Epigenetic reprogramming of Runx3 reinforces CD8 + T-cell function and improves the clinical response to immunotherapy

Epigenetic Landscapes Drive CAR-T Cell Kinetics and Fate Decisions: Bridging Persistence and Resistance

Chimeric antigen receptor-T (CAR-T)-cell therapy has revolutionized the treatment paradigm for B-cell malignancies and holds promise for solid tumor immunotherapy. However, CAR-T-cell therapy still faces many challenges, especially primary and secondary resistance. Some mechanisms of resistance, including CAR-T-cell dysfunction, an inhibitory tumor microenvironment, and tumor-intrinsic resistance, have been identified in previous studies. As insights into CAR-T-cell biology have increased, the role of epigenetic reprogramming in influencing the clinical effectiveness of CAR-T cells has become increasingly recognized. An increasing number of direct and indirect epigenetic targeting methods are being developed in combination with CAR-T-cell therapy. In this review, we emphasize the broad pharmacological links between epigenetic therapies and CAR-T-cell therapy, not only within CAR-T cells but also involving tumors and the tumor microenvironment. To elucidate the mechanisms through which epigenetic therapies promote CAR-T-cell therapy, we provide a comprehensive overview of the epigenetic basis of CAR-T-cell kinetics and differentiation, tumor-intrinsic factors and the microenvironment. We also describe some epigenetic strategies that have implications for CAR-T-cell therapy in the present and future. Because targeting epigenetics can have pleiotropic effects, developing more selective and less toxic targeting strategies and determining the optimal administration strategy in clinical trials are the focus of the next phase of research. In summary, we highlight the possible mechanisms and clinical potential of epigenetic regulation in CAR-T-cell therapy.

Targeting pyroptosis reverses KIAA1199-mediated immunotherapy resistance in colorectal cancer

BACKGROUND

Despite advancements in treatment modalities, several patients with colorectal cancer (CRC) remain unresponsive to immune checkpoint inhibitor therapy. Pyroptosis, an inflammatory programmed cell death process, holds substantial promise for tumor immunotherapy. In this study, we explored the use of pyroptosis to overcome immunotherapy resistance in CRC.

METHODS

We used a pyroptosis-related gene panel to construct an immunotherapy efficacy evaluation model and validated its performance by immunohistochemical staining of CRC patient samples. Pyroptosis and its underlying mechanisms were examined both in vitro and in vivo using PCR, western blotting, lactate dehydrogenase release assay, ELISA, co-immunoprecipitation, immunohistochemistry, fluorescence cell assays, microscopic imaging, flow cytometry analysis and bioinformatics approaches.

RESULTS

We established a model to define high or low levels of pyroptosis in CRC, revealed that low pyroptosis led to immunotherapy resistance, and identified KIAA1199 as a characteristic protein of low pyroptosis CRC. We further demonstrated that KIAA1199 contributes to low pyroptosis, resulting in resistance to immunotherapy. Mechanistically, KIAA1199 bound to and stabilized DNA methyltransferase-1 (DNMT1), thereby inhibiting GSDME-mediated pyroptosis. Importantly, our study highlighted that decitabine reversed KIAA1199-mediated immunotherapy resistance by enhancing pyroptosis to restore IL-1B release and CD8+ T cell infiltration.

CONCLUSIONS

We found a critical role of KIAA1199 in promoting immunotherapy resistance by suppressing pyroptosis via the DNMT1/GSDME pathway in CRC. Decitabine has emerged as a promising therapeutic agent for reversing KIAA1199-mediated immunotherapy resistance by enhancing pyroptosis. Our findings provide valuable insights for enhancing the efficacy of immunotherapy in patients with CRC who exhibit resistance to conventional immunotherapy approaches.

Full-length transcriptome sequencing of seven tissues of GuShi chickens

Chickens are vital economic poultry and serve as exemplary models for avian research. The incomplete reference genome of chickens and the limited availability of full-length cDNA impede the identification of alternatively spliced transcripts, thereby delaying many fundamental chicken studies. We utilized PacBio Iso-seq technology on various chicken tissues, obtaining 170,162 full-length transcripts through comprehensive transcriptome sequencing and annotation. Of the identified transcripts, 38,925 lncRNAs were predicted and categorized into five models. Our data significantly increases the known number of chickens' lncRNAs and alternatively spliced transcripts are crucial in enhancing current genome annotations. Furthermore, this data will be invaluable for functional studies of other avian species.

