Tumor-associated macrophages in diffuse large B-cell lymphoma

Critical Role of Extracellular Vesicles in Diffuse Large B-Cell Lymphoma; Pathogenesis, Potential Biomarkers, and Targeted Therapy-A Narrative Review

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin's lymphoma, characterized by its aggressive nature and heterogeneity. Despite significant advances in understanding DLBCL pathogenesis, there is still a need to elucidate the intricate mechanisms involved in disease progression and identify novel therapeutic targets. Extracellular vesicles (EVs), including exosomes and microvesicles, have emerged as crucial mediators of intercellular communication in various physiological and pathological processes, including cancer. In recent years, evidence has suggested that EVs play a vital role in DLBCL biology by facilitating the exchange of genetic material, especially miRNAs, and proteins and lipids between tumor cells, immune cells, and the tumor microenvironment. We summarize and discuss the biological functions of EVs in DLBCL and their effects on the tumor microenvironment, highlighting their influence on DLBCL pathobiology, immune evasion, angiogenesis, and drug resistance. We also investigated EVs' diagnostic and prognostic potential as circulating biomarkers in DLBCL, emphasizing their utility in the non-invasive monitoring of the disease status and treatment response. Understanding the complex interplay between EVs and DLBCL may open up new avenues for personalized medicine, improve patient stratification, and facilitate the development of innovative therapeutic interventions in this devastating hematological malignancy.

Blockade of the CD47/SIRPα checkpoint axis potentiates the macrophage-mediated antitumor efficacy of tafasitamab

Macrophages are one of the key mediators of the therapeutic effects exerted by monoclonal antibodies, such as the anti-CD19 antibody tafasitamab, approved in combination with lenalidomide for the treatment of relapsed or refractory diffuse large B-cell lymphoma (DLBCL). However, antibody-dependent cellular phagocytosis (ADCP) in the tumor microenvironment can be counteracted by increased expression of the inhibitory receptor SIRPα on macrophages and its ligand, the immune checkpoint molecule CD47, on tumor cells. The aim of this study was to investigate the impact of the CD47-SIRPα axis on tafasitamab- mediated phagocytosis and explore the potential of anti-CD47 blockade to enhance its antitumor activity. Elevated expression of both SIRPα and CD47 was observed in DLBCL patient-derived lymph node biopsies compared to healthy control lymph nodes. CRISPR-mediated CD47 overexpression affected tafasitamab-mediated ADCP in vitro and increased expression of SIRPα on macrophages correlated with decreased ADCP activity of tafasitamab against DLBCL cell lines. A combination of tafasitamab and an anti-CD47 blocking antibody enhanced ADCP activity of in vitro-generated macrophages. Importantly, tafasitamab-mediated phagocytosis was elevated in combination with CD47 blockade using primary DLBCL cells and patient-derived lymphoma-associated macrophages in an autologous setting. Furthermore, lymphoma cells with low CD19 expression were efficiently eliminated by the combination treatment. Finally, combined treatment of tafasitamab and an anti-CD47 antibody resulted in enhanced tumor volume reduction and survival benefit in lymphoma xenograft mouse models. These findings provide evidence that CD47 blockade can enhance the phagocytic potential of tumor-targeting immunotherapies such as tafasitamab and suggest that there is value in exploring the combination in the clinic.

Prognostic Significance of T-Cells and Macrophages in the Tumour Microenvironment of Nodal DLBCL

Revised International Prognostic (R-IPI) score is used widely for risk stratification of DLBCL cases, yet some patients belonging to same risk category tend to exhibit different outcomes. The role of T-cells and macrophages in prognostication of lymphomas has been a point of interest of late. We aimed to study the association of FOXP3 positive T-regulatory cells, cytotoxic T-cells and macrophages with the immunophenotypic subtypes, clinicopathological characteristics, treatment response and survival in nodal diffuse large B-cell lymphoma (DLBCL) patients. The clinicopathological and treatment data of 83 DLBCL patients diagnosed and treated at our institute from January 2015 to December 2018 were collected and followed up till June 2020. CD8, FOXP3 and CD68 immunostains were performed to highlight the cytotoxic T-cells, T-regulatory cells and macrophages respectively on the lymph node biopsies and the distribution of these cells and their association with clinico-pathological factors, treatment response and survival was analyzed. DLBCL cases with higher percentage of CD3 positive T-cells and CD8 positive cytotoxic T-cells had significant association with attainment of complete response to treatment. In addition, CD8 positive T-cells of more than 6.5% proved to be an independent predictor of treatment outcome (p = 0.022). Multivariate Cox regression survival analysis revealed that cases with 'good' R-IPI prognostic score and 'high CD68 positive macrophages in tumor microenvironment' had a significantly longer overall survival. Increased number of cytotoxic T-cells was significantly associated with complete response to treatment and higher number of macrophages correlated significantly with better overall survival signifying their antitumor effects.

Empowering macrophages: the cancer fighters within the tumour microenvironment in mantle cell lymphoma

In Mantle Cell Lymphoma (MCL), the role of macrophages within the tumour microenvironment (TME) has recently gained attention due to their impact on prognosis and response to therapy. Despite their low absolute number in MCL tumour tissue, recent findings reveal an association between the levels of macrophages and prognosis, consistent with trends observed in other lymphoma subtypes. M2-like macrophages, identified by markers such as CD163, contribute to angiogenesis and suppression of the immune response. Clinical trials with MCL patients treated with chemoimmunotherapy and targeted treatments underscore the adverse impact of high levels of M2-like macrophages. Immunomodulatory drugs like lenalidomide reduce the levels of MCL-associated CD163+ macrophages and enhance macrophage phagocytic activity. Similarly, clinical approaches targeting the CD47 "don't eat me" signalling, in combination with the anti-CD20-antibody rituximab, demonstrate increased macrophage activity and phagocytosis of MCL tumour cells. Cell-based therapies such as chimeric antigen receptor (CAR) T-cell have shown promise but various challenges persist, leading to a potential interest in CAR-macrophages (CAR-M). When macrophages are recruited to the TME, they offer advantages including phagocytic function and responsiveness to microenvironment alterations, suggesting their potential as a manipulable and inducible alternative when CAR T-cell therapies fails in the complex landscape of MCL treatment.

Spatially-resolved transcriptomics reveal macrophage heterogeneity and prognostic significance in diffuse large B-cell lymphoma

Macrophages are abundant immune cells in the microenvironment of diffuse large B-cell lymphoma (DLBCL). Macrophage estimation by immunohistochemistry shows varying prognostic significance across studies in DLBCL, and does not provide a comprehensive analysis of macrophage subtypes. Here, using digital spatial profiling with whole transcriptome analysis of CD68+ cells, we characterize macrophages in distinct spatial niches of reactive lymphoid tissues (RLTs) and DLBCL. We reveal transcriptomic differences between macrophages within RLTs (light zone /dark zone, germinal center/ interfollicular), and between disease states (RLTs/ DLBCL), which we then use to generate six spatially-derived macrophage signatures (MacroSigs). We proceed to interrogate these MacroSigs in macrophage and DLBCL single-cell RNA-sequencing datasets, and in gene-expression data from multiple DLBCL cohorts. We show that specific MacroSigs are associated with cell-of-origin subtypes and overall survival in DLBCL. This study provides a spatially-resolved whole-transcriptome atlas of macrophages in reactive and malignant lymphoid tissues, showing biological and clinical significance.

