Mouse Double Minute 2 Homolog-Mediated Ubiquitination Facilitates Forkhead Box P3 Stability and Positively Modulates Human Regulatory T Cell Function

MDM2 inhibitors in cancer immunotherapy: Current status and perspective

Murine double minute 2 (MDM2) plays an essential role in the cell cycle, apoptosis, DNA repair, and oncogene activation through p53-dependent and p53-independent signaling pathways. Several preclinical studies have shown that MDM2 is involved in tumor immune evasion. Therefore, MDM2-based regulation of tumor cell-intrinsic immunoregulation and the immune microenvironment has attracted increasing research attention. In recent years, immune checkpoint inhibitors targeting PD-1/PD-L1 have been widely used in the clinic. However, the effectiveness of a single agent is only approximately 20%-40%, which may be related to primary and secondary drug resistance caused by the dysregulation of oncoproteins. Here, we reviewed the role of MDM2 in regulating the immune microenvironment, tumor immune evasion, and hyperprogression during immunotherapy. In addition, we summarized preclinical and clinical findings on the use of MDM2 inhibitors in combination with immunotherapy in tumors with MDM2 overexpression or amplification. The results reveal that the inhibition of MDM2 could be a promising strategy for enhancing immunotherapy.

Improving regulatory T cell-based therapy: insights into post-translational modification regulation

Regulatory T (Treg) cells are pivotal for maintaining immune homeostasis and play essential roles in various diseases, such as autoimmune diseases, graft-versus-host disease (GVHD), tumors, and infectious diseases. Treg cells exert suppressive function via distinct mechanisms including inhibitory cytokines, granzyme or perforin-mediated cytolysis, metabolic disruption, and suppression of dendritic cells. Forkhead Box P3 (FOXP3), the characteristic transcription factor, is essential for Treg cell function and plasticity. Cumulative evidence has demonstrated that FOXP3 activity and Treg cell function are modulated by a variety of post-translational modifications (PTMs), including ubiquitination, acetylation, phosphorylation, methylation, glycosylation, poly(ADP-ribosyl)ation, and uncharacterized modifications. This review describes Treg cell suppressive mechanisms and summarizes the current evidence on PTM regulation of FOXP3 and Treg cell function. Understanding the regulatory role of PTMs in Treg cell plasticity and function will be helpful in designing therapeutic strategies for autoimmune diseases, GVHD, tumors, and infectious diseases.

Ubiquitin recruiting chimera: more than just a PROTAC

Ubiquitinylation of protein substrates results in various but distinct biological consequences, among which ubiquitin-mediated degradation is most well studied for its therapeutic application. Accordingly, artificially targeted ubiquitin-dependent degradation of various proteins has evolved into the therapeutically relevant PROTAC technology. This tethered ubiquitinylation of various targets coupled with a broad assortment of modifying E3 ubiquitin ligases has been made possible by rational design of bi-specific chimeric molecules that bring these proteins in proximity. However, forced ubiquitinylation inflicted by the binary warheads of a chimeric PROTAC molecule should not necessarily result in protein degradation but can be used to modulate other cellular functions. In this respect it should be noted that the ubiquitinylation of a diverse set of proteins is known to control their transport, transcriptional activity, and protein-protein interactions. This review provides examples of potential PROTAC usage based on non-degradable ubiquitinylation.

The Involvement of Ascorbic Acid in Cancer Treatment

Vitamin C (VC), also known as ascorbic acid, plays a crucial role as a water-soluble nutrient within the human body, contributing to a variety of metabolic processes. Research findings suggest that increased doses of VC demonstrate potential anti-tumor capabilities. This review delves into the mechanisms of VC absorption and its implications for cancer management. Building upon these foundational insights, we explore modern delivery systems for VC, evaluating its use in diverse cancer treatment methods. These include starvation therapy, chemodynamic therapy (CDT), photothermal/photodynamic therapy (PTT/PDT), electrothermal therapy, immunotherapy, cellular reprogramming, chemotherapy, radiotherapy, and various combination therapies.

Vitamin B6 regulates IL-33 homeostasis to alleviate type 2 inflammation

Interleukin-33 (IL-33) is a crucial nuclear cytokine that induces the type 2 immune response and maintains immune homeostasis. The fine-tuned regulation of IL-33 in tissue cells is critical to control of the type 2 immune response in airway inflammation, but the mechanism is still unclear. Here, we found that healthy individuals had higher phosphate-pyridoxal (PLP, an active form of vitamin B6) concentrations in the serum than asthma patients. Lower serum PLP concentrations in asthma patients were strongly associated with worse lung function and inflammation. In a mouse model of lung inflammation, we revealed that PLP alleviated the type 2 immune response and that this inhibitory effect relied on the activity of IL-33. A mechanistic study showed that in vivo, pyridoxal (PL) needed to be converted into PLP, which inhibited the type 2 response by regulating IL-33 stability. In mice heterozygous for pyridoxal kinase (PDXK), the conversion of PL to PLP was limited, and IL-33 levels were increased in the lungs, aggravating type 2 inflammation. Furthermore, we found that the mouse double minute 2 homolog (MDM2) protein, an E3 ubiquitin-protein ligase, could ubiquitinate the N-terminus of IL-33 and sustain IL-33 stability in epithelial cells. PLP reduced MDM2-mediated IL-33 polyubiquitination and decreased the level of IL-33 through the proteasome pathway. In addition, inhalation of PLP alleviated asthma-related effects in mouse models. In summary, our data indicate that vitamin B6 regulates MDM2-mediated IL-33 stability to constrain the type 2 response, which might help develop a potential preventive and therapeutic agent for allergy-related diseases.

