Phase I study of ombrabulin in combination with paclitaxel and carboplatin in Japanese patients with advanced solid tumors

OBJECTIVES

To evaluate the maximum tolerated dose/maximum administered dose, safety, pharmacokinetic, and efficacy profiles of ombrabulin combined with paclitaxel and carboplatin in Japanese patients with solid tumors.

METHODS

Ombrabulin (25, 30, or 35 mg/m2) combined with paclitaxel (175 or 200 mg/m2) and carboplatin (AUC5 or AUC6) was administered by intravenous infusion once every 3 weeks to patients with advanced solid tumors, including cervical, ovarian, and uterine cancers. The maximum tolerated dose/maximum administered dose was defined based on the dose-limiting toxicity at cycle 1. Efficacy was assessed based on Response Evaluation Criteria In Solid Tumors (RECIST).

RESULTS

In total, 18 patients were recruited for this dose escalation study. One out of six patients treated with the highest doses of combination of ombrabulin (35 mg/m2), paclitaxel (200 mg/m2), and carboplatin (AUC6) presented a dose-limiting toxicity consisting of grade 3 Escherichia urinary tract infection. This dose was defined as the maximum tolerated dose of ombrabulin. The most frequent treatment-emergent adverse events were alopecia (83.3%), neutropenia and fatigue (72.2% each), decreased appetite, nausea, diarrhea, arthralgia, and myalgia (66.7% each). The grade 3-4 treatment-emergent adverse events included neutropenia (61.1%), Escherichia urinary tract infection, drug hypersensitivity, syncope, pulmonary embolism, and hydronephrosis (one patient each). In efficacy evaluation, seven patients achieved partial response or better (38.9%), including one complete response, and seven of 18 patients had stable disease (38.9%). Pharmacokinetic profiles in this Japanese study were comparable with those observed in the previous study without Japanese patients.

CONCLUSIONS

Although the maximum tolerated dose/maximum administered dose of ombrabulin (35 mg/m2) with taxane-platinum combination may be tolerable in Japanese patients in the first cycle, the dosages in the repeated treatment should be carefully selected for further study.

TRIAL REGISTRATION NUMBER

NCT01293630.

Racemization of the substrate and product by serine palmitoyltransferase from Sphingobacterium multivorum yields two enantiomers of the product from d-serine

Serine palmitoyltransferase (SPT) catalyzes the pyridoxal-5'-phosphate (PLP)-dependent decarboxylative condensation of l-serine and palmitoyl-CoA to form 3-ketodihydrosphingosine (KDS). Although SPT was shown to synthesize corresponding products from amino acids other than l-serine, it is still arguable whether SPT catalyzes the reaction with d-serine, which is a question of biological importance. Using high substrate and enzyme concentrations, KDS was detected after the incubation of SPT from Sphingobacterium multivorum with d-serine and palmitoyl-CoA. Furthermore, the KDS comprised equal amounts of 2S and 2R isomers. 1H-NMR study showed a slow hydrogen-deuterium exchange at Cα of serine mediated by SPT. We further confirmed that SPT catalyzed the racemization of serine. The rate of the KDS formation from d-serine was comparable to those for the α-hydrogen exchange and the racemization reaction. The structure of the d-serine-soaked crystal (1.65 Å resolution) showed a distinct electron density of the PLP-l-serine aldimine, interpreted as the racemized product trapped in the active site. The structure of the α-methyl-d-serine-soaked crystal (1.70 Å resolution) showed the PLP-α-methyl-d-serine aldimine, mimicking the d-serine-SPT complex prior to racemization. Based on these enzymological and structural analyses, the synthesis of KDS from d-serine was explained as the result of the slow racemization to l-serine, followed by the reaction with palmitoyl-CoA, and SPT would not catalyze the direct condensation between d-serine and palmitoyl-CoA. It was also shown that the S. multivorum SPT catalyzed the racemization of the product KDS, which would explain the presence of (2R)-KDS in the reaction products.

Synthesis of 3-Phenylserine by a Two-enzyme Cascade System with PLP Cofactor

A two-enzyme cascade system containing ω-transaminase (ω-TA) and L-threonine aldolase (L-ThA) was reported for the synthesis of 3-Phenylserine starting from benzylamine, and PLP was utilized as the only cofactor in these both two enzymes reaction system. Based on the transamination results, benzylamine was optimized as an advantageous amino donor as confirmed by MD simulation results. This cascade reaction system could not only facilitate the in situ removal of the co-product benzaldehyde, enhancing the economic viability of the reaction, but also establish a novel pathway for synthesizing high-value phenyl-serine derivatives. In our study, nearly 95 % of benzylamine was converted, yielding over 54 % of 3-Phenylserine under the optimized conditions cascade reaction.

Active O-acetylserine-(thiol) lyase A and B confer improved selenium resistance and degrade l-Cys and l-SeCys in Arabidopsis

The roles of cytosolic O-acetylserine-(thiol)-lyase A (OASTLA), chloroplastic OASTLB, and mitochondrial OASTLC in plant selenate resistance were studied in Arabidopsis. Impairment in OASTLA and OASTLB resulted in reduced biomass, chlorophyll and soluble protein content compared with selenate-treated OASTLC-impaired and wild-type plants. The generally lower total selenium (Se), protein-Se, organic-sulfur and protein-sulfur (S) content in oastlA and oastlB compared with wild-type and oastlC leaves indicated that Se accumulation was not the main cause for the stress symptoms in these mutants. Notably, the application of selenate positively induced S-starvation markers and the OASTLs, followed by increased sulfite reductase, sulfite oxidase activities, and increased sulfite and sulfide concentrations. Taken together, our results indicate a futile anabolic S-starvation response that resulted in lower glutathione and increased oxidative stress symptoms in oastlA and oastlB mutants. In-gel assays of l-cysteine and l-seleno-cysteine, desulfhydrase activities revealed that two of the three OASTL activity bands in each of the oastl single mutants were enhanced in response to selenate, whereas the impaired proteins exhibited a missing activity band. The absence of differently migrated activity bands in each of the three oastl mutants indicates that these OASTLs are major components of desulfhydrase activity, degrading l-cysteine and l-seleno-cysteine in Arabidopsis.

Seriniquinones as Therapeutic Leads for Treatment of BRAF and NRAS Mutant Melanomas

Isolated from the marine bacteria Serinicoccus sp., seriniquinone (SQ1) has been characterized by its selective activity in melanoma cell lines marked by its modulation of human dermcidin and induction of autophagy and apoptosis. While an active lead, the lack of solubility of SQ1 in both organic and aqueous media has complicated its preclinical evaluation. In response, our team turned its effort to explore analogues with the goal of returning synthetically accessible materials with comparable selectivity and activity. The analogue SQ2 showed improved solubility and reached a 30-40-fold greater selectivity for melanoma cells. Here, we report a detailed comparison of the activity of SQ1 and SQ2 in SK-MEL-28 and SK-MEL-147 cell lines, carrying the top melanoma-associated mutations, BRAFV600E and NRASQ61R, respectively. These studies provide a definitive report on the activity, viability, clonogenicity, dermcidin expression, autophagy, and apoptosis induction following exposure to SQ1 or SQ2. Overall, these studies showed that SQ1 and SQ2 demonstrated comparable activity and modulation of dermcidin expression. These studies are further supported through the evaluation of a panel of basal expression of key-genes related to autophagy and apoptosis, providing further insight into the role of these mutations. To explore this rather as a survival or death mechanism, autophagy inhibition sensibilized BRAF mutants to SQ1 and SQ2, whereas the opposite happened to NRAS mutants. These data suggest that the seriniquinones remain active, independently of the melanoma mutation, and suggest the future combination of their application with inhibitors of autophagy to treat BRAF-mutated tumors.

