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Refractory/relapsed (R/R) diffuse large B-cell lymphoma (DLBCL) patients' failure of salvage chemotherapy had extremely worse prognoses. Herein, 14 R/R DLBCL patients failed to salvage chemotherapy were exposed to dual epigenetic agents (Chidamide 30 mg biw*2w and Decitabine 10 mg/m

Constitutive photomorphogenic 1 (COP1) is a p53-targeting E3 ubiquitin ligase that is downregulated by DNA damage through mechanisms that remain obscure. Here, we report that COP1 is not downregulated following DNA damage in 14-3-3σ null cells, implicating 14-3-3σ as a critical regulator in the response of COP1 to DNA damage. We also identified that 14-3-3σ, a p53 target gene product, interacted with COP1 and controlled COP1 protein stability after DNA damage. Mechanistic studies revealed that 14-3-3σ enhanced COP1 self-ubiquitination, thereby preventing COP1-mediated p53 ubiquitination, degradation, and transcriptional repression. In addition, we found that COP1 expression promoted cell proliferation, cell transformation, and tumor progression, manifesting its role in cancer promotion, whereas 14-3-3σ negatively regulated COP1 function and prevented tumor growth in a mouse xenograft model of human cancer. Immunohistochemical analysis of clinical breast and pancreatic cancer specimens demonstrated that COP1 protein levels were inversely correlated with 14-3-3σ protein levels. Together, our findings define a mechanism for posttranslational regulation of COP1 after DNA damage that can explain the correlation between COP1 overexpression and 14-3-3σ downregulation during tumorigenesis. Cancer Res; 71(3); 884–94. ©2010 AACR.

Supplementary Figures 1-3, Table 1 from 14-3-3σ Exerts Tumor-Suppressor Activity Mediated by Regulation of COP1 Stability

BACKGROUND The main aim of this study was to determine some simple but meaningful parameters that indicate immunochemotherapy-related interstitial lung disease (ILD) early in B-cell lymphoma and provide direction to hematologists. METHODS The clinical and laboratory characteristics, the treatments and outcomes of 21 B-cell lymphoma patients with ILD who underwent rituximab (RTX) -based immunochemotherapy were collected and retrospectively analyzed. RESULTS More cycles of immunochemotherapy and higher cumulative doses of RTX and doxorubicin hydrochloride liposome conferred a high risk of ILD. Compared to the baseline, patients had a significantly lower white blood cell count (WBC), absolute lymphocyte count (ALC), and albumin level (4.95×109 vs. 6.32×109, 0.71×109 vs. 1.61×109, 34.1 vs. 40.4 g/L; P

BACKGROUND: Chimeric antigen receptor T cell (CAR-T) therapy has achieved remarkable effects in refractory/relapsed (R/R) diffuse large B-cell lymphoma (DLBCL). However, many patients receiving CAR-T therapy still eventually die of disease recurrence or progression due to target antigen loss or exhaustion of CAR-T cells. Therefore, maintaining the efficacy of CAR-T has become a particular research focus. As lenalidomide can regulate T cell function, we conducted a study to evaluate the efficacy of lenalidomide maintenance after CAR-T therapy in R/R DLBCL patients. METHODS: Seven R/R DLBCL patients who received lenalidomide maintenance after CAR-T therapy and nine DLBCL patients that underwent CAR-T treatment alone were included. The clinical data of all subjects were collected to evaluate the efficacy of lenalidomide maintenance. In order to understand the possible mechanisms of lenalidomide in CAR-T therapy, CAR-T copies of peripheral blood were regularly detected by quantitative real-time polymerase chain reaction, and an in vitro test was also conducted. RESULTS: Overall survival (OS) was significantly prolonged in the lenalidomide maintenance group. Furthermore, one case responding to CAR-T therapy initially but suffering a relapse shortly achieved complete remission again after lenalidomide exposure, with an increase in the number of CAR-T copies detected. The in vitro test showed that lenalidomide could delay the exhaustion of CAR-T cells. CONCLUSIONS: Lenalidomide maintenance after CAR-T therapy is a safe and effective choice for R/R DLBCL patients. We confirmed that lenalidomide maintenance can improve patients’ OS, and the delayed exhaustion of CAR-T cells may contribute to this OS benefit.