The Oncogenic Lipid Sphingosine-1-Phosphate Impedes the Phagocytosis of Tumor Cells by M1 Macrophages in Diffuse Large B Cell Lymphoma

BACKGROUND

A total of 30-40% of diffuse large B cell lymphoma (DLBCL) patients will either not respond to the standard therapy or their disease will recur. The first-line treatment for DLBCL is rituximab and combination chemotherapy. This treatment involves the chemotherapy-induced recruitment of tumor-associated macrophages that recognize and kill rituximab-opsonized DLBCL cells. However, we lack insights into the factors responsible for the recruitment and functionality of macrophages in DLBCL tumors.

METHODS

We have studied the effects of the immunomodulatory lipid sphingosine-1-phosphate (S1P) on macrophage activity in DLBCL, both in vitro and in animal models.

RESULTS

We show that tumor-derived S1P mediates the chemoattraction of both monocytes and macrophages in vitro and in animal models, an effect that is dependent upon the S1P receptor S1PR1. However, S1P inhibited M1 macrophage-mediated phagocytosis of DLBCL tumor cells opsonized with the CD20 monoclonal antibodies rituximab and ofatumumab, an effect that could be reversed by an S1PR1 inhibitor.

CONCLUSIONS

Our data show that S1P signaling can modulate macrophage recruitment and tumor cell killing by anti-CD20 monoclonal antibodies in DLBCL. The administration of S1PR1 inhibitors could enhance the phagocytosis of tumor cells and improve outcomes for patients.

Tumor-derived Exosomal ENO2 Modulates Polarization of Tumor-associated Macrophages through Reprogramming Glycolysis to Promote Progression of Diffuse Large B-cell Lymphoma

Macrophages can be polarized into functional classically activated (M1) or alternatively activated (M2) phenotype. Tumor-associated macrophages (TAMs) mainly exhibit M2 phenotype. Previous works determined that up-regulation of enolase 2 (ENO2) in diffuse large B-cell lymphoma (DLBCL) cells can promote macrophages to an M2-like phenotype, thereby consequently promoting the progression of DLBCL. Exosomes are a subset of extracellular vesicles, carrying various bioactive molecules, mediate signals transduction and regulate immune cells. In our study, we investigated the role and related mechanisms of DLBCL-derived exosomal ENO2 in regulating macrophage polarization during DLBCL progression via bioinformatics analysis and a series of experiments. The results of bioinformatics analysis indicated that high expression of ENO2 was positively correlated with DLBCL progression and macrophages M2/M1 ratio. ENO2 protein levels were increased in the exosomes of the sera of DLBCL patients and DLBCL cells. Moreover, the DLBCL-derived exosomes were assimilated by macrophages and then regulated macrophage polarization. The results of in vitro and in vivo experiments showed that DLBCL-derived exosomal ENO2 modulated macrophages polarization (increased M2 phenotype and decreased M1 phenotype), thereby promoting DLBCL proliferation, migration, and invasion. We then revealed that the modulation of macrophages polarization by DLBCL-derived exosomal ENO2 depended on glycolysis and was promoted through GSK3β/β-catenin/c-Myc signaling pathway. These findings suggested that DLBCL-derived exosomal ENO2 accelerated glycolysis via GSK3β/β-catenin/c-Myc signaling pathway to ultimately promote macrophages to an M2-like phenotype, which can promote the proliferation, migration and invasion of DLBCL, suggesting that exosomal ENO2 may be a promising therapeutic target and prognostic biomarker for DLBCL.

The impact of sMICA/sMICB on immunochemotherapy outcomes in newly diagnosed diffuse large B-cell lymphoma

Introduction

Soluble MHC class I-related chain A (sMICA) and B (sMICB) play a critical role tumor evolution and poor prognosis through an immune evasion mechanism. Thus, this study determines the interaction between sMICA/sMICB and the tumor immune environment in newly diagnosed diffuse large B-cell lymphoma (ND-DLBCL).

Methods

We analyzed sMICA/sMICB, cytokine in serum, and macrophage polarization analysis in tissue samples before the first chemotherapy administration. This research was performed to investigate the correlation between sMICA/sMICB expression and treatment outcomes as well as their influence on the immune system within ND-DLBCL.

Results

Of the 262 patients, 47.3% (n = 124) presented stage III or IV at diagnosis and 50.8% (n = 133) had a high International Prognostic Index (IPI ≥ 3). The patients with high (p = 0.034 and 0.004), elevated lactate dehydrogenase (p = 0.002 and 0.030), advanced stage (p = 0.003 and 0.012), and higher IPI risk (p = 0.009, and 0.032) correlated with the detection of sMICA or sMICB. The median progression-free survival (PFS) of patients with sMICA (p = 0.006) or sMICB (p =0.032) was inferior. Among the patients with advanced-stage or high IPI, those with sMICA or sMICB presented an inferior PFS and OS compared to those without. TNF-a, a pro-inflammatory cytokine, showed statistical significance with detected sMICA (p = 0.035) or sMICB (p = 0.044). Among anti-inflammatory cytokines, IL-1RA (P-value = 0.013) and IL-10 (p = 0.005) were associated with detecting sMICB, but not sMICA. In tissue samples, sMICA or sMICB detection did not correlate with the CD68/CD163 ratio.

Discussion

Conclusively, the identification of sMICA/sMICB presented unfavorable immunochemotherapy outcomes, and it was assumed that sMICA or sMICB and various cytokines interact, but the relationship with macrophage differentiation is unclear. Therefore, further research is needed to determine the relationship between sMICA/sMICB and tumor microenvironment in DLBCL.

High inter-follicular spatial co-localization of CD8+FOXP3+ with CD4+CD8+ cells predicts favorable outcome in follicular lymphoma

The spatial architecture of the lymphoid tissue in follicular lymphoma (FL) presents unique challenges to studying its immune microenvironment. We investigated the spatial interplay of T cells, macrophages, myeloid cells and natural killer T cells using multispectral immunofluorescence images of diagnostic biopsies of 32 patients. A deep learning-based image analysis pipeline was tailored to the needs of follicular lymphoma spatial histology research, enabling the identification of different immune cells within and outside neoplastic follicles. We analyzed the density and spatial co-localization of immune cells in the inter-follicular and intra-follicular regions of follicular lymphoma. Low inter-follicular density of CD8+FOXP3+ cells and co-localization of CD8+FOXP3+ with CD4+CD8+ cells were significantly associated with relapse (p = 0.0057 and p = 0.0019, respectively) and shorter time to progression after first-line treatment (Logrank p = 0.0097 and log-rank p = 0.0093, respectively). A low inter-follicular density of CD8+FOXP3+ cells is associated with increased risk of relapse independent of follicular lymphoma international prognostic index (FLIPI) (p = 0.038, Hazard ratio (HR) = 0.42 [0.19, 0.95], but not independent of co-localization of CD8+FOXP3+ with CD4+CD8+ cells (p = 0.43). Co-localization of CD8+FOXP3+ with CD4+CD8+ cells is predictors of time to relapse independent of the FLIPI score and density of CD8+FOXP3+ cells (p = 0.027, HR = 0.0019 [7.19 × 10-6 , 0.49], This suggests a potential role of inter-follicular CD8+FOXP3+ and CD4+CD8+ cells in the disease progression of FL, warranting further validation on larger patient cohorts.

