Event In Lymphomagenesis Research Articles

Molecular Genetics in the Diagnosis and Biology of Lymphoid Neoplasms.

The 2017 Workshop of the Society for Hematopathology/European Association for Haematopathology reviewed the role of molecular genetics in the diagnosis and biology of lymphoid neoplasms. The Workshop Panel reviewed 82 cases. Molecular genetic testing reveals alterations that expand the spectrum of diseases such as DUSP22 rearrangement in ALK-negative anaplastic large cell lymphoma, large B-cell lymphoma with IRF4 rearrangement, MYD88 mutations in B-cell lymphomas, Burkitt-like lymphoma with 11q aberrations, and diagnostic criteria for high-grade B-cell lymphomas. Therapeutic agents and natural tumor progression may be associated with transcriptional reprogramming that lead to transdifferentiation and lineage switch. Application of emerging technical advances has revealed the complexity of genetic events in lymphomagenesis, progression, and acquired resistance to therapies. They also contribute to enhanced understanding of the biology of indolent vs aggressive behavior, clonal evolution, tumor progression, and transcriptional reprogramming associated with transdifferentiation events that may occur subsequent to therapy.

Pathogenesis of Enteropathy-Associated T Cell Lymphoma.

To provide an update on the pathogenesis of enteropathy-associated T cell lymphoma (EATL) and its relationship with refractory celiac disease (RCD), in light of current knowledge of immune, genetic, and environmental factors that promote neoplastic transformation of intraepithelial lymphocytes (IELs). EATL frequently evolves from RCD type II (RCD II) but can occur "de novo" in individuals with celiac disease. Recurrent activating mutations in members of the JAK/STAT pathway have been recently described in EATL and RCD II, which suggests deregulation of cytokine signaling to be an early event in lymphomagenesis. Intraepithelial T cells are presumed to be the cell of origin of EATL (and RCD II). Recent in vitro molecular and phenotypic analyses and in vivo murine studies, however, suggest an origin of RCD II from innate IELs (NK/T cell precursors), which could also be the cell of origin of RCD II-derived EATL. The immune microenvironment of the small intestinal mucosa in celiac disease fosters the development of EATL, often in a multistep pathway.

Oncogenic Mutations in XPO1 Promote Lymphoid Transformation By Altering Nuclear/Cytoplasmic Localization of NFκB Signaling Intermediates

Genomic analyses across cancer have identified recurrent somatic mutations in XPO1, which encodes a major nuclear cytoplasmic transport protein responsible for exporting a broad range of cargo proteins from the nucleus to the cytoplasm. Specifically, heterozygous mutations at the XPO1 hotspot residue E571 (most frequently E571K) are recurrent in B-cell malignancies including chronic lymphocytic leukemia, primary mediastinal B-cell lymphoma, and Hodgkin lymphoma. Despite the fact that XPO1 is the target of numerous small molecules in clinical development, functional evidence for precisely how altered XPO1 expression or mutations might promote transformation is not well delineated.We utilized genome editing to generate isogenic B-cell leukemia cells for physiologic expression of the XPO1 E571K mutation from the endogenous XPO1 locus. The heterozygous XPO1 E571K mutant cells had increased cell proliferation in vitro and in vivo relative to XPO1 wild-type (WT) counterparts. The effects of XPO1 mutation were distinct from XPO1 genetic depletion, which completely suppressed cell growth (Figure A). Given the high conservation of XPO1 across mammals, we next generated a conditional knock-in mouse model to express the Xpo1 E571K mutation from the endogenous Xpo1 locus. Cd19- Cre Xpo1 E571K/WTmice were born at normal Mendelian ratios, but were smaller than littermate controls and had increased number of B-cells in the blood and transitional (T1, T2) B-cells in the spleen with splenomegaly (Figure B). Colony forming assays in IL-7-containing methylcellulose using bone marrow (BM) from these mice revealed increased number of B-cell progenitors with enhanced clonogenicity.Given several recent reports suggesting that XPO1 mutations are clonal early events in lymphomagenesis, we also evaluated the effects of pan-hematopoietic expression of Xpo1 E571K. Transplantation of CAG- CreERT Xpo1 E571K/WTBM cells followed by tamoxifen administration to recipients resulted in skewing to B-lymphopoiesis and thrombocytopenia 12 weeks after tamoxifen induction. BM cells from CAG- CreERT Xpo1 E571K/WTshowed strikingly increased B-cell colony formation and serially replating capacity in IL-7 with reduced clonogenicity in myeloid cytokine-containing methylcellulose (Figure C). We next crossed the Cd19- Cre Xpo1 E571K/WTmice to transgenic mice with pan-hematopoietic BCL2 overexpression (vav-BCL2 mice). By 8 weeks, Cd19- Cre Xpo1 E571K/WT/ vav- BCL2 mice had higher B-cell lymphocytosis, increased B-cells in the BM and splenomegaly compared to Cd19- Cre Xpo1 WT/WT, Cd19- Cre Xpo1 E571K/WTor Cd19- Cre / vav - BCL2mice, suggesting cooperativity between the proliferative effects of XPO1 E571K and anti-apoptotic effects of BCL2 in B-cells. Moreover, B-cell progenitors from Cd19- Cre Xpo1 E571K/WT/ vav-BCL2 mice again demonstrated remarkable clonogenic capacity in IL-7-containing media compared with other genotypes.To understand the mechanism by which the XPO1 hotspot mutation confers growth-promoting effects, we performed mass spectrometry on fractionated nuclear and cytoplasmic lysates from XPO1 E571K knock-in and parental cell lines (Figure D). Numerous members of the K63-ubiquitination, TLR4, and NFκB pathways were differentially exported in XPO1 E571K mutant cells. Given the known oncogenic role of NFκB signaling in lymphoid malignancies, we further functionally evaluated this pathway. XPO1 mutant cells demonstrated differential localization of cIAP1/2, NFkBIB, IKKB, TAB2 and TRAF2. Differential export of NFκB signaling intermediates was confirmed by western blot and immunofluorescence revealing increased (but not complete) retention of cIAP1/2 proteins in the nucleus and increased levels of TRAF2 in the cytoplasm of mutant cells compared to WT. Phenotypically, XPO1 E571K cells demonstrated higher baseline NFkB signaling and transcriptional responses to stimulation with TNF-α than XPO1 WT counterpart cells (Figure E).Overall, these data identify that hotspot mutations in XPO1 promote lymphoid biased hematopoiesis and transformation by altering nuclear export of key proteins involved in hematopoietic regulation. Although numerous cellular pathways are altered in XPO1 E571K mutant cells, this mutation prominently affects compartmentalization of NFκB signaling components in a manner that promotes activation of this pathway and contributes to lymphomagenesis. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Exome Sequencing of Hodgkin's and Non-Hodgkin Composite Lymphomas Identifies Shared Somatic Mutations Indicative of Common Founding Precursors