Chimeric antigen receptor T-cell (CAR-T) therapy demonstrates impressive efficacy in relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL). However, CAR-T therapy-related severe cytokine release syndrome and neurological toxicity limit its clinical application in R/R DLBCL patients with high tumor burden. Here, we conducted a phase II clinical trial testing the efficacy and toxicities of CAR-T therapy in R/R non-Hodgkin lymphoma patients (NCT03196830). Among the enrolled patients, 10 R/R DLBCL patients with high tumor burden were analyzed. Before CAR-T therapy, 4 were treated with intensive combined chemotherapy (C-CAR-cohort), and 6 were exposed to radiotherapy (R-CAR-cohort). Patients in the R-CAR-T-cohort showed a higher overall response rate (100% vs. 25%, P=0.033) and less severe cytokine release syndrome (0% vs. 100%, P=0.0048) and neurotoxicity (0% vs. 75%, P=0.033) incidences than patients in the C-CAR-T-cohort. Furthermore, one case who responded to CAR-T therapy initially and who suffered a relapse shortly was exposed to radiation and achieved complete remission, with an increase in the number of CAR-T copies detected. This study demonstrates that radiotherapy is an optimal debulking regimen to managing R/R DLBCL patients before CAR-T therapy and a promising alternative salvage therapy for patients who suffer a relapse after CAR-T therapy by fuelling CAR-T copies.

Relapse is the major cause of mortality in patients with acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Effective preventive intervention in high-risk AML may be crucial. In this study, we investigated the clinical efficacy and safety of low dose decitabine (DAC) as part of a modified Busulfan-Cyclophosphamide (Bu-Cy) regimen for high-risk AML patients undergoing allo-HSCT to reduce relapse rate. Fifty-nine patients received DAC (20 mg/m2/d, i.v.) for 5 days, followed by modified Bu-Cy (DAC group). A matched-pair control (CON) group of 177 patients (matched 1:3) received modified Bu-Cy only. The differences were more substantial among patients with active disease: 2-year OS, 80.7% (DAC) versus 43.5% (CON), P = 0.011 and 2-year LFS, 64.9% (DAC) versus 39.2% (CON), P = 0.024. Median time to relapse was 8 months (DAC) versus 5 months (CON) for the entire groups and 6.5 months (DAC) versus 3.5 months (CON) for patients with active disease. In summary, our data indicated that the conditioning regimen containing low dose DAC may confer a survival advantage in high-risk AML patients with active disease undergoing allo-HSCT, and a prospective randomized trial is warranted to confirm these observations.

To investigate the prognosis of patients with adult B-cell acute lymphoblastic leukemia (B-ALL) with Ikaros family zinc-finger 1 (IKZF1) mutation and determine the role of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in improving the clinical outcome, we detected the IKZF1 mutation and BCR-ABL fusion gene at diagnosis in the bone marrow of 164 adult patients with B-ALL, and analyzed the clinical data of these patients retrospectively. Our analysis showed that grade III-IV acute graft-versus-host disease and IKZF1 mutation in the transplantation group and age and IKZF1 mutation in the non-transplantation group were independent factors for poor prognosis by univariate and multivariate analyses.The 3-year overall survival (OS) and leukemia-free survival (LFS) rates were much lower in the IKZF1+/BCR-ABL+ subgroup than in the IKZF1+/BCR-ABL- and IKZF1-/BCR-ABL- subgroups in both the transplantation and non-transplantation groups. The 3-year OS and LFS rates were significantly higher in the transplantation group than in the non-transplantation group with IKZF1 mutation.The study demonstrated that IKZF1 mutation was an independent factor indicating the poor prognosis of adult B-ALL and much worse prognosis in the BCR-ABL+ subgroup in both non-transplantation and transplantation groups. However, allo-HSCT significantly improved the OS and LFS of patients and also their clinical outcomes.

