CTLA-4 and PD-1 receptors inhibit T-cell activation by distinct mechanisms

Novel insights into the regulation of exosomal PD-L1 in cancer: From generation to clinical application

Programmed cell death ligand 1 (PD-L1) interacts with programmed cell death 1 (PD-1), leading to T cell exhaustion and promoting tumor cell survival, ultimately mediating immunosuppression. While FDA-approved monoclonal antibodies targeting the PD-1/PD-L1 interaction have shown success in cancer treatment, some patients experience limited and short-lived therapeutic outcomes. Recent studies have identified PD-L1 expression not only on tumor cell surfaces but also on exosomes, with secretion pathways including both conventional and unconventional endocytosis routes, presenting a unique therapeutic opportunity. Emerging evidence suggests that exosomal PD-L1 contributes to systemic immunosuppression, potentially counteracting the effects of anti-PD-1 checkpoint therapies. However, the significance of exosomal PD-L1 in clinical cancer patients unresponsive to anti-PD-1/PD-L1 immunotherapy, as well as the factors regulating its generation, remain unclear. Moreover, the mechanisms underlying PD-L1 expression on exosomes and its regulation in cancer are yet to be fully elucidated. This review primarily focuses on the mechanisms modulating exosomal PD-L1 generation in cancer, while also outlining its involvement in immunosuppression, tumor proliferation, and response to cancer immunotherapy. Additionally, we explore the potential of exosomal PD-L1 as a cancer biomarker and therapeutic target, aiming to provide a comprehensive overview of this emerging field and its implications for cancer treatment and diagnosis.

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.

Current research insights into the role of CTLA-4 in hepatitis B virus (HBV) infection

Chronic hepatitis B virus (HBV) infection is a significant global public health concern, and the clearance of HBV is closely linked to the activity of HBV-specific T cells, which is regulated by various co-suppressor molecules. Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is among these co-suppressor molecules which induces T cell exhaustion by competitively inhibiting CD28 and dampening the function of HBV-specific T cells. CTLA-4 also plays a role in the regulation of T helper (Th) cell differentiation and influences cytokine release. In addition, CTLA-4 can impact glucose metabolism in hepatocellular carcinoma through its interaction with T regulatory (Treg) cells. This review aims to provide a comprehensive overview of the existing literature related to the role of CTLA-4 in HBV patients across different subsets of T cells. Additionally, we propose a discussion on the possible mechanisms through which CTLA-4 may contribute to HBV infection, as well as the development of HBV-induced cirrhosis and hepatocellular carcinoma.

T cell exhaustion and senescence for ovarian cancer immunotherapy

Ovarian cancer is a common gynecological malignancy, and its treatment remains challenging. Although ovarian cancer may respond to immunotherapy because of endogenous immunity at the molecular or T cell level, immunotherapy has so far not had the desired effect. The functional status of preexisting T cells is an indispensable determinant of powerful antitumor immunity and immunotherapy. T cell exhaustion and senescence are two crucial states of T cell dysfunction, which share some overlapping phenotypic and functional features, but each status possesses unique molecular and developmental signatures. It has been widely accepted that exhaustion and senescence of T cells are important strategies for cancer cells to evade immunosurveillance and maintain the immunosuppressive microenvironment. Herein, this review summarizes the phenotypic and functional features of exhaust and senescent T cells, and describes the key drivers of the two T cell dysfunctional states in the tumor microenvironment and their functional roles in ovarian cancer. Furthermore, we present a summary of the molecular machinery and signaling pathways governing T cell exhaustion and senescence. Possible strategies that can prevent and/or reverse T cell dysfunction are also explored. An in-depth understanding of exhausted and senescent T cells will provide novel strategies to enhance immunotherapy of ovarian cancer through redirecting tumor-specific T cells away from a dysfunctional developmental trajectory.

OX40/OX40 ligand and its role in precision immune oncology

Immune checkpoint inhibitors have changed the treatment landscape for various malignancies; however, their benefit is limited to a subset of patients. The immune machinery includes both mediators of suppression/immune evasion, such as PD-1, PD-L1, CTLA-4, and LAG-3, all of which can be inhibited by specific antibodies, and immune-stimulatory molecules, such as T-cell co-stimulatory receptors that belong to the tumor necrosis factor receptor superfamily (TNFRSF), including OX40 receptor (CD134; TNFRSF4), 4-1BB (CD137; TNFRSF9), and glucocorticoid-induced TNFR-related (GITR) protein (CD357; TNFRSF18). In particular, OX40 and its binding ligand OX40L (CD134L; TNFSF4; CD252) are critical for immunoregulation. When OX40 on activated T cells binds OX40L on antigen-presenting cells, T-cell activation and immune stimulation are initiated via enhanced T-cell survival, proliferation and cytotoxicity, memory T-cell formation, and abrogation of regulatory T cell (Treg) immunosuppressive functions. OX40 agonists are in clinical trials both as monotherapy and in combination with other immunotherapy agents, in particular specific checkpoint inhibitors, for cancer treatment. To date, however, only a minority of patients respond. Transcriptomic profiling reveals that OX40 and OX40L expression vary between and within tumor types, and that only ~ 17% of cancer patients have high OX40 and low OX40L, one of the expression patterns that might be theoretically amenable to OX40 agonist enhancement. Taken together, the data suggest that the OX40/OX40L machinery is a critical part of the immune stimulatory system and that understanding endogenous expression patterns of these molecules and co-existing checkpoints merits further investigation in the context of a precision immunotherapy strategy for cancer therapy.

Activation and antitumor immunity of CD8+ T cells are supported by the glucose transporter GLUT10 and disrupted by lactic acid

CD8+ T cell activation leads to the rapid proliferation and differentiation of effector T cells (Teffs), which mediate antitumor immunity. Although aerobic glycolysis is preferentially activated in CD8+ Teffs, the mechanisms that regulate CD8+ T cell glucose uptake in the low-glucose and acidic tumor microenvironment (TME) remain poorly understood. Here, we report that the abundance of the glucose transporter GLUT10 is increased during CD8+ T cell activation and antitumor immunity. Specifically, GLUT10 deficiency inhibited glucose uptake, glycolysis, and antitumor efficiency of tumor-infiltrating CD8+ T cells. Supplementation with glucose alone was insufficient to rescue the antitumor function and glucose uptake of CD8+ T cells in the TME. By analyzing tumor environmental metabolites, we found that high concentrations of lactic acid reduced the glucose uptake, activation, and antitumor effects of CD8+ T cells by directly binding to GLUT10's intracellular motif. Disrupting the interaction of lactic acid and GLUT10 by the mimic peptide PG10.3 facilitated CD8+ T cell glucose utilization, proliferation, and antitumor functions. The combination of PG10.3 and GLUT1 inhibition or anti-programmed cell death 1 antibody treatment showed synergistic antitumor effects. Together, our data indicate that GLUT10 is selectively required for glucose uptake of CD8+ T cells and identify that TME accumulated lactic acid inhibits CD8+ T cell effector function by directly binding to GLUT10 and reducing its glucose transport capacity. Last, our study suggests disrupting lactate-GLUT10 binding as a promising therapeutic strategy to enhance CD8+ T cell-mediated antitumor effects.

