TCR-Independent Metabolic Reprogramming Precedes Lymphoma-Driven Changes in T-cell Fate

Chronic T-cell receptor (TCR) signaling in the tumor microenvironment is known to promote T-cell dysfunction. However, we reasoned that poorly immunogenic tumors may also compromise T cells by impairing their metabolism. To address this, we assessed temporal changes in T-cell metabolism, fate, and function in models of B-cell lymphoma driven by Myc, a promoter of energetics and repressor of immunogenicity. Increases in lymphoma burden most significantly impaired CD4+ T-cell function and promoted regulatory T cell (Treg) and Th1-cell differentiation. Metabolomic analyses revealed early reprogramming of CD4+ T-cell metabolism, reduced glucose uptake, and impaired mitochondrial function, which preceded changes in T-cell fate. In contrast, B-cell lymphoma metabolism remained robust during tumor progression. Finally, mitochondrial functions were impaired in CD4+ and CD8+ T cells in lymphoma-transplanted OT-II and OT-I transgenic mice, respectively. These findings support a model, whereby early, TCR-independent, metabolic interactions with developing lymphomas limits T cell-mediated immune surveillance.

CD24 is a surrogate for 'immune-cold' phenotype in aggressive large B-cell lymphoma

The tumor microenvironment (TME) is a critical regulator of the development of malignant lymphoma. Therapeutics targeting the TME, especially immune checkpoint molecules, are changing the treatment strategy for lymphoma. However, the overall response to these therapeutics for diffuse large B‐cell lymphoma (DLBCL) is modest and new targets of immunotherapy are needed. To find critical immune checkpoint molecules for DLBCL, we explored the prognostic impact of immune checkpoint molecules and their ligands using publicly available datasets of gene expression profiles. In silico analysis of three independent datasets (GSE117556, GSE10846, and GSE181063) revealed that DLBCL expressing CD24 had a poor prognosis and had a high frequency of MYC aberrations. Moreover, gene set enrichment analysis showed that the ‘MYC‐targets‐hallmark’ (false discovery rate [FDR] = 0.024) and ‘inflammatory‐response‐hallmark’ (FDR = 0.001) were enriched in CD24‐high and CD24‐low DLBCL, respectively. In addition, the expression of cell‐specific markers of various immune cells was higher in CD24‐low DLBCL than in CD24‐high DLBCL. CIBERSORT analysis of the datasets showed fewer macrophages in CD24‐high DLBCL than in CD24‐low DLBCL. Additionally, immunohistochemical analysis of 335 cases of DLBCL showed that few TME cells were found in CD24‐high DLBCL, although statistical differences were not observed. These data indicate that CD24 expression suppresses immune cell components of the TME in DLBCL, suggesting that CD24 may be a target for cancer immunotherapy in aggressive large B‐cell lymphoma.

Defining and Treating High-grade B-cell lymphoma, NOS

High-grade B-cell lymphoma, not otherwise specified (HGBL, NOS) is a recently introduced diagnostic category for aggressive B-cell lymphomas. It includes tumors with Burkitt-like or blastoid morphology that do not have double-hit cytogenetics and that cannot be classified as other well-defined lymphoma subtypes. HBCL, NOS are rare and heterogeneous; most have germinal center B-cell phenotype, and up to 45% carry a single-hit MYC rearrangement, but otherwise they have no unifying immunophenotypic or cytogenetic characteristics. Recent analyses utilizing gene expression profiling (GEP) revealed that up to 15% of tumors currently classified as diffuse large B-cell lymphoma display a HGBL-like GEP signature, indicating a potential to significantly expand the HGBL category using more objective molecular criteria. Optimal treatment of HGBL, NOS is poorly defined due to its rarity and inconsistent diagnostic patterns. A minority of patients have early-stage disease which can be managed with standard RCHOP-based approaches with or without radiation. For advanced-stage HGBL, NOS, which often presents with aggressive, disseminated disease, high lactate dehydrogenase, and involvement of extranodal organs (including the central nervous system [CNS]), intensified Burkitt lymphoma-like regimens with CNS prophylaxis may be appropriate. However, many patients diagnosed at age > 60 years are not eligible for intensive immunochemotherapy. An improved, GEP and/or genomic-based pathologic classification that could facilitate HGBL-specific trials is needed to improve outcomes for all patients. In this review, we discuss the current clinicopathologic concept of HGBL, NOS, existing data on its prognosis and treatment, and delineate potential future taxonomy enrichments based on emerging molecular diagnostics.

High-grade B-cell lymphomas with MYC and BCL2 translocations lack tumor-associated macrophages and PD-L1 expression: A possible noninflamed subgroup

