Synthesis and biological evaluation of curcumin derivatives modified with α-amino boronic acid as proteasome inhibitors.

Curcumin is a well-known pharmacophore and some of its derivatives are shown to target 20S proteasome recently. In this report, we designed and synthesized two series of curcumin derivatives modified with different α-amino boronic acids as potent proteasome inhibitors. The synthesized compounds were evaluated for their cytotoxic activities against HCT116 cells, and the results showed that all of them exhibited excellent cell growth inhibitory activity comparing with curcumin, with the IC50 values varying from 0.17 µM to 1.63 µM. Compound II-2F with free boronic acid was assayed for its proteasome inhibitory activity and the results indicated that II-2F exhibited more potent inhibitory activity against ChT-L with high subunit selectivity than any other reported curcumin derivatives.

Synthesis and biological activity of peptide proline-boronic acids as proteasome inhibitors.

On the basis of the application of proline-boronic acid as pharmacophore in the kinase inhibitors and our previous research results, using proline-boronic acid as warhead, two series of peptide proline-boronic acids, dipeptide proline-boronic acids (I) and tripeptide proline-boronic acids (II), were designed and synthesized. All the synthesized compounds were first evaluated for their biological activity against MGC803 cell, and then, the best compound II-7 was selected to test its anti-tumor spectrum on six human tumor cell lines and proteasome inhibition against three subunits. The results indicated that series II have much better biological activities than series I. The compound II-7 exhibited not only excellent biological activities with IC50 values of nM level in both cell and proteasome models, but also much better subunit selectivity. Thus, proline-boronic acid as warhead is reasonable in the design of proteasome inhibitors.

Corrigendum: Proteasome inhibitor YSY01A abrogates constitutive STAT3 signaling via down-regulation of Gp130 and JAK2 in human A549 lung cancer cells.

[This corrects the article DOI: 10.3389/fphar.2017.00476.].

Furanodiene, a natural product, inhibits breast cancer growth both in vitro and in vivo.

PURPOSE: Previous studies have reported that the Curcuma wenyujin Y.H. Chen et C. Ling extract, which has a high furanodiene content, showed anti-cancer effects in breast cancer cells in vitro. The present study was designed to evaluate the in vitro and in vivo anti-cancer activity of furanodiene. METHODS: The in vitro effects of furanodiene were examined on two human breast cancer cell lines, MCF-7 and MDA-MB-231 cells. Assays of proliferation, LDH release, mitochondrial membrane potential (ΔΨm), cell cycle distribution, apoptosis and relevant signaling pathways were performed. The in vivo effect was determined with MCF7 tumor xenograft model in nude mice. RESULTS: Furanodiene significantly inhibited the proliferation and increased the LDH release in both cell lines in a dose-dependent manner. ΔΨm depolarization, chromatin condensation, and DNA fragmentation were also observed after furanodiene treatment. Furanodiene dose-dependently induced cell cycle arrest at the G0/G1 phase. The protein expressions of p-cyclin D1, total cyclin D1, p-CDK2, total CDK2, p-Rb, total Rb, Bcl-xL, and Akt were significantly inhibited by furanodiene, whereas the protein expressions of Bad and Bax, and the proteolytic cleavage of caspase-9, caspase-7, and poly-ADP-ribose polymerase (PARP) were dramatically increased. Furthermore, the z-VAD-fmk markedly reversed the furanodiene-induced cell cytotoxicity, the proteolytic cleavage of caspase-9, and DNA fragmentation but did not affect the proteolytic cleavage of PARP, whereas the Akt inhibitor VIII increased the furanodiene-induced cytotoxicity and PARP cleavage. In addition, furanodiene dose-dependently suppressed the tumor growth in vivo, achieving 32% and 54% inhibition rates after intraperitoneal injection of 15 mg/kg and 30 mg/kg, respectively. CONCLUSIONS: Taken together, we concluded that furanodiene suppresses breast cancer cell growth both in vitro and in vivo and could be a new lead compound for breast cancer chemotherapy.

