UFL1 ablation in T cells suppresses PD-1 UFMylation to enhance anti-tumor immunity

Studies on the functional role of UFMylation in cells (Review)

Protein post‑translational modifications (PTMs) play crucial roles in various life activities and aberrant protein modifications are closely associated with numerous major human diseases. Ubiquitination, the first identified protein modification system, involves the covalent attachment of ubiquitin molecules to lysine residues of target proteins. UFMylation, a recently discovered ubiquitin‑like modification, shares similarities with ubiquitination. The precursor form of ubiquitin fold modifier 1 (UFM1) undergoes synthesis and cleavage by UFM1‑specific protease 1 or UFM1‑specific protease 2 to generate activated UFM1‑G83. Subsequently, UFM1‑G83 is activated by a specific E1‑like activase, UFM1‑activating enzyme 5. UFM1‑conjugating enzyme 1 and an E3‑like ligase, UFM1‑specific ligase 1, recognize the target protein and facilitate UFMylation, leading to the degradation of the target protein. Current knowledge regarding UFMylation remains limited. Previous studies have demonstrated that defects in the UFMylation pathway can result in embryonic lethality in mice and various human diseases, highlighting the critical biological functions of UFMylation. However, the precise mechanisms underlying UFMylation remain elusive. This present review aimed to summarize recent research advances in UFMylation, with the aim of providing novel insights and perspectives for future investigations into this essential protein modification system.

Targeting PD-1 post-translational modifications for improving cancer immunotherapy

Programmed cell death protein 1 (PD-1) is a critical immune checkpoint receptor that suppresses immune responses largely through its interaction with PD-L1. Tumors exploit this mechanism to evade immune surveillance, positioning immune checkpoint inhibitors targeting the PD-1/PD-L1 axis as groundbreaking advancements in cancer therapy. However, the overall effectiveness of these therapies is often constrained by an incomplete understanding of the underlying mechanisms. Recent research has uncovered the pivotal role of various post-translational modifications (PTMs) of PD-1, including ubiquitination, UFMylation, phosphorylation, palmitoylation, and glycosylation, in regulating its protein stability, localization, and protein-protein interactions. As much, dysregulation of these PTMs can drive PD-1-mediated immune evasion and contribute to therapeutic resistance. Notably, targeting PD-1 PTMs with small-molecule inhibitors or monoclonal antibodies (MAbs) has shown potential to bolster anti-tumor immunity in both pre-clinical mouse models and clinical trials. This review highlights recent findings on PD-1's PTMs and explores emerging therapeutic strategies aimed at modulating these modifications. By integrating these mechanistic insights, the development of combination cancer immunotherapies can be further rationally advanced, offering new avenues for more effective and durable treatments.

Monoclonal antibody immune therapy response instrument for stratification and cost-effective personalized approaches in 3PM-guided pan cancer management

Background

Immune checkpoint inhibitors (ICIs), such as anti-PD-1, anti-PD-L1, and anti-CTLA-4 therapies, have revolutionized cancer treatment by harnessing the body's immune system to eliminate cancer cells. Despite their considerable promise, the efficacy of ICIs significantly differs based on tumor types and specific patient conditions, highlighting the necessity for personalized approaches in the framework of predictive preventive personalized medicine (PPPM; 3PM).

Main body

This review proposes a stratification instrument within the 3PM framework to enhance the therapeutic efficacy of ICIs across Pan-cancer. Predictive approaches need to be utilized to enhance the effectiveness of ICIs. For example, biomarkers such as particular genetic alterations and metabolic pathways provide key information on patient treatment responses. To predict treatment outcomes, uncover resistance mechanisms, and tailor medications, we examine biomarkers including PDL-1 and CTLA4. Focusing on cancers like melanoma, bladder, and renal cell carcinoma, we highlight advances in combination therapies and cellular approaches to overcome resistance. We conducted an analysis of clinical trials and public datasets (TCGA, GEO) to evaluate ICI responses across number of cancer types. Survival analysis employed Kaplan-Meier curves and Cox regression. Pan-cancer analysis shows response rates ranging from 19.8% in bladder cancer to > 39% in melanoma when combination therapy is used, emphasizing the potential of 3PM to improve outcomes. By exploring resistance mechanisms and emerging therapeutic innovations, we propose a cost-effective model for better patient stratification and care. Validation of this model requires standardized biomarkers and prospective trials, promising a shift toward precision oncology.