Background: Composite lymphomas (CLs) describe the rare situation when two morphologically distinct lymphomas occur in the same patient. Prior studies have supported a shared origin of CLs based on shared chromosomal translocations and/or the presence of shared immunoglobulin rearrangements. We used exome sequencing to examine somatic events in two cases of CLs. We hypothesized that each lymphoma will have shared and unique mutations, consistent with the presence of a common lymphoma precursor. Further, we postulated that the shared mutations represent potential initiating events in lymphomagenesis. Finally, because each case includes a Hodgkin (HL) and non-Hodgkin lymphoma (NHL), we hypothesize that the somatic mutations found in HL may offer insight into genomic drivers of HL.Clinical Synopsis:Case 1 was a 57-year-old man who presented with abdominal pain associated with a small bowel obstruction (SBO) and lymphadenopathy (LAD). Pathology showed DLBCL (diffuse large B-cell lymphoma, non-germinal center subtype; stage IV). He was treated with 6 cycles of R-CHOP with complete response. Seven months after the completion of R-CHOP, he presented with left neck LAD. An excisional biopsy revealed classical HL (stage II). Hodgkin and Reed-Sternberg (HRS) cells comprised 10% of the sample. He was treated with 3 cycles of ABVD and involved-field radiation therapy. Case 2 was a 66-year-old man with a history of solitary LAD who presented with increasing LAD, night sweats, and a chest wall mass. An excisional biopsy revealed both follicular lymphoma (FL; grade I-II) and classical HL in distinct areas of the lymph node. HRS cells comprised 30% of the sample. FISH studies were positive for t(14;18). He was treated with ABVD for 6 cycles with partial response. Upon progression, a repeat lymph node biopsy showed persistent HL. He was treated with bendamustine and rituximab for 4 cycles with progressive disease.Methods: We performed whole exome sequencing on formalin fixed paraffin embedded tumor samples and matched normal skin samples. We used our standard somatic variant calling pipeline to call somatic variants. SNV (single nucleotide variant) and indel calls were filtered for basic quality metrics and, using in-house software, were processed through a Bayesian classifier to remove false positive somatic events. Filtered variants were manually reviewed to further verify somatic status. Somatic variants were validated using Ampliseq in Case 1.Results: Sequencing resulted in >90% of the target regions with at least 20x in all samples. The mean depth of the NHL and normal samples in Case 1 was >65x. To account for the low malignant tumor cellularity of HL, the HL sample of Case 1 was sequenced to a mean depth of 310x. The mean depth for all samples in Case 2 was >100x (FL = 188x; normal = 104x; HL = 215x). After filtering, we identified 60 and 133 variants in 57 and 101 genes in Case 1 and Case 2, respectively. In Case 1, we identified three sites inTP53, TNFRSF14, and RASAL2 that were shared. We also identified variants in HIST1H2AG, KMT2D, and STAT3 unique to the DLBCL sample, and two mutations in PTPRT unique to the HL sample of Case 1 (Figure 1). In Case 2, we identified shared variants in TNFRSF14 and HIST1H2BF. We also identified two distinct BCL10 mutations in the FL and HL samples of Case 2 (Figure 1).Conclusions: From the shared somatic mutations identified, we infer that a shared lymphoma precursor for each case is likely, and the shared mutations may be early initiating events. In both cases, a shared nonsense mutation was found at TNFRSF14. TNFRSF14 is recurrently mutated in NHL, and recurrent deletions involving TNFRSF14 have been described in HL. Further work is needed to understand how TNFRSF14 alterations drive HL vs. NHL. Finally, it is intriguing that the HL samples contain independent mutations in PTPRT and BCL10. PTPRT is a known cancer gene, and BCL10 has been shown to be associated with the pathogenesis of B-cell NHLs. These data provide new hypotheses for loci involved in HL pathogenesis. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Abstract B10: Genome-wide analysis of p53 transcriptional programs in Myc-induced lymphomas

