Immune Checkpoint Inhibitors to Treat Malignant Lymphomas

Assessment of Response to Immunotherapy in Patients with Hodgkin Lymphoma: Towards Quantifying Changes in Tumor Burden Using FDG-PET/CT

Immune checkpoint inhibitors are currently the standard of care for many advanced solid tumors, and they have been recently approved for the treatment of relapsed/refractory Hodgkin lymphoma and primary mediastinal B cell lymphoma. Assessments of the response to immunotherapy may be complicated by the occurrence of the flare/pseudoprogression phenomenon, consisting of initial tumor enlargement and even the appearance of new lesions, followed by a response, which may initially be indistinguishable from true progression. There have been efforts to characterize and capture the new patterns of response observed during immunotherapy, namely, pseudoprogression and delayed response, and several immune-related response criteria have been proposed. Confirming progression on a subsequent scan and measuring the total tumor burden are both common in immune-related criteria. Due to the peculiarity of hematologic malignancies, lymphoma-specific immune-related criteria have been developed (LYRIC), and they have been evaluated in research studies in comparison to the Lugano Classification. In this review work, we illustrate the evolution of the response criteria in lymphomas from the first CT-based criteria to the development of the PET-based Lugano Classification, further refined to take into account the flare phenomenon encountered during immunotherapy. We also describe the additional contribution of PET-derived volumetric parameters to the interpretation of responses during immunotherapy.

Recent Advances in Molecular Mechanisms of Cancer Immunotherapy

Cancer is among the current leading causes of death worldwide, despite the novel advances that have been made toward its treatment, it is still considered a major public health concern. Considering both the serious impact of cancer on public health and the significant side effects and complications of conventional therapeutic options, the current strategies towards targeted cancer therapy must be enhanced to avoid undesired toxicity. Cancer immunotherapy has become preferable among researchers in recent years compared to conventional therapeutic options, such as chemotherapy, surgery, and radiotherapy. The understanding of how to control immune checkpoints, develop therapeutic cancer vaccines, genetically modify immune cells as well as enhance the activation of antitumor immune response led to the development of novel cancer treatments. In this review, we address recent advances in cancer immunotherapy molecular mechanisms. Different immunotherapeutic approaches are critically discussed, focusing on the challenges, potential risks, and prospects involving their use.

Impact of cancer evolution on immune surveillance and checkpoint inhibitor response

Intratumour heterogeneity (ITH) is pervasive across all cancers studied and may provide the evolving tumour multiple routes to escape immune surveillance. Immune checkpoint inhibitors (CPIs) are rapidly becoming standard of care for many cancers. Here, we discuss recent work investigating the influence of ITH on patient response to immune checkpoint inhibitor (CPI) therapy. At its simplest, ITH may confound the diagnostic accuracy of predictive biomarkers used to stratify patients for CPI therapy. Furthermore, ITH is fuelled by mechanisms of genetic instability that can both engage immune surveillance and drive immune evasion. A greater appreciation of the interplay between ITH and the immune system may hold the key to increasing the proportion of patients experiencing durable responses from CPI therapy.

Expression of Immune Checkpoint Molecules PD1, PD-L1 and ICOS in Mycosis Fungoides and Sézary Syndrome: Association with Disease Stage and Clinical Outcome

Background

The relationship between immune checkpoint status and disease outcome is a major focus of research in cutaneous T‐cell lymphoma (CTCL), a disfiguring neoplastic dermatological disorder. Mycosis fungoides (MF) and Sézary syndrome (SS) are the two most common types of CTCL.

Objectives

The aim was to evaluate the immune checkpoint markers programmed death protein 1 (PD1), inducible T‐cell co‐stimulator (ICOS) and programmed death‐ligand 1 (PD‐L1) in skin biopsies from patients with CTCL relative to disease stage and overall survival.

Methods

This consecutive case series enrolled 47 patients: 57% had stage IA–IIA disease and 43% had stage IIB–IVA2 disease (including seven with SS).

Results

PD1, PD‐L1 and ICOS expression was seen in all biopsies. Notably, PD‐L1 was predominantly expressed on histiocytes/macrophages, but focal expression on CTCL cells was seen. High expression of either ICOS or PD‐L1 was associated with advanced‐stage disease (P = 0·007 for both) and with the appearance of large‐cell transformation (LCT), a histopathological feature associated with a poor prognosis (ICOS: P = 0·02; PD‐L1: P = 0·002). PD1 expression was not significantly associated with disease stage (P = 0·12) or LCT (P = 0·49), but expression was high in SS biopsies. A high combined checkpoint marker score (PD1, PD‐L1 and ICOS) was associated with advanced‐stage disease (P = 0·001), LCT (P = 0·021) and lower overall survival (P = 0·014).

