Follicular Lymphoma: The Role of the Tumor Microenvironment in Prognosis

An evaluation of epcoritamab as a treatment for relapsed or refractory follicular lymphoma

INTRODUCTION

The treatment landscape for relapsed refractory (RR) follicular lymphoma (FL) is rapidly evolving, and chemo-free immunotherapeutic strategies represent the major players in the field. CD20×CD3 bispecific antibodies are effective and easily manageable agents that are able to redirect the cytotoxic activity of T-cells against lymphoma cells by creating an immunological synapse.

AREAS COVERED

In this paper we will review the efficacy and safety profile of the bispecific antibody epcoritamab in RR FL, either as monotherapy (as it was recently approved in the United States and Europe) and in combination with other agents. We will discuss its potential role among the existing treatment options in this setting, particularly in relation with other approved bispecific antibodies and with CAR-T cell therapy. Presented data were obtained by literature search on PubMed and updated with most recent evidence presented at international hematology meetings (2022-2024).

EXPERT OPINION

The optimal treatment sequencing in FL is still an open issue; however, epcoritamab effectively combines key aspects such as high, rapid and durable responses, good tolerability, predictable cytokine release syndrome (CRS) kinetics, and ease of administration, representing an appealing option for patients and clinicians. Future efforts should aim at positioning epcoritamab-based treatments in earlier lines of FL.

A phase 2 study of frontline pembrolizumab in follicular lymphoma

Background

The tumor microenvironment (TME), including infiltrating T-cells, is thought to play a major role in the pathogenesis and prognosis of follicular lymphoma (FL) and may contribute to its widely varied disease course. We hypothesized that programmed death-1 inhibition may be most effective in untreated, immunocompetent FL patients. Thus, we developed a phase 2 study to evaluate the efficacy of pembrolizumab as the initial treatment for indolent B-cell lymphoma.

Methods

Adults with FL or marginal zone lymphoma and an indication for treatment were eligible. Patients received pembrolizumab 200 mg IV in 21-day cycles for up to 18 cycles, until progression or unacceptable toxicity. Early response assessment was obtained after cycle 3 with computed tomography (CT), and a fluorodeoxyglucose (FDG)-positron emission tomography-computed tomography (PET-CT) was obtained after cycle 6 to determine candidacy for continuation in the study. Immunosecretome profiling was performed at baseline and on cycle 2 day 1.

Results

Nine patients with FL were enrolled between February 2019 and April 2021, including eight (89%) with advanced stage, seven (78%) with intermediate/high Follicular Lymphoma International Prognostic Index, and six (67%) with high-tumor burden by Groupe d'Etude des Lymphomes Folliculaires. The best overall response rate by FDG PET-CT was 33% (three partial metabolic responses). Three patients (33%) had stable disease, and three (33%) had progressive disease (including one patient who only had a follow-up CT). By CT four (44%) experienced a reduction in target lesions, but all were less than partial responses. Grade 3 or higher immune-related adverse events (IRAEs) were seen in two (22%) patients, both with transaminitis and one of whom had concurrent hypophysitis. Another patient had grade 1 pneumonitis, requiring treatment with steroids. No associations between the immunosecretome profile and clinical outcomes could be detected.

Conclusion

Frontline pembrolizumab for FL is associated with limited responses and a clinically significant rate of IRAEs. Alternative strategies for targeting the TME in FL should be explored.

Impact of positive CD4 cells on event-free survival in follicular lymphoma patients

OBJECTIVE

Previous results about prognostic value of CD4+ T cells in follicular lymphoma (FL) remain controversial.

METHODS

Immunohistochemistry was used to examine expression of positive CD4 cells in 103 patients with FL 1-3A. Early failure was described as failing to achieve event-free survival (EFS) at 12 or 24 months.

RESULTS

There were 49 (47.6%) male and 54 (52.4%) females, with a median age of 54 years. Compared to patients with <20% of positive CD4 cells, patients with ≥20% of positive CD4 cells exhibited a significant lower risk of early failure (2-year EFS rate: 56.7% vs 73.5%, p = 0.047). When patients were stratified based on positive CD4 cell combined with FLIPI, the median EFS (p = 0.002) and median OS (p = 0.007) were significantly different.

CONCLUSIONS

This study demonstrated that higher expression of positive CD4 cells predicts lower risk of early failure in follicular lymphoma, and combination analysis of CD4 and FLIPI could better predict disease relapse and survival outcome.

Molecular Pathology of Mature Lymphoid Malignancies

Lymphoid malignancies are a broad and heterogeneous group of neoplasms. In the past decade, the genetic landscape of these tumors has been explored and cataloged in fine detail offering a glimpse into the mechanisms of lymphomagenesis and new opportunities to translate these findings into patient management. A myriad of studies have demonstrated both distinctive and overlapping molecular and chromosomal abnormalities that have influenced the diagnosis and classification of lymphoma, disease prognosis, and treatment selection.

