Molecular pathogenesis of follicular lymphoma: a cross talk of genetic and immunologic factors

Molecular Biomarkers in Prediction of High-Grade Transformation and Outcome in Patients with Follicular Lymphoma: A Comprehensive Systemic Review

Follicular lymphoma (FL) is the most prevalent indolent B-cell lymphoma entity, often characterized by the t(14;18) BCL2-IGH translocation. The malignancy represents a clinically and biologically highly heterogeneous disease. Most patients have favorable prognoses; however, despite therapeutic advancements, the disease remains incurable, with recurrent relapses or early disease progression. Moreover, transformation to an aggressive histology, most often diffuse large-B-cell lymphoma, remains a critical event in the disease course, which is associated with poor outcomes. Understanding the individual patient's risk of transformation remains challenging, which has motivated much research on novel biomarkers within the past four decades. This review systematically assessed the research on molecular biomarkers in FL transformation and outcome. Following the PRISMA guidelines for systemic reviews, the PubMed database was searched for English articles published from January 1984 through September 2024, yielding 6769 results. The identified publications were carefully screened and reviewed, of which 283 original papers met the inclusion criteria. The included studies focused on investigating molecular biomarkers as predictors of transformation or as prognostic markers of time-related endpoints (survival, progression, etc.). The effects of each biomarker were categorized based on their impact on prognosis or risk of transformation as none, favorable, or inferior. The biomarkers included genetic abnormalities, gene expression, microRNAs, markers of B cells/FL tumor cells, markers of the tumor microenvironment, and soluble biomarkers. This comprehensive review provides an overview of the research conducted in the past four decades, underscoring the persistent challenge in risk anticipation of FL patients.

Follicular helper T cells: emerging roles in lymphomagenesis

Follicular helper T cells are a subset of CD4+ T cells that are fundamental to forming germinal centers, which are the primary sites of antibody affinity maturation and the proliferation of activated B cells. Follicular helper T cells have been extensively studied over the past 10 years, especially regarding their roles in cancer genesis. This review describes the characteristics of normal follicular helper T cells and focuses on the emerging link between follicular helper T cells and lymphomagenesis. Advances in lymphoma genetics have substantially expanded our understanding of the role of follicular helper T cells in lymphomagenesis. Moreover, we detail a range of agents and new therapies, with a major focus on chimeric antigen receptor T-cell therapy; these novel approaches may offer new treatment opportunities for patients with lymphomas.

Circulating Tumor DNA as a Complementary Prognostic Biomarker during CAR-T Therapy in B-Cell Non-Hodgkin Lymphomas

The emergence of CD19-directed chimeric antigen receptor T-cell (CAR-T) therapy has revolutionized the treatment paradigm for R/R B-cell NHLs. However, challenges persist in accurately evaluating treatment response and detecting early relapse, necessitating the exploration of novel biomarkers. Circulating tumor DNA (ctDNA) via liquid biopsy is a non-invasive tool for monitoring therapy efficacy and predicting treatment outcomes in B-NHL following CAR-T therapy. By overcoming the limitations of conventional imaging modalities, ctDNA assessments offer valuable insights into response dynamics, molecular mechanisms of resistance, and early detection of molecular relapse. Integration of ctDNA monitoring into clinical practice holds promise for personalized therapeutic strategies, guiding the development of novel targeted therapies, and enhancing patient outcomes. However, standardization of assay methodologies and consensus on clinical response metrics are imperative to unlock the full potential of ctDNA in the management of B-NHL. Prospective validation of ctDNA in clinical trials is necessary to establish its role as a complementary decision aid.

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.

LINC00892 Is an lncRNA Induced by T Cell Activation and Expressed by Follicular Lymphoma-Resident T Helper Cells

Successful immunotherapy in both solid tumors and in hematological malignancies relies on the ability of T lymphocytes to infiltrate the cancer tissue and mount an immune response against the tumor. Biomarkers able to discern the amount and the types of T lymphocytes infiltrating a given tumor therefore have high diagnostic and prognostic value. Given that lncRNAs are known to have a highly cell-type-specific expression pattern, we searched for lncRNAs specifically expressed by activated T cells and at the same time in a kind of lymphoma, follicular lymphoma, where the microenvironment is known to play a critical role in the regulation of antitumor immunity. We focused on a non-coding transcript, annotated as LINC00892, which reaches extremely high expression levels following cell activation in Jurkat cells. Interestingly LINC00892 has an expression pattern resembling that of genes involved in T cell memory. Accordingly, LINC00892 is mostly expressed by the effector memory and helper CD4+ T cell sub-types but not by naïve T cells. In situ analyses of LINC00892 expression in normal lymph nodes and in follicular lymphoma biopsies show that its expression is limited to CD4+ PD1^hi T cells, with a subcellular localization within the germinal center matching that of follicular helper T cells. Our analysis therefore suggests that the previously uncharacterized lncRNA LINC00892 could be a useful biomarker for the detection of CD4+ memory T cells in both normal and tumor tissues.