Conclusions

These findings demonstrate the existence of a complex immunoregulatory microenvironment in CTCL and support the development of immunotherapies targeting ICOS and PD‐L1 in advanced disease.

Immune checkpoint inhibitors in lymphoma: challenges and opportunities

Immune checkpoint inhibitors (ICIs) are immunomodulatory antibodies that intensify the host immune response, thereby leading to cytotoxicity. The primary targets for checkpoint inhibition have included cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), programmed cell death receptor-1 (PD-1) or programmed cell death ligand-1 (PD-L1). ICIs have resulted in a change in treatment landscape of various neoplasms. Among hematologic malignancies, ICIs have been most successful in certain subtypes of lymphomas such as classic Hodgkin lymphoma (cHL) and primary mediastinal B-cell lymphoma (PMBCL). However, there have been several challenges in harnessing the host immune system through ICI use in other lymphomas. The underlying reasons for the low efficacy of ICI monotherapy in most lymphomas may include defects in antigen presentation, non-inflamed tumor microenvironment (TME), immunosuppressive metabolites, genetic factors, and an overall lack of predictive biomarkers of response. In this review, we outline the existing and ongoing studies utilizing ICI therapy in various lymphomas. We also describe the challenges leading to the lack of efficacy with ICI use and discuss potential strategies to overcome those challenges including: chimeric antigen receptor T-cell therapy (CAR-T therapy), bispecific T-cell therapy (BiTE), lymphocyte activation gene-3 (LAG-3) inhibitors, T-cell immunoglobulin and mucin-domain containing-3 (TIM-3) inhibitors, vaccines, promotion of inflammatory macrophages, indoleamine 2,3-dioxygenase 1 (IDO1) inhibitors, DNA methyltransferase inhibitors (DNMTi) and histone deacetylase inhibitors (HDACi). Tumor mutational burden and interferon-gamma release assays are potential biomarkers of ICI treatment response beyond PD-L1 expression. Further collaborations between clinicians and scientists are vital to understand the immunopathology in ICI therapy in order to improve clinical outcomes.

Long-term exposure to monoclonal anti-TNF is associated with an increased risk of lymphoma in BAFF-transgenic mice

The impact of treatment on the risk of lymphoma in patients with rheumatoid arthritis (RA) is unclear. Here, we aimed to assess if the risk of lymphoma differs according to the type of tumor necrosis factor inhibitor (TNFi), comparing monoclonal anti-TNF antibodies to the soluble TNF receptor. We used B cell activating factor belonging to the TNF family (BAFF)-transgenic (Tg) mice as a model of autoimmunity-associated lymphoma. Six-month-old BAFF-Tg mice were treated with TNFi for 12 months. Histological examination of the spleen, assessment of the cellular composition of the spleen by flow cytometry and assessment of B cell clonality were performed at euthanasia. Crude mortality and incidence of lymphoma were significantly higher in mice treated with monoclonal anti-TNF antibodies compared to both controls and mice treated with the soluble TNF receptor, even at a high dose. Flow cytometry analysis revealed decreased splenic macrophage infiltration in mice treated with monoclonal anti-TNF antibodies. Overall, this study demonstrates, for the first time, that a very prolonged treatment with monoclonal anti-TNF antibodies increase the risk of lymphoma in B cell-driven autoimmunity. These data suggest a closer monitoring for lymphoma development in patients suffering from B cell-driven autoimmune disease with long-term exposure to monoclonal anti-TNF antibodies.

Genetically Engineered Mouse Models Support a Major Role of Immune Checkpoint-Dependent Immunosurveillance Escape in B-Cell Lymphomas

These last 20 years, research on immune tumor microenvironment led to identify some critical recurrent mechanisms used in cancer to escape immune response. Through immune checkpoints, which are cell surface molecules involved in the immune system control, it is now established that tumor cells are able to shutdown the immune response. Due to the complexity and heterogeneity of Non Hodgkin B-cell Lymphomas (NHBLs), it is difficult to understand the precise mechanisms of immune escape and to explain the mitigated effect of immune checkpoints blockade for their treatment. Because genetically engineered mouse models are very reliable tools to improve our understanding of molecular mechanisms involved in B-cell transformation and, at the same time, can be useful preclinical models to predict immune response, we reviewed hereafter some of these models that highlight the immune escape mechanisms of NHBLs and open perspectives on future therapies.

