Stereotyped B-cell Receptors Research Articles

In Chronic Lymphocytic Leukemia the Gain of the Short Arm of Chromosome 2 Is Highly Associated with an Unmutated IGHV status, 11q/ATM Deletion, SF3B1 Mutation and a Complex Karyotype

Background: CLL is characterized by a distinct pattern of translocations, genomic gains and losses and molecular mutations. The most frequent abnormalities such as trisomy 12 and deletions of 6q, 11q, 13q and 17p have been intensively studied. However, data on less frequent recurrent abnormalities such as the partial gain of the short arm of chromosome 2 is lacking.Aims: a) Determine the frequency of 2p gain in CLL, b) Characterize the size and the commonly gained region, c) Analyze the spectrum of additional cytogenetic abnormalities and molecular mutations, and d) Evaluate the prognostic impact.Patients and Methods: Chromosome banding analysis (CBA) revealed a gain of 2p in 113 out of 5564 (2%) CLL cases. In 72 cases with sufficient material genomic array analysis (SurePrint G3 ISCA CGH+SNP Microarray, Agilent, Waldbronn, Germany) and determination of the mutation status of TP53, SF3B1 and IGHV were performed.Results:76% of patients with gain of 2p were male. The median WBC count was 33,700/µL (range: 5,900 - 228,000). Median age was 66 years (range: 29 - 87).The gain of 2p always encompassed the 2p telomere (2pter) while the centromeric border of the 2p gain varied between 2p21 and the centromere of chromosome 2 (2p10) (genomic positions 45,859,076 to 92,297,003).The gain of 2p was the sole chromosomal abnormality in only 8/72 cases (11%) and was accompanied by one, two or more than two additional aberrations in 10, 20, and 34 cases. In total 209 chromosome abnormalities were observed in addition to the 2p gain (median per patient: 2, range: 0-16). Of these only 21 were balanced while 188 were unbalanced abnormalities leading to gain or loss of chromosomal material. Gain of 2p was most frequently accompanied by deletions in 13q (total: 74%, homozygous: 11%), 11q (56%), 18p (18%), and 6q (13%) and gains of 8q (11%). 17p deletions were present in 6% of cases.In 49 cases (68%) the gain of 2p was present in the main clone while it was present in a subclone only in 23 cases (32%). The gain of 2p material was due to a duplication in the short arm of chromosome 2 in 10 cases, while a gain of an isochromosome 2p was present in 3 cases. In the remaining cases material of the short arm of chromosome 2p was attached to a variety of different partner chromosomes. The most frequent acceptor chromosome was chromosome 18 (n=13; 18%).In two cases (2%) 2 IGH rearrangements were observed of which one was mutated and the other unmutated. The IGHV status was unmutated (IGHV-U) in 66 (92%) and mutated in only 4 cases (6%). Three of these 4 cases with mutated IGHV showed only a low mutation rate (sequence homology to germline 97-97.9%). Stereotyped B-cell receptors were present in 14 cases (19%). SF3B1 mutations were observed in 21 cases (29%) with a median mutation load (ML) of 39% (range: 10-51%). TP53 mutations were detected in 8 (11%) cases (median ML: 60%, range: 13-100%). In 2 patients with a TP53 mutation a TP53 deletion was present and in 3 cases a copy neutral loss of heterozygosity (CN-LOH) of 17p was detected leading to TP53 wild-type loss in these 5 cases. TP53 mutations were less frequent in cases harboring the gain of 2p as the sole abnormality (3% vs 21%, p=0.02)The prognostic impact of 2p gain was evaluated in an unselected cohort of 1381 CLL cases with available follow up data (median follow up: 5.1 years) including 22 cases with 2p gain. The frequency of IGHV-Ustatus, SF3B1 mutations and 11q/ATM deletions was significantly higher in CLL with 2p gain compared to cases without (for all p<0.05). In univariate Cox regression analysis gain of 2p was significantly associated with shorter overall survival (OS) (relative risk (RR): 2.1; p=0.05). 5 year OS was 69% in CLL with 2p gain compared to 85% in cases without 2p gain (p=0.05). However, in multivariate analysis only IGHV-U, mutations in SF3B1 and TP53 and TP53/17p deletion were independently associated with shorter OS, while gain of 2p and 11q/ATM deletion were not. 2p gain was associated with shorter time to treatment (TTT) (RR: 2.0; p=0.02). In multivariate analysis only IGHV-U, SF3B1 mutation and 11q/ATM and TP53/17p deletion were independently associated with shorter TTT, while gain of 2p and TP53 mutations were not.Conclusions:CLL with gain of 2p is highly associated with an unmutated IGHV status (92%), a high frequency of 11q/ATM deletion (56%), 13q deletion (74%), SF3B1 mutation (29%) and a complex karyotype (47%). Data suggest that gain of 2p is a later event in CLL pathogenesis and might be a marker of progression. DisclosuresHaferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Jeromin:MLL Munich Leukemia Laboratory: Employment. Stengel:MLL Munich Leukemia Laboratory: Employment. Meggendorfer:MLL Munich Leukemia Laboratory: Employment. Zenger:MLL Munich Leukemia Laboratory: Employment. Kern:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.

High Resolution Igh Repertoire Analysis Reveals the Human Fetal Liver As the Origin of Life-Long, Innate B Lymphopoiesis