The Prognostic Nutritional Index (PNI) is an independent predictor of overall survival in older patients with follicular lymphoma

The Prognostic Nutritional Index (PNI), a parameter combining serum albumin concentration and absolute lymphocyte count, is considered a measure of the nutritional and inflammatory status and the host's anti-tumor response. We analyzed the clinical characteristics and outcomes according to the PNI of 351 grades 1-3 A FL patients. Forty-one patients (12%) had a PNI ≤45, who were older and showed adverse baseline features. A low PNI was associated with a shorter PFS (only for patients >60 years), and OS (for all patients, 10-year OS, 52% versus 74%, p = 0.0001). The prognostic impact of the PNI on OS was confirmed in a multivariate model for patients >60 years (HR = 3, p = 0.006). In conclusion, the PNI is a readily accessible piece of information that can identify a small subset of FL patients with shorter survival, and it could be an aid to improve the nutritional status of patients prior to treatment initiation.

First external validation of the FLIPI-L score in a single-center series of patients with follicular lymphoma

The FLIPI-L has recently been proposed as a novel prognostic index in follicular lymphoma (FL), combining FLIPI and the presence of lymphopenia. In our single-center validation in 381 FL patients, lymphopenia was less frequent than in the original publication and thus the distribution of risk categories was different. Although it was not able to properly predict time to first treatment, FLIPI-L performed slightly better than FLIPI alone in the prediction of response, early relapse, progression-free and overall survival, and histological transformation. This new tool or others encompassing parameters from the microenvironment might improve upon the prognostic ability of classical scores.

Clinicopathological factors and tumor microenvironment markers predicting watch-and-wait discontinuation in 82 patients with follicular lymphoma

OBJECTIVES

In this study, we aimed to determine the clinicopathological factors influencing the treatment-free period in patients with follicular lymphoma (FL) using a watch-and-wait (WW) strategy.

METHODS

We retrospectively assessed histopathological parameters of 82 patients with FL.

RESULTS

The median time from diagnosis to WW discontinuation was 62 months (range, 3-138), and median follow-up was 86 months (range, 3-183). Intermediate or high-risk Follicular Lymphoma International Prognostic Index score (P = .012), non-duodenal-type (P = .011), higher numbers of interfollicular CD4⁺ (P = .038) and intrafollicular FOXP3⁺ cells (P = .024) in the tumor microenvironment, and Ki-67 index ≥10% (P = .031) were significant adverse factors for WW discontinuation in univariate analyses.

CONCLUSION

Patients with adverse factors for WW discontinuation should be carefully observed during follow-up.

A low lymphocyte-to-monocyte ratio is an independent predictor of poorer survival and higher risk of histological transformation in follicular lymphoma

The lymphocyte-to-monocyte ratio (LMR) is a prognostic factor in different neoplasms, but its potential importance in follicular lymphoma (FL) is not well defined. We studied 384 FL patients for which the LMR was available at diagnosis. Baseline features and outcomes were compared between patients with an LMR ≤/>2.5. The 76 patients (20%) who had an LMR ≤2.5 were older and had a higher tumor burden. A low LMR was predictive of a lower 10-y progression-free survival (32 vs. 55%, p = .001) and overall survival (35 vs. 78%, p < .0001; HR = 2.3, p = .003 in a 6-element multivariable model). A low LMR was also an independent risk factor for histological transformation (11 vs. 6% at 10 years, p = .01). Likewise, patients with a low LMR had a higher rate of second malignancies. The potential utility of this widely available parameter and its contribution to well-established prognostic scores need to be explored in independent, prospective series.

Immune-Checkpoint Blockade Therapy in Lymphoma

Tumor cells use immune-checkpoint pathways to evade the host immune system and suppress immune cell function. These cells express programmed cell-death protein 1 ligand 1 (PD-L1)/PD-L2, which bind to the programmed cell-death protein 1 (PD-1) present on cytotoxic T cells, trigger inhibitory signaling, and reduce cytotoxicity and T-cell exhaustion. Immune-checkpoint blockade can inhibit this signal and may serve as an effective therapeutic strategy in patients with solid tumors. Several trials have been conducted on immune-checkpoint inhibitor therapy in patients with malignant lymphoma and their efficacy has been reported. For example, in Hodgkin lymphoma, immune-checkpoint blockade has resulted in response rates of 65% to 75%. However, in non-Hodgkin lymphoma, the response rate to immune-checkpoint blockade was lower. In this review, we evaluate the biology of immune-checkpoint inhibition and the current data on its efficacy in malignant lymphoma, and identify the cases in which the treatment was more effective.

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.

High serum levels of IL-2R, IL-6, and TNF-α are associated with higher tumor burden and poorer outcome of follicular lymphoma patients in the rituximab era

The clinical behavior of FL patients is heterogeneous. The levels of sIL-2R have been correlated with tumor burden and outcome in FL. However, the impact of IL-6 and TNF-α in this disease is unclear. We studied 253 patients diagnosed with grade 1-3a FL between 2002 and 2018, with available information on serum levels of sIL-2R, IL-6, and TNF-α at diagnosis. Patients with cytokine levels above the cutoff had features of a higher tumor burden and higher-risk disease. Levels of any of the studied cytokines above the cutoff and a higher number of cytokines above the cutoff impacted on a shorter PFS and OS. TNF-α levels were an independent predictor of a poorer PFS. No differences were observed in the risk of histological transformation or second malignancies. The determination of cytokine levels in FL patients is feasible in clinical practice, and elevated levels are associated with a higher tumor burden and poorer survival.

