Advances in targeting co-inhibitory and co-stimulatory pathways in transplantation settings: the Yin to the Yang of cancer immunotherapy

Reigniting hope in cancer treatment: the promise and pitfalls of IL-2 and IL-2R targeting strategies

Interleukin-2 (IL-2) and its receptor (IL-2R) are essential in orchestrating immune responses. Their function and expression in the tumor microenvironment make them attractive targets for immunotherapy, leading to the development of IL-2/IL-2R-targeted therapeutic strategies. However, the dynamic interplay between IL-2/IL-2R and various immune cells and their dual roles in promoting immune activation and tolerance presents a complex landscape for clinical exploitation. This review discusses the pivotal roles of IL-2 and IL-2R in tumorigenesis, shedding light on their potential as diagnostic and prognostic markers and their therapeutic manipulation in cancer. It underlines the necessity to balance the anti-tumor activity with regulatory T-cell expansion and evaluates strategies such as dose optimization and selective targeting for enhanced therapeutic effectiveness. The article explores recent advancements in the field, including developing genetically engineered IL-2 variants, combining IL-2/IL-2R-targeted therapies with other cancer treatments, and the potential benefits of a multidimensional approach integrating molecular profiling, immunological analyses, and clinical data. The review concludes that a deeper understanding of IL-2/IL-2R interactions within the tumor microenvironment is crucial for realizing the full potential of IL-2-based therapies, heralding the promise of improved outcomes for cancer patients.

The innate and T-cell mediated immune response during acute and chronic gammaherpesvirus infection

Immediately after entry into host cells, viruses are sensed by the innate immune system, leading to the activation of innate antiviral effector mechanisms including the type I interferon (IFN) response and natural killer (NK) cells. This innate immune response helps to shape an effective adaptive T cell immune response mediated by cytotoxic T cells and CD4+ T helper cells and is also critical for the maintenance of protective T cells during chronic infection. The human gammaherpesvirus Epstein-Barr virus (EBV) is a highly prevalent lymphotropic oncovirus that establishes chronic lifelong infections in the vast majority of the adult population. Although acute EBV infection is controlled in an immunocompetent host, chronic EBV infection can lead to severe complications in immunosuppressed patients. Given that EBV is strictly host-specific, its murine homolog murid herpesvirus 4 or MHV68 is a widely used model to obtain in vivo insights into the interaction between gammaherpesviruses and their host. Despite the fact that EBV and MHV68 have developed strategies to evade the innate and adaptive immune response, innate antiviral effector mechanisms still play a vital role in not only controlling the acute infection but also shaping an efficient long-lasting adaptive immune response. Here, we summarize the current knowledge about the innate immune response mediated by the type I IFN system and NK cells, and the adaptive T cell-mediated response during EBV and MHV68 infection. Investigating the fine-tuned interplay between the innate immune and T cell response will provide valuable insights which may be exploited to design better therapeutic strategies to vanquish chronic herpesviral infection.

Immunotherapy for hepatocellular carcinoma: Recent advances and future targets

Immunotherapy is a promising approach to treating various types of cancers, including hepatocellular carcinoma (HCC). While single immunotherapy drugs show limited effectiveness on a small subset of patients, the combination of the anti PD-L1 atezolizumab and anti-vascular endothelial growth factor bevacizumab has shown significant improvement in survival compared to sorafenib as a first-line treatment. However, the current treatment options still have a low success rate of about 30%. Thus, more effective treatments for HCC are urgently required. Several novel immunotherapeutic methods, including the use of novel immune checkpoint inhibitors, innovative immune cell therapies like chimeric antigen receptor T cells (CAR-T), TCR gene-modified T cells and stem cells, as well as combination strategies are being tested in clinical trials for the treatment of HCC. However, some crucial issues still exist such as the presence of heterogeneous antigens in solid tumors, the immune-suppressive environment within tumors, the risk of on-target/off-tumor, infiltrating CAR-T cells, immunosuppressive checkpoint molecules, and cytokines. Overall, immunotherapy is on the brink of major advancements in the fight against HCC.

A Review of the Pharmacokinetic Characteristics of Immune Checkpoint Inhibitors and Their Clinical Impact Factors

Immune checkpoint inhibitors (ICIs) have been shown to be significant in improving the overall survival rate in certain malignancies with poor prognoses. However, only 20-40% of patients achieve long-term benefits, highlighting the relevance of the factors that influence the treatment, which can help clinicians improve their results and guide the development of new immune checkpoint therapies. In this study, the current pharmacokinetic aspects associated with the ICIs and the factors influencing clinical efficacy were characterised, including in terms of drug metabolism, drug clearance, hormonal effects and immunosuppressive effects.

