TIGIT expressing CD4+T cells represent a tumor-supportive T cell subset in chronic lymphocytic leukemia

TIGIT: Will it be the next star therapeutic target like PD-1 in hematological malignancies?

Research on the mechanism and application of checkpoint inhibitory receptors in hematologic diseases has progressed rapidly. However, in the treatment of relapserefractory (R/R) hematologic malignancies and anti-programmed cell death protein 1 (PD-1), patients who are resistant to anti-cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) are in urgent need of alternative therapeutic targets. T cell immunoreceptor with immunoglobulin and ITIM domains (TIGIT) has a broad prospect as an inhibitory receptor like PD-1, but its more specific mechanism of action and application in hematologic diseases still need to be further studied. In this review, we discuss the mechanism of TIGIT pathway, combined effects with other immune checkpoints, immune-related therapy, the impact of TIGIT on hematopoietic stem cell transplantation (HSCT) and the tumor microenvironment (TME) provides a potential therapeutic target for hematologic malignancies.

Molecular and transcriptional basis of bidirectional CD4+ T cell exhaustion in oropharyngeal squamous cell carcinoma

Tumor-infiltrating CD4+ T cells orchestrate the adaptive immune response through remarkable plasticity, and the expression patterns of exhaustion-related inhibitory receptors in these cells differ significantly from those of CD8+ T cells. Thus, a better understanding of the molecular basis of CD4+ T cell exhaustion and their responses to immune checkpoint blockade (ICB) is required. Here, we integrated multiomics approaches to define the phenotypic and molecular profiles of exhausted CD4+ T cells in oropharyngeal squamous cell carcinoma (OPSCC). Two distinct immune-promoting (Module 1) and immunosuppressive (Module 2) functional modules in tumor-infiltrating CD4+ T cells were identified, and both the immune-promoting function of Module 1 cells and immunosuppressive function of Module 2 cells were positively associated with their corresponding exhaustion states. Furthermore, the application of ICBs targeting effector CD4+ T cells in Module 1 (αPD-1) and Treg cells in Module 2 (αCTLA-4) in mouse models could help reinvigorate the effector function of Module 1-exhausted CD4+ T cells and reduce the immunosuppressive function of Module 2-exhausted CD4+ T cells, ultimately promoting OPSCC tumor regression. Taken together, our study provides a crucial cellular basis for the selection of optimal ICB in treating OPSCC.

BET inhibition reforms the immune microenvironment and alleviates T cell dysfunction in chronic lymphocytic leukemia

Redundant tumor microenvironment (TME) immunosuppressive mechanisms and epigenetic maintenance of terminal T cell exhaustion greatly hinder functional antitumor immune responses in chronic lymphocytic leukemia (CLL). Bromodomain and extraterminal (BET) proteins regulate key pathways contributing to CLL pathogenesis and TME interactions, including T cell function and differentiation. Herein, we report that blocking BET protein function alleviates immunosuppressive networks in the CLL TME and repairs inherent CLL T cell defects. The pan-BET inhibitor OPN-51107 reduced exhaustion-associated cell signatures resulting in improved T cell proliferation and effector function in the Eμ-TCL1 splenic TME. Following BET inhibition (BET-i), TME T cells coexpressed significantly fewer inhibitory receptors (IRs) (e.g., PD-1, CD160, CD244, LAG3, VISTA). Complementary results were witnessed in primary CLL cultures, wherein OPN-51107 exerted proinflammatory effects on T cells, regardless of leukemic cell burden. BET-i additionally promotes a progenitor T cell phenotype through reduced expression of transcription factors that maintain terminal differentiation and increased expression of TCF-1, at least in part through altered chromatin accessibility. Moreover, direct T cell effects of BET-i were unmatched by common targeted therapies in CLL. This study demonstrates the immunomodulatory action of BET-i on CLL T cells and supports the inclusion of BET inhibitors in the management of CLL to alleviate terminal T cell dysfunction and potentially enhance tumoricidal T cell activity.

CD8 effector T cells enhance teclistamab response in BCMA-exposed and -naïve multiple myeloma

ABSTRACT

Teclistamab, a B-cell maturation antigen (BCMA)- and CD3-targeting bispecific antibody, is an effective novel treatment for relapsed/refractory multiple myeloma (R/RMM), but efficacy in patients exposed to BCMA-directed therapies and mechanisms of resistance have yet to be fully delineated. We conducted a real-world retrospective study of commercial teclistamab, capturing both clinical outcomes and immune correlates of treatment response in a cohort of patients (n = 52) with advanced R/RMM. Teclistamab was highly effective with an overall response rate (ORR) of 64%, including an ORR of 50% for patients with prior anti-BCMA therapy. Pretreatment plasma cell BCMA expression levels had no bearing on response. However, comprehensive pretreatment immune profiling identified that effector CD8+ T-cell populations were associated with response to therapy and a regulatory T-cell population associated with nonresponse, indicating a contribution of immune status in outcomes with potential utility as a biomarker signature to guide patient management.

T cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain as a promising immune checkpoint target for the treatment of SLE

Immune checkpoints (ICs) play a pivotal role in orchestrating immune regulation, crucial for the maintenance of immune tolerance and prevention of autoimmune diseases. One noteworthy example among these immune regulators is T cell immunoglobulin (Ig) and immunoreceptor tyrosine-based inhibitory motif (ITIM) domain (TIGIT). The TIGIT pathway's inhibition or the absence of TIGIT has been linked to the hyperactivation and excessive proliferation of T cells, rendering individuals more susceptible to autoimmune diseases and exacerbating inflammatory responses. Conversely, the activation of TIGIT has exhibited promising outcomes in ameliorating autoimmune disorders, as observed in murine models of systemic lupus erythematosus (SLE). Consequently, a judicious exploration of the co-inhibitory axis appears warranted for the effective management of pathogenic immune responses in SLE. In light of compelling evidence, this review undertakes a comprehensive examination of TIGIT's characteristics within the context of autoimmunity, offering insights into its potential as a therapeutic target for SLE.

TIGIT is Frequently Expressed in the Tumor Microenvironment of Select Lymphomas: Implications for Targeted Therapy

Immune checkpoint inhibitors against Programmed Cell Death Protein 1/Programmed Cell (PD-1/PD-L1) and CTLA-4/B7 axes have had limited success in hematologic malignancies, requiring the need to explore alternative targets such as T-cell immunoreceptor with Ig and ITIM domains (TIGIT)/CD155 to improve durable clinical responses. We undertook this study to investigate the expression profile of TIGIT such that the potential efficacy of TIGIT blockade could be mapped among lymphoma subtypes. We validated an immunohistochemical assay for TIGIT and evaluated its expression in lymphoma and tumor microenvironment (TME) cells in 661 lymphoma/leukemia biopsies. Multiplex immunofluorescence was used for correlation with normal TME cell subsets. Tumor or TME TIGIT-positivity was defined as moderate to strong membrane staining in at least 10% of tumor or TME cells, respectively. TME TIGIT expression was correlated with overall survival and progression-free survival and comparison with PD-L1 expression. In most cases, lymphoma cells were TIGIT-negative except for angioimmunoblastic and peripheral T-cell lymphomas, which showed 91% and 47% positivity, respectively. A high proportion of small B-cell lymphoma and anaplastic large cell lymphoma cases had TIGIT-positive TME cells. Chronic lymphocytic leukemia/small lymphocytic lymphoma patients with TIGIT-negative TME cells showed significantly shorter overall survival ( P =0.04). No other statistically significant differences were found. When TIGIT was expressed in TME cells, there were a comparable number of TIGIT-positive only and dual TIGIT/PD-L1 positive cases except for more TIGIT-positive only cases in CLL/SLL. TIGIT expression shows distinctive profiles among lymphoma subtypes. Chronic lymphocytic leukemia/small lymphocytic lymphoma and anaplastic large cell lymphoma demonstrated high TME TIGIT expression compared with PD-L1, with a high proportion of dual TIGIT and PD-L1-positivity. Our results are likely to contribute to the design and correlative study of therapeutic response in clinical trials targeting TIGIT alone or in combination with PD1/PDL1.

Targeting TIGIT for cancer immunotherapy: recent advances and future directions

As a newly identified checkpoint, T cell immunoreceptor with immunoglobulin and tyrosine-based inhibitory motif (ITIM) domain (TIGIT) is highly expressed on CD4+ T cells, CD8+ T cells, natural killer (NK) cells, regulatory T cells (Tregs), and tumor-infiltrating lymphocytes (TILs). TIGIT has been associated with NK cell exhaustion in vivo and in individuals with various cancers. It not only modulates NK cell survival but also mediates T cell exhaustion. As the primary ligand of TIGIT in humans, CD155 may be the main target for immunotherapy due to its interaction with TIGIT. It has been found that the anti-programmed cell death protein 1 (PD-1) treatment response in cancer immunotherapy is correlated with CD155 but not TIGIT. Anti-TIGIT alone and in combination with anti-PD-1 agents have been tested for cancer immunotherapy. Although two clinical studies on advanced lung cancer had positive results, the TIGIT-targeted antibody, tiragolumab, recently failed in two new trials. In this review, we highlight the current developments on TIGIT for cancer immunotherapy and discuss the characteristics and functions of TIGIT.