Origin and Pathogenesis of B Cell Lymphomas

Immunoglobulin (IG) gene remodeling by V(D)J recombination plays a central role in the generation of normal B cells, and somatic hypermutation and class switching of IG genes are key processes during antigen-driven B cell differentiation. However, errors of these processes are involved in the development of B cell lymphomas. IG locus-associated translocations of proto-oncogenes are a hallmark of many B cell malignancies. Additional transforming events include inactivating mutations in various tumor suppressor genes and also latent infection of B cells with viruses, such as Epstein-Barr virus. Many B cell lymphomas require B cell antigen receptor expression, and in several instances, chronic antigenic stimulation plays a role in lymphoma development and/or sustaining tumor growth. Often, survival and proliferation signals provided by other cells in the microenvironment are a further critical factor in lymphoma development and pathophysiology. Many B cell malignancies derive from germinal center B cells, most likely because of the high proliferation rate of these cells and the high activity of mutagenic processes.

Boosting γδ T cell-mediated antibody-dependent cellular cytotoxicity by PD-1 blockade in follicular lymphoma

Follicular lymphoma (FL) is a common non Hodgkin's lymphoma subtype in which immune escape mechanisms are implicated in resistance to chemo-immunotherapy. Although molecular studies point to qualitative and quantitative deregulation of immune checkpoints, in depth cellular analysis of FL immune escape is lacking. Here, by functional assays and in silico analyses we show that a subset of FL patients displays a 'high' immune escape phenotype. These FL cases are characterized by abundant infiltration of PD1⁺ CD16⁺ TCRVγ9Vδ2 γδ T lymphocytes. In a 3D co-culture assay (MALC), γδ T cells mediate both direct and indirect (ADCC in the presence of anti-CD20 mAbs) cytolytic activity against FL cell aggregates. Importantly, PD-1, which is expressed by most FL-infiltrating γδ T lymphocytes with ADCC capacity, impairs these functions. In conclusion, we identify a PD1-regulated γδ T cell cytolytic immune component in FL. Our data provide a treatment rational by PD-1 blockade aimed at boosting γδ T cell anti-tumor functions in FL.

Follicular lymphomas and their transformation: Past and current research

INTRODUCTION

Follicular lymphoma (FL) is the second most common type of non-Hodgkin lymphoma (NHL). Histological transformation (HT) refers to the evolution of a clinically indolent NHL to a clinically aggressive one, defined as those lymphomas in which survival is limited to a few months when untreated. Areas covered: HT is associated with rapid progression of lymphadenopathy, infiltration of extranodal sites, development of systemic symptoms, and elevated serum level of lactate dehydrogenase (LDH). It is frequently related to a poor prognosis, and the median survival after transformation is less than 2 years. Transformation to diffuse large B cell lymphoma (DLBCL) in patients with FL occurs at an annual rate of approximately 3% for the first 15 years, after which the risk of HT falls for reasons that remain unclear. Expert commentary: Although it has long been assumed that transformation reflects the emergence of an aggressive subclone of cells from the primary FL, recent studies suggest that FL transformation might also arise by divergent evolution from a more immature common progenitor cell. Studies on genomic changes and DNA sequencing have shed some light onto the process of transformation. Nowadays, we know that HT is a complex process where several molecular pathways are involved.

PD-1-PD-L1 immune-checkpoint blockade in B-cell lymphomas

Cancer cells can escape T-cell-mediated cellular cytotoxicity by exploiting the inhibitory programmed cell-death protein 1 (PD-1)/programmed cell death 1 ligand 1 (PD-L1) immune checkpoint. Indeed, therapeutic antibodies that block the PD-1-PD-L1 axis induce durable clinical responses against a growing list of solid tumours. B-cell lymphomas also leverage this checkpoint to escape immune recognition, although the outcomes of PD-1-PD-L1 blockade, and the correlations between PD-L1 expression and treatment responses, are less-well elucidated in these diseases than in solid cancers. Nevertheless, in patients with Hodgkin lymphoma, amplification of the gene encoding PD-L1 is commonly associated with increased expression of this protein on Reed-Sternberg cells. Correspondingly, PD-1 blockade with nivolumab has been demonstrated to result in response rates as high as 87% in unselected patients with relapsed and/or refractory Hodgkin lymphoma, leading to the FDA approval of nivolumab for this indication in May 2016. The PD-1/PD-L1 axis is probably also important for immune evasion of B-cell lymphomas with a viral aetiology, including those associated with human immunodeficiency virus (HIV) and Epstein-Barr virus (EBV). This Review is focused on the role of PD-1-PD-L1 blockade in unleashing host antitumour immune responses against various B-cell lymphomas, and summarizes the clinical studies of this approach performed to date.