Abstract Oncogenic activation of Myc induces cellular transformation and hyper-proliferation, while it activates intrinsic tumor surveillance pathways aimed at restraining the expansion of pre-cancerous cells. All these Myc-induced tumor suppressive mechanisms converge on p53, and loss of p53 activity is the major selected event in lymphomagenesis. Yet, the genetic programs triggered by p53 in tumor suppression have been only partially clarified. Using whole genome mapping of p53 binding and gene expression profiling, we investigated the transcriptional circuitry employed by p53 in suppressing cancer development. We studied the progression of Myc-induced lymphomas in Eµ-myc transgenic mice, as well as the regression of these lymphomas following restoration of p53 function, by either pharmacological or genetic means. We thus identified a set of p53 target genes that are strong candidates for mediating tumor suppression. Currently, we are testing the impact of these new components of the p53 transcriptional program on tumorigenesis with an RNA interference (RNAi)-based functional genetic screen. Altogether our data expand our understanding of the p53 response to Myc-induced oncogenic stress and will hopefully highlight new tumor suppressive mechanisms, paving the way for their therapeutic application. Citation Format: Claudia Tonelli, Marco J. Morelli, Arianna Sabò, Andrea Piontini, Mattia Pelizzola, Stefano Campaner, Bruno Amati. Genome-wide analysis of p53 transcriptional programs in Myc-induced lymphomas. [abstract]. In: Proceedings of the AACR Special Conference on Myc: From Biology to Therapy; Jan 7-10, 2015; La Jolla, CA. Philadelphia (PA): AACR; Mol Cancer Res 2015;13(10 Suppl):Abstract nr B10.

Epigenetic Silencing of Mir-203 Contributes to IL2Rb Overexpression and Malignant Transformation in Cutaneous T-Cell Lymphoma

IntroductionCutaneous T-cell lymphomas (CTCL) are rare malignancies, which present in the skin and presumably arise from malignant transformation of T-cells normally destined to home to the cutaneous environment. MicroRNAs (miRs) regulate gene expression at the post transcriptional level. Many studies have shown that altered miR expression is a central event in lymphomagenesis, and that miRs have potential as both diagnostic and predictive tumor markers.In CTCL we have previously identified and validated a 3 miR classifier that distinguishes CTCL from BID with > 95% accuracy, based upon the up-regulation of miR-155 combined with the down-regulation of miR-203 and miR-205. In normal adult tissues, miR-203 is mainly associated with keratinocyte differentiation, acting to repress stemness, and to induce cell cycle arrest and differentiation. In cancer, miR-203 has been shown to hold tumor suppressor properties, and may be down-regulated by promoter hyper-methylation. The function and implications of miR-203 for CTCL has not previously been described. In this study we have investigated the regulation and function of miR-203 in primary CTCL biopsies and cell lines.Materials and MethodsTwenty-one fresh frozen primary CTCL biopsies, IL-2 independent CTCL cell lines (MyLa2059 and PDB2B), and the IL-2 dependent CTCL cell lines (SeAx and SeZ4) were analyzed in this study. Promoter methylation was analyzed by methylation specific melting curve analysis. Cell lines were transfected by electroporation of miR-203 mimic or non-template-control (mirVana, Ambion). Proliferation was measured by 3H-Thymidine and apoptosis by MMT assays. MiR-203 mimic and mock transfected cells were examined by Affymetrix RNA expression arrays (GeneChip Human Gene 2.0 ST). IL2Rβ mRNA expression was confirmed by qPCR and IL2Rβ protein levels by flow cytometry as measured by CD122 (IL2Rβ-chain), compared to CD25 (IL2Rα-chain) and CD132 (IL2Rγ-chain). Cloning was done according to the manufacturers’ recommendation (In-Fusion, Clontech) and luciferase reporter assays were performed using the Dual-Glo system (Promega).ResultsWe show that miR-203 is epigenetically silenced by DNA methylation in both CTCL cell lines and in 9 of 21 (43%) of primary CTCL samples, and that miR-203 can be up-regulated by the hypo-methylating agents 5-azacytidine and 5-aza-2-deoxycytidine in vitro. We also show, that forced miR-203 expression in CTCL cells targets known oncogenes such as p63, Survivin and CREB. Furthermore, it is shown that induction of miR-203 reduces cell viability and decreases proliferation.mRNA array analysis of miR-203 mimic and mock transfected cells lead to the identification of 19 significantly de-regulated genes (P<0.5/log fold change>2), including the as yet unrecognized miR-203 target molecule IL2Rb, which is essential for IL-2 induced JAK/STAT signaling. qPCR and FACS analysis confirmed this up-regulation both at the mRNA and protein level. The IL-2 dependent cell line SeAx showed significantly more profound down-regulation of IL2Rβ upon in miR203 transfected cell lines. Preliminary luciferase reporter assays confirm that IL2Rβ expression is regulated by miR-203, providing novel evidence that miR-203 may act in concert with IL-2/STAT in CTCL pathogenesis. These experiments are currently being validated.ConclusionWe provide the first evidence that miR-203 acts as a tumor suppressor in CTCL. Furthermore we show that down-regulation of miR-203 leads to increased expression of an as yet unidentified target gene, IL2Rβ, which is directly involved in JAK/STAT signaling, that plays an essential role in the regulation of T-cell proliferation. Thus, we suggest that epigenetic miR-203 down-regulation and IL2Rβ up-regulation are important early and driving events in CTCL pathogenesis. DisclosuresNo relevant conflicts of interest to declare.