Primary testicular lymphoma (PTL) is quite rare. Immunohistochemical analyses show that the majority of cases are diffuse large B-cell lymphoma accounting for about 1–7% of all testicular malignanc...

BACKGROUND: Autologous stem cell transplantation (ASCT) is the standard treatment for refractory/relapsed B cell non-Hodgkin’s lymphoma (R/R B-NHL), whereas chimeric antigen receptor T (CAR-T) therapy targeting CD19 is emerging as an alternative strategy. Here, we report a comparative analysis of the 2 strategies in a single center. METHODS: We performed a prospective, single-arm study of CAR-T therapy in 29 patients with R/R B-NHL and compared the outcomes with 27 contemporaneous patients who received ASCT. NHL was diagnosed by histopathologic assessments, and the safety and efficacy of treatments were compared. RESULTS: The CAR-T group exhibited better rates of complete response (CR) (48.0% vs. 20.8%, P = 0.046) and 1-year overall survival (OS) (74.4% vs. 44.5%, P = 0.044) compared with the ASCT group. Subpopulation analysis showed that patients with International Prognostic Index scores of at least 3 achieved a significantly higher objective response rate and CR rate in the CAR-T group than in the ASCT group (ORR 72.0% vs. 10.0%, P = 0.002, and CR 38.9% vs. 0%, P = 0.030, respectively). The most common severe adverse events in the CAR-T group were cytokine release syndrome, neurotoxicity, and infection compared with cytopenia, gastrointestinal toxicity, and infection in the ASCT group. Additionally, the incidence of nonhematologic severe adverse events was markedly lower in the CAR-T group than in the ASCT group (20.7% vs. 48.1%, P = 0.030). CONCLUSION: CAR-T therapy exhibited superior clinical outcomes in safety and efficacy over ASCT in patients with R/R B-NHL, suggesting that CAR-T may be a recommended alternative to ASCT. TRIAL REGISTRATION: ClinicalTrials.gov NCT03196830. FUNDING: Funding was supplied by UniCar Therapy, National Natural Science Foundation of China (81730003), National Science and Technology Major Project (2017ZX09304021), and Science Planning Project of Suzhou (sys2018049).

Tumor necrosis factor receptor-associated factor 6 (TRAF6), an (K63) E3-ligase, plays a role in many biological processes and its activity is relevant in diffuse large B cell lymphoma (DLBCL) biology. Although molecules that trigger TRAF6 activation have been defined, those that stabilize TRAF6 and/or enhance TRAF6 function remain largely unclear. We found that TRAF6 amplifies pAKT signaling in DLBCL. Moreover, TRAF6 activation and stabilization of its ubiquitination profile are facilitated by smoothened (SMO), signal transducer of canonical Hedgehog signaling. Here, we report that SMO is needed to facilitate and maintain TRAF6-dependent elevated pAKT levels, and that the SMO/TRAF6 axis contributes to doxorubicin resistance in DLBCL. Mechanistically, we found that SMO, through its C-terminal tail, stabilizes and protects TRAF6 from degradation, an effect mediated by ubiquitin-specific protease-8. Moreover, this functional link between SMO and TRAF6 is reflected in DLBCL patients where high expression of both molecules correlates with poor prognosis. In summary, our study reveals a novel cell survival mechanism in which SMO stabilizes and protects TRAF6 from degradation. The axis SMO/TRAF6/AKT is highly relevant in the biology of DLBCL and is involved in doxorubicin resistance.

