Enhancing anti-cancer capacity: Novel class I/II HDAC inhibitors modulate EMT, cell cycle, and apoptosis pathways.

Cancer has been a leading cause of death over the last few decades in western countries as well as in Taiwan. However, traditional therapies are limited by the adverse effects of chemotherapy and radiotherapy, and tumor recurrence may occur. Therefore, it is critical to develop novel therapeutic drugs. In the field of HDAC inhibitor development, apart from the hydroxamic acid moiety, 2-aminobenzamide also functions as a zinc-binding domain, which is shown in well-known HDAC inhibitors such as Entinostat and Chidamide. With recent successful experiences in synthesizing 1-(phenylsulfonyl)indole-based compounds, in this study, we further combined two features of the above chemical compounds and generated indolyl benzamides. Compounds were screened in different cancer cell lines, and enzyme activity was examined to demonstrate their potential for anti-HDAC activity. Various biological functional assays evidenced that two of these compounds could suppress cancer growth and migration capacity, through regulating epithelial-mesenchymal transition (EMT), cell cycle, and apoptosis mechanisms. Data from 3D cancer cells and the in vivo zebrafish model suggested the potential of these compounds in cancer therapy in the future.

In silico identification and biological evaluation of a selective MAP4K4 inhibitor against pancreatic cancer.

Inhibiting a specific target in cancer cells and reducing unwanted side effects has become a promising strategy in pancreatic cancer treatment. MAP4K4 is associated with pancreatic cancer development and correlates with poor clinical outcomes. By phosphorylating MKK4, proteins associated with cell apoptosis and survival are translated. Therefore, inhibiting MAP4K4 activity in pancreatic tumours is a new therapeutic strategy. Herein, we performed a structure-based virtual screening to identify MAP4K4 inhibitors and discovered the compound F389-0746 with a potent inhibition (IC50 120.7 nM). The results of kinase profiling revealed that F389-0746 was highly selective to MAP4K4 and less likely to cause side effects. Results of in vitro experiments showed that F389-0746 significantly suppressed cancer cell growth and viability. Results of in vivo experiments showed that F389-0746 displayed comparable tumour growth inhibition with the group treated with gemcitabine. These findings suggest that F389-0746 has promising potential to be further developed as a novel pancreatic cancer treatment.

Structure-based virtual screening and biological evaluation of novel small-molecule BTK inhibitors.

Bruton tyrosine kinase (BTK) is linked to multiple signalling pathways that regulate cellular survival, activation, and proliferation. A covalent BTK inhibitor has shown favourable outcomes for treating B cell malignant leukaemia. However, covalent inhibitors require a high reactive warhead that may contribute to unexpected toxicity, poor selectivity, or reduced effectiveness in solid tumours. Herein, we report the identification of a novel noncovalent BTK inhibitor. The binding interactions (i.e. interactions from known BTK inhibitors) for the BTK binding site were identified and incorporated into a structure-based virtual screening (SBVS). Top-rank compounds were selected and testing revealed a BTK inhibitor with >50% inhibition at 10 µM concentration. Examining analogues revealed further BTK inhibitors. When tested across solid tumour cell lines, one inhibitor showed favourable inhibitory activity, suggesting its potential for targeting BTK malignant tumours. This inhibitor could serve as a basis for developing an effective BTK inhibitor targeting solid cancers.

Effect of phenylurea hydroxamic acids on histone deacetylase and VEGFR-2.

A series of phenylurea hydroxamic acids incorporating pharmacophores of inhibitors of HDAC inhibitors and VEGFR-2 has been designed. Most of the compounds show antiproliferative activity comparable to that of Vorinostat and Sorafenib, and better EPC inhibitory activity. Enzymatic assays and Western blotting results indicated that compound 14 not only inhibits HDAC but also has slight VEGFR-2 inhibitory activity. A docking study revealed that the polar hydroxamic acid retains the interaction with HDAC through a zinc ion and also interacts with some residues of the active site of VEGFR-2. Despite 14 displaying a weaker VEGFR-2 activity, a possible route to develop potent HDAC/VEGFR-2 inhibitors is suggested.

Ring size changes in the development of class I HDAC inhibitors.

Five pathways involving different ring structures led to generation of fourteen thienylbenzamides (7-20) which display the structure-activity relationships of class I HDAC inhibitors. All the synthesised compounds inhibit HDAC1 and HDAC2 selectively over other isoforms and many inhibit DLD1 and HCT116 cells more effectively than a parent compound. Compounds 8 and 16 inhibit HCT116 cells by activation of the apoptosis pathway.

Effect of 3-subsitution of quinolinehydroxamic acids on selectivity of histone deacetylase isoforms.