Conclusion

Within the 3PM framework, this review addresses the urgent need for cost-effective stratification tools and adaptive combinatorial strategies to optimize outcomes.

RUNX1/SLAMF3 Axis Drives Immunosuppression to Contribute to Colorectal Cancer Liver Metastasis by Blocking Phagocytosis and Depleting C1QC+ Tumor-Associated Macrophages

Colorectal cancer liver metastasis (CRLM) is a leading cause of death in colorectal cancer (CRC) patients and is characterized by an immunosuppressive tumor microenvironment (TME). This study employs mouse in vivo selection to isolate highly metastatic CRLM derivatives for profiling their transcriptomic, proteomic, and metabolomic alterations associated with CRLM. Notably, the expression of SLAMF3 is significantly upregulated in CRLM derivatives and its knockdown effectively suppresses CRLM in mice. RUNX1 transcriptionally upregulates SLAMF3 expression and combined targeting of the RUNX1/SLAMF3 axis synergistically suppresses liver metastasis in mice. In parallel, SLAMF3 suppresses macrophage-mediated phagocytosis of CRC cells through the SHP-1/2/mTORC1 pathway. Conversely, SLAMF3 knockdown promotes M1 polarization in liver metastases and activates the CCL signaling pathway between macrophages and CD8+ T cells. It also reduces the exhausted CD8+ T cells in liver metastases and the expression of inhibitory receptors PD-1 and TIM-3, thus alleviating the immunosuppressive TME. Clinically, activation of the RUNX1/SLAMF3 axis is closely associated with CRLM progression and correlates with a reduced proportion of clinically beneficial C1QC⁺ tumor-associated macrophages (TAMs). Collectively, these findings identify the RUNX1/SLAMF3 axis as a key driver of immunosuppressive TME remodeling and CRLM progression, highlighting its potential as a promising therapeutic target for CRLM.

Akt-phosphorylated UFL1 UFMylates ArpC4 to promote metastasis

The role of modification by ubiquitin-fold modifier ('UFMylation') in regulating metastasis has remained enigmatic. Cell migration, a critical step in metastasis, is driven by actin polymerization mediated by actin-related proteins 2 and 3 (Arp2/3) at the leading edge of lamellipodia. Here, we report that UFM1-specific E3 ligase 1 (UFL1) interacts with and catalyzes the UFMylation of ArpC4, a core subunit of the Arp2/3 complex. Akt has a key role in this process, which involves phosphorylating UFL1 at T426, thereby enhancing its interaction with ArpC4 and inducing ArpC4 UFMylation. Through ArpC4 UFMylation and potentially other targets, UFL1 facilitates lamellipodia formation and promotes cell migration, invasion and metastasis, making UFL1 an attractive therapeutic target for cancer.

UFMylation in tumorigenesis: Mechanistic insights and therapeutic opportunities

Post-translational modification (PTM) is an essential mechanism that regulates protein function within cells, influencing aspects such as protein activity, stability, subcellular localization, and interactions with other molecules through the addition or removal of chemical groups on amino acid residues. One notable type of PTM is UFMylation, a recently discovered modification process that involves the covalent attachment of UFM1 to lysine residues on target proteins. This process is facilitated by a specific enzyme system that includes the UFM1-activating enzyme, the UFM1-conjugating enzyme, and the UFM1-specific ligase. UFMylation is crucial for various cellular functions, such as responding to endoplasmic reticulum stress and DNA-damage response, and it is linked to the development and progression of several human diseases, including cancers, highlighting its importance in biological processes. Despite this significance, the range of substrates, regulatory mechanisms, and biological processes associated with UFMylation are not well understood, with only a few substrates having been characterized. Here, we focus on the molecular mechanisms of UFMylation, its implications in tumorigenesis, and its interactions with tumor suppressive and oncogenic signaling pathways. Furthermore, we employed bioinformatics approaches to analyze UFMylation's role in cancer, focusing on expression profiles, mutations, prognosis, drug sensitivity, and immune infiltration to explore its therapeutic potential in immunotherapy.