Comparison of the blood immune repertoire with clinical features in chronic lymphocytic leukemia patients treated with chemoimmunotherapy or ibrutinib

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of CD19+ CD5+ clonal B lymphocytes in the blood, bone marrow, and peripheral lymphoid organs. Treatment options for patients range from historical chemoimmunotherapy (CIT) to small molecule inhibitors targeting pro-survival pathways in leukemic B cells, such as the Bruton's tyrosine kinase inhibitor ibrutinib (IBR). Using biobanked blood samples obtained pre-therapy and at standard response evaluation timepoints, we performed an in-depth evaluation of the blood innate and adaptive immune compartments between pentostatin-based CIT and IBR and looked for correlations with clinical sequelae. CD4+ conventional T cells and CD8+ cytotoxic T cells responded similarly to CIT and IBR, although exhaustion status differed. Both treatments dramatically increased the prevalence and functional status of monocyte, dendritic cell, and natural killer cell subsets. As expected, both regimens reduced clonal B cell levels however, we observed no substantial recovery of normal B cells. Although improvements in most immune subsets were observed with CIT and IBR at response evaluation, both patient groups remained susceptible to infections and secondary malignancies during the study.

CAR-modified Cellular Therapies in Chronic Lymphocytic Leukemia: Is the Uphill Road Getting Less Steep?

The clinical development of chimeric antigen receptor (CAR) T-cell therapy has been more challenging for chronic lymphocytic leukemia (CLL) compared to other settings. One of the main reasons is the CLL-associated state of immune dysfunction that specifically involves patient-derived T cells. Here, we provide an overview of the clinical results obtained with CAR T-cell therapy in CLL, describing the identified immunologic reasons for the inferior efficacy. Novel CAR T-cell formulations, such as lisocabtagene maraleucel, administered alone or in combination with the Bruton tyrosine kinase inhibitor ibrutinib, are currently under investigation. These approaches are based on the rationale that improving the quality of the T-cell source and of the CAR T-cell product may deliver a more functional therapeutic weapon. Further strategies to boost the efficacy of CAR T cells should rely not only on the production of CAR T cells with an improved cellular composition but also on additional changes. Such alterations could include (1) the coadministration of immunomodulatory agents capable of counteracting CLL-related immunological alterations, (2) the design of improved CAR constructs (such as third- and fourth-generation CARs), (3) the incorporation into the manufacturing process of immunomodulatory compounds overcoming the T-cell defects, and (4) the use of allogeneic CAR T cells or alternative CAR-modified cellular vectors. These strategies may allow to develop more effective CAR-modified cellular therapies capable of counteracting the more aggressive and still incurable forms of CLL.

Checkpoint inhibition in hematologic malignancies

Checkpoint inhibitor therapy has emerged as an effective therapeutic strategy for many types of malignancies, especially in solid tumors. Within the last two decades, numerous monoclonal antibody drugs targeting the CTLA-4 and PD-1/PD-L1 checkpoint pathways have seen FDA approval. Within hematologic malignancies, Hodgkin Lymphoma has seen the greatest clinical benefits thus far with more recent data showing efficacy in the front-line setting. As our understanding of checkpoint inhibition expands, using these pathways as a therapeutic target has shown some utility in the treatment of other hematologic malignancies as well, primarily in the relapsed/refractory settings. Checkpoint inhibition also appears to have a role as a synergistic agent to augment clinical responses to other forms of therapy such as hematopoietic stem cell transplant. Moreover, alternative checkpoint molecules that bypass the well-studied CTLA-4 and PD-1/PD-L1 pathways have emerged as exciting new therapeutic targets. Most excitingly is the use of anti-CD47 blockade in the treatment of high risk MDS and TP-53 mutated AML. Overall, there has been tremendous progress in understanding the benefits of checkpoint inhibition in hematologic malignancies, but further studies are needed in all areas to best utilize these agents. This is a review of the most recent developments and progress in Immune Checkpoint Inhibition in Hematologic Malignancies in the last decade.

Current Approaches of Immune Checkpoint Therapy in Chronic Lymphocytic Leukemia

OPINION STATEMENT

Increasing understanding of the complex interaction between leukemic and immune cells, which is responsible for tumor progression and immune evasion, has paved the way for the development of novel immunotherapy approaches in chronic lymphocytic leukemia (CLL). One of the well-known immune escape mechanisms of tumor cells is the up-regulation of immune checkpoint molecules. In recent years, targeting immune checkpoint receptors is the most clinically effective immunotherapeutic strategy for cancer treatment. In this regard, various immune checkpoint blockade (ICB) drugs are currently been investigating for their potential effects on improving anti-tumor immune response and clinical efficacy in the hematological malignancies; however, their effectiveness in patients with CLL has shown less remarkable success, and ongoing research is focused on identifying strategies to enhance the efficacy of ICB in CLL.

Case Report: Molecular and microenvironment change upon midostaurin treatment in mast cell leukemia at single-cell level

Mast cell leukemia is a rare and aggressive disease, predominantly with KIT D816V mutation. With poor response to conventional poly-chemotherapy, mast cell leukemia responded to the midostaurin treatment with a 50% overall response rate (ORR), but complete remission rate is approximately 0%. Therefore, the potential mechanisms of midostaurin resistance and the exact impacts of midostaurin on both gene expression profile and mast cell leukemia microenvironment in vivo are essential for design tailored combination therapy targeting both the tumor cells and the tumor microenvironment. Here we report a 59-year-old male mast cell leukemia patient with KIT F522C mutation treated with midostaurin. Single-cell sequencing of peripheral blood and whole exome sequencing (WES) of bone marrow were performed before and 10 months after midostaurin treatment. In accordance with the clinical response, compared to the pretreatment aberration, the decline of mast cells and increase of T-, NK, B-cells in peripheral blood, and the decrease of the KIT F522C mutation burden in bone marrow were observed. Meanwhile, the emergence of RUNX1 mutation, upregulations of genes expression (RPS27A, RPS6, UBA52, RACK1) on tumor cells, and increased frequencies of T and NK cells with TIGIT, CTLA4, and LAG3 expression were observed after midostaurin treatment, predicting the disease progression of this patient. As far as we know, this is the first case reporting the clinical, immunological, and molecular changes in mast cell leukemia patients before and after midostaurin treatment, illustrating the in vivo mechanisms of midostaurin resistance in mast cell leukemia, providing important clues to develop a sequential option to circumvent tumor progression after targeting oncogene addiction and prolong patients' survival.

Role of Next Generation Immune Checkpoint Inhibitor (ICI) Therapy in Philadelphia Negative Classic Myeloproliferative Neoplasm (MPN): Review of the Literature

The Philadelphia chromosome-negative (Ph-) myeloproliferative neoplasms (MPNs), which include essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF), are enduring and well-known conditions. These disorders are characterized by the abnormal growth of one or more hematopoietic cell lineages in the body's stem cells, leading to the enlargement of organs and the manifestation of constitutional symptoms. Numerous studies have provided evidence indicating that the pathogenesis of these diseases involves the dysregulation of the immune system and the presence of chronic inflammation, both of which are significant factors. Lately, the treatment of cancer including hematological malignancy has progressed on the agents aiming for the immune system, cytokine environment, immunotherapy agents, and targeted immune therapy. Immune checkpoints are the molecules that regulate T cell function in the tumor microenvironment (TME). The first line of primary immune checkpoints are programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1), and cytotoxic T-lymphocyte antigen-4 (CTLA-4). Immune checkpoint inhibitor therapy (ICIT) exerts its anti-tumor actions by blocking the inhibitory pathways in T cells and has reformed cancer treatment. Despite the impressive clinical success of ICIT, tumor internal resistance poses a challenge for oncologists leading to a low response rate in solid tumors and hematological malignancies. A Phase II trial on nivolumab for patients with post-essential thrombocythemia myelofibrosis, primary myelofibrosis, or post-polycythemia myelofibrosis was performed (Identifier: NCT02421354). This trial tested the efficacy of a PD-1 blockade agent, namely nivolumab, but was terminated prematurely due to adverse events and lack of efficacy. A multicenter, Phase II, single-arm open-label study was conducted including pembrolizumab in patients with primary thrombocythemia, post-essential thrombocythemia or post-polycythemia vera myelofibrosis that were ineligible for or were previously treated with ruxolitinib. This study showed that pembrolizumab treatment did not have many adverse events, but there were no pertinent clinical responses hence it was terminated after the first stage was completed. To avail the benefits from immunotherapy, the paradigm has shifted to new immune checkpoints in the TME such as lymphocyte activation gene-3 (LAG-3), T cell immunoglobulin and mucin domain 3 (TIM-3), T cell immunoglobulin and ITIM domain (TIGIT), V-domain immunoglobulin-containing suppressor of T cell activation (VISTA), and human endogenous retrovirus-H long terminal repeat-associating protein 2 (HHLA2) forming the basis of next-generation ICIT. The primary aim of this article is to underscore and elucidate the significance of next-generation ICIT in the context of MPN. Specifically, we aim to explore the potential of monoclonal antibodies as targeted immunotherapy and the development of vaccines targeting specific MPN epitopes, with the intent of augmenting tumor-related immune responses. It is anticipated that these therapeutic modalities rooted in immunotherapy will not only expand but also enhance the existing treatment regimens for patients afflicted with MPN. Preliminary studies from our laboratory showed over-expressed MDSC and over-expressed VISTA in MDSC, and in progenitor and immune cells directing the need for more clinical trials using next-generation ICI in the treatment of MPN.