Fibrosis in low-grade follicular lymphoma - a link to the TH2 immune reaction

There is evidence from studies on fibrotic diseases that a TH2 polarized immune response, characterized by the production of cytokines like IL-4, IL-5, and IL-13 is important for fibrosis development. Data concerning the role of TH2 polarized immune response for fibrogenesis in lymphomas are scarce. Using immunohistochemistry, we investigated paraffin embedded tissue specimens of 58 follicular lymphomas (FL) grade 1/2 with and without fibrosis. In FL with fibrosis, we detected more interfollicular GATA-3 positive lymphocytes and a shift towards a TH2 immune response. In areas of fibrosis, which were enriched with myofibroblasts, we observed a polarization of macrophages towards a M2 phenotype with expression of CD163. Our results hold some evidence that a polarization of the adaptive immune system towards a TH2 immune response in the tumor microenvironment is associated with increased fibrosis, which may indicate its functional relevance for either development or maintenance of fibrosis in FL.

Analysis of dendritic cell subpopulations in follicular lymphoma with respect to the tumor immune microenvironment

The immune cell composition of the follicular lymphoma (FL) tumor microenvironment is increasingly recognized as an important determinant for clinical outcome. Here, we explored frequency and distribution of dendritic cell (DC) subtypes in relation to regulatory T cells (Treg) by immunohistochemistry in lymph node biopsies from patients with de novo FL. We found that neoplastic follicles contained lower DC and higher Treg frequencies than hyperplastic follicles in control lymph nodes. Treg numbers particularly correlated with the subset of conventional CD11c(+ )DCs. Additionally, both a high intra- to interfollicular ratio of CD11c(+ )DCs and increased intrafollicular Treg frequencies were associated with decreased overall survival. This suggests that functional interactions between these cells may be relevant for FL progression/recurrence. The presence of CD11c(+ )DCs in the tumor microenvironment may assist tumor infiltration by Tregs, thus contributing to the suppression of an otherwise beneficial T-cell-dominated FL microenvironment.

Lymphoma Immunotherapy: Current Status

The rationale to treat lymphomas with immunotherapy comes from long-standing evidence on their distinctive immune responsiveness. Indolent B-cell non-Hodgkin lymphomas, in particular, establish key interactions with the immune microenvironment to ensure prosurvival signals and prevent antitumor immune activation. However, reports of spontaneous regressions indicate that, under certain circumstances, patients develop therapeutic antitumor immunity. Several immunotherapeutic approaches have been thus developed to boost these effects in all patients. To date, targeting CD20 on malignant B cells with the antibody rituximab has been the most clinically effective strategy. However, relapse and resistance prevent to cure approximately half of B-NHL patients, underscoring the need of more effective therapies. The recognition of B-cell receptor variable regions as B-NHL unique antigens promoted the development of specific vaccines to immunize patients against their own tumor. Despite initial promising results, this strategy has not yet demonstrated a sufficient clinical benefit to reach the regulatory approval. Several novel agents are now available to stimulate immune effector functions or counteract immunosuppressive mechanisms, such as engineered antitumor T cells, co-stimulatory receptor agonist, and immune checkpoint-blocking antibodies. Thus, multiple elements can now be exploited in more effective combinations to break the barriers for the induction of anti-lymphoma immunity.

Rituximab-induced early and late signaling have opposite effects on dexamethasone-induced apoptosis in human follicular lymphoma cells

The addition of rituximab (RTX) to standard chemotherapy has improved the treatment of B-cell malignancies. We show here that RTX and dexamethasone (Dex) induced synergistic apoptosis in follicular lymphoma cell lines. However, apoptosis was delayed by RTX-induced early protective signaling. RTX-induced early signaling also decreased Dex-induced apoptosis and led to phosphorylation of ERK1/2, Bcl-2 (at serine 70) and phosphorylation/degradation of BimL/EL. All these events were prevented by the MEK inhibitor, UO126. Therefore, we suggest that RTX-induced ERK-mediated signaling events lead to protection from apoptosis during early signaling and that blocking of Bim and Bcl-2 phosphorylation might be used as a novel strategy for lymphoma treatment.

Transformed follicular non-Hodgkin lymphoma

Histologic transformation of follicular lymphoma to an aggressive non-Hodgkin lymphoma is a critical biologic event with profound implications on the natural history of this otherwise indolent disease. Recent insights into the genetic and epigenetic basis of transformation have been described, with the recognition of pivotal events governing the initiation and persistence of tumor evolution. Outcomes of patients with transformed lymphoma have historically been poor; however, several studies in the rituximab era suggest that survival may be more favorable than previously recognized. This review highlights our current understanding of transformed follicular lymphoma biology and pathogenesis, current treatment, and future directions.

The 3q27 and 18q21 translocations for follicular lymphoma and diffuse large B-cell lymphoma in the rituximab era

The 3q27 and 18q21 chromosomal translocations are major hallmarks in B-cell lymphoma. We aimed to determine the frequencies of these translocations in follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL) and to evaluate their prognostic impact in the rituximab era. This study included 98 FL and 93 DLBCL patients whose abnormal karyotypes had been detected using G-banding. Patients uniformly underwent R-CHOP therapy : doxorubicin, cyclophosphamide, vincristine, prednisolone, and rituximab ; survivors were followed up for 29 months (median). The 3q27 and 18q21 translocations were detected in 14 and 77 FL patients and 14 and 22 DLBCL patients, respectively. Overall survival (OS) and progression-free survival (PFS) did not differ significantly between the groups with 3q27, 18q21, concurrent 3q27 and 18q21 translocations, and other chromosomal abnormalities for FL and DLBCL. There were no significant differences in OS and PFS between patients with 3q27 translocation-positive FL and those with 3q27 translocation-positive DLBCL or between the patients with 18q21 translocation-positive FL and those with 18q21 translocation-positive DLBCL. The presence of 3q27 and 18q21 translocations did not correlate with the clinical outcomes of FL or DLBCL patients following R-CHOP treatment.