The Unique Immune Evasion Mechanisms of the Mpox Virus and Their Implication for Developing New Vaccines and Immunotherapies

Mpox is an infectious and contagious zoonotic disease caused by the mpox virus (MPXV), which belongs to the genus Orthopoxvirus. Since 2022, MPXV has posed a significant threat to global public health. The emergence of thousands of cases across the Western Hemisphere prompted the World Health Organization to declare an emergency. The extensive coevolutionary history of poxviruses with humans has enabled these viruses to develop sophisticated mechanisms to counter the human immune system. Specifically, MPXV employs unique immune evasion strategies against a wide range of immunological elements, presenting a considerable challenge for treatment, especially following the discontinuation of routine smallpox vaccination among the general population. In this review, we start by discussing the entry of the mpox virus and the onset of early infection, followed by an introduction to the mechanisms by which the mpox virus can evade the innate and adaptive immune responses. Two caspase-1 inhibitory proteins and a PKR escape-related protein have been identified as phylogenomic hubs involved in modulating the immune environment during the MPXV infection. With respect to adaptive immunity, mpox viruses exhibit unique and exceptional T-cell inhibition capabilities, thereby comprehensively remodeling the host immune environment. The viral envelope also poses challenges for the neutralizing effects of antibodies and the complement system. The unique immune evasion mechanisms employed by MPXV make novel multi-epitope and nucleic acid-based vaccines highly promising research directions worth investigating. Finally, we briefly discuss the impact of MPXV infection on immunosuppressed patients and the current status of MPXV vaccine development. This review may provide valuable information for the development of new immunological treatments for mpox.

TEDOVA: vaccine OSE2101 +/- pembrolizumab as maintenance in platinum-sensitive recurrent ovarian cancer

Ovarian cancer is a leading cause of death from gynecological cancers worldwide. Platinum-based chemotherapy provides the cornerstone of the medical management. In first line and subsequent relapses, maintenance strategies are offered to prolong intervals between lines of chemotherapy. Current maintenance options involve bevacizumab and poly ADP-ribose polymerase inhibitors, but these lines of therapy can only be used once in the disease course. Patients in first or second platinum sensitive relapse after poly ADP-ribose polymerase inhibitors and bevacizumab represent an area of unmet medical need. This academic sponsored, international Phase II randomized trial is evaluating the combination of a therapeutic cancer vaccine (OSE2101) with anti-PD1 (pembrolizumab) as maintenance therapy, in patients with platinum-sensitive recurrence regardless of number of prior lines and no progression after platinum-based chemotherapy.Clinical Trial Registration: NCT04713514 (ClinicalTrials.gov).

Strategies for Improving CAR T Cell Persistence in Solid Tumors

CAR T cells require optimization to be effective in patients with solid tumors. There are many barriers affecting their ability to succeed. One barrier is persistence, as to achieve an optimal antitumor response, infused CAR T cells must engraft and persist. This singular variable is impacted by a multitude of factors-the CAR T cell design, lymphodepletion regimen used, expansion method to generate the T cell product, and more. Additionally, external agents can be utilized to augment CAR T cells, such as the addition of novel cytokines, pharmaceutical drugs that bolster memory formation, or other agents during either the ex vivo expansion process or after CAR T cell infusion to support them in the oppressive tumor microenvironment. This review highlights many strategies being used to optimize T cell persistence as well as future directions for improving the persistence of infused cells.

Multifaceted roles of PD-1 in tumorigenesis: From immune checkpoint to tumor cell-intrinsic function

Programmed cell death 1 (PD-1), a key immune checkpoint receptor, has been extensively studied for its role in regulating immune responses in cancer. However, recent research has unveiled a complex and dual role for PD-1 in tumorigenesis. While PD-1 is traditionally associated with immune cells, this article explores its expression in various cancer cells and its impact on cancer progression. PD-1's functions extend beyond immune regulation, as it has been found to both promote and suppress tumor growth, depending on the cancer type. These findings have significant implications for the future of cancer treatment and our understanding of the immune response in the context of cancer. This article calls for further research into the multifaceted roles of PD-1 to optimize its therapeutic potential and improve patient outcomes in the fight against cancer.

Takotsubo syndrome as an outcome of the use of checkpoint inhibitor therapy in patients with COVID-19

Takotsubo Syndrome (TS) is a heart disease caused by extreme exposure of the body to physical or psychological stress. In the context of COVID-19, the virus can be a significant source of stress, with particular attention being paid to the cytokine storm as a cause of damage to the body. New research shows that the production of specific cytokines is linked to the activation of immune checkpoint proteins such as PD-1, PD-L1, and CTLA-4 on T cells. Although initially beneficial in combating infections, it can suppress defense and aid in disease progression. Therefore, checkpoint inhibitor therapy has been highlighted beyond oncological therapies, given its effectiveness in strengthening the immune system. However, this treatment can lead to excessive immune responses, inflammation, and stress on the heart, which can cause Takotsubo Syndrome in patients. Several studies investigate the direct link between this therapy and cardiac injuries in these patients, which can trigger TS. From this perspective, we must delve deeper into this treatment and consider its effects on the prognosis against SARS-CoV-2 infection.

PP2A catalytic subunit alpha is critically required for CD8+ T-cell homeostasis and antibacterial responses

Although the functions of tyrosine phosphatases in T-cell biology have been extensively studied, our knowledge on the contribution of serine/threonine phosphatases in T cells remains poor. Protein phosphatase 2A (PP2A) is one of the most abundantly expressed serine/threonine phosphatases. It is important in thymocyte development and CD4+ T-cell differentiation. Utilizing a genetic model in which its catalytic subunit alpha isoform (PP2A Cα) is deleted in T cells, we investigated its contribution to CD8+ T-cell homeostasis and effector functions. Our results demonstrate that T-cell intrinsic PP2A Cα is critically required for CD8+ T-cell homeostasis in secondary lymphoid organs and intestinal mucosal site. Importantly, PP2A Cα-deficient CD8+ T cells exhibit reduced proliferation and survival. CD8+ T-cell antibacterial response is strictly dependent on PP2A Cα. Expression of Bcl2 transgene rescues CD8+ T-cell homeostasis in spleens, but not in intestinal mucosal site, nor does it restore defective antibacterial responses. Finally, proteomics and phosphoproteomics analyses reveal potential targets dependent on PP2A Cα, including mTORC1 and AKT. Thus, PP2A Cα is a key modulator of CD8+ T-cell homeostasis and effector functions.

The Immune Landscape of Pheochromocytoma and Paraganglioma: Current Advances and Perspectives

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors derived from neural crest cells from adrenal medullary chromaffin tissues and extra-adrenal paraganglia, respectively. Although the current treatment for PPGLs is surgery, optimal treatment options for advanced and metastatic cases have been limited. Hence, understanding the role of the immune system in PPGL tumorigenesis can provide essential knowledge for the development of better therapeutic and tumor management strategies, especially for those with advanced and metastatic PPGLs. The first part of this review outlines the fundamental principles of the immune system and tumor microenvironment, and their role in cancer immunoediting, particularly emphasizing PPGLs. We focus on how the unique pathophysiology of PPGLs, such as their high molecular, biochemical, and imaging heterogeneity and production of several oncometabolites, creates a tumor-specific microenvironment and immunologically "cold" tumors. Thereafter, we discuss recently published studies related to the reclustering of PPGLs based on their immune signature. The second part of this review discusses future perspectives in PPGL management, including immunodiagnostic and promising immunotherapeutic approaches for converting "cold" tumors into immunologically active or "hot" tumors known for their better immunotherapy response and patient outcomes. Special emphasis is placed on potent immune-related imaging strategies and immune signatures that could be used for the reclassification, prognostication, and management of these tumors to improve patient care and prognosis. Furthermore, we introduce currently available immunotherapies and their possible combinations with other available therapies as an emerging treatment for PPGLs that targets hostile tumor environments.

