Reduction of toxicity in brachytherapy using a new technique

PurposeThe purpose of the study was to elucidate the usefulness of a dose evaluation method for reducing late genitourinary (GU) toxicity in high-dose-rate brachytherapy (HDR-BT) of prostate cancer.Methods and MaterialsGU toxicity was scored in accordance with the Common Terminology Criteria for Adverse Events version 4.0. The prostatic urethra was divided into three segments (base = B, midgland = M, apex = A), which were subclassified into seven subgroups (B, M, A, BM, BA, MA, BMA) using a D_10% color map of the urethra. Significance testing was conducted on urethral D_0.1% and D_10% among the seven subgroups. Grade < 2 GU toxicity was also implemented.ResultsData of 174 patients with localized prostate cancer treated with HDR-BT combined with external beam radiotherapy between November 2011 and July 2014 were analyzed retrospectively. Median age was 74 (53–84) years, and median followup period was 44 (6–69) months. The number of Grade < 2 and Grade ≥ 2 toxicity was significantly different in the M subgroup than in the other subgroups (p < 0.05), suggesting increased radioresistance in the midgland urethra.ConclusionsA high-dose-area evaluation method using a urethral D_10% color map may be helpful in reducing late GU toxicity in HDR-BT for prostate cancer.     

Stereoselective synthesis of Gly-Gly-type (E)-methylalkene and (Z)-chloroalkene dipeptide isosteres and their application to 14-mer RGG peptidomimetics

Stereoselective and efficient synthesis of Gly-Gly-type (E)-methylalkene and (Z)-chloroalkene dipeptide isosteres is realized by organocuprate-mediated single electron transfer reduction. The synthetic isosteres can be used in Fmoc-based solid phase peptide synthesis, resulting in the preparation of the 14-mer RGG peptidomimetics containing an (E)-methylalkene or a (Z)-chloroalkene unit.

An efficient synthesis of Gly-Gly-type (E)-methylalkene and (Z)-chloroalkene dipeptide isosteres is realized by organocuprate-mediated single electron transfer reduction.