Single-cell spatial analysis of tumor immune architecture in diffuse large B-cell lymphoma

Multiplexed immune cell profiling of the tumor microenvironment (TME) in cancer has improved our understanding of cancer immunology, but complex spatial analyses of tumor-immune interactions in lymphoma are lacking. Here, we used imaging mass cytometry (IMC) on 33 cases of diffuse large B-cell lymphoma (DLBCL) to characterize tumor and immune cell architecture and correlate it to clinicopathological features such as cell of origin, gene mutations, and responsiveness to chemotherapy. To understand the poor response of DLBCL to immune checkpoint inhibitors (ICI), we compared our results to IMC data from Hodgkin lymphoma, a cancer highly responsive to ICI, and observed differences in the expression of PD-L1, PD-1, and TIM-3. We created a spatial classification of tumor cells and identified tumor-centric subregions of immune activation, immune suppression, and immune exclusion within the topology of DLBCL. Finally, the spatial analysis allowed us to identify markers such as CXCR3, which are associated with penetration of immune cells into immune desert regions, with important implications for engineered cellular therapies. This is the first study to integrate tumor mutational profiling, cell of origin classification, and multiplexed immuno-phenotyping of the TME into a spatial analysis of DLBCL at the single-cell level. We demonstrate that, far from being histopathologically monotonous, DLBCL has a complex tumor architecture, and that changes in tumor topology can be correlated with clinically relevant features. This analysis identifies candidate biomarkers and therapeutic targets such as TIM-3, CCR4, and CXCR3 that are relevant for combination treatment strategies in immuno-oncology and cellular therapies.

Immunohistochemical Expression of Programmed Death Ligand 1 in Oral Extranodal Diffuse Large B Cell Lymphoma

OBJECTIVE

 Lymphomas are the third most common cancer after squamous cell carcinoma and salivary gland tumors. Extranodal diffuse B cell lymphoma (DBCL) represents 30 to 58% of non-Hodgkin's lymphoma. One of the major problems of DBCL is the high likelihood of disease relapse following treatment. A recent trend in the treatment of diffuse large B cell lymphoma (DLBCL) is blockage of an immune checkpoint inhibitor that targets the programmed death of cell ligand 1 receptors (PD-L1). PD-L1 activation results in negative regulatory signals that induce apoptosis and inhibit tumor antigen-specific T cells allowing immune evasion of the tumor.The aim of this aim is to measure the expression level of PD-L1 on oral tissue samples from DLBCL patients using immunohistochemistry.

MATERIALS AND METHODS

 This current study was performed at the Faculty of Dentistry, Tanta University, Egypt. Ethical approval was conducted from Faculty of Dentistry, Tanta University. Tissue samples were collected from 13 patients diagnosed with oral extranodal DLBCL) nongerminal center B cell like subtype. Both hematoxylin and eosin and immunohistochemical staining (The avidin-biotin-complex procedure) was performed with anti-PD-L1 antibody (clone number: 28-8, Abcam, Cambridge, Massachusetts, United States).Cytoplasmic and/or membranous positive intensity was graded as follows: very mild staining, mild staining, moderate staining, and intense staining using Image J, 1.41a (National Institutes of Health, United States) image analysis software. The mean area fraction of the stained cells was calculated by counting immunostained cells in three fields of each case by two pathologists. Data was entered in SPSS program for analysis.

RESULTS

 PD-L1 was overexpressed on tumor cells of oral extranodal DLBCL than control cells from lesion free areas of oral tissues of the same patient.

Identification and Validation of a Prognostic Prediction Model in Diffuse Large B-Cell Lymphoma

BACKGROUND

Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous group with varied pathophysiological, genetic, and clinical features, accounting for approximately one-third of all lymphoma cases worldwide. Notwithstanding that unprecedented scientific progress has been achieved over the years, the survival of DLBCL patients remains low, emphasizing the need to develop novel prognostic biomarkers for early risk stratification and treatment optimization.

METHOD

In this study, we screened genes related to the overall survival (OS) of DLBCL patients in datasets GSE117556, GSE10846, and GSE31312 using univariate Cox analysis. Survival-related genes among the three datasets were screened according to the criteria: hazard ratio (HR) >1 or <1 and p-value <0.01. Least Absolute Shrinkage and Selection Operator (LASSO) and multivariate Cox regression analysis were used to optimize and establish the final gene risk prediction model. The TCGA-NCICCR datasets and our clinical cohort were used to validate the performance of the prediction model. CIBERSORT and ssGSEA algorithms were used to estimate immune scores in the high- and low-risk groups.

RESULTS

We constructed an eight-gene prognostic signature that could reliably predict the clinical outcome in training, testing, and validation cohorts. Our prognostic signature also performed distinguished areas under the ROC curve in each dataset, respectively. After stratification based on clinical characteristics such as cell-of-origin (COO), age, eastern cooperative oncology group (ECOG) performance status, international prognostic index (IPI), stage, and MYC/BCL2 expression, the difference in OS between the high- and low-risk groups was statistically significant. Next, univariate and multivariate analyses revealed that the risk score model had a significant prediction value. Finally, a nomogram was established to visualize the prediction model. Of note, we found that the low-risk group was enriched with immune cells.

CONCLUSION

In summary, we identified an eight-gene prognostic prediction model that can effectively predict survival outcomes of patients with DLBCL and built a nomogram to visualize the perdition model. We also explored immune alterations between high- and low-risk groups.

The microenvironment of DLBCL is characterized by noncanonical macrophages recruited by tumor-derived CCL5

Tissue invasion by tumor cells induces a host inflammatory response that variably impacts tumorigenesis. This has been well documented for tumor-associated macrophages (TAMs) that could play a pro/M2- or an anti/M1-tumoral function. TAMs frequently infiltrate diffuse large B-cell lymphoma (DLBCL), an aggressive neoplasm arising from germinal center-experienced B cells. However, the pathway leading to the presence of TAMs in DLBCL remains unknown, and their impact is unclear. Here, we show that some DLBCL tumor cells expressed the chemokine CCL5, enabling the differential recruitment of blood monocytes through their expression of CCR1 and CCR5. CCL5 expression by DLBCL was not related to molecular subtypes, and healthy tonsillar B cells did not produce this chemokine, implying a posttransformation event. A single-cell analysis revealed that most DLBCL TAMs had a noncanonical gene signature with the concomitant expression of M1 and M2 genes. The presence of noncanonical TAMs may explain the lack of impact of macrophages on DLBCL development reported in some survival studies.

SPARC-positive macrophages are the superior prognostic factor in the microenvironment of diffuse large B-cell lymphoma and independent of MYC rearrangement and double-/triple-hit status

BACKGROUND

Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease with respect to outcome. Features of the tumor microenvironment (TME) are associated with prognosis when assessed by gene expression profiling. However, it is uncertain whether assessment of the microenvironment can add prognostic information to the most relevant and clinically well-established molecular subgroups when analyzed by immunohistochemistry (IHC).

PATIENTS AND METHODS

We carried out a histopathologic analysis of biomarkers related to TME in a very large cohort (n = 455) of DLBCL treated in prospective trials and correlated with clinicopathologic and molecular data, including chromosomal rearrangements and gene expression profiles for cell-of-origin and TME.

RESULTS

The content of PD1+, FoxP3+ and CD8+, as well as vessel density, was not associated with outcome. However, we found a low content of CD68+ macrophages to be associated with inferior progression-free survival (PFS) and overall survival (OS; P = 0.023 and 0.040, respectively) at both univariable and multivariable analyses, adjusted for the factors of the International Prognostic Index (IPI), MYC break and BCL2/MYC and BCL6/MYC double-hit status. The subgroup of PDL1+ macrophages was not associated with survival. Instead, secreted protein acidic and cysteine rich (SPARC)-positive macrophages were identified as the subtype of macrophages most associated with survival. SPARC-positive macrophages and stromal cells directly correlated with favorable PFS and OS (both, P[log rank] <0.001, P[trend] < 0.001). The association of SPARC with prognosis was independent of the factors of the IPI, MYC double-/triple-hit status, Bcl2/c-myc double expression, cell-of-origin subtype and a recently published gene expression signature [lymphoma-associated macrophage interaction signature (LAMIS)].