Costimulators expressed on human endothelial cells modulate antigen-dependent recruitment of circulating T lymphocytes

Endothelial cells (ECs) can present antigens to circulating effector memory T cells (T_EM) and to regulatory T cells (T regs), triggering antigen-specific extravasation at specific sites where foreign antigens are introduced, e.g. by infection or transplantation. We model human antigen-induced transendothelial migration (TEM) using presentation of superantigen by cultured human dermal microvascular (HDM)ECs to isolated resting human peripheral blood T cell subpopulations or to T effector cells activated in vitro. T cell receptor (TCR)-mediated cytokine synthesis, a common assay of T cell activation by antigen, is modulated by antigen-independent signals provided by various positive or negative costimulator proteins (the latter known as checkpoint inhibitors) expressed by antigen presenting cells, including ECs. We report here that some EC-expressed costimulators also modulate TCR-TEM, but effects differ between TEM and cytokine production and among some T cell types. Blocking EC LFA-3 interactions with T_EM CD2 boosts TEM but reduces cytokine production. Blocking EC ICOS-L interactions with T_EM CD28 (but not ICOS) reduces both responses but these involve distinct CD28-induced signals. Activated CD4+ T effector cells no longer undergo TCR-TEM. Engagement of T cell CD28 by EC ICOS-L increases TCR-TEM by activated CD8 effectors while engagement of OX40 promotes TCR-TEM by activated CD4 T regs. B7-H3 mostly affects TEM of resting T_EM and some checkpoint inhibitors affect cytokine synthesis or TEM depending upon subtype. Our data suggest that blockade or mimicry of costimulators/checkpoint inhibitors in vivo, clinically used to modulate immune responses, may act in part by modulating T cell homing.

Immunotherapy and Antivascular Targeted Therapy in Patients’ Treatment with Concurrent Malignant Tumors after Organ Transplantation: Opportunity or Challenge

Objective

To analyze the therapeutic effects and organ rejection of anti-PD-1 immunotherapy or antivascular targeting therapy on patients with combined malignancies after organ transplantation.

Methods

We collected retrospective studies on “post-transplantation, cancer, immunotherapy, and vascular targeting therapy” in Embase, Wanfang database, Cochrane Library, VIP databases, CNKI, and PubMed, and the case data were organized and analyzed.

Results

Data from only 40 papers met our requirements, which included 2 literature reviews, 4 original researches, and 34 case reports from 2016 to 2020. A total of 40 studies involving 66 patients were included, who were divided into 3 groups (patients using CTLA-4 inhibitors, group 1; patients who received sequential or concurrent anti-PD-1 and anti-CTLA-4 therapy, group 2; and patients using PD-1/PD-L1 inhibitors, group 3). There was no statistical difference in patients' DCR between the three groups (P > 0.05). Also, compared with group 2, there was no statistically significant difference in recipient organ rejection in group 1 and group 3 (P > 0.05). The DCR rate for antivascular targeted therapy is approximately 60%.

Conclusions

Immunotherapy should be carefully selected for patients with combined malignancies after organ transplantation. Antivascular targeted therapy is one of the options worth considering; the risk of side effects of drug therapy is something that needs to be closely monitored when combined with immunotherapy.

Identification of Novel Modalities Through Bibliometric Analysis for Timely Development of Regulatory Guidance: A Case Study of T Cell Immunity

Background: The mission of medicines regulatory agencies is to ensure the timely access of innovative products for patients to improve public health. Thus, regulators should foresee evolving technologies and build expertise prior to reviewing innovative products. Novel modalities and new classes of therapeutics in biological or cell-based products represent a regulatory challenge because of knowledge gaps, as exemplified by the unexpected cytokine release syndrome in the first-in-human clinical trial of the CD28 super-agonist. Meanwhile, recent treatments harnessing T cell co-signaling pathways provide an opportunity for investigation. Therefore, this study aimed to systematically identify and evaluate novel modalities for T cell immunity to assess the need for regulatory guidance. Methods: A PubMed search was carried out using the query, "immun* AND t lymph*" to select publications. Subsequently, a citation network was created, followed by clustering and text mining to identify the modalities and classes of therapeutics under development. Results and Discussion: Analysis of the top 20 clusters revealed research domains characterized by keywords such as immune checkpoint antibody, chimeric antigen receptor (CAR)-T cells, microbiota, exosome, regulatory T cells, unconventional T cells, and vaccines. After reviewing the pharmacological concepts, clinical trial information, and available guidance, we presented a perspective on the future development of guidance for these domains. Conclusion: Bibliometric analyses identified a set of innovative modalities targeted for drug development with which regulatory guidance is going to catch up. This strategy could help in the successful development of upcoming modalities to ensure readiness for clinical application as part of horizon scanning.

TIGIT Can Exert Immunosuppressive Effects on CD8+ T Cells by the CD155/TIGIT Signaling Pathway for Hepatocellular Carcinoma In Vitro

Supplemental Digital Content is available in the text.

The efficacy of adoptive cellular immunotherapy against cancer cells is limited due to the presence of immunosuppressive cells within the solid tumor microenvironment. The upregulation of certain coinhibitory receptors may lead to exhaustion of the immune effector cells. T-cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain (TIGIT) is an immune inhibitory receptor expressed by regulatory T cells and activated T cells and natural killer cells. The aim of this study was to determine the immunosuppressive effects of CD155/TIGIT signaling on CD8⁺ T cells of adoptive cellular immunotherapy in hepatocellular carcinoma (HCC). Our studies found that CD155 was overexpressed in HCC, and CD155^hi HCC cells upregulated TIGIT on CD8⁺ T cells, which decreased the secretion of interferon-γ, tumor necrosis factor-α, and interleukin-17A and increased that of interleukin-10 from the effector cells. However, TIGIT blockade or CD155-knockdown reversed the inhibitory effect of HCC cells on CD8⁺ T-cell effector function. These results indicate that TIGIT can exert an immunosuppressive effect on CD8 T cells by modulating cytokine production through CD155, and is a promising target to optimize adoptive cellular immunotherapy against HCC.

