ALBERT

Description: Abstract 2401 Background. Compelling evidence suggests that chronic infections by various pathogens are linked to lymphoma development. The transformation process is supposed to be either direct (eg for EBV) or indirect. The association between Helicobacter pylori chronic infection and gastric marginal zone lymphoma (MZL) is the best characterized example for an indirect transformation. Several other pathogens such as hepatitis C virus, Campylobacter jejuni or Streptococcus Pneumoniae (Spn) are also suspected to promote B-cell lymphoma development through repeated stimulations of the BCR and/or inflammation. However, except for gastric MZL, animal models are lacking to study potential correlations between chronic infections and lymphoma development. Methods. To amplify and precipitate lymphomagenesis by precluding repair of DNA lesions potentially generated during chronic immune response, p53-deficient mice were used as a permissive model. Given the suspected role of carbohydrates from encapsulated bacteria such as Spn in promoting chronic lymphocytic leukemia, p53−/− (n=15) and p53+/− (n=53) mice were chronically injected with heat-killed Spn until disease development. P53-deficient mice chronically injected with PBS were used as control. Results. Unexpectedly, chronic injections of Spn promoted T-cell rather than B-cell lymphomagenesis in both p53−/− and p53+/− mice and shortened survival in p53+/− mice (P=.004). Whereas mostly thymic CD4+CD8+ double positive T-cell lymphomas have been described in p53-deficient mice, a vast majority of lymphomas observed following chronic Spn injections were of peripheral origin (TdT−) and exhibited an effector memory phenotype (CD44hiCD62LloCCR7−CD25−). Clonality and transferability of those peripheral T-cell lymphomas (PTCL) were established. Furthermore, lymphoma cells showed features of chronically stimulated T cells such as TCR, CD3 or CD4/CD8 co-receptor down-regulations along with PD-1 up-regulation. Several lines of evidence suggested a contribution of the TCR to the development of these PTCL: 1/all PTCL following Spn injections exhibited a Vß repertoire usage bias (Vß8 in 100%) consistent with a transformation process originating from a chronically-stimulated T cell by a pathogen-specific immunodominant peptide; 2/cyclosporin A, a strong TCR signaling inhibitor, decreased cell survival in vitro, and prolonged mice survival following transfer of lymphoma cells into recipient mice; 3/engraftment of CD8+ PTCL in MHC class I KO mice was significantly reduced compared to wild type mice (P450 days) compared to T-cell lymphoma prompted us to dissect the potential role of p53 in mature T-cell response in a context of chronic stimulation. WT and p53−/− negatively selected CD4+ and CD8+ T cells were repeatedly (ie every 7–10 days) stimulated in vitro using anti-CD3/anti-CD28-coated beads. In agreement with previous reports, no significant difference of cell viability was observed after the first or the second stimulation confirming the minor role of p53 in initial activation and proliferation as well as in activation-induced cell death. Nonetheless, a dramatic increase in cell viability was observed 48h after the third stimulation of p53−/− T cells, indicating a crucial function of p53 in deletion of chronically activated T cells. Conclusion. Chronic stimulations with heat-killed Spn unexpectedly increased peripheral T-cell lymphoma development in p53-deficient mice. Phenotypic characterization was consistent with a transformation process occurring in a pathogen-specific chronically-stimulated T cell. The incidence of p53 mutations is higher in T-cell than in B-cell mature malignancies in humans and the p53 pathway is functionally impaired in virtually all enteropathy-associated T-cell lymphomas, which are supposed to be a key model for an antigen-driven process. Therefore, aside from its known role in immature T-cell lymphoma development and in progression of B-cell malignancies, our work sheds light on a previously unsuspected physiopathological role of the p53 pathway in peripheral T-cell lymphomagenesis. Disclosures: No relevant conflicts of interest to declare.

Description: Background: One of the main complications in CLL is Richter syndrome (RS). RS derives from the rare transformation of chronic lymphocytic leukemia (CLL) into an aggressive lymphoma, most commonly of the diffuse large B-cell lymphoma (DLBCL) type. RS occurs in 2.2% to 8% of patients with CLL and the prognostic is poor with a median survival from 5 to 8 months. Detection of RS by imaging has resulted in conflicting and non-significant results. Aim: The objective of this study was to validate recent findings correlating FDG/PET imaging and histological features in CLL and to demonstrate that a tumoral maximum standardized uptake value 〉 10 measured on 18F-FDG-PET is a new valid marker to discriminate RS. Results: From June 2006 through December 2012, 240 patients from the Division of hematology of Centre Hospitalier Lyon Sud and Créteil and from the Mayo Clinic Rochester have been analyzed with a mean age of 62 years (21-91). Clinical, histological (confirm by biopsy) and biological parameters have been identified with 10% of the patients as having RS, 34% stable CLL disease; 42% of rapid CLL progression (histological features of progression defined as increased large cell number, large confluent proliferation centers or high proliferation rate assessed by Ki-67 but not meeting criteria for diffuse large B-cell lymphoma/RS) and 14% with others diseases (e.g. infection and or cancers). For patients with stable CLL disease, the median tumoral SUV max was 2 (range: 0-2.4). Among patients with a rapid progression of CLL, 90% had a tumoral SUV max 10 (12.9; range: 5-27). A statistically significant difference between SUV max of CLL patients with stable disease and RS was observed (2.2 vs. 12.9; p〈 0.0001) and similarly for SUV max of CLL patients with rapid disease progression and RS (4.5 vs 12.9; p〈 0.0001). Regardless of the RS prevalence (2.2% to 8%), statistical tests identified a threshold of tumor SUV max 〉 10 as the more discriminating cut off. Using this threshold, the sensitivity and specificity of PET to identify RS in our cohort are 91% and 95% respectively. Assuming an RS prevalence of 2.2%, positive predictive value (PPV) and negative predictive value (NPV) using the 〉10 threshold were 28.7% and 99.8%; for an 8% prevalence of RS, the PPV and NPV are 60.8 and 99.2% respectively.The proportion of correctly classified patients with RS is more accurate using a threshold of tumoral SUV max 〉 10 than 5 (2.2% RS prevalence: 94.8% versus 71.8%; 8% RS prevalence: 94.6% versus 73.5%). Finally analysis of the area under the curve (AUC) reveals a value of 0.95 (95% confidence interval: 0.89- 0.99). Recently, Falchi et al, reported on 332 patients with CLL classified as 95 RS, 117 rapid progression and 120 stable disease and demonstrated a strong correlation between histological features and PET imaging. A SUV max ≥10 strongly correlated with a shorter overall survival. Similarly, in our study we have shown excellent sensitivity and negative predictive value estimated at 100%, revealing the ability of 18F-FDG-PET-CT to rule out the diagnosis of RS if the tumor SUV max is less than 10. Conclusion: 18F-FDG-PET-CT is a valuable tool in the diagnostic evaluation of RS for patients with CLL. It is not only useful to identify RS syndrome and guide the site of biopsy but also to identify CLL patients who will experience more rapid disease progression. An SUV max 〉 10 is the optimal threshold to distinguish RS in CLL. Disclosures No relevant conflicts of interest to declare.