The CNS Relapse in T-Cell Lymphoma Index Predicts CNS Relapse in Patients with T- and NK-Cell Lymphomas

Little is known about risk factors for central nervous system (CNS) relapse in mature T- and NK-cell neoplasms (MTNKN). We aimed to describe the clinical epidemiology of CNS relapse in patients with MTNKN and developed the CNS relapse In T-cell lymphoma Index (CITI) to predict patients at highest risk of CNS relapse. We reviewed data from 135 patients with MTNKN and CNS relapse from 19 North American institutions. After exclusion of leukemic and most cutaneous forms of MTNKN, patients were pooled with non-CNS relapse control patients from a single institution to create a CNS relapse-enriched training set. Using a complete case analysis (N=182), of whom 91 had CNS relapse, we applied a LASSO Cox regression model to select weighted clinicopathologic variables for the CITI score, which we validated in an external cohort from the Swedish Lymphoma Registry (N=566). CNS relapse was most frequently observed in patients with PTCL, NOS (25%). Median time to CNS relapse and median overall survival after CNS relapse was 8.0 months and 4.7 months, respectively. We calculated unique CITI risk scores for individual training set patients and stratified them into risk terciles. Validation set patients with low-risk (N=158) and high-risk (N=188) CITI scores had a 10-year cumulative risk of CNS relapse of 2.2% and 13.4%, respectively (HR 5.24, 95%CI 1.50-18.26, P=0.018). We developed an open-access web-based CITI calculator (https://redcap.link/citicalc) to provide an easy tool for clinical practice. The CITI score is a validated model to predict patients with MTNKN at highest risk of developing CNS relapse.

TTI-622-01: A phase 1a/1b dose-escalation and expansion trial of TTI-622 in patients with advanced hematologic malignancies, including diffuse large B-cell lymphoma (DLBCL)

TPS7595

Background: CD47 is an innate immune checkpoint that binds signal regulatory protein alpha (SIRPα) and delivers a "don’t eat me" signal to suppress macrophage phagocytosis. Overexpression of CD47 on cancer cells serves as a mechanism of immune surveillance evasion, and is associated with poor prognosis in both hematologic and solid malignancies. TTI-622 is a fusion protein consisting of the CD47-binding domain of human SIRPα linked to the Fc region of human IgG4. It is designed to enhance phagocytosis and antitumor activity by preventing CD47 from delivering its inhibitory signal as well as generating a moderate pro-phagocytic signal via IgG4 Fc. Importantly, unlike many CD47-blocking agents, TTI-622 does not bind to human red blood cells. Preclinical studies demonstrate that TTI-622 induces macrophage-mediated phagocytosis of different malignant cell lines, including DLBCL cells, decreases tumor growth and improves survival in a DLBCL xenograft tumor model. Anti-CD47 antibody enhances rituximab stimulated macrophage-mediated phagocytosis of non-GCB DLBCL cell lines (Bouwstra et al, Cancer Immunol Res. 2019). The ongoing phase 1a part of this study has been previously described. Here we describe 2 cohorts within the phase 1b part of the study that are intended to determine the safety and preliminary efficacy of TTI-622 when given in combination with anti-CD20 targeting agent in patients with CD20+ relapsed/refractory (RR) DLBCL. Methods: TTI-622-01 is a multi-center Phase 1a/1b study. Phase 1a was designed to determine the MTD, pharmacokinetics (PK), pharmacodynamics, and preliminary antitumor activity of QW, Q2W, and Q3W single-agent TTI-622 in R/R lymphoma using a 3+3 dose escalation schema. Phase 1b, ongoing, will determine the safety, recommended dose and preliminary efficacy of TTI-622 in combination with select approved anticancer treatments for patients with hematological malignancies including, but not limited to anti-CD20 therapy in patients with CD20+ RR DLBCL. Secondary objectives are to further characterize safety, PK and immunogenicity of TTI-622 when combined with approved therapies. Patients will be enrolled in 2 cohorts exploring different doses of TTI-622 in combination with anti-CD20 therapy. Cohorts will open in a staggered manner. In each cohort 3 patients will be dosed and followed for 28 days before expanding enrolment to additional 27 patients per cohort. Key eligibility criteria include: age ≥18 years; relapsed and/or refractory disease after ≥1 prior line of therapy; not eligible for or have progressed after high dose chemotherapy (HDT)/auto-SCT; ≥1 site of measurable disease (Lugano 2014 classification); ECOG PS ≤2; adequate organ functions, no known CNS involvement; no prior anti-CD47 or anti-SIRPα therapy. Patient recruitment is planned or ongoing at 40 sites worldwide. Clinical trial information: NCT03530683.