Getting the right combination to break the epigenetic code

Rapid advances in the field of epigenetics have facilitated the development of novel therapeutics targeting epigenetic mechanisms that are hijacked by cancer cells to support tumour growth and progression. Several epigenetic agents have been approved by the FDA for the treatment of cancer; however, the efficacy of these drugs is dependent on the underlying biology and drivers of the disease, with inherent differences between solid tumours and haematological malignancies. The efficacy of epigenetic drugs as single agents remains limited across most cancer types, which has spurred the clinical development of combination therapies, with the hope of attaining synergistic activity and/or overcoming treatment resistance. In this Review we discuss clinical advances that have been achieved with the use of epigenetic agents in combination with chemotherapies, immunotherapies or other targeted agents, including epigenetic-epigenetic combinations, as well as limitations and challenges associated with these combinatorial strategies. So far, the success of combination therapies targeting epigenetic mechanisms has generally been confined to haematological malignancies, with limited efficacy observed in patients with solid tumours. Nevertheless, this Review captures the field of epigenetic combination therapies across the spectra of haematology and oncology, highlighting opportunities for precision therapy to effectively harness the potential of epigenetic agents and produce meaningful improvements in clinical outcomes.

Myeloid cells meet CD8+ T cell exhaustion in cancer: What, why and how

Exhausted T cell (Tex) is a specific state of T cell dysfunction, in which these T cells gradually lose their effector function and change their phenotype during chronic antigen stimulation. The enrichment of exhausted CD8+ T cell (CD8+ Tex) in the tumor microenvironment is one of the important reasons leading to the poor efficacy of immunotherapy. Recent studies have reported many reasons leading to the CD8+ T cell exhaustion. In addition to cancer cells, myeloid cells can also contribute to T cell exhaustion via many ways. In this review, we discuss the history of the concept of exhaustion, CD8+ T cell dysfunction states, the heterogeneity, origin, and characteristics of CD8+ Tex. We then focus on the effects of myeloid cells on CD8+ Tex, including tumor-associated macrophages (TAMs), dendritic cells (DCs) and neutrophils. Finally, we systematically summarize current strategies and recent advancements in therapies reversing and CD8+ T cell exhaustion.

Novel biomarkers: the RUNX family as prognostic predictors in colorectal cancer

While biomarkers have been shown to enhance the prognosis of patients with colorectal cancer (CRC) compared to conventional treatments, there is a pressing need to discover novel biomarkers that can assist in assessing the prognostic impact of immunotherapy and in formulating individualized treatment plans. The RUNX family, consisting of RUNX1, RUNX2, and RUNX3, has been recognized as crucial regulators in developmental processes, with dysregulation of these genes also being implicated in tumorigenesis and cancer progression. In our present study, we demonstrated a crucial regulatory role of RUNX in CD8+T and CD103+CD8+T cell-mediated anti-tumor response within the tumor microenvironment (TME) of human CRC. Specifically, RUNXs were significantly differentially expressed between tumor and normal tissues in CRC. Patients with a greater proportion of infiltrating CD8+RUNX1+, CD103+CD8+RUNX1+, CD8+RUNX2+, CD103+CD8+RUNX2+, CD8+RUNX3+, or CD103+CD8+RUNX3+ T cells demonstrated improved outcomes compared to those with lower proportions. Additionally, the proportions of infiltrating CD8+RUNX1+T and CD8+RUNX3+T cells may serve as valuable prognostic predictors for CRC patients, independent of other clinicopathological factors. Moreover, further bioinformatic analysis conducted utilizing the TISIDB and TIMER platforms demonstrated significant associations between the members of the RUNX family and immune-infiltrating cells, specifically diverse subpopulations of CD8+TILs. Our study of human colorectal cancer tissue microarray (TMA) also revealed positive and statistically significant correlations between the expressions of RUNX1, RUNX2, and RUNX3 in both CD8+T cells and CD103+CD8+T cells. Our study comprehensively revealed the varied expressions and prognostic importance of the RUNX family in human colorectal cancer tissues. It underscored their potential as vital biomarkers for prognostic evaluation in colorectal cancer patients and as promising targets for immunotherapy in treating this disease.

Pim1 inactivating induces RUNX3 upregulation that improves/alleviates airway inflammation and mucus hypersecretion in vitro and in vivo

PURPOSE

Our research aimed to evaluate whether proto-oncogene serine/threonine-protein kinase Pim-1 (Pim1) inactivation could attenuate asthma by promoting runt-related transcription factor 3 (Runx3) expression and explore the underlying molecular mechanism.

