Transformation of follicular lymphoma to diffuse large B-cell lymphoma proceeds by distinct oncogenic mechanisms

Follicular lymphoma cells induce T-cell immunologic synapse dysfunction that can be repaired with lenalidomide: implications for the tumor microenvironment and immunotherapy

An important hallmark of cancer progression is the ability of tumor cells to evade immune recognition. Understanding the relationship between neoplastic cells and the immune microenvironment should facilitate the design of improved immunotherapies. Here we identify impaired T-cell immunologic synapse formation as an active immunosuppressive mechanism in follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL). We found a significant reduction in formation of the F-actin immune synapse in tumor-infiltrating T cells (P < .01) from lymphoma patients compared with age-matched healthy donor cells. Peripheral blood T cells exhibited this defect only in patients with leukemic-phase disease. Moreover, we demonstrate that this T-cell defect is induced after short-term tumor cell contact. After 24-hour coculture with FL cells, previously healthy T cells showed suppressed recruitment of critical signaling proteins to the synapse. We further demonstrate repair of this defect after treatment of both FL cells and T cells with the immunomodulatory drug lenalidomide. Tissue microarray analysis identified reduced expression of the T-cell synapse signature proteins, including the cytolytic effector molecule Rab27A associated with poor prognosis, in addition to reduced T-cell numbers and activity with disease transformation. Our results highlight the importance of identifying biomarkers and immunotherapeutic treatments for repairing T-cell responses in lymphoma.

Indolent lymphomas of mature B lymphocytes

The lymphomas of small B lymphocytes are a biologically diverse group of B cell derived neoplasms that includes B cell small lymphocytic lymphoma/chronic lymphocytic leukemia; mantle cell lymphoma; follicular lymphoma; nodal, splenic and extranodal marginal zone lymphomas; and lymphoplasmacytic lymphoma. They are distinguished from one another on clinical, morphological, phenotypic and genetic grounds. This article reviews the essential diagnostic and biologic features of these clinically indolent B cell malignancies.

A pluripotency signature predicts histologic transformation and influences survival in follicular lymphoma patients

Histologic transformation (HT) of follicular lymphoma to diffuse large B-cell lymphoma (DLBCL-t) is associated with accelerated disease course and drastically worse outcome, yet the underlying mechanisms are poorly understood. We show that a network of gene transcriptional modules underlies HT. Central to the network hierarchy is a signature strikingly enriched for pluripotency-related genes. These genes are typically expressed in embryonic stem cells (ESCs), including MYC and its direct targets. This core ESC-like program was independent of proliferation/cell-cycle and overlapped but was distinct from normal B-cell transcriptional programs. Furthermore, we show that the ESC program is correlated with transcriptional programs maintaining tumor phenotype in transgenic MYC-driven mouse models of lymphoma. Although our approach was to identify HT mechanisms rather than to derive an optimal survival predictor, a model based on ESC/differentiation programs stratified patient outcomes in 2 independent patient cohorts and was predictive of propensity of follicular lymphoma tumors to transform. Transformation was associated with an expression signature combining high expression of ESC transcriptional programs with reduced expression of stromal programs. Together, these findings suggest a central role for an ESC-like signature in the mechanism of HT and provide new clues for potential therapeutic targets.

The incidence, natural history, biology, and treatment of transformed lymphomas

Treatment of patients with transformed lymphoma presents a significant challenge to the practicing physician. Indeed, the transformation of follicular lymphoma to a more aggressive histology is inherent to the biology of this disease and is often associated with an aggressive clinical course, resulting in a poor prognosis. Recent population-based studies have better defined the incidence of this event, and recent laboratory studies have defined the molecular and immunological processes associated with transformation. These studies will be discussed in this review, as will the treatment options for these patients.

The incidence, natural history, biology, and treatment of transformed lymphomas

Treatment of patients with transformed lymphoma presents a significant challenge to the practicing physician. Indeed, the transformation of follicular lymphoma to a more aggressive histology is inherent to the biology of this disease and is often associated with an aggressive clinical course, resulting in a poor prognosis. Recent population-based studies have better defined the incidence of this event, and recent laboratory studies have defined the molecular and immunological processes associated with transformation. These studies will be discussed in this review, as will the treatment options for these patients.

Diffuse large B-cell lymphoma after transformation from low-grade follicular lymphoma: morphological, immunohistochemical, and FISH analyses

Follicular lymphoma (FL) is one of the most common subtypes of non-Hodgkin lymphoma and frequently transforms to diffuse large B-cell lymphoma (DLBCL). To clarify some aspects of the natural history of FL, we retrospectively examined 43 consecutive patients who had DLBCL with pre- or coexisting FL grade 1 or 2. The patients comprised 22 men and 21 women with a median age of 53 years. Most of the patients (34/43) showed advanced-stage (III or IV) disease initially. We examined both FL and DLBCL components morphologically, immunohistochemically, and by interface fluorescence in situ hybridization (FISH: IGH/BCL2 fusion, BCL6 translocation) analysis. Most of the DLBCLs were classified as the centroblastic subtype, with two exceptions of the anaplastic subtype. Immunohistochemical analysis of both the FL and DLBCL components revealed the following respective positivity rates: CD20 100%/100%, CD10 86%/66%, Bcl-2 96%/91%, Bcl-6 84%/88%, MUM1 16%/34%, CD30 0%/20%, CD138 0%/0%, and CD5 0%/3%. Loss of CD10 (6/36, 17%) and gain of MUM1 (7/28, 25%) and CD30 (5/21, 24%) through transformation were not infrequent. High positivity rates for Bcl-2 and Bcl-6 were maintained throughout transformation. Among the DLBCLs, 84% were classified as the germinal center B-cell phenotype (GCB) and 16% as non-GCB in accordance with the criteria of Hans et al. IGH/BCL2 fusion was detected by FISH in 89% of FLs and 82% of DLBCLs. BCL6 translocation was detected in 1/6 (17%) DLBCLs without IGH/BCL2 fusion. Thus, although the morphological features and FISH results for DLBCL were consistent with transformed FL, the immunophenotype showed wide heterogeneity.

Genome-wide profiling of follicular lymphoma by array comparative genomic hybridization reveals prognostically significant DNA copy number imbalances

The secondary genetic events associated with follicular lymphoma (FL) progression are not well defined. We applied genome-wide BAC array comparative genomic hybridization to 106 diagnostic biopsies of FL to characterize regional genomic imbalances. Using an analytical approach that defined regions of copy number change as intersections between visual annotations and a Hidden Markov model-based algorithm, we identified 71 regional alterations that were recurrent in at least 10% of cases. These ranged in size from approximately 200 kb to 44 Mb, affecting chromosomes 1, 5, 6, 7, 8, 10, 12, 17, 18, 19, and 22. We also demonstrated by cluster analysis that 46.2% of the 106 cases could be sub-grouped based on the presence of +1q, +6p/6q-, +7, or +18. Survival analysis showed that 21 of the 71 regions correlated significantly with inferior overall survival (OS). Of these 21 regions, 16 were independent predictors of OS using a multivariate Cox model that included the international prognostic index (IPI) score. Two of these 16 regions (1p36.22-p36.33 and 6q21-q24.3) were also predictors of transformation risk and independent of IPI. These prognostic features may be useful to identify high-risk patients as candidates for risk-adapted therapies.