STAT6 mutations enriched at diffuse large B-cell lymphoma relapse reshape the tumor microenvironment

Diffuse large B-cell lymphoma (DLBCL) relapses in approximately 40% of patients following frontline therapy. We reported that STAT6D419 mutations are enriched in relapsed/refractory DLBCL (rrDLBCL) samples, suggesting that JAK/STAT signaling plays a role in therapeutic resistance. We hypothesized that STAT6D419 mutations can improve DLBCL cell survival by reprogramming the microenvironment to sustain STAT6 activation. Thus, we investigated the role of STAT6D419 mutations on DLBCL cell growth and its microenvironment. We found that phospho-STAT6D419N was retained in the nucleus longer than phospho-STAT6WT following IL-4 stimulation, and STAT6D419N recognized a more restricted DNA-consensus sequence than STAT6WT. Upon IL-4 induction, STAT6D419N expression led to a higher magnitude of gene expression changes, but in a more selective list of gene targets compared with STATWT. The most significantly expressed genes induced by STAT6D419N were those implicated in survival, proliferation, migration, and chemotaxis, in particular CCL17. This chemokine, also known as TARC, attracts helper T-cells to the tumor microenvironment, especially in Hodgkin's lymphoma. To this end, in DLBCL, phospho-STAT6+ rrDLBCL cells had a greater proportion of infiltrating CD4+ T-cells than phospho-STAT6- tumors. Our findings suggest that STAT6D419 mutations in DLBCL lead to cell autonomous changes, enhanced signaling, and altered composition of the tumor microenvironment.

T-cell phenotype including CD57+ T follicular helper cells in the tumor microenvironment correlate with a poor outcome in follicular lymphoma

T-lymphocytes are prevalent in the tumor microenvironment of follicular lymphoma (FL). However, the phenotype of T-cells may vary, and the prevalence of certain T-cell subsets may influence tumor biology and patient survival. We therefore analyzed a cohort of 82 FL patients using CyTOF to determine whether specific T-cell phenotypes were associated with distinct tumor microenvironments and patient outcome. We identified four immune subgroups with differing T-cell phenotypes and the prevalence of certain T-cell subsets was associated with patient survival. Patients with increased T cells with early differentiation stage tended to have a significantly better survival than patients with increased T-cells of late differentiation stage. Specifically, CD57+ TFH cells, with a late-stage differentiation phenotype, were significantly more abundant in FL patients who had early disease progression and therefore correlated with an inferior survival. Single cell analysis (CITE-seq) revealed that CD57+ TFH cells exhibited a substantially different transcriptome from CD57- TFH cells with upregulation of inflammatory pathways, evidence of immune exhaustion and susceptibility to apoptosis. Taken together, our results show that different tumor microenvironments among FL patients are associated with variable T-cell phenotypes and an increased prevalence of CD57+ TFH cells is associated with poor patient survival.

Characterization of immune exhaustion and suppression in the tumor microenvironment of splenic marginal zone lymphoma

The role of the tumor microenvironment (TME) and intratumoral T cells in splenic marginal zone lymphoma (sMZL) is largely unknown. In the present study, we evaluated 36 sMZL spleen specimens by single cell analysis to gain a better understanding of the TME in sMZL. Using mass cytometry (CyTOF), we observed that the TME in sMZL is distinct from that of control non-malignant reactive spleen (rSP). We found that the number of TFH cells varied greatly in sMZL, ICOS+ TFH cells were more abundant in sMZL than rSP, and TFH cells positively correlated with increased numbers of memory B cells. Treg cell analysis revealed that TIGIT+ Treg cells are enriched in sMZL and correlate with suppression of TH17 and TH22 cells. Intratumoral CD8+ T cells were comprised of subsets of short-lived, exhausted and late-stage differentiated cells, thereby functionally impaired. We observed that T-cell exhaustion was present in sMZL and TIM-3 expression on PD-1low cells identified cells with severe immune dysfunction. Gene expression profiling by CITE-seq analysis validated this finding. Taken together, our data suggest that the TME as a whole, and T-cell population specifically, are heterogenous in sMZL and immune exhaustion is one of the major factors impairing T-cell function.

Novel targeted drugs for follicular and marginal zone lymphoma: a comprehensive review

Although mostly incurable, indolent non-Hodgkin lymphomas (iNHL) are chronic diseases with a median overall survival approaching 20 years. In recent years, important advances in the knowledge of the biology of these lymphomas have led to the development of new drugs, mostly chemotherapy-free, with promising outcomes. With a median age of around 70 years at diagnosis, many patients with iNHL suffer from comorbid conditions that may limit treatment options. Therefore, nowadays, in the transition towards personalized medicine, several challenges lie ahead, such as identifying predictive markers for the selection of treatment, the adequate sequencing of available therapies, and the management of new and accumulated toxicities. In this review, we include a perspective on recent therapeutic advances in follicular and marginal zone lymphoma. We describe emerging data on approved and emerging novel therapies, such as targeted therapies (PI3K inhibitors, BTK inhibitors, EZH2 inhibitors), monoclonal antibodies and antibody-drug conjugates. Finally, we describe immune-directed approaches such as combinations with lenalidomide or the even more innovative bispecific T-cell engagers and chimeric antigen receptor T-cell therapy, which can achieve a high rate of durable responses with manageable toxicities, further obviating the need for chemotherapy.

