抗肿瘤药替莫唑胺合成工艺研究进展

替莫唑胺作为一种新型口服烷化剂药物,在恶性胶质瘤的治疗中被广泛应用,且治疗效果良好。自其上市以来,不断有新的合成方法被报道,通过对已有合成方法的归纳总结,可以发现合成策略主要集中在替莫唑胺结构中四嗪酮骨架的构建,本文就替莫唑胺的合成研究进行综述。     

Ethidium bromide binding to DNA cryogels

The interaction of the classical intercalator ethidium bromide (EtBr) with the double helical network strands of DNA cryogels was investigated. The cryogels were prepared starting from aqueous solutions of DNA (about 2000 base pairs long) at ?18 °C using 1,4-butanediol diglycidyl ether crosslinker under various reaction conditions. In contrast to the solubilization of DNA hydrogels in aqueous EtBr solutions, DNA cryogels remain stable even after complete saturation of their EtBr binding sites. The total binding capacity of the cryogels is 0.6 ± 0.1 EtBr per nucleotide, which is close to the theoretical maximum number of EtBr molecules that can bind to DNA. Even in very dilute solutions (down to 3 μM), cryogels remove EtBr from aqueous solutions with an efficiency of 90%. The equilibrium binding constant and the maximum number of EtBr binding sites of the cryogels almost coincide with the reported values for the secondary binding process of EtBr by DNA in aqueous solutions. At low mole ratios of bound EtBr to DNA, the cryogels swell with increasing amount of bound EtBr, most likely caused by the lengthening of DNA due to the intercalated EtBr. The response of DNA cryogels to changes in EtBr concentration between 3 and 300 μM also suggests that they can be used to detect DNA binding substrates in aqueous solutions.     

Effects of hypoxia and transferrin on toxicity and DNA binding of ruthenium antitumor agents in hela cells

Nuclear DNA binding and inhibition of growth of HeLa cells in culture were determined after 24 h incubation with the ruthenium anticancer agents cis-[Cl(2)(NH(3))(4)Ru]Cl (CCR) and (ImH)trans-[(Im)(2)Cl(4)Ru] (ICR) as a function of [Ru], Po(2), and added transferrin. Consistent with the "activation-by-reduction" hypothesis, cytotoxicity and DNA binding for both complexes increased under reduced oxygen conditions. Consistent with the "transferrin- transport" hypothesis, inhibition of cell growth also increased with added transferrin for both complexes. Despite their differences in charge, reduction potentials and substitution rates, both complexes behaved remarkably similarly indicating a common mechanism of action for both. Under atmospheric Conditions (Po(2) = 159 torr), CCR inhibited HeLa cell growth with IC(50) = 3.5 muM, while that for ICR was 2.0 muM. The binding of both complexes to DNA (Ru(DNA)/P(DNA)) correlated with toxicity and was approximately linear in the concentration of the ruthenium complex in the culture medium, [Ru]. For both complexes, IC(50) values decrease and DNA binding increases with decreasing log(Po(2)). In general, DNA binding at all oxygen pressures for both complexes is in the range of one Ru per 1000-2000 DNA base pairs at [Ru] = IC(50).     

Interactions of metal-metal-bonded antitumor active complexes with DNA fragments and DNA

This Account summarizes the DNA binding properties of anticancer active dinuclear Rh, Re, and Ru compounds. The combined results of NMR spectroscopy, X-ray crystallography, and various biochemical tools provide incontrovertible evidence that dinuclear complexes are favorably poised to bind to purine nucleobases, DNA fragments, and double-stranded DNA. Moreover, direct DNA photocleavage in vitro is effected by dirhodium compounds in the presence of electron acceptors in solution or directly attached to the dirhodium core. This research has provided valuable insight in the interactions of dinuclear compounds with DNA, knowledge that is an excellent backdrop for rational design of promising dinuclear drugs.     

Optimising DNA binding to carbon nanotubes by non-covalent methods

The use of carbon nanotubes as a gene delivery system has been extensively studied in recent years owing to its potential advantages over viral vectors. To achieve this goal, carbon nanotubes have to be functionalized to become compatible with aqueous media and to bind the genetic material. To establish the best conditions for plasmid DNA binding, we compare the dispersion properties of single-, double- and multi-walled carbon nanotubes (SWCNTs, DWCNTs and MWCNTs, respectively) functionalized with a variety of surfactants by non-covalent attachment. The DNA binding properties of the functionalized carbon nanotubes were studied and compared by electrophoresis. Furthermore, a bilayer functionalization method for DNA binding on SWCNTs was developed that utilized RNA-wrapping to solubilize the nanotubes and cationic polymers as a bridge between nanotubes and DNA.     