Catalytic specificity of the Lactobacillus plantarum cystathionine γ-lyase presumed by the crystallographic analysis

The reverse transsulfuration pathway, which is composed of cystathionine β-synthase (CBS) and cystathionine γ-lyase (CGL), plays a role to synthesize L-cysteine using L-serine and the sulfur atom in L-methionine. A plant-derived lactic acid bacterium Lactobacillus plantarum SN35N has been previously found to harbor the gene cluster encoding the CBS- and CGL-like enzymes. In addition, it has been demonstrated that the L. plantarum CBS can synthesize cystathionine from O-acetyl-L-serine and L-homocysteine. The aim of this study is to characterize the enzymatic functions of the L. plantarum CGL. We have found that the enzyme has the high γ-lyase activity toward cystathionine to generate L-cysteine, together with the β-lyase activity toward L-cystine to generate L-cysteine persulfide. By the crystallographic analysis of the inactive CGL K194A mutant complexed with cystathionine, we have found the residues which recognize the distal amino and carboxyl groups of cystathionine or L-cystine. The PLP-bound substrates at the active site may take either the binding pose for the γ- or β-elimination reaction, with the former being the major reaction in the case of cystathionine.

Potential combinations of endocannabinoid/endocannabinoid-like compounds and antibiotics against methicillin-resistant Staphylococcus aureus

Infections caused by antibiotic-resistant strains of Staphylococcus aureus have reached epidemic proportions globally. Our previous study showed antimicrobial effects of anandamide (AEA) and arachidonoyl serine (AraS) against methicillin (MET)-resistant S. aureus (MRSA) strains, proposing the therapeutic potential of these endocannabinoid/endocannabinoid-like (EC/EC-like) agents for the treatment of MRSA. Here, we investigated the potential synergism of combinations of AEA and AraS with different types of antibiotics against MRSA grown under planktonic growth or biofilm formation. The most effective combinations under planktonic conditions were mixtures of AEA and ampicillin (AMP), and of AraS and gentamicin (GEN). The combination with the highest synergy in the biofilm formation against all tested bacterial strains was AEA and MET. Moreover, the combination of AraS and MET synergistically caused default of biofilm formation. Slime production of MRSA was also dramatically impaired by AEA or AraS combined with MET. Our data suggest the novel potential activity of combinations of EC/EC-like agents and antibiotics in the prevention of MRSA biofilm formation.

An efficient enantioselective synthesis of (S)-α-methyl-serine methyl ester hydrochloride via asymmetrically catalyzed amination

We present the synthesis of enantiomerically pure (S)-α-methyl-serine methyl ester hydrochloride from 2-methyl-3-((4-(trifluoromethyl)benzyl)oxy)propanal and di-p-chlorobenzyl azodicarboxylate via asymmetrically catalyzed amination with naphthylalanine derivative catalyst. The application of the organocatalyst of D-3-(1-Naphthyl)-alanine is the key step in the synthesis and ensures the product is obtained with high levels of stereocontrol.

HU-671, a Novel Oleoyl Serine Derivative, Exhibits Enhanced Efficacy in Reversing Ovariectomy-Induced Osteoporosis and Bone Marrow Adiposity

Oleoyl serine (OS), an endogenous fatty acyl amide (FAA) found in bone, has been shown to have an anti-osteoporotic effect. OS, being an amide, can be hydrolyzed in the body by amidases. Hindering its amide bond by introducing adjacent substituents has been demonstrated as a successful method for prolonging its skeletal activity. Here, we tested the therapeutic efficacy of two methylated OS derivatives, oleoyl α-methyl serine (HU-671) and 2-methyl-oleoyl serine (HU-681), in an ovariectomized mouse model for osteoporosis by utilizing combined micro-computed tomography, histomorphometry, and cell culture analyses. Our findings indicate that daily treatment for 6 weeks with OS or HU-671 completely rescues bone loss, whereas HU-681 has only a partial effect. The increased bone density was primarily due to enhanced trabecular thickness and number. Moreover, the most effective dose of HU-671 was 0.5 mg/kg/day, an order of magnitude lower than with OS. The reversal of bone loss resulted from increased bone formation and decreased bone resorption, as well as reversal of bone marrow adiposity. These results were further confirmed by determining the serum levels of osteocalcin and type 1 collagen C-terminal crosslinks, as well as demonstrating the enhanced antiadipogenic effect of HU-671. Taken together, these data suggest that methylation interferes with OS’s metabolism, thus enhancing its effects by extending its availability to its target cells.

Glycine transporter inhibitors: A new avenue for managing neuropathic pain

Interneurons operating with glycine neurotransmitter are involved in the regulation of pain transmission in the dorsal horn of the spinal cord. In addition to interneurons, glycine release also occurs from glial cells neighboring glutamatergic synapses in the spinal cord. Neuronal and glial release of glycine is controlled by glycine transporters (GlyTs). Inhibitors of the two isoforms of GlyTs, the astrocytic type-1 (GlyT-1) and the neuronal type-2 (GlyT-2), decrease pain sensation evoked by injuries of peripheral sensory neurons or inflammation. The function of dorsal horn glycinergic interneurons has been suggested to be reduced in neuropathic pain, which can be reversed by GlyT-2 inhibitors (Org-25543, ALX1393). Several lines of evidence also support that peripheral nerve damage or inflammation may shift glutamatergic neurochemical transmission from N-methyl-D aspartate (NMDA) NR1/NR2A receptor- to NR1/NR2B receptor-mediated events (subunit switch). This pathological overactivation of NR1/NR2B receptors can be reduced by GlyT-1 inhibitors (NFPS, Org-25935), which decrease excessive glycine release from astroglial cells or by selective antagonists of NR2B subunits (ifenprodil, Ro 25-6981). Although several experiments suggest that GlyT inhibitors may represent a novel strategy in the control of neuropathic pain, proving this concept in human beings is hampered by lack of clinically applicable GlyT inhibitors. We also suggest that drugs inhibiting both GlyT-1 and GlyT-2 non-selectively and reversibly, may favorably target neuropathic pain. In this paper we overview inhibitors of the two isoforms of GlyTs as well as the effects of these drugs in experimental models of neuropathic pain. In addition, the possible mechanisms of action of the GlyT inhibitors, i.e. how they affect the neurochemical and pain transmission in the spinal cord, are also discussed. The growing evidence for the possible therapeutic intervention of neuropathic pain by GlyT inhibitors further urges development of drugable compounds, which may beneficially restore impaired pain transmission in various neuropathic conditions.

Differences of Cd uptake and expression of OAS and IRT genes in two varieties of ryegrasses

Pot experiment was conducted to study the difference of cadmium uptake and OAS and IRT genes' expression between the two ryegrass varieties under cadmium stress. The results showed that with the increase of cadmium levels, the dry weights of roots of the two ryegrass varieties, and the dry weights of shoots and plants of Abbott first increased and then decreased. When exposed to 75 mg kg^-1 Cd, the dry weights of shoot and plant of Abbott reached the maximum, which increased by 11.13 and 10.67% compared with the control. At 75 mg kg^-1 Cd, cadmium concentrations in shoot of the two ryegrass varieties were higher than the critical value of Cd hyperaccumulator (100 mg kg^-1), 111.19 mg kg^-1 (Bond), and 133.69 mg kg^-1 (Abbott), respectively. The OAS gene expression in the leaves of the two ryegrass varieties showed a unimodal curve, which was up to the highest at the cadmium level of 150 mg kg^-1, but fell back at high cadmium levels of 300 and 600 mg kg^-1. The OAS gene expression in Bond and Abbott roots showed a bimodal curve. The OAS gene expression in Bond root and Abbott stem mainly showed a unimodal curve. The expression of IRT genes family in the leaves of ryegrass varieties was basically in line with the characteristics of unimodal curve, which was up to the highest at cadmium level of 75 or 150 mg kg^-1, respectively. The IRT expression in the ryegrass stems showed characteristics of bimodal and unimodal curves, while that in the roots was mainly unimodal. The expression of OAS and IRT genes was higher in Bond than that in Abbott due to genotype difference between the two varieties. The expression of OAS and IRT was greater in leaves than that in roots and stems. Ryegrass tolerance to cadmium can be increased by increasing the expression of OAS and IRT genes in roots and stems, and transfer of cadmium from roots and stems to the leaves can be enhanced by increasing expression OAS and IRT in leaves.

