Cyclosquaramides as kinase inhibitors with anticancer activity

We report the synthesis and biological evaluation of a new series of oligosquaramide‐based macrocycles as anticancer agents. Compound 7 , considered as representative of this series, exhibited significant antiproliferative activity against the NCI‐60 human tumor cell line panel, with IC₅₀ values ranging from 1 to 10 μM . The results show that sensitivity to cyclosquaramides is clearly dependent on cell type, underscoring a degree of biological selectivity. The observed antiproliferative effects appear to be related to deregulation of protein phosphorylation, as compounds 7 and 8 are effective inhibitors of several important kinases such as ABL1, CDK4, CHK1, PKC, c‐MET, and FGFR, among others. The corresponding acyclic oligosquaramides and smaller cyclosquaramides did not show antitumor activity, suggesting that a macrocyclic structure with minimal molecular size plays a key role in the observed antitumor activity.     

Design,Synthesis, and Biological Evaluation of Unconventional Aminopyrimidine,Aminopurine, and Amino‐1,3,5‐triazine Methyloxynucleosides

Herein we describe a class of unconventional nucleosides (methyloxynucleosides) that combine unconventional nucleobases such as substituted aminopyrimidines, aminopurines, or aminotriazines with unusual sugars in their structures. The allitollyl or altritollyl derivatives were pursued as ribonucleoside mimics, whereas the tetrahydrofuran analogues were pursued as their dideoxynucleoside analogues. The compounds showed poor, if any, activity against a broad range of RNA and DNA viruses, including human immunodeficiency virus (HIV). This inactivity may be due to lack of an efficient metabolic conversion into their corresponding 5′‐triphosphates and poor affinity for their target enzymes (DNA/RNA polymerases). Several compounds showed cytostatic activity against proliferating human CD4⁺ T‐lymphocyte CEM cells and against several other tumor cell lines, including murine leukemia L1210 and human prostate PC3, kidney CAKI‐1, and cervical carcinoma HeLa cells. A few compounds were inhibitory to Moloney murine sarcoma virus (MSV) in C3H/3T3 cell cultures, with the 2,6‐diaminotri‐O‐benzyl‐D ‐allitolyl‐ and ‐D ‐altritolyl pyrimidine analogues being the most potent among them. This series of unconventional nucleosides may represent a novel family of potential antiproliferative agents.     

芳香环状聚醚酮的合成研究进展

芳香环状聚醚酮的合成是应现代高技术领域对先进复合材料的需求而发展起来的研究领域。综述了芳香环状聚醚酮的合成研究进展、合成方法,并分析各种合成方法的优势。     

Trichodermin Induces G0/G1 Cell Cycle Arrest by Inhibiting c-Myc in Ovarian Cancer Cells and Tumor Xenograft-Bearing Mice

Ovarian cancer is a fatal gynecological cancer because of a lack of early diagnosis, which often relapses as chemoresistant. Trichodermin, a trichothecene first isolated from Trichoderma viride, is an inhibitor of eukaryotic protein synthesis. However, whether trichodermin is able to suppress ovarian cancer or not was unclear. In this study, trichodermin (0.5 µM or greater) significantly decreased the proliferation of two ovarian cancer cell lines A2780/CP70 and OVCAR-3. Normal ovarian IOSE 346 cells were much less susceptible to trichodermin than the cancer cell lines. Trichodermin predominantly inhibited ovarian cancer cells by inducing G0/G1 cell cycle arrest rather than apoptosis. Trichodermin decreased the expression of cyclin D1, CDK4, CDK2, retinoblastoma protein, Cdc25A, and c-Myc but showed little effect on the expression of p21^Waf1/Cip1, p27^Kip1, or p16^Ink4a. c-Myc was a key target of trichodermin. Trichodermin regulated the expression of Cdc25A and its downstream proteins via c-Myc. Overexpression of c-Myc attenuated trichodermin’s anti-ovarian cancer activity. In addition, trichodermin decelerated tumor growth in BALB/c nude mice, proving its effectiveness in vivo. These findings suggested that trichodermin has the potential to contribute to the treatment of ovarian cancer.     