Short-term starvation inhibits CD36 N-glycosylation and downregulates USP7 UFMylation to alleviate RBPJ-maintained T cell exhaustion in liver cancer

Rationale: Short-term starvation (STS) has been shown to enhance the sensitivity of tumors to chemotherapy while concurrently safeguarding normal cells from its detrimental side effects. Nonetheless, the extent to which STS relies on the anti-tumor immune response to impede the progression of hepatocellular carcinoma (HCC) remains uncertain. Methods: In this study, we employed mass cytometry, flow cytometry, immunoprecipitation, immunoblotting, CUT&Tag, RT-qPCR, and DNA pull-down assays to evaluate the relationship between STS and T-cell antitumor immunity in HCC. Results: We demonstrated that STS alleviated T cell exhaustion in HCC. This study elucidated the mechanism by which STS blocked CD36 N-glycosylation, leading to the upregulation of AMPK phosphorylation and the downregulation of USP7 UFMylation, thus enhancing ubiquitination and destabilized USP7. Consequently, diminished USP7 levels facilitated the ubiquitination and subsequent degradation of RBPJ, thereby inhibiting T cell exhaustion through the IRF4/TNFRSF1B axis. From a therapeutic standpoint, STS not only suppressed the growth of patient-derived orthotopic xenografts but also enhanced their sensitivity to immunotherapy. Conclusions: These findings uncovered a novel mechanism by which N-glycosylation participated in UFMylation/ubiquitination to regulate T cell exhaustion, and we underscored the potential of targeting USP7 and RBPJ in anti-tumor immunotherapy strategies.

Deubiquitinase USP24 activated by IL-6/STAT3 enhances PD-1 protein stability and suppresses T cell antitumor response

Persisting programmed cell death-1 (PD-1) signaling impairs T cell effector function, which is highly associated with T cell exhaustion and immunotherapy failure. However, the mechanism responsible for PD-1 deubiquitination and T cell dysfunction remains unclear. Here, we show that ubiquitin-specific peptidase 24 (USP24) promotes PD-1 protein stability by removing K48-linked polyubiquitin. Increased interleukin-6 level transcriptionally activates the USP24 expression, which leads to PD-1 stabilization. Furthermore, USP24 deficiency reduces PD-1 levels in CD8+ T cells and attenuates EgfrL858R-driven lung tumorigenesis in Usp24C1695A catalytic deficient mice. Targeting PD-1 stability with the USP24-specific inhibitor USP24-i-101 boosts cytotoxic T cell activity, restrains lung tumor growth, and achieves superior therapeutic effects when combined with anti-CTLA4 immunotherapy. Clinically, patients with lung cancer exhibiting high USP24 expression in tumor-infiltrating CD8+ T cells display exhausted features and show unfavorable responses to immunotherapy. Our findings dissect the mechanism for regulating enhanced PD-1 stability in tumor-infiltrating CD8+ T cells and reveal USP24 as a potential target of antitumor immunotherapy.

UFMylation of NLRP3 Prevents Its Autophagic Degradation and Facilitates Inflammasome Activation

NLRP3 (NOD, LRR and pyrin domain-containing protein 3) inflammasome is important for host defense against infections and maintaining homeostasis. Aberrant activation of NLRP3 inflammasome is closely related to various inflammatory diseases. Post-translational modifications are critical for NLRP3 inflammasome regulation. However, the mechanism of NLRP3 inflammasome activation remains incompletely understood. Here, it is demonstrated that the Ufm1 E3 ligase Ufl1 mediated UFMylation is essential for NLRP3 inflammasome activation. Mechanistically, Ufl1 binds and UFMylates NLRP3 in the priming stage of NLRP3 activation, thereby sustaining the stability of NLRP3 by preventing NLRP3 K63-linked ubiquitination and the subsequent autophagic degradation. It is further demonstrated that myeloid cell-specific Ufl1 or Ufm1 deficiency in mice significantly alleviated inflammatory responses and tissue damage following lipopolysaccharide (LPS)-induced endotoxemia and alum-induced peritonitis. Thus, the findings offer new insights into potential therapeutic targets for NLRP3 inflammasome-related diseases by targeting the UFMylation system.