Co-inhibition of TIGIT and PD-1/PD-L1 in Cancer Immunotherapy: Mechanisms and Clinical Trials

Over the past decade, immune checkpoint inhibitors (ICIs) have emerged as a revolutionary cancer treatment modality, offering long-lasting responses and survival benefits for a substantial number of cancer patients. However, the response rates to ICIs vary significantly among individuals and cancer types, with a notable proportion of patients exhibiting resistance or showing no response. Therefore, dual ICI combination therapy has been proposed as a potential strategy to address these challenges. One of the targets is TIGIT, an inhibitory receptor associated with T-cell exhaustion. TIGIT has diverse immunosuppressive effects on the cancer immunity cycle, including the inhibition of natural killer cell effector function, suppression of dendritic cell maturation, promotion of macrophage polarization to the M2 phenotype, and differentiation of T cells to regulatory T cells. Furthermore, TIGIT is linked with PD-1 expression, and it can synergize with PD-1/PD-L1 blockade to enhance tumor rejection. Preclinical studies have demonstrated the potential benefits of co-inhibition of TIGIT and PD-1/PD-L1 in enhancing anti-tumor immunity and improving treatment outcomes in several cancer types. Several clinical trials are underway to evaluate the safety and efficacy of TIGIT and PD-1/PD-L1 co-inhibition in various cancer types, and the results are awaited. This review provides an overview of the mechanisms of TIGIT and PD-1/PD-L1 co-inhibition in anti-tumor treatment, summarizes the latest clinical trials investigating this combination therapy, and discusses its prospects. Overall, co-inhibition of TIGIT and PD-1/PD-L1 represents a promising therapeutic approach for cancer treatment that has the potential to improve the outcomes of cancer patients treated with ICIs.

BTLA dysregulation correlates with poor outcome and diminished T cell-mediated antitumor responses in chronic lymphocytic leukemia

Patients with chronic lymphocytic leukemia (CLL) progressively develop marked immunosuppression, dampening innate and adaptive-driven antitumor responses. However, the underlying mechanisms promoting immune exhaustion are largely unknown. Herein, we provide new insights into the role of BTLA/HVEM axis promoting defects in T cell-mediated responses against leukemic cells. Increased expression of BTLA, an inhibitory immune checkpoint, was detected on the surface of CD4 + and CD8 + T lymphocytes in patients with CLL. Moreover, high levels of BTLA on CD4 + T cells correlated with diminished time to treatment. Signaling through BTLA activation led to decreased IL-2 and IFN-γ production ex vivo, whereas BTLA/HVEM binding disruption enhanced IFN-γ + CD8 + T lymphocytes. Accordingly, BTLA blockade in combination with bispecific anti-CD3/anti-CD19 antibody promoted CD8 + T cell-mediated anti-leukemic responses. Finally, treatment with an anti-BLTA blocking monoclonal antibody alone or in combination with ibrutinib-induced leukemic cell depletion in vitro. Altogether, our data reveal that BTLA dysregulation has a prognostic role and is limiting T cell-driven antitumor responses, thus providing new insights about immune exhaustion in patients with CLL.

Elevated levels of circulatory follicular T helper cells in chronic lymphocytic leukemia contribute to B cell expansion

Chronic lymphocytic leukemia (CLL) is characterized by an expansion of mature B cells in the bone marrow, peripheral lymphoid organs, and blood. CD4 T helper (Th) lymphocytes significantly contribute to the physiopathology of CLL, but the subset(s) of Th cell involved in CLL pathogenesis is (are) still under debate. In this study, we performed flow cytometry analysis of the circulatory T cells of untreated CLL patients and observed an increase in follicular helper T cells (Tfh), which is a subset of T cells specialized in B cell help. Elevated numbers of Tfh cells correlated with disease severity as measured by the Binet staging system. Tfh from CLL patients were activated and skewed toward a Th1 profile as evidenced by their PD-1+IL-21+IFNγ+ phenotype and their CXCR3+CCR6- chemokine receptor profile. Tfh efficiently enhanced B-CLL survival and proliferation through IL-21 but independently of IFNγ. Finally, we observed an inverse correlation between the Tfh1 and IgA and IgG serum levels in patients, suggesting a role for this Tfh subset in the immune dysfunction associated with CLL. Altogether, our data highlight an impairment in circulatory Tfh subsets in CLL patients and their critical role in CLL physiopathology.

Prediction of Clinical Outcomes with Explainable Artificial Intelligence in Patients with Chronic Lymphocytic Leukemia

BACKGROUND

The International Prognostic Index (IPI) is applied to predict the outcome of chronic lymphocytic leukemia (CLL) with five prognostic factors, including genetic analysis. We investigated whether multiparameter flow cytometry (MPFC) data of CLL samples could predict the outcome by methods of explainable artificial intelligence (XAI). Further, XAI should explain the results based on distinctive cell populations in MPFC dot plots.

METHODS

We analyzed MPFC data from the peripheral blood of 157 patients with CLL. The ALPODS XAI algorithm was used to identify cell populations that were predictive of inferior outcomes (death, failure of first-line treatment). The diagnostic ability of each XAI population was evaluated with receiver operating characteristic (ROC) curves.

RESULTS

ALPODS defined 17 populations with higher ability than the CLL-IPI to classify clinical outcomes (ROC: area under curve (AUC) 0.95 vs. 0.78). The best single classifier was an XAI population consisting of CD4+ T cells (AUC 0.78; 95% CI 0.70-0.86; p < 0.0001). Patients with low CD4+ T cells had an inferior outcome. The addition of the CD4+ T-cell population enhanced the predictive ability of the CLL-IPI (AUC 0.83; 95% CI 0.77-0.90; p < 0.0001).

CONCLUSIONS

The ALPODS XAI algorithm detected highly predictive cell populations in CLL that may be able to refine conventional prognostic scores such as IPI.

TIGIT: A promising target to overcome the barrier of immunotherapy in hematological malignancies

Immune evasion through up-regulating checkpoint inhibitory receptors on T cells plays an essential role in tumor initiation and progression. Therefore, immunotherapy, including immune checkpoint inhibitor targeting programmed cell death protein 1 (PD-1) and chimeric antigen receptor T cell (CAR-T) therapy, has become a promising strategy for hematological malignancies. T cell immunoreceptor with immunoglobulin and ITIM domain (TIGIT) is a novel checkpoint inhibitory receptor expressed on immune cells, including cytotoxic T cells, regulatory T cells, and NK cells. TIGIT participates in immune regulation via binding to its ligand CD155. Blockage of TIGIT has provided evidence of considerable efficacy in solid tumors in preclinical research and clinical trials, especially when combined with PD-1 inhibition. However, the mechanism and function of TIGIT in hematological malignancies have not been comprehensively studied. In this review, we focus on the role of TIGIT in hematological malignancies and discuss therapeutic strategies targeting TIGIT, which may provide a promising immunotherapy target for hematological malignancies.

The immune checkpoint expression in the tumor immune microenvironment of DLBCL: Clinicopathologic features and prognosis

Background & aims

The immune checkpoint recently provides a new strategy for the immunotherapy of malignant tumors. However, the role in the immune microenvironment of DLBCL is not completely clear.

Methods

We detected the expression of PD-1, LAG-3, TIM-3, and TIGIT on TILs and on tumor cells among 174 DLBCL patients by IHC.

