T-cell-mediated antitumor immunity in B-cell non-Hodgkin lymphoma: activation, suppression and exhaustion

T cell subgroup analysis and T cell exhaustion after autologous stem cell transplantation in lymphoma patients

BACKGROUND

Autologous stem cell transplantation (ASCT) is a common treatment option for relapsed/refractory (R/R) lymphomas and it is considered standard of care as primary consolidation therapy for some types of Non-Hodgkin Lymphomas (NHL). Although ASCT benefits patients by allowing cytoreduction with intensive chemotherapy and reconstituting with stem cells, the effects of immunological changes in T cell subgroups after ASCT are still poorly understood.

OBJECTIVES

We evaluated changes in frequencies of T cell subsets and T cells expressing some of the exhaustion markers (such as LAG-3 and PD-1) from peripheral blood samples before and after ASCT to investigate bone marrow reconstruction and whether exhaustion predicts relapse.

STUDY DESIGN

Blood samples were collected on the day before conditioning and at the 1st, 3rd, and 6th months post-ASCT. Flow cytometry analysis was conducted to examine T cell subgroup composition and exhaustion markers, including PD-1 and LAG-3. Additionally, functional analysis was performed using assays for IFN-g and TNF-a production. Furthermore, a CSFE proliferation assay was utilized to assess proliferation capacity.

RESULTS

In our data set, dominant cells post-transplantation were memory cells, as the naïve cell population did not recover for 6 months. Both single and combined expressions of LAG-3 and PD-1 were found to be high before transplantation, and decreased after transplantation. However, LAG-3 and PD-1 expression increased in the 3rd and 6th month after transplantation respectively. These changes were more evident for the relapsed patients when compared to non-relapsed patients within 3 months follow-up time. Notably, the expression of inhibitory receptors in the relapsed patients was significantly higher at the first month post-transplantation. CD107a+ cytotoxic T lymphocytes (CTL), IFN-g+, TNF-a.+ CTL and T helper lymphocyte (THL) populations significantly decreased in relapsed patients 3rd month after transplantation. Decreased proliferation capacities of CTLs and THLs were also observed in these patients.

CONCLUSION

These results suggest that increased surface PD-1 and LAG-3 expressions along with functional decline after 3 months of ASCT can be used as prognostic data about the relapse status of transplant patients.

CAR T-cell therapy for B-cell lymphomas: outcomes and resistance mechanisms

Chimeric antigen receptor (CAR) T cells are an exciting curative intent approach to the treatment of non-Hodgkin lymphomas (NHLs). Several products have received FDA approval for 2nd or 3rd line indications, and studies are underway for their use earlier in the disease course. These CAR T cells are ex vivo manufactured autologous cell products that specifically target tumor antigens to optimize tumor specificity and minimize off-tumor side effects-in NHLs, this is typically achieved by targeting B-cell antigens. Engagement of the CAR and corresponding antigen is designed to result in T-cell activation and subsequent tumor clearance. While curative for many NHL patients, too many patients fail to respond to or relapse following CAR T-cell treatment, and salvage options post CAR T-cell therapy are limited. Treatment failures occur because of myriad resistance mechanisms including CAR T-cell dysfunction, generalized immune dysregulation, and intrinsic tumor resistance. Focusing on patients with NHL, we review the clinical outcomes of CAR T-cell therapy and the major resistance mechanisms that lead to poor outcomes. We also review the many innovative and encouraging strategies that are being developed to improve CAR T-cell therapy for NHL.

The Interactions of T Cells with Myeloid-Derived Suppressor Cells in Peripheral Blood Stem Cell Grafts

The interaction of myeloid-derived suppressor cells (MDSCs) with T cells within G-CSF-mobilized peripheral blood stem cell (PBSC) grafts in patients undergoing autologous or allogeneic hematopoietic stem cell transplantation remains to be elucidated. Through studying allo- and auto-PBSC grafts, we observed grafts containing large numbers of T cells and MDSCs with intergraft variability in their percentage and number. T cells from autologous grafts compared to allografts expressed relative higher percentages of inhibitory receptors PD-1, CTLA-4, TIM-3, LAG-3, TIGIT and BTLA. Autograft T cells had decreased cell proliferation and IFN-γ secretion, which supported the possible presence of T cell exhaustion. On the contrary, graft monocytic MDSCs (M-MDSCs) expressed multiple inhibitory receptor ligands, including PD-L1, CD86, Galectin-9, HVEM and CD155. The expression of inhibitory receptor ligands on M-MDSCs was correlated with their corresponding inhibitory receptors on T cells in the grafts. Isolated M-MDSCs had the ability to suppress T cell proliferation and IFN-γ secretion and/or promote Treg expansion. Blocking the PD-L1-PD-1 signaling pathway partially reversed the functions of M-MDSCs. Taken together, our data indicated that T cells and M-MDSCs in PBSC grafts express complementary inhibitory receptor-ligand pairing, which may impact the quality of immune recovery and clinical outcome post transplantation.