Multifaceted roles of UFMylation in health and disease

Ubiquitin fold modifier 1 (UFM1) is a newly identified post-translational modifier that is involved in the UFMylation process. Similar to ubiquitination, UFMylation enables the conjugation of UFM1 to specific target proteins, thus altering their stability, activity, or localization. UFM1 chains have the potential to undergo cleavage from their associated proteins via UFM1-specific proteases, thus highlighting a reversible feature of UFMylation. This modification is conserved across nearly all eukaryotic organisms, and is associated with diverse biological activities such as hematopoiesis and the endoplasmic reticulum stress response. The disruption of UFMylation results in embryonic lethality in mice and is associated with various human diseases, thus underscoring its essential role in embryonic development, tissue morphogenesis, and organismal homeostasis. In this review, we aim to provide an in-depth overview of the UFMylation system, its importance in disease processes, and its potential as a novel target for therapeutic intervention.

Targeting cTRIP12 counteracts ferroptosis resistance and augments sensitivity to immunotherapy in pancreatic cancer

AIMS

Current therapeutic strategies for pancreatic ductal adenocarcinoma (PDAC) have limited efficacy in increasing patient survival rates, largely due to ferroptosis resistance and immunosuppression. The aim of this study is to identify molecular mechanisms associated with ferroptosis resistance and immunosuppression in PDAC tumour cells.

METHODS

Circular RNA sequencing (circRNA-seq) was performed on clinical samples to identify potential circRNAs that mediate ferroptosis resistance. C11-BODIPY staining, FerroOrange staining, the glutathione ratio, malondialdehyde quantification, and transmission electron microscopy were employed to assess ferroptosis. RNA pulldown, mass spectrometry, RNA immunoprecipitation, and coimmunoprecipitation assays were conducted to investigate the molecular mechanisms involved. A HuNSG mouse xenograft tumour model was utilized to validate therapeutic agents.

RESULTS

A circRNA derived from TRIP12 (cTRIP12) was identified in PDAC samples resistant to ferroptosis. cTRIP12 knockdown increased the sensitivity of PDAC cells to ferroptosis and immunotherapy. Subsequent mechanistic studies revealed that cTRIP12 specifically binds to the O-linked N-acetylglucosamine transferase (OGT) protein and increases intracellular O-GlcNAcylation levels, leading to increased protein levels of ferritin heavy chain (FTH) and PD-L1 in tumour cells. Notably, high cTRIP12 expression suppressed ferroptosis sensitivity and increased immune resistance in PDAC cells by functioning as a protein scaffold through its interaction with OGT and protein kinase R-like endoplasmic reticulum kinase (PERK). cTRIP12 inhibition induced ferroptosis in PDAC cells by reducing FTH and PD-L1 expression and synergistically increased the immunotherapy efficacy. In vivo animal experiments confirmed that the triple therapy consisting of GSK2656157, erastin, and anti-CTLA-4 effectively suppressed the progression of PDAC in tumours with high cTRIP12 expression.

CONCLUSION

We elucidated the molecular mechanisms underlying the simultaneous occurrence of ferroptosis resistance and immune suppression in PDAC patients. Our study provides a novel therapeutic strategy that could promote ferroptosis in tumour cells and increase immunotherapy efficacy.

14-3-3ε UFMylation promotes RIG-I-mediated signaling

Post-translational modifications are critical for regulating the RIG-I signaling pathway. Previously, we identified a role for the post-translation modification UFM1 (UFMylation) in promoting RIG-I signaling by stimulating the interaction between RIG-I and its membrane-targeting protein 14-3-3ε. Here, we identify UFMylation of 14-3-3ε as a novel regulatory mechanism promoting RIG-I signaling. We demonstrate that UFM1 conjugation to lysine residue K50 or K215 results in mono-UFMylation on 14-3-3ε and enhances its ability to promote RIG-I signaling. Importantly, we show that mutation of these residues (K50R/K215R) abolishes UFMylation and impairs induction of type I and III interferons without disrupting the interaction between 14-3-3ε and RIG-I. This suggests that UFMylation of 14-3-3ε likely stabilizes signaling events downstream of RIG-I activation to promote induction of interferon. Collectively, our work suggests that UFMylation-driven activation of 14-3-3ε facilitates innate immune signaling and highlights the broader role of UFMylation for antiviral defense and immune regulation.