CONCLUSIONS

SPARC expression in the TME detected by a single IHC staining with fair-to-good interobserver reproducibility is a powerful prognostic parameter. Thus SPARC expression is a strong candidate for risk assessment in DLBCL in daily practice.

Prognostic molecular biomarkers in diffuse large B-cell lymphoma in the rituximab era and their therapeutic implications

Diffuse large B-cell lymphoma (DLBCL) represents a group of tumors characterized by substantial heterogeneity in terms of their pathological and biological features, a causal factor of their varied clinical outcome. This variation has persisted despite the implementation of rituximab in treatment regimens over the last 20 years. In this context, prognostic biomarkers are of great importance in order to identify high-risk patients that might benefit from treatment intensification or the introduction of novel therapeutic agents. Herein, we review current knowledge on specific immunohistochemical or genetic biomarkers that might be useful in clinical practice. Gene-expression profiling is a tool of special consideration in this effort, as it has enriched our understanding of DLBCL biology and has allowed for the classification of DLBCL by cell-of-origin as well as by more elaborate molecular signatures based on distinct gene-expression profiles. These subgroups might outperform individual biomarkers in terms of prognostication; however, their use in clinical practice is still limited. Moreover, the underappreciated role of the tumor microenvironment in DLBCL prognosis is discussed in terms of prognostic gene-expression signatures, as well as in terms of individual biomarkers of prognostic significance. Finally, the efficacy of novel therapeutic agents for the treatment of DLBCL patients are discussed and an evidence-based therapeutic approach by specific genetic subgroup is suggested.

Infiltration of CD163-, PD-L1- and FoxP3-positive cells adversely affects outcome in patients with mantle cell lymphoma independent of established risk factors

We characterised patients with mantle cell lymphoma (MCL) with poor prognosis based on differences in immune infiltration. Different expressions of the tumour cell markers Cyclin D1 and sex-determining region Y-box transcription factor 11 (SOX11), and the immune markers cluster of differentiation 3 (CD3), CD4, CD8, CD25, forkhead box protein P3 (FoxP3), T-box transcription factor TBX21 (T-bet), programmed cell death protein 1 (PD-1), programmed-death ligand 1 (PD-L1) and CD163 were investigated for all-cause mortality in 282 patients with MCL and time-to-progression (TTP) in 106 clinical trial patients. With increasing age, a significantly lower infiltration of CD3⁺ T lymphocytes was seen. T-cell infiltration was independent of cellular tumour antigen p53 (p53) expression, Ki-67, morphology and frequency of tumour cells. The all-cause mortality was higher in patients with PD-L1-expression above cut-off [hazard ratio (HR) 1·97, 95% confidence interval (CI) 1·18-3·25, adjusted for sex and MCL International Prognostic Index (MIPI)] and a higher frequency of CD163⁺ cells (continuously, HR 1·51, 95% CI 1·03-2·23, adjusting for age, sex, morphology, Ki-67 and p53). In patients treated within the Nordic Lymphoma Group MCL2/3 trials, TTP was shorter in patients with a higher frequency of FoxP3⁺ cells (HR 3·22, 95% CI 1·40-7·43) and CD163⁺ cells (HR 6·09, 95% CI 1·84-20·21), independent of sex and MIPI. When combined a higher frequency of CD163⁺ macrophages and PD-L1⁺ cells or high CD163⁺ macrophages and FoxP3⁺ regulatory T cells indicated worse outcome independent of established risk factors. The T-cell infiltrate was in turn independent of molecular characteristics of the malignant cells and decreased with age.

Expression of programmed cell death ligand-1 by immune cells in the microenvironment is a favorable prognostic factor for primary diffuse large B-cell lymphoma of the central nervous system

Primary diffuse large B-cell lymphoma (DLBCL) of the central nervous system (PCNS-DLBCL) is rare. Thirty-nine patients consecutively diagnosed as having PCNS-DLBCL were analyzed to highlight the prognostic value of the expression of programmed cell death ligand-1 (PD-L1) by neoplastic cells and immune cells in the microenvironment. They were positive for CD20 in all (100%), CD5 in two (5%), CD10 in nine (23%), BCL-2 in 27 (69%), BCL-6 in 34 (87%), and MUM-1 in 37 (95%). Only one case was positive for neoplastic PD-L1, with an unexpectedly long clinical course of 92 months. The remaining 38 cases were further divided into three groups based on the percentage of PD-L1⁺ cells among microenvironmental immune cells. Cutoffs of < 5%, 5-40%, and ≥ 40% successfully stratified mean prognoses with three-year overall survival (OS) of 21%, 63%, and 100% (P = 0.009), respectively. Progression-free survival (PFS) and OS were different between the groups with and without methotrexate (MTX)-containing chemotherapy (P = 0.007 and P < 0.001, respectively). Multivariate analysis identified three independent adverse factors of OS: PD-L1 negativity (< 5%) on microenvironmental immune cells (P = 0.027), deep structure involvement (P = 0.034), and performance status (PS) 2-4 (P = 0.009). The study showed that PD-L1 expression on immune cells in the microenvironment was associated with prognosis among patients with PCNS-DLBCL.

Prognostic impact of tumor-associated macrophages, lymphocyte-to-monocyte and neutrophil-to-lymphocyte ratio in diffuse large B-cell lymphoma

INTRODUCTION

Microenvironment has a prognostic influence in diffuse large B-cell lymphoma (DLBCL); among its components, tumor-associated macrophages (TAM) play a leading role. TAM can be classified into M1 (anti-tumor) and M2 (pro-tumor). Another prognostic factor could be represented by lymphocyte-to-monocyte and neutrophil-to-lymphocyte ratio (LMR and NLR).

OBJECTIVE

The aim of the study is to evaluate the prognostic impact of M1 and M2 TAM subtypes, LMR and NLR in DLBCL.

METHODS

We analyzed 37 consecutive patients between 2009 and 2013. Out of 37 patients, 28/37 (75.6%) received R-CHOP/CHOP-like regimens, 9/37 (24.4%) less intensive therapies. Immunohistochemistry was performed with antibodies against CD68 and CD163. We divided our cohort into 2 categories according to the Steidl score. TAM who coexpressed CD68 and CD163 were considered as M2. For LMR and NLR we used previously published cut-offs of 2.71 and 2.81.

RESULTS

CR rate was 70.3%; we did not record a significant correlation between CD68+ TAM, CD163+ TAM, CD68+/CD163+ TAM, LMR, NLR and CR. We observed a reduced PFS in patients with IPI ≥ 2 and high M2 TAM expression and a trend between higher expression of CD68+ TAM and improved PFS.

CONCLUSION

M2 TAM could have a prognostic role for IPI ≥ 2 DLBCL patients receiving R-CHOP, which thus warrants further investigation.