The utility of the novel optimized HLH inflammatory (OHI) index for predicting the risk for mortality and causes of death in lymphoma

7570

Background: Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening inflammatory syndrome that may complicate hematologic malignancies (HM). We recently developed a simplified diagnostic and prognostic index termed the ‘optimized HLH inflammatory’ (OHI) index comprising the combined elevation of sCD25 ( > 3,900 U/mL) and serum ferritin ( > 1,000 ng/mL), which in HM patients both identifies HLH and predicts mortality more accurately than conventional criteria for HLH. In this study, we examined whether mortality in our cohort is directly related to progressive malignancy vs. HLH-associated causes in OHI+ and OHI- patients. Methods: We performed a multicenter, retrospective study of patients with newly diagnosed lymphoma from Israel, the USA, and Japan for whom sCD25 and ferritin levels were measured either as routine surveillance or during investigation for HLH and classified patients by their OHI status. The International Prognostic Index, International Prognostic Score, and Follicular Lymphoma International Prognostic Index were used to estimate the predicted prognosis of T/B cell non-Hodgkin’s lymphoma (NHL), Hodgkin’s lymphoma, and follicular lymphoma, respectively. Predicted five-year overall survival was calculated based on the relevant prognostic index and was compared between OHI+ and OHI- patients using the unpaired t-test. The actual survival at five years/last follow-up was recorded, as was the cause of death. The odds ratios (ORs) for observed vs. predicted mortality, and for HLH- vs. malignancy-related death were calculated using the Chi-square test. Results: 100 lymphoma patients were studied: 65% with B cell NHL, 18% with natural killer/ T cell lymphoma, 17% with Hodgkin’s lymphoma; 37 were OHI+, and 63 were OHI-. The disease-relevant international prognostic index-predicted five-year survival did not differ between OHI + and OHI- patients (a mean of 58% n OHI+ and 57% in OHI- p = 0.62). However, the observed five-year survival in OHI+ patients was lower (12%) than predicted, reflecting a mortality incidence that was four times higher than predicted by the relevant prognostic score (OR 3.9; CI 1.3-12.1). By contrast, OHI- patients had better survival (79%) than predicted by their prognostic scores (OR 0.15; CI 0.07-0.34). More than half of the OHI+ patients died from non-malignant causes (39% multi-organ dysfunction or HLH, 18% infection), while most OHI- patients (92%) died from progressive malignancy. The likelihood of dying from multi-organ dysfunction or HLH was 26 times higher in OHI+ vs. OHI- patients (OR 26.2; CI 4.1-286.7). Conclusions: OHI index status strongly correlated with mortality in patients with lymphoma within our cohort, and death in OHI+ patients was largely due to causes other than progressive malignancy. The OHI index appears to identify a harmful inflammatory state and deserves further prospective study.

A novel index using inflammatory markers improves the diagnosis of hemophagocytic lymphohistiocytosis in patients with hematologic malignancies