Importance

Post-translational modifications provide regulatory control of antiviral innate immune responses. Our study reveals that UFMylation of 14-3-3ε is a control point for RIG-I-mediated antiviral signaling. We demonstrate that conjugation of UFM1 to specific lysine residues on 14-3-3ε enhances downstream signaling events that facilitate interferon induction, but surprisingly it does not affect 14-3-3ε binding to RIG-I. By identifying the precise sites of UFMylation on 14-3-3ε and their functional consequences, we provide insights into the regulatory layers governing antiviral innate immunity. These findings complement emerging evidence that UFMylation serves as a versatile modulator across diverse immune pathways. Furthermore, our work highlights how protein chaperones like 14-3-3ε can be dynamically modified to orchestrate complex signaling cascades, suggesting potential therapeutic approaches for targeting dysregulated innate immunity.

UFMylation Modulates OFIP Stability and Centrosomal Localization

BACKGROUND

OFIP, also known as KIAA0753, is a centrosomal and pericentriolar satellite protein implicated in ciliogenesis, centriolar duplication, and microtubule stability. In humans, genetic mutations affecting OFIP have been implicated in the pathogenesis of Oral-Facial-Digital (OFD) Syndrome and Joubert Syndrome. Ubiquitin-fold Modifier 1 (UFM1), the most recently identified ubiquitin-like protein, is covalently transferred to its substrates, in a process known as UFMylation. This modification has recently emerged as a key regulator of various biological processes by altering their stability, activity, or localization.

METHODS

The interaction between UFL1 and OFIP, as well as the UFMylation of OFIP, were assessed through immunoprecipitation and immunoblotting analyses. The mRNA levels of OFIP were examined using reverse transcription quantitative PCR (RT-qPCR). Immunofluorescence microscopy was employed to examine the localization and distribution patterns of OFIP.

RESULTS

Our findings demonstrate that UFL1 interacts with OFIP both in vivo and in vitro. We also found that OFIP undergoes UFMylation, and UFL1 promotes the OFIP UFMylation. Mechanistic studies demonstrate that OFIP UFMylation inhibits its protein stability and maintains its proper centrosomal localization. However, the efficacy of these regulatory mechanisms varies significantly between different cell types, being notably pronounced in HeLa cells but markedly reduced in RPE1 cells.

CONCLUSIONS

OFIP is identified as a novel substrate for UFMylation. UFL1-mediated OFIP UFMylation is essential for its stability and centrosomal localization in HeLa cells. However, these effects are not observed in RPE1 cells, highlighting cell type-specific heterogeneity in the role of OFIP UFMylation.

UFL1 promotes survival and function of virtual memory CD8 T cells

In naïve mice, a fraction of CD8 T cells displaying high affinity for self-MHC peptide complexes develop into virtual memory T (TVM) cells. Due to self-reactivity, TVM cells are exposed to persistent antigenic stimulation, a condition known to induce T cell exhaustion. However, TVM cells do not exhibit characteristics similar to exhausted CD8 T (TEX) cells. Here, we tested the role of the UFL1, E3 ligase of the ufmylation pathway in TVM cells. We show that UFL1 prevents the acquisition of epigenetic, transcriptional, and phenotypic changes in TVM cells that are similar to TEX cells and thus promote their survival and function. UFL1-deficient TVM cells failed to protect mice against Listeria infection. Epigenetic analysis showed higher BATF activity in UFL1-deficient TVM cells. Deletion of BATF and not PD1 decreased inhibitory molecules expression and restored the survival and function of UFL1-deficient TVM cells. Our findings demonstrate a key role of UFL1 in inhibiting the exhaustion of TVM cells and promoting their survival and function.

The epitranscriptional factor PCIF1 orchestrates CD8+ T cell ferroptosis and activation to control antitumor immunity

T cell-based immunotherapies have revolutionized cancer treatment, yet durable responses remain elusive. Here we show that PCIF1, an RNA N6 2'-O-dimethyladenosine (m6Am) methyltransferase, negatively regulates CD8+ T cell antitumor responses. Whole-body or T cell-specific Pcif1 knockout (KO) reduced tumor growth in mice. Single-cell RNA sequencing shows an increase in the number of tumor-infiltrating cytotoxic CD8+ T cells in Pcif1-deficient mice. Mechanistically, proteomic and m6Am-sequencing analyses pinpoint that Pcif1 KO elevates m6Am-modified targets, specifically ferroptosis suppressor genes (Fth1, Slc3a2), and the T cell activation gene Cd69, imparting resistance to ferroptosis and enhancing CD8+ T cell activation. Of note, Pcif1-deficient mice had enhanced responses to anti-PD-1 immunotherapy, and Pcif1 KO chimeric antigen receptor T cells improved tumor control. Clinically, cancer patients with low PCIF1 expression in T cells have enhanced responses to immunotherapies. These findings suggest that PCIF1 suppresses CD8+ T cell activation and targeting PCIF1 is a promising strategy to boost antitumor immunity.