Elucidating CTLA-4's role in tumor immunity: a comprehensive overview of targeted antibody therapies and clinical developments

Cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) emerges as a key single-chain transmembrane glycoprotein predominantly expressed in effector T cells and regulatory T cells. It plays a crucial role in tumor immunity by modulating T cell responses. Specifically, CTLA-4 dampens T cell activation and proliferation while bolstering the survival of regulatory T cell through its competitive interaction with B7 family molecules, thereby aiding tumor cells in eluding immune detection. Given CTLA-4's significant influence on tumor immune dynamics, an array of anti-CTLA-4 antibody therapeutics have been clinically developed to combat various malignancies, including melanoma, renal cell carcinoma, colorectal carcinoma, hepatocellular carcinoma, non-small cell lung carcinoma, and pleural mesothelioma, demonstrating notable clinical therapeutic effects. This paper aims to delve into CTLA-4's integral role in tumor immunity and to encapsulate the latest advancements in the clinical research of anti-CTLA-4 antibody.

Targeting cytotoxic lymphocyte antigen 4 (CTLA-4) in breast cancer

Breast cancer (BC) has a high mortality rate and is one of the most common malignancies in the world. Initially, BC was considered non-immunogenic, but a paradigm shift occurred with the discovery of tumor-infiltrating lymphocytes (TILs) and regulatory T cells (Tregs) in the BC tumor microenvironment. CTLA-4 (Cytotoxic T-lymphocyte-associated protein 4) immunotherapy has emerged as a treatment option for BC, but it has limitations, including suboptimal antitumor effects and toxicity. Research has demonstrated that anti-CTLA-4 combination therapies, such as Treg depletion, cancer vaccines, and modulation of the gut microbiome, are significantly more effective than CTLA-4 monoclonal antibody (mAB) monotherapy. Second-generation CTLA-4 antibodies are currently being developed to mitigate immune-related adverse events (irAEs) and augment antitumor efficacy. This review examines anti-CTLA-4 mAB in BC, both as monotherapy and in combination with other treatments, and sheds light on ongoing clinical trials, novel CTLA-4 therapeutic strategies, and potential utility of biomarkers in BC.

Harnessing the capacity of phytochemicals to enhance immune checkpoint inhibitor therapy of cancers: A focus on brain malignancies

Brain cancers, particularly glioblastoma multiforme (GBM), are challenging health issues with frequent unmet aspects. Today, discovering safe and effective therapeutic modalities for brain tumors is among the top research interests. Immunotherapy is an emerging area of investigation in cancer treatment. Since immune checkpoints play fundamental roles in repressing anti-cancer immunity, diverse immune checkpoint inhibitors (ICIs) have been developed, and some monoclonal antibodies have been approved clinically for particular cancers; nevertheless, there are significant concerns regarding their efficacy and safety in brain tumors. Among the various tools to modify the immune checkpoints, phytochemicals show good effectiveness and excellent safety, making them suitable candidates for developing better ICIs. Phytochemicals regulate multiple immunological checkpoint-related signaling pathways in cancer biology; however, their efficacy for clinical cancer immunotherapy remains to be established. Here, we discussed the involvement of immune checkpoints in cancer pathology and summarized recent advancements in applying phytochemicals in modulating immune checkpoints in brain tumors to highlight the state-of-the-art and give constructive prospects for future research.

Altered cancer metabolism and implications for next-generation CAR T-cell therapies

This review critically examines the evolving landscape of chimeric antigen receptor (CAR) T-cell therapy in treating solid tumors, with a particular focus on the metabolic challenges within the tumor microenvironment. CAR T-cell therapy has demonstrated remarkable success in hematologic malignancies, yet its efficacy in solid tumors remains limited. A significant barrier is the hostile milieu of the tumor microenvironment, which impairs CAR T-cell survival and function. This review delves into the metabolic adaptations of cancer cells and their impact on immune cells, highlighting the competition for nutrients and the accumulation of immunosuppressive metabolites. It also explores emerging strategies to enhance CAR T-cell metabolic fitness and persistence, including genetic engineering and metabolic reprogramming. An integrated approach, combining metabolic interventions with CAR T-cell therapy, has the potential to overcome these constraints and improve therapeutic outcomes in solid tumors.

Single-cell technologies in psoriasis

Psoriasis is a chronic and recurrent inflammatory skin disorder. The primary manifestation of psoriasis arises from disturbances in the cutaneous immune microenvironment, but the specific functions of the cellular components within this microenvironment remain unknown. Recent advancements in single-cell technologies have enabled the detection of multi-omics at the level of individual cells, including single-cell transcriptome, proteome, and metabolome, which have been successfully applied in studying autoimmune diseases, and other pathologies. These techniques allow the identification of heterogeneous cell clusters and their varying contributions to disease development. Considering the immunological traits of psoriasis, an in-depth exploration of immune cells and their interactions with cutaneous parenchymal cells can markedly advance our comprehension of the mechanisms underlying the onset and recurrence of psoriasis. In this comprehensive review, we present an overview of recent applications of single-cell technologies in psoriasis, aiming to improve our understanding of the underlying mechanisms of this disorder.

Anaplastic Large-cell Lymphoma in Children: State of the Art in 2023

Anaplastic large-cell lymphoma is a rare disease and account for approximately 10% to 15% of pediatric non-Hodgkin lymphomas. They are characterized by extended stages, a high frequency of B signs and extra nodal involvement. Multiagent chemotherapy cures ∽60% to 75% of patients and relapse occurs in 35% of cases. For relapsed patients, various treatments ranging from vinblastine monotherapy to therapeutic intensification with hematopoietic stem cell transplantation have been evaluated, but there is currently no consensus on the optimal therapeutic strategy. New therapeutic perspectives are being evaluated for relapses and refractory forms as well as high-risk forms including monoclonal antibodies (Anti CD30), ALK inhibitors, and CART cells.

PD1 blockade improves survival and CD8+ cytotoxic capacity, without increasing inflammation, during normal microbial experience in old mice

By 2030, individuals 65 years of age or older will make up approximately 20% of the world's population1. Older individuals are at the highest risk for mortality from infections, largely due to the pro-inflammatory, dysfunctional immune response, which is collectively known as immunosenescence2. During aging, CD8+ T cells acquire an exhausted phenotype, including increased expression of inhibitory receptors, such as programmed cell death 1 (PD1), a decline in effector function and elevated expression of inflammatory factors3-7. PD1 reduces T cell receptor activity via SHP2-dependent dephosphorylation of multiple pathways; accordingly, inhibiting PD1 activity through monoclonal antibodies increases CD8+ T cell effector response in young mice8-11. Attempts to improve CD8+ T cell responses by blocking inhibitory receptors are attractive; however, they can lead to adverse immune events due to overamplification of T cell receptor signaling and T cell activation12,13. Here we investigated the effect of monoclonal anti-PD1 immunotherapy during normal microbial experience, otherwise known as exposure to dirty mice, to determine whether it either improves exhausted CD8+ T cell responses in old mice or leads to a heightened inflammatory response and increased mortality.