Spatiotemporal single-cell profiling reveals that invasive and tissue-resident memory donor CD8+ T cells drive gastrointestinal acute graft-versus-host disease

Organ infiltration by donor T cells is critical to the development of acute graft-versus-host disease (aGVHD) in recipients after allogeneic hematopoietic stem cell transplant (allo-HCT). However, deconvoluting the transcriptional programs of newly recruited donor T cells from those of tissue-resident T cells in aGVHD target organs remains a challenge. Here, we combined the serial intravascular staining technique with single-cell RNA sequencing to dissect the tightly connected processes by which donor T cells initially infiltrate tissues and then establish a pathogenic tissue residency program in a rhesus macaque allo-HCT model that develops aGVHD. Our results enabled creation of a spatiotemporal map of the transcriptional programs controlling donor CD8⁺ T cell infiltration into the primary aGVHD target organ, the gastrointestinal (GI) tract. We identified the large and small intestines as the only two sites demonstrating allo-specific, rather than lymphodepletion-driven, T cell infiltration. GI-infiltrating donor CD8⁺ T cells demonstrated a highly activated, cytotoxic phenotype while simultaneously developing a canonical tissue-resident memory T cell (T_RM) transcriptional signature driven by interleukin-15 (IL-15)/IL-21 signaling. We found expression of a cluster of genes directly associated with tissue invasiveness, including those encoding adhesion molecules (ITGB2), specific chemokines (CCL3 and CCL4L1) and chemokine receptors (CD74), as well as multiple cytoskeletal proteins. This tissue invasion transcriptional signature was validated by its ability to discriminate the CD8⁺ T cell transcriptome of patients with GI aGVHD from those of GVHD-free patients. These results provide insights into the mechanisms controlling tissue occupancy of target organs by pathogenic donor CD8⁺ T_RM cells during aGVHD in primate transplant recipients.

Insights from integrating clinical and preclinical studies advance understanding of graft-versus-host disease

As a result of impressive increases in our knowledge of rodent and human immunology, the understanding of the pathophysiologic mechanisms underlying graft-versus-host disease (GVHD) has dramatically improved in the past 15 years. Despite improved knowledge, translation to clinical care has not proceeded rapidly, and results from experimental models have been inconsistent in their ability to predict the clinical utility of new therapeutic agents. In parallel, new tools in immunology have allowed in-depth analyses of the human system and have recently been applied in the field of clinical GVHD. Notwithstanding these advances, there is a relative paucity of mechanistic insights into human translational research, and this remains an area of high unmet need. Here we review selected recent advances in both preclinical experimental transplantation and translational human studies, including new insights into human immunology, the microbiome, and regenerative medicine. We focus on the fact that both approaches can interactively improve our understanding of both acute and chronic GVHD biology and open the door to improved therapeutics and successes.

Comprehensive Characterization of Immunological Profiles and Clinical Significance in Hepatocellular Carcinoma

BACKGROUND

Therapies targeting immune molecules have rapidly been adopted and advanced the treatment of hepatocellular carcinoma (HCC). Nonetheless, no studies have reported a systematic analysis between immunological profiles and clinical significance in HCC.

METHODS

We comprehensively investigated immune patterns and systematically correlated 22 types of both adaptive and innate immune cells with genomic characteristics and clinical outcomes based on 370 HCC patients from The Cancer Genome Atlas (TCGA) database through a metagene approach (known as CIBERSORT). Based on the Quantitative Pathology Imaging and Analysis System coupled with integrated high-dimensional bioinformatics analysis, we further independently validated six immune subsets (CD4+ T cells, CD8+ T cells, CD20+ B cells, CD14+ monocytes, CD56+ NK cells, and CD68+ macrophages), and shortlisted three (CD4+ T cells, CD8+ T cells, and CD56+ NK cells) of which to investigate their association with clinical outcomes in two independent Zhongshan cohorts of HCC patients (n = 258 and n = 178). Patient prognosis was further evaluated by Kaplan-Meier analysis and univariate and multivariate regression analysis.

RESULTS

By using the CIBERSORT method, the immunome landscape of HCC was constructed based on integrated transcriptomics analysis and multiplexed sequential immunohistochemistry. Further, the patients were categorized into four immune subgroups featured with distinct clinical outcomes. Strikingly, significant inter-tumoral and intra-tumoral immune heterogeneity was further identified according to the in-depth interrogation of the immune landscape.

CONCLUSION

This work represents a potential useful resource for the immunoscore establishment for prognostic prediction in HCC patients.

Current Concepts and Advances in Graft-Versus-Host Disease Immunology

Worldwide, each year over 30,000 patients undergo an allogeneic hema-topoietic stem cell transplantation with the intent to cure high-risk hematologic malignancy, immunodeficiency, metabolic disease, or a life-threatening bone marrow failure syndrome. Despite substantial advances in donor selection and conditioning regimens and greater availability of allograft sources, transplant recipients still endure the morbidity and mortality of graft-versus-host disease (GVHD). Herein, we identify key aspects of acute and chronic GVHD pathophysiology, including host/donor cell effectors, gut dysbiosis, immune system and cytokine imbalance, and the interface between inflammation and tissue fibrosis. In particular, we also summarize the translational application of this heightened understanding of immune dysregulation in the design of novel therapies to prevent and treat GVHD.