Rewiring the T cell-suppressive cytokine landscape of the tumor microenvironment: a new frontier for precision anti-cancer therapy

T lymphocytes that infiltrate the tumor microenvironment (TME) often fail to function as effective anti-cancer agents. Within the TME, cell-to-cell inhibitory interactions play significant roles in dampening their anti-tumor activities. Recent studies have revealed that soluble factors released in the TME by immune and non-immune cells, as well as by tumor cells themselves, contribute to the exacerbation of T cell exhaustion. Our understanding of the cytokine landscape of the TME, their interrelationships, and their impact on cancer development is still at its early stages. In this review, we aim to shed light on Interleukin (IL) -6, IL-9, and IL-10, a small group of JAK/STAT signaling-dependent cytokines harboring T cell-suppressive effects in the TME and summarize their mechanisms of action. Additionally, we will explore how advancements in scientific research can help us overcoming the obstacles posed by cytokines that suppress T cells in tumors, with the ultimate objective of stimulating further investigations for the development of novel therapeutic strategies to counteract their tumor-promoting activities.

Harnessing natural killer cells for refractory/relapsed non-Hodgkin lymphoma: biological roles, clinical trials, and future prospective

Non-Hodgkin lymphomas (NHLs) are heterogeneous and are among the most common hematological malignancies worldwide. Despite the advances in the treatment of patients with NHLs, relapse or resistance to treatment is anticipated in several patients. Therefore, novel therapeutic approaches are needed. Recently, natural killer (NK) cell-based immunotherapy alone or in combination with monoclonal antibodies, chimeric antigen receptors, or bispecific killer engagers have been applied in many investigations for NHL treatment. The functional defects of NK cells and the ability of cancerous cells to escape NK cell-mediated cytotoxicity within the tumor microenvironment of NHLs, as well as the beneficial results from previous studies in the context of NK cell-based immunotherapy in NHLs, direct our attention to this therapeutic strategy. This review aims to summarize clinical studies focusing on the applications of NK cells in the immunotherapy of patients with NHL.

PD-L1 Is Involved in the Development of Non-Hodgkin's Lymphoma by Mediating Circulating Lymphocyte Apoptosis

Lymphocyte apoptosis plays a crucial role in tumor-induced immunosuppression. Programmed death ligand-1 (PD-L1) blocks lymphocyte activation via its receptor, PD-1. However, PD-L1/PD-1 expression and its role in enhancing immune suppression in non-Hodgkin lymphoma (NHL) have not been identified. The purpose of the study was to assess PD-L1/PD-1 expression in circulating lymphocytes in NHL and its role in immunosuppression. Twenty newly diagnosed NHL patients and twenty normal volunteers were enrolled in the study. PD-L1/PD-1 expression in circulating lymphocytes and the apoptosis of lymphocyte subsets were assessed using flow cytometry. The findings revealed that the PD-L1 expression in circulating CD3+, CD3+CD4+, CD3+CD8+, and CD20+ lymphocytes were dramatically upregulated in NHL patients (p < 0.001), whereas peripheral lymphocytes expressed low levels of PD-1. Compared with normal volunteers, a significant increase in lymphocyte apoptosis was revealed by annexin-V binding on T and B lymphocytes (p < 0.001). Peripheral lymphocytes expressing PD-L1 were four times more vulnerable to apoptosis than those expressing PD-1. Our findings imply that PD-L1 upregulation contributes to NHL development by promoting circulating lymphocyte apoptosis. This research adds to our understanding of the function of the PD-L1/PD-1 pathway in tumor evasion, establishing a novel therapeutic target in NHL. The results offer additional evidence for the immunomodulatory role of PD-L1 in circulating lymphocytes, providing a rationale for further investigations into immunological dysfunctions resulting from NHL. PD-L1+ lymphocytes could be employed as a biomarker to assess the effectiveness of immune systems and predict illness in patients with NHL.