Bioactive compounds derived from marine source: a potential immunotherapy treatment

Immunotherapy using checkpoint inhibitors blocks the checkpoint proteins (programmed cell death receptor-1; PD-1) from binding with their corresponding ligands (programmed cell death receptor ligand-1; PD-L1) to regulate cell signaling pathways. The marine environment holds a huge source of small molecules that are understudied which can be developed as an inhibitor. Hence, this study investigated the inhibitory effect of 19 algae-derived small molecules against PD-L1 by using molecular docking, absorption, distribution, metabolism, and elimination (ADME) properties and molecular dynamics simulations (MDS). The molecular docking revealed that the binding energy of the six best compounds ranges from -11.1 to -9.1 kcal/mol. Fucoxanthinol, in particular, has the strongest binding energy at -11.1 kcal/mol with three hydrogen bonds (ASN:63A, GLN:66A, and ASP:122A). Meanwhile, the MDS demonstrated that the ligands were strongly bound to the protein, indicating the stability of the complexes. In summary, the identified compounds are potential PD-L1 inhibitors in immunotherapy.Communicated by Ramaswamy H. Sarma.

Potential mechanisms and targeting strategies of the gut microbiota in antitumor immunity and immunotherapy

BACKGROUND

Immunotherapies, notably immune checkpoints inhibitors that target programmed death 1/programmed death ligand 1(PD-1/PD-L1) and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), had profoundly changed the way advanced and metastatic cancers are treated and dramatically improved overall and progression-free survival.

AIMS

This review article aimed to explore the underlying molecular mechanisms by which the gut microbiota affects antitumor immunity and the efficacy of cancer immunotherapy.

METHODS

We summarized the latest knowledge supporting the associations among the gut microbiota, antitumor immunity, and immunotherapy. Moreover, we disscussed the therapeutic strategy for improving immunotherapy efficacy by modulating gut microbiota in cancer treatment.

RESULTS

The potential molecular mechanisms underlying these associations are explained in terms of four aspects: immunomodulation, molecular mimicry, mamps, and microbial metabolites.

CONCLUSION

The gut microbiota significantly impacts antitumor immunity and alters the effectiveness of cancer immunotherapy.

A combination of protein phosphatase 2A inhibition and checkpoint immunotherapy: a perfect storm

Immune checkpoint blockade has emerged as a potent new tool in the war on cancer. However, only a subset of cancer patients benefit from this therapeutic modality, sparking a search for combination therapies to increase the fraction of responding patients. We argue here that inhibition of protein phosphatase 2A (PP2A) is a promising approach to increase responses to immune checkpoint blockade and other therapies that rely on the presence of tumor-reactive T cells. Inhibition of PP2A increases neoantigen expression on tumor cells, activates the cGAS/STING pathway, suppresses regulatory T cells, and increases cytotoxic T cell activation. In preclinical models, inhibition of PP2A synergizes with immune checkpoint blockade and emerging evidence indicates that patients who have tumors with mutations in PP2A respond better to immune checkpoint blockade. Therefore, inhibition of PP2A activity may be an effective way to sensitize cancer cells to immune checkpoint blockade and cell-based therapies using tumor-reactive T cells.

Advances in immunotherapy for breast cancer and feline mammary carcinoma: From molecular basis to novel therapeutic targets

The role of inflammation in cancer is a topic that has been investigated for many years. As established, inflammation emerges as a defining characteristic of cancer, presenting itself as a compelling target for therapeutic interventions in the realm of oncology. Controlling the tumor microenvironment (TME) has gained paramount significance, modifying not only the effectiveness of immunotherapy but also modulating the outcomes and prognoses of standard chemotherapy and other anticancer treatments. Immunotherapy has surfaced as a central focus within the domain of tumor treatments, using immune checkpoint inhibitors as cancer therapy. Immune checkpoints and their influence on the tumor microenvironment dynamic are presently under investigation, aiming to ascertain their viability as therapeutic interventions across several cancer types. Cancer presents a significant challenge in humans and cats, where female breast cancer ranks as the most prevalent malignancy and feline mammary carcinoma stands as the third most frequent. This review seeks to summarize the data about the immune checkpoints cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), lymphocyte activation gene-3 (LAG-3), programmed cell death protein-1 (PD-1), V-domain Ig suppressor of T cell activation (VISTA), and T-cell immunoglobulin and mucin domain 3 (TIM-3) respective ongoing investigations as prospective targets for therapy for human breast cancer, while also outlining findings from studies reported on feline mammary carcinoma (FMC), strengthening the rationale for employing FMC as a representative model in the exploration of human breast cancer.

Tumor-associated macrophages in anti-PD-1/PD-L1 immunotherapy for hepatocellular carcinoma: recent research progress

Hepatocellular carcinoma (HCC) is one of the cancers that seriously threaten human health. Immunotherapy serves as the mainstay of treatment for HCC patients by targeting the programmed cell death protein 1/programmed cell death 1 ligand 1 (PD-1/PD-L1) axis. However, the effectiveness of anti-PD-1/PD-L1 treatment is limited when HCC becomes drug-resistant. Tumor-associated macrophages (TAMs) are an important factor in the negative regulation of PD-1 antibody targeted therapy in the tumor microenvironment (TME). Therefore, as an emerging direction in cancer immunotherapy research for the treatment of HCC, it is crucial to elucidate the correlations and mechanisms between TAMs and PD-1/PD-L1-mediated immune tolerance. This paper summarizes the effects of TAMs on the pathogenesis and progression of HCC and their impact on HCC anti-PD-1/PD-L1 immunotherapy, and further explores current potential therapeutic strategies that target TAMs in HCC, including eliminating TAMs in the TME, inhibiting TAMs recruitment to tumors and functionally repolarizing M2-TAMs (tumor-supportive) to M1-TAMs (antitumor type).

Immunotherapy Based on Immune Checkpoint Molecules and Immune Checkpoint Inhibitors in Gastric Cancer-Narrative Review

Due to its rapid progression to advanced stages and highly metastatic properties, gastric cancer (GC) is one of the most aggressive malignancies and the fourth leading cause of cancer-related deaths worldwide. The metastatic process includes local invasion, metastasis initiation, migration with colonisation at distant sites, and evasion of the immune response. Tumour growth involves the activation of inhibitory signals associated with the immune response, also known as immune checkpoints, including PD-1/PD-L1 (programmed death 1/programmed death ligand 1), CTLA-4 (cytotoxic T cell antigen 4), TIGIT (T cell immunoreceptor with Ig and ITIM domains), and others. Immune checkpoint molecules (ICPMs) are proteins that modulate the innate and adaptive immune responses. While their expression is prominent on immune cells, mainly antigen-presenting cells (APC) and other types of cells, they are also expressed on tumour cells. The engagement of the receptor by the ligand is crucial for inhibiting or stimulating the immune cell, which is an extremely important aspect of cancer immunotherapy. This narrative review explores immunotherapy, focusing on ICPMs and immune checkpoint inhibitors in GC. We also summarise the current clinical trials that are evaluating ICPMs as a target for GC treatment.

Metabolic regulator LKB1 controls adipose tissue ILC2 PD-1 expression and mitochondrial homeostasis to prevent insulin resistance

Adipose tissue group 2 innate lymphoid cells (ILC2s) help maintain metabolic homeostasis by sustaining type 2 immunity and promoting adipose beiging. Although impairment of the ILC2 compartment contributes to obesity-associated insulin resistance, the underlying mechanisms have not been elucidated. Here, we found that ILC2s in obese mice and humans exhibited impaired liver kinase B1 (LKB1) activation. Genetic ablation of LKB1 disrupted ILC2 mitochondrial metabolism and suppressed ILC2 responses, resulting in exacerbated insulin resistance. Mechanistically, LKB1 deficiency induced aberrant PD-1 expression through activation of NFAT, which in turn enhanced mitophagy by suppressing Bcl-xL expression. Blockade of PD-1 restored the normal functions of ILC2s and reversed obesity-induced insulin resistance in mice. Collectively, these data present the LKB1-PD-1 axis as a promising therapeutic target for the treatment of metabolic disease.

