Synthesis and biological evaluation of the suberoylanilide hydroxamic acid (SAHA) beta-glucuronide and beta-galactoside for application in selective prodrug chemotherapy

The beta-O-glucuronide and beta-O-galactoside of SAHA have been prepared and evaluated as prodrugs for selective cancer chemotherapy (ADEPT, PMT). These new compounds are stable under physiological conditions and do not exhibit any antiproliferative activity compared to the parent drug after a 48-h treatment of H661 cells. The glucuronide derivative did not lead to the release of the drug in the presence of either Escherichia coli or bovine liver beta-glucuronidase. On the other hand, under enzymatic cleavage of galactoside prodrug by the corresponding enzyme, a rapid release of SAHA was observed demonstrating that the beta-O-galactoside of SAHA is a promising candidate for in vivo investigations.     

Synthesis and anti-melanogenic activity of hydroxyphenyl benzyl ether analogues

In order to develop potent skin whitening agents, we have synthesized 17 hydroxyphenyl benzyl ether compounds and tested their melanin synthesis inhibitory activity, DPPH free radical scavenging activity and tyrosinase inhibitory activity. Compounds 32, 35 and 36 possessing 4-hydroxyphenyl benzyl ether structure showed excellent inhibitory capacity with almost 50-fold than arbutin used as a reference in the inhibition test of α-MSH stimulated melanin synthesis in B-16 cells. 4-Hydroxyphenyl benzyl ether compounds also showed good antioxidant activity in the DPPH free radical scavenging test. The tyrosinase function was effectively inhibited by 3,5-dihydroxyphenyl benzyl ether analogues, especially compounds 18, 22, and 24.     

Degradation of benzyl ether bonds of lignin by ruminal microbes

We examined microbial activity in the rumen to cleave benzyl ether bonds of lignin model compounds that fluoresced when the bonds were cleaved. 4-Methylumbelliferone veratryl ether dimer was degraded completely within 8 h even in the presence of fungicidal antibiotics, but no significant degradation occurred with bactericidal antibiotics. Degradation of a phenolic beta-O-4 trimer incorporating 4-methylumbelliferone by a benzyl ether linkage was stimulated by ruminal microbes, although its corresponding non-phenolic model compound, 1-(4-ethoxy-3-methoxyphenyl)-1-O-(4-methylumbelliferyl)-2-(2-methoxyp henoxy)-3-propanol, was not degraded. A coniferyl dehydrogenation polymer bearing fluorescent beta-O-4 benzyl ether that contains both phenolic and non-phenolic benzyl ether bonds was partially degraded (about 20%) in 48 h. These results suggest that ruminal microbes decompose benzyl ether linkages of lignin polymers under anaerobic conditions.     

Antiproliferative activities of a library of hybrids between indanones and HDAC inhibitor SAHA and MS-275 analogues

New compounds derived from inhibitors of histone deacetylases (HDACs) have been synthesized and their antiproliferative activities towards non small lung cancer cell line H661 evaluated. Their design is based on hybrids between indanones to limit conformational mobility and other known HDAC inhibitors (SAHA, MS-275). The synthesis of these new derivatives was achieved by alkylation of appropriate indanones to introduce the side chain bearing a terminal ester group, the latter being a precursor of hydroxamic acid and aminobenzamide derivatives. These new analogues were found to be moderately active to inhibit H661 cell proliferation.     

Total synthesis of chain-length-uniform dolichyl phosphates and their fitness to accept hexoses in the enzymatic formation of lipoglycans

Dolichols of defined uniform chain length (C35, C45, and C55) and geometry were prepared by total synthesis according to the following principle: (E,E)-Farnesol, activated as its 4-tolyl sulfone, is condensed with 8-chloroneryl benzyl ether, the sulfonyl group removed and the ether linkage cleaved by lithium/triethylamine. The resulting elongated prenol is converted again to its corresponding 4-toly/sulfone; at this stage isomers are removed by chromatography. After several cycles of this C10-elongation sequence the synthesis is completed in the same way but using 8-chlorocitronellyl benzyl ether as building block to introduce the saturated alpha-isoprene unit. The dolichols obtained were chemically phosphorylated (POCl3/Et3N). Both, the alcohols and their phosphate esters, are characterized spectroscopically. 1H- and 13C-NMR data are recorded for qualitative and stereochemical comparison with natural dolichols. The authentic dolichyl phosphates (Dol-7-P, Dol-9-P, and Dol-11-P) were assayed relative to the natural dolichyl phosphate mixture from pig liver as acceptors for transglycosylation from nucleoside diphosphate sugars (glucose, mannose) by standardized membrane vesicle preparations from plants (Volvox) and animals (liver). Even the shortest chain dolichyl 7-phosphate has full activity in this lipoglycan-forming reaction.     