Backgrounds: Refractory or relapsed(R/R) acute leukemia (AL) patients with TP53 alterations have a dismal outcome with current therapy. Recently, chimeric antigen receptor T cells (CAR-T) therapy has emerged as a novel immunotherapy modality in treating patients with R/R acute B lymphocytic leukemia (B-ALL) patients, with consistently high response rates and durable remissions and even cures across multiple studies. However, successful treatment of CAR-T therapy in R/R AL with TP53 alterations has been a challenge. Here, we conducted a phase II trial testing efficacy and toxicities of CAR-T therapy in R/R AL patients with TP53 alterations. Methods: The second generation CAR-T cells were successfully made from 9 patients' autologous lymphocytes and 2 donors' allogeneic lymphocytes and qualified tests were done before infusion to patients. CAR constructs used were humanized CAR targeting CD19, CD22 or tandem CD19 and CD22 according to the expression levels of each target on blasts. In this ongoing trial, 11 R/R AL patients with TP53 alterations (10 with TP53 mutations and 1 with TP53 deletions) including 2 relapsed after allo- allogeneic hematopoietic stem cell transplantation were included to evaluate the efficacy and safety of CAR-T therapy. Among the enrolled 11 R/R patients, 9 patients were diagnosed with B-ALL, 1 was diagnosed with acute myeloid leukemia (AML) and 1 was diagnosed with mixed phenotype acute leukemia (MPAL) (B-ALL and AML). After leukapheresis, all patients received fludarabine-based lymphodepletion chemotherapy with FLAG regimen (Fludarabine 30mg/m2 × 5d, Cytarabine 2g/m2 × 5d and Granulocyte-colony stimulating factor 300ug ×6d) in two cases, FC regimen (Fludarabine 30mg/m2 × 3d and Cyclophosphamide 300mg/m2 × 3d) in five cases, and FC+DAC regimen (Decitabine 50mg × 3d, Fludarabine 30mg/m2 × 3d and Cyclophosphamide 300mg/m2 × 3d) in four cases. Two days after chemotherapy, autologous/allogeneic CAR-T cells were infused within 2 to 4 days in a dose-escalation. Results: With a median (range) dose of 1×107/kg (0.1-1.5×107/kg) CAR-T cells, we observed a high response rate with 10/11 (90.9%) evaluated R/R patients achieved complete remission (CR) and 9/11 (81.8%) patients achieved molecular CR (mCR). Moreover, Most cases (8/11, 72.7%) only experienced mild to moderate cytokine release syndrome (CRS) and no neurological toxicity were observed. With a median follow-up of 10 months, 3 cases died of progressive disease including 1 case failed to response to CAR-T therapy, 1 case achieved CR and relapsed after CAR-T therapy and 1 case achieved mCR after CAR-T therapy and relapsed after the following allo-HSCT, and the left 8 cases still kept in mCR and alive. The one-year overall survival (OS) and leukemia-free survival (LFS) rates were 68.4% and 78% respectively. The 2-year cumulative incidence of relapse was 22.2%, and the non-relapse mortality rate was 0%. Further subgroup analysis showed that all 6 cases who received decitabine therapy (DAC group) achieved and maintained in mCR, while only 2 cases achieved and kept in mCR and 3 cases died from progressive disease in the cases without receiving decitabine therapy (Non-DAC group). The median OS and LFS for Non-DAC group was 10 and 16.375 months respectively, while the median OS and LFS for DAC group were unreached. Relative IL-6 and CRP levels increased dramatically in DAC group than that in Non-DAC group. However, there were no significant difference on treatment related toxicities between cases in DAC group and Non-DAC group. Conclusions: Our trial indicates that CAR-T therapy is a safe and powerful salvage approach to R/R AL patients with TP53 alterations and application of decitabine may fuel CAR-T therapy and reduce the relapse rate without increasing therapy related mortality incidences in this high risk population. Disclosures No relevant conflicts of interest to declare.

Background: Relapse remains the main cause of treatment failure post transplantation. Relapse prevention is an important strategy for acute myeloid leukemia (AML) patients. M ethods: We retrospectively analyzed the results of21 high risk AML patients who received a median number of 3 courses (range, 2 - 8) of decitabine (DAC) maintenance treatment (20mg/m2/d ×5d every 3 months for 1 year). Meanwhile, another 63 high risk AML patients without any prophylactic treatment after transplantation were included as a control group for 1:3 pair matched study. Results: With median follow-up of 23 months, 20 out of 21 (95.2%) patients maintained complete molecular remission (CMR) in DAC group, while 35 out of 63 (55.6%) patients maintained CMR in control group. Comparing with control group, the patients of DAC group had higher 3-year overall survival (OS) rates and 3-year leukemia free survival (LFS) rates (92.9% vs 51.8%, P =0.003; 94.1% vs 54.7%, P=0.002 respectively). Moreover, DAC maintenance was well tolerated in all patients and grade 3/4 or 4/4 hematological toxicities were observed in 11 of 21 (52.4%) patients. Conclusion: Our results suggested that DAC maintenance therapy was an effective and safe treatment option to prevent relapse after transplantation for high risk AML patients. Disclosures No relevant conflicts of interest to declare.