Introduction: Development of mature B cells depends upon the expression of a functional B cell receptor (BCR) and of its immunoglobulin (Ig) heavy (H) and light (L) chains. The molecular hallmark of B cell development, somatic recombination of the genes that encode the IgH (V, D and J) and IgL (V and J) chains, takes place in B cells in primary B lymphopoiesis sites throughout development (i.e. fetal liver (FL), fetal bone marrow (FBM) and adult BM). However, the spatiotemporal relationship between the IgH repertoire in FL with that in FBM, and the impact of the fetal Ig repertoire on the long-term repertoire present in post-natal life, as well as the link between this and the development of disease, are largely unknown.Aim: To gain insights into the ontogeny of the human innate B cell repertoire by performing high resolution analysis of the IgH-Cmu repertoire of human FL, FBM and post-natal B cells.Methods: CD34negCD19pos B cells from human 2nd trimester FL and FBM, child peripheral blood (cPB) and adult peripheral blood (aPB) were isolated by flow sorting. For initial assessment of the IgM repertoire ontogeny in FL and FBM B cells, we performed CDR3 fragment length analysis of VH1-VH6 families in the B cells. To gain further insights into the ontogeny of IgH diversification, we employed 454 next generation sequencing (NGS)-based analysis of the IgVH-Cmu mRNA repertoire in FL, FBM and postnatal B cells. In total, 20 libraries generated from 17 individual, flow-sorted CD34negCD19pos B cell samples were sequenced: 5 FL (4 performed in independent duplicate libraries; GA 14-18 weeks), 3 FBM (GA 13-17 weeks), 3 cPB (age 4mo-4yrs) and 5 aPB (age 29-53 yrs) samples. Bioinformatic analysis was performed with the ARResT/Interrogate immunoprofiler, IMGT tools, and appropriate statistics.Results: Spectratyping and NGS data showed that the molecular mechanisms responsible for VDJ recombination-dependent repertoire diversification, such as convergent recombination, are active in early B cell development and as efficient as postnatal B cells in both FL and FBM. Comparably diversified B cell lymphopoiesis exists contemporaneously in FL and FBM. However, analysis of the top 100 most abundant clonotypes in each developmental stage showed that their mean abundance in FBM B cells was 10 times lower (0.12%) than in FL B cells (1.2%; p<0.0001). Reflecting this relative paucity of expanded clonotypes amongst FBM B cells, analysis of the 100 most abundant clonotypes across all developmental stages showed that 0 were present in FBM, compared to 65 in FL, 23 in cPB, and 12 in aPB. We found that this paucity of clonotypic expansions in FBM is likely due to the significant decrease in sIgM-expressing transitional and naïve B cells compared to FL (FL: 4.76±0.8% vs. FBM: 1.9±0.4%, p<0.01; and FL: 2.8±0.9% vs. FBM: 0.7±0.2%, p<0.05 respectively). Strikingly, 0.4% of all fetal life clonotypes, comprising 18.7% of the whole repertoire, were shared with the PB IgM B cell repertoire in children and adults, a pattern that is particularly pronounced for the VH6-1 gene. Reflecting the presence of high abundance clonotypes in FL but not FBM, the mean abundance of the clonotypes shared between FL and postnatal B cells was 38-fold higher than that of FBM (0.77% v 0.02%, p=0.001). Selection of these shared or public clonotypes is likely to occur in an HLA- and thus T cell-independent manner, and is therefore consistent with IgM innate humoral immune responses. Lastly, chronic lymphocytic leukemia (CLL) is the most common IgM+ mature B cell malignancy with subsets of patients with stereotyped BCR collectively accounting for ~30% of cases; we found stereotypic IgH receptors corresponding to 16/19 major CLL subsets in 3/5 FL samples and in all FBM and postnatal samples.Conclusions: The lack of mature, antigen-responsive B cells in FBM and the pronounced clonotypic expansions in FL suggest that FL is the main source of IgM natural immunity during the 2nd trimester. Our results are consistent with persisting fetal IgM+ B cells being an important source of the natural IgM repertoire also in adult life. Further, the origins of specific stereotypic IgM+ BCR associated with CLL, can be traced back to fetal B cell lymphopoiesis, suggesting that persisting fetal B cells can be subject to malignant transformation late in life. Overall, these novel data provide unique insights into the ontogeny of physiological and malignant B lymphopoiesis that spans the human lifetime. DisclosuresNo relevant conflicts of interest to declare.

Different spectra of recurrent gene mutations in subsets of chronic lymphocytic leukemia harboring stereotyped B-cell receptors.

We report on markedly different frequencies of genetic lesions within subsets of chronic lymphocytic leukemia patients carrying mutated or unmutated stereotyped B-cell receptor immunoglobulins in the largest cohort (n=565) studied for this purpose. By combining data on recurrent gene mutations (BIRC3, MYD88, NOTCH1, SF3B1 and TP53) and cytogenetic aberrations, we reveal a subset-biased acquisition of gene mutations. More specifically, the frequency of NOTCH1 mutations was found to be enriched in subsets expressing unmutated immunoglobulin genes, i.e. #1, #6, #8 and #59 (22-34%), often in association with trisomy 12, and was significantly different (P<0.001) to the frequency observed in subset #2 (4%, aggressive disease, variable somatic hypermutation status) and subset #4 (1%, indolent disease, mutated immunoglobulin genes). Interestingly, subsets harboring a high frequency of NOTCH1 mutations were found to carry few (if any) SF3B1 mutations. This starkly contrasts with subsets #2 and #3 where, despite their immunogenetic differences, SF3B1 mutations occurred in 45% and 46% of cases, respectively. In addition, mutations within TP53, whilst enriched in subset #1 (16%), were rare in subsets #2 and #8 (both 2%), despite all being clinically aggressive. All subsets were negative for MYD88 mutations, whereas BIRC3 mutations were infrequent. Collectively, this striking bias and skewed distribution of mutations and cytogenetic aberrations within specific chronic lymphocytic leukemia subsets implies that the mechanisms underlying clinical aggressiveness are not uniform, but rather support the existence of distinct genetic pathways of clonal evolution governed by a particular stereotyped B-cell receptor selecting a certain molecular lesion(s).

Auto-Immune Origin of B Cells from HCV-Associated Lymphoma

Hepatitis C virus (HCV) infection is a well-established risk factor for the development of B cell non-Hodgkin lymphoma (B-NHL). Two main pathways have been proposed to explain the role of the virus in lymphomagenesis: 1) transformation of B cells either directly by oncogenic viral proteins, or by a hit-and-run mechanism inducing a mutator phenotype, and 2) chronic antigenic stimulation through the B cell receptor (BcR) in conjunction to the binding of the viral E2 protein to its receptor CD81. There are however conflicting data regarding whether the BcR of the lymphomatous cells are capable of directly recognizing viral proteins or, rather, they possess a rheumatoid factor (RF) activity, binding instead polyclonal immunoglobulin (IG) within immune complexes trapping the virus.To further elucidate the role of antigenic stimulation in the natural history of HCV-associated B-NHL, we analyzed the IG gene repertoire of both heavy and light chains expressed by neoplastic cells in 41 cases of HCV-associated NHL, including: 29 marginal zone lymphoma (MZL); 7 diffuse large B-cell lymphoma (DLBCL) of which 3 originated from transformed MZL ; and 5 other low-grade B-cell NHL. Tumor cells were obtained from blood in 39 cases, bone marrow and a lymph node biopsy in 1 case each.Forty-three productive IGHV-IGHD-IGHJ gene rearrangements were obtained, which displayed a clear biased gene composition as 3 IGHV genes contributed to almost half of the repertoire: IGHV1-69 (11/43, 25,6%), IGHV3-7 (5/43, 11.6%), IGHV3-21 (4/43, 9.3%). This was also true for both IGHD genes (IGHD3-22: 12/43, 27.9%), and IGHJ genes (IGHJ4: 17/43, 39.5%; IGHJ3: 17/43, 25.6%). All but 3 sequences carried somatic hypermutations (SHM) in their IGHV genes with a median identity to the germline of 97.6% (range 86.5-100%).Thirty-eight productive IG light chain rearrangement sequences were obtained from 36 cases, of which 30 (78.9%) were IGK. Similarly, they exhibited strong gene usage bias with an over-representation of IGKV3-20 (9/30, 30%), as well as IGKJ1 (11/30, 33.3%) and IGKJ2 (6/30, 20%). IG light chain sequences were found to harbor similar SHM load with a 97% median identity to germline (range 91-100%). As previously described, we observed preferential pairing of heavy and light chain genes, with 6 of the 9 IGHV1-69 cases (with available light chain sequence data) being associated with IGKV3-20.Using established criteria, we found 5 cases (11.6%) carrying stereotyped BcR i.e. IGHV-IGHD-IGHJ gene rearrangements with quasi-identical amino-acid (AA) sequences, including the highly variable complementary determining region 3 (CDR3). Three cases concerned IGHV3-7/IGHD3-22/IGHJ3 rearrangements with an 18 AA-long CDR3, and 2 concerned IGHV1-69/IGHD3-22/IGHJ4 rearrangements with a 13 AA-long CDR3. Identity within the CDR3 extended to AA encoded by randomly inserted N-region nucleotides.We failed to establish correlations between histological categories and IG repertoire, probably due to the uneven distribution of lymphoma subtypes within our cohort. In contrast, most if not all sequences with biased IG gene usage, including the 5 stereotyped BcR ones, were found amongst the 28/41 cases (68.3%) with mixed cryoglobulinemia type II and/or positive for RF (MC/RF+). These two categories of patients differed also regarding the SHM load of their IGHV genes since MC/RF+ cases were signlificantly less mutated than MC/RF- cases (median identity to germline: 97.9% vs 95.9%, p= 0.048).We then searched for similar sequences in public databases and collaborative studies. Stereotyped BcR sequences similar to those of our cases were detected in HCV-associated lymphoma, but also in other HCV-negative B-cell maligancies e.g. MALT lymphoma (some associated with RF) and chronic lymphocytic leukemia, non malignant B cells with RF activity, and non malignant marginal zone splenic B cells. Sequence similarity extended to some shared AA replacements, e.g. identical AA introduced by HSM at the same positions.In conclusion we confirm the highly biased IG repertoire of HCV-associated lymphoma. However this feature seems to be linked essentially to the presence of a MC and/or RF. As quasi-identical sequences are found in HCV-negative malignant and normal B cells, our data support the hypothesis that HCV-associated lymphomatous cells originate from precursors endowed with auto-immune properties rather than B cells expressing an anti-virus BcR. DisclosuresStamatopoulos:Gilead Sciences: Research Funding; Janssen Pharmaceuticals: Research Funding.

