抗肿瘤多核铂配合物的研究

多核铂配合物作为非经典铂抗肿瘤药物,其抗肿瘤机制与现有铂类抗肿瘤药物不同,因而在克服现有铂类抗肿瘤药物耐药性方面有着巨大的潜力。本文综述了多核铂类抗肿瘤药物的研究进展,以连接铂原子的桥配体结构的不同,可分为六大类:以烷基二胺及其衍生物为桥的多核铂配合物、以含氮杂环为桥的多核铂配合物、以羧酸根为桥的多核铂配合物、以卤素离子为桥的多核铂配合物、以含硫配体为桥的多核铂配合物及以其他配体为桥的多核铂配合物。本文还介绍了这几类多核铂配合物的抗肿瘤机理及在克服顺铂耐药性机理方面的研究进展。     

铂(Ⅱ)类抗肿瘤药物

自顺铂临床用于抗肿瘤药物以来,在铂配合物中寻找新的药物已成为研究的热点,现在已有顺铂、卡铂和奥沙利铂在广泛应用于临床。根据经典的构效关系,上千个新的铂类化合物被设计与合成出来。我们综述了铂（Ⅱ）类抗肿瘤药物近五年的研究状况,介绍了包括含有生物活性基团的铂（Ⅱ）配合物,具有空间位阻的铂（Ⅱ）配合物,反式铂（Ⅱ）配合物,含S、P配位原子铂（Ⅱ）配合物和多核铂（Ⅱ）配合物,总结了这些化合物的抗肿瘤机理、活性。     

金属配合物在肿瘤化学免疫治疗中的应用前景

肿瘤化学免疫治疗是免疫疗法与化学疗法相结合通过协同作用治疗肿瘤的一种新方法。以铂类药物为代表的金属药物是一类重要的化学抗肿瘤药物,其作用机理是与肿瘤细胞DNA形成交联物并阻止其复制;但是,这类药物存在严重的毒性和耐药性问题。近年来发现有些金属配合物在产生细胞毒性的同时,也通过多种机制参与机体的免疫调节过程,其中以诱导免疫原性细胞死亡（ICD）最为常见。本文简要介绍了肿瘤化学免疫治疗的基本概念以及与免疫抑制有关的肿瘤微环境,概述了金属配合物的免疫活性和调节免疫过程的基本原理,并以铂类药物为例总结了金属配合物调节免疫过程的可能途径,最后列举了若干具有ICD诱导潜力和其他免疫调节功能的非铂类金属配合物,指出了目前化学免疫治疗存在的问题和未来的应用潜力。化学治疗与免疫治疗结合既可以利用机体免疫系统增强金属配合物的抗肿瘤效果,又可以减少药物剂量,降低毒副作用,是设计金属抗肿瘤药物的新方向之一。     

非经典铂类抗肿瘤药物研究

本文综述了非经典铂类抗肿瘤药物的发展概况,介绍了具有口服活性的铂(Ⅳ)配合物,具有空间位阻的铂(Ⅱ)配合物,反式铂(Ⅱ、Ⅳ)配合物,多核铂(Ⅱ)配合物和含有铂-硫键的铂(Ⅱ)配合物,并总结了这几类新型铂配合物的抗肿瘤机理,克服顺铂的耐药性机理及其临床进展。     

铂类抗肿瘤药物的设计开发进展

铂类抗肿瘤药物是临床上使用广泛的化疗药物,具有近40年的研究和使用历史.本文对临床上使用和处于临床研究中的铂类药物进行了简单介绍,总结了进入临床研究阶段被淘汰的铂类药物,针对目前铂类药物所处形势重点介绍了新一代铂类药物的设计开发方法.新一代铂类药物包括修饰和改进的经典构型的Pt(II)配合物、反式Pt(II)配合物、药物前体Pt(IV)配合物、单功能铂配合物、配位饱和的铂配合物和多核铂配合物等.通过列举最新研究成果,分析药物作用机制,提出铂类药物的设计开发方法,让读者了解铂类抗肿瘤药物的发展历程和未来的发展趋势.     