Background: CAR-T immunotherapy has shown remarkable promising results for relapsed/ refractory (R/R) acute lymphoblastic leukemia (ALL). However, CD19-targeted CAR T cell therapy for R/R ALL has a relapse rate of approximately 50% at 1 year after CART therapy, and the most common mechanism of relapse is due to CD19 antigen loss or decreased target expression on the surfaces of the lymphoblastic leukemia cells. Potential approaches to overcome this challenge include engineering CAR T cells to achieve multispecificity and to respond to lower expression levels of target antigens by dual target CAR T strategies. Objective: In order to evaluate the efficacy and safety of CD19/CD22 dual target CAR T cells for R/R ALL patients to determine if targeting multiple antigens can prevent treatment failure and improve response rates and durability of response. Method: A novel CAR T cells with tandem targeting CD19 and CD22 antigens and a third generation CAR construct of CD28 and OX40 co-stimulatory domains were administered to 23 patients with R/R ALL with a median age of 24(6-56)years. High-risk patients were enrolled in this cohort, including 10 with BCR-ABL+ALL (6 of 10 with T 315I mutation), 4 with TP53 mutation, 2 with Ph-like ALL and 3 with relapsed ALL post allo-HSCT. The patients received a single infusion of CAR T cells with dose escalation schedule:10%--30%--60%. The median infusion dose of CAR T cells was 1 (0.5- 2.5) ×107cells/kg. Results: The median follow-up was 9 (3.5-20) months. The day 28 CR/CRi rate was 100% with21/22 (95.5%) molecular remission. Six-month OS was 94.4% and RFS was 76.9%. One-year OS was 57.2% and RFS was 67.3%. One-year OS of high tumor burden (BM blast> 30%)(15/22) and low tumor burden(BM blast≤30%)(7/22) was 47.5% and 75% respectively (p>0.05). The 1-year OS of the CAR T- to- allo-HSCT group(14/22) was better than that of the non-transplant group(8/22) (OS 72.9% vs. 26.7%, p = 0.116). The cumulative relapse rate of 6 months and 1 year were 23.1% and 32.7% respectively. The overall incidence of CRS were 91% included 22.7%grade III CRS ,4.5% grade IV CRS and 0% severe CRES. Only one patient presented MAH syndrome and was cured with low dose dexamethasone. There was no CAR T-related death. Conclusions: The tandem CD19/CD22 dual target CAR T cells therapy is a safe and high efficacy treatment for R/R ALL patients. It is possible that multi-targeted CAR-T cell therapy may overcome this resistance mechanism and improve clinical outcomes. Disclosures No relevant conflicts of interest to declare.

