A RIPK1-specific PROTAC degrader achieves potent antitumor activity by enhancing immunogenic cell death

How has the field of immunogenic cell death in breast cancer evolved and impacted clinical practice over the past eleven years?

This study elucidates the research landscape of immunogenic cell death (ICD) in breast cancer through a bibliometric analysis of 457 Web of Science articles. Contributions from China and the USA are particularly prominent, with notable international collaborations. Core journals such as Biomaterials published influential studies, while researchers like Huang Y made impactful contributions. High-frequency keyword analysis identified key research hotspots, including immunotherapy, the tumor microenvironment, and nanomedicine. The integration of chemotherapy with immunotherapy and the identification of key proteins have driven recent advancements. Fundamental research on immunotherapy, photodynamic therapy (PDT), and triple-negative breast cancer (TNBC) points to future trends and potential breakthroughs. This study offers a strategic overview of ICD in breast cancer, providing insights into clinical practice and guiding future research in the field.

Exploiting E3 ligases for lung cancer therapy: The promise of DCAF-PROTACs

Lung cancer remains the leading cause of cancer-related mortality, underscoring the urgent need for novel therapeutic strategies. One emerging approach in drug development targets oncogenic proteins via the ubiquitin-proteasome system (UPS), specifically through proteolysis-targeting chimeras (PROTACs). Among the various E3 ligase complexes, the CRL4 complex-comprising DDB1 and CUL4-associated factors (DCAFs)-has garnered attention for its roles in cellular homeostasis, DNA repair, and oncogenesis. This review explores the therapeutic potential of DCAF-based PROTACs (DCAF-PROTACs) in lung cancer by focusing on the substrate receptors DCAF13, DCAF15, and DCAF16, which mediate CRL4-dependent ubiquitination. We first discuss the dysregulation of DCAF proteins in lung cancer and then elaborate on their mechanistic role in facilitating target-specific protein degradation via DCAF-E3 ligase complexes. Recent studies show that DCAF-PROTACs selectively degrade oncogenic proteins, addressing treatment resistance and tumor heterogeneity. Notably, DCAF13 promotes lung adenocarcinoma by destabilizing p53, while DCAF15-PROTACs target and degrade RBM39 effectively. Additionally, the development of electrophilic PROTACs targeting DCAF16 presents a promising avenue for degrading nuclear proteins. Despite these advancements, several challenges must be addressed prior to clinical translation, including issues related to drug bioavailability, stability, and emerging resistance mechanisms. This review also explores the potential of combination therapies, particularly with immunotherapy, to enhance tumor specificity and therapeutic efficacy. Ultimately, the deployment of DCAF-PROTACs marks a significant advancement in precision oncology, offering a novel and targeted approach to protein degradation-based cancer treatment.

Design, synthesis and evaluation of pyrrolobenzodiazepine (PBD)-based PROTAC conjugates for the selective degradation of the NF-κB RelA/p65 subunit

NF-κB signalling is frequently dysregulated in human cancers making it an attractive therapeutic target. Despite concerted efforts to generate NF-κB inhibitors, direct pharmacological inhibition of the kinases mediating canonical NF-κB has failed due to on-target toxicities in normal tissues. So, alternative strategies, designed to target specific components of the NF-κB signalling machinery, have the potential to selectively inhibit tumour cells whilst reducing the toxicities associated with broad inhibition of NF-κB in non-malignant cells. Here we present evidence that a C8-linked pyrrolobenzodiazepine (PBD) containing proteolysis-targeting chimera (PROTAC) selectively degrades the NF-κB subunit, RelA/p65, in a proteasome-dependent manner. Our lead PROTAC (JP-163-16, 15d) showed cytotoxicity with mean LC50 values of 2.9 μM in MDA-MB-231 cells, 0.14 μM in MEC-1 cells and 0.23 μM in primary chronic lymphocytic leukaemia cells. In contrast, 15d was two-logs less toxic in primary B- and T-lymphocytes (mean LD50 19.1 μM and 36.4 μM, respectively). Importantly, the development of 15d, by conjugating the C8-linked PBD with a cereblon-targeting ligand using a five-carbon linker, abolished the ability of the C8-linked PBD to bind to DNA, whilst demonstrating cytotoxicity in cancer cells associated with the degradation of RelA/p65. Mechanistically, 15d displayed PROTAC credentials through the selective degradation of NF-κB RelA/p65 in a proteasome-dependent manner and showed a five-fold reduction in potency in the cereblon deficient, lenalidomide resistant, myeloma cell line, RPMI-8226. To our knowledge, this work describes the first PROTAC capable of selective degradation of a single NF-κB subunit and highlights the therapeutic potential of our strategy for the treatment of RelA/p65-dependent tumours.