METHOD

Phorbol 12-myristate 13-acetate (PMA, 50 nM) was used to induce inflammation in BEAS-2B human airway epithelial cells. ELISA and immunofluorescence double staining confirmed inflammation modelling and differential expression of Pim1 and Runx3. Pim1 inhibitor (SGI-1776) and Runx3 siRNA (siRunx3) were used in this study. Apoptosis, inflammation, MUC5AC protein expression, Pim1 kinase and Runx3 protein expression, and PI3K/AKT/nuclear factor-κB (NF-κB) pathway-associated protein expression were also assessed by flow cytometry, immunofluorescence and western blot. The effects of Pim1 inactivation on airway inflammation, pathological injury and mucus secretion in wild-type and Runx3 knockout mice were observed by in vivo experiments.

RESULTS

The results of the in vitro experiments showed that PMA stimulation causes BEAS-2B cell apoptosis and promotes the MUC5AC expression. In addition, PMA stimulation activated the PI3K/AKT/NF-κB pathway. SGI-1776 treatment partially reversed these effects, whereas siRunx3 attenuated the effects of SGI-1776 on PMA-stimulated BEAS-2B cells. In vivo experiments showed that in Runx3-KO asthmatic mice, inhibition of Pim1 kinase had less effect on airway inflammation, pathological injury and mucus secretion. Meanwhile, Pim1 kinase expression was higher in Runx3-KO asthmatic mice than in wild-type asthmatic mice. Furthermore, inhibition of Pim1 kinase inhibited activation of the PI3K/AKT/NF-κB pathway, whereas these effects were attenuated in Runx3-KO mice.

CONCLUSION

Our results suggest that Pim1 inactivation can ameliorate airway inflammation and mucus hypersecretion through upregulation of Runx3 and the effect could be mediated through modulation of the PI3K/AKT/NF-κB pathway.

CD8+ T cell exhaustion and its regulatory mechanisms in the tumor microenvironment: key to the success of immunotherapy

A steady dysfunctional state caused by chronic antigen stimulation in the tumor microenvironment (TME) is known as CD8+ T cell exhaustion. Exhausted-like CD8+ T cells (CD8+ Tex) displayed decreased effector and proliferative capabilities, elevated co-inhibitory receptor generation, decreased cytotoxicity, and changes in metabolism and transcription. TME induces T cell exhaustion through long-term antigen stimulation, upregulation of immune checkpoints, recruitment of immunosuppressive cells, and secretion of immunosuppressive cytokines. CD8+ Tex may be both the reflection of cancer progression and the reason for poor cancer control. The successful outcome of the current cancer immunotherapies, which include immune checkpoint blockade and adoptive cell treatment, depends on CD8+ Tex. In this review, we are interested in the intercellular signaling network of immune cells interacting with CD8+ Tex. These findings provide a unique and detailed perspective, which is helpful in changing this completely unpopular state of hypofunction and intensifying the effect of immunotherapy.

Reversal of T-cell exhaustion: Mechanisms and synergistic approaches

T cells suffer from long-term antigen stimulation and insufficient energy supply, leading to a decline in their effector functions, memory capabilities, and proliferative capacity, ultimately resulting in T cell exhaustion and an inability to perform normal immune functions in the tumor microenvironment. Therefore, exploring how to restore these exhausted T cells to a state with effector functions is of great significance. Exhausted T cells exhibit a spectrum of molecular alterations, such as heightened expression of inhibitory receptors, shifts in transcription factor profiles, and modifications across epigenetic, metabolic, and transcriptional landscapes. This review provides a comprehensive overview of various strategies to reverse T cell exhaustion, including immune checkpoint blockade, and explores the potential synergistic effects of combining multiple approaches to reverse T cell exhaustion. It offers new insights and methods for achieving more durable and effective reversal of T cell exhaustion.

Dysregulated gene expression of SUMO machinery components induces the resistance to anti-PD-1 immunotherapy in lung cancer by upregulating the death of peripheral blood lymphocytes

Background

The majority of patients with lung cancer exhibit drug resistance after anti-PD-1 immunotherapy, leading to shortened patient survival time. Previous studies have suggested an association between epigenetic abnormalities such as methylation and clinical response to anti-PD-1 immunotherapy, while the role of SUMOylation in resistance to anti-PD-1 antibody immunotherapy is still unclear.

