Medical Library

Preclinical discovery of ixabepilone, a highly active antineoplastic agent.

The epothilones and their analogs constitute a novel class of antineoplastic agents, produced by the myxobacterium Sorangium cellulosum. These antimicrotubule agents act in a similar manner to taxanes, stabilizing microtubules and resulting in arrested tumor cell division and apoptosis. Unlike taxanes, however, epothilones and their analogs are macrolide antibiotics, with a distinct tubulin binding mode and reduced susceptibility to a range of common tumor resistance mechanisms that limit the effectiveness of taxanes and anthracyclines. While natural epothilones A and B show potent antineoplastic activity in vitro, these effects were not seen in preclinical in vivo models due to their poor metabolic stability and unfavorable pharmacokinetics. A range of epothilone analogs was synthesized, therefore, with the aim of identifying those with more favorable characteristics. Here, we describe the preclinical characterization and selection of ixabepilone, a semi-synthetic epothilone B analog, among many other epothilone analogs. Ixabepilone demonstrated superior preclinical characteristics, including high metabolic stability, low plasma protein binding and low susceptibility to multidrug resistance protein-mediated efflux, all of which were predictive of potent in vivo cell-killing activity. Ixabepilone also demonstrated in vivo antitumor activity in a range of human tumor models, several of which displayed resistance to commonly used agents such as anthracyclines and taxanes. These favorable preclinical characteristics have since translated to the clinic. Ixabepilone has shown promising phase II clinical efficacy and acceptable tolerability in a wide range of cancers, including heavily pretreated and drug-resistant tumors. Based on these results, a randomized phase III trial was conducted in anthracycline-pretreated or resistant and taxane-resistant metastatic breast cancer to evaluate ixabepilone in combination with capecitabine. Ixabepilone combination therapy showed significantly superior progression-free survival and tumor responses over capecitabine alone.

Lee FY, Borzilleri R, Fairchild CR, Kamath A, Smykla R, Kramer R, Vite G.

Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ, USA, francis.lee@bms.com.

The use of (18)F-FDG PET/CT in colorectal liver metastases-comparison with CT and liver MRI.

PURPOSE: We compared 18-fluoro-2-deoxyglucose ((18)F-FDG) positron emission tomography-CT (PETCT) with contrast-enhanced whole-body CT (ceCT) in identifying extrahepatic disease and with manganese dipyridoxyl diphosphate (Mn-DPDP) liver MRI for liver metastases in patients with colorectal liver metastases being considered for surgery. METHODS: Sixty-five patients (median age 65 years; 42 men) with colorectal cancer and known or suspicious liver metastases and who underwent a PETCT, ceCT and Mn-DPDP MRI were identified. Results were retrospectively reviewed for extrahepatic disease on PETCT and ceCT, and for the presence and number of liver metastases on PETCT and Mn-DPDP MRI. Proof of metastases was based on histopathology or clinical/imaging follow-up, demonstrating disease progression or response. RESULTS: PETCT identified unexpected extrahepatic disease not detected on ceCT, leading to change in surgical management in 17%. There were three other false-positive cases on PETCT. For liver metastases on a per-patient basis, the sensitivity and specificity of both PETCT and Mn-DPDP MRI were 98% and 100%, respectively. On a per-lesion basis, PETCT and MRI were discordant in 15% (10/66 scans). MRI correctly identified more sub-centimeter metastases in eight scans. PETCT correctly identified more metastases in one case and confirmed disease in one equivocal MRI. CONCLUSION: PETCT has incremental benefit over conventional ceCT in identifying extrahepatic disease in metastatic colorectal cancer. PETCT has high sensitivity and specificity for the presence of liver metastases and should be included early in initial pre-surgical evaluation and could potentially guide the use of Mn-DPDP MRI. However, Mn-DPDP MRI is superior for small liver metastases and remains a prerequisite for surgical planning in patients with confined liver metastases.

Kong G, Jackson C, Koh DM, Lewington V, Sharma B, Brown G, Cunningham D, Cook GJ.

Department of Nuclear Medicine and PET, The Royal Marsden NHS Foundation Trust, Downs Road, Sutton, Surrey, SM2 5PT, UK, gkong@iname.com.

Molecular microbial and chemical investigation of the bioremediation of two-phase olive mill waste using laboratory-scale bioreactors.