Assessing the frequency of CD163+ tumor-associated macrophages and CD3+ T lymphocytes between MGUS and plasma cell myeloma

Plasma cell dyscrasias (PCDs) are a heterogeneous group of diseases, and the most common is monoclonal gammopathy of undetermined significance (MGUS). This premalignant PCD consistently precedes multiple myeloma (MM), with a 1% risk of progression per year. Evading and suppressing the host immune system is an important step in the progression of MGUS to MM. This pilot study was designed to assess whether MGUS and MM have a distinct microenvironment, characterized by a unique distribution of immune cells, including tumor-associated macrophages. Evaluation of bone marrow (BM) tumor microenvironment was performed using immunohistochemical quantification of T cells (CD3), macrophages (CD68), and a macrophage subtype (CD163). The findings were compared between MGUS and MM to determine whether differences existed. The results suggest that there is a significantly lower percentage of CD3-positive, CD68-positive and CD163-positive immune effector cells in BM trephine biopsy samples from patients with MGUS than in those from patients with untreated MM (p < 0.001). Interestingly, in a patient treated for MM, the percentages of CD3+ and CD68+ cells were the same as those in other patients with untreated MM; however, the percentage of CD163+ cells reduced and correlated with low plasma cell count. Future studies are required to investigate whether the percentage of CD163+ cells is correlated with disease burden in patients with MM. If this is the case, then the level of soluble CD163 in plasma could be a potential biomarker of disease burden in patients with nonsecretory myelomas, in whom measurements of levels of paraprotein and free light chains are inconclusive.

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.

Clinical usefulness of a novel classification of T cell distribution patterns in the tumor microenvironment of follicular lymphoma to detect transformation

The clinical course of follicular lymphoma (FL) is thought to be influenced by the infiltrating immune cells in the tumor microenvironment. Focusing on the distribution patterns of T cells may be a promising approach to estimate the prognosis of FL, especially histological transformation. This study was a retrospectively cohort study in the relationship between the pathological distribution pattern of T cells in the tumor microenvironment and clinical course of FL. One hundred twenty-eight patients with FL initially diagnosed at the University of Tokyo Hospital from January 2008 to January 2017 were evaluated. We classified each patient's specimen at initial diagnosis by the distribution pattern of tumor infiltrating CD3-positive cells, intra-follicle focal (IFF), intra-follicle diffuse (IFD), extra-follicle marginal (EFM), and extra-follicle diffuse (EFD). We analyzed the distribution pattern's correlation with other prognostic factors including overall survival (OS), progression free survival (PFS), and transformation. Among 128 cases, 81 had evaluable pathological specimen. Based on our criteria, in the intra-follicle,17 cases (21%) were classified as IFF. Sixty-four cases (79%) were classified as IFD. In the extra follicle, 25 cases (31%) were classified as EFM. Fifty-six cases (69%) were classified as EFD. There was significant difference in risk of transformation between the EFM and EFD around extra-follicle area in the adjusted model (p < 0.05). Also, cases with IFF and EFM had significantly higher risk of transformation compared to cases with other T cell distribution patterns (p < 0.01). We proposed a new classification of CD3-positive T cell distribution patterns around the follicle lesions in FL and demonstrated its clinical significance.

Molecular Cytogenetic Profiling Reveals Similarities and Differences Between Localized Nodal and Systemic Follicular Lymphomas

Recently, we have developed novel highly promising gene expression (GE) classifiers discriminating localized nodal (LFL) from systemic follicular lymphoma (SFL) with prognostic impact. However, few data are available in LFL especially concerning hotspot genetic alterations that are associated with the pathogenesis and prognosis of SFL. A total of 144 LFL and 527 SFL, enrolled in prospective clinical trials of the German Low Grade Lymphoma Study Group, were analyzed by fluorescence in situ hybridization to detect deletions in chromosomes 1p, 6q, and 17p as well as BCL2 translocations to determine their impact on clinical outcome of LFL patients. The frequency of chromosomal deletions in 1p and 17p was comparable between LFL and SFL, while 6q deletions and BCL2 translocations more frequently occurred in SFL. A higher proportion of 1p deletions was seen in BCL2-translocation–positive LFL, compared with BCL2-translocation–negative LFL. Deletions in chromosomes 1p, 6q, and 17p predicted clinical outcome of patients with SFL in the entire cohort, while only deletions in chromosome 1p retained its negative prognostic impact in R-CHOP–treated SFL. In contrast, no deletions in one of the investigated genetic loci predicted clinical outcome in LFL. Likewise, the presence or absence of BCL2 translocations had no prognostic impact in LFL. Despite representing a genetic portfolio closely resembling SFL, LFL showed some differences in deletion frequencies. BCL2 translocation and 6q deletion frequency differs between LFL and SFL and might contribute to distinct genetic profiles in LFL and SFL.

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.

The follicular lymphoma epigenome regulates its microenvironment

Follicular lymphoma (FL) is a B-cell non-Hodgkin lymphoma of germinal center (GC) origin with a distinctive tumor microenvironment (TME) and a unique spectrum of mutations. Despite the important therapeutic advances, FL is still incurable. During B-cell development, the GC reaction is a complex multistep process in which epigenetic regulators dynamically induce or suppress transcriptional programs. In FL, epigenetic gene mutations perturb the regulation of these programs, changing GC B-cell function and skewing differentiation towards tumor cells and altering the microenvironment interactions. FL pathogenesis and malignant transformation are promoted by epigenetic reprogramming of GC B cells that alters the immunological synapse and niche. Despite the extensive characterization of FL epigenetic signature and TME, the functional consequences of epigenetic dysregulation on TME and niche plasticity need to be better characterized. In this review, first we describe the most frequent epigenomic alterations in FL (KMT2D, CREBBP and EZH2) that affect the immunological niche, and their potential consequences on the informational transfer between tumor B cells and their microenvironment. Then, we discuss the latest progress to harness epigenetic targets for inhibiting the FL microenvironment. Finally, we highlight unexplored research areas and outstanding questions that should be considered for a successful long-term treatment of FL.