Low NK cell counts in peripheral blood are associated with inferior overall survival in patients with follicular lymphoma

Host immune responses influence follicular lymphoma (FL) outcomes. To test our hypothesis that immune cells in blood reflect that response, we assessed by peripheral blood flow cytometry in 75 untreated FL patients the absolute counts of: lymphocytes (ALC), CD4(+)T (ACD4C), CD8(+)T (ACD8C) and natural killer (ANKC) cells. Low ANKC was the only parameter associated with inferior overall survival by univariate analysis (p=0.02), and trended to significance in multivariable analysis with ACD4C (p=0.08). Five (24%) patients with low initial ANKC died, while one (2%) with normal/high ANKC has died. In conclusion, evaluation of blood ANKC may be a useful indicator of outcome in previously untreated FL patients.

Follicular lymphoma cells induce changes in T-cell gene expression and function: potential impact on survival and risk of transformation

PURPOSE

Previous studies have demonstrated the prognostic importance of the immune microenvironment in follicular lymphoma (FL). To investigate the molecular mechanisms during which tumor-infiltrating T cells (TILs) are altered in the FL microenvironment, we studied highly purified CD4 and CD8 TILs from lymph node biopsies at diagnosis in treatment-naive patients with FL compared with reactive tonsils and the peripheral blood of healthy donors.

PATIENTS AND METHODS

Gene expression profiling of highly purified CD4 and CD8 TILs was performed on the Affymetrix platform. Diagnostic tissue microarrays from an independent patient set (n = 172) were used to verify protein expression and analyze any impact of TIL-expressed genes on outcome. Time-lapse imaging was used to assess T-cell motility.

RESULTS

The most upregulated genes in both CD4 and CD8 TILs were PMCH, ETV1, and TNFRSF9. PMCH is not expressed in peripheral blood T cells, but expression is highly induced on culture with FL. Both CD4 and CD8 TILs from patients with FL have significantly impaired motility compared with those of healthy TILs from reactive tonsils and this can be induced on healthy T cells by FL cells. During multivariate analysis, a model incorporating the number and location of T cells expressing PMCH, NAMPT, and ETV1 showed prognostic significance for overall survival and for time to transformation.

CONCLUSION

We showed altered gene expression in TILs in FL and demonstrated that altering the immune microenvironment in FL affects overall survival and time to transformation in this disease.

Somatic hypermutation analysis in follicular lymphoma provides evidence suggesting bidirectional cell migration between lymph node and bone marrow during disease progression and relapse

In follicular lymphoma, somatic hypermutation of the immunoglobulin heavy chain genes facilitates the identification of different lymphoma cell clones, and the construction of genealogical trees. To investigate the dissemination of lymphoma cells, and the role of bone marrow in disease progression, we simultaneously analyzed the somatic hypermutation patterns of lymph node and bone marrow specimens taken from three patients at onset and relapse of their disease. Immunoglobulin heavy chain genes were amplified by polymerase chain reaction, cloned and sequenced. Mutational pedigrees were constructed in a hierarchical order. When direct transition of one mutation pattern into that of a successor clones was not feasible, hypothetical predecessor clones were created, and a probability measurement calculation was introduced. Eighty-five sequenced clones were generated. The average mutation rates were 13.45% for the lymph node specimens, and 9.78% for the bone marrow ones. Forty-two hypothetical predecessor clones were introduced into inter-compartment pedigrees. The genealogical trees showed that early lymphoma clones with a low mutational load quickly migrate from lymph nodes into the bone marrow. Bi-directional lymphoma cell migration was detectable between the two compartments. In one case of follicular lymphoma, a clone identical to the initial lymph node clone was detected 2 years later in the bone marrow. The newly introduced algorithm allows the evaluation of both time and direction of follicular lymphoma cell migration. We found evidence that follicular lymphoma originates in the lymph node, and infiltrates the bone marrow early in the course of the disease. Moreover, inter-compartment migration between lymph nodes and bone marrow occurs in both directions.

Origin and pathogenesis of B cell lymphomas

Immunoglobulin (Ig) gene remodeling by V(D)J recombination plays a central role in the generation of normal B cells, and somatic hypermutation and class switching of Ig genes are key processes during antigen-driven B cell differentiation. However, errors of these processes are involved in the development of B cell lymphomas. Ig locus-associated translocations of proto-oncogenes are a hallmark of many B cell malignancies. Additional transforming events include inactivating mutations in various tumor suppressor genes, and also latent infection of B cells with viruses, such as Epstein-Barr virus. Many B cell lymphomas require B cell antigen receptor expression, and in several instances chronic antigenic stimulation plays a role in sustaining tumor growth. Often, survival and proliferation signals provided by other cells in the microenvironment are a further critical factor in lymphoma development and pathophysiology. Many B cell malignancies derive from germinal center B cells, most likely because of the high proliferation rate of these cells and the high activity of mutagenic processes.