7563

Background: Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening inflammatory syndrome that may accompany hematologic malignancies (HM). The diagnosis of HLH in patients with HM (HM-HLH) is confounded by a number of factors: the most commonly used HLH-2004 diagnostic criteria are derived from studies in infants while the Hscore used in adults is not specific for HMs; moreover, most parameters in these scoring systems may reflect features of the underlying HM rather than HLH associated inflammation; and finally specific diagnostic cutoff values for laboratory abnormalities in HM-HLH have not been defined. We therefore conducted a study to optimize the HLH-2004 laboratory thresholds for the diagnosis of HM-HLH. Methods: A multi-center retrospective study in adult patients with HM in whom testing for HLH was performed. HM-HLH was defined as fulfillment of 5/8 HLH-2004 diagnostic criteria. We established the optimal diagnostic cutoff levels for HLH-2004 laboratory parameters using receiver operating curves (ROC) and combined the best performing parameters into a combined index, using binary logistic regression. We then created a clinical decision tree using a Classification and Regression Tree (CART) analysis with all available parameters, using cross validation. We also determined the prognostic value of our combined diagnostic tool. Results: 225 adults were analyzed (112 with HM-HLH per HLH-2004 and 113 with HM only). 35% of patients were evaluated for HLH routinely upon HM diagnosis. Soluble CD25 (sCD25) and ferritin best discriminated HM-HLH from HM, with an area under the curve (AUC) of 0.83 for each. ROC analysis demonstrated an optimal cutoff of > 4190 U/mL for sCD25 (sensitivity/specificity 91%/69%) and an optimal cutoff of > 2636 ng/ml for ferritin (sensitivity/specificity 64%/86%) for HM-HLH. We term the combination of elevated sCD25 and ferritin using optimized cutoff levels the ‘optimized HLH inflammatory’ (OHI) index. This OHI index was highly specific for the diagnosis of HM-HLH (specificity of 92%, sensitivity 79%). CART analysis demonstrated that OHI index positivity was sufficient to diagnose HM-HLH. In patients without a positive OHI index an Hscore > 168 and either splenomegaly or triglycerides > 279 ng/dL can still diagnose HM-HLH. By following this decision pathway, approximately 92% of patients were accurately classified based on HLH-2004. Furthermore, the OHI was better (odds ratio (OR) 7.9; 95% confidence interval (CI) 4.2-14.6) than Hscore >169 (OR 5.5; CI 3.9-9.6) and > 5/8 HLH-2004 (OR 5.3; CI 3-9.3) at predicting mortality at 1 year. Conclusions: The OHI index derived here is a simple tool that can accurately diagnose HLH and predict mortality in patients with hematologic malignancies. Some patients may not need full HLH workup before intervening with therapy that is HLH directed and not only malignancy directed.

Characterization of BCL-2 alternative proteins and outcome in patients with peripheral T-cell lymphoma (PTCL)

e19531

Background: The outcome of patients with PTCL, NOS is generally very poor, and the identification of biologically rational targets, which may translate into effective and non-toxic treatment strategies, is a high priority. The pro-survival BCL-2 family members BCL-2, BCL-XL (BCL2L1), BCL-W (BCL2L2), BCL2A1 and MCL-1 contribute to tumor maintenance, progression, and chemo-resistance across a range of cancers, but their contributions in PTCL, NOS are poorly understood. Methods: Patients with PTCL, NOS treated between 09/2000 and 09/2019 and with available tissue biopsy were included in the study. Diagnosis was retrospectively confirmed by two expert hematopathologists. BCL-2, BCL-XL, BCL-W, BCL2A1 and MCL-1 expression was assessed by immunohistochemistry (IHC), and the percentage of positive tumor cells assessed by standard microscopy. The 2014 Lugano Classification was used to define response to therapy. Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method, and were compared using log-rank test between patient groups. Results: Twenty-seven patients were included in the study: 67% were male, 52% ≥ 65 year old, and 48% had stage IV disease; 59% were previously treated and 41% received > 2 lines of therapy, including stem cell transplant (SCT) in 19%. The median expression of BCL-2, BCL-XL, BCL-W, BCL2A1 and MCL-1 by IHC was: 30% (range: 0-100%), 10% (range: 0-90%), 100% (range: 40-100%), 20% (range: 0-90%), and 70% (range: 1-100%), respectively. BCL-2A1 was significantly higher in previously treated patients (35% vs 5%, p = 0.02), and in those who had previously received > 2 lines of therapy (40% vs 5%, p = 0.02). Twenty-four (89%) patients were treated after tissue biopsy, 17 (63%) with chemotherapy, 7 (26%) with biological therapy, and 6 (22%) received subsequent SCT. Five (24%) patients achieved complete remission (CR); only BCL-W associated with response, a higher expression (quartiles 3 and 4) being observed among patients not achieving CR (median 100% vs 90%, p = 0.07). After a median follow-up of 28 months (95% CI, 14-42 months), 22 (81%) patients progressed or died, and median PFS was 4 months (95% CI, 2-6 months); only BCL-W associated with PFS, a shorter median PFS being observed for patients with higher expression (3 months vs 7 months, p = 0.001). At most recent follow-up, 17 (63%) patients died, and median OS was 6 months (95% CI, 1-12 months). only BCL-W associated with OS, a shorter median OS being observed for patients with higher expression (4 months vs not reached, p = 0.004). Conclusions: High expression of BCL-W associates with significantly worse outcome in patients with PTCL, NOS. While clinical trials investigating the safety and efficacy of BCL-2 inhibition in PTCL, NOS are ongoing, these results suggest that concomitant BCL-W inhibition may be beneficial, and functional studies aimed at confirming these findings are highly needed.

