Iron-Catalyzed C(sp3)-C(sp3) Coupling to Construct Quaternary Carbon Centers.

The construction of quaternary carbon centers via C-C coupling protocols remains challenging. The coupling of tertiary C(sp3) with secondary or tertiary C(sp3) counterparts has been hindered by pronounced steric clashes and many side reactions. Herein, we have successfully developed a type of bisphosphine ligand iron complex-catalyzed coupling reactions of tertiary alkyl halides with secondary alkyl zinc reagents and efficiently realized the coupling reaction between tertiary C(sp3) and secondary C(sp3) with high selectivity for the initial instance, which provided an efficient method for the construction of quaternary carbon centers with high steric hindrance. The combination of an iron catalyst and directing group of the substrate makes the great challenging transformation possible.

Enantioselective α-Boryl Carbene Transformations.

Carbenes, recognized as potent intermediates, enable unique chemical transformations, and organoborons are pivotal in diverse chemical applications. As a hybrid of carbene and the boryl group, α-boryl carbenes are promising intermediates for the construction of organoborons; unfortunately, such carbenes are hard to access and have low structural diversity with their asymmetric transformations largely uncharted. In this research, we utilized boryl cyclopropenes as precursors for the swift synthesis of α-boryl metal carbenes, a powerful category of intermediates for chiral organoboron synthesis. These α-boryl carbenes undergo a series of highly enantioselective transfer reactions, including B-H and Si-H insertion, cyclopropanation, and cyclopropanation/Cope rearrangement, catalyzed by a singular chiral copper complex. This approach opens paths to previously unattainable but easily transformable chiral organoborons, expanding both carbene and organoboron chemistry.

Discovery of a proliferation essential gene signature and actin-like 6A as potential biomarkers for predicting prognosis and neoadjuvant chemotherapy response in triple-positive breast cancer.

BACKGROUND: Patients with triple-positive breast cancer (TPBC) have a higher risk of recurrence and lower survival rates than patients with other luminal breast cancers. However, there are few studies on the predictive biomarkers of prognosis and treatment responses in TPBC. METHODS: Proliferation essential genes (PEGs) were acquired from clustered regularly interspaced short palindromic repeats-associated protein 9 (CRISPR-Cas9) technology, and cohorts of patients with TPBC were obtained from public databases and our cohort. To develop a TPBC-PEG signature, Cox regression and least absolute shrinkage and selection operator regression analyses were applied. Functional analyses were performed with gene set enrichment analysis. The relationship between candidate genes and neoadjuvant chemotherapy (NACT) sensitivity was explored via real-time quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry (IHC) on the basis of clinical samples. RESULTS: Among 900 TPBC-PEGs, 437 showed significant differential expression between TPBC and normal tissues. Three prognostic PEGs (actin-like 6A [ACTL6A], chaperonin containing TCP1 subunit 2 [CCT2], and threonyl-TRNA synthetase [TARS]) were identified and used to construct the PEG signature. Patients with high PEG signature scores exhibited a worse overall survival and lower sensitivity to NACT than patients with low PEG signature scores. RT-qPCR results indicated that ACTL6A and CCT2 expression were significantly upregulated in patients who lacked sensitivity to NACT. IHC results showed that the ACTL6A protein was highly expressed in patients with NACT resistance and nonpathological complete responses. CONCLUSIONS: This efficient PEG signature prognostic model can predict the outcomes of TPBC. Furthermore, ACTL6A expression level was associated with the response to NACT, and could serve as an important factor in predicting prognosis and drug sensitivity of patients with TPBC.

The immune checkpoint TIGIT/CD155 promotes the exhaustion of CD8 + T cells in TNBC through glucose metabolic reprogramming mediated by PI3K/AKT/mTOR signaling.