A series of 3-subsituted quinolinehydroxamic acids has been synthesised and evaluated for their effect on human lung cancer cell line (A549), human colorectal cancer cell line (HCT116) and HDAC isoforms 1, 2, 6, and 8. The results indicated that substitution at C3 of quinoline is favoured for HDAC6 selectivity. Two compounds (25 and 26) were also found to be potent anti-proliferative compounds with IC50 values ranging from 1.29 to 2.13 µM against A549 and HCT116 cells. These compounds displayed remarkable selectivity for HDAC6 over other HDAC isoforms with nanomolar IC50 values. Western blot analysis revealed that compounds of this series activate apoptotic caspase pathway as indicated by cleavage of caspase 3, 8, and 9 and also increase phosphorylated H2AX thus inducing DNA double strand fragmentation in a concentration dependent manner. Flow cytometric analysis also displayed a dose dependent increase of cell population in sub G1 phase.

HDAC inhibitor protects chronic cerebral hypoperfusion and oxygen-glucose deprivation injuries via H3K14 and H4K5 acetylation-mediated BDNF expression.

Vascular dementia (VaD) is the second most common cause of dementia, but the treatment is still lacking. Although many studies have reported that histone deacetylase inhibitors (HDACis) confer protective effects against ischemic and hypoxic injuries, their role in VaD is still uncertain. Previous studies shown, one HDACi protected against cognitive decline in animals with chronic cerebral hypoperfusion (CCH). However, the underlying mechanisms remain elusive. In this study, we tested several 10,11-dihydro-5H-dibenzo[b,f]azepine hydroxamates, which act as HDACis in the CCH model (in vivo), and SH-SY5Y (neuroblastoma cells) with oxygen-glucose deprivation (OGD, in vitro). We identified a compound 13, which exhibited the best cell viability under OGD. The compound 13 could increase, in part, the protein levels of brain-derived neurotrophic factor (BDNF). It increased acetylation status on lysine 14 residue of histone 3 (H3K14) and lysine 5 of histone 4 (H4K5). We further clarified which promoters (I, II, III, IV or IX) could be affected by histone acetylation altered by compound 13. The results of chromatin immunoprecipitation and Q-PCR analysis indicate that an increase in H3K14 acetylation leads to an increase in the expression of BDNF promoter II, while an increase in H4K5 acetylation results in an increase in the activity of BDNF promoter II and III. Afterwards, these cause an increase in the expression of BDNF exon II, III and coding exon IX. In summary, the HDACi compound 13 may increase BDNF specific isoforms expression to rescue the ischemic and hypoxic injuries through changes of acetylation on histones.

Synthesis and biological evaluation of 2-quinolineacrylamides.

A series of C6-substituted N-hydroxy-2-quinolineacrylamides (3-15), with four types of bridging groups have been synthesized. Most of these compounds exhibit antiproliferative activity against A549 and HCT116 cells and Western blot analysis revealed that they are able to inhibit HDAC. Measurement of the HDAC isoform activity of ether-containing compounds showed that compound 9 has distinct HDAC6 selectivity, more than 300-fold over other isoforms. This paper describes the development of 6-aryloxy-N-hydroxy-2-quinolineacrylamides as potential HDAC6 inhibitors.

Structure-guided design of anti-cancer ribonucleotide reductase inhibitors.

Ribonucleotide reductase (RR) catalyses the rate-limiting step of dNTP synthesis, establishing it as an important cancer target. While RR is traditionally inhibited by nucleoside-based antimetabolites, we recently discovered a naphthyl salicyl acyl hydrazone-based inhibitor (NSAH) that binds reversibly to the catalytic site (C-site). Here we report the synthesis and in vitro evaluation of 13 distinct compounds (TP1-13) with improved binding to hRR over NSAH (TP8), with lower KD's and more predicted residue interactions. Moreover, TP6 displayed the greatest growth inhibiting effect in the Panc1 pancreatic cancer cell line with an IC50 of 0.393 µM. This represents more than a 2-fold improvement over NSAH, making TP6 the most potent compound against pancreatic cancer emerging from the hydrazone inhibitors. NSAH was optimised by the addition of cyclic and polar groups replacing the naphthyl moiety, which occupies the phosphate-binding pocket in the C-site, establishing a new direction in inhibitor design.

Correction: 2-Aroylquinoline-5,8-diones as potent anticancer agents displaying tubulin and heat shock protein 90 (HSP90) inhibition.

Correction for '2-Aroylquinoline-5,8-diones as potent anticancer agents displaying tubulin and heat shock protein 90 (HSP90) inhibition' by Kunal Nepali et al., Org. Biomol. Chem., 2016, 14, 716-723.

Total Synthesis of Two Glycosylated Stilbenes, Oxyresveratrol 2-O-ß-d-Glucopyranoside and 2,3,5,4'-Tetrahydroxystilbene 2-O-ß-d-Glucopyranoside.