Aberrant spliceosome activity via elevated intron retention and upregulation and phosphorylation of SF3B1 in chronic lymphocytic leukemia

Splicing factor 3b subunit 1 (SF3B1) is the largest subunit and core component of the spliceosome. Inhibition of SF3B1 was associated with an increase in broad intron retention (IR) on most transcripts, suggesting that IR can be used as a marker of spliceosome inhibition in chronic lymphocytic leukemia (CLL) cells. Furthermore, we separately analyzed exonic and intronic mapped reads on annotated RNA-sequencing transcripts obtained from B cells (n = 98 CLL patients) and healthy volunteers (n = 9). We measured intron/exon ratio to use that as a surrogate for alternative RNA splicing (ARS) and found that 66% of CLL-B cell transcripts had significant IR elevation compared with normal B cells (NBCs) and that correlated with mRNA downregulation and low expression levels. Transcripts with the highest IR levels belonged to biological pathways associated with gene expression and RNA splicing. A >2-fold increase of active pSF3B1 was observed in CLL-B cells compared with NBCs. Additionally, when the CLL-B cells were treated with macrolides (pladienolide-B), a significant decrease in pSF3B1, but not total SF3B1 protein, was observed. These findings suggest that IR/ARS is increased in CLL, which is associated with SF3B1 phosphorylation and susceptibility to SF3B1 inhibitors. These data provide additional support to the relevance of ARS in carcinogenesis and evidence of pSF3B1 participation in this process.

Exploring the Complexity and Promise of Tumor Immunotherapy in Drug Development

Cancer represents a significant threat to human health, and traditional chemotherapy or cytotoxic therapy is no longer the sole or preferred approach for managing malignant tumors. With advanced research into the immunogenicity of tumor cells and the growing elderly population, tumor immunotherapy has emerged as a prominent therapeutic option. Its significance in treating elderly cancer patients is increasingly recognized. In this study, we review the conceptual classifications and benefits of immunotherapy, and discuss recent developments in new drugs and clinical progress in cancer treatment through various immunotherapeutic modalities with different mechanisms. Additionally, we explore the impact of immunosenescence on the effectiveness of cancer immunotherapy and propose innovative and effective strategies to rejuvenate senescent T cells.

Identification of a metabolism-linked genomic signature for prognosis and immunotherapeutic efficiency in metastatic skin cutaneous melanoma

Metastatic skin cutaneous melanoma (MSCM) is the most rapidly progressing/invasive skin-based malignancy, with median survival rates of about 12 months. It appears that metabolic disorders accelerate disease progression. However, correlations between metabolism-linked genes (MRGs) and prognosis in MSCM are unclear, and potential mechanisms explaining the correlation are unknown. The Cancer Genome Atlas (TCGA) was utilized as a training set to develop a genomic signature based on the differentially expressed MRGs (DE-MRGs) between primary skin cutaneous melanoma (PSCM) and MSCM. The Gene Expression Omnibus (GEO) was utilized as a validation set to verify the effectiveness of genomic signature. In addition, a nomogram was established to predict overall survival based on genomic signature and other clinic-based characteristics. Moreover, this study investigated the correlations between genomic signature and tumor micro-environment (TME). This study established a genomic signature consisting of 3 genes (CD38, DHRS3, and TYRP1) and classified MSCM patients into low and high-risk cohorts based on the median risk scores of MSCM cases. It was discovered that cases in the high-risk cohort had significantly lower survival than cases in the low-risk cohort across all sets. Furthermore, a nomogram containing this genomic signature and clinic-based parameters was developed and demonstrated high efficiency in predicting MSCM case survival times. Interestingly, Gene Set Variation Analysis results indicated that the genomic signature was involved in immune-related physiological processes. In addition, this study discovered that risk scoring was negatively correlated with immune-based cellular infiltrations in the TME and critical immune-based checkpoint expression profiles, indicating that favorable prognosis may be influenced in part by immunologically protective micro-environments. A novel 3-genomic signature was found to be reliable for predicting MSCM outcomes and may facilitate personalized immunotherapy.

Fully equipped CARs to address tumor heterogeneity, enhance safety, and improve the functionality of cellular immunotherapies

Although adoptive transfer of chimeric antigen receptor (CAR)-engineered T cells has achieved unprecedented response rates in patients with certain hematological malignancies, this therapeutic modality is still far from fulfilling its remarkable potential, especially in the context of solid cancers. Antigen escape variants, off-tumor destruction of healthy tissues expressing tumor-associated antigens (TAAs), poor CAR-T cell persistence, and the occurrence of functional exhaustion represent some of the most prominent hurdles that limit CAR-T cell ability to induce long-lasting remissions with a tolerable adverse effect profile. In this review, we summarize the main approaches that have been developed to face such bottlenecks, including the adapter CAR (AdCAR) system, Boolean-logic gating, epitope editing, the modulation of cell-intrinsic signaling pathways, and the incorporation of safety switches to precisely control CAR-T cell activation. We also discuss the most pressing issues pertaining to the selection of co-stimulatory domains, with a focus on strategies aimed at promoting CAR-T cell persistence and optimal antitumor functionality.

Soluble immune checkpoints: implications for cancer prognosis and response to immune checkpoint therapy and conventional therapies

Longitudinal sampling of tumor tissue from patients with solid cancers, aside from melanoma and a few other cases, is often unfeasible, and thus may not capture the plasticity of interactions between the tumor and immune system under selective pressure of a given therapy. Peripheral blood analyses provide salient information about the human peripheral immunome while offering technical and practical advantages over traditional tumor biopsies, and should be utilized where possible alongside interrogation of the tumor. Some common blood-based biomarkers used to study the immune response include immune cell subsets, circulating tumor DNA, and protein analytes such as cytokines. With the recent explosion of immune checkpoint inhibitors (ICI) as a modality of treatment in multiple cancer types, soluble immune checkpoints have become a relevant area of investigation for peripheral immune-based biomarkers. However, the exact functions of soluble immune checkpoints and their roles in cancer for the most part remain unclear. This review discusses current literature on the production, function, and expression of nine soluble immune checkpoints - sPD-L1, sPD-1, sCTLA4, sCD80, sTIM3, sLAG3, sB7-H3, sBTLA, and sHVEM - in patients with solid tumors, and explores their role as biomarkers of response to ICI as well as to conventional therapies (chemotherapy, radiotherapy, targeted therapy, and surgery) in cancer patients.

Apoptosis, a Metabolic "Head-to-Head" between Tumor and T Cells: Implications for Immunotherapy

Induction of apoptosis represents a promising therapeutic approach to drive tumor cells to death. However, this poses challenges due to the intricate nature of cancer biology and the mechanisms employed by cancer cells to survive and escape immune surveillance. Furthermore, molecules released from apoptotic cells and phagocytes in the tumor microenvironment (TME) can facilitate cancer progression and immune evasion. Apoptosis is also a pivotal mechanism in modulating the strength and duration of anti-tumor T-cell responses. Combined strategies including molecular targeting of apoptosis, promoting immunogenic cell death, modulating immunosuppressive cells, and affecting energy pathways can potentially overcome resistance and enhance therapeutic outcomes. Thus, an effective approach for targeting apoptosis within the TME should delicately balance the selective induction of apoptosis in tumor cells, while safeguarding survival, metabolic changes, and functionality of T cells targeting crucial molecular pathways involved in T-cell apoptosis regulation. Enhancing the persistence and effectiveness of T cells may bolster a more resilient and enduring anti-tumor immune response, ultimately advancing therapeutic outcomes in cancer treatment. This review delves into the pivotal topics of this multifaceted issue and suggests drugs and druggable targets for possible combined therapies.