(20S) Ginsenoside Rh2 Exerts Its Anti-Tumor Effect by Disrupting the HSP90A-Cdc37 System in Human Liver Cancer Cells

(20S) ginsenoside Rh2 (G-Rh2), a major bioactive metabolite of ginseng, effectively inhibits the survival and proliferation of human liver cancer cells. However, its molecular targets and working mechanism remain largely unknown. Excitingly, we screened out heat shock protein 90 alpha (HSP90A), a key regulatory protein associated with liver cancer, as a potential target of (20S) G-Rh2 by phage display analysis and mass spectrometry. The molecular docking and thermal shift analyses demonstrated that (20S) G-Rh2 directly bound to HSP90A, and this binding was confirmed to inhibit the interaction between HSP90A and its co-chaperone, cell division cycle control protein 37 (Cdc37). It is well-known that the HSP90A-Cdc37 system aids in the folding and maturation of cyclin-dependent kinases (CDKs). As expected, CDK4 and CDK6, the two G₀-G₁ phase promoting kinases as well as CDK2, a key G₁-S phase transition promoting kinase, were significantly downregulated with (20S) G-Rh2 treatment, and these downregulations were mediated by the proteasome pathway. In the same condition, the cell cycle was arrested at the G₀-G₁ phase and cell growth was inhibited significantly by (20S) G-Rh2 treatment. Taken together, this study for the first time reveals that (20S) G-Rh2 exerts its anti-tumor effect by targeting HSP90A and consequently disturbing the HSP90A-Cdc37 chaperone system. HSP90A is frequently overexpressed in human hepatoma cells and the higher expression is closely correlated to the poor prognosis of liver cancer patients. Thus, (20S) G-Rh2 might become a promising alternative drug for liver cancer therapy.     

Benzyl Isothiocyanate Inhibits Prostate Cancer Development in the Transgenic Adenocarcinoma Mouse Prostate (TRAMP) Model,Which Is Associated with the Induction of Cell Cycle G1 Arrest

Benzyl isothiocyanate (BITC) is a hydrolysis product of glucotropaeolin, a compound found in cruciferous vegetables, and has been shown to have anti-tumor properties. In the present study, we investigated whether BITC inhibits the development of prostate cancer in the transgenic adenocarcinoma mouse prostate (TRAMP) mice. Five-week old, male TRAMP mice and their nontransgenic littermates were gavage-fed with 0, 5, or 10 mg/kg of BITC every day for 19 weeks. The weight of the genitourinary tract increased markedly in TRAMP mice and this increase was suppressed significantly by BITC feeding. H and E staining of the dorsolateral lobes of the prostate demonstrated that well-differentiated carcinoma (WDC) was a predominant feature in the TRAMP mice. The number of lobes with WDC was reduced by BITC feeding while that of lobes with prostatic intraepithelial neoplasia was increased. BITC feeding reduced the number of cells expressing Ki67 (a proliferation marker), cyclin A, cyclin D1, and cyclin-dependent kinase (CDK)2 in the prostatic tissue. In vitro cell culture results revealed that BITC decreased DNA synthesis, as well as CDK2 and CDK4 activity in TRAMP-C2 mouse prostate cancer cells. These results indicate that inhibition of cell cycle progression contributes to the inhibition of prostate cancer development in TRAMP mice treated with BITC.     

Monocillin II inhibits human breast cancer growth partially by inhibiting MAPK pathways and CDK2 Thr160 phosphorylation

Twenty-two β-resorcylic acid lactones (RALs) were evaluated for cytotoxicity against human breast cancer cells to find their structure-activity relationship (SAR). Monocillin II, a trans-enone RAL without epoxy and conjugated dienone, was found to have higher activity in inhibiting tumor cell growth in both in vitro experiment and in vivo nude xenografted mice model than its analogue radicicol, an anticancer lead compound. We demonstrated for the first time that monocillin II could arrest breast cancer cell cycle in G1 phase, which might partially be the result of its inhibition effect on the phosphorylation of the Thr160 residue of cyclin dependent kinase 2 (CDK2), a key enzyme in cell-cycle regulation. Moreover, monocillin II exhibited inhibition of heat shock protein 90 (Hsp90) and depleted its target proteins, Raf-1 and A-Raf, which are involved in Ras/Raf/MEK/ERK mitogen-activated protein kinase (MAPK) pathway. Remarkably, we found that monocillin II could inhibit activation of MAPKs including ERK, JNK and p38, which might be involved in the inactivation of CDK2. These results suggest that monocillin II has potential therapeutic benefits in breast cancer prevention and intervention.     

