonucleotide activity in human umbilical vein endothelial cells. A liposomal preparation containing the cationic lipid N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA) was found to increase by at least 1000-fold the potency of an antisense oligonucleotide (ISIS 1570) that hybridizes to the AUG translation initiation codon of human intercellular adhesion molecule-1. In the presence of 8 microM DOTMA, 6-15-fold more 35S-ISIS 1570 associated with cells, at oligonucleotide concentrations from 0.01 to 5 microM, than did in the absence of DOTMA. Both 35S-ISIS 1570 association with cells and antisense activity were increased as a function of DOTMA concentration and with increasing time of incubation with the cationic lipid. Fluorescein-labeled ISIS 1570 was used to assess the intracellular distribution of the oligonucleotide in the presence and absence of DOTMA. In the absence of DOTMA, the oligonucleotide localized to discrete structures in the cytoplasm of the cell, resulting in a punctate fluorescence pattern. In the presence of DOTMA, cellular fluorescence markedly increased and the oligonucleotide localized within the nucleus, as well as to discrete structures in the cytoplasm. Accumulation of the oligonucleotide in the nucleus in the presence of DOTMA was time and temperature dependent. Nuclear accumulation was inhibited by preincubation of the cells with monensin but not chloroquine, NH4Cl, nocodazole, colcemid, or brefeldin A. These data demonstrate that cationic lipids increase antisense activity by increasing the amount of oligonucleotide associated with cells and altering intracellular distribution of the oligonucleotide.     

Structural modifications of antisense oligonucleotides

Antisense oligonucleotides are efficient tools for the inhibition of gene expression in a sequence specific way. Natural oligonucleotides are decomposed rapidly in biological systems, which strongly restrict their application. In contrast, artificial oligonucleotides are designed to be more stable against degradation than the target mRNA, which results in a catalytic effect of the drug. Modification of the phosphate linkage has been the first successful strategy for antisense drug developments and Fomivirsene the first antisense drug in therapy. The launch of Fomivirsene has resulted in a revolutionary spin off to antisense research leading to a second generation of antisense oligonucleotides, which are stable against oligonucleotide cleaving enzymes. Among these, oligonucleotides bearing an alkoxy substituent in position 2' were the most successful ones. The third generation of antisense oligonucleotides contains structure elements, which enhance the antisense action. Zwitterionic oligonucleotides show remarkable results, first, because the stability against ribozymes is largely increased, and secondly, because the electrostatic repulsion between the anionic sense and the zwitterionic antisense cords is minimized. Promising new target molecules in antisense research are oligonucleotide chim?res, which enhance the antisense action (chim?res with intercalators, chelators or polyamines) or enable an application as sequence specific detectors (chim?res with biotin, fluorescein or radioligands).     

Cellular uptake of antisense oligonucleotides

Antisense oligonucleotides (AS ONs) selectively bind to the target mRNA and prevent its translation into the corresponding protein. Various tissue culture studies demonstrated that AS ONs enter into cells via the receptor-mediated endocytosis pathway. There are many different types of receptors, and their characteristics and expression vary with cell types. In this review, we will discuss the characteristics of the various receptors that have been isolated in vitro. We will also discuss the uptake and the bioavailability of AS ONs after being administered in vivo.     

抗肿瘤反义寡核苷酸药物研究现状和趋势

以基因为靶的反义药物是抗肿瘤新药研究和开发的重要方向之一，已有近10种不同抗肿瘤反义寡核苷酸药物正在进行Ⅱ或Ⅲ期临床试验。基于肿瘤相关基因的多样性和复杂性，抗肿瘤反义药物的发展趋势是研究和开发靶向特定基因治疗特定类型肿瘤的“窄谱”抗肿瘤反义药物，以及由靶向多个肿瘤相关基因的反义寡核苷酸组成的“复方”式“广谱”抗肿瘤反义药物。