基于天然产物的铂类和芳基金属抗癌药物研究进展

临床使用的现代药物超过50%都来自于天然产物,它们不仅能够通过阻止细胞周期进程、抑制癌细胞存活信号通路以及调节免疫细胞等多种生物途径来阻止肿瘤生长及其进程,而且对正常组织表现出较低的毒性。虽然以顺铂为代表的金属抗肿瘤药物广泛用于临床,但是它们存在严重的耐药性和毒副作用,包括肾毒性、神经毒性等。因此,利用天然产物中的优势来改造铂类配合物,有望开发出新型铂类抗癌药物以克服铂药的缺陷。另一方面,芳基金属配合物因其良好的水溶性和对正常组织的低毒性受到了广泛关注,将天然产物与芳基金属配合物相结合,也为开发高效低毒的新型抗癌药物提供了更多可能。结合天然产物和金属各自优势开发基于天然产物的金属配合物作为抗癌剂已成为研究热点,开辟了抗癌的新途径。本文对已经报道的有关天然产物的铂类和芳基金属配合物的研究及作用机理进行了较为全面的综述,并对该领域的未来发展进行了展望。     

钌多吡啶配合物的合成、表征及其与DNA相互作用的研究

二十世纪七十年代,顺铂作为抗肿瘤药物在临床上的广泛使用,使无机过渡金属配合物的抗肿瘤活性成为生物医药领域的研究热点之一;随后研究者在数千个铂系金属配合物中又筛选出了毒性相对较低的广谱抗肿瘤药物卡铂和环硫铂[1].但是临床上化疗药物的疗效、毒副作用和肿瘤细胞的耐药性等问题仍是生物医药领域亟待解决的关键问题之一.钌和钌配合物在生物体内易于吸收和代谢,属于低毒性的化合物;而且钌配合物具有与铂配合物相似的分子结构,能够以插入方式、沟结合方式和静电作用方式与DNA分子交联,干扰核酸的生物功能.国际上已普遍认为,钌配合物将成为最有前途的抗肿瘤药物之一[2].     

符合经典构效关系的抗肿瘤铂类药物

综述了自顺铂、卡铂后符合经典构效关系的铂类抗肿瘤药物的发展概况，按载体配基和离去基团的结构特征进行了分类，总结了各类配合物的构效关系和临床进展，其中重点对手性二胺配体的铂(Ⅱ)配合物进行了介绍。并讨论了顺铂、卡铂、奥沙利铂的作用机理。     

钯(Ⅱ)类抗肿瘤药物研究进展

20世纪60年代,美国密执安州立大学Rosenberg发现了顺铂具有抗癌活性,开辟了金属类抗肿瘤药物研究的新领域.经过40余年的研究,已相继成功开发了卡铂、奈达铂、奥沙利铂、舒铂、洛铂和双环铂等铂类抗肿瘤药物.虽然对于铂类抗肿瘤药物研究取得了一定的成绩,但在临床使用过程中也存在一些问题,如其毒副作用和抗药性,限制了其在临床上的进一步广泛应用.为了解决这些问题,科研工作者开始寻找新的金属类抗肿瘤药物以弥补现有铂类抗肿瘤药物的不足.在金属元素中,唯有钯(II)与铂(II)配合物具有相似或相同的结构特征,进而表现出相近或相似的化学性质.因此,继铂类抗肿瘤配合物后,钯(II)配合物作为潜在抗肿瘤药物成为一个诱人的领域.本文综述了近年来钯(II)类抗肿瘤药物的研究进展,并探讨了其构效关系,这对于指导新型钯(II)类抗肿瘤药物的合成具有重要的参考价值.     

靶向抑制拓扑异构酶和端粒酶的钌配合物研究进展

金属配合物抗肿瘤研究,尤其是铂类药物,已取得了相对令人瞩目的成功,但同时也面临着包括耐药性和毒副作用等诸多问题。近年来钌配合物作为新的抗癌药物引起了人们的注意。在非铂系药物中,金属钌配合物是最有前途的抗癌药物之一,国际上普遍认为钌和钌的配合物属于低毒性,容易吸收并在体内很快排泄。本文将着重介绍钌配合物与DNA结合后进一步引发的细胞内核酶活性抑制研究,从新的角度来诠释钌配合物的抗肿瘤研究最新进展。     

