5,7,4'-Trimethoxyflavone triggers cancer cell PD-L1 ubiquitin-proteasome degradation and facilitates antitumor immunity by targeting HRD1.

Targeting the programmed cell death 1/programmed cell death ligand 1 (PD-1/PD-L1) pathway has been identified as a successful approach for tumor immunotherapy. Here, we identified that the small molecule 5,7,4'-trimethoxyflavone (TF) from Kaempferia parviflora Wall reduces PD-L1 expression in colorectal cancer cells and enhances the killing of tumor cells by T cells. Mechanistically, TF targets and stabilizes the ubiquitin ligase HMG-CoA reductase degradation protein 1 (HRD1), thereby increasing the ubiquitination of PD-L1 and promoting its degradation through the proteasome pathway. In mouse MC38 xenograft tumors, TF can activate tumor-infiltrating T-cell immunity and reduce the immunosuppressive infiltration of myeloid-derived suppressor cells and regulatory T cells, thus exerting antitumor effects. Moreover, TF synergistically exerts antitumor immunity with CTLA-4 antibody. This study provides new insights into the antitumor mechanism of TF and suggests that it may be a promising small molecule immune checkpoint modulator for cancer therapy.

Posttranslational regulatory mechanism of PD-L1 in cancers and associated opportunities for novel small-molecule therapeutics.

Despite the tremendous progress in cancer research over the past few decades, effective therapeutic strategies are still urgently needed. Accumulating evidence suggests that immune checkpoints are the cause of tumor immune escape. PD-1/PD-L1 are among them. Posttranslational modification is the most critical step for protein function, and the regulation of PD-L1 by small molecules through posttranslational modification is highly valuable. In this review, we discuss the mechanisms of tumor cell immune escape and several posttranslational modifications associated with PD-L1 and describe examples in which small molecules can regulate PD-L1 through posttranslational modifications. Herein, we propose that the use of small molecule compounds that act by inhibiting PD-L1 through posttranslational modifications is a promising therapeutic approach with the potential to improve clinical outcomes for cancer patients.

Qijiao Shengbai Capsule alleviated leukopenia by interfering leukotriene pathway: Integrated network study of multi-omics.

BACKGROUND: Leukopenia could be induced by chemotherapy, which leads to bone marrow suppression and even affects the therapeutic progression of cancer. Qijiao Shengbai Capsule (QSC) has been used for the treatment of leukopenia in clinic, but its bioactive components and mechanisms have not yet been elucidated clearly. PURPOSE: This study aimed to elucidate the molecular mechanisms of QSC in treating leukopenia. STUDY DESIGN: Serum pharmacochemistry, multi-omics, network pharmacology, and validation experiment were combined to study the effect of QSC in murine leukopenia model. METHODS: First, UPLC-QTOF-MS was used to clarify the absorbed components of QSC. Then, cyclophosphamide (CTX) was used to induce mice model with leukopenia, and the therapeutic efficacy of QSC was assessed by an integrative approach of multi-omics and network pharmacology strategy. Finally, molecular mechanisms and potential therapeutic targets were identified by validated experiments. RESULTS: 121 compounds absorbed in vivo were identified. QSC significantly increase the count of white blood cells (WBCs) in peripheral blood of leukopenia mice with 15 days treatment. Multi-omics and network pharmacology revealed that leukotriene pathway and MAPK signaling pathway played crucial roles during the treatment of leukopenia with QSC. Six targets (ALOX5, LTB4R, CYSLTR1, FOS, JUN, IL-1ß) and 13 prototype compounds were supposed to be the key targets and potential active components, respectively. The validation experiment further confirmed that QSC could effectively inhibit the inflammatory response induced by leukopenia. The inhibitors of ALOX5 activity can significantly increase the number of WBCs in leukopenia mice. Molecular docking of ALOX5 suggested that calycosin, daidzein, and medicarpin were the potentially active compounds of QSC. CONCLUSION: Leukotriene pathway was found for the first time to be a key role in the development of leukopenia, and ALOX5 was conformed as the potential target. QSC may inhibit the inflammatory response and interfere the leukotriene pathway, it is able to improve hematopoiesis and achieve therapeutic effects in the mice with leukopenia.

Benzosceptrin C induces lysosomal degradation of PD-L1 and promotes antitumor immunity by targeting DHHC3.

Programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) blockade has become a mainstay of cancer immunotherapy. Targeting the PD-1/PD-L1 axis with small molecules is an attractive approach to enhance antitumor immunity. Here, we identified a natural marine product, benzosceptrin C (BC), that enhances the cytotoxicity of T cells to cancer cells by reducing the abundance of PD-L1. Furthermore, BC exerts its antitumor effect in mice bearing MC38 tumors by activating tumor-infiltrating T cell immunity. Mechanistic studies suggest that BC can prevent palmitoylation of PD-L1 by inhibiting DHHC3 enzymatic activity. Subsequently, PD-L1 is transferred from the membrane to the cytoplasm and cannot return to the membrane via recycling endosomes, triggering lysosome-mediated degradation of PD-L1. Moreover, the combination of BC and anti-CTLA4 effectively enhances antitumor T cell immunity. Our findings reveal a previously unrecognized antitumor mechanism of BC and represent an alternative immune checkpoint blockade (ICB) therapeutic strategy to enhance the efficacy of cancer immunotherapy.