Immunogenic Cell Death in Hematological Malignancy Therapy

Although the curative effect of hematological malignancies has been improved in recent years, relapse or drug resistance of hematological malignancies will eventually recur. Furthermore, the microenvironment disorder is an important mechanism in the pathogenesis of hematological malignancies. Immunogenic cell death (ICD) is a unique mechanism of regulated cell death (RCD) that triggers an intact antigen-specific adaptive immune response by firing a set of danger signals or damage-associated molecular patterns (DAMPs), which is an immunotherapeutic modality with the potential for the treatment of hematological malignancies. This review summarizes the existing knowledge about the induction of ICD in hematological malignancies and the current research on combining ICD inducers with other treatment strategies for hematological malignancies.

Pretreatment soluble Siglec-5 protein predicts early progression and R-CHOP efficacy in diffuse large B-cell lymphoma

Aims: To explore the clinical association between soluble Siglec-5/CD163 and clinical feature and prognosis in peripheral blood samples of patients with diffuse large B-cell lymphoma. Method: Significantly elevated cytokines in peripheral blood were characterized by cytokines array and validated by ELISA. Results: Compared with CD163, Siglec-5 exhibited superiority in discriminating patients into low- and high-risk subgroups based on overall survival and progression-free survival. In addition, Siglec-5 was an indicator of rituximab plus cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP) treatment efficacy. Conclusion: Siglec-5 may be applied as a reliable independent immune indicator for overall survival and progression-free survival. It may also predict R-CHOP efficacy in diffuse large B-cell lymphoma.

Bispecific T cell engagers: an emerging therapy for management of hematologic malignancies

Harnessing the power of immune cells, especially T cells, to enhance anti-tumor activities has become a promising strategy in clinical management of hematologic malignancies. The emerging bispecific antibodies (BsAbs), which recruit T cells to tumor cells, exemplified by bispecific T cell engagers (BiTEs), have facilitated the development of tumor immunotherapy. Here we discussed the advances and challenges in BiTE therapy developed for the treatment of hematologic malignancies. Blinatumomab, the first BiTE approved for the treatment of acute lymphocytic leukemia (ALL), is appreciated for its high efficacy and safety. Recent studies have focused on improving the efficacy of BiTEs by optimizing treatment regimens and refining the molecular structures of BiTEs. A considerable number of bispecific T cell-recruiting antibodies which are potentially effective in hematologic malignancies have been derived from BiTEs. The elucidation of mechanisms of BiTE action and neonatal techniques used for the construction of BsAbs can improve the treatment of hematological malignancies. This review summarized the features of bispecific T cell-recruiting antibodies for the treatment of hematologic malignancies with special focus on preclinical experiments and clinical studies.

Activating the Antitumor Immune Response in Non-Hodgkin Lymphoma Using Immune Checkpoint Inhibitors

Non-Hodgkin lymphomas comprise a heterogenous group of disorders which differ in biology. Although response rates are high in some groups, relapsed disease can be difficult to treat, and newer approaches are needed for this patient population. It is increasingly apparent that the immune system plays a significant role in the propagation and survival of malignant cells. Immune checkpoint blocking agents augment cytotoxic activity of the adaptive and innate immune systems and enhance tumor cell killing. Anti-PD-1 and anti-CTLA-4 antibodies have been tested as both single agents and combination therapy. Although success rates with anti-PD-1 antibodies are high in patients with Hodgkin lymphoma, the results are yet to be replicated in those with non-Hodgkin lymphomas. Some lymphoma histologies, such as primary mediastinal B cell lymphoma (PMBL), central nervous system, and testicular lymphomas and gray zone lymphoma, respond favorably to PD-1 blockade, but the response rates in most lymphoma subtypes are low. Other agents including those targeting the adaptive immune system such as TIM-3, TIGIT, and BTLA and innate immune system such as CD47 and KIR are therefore in trials to test alternative ways to activate the immune system. Patient selection based on tumor biology is likely to be a determining factor in treatment response in patients, and further research exploring optimal patient populations, newer targets, and combination therapy as well as identifying biomarkers is needed.