OBJECTIVE: The CD155/TIGIT axis has attracted considerable interest as an emerging immune checkpoint with potential applications in cancer immunotherapy. Our research focused on investigating the role of CD155/TIGIT checkpoints in the progression of triple-negative breast cancer (TNBC). METHODS: We evaluated CD155 and TIGIT expression in TNBC tissues using both immunohistochemistry (IHC) and gene expression profiling. Our experiments, both in vivo and in vitro, provided evidence that inhibiting the CD155/TIGIT pathway reinstates the ability of CD8 + T cells to generate cytokines. To assess the impact of CD155/TIGIT signaling blockade, we utilized Glucose Assay Kits and Lactate Assay Kits to measure alterations in glucose and lactate levels within CD8 + T cells. We employed western blotting (WB) to investigate alterations in glycolytic-related proteins within the PI3K/AKT/mTOR pathways following the inhibition of CD155/TIGIT signaling. RESULTS: CD155 exhibits heightened expression within TNBC tissues and exhibits a negative correlation with the extent of infiltrating CD8 + T cells. Furthermore, patients with TNBC demonstrate elevated levels of TIGIT expression. Our findings indicate that the interaction between CD155 and TIGIT disrupts the glucose metabolism of CD8 + T cells by suppressing the activation of the PI3K/AKT/mTOR signaling pathway, ultimately leading to the reduced production of cytokines by CD8 + T cells. Both in vivo and in vitro experiments have conclusively demonstrated that the inhibition of CD155/TIGIT interaction reinstates the capacity of CD8 + T cells to generate cytokines. Moreover, in vivo administration of the blocking antibody against TIGIT not only inhibits tumor growth but also augments the functionality of CD8 + T lymphocytes. CONCLUSIONS: Our research findings strongly suggest that CD155/TIGIT represents a promising therapeutic target for treating TNBC.

Iron-Catalyzed Allylic C(sp3)-H Silylation: Spin-Crossover-Efficiency-Determined Chemoselectivity.

The nuanced role of spin effects remains a critical gap in designing proficient open-shell catalysts. This study elucidates an iron-catalyzed allylic C(sp3)-H silylation/alkyne hydrosilylation reaction, in which the spin state of the open-shell iron catalyst dictates the reaction kinetics and pathway. Specifically, spin crossover led to alkyne hydrosilylation, whereas spin conservation resulted in a novel allylic C(sp3)-H silylation reaction. This chemoselectivity, governed by the spin-crossover efficiency, reveals an unexpected dimension in spin effects and a first in the realm of transition-metal-catalyzed in situ silylation of allylic C(sp3)-H bonds, which had been previously inhibited by the heightened reactivity of alkenes in hydrosilylation reactions. Furthermore, this spin crossover can either accelerate or hinder the reaction at different stages within a single catalytic reaction, a phenomenon scarcely documented. Moreover, we identify a substrate-assisted C-H activation mechanism, a departure from known ligand-assisted processes, offering a fresh perspective on C-H activation strategies.

Iron-Catalyzed Stereoconvergent 1,4-Hydrosilylation of Conjugated Dienes.

Stereoconvergent transformation of E/Z mixtures of olefins to products with a single steric configuration is of great practical importance but hard to achieve. Herein, we report an iron-catalyzed stereoconvergent 1,4-hydrosilylation reactions of E/Z mixtures of readily available conjugated dienes for the synthesis of Z-allylsilanes with high regioselectivity and exclusive stereoselectivity. Mechanistic studies suggest that the reactions most likely proceed through a two-electron redox mechanism. The stereoselectivity of the reactions is ultimately determined by the crowded reaction cavity of the α-diimine ligand-modified iron catalyst, which forces the conjugated diene to coordinate with the iron center in a cis conformation, which in turn results in generation of an anti-π-allyl iron intermediate. The mechanism of this stereoconvergent transformation differs from previously reported mechanisms of other related reactions involving radicals or metal-hydride species.

Exosomes in the hypoxic TME: from release, uptake and biofunctions to clinical applications.

Hypoxia is a remarkable trait of the tumor microenvironment (TME). When facing selective pressure, tumor cells show various adaptive characteristics, such as changes in the expression of cancer hallmarks (increased proliferation, suppressed apoptosis, immune evasion, and so on) and more frequent cell communication. Because of the adaptation of cancer cells to hypoxia, exploring the association between cell communication mediators and hypoxia has become increasingly important. Exosomes are important information carriers in cell-to-cell communication. Abundant evidence has proven that hypoxia effects in the TME are mediated by exosomes, with the occasional formation of feedback loops. In this review, we equally focus on the biogenesis and heterogeneity of cancer-derived exosomes and their functions under hypoxia and describe the known and potential mechanism ascribed to exosomes and hypoxia. Notably, we call attention to the size change of hypoxic cancer cell-derived exosomes, a characteristic long neglected, and propose some possible effects of this size change. Finally, jointly considering recent developments in the understanding of exosomes and tumors, we describe noteworthy problems in this field that urgently need to be solved for better research and clinical application.