Resident Memory T Cells in the Tumor Microenvironment

Tissue-resident memory T (T_RM) cells are strategically positioned within the epithelial layers of many tissues to provide enduring site-specific immunological memory. This unique T-cell lineage is endowed with the capacity to rapidly respond to tissue perturbations and has a well-documented role in eradicating pathogens upon reexposure. Emerging evidence has highlighted a key role for T_RM cells in cancer immunity. Single-cell approaches have identified T_RM cells among other CD8⁺ tumor-infiltrating lymphocyte (TIL) subsets, and their presence is a positive indicator of clinical outcome in cancer patients. Furthermore, recent preclinical studies have elegantly demonstrated that T_RM cells are a critical component of the antitumor immune response. Given their unique functional abilities, T_RM cells have emerged as a potential immunotherapeutic target. Here, we discuss T_RM cells in the framework of the cancer-immunity cycle and in the context of the T cell- and non-T cell-inflamed tumor microenvironments (TME). We highlight how their core features make T_RM cells uniquely suited to function within the metabolically demanding TME. Finally, we consider potential therapeutic avenues that target T_RM cells to augment the antitumor immune response.

CD2 Immunobiology

The glycoprotein CD2 is a costimulatory receptor expressed mainly on T and NK cells that binds to LFA3, a cell surface protein expressed on e.g., antigen-presenting cells. CD2 has an important role in the formation and organization of the immunological synapse that is formed between T cells and antigen-presenting cells upon cell-cell conjugation and associated intracellular signaling. CD2 expression is upregulated on memory T cells as well as activated T cells and plays an important role in activation of memory T cells despite the coexistence of several other costimulatory pathways. Anti-CD2 monoclonal antibodies have been shown to induce immune modulatory effects in vitro and clinical studies have proven the safety and efficacy of CD2-targeting biologics. Investigators have highlighted that the lack of attention to the CD2/LFA3 costimulatory pathway is a missed opportunity. Overall, CD2 is an attractive target for monoclonal antibodies intended for treatment of pathologies characterized by undesired T cell activation and offers an avenue to more selectively target memory T cells while favoring immune regulation.

Immune checkpoint: The novel target for antitumor therapy

Inhibitory checkpoint molecules include programmed cell death-1 (PD-1), programmed cell death ligand-1 (PD-L1), cytotoxic T lymphocyte antigen-4 (CTLA-4), human endogenous retrovirus-H Long terminal repeat-associating 2 (HHLA2), B7 homolog 4 protein (B7-H4), T cell membrane protein-3 (TIM-3) and Lymphocyte-activation gene 3 (LAG-3), which are up-regulated during tumorigenesis. These pathways are essential to down-regulate the immune system by blocking the activation of T cells. In recent years, immune checkpoint blockers (ICBs) against PD-1, PD-L1, CTLA-4 or TIM-3 has made remarkable progress in the clinical application, revolutionizing the treatment of malignant tumors and improving patients' overall survival. However, the efficacy of ICBs in some patients does not seem to be good enough, and more immune-related adverse events (irAEs) will inevitably occur. Therefore, biomarkers research provides practical guidance for clinicians to identify patients who are most likely to benefit from or exhibit resistance to particular types of immune checkpoint therapy. There are two points in general. On the one hand, given the spatial and temporal differential expression of immune checkpoint molecules during immunosuppression process, it is essential to understand their mechanisms to design the most effective individualized therapy. On the other hand, due to the lack of potent immune checkpoints, it is necessary to combine them with novel biomarkers (such as exosomes and ctDNA) and other anticancer modalities (such as chemotherapy and radiotherapy).

Costimulation Blockade in Transplantation

T cells play a pivotal role in orchestrating immune responses directed against a foreign (allogeneic) graft. For T cells to become fully activated, the T-cell receptor (TCR) must interact with the major histocompatibility complex (MHC) plus peptide complex on antigen-presenting cells (APCs), followed by a second "positive" costimulatory signal. In the absence of this second signal, T cells become anergic or undergo deletion. By blocking positive costimulatory signaling, T-cell allo-responses can be aborted, thus preventing graft rejection and promoting long-term allograft survival and possibly tolerance (Alegre ML, Najafian N, Curr Mol Med 6:843-857, 2006; Li XC, Rothstein DM, Sayegh MH, Immunol Rev 229:271-293, 2009). In addition, costimulatory molecules can provide negative "coinhibitory" signals that inhibit T-cell activation and terminate immune responses; strategies to promote these pathways can also lead to graft tolerance (Boenisch O, Sayegh MH, Najafian N, Curr Opin Organ Transplant 13:373-378, 2008). However, T-cell costimulation involves an incredibly complex array of interactions that may act simultaneously or at different times in the immune response and whose relative importance varies depending on the different T-cell subsets and activation status. In transplantation, the presence of foreign alloantigen incites not only destructive T effector cells but also protective regulatory T cells, the balance of which ultimately determines the fate of the allograft (Lechler RI, Garden OA, Turka LA, Nat Rev Immunol 3:147-158, 2003). Since the processes of alloantigen-specific rejection and regulation both require activation of T cells, costimulatory interactions may have opposing or synergistic roles depending on the cell being targeted. Such complexities present both challenges and opportunities in targeting T-cell costimulatory pathways for therapeutic purposes. In this chapter, we summarize our current knowledge of the various costimulatory pathways in transplantation and review the current state and challenges of harnessing these pathways to promote graft tolerance (summarized in Table 10.1).