Structural modifications of a 3-methoxy-2-aminopyridine compound to reduce potential for mutagenicity and time-dependent drug-drug interaction.

(S)-1-((4-(3-(6-Amino-5-methoxypyridin-3-yl)-1-isopropyl-1H-pyrazol-4-yl)pyrimidin-2-yl)amino)propan-2-ol, 1, was recently identified as a potent inhibitor of the oncogenic kinase bRAF. Compounds containing 3-methoxy-2-aminopyridine, as in 1, comprised a promising lead series because of their high ligand efficiency and excellent ADME profile. However, following metabolic oxidation, compounds in this series also demonstrated two significant safety risks: mutagenic potential and time-dependent drug-drug interaction (TDI). Metabolite identification studies revealed formation of a reactive metabolite. We hypothesized that minimizing or blocking the formation of such a metabolite would mitigate the safety liabilities. Our investigation demonstrated that structural modifications which either reduced the electron density of the 3-methoxy-2-aminopyridine ring or blocked the reactive site following metabolic oxidation were successful in reducing TDI and AMES mutagenicity.

Determination of 4-methylpiperaine-1-carbodithioc acid 3-cyano-3,3-diphenylpropyl ester hydrochloride in rats' plasma by online-SPE-HPLC-DAD: application to a pharmacokinetic study.

A specific, simple, and fast online-solid-phase extraction-high performance liquid chromatography-diode array detector (SPE-HPLC-DAD) method was developed and validated to quantify 4-methylpiperaine-1-carbodithioc acid 3-cyano-3,3-diphenylpropyl ester hydrochloride (TM208) in small volume samples of rats' plasma for the first time. In this method, the 50-µL plasma sample was taken to perform protein precipitation with 75 µL methanol, and then 50 µL supernatant containing the target analytes was injected and concentrated automatically in a C18 solid-phase extraction (SPE) cartridge. After that the sample was separated on a C18 RP analytical column and analyzed by DAD. The run cycle time is 6.0 min for each sample, and the calibration curve over the range of 0.03 to 25.00 µg/mL has a good linear relationship (r > 0.9998). The recoveries of the quality control samples were all greater than 90%. The limit of detection and the lowest limit of quantification were 0.01 and 0.03 µg/mL, respectively. Finally, this method was successfully applied to a pharmacokinetic study of TM208 in rats.

Angiogenesis inhibition and cell cycle arrest induced by treatment with Pseudolarix acid B alone or combined with 5-fluorouracil.

Angiogenesis inhibitors combined with chemotherapeutic drugs have significant efficacy in the treatment of a variety of cancers. Pseudolarix acid B (PAB) is a traditional pregnancy-terminating agent, which has previously been shown to reduce tumor growth and angiogenesis. In this study, we used the high content screening assay to examine the effects of PAB on human umbilical vein endothelial cells (HUVECs). Two hepatocarcinoma 22-transplanted mouse models were used to determine PAB efficacy in combination with 5-fluorouracil (5-Fu). Our results suggested that PAB (0.156-1.250 µM) inhibited HUVECs motility in a concentration-dependent manner without obvious cytotoxicity in vitro. In vivo, PAB (25 mg/kg/day) promoted the anti-tumor efficacy of 5-Fu (5 mg/kg/2 days) in combination therapy, resulting in significantly higher tumor inhibition rates, lower microvessel density values, and prolonged survival times. It was also demonstrated that PAB acted by blocking the cell cycle at both the G(1)/S boundary and M phase, down-regulation of vascular endothelial growth factor, hypoxia-inducible factor 1α and cyclin E expression, and up-regulation of cdc2 expression. These observations provide the first evidence that PAB in combination with 5-Fu may be useful in cancer treatment.

Effects of CS-1 on A431 cell proliferation, cell cycle, and epidermal growth factor receptor signal transduction.