Background: Chemo-resistance is a core challenge in successful treatment of diffuse large B cell lymphoma (DLBCL). It has been previously reported that DNA hypermethylation and histone deacetylation are two major epigenetic modifications contributing to chemo-resistance in multiple tumors. Moreover, combination of histone deacetylase inhibitors (HDI) and DNA methyltransferase inhibitors (DNMTI) resulted in synergistic anti-lymphoma effect toward refractory and/or relapsed (R/R) DLBCL cells in vitro and in vivo xenografts. R-GemOx (rituximab, gemcitabine, and oxaliplatin), as a first-line chemotherapy regimen for elderly primary DLBCL patients or a salvage chemotherapy regimen for R/R DLBCL patients not candidates for high-dose therapy, has shown high activity with a relative low toxicity profile. Herein, we therefore aimed to assess the efficacy, safety, and feasibility of the dual epigenetic agents plus R-GemOx regimen (CD-R-GemOx) as a salvage treatment in R/R DLBCL patients. Methods: 13 R/R DLBCL patients including 8 males and 5 females, diagnosed with R/R DLBCL on the basis of the 2008 World Health Organization guidelines, who had failed from previous salvage treatment were exposed to dual epigenetic agents (Chidamide 30mg biw and Decitabine 10mg/m2 qd d1-d5) and sequential R-GemOx(rituximab 375 mg/m² qd d6; gemcitabine 1 g/m² d7,d14; and oxaliplatin 100 mg/m² d8) for salvage chemotherapy. Median age of these patients was 56 (35-67) years old. Most (10/13) patients have advanced Ann Arbor stages. The cycle was repeated every 4 weeks. Clinical efficacy were assessed after two cycles. Results: All thirteen (100%) patients achieved disease control response. Ten (76.9%) patients achieved an overall response at the end of the treatment, with three (23.1%) achieving a complete response. Common grade 3-4 adverse events were haematological toxicities (thrombocytopenia in ten [76.9%] patients, anaemia in six [46.2%], and neutropenia in twelve [92.3%]) and gastrointestinal complications (nausea in four [30.8%] patients, vomiting in one [7.7%], diarrhoea in six [46.2%] and mucositis in six [46.2%]). Besides, 6/13 (46.2%) cases manifested with pyrexia; 3/13(23.8%) cases manifested with increase of ALT and hyperbilirubinemia. All above toxicities were reversible and recovered within 1 month after chemotherapy. No neurological toxicities and treatment-related deaths were observed. Conclusions: Our study indicates that combination of dual epigenetic agents and R-GemOx is a safe and promising salvage approach to managing R/R DLBCL patients and may serve as an optimal salvage treatment for bridging autologous transplantation. Disclosures No relevant conflicts of interest to declare.

Background: Chemoresistance is a core challenge in successful treatment of diffuse large B cell lymphoma (DLBCL). Chimeric antigen receptor T cells (CAR-T) therapy, as a novel immunotherapy modality, demonstrates impressive efficacy and durable remissions in relapsed/refractory(R/R) B-cell malignancies including DLBCL. However, CAR-T therapy is also associated with potentially fatal toxicities, including cytokine release syndrome (CRS) and neurological toxicities which limit the clinical application of CAR-T therapy in R/R DLBCL with high tumor burden. How to improve the prognosis of this population is urgently underway. Here, we conducted a trial testing efficacy and toxicities of CAR-T therapy in R/R lymphoma patients (This study is registered at www.clinicaltrials.gov as NCT03196830). Methods:Human T cells were collected from autologous/allogenous peripheral blood mononuclear cells (PBMC) . CD3+T cells were separated from PBMS of patients or donors by degradable anti-CD3 magnetic microbeads followed by 24h stimulation with CD3 and CD28 monoclonal antibody (5ug/ml). Then CD3+T cells were transduced with lentivirus particles incorporated with a humanized CAR construct targeting CD19, CD20 and CD22 and further expanded for 7 to 10 days in vitro. The transfection efficacy, ratio of CD4+ versus CD8+, antitumor activities, pathogen detection as well as cytokines releasing of CAR-T cells were evaluated before infusion to patients. In this ongoing trial, 14 patients were diagnosed as R/R DLBCL with high tumor burden. Two debulking conditioning regimens including intensive combined chemotherapy or radiation (40 gray in 20 fractions) were carried out before CAR-T therapy followed by sequential FC regimen (cyclophosphamide 300mg/m2 and fludarabine 30mg/m2 X 3d) for lymphodepletion chemotherapy. Two days after FC regimen, autologous/allogenous CAR-T cells targeting CD19 and CD20 or CD22 provided by the unicar-therapy bio-medicine technology co.(Shanghai, China) at average dose of 1-2×107 cells for each target per kilogram(kg) were infused within 3 days. Results: 14 R/R DLBCL patients with high tumor burden were enrolled in the study. Patients ranged from 39 to 66 years of age had received two to four prior lines of therapy. Out of the 14 patients, 7 patients received intensive second-line chemotherapy (median age, 46 years) and 7 received radiotherapy (median age, 63years) to debulking tumor after leukapheresis and during CAR-T cells preparation. All Adverse Events occurring within 30 days of CAR-T cells infusion were graded and reported for the 14(100%) treated patients. All patients experienced CAR-T-related CRS of any grade with severe CRS (grade 3/4/5) reported in all patients of chemotherapy cohort experienced and mild CRS (grade 1/2) reported in all patients of radiation cohort. 4 patients (57.1%) in chemotherapy cohort manifested with neurological toxicity while no patient in radiation cohort manifested with neurological toxicity. Comparable hematological toxicity as well as non-hematological and non-neurological toxicity were observed in two groups. Four of seven (57.1%) patients achieved an objective response after CAR-T infusion, with three of seven (42.9%) achieving a CR in chemotherapy cohort, while seven of seven (100%) achieved an objective response after CAR-T therapy, with four of seven (57.1%) achieving a CR in radiation cohort. Conclusions:Our clinical trial indicates that compared to intensive second-line chemotherapy, radiation is a better approach to enhancing efficacy and decreasing toxicity of CAR-T therapy in R/R DLBCL patients with high tumor burden. Radiotherapy in combination with CAR-T cell infusion may be the optimal alternative treatment model of R/R DLBCL with high tumor burden. Disclosures No relevant conflicts of interest to declare.

