ALBERT

Description: Burkitt lymphoma (BL) predominates in pediatric patients, whereas diffuse large B-cell lymphoma (DLBCL) is uncommon. In contrast to adults, BL and DLBCL are treated similarly in children and both entities have superior outcomes in children compared with adults. Gene expression profiling (GEP) and miRNA expression profiling clearly differentiated pediatric DLBCL from BL, forming distinct clusters regardless of patient age. However, pathway analysis of GEP data identified minor differences between corresponding pediatric and adult tumors. Predominance (6:1) of the germinal center B-cell subtype to activated B-cell subtype was found among pediatric DLBCL. Two cases were molecularly classified as primary mediastinal B-cell lymphoma. We observed frequent abnormalities in 8q24 in pediatric DLBCL, including MYC rearrangement in 31% (5 of 16) and gain or amplification in 50% (6 of 12) nonrearranged cases. MYC rearrangement was present in 96% (23 of 24) BL cases. Array-based CGH analysis identified abnormalities that are shared between adult and pediatric DLBCL (+12q15, +19q13, −6q), and abnormalities unique to the pediatric cases (−4p14, −19q13.32, +16p11.2), suggesting distinct pathogenetic mechanisms relative to age. Elucidation of the underlying target genes may provide insight into factors that modulate outcome and could provide potential novel therapeutic targets with less toxicity for pediatric patients with B-cell non-Hodgkin lymphoma.

Description: Abstract 2648 Follicular lymphoma (FL) is an indolent lymphoma and the second most common type of non-Hodgkin lymphoma in the Western world. It is characterized by the t(14;18) chromosomal translocation, which is present in up to 90% of cases. About 40% of FL cases eventually transform into a more aggressive lymphoma (tFL), most commonly diffuse large B-cell lymphoma (DLBCL). To identify the secondary chromosomal abnormalities that contribute to the development of FL, and to its transformation, we undertook a large study using the Affymetrix 250k NspI SNP array to identify copy number abnormalities (CNAs) in 198 FL and 79 tFL samples, 75% of which have concurrent gene expression profiling studies using Affymetrix U133+2 or A+B arrays for correlative analysis. There were 22 recurrent chromosomal abnormalities that were present in over 10% of FL cases, including gains of 7, 12, 18, 21, X, 1q, 2q, 5p, 6p, 8q, 17q and loss of 6q. We also identified 20 smaller CNAs that occurred in over 5% of FL cases, the most frequent being loss of chromosome 1p36.33-p36.31 including TNFRSF14, loss of chromosome 10q23.1-q25.1 encompassing several possible cancer-related genes such as PTEN, gain of chromosome 2p16.1-p15 including REL, and gain of chromosome 8q24.13-q24.3 including MYC. Univariate Cox regression models were used to analyze the CNA regions that occurred in at least 10 FL cases as predictors of overall survival. Four recurrent CNAs were predictive of survival in univariate analysis below the p=0.05 significance level, and two were found to be borderline significant. A gain of X or the p arm of X was predictive of poor survival. Additionally, two losses on 6q (6q13–15 and 6q23.3–24.1) were associated with poor survival. The 6q23.3–24.1 loss contains TNFAIP3, which encodes a negative regulator of the NF-kB pathway, and is a frequent site of homozygous loss. Additionally, a gain of chromosome 8 that includes the MYC gene, and a loss of chromosome 9 that includes CDKN2A, were borderline predictors of poor survival. Patients with FLs that have 7 or more abnormalities had worse survival than those with fewer abnormalities. We also compared the CNAs found in tFL samples to FL samples and identified 26 abnormalities that were at least 5 times more frequent in tFL and present in at least 5% of tFLs. A gain of 3q27.3-q28 containing 5 genes including BCL6 and LPP, for example, was found in 11% of tFL case, but only 2% of FL cases. We also found differences in the deletion of Beta-2 Microglobulin (B2M) between FL and tFL. The B2M locus is deleted in 8% of FLs, but in 21% of tFLs. B2M, a subunit of the MHC class I molecule, is known to be repressed by mechanisms such as mutation and deletion in de novo DLBCL, as a way for the tumor to evade immune surveillance. HLA-A- B, and/or -C were deleted in 5% of FLs and almost 9% of tFLs. CD58, which plays a role in T- and NK-cell immune responses, was deleted in 3% of FLs and 11% of tFLs. Overall, 19% of FLs and 37% of tFLs had an abnormality in CD58, B2M, and/or HLA class I, indicating that evasion of immune surveillance is important in transformation to a more aggressive disease. We also compared CNAs from tFL cases to those found in de novo GCB-DLBCL cases and identified several that differed markedly between the 2 diseases, such as a gain of chromosome 21 which was present in 21% of tFL cases but only 3% of DLBCL cases. In conclusion, FL, tFL, and de novo GCB-DLBCL share common CNAs, but the prevalence of the individual lesions differ among the 3 entities. Functional validation of potential candidate genes will determine important pathways in the development and progression of FL, and identify possible targets for therapeutic intervention. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 2922 Poster Board II-898 Introduction: Lymphomas derived from mature lymphocytes in children and adolescents are predominantly aggressive B-cell non-Hodgkin lymphomas (B-NHL), including Burkitt lymphoma (BL) and diffuse large B-cell lymphoma (DLBCL). Differences in the clinical course between pediatric and adult aggressive B-NHL suggest distinct pathogenetic mechanisms. This study sought to identify both shared and unique genetic alterations between gene expression-defined pediatric and adult cases of BL and DLBCL. Patients and Methods: Gene expression profiling (GEP) was done on 45 BL and 18 DLBCL specimens from patients 18 years of age or younger, and 38 BL and 106 DLBCL from adult patients. Pediatric specimens were collected from the Cooperative Human Tissue Network (CHTN) pediatric NHL repository through the Children's Oncology Group (COG) and adult specimens were collected from the Nebraska Lymphoma Study Group Registry and Tissue Bank through the Lymphoma/Leukemia Molecular Profiling Project (LLMPP). Previously-published gene signatures were used to classify lymphomas molecularly into mBL and mDLBCL groups (Dave et al., NEJM, 2006). The mDLBCL tumors were further classified into activated B-cell-like (ABC), germinal center B-cell-like (GCB), and primary mediastinal B-cell lymphoma (PMBL) subtypes (Rosenwald et al., JEM, 2003). High resolution array comparative genomic hybridization (aCGH) was done on a subset of the pediatric cases using the 250K NspI Human Mapping Array (Affymetrix) to detect DNA copy number alterations (CNA). Results: Molecular classification of the pediatric cases resulted in a 20% reclassification rate for cases with a morphologic diagnosis of BL or DLBCL. Among the 63 pediatric cases, there were 38 mBL (3 of which were DLBCL by morphology), 23 mDLBCL (9 of which were BL by morphology) and two cases which were unclassifiable by the molecular gene signatures. Comparison of the GEP profiles for adult and pediatric mBL failed to identify pathways that differed significantly; however high resolution aCGH analysis revealed a number of abnormalities in the pediatric cases not previously reported in BL, including gains of 3q21, 11q13 and 16p11. A predominance of the GCB to ABC subtype (3:1) was found among pediatric mDLBCL patients. Two cases with mediastinal tumors were classified as PMBL molecularly. Both PMBL cases were female and carried copy number gains of the Rel/BCL11A locus. Comparison of adult and pediatric GCB mDLBCL gene expression revealed enrichment in B-cell surface molecules and markers of antigen-dependent B-cell activation in the adult cases. aCGH analysis identified abnormalities that were both shared (+12q15, +19q13, -6q) between adult and pediatric mDLBCL and unique (-4p14, -19q13.32, +16p11.2) to the pediatric cases. Correlation of DNA copy number and gene expression revealed potential candidate genes for these loci. Conclusions: Pediatric BL and DLBCL classified by morphology were reclassified molecularly in a significant fraction of cases. Although pediatric BL and DLBCL are treated similarly, defining homogeneous molecular entities will be relevant for developing new therapies and future clinical trials. In general, pediatric cases have a more favorable outcome relative to adult patients. However, it is unclear whether this is due to the ability of children to tolerate very intensive therapies or whether distinct pathogenetic mechanisms modulate the disease course. Higher B-cell receptor signaling in adult relative to pediatric GCB DLBCL may be relevant to the outcome. The identification of previously undetected chromosomal alterations unique to the pediatric cases also suggests distinct pathogenetic mechanisms. Elucidation of the underlying genes may provide insight into factors which modulate outcome and could provide novel therapeutic targets with reduced toxicity. Disclosures: Gascoyne: Roche Canada: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Description: Background: Follicular lymphoma (FL) is the most common indolent B-cell lymphoma and remains incurable by current therapeutic approaches. Clinical course is variable, and transformation into an aggressive lymphoma (t-FL) with marked worsening of prognosis occurs in 20–60% of patients. While Bcl2 gene translocation is a critical initiating event in the majority of FL cases, evidence indicates it is not sufficient for the development of a FL. Characterization of the genetic alterations subsequent to Bcl2 translocation will lend insight into the oncogenic pathways that contribute to FL pathogenesis and the molecular mechanisms underlying variability in clinical course. Methods: To define recurrent genomic copy number alterations (CNA) in FL, we performed high resolution array comparative genomic hybridization (aCGH) using the Affymetrix 500K SNP array platform. aCGH data were generated on a series of 112 FL cases with available gene expression profiling (GEP) and clinical information. Gene expression data were correlated with copy number data using the Gene Expression and Dosage Integrator (GEDI) algorithm developed at the NCI. Results: Selecting for abnormalities occurring in 〉10% of cases, the minimal common region (MCR) for 38 losses and 31 gains were defined. Novel common regions included gains on 15q11, 16p11, 5p14 and 19q13, and losses on 3q29, and 16p13. The MCR identified by aCGH were also compared with our existing cytogenetic data on 360 FL cases. MCR residing within the most frequent cytogenetic imbalances (〉5%) were selected for analysis at the gene level to further refine these regions. These include gains on 1q21, 2p16, 7q11, 8q24, 12q13, 17q21, 18q21, 21q11, and X, and losses on 1p36, 6q, 10q, 13q34, and 17p13. Recurrent amplifications were detected for the 2p16, 15q11, and 17q21 MCR, while frequent uniparental disomy (UPD) was found to overlap the region of loss on 1p36. Recurrent UPD was also noted on 6p, 12q, 15q and 16p. For the majority of selected MCR, global expression of the genes residing in the MCR demonstrated an association with copy number status. Within these abnormalities, individual genes showing significant correlation with copy number were also identified. Conclusion: The combination of high resolution aCGH and GEP facilitated the identification of functionally relevant genes within the chromosomal abnormalities in FL. Delineation of these molecular targets will provide insight into the oncogenic pathways that contribute to FL disease pathogenesis and may provide novel therapeutic targets.

Description: Abstract 313 Background: Natural Killer (NK) cell lymphomas (NKCL) are rare with aggressive clinical behavior. The majority of these cases belong to extra-nodal NK/T-cell lymphoma of nasal type (ENKTL) of the current World Health Organization (WHO) classification scheme. ENKTL also includes peripheral T-cell lymphomas (PTCL) that are similar in many respects to the NK cell counterpart. Due to rarity of the disease and difficulty in obtaining adequate biopsy specimens, the molecular mechanisms underlining ENKTL are largely unknown. We profiled a series of NK-cell lymphoma cases and many well- characterized cell lines of NK- and T-cell lineages to define molecular classifiers that can distinguish NKCL from PTCL, including lymphomas of cytotoxic T-cells. We also evaluated oncogenic pathways in these tumors and the therapeutic potential of a novel inhibitor of a cell cycle regulator (aurora kinase A). Patients and Methods: The gene expression profiling (GEP) of ENKTL (n=21) and PTCL-U (n=50) cases were performed using HG U133 plus 2 arrays (Affymetrix Inc, CA). GEP of other PTCL subtypes (n=90), normal NK and T cells (resting and activated), NK and T cell lines (n=14) and indolent NK- cell/large granular lymphocytic proliferation (NK-LGLP) (n=5) were used for comparative analysis. Immunohistochemistry (IHC) was used to validate the GEP findings. A novel aurora-kinase-A inhibitor (MK-8745) was obtained from Merck & Co (Merck & Co., Inc. NJ, USA) and incubated with the cell lines for 2 -24 hours at 0.1-1 μM concentrations. Results: The ENKTL showed a male predominance (2:1) with a median age of 55 years at diagnosis and aggressive clinical behavior [5-year OS (

Description: Key Points Chromosome copy-number alterations that may affect immune surveillance and the NF-κB and p53 pathways are more frequent in tFL than FL. Abnormalities involving chromosomes 6 and X are predictive of overall survival in FL.