Phase 1/2 study of intratumoral G100 (TLR4 agonist) with or without pembrolizumab in follicular lymphoma

Intratumoral injection of G100, a toll-like receptor 4 (TLR4) agonist, was shown pre-clinically to stimulate anti-tumor immune responses and tumor regression. This open-label, multicenter, phase 1/2 trial evaluated the safety, tolerability, and preliminary efficacy of intratumoral G100 injections following localized low-dose radiation in patients with follicular lymphoma (ClinicalTrials.gov #NCT02501473). The study was comprised of a G100 dose escalation (5 or 10 µg/dose, or 20 µg/dose for large tumors); a randomized component comparing G100 to G100 plus pembrolizumab; and G100 20 µg/dose expansion. Adverse events grade ≥3 were uncommon in patients treated with G100, and no unexpected toxicities were observed when combined with pembrolizumab. G100 20 µg (n = 18) resulted in an overall response rate of 33.3% and abscopal tumor regression in 72.2% of patients. This early-phase study provides a foundation for combining an intratumoral TLR4 agonist with agents to produce immune-mediated responses in follicular lymphoma with limited added toxicity.

Targeting the tumor microenvironment in B-cell lymphoma: challenges and opportunities

B-cell lymphoma is a group of hematological malignancies with high clinical and biological heterogeneity. The pathogenesis of B-cell lymphoma involves a complex interaction between tumor cells and the tumor microenvironment (TME), which is composed of stromal cells and extracellular matrix. Although the roles of the TME have not been fully elucidated, accumulating evidence implies that TME is closely relevant to the origination, invasion and metastasis of B-cell lymphoma. Explorations of the TME provide distinctive insights for cancer therapy. Here, we epitomize the recent advances of TME in B-cell lymphoma and discuss its function in tumor progression and immune escape. In addition, the potential clinical value of targeting TME in B-cell lymphoma is highlighted, which is expected to pave the way for novel therapeutic strategies.

Molecular Pathology of Mature Lymphoid Malignancies

Lymphoid malignancies are a broad and heterogeneous group of neoplasms. In the past decade, the genetic landscape of these tumors has been explored and cataloged in fine detail offering a glimpse into the mechanisms of lymphomagenesis and new opportunities to translate these findings into patient management. A myriad of studies have demonstrated both distinctive and overlapping molecular and chromosomal abnormalities that have influenced the diagnosis and classification of lymphoma, disease prognosis, and treatment selection.

Expression of KLRG1 and CD127 defines distinct CD8+ subsets that differentially impact patient outcome in follicular lymphoma

Background

CD8⁺ T-lymphocyte subsets defined by killer lectin-like receptor G1 (KLRG1) and CD127 expression have been reported to have an important role in infection, but their role in the setting of lymphoid malignancies, specifically follicular lymphoma (FL), has not been studied.

Methods

To characterize the phenotype of KLRG1/CD127-defined CD8⁺ subsets, surface and intracellular markers were measured by flow cytometry and Cytometry by time of flight (CyTOF), and the transcriptional profile of these cells was determined by CITE-Seq (Cellular Indexing of Transcriptomes and Epitopes by Sequencing). The functional capacity of each subset was determined, as was their impact on overall survival (OS) and event-free survival (EFS) of patients with FL.

Results

We found that intratumoral CD8⁺ cells in FL are skewed toward effector cell subsets, particularly KLRG⁺CD127^- and KLRG1^-CD127^- cells over memory cell subsets, such as KLRG1^-CD127⁺ and KLRG1⁺CD127⁺ cells. While effector subsets exhibited increased capacity to produce cytokines/granules when compared with memory subsets, their proliferative capacity and viability were found to be substantially inferior. Clinically, a skewed distribution of intratumoral CD8⁺ T cells favoring effector subtypes was associated with an inferior outcome in patients with FL. Increased numbers of CD127⁺KLRG1^- and CD127⁺KLRG1⁺ were significantly associated with a favorable OS and EFS, while CD127^-KLRG1^- correlated with a poor EFS and OS in patients with FL. Furthermore, we demonstrated that interleukin (IL)-15 promotes CD127^-KLRG1⁺ cell development in the presence of dendritic cells via a phosphoinositide 3-kinase (PI3K)-dependent mechanism, and treatment of CD8⁺ T cells with a PI3K inhibitor downregulated the transcription factors responsible for CD127^-KLRG1⁺ differentiation.

Conclusions

Taken together, these results reveal not only a biological and prognostic role for KLRG1/CD127-defined CD8⁺ subsets in FL but also a potential role for PI3K inhibitors to manipulate the differentiation of CD8⁺ T cells, thereby promoting a more effective antitumor immune response.