Self-antigen recognition by follicular lymphoma B-cell receptors

Follicular lymphoma is a monoclonal B-cell malignancy with each patient's tumor expressing a unique cell surface immunoglobulin (Ig), or B-cell receptor (BCR), that can potentially recognize antigens and/or transduce signals into the tumor cell. Here we evaluated the reactivity of tumor derived Igs for human tissue antigens. Self-reactivity was observed in 26% of tumor Igs (25 of 98). For one follicular lymphoma patient, the recognized self-antigen was identified as myoferlin. This patient's tumor cells bound recombinant myoferlin in proportion to their level of BCR expression, and the binding to myoferlin was preserved despite ongoing somatic hypermutation of Ig variable regions. Furthermore, BCR-mediated signaling was induced after culture of tumor cells with myoferlin. These results suggest that antigen stimulation may provide survival signals to tumor cells and that there is a selective pressure to preserve antigen recognition as the tumor evolves.

Inherited genetic variation and overall survival following follicular lymphoma

Follicular lymphoma (FL) has variable progression and survival, and improved identification of patients at high risk for progression would aid in identifying patients most likely to benefit from alternative therapy.In a sample of 244 FL cases identified during a population-based case-control study of non-Hodgkin lymphoma (NHL), we examined 6,679 tag SNPs in 488 gene regions for associations with overall FL survival. Over a median follow-up of 89 months with 65 deaths in this preliminary study, we identified 5 gene regions (BMP7, GALNT12,DUSP2, GADD45B, and ADAM17) that were associated with overall survival from FL. Results did not meet the criteria for statistical significance after adjustment for multiple hypothesis testing. These results,which support a role for host factors in determining the variable progression of FL, serve as an initial examination that can inform future studies of genetic variation and FL survival. However, they require replication in independent populations, as well as assessment in rituximab-treated patients.

Early steps of follicular lymphoma pathogenesis

Follicular lymphoma (FL) pathogenesis is a complex and fascinating multi-hit process, escalating along successive derailments of the distinctive molecular and cellular mechanisms paving B-cell differentiation and activation. This progressive subversion of B-cell receptor diversification mechanisms and B-cell homeostasis likely occurs during a protracted preclinical phase of asymptomatic growth, in which premalignant clones already disseminate and establish "niches" in secondary lymphoid organs. Following FL diagnosis, a parallel indolent behavior is observed in most patients, slowly progressing over a period of many years, to eventually generate a highly refractory (and in some case transform into an aggressive subtype of) lymphoma. Novel insights in human germinal center B-cell biology recently allowed a more comprehensive understanding of the various illegitimate events sequentially involved in the premalignant progression phases. In this review, we will discuss how these new data have modified our perception of early FL pathogenesis, the new questions and challenges it opened up, and how this knowledge could impact on innovative programs of early detection, follow-up, and patient management.

The four types of Tregs in malignant lymphomas

Regulatory T cells (Tregs) are a specialized subpopulation of CD4⁺ T cells, which act to suppress the activation of other immune cells. Tregs represent important modulators for the interaction between lymphomas and host microenvironment. Lymphomas are a group of serious and frequently fatal malignant diseases of lymphocytes. Recent studies revealed that some lymphoma T cells might adopt a Treg profile. Assessment of Treg phenotypes and genotypes in patients may offer prediction of outcome in many types of lymphomas including diffuse large B-cell lymphoma, follicular lymphoma, cutaneous T cell lymphoma, and Hodgkin's lymphoma. Based on characterized roles of Tregs in lymphomas, we can categorize the various roles into four groups: (a) suppressor Tregs; (b) malignant Tregs; (c) direct tumor-killing Tregs; and (d) incompetent Tregs. The classification into four groups is significant in predicting prognosis and designing Tregs-based immunotherapies for treating lymphomas. In patients with lymphomas where Tregs serve either as suppressor Tregs or malignant Tregs, anti-tumor cytotoxicity is suppressed thus decreased numbers of Tregs are associated with a good prognosis. In contrast, in patients with lymphomas where Tregs serve as tumor-killing Tregs and incompetent Tregs, anti-tumor cytotoxicity is enhanced or anti-autoimmune Tregs activities are weakened thus increased numbers of Tregs are associated with a good prognosis and reduced numbers of Tregs are associated with a poor prognosis. However, the mechanisms underlying the various roles of Tregs in patients with lymphomas remain unknown. Therefore, further research is needed in this regard as well as the utility of Tregs as prognostic factors and therapy strategies in different lymphomas.

MicroRNA profiling of follicular lymphoma identifies microRNAs related to cell proliferation and tumor response

BACKGROUND

MicroRNAs can play an important role in tumorigenesis through post-transcriptional regulation of gene expression, and are not well characterized in follicular lymphoma.

DESIGN AND METHODS

MicroRNA profiles of enriched follicular lymphoma tumor cells from 16 patients were generated by assaying 851 human microRNAs. Tandem gene expression profiles were obtained for predicting microRNA targets.