细胞周期蛋白依赖性激酶抑制剂（CDKs）中间体的设计与合成

简述了细胞周期蛋白依赖性激酶CDK4抑制剂及其抑制剂的相关概念，详细介绍了细胞周期蛋白激酶的研究进展，重点研究了中间体2一溴-1-（4-吗啉苯基）乙酮的路线选择与合成。4-氟苯乙酮为起始原料，经过溴代反应合成2-溴-1-（4-吗啉苯基）乙酮。依据文献报道，比较不同的合成路线，最终选择先溴代再脱溴的方法合成目标化合物。     

Synthesis and antitumor activity of 3-(2-phenyl-1,3-thiazol-4-yl)-1H-indoles and 3-(2-phenyl-1,3-thiazol-4-yl)-1H-7-azaindoles

Given the potent antimicrobial, antiviral, and antitumor activities of many natural products, there is an increasing interest in the synthesis of new molecules based on natural compound scaffolds. Based on a 2,4-bis(3'-indolyl)imidazole skeleton, two new series of phenylthiazolylindoles and phenylthiazolyl-7-azaindoles were obtained by Hantzsch reaction between substituted phenylthioamides and the α-bromoacetyl derivatives. Some azaindole derivatives, tested at the National Cancer Institute against a panel of ～60 tumor cell lines derived from nine human cancer cell types, showed inhibitory effects against all cell lines investigated at micromolar to nanomolar concentrations. Two of them exhibited a high affinity for CDK1, with IC(50) values of 0.41 and 0.85 μM. These promising results will set the foundation for future investigations into the development of anticancer therapies.     

Inhibition of Eimeria tenella CDK‐Related Kinase 2: From Target Identification to Lead Compounds

Apicomplexan parasites encompass several human‐ and animal‐pathogenic protozoans such as Plasmodium falciparum, Toxoplasma gondii, and Eimeria tenella. E. tenella causes coccidiosis, a disease that afflicts chickens, leading to tremendous economic losses to the global poultry industry. The considerable increase in drug resistance makes it necessary to develop new therapeutic strategies against this parasite. Cyclin‐dependent kinases (CDKs) are key molecules in cell‐cycle regulation and are therefore prominent target proteins in parasitic diseases. Bioinformatics analysis revealed four potential CDK‐like proteins, of which one—E. tenella CDK‐related kinase 2 (EtCRK2)—has already been characterized by gene cloning and expression. 1 By using the CDK‐specific inhibitor flavopiridol in EtCRK2 enzyme assays and schizont maturation assays (SMA), we could chemically validate CDK‐like proteins as potential drug targets. An X‐ray crystal structure of human CDK2 (HsCDK2) served as a template to build protein models of EtCRK2 by comparative homology modeling. Structural differences in the ATP binding site between EtCRK2 and HsCDK2, as well as chicken CDK3, were addressed for the optimization of selective ATP‐competitive inhibitors. Virtual screening and “wet‐bench” high‐throughput screening campaigns on large compound libraries resulted in an initial set of hit compounds. These compounds were further analyzed and characterized, leading to a set of four promising lead compounds for development as EtCRK2 inhibitors.     

