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Immune checkpoint inhibitors highlight the importance of anticancer immunity. However, their clinical utility and safety are limited by the low response rates and adverse effects. We focused on progesterone (P4), a hormone produced by the placenta during pregnancy, because it has multiple biological activities related to anticancer and immune regulation effects. P4 has a reversible immune regulatory function distinct from that of the stress hormone cortisol, which may drive irreversible immune suppression that promotes T cell exhaustion and apoptosis in patients with cancer. Because the anticancer effect of P4 is induced at higher than physiological concentrations, we aimed to develop a new anticancer drug by encapsulating P4 in liposomes. In this study, we prepared liposome-encapsulated anti-programmed death ligand 1 (PD-L1) antibody-conjugated P4 (Lipo-anti-PDL1-P4) and evaluated the effects on the growth of MDA-MB-231 cells, a PD-L1-expressing triple-negative breast cancer cell line, in vitro and in NOG-hIL-4-Tg mice transplanted with human peripheral blood mononuclear cells (humanized mice). Lipo-anti-PD-L1-P4 at physiological concentrations reduced T cell exhaustion and proliferation of MDA-MB-231 in vitro. Humanized mice bearing MDA-MB-231 cells expressing PD-L1 showed suppressed tumor growth and peripheral tissue inflammation. The proportion of B cells and CD4+ T cells decreased, whereas the proportion of CD8+ T cells increased in Lipo-anti-PDL1-P4-administrated mice spleens and tumor-infiltrated lymphocytes. Our results suggested that Lipo-anti-PD-L1-P4 establishes a systemic anticancer immune environment with minimal toxicity. Thus, the use of P4 as an anticancer drug may represent a new strategy for cancer treatment. [ABSTRACT FROM AUTHOR]

The efficient Pd-catalyzed coupling of unstable bicyclic pyrimidines and pyrazoles under basic conditions was established for the first time. The reactions proceeded with excellent yields without hydrolysis using Pd2(dba)3, tBuXPhos, and K3PO4. [ABSTRACT FROM AUTHOR]

Lipopolysaccharides (LPS) are potent activator of the innate immune response through the binding to the myeloid differentiation protein-2 (MD-2)/toll-like receptor 4 (TLR4) receptor complexes. Although a variety of LPSs have been characterized so far, a detailed molecular description of the structure-activity relationship of the lipid A part has yet to be clarified. Photosynthetic Bradyrhizobium strains, symbiont of Aeschynomene legumes, express distinctive LPSs bearing very long-chain fatty acids with a hopanoid moiety covalently linked to the lipid A region. Here, we investigated the immunological properties of LPSs isolated from Bradyrhizobium strains on both murine and human immune systems. We found that they exhibit a weak agonistic activity and, more interestingly, a potent inhibitory effect on MD-2/TLR4 activation exerted by toxic enterobacterial LPSs. By applying computational modeling techniques, we also furnished a plausible explanation for the Bradyrhizobium LPS inhibitory activity at atomic level, revealing that its uncommon lipid A chemical features could impair the proper formation of the receptorial complex, and/or has a destabilizing effect on the pre-assembled complex itself. [ABSTRACT FROM AUTHOR]

The TLR2 agonist, dipalmitoyl lipopeptide (Pam2LP), has been used as an immune adjuvant without much success. Pam2LP is recognised by TLR2/6 receptors in humans and in mice. This study examined the proliferative activity of cytotoxic T lymphocytes (CTL) using mouse Ag-presenting dendritic cells (DCs) and OT-I assay system, where a library of synthetic Pam2LP was utilised from the Staphylococcus aureus database. Ag-specific CTL expansion and IFN-γ levels largely depended on the Pam2LP peptide sequence. The first Aa is cysteine (Cys), which has an active SH residue to bridge fatty acids, and the second and third Aa are hydrophilic or non-polar. The sequence structurally adapted to the residual constitution of the reported TLR2/6 pocket. The inactive sequence contained proline or leucine/isoleucine after the first Cys. Notably, no direct activation of OT-I cells was detected without DCs by stimulation with the active Pam2LP having the Cys-Ser sequence. MyD88, but not TICAM-1 or IFN pathways, in DCs participates in DC maturation characterised by upregulation of CD40, CD80 and CD86. Hence, the active Pam2LPs appear suitable for dimeric TLR2/6 on DCs, resulting in induction of DC maturation. [ABSTRACT FROM AUTHOR]

4-Chlorophenyl ether was utilized as a new protecting group for the hydroxy function. This group was readily introduced to a sugar hydroxy group by using diaryliodonium triflate. Regioselective introduction of this protecting group at the vicinal cis-diol was achieved by using a copper catalyst and diaryliodonium triflate. This protecting group is stable under the Lewis acidic conditions of glycosylation, but it can be readily removed by the initial conversion into the corresponding 4-methoxyphenyl ether with use of a Pd catalyst, followed by oxidation with ammonium cerium (IV) nitrate [(NH4)2Ce(NO3)6] (CAN). [ABSTRACT FROM AUTHOR]

