Amine adducts of triallylborane as highly reactive allylborating agents for Cu(I)-catalyzed allylation of chiral sulfinylimines.

The implementation of selective catalytic processes with highly active reagents is an attractive strategy that meets the modern principles of sustainable development of chemistry. In the current study, we for the first time describe the method and general principles of Cu(I)-catalyzed allylation of imines with amine adducts of allylic triorganoboranes. Triallylborane is an extremely reactive compound and cannot be used for the catalytic allylation of imines, whereas its amine adducts are ideal substrates for catalysis. The structure of the amine fragment successfully balances the safety, selectivity and stability of the allylboron reagent, allowing it to demonstrate high activity in catalytic allylation reactions, exceeding many times any known allylboranes. The obtained results are supported by quantitative kinetics data and DFT calculations. The catalytic efficacy of the system was demonstrated on model sulfinylimines (23 examples). High diastereoselectivity up to >99% was achieved, including for the gram-scale synthesis of 2-hydroxyphenyl-derivatives. Taking into account the high reactivity and unsurpassed atom-economy of amine adducts of triallylborane (AAT), they can be considered as prospective allylation reagents with Cu(I) and other appropriate metallocatalysts.

Cancer Relevance of Circulating Antibodies Against LINE-1 Antigens in Humans.

Long interspersed nuclear element-1 (LINE-1 or L1), the most abundant family of autonomous retrotransposons occupying over 17% of human DNA, is epigenetically silenced in normal tissues by the mechanisms involving p53 but is frequently derepressed in cancer, suggesting that L1-encoded proteins may act as tumor-associated antigens recognized by the immune system. In this study, we established an immunoassay to detect circulating autoantibodies against L1 proteins in human blood. Using this assay in >2,800 individuals with or without cancer, we observed significantly higher IgG titers against L1-encoded ORF1p and ORF2p in patients with lung, pancreatic, ovarian, esophageal, and liver cancers than in healthy individuals. Remarkably, elevated levels of anti-ORF1p-reactive IgG were observed in patients with cancer with disease stages 1 and 2, indicating that the immune response to L1 antigens can occur in the early phases of carcinogenesis. We concluded that the antibody response against L1 antigens could contribute to the diagnosis and determination of immunoreactivity of tumors among cancer types that frequently escape early detection. SIGNIFICANCE: The discovery of autoantibodies against antigens encoded by L1 retrotransposons in patients with five poorly curable cancer types has potential implications for the detection of an ongoing carcinogenic process and tumor immunoreactivity.

A deimmunized and pharmacologically optimized Toll-like receptor 5 agonist for therapeutic applications.

The Toll-like receptor 5 (TLR5) agonist entolimod, a derivative of Salmonella flagellin, has therapeutic potential for several indications including radioprotection and cancer immunotherapy. However, in Phase 1 human studies, entolimod induced a rapid neutralizing immune response, presumably due to immune memory from prior exposure to flagellated enterobacteria. To enable multi-dose applications, we used structure-guided reengineering to develop a next-generation, substantially deimmunized entolimod variant, GP532. GP532 induces TLR5-dependent NF-κB activation like entolimod but is smaller and has mutations eliminating an inflammasome-activating domain and key B- and T-cell epitopes. GP532 is resistant to human entolimod-neutralizing antibodies and shows reduced de novo immunogenicity. GP532 also has improved bioavailability, a stronger effect on key cytokine biomarkers, and a longer-lasting effect on NF-κB. Like entolimod, GP532 demonstrated potent prophylactic and therapeutic efficacy in mouse models of radiation-induced death and tissue damage. These results establish GP532 as an optimized TLR5 agonist suitable for multi-dose therapies and for patients with high titers of preexisting flagellin-neutralizing antibodies.

Rapid DNA double-strand breaks resulting from processing of Cr-DNA cross-links by both MutS dimers.

