Preclinical development of a novel inhibitor of oncogenic B-Raf

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Background: The discovery of oncogenic B-Raf mutations in a majority of patients with metastatic melanoma, and in many tumors from patients with colorectal cancer and other cancers, presents the opportunity to develop oncogene-selective inhibitors with a favorable safety profile. Methods: Guided by co-crystallography, a novel chemical scaffold has been developed into a series of potent inhibitors of oncogenic B-Raf with selectivity versus wild-type B-Raf. From this series, a potent inhibitor has been chosen as a candidate for development. Results: Consistent with the structure-guided approach, this compound shows pronounced selectivity versus a wide array of over 70 other kinases covering all branches of the kinome. This selectivity translates to a wide cellular therapeutic index: inhibition of proliferation of a panel of cell lines bearing the V600E oncogenic B-Raf mutation occurs at IC50s ranging from 40–400 nM while inhibition of cell lines lacking oncogenic B-Raf occurs at IC50s greater than 6500 nM. This cell-based selectivity for the oncogenic B-Raf is greater than the selectivity shown in biochemical assays, supporting that tumor cells bearing the oncogenic B-Raf protein are more dependent on the MAP kinase pathway. Combination experiments with a series of cytotoxic and targeted clinical anti-cancer agents reveal multiple examples of synergistic inhibition of proliferation in vitro, and this synergy generally appears selectively in oncogenic B-Raf-bearing cells. The good oral bioavailability (F > 70%) allows for prolonged exposure in both rodents and non-rodents. Robust efficacy is evident in a murine COLO205 tumor xenograft model, with once-daily oral dosing at 20 mg/kg over 14 days resulting in > 80% inhibition of tumor growth with no effect on body weight. Conclusions: Since this compound is highly selective and targets a B-Raf variant that is absent in all non-transformed cells, it may have a broad therapeutic index, alone or in combination, for the treatment of patients with V600E oncogenic B-Raf tumors.

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Fast imaging with the MMME sequence

The multiple-modulation-multiple-echo sequence, previously used for rapid measurement of diffusion, is extended to a method for single shot imaging. Removing the gradient switching requirement during the application of RF pulses by a constant frequency encoding gradient can shorten experiment time for ultrafast imaging. However, having the gradient on during the pulses gives rise to echo shape variations from off-resonance effects, which make the image reconstruction difficult. In this paper, we propose a simple method to deconvolve the echo shape variation from the true one-dimensional image. This method is extended to two-dimensional imaging by adding phase encoding gradients between echoes during the acquisition period to phase encode each echo separately. Slice selection is achieved by a frequency selective pulse at the beginning of the sequence. Imaging speed is mainly limited by the phase encoding gradients' switching times and echo overlap when echo spacing is very short. This technique can produce a single-shot image of sub-millimeter resolution in 5 ms.

Superconducting phase coherent electron transport in proximity conical ferromagnets

We report superconducting phase-periodic conductance oscillations in ferromagnetic wires with interfaces to conventional superconductors. The ferromagnetic wires were made of Ho, a conical ferromagnet. The distance between the interfaces was much larger than the singlet superconducting penetration depth. We explain the observed oscillations as due to the long-range penetration of an unusual helical triplet component of the order parameter that is generated at the superconductor/ferromagnet interfaces and maintained by the intrinsic rotating magnetization of Ho.

Repeated brief epileptic seizures by pentylenetetrazole cause neurodegeneration and promote neurogenesis in discrete brain regions of freely moving adult rats

Recurrent epileptic seizures are known to provoke various forms of cellular reorganization in the brains of humans and experimental animals. However, little is known about the mechanism of neuronal cell death resulting from epileptic seizures elicited by GABA antagonists. In the present study, we explored the effect on the central nervous systems of freely moving adult rats, of repeated brief epileptic seizures induced by systemic injection of pentylenetetrazole, a GABA-A receptor antagonist. Starting with minor convulsions, repeated epileptic seizures elicited a progressive increase in seizure severity, culminating in the fully kindled state. Histological examination showed that the epileptic seizures caused overt neuronal cell death in the limbic system, including the hippocampus and amygdala, and its adjoining cortex. During the recurrent epileptic seizures, neurogenesis occurred in the subgranular zone of the hippocampus, the subventricular zone of the lateral ventricle, and the amygdala. This type of pentylenetetrazole-induced neurogenesis was seen at an early stage of epileptogenesis in some regions in which massive cell loss was not evident. This suggests that neurogenesis is not a secondary consequence of neuronal cell death, but rather an independent effect of recurrent epileptic seizures.