Haemophagocytic lymphohistiocytosis (HLH) in patients with large B-cell lymphoma treated with standard of care (SOC) axicabtagene ciloleucel (Axi-cel)

8057

Background: HLH is a rare but serious complication of chimeric antigen receptor (CAR) T cell therapy, characterized by severe immune activation, and immune mediated multi-organ failure. Diagnosis is difficult in the context of cytokine release syndrome (CRS) and optimal treatment and outcomes are unclear. Methods: Retrospective, descriptive analysis of patients with relapsed/refractory LBCL treated with SOC axi-cel at MD Anderson Cancer Center between 01/2018 - 10/2019 (data cut-off 12/21/2019). Progression-free survival (PFS) defined as time from axi-cel infusion to progression/death or last follow-up. Diagnosis of HLH per HLH-2004 and CART cell therapy toxicity guidelines (Neelapu, 2018) Results: One hundred and five patients with relapsed/refractory LBCL included, 6 diagnosed with HLH. No significant difference in baseline characteristics, disease stage, international prognostic index or inflammatory markers at baseline between groups, with exception of platelet count which was lower in HLH group 116 [37-129] versus 141 [9-391] (p = 0.07). Development of HLH was early after CART cell infusion at a median 11 days [7 – 78 days] with 3 patients having bone marrow hemophagocytosis; all 6 had abnormalities in liver function tests, fibrinogen, triglycerides, and at least 1 ferritin level > 10,000. CART toxicity in HLH cohort: 4 patients experienced grade 0-1 CRS, and 1 with grade 2 CRS while 3 HLH patients experienced grade 3-4 IEC-associated neurotoxicity syndrome ( ICANS), and 2 patients had grade 0-1 ICANS. Five HLH patients treated with high dose steroids, and tocilizumab; anakinra administered in 2 patients. Four of 6 patients had resolution of HLH with treatment and didn’t require escalation to HLH specific therapy however 1 patient was treated with steroids/etoposide. PFS and overall survival (OS) were significantly shorter in HLH group, PFS 1 months vs 8 months, respectively (p < 0.001) and median OS 2 months vs not reached, respectively (p = 0.001) follow up 10 months (95% CI 8-12 months). One patient died of acute respiratory failure, 2 patients died of HLH and multi-organ failure without progressive disease (PD). Of 3 remaining patients, all had radiographic PD at day 30, 2 of whom died of PD. Conclusions: HLH is likely an underreported complication of CART cell therapy, and patients with HLH have significantly worse outcomes. In this series the majority of patients died of PD, not the syndrome itself. More information is necessary to design treatment strategies that won’t compromise CART outcomes.

Prognostic impact of dose, duration, and timing of corticosteroid therapy in patients with large B-cell lymphoma treated with standard of care axicabtagene ciloleucel (Axi-cel)