RIPK3 in necroptosis and cancer

Receptor-interacting protein kinase-3 is essential for the cell death pathway called necroptosis. Necroptosis is activated by the death receptor ligands and pattern recognition receptors of the innate immune system, leading to significant consequences in inflammation and in diseases, particularly cancer. Necroptosis is highly proinflammatory compared with other modes of cell death because cell membrane integrity is lost, resulting in releases of cytokines and damage-associated molecular patterns that potentiate inflammation and activate the immune system. We discuss various ways that necroptosis is triggered along with its potential role in cancer and therapy.

Exploring necroptosis: mechanistic analysis and antitumor potential of nanomaterials

Necroptosis, a non-apoptotic mode of programmed cell death, is characterized by the disintegration of the plasma membrane, ultimately leading to cell perforation and rupture. Recent studies have disclosed the mechanism of necroptosis and its intimate link with nanomaterials. Nanomedicine represents a novel approach in the development of therapeutic agents utilizing nanomaterials to treat a range of cancers with high efficacy. This article provides an overview of the primary mechanism behind necroptosis, the current research progress in nanomaterials, their potential use in various diseases-notably cancer, safety precautions, and prospects. The goal is to aid in the development of nanomaterials for cancer treatment.

Oligomerised RIPK1 is the main core component of the CD95 necrosome

The necrosome is the key macromolecular signaling platform initiating necroptosis, i.e., a RIPK1/RIPK3-dependent program of cell death with an important role in the control of inflammation in multicellular organisms. However, the composition and structure of the necrosome remain incompletely understood. Here we use biochemical assays, quantitative mass spectrometry, and AlphaFold modeling to decipher the composition and derive a structural model of the CD95L/BV6-induced necrosome. We identify RIPK1 as the central component of the necrosome, forming the core of this complex. In addition, AlphaFold modeling provides insights into the structural mechanisms underlying RIPK1 oligomerization, highlighting the critical role of type-II interactions between the Death Domains (DDs) of FADD and RIPK1 in the assembly of RIPK1-mediated complexes. The role of type-II DD interactions in necroptosis induction is further validated through structure-guided site-directed mutagenesis. Our findings could be useful for the pharmacological targeting of the necroptosis network to treat diseases associated with dysregulated cell death and inflammation.

Celastrol loaded nanocomplex for painless tumor therapy via YAP inhibition

Cancer-related pain is prevalent and severely impairs patients' quality of life. However, conventional cancer therapies primarily target tumor cell destruction, often overlooking the management of cancer pain. Thus, there is an immediate necessity to develop therapeutic agents that can both suppress tumor growth and alleviate cancer pain. In this study, we report a celastrol (CEL)-based nanocomposites (PDA-BSA-MnO2-CEL) for pain-less cancer immunotherapy. Results from in vitro and in vivo experiments demonstrate the efficacy and mechanism of the nanocomposites in pain-less immunotherapy. MnO2 and CEL induce immunogenic cell death (ICD), mediating immunotherapy. Additionally, CEL significantly reduces the secretion of the immunosuppressive factor Yes-associated protein (YAP) within the tumor microenvironment, thereby enhancing the efficacy of immunotherapy. The downregulation of YAP leads to reduced expression of vascular endothelial growth factor (VEGF), inhibiting tumor growth and decreasing activation of the pain-associated VEGF receptor 1 (VEGFR1), thus providing an analgesic effect. Moreover, CEL reduces inflammatory pain by lowering levels of inflammatory factors in tumors. The design of this nanocomposites system integrates immunotherapy with cancer pain inhibition, offering a novel approach to patient-centered tumor therapy.

Dying to survive: harnessing inflammatory cell death for better immunotherapy

Immunotherapy has transformed cancer treatment paradigms, but its effectiveness depends largely on the immunogenicity of the tumor. Unfortunately, the high resemblance of cancer to normal tissues makes most tumors immunologically 'cold', with a poor response to immunotherapy. Danger signals are critical for breaking immune tolerance and mobilizing robust, long-lasting antitumor immunity. Recent studies have identified inflammatory cell death modalities and their power in providing danger signals to trigger optimal tumor suppression. However, key mediators of inflammatory cell death are preferentially silenced during early tumor immunoediting. Strategies to rejuvenate inflammatory cell death hold great promise for broadening immunotherapy-responsive tumors. In this review, we examine how inflammatory cell death enhances tumor immunogenicity, how it is suppressed during immunoediting, and the potential of harnessing it for improved immunotherapy.