Results

In TILs, the positive rates of PD-1, LAG-3, TIM-3 and TIGIT were 79.3%, 78.8%, 62.7% and 69.5%, respectively.TIM-3 and TIGIT were expressed in 44.8% and 45.4% of tumor cells. The expression of TIM-3 in TILs was significantly correlated with the Ann-Arbor stage (P=0.039). There was a positive correlation Between PD-1 and LAG-3 or TIM-3 and TIGIT.In addition, LAG-3 expression in TILs was associated with inferior prognosis.Multivariate analysis showed that PS score and R-CHOP therapy were independent risk factors for OS and PFS in patients with DLBCL (P=0.000).

Conclusions

The expression level of TIM-3 is closely related to the Ann-Arbor stage, which may be expected to be a new index to evaluate the invasiveness of DLBCL. PD-1 was correlated with the expression of LAG-3, and the high expression of LAG-3 and LAG-3/PD-1 predicted the poor prognosis of DLBCL. Therefore, LAG-3 may become a new target of immunotherapy, or be used in combination with PD-1 inhibitors to improve the drug resistance of current patients with DLBCL.

CD160 receptor in CLL: Current state and future avenues

CD160 is a glycosylphosphatidylinositol (GPI)-anchored cell surface glycoprotein expressed on cytotoxic natural killer (NK) cells and T-cell subsets. It plays a crucial role in the activation of NK-cell cytotoxicity and cytokine production. It also modulates the immune system and is involved in some pathologies, such as cancer. CD160 is abnormally expressed in B-cell chronic lymphocytic leukemia (CLL) but not expressed in normal B lymphocytes. Its expression in CLL enhances tumor cell proliferation and resistance to apoptosis. CD160 is also a potential prognostic marker for the detection of minimal residual disease (MRD) in CLL, which is important for the clinical management of CLL, the prevention of disease relapse, and the achievement of complete remission. In this review, we present an overview of CD160 and its involvement in the pathophysiology of CLL. We also discuss its use as a prognostic marker for the assessment of MRD in CLL.

Next Generation Immuno-Oncology Strategies: Unleashing NK Cells Activity

In recent years, immunotherapy has become a powerful therapeutic option against multiple malignancies. The unique capacity of natural killer (NK) cells to attack cancer cells without antigen specificity makes them an optimal immunotherapeutic tool for targeting tumors. Several approaches are currently being pursued to maximize the anti-tumor properties of NK cells in the clinic, including the development of NK cell expansion protocols for adoptive transfer, the establishment of a favorable microenvironment for NK cell activity, the redirection of NK cell activity against tumor cells, and the blockage of inhibitory mechanisms that constrain NK cell function. We here summarize the recent strategies in NK cell-based immunotherapies and discuss the requirement to further optimize these approaches for enhancement of the clinical outcome of NK cell-based immunotherapy targeting tumors.

The role of BTK inhibitors on the tumor microenvironment in CLL

The CLL disease course is heterogeneous with many patients never requiring treatment and some having very aggressive rapid onset disease.Innate and adaptive immune compensatory mechanisms driven by malignant cells often lead to clonal proliferation, migration and resistance to treatment in CLL. Cell-to-cell interactions occurring within the tumor Micro-environment (TME) can impact greatly on the course of the disease as well as contribute to the variable spread of CLL cells, known as spatial heterogeneity. Following evidence showing the expression of BTK on many hematopoietic cells (an exception beting T lymphocytes) has given rise to the idea that inhibition of BTK with BTK inhibitors (BTKi) such as ibrutinib can help treat CLL.As BTK has a wide variation of expression among cells the use of BTKi has been shown to not only control CLL clones but also redistribute the balance of humoral immunity back toward those of healthy control. n this review article we look at role of BTK in the pathogenesis of CLL, the use of BTKi and their effect on humoral immunity.

Update in TIGIT Immune-Checkpoint Role in Cancer

The in-depth characterization of cross-talk between tumor cells and T cells in solid and hematological malignancies will have to be considered to develop new therapeutical strategies concerning the reactivation and maintenance of patient-specific antitumor responses within the patient tumor microenvironment. Activation of immune cells depends on a delicate balance between activating and inhibitory signals mediated by different receptors. T cell immunoreceptor with immunoglobulin and ITIM domain (TIGIT) is an inhibitory receptor expressed by regulatory T cells (Tregs), activated T cells, and natural killer (NK) cells. TIGIT pathway regulates T cell-mediated tumor recognition in vivo and in vitro and represents an exciting target for checkpoint blockade immunotherapy. TIGIT blockade as monotherapy or in combination with other inhibitor receptors or drugs is emerging in clinical trials in patients with cancer. The purpose of this review is to update the role of TIGIT in cancer progression, looking at TIGIT pathways that are often upregulated in immune cells and at possible therapeutic strategies to avoid tumor aggressiveness, drug resistance, and treatment side effects. However, in the first part, we overviewed the role of immune checkpoints in immunoediting, the TIGIT structure and ligands, and summarized the key immune cells that express TIGIT.

TIGIT axis: novel immune checkpoints in anti-leukemia immunity

Hematologic malignancy evades immune-mediated recognition through upregulating various checkpoint inhibitory receptors (IRs) on several types of lymphocytes. Immunotherapies targeting IRs have provided ample evidence supporting regulating innate and adaptive immunity and obtaining clinical benefits. Newly described IRs have received considerable attention and are under investigation in cancer immunotherapy. Specifically, T cell immunoglobulin and ITIM domain is a novel inhibitory checkpoint receptor, and its immune checkpoint axis includes additional receptors such as CD96 and CD226, which are very promising targets. However, how the dynamics and functions of these receptor networks remain unknown, this review addresses the recent findings of the relevance of this complex receptor-ligand system and discusses their potential approaches in translating these preclinical findings into novel clinical agents in anti-leukemia immunotherapy.

CD4 T-Cell Exhaustion: Does It Exist and What Are Its Roles in Cancer?

In chronic infections and in cancer, persistent antigen stimulation under suboptimal conditions can lead to the induction of T-cell exhaustion. Exhausted T cells are characterized by an increased expression of inhibitory markers and a progressive and hierarchical loss of function. Although cancer-induced exhaustion in CD8 T cells has been well-characterized and identified as a therapeutic target (i.e., via checkpoint inhibition), in-depth analyses of exhaustion in other immune cell types, including CD4 T cells, is wanting. While perhaps attributable to the contextual discovery of exhaustion amidst chronic viral infection, the lack of thorough inquiry into CD4 T-cell exhaustion is particularly surprising given their important role in orchestrating immune responses through T-helper and direct cytotoxic functions. Current work suggests that CD4 T-cell exhaustion may indeed be prevalent, and as CD4 T cells have been implicated in various disease pathologies, such exhaustion is likely to be clinically relevant. Defining phenotypic exhaustion in the various CD4 T-cell subsets and how it influences immune responses and disease severity will be crucial to understanding collective immune dysfunction in a variety of pathologies. In this review, we will discuss mechanistic and clinical evidence for CD4 T-cell exhaustion in cancer. Further insight into the derivation and manifestation of exhaustive processes in CD4 T cells could reveal novel therapeutic targets to abrogate CD4 T-cell exhaustion in cancer and induce a robust antitumor immune response.

PD-1 and TIGIT Are Highly Co-Expressed on CD8+ T Cells in AML Patient Bone Marrow

Despite the great success of immune-checkpoint inhibitor (ICI) treatment for multiple cancers, evidence for the clinical use of ICIs in acute myeloid leukemia (AML) remains inadequate. Further exploration of the causes of immune evasion in the bone marrow (BM) environment, the primary leukemia site, and peripheral blood (PB) and understanding how T cells are affected by AML induction chemotherapy or the influence of age may help to select patients who may benefit from ICI treatment. In this study, we comprehensively compared the distribution of PD-1 and TIGIT, two of the most well-studied IC proteins, in PB and BM T cells from AML patients at the stages of initial diagnosis, complete remission (CR), and relapse-refractory (R/R) disease after chemotherapy. Our results show that PD-1 was generally expressed higher in PB and BM T cells from de novo (DN) and R/R patients, while it was partially recovered in CR patients. The expression of TIGIT was increased in the BM of CD8+ T cells from DN and R/R patients, but it did not recover with CR. In addition, according to age correlation analysis, we found that elderly AML patients possess an even higher percentage of PD-1 and TIGIT single-positive CD8+ T cells in PB and BM, which indicate greater impairment of T cell function in elderly patients. In addition, we found that both DN and R/R patients accumulate a higher frequency of PD-1+ and TIGIT+ CD8+ T cells in BM than in corresponding PB, indicating that a more immunosuppressive microenvironment in leukemia BM may promote disease progression. Collectively, our study may help guide the combined use of anti-PD-1 and anti-TIGIT antibodies for treating elderly AML patients and pave the way for the exploration of strategies for reviving the immunosuppressive BM microenvironment to improve the survival of AML patients.