Glyphosate induces the synthesis of ppGpp

Glyphosate, the most widely used herbicide in both agricultural and urban areas is toxic for plants and for many bacterial species. The mechanism of action of glyphosate is through the inhibition of the EPSP synthase, a key enzyme in the biosynthetic pathway of aromatic amino acids. Here we show that glyphosate induces the stringent response in Escherichia coli. Bacteria treated with glyphosate stop growing and accumulate ppGpp. Both growth arrest and ppGpp accumulation are restored to normal levels upon addition of aromatic amino acids. Glyphosate-induced ppGpp accumulation is dependent on the presence of the (p)ppGpp synthetase RelA. However, unlike other cases of amino acid starvation, pppGpp could not be discerned. In a gppA background both ppGpp and pppGpp accumulated when exposed to glyphosate. Conversely, the wild-type strain and gppA mutant treated with serine hydroxamate accumulated high levels of both ppGpp and pppGpp. Altogether, the data indicate that glyphosate induces amino acid starvation resulting in a moderate accumulation of ppGpp and a reversible stringent response.

Rigid Peptide Macrocycles from On-Resin Glaser Stapling

Peptide macrocycles are widely utilized in the development of high affinity ligands, including stapled α-helices. The linear rigidity of a 1,3-diynyl linkage provides an optimal distance (7 Å) between β-carbons of the i,i+4 amino acid side chains, thus suggesting its utility in stabilizing α-helical structures. Here, we report the development of an on-resin strategy for an intramolecular Glaser reaction between two alkyne-terminated side chains by using copper chloride, an essential bpy-diol ligand, and diisopropylethylamine at room temperature. The efficiency of this ligation was illustrated by the synthesis of (i,i+4)-, (i,i+5)-, (i,i+6)-, and (i,i+7)-stapled BCL-9 α-helical peptides using the unnatural amino acid propargyl serine. Overall, this procedurally simple method relies on inexpensive and widely available reagents to generate low molecular weight 23-, 26-, 29-, and 32-membered peptide macrocycles.

Cysteine Biosynthesis Controls Serratia marcescens Phospholipase Activity

Serratia marcescens causes health care-associated opportunistic infections that can be difficult to treat due to a high incidence of antibiotic resistance. One of the many secreted proteins of S. marcescens is the PhlA phospholipase enzyme. Genes involved in the production and secretion of PhlA were identified by screening a transposon insertion library for phospholipase-deficient mutants on phosphatidylcholine-containing medium. Mutations were identified in four genes (cyaA, crp, fliJ, and fliP) that are involved in the flagellum-dependent PhlA secretion pathway. An additional phospholipase-deficient isolate harbored a transposon insertion in the cysE gene encoding a predicted serine O-acetyltransferase required for cysteine biosynthesis. The cysE requirement for extracellular phospholipase activity was confirmed using a fluorogenic phospholipase substrate. Phospholipase activity was restored to the cysE mutant by the addition of exogenous l-cysteine or O-acetylserine to the culture medium and by genetic complementation. Additionally, phlA transcript levels were decreased 6-fold in bacteria lacking cysE and were restored with added cysteine, indicating a role for cysteine-dependent transcriptional regulation of S. marcescens phospholipase activity. S. marcescenscysE mutants also exhibited a defect in swarming motility that was correlated with reduced levels of flhD and fliA flagellar regulator gene transcription. Together, these findings suggest a model in which cysteine is required for the regulation of both extracellular phospholipase activity and surface motility in S. marcescensIMPORTANCESerratia marcescens is known to secrete multiple extracellular enzymes, but PhlA is unusual in that this protein is thought to be exported by the flagellar transport apparatus. In this study, we demonstrate that both extracellular phospholipase activity and flagellar function are dependent on the cysteine biosynthesis pathway. Furthermore, a disruption of cysteine biosynthesis results in decreased phlA and flagellar gene transcription, which can be restored by supplying bacteria with exogenous cysteine. These results identify a previously unrecognized role for CysE and cysteine in the secretion of S. marcescens phospholipase and in bacterial motility.

Spontaneous Vesiculation and pH-Induced Disassembly of a Lysosomotropic Detergent: Impacts on Lysosomotropism and Lysosomal Delivery

Lysosomotropic detergents (LDs) selectively rupture lysosomal membranes through mechanisms that have yet to be characterized. A consensus view, currently, holds that LDs, which are weakly basic, diffuse across cellular membranes as monomers in an uncharged state, and via protonation in the acidic lysosomal compartment, they become trapped, accumulate, and subsequently solubilize the membrane and induce lysosomal membrane permeabilization. Here we demonstrate that the lysosomotropic detergent O-methyl-serine dodecylamide hydrochloride (MSDH) spontaneously assembles into vesicles at, and above, cytosolic pH, and that the vesicles disassemble as the pH reaches 6.4 or lower. The aggregation commences at concentrations below the range of those used in cell studies. Assembly and disassembly of the vesicles was studied via dynamic light scattering, zeta potential measurements, cryo-TEM, and fluorescence correlation spectroscopy and was found to be reversible via control of the pH. Aggregation of MSDH into closed vesicles under cytosolic conditions is at variance with the commonly held view of LD behavior, and we propose that endocytotic pathways should be considered as possible routes of LD entry into lysosomes. We further demonstrate that MSDH vesicles can be loaded with fluorophores via a solution transition from low to high pH, for subsequent release when the pH is lowered again. The ability to encapsulate molecular cargo into MSDH vesicles together with its ability to disaggregate at low pH and to permeabilize the lysosomal membrane presents an intriguing possibility to use MSDH as a delivery system.

Design and synthesis of a series of serine derivatives as small molecule inhibitors of the SARS coronavirus 3CL protease

Synthesis of serine derivatives having the essential functional groups for the inhibitor of SARS 3CL protease and evaluation of their inhibitory activities using SARS 3CL R188I mutant protease are described. The lead compounds, functionalized serine derivatives, were designed based on the tetrapeptide aldehyde and Bai's cinnamoly inhibitor, and additionally performed with simulation on GOLD softwear. Structure activity relationship studies of the candidate compounds were given reasonable inhibitors ent-3 and ent-7k against SARS 3CL R188I mutant protease. These inhibitors showed protease selectivity and no cytotoxicity.

The crystal structure of D-threonine aldolase from Alcaligenes xylosoxidans provides insight into a metal ion assisted PLP-dependent mechanism

Threonine aldolases catalyze the pyridoxal phosphate (PLP) dependent cleavage of threonine into glycine and acetaldehyde and play a major role in the degradation of this amino acid. In nature, L- as well as D-specific enzymes have been identified, but the exact physiological function of D-threonine aldolases (DTAs) is still largely unknown. Both types of enantio-complementary enzymes have a considerable potential in biocatalysis for the stereospecific synthesis of various β-hydroxy amino acids, which are valuable building blocks for the production of pharmaceuticals. While several structures of L-threonine aldolases (LTAs) have already been determined, no structure of a DTA is available to date. Here, we report on the determination of the crystal structure of the DTA from Alcaligenes xylosoxidans (AxDTA) at 1.5 Å resolution. Our results underline the close relationship of DTAs and alanine racemases and allow the identification of a metal binding site close to the PLP-cofactor in the active site of the enzyme which is consistent with the previous observation that divalent cations are essential for DTA activity. Modeling of AxDTA substrate complexes provides a rationale for this metal dependence and indicates that binding of the β-hydroxy group of the substrate to the metal ion very likely activates this group and facilitates its deprotonation by His193. An equivalent involvement of a metal ion has been implicated in the mechanism of a serine dehydratase, which harbors a metal ion binding site in the vicinity of the PLP cofactor at the same position as in DTA. The structure of AxDTA is completely different to available structures of LTAs. The enantio-complementarity of DTAs and LTAs can be explained by an approximate mirror symmetry of crucial active site residues relative to the PLP-cofactor.