RESULTS

The expression of 133 microRNAs was significantly different (> 2-fold; P<0.05) between follicular lymphoma and follicular hyperplasia. Forty-four microRNAs in three groups generated a unique follicular lymphoma signature. Of these, ten microRNAs were increased (miR-193a-5p, -193b*, -345, -513b, -574-3p, -584, -663, -1287, -1295, and -1471), 11 microRNAs were decreased (miR-17*, -30a, -33a, -106a*, -141, -202, -205, -222, -301b, -431*, and -570), and 23 microRNAs formed a group that was increased in most cases of follicular lymphoma but showed lower expression in a subset of cases (let-7a, let-7f, miR-7-1*, -9, -9*, -20a, -20b, -30b, -96, -98, -194, -195, -221*, -374a, -374b, -451, -454, -502-3p, -532-3p, -664*, -1274a, -1274b, and -1260). Higher expression of this last group was associated with improved response to chemotherapy. Gene expression analysis revealed increased expression of MAPK1, AKT1, PRKCE, IL4R and DROSHA and decreased expression of CDKN1A/p21, SOCS2, CHEK1, RAD51, KLF4, BLIMP1 and IRF4 in follicular lymphoma. Functional studies indicated that CDKN1A/p21 and SOCS2 expression is directly regulated by miR-20a/-20b and miR-194, respectively.

CONCLUSIONS

Follicular lymphoma is characterized by a unique microRNA signature, containing a subset of microRNAs whose expression correlate with response to chemotherapy. miR-20a/b and miR-194 target CDKN1A and SOCS2 in follicular lymphoma, potentially contributing to tumor cell proliferation and survival.

Risk Factors of Non-Hodgkin Lymphoma

INTRODUCTION: Despite decades of intensive research, Non-Hodgkin Lymphoma (NHL) remains poorly understood and is largely incurable. NHL is a heterogeneous group of malignancies with multiple subtypes, each of which has distinct morphologic, immunophenotypic, and clinical features. Identifying the risk factors for NHL may improve our understanding of the underlying biological mechanisms and have an impact on clinical practice. AREAS COVERED: This article provides a review of several aspects of NHL, including epidemiology and subtype classification, clinical, environmental, genetic, and genomic risk factors identified for etiology and prognosis, and available statistical and bioinformatics tools for identification of genetic and genomic risk factors from the analysis of high-throughput studies. EXPERT OPINION: Multiple clinical and environmental risk factors have been identified. However, they have failed to provide practically effective prediction. Genetic and genomic risk factors identified from high-throughput studies have suffered a lack of reproducibility. The identification of genetic/genomic risk factors demands innovative statistical and bioinformatics tools. Although multiple analysis methods have been developed, there is still room for improvement. There is a critical need for well-designed, prospective, large-scale pangenomic studies.

Caspases and cancer

Evasion of apoptosis is considered to be one of the hallmarks of human cancers. This cell death modality is executed by caspases and several upstream regulatory factors, which direct their proteolytic activity, have been defined as either tumor suppressors or oncogenes. Often these regulatory factors, in addition to being potent apoptosis inducers, function in cell survival or repair signaling pathways in response to cellular stress. Thus, loss of function in a distinct regulatory mechanism does not necessarily mean that tumor formation is due to apoptosis malfunction resulting from insufficient caspase activation. Although each caspase has been assigned a distinct role in apoptosis, some redundancy with respect to their regulatory functions and substrate recognition is evident. Jointly, these proteases could be considered to possess solid tumor suppressor function, but what is the evidence that deregulation of specific caspases per se induces inappropriate cell survival, leading to enhanced tumorigenic potential? This question will be addressed in this review, which covers basic molecular mechanisms derived from in vitro analyses and emphasizes new insights that have emerged from in vivo and clinical studies.

Transformation of follicular lymphoma

Histological transformation of follicular lymphoma (FL) to a more aggressive non-Hodgkin's lymphomas is a pivotal event in the natural history of FL and is associated with poor outcome. While commonly observed in clinical practice and despite multiple studies designed to address its pathogenesis, the biology of this process represents an enigma. In this chapter we present a state of the art review summarizing the definition of histologic transformation, its incidence, pathogenesis, clinical manifestations, treatment and outcome. Furthermore, we specifically emphasize gaps in our knowledge that should be addressed in future studies.

Host genetics in follicular lymphoma

The role of inherited (host) genetic susceptibility in the pathogenesis of follicular lymphoma (FL) is reviewed. First degree relatives of FL patients are at an increased risk of FL, suggesting a role for inherited factors. While there have been no linkage studies in FL families, candidate gene and genome-wide association studies have identified several risk loci which have been confirmed in independent studies. These include regions on 6p21.32-33 and TNF family members. Host genetics has also been hypothesized to influence treatment response, disease progression and overall survival. Early leads in FL prognosis include pathways that regulate immune function, antibody-dependent cellular cytotoxicity, chemotaxis, and one-carbon metabolism, although few of these associations have been independently confirmed. While the use of host genetics to identify individuals at high risk of FL or to predict FL treatment response and prognosis appears to be very promising, it is not yet ready for the clinic.