We describe a simple chiral-pool synthesis of (-)-longamide B, (-)-longamide B methyl ester, and (-)-hanishin. The key feature of the total synthesis is the formation of a piperazinone from a 1,2-cyclic sulfamidate and methyl 2-pyrrolecarboxylate, which permits efficient construction of the pyrrolopiperazinone core scaffold. [ABSTRACT FROM AUTHOR]

Guanylation proceeded efficiently upon treatment of the various amines with cyanamide in the presence of catalytic amounts of scandium(III) triflate under mild conditions. The method did not require the guanylation reagents to be preactivated, and the reaction proceeded efficiently in water. The method, therefore, has practical utility for substrates that dissolve only in aqueous solutions, for example, peptides or pharmacologically important compounds. [ABSTRACT FROM AUTHOR]

Hydroxyl groups on an unsaturated imine, which may be readily obtained from the corresponding unsaturated aldehyde and the 1,2-ethanolamine derivative, were found to efficiently activate a [4+4] dimerization reaction to produce the eight-membered 1,5-diazacyclooctane. A novel OH-π interaction between the two imines, in addition to the stabilization of the eight-membered diacetals, was proposed based on density functional theory calculations. [ABSTRACT FROM AUTHOR]

Toll‐like receptor 4 (TLR4) and MD‐2 recognizes lipid A, the active moiety of microbial lipopolysaccharide (LPS). Little is known about mechanisms for LPS recognition by TLR4–MD‐2. Here we show ligand‐induced TLR4 oligomerization, homotypic interaction of TLR4, which directly leads to TLR4 signaling. Since TLR4 oligomerization normally occurred in the absence of the cytoplasmic portion of TLR4, TLR4 oligomerization works upstream of TLR4 signaling. Lipid IVa, a lipid A precursor, is agonistic on mouse TLR4–MD‐2 but turns antagonistic on chimeric mouse TLR4–human MD‐2, demonstrating that the antagonistic activity of lipid IVa is determined by human MD‐2. Binding studies with radioactive lipid A and lipid IVa revealed that lipid IVa is similar to lipid A in dose‐dependent and saturable binding to mouse TLR4–human MD‐2. Lipid IVa, however, did not induce TLR4 oligomerization, and inhibited lipid A‐dependent oligomerization of mouse TLR4–human MD‐2. Thus, lipid IVa binds mouse TLR4–human MD‐2 but does not trigger TLR4 oligomerization. Binding study further revealed that the antagonistic activity of lipid IVa correlates with augmented maximal binding to mouse TLR4–human MD‐2, which was ∼2‐fold higher than lipid A. Taken together, lipid A antagonist lipid IVa is distinct from lipid A in binding to TLR4–MD‐2 and in subsequent triggering of TLR4 oligomerization. Given that the antagonistic activity of lipid IVa is determined by MD‐2, MD‐2 has an important role in a link between ligand interaction and TLR4 oligomerization. [ABSTRACT FROM AUTHOR]

Summary Lipid A is the bioactive centre of lipopolysaccharide (LPS), and its properties exhibit various endotoxic and biological effects toward host cells. We examined whether Toll-like receptors (TLRs) are mediated by the signals from various synthetic acylated derivatives of d-glucosamine monophosphate. All test synthetic monosaccharide lipid A analogues similar to acylated β-(1-6)-d-glucosamine disaccharide bisphosphates, such as Escherichia coli -type lipid A (compound 506) and its precursor (compound 406), clearly induced nuclear factor (NF)-κB activation in Ba/F3 cells expressing murine TLR4 and its accessory protein MD-2 (Ba/mTLR4/mMD-2), but no induction was found in those expressing murine TLR2 (Ba/mTLR2). Compound 411, the non-reducing sugar moiety of compound 506, exhibited interleukin-8 (IL-8) and tumour necrosis factor-α (TNF-α)-producing activities in human peripheral blood mononuclear cells (PBMC), whereas compound 401, the reducing moiety of compounds 506 and 406, and Gifu lipid A-46 (GLA-46), the non-reducing moiety of compound 406, induced no production of IL-8 and TNF-α, which was similar to the findings for compound 406. Among the synthetic triacylated monosaccharide lipid A analogues, some compounds with three tetradecanoyl (C[sub 14] ) groups or that included a dodecanoyl (C[sub 12] ) group were more active toward murine and human cells than were other analogues with a decanoyl (C[sub 10] ) or hexadecanoyl (C[sub 16] ) group. Furthermore, IL-8 production in PBMC stimulated with the active monosaccharide lipid A analogues as well as compound 506 was clearly inhibited by the monoclonal antibody to human TLR4. These findings suggest that monosaccharide lipid A analogues similar to disaccharide lipid As are capable of activating both murine and human cells through TLR4. [ABSTRACT FROM AUTHOR]