Lymphocyte-to-Monocyte Ratio May Serve as a Better Prognostic Indicator Than Tumor-associated Macrophages in DLBCL Treated With Rituximab

There are multiple prognostic indicators for diffuse large B-cell lymphoma (DLBCL) including the international prognostic index (IPI), and gene expression profiling (GEP) to classify the disease into germinal center B-cell and activated B-cell subtypes, the latter harboring inferior prognosis. More recently, tumor-associated macrophages (TAM) and lymphocyte-to-monocyte ratio (LMR) were found to have prognostic implications in DLBCL. However, consensus is yet to be reached in terms of the significance of each. In this study, we evaluated the prognostic value of TAM as assessed by CD163 or CD68 positivity by immunohistochemistry on tissue biopsies and LMR was calculated from peripheral blood differential, with focus on the inclusion of rituximab as a treatment modality. The number of CD68-positive cells in the tumor microenvironment did not exhibit significant prognostic value, whereas higher number of CD163-positive cells was associated with inferior overall survival in patients treated with chemotherapy alone. This effect was no longer evident in patients treated with rituximab containing chemoimmunotherapy. In contrast, the prognostic significance of LMR on survival was more persistent regardless of treatment. There was no association between LMR and the number of CD163-positive cells. Our results suggest that LMR is the more easily and widely available prognostic marker in this era of chemoimmunotherapy. Our finding supports previous literature that the effect of TAM can vary according to treatment. Interaction between rituximab and TAM warrant further scientific investigation for mechanistic insights into targeted therapeutics.

Immunohistochemical Markers of Tumor Microenvironment as Prognostic Predictors in Diffuse Large B-Cell Lymphoma: Study from an Oncology Centre in South India

Introduction Diffuse large B-cell lymphoma (DLBCL) accounts for 60% of lymphomas in India. Although the survival of DLBCL patients has improved following the addition of rituximab, a subset of patients do not respond well to therapy. Among the several factors responsible for this varied response, tumor microenvironment is considered to be crucial. This study is a search for such prognostic markers in the tumor microenvironment.

Materials and Methods A total of 97 patients were selected, of whom 34 were treated with the CHOP regimen and 63 with RCHOP. Immunohistochemistry for CD68 was performed to study the stromal-1 signature and CD34 for stromal-2 signature.

Results There was a significant increase in the counts of CD68-positive cells among patients free of events. CD34 count was higher in patients with events in both CHOP and RCHOP groups.

Conclusion Additional assessment of stromal microenvironment along with the cell of origin might predict the clinical outcome better in DLBCL.

Gene expression profiling of gray zone lymphoma

Gray zone lymphoma (GZL), a B-cell lymphoma with features intermediate between large B-cell lymphoma (LBCL) and classic Hodgkin lymphoma (cHL), is a rare and poorly defined entity. Alongside GZL, a subset of Epstein-Barr virus (EBV)-positive diffuse large B-cell lymphoma (DLBCL) has been described with polymorphic/GZL-like morphology (polymorphic-EBV-L). To fill the important gap in our understanding of the pathogenic process underlying these entities, we performed a gene expression study of a large international cohort of GZL and polymorphic-EBV-L, combined with cHL and primary mediastinal large B-cell lymphoma (PMBCL) cases. In an unsupervised principal component analysis, GZL cases presented with intermediate scores in a spectrum between cHL and PMBCL, whereas polymorphic-EBV-L clustered distinctly. The main biological pathways underlying the GZL spectrum were related to cell cycle, reflecting tumor cell content, and extracellular matrix signatures related to the cellular tumor microenvironment. Differential expression analysis and phenotypic characterization of the tumor microenvironment highlighted the predominance of regulatory macrophages in GZL compared with cHL and PMBCL. Two distinct subtypes of GZL were distinguishable that were phenotypically reminiscent of PMBCL and DLBCL, and we observed an association of PMBCL-type GZL with clinical presentation in the "thymic" anatomic niche. In summary, gene expression profiling (GEP) enabled us to add precision to the GZL spectrum, describe the biological distinction compared with polymorphic-EBV-L, and distinguish cases with and without thymic involvement as 2 subgroups of GZL, namely PMBCL-like and DLBCL-like GZL.

The Tumor Microenvironment of DLBCL in the Computational Era

Among classical exemplifications of tumor microenvironment (TME) in lymphoma pathogenesis, the “effacement model” resembled by diffuse large B cell lymphoma (DLBCL) implies strong cell autonomous survival and paucity of non-malignant elements. Nonetheless, the magnitude of TME exploration is increasing as novel technologies allow the high-resolution discrimination of cellular and extra-cellular determinants at the functional, more than morphological, level. Results from genomic-scale studies and recent clinical trials revitalized the interest in this field, prompting the use of new tools to dissect DLBCL composition and reveal novel prognostic association. Here we revisited major controversies related to TME in DLBCL, focusing on the use of bioinformatics to mine transcriptomic data and provide new insights to be translated into the clinical setting.

PD-L1 and tumor-associated macrophages in de novo DLBCL

Programmed death-ligand 1 (PD-L1) and its receptor, programmed cell death-1 (PD-1), are important negative regulators of immune cell activation. Therapeutically targeting PD-1/PD-L1 in diffuse large B-cell lymphoma (DLBCL) patients with a single agent has limited activity, meriting a deeper understanding of this complex biology and of available PD-L1 clinical assays. In this study, we leveraged 2 large de novo DLBCL phase 3 trials (GOYA and MAIN) to better understand the biologic and clinical relevance of PD-L1 in de novo DLBCL. PD-L1 was expressed on myeloid cells in 85% to 95% of DLBCL patients (depending on staining procedure), compared with 10% on tumor cells, and correlated with macrophage gene expression. PD-L1 did not identify high-risk patients in de novo DLBCL; it correlated with STAT3, macrophage gene expression, and improved outcomes among a subset of patients. These results may help identify immunologically distinct DLBCL subsets relevant for checkpoint blockade. GOYA and MAIN trials were registered at www.clinicaltrials.gov as #NCT01287741 and #NCT00486759, respectively.

Mass cytometry defines distinct immune profile in germinal center B-cell lymphomas

Tumor-associated macrophage and T-cell subsets are implicated in the pathogenesis of diffuse large B-cell lymphoma, follicular lymphoma, and classical Hodgkin lymphoma. Macrophages provide essential mechanisms of tumor immune evasion through checkpoint ligand expression and secretion of suppressive cytokines. However, normal and tumor-associated macrophage phenotypes are less well characterized than those of tumor-infiltrating T-cell subsets, and it would be especially valuable to know whether the polarization state of macrophages differs across lymphoma tumor microenvironments. Here, an established mass cytometry panel designed to characterize myeloid-derived suppressor cells and known macrophage maturation and polarization states was applied to characterize B-lymphoma tumors and non-malignant human tissue. High-dimensional single-cell analyses were performed using dimensionality reduction and clustering tools. Phenotypically distinct intra-tumor macrophage subsets were identified based on abnormal marker expression profiles that were associated with lymphoma tumor types. While it had been proposed that measurement of CD163 and CD68 might be sufficient to reveal macrophage subsets in tumors, results here indicated that S100A9, CCR2, CD36, Slan, and CD32 should also be measured to effectively characterize lymphoma-specific tumor macrophages. Additionally, the presence of phenotypically distinct, abnormal macrophage populations was closely linked to the phenotype of intra-tumor T-cell populations, including PD-1 expressing T cells. These results further support the close links between macrophage polarization and T-cell functional state, as well as the rationale for targeting tumor-associated macrophages in cancer immunotherapies.