Design, synthesis, and biological evaluation of RIPK1-targeting PROTACs

Cancer cells can hijack receptor-interacting protein kinase 1 (RIPK1) and exploit its scaffolding function to orchestrate pro-survival signaling and fuel immunosuppressive program. Accordingly, targeting RIPK1 for elimination has emerged as a promising anti-cancer strategy. Based on the RIPK1 inhibitor 4 previously reported by our group, we employed proteolysis targeting chimera (PROTAC) technology and designed a series of RIPK1 degraders. Structure-activity relationship (SAR) study revealed three types of ligands for E3 ligase - cereblon (CRBN), von Hippel-Lindau (VHL) and inhibitor of apoptosis protein (IAP) - demonstrated varied efficacy in RIPK1 degradation of human and mouse cells. The VHL-based compound 18 exhibited potent RIPK1 degradation activity in both human and mouse cellular scenarios. Further biological evaluation confirmed that compound 18 potently induced RIPK1 degradation of I2.1 cells with a DC50 value of 274.4 nM and maintained long-term and dramatic RIPK1 degradation within 72 h. This study provided important insights into future development of RIPK1-PORTACs, and compound 18 was a promising RIPK1 degrader candidate.

Glucose Metabolism-Targeted Poly(amino acid) Nanoformulation of Oxaliplatin(IV)-Aspirin Prodrug for Enhanced Chemo-Immunotherapy

Inappropriate glucose metabolism in cancer cells is associated with immunosuppressive tumor microenvironments (TMEs). Although glycolysis inhibition enhances T cell-mediated immune responses, the integrated platforms combining glycolysis inhibition with immunotherapy remain underdeveloped. To address this gap, a glucose metabolism-targeted poly(amino acid) nanoformulation of oxaliplatin(IV)-aspirin prodrug (NP/OXA-ASP2) is developed to improve chemo-immunotherapy by suppressing tumor glycolysis. This poly(amino acid) nanoparticle exhibits selective release, discharging 90.0% of OXA-ASP2 under reductive conditions within 36 h. Furthermore, over 80% of the prodrug converts to OXA and ASP within 12 h, promoting mitochondrial damage and glycolysis inhibition, which amplifies immunogenic cell death induced by OXA. In addition, suppressing glycolytic flux reduces lactate leakage, mitigating the immunosuppressive TMEs. Together, these mechanisms contribute to stronger chemo-immunotherapy efficacy. Compared to the OXA plus ASP formulation, NP/OXA-ASP2 demonstrates superior performances, reducing lactate levels at the tumor site by 25.4%, increasing the proportion of cytotoxic T lymphocytes by 1.53 times, decreasing the proportion of regulatory T cells by 2.20 times, and improving 1.39-fold of the tumor inhibition rate. These findings underscore that NP/OXA-ASP2 is a promising platform for integrating tumor metabolic regulation with immunomodulation and holds significant potential for advancing clinical chemo-immunotherapy.

RIPK1 is required for ZBP1-driven necroptosis in human cells

Necroptosis initiated by the host sensor Z-NA binding protein 1 (ZBP1) is essential for host defense against a growing number of viruses, including herpes simplex virus 1 (HSV-1). Studies with HSV-1 and other necroptogenic stimuli in murine settings have suggested that ZBP1 triggers necroptosis by directly complexing with the kinase RIPK3. Whether this is also the case in human cells, or whether additional co-factors are needed for ZBP1-mediated necroptosis, is unclear. Here, we show that ZBP1-induced necroptosis in human cells requires RIPK1. We have found that RIPK1 is essential for forming a stable and functional ZBP1-RIPK3 complex in human cells, but is dispensable for the formation of the equivalent murine complex. The receptor-interacting protein (RIP) homology interaction motif (RHIM) in RIPK3 is responsible for this difference between the 2 species, because replacing the RHIM in human RIPK3 with the RHIM from murine RIPK3 is sufficient to overcome the requirement for RIPK1 in human cells. These observations describe a critical mechanistic difference between mice and humans in how ZBP1 engages in necroptosis, with important implications for treating human diseases.

Prognostic models of immune-related cell death and stress unveil mechanisms driving macrophage phenotypic evolution in colorectal cancer

BACKGROUND

Tumor microenvironment (TME), particularly immune cell infiltration, programmed cell death (PCD) and stress, has increasingly become a focal point in colorectal cancer (CRC) treatment. Uncovering the intricate crosstalk between these factors can enhance our understanding of CRC, guide therapeutic strategies, and improve patient prognosis.