Chimeric CTLA4-CD28-CD3z T Cells Potentiate Antitumor Activity Against CD80/CD86-Positive B Cell Malignancies

The adoptive transfer of chimeric antigen receptor T (CAR T) cells have been recognized as a promising therapeutic strategy for the treatment of hematological malignancies; however, clinical success using CAR T cells for the treatment of solid tumors are still limited since the T-cell function is inhibited by negative signals in the microenvironment of solid tumors. CTLA4 is a well-known immune checkpoint molecule, thus we developed a novel CAR by converting this negative signal to positive signal. The CAR developed consists of the extracellular and transmembrane domains of CTLA4 and the cytoplasmic domains of CD28 and CD3z (CTLA4-CAR T). CTLA4-CAR T cells exhibited superior cytokine secreting activities and cytotoxic to tumor cells in vitro and in xenograft models. CTLA4-CAR T cells were found to accumulate in tumors and are toxic to myeloid-derived suppressor cells (MDSCs) without signs of severe GVHD and CRS in preclinical models. Thus, this chimeric CTLA4-CAR can enhance the antitumor activity of CAR T cells and shed light on the strategy of using armed CAR T cells to target the immunomodulatory tumor microenvironment.

In Vivo Antitumor Effect against Murine Cells of CT26 Colon Cancer and EL4 Lymphoma by Autologous Whole Tumor Dead Cells

Active immunotherapy against cancer is based on immune system stimulation, triggering efficient and long-lasting antigen-specific immune responses. Immunization strategies using whole dead cells from tumor tissue, containing specific antigens inside, have become a promising approach, providing efficient lymphocyte activation through dendritic cells (DCs). In this work, we generate whole dead tumor cells from CT26, E.G7, and EL4 live tumor cells as antigen sources, which termed immunogenic cell bodies (ICBs), generated by a simple and cost-efficient starvation-protocol, in order to determine whether are capable of inducing a transversal anticancer response regardless of the tumor type, in a similar way to what we describe previously with B16 melanoma. We evaluated the anticancer effects of immunization with doses of ICBs in syngeneic murine tumor models. Our results showed that mice's immunization with ICBs-E.G7 and ICBs-CT26 generate 18% and 25% of tumor-free animals, respectively. On the other hand, all carrying tumor-animals and immunized with ICBs, including ICBs-EL4, showed a significant delay in their growth compared to not immunized animals. These effects relate to DCs maturation, cytokine production, increase in CD4+T-bet+ and CD4+ROR-γt+ population, and decrease of T regulatory lymphocytes in the spleen. Altogether, our data suggest that whole dead tumor cell-based cancer immunotherapy generated by a simple starvation protocol is a promising way to develop complementary, innovative, and affordable antitumor therapies in a broad spectrum of tumors.

Management of Drug Resistance in Mantle Cell Lymphoma

Mantle cell lymphoma (MCL) is a rare but aggressive B-cell hemopathy characterized by the translocation t(11;14)(q13;q32) that leads to the overexpression of the cell cycle regulatory protein cyclin D1. This translocation is the initial event of the lymphomagenesis, but tumor cells can acquire additional alterations allowing the progression of the disease with a more aggressive phenotype and a tight dependency on microenvironment signaling. To date, the chemotherapeutic-based standard care is largely inefficient and despite the recent advent of different targeted therapies including proteasome inhibitors, immunomodulatory drugs, tyrosine kinase inhibitors, relapses are frequent and are generally related to a dismal prognosis. As a result, MCL remains an incurable disease. In this review, we will present the molecular mechanisms of drug resistance learned from both preclinical and clinical experiences in MCL, detailing the main tumor intrinsic processes and signaling pathways associated to therapeutic drug escape. We will also discuss the possibility to counteract the acquisition of drug refractoriness through the design of more efficient strategies, with an emphasis on the most recent combination approaches.