Methods

Here, the mRNA expression of 15 SUMO machinery components in PBMC from lung cancer patients receiving anti-PD-1 immunotherapy were analyzed using real-time PCR. Base on the percentage change in mRNA levels, the relationship between the expression of SUMO machinery components and outcomes of anti-PD-1 immunotherapy, and the influencing factors of SUMOylation were evaluated. PBMC was treated with different concentrations of 2-D08 (a specific inhibitor of SUMOylation) in vitro, and analyzed the activation and the death rates of lymphocyte subsets by flow cytometry analysis.

Results

A predictive method, base on the gene expression of three SUMO machinery components (SUMO1, SUMO3 and UBE2I), were developed to distinguish non-responders to PD-1 inhibitors. Furthermore, the number of lymphocytes in peripheral blood significantly reduced in the dysregulated SUMOylation groups (the percentage change >100 or -50 ~ -100 groups). In vitro studies confirmed that lightly low SUMOylation level improved the activation status of T and NK lymphocytes, but extremely low SUMOylation level lead to the increased death rates of lymphocytes.

Conclusion

Our findings implied that dysregulated gene expression of SUMO machinery components could induce the resistance of anti-PD-1 immunotherapy in lung cancer by upregulating the death of peripheral blood lymphocytes. These data might provide effective circulating biomarkers for predicting the efficacy of anti-PD-1 immunotherapy, and uncovered a novel regulatory mechanism of resistance to anti-PD-1 immunotherapy.

Interferon signaling and ferroptosis in tumor immunology and therapy

This study sought to elucidate the mechanisms underlying the impact of the interferon signaling pathway on Ferroptosis in tumor cells and its correlation with CD8 + T cell exhaustion. Using mouse models and single-cell sequencing, the researchers studied the interaction between CD8 + T cells and the interferon signaling pathway. Differential gene analysis revealed key genes involved in CD8 + T cell exhaustion, and their downstream factors were explored using bioinformatics tools. The expression levels of interferon-related genes associated with Ferroptosis were analyzed using data from the TCGA database, and their relevance to tumor tissue Ferroptosis and patients' prognosis was determined. In vitro experiments were conducted to measure the levels of IFN-γ, MDA, and LPO, as well as tumor cell viability and apoptosis. In vivo validation using a mouse tumor model confirmed the results obtained from the in vitro experiments, highlighting the potential of silencing HSPA6 or DNAJB1 in enhancing the efficacy of PD-1 therapy and inhibiting tumor growth and migration.

Mutual exclusivity and co-occurrence patterns of immune checkpoints indicate NKG2A relates to anti-PD-1 resistance in gastric cancer

BACKGROUND

An increasing number of clinical studies have begun to explore combination strategies with immune checkpoint inhibitors, aiming to present new opportunities for overcoming anti-PD-1 treatment resistance in gastric cancer. Unfortunately, the exploration of certain immune checkpoint inhibitor combination strategies has yielded suboptimal results. Therefore, it is necessary to comprehensively analyze the expression patterns of immune checkpoints and identify optimal combination regimens of anti-PD-1 inhibitors with other immune checkpoint inhibitors.

METHODS

Leveraging single-cell RNA sequencing (scRNA-seq) and multivariate linear regression interaction models, we dissected the immune checkpoint expression characteristics of CD8+ T cells in gastric cancer and the immune checkpoint expression pattern (ICEP) mediating anti-PD-1 treatment resistance. Furthermore, we employed transcription factor analysis and CellOracle to explore the transcriptional regulatory mechanisms governing CD8+ T cell differentiation fates. Finally, we utilized Nichenet and spatial transcriptomic analysis to investigate the spatial expression patterns of immune checkpoints.

RESULTS

Interaction analysis indicated that, among the known immune checkpoints, co-expression of NKG2A and PD-1 might exert a more profound inhibitory effect on the proliferative capacity of CD8+ T cells. The co-expression analysis revealed differential co-expression pattern of PD-1 and NKG2A, defined as ICEP1 (CD8+ T cells co-expressing PD-1, CTLA-4, TIGIT, LAG-3 or CD38) and ICEP2 (CD8+ T cells solely expressing NKG2A or co-expressing with other immune checkpoints), reflecting the co-occurrence pattern of PD-1 and the mutual exclusivity of NKG2A. Further, these two ICEP CD8+ T cell subsets represented distinct CD8+ T cell differentiation fates governed by MSC and RUNX3. Notably, ICEP2 CD8+ T cells were associated with anti-PD-1 therapy resistance in gastric cancer. This phenomenon may be attributed to the recruitment of LGMN+ macrophages mediated by the CXCL16-CXCR6 signaling pathway.