Deep sequencing reveals clonal evolution patterns and mutation events associated with relapse in B-cell lymphomas.

BackgroundMolecular mechanisms associated with frequent relapse of diffuse large B-cell lymphoma (DLBCL) are poorly defined. It is especially unclear how primary tumor clonal heterogeneity contributes to relapse. Here, we explore unique features of B-cell lymphomas - VDJ recombination and somatic hypermutation - to address this question.ResultsWe performed high-throughput sequencing of rearranged VDJ junctions in 14 pairs of matched diagnosis-relapse tumors, among which 7 pairs were further characterized by exome sequencing. We identify two distinctive modes of clonal evolution of DLBCL relapse: an early-divergent mode in which clonally related diagnosis and relapse tumors diverged early and developed in parallel; and a late-divergent mode in which relapse tumors developed directly from diagnosis tumors with minor divergence. By examining mutation patterns in the context of phylogenetic information provided by VDJ junctions, we identified mutations in epigenetic modifiers such as KMT2D as potential early driving events in lymphomagenesis and immune escape alterations as relapse-associated events.ConclusionsAltogether, our study for the first time provides important evidence that DLBCL relapse may result from multiple, distinct tumor evolutionary mechanisms, providing rationale for therapies for each mechanism. Moreover, this study highlights the urgent need to understand the driving roles of epigenetic modifier mutations in lymphomagenesis, and immune surveillance factor genetic lesions in relapse.Electronic supplementary materialThe online version of this article (doi:10.1186/s13059-014-0432-0) contains supplementary material, which is available to authorized users.

Immune Escape Mechanisms in Diffuse Large B-Cell Lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most frequent subtype of non-Hodgkin lymphomas in Western countries. Implementation of immunotherapy using monoclonal antibodies to therapeutic protocols has led to dramatic improvements in overall survival. DLBCL became a model of a successful immunochemotherapy concept. Despite this fact, there is still a proportion of patients who do not respond to or relapse early after treatment. Growing evidence suggests that host antitumor immunity is suppressed by lymphoma cells in many ways. First, host cytotoxic T cells are directly suppressed by interaction with programmed cell death (PD) ligand on lymphoma cell surface and a similar mechanism enhances the activity of suppressive regulatory T cells (Tregs). Second, tumor cells escape host cytotoxic cells due to lower immunogenicity caused by reduced expression of HLA antigens. Both mechanisms have an origin in primary genetic events in lymphomagenesis. Rearrangement of MHC class II transcriptional activator (CIITA) gene and amplification of Janus kinase (JAK2) gene lead to enhanced expression of PD ligands 1 and 2, higher proliferation activity, and lower expression of HLA. This paper summarizes current knowledge about clinically relevant immune escape mechanisms in DLBCL.

Epidemiology: clues to the pathogenesis of Burkitt lymphoma

The two major epidemiological clues to the pathogenesis of Burkitt lymphoma (BL) are the geographical association with malaria--BL incidence relates to the malaria transmission rate--and early infection by Epstein-Barr virus (EBV). Both agents cause B cell hyperplasia, which is almost certainly an essential component of lymphomagenesis in BL. The critical event in lymphomagenesis is the creation of a MYC translocation, bringing the MYC gene into juxtaposition with immunoglobulin genes and causing its ectopic expression, thereby driving the proliferation of BL cells. It is highly likely that such translocations are mediated by the activation-induced cytidine deaminase (AID) gene, which is responsible for hypervariable region mutations as well as class switching. Stimulation of the Toll-like receptor 9 by malaria-associated agonists induces AID, providing a mechanism whereby malaria could directly influence BL pathogenesis. EBV-containing cells must reach the memory cell compartment in order to survive throughout the life of the individual, which probably requires traversal of the germinal centre. Normally, cells that do not produce high affinity antibodies do not survive this passage, and are induced to undergo apoptosis. EBV, however, prevents this, and in doing so may also enhance the likelihood of survival of rare translocation-containing cells.