8011

Background: Corticosteroids are commonly used for management of severe toxicities associated with chimeric antigen receptor (CAR) T-cell therapy. However, it remains unclear whether the dose, duration, and timing of corticosteroid therapy may impact clinical efficacy of CAR T-cell therapy. Methods: This is a retrospective analysis of patients with relapsed or refractory LBCL treated with standard of care axi-cel at MD Anderson Cancer Center, Houston, Texas between 01/2018 and 05/2019 (data cut-off 12/21/2019). Progression-free survival (PFS) was defined as time from axi-cel infusion to progression/death or last follow-up, and the Breslow test was used for comparisons between subgroups. Results: One hundred patients with relapsed or refractory LBCL were included in the study, and 60 (60%) received corticosteroids for management of toxicities after axi-cel infusion. There was no significant difference in baseline tumor burden, disease stage or international prognostic index between the 2 groups. The median cumulative dexamethasone-equivalent dose was 186 mg (range, 8-1803 mg) and the median duration of corticosteroid treatment was 9 days (range 1-30); 45 (45%) patients started corticosteroid treatment between day 0 and 7, and 15 (15%) beyond day 7. After a median follow-up of 10 months (95% CI 8-10 months), median PFS was 8 months (95% CI, 3-13 months), and use of corticosteroids (any dose) showed a trend for association with shorter PFS (6 vs 9 months, p = 0.13). Use of high-dose corticosteroids (Quartiles (Q) 3-4, 195-1803 mg) significantly associated with shorter PFS (2 vs 9 months, p = 0.005). A trend for shorter PFS was observed among patients receiving corticosteroids for a prolonged time (Q3-Q4, 10-30 days) (5 vs 8 months, p = 0.12) and among patients starting corticosteroids within the first 7 days after axi-cel infusion (6 vs 11 months, p = 0.07). At most recent follow-up, 36 patients died, 28 of progression. Median overall survival has not been reached, and was significantly shorter among patients who received corticosteroids (13 vs not reached, p = 0.006). Conclusions: Early and prolonged use of high-dose corticosteroids is associated with early progression and death in patients with LBCL treated with axi-cel. Additional evaluation is needed to understand the mechanism underlying this association.

M.D. Anderson experience of immune checkpoint inhibitor therapy in classical Hodgkin lymphoma

e20013

Background: Nivolumab and Pembrolizumab are effective immune checkpoint inhibitor (ICI) therapies targeting PD-1/ PDL-1 immune axis. The drugs are currently approved for relapsed/ refractory classical Hodgkin lymphoma (cHL)based on phase I and II trial data. Methods: We conducted a retrospective study of patients (pts) with relapsed refractory cHL treated with ICI therapy at M.D. Anderson Cancer center from 4/2013 to 5/2019 to evaluate the efficacy of this treatment. The responses were assessed using revised response criteria according to the Lugano classification Results: Ninety-two pts treated with nivolumab (66) and pembrolizumab (26) were included. Fifty six pts (63%) were advanced stage at diagnosis, most treated initially with ABVD (88%) and BV-AVD (3%). Seventy percent pts had primary refractory disease or relapsed < 12 months after frontline therapy. At the time of ICI initiation, pts had the following characteristics: median age 35 (range 18-86), extranodal disease - 28 pts (37%), prior BV exposure in 81 pts (89%) with 66% considered BV refractory. Sixty one percent patients were refractory to the last prior line of salvage therapy. Median prior lines of therapy was of 3 (range 1-13) and 53 pts (58%) had a prior HSCT. At a median follow-up time of 20.2 months (range: 1.58 - 55.98 months), median progression free survival was 12.3 months and median overall survival was not reached. Among the 39 patients with no prior transplant, 11 patients who achieved CR with ICI were consolidated with HSCT (autologous - 7 and allogeneic - 4). Of this cohort, 2 pts (1 post auto, 1 post-allo) have relapsed. Five patients in our cohort were treated with an alternative ICI for subsequent relapse; of four patients with response assessment, 3 achieved CR and 1 experienced PD. Conclusions: In this cohort of cHL pts, ICI offered high response rates before and after HSCT supporting the possibility for using ICI earlier in the treatment course for refractory or early relapsed HL.

Ongoing, first-in-human, phase I dose escalation study of the investigational CD47-blocker TTI-622 in patients with advanced relapsed or refractory lymphoma

