Utility of a Histone Deacetylase Inhibitor (PXD101) for Thyroid Cancer Treatment

Background

We evaluated the therapeutic effects of the histone deacetylase inhibitor PXD101 alone and in combination with conventional chemotherapy in treating thyroid cancer.

Methodology/Principal Findings

We studied eight cell lines from four types of thyroid cancer (papillary, follicular, anaplastic and medullary). The cytotoxicity of PXD101 alone and in combination with three conventional chemotherapeutic agents (doxorubicin, paclitaxel and docetaxel) was measured using LDH assay. Western blot assessed expression of acetylation of histone H3, histone H4 and tubulin, proteins associated with apoptosis, RAS/RAF/ERK and PI3K/AKT/mTOR signaling pathways, DNA damage and repair. Apoptosis and intracellular reactive oxygen species (ROS) were measured by flow cytometry. Mice bearing flank anaplastic thyroid cancers (ATC) were daily treated with intraperitoneal injection of PXD101 for 5 days per week. PXD101 effectively inhibited thyroid cancer cell proliferation in a dose-dependent manner. PXD101 induced ROS accumulation and inhibited RAS/RAF/ERK and PI3K/mTOR pathways in sensitive cells. Double-stranded DNA damage and apoptosis were induced by PXD101 in both sensitive and resistant cell lines. PXD101 retarded growth of 8505C ATC xenograft tumors with promising safety. Combination therapy of PXD101with doxorubicin and paclitaxel demonstrated synergistic effects against four ATC lines in vitro.

Conclusions

PXD101 represses thyroid cancer proliferation and has synergistic effects in combination with doxorubicin and paclitaxel in treating ATC. These findings support clinical trials using PXD101 for patients with this dismal disease.     

Pyrrolopyrimidine inhibitors of DNA gyrase B (GyrB) and topoisomerase IV (ParE). Part I: Structure guided discovery and optimization of dual targeting agents with potent,broad-spectrum enzymatic activity

The bacterial topoisomerases DNA gyrase (GyrB) and topoisomerase IV (ParE) are essential enzymes that control the topological state of DNA during replication. The high degree of conservation in the ATP-binding pockets of these enzymes make them appealing targets for broad-spectrum inhibitor development. A pyrrolopyrimidine scaffold was identified from a pharmacophore-based fragment screen with optimization potential. Structural characterization of inhibitor complexes conducted using selected GyrB/ParE orthologs aided in the identification of important steric, dynamic and compositional differences in the ATP-binding pockets of the targets, enabling the design of highly potent pyrrolopyrimidine inhibitors with broad enzymatic spectrum and dual targeting activity.     

Atrial Arrhythmia in Ageing Spontaneously Hypertensive Rats: Unraveling the Substrate in Hypertension and Ageing

Background

Both ageing and hypertension are known risk factors for atrial fibrillation (AF) although the pathophysiological contribution or interaction of the individual factors remains poorly understood. Here we aim to delineate the arrhythmogenic atrial substrate in mature spontaneously hypertensive rats (SHR).

Methods

SHR were studied at 12 and 15 months of age (n = 8 per group) together with equal numbers of age-matched normotensive Wistar-Kyoto control rats (WKY). Electrophysiologic study was performed on superfused isolated right and left atrial preparations using a custom built high-density multiple-electrode array to determine effective refractory periods (ERP), atrial conduction and atrial arrhythmia inducibility. Tissue specimens were harvested for structural analysis.

Results

Compared to WKY controls, the SHR demonstrated: Higher systolic blood pressure (p<0.0001), bi-atrial enlargement (p<0.05), bi-ventricular hypertrophy (p<0.05), lower atrial ERP (p = 0.008), increased atrial conduction heterogeneity (p = 0.001) and increased atrial interstitial fibrosis (p = 0.006) & CD68-positive macrophages infiltration (p<0.0001). These changes resulted in higher atrial arrhythmia inducibility (p = 0.01) and longer induced AF episodes (p = 0.02) in 15-month old SHR. Ageing contributed to incremental bi-atrial hypertrophy (p<0.01) and atrial conduction heterogeneity (p<0.01) without affecting atrial ERP, fibrosis and arrhythmia inducibility. The limited effect of ageing on the atrial substrate may be secondary to the reduction in CD68-positive macrophages.