Impact of Immune Parameters and Immune Dysfunctions on the Prognosis of Patients with Chronic Lymphocytic Leukemia

Simple Summary

In chronic lymphocytic leukemia (CLL), immune alterations—affecting both the innate and adaptive immunity—are very common. As a clinical consequence, patients with CLL frequently present with autoimmune phenomena, increased risk of infections and second malignancies. The aim of this review article is to present available data on CLL-associated alterations of immune parameters that correlate with known prognostic markers and with clinical outcome. Also, data on the impact of immune-related clinical manifestations on the prognosis of patients with CLL will be discussed.

Abstract

Chronic lymphocytic leukemia (CLL) is characterized by a wide spectrum of immune alterations, affecting both the innate and adaptive immunity. These immune dysfunctions strongly impact the immune surveillance, facilitate tumor progression and eventually affect the disease course. Quantitative and functional alterations involving conventional T cells, γδ T cells, regulatory T cells, NK and NKT cells, and myeloid cells, together with hypogammaglobulinemia, aberrations in the complement pathways and altered cytokine signature have been reported in patients with CLL. Some of these immune parameters have been shown to associate with other CLL-related characteristics with a known prognostic relevance or to correlate with disease prognosis. Also, in CLL, the complex immune response dysfunctions eventually translate in clinical manifestations, including autoimmune phenomena, increased risk of infections and second malignancies. These clinical issues are overall the most common complications that affect the course and management of CLL, and they also may impact overall disease prognosis.

Impacts of pembrolizumab therapy on immune phenotype in patients with high-grade neuroendocrine neoplasms

High grade neuroendocrine neoplasms (G3 NENs) are rare aggressive tumors with limited treatment options. Twenty-one previously treated patients with metastatic extra-pulmonary G3 NENs were treated with pembrolizumab. Baseline tumor samples were assessed for PD-L1 and tumor infiltrating lymphocytes (TIL). Peripheral blood samples drawn pre-treatment, prior to cycle three, and at disease progression were analyzed by flow cytometry. One patient achieved partial response, two had stable disease, and 18 exhibited progressive disease. The partially responding patient did not progress after 392 days, and the median progression-free survival (PFS) was 59 days. Longer PFS correlated independently with higher pre-treatment peripheral blood T-cell counts and lower pre-treatment activation state (CD69 expression) of naïve T cells and NK cells. Peripheral T-cell viability was reduced in patients with greater TILs. Post-treatment, T cells had reduced numbers of CD4+ cells, reduced PD-1 expression, increased activation of effector (CD62L-) cells, and increased expression of TIGIT. Baseline TIGIT expression on peripheral T cells also correlated positively with Ki67 in tumor. Patients with higher baseline T-cell expression of TIM-3 had shorter PFS. Despite limited activity of pembrolizumab, this study highlights the immune phenotype in this rare tumor type before and after treatment. High baseline peripheral T-cell count and reduced activation of T and NK cell subsets were associated with improved outcomes. Furthermore, increased post-treatment TIGIT and elevated baseline TIM-3 expression suggest that these may limit the efficacy of pembrolizumab, providing a rationale for combination immunotherapy (PD-1 with TIGIT and/or TIM-3 antibodies) to treat extra-pulmonary G3 NENs.

T Cell Defects and Immunotherapy in Chronic Lymphocytic Leukemia

In the past few years, independent studies have highlighted the relevance of the tumor microenvironment (TME) in cancer, revealing a great variety of TME-related predictive markers, as well as identifying novel therapeutic targets in the TME. Cancer immunotherapy targets different components of the immune system and the TME at large in order to reinforce effector mechanisms or relieve inhibitory and suppressive signaling. Currently, it constitutes a clinically validated treatment for many cancers, including chronic lymphocytic leukemia (CLL), an incurable malignancy of mature B lymphocytes with great dependency on microenvironmental signals. Although immunotherapy represents a promising therapeutic option with encouraging results in CLL, the dysfunctional T cell compartment remains a major obstacle in such approaches. In the scope of this review, we outline the current immunotherapeutic treatment options in CLL in the light of recent immunogenetic and functional evidence of T cell impairment. We also highlight possible approaches for overcoming T cell defects and invigorating potent anti-tumor immune responses that would enhance the efficacy of immunotherapy.

Evidence for Non-Cancer-Specific T Cell Exhaustion in the Tcl1 Mouse Model for Chronic Lymphocytic Leukemia

The reinvigoration of anti-cancer immunity by immune checkpoint therapies has greatly improved cancer treatment. In chronic lymphocytic leukemia (CLL), patients as well as in the Tcl1 mouse model for CLL, PD1-expressing, exhausted T cells significantly expand alongside CLL development; nevertheless, PD1 inhibition has no clinical benefit. Hence, exhausted T cells are either not activatable by simple PD1 blocking in CLL and/or only an insufficient number of exhausted T cells are CLL-specific. In this study, we examined the latter hypothesis by exploiting the Tcl1 transgenic CLL mouse model in combination with TCR transgene expression specific for a non-cancer antigen. Following CLL tumor development, increased PD1 levels were detected on non-CLL specific T cells that seem dependent on the presence of (tumor-) antigen-specific T cells. Transcriptome analysis confirmed a similar exhaustion phenotype of non-CLL specific and endogenous PD1pos T cells. Our results indicate that in the CLL mouse model, a substantial fraction of non-CLL specific T cells becomes exhausted during disease progression in a bystander effect. These findings have important implications for the general efficacy assessment of immune checkpoint therapies in CLL.

Specific features of T- and NK-cellular immunity in chronic lymphocytic leukemia

Profound immunological dysfunction is the key factor determining the development of infectious complications in chronic lymphocytic leukemia (CLL). The aim of this work is to assess the features of the subpopulation composition of T-lymphocytes (T-helpers (Th), cytotoxic T-lymphocytes (Tcyt), T regulatory cells (Treg), T-NK cells, naive Th, Th-memory, activated T-lymphocytes, TCRγδ cells) and NK cells in peripheral blood of patients with newly diagnosed chronic lymphocytic leukemia (CLL) and receiving ibrutinib therapy. Hematological and immunophenotypic studies have been performed in 30 patients with previously untreated CLL, 122 patients on ibrutinib therapy and 20 healthy donors. The subpopulation composition of T-lymphocytes (Th, Tcyt, Treg, T-NK, naive T-helpers, memory T-helpers, TCRγδ cells, activated T-lymphocytes) and NK cells has been assessed on flow cytometer (FACSCanto II (BD)) using the following panel of monoclonal antibodies: CD45, CD19, CD3, CD4, CD5, CD8, TCRγδ, CD127, CD16, CD56, CD57 CD45RA, CD45R0, HLA-DR, CD25. Compared to controls all CLL samples were found to have higher the absolute number of T-lymphocytes, NK cells and their subpopulations, T-helpers (especially of memory T-cells), cytotoxic T-cells, regulatory T-cells, TCRγδ T-cells, activated T-lymphocytes, increased cytotoxic potential of NK cells in previously untreated CLL patients. Patients who received ibrutinib therapy have registered a positive trend towards recovery of the subpopulation composition of T-lymphocytes and NK-cells. CLL patients have been found to have quantitative and functional changes in the subpopulations of T-lymphocytes and NK cells, indicating dysregulation of the immune response, and a high risk of developing infections. Monitoring of immunological parameters for ibrutinib therapy make possible to estimate impact of ibrutinib on the adaptive anti-CLL immune response.

T-cell dysfunction in chronic lymphocytic leukemia from an epigenetic perspective

Cellular immunotherapeutic approaches such as chimeric antigen receptor (CAR) T-cell therapy in chronic lymphocytic leukemia (CLL) thus far have not met the high expectations. Therefore it is essential to better understand the molecular mechanisms of CLLinduced T-cell dysfunction. Even though a significant number of studies are available on T-cell function and dysfunction in CLL patients, none examine dysfunction at the epigenomic level. In non-malignant T-cell research, epigenomics is widely employed to define the differentiation pathway into T-cell exhaustion. Additionally, metabolic restrictions in the tumor microenvironment that cause T-cell dysfunction are often mediated by epigenetic changes. With this review paper we argue that understanding the epigenetic (dys)regulation in T cells of CLL patients should be leveled to the knowledge we currently have of the neoplastic B cells themselves. This will permit a complete understanding of how these immune cell interactions regulate T- and B-cell function. Here we relate the cellular and phenotypic characteristics of CLL-induced T-cell dysfunction to epigenetic studies of T-cell regulation emerging from chronic viral infection and tumor models. This paper proposes a framework for future studies into the epigenetic regulation of CLL-induced Tcell dysfunction, knowledge that will help to guide improvements in the utility of autologous T-cell based therapies in CLL.