Systematic Analysis of UFMylation Family Genes in Tissues of Mice with Metabolic Dysfunction-Associated Steatotic Liver Disease

BACKGROUND/OBJECTIVES

UFMylation, a newly identified ubiquitin-like modification, modulates a variety of physiological processes, including endoplasmic reticulum homeostasis maintenance, DNA damage response, embryonic development, and tumor progression. Recent reports showed that UFMylation plays a protective role in preventing liver steatosis and fibrosis, serving as a defender of liver homeostasis in the development of metabolic dysfunction-associated steatotic liver disease (MASLD). However, the regulation of UFMylation in MASLD remains unclear. This study aimed to determine the expressed patterns of UFMylation components in multiple tissues of leptin-deficient ob/ob mice and high-fat diet (HFD)-fed mice, which are mimicking the conditions of MASLD.

METHODS

The ob/ob mice and HFD-fed mice were sacrificed to collect tissues indicated in this study. Total RNA and proteins were extracted from tissues to examine the expressed patterns of UFMylation components, including UBA5, UFC1, UFL1, DDRGK1, UFSP1, UFSP2 and UFM1, by real-time PCR and western blot analysis.

RESULTS

The protein levels of UBA5, UFC1 and UFL1 were down-regulated in liver, brown adipose tissue (BAT) and inguinal white adipose tissue (iWAT), whereas the messenger RNA (mRNA) levels of Ufl1 and Ufsp1 were both decreased in skeletal muscle, BAT, iWAT and epididymal white adipose tissue (eWAT) of ob/ob mice. In contrast, the mRNA levels of Ufsp1 in skeletal muscle, BAT, iWAT and heart, and the protein levels of UFL1 were decreased in BAT, iWAT, heart and cerebellum of HFD-fed mice.

CONCLUSIONS

Our findings established the expressed profiles of UFMylaiton in multiple tissues of mice mimicking MASLD, indicating an important regulation for UFMylation in these tissues' homeostasis maintenance.

UFMylation is involved in serum inflammatory cytokines generation and splenic T cell activation induced by lipopolysaccharide

UFMylation, a novel ubiquitin-like protein modification system, has been recently found to be activated in inflammation. However, the effects of UFMylation activation on inflammation in vivo remains unclear. In the present study, we generated a UFMylation activated mice using transgenic (TG) techniques. Lipopolysaccharide (LPS) was used to induce systemic inflammation in both TG and non-transgenic (NTG) mice. Serum cytokines were detected using a Mouse Cytokine Array, and the proportions of splenic NK, B and T cells were determined by using flow cytometry. We found that TG mice showed increased serum G-CSF, TNF RII and decreased serum TCA-3, CD30L, bFGF, IL-15 and MIG compared with NTG mice at baseline. Furthermore, serum cytokines in TG mice exhibited different responses to LPS compared to NTG mice. LPS up-regulated serum TNF RII, G-CSF, MCP-5, RANTES, KC, BLC, MIG and down-regulated IL-1b, IL-2, IL-3, IL-4, IL-5, IL-7, IL-10, IL-12p40, IL-15, IL-17, IFN-γ, TCA-3, Eotaxin-2, LIX, MCP-1, TNFα, GM-CSF in NTG mice, whereas LPS up-regulated G-CSF, MCP-5, RANTES, KC, BLC, MIG, ICAM-1, PF4, Eotaxin, CD30L, MIP-1a, TNFRI and down-regulated IL-1b, IL-3, LIX, MCP-1, TNFα, GM-CSF in TG mice. Data from flow cytometry indicated that LPS significantly reduced the percentages of NK and NKT cells in NTG mice, whereas UFMylation activation inhibited LPS-induced NKT cell decrease. The proportions of B cells, total CD4+ and total CD8+ T cells were comparable between TG and NTG mice in response to LPS treatment, whereas the percentages of CD4+CD69+ and CD8+CD69+T cells were lower in TG mice. These findings suggest that UFMylation may alter LPS-induced serum cytokine profile and participate in splenic T cell activation in vivo.