Conclusions

Significant atrial electrical and structural remodeling is evident in the ageing spontaneously hypertensive rat atria. Concomitant hypertension appears to play a greater pathophysiological role than ageing despite their compounding effect on the atrial substrate. Inflammation is pathophysiologically linked to the pro-fibrotic changes in the hypertensive atria.     

Lipase Maturation Factor LMF1, Membrane Topology and Interaction with Lipase Proteins in the Endoplasmic Reticulum

Lipase maturation factor 1 (LMF1) is predicted to be a polytopic protein localized to the endoplasmic reticulum (ER) membrane. It functions in the post-translational attainment of enzyme activity for both lipoprotein lipase and hepatic lipase. By using transmembrane prediction methods in mouse and human orthologs, models of LMF1 topology were constructed and tested experimentally. Employing a tagging strategy that used insertion of ectopic glycan attachment sites and terminal fusions of green fluorescent protein, we established a five-transmembrane model, thus dividing LMF1 into six domains. Three domains were found to face the cytoplasm (the amino-terminal domain and loops B and D), and the other half was oriented to the ER lumen (loops A and C and the carboxyl-terminal domain). This representative model shows the arrangement of an evolutionarily conserved domain within LMF1 (DUF1222) that is essential to lipase maturation. DUF1222 comprises four of the six domains, with the two largest ones facing the ER lumen. We showed for the first time, using several naturally occurring variants featuring DUF1222 truncations, that Lmf1 interacts physically with lipoprotein lipase and hepatic lipase and localizes the lipase interaction site to loop C within DUF1222. We discuss the implication of our results with regard to lipase maturation and DUF1222 domain structure.     

Improving simvastatin bioconversion in Escherichia coli by deletion of bioH

Simvastatin is an important cholesterol lowering compound and is currently synthesized from the natural product lovastatin via multistep chemical synthesis. We have previously reported the use of an Escherichia coli strain BL21(DE3)/pAW31 as the host for whole-cell biocatalytic conversion of monacolin J acid to simvastatin acid. During fermentation and bioconversion, unknown E. coli enzyme(s) hydrolyzed the membrane permeable thioester substrate dimethylbutyryl-S-methyl mercaptopropionate (DMB-S-MMP) to the free acid, significantly decreased the efficiencies of the whole-cell bioconversion and the downstream purification steps. Using the Keio K-12 Singe-Gene Knockout collection, we identified BioH as the sole enzyme responsible for the observed substrate hydrolysis. Purification and reconstitution of E. coli BioH activity in vitro confirmed its function. BioH catalyzed the rapid hydrolysis of DMB-S-MMP with kcat and Km values of 260+/-45 s(-1) and 229+/-26 microM, respectively. This is in agreement with previous reports that BioH can function as a carboxylesterase towards fatty acid esters. YT2, which is a delta bioH mutant of BL21(DE3), did not hydrolyze DMB-S-MMP during prolonged fermentation and was used as an alternative host for whole-cell biocatalysis. The rate of simvastatin acid synthesis in YT2 was significantly faster than in BL21(DE3) and 99% conversion of 15 mM simvastatin acid in less than 12 h was achieved. Furthermore, the engineered host required significantly less DMB-S-MMP to be added to accomplish complete conversion. Finally, simvastatin acid synthesized using YT2 can be readily purified from fermentation broth and no additional steps to remove the hydrolyzed dimethylbutyryl-S-mercaptopropionic acid is required. Together, the proteomic and metabolic engineering approaches render the whole-cell biocatalytic process more robust and economically attractive.     