Altered T Follicular Helper Cell Subsets and Function in Chronic Lymphocytic Leukemia

Follicular helper T cells (T_FH) have specialized properties in promoting normal B cell activation but their role in chronic lymphocytic leukemia (CLL) is unknown. We find that T_FH cells are elevated in CLL patients and are phenotypically abnormal, expressing higher levels of PD-1, TIGIT, CD40L, IFNγ and IL-21, and exhibiting abnormal composition of T_FH1, T_FH2 and T_FH17 subsets. Frequencies of CD4-positive T cells expressing T_FH1 markers and IL-21 were positively correlated with patient lymphocyte counts and RAI stage, suggesting that accumulation of abnormal T_FH cells is concomitant with expansion of the leukemic B cell clone. Treatment with ibrutinib led to normalization of T_FH frequencies and phenotype. T_FH cells identified in CLL bone marrow display elevated expression of several functional markers compared to blood T_FH cells. CLL T cell-B cell co-culture experiments revealed a correlation of patient T_FH frequencies with functional ability of their CD4-positive T cells to promote CLL proliferation. Conversely, CLL cells can preferentially activate the T_FH cell subset in co-culture. Together our results indicate that CLL development is associated with expansion of abnormal T_FH populations that produce elevated levels of cytokines and costimulatory molecules which may help support CLL proliferation.

T Cells in Chronic Lymphocytic Leukemia: A Two-Edged Sword

Chronic lymphocytic leukemia (CLL) is a malignancy of mature, antigen-experienced B lymphocytes. Despite great progress recently achieved in the management of CLL, the disease remains incurable, underscoring the need for further investigation into the underlying pathophysiology. Microenvironmental crosstalk has an established role in CLL pathogenesis and progression. Indeed, the malignant CLL cells are strongly dependent on interactions with other immune and non-immune cell populations that shape a highly orchestrated network, the tumor microenvironment (TME). The composition of the TME, as well as the bidirectional interactions between the malignant clone and the microenvironmental elements have been linked to disease heterogeneity. Mounting evidence implicates T cells present in the TME in the natural history of the CLL as well as in the establishment of certain CLL hallmarks e.g. tumor evasion and immune suppression. CLL is characterized by restrictions in the T cell receptor gene repertoire, T cell oligoclonal expansions, as well as shared T cell receptor clonotypes amongst patients, strongly alluding to selection by restricted antigenic elements of as yet undisclosed identity. Further, the T cells in CLL exhibit a distinctive phenotype with features of “exhaustion” likely as a result of chronic antigenic stimulation. This might be relevant to the fact that, despite increased numbers of oligoclonal T cells in the periphery, these cells are incapable of mounting effective anti-tumor immune responses, a feature perhaps also linked with the elevated numbers of T regulatory subpopulations. Alterations of T cell gene expression profile are associated with defects in both the cytoskeleton and immune synapse formation, and are generally induced by direct contact with the malignant clone. That said, these abnormalities appear to be reversible, which is why therapies targeting the T cell compartment represent a reasonable therapeutic option in CLL. Indeed, novel strategies, including CAR T cell immunotherapy, immune checkpoint blockade and immunomodulation, have come to the spotlight in an attempt to restore the functionality of T cells and enhance targeted cytotoxic activity against the malignant clone.

Overcoming the Hurdles of Autologous T-Cell-Based Therapies in B-Cell Non-Hodgkin Lymphoma

Simple Summary

The activity of novel therapies that utilize patient’s own T-cells to induce remission of B-cell non-Hodgkin lymphoma (B-NHL), including chronic lymphocytic leukemia (CLL), is still suboptimal. In this review, we summarize the clinical efficacy of T-cell-based therapies in B-NHL and provide a biologic rationale for the observed (lack of) responses. We describe and compare the acquired T-cell dysfunctions that occur in the different subtypes of B-NHL. Furthermore, we discuss new insights that could enhance the efficacy of T-cell-based therapies for B-NHL and CLL.

Abstract

The next frontier towards a cure for B-cell non-Hodgkin lymphomas (B-NHL) is autologous cellular immunotherapy such as immune checkpoint blockade (ICB), bispecific antibodies (BsAbs) and chimeric antigen receptor (CAR) T-cells. While highly successful in various solid malignancies and in aggressive B-cell leukemia, this clinical success is often not matched in B-NHL. T-cell subset skewing, exhaustion, expansion of regulatory T-cell subsets, or other yet to be defined mechanisms may underlie the lack of efficacy of these treatment modalities. In this review, a systematic overview of results from clinical trials is given and is accompanied by reported data on T-cell dysfunction. From these results, we distill the underlying pathways that might be responsible for the observed differences in clinical responses towards autologous T-cell-based cellular immunotherapy modalities between diffuse large B-cell lymphoma (DLBCL), chronic lymphocytic leukemia (CLL), follicular lymphoma (FL), mantle cell lymphoma (MCL), and marginal zone lymphoma (MZL). By integration of the clinical and biological findings, we postulate strategies that might enhance the efficacy of autologous-based cellular immunotherapy for the treatment of B-NHL.

Immune Dysfunctions and Immune-Based Therapeutic Interventions in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy characterized by a wide range of tumor-induced alterations, which affect both the innate and adaptive arms of the immune response, and accumulate during disease progression. In recent years, the development of targeted therapies, such as the B-cell receptor signaling inhibitors and the Bcl-2 protein inhibitor venetoclax, has dramatically changed the treatment landscape of CLL. Despite their remarkable anti-tumor activity, targeted agents have some limitations, which include the development of drug resistance mechanisms and the inferior efficacy observed in high-risk patients. Therefore, additional treatments are necessary to obtain deeper responses and overcome drug resistance. Allogeneic hematopoietic stem cell transplantation (HSCT), which exploits immune-mediated graft-versus-leukemia effect to eradicate tumor cells, currently represents the only potentially curative therapeutic option for CLL patients. However, due to its potential toxicities, HSCT can be offered only to a restricted number of younger and fit patients. The growing understanding of the complex interplay between tumor cells and the immune system, which is responsible for immune escape mechanisms and tumor progression, has paved the way for the development of novel immune-based strategies. Despite promising preclinical observations, results from pilot clinical studies exploring the safety and efficacy of novel immune-based therapies have been sometimes suboptimal in terms of long-term tumor control. Therefore, further advances to improve their efficacy are needed. In this context, possible approaches include an earlier timing of immunotherapy within the treatment sequencing, as well as the possibility to improve the efficacy of immunotherapeutic agents by administering them in combination with other anti-tumor drugs. In this review, we will provide a comprehensive overview of main immune defects affecting patients with CLL, also describing the complex networks leading to immune evasion and tumor progression. From the therapeutic standpoint, we will go through the evolution of immune-based therapeutic approaches over time, including i) agents with broad immunomodulatory effects, such as immunomodulatory drugs, ii) currently approved and next-generation monoclonal antibodies, and iii) immunotherapeutic strategies aiming at activating or administering immune effector cells specifically targeting leukemic cells (e.g. bi-or tri-specific antibodies, tumor vaccines, chimeric antigen receptor T cells, and checkpoint inhibitors).

Dysfunctional role of elevated TIGIT expression on T cells in oral squamous cell carcinoma patients

OBJECTIVE

This study was aimed to analyze the role of T-cell immunoreceptor with immunoglobulin and tyrosine-based inhibitory motif domains (TIGIT) expression on T cells in patients with oral squamous cell carcinoma (OSCC).

MATERIALS AND METHODS

Peripheral blood mononuclear cells (PBMC) and tumor-infiltrating lymphocytes (TILs) were collected from OSCC patients. The correlation between TIGIT expression and clinicopathologic features was analyzed by chi-square test. Phenotypic and functional study of TIGIT⁺ T cells were performed by flow cytometry.

RESULTS

TIGIT was highly expressed on T cells from PBMC and TILs. High expression of TIGIT on CD4⁺ T cells (19.0%) and CD8⁺ T cells (35.9%) was also associated with higher T stage and nodal invasion. Moreover, TIGIT⁺ CD4⁺ and TIGIT⁺ CD8⁺ T cells sorted from OSCC patients showed a dysfunctional phenotype (low cell proliferation and low secretion of IL-2, TNF-α and IFN-γ), and TIGIT⁺ CD4⁺ T cells exhibited inhibitory function (high expression of Foxp3 and high amounts of IL-10). Importantly, TIGIT blockade can enhance the proliferation ability and effective cytokine production (IL-2, TNF-α, and IFN-γ) of CD4⁺ and CD8⁺ T cells from OSCC patients in vitro.