Synthesis and in vitro antiproliferative evaluation of d-secooxime derivatives of 13β- and 13α-estrone

d-Secooximes were synthesized from the d-secoaldehydes in the 13β- and 13α-estrone series. The oximes were modified at three sites in the molecule: the oxime function was transformed into an oxime ether, oxime ester or nitrile group, the propenyl side-chain was saturated and the 3-benzyl ether was removed in order to obtain a phenolic hydroxy function. Triazoles were formed via Cu(I)-catalysed azide–alkyne cycloaddition (CuAAC) from 3-(prop-2-yniloxy)-d-secooximes and benzyl azides. All the products were evaluated in vitro by means of MTT assays for antiproliferative activity against a panel of human adherent cell lines (HeLa, MCF-7, A2780 and A431). Some of them exhibited activities with submicromolar IC₅₀ values, better than that of the reference agent cisplatin. The structural modifications led to significant differences in the cytostatic properties. Flow cytometry indicated that one of the most potent agents resulted in a cell cycle blockade.     

Discovery of indole-3-butyric acid derivatives as potent histone deacetylase inhibitors

In discovery of HDAC inhibitors (HDACIs) with improved anticancer potency, structural modification was performed on the previous derived indole-3-butyric acid derivative. Among all the synthesised compounds, molecule I13 exhibited high HDAC inhibitory and antiproliferative potencies in the in vitro investigations. The IC₅₀ values of I13 against HDAC1, HDAC3, and HDAC6 were 13.9, 12.1, and 7.71 nM, respectively. In the cancer cell based screening, molecule I13 showed increased antiproliferative activities in the inhibition of U937, U266, HepG2, A2780, and PNAC-1 cells compared with SAHA. In the HepG2 xenograft model, 50 mg/kg/d of I13 could inhibit tumour growth in athymic mice compared with 100 mg/kg/d of SAHA. Induction of apoptosis was revealed to play an important role in the anticancer potency of molecule I13. Collectively, a HDACI (I13) with high anticancer activity was discovered which can be utilised as a lead compound for further HDACI design.     

Molecular dynamics simulation of complex Histones Deacetylase (HDAC) Class II Homo Sapiens with suberoylanilide hydroxamic acid (SAHA) and its derivatives as inhibitors of cervical cancer

Cervical cancer is second most common cancer in woman worldwide. Cervical cancer caused by human papillomavirus (HPV) oncogene. Inhibition of histone deacetylase (HDAC) activity has been known as a potential strategy for cancer therapy. SAHA is an HDAC inhibitor that has been used in cancer therapy but still has side effects. SAHA modification proposed to minimize side effects. Triazole attachment on the chain of SAHA has been known to enhance the inhibition ability of SAHA and less toxic. In this study, it will be carried out with molecular dynamic simulations of SAHA modifications consisting ligand 1a, 2a and, 2c to interact with six HDAC in hydrated conditions. To all six HDAC Class II, performed docking with SAHA and a modified inhibitor. The docking results were then carried out molecular dynamics simulations to determine the inhibitor affinities in hydrated conditions. The molecular dynamic simulations results show better affinities of ligand 2c with HDAC 4, 6, and 7 than SAHA itself, and good affinity was also shown by ligand 2a and 1c on HDAC 5 and 9. The results of this study can be a reference to obtain better inhibitors.     

Antitumor agents 283. Further elaboration of desmosdumotin C analogs as potent antitumor agents: activation of spindle assembly checkpoint as possible mode of action

In our ongoing study of the desmosdumotin C (1) series, twelve new analogues, 21-32, mainly with structural modifications in ring-A, were prepared and evaluated for in vitro antiproliferative activity against several human tumor cell lines. Among them, the 4'-iodo-3,3,5-tripropyl-4-methoxy analogue (31) showed significant antiproliferative activity against multiple human tumor cell lines with ED(50) values of 1.1-2.8 μM. Elongation of the C-3 and C-5 carbon chains reduced activity relative to propyl substituted analogues; however, activity was still better than that of natural compound 1. Among analogues with various ether groups on C-4, compounds with methyl (2) and propyl (26) ethers inhibited cell growth of multiple tumor cells lines, while 28 with an isobutyl ether showed selective antiproliferative activity against lung cancer A549 cells (ED(50) 1.7 μM). The gene expression profiles showed that 3 may modulate the spindle assembly checkpoint (SAC) and chromosome separation, and thus, arrest cells at the G2/M-phase.     

Exploring alternative Zn-binding groups in the design of HDAC inhibitors: squaric acid, N-hydroxyurea, and oxazoline analogues of SAHA

Analogues of suberoylanilide hydroxamic acid (SAHA) were prepared by replacing the Zn-binding group with squaric acid, N-hydroxyurea, and 4-hydroxymethyl oxazoline units, also varying the length of the aliphatic chain. No inhibitory activity on HDAC was observed below 1.0 microM and no cytotoxic activity on different tumor cell lines was seen below 20.0 microM.     