Prognostic tools in follicular lymphomas

Despite significant improvements in treatment modalities over the 10 years, the clinical course of patients with follicular lymphoma (FL) remains heterogeneous. Thus, prognostic indexes are still required to direct treatment choices and for the design of clinical trials. Investigators have conducted a variety of studies aimed at integrated assessment of biological and clinical features in order to identify novel prognostic factors and scoring systems. Genetic studies focused on tumor cells and the tumor microenvironment represent a step forward in understanding the biology of FL and are likely to provide new prognostic tools for future clinical use. Several prognostic factors have been identified and are currently used in combination to establish prognostic scores and to support therapeutic decisions. The FL International Prognostic Index (FLIPI) is currently used for defining individual risk of death. More recently, FLIPI2 was developed by the same group that built FLIPI as a new model for prognostic definition of patients with FL. The model was defined using prospectively collected data from patients who also received the monoclonal therapeutic antibody rituximab and stratifies patients into three risk categories for disease progression. Since many biological factors are not yet clinically validated or easily assessable, clinical data still represent the major source of prognostic information. The progressive development of new and more effective therapies for the treatment of FL makes the study of prognosis a dynamic and evolving area of clinical research.

Activation of the p53 pathway by the MDM2 inhibitor nutlin-3a overcomes BCL2 overexpression in a preclinical model of diffuse large B-cell lymphoma associated with t(14;18)(q32;q21)

p53 is frequently wild type (wt) in diffuse large B-cell lymphoma (DLBCL) associated with t(14;18)(q32;q21) that overexpresses BCL2. Nutlin-3a is a small molecule that activates the p53 pathway by disrupting p53–MDM2 interaction. We show that nutlin-3a activates p53 in DLBCL cells associated with t(14;18)(q32;q21), BCL2 overexpression and wt p53, resulting in cell cycle arrest and apoptosis. Nutlin-3a treatment had similar effects on DLBCL cells of activated B-cell phenotype with wt p53. Cell cycle arrest was associated with upregulation of p21. Nutlin-3a-induced apoptosis was accompanied by BAX and PUMA upregulation, BCL-XL downregulation, serine-70 dephosphorylation of BCL2, direct binding of BCL2 by p53, caspase-9 upregulation and caspase-3 cleavage. Cell death was reduced when p53-dependent transactivation activity was inhibited by pifithrin-α (PFT-α), or PFT-μ inhibited direct p53 targeting of mitochondria. Nutlin-3a sensitized activation of the intrinsic apoptotic pathway by BCL2 inhibitors in t(14;18)-positive DLBCL cells with wt p53, and enhanced doxorubicin cytotoxicity against t(14;18)-positive DLBCL cells with wt or mutant p53, the latter in part via p73 upregulation. Nutlin-3a treatment in a xenograft animal lymphoma model inhibited growth of t(14;18)-positive DLBCL tumors, associated with increased apoptosis and decreased proliferation. These data suggest that disruption of the p53–MDM2 interaction by nutlin-3a offers a novel therapeutic approach for DLBCL associated with t(14;18)(q32;q21).

Definition and characterization of the systemic T-cell dysregulation in untreated indolent B-cell lymphoma and very early CLL

Epidemiologic data show that the immune system may control or promote the emergence and growth of neoplastic lymphomatous clones. Conversely, systemic lymphomas, especially myeloma and chronic lymphocytic leukemia (CLL), are associated with clinical immunodeficiency. This prospective controlled study demonstrates substantially reduced circulating T helper cells, predominantly naive CD4(+) cells, in patients with nonleukemic follicular lymphoma and extranodal marginal zone lymphoma, but not in monoclonal gammopathy and early CLL. These changes were correlated with a preactivated phenotype, hyperreactivity in vitro, pre-senescence, and a T helper 2 shift of peripheral T helper cells. No prominent alterations existed in the regulatory T-cell compartment. Gene expression profiling of in vitro-stimulated CD4(+) cells revealed an independent second alteration of T helper cell physiology, which was most pronounced in early CLL but also detectable in follicular lymphoma/extranodal marginal zone lymphoma. This pattern consisted of down-regulation of T-cell receptor signaling cascades and globally reduced cytokine secretion. Both types of T-cell dysfunction may contribute to significant immunodeficiency in nonleukemic indolent B-cell lymphomas as demonstrated by unresponsiveness to hepatitis B vaccination. The precise definition of systemic T-cell dysfunction serves as the basis to study its prognostic impact, its relationship to the established influence of the lymphoma microenvironment, and its therapeutic manipulation.

Prognostic biomarkers in malignant lymphomas

There has recently been a rapid expansion in research aimed at identifying biomarkers that could improve the prognosis for patients with various subtypes of malignant lymphoma. Genomic and genetic studies have led to the identification of biological and clinical subgroups of diffuse large B-cell lymphomas with distinct underlying molecular features, divergent activation of oncogenetic pathways, and clinical course. Molecular studies of follicular lymphoma have suggested complex interactions between malignant cells and the surrounding immunological network that could affect disease progression. Moreover, the inflammatory cells of Hodgkin lymphoma have been shown to produce a complex network of cytokines and chemokines that provide a permissive microenvironment for tumor growth. Research into specific biomarkers and signaling pathways of malignant lymphomas might therefore result in the identification of novel targets for future therapeutic strategies. As gene expression profiling techniques are not yet feasible in the clinical laboratory, studies have aimed to translate the findings into more widely applicable techniques that might allow this research to be applied to routine clinical practice. This review focuses on recent advances in translational and clinical research on biomarkers in malignant lymphomas.