Evolving therapeutic landscape in follicular lymphoma: a look at emerging and investigational therapies

Follicular Lymphoma (FL) is the most common subtype of indolent B cell non-Hodgkin lymphoma. The clinical course can be very heterogeneous with some patients being safely observed over many years without ever requiring treatment to other patients having more rapidly progressive disease requiring multiple lines of treatment for disease control. Front-line treatment of advanced FL has historically consisted of chemoimmunotherapy but has extended to immunomodulatory agents such as lenalidomide. In the relapsed setting, several exciting therapies that target the underlying biology and immune microenvironment have emerged, most notable among them include targeted therapies such as phosphoinositide-3 kinase and Enhancer of Zeste 2 Polycomb Repressive Complex 2 inhibitors and cellular therapies including chimeric antigen receptor T cells and bispecific T cell engagers. There are several combination therapies currently in clinical trials that appear promising. These therapies will likely reshape the treatment approach for patients with relapsed and refractory FL in the coming years. In this article, we provide a comprehensive review of the emerging and investigational therapies in FL and discuss how these agents will impact the therapeutic landscape in FL.

Immune infiltrate diversity confers a good prognosis in follicular lymphoma

Background

Follicular lymphoma (FL) prognosis is influenced by the composition of the tumour microenvironment. We tested an automated approach to quantitatively assess the phenotypic and spatial immune infiltrate diversity as a prognostic biomarker for FL patients.

Methods

Diagnostic biopsies were collected from 127 FL patients initially treated with rituximab-based therapy (52%), radiotherapy (28%), or active surveillance (20%). Tissue microarrays were constructed and stained using multiplex immunofluorescence (CD4, CD8, FOXP3, CD21, PD-1, CD68, and DAPI). Subsequently, sections underwent automated cell scoring and analysis of spatial interactions, defined as cells co-occurring within 30 μm. Shannon’s entropy, a metric describing species biodiversity in ecological habitats, was applied to quantify immune infiltrate diversity of cell types and spatial interactions. Immune infiltrate diversity indices were tested in multivariable Cox regression and Kaplan–Meier analysis for overall (OS) and progression-free survival (PFS).

Results

Increased diversity of cell types (HR = 0.19 95% CI 0.06–0.65, p = 0.008) and cell spatial interactions (HR = 0.39, 95% CI 0.20–0.75, p = 0.005) was associated with favourable OS, independent of the Follicular Lymphoma International Prognostic Index. In the rituximab-treated subset, the favourable trend between diversity and PFS did not reach statistical significance.

Conclusion

Multiplex immunofluorescence and Shannon’s entropy can objectively quantify immune infiltrate diversity and generate prognostic information in FL. This automated approach warrants validation in additional FL cohorts, and its applicability as a pre-treatment biomarker to identify high-risk patients should be further explored. The multiplex image dataset generated by this study is shared publicly to encourage further research on the FL microenvironment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00262-021-02945-0.

PD-1 Expression in Pre-Treatment Follicular Lymphoma Predicts the Risk of Subsequent High-Grade Transformation

Purpose

Follicular lymphoma (FL) is an indolent, yet generally incurable neoplasia with a median survival exceeding 10 years. However, a subset of FL patients experiences histological transformation (HT) to a more aggressive lymphoma, in the majority of cases to diffuse large B-cell lymphoma (DLBCL). This affects both the clinical course and the prognostic outcome, resulting in a markedly reduced survival after transformation. Thus, early risk stratification and prediction of patients at risk of HT would be highly valuable in the clinical setting. Here, we investigated the potential of the immune inhibitory programmed death 1 (PD-1) receptor as a biomarker predictive of HT.

Patients and Methods

Immunohistochemical staining and quantification by digital image analysis of PD-1 was performed on diagnostic tumor-tissue samples from FL patients with and without subsequent transformation (n=34 and n=46, respectively), and on paired samples from the transformed lymphoma (n=34).

Results

At the time of initial FL diagnosis, samples from patients with subsequent HT had significantly higher tumor-tissue expression of PD-1 compared with diagnostic FL samples from patients without subsequent HT (p=0.010). At the time of transformation, PD-1 expression was significantly reduced (p<0.001). No difference was observed in intra-follicular PD-1 expression at FL diagnosis between samples from patients with or without HT; however, high intra-follicular levels of PD-1 were associated with significantly shorter transformation-free survival times (p<0.043).

Conclusion

Our data suggest that pre-treatment tumor-tissue PD-1 expression already predicts the risk of subsequent transformation to DLBCL, as early as the time of FL diagnosis.

Gene expression profiling-based risk prediction and profiles of immune infiltration in diffuse large B-cell lymphoma

The clinical risk stratification of diffuse large B-cell lymphoma (DLBCL) relies on the International Prognostic Index (IPI) for the identification of high-risk disease. Recent studies suggest that the immune microenvironment plays a role in treatment response prediction and survival in DLBCL. This study developed a risk prediction model and evaluated the model’s biological implications in association with the estimated profiles of immune infiltration. Gene-expression profiling of 718 patients with DLBCL was done, for which RNA sequencing data and clinical covariates were obtained from Reddy et al. (2017). Using unsupervised and supervised machine learning methods to identify survival-associated gene signatures, a multivariable model of survival was constructed. Tumor-infiltrating immune cell compositions were enumerated using CIBERSORT deconvolution analysis. A four gene-signature-based score was developed that separated patients into high- and low-risk groups. The combination of the gene-expression-based score with the IPI improved the discrimination on the validation and complete sets. The gene signatures were successfully validated with the deconvolution output. Correlating the deconvolution findings with the gene signatures and risk score, CD8+ T-cells and naïve CD4+ T-cells were associated with favorable prognosis. By analyzing the gene-expression data with a systematic approach, a risk prediction model that outperforms the existing risk assessment methods was developed and validated.