3030

Background: CD47 is an immune checkpoint that binds signal regulatory protein alpha (SIRPα) and delivers a "do not eat" signal to suppress macrophage phagocytosis. Cancer cells frequently overexpress CD47 to escape immune surveillance. TTI-622 is a fusion protein consisting of the CD47-binding domain of human SIRPα linked to the Fc region of human IgG4. TTI-622 acts as a decoy receptor, preventing CD47 from delivering its inhibitory signal and enabling macrophage activation and anti-cancer activity via pro-phagocytic signals present on cancer cells. Unlike many CD47-blocking antibodies, TTI-622 does not bind to human erythrocytes and thus may not cause anemia in patients. Methods: In phase 1A, patients with advanced relapsed or refractory lymphoma received IV TTI-622 once per week with dose increased based on traditional 3+3 escalation. Dosing was on a mg/kg basis with the third and subsequent weekly doses approximately 2-fold higher than the first 2 doses (e.g., 0.05, 0.05, and 0.1 mg/kg for weeks 1, 2 and 3). Blood samples were obtained for PK analysis and assessment of CD47 receptor occupancy (RO) on peripheral T cells. Results: At data cut-off, 19 patients (11 M, 8 F) of median age 62 years (range, 24-86) with the following lymphomas: DLBCL 10; HL 6; and TCL, MCL and FL, 1 each, with a median of 3 prior therapies (range, 1-8) were enrolled. No DLTs have been observed in 5 dose levels (0.05 to 4.0 mg/kg). Grade ≥3 related neutropenia occurred in 2 patients; other related AEs occurring in 2 patients each included abdominal pain, fatigue, and nausea; no patients experienced a related SAE. Acute, post-dose platelet decreases occurred transiently and generally were Grade 1- 2; no related Grade ≥3 thrombocytopenia or anemia AEs have been observed. Preliminary PK data indicate a dose-proportional increase in exposure and a T1/2 of approximately 4-5 days following repeat infusions (Week 6). Preliminary biomarker data reveal approximately 60% RO at the end of the first infusion of 2 mg/kg and more sustained 24-hour RO at 1 and 2 mg/kg vs ≤ 0.8 mg/kg. To date, 1 patient with stage 4 non-GCB DLBCL (5 prior therapies) initially achieved PR by Wk 8 and CR by Wk 36, with response ongoing. Conclusions: TTI-622 is well tolerated at doses up to 4 mg/kg per week. Preliminary data indicate dose-dependent increases in PK exposure and target engagement with 1 DLBCL patient having achieved a durable, ongoing CR. Dose escalation is ongoing and additional safety, PK, biomarker and response data will be available at the time of meeting presentation. Clinical trial information: NCT03530683 .

Comprehensive report of anti-CD19 chimeric antigen receptor T cells (CAR-T) associated non-relapse mortality (CART-NRM) from FAERS

2540

Background: CAR-T cells targeting CD19 positive B-cells have improved outcomes for relapsed/refractory non-Hodgkin lymphoma (NHL) and B-cell acute lymphoblastic leukemia (B-ALL). CAR-T emergent toxicities for FDA approved therapies leading to non-progression related death have been reported in the pivotal studies. However, they are underreported and there remains a need to obtain a comprehensive report of NRM emergent with anti-CD19 CAR-T. Methods: We retrospectively searched FDA adverse events reporting system (FAERS) for all adverse events (AE) related to “Tisagenlecleucel(T)” and “Axicabtagene ciloleucel(AC)” reported from 2013-2018. FAERS contains AEs from clinical trials and standard of care patients. All cases with the outcome of death were analyzed. Results: Total numbers of anti-CD19 CAR-T pts reported were 636, out of which 288 cases received “T” and 348 received “AC”. Out of total 129 total deaths, 95 died due to non-disease progression. Patient characteristics are summarized in Table. CART-NRM for entire cohort was 15%; 21% for “T” and 10% for “AC”. Major toxicities reported include CRS, hematological, cardiovascular, neurological and infectious. Difference in mortality is likely related to different patient population, diagnoses and the CAR-T construct. Conclusions: CART-NRM remains considerably high at 15%. Our analysis highlights the major toxicities and informs the potential opportunities for interventions to reduce mortality. We will present updated data with comparative analysis of published clinical studies at the upcoming ASCO Meeting in Chicago. [Table: see text]