STUB1 directs FOXQ1-mediated transactivation of Ldha gene and facilitates lactate production in mouse Sertoli cells

Sertoli cells (SCs) preferentially use glucose to convert to lactate. As an energy source, lactate is essential for survival of developed germ cells (GCs) due to its anti-apoptotic effect. Failure to maintain lactate metabolism homeostasis leads to infertility or germ cell apoptosis. Several Sertoli cell-expressed genes, such as Foxq1 and Gata4, have been identified as critical regulators for lactate synthesis, but the pathways that potentially modulate their expression remain ill defined. Although recent work from our collaborators pointed to an involvement of STIP1 homology and U-box-containing protein 1 (STUB1) in the modulation of Sertoli cell response to GCs-derived IL-1α, a true physiological function of STUB1 signaling in SCs has not been demonstrated. We therefore conditionally ablated Stub1 in SCs using Amh-Cre. Stub1 knockout males exhibited impaired fertility due to oligozoospermia and asthenospermia, possibly caused by lactate deficiency. Furthermore, by means of chromatin immunoprecipitation, in vivo ubiquitination, and luciferase reporter assays, we showed that STUB1 directed forkhead box Q1 (FOXQ1)-mediated transactivation of the lactate dehydrogenase A (Ldha) gene via K63-linked non-proteolytic polyubiquitination, thus facilitating lactate production in follicle-stimulating hormone (FSH)-stimulated SCs. In agreement, overexpression of LDHA by lentivirus infection effectively rescued the lactate production in TM4Stub1-/- cells. Our results collectively identify STUB1-mediated transactivation of FOXQ1 signaling as a post-translationally modified transcriptional regulatory network underlying nursery function in SCs, which may nutritionally contribute to Sertoli cell dysfunction of male infertility.

USP7 - a crucial regulator of cancer hallmarks

Over the course of three decades of study, the deubiquitinase Herpesvirus associated Ubiquitin-Specific Protease/Ubiquitin-Specific Protease 7 (HAUSP/USP7) has gradually come to be recognized as a crucially important molecule in cellular physiology. The fact that USP7 is overexpressed in a number of cancers, including breast, prostate, colorectal, and lung cancers, supports the idea that USP7 is also an important regulator of tumorigenesis. In this review, we discuss USP7's function in relation to the cancer hallmarks described by Hanahan and Weinberg. This post-translational modifier can support increased proliferation, block unfavorable growth signals, stop cell death, and support an unstable cellular genome by manipulating key players in the pertinent signalling circuit. It is interesting to note that USP7 also aids in the stabilization of molecules that support angiogenesis and metastasis. Targeting USP7 has now emerged as a crucial component of USP7 research because pharmacological inhibition of USP7 supports p53-mediated cell cycle arrest and apoptosis. Efficacious USP7 inhibition is currently being investigated in both synthetic and natural compounds, but issues with selectivity and a lack of co-crystal structure have hindered USP7 inhibition from being tested in clinical settings. Moreover, the development of new, more effective USP7 inhibitors and their encouraging implications by numerous groups give us a glimmer of hope for USP7-targeting medications as effective substitutes for hazardous cancer chemotherapeutics.

The Dynamic Role of FOXP3+ Tregs and Their Potential Therapeutic Applications During SARS-CoV-2 Infection

Coronavirus disease 2019 (COVID-19) has been raging all around the world since the beginning of 2020, and leads to acute respiratory distress syndrome (ARDS) with strong cytokine storm which contributes to widespread tissue damage and even death in severe patients. Over-activated immune response becomes one of the characteristics of severe COVID-19 patients. Regulatory T cells (Treg) play an essential role in maintaining the immune homeostasis, which restrain excessive inflammation response. So FOXP3+ Tregs might participate in the suppression of inflammation caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Besides suppressive function, tissue resident Tregs are also responsible for tissue repair. In this review, we mainly summarize the latest research focusing on the change of FOXP3+ Tregs in the COVID-19 patients, discuss the relationship between disease severity and number change of Tregs and speculate the potential role of FOXP3+ Tregs during SARS-CoV-2 infection. Furthermore, we introduce some potential Treg-based therapies to improve patients’ outcomes, which include small molecular drugs, antibody drugs, CAR-Treg and cytokine treatment. We hope to reduce tissue damage of severe COVID-19 patients and offer better prognosis through Treg-based therapy.