Exosomal circGSE1 promotes immune escape of hepatocellular carcinoma by inducing the expansion of regulatory T cells.

Studies have shown exosomal circRNAs can regulate the immune escape of tumors by carrying cancer-derived molecules. Regulatory T cells (Tregs) participate in the process of tumor immune escape. However, the mechanism by which exosomal circRNAs regulate Tregs to create a microenvironment for tumor immune escape is unclear. The effect of exosomes on the proliferation, migration, and invasion of tumor cells was evaluated by CCK-8, transwell, and wound-healing assays. The expression of circGSE1 was evaluated by real-time quantitative PCR, and the function of exosomal circGSE1 was explored by Western blot and RNA pull-down assays. In vivo animal metastasis models and bioluminescence imaging were used to verify the effect of exosomal circGSE1 on tumor progression. Collectively, we revealed that exosomal circGSE1 derived from hepatocellular carcinoma (HCC) cells promotes the progression of HCC by inducing Tregs expansion via regulating the miR-324-5p/TGFBR1/Smad3 axis. Therefore, in the future, exosomal circGSE1 can be used as a promising biomarker for immunotherapy of HCC.

Extracellular vesicle PD-L1 in reshaping tumor immune microenvironment: biological function and potential therapy strategies.

Programmed cell death 1 ligand 1 (PD-L1) is the ligand for programmed death protein-1 (PD-1), is associated with immunosuppression. Signaling via PD-1/PD-L1 will transmits negative regulatory signals to T cells, inducing T-cell inhibition, reducing CD8+ T-cell proliferation, or promoting T-cell apoptosis, which effectively reduces the immune response and leads to large-scale tumor growth. Accordingly, many antibody preparations targeting PD-1 or PD-L1 have been designed to block the binding of these two proteins and restore T-cell proliferation and cytotoxicity of T cells. However, these drugs are ineffective in clinical practice. Recently, numerous of studies have shown that, in addition to the surface of tumor cells, PD-L1 is also found on the surface of extracellular vesicles secreted by these cells. Extracellular vesicle PD-L1 can also interact with PD-1 on the surface of T cells, leading to immunosuppression, and has been proposed as a potential mechanism underlying PD-1/PD-L1-targeted drug resistance. Therefore, it is important to explore the production, regulation and tumor immunosuppression of PD-L1 on the surface of tumor cells and extracellular vesicles, as well as the potential clinical application of extracellular vesicle PD-L1 as tumor biomarkers and therapeutic targets. Video Abstract.

Highly Regio-, Stereo-, and Enantioselective Copper-Catalyzed B-H Bond Insertion of α-Silylcarbenes: Efficient Access to Chiral Allylic gem-Silylboranes.

Herein, we report the development of a method for highly regio-, stereo-, and enantioselective B-H bond insertion reactions of α-silylcarbenes generated from 1-silylcyclopropenes in the presence of a chiral copper(I)/bisoxazoline catalyst for the construction of chiral γ,γ-disubstituted allylic gem-silylboranes, which cannot be prepared by any other known methods. This reaction is the first highly enantioselective carbene insertion reaction of α-silylcarbenes ever to be reported. The method shows general applicability for various 3,3-disubstituted silylcyclopropenes and exclusively affords E-products. The novel chiral γ,γ-disubstituted allylic gem-silylborane products are versatile allylic bimetallic reagents with high stability and have great synthetic potential, especially for the construction of complex molecules with continuous chiral centers.

Development and Clinical Evaluation of a CRISPR-Based Diagnostic for Rapid Group B Streptococcus Screening.

Vertical transmission of group B Streptococcus (GBS) is among the leading causes of neonatal illness and death. Colonization with GBS usually is screened weeks before delivery during pregnancy, on the basis of which preventive measures, such as antibiotic prophylaxis, were taken. However, the accuracy of such an antenatal screening strategy has been questionable because of the intermittent nature of GBS carriage. We developed a simple-to-use, rapid, CRISPR-based assay for GBS detection. We conducted studies in a prospective cohort of 412 pregnant women and a retrospective validation cohort to evaluate its diagnostic performance. We demonstrated that CRISPR-GBS is highly sensitive and offered shorter turnaround times and lower instrument demands than PCR-based assays. This novel GBS test exhibited an overall improved diagnostic performance over culture and PCR-based assays and represents a novel diagnostic for potential rapid, point-of-care GBS screening.