The Highs and Lows of Immune-Checkpoint Blockade in Lymphoma

Immunologic approaches to treating patients with cancer have shown promise, and immune-checkpoint blockade has been particularly successful. In many solid tumors, the presence of intratumoral immune cells has been predictive of a response to therapy, and blockade of inhibitory signals that dampen an effective antitumor response has resulted in clinical benefit for patients. Lymphoid malignancies, including Hodgkin lymphoma and non-Hodgkin lymphoma, are cancers of the immune system, and in these diseases, the malignant cells interact with the immune system and commonly provide signals that regulate immune function. Therefore, many of the immunologic lessons learned from solid tumors may not directly translate to lymphoid malignancies, and the mechanisms of effective antitumor responses in these diseases may be different. In Hodgkin lymphoma, for example, immune-checkpoint blockade has resulted in response rates of 65% to 75%. In contrast, in non-Hodgkin lymphoma, responses to immune-checkpoint blockade in phase II trials have been seen in fewer than 10% of patients, and the reasons for this substantial difference are largely unknown. Combination approaches are likely needed, particularly in the various subtypes of non-Hodgkin lymphoma, and combinations that include cytotoxic agents seem more effective than combinations of immunologic therapies. Successful therapeutic combinations in lymphomas may require an approach that simultaneously blocks inhibitory immune signals, provides direct activation of the immune response, and directly inhibits the malignant clone.

Immunotherapy in Hodgkin and non-Hodgkin lymphoma: Innate, adaptive and targeted immunological strategies

Since the clinical introduction of anti-CD20 monoclonal antibodies into lymphoma treatment, immunologic approaches in lymphoma have made substantial progress. Advances in our understanding of tumor immunology have led to the development of strategies to overcome immunologic barriers responsible for an ineffective immune response. Specifically, therapeutic agents have been developed and tested against molecules that are responsible for T-cell exhaustion. The use of monoclonal antibodies against immune checkpoints in the adaptive immune system, such as programmed cell death-1 and cytotoxic T-lymphocyte-associated protein 4, has changed the landscape of cancer therapy including the treatment of lymphoma. This achievement has recently been accompanied by the development of novel immune checkpoint inhibitors targeting the innate immune system, including the CD47-SIRPα signaling pathway, and this approach has yielded promising results. To overcome impaired antigen presentation, antibody-based cytotoxic strategies, namely antibody-drug conjugates (polatuzumab vedotin and brentuximab vedotin) and bispecific T-cell or NK-cell engagers (blinatumomab, REGN1979, RG6206, and AFM13), have rapidly evolved with promising clinical activity. As additional tools become available for lymphoma treatment, formulation of safe, rational combination strategies to combine them with standard therapy will be of paramount importance. A successful approach to the treatment of lymphoma may require both an optimized anti-tumor immune response as well as effective depletion of malignant lymphoid cells.

Immunotherapy of lymphomas

Lymphoid malignancies typically promote an infiltrate of immune cells at sites involved by the disease. While some of the immune cells present in lymphoma have effector function, the immune system is unable to eradicate the malignant clone. Therapies that optimize immune function therefore have the potential to improve the outcome of lymphoma patients. In this Review, we discuss immunologic approaches that directly target the malignant cell as well as approaches to optimize both the innate and adaptive immune response to the tumor. While many of these therapies have shown single-agent activity, the future will clearly require thoughtful combinations of these approaches.

Immunotherapy in Hodgkin Lymphoma: The Road Ahead

An extensive infiltrate of intratumoral immune cells is a hallmark of classic Hodgkin lymphoma (cHL) but these cells do result in an effective antitumor response. Immune checkpoint therapy, which activates 'exhausted' T cells, has been found to be highly effective in cHL, but responding patients commonly relapse. Combination approaches are currently being investigated but the assessment of benefit when adding immunotherapy is challenging. The pitfalls in designing combination studies derive from response endpoints that are difficult to measure, a lack of biomarkers that predict response, and a limited understanding of tumor biology. While progress in treating patients with cHL has been exceptional so far, further progress may require a review of clinical trial endpoints and a greater understanding of cHL biology.

Haploidentical natural killer cells induce remissions in non-Hodgkin lymphoma patients with low levels of immune-suppressor cells