New therapies for unresectable or metastatic cutaneous eyelid and orbital melanoma

PURPOSE

Newer treatment options offer the promise of improved outcomes for metastatic and unresectable melanoma. This investigation was performed to review these modalities for cutaneous eyelid and orbital disease.

METHODS

A search for articles that were related to this subject was performed in the PubMed database, and the bibliographies of these manuscripts were reviewed to ensure capture of the appropriate literature. Data was abstracted and analyzed.

RESULTS

Historically, patients who suffer from melanoma of the ocular adnexa have fared poorly. Approaches that employ BRAF and mitogen-associated protein kinase inhibitors, immunotherapy, and novel cellular therapies improve outcomes and survival rates, although the side effect profiles of these agents are problematic. Most of the existing strategies have not explored ocular adnexal disease specifically, and treatment plans are generally adapted from the general cutaneous oncology literature.

CONCLUSIONS

Thanks to advances in our comprehension of the cellular biology of the disease, the management of unresectable and metastatic melanoma has evolved considerably over the past several years. Newer modalities will likely continue to improve survival and reduce adverse events.

Immunomodulatory Precision: A Narrative Review Exploring the Critical Role of Immune Checkpoint Inhibitors in Cancer Treatment

An immune checkpoint is a signaling pathway that regulates the recognition of antigens by T-cell receptors (TCRs) during an immune response. These checkpoints play a pivotal role in suppressing excessive immune responses and maintaining immune homeostasis against viral or microbial infections. There are several FDA-approved immune checkpoint inhibitors (ICIs), including ipilimumab, pembrolizumab, and avelumab. These ICIs target cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), and programmed death ligand 1 (PD-L1). Furthermore, ongoing efforts are focused on developing new ICIs with emerging potential. In comparison to conventional treatments, ICIs offer the advantages of reduced side effects and durable responses. There is growing interest in the potential of combining different ICIs with chemotherapy, radiation therapy, or targeted therapies. This article comprehensively reviews the classification, mechanism of action, application, and combination strategies of ICIs in various cancers and discusses their current limitations. Our objective is to contribute to the future development of more effective anticancer drugs targeting immune checkpoints.

Uncommon Adverse Events of Immune Checkpoint Inhibitors in Small Cell Lung Cancer: A Systematic Review of Case Reports

BACKGROUND

This study aimed to systematically review case reports documenting rare adverse events in patients with small cell lung cancer (SCLC) following the administration of immune checkpoint inhibitors (ICIs).

METHODS

A systematic literature review was conducted to identify case reports detailing previously unreported adverse drug reactions to ICIs in patients with SCLC. The scope of the literature reviewed was restricted to case studies on SCLC published up to 31 December 2023.

RESULTS

We analyzed twenty-four studies on ICI use for patients with SCLC. There were six reports on atezolizumab, four on durvalumab, and three on adverse events from monotherapy with nivolumab. Reports involving combination treatments were the most frequent, with a total of six, predominantly involving using nivolumab in combination with ipilimumab. Additionally, there was one report each on using pembrolizumab, nofazinilimab, sintilimab, tislelizumab, and toripalimab. We collected detailed information on the clinical course, including patient and disease characteristics, symptoms, treatment for each adverse event, and recovery status. Among the patients included in the case reports, 21 out of 24 (87.5%) had extensive-stage SCLC when initiating ICI therapy, with only 1 patient diagnosed with limited-stage SCLC. Respiratory system adverse events were most common, with seven cases, followed by neurological, endocrinological, and gastroenterological events. Three case reports documented adverse events across multiple systems in a single patient. In most cases, patients showed symptom improvement; however, four studies reported cases where patients either expired without symptom improvement or experienced sequelae.

CONCLUSIONS

Efforts to develop reliable biomarkers for predicting irAEs continue, with ongoing research to enhance predictive precision. Immunotherapy presents diverse and unpredictable adverse events, underscoring the need for advanced diagnostic tools and a multidisciplinary approach to improve patient management.

The synergistic immunotherapeutic impact of engineered CAR-T cells with PD-1 blockade in lymphomas and solid tumors: a systematic review

Currently, therapies such as chimeric antigen receptor-T Cell (CAR-T) and immune checkpoint inhibitors like programmed cell death protein-1 (PD-1) blockers are showing promising results for numerous cancer patients. However, significant advancements are required before CAR-T therapies become readily available as off-the-shelf treatments, particularly for solid tumors and lymphomas. In this review, we have systematically analyzed the combination therapy involving engineered CAR-T cells and anti PD-1 agents. This approach aims at overcoming the limitations of current treatments and offers potential advantages such as enhanced tumor inhibition, alleviated T-cell exhaustion, heightened T-cell activation, and minimized toxicity. The integration of CAR-T therapy, which targets tumor-associated antigens, with PD-1 blockade augments T-cell function and mitigates immune suppression within the tumor microenvironment. To assess the impact of combination therapy on various tumors and lymphomas, we categorized them based on six major tumor-associated antigens: mesothelin, disialoganglioside GD-2, CD-19, CD-22, CD-133, and CD-30, which are present in different tumor types. We evaluated the efficacy, complete and partial responses, and progression-free survival in both pre-clinical and clinical models. Additionally, we discussed potential implications, including the feasibility of combination immunotherapies, emphasizing the importance of ongoing research to optimize treatment strategies and improve outcomes for cancer patients. Overall, we believe combining CAR-T therapy with PD-1 blockade holds promise for the next generation of cancer immunotherapy.

Modulation of the tumor microenvironment and mechanism of immunotherapy-based drug resistance in breast cancer

Breast cancer, the most frequent female malignancy, is often curable when detected at an early stage. The treatment of metastatic breast cancer is more challenging and may be unresponsive to conventional therapy. Immunotherapy is crucial for treating metastatic breast cancer, but its resistance is a major limitation. The tumor microenvironment (TME) is vital in modulating the immunotherapy response. Various tumor microenvironmental components, such as cancer-associated fibroblasts (CAFs), tumor-associated macrophages (TAMs), and myeloid-derived suppressor cells (MDSCs), are involved in TME modulation to cause immunotherapy resistance. This review highlights the role of stromal cells in modulating the breast tumor microenvironment, including the involvement of CAF-TAM interaction, alteration of tumor metabolism leading to immunotherapy failure, and other latest strategies, including high throughput genomic screening, single-cell and spatial omics techniques for identifying tumor immune genes regulating immunotherapy response. This review emphasizes the therapeutic approach to overcome breast cancer immune resistance through CAF reprogramming, modulation of TAM polarization, tumor metabolism, and genomic alterations.