Comprehensive Biological and Molecular Characterization of a RARE Case of Cutaneous Richter Syndrome

BACKGROUNDRichter syndrome (RS) is associated with unmutated VHIG status, VHIG 4 -39 sequences, stereotyped B-cell receptors and expression of ZAP70, CD38 and CD49d, as well as with a frequent disruption of TP53, ATM and CDKN2A, and mutational activation of NOTCH1. RS presents with extranodal involvement including gastrointestinal tract, lung, kidney, eye, testis, central nervous system, and skin. Extranodal RS presenting as skin lesion is extremely rare with only few cases reported and a biological and molecular characterization of these cases is still lacking. On the basis of these observations, we undertook a comprehensive characterization of a rare cutaneous RS transformation of CLL to DLBCL and investigated prognostic biological implications.CASEA 59 year-old woman affected by CLL, stage III/B, 13q14 and 11q23 deletion, presenting massive splenomegaly and pleural effusion underwent treatment with fludarabine-cyclophosphamide and rituximab (FCR). Third cycle was complicated by prolonged neutropenia, and chemotherapy was discontinuated. CT scan documented complete remission and bone marrow (BM) biopsy showed initial myelodysplastic features and presence of 7q deletion. Complete remission (CR) with incomplete recovery was achieved, and patient continued follow-up. As persistent neutropenia was observed, subsequent BM evaluation was performed showing unchanged morphology and normal cytogenetic. No signs of CLL relapse were present.Eight years later, the patient presented edema of the right foot, rapidly worsened until prevent independent walking. Numerous hard papules and plaques appeared and multiple nodules were appreciable in subcutaneous tissue of both thighs and legs. B symptoms were absent.CBC count showed persistent mild leucopenia and LDH levels were not increased,Ultrasound of foot soft tissues revealed an organized anechoic nodal mass. Hystological examination documented a diffuse proliferation of large lymphoid cells, with a centroblastic morphology infiltrating the subcutaneous soft tissues displaying the following immunophenotype: CD20+, CD3-, CD5+, CD23+/-, cyclinD1-, bcl2+, CD10- bcl6-, MUM1+/-, EBV-, ZAP70-, p53 -, Ki67 40-50%.11q23 deletion was also observed by FISH on formalin-fixed, paraffin embedded section suggesting that cutaneous lymphoma and leukemia arose from the same clone.Furthermore, NOTCH1 hotspot mutation (c.7544_7545delCT) was absent both on foot soft tissues sample and on cryopreserved peripheral blood of CLL diagnosis.CT scan was normal except for mild splenomegaly, while Positron Emission Tomography (PET) showed intense uptake on right ankle, multiple nodular in subcutaneous tissue of lower limbs and feet.Cutaneous DLBCL consistent with RS was diagnosed and patient received 6 courses of R-CHOP. PET after 3 cycles of treatment show reduction of uptake and an evaluation at the end of therapy confirmed CR of RS that continued after 12 months of follow-up.CONCLUSIONCutaneous RS is exceptionally rare with only few reports or small case series described in literature In this study, we present a case of cutaneous RS occurred in patient in CR after chemo-immunotherapy for CLL. To the best of our knowledge, this is the first investigation assessing a comprehensive biological and molecular characterization of cutaneous RS case. Finally, we pointed out as the present case is interesting since it may represent a model of RS that diverges in prognosis from nodal involvement. DisclosuresNo relevant conflicts of interest to declare.

Identifying High-Risk Chronic Lymphocytic Leukemia: A Reappraisal of the Impact of Prognostic and Predictive Factors

Background: Chronic lymphocytic leukemia displays an extremely variable clinical behaviour. The availability of effective first-line regimens and recent data on the efficacy of novel molecules targeting B-cell receptor (BCR) signalling make prognostication and prediction of response to treatment a mandatory exercise in clinical practice. A plethora of prognostic biomarkers have been identified, but few of them were validated by multivariable analysis in the context of prospective studies.Methods: Based on previous analyses, 18 biomarkers known to have prognostic significance were included in this survey: stereotyped receptors and BCR subsets, CD38, ZAP70, CD49d, IGHV gene mutational status, 17p-/TP53 mutations, 11q-, telomere length, complex karyotype, NOTCH1 and SF3B1 mutations, age, gender, performance status (PS), stage, lymphocytosis, beta-2-microglobulin, thymidine kinase (TK).A literature search was performed to identify reports describing the prognostic impact of each biomarker. Twenty-one papers fulfilling the following stringent requirements were included in this analysis: i) thorough assessment of the main known prognostic parameters, i.e. salient clinical and genetic data; ii) prospective design of the study (clinical trial) or single/multicentre study using a learning cohort and a validation cohort.Each prognostic marker was analysed: i) as a prognostic factor, with reference to its impact on time to first treatment (TTFT), complete response (CR) rate, progression free survival (PFS) and overall survival (OS); ii) as a predictive factor, in terms of response to specific treatment and transformation into Richter's syndrome.Results: Sixteen of the 18 parameters showed unfavourable prognostic significance in at least 1 study (Figure 1). No paper fulfilling our stringent inclusion criteria was found to address the impact of stereotyped BCR or BCR subsets and ZAP70 expression did not show independent significance in any of the selected studies. Eleven parameters showed unfavourable impact on TTFT, PFS and/or OS in at least 2/3 of the selected studies (Table 1), thus representing reproducible markers of outcome. 17p-/TP53 mutations and unmutated IGHV proved independent predictors for all outcome measures in the majority of the studies; the same applies to 11q- for TTFT and PFS and serum beta-2-microglobulin for OS (Figure 1). Telomere length proved a reproducible predictor of outcome, but the detection method is not standardized yet. No univocal data emerged from our survey on the predictivity of NOTCH1 and SF3B1 mutations. Host characteristics such as poor PS, advanced age and gender maintained a relevant role in predicting OS (Figure 1).Even though no paper with the required characteristics was found to address the impact of biomarkers on evolution to Richter's syndrome and on response rate, available evidence points to a role for 17p-/TP53 mutations in identifying cases with an inferior CR rate, that was not assessed by multivariable analysis.Conclusions: This review shows that 17p-/TP53 mutations and unmutated IGHV are to be considered the most reliable markers for usage in clinical practice. 11q- has a solid prognostic impact but lost its predictivity on OS in patients eligible to modern chemoimmunotherapy regimens. Beta-2 microglobulin levels along with basic patient's characteristics strongly correlate with OS, while measures of disease burden do not retain a prognostic role. The prognostic significance of CD38 and ZAP70 was overcome by more robust genetic parameters. Adequate clinical trials are needed to assess the impact of biomarkers on predicting response to specific treatments. [Display omitted] [Display omitted] DisclosuresCuneo:Roche: Speakers Bureau; Gilead: Speakers Bureau; Jannsen: Speakers Bureau; Celgene: Speakers Bureau; Novartis: Speakers Bureau.