Epigenetic abnormalities of classical Hodgkin lymphoma and its effect on immune escape

Classical Hodgkin lymphoma (cHL) is a particular kind of malignant tumour that originates from the B cells. The malignant phenotype of cHL is, at least in part, maintained by epigenetic aberrations, which primarily consist of abnormal histone methylation and acetylation. Progress has been made in clinical trials concerning the histone deacetylases inhibitors (HDACis) in cHL. Also, some demethylation regimens could serve the purpose of preventing and treating tumours. Programmed death-ligand receptor 1 (PD-L1, CD274) inhibitors or apoptosis receptor 1 (PD-1, CD279) inhibitors are used in treating patients with relapsed cHL in recent years. Academic researches indicated that PD-1/PD-L1 inhibitors, including nivolumab and pembrolizumab, demonstrate remarkable activity in relapsed cHL. In addition, in recent years, a close association between epigenetic aberrations and immune escape has been explored in cHL. DNA methyltransferase (DNMT) inhibitors, HDACis, and immune checkpoint blockade exhibit synergistic effects. Thus, this review aims to provide an overview on the epigenetic abnormalities of cHL and its effect on immune escape, in order to explore the optimal combination approach to treat the disease. SIGNIFICANCE OF THE STUDY: Cancer Statistics 2018 reported that more than 8000 new cases of Hodgkin lymphoma were diagnosed. In recent years, PD-1/PD-L1 inhibitors for cHL have been utilized, and the therapeutic strategies of HDACis combined with PD-1/PD-L1 inhibitors have been raised. It is critical for improving the efficacy and decreasing the toxicity in treating the patients with cHL.

Overview of Targeted Drugs for Mature B-Cell Non-hodgkin Lymphomas

The improved knowledge of pathogenetic mechanisms underlying lymphomagenesis and the discovery of the critical role of tumor microenvironments have enabled the design of new drugs against cell targets and pathways. The Food and Drug Administration (FDA) has approved several monoclonal antibodies (mAbs) and small molecule inhibitors (SMIs) for targeted therapy in hematology. This review focuses on the efficacy results of the currently available targeted agents and recaps the main ongoing trials in the setting of mature B-Cell non-Hodgkin lymphomas. The objective is to summarize the different classes of novel agents approved for mature B-cell lymphomas, to describe in synoptic tables the results they achieved and, finally, to draw future scenarios as we glimpse through the ongoing clinical trials. Characteristics and therapeutic efficacy are summarized for the currently approved mAbs [i.e., anti-Cluster of differentiation (CD) mAbs, immune checkpoint inhibitors, chimeric antigen receptor (CAR) T-cell therapy, and bispecific antibodies] as well as for SMIs i.e., inhibitors of B-cell receptor signaling, proteasome, mTOR BCL-2 HDAC pathways. The biological disease profiling of B-cell lymphoma subtypes may foster the discovery of innovative drug strategies for improving survival outcome in lymphoid neoplasms, as well as the trade-offs between efficacy and toxicity. The hope for clinical advantages should carefully be coupled with mindful awareness of the potential pitfalls and the occurrence of uneven, sometimes severe, toxicities.

miR-155 expression in antitumor immunity: The higher the better?

MicroRNAs are small noncoding RNAs that modulate gene expression either directly, by impairing the stability and/or translation of transcripts that contain their specific target sequence, or indirectly through the targeting of transcripts that encode transcription factors, factors implicated in signal transduction pathways, or epigenetic regulators. Abnormal expression of micro-RNAs has been found in nearly all types of pathologies, including cancers. MiR-155 has been the first microRNA to be implicated in the regulation of the innate and adaptative immune responses, and its expression is either increased or decreased in a variety of liquid and solid malignancies. In this review, we examine the oncogenic and antitumor potentials of miR-155, with special emphasize on its dose-dependent effects. We describe the impact of miR-155 levels on antitumor activity of lymphocytes and myeloid cells. We discuss miR-155 dose-dependent effects in leukemias and analyze results showing that miR-155 intermediate levels tend to be detrimental, whereas high levels of miR-155 expression usually prove beneficial. We also examine the beneficial effects of high levels of miR-155 expression in solid tumors. We discuss the possible causal involvement of miR-155 in leukemias and dementia in individuals with Down's syndrome. We finally propose that increasing miR-155 levels in immune cells might increase the efficiency of newly developed cancer immunotherapies, due to miR-155 ability to target transcripts encoding immune checkpoints such as cytotoxic T lymphocyte antigen-4 or programmed death-ligand 1.