Glycosylated stilbenes are biologically active secondary metabolites of plants and have the potential to alleviate a broad range of human diseases. However, some of these compounds are not naturally abundant, and thus the synthesis of such molecules is desirable. This paper reports the first synthesis of oxyresveratrol 2-O-ß-d-glucopyranoside (1) and 2,3,5,4'-tetrahydroxystilbene 2-O-ß-d-glucopyranoside (1'), which are stilbene glycosides obtained from the rhizomes of Schoenocaulon officinale and Polygonum multiflorum, respectively. A facile four-step synthesis of 1 involved selective protection of the hydroxy groups and Wittig olefination to generate the compound in 8% overall yield. For compound 1', a 10-step synthesis utilized selective protection of the hydroxy groups, Baeyer-Villiger oxidation, modified Duff formylation, and Wittig olefination to generate the compound in 6.9% overall yield.

2-Aroylquinoline-5,8-diones as potent anticancer agents displaying tubulin and heat shock protein 90 (HSP90) inhibition.

This study reports the synthesis of a series of 2-aroylquinoline-5,8-diones (11-23) on the basis of scaffold hopping. The presence of a methoxy group at C6 assists the highly regioselective incorporation with various amines, and simplifies the structural identification process. Among the synthetic compounds, 6-dimethylamino-2-(3,4,5-trimethoxybenzoyl)-quinoline-5,8-dione (12) and 7-pyrrolidin-1-yl-2-(3,4,5-trimethoxybenzoyl)-quinoline-5,8-dione (23) exhibit remarkable anti-proliferative activity against the cancer cell lines tested with mean IC50 values of 0.14 and 0.27 µM, respectively. Compound 23 showed moderate inhibitory activity against tubulin polymerization with an IC50 value of 5.9 µM. In a western blot analysis, 23 caused induction of HSP70 and degradation of Akt, revealing that it possesses HSP90 inhibitory activity.

Total Synthesis of Denbinobin.

A total synthesis of denbinobin (1) in seven steps with an overall yield of 10% is reported. This synthesis used an FeCl3-assisted cyclization of stilbene to form a phenanthrene. The poor yields of the decarboxylation and methoxylation steps were improved upon to become essentially quantitative. This scalable methodology was carried out using ordinary laboratory reagents.

Pyrimidinedione-mediated selective histone deacetylase 6 inhibitors with antitumor activity in colorectal cancer HCT116 cells.

We synthesized a series of pyrimidinedione derivatives and evaluated their activities. The results indicate that compound 6, 4-[5-fluoro-2,6-dioxo-3-(tetrahydro-furan-2-yl)-3,6-dihydro-2H-pyrimidin-1-ylmethyl]-N-hydroxy-benzamide, exhibits potent antiproliferative activity, apoptosis induction with cleavage of caspase and PARP, and enhanced tendency to inhibit HDAC6 (IC50 = 12.4 nM) activity over HDAC1 (IC50 = 1710 nM) and HDAC2 (IC50 = 5500 nM). Compound 6 also inhibits tumor growth and is less toxic than parent 4 in vivo. These data provide compelling evidence that compound 6 is a potential antitumor compound with HDAC6 targeted inhibitory activity and may be tested for preclinical investigation for cancer treatment.

Antimitotic and antivascular activity of heteroaroyl-2-hydroxy-3,4,5-trimethoxybenzenes.

This study reports the synthesis of a series of heteroaroyl-2-hydroxy-3,4,5-trimethoxybenzenes, which are potent antitubulin agents. Compound 13, (2-hydroxy-3,4,5-trimethoxyphenyl)-(6-methoxy-1H-indol-3-yl)-methanone exhibits marked antiproliferative activity against KB and MKN45 cells with IC50 values of 8.8 and 10.5 nM, respectively, binds strongly to the colchicine binding site and leads to inhibition of tubulin polymerization. It also behaves as a vascular disrupting agent which suppresses the formation of capillaries. The C2-OH group in the A-ring of this compound not only retains the biological activity but has valuable physicochemical properties.

Effect of C7-substitution of 1-arylsulfonyl-5-(N-hydroxyacrylamide)indolines on the selectivity towards a subclass of histone deacetylases.

This study focused on the substitution effect at position C7 of 1-arylsulfonyl-5-(N-hydroxyacrylamide)indolines. Compound 9, (E)-3-(7-amino-1-(4-methoxyphenylsulfonyl)indolin-5-yl)-N-hydroxyacrylamide, displayed 4- to 14-fold more potent antiproliferative activity than vorinostat (SAHA, 1). Notably, 9 possessed specific histone deacetylase (HDAC) inhibitory activity toward HDAC1 and HDAC2, but had no effect on HDAC6, indicating that 9 has the potential to be developed as a class I HDAC inhibitor. In a xenograft tumor model, 9 suppressed the growth of HCT116 cells at 100 mg kg(−1), which led to a TGI (tumor growth inhibition) of 40.3%. Taken together, the C7 substitutions have a crucial effect on class I HDACs, which is beneficial for synthesizing efficient anticancer agents.