CS-1, a new alkaloid with a molecular formula of C(21)H(20)O(8)N(2)S, is extracted from traditional Chinese medicine. Previous studies have shown that CS-1 can inhibit the proliferation of several human carcinoma cells in vivo and in vitro. The aims of this study are to investigate the anti-tumor effect and mechanism of CS-1 in epidermal growth factor receptor (EGFR) signaling pathway in human A431 cell line. Through the sulforhodamine B assay, we found that CS-1 inhibited A431 cell proliferation in the concentration- and time-dependent manners. The inhibitory rate ranged from 14.5% to 87.8% after 24 h of incubation. High content screening (HCS) multi-parameters cytotoxicity analysis showed that CS-1 at high concentration had slight cytotoxicity that resulted from the cell permeabilization and slight reduction in total mitochondrial mass, whereas no change in nucleus size/morphology and lysosomal mass-pH was found. The cytotoxicity of CS-1 was not a major reason for its anti-proliferative effect. Cell cycle analysis indicated that CS-1 induced G1-phase arrest in A431 cells in a time-dependent manner at high concentration (2.5 µM), and S-phase arrest at low concentration (0.625 µM). The HCS assay also showed that CS-1 could inhibit the EGFR internalization, extracellular-signal-regulated kinase (Erk)/mitogen-activated protein kinase translocation to nucleus, the accumulation of phosphorylated protein kinase B (Akt), signal transducer and activator of transcription 3 (STAT3), and cyclin D1 in the nucleus. These results were confirmed by the western blot analysis. CS-1 might inhibit the epidermal growth factor binding to its receptor, resulting in the inhibition of the accumulation of phosphorylated Erk and Akt, and STAT3 in the nucleus, and affecting the transcription of cyclin D1 and cell cycle arrest in G1/S phase.

[Design, synthesis and biological assay of novel tripeptidic tetrazoles as inhibitors of 20S proteasome].

Ubiquitin-proteasome pathway (UPP) is one of the ways utilized for selective degradation of many proteins in cells, and the 20S proteasome takes the functional machinery where hydrolysis of targeted proteins takes place. Based on existing peptide inhibitors, a series of novel tripeptidic tetrazoles have been designed, synthesized, and the structures have been confirmed with 1H NMR, MS and elemental analysis. Among them, three compounds (6b, 6d and 6h) showed inhibitory activities of ChT-L of 20S proteasome.

Molecular design, synthesis and bioactivity of glycosyl hydrazine and hydrazone derivatives: notable effects of the sugar moiety.

Assuming that the water solubility of our previous hydrazone derivatives would improve after modification with sugars while keeping or modulating their notable biological activities, we designed and synthesized some glycosyl hydrazine and hydrazone derivatives. Bioassay results indicated that the antitumor activity of our previously prepared hydrazones reduced or disappeared after modification with sugars. On the contrary, some glycosyl derivatives displayed much better antifungal activity against selected fungi. Obviously, a small sugar can change the biological activity of hydrazones significantly.

Synthesis and structure-activity relationships of a novel class of dithiocarbamic acid esters as anticancer agent.