Tumor necrosis factor receptor-associated factor 6 (TRAF6), an (K63) E3-ligase, plays a crucial role in many biological processes and its activity is relevant in the biology of multiple cancers including diffuse large B cell lymphoma (DLBCL). Although molecules that trigger TRAF6 activation have been defined, those that stabilize TRAF6 levels and/or enhance TRAF6 function remain largely unclear. Previously, we found that activation of smoothened (SMO) with recombinant Hedgehog (Hh) ligand increased the binding between SMO with TRAF6, as well as TRAF6 protein levels (Blood 2013; 121:4718-28). In addition, transient overexpression of SMO resulted in increased K63-Ub of both TRAF6 and NEMO indicating stabilization of these proteins resulting in NF-kB activation. This is relevant, as more recently we found that TRAF6 amplifies pAKT signaling in DLBCL and that TRAF6 is the dominant E3 ligase for the K63-Ub of AKT in DLBCL. Moreover, TRAF6 recruitment to the cell membrane, and stabilization of its ubiquitination profile are facilitated by SMO. SMO is a member of the Frizzled-class G-protein-coupled receptor (GPCRs) and is traditionally known for its role as signal transducer in canonical Hedgehog (Hh) signaling. These observations prompted us to investigate whether the ability of SMO to increase TRAF6 levels is limited to ligand induced signaling, whether it contributes to chemoresistance in DLBCL cells, and whether SMO directly participates in controlling TRAF6 levels. To confirm the regulatory role of SMO in the TRAF6/AKT axis in DLBCL cells (HBL1 and HT) and further outline the nature of the underlying regulation, we measured the impact of activation of the Hh pathway with recombinant Shh ligand on TRAF6 levels, with and without SMO knockdown or recombinant SMO overexpression. Canonical Hh signaling results in the activation of the GLI1 transcription factor and the subsequent elevation of GLI1 mRNA levels is an established indicator of activation of the Hh pathway. However, neither SMO activation nor the knockdown of GLI1 had a significant impact on TRAF6 mRNA levels. These findings indicate that TRAF6 is not transcriptionally regulated by SMO signaling through GLI1 (canonical Hh signaling). In contrast, overexpression of SMO or siRNA knockdown of SMO resulted in an increase or decrease of TRAF6 protein levels, respectively. Consistent with the decrease of AKT activation (pAKT T308 and S473) after TRAF6 knockdown, the increase in TRAF6 levels that follows SMO overexpression resulted in an increase in the levels of AKT phosphorylation. Altogether, these observations suggest a post-translational regulation of TRAF6 by SMO. Indeed, stable knockdown of SMO dramatically reduces the half-life of TRAF6 in both HBL1 and HT cells in the presence of cyclohexamide. Furthermore, overexpression of SMO increases K63-Ub of both TRAF6 and AKT. In contrast, the SMO induced decrease in K48-Ub occurred only for TRAF6 but not for AKT. These data link the SMO-stimulated activation of TRAF6 to the enhancement of AKT signaling and protection of TRAF6 from proteasomal degradation. Mechanistically, we found that SMO, through its C-terminal tail, stabilizes TRAF6 and protects TRAF6 from proteosomal degradation, an effect mediated by ubiquitin-specific protease-8 (USP8). Importantly, this functional link between SMO and TRAF6 is reflected in DLBCL patient samples where high expression of both molecules correlates with poor prognosis. Resistance to DXR is a serious challenge in the treatment of DLBCL, and activated AKT is known to contribute to DXR resistance in multiple cancers including DLBCL. We evaluated whether SMO and TRAF6 support resistance to DXR in DLBCL cell lines. We exposed HT and HBL1 cells as well as their counterparts with stable knockdown of TRAF6 or SMO to DXR for 96hrs. Cell viability after exposure to DXR was determined by an Annexin V and PI staining assay. Silencing SMO or TRAF6 dramatically decreased cell survival after treatment with DXR. In summary, we report that SMO is needed to facilitate and maintain TRAF6-dependent elevated pAKT levels in DLBCL cell lines of germinal (GC) and non-GC subtypes, and that the SMO/TRAF6 axis contributes to DXR resistance in DLBCL. Our study reveals a novel and potential central cell survival signaling mechanism in which SMO stabilizes and protects TRAF6 from proteosomal degradation. Disclosures Lossos: Affimed: Research Funding.