Restricted, canonical, stereotyped and convergent immunoglobulin responses.

It is becoming evident that B-cell responses to particular epitopes or in particular contexts can be highly convergent at the molecular level. That is, depending on the epitope targeted, persons of diverse genetic backgrounds and immunological histories can use highly similar, stereotyped B-cell receptors (BCRs) for a particular response. In some cases, multiple people with immunity to a particular epitope or with a type of B-cell neoplasia will elicit antibodies encoded by essentially identical immunoglobulin gene rearrangements. In other cases, particular VH genes encode antibodies important for immunity against pathogens such as influenza and HIV. It appears that the conserved antibody structures driving these stereotyped responses are highly limited and selected. There are interesting and important convergences in the types of stereotyped BCRs induced in conditions of immunity and B-cell-related pathology such as cancer and autoimmunity. By characterizing and understanding stereotyped B-cell responses, novel approaches to B-cell immunity and in understanding the underlying causes of B-cell pathology may be discovered. In this paper, we will review stereotyped BCR responses in various contexts of B-cell immunity and pathology.

Functional loss of IκBε leads to NF-κB deregulation in aggressive chronic lymphocytic leukemia.

NF-κB is constitutively activated in chronic lymphocytic leukemia (CLL); however, the implicated molecular mechanisms remain largely unknown. Thus, we performed targeted deep sequencing of 18 core complex genes within the NF-κB pathway in a discovery and validation CLL cohort totaling 315 cases. The most frequently mutated gene was NFKBIE (21/315 cases; 7%), which encodes IκBε, a negative regulator of NF-κB in normal B cells. Strikingly, 13 of these cases carried an identical 4-bp frameshift deletion, resulting in a truncated protein. Screening of an additional 377 CLL cases revealed that NFKBIE aberrations predominated in poor-prognostic patients and were associated with inferior outcome. Minor subclones and/or clonal evolution were also observed, thus potentially linking this recurrent event to disease progression. Compared with wild-type patients, NFKBIE-deleted cases showed reduced IκBε protein levels and decreased p65 inhibition, along with increased phosphorylation and nuclear translocation of p65. Considering the central role of B cell receptor (BcR) signaling in CLL pathobiology, it is notable that IκBε loss was enriched in aggressive cases with distinctive stereotyped BcR, likely contributing to their poor prognosis, and leading to an altered response to BcR inhibitors. Because NFKBIE deletions were observed in several other B cell lymphomas, our findings suggest a novel common mechanism of NF-κB deregulation during lymphomagenesis.

Not all IGHV3-21 chronic lymphocytic leukemias are equal: prognostic considerations

AbstractAn unresolved issue in chronic lymphocytic leukemia (CLL) is whether IGHV3-21 gene usage, in general, or the expression of stereotyped B-cell receptor immunoglobulin defining subset #2 (IGHV3-21/IGLV3-21), in particular, determines outcome for IGHV3-21-utilizing cases. We reappraised this issue in 8593 CLL patients of whom 437 (5%) used the IGHV3-21 gene with 254/437 (58%) classified as subset #2. Within subset #2, immunoglobulin heavy variable (IGHV)-mutated cases predominated, whereas non–subset #2/IGHV3-21 was enriched for IGHV-unmutated cases (P = .002). Subset #2 exhibited significantly shorter time-to-first-treatment (TTFT) compared with non–subset #2/IGHV3-21 (22 vs 60 months, P = .001). No such difference was observed between non–subset #2/IGHV3-21 vs the remaining CLL with similar IGHV mutational status. In conclusion, IGHV3-21 CLL should not be axiomatically considered a homogeneous entity with adverse prognosis, given that only subset #2 emerges as uniformly aggressive, contrasting non–subset #2/IGVH3-21 patients whose prognosis depends on IGHV mutational status as the remaining CLL.

Subset-Specific Spectra of Recurrent Gene Mutations in Chronic Lymphocytic Leukemia with Stereotyped B-Cell Receptors