Glycylglycine (Gly-Gly) is the smallest dipeptide and has been synthesized by many approaches in the last 100 years.¹ Due to its versatile nature and ready availability, glycylglycine has been used as a chemical probe² and buffer³ in biochemical studies and also as a reagent which can enhance the solubility of overexpressed proteins.⁴ In addition to the utility of Gly-Gly itself, oligoglycine (oligo-Gly) motifs are notable for being more flexible and less-functionalized than any combination of other amino acids. These features are useful in bioconjugation strategies which link multiple biomolecules without interfering with the function of each biomolecule, allowing synthesis of bioconjugated artificial molecules including dimeric, multi-domain, and fusion proteins.⁵ The flexibility of oligo-Gly enables the formation of unusual secondary structures of peptides and proteins.⁶ Thus, the oligo-Gly motif can be found in the biologically important peptides and proteins such as Met/Leu-enkephalin ( and ), the C-terminus of ubiquitin , ctenidin,⁷ shepherin I,⁸ and DNA/RNA-binding proteins with repeated sequences related to the various physiological processes via protein–protein and protein–nucleic acids interactions.⁹ These proteins relate with gene expression, DNA damage signal and apoptosis, however, the detail effects of Gly-Gly with steric and electronic factors to these functions are unknown. Given the importance of oligo-Gly in various fields, non-hydrolyzable peptidomimetics of oligo-Gly could be attractive building blocks for the synthesis of novel bioconjugated molecules and complex peptidomimetics with improved chemical stability and functionality. For example, even the Gly-Gly dipeptide mimic with the tetra-substituted alkene unit replacing the Gly-Gly peptide bond has been shown to promote the β-hairpin formation, and is thus the smallest peptidomimetic that is known to control a peptide structure.¹⁰ There are two reports of the synthesis of Gly-Gly-type fluoroalkene dipeptide isosteres.¹¹ However, the poor synthetic access to such molecules has hindered their application to the peptidomimetics. Our long-standing interest in the drug discovery with amide-to-alkene isosteric switching prompted this investigation into the stereoselective synthesis of Gly-Gly-type (E)-methylalkene and (Z)-chloroalkene dipeptide isosteres.In this report, we describe the beginning of our oligo-Gly-based peptidomimetic study with the stereoselective synthesis of Gly-Gly-type (E)-methylalkene and (Z)-chloroalkene dipeptide isosteres and their use in Fmoc-based solid phase peptide synthesis (SPPS). In the first application of isosteres of this type to access complex peptidomimetics, we synthesize 14-mer RGG peptidomimetics containing (E)-methylalkene or (Z)-chloroalkene unit as surrogates for a Gly-Gly peptide bond. These two isosteres were selected because the potentials of both isosteres have not been fully uncovered, though there are several promising examples.^12,13 Since the carbonyl oxygen equivalents of those isosteres are similar in their size¹⁴ but differ in their electronic properties,¹⁵ comparative studies of these isosteres would have the advantage of exploring the role of peptide bonds in terms of their steric and electronic natures. This work also uncovered the unique ability of the Gly-Gly-type (Z)-chloroalkene isostere to induce β-turn structures in the almost unfoled peptides (Fig. 1).Open in a separate windowFig. 1Gly-Gly peptide and its alkene-type peptidomimetics.The main challenges in this study include the stereoselective formation of the (E)-methylalkene and (Z)-chloroalkene moieties as the surrogates of the Gly-Gly trans-peptide bond, together with the control of the olefine isomerization under the condition of the isostere synthesis and Fmoc-based SPPS. There are several synthetic approaches toward tri-substituted alkene-type isosteres, including the Overman rearrangement,¹³ the S_N2′-type opening of alkenylaziridines,^12a Cu-mediated CF₃-coupling of vinyl iodide,¹⁶ and cross-couplings of vinyl stannane.¹⁷ Organocuprate-mediated reactions of α,β-unsaturated carbonyl compounds with γ-leaving group(s) are also powerful methods to produce tri-substituted alkene-type isosteres, and are particularly suitable for the stereoselective synthesis of (Z)-fluoroalkene¹⁸ and (Z)-chloroalkene isosteres.¹⁹The preparation of Gly-Gly-type alkene dipeptide isosteres was facilitated by the organocuprate-mediated SET reduction that was used in the stereoselective formation of the (E)-methylalkene and (Z)-chloroalkene moieties. Scheme 1 shows the synthesis of (E)-methylalkene isosteres (5). A Witting reaction of methacrolein (1) with ethyl (triphenylphosphoranylidene)acetate followed by epoxidation with m-CPBA afforded the alkenyl oxirane (2) which, treated with Gillman reagent (n-Bu₂CuLi), produced the allylic alcohol (3) with high E-selectivity. A Mitsunobu reaction of 3 with Ns(Boc)NH and deprotection provided the Gly-Gly-type (E)-methylalkene dipeptide isostere 5 that can be applied to the Fmoc-based SPPS. All reactions leading to the synthesis of 5 were performed on a gram scale.Open in a separate windowScheme 1Synthesis of Gly-Gly-type (E)-methylalkene dipeptide isosteres (5).Synthesis of chloroalkene isostere (14) is shown in Scheme 2. Based on previous results for the successful, efficient synthesis of Val-Xaa-type chloroalkene isosteres,^19c we assumed that a similar protocol would allow for the synthesis of 14. However, our attempts revealed that the Gly substrate used has different reactivity and selectivity compared to the other substrates, particularly in the SET reduction step. Consequently, Gly-specific reaction conditions are necessary. The nucleophilic addition of the lithium enolate of methyl dichloroacetate to the N-sulfinylaldimine (7), prepared from (±)-tert-butylsulfinamide (6) and paraformaldehyde and m-CPBA oxidation of 6 gave the N-tert-butylsulfonyl (Bus)-protected α,α-dichloro-β-amino ester (8). Precise control of the amount of DIBAL-H at low temperatures enables the partial reduction of 8, and this is followed by a Horner–Wadsworth–Emmons reaction to produce the corresponding (E)-enoate (9). Initial efforts to apply our established conditions for SET reduction with Me₂CuLi identified the poor Z-selectivity of the reaction and also its propensity to form the α-methylated side products 11 and 12 (Open in a separate windowScheme 2Synthesis of Gly-Gly-type (Z)-chloroalkene dipeptide isosteres (14).Reactivity of (E)-enoate (9) with organocuprates^a

What is the primary antigen in systemic lupus erythematosus?

The mechanism by which anti-DNA antibodies cause glomerulonephritis in systemic lupus erythematosus (SLE) has not been fully elucidated. However, not a few recent studies suggest the pivotal role of nucleosomal histones in the binding of immune complexes to the glomerular basement membrane. Some antibodies cross-react with both double-stranded (ds) DNA and nucleosome, but antibodies exclusively specific to the nucleosome have also been described. In lupus model mice, anti-nucleosome antibodies are reported to emerge even before the production of anti-dsDNA antibodies. BK virus T antigen, bacterial DNA, a DNA binding protein nucleobindin and autoreactive helper T cells specific to nucleosome or anti-DNA antibody-derived peptides have been shown to induce or enhance anti-DNA antibody production in normal or lupus-prone animals. These new experimental models are expected to be helpful in the exploration of the true antigen that elicits autoimmune reactions in SLE.