Based on a novel lead compound 4-methylpiperazine-1-carbodithioic acid 3-cyano-3,3-diphenylpropyl ester 1, the systematic structural modification was carried out. All the synthesized compounds were evaluated for their in-vitro anticancer activities on four to six different cell lines at three different concentrations. Most of the tested compounds could selectively inhibit the growth of HL-60 and Bel-7402 cell lines at a medium concentration. Four compounds (3f, 3g, 3n, and 5) were selected for the IC(50) test, and the results revealed that three compounds (3g, 3n, and 5) showed almost the same or a slightly weaker activity than compound 1 against HL-60, and three compounds (3f, 3g, and 3n) showed >2-fold higher potency than compound 1 against Bel-7402. The in-vivo efficacy of 3n · HCl was evaluated with transplanted hepatocyte carcinoma 22 as an in-vivo test model. It was found that 3n · HCl could inhibit significantly the growth of tumor, and that this effect was dose-dependent. Meanwhile, the compound 3n · HCl showed low toxicity compared with compound 1 · HCl as evidenced by the little body-weight loss. These results confirmed that compound 3n · HCl is more potent than the lead compound 1 · HCl. Preliminary structure-activity relationships indicated that: a) Both nitrile group and the cyclic amine containing at least two nitrogens were indispensable moieties to keep the activity; b) substitution of the piperazine ring is unfavorable for the improvement of activity; c) the suitable linker joining the piperazinyl dithiocarboxyl and diphenylacetonitril group should be ethylene; d) a non-coplanar arrangement of the two benzene rings appears to be essential for activity.

Synthesis and SAR study of novel peptide aldehydes as inhibitors of 20S proteasome.

Based on the analysis of the crystal structure of MG101 (1) and 20S proteasomes, a new series of peptide aldehyde derivatives were designed and synthesized. Their ability to inhibit 20S proteasome was assayed. Among them, Cbz-Glu(OtBu)-Phe-Leucinal (3c), Cbz-Glu(OtBu)-Leu-Leucinal (3d), and Boc-Ser(OBzl)-Leu-Leucinal (3o) exhibited the most activity, which represented an order of magnitude enhancement compared with MG132 (2). The covalent docking protocol was used to explore the binding mode. The structure-activity relationship of the peptide aldehyde inhibitors is discussed.

Oleanane-type saponins and prosapogenins from Albizia julibrissin and their cytotoxic activities.

Two undescribed oleanane-type saponins, julibrosides K-L, along with three undescribed oleanane-type prosapogenins, julibrosides M-O, were isolated from the stem bark of Albizia julibrissin Durazz. and the mild alkaline hydrolysate of the total saponin, respectively. Their structures were established by extensive analysis of 1D and 2D NMR experiments (COSY, TOCSY, HSQC, HMBC, and HSQC-TOCSY) and mass spectrometry. Furthermore, the cytotoxic activities of the isolated compounds against BGC-823, A549, HCT-116, and HepG2 cell lines were evaluated, and julibroside L showed significant cytotoxic activities against the four cancer cell lines with IC50 values of 5.77, 4.80, 4.26, and 4.93 µM, respectively.

Gas-fragmentation study of the novel synthetic zwitterionic drug 3-methyl-9-(2-oxa-2lambda5-2H-1,3,2-oxazaphosphorine-2-cyclohexyl)-3,6,9-triazaspiro[5,5]undecane chloride (SLXM-2) by electrospray ionization tandem mass spectrometry.

The zwitterionic drug 3-methyl-9-(2-oxa-2lambda5-2H-1,3,2-oxazaphosphorine-2-cyclohexyl)-3,6,9-triazaspiro[5,5]undecane chloride (SLXM-2) is a novel synthetic compound which has shown anticancer activity and low toxicity in vivo. In this study, the various gas-phase fragmentation routes were analyzed by electrospray ionization mass spectrometry (positive ion mode) in conjunction with tandem mass spectrometry (ESI-MS(n)) for the first time. In ESI-MS the fragment ion at m/z 289 (base peak) was formed by loss of the chlorine anion from the zwitterionic precursor SLXM-2. The fragment ion at m/z 232 was formed from the ion at m/z 289 by loss of 1-methylaziridine. The detailed gas-phase collision-induced dissociation (CID) fragmentation mechanisms obtained from the various precursor ions extracted from the zwitterionic SLXM-2 drug was obtained by tandem mass spectrometry analyses.

Synthesis and bioactivity of N-benzoyl-N'-[5-(2'-substituted phenyl)-2-furoyl] semicarbazide derivatives.

