ERK and USP5 govern PD-1 homeostasis via deubiquitination to modulate tumor immunotherapy

GSK3β and UCHL3 govern RIPK4 homeostasis via deubiquitination to enhance tumor metastasis in ovarian cancer

Receptor-interacting protein kinase 4 (RIPK4) is increasingly recognized as a pivotal player in ovarian cancer, promoting tumorigenesis and disease progression. Despite its significance, the posttranslational modifications dictating RIPK4 stability in ovarian cancer remain largely uncharted. In this study, we first established that RIPK4 levels are markedly higher in metastatic than in primary ovarian cancer tissues through single-cell sequencing. Subsequently, we identified UCHL3 as a key deubiquitinase that regulates RIPK4. We elucidate the mechanism that UCHL3 interacts with and deubiquitinates RIPK4 at the K469 site, removing the K48-linked ubiquitin chain and thus enhancing RIPK4 stabilization. Intriguingly, inhibition of UCHL3 activity using TCID leads to increased RIPK4 ubiquitination and degradation. Furthermore, we discovered that GSK3β-mediated phosphorylation of RIPK4 at Ser420 enhances its interaction with UCHL3, facilitating further deubiquitination and stabilization. Functionally, RIPK4 was found to drive the proliferation and metastasis of ovarian cancer in a UCHL3-dependent manner both in vitro and in vivo. Importantly, positive correlations between RIPK4 and UCHL3 protein expression levels were observed, with both serving as indicators of poor prognosis in ovarian cancer patients. Overall, this study uncovers a novel pathway wherein GSK3β-induced phosphorylation of RIPK4 strengthens its interaction with UCHL3, leading to increased deubiquitination and stabilization of RIPK4, thereby promoting ovarian cancer metastasis. These findings offer new insights into the molecular underpinnings of ovarian cancer and highlight potential therapeutic targets for enhancing antitumor efficacy.

Deubiquitinating enzymes: potential regulators of the tumor microenvironment and implications for immune evasion

Ubiquitination and deubiquitination are important forms of posttranslational modification that govern protein homeostasis. Deubiquitinating enzymes (DUBs), a protein superfamily consisting of more than 100 members, deconjugate ubiquitin chains from client proteins to regulate cellular homeostasis. However, the dysregulation of DUBs is reportedly associated with several diseases, including cancer. The tumor microenvironment (TME) is a highly complex entity comprising diverse noncancerous cells (e.g., immune cells and stromal cells) and the extracellular matrix (ECM). Since TME heterogeneity is closely related to tumorigenesis and immune evasion, targeting TME components has recently been considered an attractive therapeutic strategy for restoring antitumor immunity. Emerging studies have revealed the involvement of DUBs in immune modulation within the TME, including the regulation of immune checkpoints and immunocyte infiltration and function, which renders DUBs promising for potent cancer immunotherapy. Nevertheless, the roles of DUBs in the crosstalk between tumors and their surrounding components have not been comprehensively reviewed. In this review, we discuss the involvement of DUBs in the dynamic interplay between tumors, immune cells, and stromal cells and illustrate how dysregulated DUBs facilitate immune evasion and promote tumor progression. We also summarize potential small molecules that target DUBs to alleviate immunosuppression and suppress tumorigenesis. Finally, we discuss the prospects and challenges regarding the targeting of DUBs in cancer immunotherapeutics and several urgent problems that warrant further investigation.

Drug resistance mechanisms and treatment strategies mediated by Ubiquitin-Specific Proteases (USPs) in cancers: new directions and therapeutic options

Drug resistance represents a significant obstacle in cancer treatment, underscoring the need for the discovery of novel therapeutic targets. Ubiquitin-specific proteases (USPs), a subclass of deubiquitinating enzymes, play a pivotal role in protein deubiquitination. As scientific research advances, USPs have been recognized as key regulators of drug resistance across a spectrum of treatment modalities, including chemotherapy, targeted therapy, immunotherapy, and radiotherapy. This comprehensive review examines the complex relationship between USPs and drug resistance mechanisms, focusing on specific treatment strategies and highlighting the influence of USPs on DNA damage repair, apoptosis, characteristics of cancer stem cells, immune evasion, and other crucial biological functions. Additionally, the review highlights the potential clinical significance of USP inhibitors as a means to counter drug resistance in cancer treatment. By inhibiting particular USP, cancer cells can become more susceptible to a variety of anti-cancer drugs. The integration of USP inhibitors with current anti-cancer therapies offers a promising strategy to circumvent drug resistance. Therefore, this review emphasizes the importance of USPs as viable therapeutic targets and offers insight into fruitful directions for future research and drug development. Targeting USPs presents an effective method to combat drug resistance across various cancer types, leading to enhanced treatment strategies and better patient outcomes.