Genetic variation at the perilipin locus is associated with changes in serum free fatty acids and abdominal fat following mild weight loss

OBJECTIVE

Perilipin (PLIN) is a class of protein-coating lipid droplets in adipocytes. We aimed to examine the association between common single-nucleotide polymorphisms (SNPs) at PLIN locus with circulating free fatty acid (FFA) and abdominal fat distribution in response to weight loss.

METHODS

Non-diabetic/overweight-obese Koreans (n=177) participated in a 12-week calorie restriction (-300kcal/day) program. Seven SNPs (6209T>C, 10076C>G, 10171A>T, 11482G>A, 13042A>G, 13048C>T and 14995A>T), abdominal fat areas (visceral/subcutaneous fat areas at 1st lumbar and 4th lumbar levels), serum lipids, glucose, insulin, FFA, oxidized low-density lipoprotein (LDL) and urinary 8-epi-prostaglandin F(2alpha) (PGF(2alpha)) were examined.

RESULTS

Single-nucleotide polymorphisms 10076C>G/10171A>T showed the strongest positive linkage disequilibrium (LD) (D'=0.923, R (2)=0.839, P<0.001) and SNPs11482G>A/14995A>T showed moderate positive LD (D'=0.824, R (2)=0.578, P<0.001). Calorie restriction induced 4.6% weight loss with significant abdominal fat reduction. In response to weight loss, subjects with nCA/nCA haplotypes at SNPs 10076C>G/10171A>T showed greater reduction in FFA levels than those with CA/CA haplotype (CA/CA: C/C at SNP 10076 and A/A at SNP 10171, nCA: non-CA haplotype carrier). On the other hand, subjects with nGA/nGA haplotype at SNPs 11482G>A/14995A>T had increased FFA levels with a rapid loss in abdominal fat, whereas GA/GA haplotype carriers had reduction in FFA levels. These results still remained significant after adjusting for age, gender and BMI. Prostaglandin F(2alpha) and oxidized LDL were also more reduced in GA/GA haplotype carriers than in nGA haplotype carriers. This effect remained significant after adjusting for baseline level, age, gender and BMI. Paradoxically, nGA haplotype carriers had increased levels of urinary PGF(2alpha) after weight reduction.

CONCLUSION

Fasting plasma FFA changes following a modest weight loss in overweight-obese subjects are influenced by the genetic variability at the PLIN locus. Furthermore, circulating FFA changes rather than body fat itself may determine changes in lipid peroxides such as urinary PGF(2alpha) and oxidized LDL.

Production and characterization of guinea pig recombinant gamma interferon and its effect on macrophage activation

Gamma interferon (IFN-gamma) plays a critical role in the protective immune responses against mycobacteria. We previously cloned a cDNA coding for guinea pig IFN-gamma (gpIFN-gamma) and reported that BCG vaccination induced a significant increase in the IFN-gamma mRNA expression in guinea pig cells in response to living mycobacteria and that the virulent H37Rv strain of Mycobacterium tuberculosis stimulated less IFN-gamma mRNA than did the attenuated H37Ra strain. In this study, we successfully expressed and characterized recombinant gpIFN-gamma with a histidine tag at the N terminus (His-tagged rgpIFN-gamma) in Escherichia coli. rgpIFN-gamma was identified as an 18-kDa band in the insoluble fraction; therefore, the protein was purified under denaturing conditions and renatured. N-terminal amino acid sequencing of the recombinant protein yielded the sequence corresponding to the N terminus of His-tagged gpIFN-gamma. The recombinant protein upregulated major histocompatibility complex class II expression in peritoneal macrophages. The antiviral activity of rgpIFN-gamma was demonstrated with a guinea pig fibroblast cell line (104C1) infected with encephalomyocarditis virus. Interestingly, peritoneal macrophages treated with rgpIFN-gamma did not produce any nitric oxide but did produce hydrogen peroxide and suppressed the intracellular growth of mycobacteria. Furthermore, rgpIFN-gamma induced morphological alterations in cultured macrophages. Thus, biologically active rgpIFN-gamma has been successfully produced and characterized in our laboratory. The study of rgpIFN-gamma will further increase our understanding of the cellular and molecular responses induced by BCG vaccination in the guinea pig model of pulmonary tuberculosis.

Scoring and staging systems using cox linear regression modeling and recursive partitioning

OBJECTIVES

Scoring and staging systems are used to determine the order and class of data according to predictors. Systems used for medical data, such as the Child-Turcotte-Pugh scoring and staging systems for ordering and classifying patients with liver disease, are often derived strictly from physicians' experience and intuition. We construct objective and data-based scoring/staging systems using statistical methods.