Sequential mutations in Notch1, Fbxw7, and Tp53 in radiation-induced mouse thymic lymphomas

AbstractT-cell acute lymphoblastic lymphomas commonly demonstrate activating Notch1 mutations as well as mutations or deletions in Fbxw7. However, because Fbxw7 targets Notch1 for degradation, genetic alterations in these genes are expected to be mutually exclusive events in lymphomagenesis. Previously, by using a radiation-induced Tp53-deficient mouse model for T-cell acute lymphoblastic lymphoma, we reported that loss of heterozygosity at the Fbxw7 locus occurs frequently in a Tp53-dependent manner. In the current study, we show that these thymic lymphomas also commonly exhibit activating Notch1 mutations in the proline-glutamic acid-serine-threonine (PEST) domain. Moreover, concurrent activating Notch1 PEST domain mutations and single-copy deletions at the Fbxw7 locus occur with high frequency in the same individual tumors, indicating that these changes are not mutually exclusive events. We further demonstrate that although Notch1 PEST domain mutations are independent of Tp53 status, they are completely abolished in mice with germline Fbxw7 haploinsufficiency. Therefore, Notch1 PEST domain mutations only occur when Fbxw7 expression levels are intact. These data suggest a temporal sequence of mutational events involving these important cancer-related genes, with Notch1 PEST domain mutations occurring first, followed by Fbxw7 deletion, and eventually by complete loss of Tp53.

Oncogene Amplification as an Incidental Finding in FISH Testing for Gene Rearrangements in Lymphoid Hematopoietic Neoplasms

Abstract 2505Oncogene amplification resulting in overexpression, although common in solid tumors, is rare in hematopoietic neoplasms. This is particularly true in lymphoid neoplasms compared to AML where MYC, MLL or RUNX1 (AML1) amplification has been mostly seen, and to CML where BCR/ABL fusion gene amplification has been also reported. Typically, lymphoid neoplasms are tested at diagnosis by FISH for specific reciprocal chromosome translocations that lead to overexpression of deregulated oncogenes such as BCL1, BCL2, BCL6 and MYC in B-cell lymphoma and myeloma or BCR/ABL gene fusion in ALL. Nevertheless, we have unexpectedly seen oncogene amplification from time to time in our FISH lab. To study the incidence of gene amplification and its diagnostic and clinical implications, we retrospectively analyzed FISH results routinely performed on paraffin embedded lymphoma tissues, lymph nodes, bone marrow aspirates and peripheral bloods in the past three and half years using translocation probes for BCL2/IGH, BCL1/IGH, MYC/IGH and BCR/ABL and break apart probes for BCL6 and MYC. The highest amplification rate seen was in BCL2/IGH testing: 11 of the 1,710 cases were positive (0.643%). In 2 cases with follicular lymphoma (FL), BCL2 amplification presented as homogenously staining regions (hsr), one case with diffuse large B-cell lymphoma (DLBCL) showed double minutes (dmin), and two cases with FL had a pattern of combined hsr and dmin. Five cases with low grade FL intriguingly showed a similar pattern of BCL2/IGH translocation and concomitant amplification of the rearranged BCL2 as a small hsr. The remaining case diagnosed as Burkitt lymphoma (BL) was positive for MYC/IGH translocation and for BCL2 amplification present as large hsr. BCL6 amplification was observed in 4 of 1,537 cases tested (0.26%). In all these cases, amplification presented as hsr. One case diagnosed as EBV+ DLBLC was positive for MYC/IGH translocation and 3’ BCL6 high level amplification. Another case with FL showed BCL6 rearrangement and 5’ BCL6 amplification. BCL1 amplification with translocation was seen as hsr in 1 case with mantle cell lymphoma out of 2,898 tested. BCL1 amplification was observed in another case with plasma cell myeloma as hsr out of 3,413 tests performed. MYC gene amplification was positive in 3 of 2,186 (0.137%). One case with BL showed MYC rearrangement with a concomitant 3’ deletion and 5’ amplification. The second case diagnosed as B-cell lymphoma with features intermediate between DLBCL and BL showed highly amplified MYC gene as hsr. The third case was DLBCL with 15–50 copies of MYC gene per cell as dmin. Among 530 BCR/ABL tests ordered for acute leukemia or ALL, 2 (0.377%) cases with T cell lymphoblastic leukemia/lymphoma (T-ALL/LBL) showed ABL amplification as episomes (4–8 copies in one case; 6–30 in another). Both were abnormal by cytogenetics analysis, but negative for t(9;22)(q34;q11.2) and without dmin or hsr identified. Although detection rates of oncogene amplification seem to be very low with limited specific translocation probes applied to lymphoid neoplasms, they may well be higher when FISH signal patterns are analyzed more carefully. In our study, 5 of the 11 FL cases tested for IGH/BCL2 showed a peculiar pattern positive for the t(14;18)-IGH/BCL2 and a concomitant red signal amplification of BCL2, the size of which is usually small and may be overlooked under microscope. All these 5 cases had low grade FL, suggesting that oncogene amplification can be an early genomic event in lymphomagenesis. MYC gene amplification is generally considered a late stage genomic alteration. When MYC is rearranged, amplification of BCL2, BCL6 or BCL1 may need to be taken into consideration for disease stratification, or vice versa. For instance, so called “double-hit” or “triple-hit” lymphomas currently require two or three concurrent translocations for diagnosis. Oncogene amplification, equally important for deregulation/overexpression as a translocation, should be considered as a second or a third hit in diagnosis and differential diagnosis of B-cell lymphoma unclassifiable with features intermediate between DLBCL and BL. FISH is a very useful tool to identify episomal oncogene amplification. Episomes, unlike cytogenetically evident dmin and hrs, are invisible by chromosome analysis, but their detection is important as reported for integration of targeted tyrosine kinase inhibitors into chemotherapeutic regimens. Disclosures:No relevant conflicts of interest to declare.