Prognostic biomarkers associated with immune checkpoint inhibitors in hepatocellular carcinoma

The treatment of hepatocellular carcinoma (HCC), particularly advanced HCC, has been a serious challenge. Immune checkpoint inhibitors (ICIs) are landmark drugs in the field of cancer therapy in recent years, which have changed the landscape of cancer treatment. In the field of HCC treatment, this class of drugs has shown good therapeutic prospects. For example, atezolizumab in combination with bevacizumab has been approved as first-line treatment for advanced HCC due to significant efficacy. However, sensitivity to ICI therapy varies widely among HCC patients. Therefore, there is an urgent need to search for determinants of resistance/sensitivity to ICIs and to screen biomarkers that can predict the efficacy of ICIs. This manuscript reviews the research progress of prognostic biomarkers associated with ICIs in HCC in order to provide a scientific basis for the development of clinically individualised precision medication regimens.

Adaptive immune changes associate with clinical progression of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the most frequent cause of dementia. Recent evidence suggests the involvement of peripheral immune cells in the disease, but the underlying mechanisms remain unclear.

METHODS

We comprehensively mapped peripheral immune changes in AD patients with mild cognitive impairment (MCI) or dementia compared to controls, using cytometry by time-of-flight (CyTOF).

RESULTS

We found an adaptive immune signature in AD, and specifically highlight the accumulation of PD1+ CD57+ CD8+ T effector memory cells re-expressing CD45RA in the MCI stage of AD. In addition, several innate and adaptive immune cell subsets correlated to cerebrospinal fluid (CSF) biomarkers of AD neuropathology and measures for cognitive decline. Intriguingly, subsets of memory T and B cells were negatively associated with CSF biomarkers for tau pathology, neurodegeneration and neuroinflammation in AD patients. Lastly, we established the influence of the APOE ε4 allele on peripheral immunity.

CONCLUSIONS

Our findings illustrate significant peripheral immune alterations associated with both early and late clinical stages of AD, emphasizing the necessity for further investigation into how these changes influence underlying brain pathology.

Cabozantinib in combination with immune checkpoint inhibitors for renal cell carcinoma: a systematic review and meta-analysis

Context

Cabozantinib combined with immune checkpoint inhibitors (ICIs) has brought a new therapeutic effect for the medical treatment of renal cell carcinoma (RCC).

Objectives

We performed a meta-analysis of randomized controlled trials and single-arm trials to evaluate the efficacy and safety of cabozantinib plus ICIs in RCC.

Methods

We extracted data from PubMed, Cochrane, Medline and Embase databases, and rated literature quality through Cochrane risk of bias tool and MINORS. RevMan5.3 software was used to analyze the results of randomized controlled trials and single-arm trials.

Results

A total of 7 studies were included. Treatment with cabozantinib plus ICIs improved PFS [HR 0.75, (95%CI: 0.52, 1.08), p = 0.12] and the OS [HR 0.80, (95%CI: 0.60, 1.07), p = 0.13] in randomized controlled trials. Meanwhile, the result of the ORR in randomized controlled trials was [risk ratio (RR) 1.37, (95%CI: 1.21, 1.54), p < 0.00001] and in single-arm trials was [risk difference (RD) 0.49, (95%CI: 0.26, 0.71), p < 0.0001].

Conclusion

Cabozantinib plus ICIs prolonged the PFS and OS, and improved ORR in patients with RCC. Our recommendation is to use cabozantinib plus ICIs to treat advanced RCC, and to continuous monitor and manage the drug-related adverse events.

Systematic Review Registration

identifier CRD42023455878.

Counterproductive effects of anti-CD38 and checkpoint inhibitor for the treatment of NK/T cell lymphoma

Introduction

Natural killer/T cell lymphoma (NKTL) is an aggressive malignancy associated with poor prognosis. This is largely due to limited treatment options, especially for relapsed patients. Immunotherapies like immune checkpoint inhibitors (ICI) and anti-CD38 therapies have shown promising but variable clinical efficacies. Combining these therapies has been suggested to enhance efficacy.

Methods

We conducted a case study on a relapsed NKTL patient treated sequentially with anti-CD38 followed by ICI (anti-PD1) using cytometry analyses.

Results and Discussion

Our analysis showed an expected depletion of peripheral CD38+ B cells following anti-CD38 treatment. Further analysis indicated that circulating anti-CD38 retained their function for up to 13 weeks post-administration. Anti-PD1 treatment triggered re-activation and upregulation of CD38 on the T cells. Consequently, these anti-PD1-activated T cells were depleted by residual circulating anti-CD38, rendering the ICI treatment ineffective. Finally, a meta-analysis confirmed this counterproductive effect, showing a reduced efficacy in patients undergoing combination therapy. In conclusion, our findings demonstrate that sequential anti-CD38 followed by anti-PD1 therapy leads to a counterproductive outcome in NKTL patients. This suggests that the treatment sequence is antithetic and warrants re-evaluation for optimizing cancer immunotherapy strategies.

Molecular insights into clinical trials for immune checkpoint inhibitors in colorectal cancer: Unravelling challenges and future directions

Colorectal cancer (CRC) is a complex disease with diverse etiologies and clinical outcomes. Despite considerable progress in development of CRC therapeutics, challenges remain regarding the diagnosis and management of advanced stage metastatic CRC (mCRC). In particular, the five-year survival rate is very low since mCRC is currently rarely curable. Over the past decade, cancer treatment has significantly improved with the introduction of cancer immunotherapies, specifically immune checkpoint inhibitors. Therapies aimed at blocking immune checkpoints such as PD-1, PD-L1, and CTLA-4 target inhibitory pathways of the immune system, and thereby enhance anti-tumor immunity. These therapies thus have shown promising results in many clinical trials alone or in combination. The efficacy and safety of immunotherapy, either alone or in combination with CRC, have been investigated in several clinical trials. Clinical trials, including KEYNOTE-164 and CheckMate 142, have led to Food and Drug Administration approval of the PD-1 inhibitors pembrolizumab and nivolumab, respectively, for the treatment of patients with unresectable or metastatic microsatellite instability-high or deficient mismatch repair CRC. Unfortunately, these drugs benefit only a small percentage of patients, with the benefits of immunotherapy remaining elusive for the vast majority of CRC patients. To this end, primary and secondary resistance to immunotherapy remains a significant issue, and further research is necessary to optimize the use of immunotherapy in CRC and identify biomarkers to predict the response. This review provides a comprehensive overview of the clinical trials involving immune checkpoint inhibitors in CRC. The underlying rationale, challenges faced, and potential future steps to improve the prognosis and enhance the likelihood of successful trials in this field are discussed.

Single-cell data revealed exhaustion of characteristic NK cell subpopulations and T cell subpopulations in hepatocellular carcinoma

BACKGROUND

The treatment and prognosis of patients with advanced hepatocellular carcinoma (HCC) have been a major medical challenge. Unraveling the landscape of tumor immune infiltrating cells (TIICs) in the immune microenvironment of HCC is of great significance to probe the molecular mechanisms.

METHODS

Based on single-cell data of HCC, the cell landscape was revealed from the perspective of TIICs. Special cell subpopulations were determined by the expression levels of marker genes. Differential expression analysis was conducted. The activity of each subpopulation was determined based on the highly expressed genes. CTLA4+ T-cell subpopulations affecting the prognosis of HCC were determined based on survival analysis. A single-cell regulatory network inference and clustering analysis was also performed to determine the transcription factor regulatory networks in the CTLA4+ T cell subpopulations.

RESULTS

10 cell types were identified and NK cells and T cells showed high abundance in tumor tissues. Two NK cells subpopulations were present, FGFBP2+ NK cells, B3GNT7+ NK cells. Four T cells subpopulations were present, LAG3+ T cells, CTLA4+ T cells, RCAN3+ T cells, and HPGDS+ Th2 cells. FGFBP2+ NK cells, and CTLA4+ T cells were the exhaustive subpopulation. High CTLA4+ T cells contributed to poor prognostic outcomes and promoted tumor progression. Finally, a network of transcription factors regulated by NR3C1, STAT1, and STAT3, which were activated, was present in CTLA4+ T cells.