Response to A+CHP by CD30 expression in the ECHELON-2 trial

7538

Background: Brentuximab vedotin (BV) is an antibody-drug conjugate that targets CD30. The ECHELON-2 (E-2) study demonstrated significantly longer progression-free and overall survival with BV plus cyclophosphamide, doxorubicin, and prednisone (A+CHP) versus CHOP in frontline treatment of patients (pts) with CD30+ peripheral T-cell lymphoma (PTCL). Complete remission (CR) rate (A+CHP 68%; CHOP 56%) and objective response rate (ORR) (A+CHP 83%; CHOP 72%) were also significantly increased. Expression of CD30 is universal in systemic anaplastic large-cell lymphoma (sALCL) but variable among non-sALCL subtypes. As ORR is a direct measure of antitumor activity, we examined response to A+CHP by CD30 expression. Methods: Pts with CD30+ (≥10% by local review) PTCL were included in E-2. Eligible histologies included ALK+ sALCL (IPI ≥2), ALK− sALCL, PTCL-not otherwise specified (PTCL-NOS), angioimmunoblastic T-cell lymphoma (AITL), adult T-cell leukemia/lymphoma, enteropathy-associated T-cell lymphoma, and hepatosplenic T-cell lymphoma. We analyzed the relationship between CD30 expression (IHC Ber H2 antibody) above and below the median (median CD30=18% PTCL-NOS; 25% AITL) and CR rate, ORR, and duration of CR (DOCR) in pts with AITL and PTCL-NOS treated with A+CHP. Results: Most (26/29, 90%) AITL pts had CD30 expression between 10% and 30%. PTCL-NOS pts were more evenly distributed across levels of CD30 expression ranging from 10% to 100%. CD30 levels were neither predictive of response (Table) nor significantly associated with DOCR in pts with AITL (P=0.30) or PTCL-NOS (P=0.90) (log-rank test). Response by CD30 expression. Clinical trial information: NCT01777152. Conclusions: CD30 expression above vs below median (or at 10%) did not predict response to A+CHP in E-2 non-ALCL subtypes, as responses were seen across CD30 levels. This may be due to intra- and inter-tumoral heterogeneity of CD30 expression, limitations of IHC, the nature of CD30 on the cell surface, and multiple mechanisms of action of BV. Further evaluation of the expression-response relationship in PTCL pts with CD30 <10% is warranted.[Table: see text]

T-cell lymphoma secondary to checkpoint inhibitor (CPI) used for other malignancies

88

Background: Wartewig et al. (Nature 2017) proved in a preclinical mouse model that anti-PD1 therapy could cause T-cell lymphoma. T-cell lymphoma as an adverse event of CPIs has never been reported. A 75-year-old male with h/o urothelial carcinoma presented with lung metastasis of adenocarcinoma of unknown primary that showed PDL1 staining 5% of cells. Patient was treated with carboplatin & paclitaxel. For progressive disease, the patient received Pembrolizumab. After 4 cycles of CPI he developed lymphocytosis and lymphadenopathy and diagnosed with peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS), with bone marrow (BM) involvement. Patient died before receiving any treatment for lymphoma. We hypothesized that CPI caused clonal expansion of T cells. Methods: We performed T-cell receptor (TCR) sequencing by Immunoseq assay in biopsy specimens. We queried FDA Adverse Events Reporting System (FAERS) and VigiBase databases for T-cell lymphoma/leukemia, PTCL, NOS, Mycosis Fungoides, Anaplastic Large & Cutaneous T-cell Lymphoma as an adverse event (AE) secondary to nivolumab, pembrolizumab or ipilimumab. Results: Through TCR sequencing we identified single clonal expansion before PD1 therapy in lung (0.008%) to 11% in bone marrow and 40% in lymph node (post treatment samples). Additional targeted exome sequencing of the lymphoma revealed a TET2 mutation. We conclude that anti-PD1 caused clonal expansion of the T cells harboring TET2 mutation leading to T-cell lymphoma. Findings of FARES and VigiBase review are shown in the Table. Conclusions: T-cell lymphoma is a rare complication of CPIs, with high mortality (20%). Long term follow up of patients receiving CPIs is needed. [Table: see text]

Phase I Study of the Investigational Aurora A Kinase Inhibitor Alisertib plus Rituximab or Rituximab/Vincristine in Relapsed/Refractory Aggressive B-cell Lymphoma

PURPOSE

The aurora A kinase inhibitor alisertib demonstrated single-agent clinical activity and preclinical synergy with vincristine/rituximab in B-cell non-Hodgkin lymphoma (B-NHL). This phase I study aimed to determine the safety and recommended phase II dose (RP2D) of alisertib in combination with rituximab ± vincristine in patients with relapsed/refractory aggressive B-NHL.