Fatty Acid Binding Protein 6 Inhibition Decreases Cell Cycle Progression,Migration and Autophagy in Bladder Cancers

Bladder cancer (BC) has a high recurrence rate worldwide. The aim of this study was to evaluate the role of fatty acid binding protein 6 (FABP6) in proliferation and migration in human bladder cancer cells. Cell growth was confirmed by MTT and colony formation assay. Western blotting was used to explore protein expressions. Wound healing and Transwell assays were performed to evaluate the migration ability. A xenograft animal model with subcutaneous implantation of BC cells was generated to confirm the tumor progression. Knockdown of FABP6 reduced cell growth in low-grade TSGH-8301 and high-grade T24 cells. Cell cycle blockade was observed with the decrease of CDK2, CDK4, and Ki67 levels in FABP6-knockdown BC cells. Interestingly, knockdown of FBAP6 led to downregulation of autophagic markers and activation of AKT-mTOR signaling. The application of PI3K/AKT inhibitor decreased cell viability mediated by FABP6-knockdown additionally. Moreover, FABP6-knockdown reduced peroxisome proliferator-activated receptor γ and retinoid X receptor α levels but increased p-p65 expression. Knockdown of FABP6 also inhibited BC cell motility with focal adhesive complex reduction. Finally, shFABP6 combined with cisplatin suppressed tumor growth in vivo. These results provide evidence that FABP6 may be a potential target in BC cells progression.     

Tampering with Cell Division by Using Small‐Molecule Inhibitors of CDK–CKS Protein Interactions

Cyclin‐dependent kinases (CDKs) control many cellular processes and are considered important therapeutic targets. Large collections of inhibitors targeting CDK active sites have been discovered, but their use in chemical biology or drug development has been often hampered by their general lack of specificity. An alternative approach to develop more specific inhibitors is targeting protein interactions involving CDKs. CKS proteins interact with some CDKs and play important roles in cell division. We discovered two small‐molecule inhibitors of CDK–CKS interactions. They bind to CDK2, do not inhibit its enzymatic activity, inhibit the proliferation of tumor cell lines, induce an increase in G1 and/or S‐phase cell populations, and cause a decrease in CDK2, cyclin A, and p27^Kip1 levels. These molecules should help decipher the complex contributions of CDK–CKS complexes in the regulation of cell division, and they might present an interesting therapeutic potential.     

超声催化合成新型含硫席夫碱大环化合物

以草酸、邻胺基硫酚为原料,合成中间体S,S′-双(2-苯氨基)-乙二酰硫(1),采用超声波技术在温和条件下将中间体(1)与邻苯二甲醛反应,合成得到了新型含硫席夫碱大环化合物(L)。并与常规加热法进行了对比。结果表明:超声波催化法具有操作简单、反应时间短、条件温和、产率高及副反应少等优点。并探讨了超声波催化下目标大环化合物的最佳合成条件:以乙醇做溶剂,在中间体(1)与邻苯二甲醛摩尔比为1∶1,于50℃条件下超声1.5h。所有化合物均通过元素分析、1 HNMR、IR和MS进行组成和结构表征。     

Polymer-supported syntheses of oxo-crown ethers and derivatives containing α-amino-acid residues

A simple polymer-supported cyclization–cleavage method is described for the small-scale synthesis of macrocyclic oligomers, with from 12 to 18 ring atoms per repeat unit, which are either 2-oxo-crown ethers, or derivatives containing, except in one case, chiral α-amino-acid residues. In each case the major cyclic product was isolated and characterized. In all except one case this was the cyclic monomer. If the macrocyclic oligomers are needed either for the preparation of static or dynamic combinatorial libraries or for entropically-driven ring-opening polymerizations, all members of the family are of interest as they all react through equilibration to give the same final products.     

Label-Free Detection of Protein interactions with peptide aptamers by open circuit potential measurement

Label-free electrical detection of protein interactions has been achieved by direct measurement of variations in open circuit potential (OCP) using an accurate differential voltage measurement. Our model system involves a panel of peptide aptamers that recognise specific protein partners of the cyclin-dependent kinase (CDK) family.Different peptide aptamers immobilized on gold electrodes were used for the detection of human CDK2 and CDK4. The formation of the peptide aptamer recognition layer and the efficiency of its interaction with CDK proteins in yeast cell lysates were characterized by quartz crystal microbalance measurements. The interaction of the peptide aptamers with CDK proteins was successfully detected by direct OCP measurements. The OCP dependence on the pH of the measurement buffer confirms that the effects observed are due to the change in charge upon protein interaction. Variations in charge transfer resistance and in protein/double-layer capacitance were investigated by means of electrochemical impedance spectroscopy with charged redox markers in solution.The present work shows that electrical detection of protein interactions can be achieved by direct measurement of OCP variations using suitable differential voltage instrumentation. The results indicate that label-free detection of protein interactions is possible with potentiometric transducers such as field-effect transistors.     