We report a novel phase 2 clinical trial in patients with poor prognosis refractory non-Hodgkin lymphoma (NHL) testing the efficacy of haploidentical donor natural killer (NK) cell therapy (NK dose 0.5-3.27 × 107 NK cells/kg) with rituximab and IL-2 (clinicaltrials.gov NCT01181258). Therapy was tolerated without graft-versus-host disease, cytokine release syndrome, or neurotoxicity. Of 14 evaluable patients, 4 had objective responses (29%; 95% CI 12-55%) at 2 months: 2 had complete response lasting 3 and 9 months. Circulating donor NK cells persisted for at least 7 days after infusion at the level 0.6-16 donor NK cells/µl or 0.35-90% of total CD56 cells. Responding patients had lower levels of circulating host-derived Tregs (17 ± 4 vs. 307 ± 152 cells/µL; p = 0.008) and myeloid-derived suppressor cells at baseline (6.6 ± 1.4% vs. 13.0 ± 2.7%; p = 0.06) than non-responding patients. Lower circulating Tregs correlated with low serum levels of IL-10 (R 2 = 0.64; p < 0.003; n = 11), suggestive of less immunosuppressive milieu. Low expression of PD-1 on recipient T cells before therapy was associated with response. Endogenous IL-15 levels were higher in responders than non-responding patients at the day of NK cell infusion (mean ± SEM: 30 ± 4; n = 4 vs. 19.0 ± 4.0 pg/ml; n = 8; p = 0.02) and correlated with day 14 NK cytotoxicity as measured by expression of CD107a (R 2 = 0.74; p = 0.0009; n = 12). In summary, our observations support development of donor NK cellular therapies for advanced NHL as a strategy to overcome chemoresistance. Therapeutic efficacy may be further improved through disruption of the immunosuppressive environment and infusion of exogenous IL-15.

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.

Peripheral blood T cell alterations in newly diagnosed diffuse large B cell lymphoma patients and their long-term dynamics upon rituximab-based chemoimmunotherapy

The importance of T cell-dependent immune responses in achieving long-term cure of chemoimmunotherapy-treated cancer patients is underscored by the recently described "vaccinal effect" exerted by therapeutic mAbs. In accordance, pre- and post-therapy peripheral blood lymphopenia represents a well-established negative prognostic factor in DLBCL. We analyzed the phenotypic and functional (IFNγ production, and Granzyme B (GrzB) cytotoxic granule marker expression) profile of peripheral blood T lymphocyte subsets ("conventional" CD4+ and CD8+, FOXP3+CD25bright Treg, and "innate-like" CD56+) in DLBCL patients at diagnosis, and assessed the long-term impact of R-CHOP chemoimmunotherapy, in a prospective study. At diagnosis, DLBCL patients showed lower lymphocyte counts, due to selective decrement of CD4+ T (including Treg) and B lymphocytes. While all T cell subsets transiently decreased during therapy, CD4+ T cell and Treg remained significantly lower than controls, up to 1 year after R-CHOP. Phenotypically skewed profile of CD4+ and CD8+ T cell subsets associated with higher frequencies of IFNγ+ and GrzB+ cells at diagnosis, that transiently decreased during therapy, and re-attained persistently elevated levels, till up to 1 year after therapy. Differently, the pre-therapy elevated levels of circulating monocytes, and of plasma IL-6 and IL-10 rapidly normalized upon R-CHOP. In sum, we describe a quantitatively and functionally altered status of the peripheral blood T cell compartment in DLBCL patients at diagnosis, that persists long-term after tumor eradication, and it is only transiently perturbed by R-CHOP chemoimmunotherapy. Moreover, data suggest the association of selected T cell functional features with DLBCL phenotype, and with therapy outcome.

Emerging role of checkpoint blockade therapy in lymphoma

Following the successful application of immune checkpoint blockade therapy (CBT) in refractory solid tumors, it has recently gained momentum as a promising modality in the treatment of relapsed lymphoma. This significant therapeutic advance stems from decades of research that elucidated the role of immune regulation pathways and the mechanisms by which tumors can engage these critical pathways to escape immune detection. To date, two main pathways, the cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed death 1 (PD-1), have emerged as key targets of CBT demonstrating unprecedented activity particularly in heavily pretreated relapsed/refractory Hodgkin lymphoma and some forms of non-Hodgkin disease. Herein we provide a brief discussion of checkpoint blockade in the context of lymphoma biology with a specific focus on novel checkpoint inhibitors and their therapeutic activity. We discuss current clinical trials and the landscape of CBT to underscore both the remarkable progress and foreseeable limitations of this novel treatment strategy. In particular, we build upon state-of-the-art knowledge and clinical insights gained from the early trials to review potential approaches to how CBT may be integrated with other treatment modalities, including chemoimmunotherapy to improve patient outcomes in the future. Finally, as the role of CBT evolves to potentially become a cornerstone of therapy in refractory/relapsed lymphoma, we briefly emphasize the importance of predictive biomarkers in an effort to select appropriate patients who are most likely to derive benefit from CBT.