Dracorhodin targeting CMPK2 attenuates inflammation: A novel approach to sepsis therapy.

BACKGROUND: Despite all modern advances in medicine, an effective drug for treating sepsis has yet to be found. The discovery of CMPK2 spurred hopes for the treatment of sepsis. However, CMPK2-untapped target inhibitors are still an enormous obstacle that has hindered the CMPK2-centric treatment of sepsis. METHODS: Here, we found that the CMPK2 gene is highly expressed in the whole blood of sepsis patients by RNA-Seq. First, recombinant CMPK2 was purified by a eukaryotic expression purification system, and the activity of recombinant CMPK2 was detected by the ADP-GLO assay. Second, we developed an affinity MS strategy combined with quantitative lysine reactivity profiling to discover CMPK2 ligands from the active ingredients of Chinese herbs. In addition, the dissociation constant Kd of the ligand and the target protein CMPK2 was further detected by microscale thermophoresis technology. Third, we used this strategy to identify a naturally sourced small molecule, dracorhodin (DP). Using mass spectrometry-based quantitative lysine reactivity profiling combined with a series of mutant tests, the results show that K265 acts as a bright hotspot of DP inhibition of CMPK2. Fourth, immune-histochemical staining, ELISAs, RT-qPCR, flow cytometry and immunoblotting were used to illustrate the potential function and related mechanism of DP in regulating sepsis injury. RESULTS: Our results suggest that DP exerts powerful anti-inflammatory effects by regulating the NLRP3 inflammasome via the lipopolysaccharide (LPS)-induced CMPK2 pathway. Strikingly, DP significantly attenuated LPS-induced sepsis in a mouse model, but its effect was weakened in mice with myeloid-specific Cmpk2 ablation. CONCLUSION: We provide a new framework that provides more valuable information for new therapeutic approaches to sepsis, including the establishment of screening strategies and the development of target drugs to provide a theoretical basis for ultimately improving clinical outcomes for sepsis patients. Collectively, these findings reveal that DP is a promising CMPK2 inhibitor for the treatment of sepsis.

Molecular mechanisms of ferroptosis and its antitumor applications in natural products.

Ferroptosis, an iron-dependent form of regulated cell death, results in lipid peroxidation of polyunsaturated fatty acids in the cell membrane, which is catalyzed by iron ions and accumulated to lethal levels. It is mechanistically distinct from other forms of cell death, such as apoptosis, pyroptosis, and necroptosis, so it may address the problem of cancer resistance to apoptosis and provide new therapeutic strategies for cancer treatment, which has been intensively studied over the past few years. Notably, considerable advances have been made in the antitumor research of natural products due to their multitargets and few side effects. According to research, natural products can also induce ferroptosis in cancer therapies. In this review we summarize the molecular mechanisms of ferroptosis, introduce the key regulatory genes of ferroptosis, and discuss the progress of natural product research in the field of ferroptosis to provide theoretical guidance for research on natural product-induced ferroptosis in tumors.

LncGMDS-AS1 promotes the tumorigenesis of colorectal cancer through HuR-STAT3/Wnt axis.

Chronic inflammation promotes the tumorigenesis and cell stemness maintenance of colorectal cancer (CRC). However, the bridge role of long noncoding RNA (lncRNA) in linking chronic inflammation to CRC development and progression needs better understanding. Here, we elucidated a novel function of lncRNA GMDS-AS1 in persistently activated signal transducer and transcription activator 3 (STAT3) and Wnt signaling and CRC tumorigenesis. Interleukin-6 (IL-6) and Wnt3a induced lncRNA GMDS-AS1 expression, which was highly expressed in the CRC tissues and plasma of CRC patients. GMDS-AS1 knockdown impaired the survival, proliferation and stem cell-like phenotype acquisition of CRC cells in vitro and in vivo. We performed RNA sequencing (RNA-seq) and mass spectrometry (MS) to probe target proteins and identify their contributions to the downstream signaling pathways of GMDS-AS1. In CRC cells, GMDS-AS1 physically interacted with the RNA-stabilizing protein HuR, thereby protecting the HuR protein from polyubiquitination- and proteasome-dependent degradation. HuR stabilized STAT3 mRNA and upregulated the levels of basal and phosphorylated STAT3 protein, persistently activating STAT3 signaling. Our research revealed that the lncRNA GMDS-AS1 and its direct target HuR constitutively activate STAT3/Wnt signaling and promote CRC tumorigenesis, the GMDS-AS1-HuR-STAT3/Wnt axis is a therapeutic, diagnostic and prognostic target in CRC.