Development of a PROTAC-Based Targeting Strategy Provides a Mechanistically Unique Mode of Anti-Cytomegalovirus Activity

Human cytomegalovirus (HCMV) is a major pathogenic herpesvirus that is prevalent worldwide and it is associated with a variety of clinical symptoms. Current antiviral therapy options do not fully satisfy the medical needs; thus, improved drug classes and drug-targeting strategies are required. In particular, host-directed antivirals, including pharmaceutical kinase inhibitors, might help improve the drug qualities. Here, we focused on utilizing PROteolysis TArgeting Chimeras (PROTACs), i.e., hetero-bifunctional molecules containing two elements, namely a target-binding molecule and a proteolysis-inducing element. Specifically, a PROTAC that was based on a cyclin-dependent kinase (CDK) inhibitor, i.e., CDK9-directed PROTAC THAL-SNS032, was analyzed and proved to possess strong anti-HCMV AD169-GFP activity, with values of EC₅₀ of 0.030 µM and CC₅₀ of 0.175 µM (SI of 5.8). Comparing the effect of THAL-SNS032 with its non-PROTAC counterpart SNS032, data indicated a 3.7-fold stronger anti-HCMV efficacy. This antiviral activity, as illustrated for further clinically relevant strains of human and murine CMVs, coincided with the mid-nanomolar concentration range necessary for a drug-induced degradation of the primary (CDK9) and secondary targets (CDK1, CDK2, CDK7). In addition, further antiviral activities were demonstrated, such as the inhibition of SARS-CoV-2 replication, whereas other investigated human viruses (i.e., varicella zoster virus, adenovirus type 2, and Zika virus) were found insensitive. Combined, the antiviral quality of this approach is seen in its (i) mechanistic uniqueness; (ii) future options of combinatorial drug treatment; (iii) potential broad-spectrum activity; and (iv) applicability in clinically relevant antiviral models. These novel data are discussed in light of the current achievements of anti-HCMV drug development.     

Organic metal-complexes. XXI. Synthesis and structure of 3,5,15,17-tetraoxo-1,7,10,13,19,22-hexaoxa-cyclotetracosane and 2,12,14,24-tetraoxo-4,7,10,16,19,22-hexaoxa-25-mercurato-bicyclo[11.11.1]pentacosane

A new synthesis of the title crown via isoxazolo crown ether 7 and macrocyclic bis-β-eneaminoketone 10 is described. 7 can be synthesized in 14% yield by a non-template double-[3+2] cycloaddition of dinitrileoxide 5 prepared in situ from dinitropolyether 19 by dehydration with Ph–NCO and alkyne 6 . The compounds 16, 17 and 18 are synthesized by the same synthetic strategy. Comparable IR and ¹H NMR spectroscopic data of macrocyclic and non-cyclic compounds show, that macrocyclic conformation stabilizing effects can be ruled out. The structures of the macrocycles 1, 7, 10 and that of the Hg(II)-complex 25 , synthesized by reaction of 1 with Hg(OAc)₂ were established by single-crystal X-ray structure analyses. Both inter- and intramolecular hydrogen bonds are observed for the macrocyclic bis-β-eneaminoketone 10 , whereas only intramolecular hydrogen bonds are formed by 1 . In the Hg(II)-complex of 1 the mercury is bonded to two methylene groups. C Hg C is almost linear [177(1)°], the mean Hg C distance amounts to 215(1) pm. In addition to the Hg C bonds, each Hg makes a short contact to a carbonyl oxygen in a neighbouring molecule in the plane perpendicular to the C Hg C axis [Hg(1) O(1) = 279(1) pm, Hg(2) O(5) = 284(1) pm].