CONCLUSIONS

TIGIT-expressing T cells exhibit a lower effector cytokine-releasing phenotype in OSCC patients.

Distinct immune composition in lymph node and peripheral blood of CLL patients is reshaped during venetoclax treatment

Morbidity and mortality due to immunosuppression remain among the foremost clinical challenges in chronic lymphocytic leukemia (CLL). Although immunosuppression is considered to originate within the lymph node (LN) microenvironment, alterations in T and natural killer (NK) cells have almost exclusively been studied in peripheral blood (PB). Whereas chemoimmunotherapy further deteriorates immune function, novel targeted agents like the B-cell lymphoma 2 inhibitor venetoclax potentially spare nonmalignant lymphocytes; however, the effects of venetoclax on nonleukemic cells have not been explored. We address these unresolved issues using a comprehensive analysis of nonmalignant lymphocytes in paired LN and PB samples from untreated CLL patients, and by analyzing the effects of venetoclax-based treatment regimens on the immune system in PB samples from previously untreated and relapsed/refractory patients. CLL-derived LNs contained twice the amount of suppressive regulatory T cells (T_regs) and CLL supportive follicular T helper (T_fh) cells compared with PB. This was accompanied by a low frequency of cytotoxic lymphocytes. The expression of PD-1 by CD8⁺ T cells was significantly higher in LN compared with PB. Venetoclax-based treatment led to deep responses in the majority of patients, but also to decreased absolute numbers of B, T, and NK cells. T_fh cell, T_reg, and PD-1⁺ CD8⁺ T cell numbers were reduced more than fivefold after venetoclax-based therapy, and overproduction of inflammatory cytokines was reduced. Furthermore, we observed restoration of NK cell function. These data support the notion that the immunosuppressive state in CLL is more prominent within the LN. Venetoclax-based regimens reduced the immunosuppressive footprint of CLL, suggesting immune recovery after the elimination of leukemic cells.

T-cells in chronic lymphocytic leukemia: Guardians or drivers of disease?

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy, which is associated with profound alterations and defects in the immune system and a prevalent dependency on the microenvironmental niche. An abnormal T-cell compartment in the blood of CLL patients was already reported 40 years ago. Since then, our knowledge of T-cell characteristics in CLL has grown steadily, but the question of whether T-cells act as pro-tumoral bystander cells or possess anti-tumoral activity is still under debate. Increased numbers of CD4+ T-helper cell subsets are present in the blood of CLL patients, and T-helper cell cytokines have been shown to stimulate CLL cell survival and proliferation in vitro. In line with this, survival and growth of CLL cells in murine xenograft models have been shown to rely on activated CD4+ T-cells. This led to the hypothesis that T-cells are tumor-supportive in CLL. In recent years, evidence for an enrichment of antigen-experienced CD8+ T-cells in CLL has accumulated, and these cells have been shown to control leukemia in a CLL mouse model. Based on this, it was suggested that CD8+ T-cells recognize CLL-specific antigens and exert an anti-leukemia function. As described for other cancer entities, T-cells in CLL express multiple inhibitory receptors, such as PD-1, and lose their functional capacity, leading to an exhaustion phenotype which has been shown to be more severe in T-cells from secondary lymphoid organs compared with peripheral blood. This exhausted phenotype has been suggested to be causative for the poor response of CLL patients to CAR T-cell therapies. In addition, T-cells have been shown to be affected by drugs that are used to treat CLL, which likely impacts therapy response. This review provides an overview of the current knowledge about alterations of T-cells in CLL, including their distribution, function, and exhaustion state in blood and lymphoid organs, and touches also on the topic of how CLL drugs impact on the T-cell compartment and recent results of T-cell-based immunotherapy. We will discuss potential pathological roles of T-cell subsets in CLL and address the question of whether they foster progression or control of disease.

TIGIT Expression Is Associated with T-cell Suppression and Exhaustion and Predicts Clinical Outcome and Anti-PD-1 Response in Follicular Lymphoma

PURPOSE

T-cell immunoglobulin and ITIM domain (TIGIT), a member of the immune checkpoint family, is important in normal T-cell biology. However, the phenotypical profile and clinical relevance of TIGIT in follicular lymphoma is largely unknown.

EXPERIMENTAL DESIGN

Biopsy specimens from a cohort of 82 patients with follicular lymphoma were analyzed using mass cytometry to explore the phenotype and biological and clinical significance of TIGIT⁺ T cells.

RESULTS

TIGIT is highly expressed on intratumoral T cells and its expression alters T-cell phenotype in follicular lymphoma. TIGIT is abundantly expressed on T_reg cells, resulting in an enhanced suppressive property. TIGIT expression on non-T_reg/T_FH T cells defines a population that exhibits an exhausted phenotype. Clinically, increased numbers of TIGIT⁺ T cells are associated with inferior patient outcomes and poor survival. We observe that anti-PD-1 therapy with pembrolizumab alters the phenotype of TIGIT⁺ T subsets and identifies a role for CD28 expression on TIGIT⁺ T cells in treatment response.

CONCLUSIONS

The current study provides a comprehensive analysis of the phenotypic profile of intratumoral TIGIT⁺ T subsets and their prognostic relevance in follicular lymphoma. Inhibition of TIGIT signaling may be an additional mechanism to prevent T-cell suppression and exhaustion in B-cell lymphoma.

The yin and yang of co-inhibitory receptors: toward anti-tumor immunity without autoimmunity

Co-inhibitory receptors are important regulators of T-cell function that define the balance between tolerance and autoimmunity. The immune regulatory function of co-inhibitory receptors, including CTLA-4, PD-1, TIM-3, TIGIT, and LAG-3, was first discovered in the setting of autoimmune disease models, in which their blockade or deficiency resulted in induction or exacerbation of the disease. Later on, co-inhibitory receptors on lymphocytes have also been found to influence outcomes in tumor and chronic viral infection settings. These receptors suppress T-cell function in the tumor microenvironment (TME), thereby making the T cells dysfunctional. Based on this observation, blockade of co-inhibitory receptors (also known as checkpoint molecules) has emerged as a successful treatment option for a number of human cancers. However, severe autoimmune-like side effects limit the use of therapeutics that block individual or combinations of co-inhibitory receptors for cancer treatment. In this review we provide an overview of the role of co-inhibitory receptors in autoimmunity and anti-tumor immunity. We then discuss current approaches and future directions to leverage our knowledge of co-inhibitory receptors to target them in tumor immunity without inducing autoimmunity.

Methylome-based cell-of-origin modeling (Methyl-COOM) identifies aberrant expression of immune regulatory molecules in CLL

Background

In cancer, normal epigenetic patterns are disturbed and contribute to gene expression changes, disease onset, and progression. The cancer epigenome is composed of the epigenetic patterns present in the tumor-initiating cell at the time of transformation, and the tumor-specific epigenetic alterations that are acquired during tumor initiation and progression. The precise dissection of these two components of the tumor epigenome will facilitate a better understanding of the biological mechanisms underlying malignant transformation. Chronic lymphocytic leukemia (CLL) originates from differentiating B cells, which undergo extensive epigenetic programming. This poses the challenge to precisely determine the epigenomic ground state of the cell-of-origin in order to identify CLL-specific epigenetic aberrations.

Methods

We developed a linear regression model, methylome-based cell-of-origin modeling (Methyl-COOM), to map the cell-of-origin for individual CLL patients based on the continuum of epigenomic changes during normal B cell differentiation.

Results

Methyl-COOM accurately maps the cell-of-origin of CLL and identifies CLL-specific aberrant DNA methylation events that are not confounded by physiologic epigenetic B cell programming. Furthermore, Methyl-COOM unmasks abnormal action of transcription factors, altered super-enhancer activities, and aberrant transcript expression in CLL. Among the aberrantly regulated transcripts were many genes that have previously been implicated in T cell biology. Flow cytometry analysis of these markers confirmed their aberrant expression on malignant B cells at the protein level.

Conclusions

Methyl-COOM analysis of CLL identified disease-specific aberrant gene regulation. The aberrantly expressed genes identified in this study might play a role in immune-evasion in CLL and might serve as novel targets for immunotherapy approaches. In summary, we propose a novel framework for in silico modeling of reference DNA methylomes and for the identification of cancer-specific epigenetic changes, a concept that can be broadly applied to other human malignancies.

Electronic supplementary material

Supplementary information accompanies this paper at 10.1186/s13073-020-00724-7.