Hexadecylphosphocholine: Preclinical and the first clinical results of a new antitumor drug

Dose-response studies on cytotoxic alkyl lysophospholipids with various chemical structures revealed that a long alkyl chain and a polar group are essential for antitumor activity. The combination of both the long alkyl chain and a phosphocholine group thus results in alkyl phosphocholines. Preclinical, studies with hexadecylphosphocholine (He-PC) as a representative compound indicate distinct antineoplastic activity on leukemia cells of human origin. He-PC is highly effective in inhibiting the growth of chemically induced rat mammary carcinomas. Even more striking is the fact that a high percentage of the tumors regressed completely. In a clinical phase I trial on breast cancer patients with local recurrences, topically applied He-PC resulted in regression of skin metastases. A phase II trial for topical treatment and a phase I trial for orally applied He-PC have been initiated to further evaluate the antitumoral activity of this new compound. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

SOD mimic activity,DNA binding and in-vitro antibacterial studies of drug based copper(II) complexes

Square pyramidal complexes [Cu^II(PFL)(bpa)Cl]?5H₂O (1) and [Cu^II(LFL)(bpa)Cl]?5H₂O (2) have been synthesized and characterized. Compounds were checked for their in-vitro antimicrobial activity against two Gram^(+ ve) and three Gram^(–ve) bacterial species. Intrinsic binding constant (K_b) of complexes with CT DNA were determined using absorption titration. Viscosity measurement suggests that complexes bind with CT DNA through partial nonclassical intercalative mode. Superoxide dismutase (SOD) like activity of the complexes was also compared with previously reported compounds.     

NEIL1 binding to DNA containing 2'-fluorothymidine glycol stereoisomers and the effect of editing

Thymine glycol (Tg), one of the oxidized bases formed in DNA by reactive oxygen species, is repaired by the DNA glycosylases such as NEIL1, NTH1 and Endo III. In our recent studies, we showed that NEIL1's catalytic efficiency and lesion specificity are regulated by an RNA-editing adenosine deamination reaction. In this study, we synthesized oligodeoxynucleotides containing 2'-fluorothymidine glycol with either ribo or arabino configuration and investigated the binding of these modified DNAs with the unedited and edited forms of human NEIL1 along with E. coli Endo III. For the two forms of hNEIL1, binding affinities to FTg-containing DNA were similar indicating that the editing effect is more subtle than to simply alter substrate affinity. While the NEIL1-binding to FTg-containing DNAs was largely insensitive to C5 and 2' stereochemistry, a preference was observed for the FTg-G pair over the FTg-A pair. In addition, we found that optimal binding is observed with Endo III and duplex DNA with riboFTg(5S) paired with dG. The modified DNAs reported here will provide useful tools for further characterizing the interaction between DNA repair glycosylases and thymine glycol containing DNA.     

Use of triplet excited States for the study of drug binding to human and bovine serum albumins

The triplet excited states of (S)- and (R)-flurbiprofen (FBP) have been used as reporters for the microenvironments experienced within the binding sites of human and bovine serum albumins. Regression analysis of triplet decay provides valuable information on the degree of protection that these excited states are afforded from attack by a second FBP molecule, oxygen, or other reagents. The multiexponential fitting of these decays can be satisfactorily correlated with the distribution of the drug among the two binding sites and its presence as the noncomplexed form in the bulk solution. This assignment has been confirmed by using (S)-ibuprofen or capric acid as selective site II replacement probes. Triplet lifetimes and site occupancy are sensitive to the type of serum albumin employed (human versus bovine). Finally, the binding behaviour of (S)- and (R)-FBP exhibits little stereoselectivity.     

Biochemical studies of the thermal effects on DNA modifications by the antitumor cisplatin and their repair

Using biochemical methods, we have examined the effect of two factors that might play a role in the mechanism of the biological activity of cisplatin at elevated temperatures (>37 degrees C). We show that increased temperatures result in distinct alterations in the modification of the target DNA by cisplatin, and in the repair of these modifications. Our in vitro results support the view that the enhanced DNA-cross-linking efficiency of cisplatin and the lower efficiency of native DNA repair mechanisms at higher temperature play at least a partial role in the potentiation of the antitumor effects of cisplatin under conditions of mild hyperthermia.     