Two-phase olive mill waste (TPOMW) is a semi-solid effluent that is rich in contaminating polyphenols and is produced in large amounts by the industry of olive oil production. Laboratory-scale bioreactors were used to investigate the biodegradation of TPOMW by its indigenous microbiota. The effect of nutrient addition (inorganic N and P) and aeration of the bioreactors was studied. Microbial changes were investigated by PCR-temperature time gradient electrophoresis (TTGE) and following the dynamics of polar lipid fatty acids (PLFA). The greatest decrease in the polyphenolic and organic matter contents of bioreactors was concomitant with an increase in the PLFA fungal/bacterial ratio. Amplicon sequences of nuclear ribosomal internal transcribed spacer region (ITS) and16S rDNA allowed identification of fungal and bacterial types, respectively, by comparative DNA sequence analyses. Predominant fungi identified included members of the genera Penicillium, Candida, Geotrichum, Pichia, Cladosporium, and Aschochyta. A total of 14 bacterial genera were detected, with a dominance of organisms that have previously been associated with plant material. Overall, this work highlights that indigenous microbiota within the bioreactors through stimulation of the fungal fraction, is able to degrade the polyphenolic content without the inoculation of specific microorganisms.

Morillo JA, Aguilera M, Antízar-Ladislao B, Fuentes S, Ramos-Cormenzana A, Russell NJ, Monteoliva-Sánchez M.

Departamento de Microbiología, Facultad de Farmacia, Universidad de Granada, Campus de Cartuja, s/n, 18071, Granada, Spain, jamorillo@yahoo.com.

Quantifying the surface characteristics and flocculability of Ralstonia eutropha.

The microbial surface and flocculability were qualitatively characterized through the combination of the surface thermodynamic and the extended DLVO approaches, with Ralstonia eutropha, a polyhydroxybutyrate-producing bacterium, as an example. The negativity of the zeta potential of R. eutropha decreased from the initial -19.5 to -11 mV in its cultivation with the consumption of glucose. The total interfacial free energy (DeltaG (adh)) was changed from -80 to 28.5 mJ m(-2) in its entire growth process. This suggests that the bacterial surface changed from hydrophobic into hydrophilic, resulting in an alteration of its surface characteristics and flocculability in its different growth phases. As a result, the stability ratio of suspensions increased with the increasing cultivation time, indicating that the cell particles became more repulsive with each other and led to a more stable suspension of R. eutropha in its cultivation. The obtained information in this work might be useful for better understanding the surface characteristics and the flocculability and even manipulating its flocculability in the microbial growth process.

Liu XM, Sheng GP, Wang J, Yu HQ.

Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China.

Construction of a stress-induced system in Escherichia coli for efficient polyhydroxyalkanoates production.

In the application of engineered Escherichia coli in industrial polyhydroxybutyrate production process, one of the major concerns is the induction of the metabolic pathway. In this study, we developed a stress-induced system by which the PHB biosynthesis pathways can be induced under stress conditions. Fermentation results showed that recombinant E. coli DH5alpha (pQKZ103) harboring this system was able to accumulate polyhydroxybutyrate up to 85.8% of cell dry weight in minimal glucose medium without adding any inducer. Growth experiment with GFP as a reporter indicated that the induction of this system happened at the late exponential phase and was sensitive to stressed environment. This system can also be applied in many other biotechnological processes.

Kang Z, Wang Q, Zhang H, Qi Q.

State Key Laboratory of Microbial Technology, National Glycoengineering Research Center, Shandong University, Jinan, 250100, People’s Republic of China.

Effect of polar and non-polar carotenoids on Xanthophylomyces dendrorhous membranes by EPR.

The red yeast Xanthophyllomyces dendrorhous is one of the microbiological production systems for natural carotenoids. High-performance liquid chromatography (HPLC) and electron paramagnetic resonance spectroscopy (EPR) experiments were performed on X. dendrorhous membranes in order to study the effect of incorporation rates of different type of carotenoids. In the case of fluid-phase membranes, it was found that polar carotenoids, such as astaxanthin and cis-astaxanthin, increased the EPR order parameter and decreased the motional freedom and phase-transition temperature. In contrast the non-polar carotenoids beta-cryptoxanthin and beta-carotene decreased the EPR order parameter and increased motional freedom and phase-transition temperature. A noteworthy coherence was observed between the polarities of the strains and the phase-transition temperatures.

Blasko A, Belagyi J, Dergez T, Deli J, Papp G, Papp T, Vagvolgyi C, Pesti M.

Department of General and Environmental Microbiology, Faculty of Sciences, University of Pécs, P.O. Box 266, 7601, Pecs, Hungary, agnesblasko@hotmail.com.

Modulation of the conductance of a 2,2\’-bipyridine-functionalized peptidic ion channel by Ni(2+).