Pharmacokinetic and pharmacodynamic study of a clinically effective anti-CD2 monoclonal antibody

The humanized IgG1κ monoclonal antibody siplizumab and its rat parent monoclonal IgG2b antibody BTI-322 are directed against the CD2 antigen. Siplizumab is species-specific, reacting with human and chimpanzee cells but not with cells from any other species, including other non-human primates. Because siplizumab treatment has recently shown great potential in clinical transplantation, we now present the results of our previous pharmacokinetic, pharmacodynamic and safety studies of both antibodies. Fourteen chimpanzees received 1-3 doses of 0.143 to 5.0 mg/kg iv The effects were followed with flow cytometry on peripheral lymphocytes and staining of lymph nodes. Side effects were recorded. Serum antibody concentrations were followed. Across the doses, a rapid, transient depletion of CD2, CD3, CD4 and CD8 lymphocytes and NK cells was observed for both antibodies. Immune reconstitution was more rapid for BTI-322 compared to siplizumab. Paracortical lymph node T cell depletion was moderate, estimated at 45% with doses of >0.6 mg/kg. Restoration of lymph node architecture was seen after two weeks to two months for all animals. All four subjects receiving BTI-322 experienced AEs on the first dosing day, while the eight subjects dosed with siplizumab experienced few mild, transient AEs. Infusion with siplizumab and BTI-322 resulted in rapid depletion of CD2⁺ cells in circulation and tissue. Siplizumab had a longer t_1/2 and fewer AEs compared to BTI-322.

Blocking the PD-1/PD-L1 axis in dendritic cell-stimulated Cytokine-Induced Killer Cells with pembrolizumab enhances their therapeutic effects against hepatocellular carcinoma

Immune checkpoint therapies for cancer, like the anti-programmed cell death 1 (PD-1) agent pembrolizumab, have gained considerable attention. However, the use of immune checkpoint inhibitors in the context of adoptive immunotherapy is poorly characterized. We investigated the therapeutic efficacy of dendritic cell-stimulated CIK (DC-CIK) cells pretreated with pembrolizumab against hepatocellular carcinoma (HCC) in cytotoxicity assay in vitro and in a nude mouse xenograft model. We used time-lapse imaging to investigate tumor killing. We also performed a survival analysis based on lymphocyte subpopulation-specific mRNA signatures using The Cancer Genome Atlas (TCGA) HCC cohort (n=371 patients). The results indicated that PD-1 inhibition increased the anti-tumor effects of DC-CIK cells over those of DC-CIK cells alone, resulting in a survival benefit importantly. Time-lapse imaging revealed that DC-CIK cells appeared to be more effective and aggressive after anti-PD-1 treatment than after culture in control conditions. The PD-1 inhibitor also induced more effective immune cell infiltration of the tumor. Our analysis of the TCGA HCC cohort confirmed that a genetic signature consistent with a high degree of intratumoral CD8+ T cell infiltration is associated with good prognosis. These results suggest that blockade of the PD-1/PD-L1 axis in DC-CIK cells with a PD-1 inhibitor prior to infusion is a promising therapeutic strategy against HCC.

Programmed Cell Death 1 (PD-1) Inhibitors in Renal Transplant Patients with Advanced Cancer: A Double-Edged Sword?

Given advancements in cancer immunity, cancer treatment has gained breakthrough developments. Immune checkpoint inhibitors, such as programmed cell death 1 (PD-1) inhibitors, are the most promising drugs in the field and have been approved to treat various types of cancer, such as metastatic melanoma, head and neck squamous cell carcinoma, and urothelial carcinoma. However, whether PD-1 inhibitors should be administered to renal transplant patients with advanced cancer remains unclear because the T-cells produced after administration of these inhibitors act against not only tumor antigens but also donor alloantigens. Thus, the use of PD-1 inhibitors in kidney-transplanted patients with advanced cancer is limited on account of the high risk of graft failure due to acute rejection. Hence, finding optimal treatment regimens to enhance the tumor-specific T-cell response and decrease T-cell-mediated alloreactivity after administration of a PD-1 inhibitor is necessary. Thus far, no recommendations for the use of PD-1 inhibitors to treat cancer in renal transplant patients are yet available, and very few cases reporting kidney-transplanted patients treated with PD-1 inhibitors are available in the literature. Therefore, in this work, we review the published cases and suggest feasible approaches for renal transplant patients with advanced malignancy treated by a PD-1 inhibitor. Of the 22 cases we obtained, four patients maintained intact grafts without tumor progression after treatment with a PD-1 inhibitor. Among these patients, one maintained steroid dose before initiation of anti-PD1, two received immunosuppressive regimens with low-dose steroid and calcineurin inhibitor (CNI)-elimination with sirolimus before initiation of anti-PD-1 therapy, and one received combined anti-PD-1, anti-vascular endothelial growth factor (VEGF), and chemotherapy with unchanged immunosuppressive regimens. mammalian target of rapamycin (mTOR) inhibitors and anti-VEGF may act as regulators of tumor-specific and allogenic T-cells. However, more studies are necessary to explore the optimal therapy and ensure the safety and efficacy of PD-1 inhibitors in kidney-transplanted patients.