A Phase I Study of the Combination of Azacitidine, Cyclophosphamide, Vincristine, and Rituximab in Relapsed and Refractory Lymphoma

Abstract 1624Tumor suppressor gene silencing via mechanisms including DNA hypermethylation is a recognized event in lymphomagenesis and lymphoma recurrence and transformation. DNA methyltransferase inhibitor, azacitidine, reduces epigenetic methylation in lymphoma and numerous other tumor models. Given the poor outcome of patients with transformed or refractory lymphoma, there is an immediate need to find novel therapies.We report the first results of an ongoing Phase I trial evaluating the maximal tolerated dose (MTD) of azacitidine given in a schedule intended to sensitize lymphoma to a regimen of oral cyclophosphamide, intravenous vincristine, and rituximab (for those patients whose lymphoma expresses CD20) for patients with recurrent or refractory lymphoma. Participants receive azacitidine (days 1–5, starting with 25 mg/m2) followed by oral cyclophosphamide (days 6–9, 300 mg/m2), vincristine (day 8, 1.4 mg/m2, maximum of 2 mg), and rituximab (day 8, 375 mg/m2). All patients receive pegfilgrastim (day 10, 6 mg) with each cycle. Cycles are repeated every 21 days for up to eight cycles if participants continue to benefit from therapy.To determine the MTD, a “3+3” design was employed. Dose limiting toxicity (DLT) is assessed during cycle 1. DLT is defined as the following: grade 3 or 4 non-hematologic toxicity (excluding emesis or isolated elevation of alkaline phosphatase); grade 4 neutropenia or thrombocytopenia of ≥7 days duration; increased serum creatinine > 2.0 times upper limit of normal; inability to receive all doses of azacitidine or cyclophosphamide within the first cycle or inability to initiate cycle 2 within two weeks of completing cycle 1 due to drug-related toxicity.Of the first 10 patients enrolled (8 patients in 25 mg/m2 azacitidine cohort, and 2 patients in 50 mg/m2 cohort), median age was 56 years (range 39–73). Median number of prior lines of therapy was 3 (range 2–4). Lymphoma subtypes included diffuse large B cell lymphoma (DLBCL; n=4), follicular lymphoma (FL; n=3), Hodgkins lymphoma (HL; n=1), small lymphocytic lymphoma (SLL; n=1), and cutaneous T-cell lymphoma (CTCL; n=1).A median of 2 cycles (range 1–6) have been received. The MTD has not yet been reached. One patient experienced thrombocytopenia as a DLT. The DLT criteria were subsequently revised to allow grade 4 thrombocytopenia of < 7 days after initially noting that some patients experienced asymptomatic grade 4 thrombocytopenia lasting only a short duration. An additional three patients were accrued to the first dose level after this adjustment to the current DLT, with no additional patients experiencing a DLT. Grade 3–4 toxicities during any cycle of therapy were as follows: neutropenia (n=5); thrombocytopenia (n=4); anemia (n=2); and abscess, anorexia, bacteremia, hypoalbuminemia, and nausea (n=1 each). Additionally, grade 3 cardiac ischemia and deep venous thrombosis each occurred in one patient but were considered unrelated to treatment by the investigator. Of the 8 patients who have completed treatment, 1 patient with FL achieved a complete response (CR), 1 patient with FL achieved a partial response (PR), 2 had stable disease (SD), 2 experienced progressive disease (PD), and 2 were not evaluable (NE) for response. Interestingly, the CR was maintained for 7 months and the PR has been ongoing for 6 months since completion of therapy. These preliminary data suggest the therapeutic potential of this novel combination and enrollment remains ongoing to define the MTD. Additional correlative assessments of tumor and peripheral blood mononuclear cells are also underway. Disclosures:Off Label Use: Azacitidine is the test article in this study and is not FDA approved for the treatment of lymphoma. Hayslip:Celgene: Research Funding.