Precision medicine in follicular lymphoma: Focus on predictive biomarkers

Current care for patients with follicular lymphoma (FL) offers most of them long-term survival. Improving it further will require careful patient selection. This review focuses on predictive biomarkers (ie, those whose outcome correlations depend on the treatment strategy) in FL, because awareness of what patient subsets benefit most or least from each therapy will help in this task. The first part of this review aims to summarize what biomarkers are predictive in FL, the magnitude of the effect and the quality of the evidence. We find predictive biomarkers in the setting of (a) indication of active treatment, (b) front-line induction (use of anthracyline-based regimens, CHOP vs bendamustine, addition of rituximab), (c) post-(front-line)induction (rituximab maintenance, radioimmunotherapy), and (d) relapse (hematopoietic stem cell transplant) and targeted agents. The second part of this review discusses the challenges of precision medicine in FL, including (a) cost, (b) clinical relevance considerations, and (c) difficulties over the broad implementation of biomarkers. We then provide our view on what biomarkers may become used in the next few years. We conclude by underscoring the importance of assessing the potential predictiveness of available biomarkers to improve patient care but also that there is a long road ahead before reaching their broad implementation due to remaining scientific, technological, and economic hurdles.

Absolute B cell counts in blood predict long-term response in follicular lymphoma patients treated with rituximab without chemotherapy

Rituximab monotherapy is widely used for follicular lymphoma. However, there are no established predictors for response or response duration. We analyzed the long-term prognostic relevance of pre-treatment absolute blood counts of lymphocytes with subsets and monocytes in 265 follicular lymphoma patients, uniformly treated with rituximab without chemotherapy, in two Nordic Lymphoma Group trials. There were 265 previously untreated, stage II–IV follicular lymphoma patients with a median follow-up of over 10 years. Absolute B cell counts ≥ median (0.09 × 10⁹/L) were an independent predictor for shorter time to next treatment or death (multivariable analysis P = 0.010). In univariate analysis, absolute monocyte counts ≥ median (0.5 × 10⁹/L) did not correlate with time to next treatment or death, but with inferior overall survival (P = 0.034). Absolute T cell or T cell subset counts were not predictive for outcome. High absolute B cell counts, possibly reflecting circulating lymphoma cells, have an unfavorable impact on time to next treatment or death in patients treated with rituximab without chemotherapy.

PD1 distribution pattern, regardless of the cell origin, is an independent microenvironmental prognostic factor for progression-free survival in follicular lymphoma

Follicular lymphoma (FL) is a well-studied microenvironment-dependent hematological malignancy, but the crosstalk between various involved cell subtypes is still not fully understood. Recent promising results of immunotherapy in recurrent FL warrant the need for an in-depth analysis of the expression and role of immune system-related proteins in the FL microenvironment. Seventy-one patients with FL and available diagnostic paraffin blocks were enrolled in the retrospective analysis. Histopathological diagnoses were revised according to the World Health Organization recommendations. Patients were either observed (watch and wait/W&W group) or immediately treated with chemo(immuno)therapy regimens according to their clinical status. Immunohistochemical assessment of PD1, PDL1, CD4, CD8, CD163, CD68-KP1, CD68-PGM1 was performed. The scoring methods included both semi-quantitative estimation of positive cells and architectural pattern distribution. The differences between PD1 staining distribution and intensity were classified as intra/perifollicular vs. interfollicular/diffuse cells and presented bright vs. dim immunoreactivity, respectively. No statistically significant differences in the density distribution of the immunohistochemical stainings were found between W&W and chemo(immuno)therapy groups. Interfollicular/diffuse pattern of PD1 expression had significantly decreased progression-free survival when analyzing the whole cohort and patients on chemo(immuno)therapy (p = 0.014 and p = 0.07, respectively). The high dependence was not significant in the W&W group. PD1 positivity of cells did not correlate with CD4 or CD8 immunophenotype. Morphologically FL neoplastic cells were entirely PDL1 negative, but granular and membranous staining was detected in the FL microenvironment. In line with previous studies, PD1/PDL1 expression was predominantly localized in the FL microenvironment, indicating that FL cells might not be the direct target for anti-PDL1 therapy. However, we show that the localization of PD1 expression could be a viable progression-free survival biomarker for FL.