Preliminary observations from essentially small patient series indicate that certain recurrent gene mutations may be enriched in subsets of chronic lymphocytic leukemia (CLL) with stereotyped B-cell receptors (BcR). On these grounds, it could be argued that differential modes of immune signaling, in the context of subset-biased antigen-immunoglobulin (IG) interactions, may be associated with the acquisition and/or selection of certain genomic aberrations within various stereotyped CLL subsets. With this in mind, we here sought to explore the genetic background of 10 major stereotyped subsets which collectively account for ~11% of all CLL and represent both IGHV unmutated (U-CLL) and/or mutated (M-CLL) cases. We focused on recurrent mutations within the NOTCH1 (entire exon 34 or targeted analysis for del7544-45), TP53 (exons 4-9), SF3B1 (exons 14-16), BIRC3 (exons 6-9) and MYD88 (exon 5) genes. Overall, 647 cases were analyzed, belonging to the following major subsets: (i) U-CLL: #1 (the largest within U-CLL, clinically aggressive), n=139; #3, n=39; #5, n=22; #6, n=48; #7, n=74; #8, n=46; #59, n=19 and #99, n=18; (ii) M-CLL: #4 (the largest within M-CLL, particularly indolent), n=78; and, (iii) subset #2 (the largest overall, variable mutational status and clinically aggressive), n=164. All cases were devoid of MYD88 mutations, which was not surprising given that our cohort was predominantly composed of U-CLL. Mutations within the BIRC3 gene were either absent (#2, #4, #6 and #59) or rare (#1, #3, #5, #7, #8 and #99; frequency 1.5%-7%) with no clear bias to any subset. BIRC3-mutant cases frequently co-existed with either del(11q) or trisomy 12. NOTCH1 mutations were more frequent in subsets #1, #6, #8, #59 and #99 (frequency, 22%-32%), sharply contrasting subsets #2 or #3 (4% and 7%, respectively) (p<0.0001). Of note, although NOTCH1 mutations tended to coincide with trisomy 12 in certain subsets e.g. #1 and #8, their co-occurrence differed significantly with only 33% of NOTCH1mut subset #1 cases carrying trisomy 12 compared to 75% of NOTCH1mut subset #8 cases (p=0.036). Moving to SF3B1, we noted that subsets harboring NOTCH1 mutations were either absent for or carried few SF3B1 mutations, while the inverse was also true i.e. very high frequency of SF3B1 mutations in subsets #2 and #3, 45% and 36%, respectively. Almost 80% of mutations observed in subset #2 were localized to two codons (p.K700E: n=44/76, 58%: p.G742D: n=15/76, 20%) within the HEAT domain of the SF3B1 protein; p.K700E accounted for only 29% (4/14) of all SF3B1 mutations detected in subset #3 while p.G742D was absent (p=0.043 and p=0.068 respectively). Thus, although the functional relevance of these mutations is currently unknown, their high frequency and striking bias to subset #2 bodes strongly for their critical role in the pathobiology of subset #2. Finally, TP53 mutations were: (i) enriched in subsets #3 (11%) and #7 (19%) and, in contrast, absent or rare in subsets #5 (0%) and #6 (4%), despite all utilizing the IGHV1-69 gene (p=0.02); (ii) enriched in subset #1 (15%) and subset #99 (33%), a less populated subset that is highly similar to subset #1; and, (iii) very rare in subsets #2 and #8 (2% in both), the latter known to display the highest risk for Richter’s transformation among all CLL. In conclusion, we confirm and significantly extend recent observations indicating that different CLL stereotyped subsets display distinct genetic makeup. These findings imply that distinctive modes of microenvironmental interactions, mediated by certain stereotyped BcRs, may be associated with selection or occurrence of particular genetic aberrations, with the combined effect determining both clonal and clinical evolution, and ultimately disease outcome. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Revisiting Hypogammaglobulinemia in Chronic Lymphocytic Leukemia: A Combined Clinicobiological Approach

Chronic lymphocytic leukemia (CLL) is characterized by progressive hypogammaglobulinemia that can affect one or more immunoglobulin subclasses. Although many underlying mechanisms have been suggested, the pathogenesis of this phenomenon remains to be elucidated. In the present study, we revisit hypogammaglobulinemia in CLL through a combined clinicobiological approach aiming at identifying associations with particular disease profiles that would offer pathogenetic insight and guidance for further research. The study group included 412 CLL patients with available information about serum immunoglobulins either at diagnosis (n=380) or before treatment initiation (n=32). Patient characteristics were as follows: median age: 65 years; males/females: 266/146; Binet stage A: 272/335, unmutated IGHV genes (U-CLL): 140/412 cases (34%); CD38 expression: 59/330 cases (18%); clonotypic IG of the MD or G isotype: 250 and 43 cases, respectively; isolated del(13q): 64/136 (47%); trisomy 12: 18/183 (10%); del(11q): 18/186 (10%); del(17p): 11/189 (6%); NOTCH1 del7544-45/p.P2514Rfs*4: 8/219 (4%). With a median follow up of 5 years, 152/329 cases (46%) received treatment. Decreased immunoglobulin serum levels in at least one subclass were identified in 220/412 patients (53%), as follows: (i) decreased IgM, 172/412 cases (41%); (ii) decreased IgG, 78/412 cases (19%); (iii) decreased IgA, 100/412 cases (24%). In 36/412 cases (9%), a decrease in all serum immunoglobulin subclasses was noted. No statistically significant differences were identified between patients with normal serum immunoglobulin levels versus those with hypogammaglobulinemia regarding age, gender, disease burden at diagnosis, IGHV gene mutational status, CD38 expression, cytogenetic aberrations, NOTCH1 mutations and the incidence of a second malignancy. However patients with hypogammaglobulinemia exhibited increased need for treatment compared to patients with normal serum immunoglobulins (91/175 vs 61/154 respectively, p=0.025). Among cases with hypogammaglobulinemia, 90 (41%) and 26 (12%) exhibited isolated IgM and IgA subclass deficiency, respectively; isolated IgG decrease, was relatively rare (10/220 cases, 4%). Interestingly, when comparing isolated IgA versus other subclass deficiencies, statistically significant associations were identified with (i) advanced clinical stage (Binet B/C, Rai III/IV) (p=0.002); (ii) female gender (p=0.041); and, (iii) NOTCH1 mutations (p=0.004). A propos of the latter, it is noteworthy that in 5/8 (63%) mutant NOTCH1 cases with hypogammaglobulinemia, the affected subclass was IgA. Within our cohort, we identified cases belonging to one of three different, well characterized subsets with stereotyped B-cell receptor immunoglobulin (BcR IG), namely: (1) subset #1 (clan I IGHV genes/IGKV1(D)-39): U-CLL, clinically aggressive, n=12; (2) subset #2 (IGHV3-21/IGLV3-21), mixed IGHV mutational status, noted clinical aggressiveness, n=5; and, (3) subset #4, mutated IGHV4-34/IGKV2-30 BcR IG, clinically indolent, n=12. Notably, all subset #2 cases showed low levels of at least one serum subclass, while in 4/5 and 3/5 cases, two or all three immunoglobulin subclasses were affected. Although numbers are small, the incidence of hypogammaglobulinemia in subset #2 was significantly (p<0.05) higher compared to either subset #1 or subset #4). Univariate analysis revealed clinical stage, CD38 expression and IGHV mutational status as statistically important parameters (p<0.05) for both time-to-first–treatment (TTFT) and overall survival (OS); in contrast, hypogammaglobulinemia had no impact either on on TTFT or OS. In multivariate analysis, clinical stage and IGHV gene mutational status retained independent significance. In conclusion, abnormalities of serum immunoglobulins are detected in CLL patients with heterogeneous clinicobiological profiles, including different disease burden (clinical stage), cytogenetic aberrations and IGHV gene mutational status. However, certain observations reported herein, in particular the high incidence of hypogammaglobulinemia in subset #2 and the association of NOTCH1 mutations with IgA subclass deficiency, are noteworthy and indicate the need for research towards unraveling causal mechanisms among the observed interwined events. DisclosuresNo relevant conflicts of interest to declare.