Immune Response Dysfunction in Chronic Lymphocytic Leukemia: Dissecting Molecular Mechanisms and Microenvironmental Conditions

Representing the major cause of morbidity and mortality for chronic lymphocytic leukemia (CLL) patients, immunosuppression is a common feature of the disease. Effectors of the innate and the adaptive immune response show marked dysfunction and skewing towards the generation of a tolerant environment that favors disease expansion. Major deregulations are found in the T lymphocyte compartment, with inhibition of CD8⁺ cytotoxic and CD4⁺ activated effector T cells, replaced by exhausted and more tolerogenic subsets. Likewise, differentiation of monocytes towards a suppressive M2-like phenotype is induced at the expense of pro-inflammatory sub-populations. Thanks to their B-regulatory phenotype, leukemic cells play a central role in driving immunosuppression, progressively inhibiting immune responses. A number of signaling cascades triggered by soluble mediators and cell–cell contacts contribute to immunomodulation in CLL, fostered also by local environmental conditions, such as hypoxia and derived metabolic acidosis. Specifically, molecular pathways modulating T-cell activity in CLL, spanning from the best known cytotoxic T lymphocyte antigen-4 (CTLA-4) and programmed cell death 1 (PD-1) to the emerging T cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibition motif domains (TIGIT)/CD155 axes, are attracting increasing research interest and therapeutic relevance also in the CLL field. On the other hand, in the microenvironment, the B cell receptor (BCR), which is undoubtedly the master regulator of leukemic cell behavior, plays an important role in orchestrating immune responses, as well. Lastly, local conditions of hypoxia, typical of the lymphoid niche, have major effects both on CLL cells and on non-leukemic immune cells, partly mediated through adenosine signaling, for which novel specific inhibitors are currently under development. In summary, this review will provide an overview of the molecular and microenvironmental mechanisms that modify innate and adaptive immune responses of CLL patients, focusing attention on those that may have therapeutic implications.

Increased frequency of CD4+ PD-1+ HLA-DR+ T cells is associated with disease progression in CLL

Chronic lymphocytic leukaemia (CLL) patients often have abnormal expansions of CD4+ and CD8+ T cells and this can be associated with progressive disease. To characterise the key T-cell populations involved in this phenomenon, we used flow cytometry and 11 phenotypic markers to study 74 CLL patients and 14 controls. T cells of CLL patients were more phenotypically complex than those of healthy controls with significant increases in the frequencies of CD4 and CD8 memory T cells expressing exhaustion-, activation- and senescence-associated markers. Multivariate analysis of 111 different T-cell subsets showed that high frequencies of four subsets (three CD8 and one CD4) were associated with shorter progression-free survival. The most significant association was with CD4+ HLA-DR+ PD-1+ T cells, and patients could be stratified into high- and low-risk groups based on the frequency of these T cells. The expansion of this CD4+ subset could not be accounted for by age, cytomegalovirus infection or increases in Treg cells. Overall, these results highlight two relatively simple biomarkers, percentage CD8+ and percentage CD4+ PD-1+ HLA-DR+ T cells, which can be used to risk-stratify CLL patients, independent of other tumour-associated markers. They also provide further evidence for the pivotal role of T cells in modulating the pathology of CLL.

Inflammatory Infiltrate and Angiogenesis in Mantle Cell Lymphoma

Mantle cell lymphoma (MCL) is an aggressive and rare B-cell non-Hodgkin lymphoma classified in two clinicopathological subtypes according to SOX11 expression and mutation state of immunoglobulin variable region heavy chain (IgVH) gene. The transcription factor SOX11, overexpressed in 78%-93% of MCL patients, plays a central role in modulating tumor microenvironment prosurvival signals and angiogenic genes. In this work, we have explored the lymph node microenvironment of three subgroups of MCL patients classified according to SOX11 expression as negative, light, and strong. CD34⁺ microvessels, CD4⁺ and CD8⁺ T-lymphocytes, CD68⁺ and CD163⁺ macrophages, and the oncogene p53 expression were evaluated by immunohistochemistry. Moreover, STAT3 mRNA expression was analyzed by RNA-scope assay.

Our results confirmed increased angiogenesis in the sample of patients positive to SOX11 compared to the negative ones and demonstrated that angiogenesis and SOX11 expression positively correlate to a higher T-lymphocytes inflammatory infiltrate. On the contrary, angiogenesis and SOX11 expression negatively correlate with macrophage's inflammatory infiltrate and p53 expression. STAT3 mRNA expression level was not relevant concerning angiogenesis or SOX11 expression. Overall, our data indicate that, in MCL, SOX11 expression is associated with increased angiogenesis and a high CD4⁺ and CD8⁺ T-cell infiltration, which are not sustained by CD163⁺ macrophages infiltrate and p53 expression.

Carboplatin chemoresistance is associated with CD11b+/Ly6C+ myeloid release and upregulation of TIGIT and LAG3/CD160 exhausted T cells

Immunosuppressive chemoresistance is a major barrier in lung cancer treatment. Tumor immunosuppressive environments mediated by myeloid-derived suppressor cells (MDSCs) play a key role in chemotherapy induced MDSC development and differentiation but their mechanistic role has not been elucidated. Here, we define a role for carboplatin based chemotherapy in potentiating an MDSC-dependent pathway that triggers the chemoresistance mechanism. Findings reveal MDSC differentiation and activation of IL-13/IL-33-mediated pathway through VCAM/RANTES following carboplatin treatment. Furthemore, secretion of T regulatory IL-10-producing CD4⁺Foxp3⁺ cells was increased followed by expression of co-inhibitory receptor TIGIT on T cells, leading to a dysfunctional T cell phenotype. These cells were characterized by an immunosuppressive phenotype with impaired activation, proliferation and cytokine production. Lung cancer tissues expressed CD155, which bound TIGIT receptors and inactivated CD8 T cells. This TIGIT expression on tumor-infiltrating T cells was found to be associated with tumor progression and was linked to functional exhaustion of T cells. In addition, the presence of plasmacytoid dendritic cells (pDCs) exposed to tumor-derived factors further enhanced tumor progression through IL-10 production and up-regulation of the inducible co-stimulatory ligand (ICOS-L). Deciphering these deranged immune mechanisms and how they are impacted by chemotherapy induction is essential for incorporation of novel immune-based strategies in order to restore immunity and inhibit the immunosuppressive phenotype of metastatic lung cancer.

A TIGIT-based chimeric co-stimulatory switch receptor improves T-cell anti-tumor function

Background

Tumors can employ different mechanisms to evade immune surveillance and function. Overexpression of co-inhibitory ligands that bind to checkpoint molecules on the surface of T-cells can greatly impair the function of latter. TIGIT (T cell immunoreceptor with Ig and ITIM domains) is such a co-inhibitory receptor expressed by T and NK cells which, upon binding to its ligand (e.g., CD155), can diminish cytokine production and effector function. Additionally, the absence of positive co-stimulation at the tumor site can further dampen T-cell response.

Methods

As T-cell genetic engineering has become clinically-relevant in the recent years, we devised herein a strategy aimed at enhancing T-cell anti-tumor function by diverting T-cell coinhibitory signals into positive ones using a chimeric costimulatory switch receptor (CSR) composed of the TIGIT exodomain fused to the signaling domain of CD28.

Results

After selecting an optimized TIGIT-28 CSR, we co-transduced it along with tumor-specific TCR or CAR into human T-cells. TIGIT-28-equipped T-cells exhibited enhanced cytokine secretion and upregulation of activation markers upon co-culture with tumor cells. TIGIT-28 enhancing capability was also demonstrated in an original in vitro model of T-cell of hypofunction induction upon repetitive antigen exposure. Finally, we tested the function of this molecule in the context of a xenograft model of established human melanoma tumors and showed that TIGIT-28-engineered human T-cells demonstrated superior anti-tumor function.

Conclusion

Overall, we propose that TIGIT-based CSR can substantially enhance T-cell function and thus contribute to the improvement of engineered T cell-based immunotherapy.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0721-y) contains supplementary material, which is available to authorized users.

Engaging Cytotoxic T and NK Cells for Immunotherapy in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is characterized by an acquired immune dysfunction. CLL cells affect the phenotype and function of the entire spectrum of innate and adaptive immune cells, including monocytes, T cells, and natural killer (NK) cells, leading to a tumor-supportive environment and reduced immunosurveillance. Novel immunotherapies like immune checkpoint blockade, bi- and tri-specific antibodies, and chimeric antigen receptor (CAR) T cells use the patients' immune system to induce therapeutic responses. Although these novel immunotherapies showed impressive results in several B cell lymphomas, responses in CLL were often disappointing. The strong immunomodulatory effect of CLL is believed to play a pivotal role in the low response rates to these immunotherapeutic strategies. In this review, we summarize how CLL influences the function of non-malignant lymphocytes, with a special focus on T and NK cells, two important cellular mediators for immunotherapy. Secondly, we provide a short overview of the activity of several immunotherapeutics in CLL, and discuss how novel strategies may overcome the disappointing response rates in CLL.