Asymmetric organocatalytic synthesis of quaternary α-hydroxy phosphonates: en route to α-aryl phosphaisoserines

The dual activation of acyl phosphonates and formaldehyde tert-butyl hydrazone by a BINAM-derived bis-urea catalyst is the key to achieve high reactivities and enantioselectivities in the synthesis of densely functionalized quaternary α-hydroxy phosphonates. Subsequent high-yielding transformations in a 'one-pot' fashion provide direct access to valuable azoxy compounds and quaternary α-aryl-phosphaisoserines.

L-Cysteine inhibits root elongation through auxin/PLETHORA and SCR/SHR pathway in Arabidopsis thaliana

L-Cysteine plays a prominent role in sulfur metabolism of plants. However, its role in root development is largely unknown. Here, we report that L-cysteine reduces primary root growth in a dosage-dependent manner. Elevating cellular L-cysteine level by exposing Arabidopsis thaliana seedlings to high L-cysteine, buthionine sulphoximine, or O-acetylserine leads to altered auxin maximum in root tips, the expression of quiescent center cell marker as well as the decrease of the auxin carriers PIN1, PIN2, PIN3, and PIN7 of primary roots. We also show that high L-cysteine significantly reduces the protein level of two sets of stem cell specific transcription factors PLETHORA1/2 and SCR/SHR. However, L-cysteine does not downregulate the transcript level of PINs, PLTs, or SCR/SHR, suggesting that an uncharacterized post-transcriptional mechanism may regulate the accumulation of PIN, PLT, and SCR/SHR proteins and auxin transport in the root tips. These results suggest that endogenous L-cysteine level acts to maintain root stem cell niche by regulating basal- and auxin-induced expression of PLT1/2 and SCR/SHR. L-Cysteine may serve as a link between sulfate assimilation and auxin in regulating root growth.

Antinociceptive effect of intracerebroventricular administration of glycine transporter-2 inhibitor ALX1393 in rat models of inflammatory and neuropathic pain

Glycinergic transmission has an important role in regulating nociception in the spinal cord. The glycine transporter-2 (GlyT2) is localized at presynaptic terminals of glycinergic neurons and eliminates glycine from the synaptic cleft to terminate glycinergic transmission. Systemic and intrathecal administration of GlyT2 inhibitors alleviate various types of pain. Although the GlyT2s and glycine receptors are widely distributed in the central nervous system, little is known about the role of glycinergic transmission in pain perception at supraspinal regions. The present study examined the antinociceptive effect of intracerebroventricular (i.c.v.) administration of the selective GlyT2 inhibitor ALX1393 on inflammatory and neuropathic pain in experimental models. For i.c.v. administration, a guide cannula was implanted into the right lateral ventricle of male Sprague-Dawley rats. Normal rats were used to assess inflammatory nociception using the formalin test and motor function using the rotarod test. Chronic constriction injury (CCI) to the sciatic nerve was induced in the rats. The CCI rats were then used to assess mechanical, cold, and thermal hyperalgesia using the electronic von Frey test, cold plate test, and the plantar test, respectively. ALX1393 (25, 50, and 100 μg) was administered i.c.v. to examine its effects on supraspinal antinociception. Supraspinal ALX1393 in normal rats suppressed the late-phase response in the formalin test but did not affect motor performance. In the CCI rats, ALX1393 inhibited mechanical and cold hyperalgesia in a dose-dependent manner. The antihyperalgesic effects of ALX1393 (100 μg) were reversed completely by i.c.v. pretreatment with a glycine receptor antagonist strychnine (10 μg). These results suggest that GlyT2 contributes to nociceptive transmission at supraspinal level and that the selective GlyT2 inhibitor is a promising candidate for the treatment of inflammatory and neuropathic pain without causing motor dysfunction.

Copper(II)-mediated O-arylation of protected serines and threonines

An effective protocol toward the O-arylation of β-hydroxy-α-amino acid substrates serine and threonine has been developed via Chan-Lam cross-coupling. This Cu(II)-catalyzed transformation involves benign open-flask conditions that are well-tolerated with a variety of protected (Boc-, Cbz-, Tr-, and Fmoc-) serine and threonine derivatives and various potassium organotrifluoroborates and boronic acids.

N-Acyl amino acids and their impact on biological processes

Over the last two decades a large number of N-long-chain acyl amino acids have been identified in the mammalian body. The pharmacological activities of only a few of them have been investigated and some have been found to be of considerable interest. Thus arachidonoyl serine is vasodilatory and neuroprotective, arachidonoyl glycine is antinociceptive, and oleoyl serine rescues bone loss. However, the pathophysiological/biochemical roles of these amides are mostly unknown.

Novel cysteine-centered sulfur metabolic pathway in the thermotolerant methylotrophic yeast Hansenula polymorpha

In yeast and filamentous fungi, sulfide can be condensed either with O-acetylhomoserine to generate homocysteine, the precursor of methionine, or with O-acetylserine to directly generate cysteine. The resulting homocysteine and cysteine can be interconverted through transsulfuration pathway. Here, we systematically analyzed the sulfur metabolic pathway of the thermotolerant methylotrophic yeast Hansenula polymorpha, which has attracted much attention as an industrial yeast strain for various biotechnological applications. Quite interestingly, the detailed sulfur metabolic pathway of H. polymorpha, which was reconstructed based on combined analyses of the genome sequences and validation by systematic gene deletion experiments, revealed the absence of de novo synthesis of homocysteine from inorganic sulfur in this yeast. Thus, the direct biosynthesis of cysteine from sulfide is the only pathway of synthesizing sulfur amino acids from inorganic sulfur in H. polymorpha, despite the presence of both directions of transsulfuration pathway Moreover, only cysteine, but no other sulfur amino acid, was able to repress the expression of a subset of sulfur genes, suggesting its central and exclusive role in the control of H. polymorpha sulfur metabolism. 35S-Cys was more efficiently incorporated into intracellular sulfur compounds such as glutathione than 35S-Met in H. polymorpha, further supporting the cysteine-centered sulfur pathway. This is the first report on the novel features of H. polymorpha sulfur metabolic pathway, which are noticeably distinct from those of other yeast and filamentous fungal species.

An open-label, dose-escalation, safety, and pharmacokinetics phase I study of ombrabulin, a vascular disrupting agent, administered as a 30-min intravenous infusion every 3 weeks in Japanese patients with advanced solid tumors

PURPOSE

To determine ombrabulin's maximum tolerated dose and dose recommended for Japanese patients with advanced solid tumors and to assess its antitumor activity and overall safety and pharmacokinetic profiles.

METHODS

This was a multi-center, open-label, sequential-cohort, dose-escalation phase I study of ombrabulin, a vascular disrupting agent, administered once every 3 weeks. Patients were treated with 15.5, 25, 35, or 50 mg/m(2) ombrabulin over a 30-min intravenous infusion. The recommended dose was the highest dose at which <33 % of all evaluable patients experienced dose-limiting toxicities (DLTs) during the first treatment cycle or 50 mg/m(2) (recommended in Caucasian patients) if the previous definition was not met.

RESULTS

Fifteen patients were treated. No DLT occurred with 15.5, 25, or 35 mg/m(2) ombrabulin. In the 50 mg/m(2) group, one patient had Grade 3 lymphopenia, and another experienced Grade 2 hypertension and Grade 3 diarrhea judged as DLTs. The most frequent related adverse events in this group were diarrhea, nausea, and hypertension. Two patients had Grade 3 anemia, one at the 15.5 mg/m(2) and the other at the 50 mg/m(2). No AEs necessitating dose reduction or Grade 4 AEs were observed. Overall, five patients had stable disease. Pharmacokinetic parameters were comparable to those in non-Japanese patients.

CONCLUSIONS

Ombrabulin treatment once every 3 weeks was well tolerated in Japanese patients with advanced solid tumors. The dose recommended is 50 mg/m(2), as in Caucasian patients. The safety and pharmacokinetic profiles were comparable between Japanese and Caucasian patients (funded by Sanofi; ClinicalTrials.gov number, NCT00968916).