Identification of the Antigenic Targets of the Major CLL-Derived Stereotyped BCRs and First Demonstration of Sub-Subsets

Background: The B-cell receptor (BCR) is the hallmark of mature B cells and a clonal BCR is expressed on the neoplastic cells of B-cell malignancies. The BCR mediated signalling provides proliferative and anti-apoptotic signals for the neoplastic B cells and represents an attractive therapeutic target. The BCRs of about 1/3 of CLL cases display highly homologous complementary determining regions 3 (CDR3), on the basis of which stereotyped subsets have been defined. The homologies of the BCR of a given subset suggest selection by shared antigen(s), which might play an important role in the pathogenesis of the respective B-cell neoplasm by chronic antigenic stimulation.Methods: Tumor cells from CLL patients belonging to subsets 2, 3, 4, 5, 6, 8 were studied. Natural Fabs (nFab) were obtained by papain digestion of membrane-bound Igs. Subset-derived nFabs were used to screen for reactivity with proteins represented in two high-density protein macroarrays, one derived from human fetal brain cDNA and a second derived from a mixture of expression libraries derived from activated T-cells, lung and colon. Identified antigens were analysed by standard techniques. All methods used (nFab generation by papain digestion, BCR cloning, membrane screening, epitope mapping etc.) are described in detail in Zwick C et al., Blood 2013;121(23):4708-4717.Results: Our ongoing systematic search for CLL subset-specific antigens together with our previously published data (Zwick et al) led to the identification and epitope characterization of the antigenic targets for the 6 most common CLL subsets: MARK3 as antigen for subset 2, NCOR2 as antigen for subset 3, CaCyBP as antigen for subset 4, FAM32A protein as antigen for subset 5 and GLDC as antigen for subset 8. In addition we could confirm MYHIIA as antigen for subset 6 (in accordance with Chu CC et al, Blood 2010;115(19):3907-3915). The analysis of the BCR binding revealed (except for oxLDL) in minimum 2 different epitopes for each subset-specific antigen, thus defining sub-subsets with BCRs binding to distinct epitopes. Sequence analysis of the respective BCR suggests that this epitope-spreading is due to antigen-driven mutation/maturation of BCRs with a highly homologous CDR3.Conclusions: The antigenic targets (and stimulus) for the clonal BCRs of the major sterotyped subsets have been identified providing for the first time experimental evidence for the hypothesis that BCRs of a given subset indeed target the identical antigen. Moreover, based on the BCR-binding epitopes, sub-subsets of stereotypes have been defined by BCRs obviously originating from the same germline, but having undergone different antigen-driven mutations.Supported by Deutsche Forschungsgemeinschaft DFG, Deutsche José Carreras Leukämie Stiftung, Wilhelm-Sander-Stiftung, Deutsche Krebshilfe e.V. DisclosuresStilgenbauer:Pharmacyclics, Janssen: Honoraria, Research Funding.

Immunoglobulin repertoire of primary lymphomas of the central nervous system.

Primary lymphoma of the central nervous system (PCNSL) is a diffuse large B-cell lymphoma confined to the CNS. It has been hypothesized that antigen(s) in the CNS may trigger tumor cell proliferation. Because efforts to identify potential antigens have been unsuccessful to date, we studied the B-cell receptor in detail in a comprehensive series of 50 PCNSLs to obtain indirect information on potential antigens. Potentially functional V-D-J rearrangements were identified in all PCNSLs analyzed. Immunoglobulin heavy-chain variable gene segment (IGHV), IGHV4, was the predominant family used by 66% (33 of 50) of PCNSLs with a preferential rearrangement of the IGHV4-34 gene segment (18 [55%] of 33). The IGHV genes showed mutation frequencies from 0% to 29%, with a high average mutation frequency of 10%. In addition to 48% (24 of 50) of PCNSLs being highly mutated, 22% (11 of 50) defined a low-level mutated group. Antigen selection of the tumor cells or their precursors was indicated by replacement/silent mutation ratios and ongoing somatic hypermutation. Complementarity determining region 3 length and composition as well as the lack of stereotyped B-cell receptors suggest involvement of several antigens instead of a unique antigen recognized by the tumor cells.

Clinical effect of stereotyped B-cell receptor immunoglobulins in chronic lymphocytic leukaemia: a retrospective multicentre study

About 30% of cases of chronic lymphocytic leukaemia (CLL) carry quasi-identical B-cell receptor immunoglobulins and can be assigned to distinct stereotyped subsets. Although preliminary evidence suggests that B-cell receptor immunoglobulin stereotypy is relevant from a clinical viewpoint, this aspect has never been explored in a systematic manner or in a cohort of adequate size that would enable clinical conclusions to be drawn. For this retrospective, multicentre study, we analysed 8593 patients with CLL for whom immunogenetic data were available. These patients were followed up in 15 academic institutions throughout Europe (in Czech Republic, Denmark, France, Greece, Italy, Netherlands, Sweden, and the UK) and the USA, and data were collected between June 1, 2012, and June 7, 2013. We retrospectively assessed the clinical implications of CLL B-cell receptor immunoglobulin stereotypy, with a particular focus on 14 major stereotyped subsets comprising cases expressing unmutated (U-CLL) or mutated (M-CLL) immunoglobulin heavy chain variable genes. The primary outcome of our analysis was time to first treatment, defined as the time between diagnosis and date of first treatment. 2878 patients were assigned to a stereotyped subset, of which 1122 patients belonged to one of 14 major subsets. Stereotyped subsets showed significant differences in terms of age, sex, disease burden at diagnosis, CD38 expression, and cytogenetic aberrations of prognostic significance. Patients within a specific subset generally followed the same clinical course, whereas patients in different stereotyped subsets-despite having the same immunoglobulin heavy variable gene and displaying similar immunoglobulin mutational status-showed substantially different times to first treatment. By integrating B-cell receptor immunoglobulin stereotypy (for subsets 1, 2, and 4) into the well established Döhner cytogenetic prognostic model, we showed these, which collectively account for around 7% of all cases of CLL and represent both U-CLL and M-CLL, constituted separate clinical entities, ranging from very indolent (subset 4) to aggressive disease (subsets 1 and 2). The molecular classification of chronic lymphocytic leukaemia based on B-cell receptor immunoglobulin stereotypy improves the Döhner hierarchical model and refines prognostication beyond immunoglobulin mutational status, with potential implications for clinical decision making, especially within prospective clinical trials. European Union; General Secretariat for Research and Technology of Greece; AIRC; Italian Ministry of Health; AIRC Regional Project with Fondazione CARIPARO and CARIVERONA; Regione Veneto on Chronic Lymphocytic Leukemia; Nordic Cancer Union; Swedish Cancer Society; Swedish Research Council; and National Cancer Institute (NIH).

Targeted DNA vaccines eliciting crossreactive anti-idiotypic antibody responses against human B cell malignancies in mice.