Repair processes on deoxyribonucleic acid

Many cells have the ability to recognize and eliminate damage to their DNA, particularly thymine dimers formed by UV light. The elimination of this damage may be achieved by enzymatic, light-dependent cleavage of the dimers into the monomers (photoreactivation) or more frequently by dark repair, in which the damaged part is completely removed from the, DNA. In this repair process, the DNA is incised by an endonuclease in the immediate vicinity of the thymine dimers. Oligonucleotides containing the thymine dimer are removed hydrolytically from the DNA by the 5→3′ exonuclease activity of DNA polymerase I (Kornberg enzyme). The resulting gaps are immediately closed by a de novo synthesis with the aid of the same DNA polymerase I, the complementary strand serving as a template (excision repair). The final step is the formation of the phosphodiester bond between the newly synthesized DNA fragment and the old DNA strand by a DNA ligase. Xeroderma pigmentosum patients lack the endonuclease as a result of a genetic defect; they therefore cannot eliminate thymine dimers from their DNA, and are extremely sensitive to sunlight. All information so far suggests that genetic recombination and DNA repair are performed by the same enzyme system.     

Dissecting the differences between the alpha and beta anomers of the oxidative DNA lesion FaPydG

The oxidative DNA lesion, FaPydG rapidly anomerizes to form a mixture of the alpha and beta anomer. To investigate the mutagenic potential of both forms, we prepared stabilized bioisosteric analogues of both configurational isomers and incorporated them into oligonucleotides. These were subsequently used for thermodynamic melting-point studies and for primer-extension experiments. While the beta compound, in agreement with earlier data, prefers cytidine as the pairing partner, the alpha compound is not able form a stable base pair with any natural base. In primer-extension studies with the high-fidelity polymerase Bst Pol I, the polymerase was able to read through the lesion. The beta compound showed no strong mutagenic potential. The alpha compound, in contrast, strongly destabilized DNA duplexes and also blocked all of the tested DNA polymerases, including two low-fidelity polymerases of the Y-family.     

Selective Stabilization of Abasic Site‐Containing DNA by Insertion of Sterically Demanding Biaryl Ligands

Biaryl derivatives that consist of one DNA‐intercalating unit and a sterically demanding component exhibit a specific behavior towards abasic site‐containing DNA (AP‐DNA) as determined by thermal DNA denaturation experiments, spectrometric titrations and CD spectroscopic analysis. Specifically, these ligands strongly stabilize AP‐DNA towards dissociation, whereas they do not or only marginally affect the melting temperature of regular duplex DNA.     

Synthesis and pairing properties of alpha-tricyclo-DNA

We describe the synthesis of the phosphoramidite building blocks of alpha-tricyclo-DNA (alpha-tc-DNA) covering all four natural bases, starting from the already known corresponding alpha-tc-nucleosides. These building blocks were used for the preparation of three alpha-tc-oligonucleotide 10-mers representing a homopurine, a homopyrimidine, and a mixed purine/pyrimidine base sequence. The base-pairing properties with complementary parallel and antiparallel oriented DNA and RNA were studied by UV-melting analysis and CD spectroscopy. We found that alpha-tc-DNA binds preferentially to parallel nucleic acid complements through Watson-Crick duplex formation, with a preference for RNA over DNA. In comparison with natural DNA, alpha-tc-DNA shows equal to enhanced affinity to RNA and also pairs to antiparallel DNA or RNA complements, although with much lower affinity. In the mixed-base sequence these antiparallel duplexes are of the reversed Watson-Crick type, while in the homopurine/homopyrimidine sequences Hoogsteen and/or reversed Hoogsteen pairing is observed. Antiparallel duplex formation of two alpha-tc-oligonucleotides was also observed, although the thermal stability of this duplex was surprisingly low. The base-pairing properties of alpha-tc-DNA are discussed in the context of alpha-DNA, alpha-RNA, and alpha-LNA.     