Harnessing immunotherapy for liver recipients with hepatocellular carcinoma: a review from a transplant oncology perspective

Without stringent criteria, liver transplantation for hepatocellular carcinoma (HCC) can lead to high cancer recurrence and poor prognosis in the current treatment context. Checkpoint inhibitors can lead to long survival by targeting coinhibitory pathways and promoting T-cell activity; thus, they have great potential for cancer immunotherapy. Therapeutic modulation of cosignaling pathways may shift paradigms from surgical prevention of recurrence to oncological intervention. Herein, we review the available evidence from a therapeutic perspective and focus on immune microenvironment perturbation by immunosuppressants and checkpoint inhibitors. Partial and reversible interleukin-2 signaling blockade is the mainstream strategy of immunosuppression for graft protection. Programmed cell death protein 1 (PD-1) is abundantly expressed on human liver allograft-infiltrating T-cells, which proliferate considerably after programmed death-ligand 1 (PD-L1) blockade. Clinically, checkpoint inhibitors are used in heart, liver, and kidney recipients with various cancers. Rejection can occur after checkpoint inhibitor administration through acute T-cell-mediated, antibody-mediated, or chronic allograft rejection mechanisms. Nevertheless, liver recipients may demonstrate favorable responses to treatment for HCC recurrence without rejection. Pharmacodynamically, substantial degrees of receptor occupancy can be achieved with lower doses, with favorable clinical outcomes. Manipulation of the immune microenvironment is a therapeutic niche that balances seemingly conflicting anticancer and graft protection needs. Additional translational and clinical studies emphasizing the comparative effectiveness of signaling networks within the immune microenvironment and conducting overall assessment of the immune microenvironment may aid in creating a therapeutic window and benefiting future liver recipients with HCC recurrence.

Achievement of Tolerance Induction to Prevent Acute Graft-vs.-Host Disease

Acute graft-vs.-host disease (GVHD) limits the efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT), a main therapy to treat various hematological disorders. Despite rapid progress in understanding GVHD pathogenesis, broad immunosuppressive agents are most often used to prevent and remain the first line of therapy to treat GVHD. Strategies enhancing immune tolerance in allo-HSCT would permit reductions in immunosuppressant use and their associated undesirable side effects. In this review, we discuss the mechanisms responsible for GVHD and advancement in strategies to achieve immune balance and tolerance thereby avoiding GVHD and its complications.

Evaluating the Remote Control of Programmed Cell Death, with or without a Compensatory Cell Proliferation

Organisms and their different component levels, whether organelle, cellular or other, come by birth and go by death, and the deaths are often balanced by new births. Evolution on the one hand has built demise program(s) in cells of organisms but on the other hand has established external controls on the program(s). For instance, evolution has established death program(s) in animal cells so that the cells can, when it is needed, commit apoptosis or senescent death (SD) in physiological situations and stress-induced cell death (SICD) in pathological situations. However, these programmed cell deaths are not predominantly regulated by the cells that do the dying but, instead, are controlled externally and remotely by the cells' superior(s), i.e. their host tissue or organ or even the animal's body. Currently, it is still unclear whether a cell has only one death program or has several programs respectively controlling SD, apoptosis and SICD. In animals, apoptosis exterminates, in a physiological manner, healthy but no-longer needed cells to avoid cell redundancy, whereas suicidal SD and SICD, like homicidal necrosis, terminate ill but useful cells, which may be followed by regeneration of the live cells and by scar formation to heal the damaged organ or tissue. Therefore, “who dies” clearly differentiates apoptosis from SD, SICD and necrosis. In animals, apoptosis can occur only in those cell types that retain a lifelong ability of proliferation and never occurs in those cell types that can no longer replicate in adulthood. In cancer cells, SICD is strengthened, apoptosis is dramatically weakened while SD has been lost. Most published studies professed to be about apoptosis are actually about SICD, which has four basic and well-articulated pathways involving caspases or involving pathological alterations in the mitochondria, endoplasmic reticula, or lysosomes.

Viral hepatitis, inflammation, and cancer: A lesson for autoimmunity

In the present review, we analyzed the various overlapping and non-mutually exclusive mechanisms that intersect and form complex and highly flexible immunological networks allowing the defense against liver infections and tumors. Liver immunity results from the combination of the skills of systemic and local immune system(s) to sense and recognize pathogen or tumor antigens, to sensitize a wide range of innate and adaptive immune cells, and to clear the "invaders", through the establishment of a transient liver immunopathology state undergoing resolution/control of infections or tumors, and memory development. Then, a special emphasis is placed on discussing about the capacity of the immune system(s) to develop a state of chronic low-level immunopathology adapting through the intervention of simultaneous immunoregulatory mechanisms, when the liver is infected by highly mutable viruses (e.g., hepatitis B or C viruses [HBV or HCV]) capable to escape from the immune recognition. The establishment of chronic inflammation represents an advantage for the species survival, because it guarantees the long-term survival of human hosts despite the virus persistence. However, chronic inflammation, in the long run, can evolve towards severe consequences (decompensated cirrhosis and hepatocellular carcinoma) in some individuals, finding requiring the impelling need of discovering new therapeutic anti-viral and immunostimulatory agents addressed, in combination, to fight especially HBV that, in contrast to HCV, lacks antivirals capable to eradicate the virus. Finally, we discussed the concept proposing that the divergent immunoregulatory mechanisms that develop in persisting infections or tumors, on the one hand, and autoimmunity, on the other hand, are the mirror image of each other, whose understanding is also relevant for preparing novel immunotherapeutic approaches in autoimmune diseases.