METHODS

We constructed an immune-related cell death and stress (ICDS) prognostic model utilizing machine learning methodologies. Furthermore, we performed enrichment analyses and deconvolution algorithms to elucidate the complex interactions between immune cell infiltration and the processes of PCD and stress within a substantial array of transcriptomic data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus data base (GEO) related to CRC. Single-cell sequencing and biochemical experiments were used to validate the interaction between the model genes and programmed cell death in tumor cells.

RESULTS

The ICDS prognostic model exhibited robust predictive performance in seven independent cohorts, revealing an inverse correlation between model scores and patient prognosis. Meanwhile, the ICDS index was positively correlated with clinical stage. Model analysis indicated that patient subgroups with low ICDS index exhibited heightened immune activation features and elevated activity in PCD and stress pathways. Single-cell analysis further revealed that macrophages were the central drivers of immune characteristics underlying prognostic differences within the ICDS prognostic model. Pseudotime analysis and cellular experiments indicated that the model gene GAL3ST4 promotes the transition of macrophages toward an M2 pro-tumor phenotype. Furthermore, cell communication analysis and experimental validation revealed that the cuproptosis in tumor cells suppress GAL3ST4 expression, thereby inhibiting M2-like macrophage polarization.

CONCLUSION

In summary, we constructed the ICDS prognostic model and uncovered the mechanism by which tumor cells downregulate GAL3ST4 expression via cuproptosis to inhibit M2-like macrophage polarization, providing new targets and biomarkers for CRC treatment and prognosis evaluation.

DNA Tetrahedron-Driven Multivalent Proteolysis-Targeting Chimeras: Enhancing Protein Degradation Efficiency and Tumor Targeting

Proteolysis-targeting chimeras (PROTACs) are dual-functional molecules composed of a protein of interest (POI) ligand and an E3 ligase ligand connected by a linker, which can recruit POI and E3 ligases simultaneously, thereby inducing the degradation of POI and showing great potential in disease treatment. A challenge in developing PROTACs is the design of linkers and the modification of ligands to establish a multifunctional platform that enhances degradation efficiency and antitumor activity. As a programmable and modifiable nanomaterial, DNA tetrahedron can precisely assemble and selectively recognize molecules and flexibly adjust the distance between molecules, making them ideal linkers. Herein, we developed a multivalent PROTAC based on a DNA tetrahedron, named AS-TD2-PRO. Using DNA tetrahedron as a linker, we combined modules targeting tumor cells, recognizing E3 ligases, and multiple POI together. We took the undruggable target protein signal transducer and activator of transcription 3 (STAT3), associated with the etiology and progression in a variety of malignant tumors, as an example in this study. AS-TD2-PRO with two STAT3 recognition modules demonstrated good potential in enhancing tumor-specific targeting and degradation efficiency compared to traditional bivalent PROTACs. Furthermore, in a mouse tumor model, the superior therapeutic activity of AS-TD2-PRO was observed. Overall, DNA tetrahedron-driven multivalent PROTACs both serve as a proof of principle for multifunctional PROTAC design and introduce a promising avenue for cancer treatment strategies.

RIPK1 inhibition in malignant cells potentiates immunotherapy and radiotherapy outcome

Apoptosis, necroptosis and pro-inflammatory NF-κB-dependent signaling are repressed by receptor-interacting serine/threonine-protein kinase 1 (RIPK1). A recent paper in Immunity describes a small molecule inducing the proteolytic degradation of RIPK1. In preclinical experiments, this RIPK1 inhibitor improved the anticancer efficacy of radiotherapy, immunotherapy (with PD-1 blockade) and radioimmunotherapy (with CTLA-4 blockade).

PTGES3 proteolysis using the liposomal peptide-PROTAC approach

BACKGROUND

Hepatocellular carcinoma (HCC) is the leading cause of cancer-related deaths worldwide, and the lack of effective biomarkers for early detection leads to poor therapeutic outcomes. Prostaglandin E Synthase 3 (PTGES3) is a putative prognostic marker in many solid tumors; however, its expression and biological functions in HCC have not been determined. The proteolysis-targeting chimera (PROTAC) is an established technology for targeted protein degradation. Compared to the small-molecule PROTAC, the peptide PROTAC (p-PROTAC) utilizes peptides bound to target proteins to mediate the ubiquitination and degradation of undruggable proteins. This study aimed to use the PROTAC technology to develop a PTGES3 degrader liposome complex containing a PTGES3-binding peptide and the E3 ubiquitin ligase ligand pomalidomide for regulating cell function and provide a novel pathway for treating HCC.