In order to find novel chitin synthesis inhibitors (CSIs) with good activity, benzoylphenylurea, a typical kind of CSIs, was chosen as the lead compound and 15 novel derivatives containing furan moieties were designed by converting the urea linkage of benzoylphenylureas into a semicarbazide and changing the aniline part into furoyl groups. The title compounds were synthesized by the reaction of substituted benzoyl isocyanates with 5-(substituted phenyl)-2-furoyl hydrazine, and the structures were confirmed by IR, (1)H-NMR, elemental analysis and single crystal X-ray diffraction analyses (compound E2). The bioassay results indicated that the title compounds exhibit good insecticidal activity, especially towards Plutella xylostella L., but had lower fungicidal activity. Inspiringly, the title compounds possessed obvious anticancer activity against human promyelocytic leukemic cell line (HL-60), and some of the title compounds also had activity against human hepatocellular carcinoma cell line (Bel-7402), human gastric carcinoma cell line (BGC-823), and human nasopharyngeal carcinoma cell line (KB). The results indicated that the linkage in the lead compounds was important to the bioactivity and spectra. The modification on the urea linkage is an effective strategy to discover new pesticide and drug candidates.

Capillary electrophoresis for screening of 20S proteasome inhibitors.

A method for studying 20S proteasome inhibitors by capillary electrophoresis (CE) has been developed. Proteasome plays a fundamental role in degrading key regulatory proteins. The 20S proteasome can degrade intrinsically disordered proteins in an ATP-independent manner without additional "helper" molecules. The discovery of new proteasome inhibitors with little or no toxicity is highly desirable in anticancer therapy. In this study, the inhibitory effects of MG132 and MG115 on the 20S proteasome were evaluated by CE for the first time. The optimized CE conditions were as follows: fused-silica capillary of 30 cm effective length and 75 microm internal diameter, pressure injection of 0.5 psi for 5 s, 50 mM Hepes buffer (pH 7.6) with 2% dimethyl sulfoxide, constant voltage of 20 kV, and detection wavelength at 340 nm. Also, the new method was used to study the inhibitory effects of 30 novel peptidyl vinyl ester derivatives of MG132. The 50% inhibition concentrations (IC(50) values) of MG132 and MG115 were 40.0 and 84.7 nM, respectively. Two new compounds, XP32 and XP35, showed considerable inhibitory effects on the 20S proteasome. When the concentrations of them were fixed at 172 nM, their inhibition rates were 36.2% and 29.1%, respectively. The results showed that the CE method was powerful, sensitive, and fast and required little sample. It could be employed as one of the reliable drug screening methods for 20S proteasome inhibitors.

Design, synthesis and biological evaluation of tripeptide boronic acid proteasome inhibitors.

A series of tripeptide boronate proteasome inhibitors were designed and synthesized on the basis of our previously built tripeptide aldehyde 3D-QSAR models. All the synthesized compounds were evaluated for their proteasome-inhibitory activities in an isolated 20S rabbit proteasome, and selected compounds were evaluated for their antitumor activities in vitro against four human cancer cell lines. Biological results showed bulky and negative substituents at P(2) position improved the proteasome-inhibitory potency obviously, which completely conformed to the theoretical models, while those at P(3) position thoroughly deviated from the 3D-QSAR model. Most of the screened compounds showed less than 1 nM inhibitory potency and high selectivity against 20S proteasome, of which 7f is the most potent (IC(50)=0.079 nM) and twofold more active than bortezomib (IC(50)=0.161 nM). Cell viability indicated hydrophilic 4-hydroxyphenyl substituent at P(2) or P(3) position was not favorable to the cellular activities. Especially for the two hematologic cancer cell lines, HL-60 and U266, 7f inhibited them at the level of less than 10 nM and was more potent than the control bortezomib. It is being considered a promising new lead to be developed for the treatment of various cancers.

In vitro anticancer property of a novel thalidomide analogue through inhibition of NF-kappaB activation in HL-60 cells.