Clinical implications of monitoring nivolumab immunokinetics in non-small cell lung cancer patients

BACKGROUND. The PD-1–blocking antibody nivolumab persists in patients several weeks after the last infusion. However, no study has systematically evaluated the maximum duration that the antibody persists on T cells or the association between this duration and residual therapeutic efficacy or potential adverse events.

METHODS. To define the duration of binding and residual efficacy of nivolumab after discontinuation, we developed a simplified strategy for T cell monitoring and used it to analyze T cells from peripheral blood from 11 non–small cell lung cancer patients previously treated with nivolumab. To determine the suitability of our method for other applications, we compared transcriptome profiles between nivolumab-bound and nivolumab-unbound CD8 T cells. We also applied T cell monitoring in 2 nivolumab-treated patients who developed progressive lung tumors during long-term follow-up.

RESULTS. Prolonged nivolumab binding was detected more than 20 weeks after the last infusion, regardless of the total number of nivolumab infusions (2–15 doses) or type of subsequent treatment, in 9 of the 11 cases in which long-term monitoring was possible. Ki-67 positivity, a proliferation marker, in T cells decreased in patients with progressive disease. Transcriptome profiling identified the signals regulating activation of nivolumab-bound T cells, which may contribute to nivolumab resistance. In 2 patients who restarted nivolumab, T cell proliferation markers exhibited the opposite trend and correlated with clinical response.

CONCLUSIONS. Although only a few samples were analyzed, our strategy of monitoring both nivolumab binding and Ki-67 in T cells might help determine residual efficacy under various types of concurrent or subsequent treatment.

TRIAL REGISTRATION. University Hospital Medical Information Network Clinical Trials Registry, UMIN000024623.

FUNDING. This work was supported by Japan Society for the Promotion of Science KAKENHI (JP17K16045, JP18H05282, and JP15K09220), Japan Agency for Medical Research and Development (JP17cm0106310, JP18cm0106335 and JP18cm059042), and Core Research for Evolutional Science and Technology (JPMJCR16G2).

A method for detecting nivolumab binding and T cell activation status, which could be used to predict residual efficacy and toxicity, is developed.

2016 Jeffrey M. Hoeg Award Lecture

Innate and adaptive immune effector mechanisms, in conjunction with hyperlipidemia, are important drivers of atherosclerosis. The interaction between the different immune cells and the secretion of cytokines and chemokines determine the progression of atherosclerosis. The activation or dampening of the immune response is tightly controlled by immune checkpoints. Costimulatory and coinhibitory immune checkpoints represent potential targets for immune modulatory therapies for atherosclerosis. This review will discuss the current knowledge on immune checkpoints in atherosclerosis and the clinical potential of immune checkpoint targeted therapy for atherosclerosis.

Phase 1 clinical trial evaluating abatacept in patients with steroid-refractory chronic graft-versus-host disease

Costimulatory blockade using abatacept represents a novel therapeutic approach for the treatment of cGVHD. Abatacept resulted in a clinical response in 44% of patients with both decreased prednisone use and T-cell PD-1 expression in responders.

Immune checkpoint therapy in liver cancer

Immune checkpoints include stimulatory and inhibitory checkpoint molecules. In recent years, inhibitory checkpoints, including cytotoxic T lymphocyte–associated antigen 4 (CTLA-4), programmed cell death protein-1 (PD-1), and programmed cell death ligand 1 (PD-L1), have been identified to suppress anti-tumor immune responses in solid tumors. Novel drugs targeting immune checkpoints have succeeded in cancer treatment. Specific PD-1 blockades were approved for treatment of melanoma in 2014 and for treatment of non-small-cell lung cancer in 2015 in the United States, European Union, and Japan. Preclinical and clinical studies show immune checkpoint therapy provides survival benefit for greater numbers of patients with liver cancer, including hepatocellular carcinoma and cholangiocarcinoma, two main primary liver cancers. The combination of anti-PD-1/PD-L1 with anti-CTLA-4 antibodies is being evaluated in phase 1, 2 or 3 trials, and the results suggest that an anti-PD-1 antibody combined with locoregional therapy or other molecular targeted agents is an effective treatment strategy for HCC. In addition, studies on activating co-stimulatory receptors to enhance anti-tumor immune responses have increased our understanding regarding this immunotherapy in liver cancer. Epigenetic modulations of checkpoints for improving the tumor microenvironment also expand our knowledge of potential therapeutic targets in improving the tumor microenvironment and restoring immune recognition and immunogenicity. In this review, we summarize current knowledge and recent developments in immune checkpoint-based therapies for the treatment of hepatocellular carcinoma and cholangiocarcinoma and attempt to clarify the mechanisms underlying its effects.