RESULTS

In this study, we demonstrated that PTGES3 is highly expressed in HCC at the transcriptional and protein levels; furthermore, PTGES3 was identified as a novel drug target that could potentially treat HCC. Hence, we developed PTGES3-PROTACs by adjusting the ligand ratio to optimize the efficacy of degradation agents. The results revealed that PTGES3-PROTAC effectively degraded PTGES3 protein and strongly weakened the HCC malignant phenotype in vitro and in vivo.

CONCLUSIONS

Our findings revealed that the highly selective PTGES3 proteolysis is a potential therapeutic strategy for HCC, and PTGES3 degraders PTGES3-PROTACs can be developed as safe and effective drugs for HCC treatment.

Development of a RIPK1 degrader to enhance antitumor immunity

The scaffolding function of receptor interacting protein kinase 1 (RIPK1) confers intrinsic and extrinsic resistance to immune checkpoint blockades (ICBs) and emerges as a promising target for improving cancer immunotherapies. To address the challenge posed by a poorly defined binding pocket within the intermediate domain of RIPK1, here we harness proteolysis targeting chimera (PROTAC) technology to develop a RIPK1 degrader, LD4172. LD4172 exhibits potent and selective RIPK1 degradation both in vitro and in vivo. Degradation of RIPK1 by LD4172 triggers immunogenic cell death, enhances tumor-infiltrating lymphocyte responses, and sensitizes tumors to anti-PD1 therapy in female C57BL/6J mice. This work reports a RIPK1 degrader that serves as a chemical probe for investigating the scaffolding functions of RIPK1 and as a potential therapeutic agent to enhance tumor responses to ICBs therapy.

Targeted Degradation of Receptor-Interacting Protein Kinase 1 to Modulate the Necroptosis Pathway

Necroptosis is a highly regulated form of necrotic cell death that plays an essential role in pathogen defense and tissue homeostasis. Abnormal regulation of the necroptotic pathway has been implicated in the pathogenesis of various human diseases, including cancer, inflammatory, and neurodegenerative diseases. Receptor-interacting protein kinase 1 (RIPK1) serves as a crucial regulator of the necroptotic signaling pathway and has been identified as a potential therapeutic target. Mechanistically, RIPK1 serves as both a protein kinase and a scaffolding protein, fulfilling its dual function through a combination of kinase activity-dependent and kinase activity-independent mechanisms. Thus, employing a targeted RIPK1 knockdown strategy is a highly effective means of inhibiting RIPK1 functions. To achieve a targeted RIPK1 knockdown, we generated a RIPK1-PROTAC, MS2031, by connecting the ZB-R-55 RIPK1 binder to the VHL ligand, thereby recruiting the CUL2-RING-VHL (CRL2VHL) E3 ubiquitin ligase complex for targeted degradation of RIPK1 through the 26S proteasome. Notably, MS2031 treatment effectively reduced the abundance of RIPK1 protein in the nanomolar range in various cell lines we examined, including HT-29 and T47D cells, and modulated the necroptosis signaling pathway. These results suggest that MS2031 may hold potential for the treatment of human diseases resulting from aberrant regulation of RIPK1.

RIPK1 is essential for Herpes Simplex Virus-triggered ZBP1-dependent necroptosis in human cells

Necroptosis initiated by the host sensor Z-NA Binding Protein-1 (ZBP1) is essential for host defense against a growing number of viruses, including Herpes Simplex Virus-1 (HSV-1). Studies with HSV-1 and other necroptogenic stimuli in murine settings have suggested that ZBP1 triggers necroptosis by directly complexing with the kinase RIPK3. Whether this is also the case in human cells, or whether additional co-factors are needed for ZBP1-mediated necroptosis, is unclear. Here, we show that ZBP1-induced necroptosis in human cells requires RIPK1. We have found that RIPK1 is essential for forming a stable and functional ZBP1-RIPK3 complex in human cells, but is dispensable for the formation of the equivalent murine complex. The RIP Homology Interaction Motif (RHIM) in RIPK3 is responsible for this difference between the two species, because replacing the RHIM in human RIPK3 with the RHIM from murine RIPK3 is sufficient to overcome the requirement for RIPK1 in human cells. These observations describe a critical mechanistic difference between mice and humans in how ZBP1 engages in necroptosis, with important implications for treating human diseases.

RIPK1: Inflamed if you do, inflamed if you don't

RIPK1 is known as a driver of cell death and inflammation. In this issue of Immunity, Imai et al. and Mannion et al. find that these same processes are also induced by RIPK1 inactivation and highlight the therapeutic potential of RIPK1 elimination.