Enzymatic nanoreactors for environmentally benign biotransformations. 1. Formation and catalytic activity of supramolecular complexes of laccase and linear-dendritic block copolymers

We describe the construction of enzymatic nanoreactors through noncovalent envelopment of a glycoprotein by amphiphilic linear-dendritic AB or ABA copolymers. The synthetic procedure is based on the regioselective adsorption of dendritic poly(benzyl ether)-block-linear poly(ethylene glycol)-block-dendritic poly(benzyl ether) or linear poly(ethylene oxide)-block-dendritic poly(benzyl ether) copolymers onto the oxidative enzyme laccase from Trametes versicolor in aqueous medium. The complexes formed have improved catalytic activity compared with the native enzyme (77-85 nkat/mL vs 60 nkat/mL, respectively) and are more stable at elevated temperatures up to 70 degrees C. Experiments with deglycosylated laccase confirm that the glycoside fragments in the native enzyme serve as the anchor sites for the linear-dendritic copolymers. The enzymatic nanoreactors are able to effectively oxidize series of substrates: phenolic compounds (syringaldazine) and hydrophobic polyaromatic hydrocarbons (anthracene and benzo[a]pyrene) under "green" chemistry conditions.     

Improved antiproliferative activity of 1,3,4-thiadiazole-containing histone deacetylase (HDAC) inhibitors by introduction of the heteroaromatic surface recognition motif

A series of 1,3,4-thiadiazole-containing hydroxamic acids, in accord with the common pharmacophore of histone deacetylase (HDAC) inhibitors (a Zn²⁺ binding moiety–a linker–a surface recognition motif), was identified as submicromolar HDAC inhibitors by our group. In this study, we continued our efforts to develop 1,3,4-thiadiazole bearing hydroxamate analogues by modifying the surface recognition motif. We found that 1,3,4-thiadiazoles having a heteroaromatic substituent showed better HDAC inhibitory activity in enzymatic assay and higher antiproliferative potency in cellular assay compared to SAHA.     

Utilization of tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidinone as a cap moiety in design of novel histone deacetylase inhibitors

A series of novel 5,6,7,8-Tetrahydro[1]benzothieno[2,3-d]pyrimidin-4(3H)-one derivatives bearing a hydroxamic acid, 2-aminoanilide and hydrazide moieties as zinc-binding group (ZBG) were designed, synthesized and evaluated for the HDAC inhibition activity and antiproliferative activity. Most of the tested compounds displayed strong to moderate HDAC inhibitory activity. Some of these compounds showed potent anti-proliferative activity against human HepG2, MCF-7 and HCT-116 cell lines. In particular, compounds IVa, IVb, IXa and IXb exhibited significant anti-proliferative activity against the three cell lines tested compared to SAHA as a reference. Compound IVb is equipotent inhibitor for HDAC1 and HDAC2 as SAHA. It is evident that the presence of free hydroxamic acid group is essential for Zn binding affinity with maximal activity with a linker of aliphatic 6 carbons. Docking study results revealed that compound IVb could occupy the HDAC2 binding site and had the potential to exhibit antitumor activity through HDAC inhibition, which merits further investigation.     

Design,synthesis and preliminary bioactivity studies of 1,2-dihydrobenzo[d]isothiazol-3-one-1,1-dioxide hydroxamic acid derivatives as novel histone deacetylase inhibitors

Histone deacetylase (HDAC) is a clinically validated target for antitumor therapy. In order to increase HDAC inhibition and efficiency, we developed a novel series of saccharin hydroxamic acids as potent HDAC inhibitors. Among them, compounds 11e, 11m, 11p exhibited similar or better HDACs inhibitory activity compared with the approved drug SAHA. Further biological evaluation indicated that compound 11m had potent antiproliferative activities against MDA-MB-231 and PC-3.     

Benzyl esters in the gas-chromatographic purification of radioactive acetic acid from bacteria, and for the possible analysis of other short-chain acids

A method has been developed for the purification of small quantities of acetic acid from bacteria. The acetic acid, with added carrier and a second isotopic species as an internal standard, was extracted into diethyl ether, the benzyl ester was formed using diazotoluene (phenyldiazomethane) and the resultant benzyl acetate purified by small-scale preparative gas-liquid chromatography on a nonpolar stationary phase. Overall recoveries were in the range 26–40%. The method was extended to show the feasibility of the preparative purification of other short chain acids, and also for the analysis of C₁ to C₁₀ acids, as their benzyl esters.     