Dirhodium-Catalyzed Enantioselective B-H Bond Insertion of gem-Diaryl Carbenes: Efficient Access to gem-Diarylmethine Boranes.

The scarcity of reliable methods for synthesizing chiral gem-diarylmethine borons limits their applications. Herein, we report a method for highly enantioselective dirhodium-catalyzed B-H bond insertion reactions with diaryl diazomethanes as carbene precursors. These reactions afforded chiral gem-diarylmethine borane compounds in high yield (up to 99 % yield), high activity (turnover numbers up to 14 300), high enantioselectivity (up to 99 % ee) and showed unprecedented broad functional group tolerance. The borane compounds synthesized by this method could be efficiently transformed into diaryl methanol, diaryl methyl amine, and triaryl methane derivatives with good stereospecificity. Mechanistic studies suggested that the borane adduct coordinated to the rhodium catalyst and thus interfered with decomposition of the diazomethane, and that insertion of a rhodium carbene (generated from the diaryl diazomethane) into the B-H bond was most likely the rate-determining step.

Insertion of Alkylidene Carbenes into B-H Bonds.

We have developed a protocol for insertion of alkylidene carbenes into the B-H bonds of amine-borane adducts, enabling, for the first time, the construction of C(sp2)-B bonds by means of carbene-insertion reactions. Various acyclic and cyclic alkenyl borane-amine adducts were prepared from readily accessible starting materials in good to high yields and were subsequently subjected to a diverse array of functional group transformations. The unprecedented spiro B-N heterocycles prepared in this study have potential utility as building blocks for the synthesis of pharmaceuticals. Preliminary mechanistic studies suggest that insertion of the alkylidene carbenes into the B-H bonds of the amine-borane adducts proceeds via a concerted process involving a three-membered-ring transition state.

Highly Enantioselective O-H Bond Insertion Reaction of α-Alkyl- and α-Alkenyl-α-diazoacetates with Water.

Catalytic asymmetric reactions in which water is a substrate are rare. Enantioselective transition-metal-catalyzed insertion of carbenes into the O-H bond of water can be used to incorporate water into the stereogenic center, but the reported chiral catalysts give good results only when α-aryl-α-diazoesters are used as the carbene precursors. Herein we report the first highly enantioselective O-H bond insertion reactions between water and α-alkyl- and α-alkenyl-α-diazoesters as carbene precursors, with catalysis by a combination of achiral dirhodium complexes and chiral phosphoric acids or chiral phosphoramides. Participation of the phosphoric acids or phosphoramides in the carbene transfer reaction markedly suppressed competing side reactions, such as ß-H migration, carbene dimerization, and olefin isomerization, and thus ensured good yields of the desired products. Fine-tuning of the ester moiety facilitated enantiocontrol of the proton transfer reactions of the enol intermediates and resulted in excellent enantioselectivity. This protocol represents an efficient new method for preparation of multifunctionalized chiral α-alkyl and α-alkenyl hydroxyl esters, which readily undergo various transformations and can thus be used for the synthesis of bioactive compounds. Mechanistic studies revealed that the phosphoric acids and phosphoramides promoted highly enantioselective [1,2]- and [1,3]-proton transfer reactions of the enol intermediates. Maximization of molecular orbital overlap in the transition states of the proton transfer reactions was the original driving force to involve the proton shuttle catalysts in this process.

Dendritic cell vaccines in breast cancer: Immune modulation and immunotherapy.

Breast cancer (BC) is the most common cancer in women worldwide. Although substantial progress has been made in the diagnosis and treatment of breast cancer, the efficacy and side effects of traditional treatment methods are still unsatisfactory. In recent years, immunotherapy including tumor vaccine has achieved great success in the treatment of BC. Dendritic cells (DCs) are multifunctional antigen-presenting cells that play an important role in the initiation and regulation of innate and adaptive immune responses. Numerous studies have shown that DC-based treatments might have a potential effect on BC. Among them, the clinical study of DC vaccine in BC has demonstrated considerable anti-tumor effect, and some DC vaccines have entered the stage of clinical trials. In this review, we summarize the immunomodulatory effects and related mechanisms of DC vaccine in breast cancer as well as the progress of clinical trials to propose possible challenges of DC vaccines and new development directions.