METHODS

We consider Cox linear regression modeling and recursive partitioning techniques for censored survival data. In particular, to obtain a target number of stages we propose cross-validation and amalgamation algorithms. We also propose an algorithm for constructing scoring and staging systems by integrating local Cox linear regression models into recursive partitioning, so that we can retain the merits of both methods such as superior predictive accuracy, ease of use, and detection of interactions between predictors. The staging system construction algorithms are compared by cross-validation evaluation of real data.

RESULTS

The data-based cross-validation comparison shows that Cox linear regression modeling is somewhat better than recursive partitioning when there are only continuous predictors, while recursive partitioning is better when there are significant categorical predictors. The proposed local Cox linear recursive partitioning has better predictive accuracy than Cox linear modeling and simple recursive partitioning.

CONCLUSIONS

This study indicates that integrating local linear modeling into recursive partitioning can significantly improve prediction accuracy in constructing scoring and staging systems.

Vaccine-induced cytokine responses in a guinea pig model of pulmonary tuberculosis

Guinea pigs exposed to very small numbers of virulent tubercle bacilli by the respiratory route develop a disease which mimics many of the important features of the pathogenesis of human tuberculosis (TB), including the expression of strong protective immunity following vaccination with BCG. In order to elucidate the precise immunological mechanisms of vaccine-induced resistance in this model, both mRNA and protein assays for several guinea pig cytokines and chemokines have been developed. The coordinated expression of cytokine and chemokine mRNA and protein was examined in various leukocyte populations and in inflammatory cells and fluid collected following the induction of tuberculous pleurisy in BCG-vaccinated guinea pigs. Real-time RT-PCR assays revealed that the mRNA levels for IFNgamma, TNFalpha, and IL-8 rose over the first few days of TB pleuritis and then declined over the 9 days of the study. Injection of anti-TGFbeta on day 8 following pleurisy induction resulted in significant changes in cytokine mRNA levels and PPD-induced proliferation in pleural effusion lymphocytes taken 24h later. BCG vaccination induced significantly higher levels of bioactive TNFalpha protein in the supernatants of alveolar, peritoneal and splenic cells from BCG-vaccinated guinea pigs cultured in the presence of attenuated or virulent mycobacteria. In sharp contrast, following virulent challenge, all three cell types from BCG-vaccinated guinea pigs produced significantly less TNFalpha. Thus, BCG vaccination appears to modulate the potentially harmful effects of TNFalpha in this model of pulmonary TB. Levels of mRNA for IL-12p40 were upregulated by exposure of infected and uninfected macrophages to recombinant guinea pig (rgp)TNFalpha. The intracellular survival of mycobacteria was enhanced when endogeous TNFalpha activity was neutralized with anti-rgpTNFalpha antiserum. rgp RANTES (CCL5) upregulated mRNA levels for TNFalpha, IL-1beta, MCP-1 (CCL2), and IL-8 (CXCL8) in alveolar and peritoneal macrophages. These results illustrate the profound effects of prior vaccination with BCG on the cytokine and chemokine responses of distinct cell populations in the guinea pig following exposure to attenuated and virulent strains of M. tuberculosis.

Individual fundamental mode dependence of H2O vibrational excitation in the 6–8 eV resonance region by electron impact

Resonance phenomena in the bending (010), symmetric (100), and asymmetric (001) stretching vibrational modes in water (H(2)O) molecules have been investigated by measuring differential cross sections (DCSs) at fixed energy losses of 0.43, 0.46, 0.49, and 0.51 eV while sweeping the impact energies from 1.6 to 10 eV, at angles 60 degrees and 90 degrees, using a crossed-beam method. No resonancelike enhanced features have been observed in the study of the (010) mode. In the DCSs for the combined (100+001) mode, a single broad hump was observed at each angle, whose position shifts towards the higher energy side with increasing scattering angle, a feature typical of the interference profiles previously observed in a study of the (301) vibrational mode. DCSs for the (001) mode exhibited a rather isotropic angular distribution with no evidence of resonances. However, enhancement of DCSs were indeed observed for the (100) mode, at the energy loss of 0.46 eV, which is attributable to the A(1) symmetry resonance that was studied by Seng and Linder [J. Phys. B 9, 2539 (1976)], with a typical s-wave characteristic angular distribution. Theoretical analysis based on the continuum multiple-scattering approach has been carried out to provide rationale to the experimental results.