Characterization of the DNA binding domain of the mouse IRF-2 protein

The DNA binding domain of the interferon regulatory factor-2protein (IRF-2) has been produced and characterized, -chymotrypsindigestion of the purified IRF-2 protein bound to a syntheticbinding site yields a peptide fragment of 14 K in molecularweight. N-terminal analysis of this peptide fragment showedthat its sequence is the same as that of the intact IRF-2. Apeptide fragment of {small tilde} 14 K, IRF-2(113), which correspondsto the N-terminal 113 amino acids of the intact IRF-2 protein,has been expressed in a functional form in Escherichia coli.The first methionine was processed during the expression andthe purified IRF-2(113) thus contains 112 amino acids. DNaseI footprinting and gel retardation assaying showed that IRF-2(113)binds to a synthetic DNA having the consensus binding site andto the upstream regulatory sequence of the IFN-ß geneas intact IRF-2 does. These results showed that this peptidefragment, IRF-2(113), may be a good material for investigationof the DNA binding domain of IRF-2 and of the DNA–proteininteraction.     

Efficient DNA binding and nuclear uptake by distamycin derivatives conjugated to octa-arginine sequences

Efficient targeting of DNA by designed molecules requires not only careful fine-tuning of their DNA-recognition properties, but also appropriate cell internalization of the compounds so that they can reach the cell nucleus in a short period of time. Previous observations in our group on the relatively high affinity displayed by conjugates between distamycin derivatives and bZIP basic regions for A-rich DNA sites, led us to investigate whether the covalent attachment of a positively charged cell-penetrating peptide to a distamycin-like tripyrrole might yield high affinity DNA binders with improved cell internalization properties. Our work has led to the discovery of synthetic tripyrrole-octa-arginine conjugates that are capable of targeting specific DNA sites that contain A-rich tracts with low nanomolar affinity; they simultaneously exhibit excellent membrane and nuclear translocation properties in living HeLa cells.     

In situ gelation and sustained release of an antitumor drug by graphene oxide nanosheets

Graphene oxide nanosheets were used to induce the in situ gelation of doxorubicin hydrochloride as an antitumor drug. When a very small amount of the graphene oxide was introduced into an aqueous solution of doxorubicin hydrochloride at room temperature, a strong and thixotropic gel was rapidly formed without any polymers or chemical additives. The gelation mechanism was investigated by fluorescence spectroscopy, X-ray diffraction and scanning electron microscopy. The encapsulated doxorubicin hydrochloride was found to show sustained release and antitumor efficacy.     

Hyrtiosal, from the marine sponge Hyrtios erectus, inhibits HIV-1 integrase binding to viral DNA by a new inhibitor binding site

HIV-1 integrase (IN) is composed of three domains, the N-terminal domain (NTD, residues 1-50), the catalytic core domain (CCD, residues 51-212), and the C-terminal domain (CTD, residues 213-288). All the three domains are required for the two known integration reactions. CCD contains the catalytic triad and is believed to bind viral DNA specifically, and CTD binds viral DNA in a nonspecific manner. As no clear evidence has confirmed the involvement of NTD in DNA binding directly, NTD has not been seriously considered and less is known about its function in viral replication. In the current work, using a SPR technology-based assay, the HIV-1 viral DNA was determined to bind directly to NTD with a K(D) value of 8.8 microM, suggesting that the process of preintegrated complex formation for HIV-1 IN might involve the direct interaction of NTD with viral DNA in addition to binding of viral DNA to the catalytic core domain and C-terminal domain. Moreover, such viral DNA/IN binding could be inhibited by the marine product hyrtiosal from the marine sponge Hyrtios erectus with an IC(50) of 9.60+/-0.86 microM. Molecular dynamic analysis correlated with a site-directed mutagenesis approach further revealed that such hyrtiosal-induced viral DNA/IN binding inhibition was caused by the fact that hyrtiosal could bind HIV-1 NTD at Ser17, Trp19, and Lys34. As hyrtiosal was recently discovered by us as a protein tyrosine phosphatase 1B (PTP1B) inhibitor,1 this work might also supply multiple-target information for this marine product, and the verified HIV-NTD/HIV-1 IN interaction model could have further implications for new HIV-1 IN inhibitor design and evaluation.