We investigated the intratumoral source of PD-L1 expression and the infiltration of tumor-associated macrophages (TAMs) in large B-cell lymphomas (LBCLs) with or without MYC-translocation, as well as possible correlations to BCL2-and BCL6-translocations and cell of origin (COO). One-hundred and twenty-six patient samples were studied in a cohort enriched for MYC-translocated tumors with 34 samples carrying this translocation. Demonstration of intratumoral distribution and cellular source of PD-L1 was enabled by immunohistochemical (IHC) dual staining specifically highlighting PD-L1 expression in lymphoma B-cells with antibodies against PD-L1 and PAX5. Additional IHC with antibodies against CD68 and CD163 identified TAMs. We found that CD68-positive TAMs were the main source of PD-L1 protein expression in contrast to lymphoma B cells which rarely expressed PD-L1. Semiquantitative IHC demonstrated a significant correlation between CD68 and PD-L1 protein expression. Unsupervised hierarchical analysis of PD-L1, CD68, and CD163 IHC data subsequently demonstrated three potential clusters defined by expression of the three biomarkers. Cluster A consisted of patient samples with significantly lower expression of PD-L1, CD68, and CD163, but also significantly higher prevalence of BCL2-translocation and MYC-BCL2-double-hit (DH) compared to the other two clusters. In cluster C we found a significant accumulation of BCL6 translocated tumors. This cluster in contrast had the highest protein expression of PD-L1, CD68, and CD163. Cluster B tumors had an intermediate expression of the three biomarkers, but no accumulation of the specific genetic translocations. Our data, which were based on morphological analysis, immunophenotyping and genotyping by fluorescence in situ hybridization were in line with new concepts of LBCL taxonomy integrating genetic, phenotypical, and immunological characteristics with identification of new subgroups where MYC translocation and MYC-BCL2 DH may identify a noninflamed subtype. These findings may furthermore hold significant predictive value especially regarding immune checkpoint blockade therapy, but further molecular characterization should be done to substantiate this hypothesis.

Impact of MYC on Anti-Tumor Immune Responses in Aggressive B Cell Non-Hodgkin Lymphomas: Consequences for Cancer Immunotherapy

Simple Summary

The human immune system has several mechanisms to attack and eliminate lymphomas. However, the MYC oncogene is thought to facilitate escape from this anti-tumor immune response. Since patients with MYC overexpressing lymphomas face a significant dismal prognosis after treatment with standard immunochemotherapy, understanding the role of MYC in regulating the anti-tumor immune response is highly relevant. In this review, we describe the mechanisms by which MYC attenuates the anti-tumor immune responses in B cell non-Hodgkin lymphomas. We aim to implement this knowledge in the deployment of novel immunotherapeutic approaches. Therefore, we also provide a comprehensive overview of current immunotherapeutic options and we discuss potential future treatment strategies for MYC overexpressing lymphomas.

Abstract

Patients with MYC overexpressing high grade B cell lymphoma (HGBL) face significant dismal prognosis after treatment with standard immunochemotherapy regimens. Recent preclinical studies indicate that MYC not only contributes to tumorigenesis by its effects on cell proliferation and differentiation, but also plays an important role in promoting escape from anti-tumor immune responses. This is of specific interest, since reversing tumor immune inhibition with immunotherapy has shown promising results in the treatment of both solid tumors and hematological malignancies. In this review, we outline the current understanding of impaired immune responses in B cell lymphoid malignancies with MYC overexpression, with a particular emphasis on diffuse large B cell lymphoma. We also discuss clinical consequences of MYC overexpression in the treatment of HGBL with novel immunotherapeutic agents and potential future treatment strategies.

Patterns of immune checkpoint protein expression in MYC-overexpressing aggressive B-cell non-Hodgkin lymphomas

Given the poor prognosis of MYC-overexpressing diffuse large B cell lymphoma (DLBCL) and B cell lymphoma unclassifiable with features intermediate between DLBCL and Burkitt lymphoma/high grade B cell lymphoma (BCLU/HGBL), and preclinical data suggesting that MYC may regulate the antitumor immune response, we sought to characterize expression of immune checkpoint proteins on tumor tissue from patients diagnosed with these lymphomas. Immunohistochemical staining for immune checkpoint protein expression was applied to 56 cases of MYC-overexpressing DLBCL and BCLU/HGBL, 35 of which also harbored MYC rearrangement (MYC-R). Analysis revealed both frequent overexpression of immune checkpoint proteins as well as differences in overexpression patterns based upon MYC-R status, with MYC-R cases more likely to overexpress PD-L1 and PD-1 in the tumor microenvironment (50 vs. 15%, p = 0.02 and 32 vs. 5%, p = 0.02, respectively) but less likely to overexpress CTLA-4 and CD80 on tumor cells (34 vs. 71%, p = 0.01 and 34 vs. 81%, p = 0.001, respectively), as compared to cases without MYC-R. These data may suggest a biologic rationale for investigation of the effect of checkpoint inhibitor therapies in these subgroups of MYC-overexpressing DLBCL and BCLU/HGBL.

Drug therapy for double-hit lymphoma

Double-hit lymphoma (DHL) is a rare type of aggressive B-cell lymphoma defined as a high-grade B-cell lymphoma (HGBCL) with the presence of MYC, BCL2 and/or BCL6 rearrangements. Patients usually present with rapidly progressive and advanced stage of disease and, commonly, with extranodal involvement. Typically, patients become refractory to standard R-CHOP, and more aggressive regimens such as DA-EPOCH-R, R-hyperCVAD or CODOX-R regimens are typically needed. MYC is considered an “undruggable” mutation. Recent evidence suggests that pathogenic mechanisms associated with MYC could be potential targets. In this review, we also discuss the role of hematopoietic stem cell transplantation (HCT) and chimeric antigen receptor (CAR) T-cell therapy in DHL. We also discuss the role of potential novel agents such as BCL2 inhibitors, checkpoint inhibitors, bromodomain and extraterminal (BET) family inhibitors, Pi3K inhibitors, and others.