BackgroundTherapeutic idiotypic (Id) vaccination is an experimental treatment for selected B cell malignancies. A broader use of Id-based vaccination, however, is hampered by the complexity and costs due to the individualized production of protein vaccines. These limitations may be overcome by targeted DNA vaccines encoding stereotyped immunoglobulin V regions of B cell malignancies. We have here investigated whether such vaccines might elicit cross-reactive immune responses thus offering the possibility to immunize subsets of patients with the same vaccine.MethodsFusion vaccines targeting patient Id to mouse Major Histocompatibility Complex (MHC) class II molecules (chimeric mouse/human) or chemokine receptors (fully human) on antigen-presenting cells (APC) were genetically constructed for two Chronic Lymphocytic Leukemia (CLL) patients and one prototypic stereotyped B-cell receptor (BCR) commonly expressed by Hepatitis C Virus (HCV)-associated Non Hodgkin Lymphoma (NHL). The A20 murine B lymphoma cells were engineered to express prototypic HCV-associated B cell lymphoma BCR. Anti-Id antibody responses were studied against stereotyped and non-stereotyped BCRs on CLL patients’ cells as well as transfected A20 cells.ResultsDNA vaccination of mice with Id vaccines that target APC elicited increased amounts of antibodies specific for the patient’s Id as compared with non targeted control vaccines. Anti–Id antibodies cross-reacted between CLL cells with closely related BCR. A20 cells engineered to express patients’ V regions were not tumorigenic in mice, preventing tumor challenge experiments.ConclusionsThese findings provide experimental support for use of APC-targeted fusion Id DNA vaccines for the treatment of B cell lymphoma and CLL that express stereotyped BCRs.

Antigen stimulation in the development of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common leukemia in the western world. The mechanism the mechanism of the disease development still remains unrevealed. In recent years new unique molecular and clinical features of CLL have emerged leading to a unified hypothesis of CLL origin. Major progress in understanding CLL biology was made after identification of mutational status of immunoglobulin variable heavy chain (IGHV) genes, which also improved prediction of patients' clinical outcome. Preferential usage of IGHV genes has led to recognition of CLL-specific B cell receptors (BCRs), called stereotyped BCRs. Taken together, these data point to antigen stimulation of CLL progenitor cells. Studies on CLL antibody reactivity have shown affinity to molecular motifs on apoptotic cells and bacterial cell structures, supporting the current hypothesis of the CLL pathomechanism. In this paper we have summarized information available to date regarding current theory of cellular origin and pathology of CLL.

Stereotyped Subset #4 In Chronic Lymphocytic Leukemia Is Associated With Distinct Gene and Microrna Transcriptional Profile

Chronic lymphocytic leukemia (CLL) is a lymphoproliferative disorder characterized by the monoclonal accumulation of B lymphocytes and a variable clinical course. Specific B-Cell Receptor (BCR) utilized by leukemic cells may influence disease progression and outcome. Highly homologous BCR, “stereotyped BCR”, are expressed in a recurrent fraction of patients with CLL and in some cases they were associated with distinct biological and clinical features. Stereotyped subset #4 have been reported to exhibit a favorable clinical course and to be the most frequent stereotyped BCR among the IGHV mutated (IGHV-M) cases. In this study we performed a comprehensive clinical, biological and molecular characterization of leukemic cells from 16 patients utilizing stereotyped subset #4 BCR (IGHV4-34) among a representative prospective cohort of 462 Binet stage A CLL patients enrolled in O-CLL1 protocol (clinicaltrial.gov identifier NCT00917540). In all cases, biological and molecular analyses were performed in peripheral CD19+ B-cells. All subset #4 patients were characterized by lower CD38 expression, unique IGHV-M configuration and absence of NOTCH1 and SF3B1 mutations. None subset #4 patients showed unfavorable cytogenetic deletions (i.e del11q23 and del17p13). Gene expression profiling (GEP) analysis was performed on 217 patients, including 9 subset #4 cases for whom RNA material was available. Supervised analysis comparing subset #4 vs all other patients (208) revealed 14 differentially expressed genes. Furthermore subset #4 patients were characterized by a significant downregulation of WDFY4, MEF2A and upregulation of PDGFA, FGFR1 and TFEC genes when compared with the remaining IGHV-M patients. miRNA profiles were analyzed in 229 patients including 10 subset #4 patients for whom RNA material was available. A specific miRNA expression pattern involving the upregulation of miR-497 and miR-29c was found in subset# 4 cases. Furthermore, we demonstrated that transfection of the miR-497 mimic in primary leukemic CLL cells induces, after 48 and/or 72 h, a downregulation of BCL2, known to be a validated target in different solid cancers. Our data provide a contribution to the biological definition of CLL patients with specific stereotyped IGHV4-34 BCR and identify for the first time distinct gene and miRNA expression profiles associated with this subset, providing further evidence of the putative leading role of HCDR3 conformation in CLL. Disclosures:No relevant conflicts of interest to declare.

Stereotyped subset #1 chronic lymphocytic leukemia: a direct link between B‐cell receptor structure, function, and patients' prognosis

Chronic lymphocytic leukemia (CLL) with stereotyped B-cell receptor (BCR) belonging to subset #1 (IGHV1-5-7/ IGKV1-39) display a poor outcome. To characterize their genetic and genomic features and BCR function, we selected 20 subset #1 CLL from a series of 579 cases. Subset #1 CLL, all showing unmutated IGHV, were associated with the presence of del(11q) (50%) in comparison with unmutated CLL, unmutated stereotyped CLL other than subset #1 and with cases using the same IGHV genes but a heterogeneous VH CDR3 (non-subset #1 CLL). There were no distinctive features regarding CD38, ZAP-70, and TP53 disruption. NOTCH1, SF3B1, and BIRC3 were mutated in 15%, 0%, and 5% of cases, respectively, while BIRC3 was deleted in 22% of cases. Microarray unsupervised analysis on 80 unmutated/mutated/stereotyped/non-stereotyped CLL showed a tight clustering of subset #1 cases. Their genomic signature exhibited several differentially expressed transcripts involved in BCR signal transduction, apoptosis regulation, cell proliferation, and oxidative processes, regardless of del(11q). Accordingly, BCR ligation with anti-IgM revealed a significant higher proliferation of subset #1 versus unmutated non-subset #1 CLL, both at baseline and after 24–48 hr stimulation. Subset #1 CLL represent a paradigmatic example of the direct link between BCR structure, function, and patients prognosis.