Histone hyperacetylation is associated with amelioration of experimental colitis in mice

Inhibitors of histone deacetylases (HDAC) are being studied for their antiproliferative effects in preclinical cancer trials. Recent studies suggest an anti-inflammatory role for this class of compounds. Because inflammatory bowel disease is associated with an increased risk of malignancies, agents with antiproliferative and anti-inflammatory properties would be of therapeutic interest. HDAC inhibitors from various classes were selected and evaluated for their in vitro capacity to suppress cytokine production and to induce apoptosis and histone acetylation. Valproic acid (VPA) and suberyolanilide hydroxamic acid (SAHA) were chosen for further studies in dextran sulfate sodium- and trinitrobenzene sulfonic acid-induced colitis in mice. In vitro, inhibition of HDAC resulted in a dose-dependent suppression of cytokine synthesis and apoptosis induction requiring higher concentrations of HDAC inhibitors for apoptosis induction compared with cytokine inhibition. Oral administration of either VPA or SAHA reduced disease severity in dextran sulfate sodium-induced colitis. The macroscopic and histologic reduction of disease severity was associated with a marked suppression of colonic proinflammatory cytokines. In parallel to the beneficial effect observed, a dose-dependent increase in histone 3 acetylation at the site of inflammation was shown under VPA treatment. Furthermore, SAHA as well as VPA treatment resulted in amelioration of trinitrobenzene sulfonic acid-induced colitis, which was associated with an increase of apoptosis of lamina propria lymphocytes. Inhibitors of HDAC reveal strong protective effects in different models of experimental colitis by inducing apoptosis and suppressing proinflammatory cytokines, thereby representing a promising class of compounds for clinical studies in human inflammatory bowel disease.     

Exploring the connection unit in the HDAC inhibitor pharmacophore model: novel uracil-based hydroxamates

Starting from the pharmacophore model for HDAC inhibitor design, a novel series of hydroxamates bearing a uracil moiety as connecting unit (CU) has been prepared and tested. Almost all compounds exhibited HDAC inhibiting activity at low nanomolar concentrations, the N-hydroxy-6-(3,4-dihydro-4-oxo-6-benzyl- and -6-phenyl-2-pyrimidinylthio)hexanamides 1d and 1l being more potent than SAHA in enzymatic assays. Such compounds also caused hyperacetylation in NIH3T3 cell core histones and were endowed with interesting antiproliferative and cytodifferentiating effects in human leukemia (HL-60) cells.     

Synthesis and biological evaluation of N-aryl salicylamides with a hydroxamic acid moiety at 5-position as novel HDAC-EGFR dual inhibitors

A novel series of N-aryl salicylamides with a hydroxamic acid moiety at 5-position were synthesized efficiently. Their activities against EGFR kinase and HDACs were evaluated. All compounds displayed inhibitory activity against EGFR and HDACs. The antiproliferative activities of synthesized compounds were evaluated by MTT method against human cancer cell lines A431, A549 and HL-60. Compound 1o showed the most potent inhibitory activity against A431 and A549. Compounds 1k and 1n exhibited higher potency against HL-60 than gefitinib and SAHA. N-Aryl salicylamides with a hydroxamic acid moiety at 5-position is another new HDAC-EGFR dual inhibitors.     

Modulation of pro- and anti-apoptotic factors in human melanoma cells exposed to histone deacetylase inhibitors

Valproic acid (VPA, 2-propylpentanoic acid) is an established drug in the long-term therapy of epilepsy. Recently, VPA was demonstrated to inhibit histone deacetylases (HDACs) class I enzyme at therapeutically relevant concentrations, thereby, mimicking the prototypical histone deacetylase inhibitors, tricostatin A (TSA) or suberoylanilide hydroxamic acid (SAHA). In the present study, we investigated the cellular effects of VPA, TSA and SAHA on four human melanoma cell lines (WM115, WM266, A375, SK-Mel28) with particular reference to the modulation of regulators of apoptosis, including Bcl-2, BclXL, Mcl-1, Apaf-1, BclXs, NOXA, TRAIL-R1, TRAIL-R2, caspase 8, and survivin). Firstly, we found that VPA induced apoptosis in two of the four human melanoma cell lines, while both TSA and SAHA exhibited an antiproliferative and apoptotic effects in all four cell lines, a different expression of Bcl-2 and BclX(L/S) occurred. On the other hand, SAHA and VPA modulated differently pro- and anti-apoptotic factors. In particular, the treatment with VPA enhanced the level of expression of survivin only in VPA-resistant cell lines, whereas down-regulation of survivin was induced by VPA and SAHA in VPA-sensitive cells. In the latter, since activation of caspase 8 was documented, a receptor-mediated apoptosis was suggested. Taken together, our results suggest that HDAC inhibitors may represent a promising therapeutic strategy to treat melanoma.