Plasmablastic Lymphomas: Characterization of Tumor Microenvironment Using CD163 and PD-1 Immunohistochemistry

This study aims to characterize the tumor microenvironment of plasmablastic lymphoma (PBL) in regard to the quantities of CD163(+) tumor associated macrophages (TAM) and PD1(+) tumor infiltrating lymphocytes (TIL). This article also reviews the existing knowledge of the role of PD-1/PD-L1 pathway in the tumor microenvironment of hematopoietic neoplasms, discusses potential mechanisms to explain our findings, and outlines areas for future studies. We performed CD163 and PD1 immunohistochemical studies in 11 cases classified as plasmablastic lymphoma, and recorded the percentages of positive TAMs and TILs. Based on previous studies, cut off values of ≥30% and >5% were used to classify the cases into high TAMs and TILs, respectively. We determined that the majority of cases (8 of 11, or 73%) had high percentage of TAMs, while only a minority had high percentage of TILs (3 of 11, or 27%). Our data shows a trend towards a negative correlation between TAMs and TILs (p=0.08), and a predominance of the pattern TAM^high/TIL^low (7 of 11, or 63%) compared to other patterns. The microenvironment of plasma-blastic lymphoma tends to show high percentage of TAMs (≥30%) combined with low percentage of TILs (≤5%). Additional studies are needed to determine the clinical significance of TILs and the influence of EBV and HIV infections on numbers of TILs in PBL. As high microenvironment TAMs have been associated with high microenvironment PD-L1 in other hematopoietic malignancies, our data supports the need for future studies on the expression of PD-L1 in PBL.

High CD206 levels in Hodgkin lymphoma-educated macrophages are linked to matrix-remodeling and lymphoma dissemination

Macrophages (Mφ) are abundantly present in the tumor microenvironment and may predict outcome in solid tumors and defined lymphoma subtypes. Mφ heterogeneity, the mechanisms of their recruitment, and their differentiation into lymphoma‐promoting, alternatively activated M2‐like phenotypes are still not fully understood. Therefore, further functional studies are required to understand biological mechanisms associated with human tumor‐associated Mφ (TAM). Here, we show that the global mRNA expression and protein abundance of human Mφ differentiated in Hodgkin lymphoma (HL)‐conditioned medium (CM) differ from those of Mφ educated by conditioned media from diffuse large B‐cell lymphoma (DLBCL) cells or, classically, by macrophage colony‐stimulating factor (M‐CSF). Conditioned media from HL cells support TAM differentiation through upregulation of surface antigens such as CD40, CD163, CD206, and PD‐L1. In particular, RNA and cell surface protein expression of mannose receptor 1 (MRC1)/CD206 significantly exceed the levels induced by classical M‐CSF stimulation in M2‐like Mφ; this is regulated by interleukin 13 to a large extent. Functionally, high CD206 enhances mannose‐dependent endocytosis and uptake of type I collagen. Together with high matrix metalloprotease9 secretion, HL‐TAMs appear to be active modulators of the tumor matrix. Preclinical in ovo models show that co‐cultures of HL cells with monocytes or Mφ support dissemination of lymphoma cells via lymphatic vessels, while tumor size and vessel destruction are decreased in comparison with lymphoma‐only tumors. Immunohistology of human HL tissues reveals a fraction of cases feature large numbers of CD206‐positive cells, with high MRC1 expression being characteristic of HL‐stage IV. In summary, the lymphoma‐TAM interaction contributes to matrix‐remodeling and lymphoma cell dissemination.

Expression of IL-34 correlates with macrophage infiltration and prognosis of diffuse large B-cell lymphoma

Objectives

Infiltration of macrophages through the tyrosine kinase receptor CSF1R is a poor prognosis factor in various solid tumors. Indeed, these tumors produce CSF1R ligand, macrophage colony‐stimulating factor (M‐CSF) or interleukin‐34 (IL‐34). However, the significance of these cytokines, particularly, the newly discovered IL‐34 in haematological malignancies, is not fully understood. We therefore analysed the role of IL‐34 in diffuse large B‐cell lymphoma (DLBCL), the most common subtype of malignant lymphoma.

Methods

We analysed formalin‐fixed paraffin‐embedded lymphoma tissues of 135 DLBCL patients for the expression of IL‐34 and the number of macrophages, and the survival of these patients. The expression of IL‐34 in DLBCL cell lines and the activity of IL‐34 to induce the migration of monocytic cells were also characterised.

Results

Several lymphoma tissues showed a clear IL‐34 signal, and such signal was detectable in 36% of patients. DLBCL cell lines also expressed IL‐34. Interestingly, the percentage of IL‐34⁺ patients in the activated B‐cell subtype was significantly higher than that in the germinal centre B‐cell subtype. More interestingly, IL‐34⁺ patients showed shorter survival periods and higher number of macrophages in lymphoma tissues. The recruitment of monocytes is likely the first step for the higher macrophage density in the IL‐34⁺ lymphoma tissues. Indeed, IL‐34 induced the migration of monocytic cells.

Conclusion

Our results raise the possibility that IL‐34 in lymphoma tissues of DLBCL patients recruits monocytes, leading to the higher number of macrophages in the tissues and poor prognosis of patients. IL‐34 may be an additional therapeutic target of DLBCL.

Automated macrophage counting in DLBCL tissue samples: a ROF filter based approach

BACKGROUND

For analysis of the tumor microenvironment in diffuse large B-cell lymphoma (DLBCL) tissue samples, it is desirable to obtain information about counts and distribution of different macrophage subtypes. Until now, macrophage counts are mostly inferred from gene expression analysis of whole tissue sections, providing only indirect information. Direct analysis of immunohistochemically (IHC) fluorescence stained tissue samples is confronted with several difficulties, e.g. high variability of shape and size of target macrophages and strongly inhomogeneous intensity of staining. Consequently, application of commercial software is largely restricted to very rough analysis modes, and most macrophage counts are still obtained by manual counting in microarrays or high power fields, thus failing to represent the heterogeneity of tumor microenvironment adequately.

METHODS

We describe a Rudin-Osher-Fatemi (ROF) filter based segmentation approach for whole tissue samples, combining floating intensity thresholding and rule-based feature detection. Method is validated against manual counts and compared with two commercial software kits (Tissue Studio 64, Definiens AG, and Halo, Indica Labs) and a straightforward machine-learning approach in a set of 50 test images. Further, the novel method and both commercial packages are applied to a set of 44 whole tissue sections. Outputs are compared with gene expression data available for the same tissue samples. Finally, the ROF based method is applied to 44 expert-specified tumor subregions for testing selection and subsampling strategies.

RESULTS

Among all tested methods, the novel approach is best correlated with manual count (0.9297). Automated detection of evaluation subregions proved to be fully reliable. Comparison with gene expression data obtained for the same tissue samples reveals only moderate to low correlation levels. Subsampling within tumor subregions is possible with results almost identical to full sampling. Mean macrophage size in tumor subregions is 152.5±111.3 μm2.

CONCLUSIONS

ROF based approach is successfully applied to detection of IHC stained macrophages in DLBCL tissue samples. The method competes well with existing commercial software kits. In difference to them, it is fully automated, externally repeatable, independent on training data and completely documented. Comparison with gene expression data indicates that image morphometry constitutes an independent source of information about antibody-polarized macrophage occurence and distribution.

Targeting the Immune Microenvironment in Lymphomas of B-Cell Origin: From Biology to Clinical Application

In lymphomas of B-cell origin, cancer cells orchestrate an inflammatory microenvironment of immune and stromal cells that sustain the tumor cell survival and growth, known as a tumor microenvironment (TME). The features of the TME differ between the different lymphoma types, ranging from extremely inflammatory, such as in Hodgkin lymphoma, to anergic, leading to immune deficiency and susceptibility to infections, such as in chronic lymphocytic leukemia. Understanding the characteristic features of the TME as well as the interactions between cancer and TME cells has given insight into the pathogenesis of most lymphomas and contributed to identify novel therapeutic targets. Here, we summarize the preclinical data that contributed to clarifying the role of the immune cells in the TME of different types of lymphomas of B-cell origin, and explain how the understanding of the biological background has led to new clinical applications. Moreover, we provide an overview of the clinical results of trials that assessed the safety and efficacy of drugs directly targeting TME immune cells in lymphoma patients.