Targeting tumor-associated macrophages in hepatocellular carcinoma: biology, strategy, and immunotherapy.

Hepatocellular carcinoma (HCC), one of the most malignant tumors, is characterized by its stubborn immunosuppressive microenvironment. As one of the main members of the tumor microenvironment (TME) of HCC, tumor-associated macrophages (TAMs) play a critical role in its occurrence and development, including stimulating angiogenesis, enhancing immunosuppression, and promoting the drug resistance and cancer metastasis. This review describes the origin as well as phenotypic heterogeneity of TAMs and their potential effects on the occurrence and development of HCC and also discusses about various adjuvant therapy based strategies that can be used for targeting TAMs. In addition, we have highlighted different treatment modalities for TAMs based on immunotherapy, including small molecular inhibitors, immune checkpoint inhibitors, antibodies, tumor vaccines, adoptive cellular immunotherapy, and nanocarriers for drug delivery, to explore novel combination therapies and provide feasible therapeutic options for clinically improving the prognosis and quality of life of HCC patients.

Chiral gem-difluoroalkyl reagents: gem-difluoroalkyl propargylic borons and gem-difluoroalkyl α-allenols.

Chiral fluorinated reagents provide new opportunities for the discovery of drugs and functional materials because the introduction of a fluorinated group significantly alters a molecule's physicochemical properties. Chiral gem-difluoroalkyl fragments (R-CF2-C*) are key motifs in many drugs. However, the scarcity of synthetic methods and types of chiral gem-difluoroalkyl reagents limits the applications of these compounds. Herein, we report two types of chiral gem-difluoroalkyl reagents chiral gem-difluoroalkyl propargylic borons and gem-difluoroalkyl α-allenols and their synthesis by means of methods involving rhodium-catalyzed enantioselective B-H bond insertion reactions of carbenes and Lewis acid-promoted allenylation reactions. The mild, operationally simple method features a broad substrate scope and good functional group tolerance. These two types of reagents contain easily transformable boron and alkynyl or allenyl moieties and thus might facilitate rapid modular construction of chiral molecules containing chiral gem-difluoroalkyl fragments and might provide new opportunities for the discovery of chiral gem-difluoroalkyl drugs and other functional molecules.

Wittig/B─H insertion reaction: A unique access to trisubstituted Z-alkenes.

The Wittig reaction, which is one of the most effective methods for synthesizing alkenes from carbonyl compounds, generally gives thermodynamically stable E-alkenes, and synthesis of trisubstituted Z-alkenes from ketones presents notable challenges. Here, we report what we refer to as Wittig/B─H insertion reactions, which innovatively combine a Wittig reaction with carbene insertion into a B─H bond and constitute a promising method for the synthesis of thermodynamically unstable trisubstituted Z-boryl alkenes. Combined with the easy transformations of boryl group, this methodology provides efficient access to a variety of previously unavailable trisubstituted Z-alkenes and thus provides a platform for discovery of pharmaceuticals. The unique Z-selectivity of the reaction is determined by the maximum overlap of the orbitals between the B─H bond of the borane adduct and the alkylidene carbene intermediate in the transition state.

Tumor-derived exosomes in hypoxic microenvironment: release mechanism, biological function and clinical application.

Hypoxia is a key feature of solid tumors and is related to disease aggressiveness and adverse outcomes. It is recognized that the two-way communication between cancer cells and their microenvironment is critical to cancer progression. Increasing evidences show that the cellular communication and crosstalk between tumor cells and their microenvironment is not limited to secreted molecules, but also includes exosomes secreted by tumor cells. Exosomes are nano-scale extracellular vesicles (30-100 nm in diameter), which carry the molecular characteristics and cargo of the source cell, participating in intercellular communication through autocrine, paracrine and near-crine pathways. Recent studies have shown that cancer cells produce more exosomes under hypoxic conditions than normoxia conditions. The secretion and function of exosomes could be influenced by hypoxia in various types of cancer. Therefore, in this review, we summarize and discuss the latest research on the physiological mechanism of hypoxia regulating the secretion of exosomes, and the involvement of hypoxic exosomes in cancer progression and immune escape processes, and expounds the potential for targeting hypoxia-induced exosomes for cancer therapy strategies.