Double-Hit Lymphoma at Second Relapse of Burkitt-Like Lymphoma : A Case Report

Double-hit lymphoma (DHL) is a rare and extremely unfavorable type of lymphoma with concurrent chromosomal translocations of BCL2 and MYC. It is considered that BCL2 translocation precedes MYC events in lymphomagenesis of DHL. In fact, most cases of DHL arise de novo or following FL. We describe a very rare case of DHL arising from Burkitt-like lymphoma according to the revised European-American classification of lymphoid neoplasms. A 67-year-old Japanese male presented with persistent fever. [(18)F]-fluorodeoxyglucose positron emission tomography revealed multiple abnormal accumulations in the bone marrow, pancreas, and periphery of the left kidney. The patient was diagnosed with Burkitt-like lymphoma according to a bone marrow biopsy. At the disease onset and the first relapse, chemotherapy was effective and the patient experienced sustained and complete remission. At the second relapse, however, the clinical presentation and morphology of lymphoma cells were nearly identical, but a high level of chemoresistance was acquired, and the patient succumbed almost 1 month after hospitalization. Chromosomal analyses revealed a complex karyotype with concurrent t(14;18) and t(8;22) translocations, which have not been previously detected. It is therefore important to note that DHL cannot be diagnosed without chromosomal analysis. Cytogenetic analyses should thus be performed for patients with high-grade B-cell lymphoma and who experience a recurrence of this lymphoma.

An expanded set of direct BLIMP-1 targets identifies novel links in differentiation, immune response and lymphoma

Abstract Abstract 1466 Poster Board I-489 B-lymphocyte induced maturation protein 1 (BLIMP-1) has been defined as a key driver of the genetic reprogramming during differentiation of B-cells to plasma cells. Frequent inactivation of PRDM1, the BLIMP-1 gene, in diffuse large B-cell lymphoma (DLBCL) indicates that loss of function is an important event in lymphomagenesis. Only a limited set of direct BLIMP-1 target genes have been defined. In order to better understand the function of human BLIMP-1 in differentiation and malignancy we have established a more comprehensive set of occupied promoters. These data provide an extended view of the regulatory network controlled by BLIMP-1, and identify novel sets of targets involved in transcription and immune response. The composition of occupied promoters identifies complexity in BLIMP-1 binding motif selection, and substantial overlap between BLIMP-1 sites and Interferon regulatory factor (IRF) elements. Consistent with active competition between BLIMP-1 and IRFs, target genes associated with such overlapping motifs are found to be preferentially induced in response to BLIMP-1 knockdown. Finally BLIMP-1 targets are found to include key components of DLBCL gene expression signatures. This map of BLIMP-1 occupied promoters thus illuminates key aspects of function in normal and malignant cell biology. Disclosures: No relevant conflicts of interest to declare.

An Expanded Set of Direct BLIMP-1 Targets Identifies Novel Links in Differentiation, Immune Response and Lymphoma.

Abstract 1466Poster Board I-489B-lymphocyte induced maturation protein 1 (BLIMP-1) has been defined as a key driver of the genetic reprogramming during differentiation of B-cells to plasma cells. Frequent inactivation of PRDM1, the BLIMP-1 gene, in diffuse large B-cell lymphoma (DLBCL) indicates that loss of function is an important event in lymphomagenesis. Only a limited set of direct BLIMP-1 target genes have been defined. In order to better understand the function of human BLIMP-1 in differentiation and malignancy we have established a more comprehensive set of occupied promoters. These data provide an extended view of the regulatory network controlled by BLIMP-1, and identify novel sets of targets involved in transcription and immune response. The composition of occupied promoters identifies complexity in BLIMP-1 binding motif selection, and substantial overlap between BLIMP-1 sites and Interferon regulatory factor (IRF) elements. Consistent with active competition between BLIMP-1 and IRFs, target genes associated with such overlapping motifs are found to be preferentially induced in response to BLIMP-1 knockdown. Finally BLIMP-1 targets are found to include key components of DLBCL gene expression signatures. This map of BLIMP-1 occupied promoters thus illuminates key aspects of function in normal and malignant cell biology. Disclosures:No relevant conflicts of interest to declare.

Array-based DNA methylation profiling in follicular lymphoma

Quantitative methylation profiling was performed using the Illumina GoldenGate Assay in untreated Follicular Lymphoma (FL) (164), paired pre- and post-transformation FL (20), benign haematopoietic (24) samples and purified B & T cells from two FL cases. Methylation values allowed separation of untreated FL samples from controls with one exception based primarily on tumour-specific gains of methylation typically occurring within CpG islands. Genes which are targets for epigenetic repression in stem cells by Polycomb Repressor Complex 2 were significantly overrepresented among hypermethylated genes. Methylation profiles were conserved in sequential FL and t-FL biopsies suggesting that widespread methylation represents an early event in lymphomagenesis and may not contribute substantially to transformation. Significant (p<0.05) correlation between FL methylation values and reduced gene expression was demonstrated for up to 28% of loci. Methylation changes occurred predominantly in B cells with variability in the amount of non-malignant tissue between samples preventing conclusive correlation with survival. This represents an important caveat in attributing prognostic relevance to methylation and future studies in cancer will optimally require purified tumour populations to address the impact of methylation on clinical outcome.