Outcomes Of Chronic Lymphocytic Leukemia Patients With Richter Syndrome

▪ IntroductionApproximately 2-8% chronic lymphocytic leukemia (CLL) patients develop diffuse large B-cell lymphoma (DLBCL, so-called Richter syndrome [RS]) over long-term follow-up. The outcomes of patients with RS are variable and poorly understood. MethodsCLL patients seen at Mayo Clinic from January 1995 to April 2013 who developed biopsy-proven DLBCL during follow-up were included in this analysis. Clinical characteristics, therapy and overall survival (OS) of all patients with RS were analyzed. ResultsOne hundred and twenty patients with biopsy-proven RS were identified in the Mayo Clinic database. The median age at diagnosis of RS was 67 years (range, 29-88 years), 87 (73%) were male, and 83 (69%) had received prior CLL therapy. The median duration between diagnosis of CLL and development of RS was 3.8 years (range, 0-34.5 years). Stereotyped B-cell receptors were found in 9/30 (30%) RS patients compared to 219/1294 (17%) non-RS patients (OR=2.1, p=0.07). IGHV4-39 gene usage was present in 2/26 (8%) RS patients compared to 57/1354 (4%) non-RS patients (p=0.3). Of the 30 RS biopsy samples in which Epstein Barr virus (EBV) in-situ hybridization studies were performed, EBV was detected in 7 (23%) patients.After a median follow-up of 5.2 years, 86 (72%) patients have died. Causes of death were as follows: progressive DLBCL (n=46, 53%), progressive CLL (n=2, 2%), infection (n=8, 9%), unknown (n=20, 23%) and other (n=10, 12%). The median OS of the entire cohort was 0.9 years (95% CI, 0.5-1.3 years). Tsimberidou and colleagues proposed a prognosis score (RS score) based on the following variables at the time of RS diagnosis: Eastern Co-operative Group performance status of 2-4, lactate dehydrogenase >1.5 x normal, platelets<100 x 109/L, tumour size >5 cm and >1 prior therapy for CLL. Each parameter was assigned one point, and patients were then assigned to one of four risk groups based on their calculated RS score: 0 or 1, low risk; 2, low-intermediate risk; 3, high-intermediate risk; 4 or 5, high risk. The OS according to the RS score for our group of patients is shown in Figure 1. Median survival in the low, intermediate-1, intermediate-2 and high-risk groups were 2.4 years, 0.7 years, 0.3 years and 0.2 years, respectively (p<0.001). [Display omitted] Fifteen (12%) patients received cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) as initial therapy for RS, and 68 (57%) received rituximab in addition to CHOP (R-CHOP). There was no difference in survival among patients who received CHOP compared to R-CHOP (median, 1.8 years. vs. 1.2 years, p=0.5). Twenty-four patients (20%) received non-CHOP-based chemotherapy, and treatment was unknown in 4 (3%) patients. Nine patients (7%) died before definitive therapy could be instituted.Thirteen (11%) patients were able to proceed to stem cell transplantation (SCT): 10 (8%) autologous SCT, 2 (2%) allogeneic SCT and 1 (1%) autologous SCT followed by an allogeneic SCT. Although RS patients who underwent SCT were younger compared to those who did not undergo SCT (median, 59 years. vs. 69 years, p=0.001), no differences in prior CLL therapy or receipt of R-CHOP therapy for DLBCL was noted between the two groups. The median survival of patients who proceeded to SCT was superior compared to those who did not (5.2 years vs. 0.7 years; p=0.005). ConclusionStereotyped B-cell receptors but not VH4-39 had a suggested evidence of an increased risk of RS in our cohort. Although 90% RS patients received intensive chemotherapy, only 11% patients were able to proceed to SCT. Median survival of RS patients remains dismal at 1 year, and newer therapies are needed to improve outcomes. Disclosures:Shanafelt:Genentech: Research Funding; Glaxo-Smith-Kline: Research Funding; Cephalon: Research Funding; Hospira: Research Funding; Celgene: Research Funding; Polyphenon E International: Research Funding.

Differential Distribution Of Recurrent Gene Mutations In Subsets Of Chronic Lymphocytic Leukemia Patients With Stereotyped B-Cell Receptors: Results From A Multicenter Project Of The European Research Initiative On CLL In A Series Of 2482 Cases

▪A remarkable feature of chronic lymphocytic leukemia (CLL) is the existence of quasi-identical, stereotyped B-cell receptor immunoglobulins (BcR IGs), strongly supporting an antigen-driven pathway to CLL development. Subsets of cases with distinct stereotyped BcRs collectively account for almost one-third of all CLL. Furthermore, just a handful of major stereotyped subsets represent a substantial fraction of the entire cohort and, perhaps more importantly, an even larger fraction of clinically aggressive CLL. In several major subsets, stereotypy extends from shared primary IG sequences to shared clinical and biological features, including immune signaling, mRNA and miRNA expression, DNA methylation, and genomic aberrations. Regarding the latter, recent evidence indicates that different subsets display distinct profiles of recurrent gene mutations, even when limiting the analysis to subsets with similar IGHV gene mutational status. However, it should be emphasized that even the largest subsets account for only ∼3% of the cases with available IGHV-D-J sequence information, indicating that for meaningful conclusions to be reached, large patient cohorts are essential. Here, taking advantage of a series of 2482 CLL cases consolidated in the context of a multicenter collaboration coordinated by ERIC, the European Research Initiative on CLL, we systematically explored the genetic background of stereotyped subsets. Our main focus was on recurrent mutations in the NOTCH1 (entire exon 34 or targeted analysis for del7544-45), TP53 (exons 4-9), SF3B1 (exons 14-16), BIRC3 (exons 6-9) and MYD88 (exon 5) genes. Overall, 1313 cases (52.9%) carried mutated IGHV genes (M-CLL), whereas the remaining 1169 cases (47.1%) carried unmutated IGHV genes (U-CLL). Cases were sub-classified into the following major subsets: (i) U-CLL: #1, n=72; #3, n=25; #5, n=11; #6, n=22; #7, n=37; #8, n=20; (ii) M-CLL: #4, n=32; #77, n=12; #148, n=20; and, (iii) subset #2 (IGHV3-21, variable mutational status), n=57. Mutations in the MYD88 and BIRC3 genes were relatively rare, with no clear bias to any subset. With regards to the other three genes, only a single mutation in the TP53 gene was identified in a total of 80 M-CLL subset cases. Among U-CLL subsets and clinically aggressive subset #2, we noted asymmetric mutation frequencies, summarized as follows. (1) TP53 mutations were (a) enriched in subsets #3 and #7 (frequency >10%) and, in contrast, absent in subsets #5 and #6, though all these subsets utilize the IGHV1-69 gene; (b) enriched in subset #1 (9%) and, interestingly, subset #99, a less populated subset that is highly similar to subset #1 (2/4 cases positive for TP53 mutations); (c) absent in subset #2; and, (d) relatively infrequent in subset #8 (5%), the latter known to display the highest risk for Richter's transformation among all CLL. Differences between these subsets showed a trend for statistical significance (p=0.09). (2) NOTCH1 mutations exhibited (a) increased frequency in subsets #1 (28%) and #8 (25%); (b) among IGHV1-69 expressing subsets, lower frequencies in subsets #3 (8%), #5 (10%) and #7 (3%) compared to subset #6 (25%); and (c) intermediate frequency (9%) in subset #2 (p=0.0078 for comparison between subsets). (3) SF3B1 mutations were (a) significantly (p<0.001) enriched in subsets #2 (47.6%), #3 (40%) and #7 (25%) compared to all other major subsets (subset #1: 7.5%; subset #5: 0%; subset #6: 7.7%; subset #8: 0%); and, (b) positive in 3/7 cases (42.8%) of subset #169, a minor subset sharing remarkable IG sequence similarities to subset #2. In conclusion, in the largest study thus far conducted, we confirm and significantly extend recent observations indicating that different CLL stereotyped subsets display distinct genetic makeup. On these grounds, we propose that differential modes of immune signaling in the context of subset-biased antigen-IG interactions may be associated with the acquisition and/or selection of certain genomic aberrations in various stereotyped subsets, ultimately underlying clinical aggressiveness through distinct mechanisms. Finally, our findings suggest that sequence similarities between different subsets (e.g. #1 and #99, #2 and #169) likely reflect similar pathobiology, underscoring the relevance of the molecular sub-classification of CLL based on BcR stereotypy. Disclosures:Stamatopoulos:Roche: Research Funding.