Biochemical properties of nematode O-acetylserine(thiol)lyase paralogs imply their distinct roles in hydrogen sulfide homeostasis

O-Acetylserine(thiol)lyases (OAS-TLs) play a pivotal role in a sulfur assimilation pathway incorporating sulfide into amino acids in microorganisms and plants, however, these enzymes have not been found in the animal kingdom. Interestingly, the genome of the roundworm Caenorhabditis elegans contains three expressed genes predicted to encode OAS-TL orthologs (cysl-1-cysl-3), and a related pseudogene (cysl-4); these genes play different roles in resistance to hypoxia, hydrogen sulfide and cyanide. To get an insight into the underlying molecular mechanisms we purified the three recombinant worm OAS-TL proteins, and we determined their enzymatic activities, substrate binding affinities, quaternary structures and the conformations of their active site shapes. We show that the nematode OAS-TL orthologs can bind O-acetylserine and catalyze the canonical reaction although this ligand may more likely serve as a competitive inhibitor to natural substrates instead of being a substrate for sulfur assimilation. In addition, we propose that S-sulfocysteine may be a novel endogenous substrate for these proteins. However, we observed that the three OAS-TL proteins are conformationally different and exhibit distinct substrate specificity. Based on the available evidences we propose the following model: CYSL-1 interacts with EGL-9 and activates HIF-1 that upregulates expression of genes detoxifying sulfide and cyanide, the CYSL-2 acts as a cyanoalanine synthase in the cyanide detoxification pathway and simultaneously produces hydrogen sulfide, while the role of CYSL-3 remains unclear although it exhibits sulfhydrylase activity in vitro. All these data indicate that C. elegans OAS-TL paralogs have distinct cellular functions and may play different roles in maintaining hydrogen sulfide homeostasis.

Cyclopeptide alkaloids: stereochemistry and synthesis of the precursors of discarines C and D and myrianthine A

The stereochemistry of discarines C (1) and D (2) and myrianthine A (3), three cyclopeptide alkaloids isolated from Discaria febrifuga, was determined by a combination of NMR studies of 1-3, enantioselective gas chromatography, and comparison of NMR data with those of synthetic tripeptides. For the synthesis of peptides, the nonproteinogenic amino acid 3-phenylserine was also obtained in its four diastereoisomeric forms (l and d threo, obtained by recrystallization of the diastereoisomeric tripeptide, and l and d erythro, obtained by a Mitsunobu reaction with the threo-tripeptides). The general synthetic strategy described in this paper allows the tripeptide to be obtained with the free N-terminal extremity protected or dimethylated. This strategy also allows the synthesis of the corresponding peptide with an imidazolidinone ring.

Direct targeting of Arabidopsis cysteine synthase complexes with synthetic polypeptides to selectively deregulate cysteine synthesis

Biosynthesis of cysteine is one of the fundamental processes in plants providing the reduced sulfur for cell metabolism. It is accomplished by the sequential action of two enzymes, serine acetyltransferase (SAT) and O-acetylserine (thiol) lyase (OAS-TL). Together they constitute the hetero-oligomeric cysteine synthase (CS) complex through specific protein-protein interactions influencing the rate of cysteine production. The aim of our studies was to deregulate the CS complex formation in order to investigate its function in the control of sulfur homeostasis and optimize cysteine synthesis. Computational modeling was used to build a model of the Arabidopsis thaliana mitochondrial CS complex. Several polypeptides based on OAS-TL C amino-acid sequence found at SAT-OASTL interaction sites were designed as probable competitors for SAT3 binding. After verification of the binding in a yeast two-hybrid assay, the most strongly interacting polypeptide was introduced to different cellular compartments of Arabidopsis cell via genetic transformation. Moderate increase in total SAT and OAS-TL activities, but not thiols content, was observed dependent on the transgenic line and sulfur availability in the hydroponic medium. Though our studies demonstrate the proof of principle, they also suggest more complex interaction of both enzymes underlying the mechanism of their reciprocal regulation.

D-Serine facilitates the effectiveness of extinction to reduce drug-primed reinstatement of cocaine-induced conditioned place preference

Addiction is a disease that is characterized by compulsive drug-seeking and use despite negative health and social consequences. One obstacle in treating addiction is a high susceptibility for relapse which persists despite prolonged periods of abstinence. Relapse can be triggered by drug predictive stimuli such as environmental context and drug associated cues, as well as the addictive drug itself. The conditioned place preference (CPP) behavioral model is a useful paradigm for studying the ability of these drug predictive stimuli to reinstate drug-seeking behavior. The present study investigated the dose-dependent effects of D-serine (10 mg/kg, 30 mg/kg and 100 mg/kg) on extinction training and drug-primed reinstatement in cocaine-conditioned rats. In the first experiment, D-serine had no effect on the acquisition or development of cocaine-induced locomotor sensitization or CPP. In the second experiment, D-serine treatment resulted in significantly decreased time spent in the drug-paired compartment following completion of an extinction protocol. A cocaine-primed reinstatement test indicated that the combination of extinction training along with D-serine treatment resulted in a significant reduction of drug-seeking behavior. The third experiment assessed D-serine's long-term effects to diminish drug-primed reinstatement. D-serine treatment given during extinction was effective in reducing drug-seeking for more than four weeks of abstinence after the last cocaine exposure. These findings demonstrate that D-serine may be an effective adjunct therapeutic agent along with cognitive behavioral therapy for the treatment of cocaine addiction. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Local and systemic regulation of sulfur homeostasis in roots of Arabidopsis thaliana

Nutrients are limiting for plant growth and vigour. Hence, nutrient uptake and homeostasis must be adjusted to the needs of the plant according to developmental stages and environmental conditions. A split-root system was applied to analyse the systemic and local response of Arabidopsis thaliana to sulfur starvation. Arabidopsis thaliana plants in which only one root half was starved while the other root half was supplied with sulfate were analysed at the metabolic and transcriptional level. No systemic induction of sulfate uptake or expression of sulfate starvation marker genes was observed in split-roots sufficiently supplied with sulfate. Our data suggest that no activation of sulfur uptake takes part in sulfur-supplied root patches when the general sulfur status declines. When comparing roots of fully sulfate-starved plants with sulfate-starved split-root roots, expression of several potentially OAS responsive genes was attenuated in split-roots depending on the shoot sulfate status and the local root O-acetylserine concentration. In contrast, high-affinity sulfate transporters displayed similar expression in sulphate-starved split-roots and the corresponding controls. Feeding of (35) SO(4) (2-) to the shoot or to either part of a split-root system revealed that sulfate is the most prominent mobile sulfur-containing compound within the plant. Hence, we postulate a model whereby the soil sulfate availability regulates the sulfate uptake system of roots while the shoot sulfur status modulates the local O-acetylserine response in the root by passive 'plant sulfur status-dependent' transport of sulfate.

Transcripts of sulphur metabolic genes are co-ordinately regulated in developing seeds of common bean lacking phaseolin and major lectins

The lack of phaseolin and phytohaemagglutinin in common bean (dry bean, Phaseolus vulgaris) is associated with an increase in total cysteine and methionine concentrations by 70% and 10%, respectively, mainly at the expense of an abundant non-protein amino acid, S-methyl-cysteine. Transcripts were profiled between two genetically related lines differing for this trait at four stages of seed development using a high density microarray designed for common bean. Transcripts of multiple sulphur-rich proteins were elevated, several previously identified by proteomics, including legumin, basic 7S globulin, albumin-2, defensin, albumin-1, the Bowman-Birk type proteinase inhibitor, the double-headed trypsin inhibitor, and the Kunitz trypsin inhibitor. A co-ordinated regulation of transcripts coding for sulphate transporters, sulphate assimilatory enzymes, serine acetyltransferases, cystathionine β-lyase, homocysteine S-methyltransferase and methionine gamma-lyase was associated with changes in cysteine and methionine concentrations. Differential gene expression of sulphur-rich proteins preceded that of sulphur metabolic enzymes, suggesting a regulation by demand from the protein sink. Up-regulation of SERAT1;1 and -1;2 expression revealed an activation of cytosolic O-acetylserine biosynthesis. Down-regulation of SERAT2;1 suggested that cysteine and S-methyl-cysteine biosynthesis may be spatially separated in different subcellular compartments. Analysis of free amino acid profiles indicated that enhanced cysteine biosynthesis was correlated with a depletion of O-acetylserine. These results contribute to our understanding of the regulation of sulphur metabolism in developing seed in response to a change in the composition of endogenous proteins.