Good prognosis for follicular lymphoma with estrogen receptor α-positive follicular dendritic cells

Follicular lymphoma (FL) has a meshwork of follicular dendritic cells (FDCs). We previously demonstrated the presence of estrogen receptor alpha (ERα)⁺CD23⁺ FDCs in grades 1‐2 FL. The significance of FDCs as a prognostic factor in FL remains unknown. The current study aimed to compare clinicopathological features, including prognosis, between FL with and without ERα⁺ FDCs. This study evaluated the clinicopathological significance of ERα expression in 70 FL patients by immunostaining. The presence of ERα mRNA on FDCs from 5 FL patients was confirmed by CD21/ERα double staining (immunohistochemistry and in situ hybridization). We defined patients with frequent ERα expression as the ERα^high group and those with infrequent ERα expression as the ERα^low group. Thirty‐two patients were assigned to the ERα^high group (45.7%), and 38 patients were assigned to the ERα^low group (54.3%). Both overall survival (OS) and progression‐free survival (PFS) were significantly better in the ERα^high group than in the ERα^low group (OS, log‐rank, P = .0465; PFS, log‐rank, P = .0336). Moreover, high ERα expression on FDCs was an independent prognostic factor for OS in both the univariate ([hazard ratio] HR, 0.163; P = .0260) and multivariate (HR, 0.050; P = .0188) analyses and for PFS in both the univariate (HR, 0.232; P = .0213) and multivariate (HR, 0.084; P = .0243) analyses. ERα mRNA expression was detected in CD21⁺ FDCs within the neoplastic follicles of FL patients. In conclusion, a neoplastic follicular microenvironment with ERα‐positive FDCs might affect the grade and presence of the follicular pattern of FL and improve patient prognosis.

B Cell Lymphoma

B cell development and activation are accompanied by dynamic genetic alterations including V(D)J rearrangements and immunoglobulin-gene somatic hypermutation and class-switch recombination. Abnormalities in these genetic events can cause chromosomal translocations and genomic mutations, leading to altered expression and function of genes involved in B cell survival or proliferation and consequently B lymphomagenesis. In fact, B cell lymphoma accounts for 95% of the lymphomas. In this chapter, we summarize the morphology, immunophenotypes, clinical features, genetic defects that cause the malignancies, treatments, and prognosis of the most prevalent types of B cell lymphomas, including typical precursor B cell malignance (B-ALL/LBL) and mature B cell lymphoma (Hodgkin lymphoma and B cell non-Hodgkin lymphoma).

Unraveling Tumor Heterogeneity in an Apparently Monolithic Disease: BCL2 and Other Players in the Genetic Landscape of Nodal Follicular Lymphoma

Follicular lymphoma (FL) is the most common form of non-Hodgkin lymphoma in Western countries. Although traditionally considered a well-defined, easy to diagnose lymphoproliferative disorder, in the last few years it has become clear that it is in fact composed of many different clinicopathological entities, encompassing a variegated and complex genetic background. This has led to the inclusion of specific FL variants and separate entities in the latest update of the WHO classification. However, even in the context of classical FL, many aspects of intra- and inter-tumoral heterogeneity have been recognized, with a major influence on diagnosis and clinical practice at different time points during the course of the disease. This review focuses on the molecular cytogenetic heterogeneity in classical FL from precursors and early development to progression and transformation, in terms of both clonal heterogeneity and unusual genetic features. Several factors have been investigated and suggested to contribute to the broad spectrum of clinicopathological, phenotypic, and genetic features observed in otherwise morphologically classical cases. Among them, deregulation of the epigenetic machinery and interactions with tumor microenvironment seem to play a pivotal role, together with genetic aberrations involving well-known molecular pathways and mechanisms physiologically operating in the germinal center. In the era of personalized medicine, precision diagnostics based both on understanding of the complex interplay among all these factors and on novel developments will become crucial to predict the outcome and guide the treatment of FL patients.

Novel risk stratification of de novo diffuse large B cell lymphoma based on tumour-infiltrating T lymphocytes evaluated by flow cytometry

The prognostic value of tumour-infiltrating T lymphocytes (TIL-Ts) has been demonstrated in many solid tumours but remained unclear in diffuse large B cell lymphoma (DLBCL). We conducted a retrospective cohort study reviewing the TIL-Ts proportion and CD4:CD8 of 66 de novo DLBCL by flow cytometry to construct a risk stratification based on TIL-Ts-related prognostic factors. In univariate analysis, low TIL-Ts (< 14%) was significantly related to shorter survival (HR = 2.58, 95% CI 1.11-5.99, p = 0.028). In multivariate analysis, low TIL-Ts (HR = 6.48, 95% CI 2.16-19.46, p = 0.001) and high CD4:CD8 (> 1.2) (HR = 4.22, 95% CI 1.43-12.35, p = 0.009) were independent risk factors. For the risk stratification, three groups were defined based on TIL-Ts-related risk factors: low-risk group (high TIL-Ts and low CD4:CD8), intermediate risk group (low TIL-Ts, low CD4:CD8 or high TIL-Ts, high CD4:CD8) and high-risk group (low TIL-Ts and high CD4:CD8). The patients in high-risk group have significantly shorter survival than that in intermediate risk group (p = 0.025) and low-risk group (p = 0.002). This new risk stratification which is independent of performance status and age of the patients could hint the prognosis and may guide treatment of DLBCL.