Background: Constitutive activation of NF-κB signaling is a hallmark of DLBCL. Activation of NF-κB is a multifactorial process resulting from oncogenic mutations (CARD11, MYD88…), chromosomal abnormalities, chronic activation of B-cell receptor signaling (BCR) as well as stimuli from the microenvironment. Chronic activation of BCR is not only the result of gene mutations (e.g.CD79B) but also is the result of stimuli generated from the lymphoma microenvironment. We previously found that smoothened (SMO), transducer of hedgehog (Hh) signaling, enhanced NF-κB activation in lymphoma cells, independently of the presence of oncogenic mutations (Changju et al., Blood 2013). Hh ligands are provided by the lymphoma microenvironment (e.g. stromal cells) to activate SMO in the lymphoma cells. Activated SMO, recruits and activates trimeric-G-coupled proteins to activate PKCβ/CARMA1/TRAF6/NEMO axis, followed by assembling of the CARMA1/BCL10/MALT1/TRAF6 complex to SMO resulting in NF-κB activation. Now, we reveal an additional mechanism by which SMO further contributes to the activation of NF-κB in DLBCL. Summary of results: We explored if recombinant Hh ligand can activate NF-κB signaling in the presence of the BTK inhibitor (PCI-32765). Hh stimulation resulted in phosphorylation of PLCg2 (downstream of BTK) and partially rescued the inhibitory effect of the BTK inhibitor on phosphorylation of PLCg2 suggesting a crosstalk between SMO and BCR receptor signaling. We identified that SMO forms a complex with TRAF-6 and PLCg2 using immunoprecipitation and Duolink in situ proximity ligation assays. We found that SMO stabilizes and protects TRAF-6 from proteosomal degradation. SMO-dependent TRAF6 stabilization is mediated by the ubiquitin-specific protease-8 (USP-8) by removing ubiquitin from K48-linked lysine of TRAF6. Conclusions: Collectively, our data reveals multilayer crosstalk between Hh and BCR/NF-κB pathways and provide significant insights into how SMO contributes to chemotolerance and progression of DLBCL. We expect that our results will delineate novel molecular mechanisms involved in the pathobiology of DLBCL that may serve as therapeutic targets. Disclosures Vega: Seatle Genetics: Honoraria; NIH: Research Funding.