PD-1 regulation in immune homeostasis and immunotherapy

Harnessing the programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) axis is pivotal in autoimmunity and cancer immunotherapy. PD-1 receptors on immune cells engage with one of its ligands, PD-L1 or PD-L2, expressed on antigen-presenting cells or tumor cells, driving T-cell dysfunction and tumor immune escape. Thus, targeting PD-1/PD-L1 revitalizes cytotoxic T cells for cancer elimination. However, a majority of cancer patients don't respond to PD-1/PD-L1 blockade, and the underlying mechanisms remain partially understood. Recent studies have revealed that PD-1 expression levels or modifications impact the effectiveness of anti-PD-1/PD-L1 treatments. Therefore, understanding the molecular mechanisms governing PD-1 expression and modifications is crucial for innovating therapeutic strategies to enhance the efficacy of PD-1/PD-L1 inhibition. This article presents a comprehensive overview of advancements in PD-1 regulation and highlights their potential in modulating immune homeostasis and cancer immunotherapy, aiming to refine clinical outcomes.

Emerging therapeutic frontiers in cancer: insights into posttranslational modifications of PD-1/PD-L1 and regulatory pathways

The interaction between programmed cell death ligand 1 (PD-L1), which is expressed on the surface of tumor cells, and programmed cell death 1 (PD-1), which is expressed on T cells, impedes the effective activation of tumor antigen-specific T cells, resulting in the evasion of tumor cells from immune-mediated killing. Blocking the PD-1/PD-L1 signaling pathway has been shown to be effective in preventing tumor immune evasion. PD-1/PD-L1 blocking antibodies have garnered significant attention in recent years within the field of tumor treatments, given the aforementioned mechanism. Furthermore, clinical research has substantiated the efficacy and safety of this immunotherapy across various tumors, offering renewed optimism for patients. However, challenges persist in anti-PD-1/PD-L1 therapies, marked by limited indications and the emergence of drug resistance. Consequently, identifying additional regulatory pathways and molecules associated with PD-1/PD-L1 and implementing judicious combined treatments are imperative for addressing the intricacies of tumor immune mechanisms. This review briefly outlines the structure of the PD-1/PD-L1 molecule, emphasizing the posttranslational modification regulatory mechanisms and related targets. Additionally, a comprehensive overview on the clinical research landscape concerning PD-1/PD-L1 post-translational modifications combined with PD-1/PD-L1 blocking antibodies to enhance outcomes for a broader spectrum of patients is presented based on foundational research.

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

UFMylation is an emerging ubiquitin-like post-translational modification that regulates various biological processes. Dysregulation of the UFMylation pathway leads to human diseases, including cancers. However, the physiological role of UFMylation in T cells remains unclear. Here, we report that mice with conditional knockout (cKO) Ufl1, a UFMylation E3 ligase, in T cells exhibit effective tumor control. Single-cell RNA sequencing analysis shows that tumor-infiltrating cytotoxic CD8+ T cells are increased in Ufl1 cKO mice. Mechanistically, UFL1 promotes PD-1 UFMylation to antagonize PD-1 ubiquitination and degradation. Furthermore, AMPK phosphorylates UFL1 at Thr536, disrupting PD-1 UFMylation to trigger its degradation. Of note, UFL1 ablation in T cells reduces PD-1 UFMylation, subsequently destabilizing PD-1 and enhancing CD8+ T cell activation. Thus, Ufl1 cKO mice bearing tumors have a better response to anti-CTLA-4 immunotherapy. Collectively, our findings uncover a crucial role of UFMylation in T cells and highlight UFL1 as a potential target for cancer treatment.

Post-translational Modification of PD-1: Potential Targets for Cancer Immunotherapy

Activation of effector T cells leads to upregulation of PD-1, which can inhibit T-cell activity following engagement with its ligand PD-L1. Post-translational modifications (PTM), including glycosylation, phosphorylation, ubiquitination, and palmitoylation, play a significant role in regulating PD-1 protein stability, localization, and interprotein interactions. Targeting PTM of PD-1 in T cells has emerged as a potential strategy to overcome PD-1-mediated immunosuppression in cancer and enhances antitumor immunity. The regulatory signaling pathways that induce PTM of PD-1 can be suppressed with small-molecule inhibitors, and mAbs can directly target PD-1 PTMs. Preliminary outcomes from exploratory studies suggest that focusing on the PTM of PD-1 has strong therapeutic potential and can enhance the response to anti-PD-1.