Recent advances in CD8+ regulatory T cell research

Various subgroups of CD8⁺ T lymphocytes do not only demonstrate cytotoxic effects, but also serve important regulatory roles in the body's immune response. In particular, CD8⁺ regulatory T cells (CD8⁺ Tregs), which possess important immunosuppressive functions, are able to effectively block the overreacting immune response and maintain the body's immune homeostasis. In recent years, studies have identified a small set of special CD8⁺ Tregs that can recognize major histocompatibility complex class Ib molecules, more specifically Qa-1 in mice and HLA-E in humans, and target the self-reactive CD4⁺ T ce lls. These findings have generated broad implications in the scientific community and attracted general interest to CD8⁺ Tregs. The present study reviews the recent research progress on CD8⁺ Tregs, including their origin, functional classification, molecular markers and underlying mechanisms of action.

Current prognostic and predictive factors in follicular lymphoma

Follicular lymphoma (FL) is generally considered an indolent disorder. With modern day treatments, long remissions are often achieved both in the front-line and relapsed setting. However, a subset of patients has a more aggressive course and a worse outcome. Their identification is the main purpose of modern day prognostic tools. In this review, we attempt to summarize the evidence concerning prognostic and predictive factors in FL, including (1) pre-treatment factors, from baseline clinical characteristics and imaging tests to histological grade, the microenvironment and genomic abnormalities; (2) post-treatment factors, i.e., depth of response, measured both by imaging tests and minimal residual disease; (3) factors at relapse and duration of response; and (4) prognostic factors in histological transformation. We conclude that, despite the existence of numerous tools, the availability of some of them is still limited; they generally suffer from notable downsides, and most have unproven predictive value, thus having scarce bearing on the choice of regimen at present. However, with the technological and scientific developments of the last few years, the potential for these prognostic factors is promising, particularly in combination, which will probably, in time, help guide therapeutic decisions.

Optimum immunohistochemical procedures for analysis of macrophages in human and mouse formalin fixed paraffin-embedded tissue samples

Macrophages are closely related to various diseases and it is therefore important that the properties of macrophages are adequately evaluated in human diseases and mouse disease models. Immunohistochemistry (IHC) of formalin fixed paraffin-embedded (FFPE) samples is a very useful tool for examination of macrophages; however, an adequate IHC protocol is required for the examination of macrophage states. In this study, we assessed various antigen retrieval methods in order to devise the optimal protocols for staining of macrophages with a range of antibodies. Optimum combinations of primary antibodies and antigen retrieval protocols were determined; for example, heat treatment with ethylenediamine tetraacetic acid solution, pH 8.0, was the best procedure for IHC using mouse anti-Iba1 and human anti-CD11b, -CD163, -CD169, -CD204, and -CD206 antibodies. Moreover, we found that the immunoreactivity of sliced tissue sections decreased gradually over time in long term storage but that this immunoreactivity was preserved in storage at -80 °C in a deep freezer. The optimal IHC protocols and storage procedures that were determined in this study should be a useful tool for macrophage research.

Stat3 inhibitor abrogates the expression of PD-1 ligands on lymphoma cell lines

Recent studies have indicated the significance of immune checkpoint molecules including programmed death-1 (PD-1), cytotoxic T-lymphocyte associated protein 4, and T-cell immunoglobulin and mucin domain-containing molecule-3 for anti-tumor immune responses. We previously investigated PD-1 ligand 1/2 (PD-L1/2) expression in lymphoma cell lines, and found that PD-L1/2 is expressed on the adult T-cell leukemia/lymphoma (ATL-T) and B-cell lymphoma (SLVL) cell lines. In the present study, we investigated whether the Stat3 inhibitor WP1066 abrogated PD-L1/2 expression in lymphoma cell lines. Incubation with WP1066 inhibited lymphoma cell growth and induced cell apoptosis. PD-L1/2 expression in the ATL-T, SLVL, and human brain malignant lymphoma (HKBML) cell lines was significantly abrogated by WP1066 treatment. These data indicated that a Stat3 inhibitor abrogated PD-L1/2 expression in lymphoma cells. Such an inhibitor is therefore considered to be useful for additional immunotherapy in patients with advanced lymphoma.

Follicular Lymphoma: The Management of Elderly Patient

Follicular lymphoma (FL) is the most common indolent non-Hodgkin lymphoma, which typically affects mature adults and elderly, whose median age at diagnosis is 65 years. The natural history of FL appears to have been favorably impacted by the introduction of Rituximab. Randomized clinical trials demonstrated that the addition of rituximab to standard chemotherapy induction has improved the overall survival and new strategies of chemo-immunotherapy, such as Bendamustine combined with Rituximab, showed optimal results on response and reduced hematological toxicity, becoming one of the standard treatments, particularly in elderly patients. Moreover, maintenance therapy with Rituximab demonstrated improvement of progression-free survival. Despite these exciting results, FL is still an incurable disease. It remains a critical unmet clinical need finding new prognostic factors to identify poor outcome patients better, to reduce the risk of transformation and to explore new treatment strategies, especially for patients not candidate to intensive chemotherapy regimens, such as elderly patients. Some progress were already reached with novel agents, but larger and more validated studies are needed. Elderly patients are the largest portion of patients with FL and represent a subgroup with higher treatment difficulties, because of comorbidities and smaller spectrum for treatment choice. Further studies, focused on elderly follicular lymphoma patients, with their peculiar characteristics, are needed to define the best-tailored treatment at diagnosis and at the time of relapse in this setting.