CONCLUSION

CTLA4+ T cell subsets in HCC exhibited functional exhaustion characteristics that probably inhibited T cell function through a transcription factor network dominated by NR3C1, STAT1, and STAT3.

Fish Uses CTLA-4 Immune Checkpoint to Suppress mTORC1-Controlled T-Cell Glycolysis and Immunity

As an immune checkpoint, cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) suppresses the activation, proliferation, and effector function of T cells, thus preventing an overexuberant response and maintaining immune homeostasis. However, whether and how this immune checkpoint functions in early vertebrates remains unknown. In the current study, using a Nile tilapia (Oreochromis niloticus) model, we investigated the suppression of T cell response by CTLA-4 in bony fish. Tilapia CTLA-4 is constitutively expressed in lymphoid tissues, and its mRNA and protein expression in lymphocytes are upregulated following PHA stimulation or Edwardsiella piscicida infection. Blockade of CTLA-4 signaling enhanced T cell activation and proliferation but inhibited activation-induced T cell apoptosis, indicating that CTLA-4 negatively regulated T cell activation. In addition, blocking CTLA-4 signaling in vivo increased the differentiation potential and cytotoxicity of T cells, resulting in an enhanced T cell response during E. piscicida infection. Tilapia CTLA-4 competitively bound the B7.2/CD86 molecule with CD28, thus antagonizing the CD28-mediated costimulatory signal of T cell activation. Furthermore, inhibition of mammalian/mechanistic target of rapamycin complex 1 (mTORC1) signaling, c-Myc, or glycolysis markedly impaired the CTLA-4 blockade-enhanced T cell response, suggesting that CTLA-4 suppressed the T cell response of tilapia by inhibiting mTORC1/c-Myc axis-controlled glycolysis. Overall, the findings indicate a detailed mechanism by which CTLA-4 suppresses T cell immunity in tilapia; therefore, we propose that early vertebrates have evolved sophisticated mechanisms coupling immune checkpoints and metabolic reprogramming to avoid an overexuberant T cell response.

Immmunometabolism of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a potentially fatal chronic autoimmune disease which is underlain by complex dysfunction of the innate and adaptive immune systems. Although a series of well-defined genetic and environmental factors have been implicated in disease etiology, neither the development nor the persistence of SLE is well understood. Given that several disease susceptibility genes and environmental factors interact and influence inflammatory lineage specification through metabolism, the field of immunometabolism has become a forefront of cutting edge research. Along these lines, metabolic checkpoints of pathogenesis have been identified as targets of effective therapeutic interventions in mouse models and validated in clinical trials. Ongoing studies focus on mitochondrial oxidative stress, activation of the mechanistic target of rapamycin, calcium signaling, glucose utilization, tryptophan degradation, and metabolic cross-talk between gut microbiota and the host immune system.

PP2A as a potential therapeutic target for breast cancer: Current insights and future perspectives

Breast cancer has become the most prevalent malignancy worldwide; however, therapeutic efficacy is far from satisfactory. To alleviate the burden of this disease, it is imperative to discover novel mechanisms and treatment strategies. Protein phosphatase 2 A (PP2A) comprises a family of mammalian serine/threonine phosphatases that regulate many cellular processes. PP2A is dysregulated in several human diseases, including oncological pathologies, and plays a pivotal role in the initiation and progression of tumours. The role of PP2A as a tumour suppressor has been extensively studied, and its regulation can serve as a target for anticancer therapy. Recent studies have shown that PP2A is a tumour promotor. PP2A-mediated anticancer therapy may involve two opposing mechanisms: activation and inhibition. In general, the contradictory roles of PP2A should not be overlooked, and more work is needed to determine the molecular mechanism by which PP2A affects in tumours. In this review, the literature on the role of PP2A in tumours, especially in breast cancer, was analysed. This review describes relevant targets of breast cancer, such as cell cycle control, DNA damage responses, epidermal growth factor receptor, immune modulation and cell death resistance, which may lead to effective therapeutic strategies or influence drug development in breast cancer.

PD-1-mediated inhibition of T cell activation: Mechanisms and strategies for cancer combination immunotherapy

The programmed cell death 1 (PD-1) immune checkpoint of co-inhibitory signaling plays crucial roles in controlling the magnitude and duration of T cell activation to limit tissue damage and maintain self-tolerance. Cancer cells hijack the co-inhibitory pathway and escape immune surveillance by overexpressing the PD-1 ligand PD-L1. Immune checkpoint inhibitors, such as PD-1 blocking antibody have been approved for tumor immunotherapy. However, not all patients can benefit from PD-1 monotherapy. Combination immunotherapy based on PD-1 axis blockade substantially improves clinical anti-tumor efficacy. In this review, we briefly summarize the current progress on the mechanisms of PD-1-mediated inhibition of T cell activation and strategies for cancer combination immunotherapy.

The development and characterization of a CRISPR/Cas9-mediated PD-1 functional knockout rat as a tool to study idiosyncratic drug reactions

Idiosyncratic drug reactions are rare but serious adverse drug reactions unrelated to the known therapeutic properties of the drug and manifest in only a small percentage of the treated population. Animal models play an important role in advancing mechanistic studies examining idiosyncratic drug reactions. However, to be useful, they must possess similarities to those seen clinically. Although mice currently represent the dominant mammalian genetic model, rats are advantageous in many areas of pharmacologic study where their physiology can be examined in greater detail and is more akin to that seen in humans. In the area of immunology, this includes autoimmune responses and susceptibility to diabetes, in which rats more accurately mimic disease states in humans compared with mice. For example, oral nevirapine treatment can induce an immune-mediated skin rash in humans and rats, but not in mice due to the absence of the sulfotransferase required to form reactive metabolites of nevirapine within the skin. Using CRISPR-mediated gene editing, we developed a modified line of transgenic rats in which a segment of IgG-like ectodomain containing the core PD-1 interaction motif containing the native ligand and therapeutic antibody domain in exon 2 was deleted. Removal of this region critical for mediating PD-1/PD-L1 interactions resulted in animals with an increased immune response resulting in liver injury when treated with amodiaquine.

A new strategy for immunotherapy of microsatellite-stable (MSS)-type advanced colorectal cancer: Multi-pathway combination therapy with PD-1/PD-L1 inhibitors

Colorectal cancer (CRC) is a frequent gastrointestinal malignancy with high rates of morbidity and mortality; 85% of these tumours are proficient mismatch repair (pMMR)-microsatellite instability-low (MSI-L)/microsatellite stable (MSS) CRC known as 'cold' tumours that are resistant to immunosuppressive drugs. Monotherapy with programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) inhibitors is ineffective for treating MSS CRC, making immunotherapy for MSS CRC a bottleneck. Recent studies have found that the multi-pathway regimens combined with PD-1/PD-L1 inhibitors can enhance the efficacy of anti-PD-1/PD-L1 in MSS CRC by increasing the number of CD8+ T cells, upregulating PD-L1 expression and improving the tumour microenvironment. This paper reviews the research progress of PD-1/PD-L1 inhibitors in combination with cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) inhibitors, oncolytic virus, intestinal flora, antiangiogenic agents, chemotherapy, radiotherapy and epigenetic drugs for the treatment of pMMR-MSI-L/MSS CRC.