A novel in-gel assay and an improved kinetic assay for determining in vitro sulfite reductase activity in plants

Sulfite reductase (SiR; EC 1.8.7.1), an essential enzyme in the sulfate reduction pathway, catalyzes the reduction of sulfite to sulfide, as an intermediate for cysteine biosynthesis. The commonly used kinetic assay for the detection of in vitro SiR activity in plants is based on a coupled reaction, in which the sulfide produced is converted to cysteine through the presence, in the assay medium, of O-acetylserine sulfhydralase (EC 2.5.1.47) and its substrate, O-acetylserine. An improved kinetic assay for SiR activity in crude desalted protein extracts was developed. The improvement was based on pre-treatment of the protein with tungstate, which improved SiR activity in Arabidopsis and tomato leaf by 29 and 12%, respectively, and the addition of NADPH to the reaction medium, which increased SiR activity by 1.6- and 2.8-fold in Arabidopsis and tomato, respectively, in comparison with the current protocols. Despite the availability and reliability of the kinetic assay, there is currently no assay that enables the direct detection of SiR in relatively large numbers of samples. To meet this need, we developed a novel in-gel assay to detect SiR activity in crude extracts. The method is based on the detection of a brownish-black precipitated band of lead sulfide, formed by the reaction of lead acetate with sulfide. The in-gel assay for SiR activity is reliable, sensitive and technically simpler than the kinetic assay, and opens up the possibility for detecting active SiR isoenzymes and splice variants.

The vascular disrupting agent ombrabulin (AVE8062) enhances the efficacy of standard therapies in head and neck squamous cell carcinoma xenograft models

Targeting tumor vasculature is an emerging strategy in cancer treatment. Promising results have been shown in preclinical studies when vascular disrupting agents (VDAs) are used in combination with other anticancer therapies. Because radiation therapy with concurrent cisplatin or cetuximab has become standard treatment for patients with locally advanced head and neck squamous cell carcinoma (HNSCC), we investigated whether the VDA ombrabulin (AVE8062) could improve the antitumor activity of radiation plus cisplatin and radiation plus cetuximab combinations. HNSCC HEP2 or FaDu tumor bearing mice were treated with ombrabulin, cisplatin, cetuximab, local radiation therapy or combinations of these treatments. Ombrabulin attenuated tumor growth of HEP2 and FaDu xenografts compared to control tumors. A more pronounced tumor growth delay and tumor regression were induced when ombrabulin was added to local irradiation, cisplatin or cetuximab in FaDu tumors compared to single agent treatments. Finally, triple agent therapies combining ombrabulin, irradiation, and either cisplatin or cetuximab were more effective than double combination treatment regimens and increased tumor growth delay in both HEP2 and FaDu tumor models. Of note, complete tumor regression was achieved in FaDu tumor model for the triple combination including platinum. Immunohistochemistry on FaDu tumors demonstrated a specificity of ombrabulin towards intratumoral vessels, in contrast to peritumoral vasculature. Our results provide a rationale for the use of ombrabulin in combination with two standard treatment regimens that are concurrent cisplatin-based chemoradiation and cetuximab plus ionizing radiation therapies, for the treatment of HNSCC.

A convenient route to optically pure α-alkyl-β-(sec-amino)alanines

The cyclization of N-Boc-α-alkylserines to corresponding β-lactones under Mitsunobu reaction conditions and the ring opening with heterocyclic amines (pyrrolidine, piperidine, morpholine and thiomorpholine) produced N-Boc-α-alkyl-β-(sec-amino)alanines. The removal of the Boc group gives di-hydrochlorides of non-protein amino acids.

Additional role of O-acetylserine as a sulfur status-independent regulator during plant growth

O-acetylserine (OAS) is one of the most prominent metabolites whose levels are altered upon sulfur starvation. However, its putative role as a signaling molecule in higher plants is controversial. This paper provides further evidence that OAS is a signaling molecule, based on computational analysis of time-series experiments and on studies of transgenic plants conditionally displaying increased OAS levels. Transcripts whose levels correlated with the transient and specific increase in OAS levels observed in leaves of Arabidopsis thaliana plants 5-10 min after transfer to darkness and with diurnal oscillation of the OAS content, showing a characteristic peak during the night, were identified. Induction of a serine-O-acetyltransferase gene (SERAT) in transgenic A. thaliana plants expressing the genes under the control of an inducible promoter resulted in a specific time-dependent increase in OAS levels. Monitoring the transcriptome response at time points at which no changes in sulfur-related metabolites except OAS were observed and correlating this with the light/dark transition and diurnal experiments resulted in identification of six genes whose expression was highly correlated with that of OAS (adenosine-5'-phosphosulfate reductase 3, sulfur-deficiency-induced 1, sulfur-deficiency-induced 2, low-sulfur-induced 1, serine hydroxymethyltransferase 7 and ChaC-like protein). These data suggest that OAS displays a signalling function leading to changes in transcript levels of a specific gene set irrespective of the sulfur status of the plant. Additionally, a role for OAS in a specific part of the sulfate response can be deduced.

The key enzyme of sulfate assimilation, adenosine 5'-phosphosulfate reductase, is regulated by HY5 in Arabidopsis

Plant sulfate assimilation is regulated by demand for reduced sulfur, as is its key enzyme, adenosine 5'-phosphosulfate reductase (APR). In a genetic screen for mutants lacking this regulation, we identified the bZIP transcription factor LONG HYPOCOTYL 5 (HY5) as a necessary component of the regulatory circuit. Regulation of APR activity by the inhibitor of glutathione synthesis, buthionine sulfoximine, or by the precursor of cysteine, O-acetylserine, was disrupted in the hy5 mutant. When dark-adapted plants were re-illuminated, the rapid induction of APR1 and APR2 mRNA levels was attenuated in hy5 seedlings, but APR3 regulation was not affected. Chromatin immunoprecipitation revealed that HY5 binds directly to the APR1 and APR2 promoters but not to the APR3 promoter. Accordingly, the regulation of APR1 and APR2 by O-acetylserine was disturbed in hy5 roots. HY5 is also important for the coordination of nitrogen and sulfur assimilation, as, unlike the wild-type, hy5 mutants do not undergo a reduction in sulfate uptake and APR activity during nitrogen starvation. Altogether, these data show that HY5 plays an important role in regulation of APR gene expression and plant sulfate assimilation.

Cardiovascular toxicity profiles of vascular-disrupting agents

BACKGROUND

Vascular-disrupting agents (VDAs) represent a new class of chemotherapeutic agent that targets the existing vasculature in solid tumors. Preclinical and early-phase trials have demonstrated the promising therapeutic benefits of VDAs but have also uncovered a distinctive toxicity profile highlighted by cardiovascular events.

METHODS

We reviewed all preclinical and prospective phase I-III clinical trials published up to August 2010 in MEDLINE and the American Association of Cancer Research and American Society of Clinical Oncology meeting abstracts of small-molecule VDAs, including combretastatin A4 phosphate (CA4P), combretastatin A1 phosphate (CA1P), MPC-6827, ZD6126, AVE8062, and ASA404.

RESULTS

Phase I and II studies of CA1P, ASA404, MPC-6827, and CA4P all reported cardiovascular toxicities, with the most common cardiac events being National Cancer Institute Common Toxicity Criteria (version 3) grade 1-3 hypertension, tachyarrhythmias and bradyarrhythmias, atrial fibrillation, and myocardial infarction. Cardiac events were dose-limiting toxicities in phase I trials with VDA monotherapy and combination therapy.