A Review on the Immunomodulatory Mechanism of Acupuncture in the Treatment of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease with a high prevalence and canceration rate. The immune disorder is one of the recognized mechanisms. Acupuncture is widely used to treat patients with IBD. In recent years, an increasing number of studies have proven the effectiveness of acupuncture in the treatment of IBD, and some progress has been made in the mechanism. In this paper, we reviewed the studies related to acupuncture for IBD and focused on the immunomodulatory mechanism. We found that acupuncture could regulate the innate and adaptive immunity of IBD patients in many ways. Acupuncture exerts innate immunomodulatory effects by regulating intestinal epithelial barrier, toll-like receptors, NLRP3 inflammasomes, oxidative stress, and endoplasmic reticulum stress and exerts adaptive immunomodulation by regulating the balance of Th17/Treg and Th1/Th2 cells. In addition, acupuncture can also regulate intestinal flora.

Transcriptional and posttranslational regulation of Th17/Treg balance in health and disease

Regulatory T (Treg) cells and T helper type 17 (Th17) cells play important roles in adaptive immune responses, antagonizing each other in immune disorders. Th17/Treg balance is critical to maintaining the immune homeostasis of human bodies and is tightly regulated under healthy conditions. The transcription factors that are required for driving Th17 and Treg cell lineages differentiation respectively, RORγt and FOXP3 are tightly regulated under different tissue microenvironment, especially the transcriptional induction, posttranslational modifications, and dynamic enzymatic cofactors binding. The imbalance caused by alteration of the quantity or properties of RORγt⁺ Th17 or FOXP3⁺ Treg can contribute to inflammatory disorders in humans. Restoring Th17/Treg balance by modifying the enzymatic activities of RORγt and FOXP3 binding partners may be therapeutically applied to treat severe immune disorders. In this review, we focus on the transcriptional and posttranslational regulations of Th17/Treg balance, immune disorders caused by Th17/Treg imbalance, and new therapeutic strategies for restoring immune homeostasis.

hnRNPA1 enhances FOXP3 stability to promote the differentiation and functions of regulatory T cells

Regulatory T cells (Tregs) are indispensable for the maintenance of immunological self-tolerance and homeostasis. Heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) is required for optimal Treg induction. Here, we reveal that human-induced Tregs (iTregs) lacking hnRNPA1 show reduced expression of the transcription factor FOXP3, increased ubiquitination level of FOXP3, and impaired suppressive abilities. Human naïve CD4 T cells with hnRNPA1 knockdown show a decreased Treg differentiation ratio. hnRNPA1 could interact with FOXP3 as well as with the E3 ligase Stub1. The phosphorylation at hnRNPA1 S199 could increase both interactions. The overexpression of FOXP3 in Tregs containing shhnRNPA1 could not recover the phenotype caused by hnRNPA1 knockdown. Therefore, there might be multiple essential pathways regulated by hnRNPA1 in Tregs. In conclusion, we present a new role of hnRNPA1 in promoting Treg function, indicating it as a promising target for tumor therapies.

Ferroptosis and its emerging roles in cardiovascular diseases

Ferroptosis is a new form of regulated cell death (RCD) driven by iron-dependent lipid peroxidation, which is morphologically and mechanistically distinct from other forms of RCD including apoptosis, autophagic cell death, pyroptosis and necroptosis. Recently, ferroptosis has been found to participate in the development of various cardiovascular diseases (CVDs) including doxorubicin-induced cardiotoxicity, ischemia/reperfusion-induced cardiomyopathy, heart failure, aortic dissection and stroke. Cardiovascular homeostasis is indulged in delicate equilibrium of assorted cell types composing the heart or vessels, and how ferroptosis contributes to the pathophysiological responses in CVD progression is unclear. Herein, we reviewed recent discoveries on the basis of ferroptosis and its involvement in CVD pathogenesis, together with related therapeutic potentials, aiming to provide insights on fundamental mechanisms of ferroptosis and implications in CVDs and associated disorders.

FOXP3+ regulatory T cells and age-related diseases

Regulatory T (Treg) cells are critical for the maintenance of immune homeostasis. Dysregulation of Treg cells has been implicated in the pathogenesis of autoimmunity and chronic inflammation, while aging is characterized by an accumulation of inflammatory markers in the peripheral blood, a phenomenon known as 'inflammaging'. The relationship between Treg cells and age-related diseases remains to be further studied. Increasing evidence revealed that Treg cells' dysfunction occurs in aged patients, suggesting that immune therapies targeting Treg cells may be a promising approach to treat diseases such as cancers and autoimmune diseases. Furthermore, drugs targeting Treg cells show encouraging results and contribute to CD8⁺ T-cell-mediated cytotoxic killing of tumor and infected cells. In general, a better understanding of Treg cell function may help us to develop new immune therapies against aging. In this review, we discuss potential therapeutic strategies to modify immune responses of relevance for aging to prevent and treat age-related diseases, as well as the challenges posed by the translation of novel immune therapies into clinical practice.