CONCLUSION

This study unveiled two distinct ICEPs and the mutually exclusivity and co-occurrence characteristics of CD8+ T cells in gastric cancer. The ICEP2 CD8+ T cell subset, highly expressed in gastric cancer patients resistant to anti-PD-1 therapy, may be recruited by LGMN+ macrophages through CXCL16-CXCR6 axis. These findings provide evidence for NKG2A as a novel immunotherapeutic target in gastric cancer and offer new insights into combination strategies for immune checkpoint inhibitors in gastric cancer.

[18F]FDG PET-CT radiomics signature to predict pathological complete response to neoadjuvant chemoimmunotherapy in non-small cell lung cancer: a multicenter study

OBJECTIVES

This study aims to develop and validate a radiomics model based on 18F-fluorodeoxyglucose positron emission tomography-computed tomography ([18F]FDG PET-CT) images to predict pathological complete response (pCR) to neoadjuvant chemoimmunotherapy in non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

One hundred eighty-five patients receiving neoadjuvant chemoimmunotherapy for NSCLC at 5 centers from January 2019 to December 2022 were included and divided into a training cohort and a validation cohort. Radiomics models were constructed via the least absolute shrinkage and selection operator (LASSO) method. The performances of models were evaluated by the area under the receiver operating characteristic curve (AUC). In addition, genetic analyses were conducted to reveal the underlying biological basis of the radiomics score.

RESULTS

After the LASSO process, 9 PET-CT radiomics features were selected for pCR prediction. In the validation cohort, the ability of PET-CT radiomics model to predict pCR was shown to have an AUC of 0.818 (95% confidence interval [CI], 0.711, 0.925), which was better than the PET radiomics model (0.728 [95% CI, 0.610, 0.846]), CT radiomics model (0.732 [95% CI, 0.607, 0.857]), and maximum standard uptake value (0.603 [95% CI, 0.473, 0.733]) (p < 0.05). Moreover, a high radiomics score was related to the upregulation of pathways suppressing tumor proliferation and the infiltration of antitumor immune cell.

CONCLUSION

The proposed PET-CT radiomics model was capable of predicting pCR to neoadjuvant chemoimmunotherapy in NSCLC patients.

CLINICAL RELEVANCE STATEMENT

This study indicated that the generated 18F-fluorodeoxyglucose positron emission tomography-computed tomography radiomics model could predict pathological complete response to neoadjuvant chemoimmunotherapy, implying the potential of our radiomics model to personalize the neoadjuvant chemoimmunotherapy in lung cancer patients.

KEY POINTS

• Recognizing patients potentially benefiting neoadjuvant chemoimmunotherapy is critical for individualized therapy of lung cancer. • [18F]FDG PET-CT radiomics could predict pathological complete response to neoadjuvant immunotherapy in non-small cell lung cancer. • [18F]FDG PET-CT radiomics model could personalize neoadjuvant chemoimmunotherapy in lung cancer patients.

The roles of epigenetic regulation in graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation (aHSCT) is utilized as a potential curative treatment for various hematologic malignancies. However, graft-versus-host disease (GVHD) post-aHSCT is a severe complication that significantly impacts patients' quality of life and overall survival, becoming a major cause of non-relapse mortality. In recent years, the association between epigenetics and GVHD has garnered increasing attention. Epigenetics focuses on studying mechanisms that affect gene expression without altering DNA sequences, primarily including DNA methylation, histone modifications, non-coding RNAs (ncRNAs) regulation, and RNA modifications. This review summarizes the role of epigenetic regulation in the pathogenesis of GVHD, with a focus on DNA methylation, histone modifications, ncRNA, RNA modifications and their involvement and applications in the occurrence and development of GVHD. It also highlights advancements in relevant diagnostic markers and drugs, aiming to provide new insights for the clinical diagnosis and treatment of GVHD.