The emerging roles of UFMylation in the modulation of immune responses

Post-translational modification is a rite of passage for cellular functional proteins and ultimately regulate almost all aspects of life. Ubiquitin-fold modifier 1 (UFM1) system represents a newly identified ubiquitin-like modification system with indispensable biological functions, and the underlying biological mechanisms remain largely undiscovered. The field has recently experienced a rapid growth of research revealing that UFMylation directly or indirectly regulates multiple immune processes. Here, we summarised important advances that how UFMylation system responds to intrinsic and extrinsic stresses under certain physiological or pathological conditions and safeguards immune homeostasis, providing novel perspectives into the regulatory framework and functions of UFMylation system, and its therapeutic applications in human diseases.

Role of UFMylation in tumorigenesis and cancer immunotherapy

Protein post-translational modifications (PTMs) represent a crucial aspect of cellular regulation, occurring after protein synthesis from mRNA. These modifications, which include phosphorylation, ubiquitination, acetylation, methylation, glycosylation, Sumoylation, and palmitoylation, play pivotal roles in modulating protein function. PTMs influence protein localization, stability, and interactions, thereby orchestrating a variety of cellular processes in response to internal and external stimuli. Dysregulation of PTMs is linked to a spectrum of diseases, such as cancer, inflammatory diseases, and neurodegenerative disorders. UFMylation, a type of PTMs, has recently gained prominence for its regulatory role in numerous cellular processes, including protein stability, response to cellular stress, and key signaling pathways influencing cellular functions. This review highlights the crucial function of UFMylation in the development and progression of tumors, underscoring its potential as a therapeutic target. Moreover, we discuss the pivotal role of UFMylation in tumorigenesis and malignant progression, and explore its impact on cancer immunotherapy. The article aims to provide a comprehensive overview of biological functions of UFMylation and propose how targeting UFMylation could enhance the effectiveness of cancer immunotherapy strategies.

USP8-governed GPX4 homeostasis orchestrates ferroptosis and cancer immunotherapy

Ferroptosis is an iron-dependent type of regulated cell death resulting from extensive lipid peroxidation and plays a critical role in various physiological and pathological processes. However, the regulatory mechanisms for ferroptosis sensitivity remain incompletely understood. Here, we report that homozygous deletion of Usp8 (ubiquitin-specific protease 8) in intestinal epithelial cells (IECs) leads to architectural changes in the colonic epithelium and shortens mouse lifespan accompanied by increased IEC death and signs of lipid peroxidation. However, mice with heterozygous deletion of Usp8 in IECs display normal phenotype and become resistant to azoxymethane/dextran sodium sulfate-induced colorectal tumorigenesis. Mechanistically, USP8 interacts with and deubiquitinates glutathione peroxidase 4 (GPX4), leading to GPX4 stabilization. Thus, USP8 inhibition destabilizes GPX4 and sensitizes cancer cells to ferroptosis in vitro. Notably, USP8 inhibition in combination with ferroptosis inducers retards tumor growth and enhances CD8+ T cell infiltration, which potentiates tumor response to anti-PD-1 immunotherapy in vivo. These findings uncover that USP8 counteracts ferroptosis by stabilizing GPX4 and highlight targeting USP8 as a potential therapeutic strategy to boost ferroptosis for enhancing cancer immunotherapy.

PTMs of PD-1/PD-L1 and PROTACs application for improving cancer immunotherapy

Immunotherapy has been developed, which harnesses and enhances the innate powers of the immune system to fight disease, particularly cancer. PD-1 (programmed death-1) and PD-L1 (programmed death ligand-1) are key components in the regulation of the immune system, particularly in the context of cancer immunotherapy. PD-1 and PD-L1 are regulated by PTMs, including phosphorylation, ubiquitination, deubiquitination, acetylation, palmitoylation and glycosylation. PROTACs (Proteolysis Targeting Chimeras) are a type of new drug design technology. They are specifically engineered molecules that target specific proteins within a cell for degradation. PROTACs have been designed and demonstrated their inhibitory activity against the PD-1/PD-L1 pathway, and showed their ability to degrade PD-1/PD-L1 proteins. In this review, we describe how PROTACs target PD-1 and PD-L1 proteins to improve the efficacy of immunotherapy. PROTACs could be a novel strategy to combine with radiotherapy, chemotherapy and immunotherapy for cancer patients.