Efficacy and safety of immune checkpoint inhibitors in non-small cell lung cancer

Immune checkpoint inhibitors (ICIs) are new therapeutic strategies for non-small cell lung cancer (NSCLC). We aimed to quantitatively evaluate the efficacy and safety of ICIs in NSCLC. Pubmed, Embase, Cochrane Library, and Web of Science were searched for randomized clinical trials comparing ICIs with control therapies in NSCLC. Data were pooled according to Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. A total of 12 trails comprising 6,919 NSCLC patients were included in this meta-analysis. ICIs therapies significantly improved progression-free survival (PFS) (HR, 0.838; P < 0.001), overall survival (OS) (HR, 0.747; P < 0.001) and objective response rates (ORR) (RR, 1.311; P < 0.001) in NSCLC. Prognostic benefit was observed irrespective of age, sex, treatment line, performance status and histology. Survival improvement of ICIs was limited for NSCLC patients with non-smoker (PFS, P = 0.468; OS, P = 0.317) or central nervous system (CNS) metastasis (PFS, P = 0.209; OS, P = 0.090), or positive EGFR mutation (PFS, P = 0.083; OS, P = 0.522) or PD-L1 expression level less than 5% (PFS, P = 0.370; OS, P = 0.047). The relative risks of all-grade and high-grade (≥3) anemia, neutropenia, leukopenia, thrombocytopenia, stomatitis, nausea, pyrexia, asthenia and neuropathy were all decreased in patients received ICIs compared with control therapies. This meta-analysis provides clinical evidence that ICIs improve PFS, OS, and ORR in NSCLC with fewer adverse effects. Our data establish ICIs as a prefer treatment option for NSCLC patients with smoker, no CNS metastasis, wild type EGFR, and high PD-L1 expression.

Harnessing the power of the immune system in non-Hodgkin lymphoma: immunomodulators, checkpoint inhibitors, and beyond

Non-Hodgkin lymphoma is a malignancy of B lymphocytes that typically infiltrate sites of disease, including the lymph nodes, spleen, and bone marrow. Beyond the presence of malignant cells, many immune cells are also present within the tumor microenvironment. Although these immune cells have the potential to regulate the growth of malignant B cells, intratumoral immune cells are unable to eradicate lymphoma cells and most patients with lymphoma have clinical evidence of disease progression. Recent data have identified some of the mechanisms that account for the suppressed antitumor immune response and have created opportunities for treatment to overcome the deficiencies. Two general categories of immunological therapies are available. The first approach is to use agents that prevent inhibitory signals via immune checkpoint receptors that downregulate immune cell function. Blockade of suppressive programmed cell death 1 (PD-1) or CTLA-4 signaling has resulted in significant clinical activity by allowing intratumoral T cells to remain activated and target malignant cells. A second approach is to additionally activate T cells that are suboptimally active or suppressed, by providing signals through costimulatory molecules including CD27 or CD40 or by adding immunostimulatory cytokines. There has been significant heterogeneity in the responses to these treatment approaches. Clinical responses are seen in many diseases, but the most promising responses have been with PD-1 blockade in Hodgkin lymphoma. In other lymphomas, responses are seen but only in a subset of patients. Further research is needed to identify the mechanisms that account for response and to identify patients most likely to benefit from immune modulation.

Cancer immunotherapy in a neglected population: The current use and future of T-cell-mediated checkpoint inhibitors in organ transplant patients

Although the indications for immune checkpoint inhibitors continue to grow, organ transplant recipients with advanced malignancies have been largely excluded from clinical trials testing the safety and efficacy of these therapies given their need for chronic immunosuppression and the risk of allograft rejection. With the rapid growth of transplant medicine and the increased risk of malignancy associated with chronic immunosuppression, it is critical that we systematically analyze the available data describing immune checkpoint blockade in the organ transplant population. Herein we provide a current and comprehensive review of cases in which immune checkpoint blockade was used on organ transplant recipients. Furthermore, we discuss the differences in efficacy and risk of allograft rejection between CTLA-4 and PD-1 inhibitors and make recommendations based on the limited available clinical data. We also discuss the future of immune checkpoint blockade in this subpopulation and explore the emerging data of promising combination therapies with mTOR, BRAF/MEK, and BTK/ITK inhibitors. Further clinical experience and larger clinical trials involving immune checkpoint inhibitors, whether as monotherapies or combinatorial therapies, will help develop regimens that optimize anti-tumor response and minimize the risk of allograft rejection in organ transplant patients.

PD-1/PD-L blockade in gastrointestinal cancers: lessons learned and the road toward precision immunotherapy

Gastrointestinal (GI) malignancies are the most prevalent tumors worldwide, with increasing incidence and mortality. Although surgical resection, chemotherapy, radiotherapy, and molecular targeted therapy have led to significant advances in the treatment of GI cancer patients, overall survival is still low. Therefore, alternative strategies must be identified to improve patient outcomes. In the tumor microenvironment, tumor cells can escape the host immune response through the interaction of PD-1 and PD-L, which inhibits the function of T cells and tumor-infiltrating lymphocytes while increasing the function of immunosuppressive T regulatory cells. The use of an anti-PD-1/PD-L blockade enables reprogramming of the immune system to efficiently identify and kill tumor cells. In recent years, the efficacy of PD-1/PD-L blockade has been demonstrated in many tumors, and this treatment is expected to be a pan-immunotherapy for tumors. Here, we review the signaling pathway underlying the dysregulation of PD-1/PD-L in tumors, summarize the current clinical data for PD-1/PD-L inhibitors in GI malignancies, and discuss road toward precision immunotherapy in relation to PD-1/PD-L blockade. The preliminary data for PD-1/PD-L inhibitors are encouraging, and the precision immunotherapy of PD-1/PD-L inhibitors will be a viable and pivotal clinical strategy for GI cancer therapy.