Flavonol glycosides with free radical-scavenging activity of Saururus chinensis

An activity-guided fractionation procedure was used to identify the antioxidative components of the aerial parts of Saururus chinensis. The antioxidant activity was investigated with the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical- and superoxide anion-scavenging assays. Three active compounds (flavonol glycosides) were identified.

Electron scattering from tetrafluoroethylene

We report experimental results for electron scattering from tetrafluoroethylene, C2F4, obtained from measurements in two laboratories. An extensive set of differential, integral, and momentum transfer cross sections is provided for elastic scattering for incident electron energies from 1 to 100 eV and inelastic (vibrational excitation) scattering for incident electron energies at 3, 6, 7.5, 8, and 15 eV, and for scattering angles ranging from 10 degrees to 130 degrees. To highlight the role of intermediate negative ions (resonances) in the scattering process we have also measured excitation functions for elastic scattering and vibrational excitation of the ground electronic state of C2F4 for incident energies between 1.5 and 20 eV. Our results are compared with recent theoretical calculations and a limited number of other experimental results.

Regulators of G protein signaling: potential drug targets for controlling cardiovascular and immune function

Heterotrimeric G-protein-coupled receptors (GPCRs) mediate a wide variety of organismal functions ranging from vision, olfaction, and gustation to the development and physiology of the cardiovascular, neuronal, and immune system. Naturally they are targets of a large number of therapeutic drugs. The regulators of G protein signaling (RGS) are a family of diverse proteins that regulate the GPCR-mediated signaling pathways principally by acting as GTPase activating proteins (GAPs) for the alpha subunit of the heterotrimeric G-proteins. Certain members of the RGS family contain multiple domains and motifs that mediate interactions with other signaling molecules, thus linking GPCR-dependent and GPCR-independent signaling pathways. Because of their ability to fine-tune vital GPCR-mediated processes and recent findings linking them to brain disorders, retinitis pigmentosa, and cancer RGS proteins have become excellent candidates for new drug discovery. The focus of this review is to discuss the roles of the RGS proteins in the development and normal physiology of cardiovascular and immune system, and to explore their potential as drug targets useful for the treatment of pathological conditions of the cardiovascular and immune systems.

Spin diffusion of correlated two-spin states in a dielectric crystal

Reciprocal space measurements of spin diffusion in a single crystal of calcium fluoride (CaF2) have been extended to dipolar ordered states. The experimental results for the component of the spin diffusion rate parallel to the external field are D(parallel)(D)=29+/-3x10(-12) cm(2)/s for the [001] direction and D(parallel)(D)=33+/-4x10(-12) cm(2)/s for the [111] direction. The measured diffusion rates for dipolar order are faster than those for Zeeman order and are considerably faster than predicted by simple theoretical models. It is suggested that constructive interference in the transport of the two-spin states is responsible for this enhancement. As expected, the anisotropy in the diffusion rates is observed to be significantly less for dipolar order compared to the Zeeman case.

Nonradiometric HPLC measurement of 13(S)-hydroxyoctadecadienoic acid from rat tissues

A major bioactive metabolite of linoleic acid formed by the action of 15-lipoxygenase-1 is 13(S)-hydroxy-cis-9, trans-11-octadecadienoic acid (13(S)-HODE). 13(S)-HODE is an important intracellular signal agent and is involved in cell proliferation and differentiation in various biological systems. Separation and quantification of 13(S)-HODE from biological materials has previously been achieved only by using radiolabeled linoleic acid as the substrate and two serially connected or two separate HPLC columns to achieve separation of 13(S)-HODE. In the current method, separation and quantification of 13(S)-HODE was achieved by use of a normal-phase HPLC and a solvent system containing hexane/isopropanol/acetonitrile/acetic acid (800/8/30/1, v/v) using isocratic elution with detection at 235 nm. With the currently described method, good separation from unreacted interfering compounds and quantification for 13(S)-HODE were achieved within 35 min with a minimum detection limit of 0.5 ng per injection.

Pulse error compensating symmetric magic-echo trains

We present improved line-narrowing sequences for dipolar coupled spin systems, based on a train of magic-echoes which are compensated for the effects of finite pulse widths and utilize symmetry properties of supercycles. Sequences are introduced for spectroscopy and imaging by proper choice of a phase alternating scheme. Using a 16 pulse time-suspension magic-echo cycle, the highest level of line-narrowing achieved was 2.7 Hz for the [100] direction of a single crystal of calcium fluoride, a reduction in linewidth by 4 orders of magnitude.