The tumor-intrinsic role of the m6A reader YTHDF2 in regulating immune evasion

Tumors evade attacks from the immune system through various mechanisms. Here, we identify a component of tumor immune evasion mediated by YTH domain-containing family protein 2 (YTHDF2), a reader protein that usually destabilizes m6A-modified mRNA. Loss of tumoral YTHDF2 inhibits tumor growth and prolongs survival in immunocompetent tumor models. Mechanistically, tumoral YTHDF2 deficiency promotes the recruitment of macrophages via CX3CL1 and enhances mitochondrial respiration of CD8+ T cells by impairing tumor glycolysis metabolism. Tumoral YTHDF2 deficiency promotes inflammatory macrophage polarization and antigen presentation in the presence of IFN-γ. In addition, IFN-γ induces autophagic degradation of tumoral YTHDF2, thereby sensitizing tumor cells to CD8+ T cell-mediated cytotoxicity. Last, we identified a small molecule compound that preferentially induces YTHDF2 degradation, which shows a potent antitumor effect alone but a better effect when combined with anti-PD-L1 or anti-PD-1 antibodies. Collectively, YTHDF2 appears to be a tumor-intrinsic regulator that orchestrates immune evasion, representing a promising target for enhancing cancer immunotherapy.

Nuclear-targeted chimeric peptide nanorods to amplify innate anti-tumor immunity through localized DNA damage and STING activation

Stimulator of the interferon genes (STING) pathway is appealing but challenging to potentiate the innate anti-tumor immunity. In this work, nuclear-targeted chimeric peptide nanorods (designated as PFPD) are constructed to amplify innate immunity through localized DNA damage and STING activation. Among which, the chimeric peptide (PpIX-FFVLKPKKKRKV) is fabricated with photosensitizer and nucleus targeting peptide sequence, which can self-assemble into nanorods and load STING agonist of DMXAA. The uniform nanosize distribution and good stability of PFPD improve the sequential targeting delivery of drugs towards tumor cells and nuclei. Under light irradiation, PFPD produce a large amount of reactive oxygen species (ROS) to destroy nuclear DNA in situ, and the released cytosolic DNA fragment will efficiently activate innate anti-tumor immunity in combination with STING agonist. In vitro and in vivo results indicate the superior ability of PFPD to activate natural killer cells and T cells, thus efficiently eradicating lung metastatic tumor without inducing unwanted side effects. This work provides a sophisticated strategy for localized activation of innate immunity for systemic tumor treatment, which may inspire the rational design of nanomedicine for tumor precision therapy.

Functional diversification and dynamics of CAR-T cells in patients with B-ALL

Understanding of cellular evolution and molecular programs of chimeric antigen receptor-engineered (CAR)-T cells post-infusion is pivotal for developing better treatment strategies. Here, we construct a longitudinal high-precision single-cell transcriptomic landscape of 7,578 CAR-T cells from 26 patients with B cell acute lymphoblastic leukemia (B-ALL) post-infusion. We molecularly identify eight CAR-T cell subtypes, including three cytotoxic subtypes with distinct kinetics and three dual-identity subtypes with non-T cell characteristics. Remarkably, long-term remission is coincident with the dominance of cytotoxic subtypes, while leukemia progression is correlated with the emergence of subtypes with B cell transcriptional profiles, which have dysfunctional features and might predict relapse. We further validate in vitro that the generation of B-featured CAR-T cells is induced by excessive tumor antigen stimulation or suppressed TCR signaling, while it is relieved by exogenous IL-12. Moreover, we define transcriptional hallmarks of CAR-T cell subtypes and reveal their molecular changes along computationally inferred cellular evolution in vivo. Collectively, these results decipher functional diversification and dynamics of peripheral CAR-T cells post-infusion.

Natural epidithiodiketopiperazine alkaloids as potential anticancer agents: Recent mechanisms of action, structural modification, and synthetic strategies

Cancer has become a grave health crisis that threatens the lives of millions of people worldwide. Because of the drawbacks of the available anticancer drugs, the development of novel and efficient anticancer agents should be encouraged. Epidithiodiketopiperazine (ETP) alkaloids with a 2,5-diketopiperazine (DKP) ring equipped with transannular disulfide or polysulfide bridges or S-methyl moieties constitute a special subclass of fungal natural products. Owing to their privileged sulfur units and intriguing architectural structures, ETP alkaloids exhibit excellent anticancer activities by regulating multiple cancer proteins/signaling pathways, including HIF-1, NF-κB, NOTCH, Wnt, and PI3K/AKT/mTOR, or by inducing cell-cycle arrest, apoptosis, and autophagy. Furthermore, a series of ETP alkaloid derivatives obtained via structural modification showed more potent anticancer activity than natural ETP alkaloids. To solve supply difficulties from natural resources, the total synthetic routes for several ETP alkaloids have been designed. In this review, we summarized several ETP alkaloids with anticancer properties with particular emphasis on their underlying mechanisms of action, structural modifications, and synthetic strategies, which will offer guidance to design and innovate potential anticancer drugs.