DNA Nanotechnology-based Biocomputing

With silicon-based microelectronic technology pushed to its limit,scientists hunt to exploit biomolecules to power the bio-computer as substitutes.As a typical biomolecule,DNA now has been employed as a tool to create computing systems because of its superior parallel computing ability and outstanding data storage capability.However,the key challenges in this area lie in the human intervention during the computation process and the lack of platforms for central processor.DNA nanotechnology has created hundreds of complex and hierarchical DNA nanostructures with highly controllable motions by exploiting the unparalleled self-recognition properties of DNA molecule.These DNA nanostructures can provide platforms for central processor and reduce the human intervention during the computation process,which can offer unprecedented opportunities for biocomputing.In this review,recent advances in DNA nanotechnology are briefly summarized and the newly emerging concept of biocomputing with DNA nanostructures is introduced.     

Interlocked DNA Nanojoints for Reversible Thermal Sensing

The ability to precisely measure and monitor temperature at high resolution at the nanoscale is an important task for better understanding the thermodynamic properties of functional entities at the nanoscale in complex systems, or at the level of a single cell. However, the development of high‐resolution and robust thermal nanosensors is challenging. The design, assembly, and characterization of a group of thermal‐responsive deoxyribonucleic acid (DNA) joints, consisting of two interlocked double‐stranded DNA (dsDNA) rings, is described. The DNA nanojoints reversibly switch between the static and mobile state at different temperatures without a special annealing process. The temperature response range of the DNA nanojoint can be easily tuned by changing the length or the sequence of the hybridized region in its structure, and because of its interlocked structure the temperature response range of the DNA nanojoint is largely unaffected by its own concentration; this contrasts with systems that consist of separated components.     

Nick sealing by T4 DNA ligase on a modified DNA template: tethering a functional molecule on D-threoninol

Efficient DNA nick sealing catalyzed by T4 DNA ligase was carried out on a modified DNA template in which an intercalator such as azobenzene had been introduced. The intercalator was attached to a D-threoninol linker inserted into the DNA backbone. Although the structure of the template at the point of ligation was completely different from that of native DNA, two ODNs could be connected with yields higher than 90% in most cases. A systematic study of sequence dependence demonstrated that the ligation efficiency varied greatly with the base pairs adjacent to the azobenzene moiety. Interestingly, when the introduced azobenzene was photoisomerized to the cis form on subjection to UV light (320-380 nm), the rates of ligation were greatly accelerated for all sequences investigated. These unexpected ligations might provide a new approach for the introduction of functional molecules into long DNA strands in cases in which direct PCR cannot be used because of blockage of DNA synthesis by the introduced functional molecule. The biological significance of this unexpected enzymatic action is also discussed on the basis of kinetic analysis.     

Development of a multiplex system to assess DNA persistence in taphonomic studies

In this study, we have developed a PCR multiplex that can be used to assess DNA degradation and at the same time monitor for inhibition: primers have been designed to amplify human, pig, and rabbit DNA, allowing pig and rabbit to be used as experimental models for taphonomic research, but also enabling studies on human DNA persistence in forensic evidence. Internal amplified controls have been added to monitor for inhibition, allowing the effects of degradation and inhibition to be differentiated. Sequence data for single‐copy nuclear recombination activation gene (RAG‐1) from human, pig, and rabbit were aligned to identify conserved regions and primers were designed that targeted amplicons of 70, 194, 305, and 384 bp. Robust amplification in all three species was possible using as little as 0.3 ng of template DNA. These have been combined with primers that will amplify a bacterial DNA template within the PCR. The multiplex has been evaluated in a series of experiments to gain more knowledge of DNA persistence in soft tissues, which can be important when assessing what material to collect following events such as mass disasters or conflict, when muscle or bone material can be used to aid with the identification of human remains. The experiments used pigs as a model species. When whole pig bodies were exposed to the environment in Northwest England, DNA in muscle tissue persisted for over 24 days in the summer and over 77 days in the winter, with full profiles generated from these samples. In addition to time, accumulated degree days (ADD) were also used as a measure that combines both time and temperature—24 days was in summer equivalent to 295 ADD whereas 77 days in winter was equivalent to 494 ADD.     

Energetics,Conformation, and Recognition of DNA Duplexes Modified by Methylated Analogues of [PtCl(dien)]+

Monodentate DNA binding of [PtCl(dien)]⁺ (dien=diethylenetriamine) complexes may considerably affect the biophysical properties of DNA and consequently downstream cellular processes as a result of a large increase in the bulkiness of the nonleaving ligand by multiple methylation (see illustration).