CONCLUSIONS

Early-phase trials of VDAs have revealed a cardiovascular toxicity profile similar to that of their vascular-targeting counterparts, the angiogenesis inhibitors. As these agents are added to the mainstream chemotherapeutic arsenal, careful identification of baseline cardiovascular risk factors would seem to be a prudent strategy. Close collaboration with cardiology colleagues for early indicators of serious cardiac adverse events will likely minimize toxicity while optimizing the therapeutic potential of VDAs and ultimately enhancing patient outcomes.

[Spectral study on the interaction of [Cu(DPPZ)(L-Ser)]+ complex with DNA and its analytical application]

The characteristics of resonance light scattering (RLS), UV-visible absorption spectra and fluorescence spectra of [Cu(DPPZ)(L-Ser)]+ with DNA were studied and a RLS method for the determination of DNA was established. [Cu(DPPZ) (L-Ser)]+ could assemble on the surface of DNA through intercalation, and enhanced the RLS of DNA in the tris buffer of pH 7. 2. The maximum resonance light scattering peak appeared at 400 nm. Under the optimum conditions, the enhanced intensity of RLS was proportional to the concentration of DNA over the range of 0.42 - 4.2 ng x mL(-1), with a detection limit (3sigma/k) of 0.29 ng x mL(-1). The method was used for the determination of DNA samples with the recoveries between 97.8% and 106%.

Contrast ultrasonography: necessity of linear data processing for the quantification of tumor vascularization

PURPOSE

This study is intended to compare the value of uncompressed ultrasonic data, obtained after linear power detection of the ultrasonic radiofrequencies that we call linear data, with usual compressed video data for the quantification of tumor perfusion, particularly for monitoring antivascular therapy.

MATERIALS AND METHODS

To form a clinically useful ultrasonic image, the detected power of the received signals (linear data) is compressed in a quasi-logarithmic fashion in order to match the limited dynamic range of the video monitor. The resulting reduced range of signals from an injected contrast agent may limit the sensitivity to changes in the time-intensity curves. Following a theoretical evaluation of the effects of compression on time-intensity curves and as an in vivo example, we measured at different times the effects of an antivascular drug administered to mice bearing melanoma tumors. The mean time-intensity curves within the tumors after bolus injection of a contrast agent were determined using both linear and video data. Linearized data was recovered using the inverse of the true scanner's compression law, which was experimentally determined. Three features were extracted from the time-intensity curves: peak intensity (PI), time to peak intensity (TPI) and area under the curve in the wash-in phase (AUC (wash-in)). When contrast reached its maximum value, the coefficient of variation reflecting the heterogeneity of the intensity of contrast uptake within the tumor, was computed using both data sets.

RESULTS

TPI was found to be similar with either data set (r = 0.98, p < 0.05, factor of 1.09). Linear PI and AUC (wash-in) had significantly earlier decreases after drug administration than video data (p = 0.015 and p = 0.03, respectively). The coefficient of variation was significantly lower when using video rather than linear data (p < 10 (-4)).

CONCLUSION

In conclusion, the use of linear data is the only mathematically valid methodology for determining a tumor's time-intensity curve and, in practice, it allows earlier demonstration of responses to antivascular drugs.

[Advances in the study of the anti-tumor activity of small molecule vascular disrupting agents]

Vascular disrupting agents (VDAs) have presented a new kind of anti-cancer drug in recent years. VDAs take advantage of the weakness of established tumor endothelial cells and their supporting structures. In contrast to anti-angiogenic therapy, which inhibits the outgrowth of new blood vessels, vascular targeting treatments selectively attack the existing tumor vasculature. Here we summarized the anti-tumor activities, mechanisms and clinical applications of small molecule VDAs.

Overexpression of serine acetlytransferase produced large increases in O-acetylserine and free cysteine in developing seeds of a grain legume

There have been many attempts to increase concentrations of the nutritionally essential sulphur amino acids by modifying their biosynthetic pathway in leaves of transgenic plants. This report describes the first modification of cysteine biosynthesis in developing seeds; those of the grain legume, narrow leaf lupin (Lupinus angustifolius, L.). Expression in developing lupin embryos of a serine acetyltransferase (SAT) from Arabidopsis thaliana (AtSAT1 or AtSerat 2;1) was associated with increases of up to 5-fold in the concentrations of O-acetylserine (OAS), the immediate product of SAT, and up to 26-fold in free cysteine, resulting in some of the highest in vivo concentrations of these metabolites yet reported. Despite the dramatic changes in free cysteine in developing embryos of SAT overexpressers, concentrations of free methionine in developing embryos, and the total cysteine and methionine concentrations in mature seeds were not significantly altered. Pooled F(2) seeds segregating for the SAT transgene and for a transgene encoding a methionine- and cysteine-rich sunflower seed storage protein also had increased OAS and free cysteine, but not free methionine, during development, and no increase in mature seed total sulphur amino acids compared with controls lacking SAT overexpression. The data support the view that the cysteine biosynthetic pathway is active in developing seeds, and indicate that SAT activity limits cysteine biosynthesis, but that cysteine supply is not limiting for methionine biosynthesis or for storage protein synthesis in maturing lupin embryos in conditions of adequate sulphur nutrition. OAS and free methionine, but not free cysteine, were implicated as signalling metabolites controlling expression of a gene for a cysteine-rich seed storage protein.

Total synthesis of (+)-conagenin

A new approach for the synthesis of the (+)-conagenin has been achieved based on Evans asymmetry syn-aldol reaction and the self-regeneration of stereocenters strategy.

A genome-wide and metabolic analysis determined the adaptive response of Arabidopsis cells to folate depletion induced by methotrexate

Control of folate homeostasis is essential to sustain the demand for one-carbon (C1) units that are necessary for major biological functions, including nucleotide synthesis and methylation reactions. In this study, we analyzed the genome-wide and metabolic adaptive response of Arabidopsis (Arabidopsis thaliana) cells to folate depletion induced by the antifolate methotrexate. Drug treatment induced a response typical to xenobiotic stress and important changes in folate content and composition. This resulted in a reduction of cell division and primary energy metabolism that was likely associated with perturbation of nucleotide homeostasis. Through a modification of serine metabolism, folate depletion also induced O-acetylserine accumulation and mimicked sulfur deficiency response. The major adaptive response to folate limitation concerned the composition of the folate pool rather than the intracellular level of cofactors. Thus, no significant change in the expression of genes involved in cofactor synthesis, degradation, or trafficking was observed. However, changes in the distribution of C1 derivative pools and increased expression levels for transcripts coding enzymes manipulating C1 moieties in plastids suggested a reorientation of C1 units toward the synthesis of purine and thymidylate. Also, no genomic or metabolic adaptation was built up to counterbalance the major impairment of the methyl index, which controls the efficiency of methylation reactions in the cell. Together, these data suggested that the metabolic priority of Arabidopsis cells in response to folate limitation was to shuttle the available folate derivatives to the synthesis of nucleotides at the expense of methylation reactions.

Mitochondrial serine acetyltransferase functions as a pacemaker of cysteine synthesis in plant cells

Cysteine (Cys) synthesis in plants is carried out by two sequential reactions catalyzed by the rate-limiting enzyme serine acetyltransferase (SAT) and excess amounts of O-acetylserine(thiol)lyase. Why these reactions occur in plastids, mitochondria, and cytosol of plants remained unclear. Expression of artificial microRNA (amiRNA) against Sat3 encoding mitochondrial SAT3 in transgenic Arabidopsis (Arabidopsis thaliana) plants demonstrates that mitochondria are the most important compartment for the synthesis of O-acetylserine (OAS), the precursor of Cys. Reduction of RNA levels, protein contents, SAT enzymatic activity, and phenotype strongly correlate in independent amiSAT3 lines and cause significantly retarded growth. The expression of the other four Sat genes in the Arabidopsis genome are not affected by amiRNA-SAT3 according to quantitative real-time polymerase chain reaction and microarray analyses. Application of radiolabeled serine to leaf pieces revealed severely reduced incorporation rates into Cys and even more so into glutathione. Accordingly, steady-state levels of OAS are 4-fold reduced. Decrease of sulfate reduction-related genes is accompanied by an accumulation of sulfate in amiSAT3 lines. These results unequivocally show that mitochondria provide the bulk of OAS in the plant cell and are the likely site of flux regulation. Together with recent data, the cytosol appears to be a major site of Cys synthesis, while plastids contribute reduced sulfur as sulfide. Thus, Cys synthesis in plants is significantly different from that in nonphotosynthetic eukaryotes at the cellular level.