Epigenetic inactivation of the miR-124-1 in haematological malignancies

miR-124-1 is a tumour suppressor microRNA (miR). Epigenetic deregulation of miRs is implicated in carcinogenesis. Promoter DNA methylation and histone modification of miR-124-1 was studied in 5 normal marrow controls, 4 lymphoma, 8 multiple myeloma (MM) cell lines, 230 diagnostic primary samples of acute myeloid leukaemia (AML), acute lymphoblastic leukaemia (ALL), chronic myeloid leukaemia (CML), chronic lymphocytic leukaemia (CLL), MM, and non-Hodgkin's lymphoma (NHL), and 53 MM samples at stable disease or relapse. Promoter of miR-124-1 was unmethylated in normal controls but homozygously methylated in 4 of 4 lymphoma and 4 of 8 myeloma cell lines. Treatment of 5-Aza-2'-deoxycytidine led to miR-124-1 demethylation and re-expression of mature miR-124, which also associated with emergence of euchromatic trimethyl H3K4 and consequent downregulation of CDK6 in myeloma cells harboring homozygous miR-124-1 methylation. In primary samples at diagnosis, miR-124-1 methylation was absent in CML but detected in 2% each of MM at diagnosis and relapse/progression, 5% ALL, 15% AML, 14% CLL and 58.1% of NHL (p<0.001). Amongst lymphoid malignancies, miR-124-1 was preferentially methylated in NHL than MM, CLL or ALL. In primary lymphoma samples, miR-124-1 was preferentially hypermethylated in B- or NK/T-cell lymphomas and associated with reduced miR-124 expression. In conclusion, miR-124-1 was hypermethylated in a tumour-specific manner, with a heterochromatic histone configuration. Hypomethylation led to partial restoration of euchromatic histone code and miR re-expression. Infrequent miR-124-1 methylation detected in diagnostic and relapse MM samples showed an unimportant role in MM pathogenesis, despite frequent methylation found in cell lines. Amongst haematological cancers, miR-124-1 was more frequently hypermethylated in NHL, and hence warrants further study.     

Photosynthesis in Tall Fescue : IV. Carbon Assimilation Pattern in two Genotypes of Tall Fescue Differing in Net Photosynthesis Rates

We previously reported that the net photosynthetic rate of a decaploid genotype (I-16-2) of tall fescue (Festuca arundinacea Schreb.) was 32 to 41 versus 22 milligrams CO₂ per square decimeter per hour in a hexaploid genotype (V6-802) (Randall, Nelson, Asay Plant Physiol 59: 38-41). The high rate was later correlated with increases in total ribulose 1,5-bisphosphate carboxylase protein (17%) and activity (27%) (Joseph, Randall, Nelson Plant Physiol 68: 894-898). This report characterizes photosynthesis with respect to light saturation and early products of photosynthesis in an attempt to identify regulatory metabolic site(s) in these two genotypes. Analysis of the early products of photosynthesis indicated that both genotypes fixed CO₂ via the Calvin-Benson cycle with phosphoglyceric acid as the initial primary product. Both genotypes had similar ¹⁴C-labeled intermediates. Sucrose was the primary sink of ¹⁴CO₂ assimilation. After 10 min of ¹⁴CO₂ assimilation with attached leaves, sucrose accounted for 89% (decaploid) and 81% (hexaploid) of the total ¹⁴C incorporated. In 10 min, this amounted to 1.3 (decaploid) and 0.8 (hexaploid) μmol [¹⁴C]sucrose formed g fresh weight⁻¹ and reflected the observed differences in photosynthetic rates. There was limited labeling of starch (1%) and fructan (1%). Results of total nonstructural carbohydrates and P_i analysis also demonstrated sucrose was the predominant carbohydrate in fescue leaves. Quantitative differences in sucrose and P_i between the two genotypes may reflect changes in partitioning and this possibility is discussed.     

Web-based telemicroscopy

By taking advantage of network-based computing and the recent developments in Web interfaces, centralized research facilities housing specialized and unique imaging instruments along with associated high-performance computing can be made available to researchers for use from their own laboratories. In addition to increasing access and utilization of these facilities, operation over the Internet is expected to enhance research by facilitating collaboration between researchers. We describe the implementation of a platform-independent Web-based system written in Java that supplements automated functions with video-guided interactive, collaborative remote control and data acquisition from an intermediate-high-voltage electron microscope.     

Donor–Acceptor–Acceptor's Molecules for Vacuum‐Deposited Organic Photovoltaics with Efficiency Exceeding 9%

Three vacuum‐deposited donor–acceptor–acceptor (d–a–a') small molecule donors are studied with different side chains attached to an asymmetric heterotetracene donor block for use in high efficiency organic photovoltaics (OPVs). The donor with an isobutyl side chain yields the highest crystal packing density compared to molecules with 2‐ethylhexyl or n‐butyl chains, leading to the largest absorption coefficient and short circuit current in an OPV. It also exhibits a higher fill factor, consistent with its preferred out‐of‐plane molecular π–π stacking arrangement that facilitates charge transport in the direction perpendicular to the substrate. A power conversion efficiency of 9.3 ± 0.5% is achieved under 1 sun intensity, AM 1.5 G simulated solar illumination, which is significantly higher than 7.5 ± 0.4% of the other two molecules. These results indicate that side chain modification of d–a–a' small molecules offers an effective approach to control the crystal packing configuration, thereby improving the device performance.