AIM: To investigate the anticancer property and possible mechanism of action of a novel sugar-substituted thalidomide derivative (STA-35) on HL-60 cells in vitro. METHODS: TNF-alpha-induced NF-kappaB activation was determined using a reporter gene assay. The MTT assay was used to measure cytotoxicity of the compound. The appearance of apoptotic Sub-G1 cells was detected by flow cytometry analysis. PARP cleavage and protein expression of NF-kappaB p65 and its inhibitor IkappaB were viewed by Western blotting. RESULTS: TA-35 (1-20 micromol/L) suppressed TNF-alpha-induced NF-kappaB activation in transfected cells (HEK293/pNiFty-SEAP) in a dose- (1-20 micromol/L) and time-dependent (0-48 h) manner. It was also shown that STA-35 exerted a dose-dependent inhibitory effect on HL-60 cell proliferation with an IC(50) value of 9.05 micromol/L. In addition, STA-35 induced apoptosis in HL-60 cells, as indicated by the appearance of a Sub-G1 peak in the cell cycle distribution, as well as poly ADP-ribose polymerase (PARP) cleavage. Subsequently, both NF-kappaB p65 and its inhibitor IkappaB gradually accumulated in cytoplasmic extracts in a dose- and time-dependent manner, indicating the blockage of NF-kappaB translocation induced by TNF-alpha from the cytoplasm to the nucleus. CONCLUSION: A novel sugar-substituted thalidomide derivative, STA-35, is potent toward HL-60 cells in vitro and induces apoptosis by the suppression of NF-kappaB activation.

Synthesis of 3-N-sugar-substituted-2, 4(1H,3H)-quinazolinedionesas anti-angiogenesis agents.

A series of novel 3-N-sugar-substituted quinazolinediones were synthesizedthrough the cyclization of the intermediate 2-aminobenzamides using triphosgene as the condensing reagent. Their anti-angiogenesis activities were investigated. The compound 3-(2'-aminoglucosyl)-2,4-(1H,3H)-quinazolinedione, (5d) showed good anti-angiogenesis activity.

An orally available small-molecule inhibitor of c-Met, PF-2341066, exhibits cytoreductive antitumor efficacy through antiproliferative and antiangiogenic mechanisms.

The c-Met receptor tyrosine kinase and its ligand, hepatocyte growth factor (HGF), have been implicated in the progression of several human cancers and are attractive therapeutic targets. PF-2341066 was identified as a potent, orally bioavailable, ATP-competitive small-molecule inhibitor of the catalytic activity of c-Met kinase. PF-2341066 was selective for c-Met (and anaplastic lymphoma kinase) compared with a panel of >120 diverse tyrosine and serine-threonine kinases. PF-2341066 potently inhibited c-Met phosphorylation and c-Met-dependent proliferation, migration, or invasion of human tumor cells in vitro (IC(50) values, 5-20 nmol/L). In addition, PF-2341066 potently inhibited HGF-stimulated endothelial cell survival or invasion and serum-stimulated tubulogenesis in vitro, suggesting that this agent also exhibits antiangiogenic properties. PF-2341066 showed efficacy at well-tolerated doses, including marked cytoreductive antitumor activity, in several tumor models that expressed activated c-Met. The antitumor efficacy of PF-2341066 was dose dependent and showed a strong correlation to inhibition of c-Met phosphorylation in vivo. Near-maximal inhibition of c-Met activity for the full dosing interval was necessary to maximize the efficacy of PF-2341066. Additional mechanism-of-action studies showed dose-dependent inhibition of c-Met-dependent signal transduction, tumor cell proliferation (Ki67), induction of apoptosis (caspase-3), and reduction of microvessel density (CD31). These results indicated that the antitumor activity of PF-2341066 may be mediated by direct effects on tumor cell growth or survival as well as antiangiogenic mechanisms. Collectively, these results show the therapeutic potential of targeting c-Met with selective small-molecule inhibitors for the treatment of human cancers.