NSE from diffuse large B-cell lymphoma cells regulates macrophage polarization

Background/aims: Diffuse large B-cell lymphoma (DLBCL) is a highly common type of malignant and heterogeneous non-Hodgkin's lymphoma. Tumor-associated macrophages, specially the M2-type, promote tumor progression and drug resistance. The clinical outcome of patients with high neuron-specific enolase (NSE) expression is worse than that with low NSE expression. The tumor-promoting mechanism of NSE, however, remains unclear. This study explored the role of NSE in macrophage polarization associated with the immune microenvironment of DLBCL. Results: Our results showed that NSE protein expression was higher in lymphoma cell lines than in the B lymphocytes. Functional studies demonstrated that upregulation of NSE in lymphoma cells could promote M2 polarization and migration ability of macrophage, thereby consequently promoting the progression of lymphoma in vitro and in vivo. Further mechanism studies revealed that lymphoma-derived exosomes could mediate NSE into macrophages, NSE enhanced nuclear p50 translocation with subsequent defective classical nuclear factor-κB activity in macrophages. Conclusions: These results indicate that NSE may be a potential target for lymphoma therapy and a prognosis marker for lymphoma.

slan+ Monocytes and Macrophages Mediate CD20-Dependent B-cell Lymphoma Elimination via ADCC and ADCP

Terminal tissue differentiation and function of slan⁺ monocytes in cancer is largely unexplored. Our recent studies demonstrated that slan⁺ monocytes differentiate into a distinct subset of dendritic cells (DC) in human tonsils and that slan⁺ cells colonize metastatic carcinoma-draining lymph nodes. Herein, we report by retrospective analysis of multi-institutional cohorts that slan⁺ cells infiltrate various types of non-Hodgkin lymphomas (NHL), particularly the diffuse large B-cell lymphoma (DLBCL) group, including the most aggressive, nodal and extranodal, forms. Nodal slan⁺ cells displayed features of either immature DC or macrophages, in the latter case ingesting tumor cells and apoptotic bodies. We also found in patients with DLBCL that peripheral blood slan⁺ monocytes, but not CD14⁺ monocytes, increased in number and displayed highly efficient rituximab-mediated antibody-dependent cellular cytotoxicity, almost equivalent to that exerted by NK cells. Notably, slan⁺ monocytes cultured in conditioned medium from nodal DLBCL (DCM) acquired a macrophage-like phenotype, retained CD16 expression, and became very efficient in rituximab-mediated antibody-dependent cellular phagocytosis (ADCP). Macrophages derived from DCM-treated CD14⁺ monocytes performed very efficient rituximab-mediated ADCP, however, using different FcγRs from those used by slan⁺ macrophages. Our observations shed new light on the complexity of the immune microenvironment of DLBCL and demonstrate plasticity of slan⁺ monocytes homing to cancer tissues. Altogether, data identify slan⁺ monocytes and macrophages as prominent effectors of antibody-mediated tumor cell targeting in patients with DLBCL.Significance: slan⁺ monocytes differentiate into macrophages that function as prominent effectors of antibody-mediated tumor cell targeting in lymphoma.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/13/3544/F1.large.jpg Cancer Res; 78(13); 3544-59. ©2018 AACR.

Mechanisms of PD-1/PD-L1 expression and prognostic relevance in non-Hodgkin lymphoma: a summary of immunohistochemical studies

Immune checkpoint blockade therapeutics, notably antibodies targeting the programmed death 1 (PD-1) receptor and its PD-L1 and PD-L2 ligands, are currently revolutionizing the treatment of cancer. For a sizeable fraction of patients with melanoma, lung, kidney and several other solid cancers, monoclonal antibodies that neutralize the interactions of the PD-1/PD-L1 complex allow the reconstitution of long-lasting antitumor immunity. In hematological malignancies this novel therapeutic strategy is far less documented, although promising clinical responses have been seen in refractory and relapsed Hodgkin lymphoma patients. This review describes our current knowledge of PD-1 and PD-L1 expression, as reported by immunohistochemical staining in both non-Hodgkin lymphoma cells and their surrounding immune cells. Here, we discuss the multiple intrinsic and extrinsic mechanisms by which both T and B cell lymphomas up-regulate the PD-1/PD-L1 axis, and review current knowledge about the prognostic significance of its immunohistochemical detection. This body of literature establishes the cell surface expression of PD-1/PD-L1 as a critical determinant for the identification of non-Hodgkin lymphoma patients eligible for immune checkpoint blockade therapies.

Targeting B cell receptor signalling in cancer: preclinical and clinical advances

B cell receptor (BCR) signalling is crucial for normal B cell development and adaptive immunity. BCR signalling also supports the survival and growth of malignant B cells in patients with B cell leukaemias or lymphomas. The mechanism of BCR pathway activation in these diseases includes continuous BCR stimulation by microbial antigens or autoantigens present in the tissue microenvironment, activating mutations within the BCR complex or downstream signalling components and ligand-independent tonic BCR signalling. The most established agents targeting BCR signalling are Bruton tyrosine kinase (BTK) inhibitors and PI3K isoform-specific inhibitors, and their introduction into the clinic is rapidly changing how B cell malignancies are treated. B cells and BCR-related kinases, such as BTK, also play a role in the microenvironment of solid tumours, such as squamous cell carcinoma and pancreatic cancer, and therefore targeting B cells or BCR-related kinases may have anticancer activity beyond B cell malignancies.

Immune cells regulate VEGF signalling via release of VEGF and antagonistic soluble VEGF receptor-1

Vascular endothelial growth factor (VEGF) is an important regulator of physiological and pathological angiogenesis. Besides malignant and stromal cells, local immune cells shape VEGF signalling in the tumour microenvironment. Aminobisphosphonates such as zoledronic acid (Zol) are drugs known to inhibit osteoclast activity and bone resorption, but also have immunomodulatory and anti-tumour effects. These properties have been linked previously to the down-regulation of VEGF and interference with tumour neo-angiogenesis. It was therefore surprising to find that treatment with Zol in combination with low-dose interleukin (IL)-2 increased serum VEGF levels in cancer patients. In this study we aimed to characterize the effect of Zol and IL-2 on VEGF signalling of blood-derived immune cells in vitro. Upon stimulation with IL-2, T cells and natural killer (NK) cells increase production of VEGF consecutively to the release of proinflammatory interferon (IFN)-γ, and Zol accelerates this response specifically in γδ T cells. VEGF can, in turn, be antagonized by soluble VEGF receptor (sVEGFR)-1, which is released depending on stimulatory conditions and the presence of monocytes. Additionally, malignant cells represented by leukaemia and lymphoma cell lines produce VEGF and some release sVEGFR-1 simultaneously. Our findings indicate a mechanism by which the VEGF and the sVEGFR-1 production by immune cells regulates local VEGF signalling. Therefore, immunotherapeutic interventions may enable both pro- as well as anti-tumour effects via immune cell-mediated alterations of VEGF homeostasis.

Role of the microenvironment across histological subtypes of NHL

Recent progress in next-generation sequencing strategies has revealed the genetic landscape of B-cell non-Hodgkin lymphoma, but the tumor microenvironment is increasingly recognized as crucial to sustaining malignant B-cell survival and growth, subclonal evolution, and drug resistance. The tumor niche is made up of a dynamic and organized network of strongly heterogeneous immune and stromal cell subsets characterized by specific phenotypic, transcriptomic, and functional features. Nonmalignant cell recruitment and plasticity are dictated by lymphoma B cells, which convert their surrounding microenvironment into a supportive niche. In addition, they are also influenced by the crosstalk between the various components of this niche. In agreement with this, the B-cell lymphoma subtype is a key determinant of the organization of the tumor niche, but genetic alteration patterns, tumor localization, stage of the disease, and treatment strategy may also modulate its composition and activity. Moreover, the complex set of bidirectional interactions between B cells and their microenvironment has been proposed as a promising therapeutic target with the aim of reinforcing antitumor immunity and/or of abbrogating the lymphoma-promoting signals delivered by the tumor niche.