The 2008 WHO classification of lymphomas: implications for clinical practice and translational research

The 4th edition of the WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues published in 2008 builds upon the success of the 2001 3rd edition; new entities are defined, and solutions for problematic categories are sought. Recent studies have drawn attention to the biological overlap between classical Hodgkin lymphoma (CHL) and diffuse large B-cell lymphomas (DLBCL). Similarly, there is a greater appreciation of the borderlands between Burkitt lymphoma and DLBCL. Strategies for the management of these borderline lesions are proposed. Additionally, age-specific and site-specific factors play an important role in the definition of several new entities, which also have biological underpinnings. Among the peripheral T-cell lymphomas (PTCL), more precise definitions were introduced for several entities, including anaplastic large cell lymphoma, angioimmunoblastic T-cell lymphoma, enteropathy-associated T-cell lymphoma, and subcutaneous panniculitis-like T-cell lymphoma. Several new variants of primary cutaneous T-cell lymphomas are proposed. Finally, the subclassification and categorization of the most common lymphoma subtypes, follicular lymphoma (FL) and DLBCL, were altered to enhance diagnostic accuracy and aid in clinical management. The 2008 WHO classification also draws attention to early events in lymphomagenesis. These lesions help delineate the earliest steps in neoplastic transformation and generally mandate a conservative therapeutic approach. The 2001 classification was rapidly adopted for clinical trials and successfully served as a common language for scientists comparing genetic and functional data. The modifications made in the 2008 classification are the result of this successful partnership among pathologists, clinicians, and biologists, but are only a stepping stone to the future.

The 2008 WHO classification of lymphomas: implications for clinical practice and translational research

The 4(th) edition of the WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues published in 2008 builds upon the success of the 2001 3(rd) edition; new entities are defined, and solutions for problematic categories are sought. Recent studies have drawn attention to the biological overlap between classical Hodgkin lymphoma (CHL) and diffuse large B-cell lymphomas (DLBCL). Similarly, there is a greater appreciation of the borderlands between Burkitt lymphoma and DLBCL. Strategies for the management of these borderline lesions are proposed. Additionally, age-specific and site-specific factors play an important role in the definition of several new entities, which also have biological underpinnings. Among the peripheral T-cell lymphomas (PTCL), more precise definitions were introduced for several entities, including anaplastic large cell lymphoma, angioimmunoblastic T-cell lymphoma, enteropathy-associated T-cell lymphoma, and subcutaneous panniculitis-like T-cell lymphoma. Several new variants of primary cutaneous T-cell lymphomas are proposed. Finally, the subclassification and categorization of the most common lymphoma subtypes, follicular lymphoma (FL) and DLBCL, were altered to enhance diagnostic accuracy and aid in clinical management. The 2008 WHO classification also draws attention to early events in lymphomagenesis. These lesions help delineate the earliest steps in neoplastic transformation and generally mandate a conservative therapeutic approach. The 2001 classification was rapidly adopted for clinical trials and successfully served as a common language for scientists comparing genetic and functional data. The modifications made in the 2008 classification are the result of this successful partnership among pathologists, clinicians, and biologists, but are only a stepping stone to the future.

AUPD in the Clonal Evolution of Follicular Lymphoma.

The use of Single Nucleotide Polymorphism (SNP) array profiling has uncovered extensive regions of acquired uniparental disomy (aUPD) in the cancer genome that go undetected using cytogenetics or array-CGH platforms. These regions usually arise by mitotic recombination and can render a cell homozygous for a pre-existing abnormality. SNP array analysis was performed using the Affymetrix 10K Gene-chip mapping array on DNA extracted from a series of Follicular Lymphoma (FL) lymph nodes biopsies from 42 patients, taken at time of diagnosis (n=20), progression (n=16) and transformation (t-FL) (n=32), and the t(14;18) positive lymphoma cell lines DoHH2 and RL 2261. Analysis was performed using the genome oriented laboratory file system, a software package designed to interpret SNP data. The criteria of > 96% homozygosity in at least 50 contiguous SNPs was found to detect no abnormalities in 24 normal remission bone marrows and was therefore adopted for the detection of abnormal runs of homozygosity. Abnormalities were detected in 53/68 primary specimens; these were non-random with recurring sites of aUPD on several chromosomes including 6p, 9p, 12q and 17p. This panel included 26 paired FL and t-FL samples; in 9 FL cases regions of homozygosity were identified which were not present in the subsequent t-FL sample, suggesting that t-FL may arise in a proportion of patients by a mechanism other than a process of direct clonal evolution. Homozygosity of 9p and 17p was seen primarily in the transformation samples and in three cases rendered the cell homozygous for a pre-existing mutation of either CDKN2A or TP53. Thus mutation precedes mitotic recombination which leads to the removal of the remaining wild-type allele. Nine out of 42 patients studied (21%) have aUPD of chromosome 6p. This appears to be an early event in lymphomagenesis as it was present in both FL and t-FL samples obtained from the same patient. The sites of mitotic recombination cluster in a region immediately proximal to the MHC complex at 6p21-12 in 8/9 cases. Mutations in CCND3, CDKN1A, and two translocation partners of BCL6: SRP20 and HIST1H4I, which are all located within or just distal of this cluster, were excluded by direct sequence analysis. Loss of MHC class II expression has been frequently observed in Diffuse Large B-cell lymphoma and a selective advantage gained by the lymphoma cell here would have implications in tumour surveillance. This study highlights the frequency of aUPD in follicular lymphoma and ongoing studies will elucidate the selective basis of a UPD at this location in the pathogenesis of lymphoma.

Historical review of lymphomas.

Historical review of lymphomas.