Mismatch repair (MMR) strongly enhances cyto- and genotoxicity of several chemotherapeutic agents and environmental carcinogens. DNA double-strand breaks (DSB) formed after two replication cycles play a major role in MMR-dependent cell death by DNA alkylating drugs. Here, we examined DNA damage detection and the mechanisms of the unusually rapid induction of DSB by MMR proteins in response to carcinogenic chromium(VI). We found that MSH2-MSH6 (MutSalpha) dimer effectively bound DNA probes containing ascorbate-Cr-DNA and cysteine-Cr-DNA cross-links. Binary Cr-DNA adducts, the most abundant form of Cr-DNA damage, were poor substrates for MSH2-MSH6, and their toxicity in cells was weak and MMR independent. Although not involved in the initial recognition of Cr-DNA damage, MSH2-MSH3 (MutSbeta) complex was essential for the induction of DSB, micronuclei, and apoptosis in human cells by chromate. In situ fractionation of Cr-treated cells revealed MSH6 and MSH3 chromatin foci that originated in late S phase and did not require replication of damaged DNA. Formation of MSH3 foci was MSH6 and MLH1 dependent, whereas MSH6 foci were unaffected by MSH3 status. DSB production was associated with progression of cells from S into G(2) phase and was completely blocked by the DNA synthesis inhibitor aphidicolin. Interestingly, chromosome 3 transfer into MSH3-null HCT116 cells activated an alternative, MSH3-like activity that restored dinucleotide repeat stability and sensitivity to chromate. Thus, sequential recruitment and unprecedented cooperation of MutSalpha and MutSbeta branches of MMR in processing of Cr-DNA cross-links is the main cause of DSB and chromosomal breakage at low and moderate Cr(VI) doses.

A new technique for the quantitative assessment of 8-oxoguanine in nuclear DNA as a marker of oxidative stress. Application to dystrophin-deficient DMD skeletal muscles.

This is the first report on the development of an immunohistochemical technique, combined with quantitative image analysis, for the assessment of oxidative stress quantitatively in nuclear DNA in situ, and its application to measure DNA damage in Duchenne muscular dystrophic (DMD) muscles. Three sequential staining procedures for cell nuclei, a cell marker, and a product of oxidative DNA damage, 8-oxoguanine (8-oxoG), were performed. First, the nuclei in muscle sections were stained with Neutral Red followed by the capture of their images with an image analysis system used for absorbance measurements. Second, the same sections were then immunostained for laminin in basement membranes as the cell marker. Next, the sections were treated with 2 N HCl to remove the bound Neutral Red and to denature tissue DNA. Third, the sections were immunostained for 8-oxoG in DNA, using diaminobenzidine (DAB) to reveal the antibody complex. This was followed by capture of the images of the immunostained sections as previously. The absorbances at 451.2 nm of bound Neutral Red and DAB polymer oxides, the final product of 8-oxoG immunostaining, were measured in the same myonuclei in the sections. Analysis of these absorbances permitted indices of the 8-oxoG content, independent of the nuclear densities, to be determined in nuclear DNA in single myofibres and myosatellite cells surrounded by basement membranes. We found that the mean index for the myonuclei in biceps brachii muscles of 2- to 7-year-old patients was 14% higher than that in age-matched normal controls. This finding of the increased oxidative stress in the myonuclei in young DMD muscles agrees with the previous reports of increased oxidative stress in the cytoplasm in the DMD myofibres and myosatellite cells. The present technique for the quantitative assessment of oxidative stress in nuclear DNA in situ is applicable not only in biomedical research but also in the development of effective drugs for degenerative diseases related to oxidative stress.

Characterization of a novel metabolic strategy used by drug-resistant tumor cells.

Acquired or inherent drug resistance is the major problem in achieving successful cancer treatment. However, the mechanism(s) of pleiotropic drug resistance remains obscure. We have identified and characterized a cellular metabolic strategy that differentiates drug-resistant cells from drug-sensitive cells. This strategy may serve to protect drug-resistant cells from damage caused by chemotherapeutic agents and radiation. We show that drug-resistant cells have low mitochondrial membrane potential, use nonglucose carbon sources (fatty acids) for mitochondrial oxygen consumption when glucose becomes limited, and are protected from exogenous stress such as radiation. In addition, drug-resistant cells express high levels of mitochondrial uncoupling protein 2 (UCP2). The discovery of this metabolic strategy potentially facilitates the design of novel therapeutic approaches to drug resistance.