Regulatory myeloid cells: an underexplored continent in B-cell lymphomas

In lymphomas arising from the germinal center, prognostic factors are linked to the myeloid compartment. In particular, high circulating monocyte or myeloid-derived suppressor cell counts are associated with poor prognosis for patients with high-grade B-cell lymphomas. Macrophages with an M2 phenotype are enriched within lymphoma tumors. However, the M1/M2 nomenclature is now deprecated and the clinical impact of this phenotype remains controversial. Across cancer types, myeloid cells are primarily thought to function as immune suppressors during tumor initiation and maintenance, but the biological mechanisms behind the myeloid signatures are still poorly understood in germinal center B-cell lymphomas. Herein, we describe the role and clinical relevance of myeloid cells in B-cell lymphoma and propose innovative approaches to decipher this complex cellular compartment. Indeed, characterization of this heterogeneous cell ecosystem has been largely accomplished with "low-resolution" approaches like morphological evaluation and immunohistochemistry, where cells are characterized using a few proteins and qualitative metrics. High-resolution, quantitative approaches, such as mass cytometry, are valuable to better understand myeloid cell diversity, functions, and to identify potential targets for novel therapies.

Implications of infiltrating immune cells within bone marrow of patients with diffuse large B-cell lymphoma

The implications of infiltrating immune cells, especially T cells and macrophages, in the bone marrow (BM) microenvironment of patients with diffuse large B-cell lymphoma (DLBCL) have rarely been studied. We aimed to investigate the significance of infiltrating immune cells in the BM microenvironment as a prognostic factor for DLBCL patients. Using the initial pretreatment BM biopsy obtained from 198 DLBCL patients, we semiquantitatively evaluated CD3+ T cells, CD8+ T cells, and CD163+ macrophages that infiltrate into the paratrabecular and interstitial areas of BM by immunohistochemistry and analyzed their clinicopathological and prognostic implications. Levels of infiltrating CD3+ T cells, CD8+ T cells, and CD163+ macrophages were significantly higher in BM with DLBCL involvement (BMI-positive group) than in that without DLBCL involvement (BMI-negative group). Infiltration of CD8+ T cells significantly increased in cases with advanced Ann Arbor stage, elevated lactate dehydrogenase level, extranodal site involvement ≥2 sites, higher Eastern Cooperative Oncology Group performance status, and higher International Prognostic Index (IPI) risk. High levels of CD3+ T cells were significantly associated with age ≤60, and high levels of CD163+ macrophages were associated with advanced Ann Arbor stage and higher IPI risk. High infiltration of CD8+ T cells was significantly related to inferior overall and recurrence-free survival rate, even in the BMI-negative group. High infiltration of CD8+ T cells within the pretreatment BM was related to poor prognosis, and might be a useful prognostic factor of DLBCL patients. Therefore, evaluation of CD8+ T cells is helpful for predicting prognosis in initial pretreatment BM biopsy of DLBCL patients.

Tumor-Associated Macrophages Can Contribute to Antitumor Activity through FcγR-Mediated Processing of Antibody-Drug Conjugates

The primary mechanism of antibody-drug conjugates (ADC) is targeted delivery of a cytotoxic payload to tumor cells via cancer-associated membrane receptors. However, the tumor microenvironment likely plays a role in ADC penetration, distribution, and processing and thus impacts the overall antitumor activity. Here, we report on the potential contribution of Fc-FcγR interactions between ADCs and tumor-associated macrophages (TAM) to the preclinical antitumor activities of ADCs. In the CD30⁺ L-428 Hodgkin lymphoma model, anti-CD30-vcMMAE and a non-binding control (hIgG-vcMMAE) demonstrated similar antitumor activity as well as similar payload release in the tumors. IHC analysis revealed L-428 tumors contained highly abundant TAMs, which were confirmed to bind ADCs by IHC and flow cytometry. The infiltration of TAMs was further found to correlate with the antitumor activity of the non-binding hIgG-vcMMAE in five additional xenograft models. hIgG1V1-vcMMAE, bearing a mutation in the Fc region which ablates Fc gamma receptor (FcγR) binding, lost antitumor activity in three TAM-high xenograft models, suggesting Fc-FcγR interactions modulate the TAM-ADC interaction. Our results suggest that TAMs can contribute to ADC processing through FcγR interaction in preclinical tumor models and may represent an important additional mechanism for drug release from ADCs. Correlative studies in clinical trials will further shed light on whether TAMs play a role in patients' response to ADC therapies. Mol Cancer Ther; 16(7); 1347-54. ©2017 AACR.

Cutaneous T-Cell Lymphoma: A Review with a Focus on Targeted Agents

Cutaneous T-cell lymphomas (CTCLs) are a heterogeneous group of extranodal lymphomas involving the skin. Diagnosis of the two main subtypes of CTCL-mycosis fungoides (MF) and Sézary syndrome (SS)-is based on the International Society for Cutaneous Lymphomas/European Organization for Research and Treatment of Cancer (ISCL/EORTC) classification system, which utilizes clinical, histopathological, molecular biologic, and immunopathologic features. Risk stratification, based on TNMB (tumor, node, metastasis, and blood) staging, provides prognostic information, with limited-stage disease conferring the longest median overall survival. Skin-directed therapies are preferred in the management of limited-stage disease, whereas advanced-stage disease requires systemic therapies. As the mechanisms of CTCL pathogenesis are increasingly understood, new monoclonal antibodies, checkpoint inhibitors, immunomodulatory agents, and small molecules are under investigation and may provide additional therapeutic options for those with advanced CTCL. This review examines the current landscape of targeted therapies in the treatment of CTCLs.

High numbers of CD68+ tumor-associated macrophages correlate with poor prognosis in extranodal NK/T-cell lymphoma, nasal type

Many studies have demonstrated that tumor-associated macrophages (TAMs) were a prognostic indicator in patients with B cell lymphoma. But, we know little about the clinical significance of TAMs in extranodal natural killer/T cell lymphoma(ENKTL), nasal type. CD68 expression was detected using immunohistochemistry to determine the numbers of TAMs in 70 ENKTL patients, and the data were used to evaluate its relationship with clinicopathological features, treatment response, and prognosis. Patients with high number of infiltrated CD68+ TAMs (>60/hpf) at diagnosis tended to have more adverse clinical characteristics. Patients with low CD68+ TAM content (<60/hpf) at diagnosis had better overall survival (P = 0.003) and progression-free survival (P = 0.002) and achieved higher complete remission rates (P = 0.008). Multivariate analysis revealed that CD68 + TAM content, Ki-67 index, and stage III and IV were independent prognostic factors for both OS and PFS. Using the International Prognostic Index or Korean Prognostic Index for extranodal NK/T cell lymphoma, nasal type, the majority of patients were in the low-risk category. CD68 + TAM content was helpful to differentiate the low-risk patients with different survival outcomes. Our data suggest that CD68+ TAM content at diagnosis is a powerful predictor of prognosis for ENKTL, which suggests a role for TAMs in the pathogenesis of this disease and offers new insight into potential therapeutic strategies.