An alpha-helical amphipathic peptide with the sequence H(2)N-(LSSLLSL)(3)-CONH(2) was obtained by solid phase synthesis and a 2,2\’-bipyridine was coupled to its N-terminus, which allows complexation of Ni(2+). Complexation of the 2,2\’-bipyridine residues was proven by UV/Vis spectroscopy. The peptide helices were inserted into lipid bilayers (nano black lipid membranes, nano-BLMs) that suspend the pores of porous alumina substrates with a pore diameter of 60 nm by applying a potential difference. From single channel recordings, we were able to distinguish four distinct conductance states, which we attribute to an increasing number of peptide helices participating in the conducting helix bundle. Addition of Ni(2+) in micromolar concentrations altered the conductance behaviour of the formed ion channels in nano-BLMs considerably. The first two conductance states appear much more prominent demonstrating that the complexation of bipyridine by Ni(2+) results in a considerable confinement of the observed multiple conductance states. However, the conductance levels were independent of the presence of Ni(2+). Moreover, from a detailed analysis of the open lifetimes of the channels, we conclude that the complexation of Ni(2+) diminishes the frequency of channel events with larger open times.

Pilz CS, Steinem C.

Institut für Organische und Biomolekulare Chemie, Georg-August Universität, Tammannstr. 2, 37077, Göttingen, Germany.

Unusual stress fracture in an adolescent baseball pitcher affecting the trochlear groove of the olecranon.

Stress fractures of the proximal ulna are known to occur in throwing athletes. Most cases extend to involve the olecranon, and cases limited to the trochlear groove are rare. In this report we present a 17-year-old elite baseball pitcher with a stress fracture of the trochlear groove of the proximal ulna. Diagnosis was made by demonstration of characteristic signal changes on MRI of the elbow. The fracture occurred at the cortical notch, also known as the pseudodefect of the trochlear groove. This case suggests that the cortical notch serves as an area of weakness predisposing pitchers to development of a stress fracture.

Blake JJ, Block JJ, Hannah GA, Kan JH.

Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, 37232, USA.

Effect of aging on the coordination between equilibrium and movement: what changes?

This investigation studies the effect of aging on the coordination between equilibrium and trunk movement. Eight young adults and seven adults at the end of middle age bent their trunk forward and stabilized their position. The center of mass shift was studied as an indicator of equilibrium control as was the electromyographic pattern of the main muscles involved in the movement. The kinematic strategy responsible for both the movement and equilibrium control was quantified by performing a principal components analysis on the hip, knee, ankle angle changes occurring during the movement. We observed that the effect of aging can be detected early. It is not expressed as a deterioration of equilibrium control but rather as \”over control\”. The kinematic strategy is modified, the central command adapted. These results could express the onset of a lesser ability to simplify the coordination between equilibrium and movement as young adults leading to its deterioration in the elderly.

Vernazza-Martin S, Tricon V, Martin N, Mesure S, Azulay JP, Le Pellec-Muller A.

Laboratoire Sport et Culture EA2931, UFR STAPS Paris X Nanterre, Bât S, 200 avenue de la République, 92001, Nanterre, France, sylvie-martin@freesurf.fr.

ERP correlates of anticipatory attention: spatial and non-spatial specificity and relation to subsequent selective attention.

Brain-based models of visual attention hypothesize that attention-related benefits afforded to imperative stimuli occur via enhancement of neural activity associated with relevant spatial and non-spatial features. When relevant information is available in advance of a stimulus, anticipatory deployment processes are likely to facilitate allocation of attention to stimulus properties prior to its arrival. The current study recorded EEG from humans during a centrally-cued covert attention task. Cues indicated relevance of left or right visual field locations for an upcoming motion or orientation discrimination. During a 1 s delay between cue and S2, multiple attention-related events occurred at frontal, parietal and occipital electrode sites. Differences in anticipatory activity associated with the non-spatial task properties were found late in the delay, while spatially-specific modulation of activity occurred during both early and late periods and continued during S2 processing. The magnitude of anticipatory activity preceding the S2 at frontal scalp sites (and not occipital) was predictive of the magnitude of subsequent selective attention effects on the S2 event-related potentials observed at occipital electrodes. Results support the existence of multiple anticipatory attention-related processes, some with differing specificity for spatial and non-spatial task properties, and the hypothesis that levels of activity in anterior areas are important for effective control of subsequent S2 selective attention.

Dale CL, Simpson GV, Foxe JJ, Luks TL, Worden MS.

Dynamic NeuroImaging Laboratory, University of California, San Francisco, CA, USA, corby.dale@radiology.ucsf.edu.