KRAS4A and KRAS4B in liquid biopsy of metastatic lung adenocarcinoma patients treated with Pembrolizumab or chemotherapy plus Pembrolizumab

KRAS is involved in the stability and expression of PD-L1. We investigated the expression of circulating mRNA (cmRNA) of KRAS4A and KRAS4B and the possible impact on progression-free survival (PFS) of patients with metastatic lung adenocarcinoma treated with immunotherapy. Patients without driver mutations undergoing Pembrolizumab (P) or P plus chemotherapy (PC) were prospectively accrued for liquid biopsy analysis of KRAS4A, KRAS4B, and PD-L1 cmRNA. Both KRAS isoforms were also studied for association with PD-L1 cmRNA. Of 56 patients, 28 received P and 28 PC. Patients with high levels of both KRAS isoforms showed significantly better PFS. The median PFS for KRAS4A was 29 months (95% CI 22-29 months) and KRAS4B 24 months (95% CI 13-29 months), respectively. The median PFS of patients with low levels of both isoforms was 12 months (95% CI 6-15 months for KRAS4A and 95% CI 5-20 months for KRAS4B). High KRAS4A retained a significant positive association with PFS in the multivariate model. An exploratory analysis in treatment subgroups found a positive association between high KRAS4A and KRAS4B with PFS in patients treated with P. PD-L1 cmRNA was significantly higher in patients with high KRAS isoforms levels and this effect was pronounced for high KRAS4A carriers. KRAS4A deserves further investigation as a potential marker for defining patients who may benefit the most from immune checkpoint inhibitors therapy and improving personalized cancer immunotherapeutic strategies.

Ultrasound-Induced Gold Nanoparticle United with Acoustic Reprogramming of Macrophages for Enhanced Cancer Therapy

Sonodynamic therapy (SDT) has considerable potential in cancer treatment and exhibits high tissue penetration with minimal damage to healthy tissues. The efficiency of SDT is constrained by the complex immunological environment and tumor treatment resistance. Herein, a specific acoustic-actuated tumor-targeted nanomachine is proposed to generate mechanical damage to lysosomes for cancer SDT. The hybrid nanomachine was assembled with gold nanoparticles (GNPs) as the core and encapsulated with macrophage exosomes modified by AS1411 aptamers (GNP@EXO-APs) to optimize the pharmacokinetics and tumor aggregation. GNP@EXO-APs could be specifically transferred to the lysosomes of tumor cells. After induction with ultrasound, GNP@EXO-APs generated strong mechanical stress to produce lysosomal-dependent cell death in cancer cells. Notably, tumor-associated macrophages were reprogrammed in the ultrasound environment to an antitumor phenotype. Enhanced mechanical destruction via GNP@EXO-APs and immunotherapy of cancer cells were verified both in vitro and in vivo under SDT. This study provides a new direction for inside-out killing effects on tumor cells for cancer treatment.

Deubiquitinating enzyme JOSD2 affects susceptibility of non-small cell lung carcinoma cells to anti-cancer drugs through DNA damage repair

OBJECTIVES

To investigate the effects and mechanisms of deubiquitinating enzyme Josephin domain containing 2 (JOSD2) on susceptibility of non-small cell lung carcinoma (NSCLC) cells to anti-cancer drugs.

METHODS

The transcriptome expression and clinical data of NSCLC were downloaded from the Gene Expression Omnibus. Principal component analysis and limma analysis were used to investigate the deubiquitinating enzymes up-regulated in NSCLC tissues. Kaplan-Meier analysis was used to investigate the relationship between the expression of deubiquitinating enzymes and overall survival of NSCLC patients. Gene ontology enrichment and gene set enrichment analysis (GSEA) were used to analyze the activation of signaling pathways in NSCLC patients with high expression of JOSD2. Gene set variation analysis and Pearson correlation were used to investigate the correlation between JOSD2 expression levels and DNA damage response (DDR) pathway. Western blotting was performed to examine the expression levels of JOSD2 and proteins associated with the DDR pathway. Immunofluorescence was used to detect the localization of JOSD2. Sulforhodamine B staining was used to examine the sensitivity of JOSD2-knock-down NSCLC cells to DNA damaging drugs.

RESULTS

Compared with adjacent tissues, the expression level of JOSD2 was significantly up-regulated in NSCLC tissues (P<0.05), and was significantly correlated with the prognosis in NSCLC patients (P<0.05). Compared with the tissues with low expression of JOSD2, the DDR-related pathways were significantly upregulated in NSCLC tissues with high expression of JOSD2 (all P<0.05). In addition, the expression of JOSD2 was positively correlated with the activation of DDR-related pathways (all P<0.01). Compared with the control group, overexpression of JOSD2 significantly promoted the DDR in NSCLC cells. In addition, DNA damaging agents significantly increase the nuclear localization of JOSD2, whereas depletion of JOSD2 significantly enhanced the sensitivity of NSCLC cells to DNA damaging agents (all P<0.05).

CONCLUSIONS

Deubiquitinating enzyme JOSD2 may regulate the malignant progression of NSCLC by promoting DNA damage repair pathway, and depletion of JOSD2 significantly enhances the sensitivity of NSCLC cells to DNA damaging agents.