Recent advances in understanding plant response to sulfur-deficiency stress

Sulfur is an essential macronutrient for all living organisms. Plants are able to assimilate inorganic sulfur and incorporate it into organic compounds, while animals rely entirely on organic sources of sulfur. In the last decades sulfate availability in soils has become the major limiting factor for plant production in many countries due to significant reduction of anthropogenic sulfur emission forced by introducing stringent environmental legislation. The sulfur flux after transferring plants from optimal conditions to sulfur deficiency is regulated on multiple levels including transcription, translation and activity of enzymes needed for sulfate assimilation and synthesis of sulfur-containing metabolites. Most of these regulatory steps are not yet fully characterized. Plant responses to sulfur limitation are complex and can be divided into phases depending on the degree of sulfur shortage. The initial responses are limited to adaptations within sulfur metabolic pathway, while multiple metabolic pathways and developmental process are affected when sulfur shortage becomes more severe. The major aim of this work is a comprehensive review of recent progress in understanding the regulation of plant adaptations to sulfur deficit.

Comparative genomics and reverse genetics analysis reveal indispensable functions of the serine acetyltransferase gene family in Arabidopsis

Ser acetyltransferase (SERAT), which catalyzes O-acetyl-Ser (OAS) formation, plays a key role in sulfur assimilation and Cys synthesis. Despite several studies on SERATs from various plant species, the in vivo function of multiple SERAT genes in plant cells remains unaddressed. Comparative genomics studies with the five genes of the SERAT gene family in Arabidopsis thaliana indicated that all three Arabidopsis SERAT subfamilies are conserved across five plant species with available genome sequences. Single and multiple knockout mutants of all Arabidopsis SERAT gene family members were analyzed. All five quadruple mutants with a single gene survived, with three mutants showing dwarfism. However, the quintuple mutant lacking all SERAT genes was embryo-lethal. Thus, all five isoforms show functional redundancy in vivo. The developmental and compartment-specific roles of each SERAT isoform were also demonstrated. Mitochondrial SERAT2;2 plays a predominant role in cellular OAS formation, while plastidic SERAT2;1 contributes less to OAS formation and subsequent Cys synthesis. Three cytosolic isoforms, SERAT1;1, SERAT3;1, and SERAT3;2, may play a major role during seed development. Thus, the evolutionally conserved SERAT gene family is essential in cellular processes, and the substrates and products of SERAT must be exchangeable between the cytosol and organelles.

LMP2-specific inhibitors: chemical genetic tools for proteasome biology

The immunoproteasome, having been linked to neurodegenerative diseases and hematological cancers, has been shown to play an important role in MHC class I antigen presentation. However, its other pathophysiological functions are still not very well understood. This can be attributed mainly to a lack of appropriate molecular probes that can selectively modulate the immunoproteasome catalytic subunits. Herein, we report the development of molecular probes that selectively inhibit the major catalytic subunit, LMP2, of the immunoproteasome. We show that these compounds irreversibly modify the LMP2 subunit with high specificity. Importantly, LMP2-rich cancer cells compared to LMP2-deficient cancer cells are more sensitive to growth inhibition by the LMP2-specific inhibitor, implicating an important role of LMP2 in regulating cell growth of malignant tumors that highly express LMP2.

Antitumor and antivascular effects of AVE8062 in ovarian carcinoma

The purpose of this study was to examine the therapeutic efficacy and underlying mechanisms of action of a vascular-disrupting agent, AVE8062, and to determine its effects on tumor metabolic activity. The in vitro and in vivo effects of AVE8062 alone and in combination with docetaxel were tested in chemotherapy-sensitive and chemotherapy-resistant ovarian cancer models. Tumors were analyzed for necrosis, microvessel density, endothelial cell apoptosis, and proliferation following treatment. The effect of AVE8062 on tumor regression and metabolic activity was examined by magnetic resonance (MR) or by [18F]fluorodeoxyglucose ([18F]FDG) uptake by positron emission tomography (PET) with MR imaging, respectively. AVE8062 monotherapy was effective in inhibiting tumor growth in all models (range 43-51% versus control; P < 0.05). Combination therapy was even more effective in inhibiting tumor growth (range 76-90% compared with controls, P < 0.01). AVE8062 in combination with chemotherapy significantly prolonged survival in HeyA8-injected mice (P < 0.001) compared with other groups. AVE8062-based therapy resulted in rapid development of central tumor necrosis, decreased microvessel density, decreased proliferation, and induction of apoptosis of tumor-associated endothelial cells. MR imaging showed regression of established HeyA8 ovarian tumors and [18F]FDG PET with MR showed rapid decrease in metabolic activity after AVE8062 therapy. Combination of AVE8062 plus docetaxel results in potent inhibition of ovarian cancer growth. These results suggest that AVE8062 may be useful as a clinical therapeutic approach for ovarian cancer patients and that functional [18F]FDG PET imaging may predict clinical response before an anatomic reduction in tumor size.

Ceramide analogue 14S24 selectively recovers perturbed human skin barrier

BACKGROUND

Topical ceramide application is an effective therapeutic approach in skin disorders with disturbed barrier function, including atopic dermatitis and psoriasis.

OBJECTIVES

To evaluate ceramide analogue N-tetracosanoyl-(l)-serine tetradecyl ester (14S24) using a novel ex vivo model.

METHODS

Freshly excised human skin was disrupted by lipid extraction, tape stripping and sodium lauryl sulphate (SLS) treatment. Barrier perturbation was evaluated by the measurement of transepidermal water loss (TEWL), skin hydration and the penetration of model compound, theophylline (TH), assessed by microdialysis. The effect of topical 5% 14S24 was compared with a commercial formulation containing a skin lipid mixture (LR) and control formulation with no skin lipids (L).

RESULTS

Both LR and 14S24 produced significant recovery of TEWL and TH penetration in extracted and tape-stripped skin with 14S24 being significantly more effective. In SLS-treated skin, 14S24 decreased TEWL but not TH penetration; LR was inactive. L improved skin hydration but not barrier characteristics. Weak correlation between TEWL and TH penetration was observed in extracted and tape-stripped skin but not in SLS-treated skin.

CONCLUSIONS

Cutaneous microdialysis can serve as a useful tool for the evaluation of skin barrier recovery by topical formulations ex vivo whereas TEWL may not be an appropriate measure of skin barrier function in such studies. The excellent barrier repair activity of 14S24 could be beneficial in skin disorders with ceramide deficiency.

Conversion of cyclic vinyl sulfones to transposed vinyl phosphonates

Functionalized cyclic vinyl sulfones were directly converted to the "polarity reversed" vinyl phosphonates through an efficient one pot procedure. Ozonolysis of these vinyl sulfones and vinyl phosphonates furnish complementary sets of termini-differentiated ester-aldehydes. This strategy has been applied for preparation of segments needed for the synthesis of Aplyronine A. The scope and limitations of this transformation were defined.

Synthesis of Unnatural Amino Acids from Serine Derivatives by β-Fragmentation of Primary Alkoxyl Radicals

The fragmentation of primary alkoxyl radicals has been scarcely used in synthesis since other competing processes (such as oxidation or hydrogen abstraction) usually predominate. However, when serine derivatives were used as substrates, the scission took place in excellent yields. Tandem scission-allylation, -alkylation, or -arylation reactions were subsequently developed. This one-pot methodology was applied to the synthesis of unnatural amino acids, which are useful synthetic blocks or amino acid surrogates in peptidomimetics.