Concise syntheses of 7-anilino-indoline-N-benzenesulfonamides as antimitotic and vascular disrupting agents.

Described herein is the development of a novel series of 7-anilino-indoline-N-benzenesulfonamides, derived from ABT751 (1), as potent anticancer agents. Amongst the synthesized series, compounds 6, 12, 13, and 14 have shown comparable to better anticancer activity on comparing with compound 1. 7-(4-Cyanophenylamino)-1-(4-methoxybenzenesulfonyl)indoline (13) was found to be the most potent one with up to 6 fold better activity against KB, HT29, and MKN45 cancer cell lines with IC50 values of 49.7, 149, and 92nM, respectively. Compound 13 was also found inhibiting multidrug resistant cancer cell lines, blocking cell cycle at G2/M phase, and inhibiting tubulin polymerization. Capillary disruption assay results revealed that compound 13 was able to disrupt formed capillaries in a concentration-dependent manner without affecting cell viability.

1-arylsulfonyl-5-(N-hydroxyacrylamide)indolines histone deacetylase inhibitors are potent cytokine release suppressors.

A series of 1-arylsulfonyl-5-(N-hydroxyacrylamide)indolines (7-15) has been developed; the compounds exhibited potent histone deacetylase (HDAC) inhibitory activities. Notably, almost all of this series exhibited better HDAC-inhibitory and antiproliferative activities than 3-(1-benzenesulfonyl-1H-indol-5-yl)-N-hydroxyacrylamide (6), as reported in a previous study. Among these compounds, 3-[1-(4-methoxybenzenesulfonyl)-2,3-dihydro-1H-indol-5-yl]-N-hydroxyacrylamide (9) showed a two- to tenfold increase in activity compared to SAHA (1) in the suppression of lipopolysaccharide-induced cytokine production. Compound 9 also caused a marked reduction in carrageenan-induced acute inflammation in a rat model. Taken together, these data indicated that 1-arylsulfonyl-5-(N-hydroxyacrylamide)indolines HDAC inhibitors exhibit potent anti-inflammatory activity.

CuI-mediated synthesis of 1-aryl-5,6,7-trimethoxybenzimidazoles as potent antitubulin agents.

In situ CuI-mediated cyclization methodology helped yield benzimidazoles with different substitution manner, such as 1,2-diarylbenzimidazoles (4 and 5) and 1-arylbenzimidazoles (6-15). The result of structure-activity relationship (SAR) study confirmed the significance of the 5,6,7-trimethoxybenzimidazole moiety, and the representative derivatives (8-10) exhibited marked antiproliferative activity against A549, HCT-116, and PC-3 cells; in addition, they are able to inhibit the polymerization of tubulin. Among them, compound 10 inhibited the growth of A549, HCT-116, and PC-3 cells with a mean IC50 value of 0.07 µM, and its IC50 value of tubulin polymerization is 0.26 µM.

6-Regioisomeric 5,8-quinolinediones as potent CDC25 inhibitors against colorectal cancers.

Precise and accurate control of cell cycle progression is required to maintain cell identity and proliferation. Failing to keep it will lead to genome instability and tumorigenesis. Cell Division Cycle 25 (CDC25) phosphatases are the key to regulating the activity of the master cell cycle controller, cyclin-dependent kinases (CDKs). Dysregulation of CDC25 has been shown to associate with several human malignancies. Here, we reported a series of derivatives of the CDC25 inhibitor, NSC663284, bearing quinones as core scaffolds and morpholin alkylamino side chains. Among these derivatives, the cytotoxic activity of the 6-isomer of 5,8-quinolinedione derivatives (6b, 16b, 17b, and 18b) displayed higher potency against colorectal cancer (CRC) cells. Compound 6b possessed the most antiproliferative activity, with IC50 values of 0.59 µM (DLD1) and 0.44 µM (HCT116). The treatment of compound 6b resulted in a remarkable effect on cell cycle progression, blocking S-phase progression in DLD1 cells straight away while slowing S-phase progression and accumulated cells in the G2/M phase in HCT116 cells. Furthermore, we showed that compound 6b inhibited CDK1 dephosphorylation and H4K20 methylation in cells. The treatment with compound 6b induced DNA damage and triggered apoptosis. Our study identifies compound 6b as a potent CDC25 inhibitor that induces genome instability and kills cancer cells through an apoptotic pathway, deserving further investigation to fulfill its candidacy as an anti-CRC agent.