PATIENTS AND METHODS

Patients with relapsed/refractory, diffuse, large, or other aggressive B-NHL received oral alisertib 50 mg b.i.d. days 1 to 7, plus i.v. rituximab 375 mg/m² on day 1, for up to eight 21-day cycles (MR). Patients in subsequent cohorts (3 + 3 design) received increasing doses of alisertib (30 mg starting dose; 10 mg increments) b.i.d. days 1 to 7 plus rituximab and vincristine [1.4 mg/m² (maximum 2 mg) days 1, 8] for 8 cycles (MRV). Patients benefiting could continue single-agent alisertib beyond 8 cycles. Cell-of-origin and MYC/BCL2 IHC was performed on available archival tissue.

RESULTS

Forty-five patients participated. The alisertib RP2D for MR was 50 mg b.i.d. For MRV (n = 32), the RP2D was determined as 40 mg b.i.d. [1 dose-limiting toxicity (DLT) at 40 mg; 2 DLTs at 50 mg]. Drug-related adverse events were reported in 89% of patients, the most common was neutropenia (47%). Seven patients had complete responses (CR), 7 had partial responses (PRs); 9 of 20 (45%) patients at the MRV RP2D responded (4 CRs, 5 PRs), all with non-germinal center B-cell (GCB) diffuse large B-cell lymphoma (DLBCL).

CONCLUSIONS

The combination of alisertib 50 mg b.i.d. plus rituximab or alisertib 40 mg b.i.d. plus rituximab and vincristine was well tolerated and demonstrated activity in non-GCB DLBCL.

ESKAPEade in hematological malignancies: Dare to review!

e18110

Background: Patients with hematological cancers are at a high risk for increasingly resistant and severe infections. The Infectious Diseases Society of America has defined commonly resistant bacteria as ESKAPE (Enterococcus, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter, Pseudomonas aeruginosa, Enterobacter/Enterobacteriaceae). We performed a retrospective review of the rate of ESKAPE infections, resistance profile, and outcomes in patients with various hematological malignancies at the Houston Methodist Hospital from 2006 to 2015. Methods: The patient data was obtained from METEOR (Methodist Environment for Translational Enhancement and Outcomes Research), a clinical data warehouse that contains records dating back to January 1, 2006 with over 3 million patients and over 10 million unique patient encounters. We queried for leukemia (AML, CML, ALL, CLL), amyloidosis and myelodysplastic syndrome (MDS) along with hospitalizations due to bacterial infections. Baseline demographics and overall outcomes were also obtained. Results: Out of 6017 patients with Hematological Malignancies, 632 patients were found; 322 had MDS, 225 had AML, 136 had CLL, 49 had ALL, 60 had CML, 97 had amyloidosis and 13 had an unspecified hematological cancer. Of 1091 infectious events, 60.5% were ESKAPE infections. The bacteria most frequently isolated were Enterococcus (24.7%), MRSA (19.8%) and Pseudomonas (18.0%). Patients with MDS (41.5%), AML (20.6%) and CLL (14.4%) were mostly affected. A prevalent resistance to levofloxacin was detected in gram positives and gram negatives (29-54%). Pseudomonas, E. coli, Proteus and K. pneumoniae showed a significant resistance to broad spectrum antibiotics including aztreonam (23-34%), cefepime (7-23%) and imipenem (22%). Proteus had the highest mortality rate (45.2%), followed by Enterococcus (44.2%) and Pseudomonas. (36.7%). Conclusions: Hematological cancers with risk for neutropenia such as MDS and AML were the most affected by ESKAPE. A significant resistance to levofloxacin, a prophylactic antibiotic, was seen. Gram negative pathogens had an increased resistance to broad spectrum antibiotics and higher mortality rates. New strategies for reducing ESKAPE in MDS and AML are required.

Results of the Phase I Trial of RG7112, a Small-Molecule MDM2 Antagonist in Leukemia

PURPOSE

RG7112 is a small-molecule MDM2 antagonist. MDM2 is a negative regulator of the tumor suppressor p53 and frequently overexpressed in leukemias. Thus, a phase I study of RG7112 in patients with hematologic malignancies was conducted.

EXPERIMENTAL DESIGN

Primary study objectives included determination of the dose and safety profile of RG7112. Secondary objectives included evaluation of pharmacokinetics; pharmacodynamics, such as TP53-mutation status and MDM2 expression; and preliminary clinical activity. Patients were divided into two cohorts: Stratum A [relapsed/refractory acute myeloid leukemia (AML; except acute promyelocytic leukemia), acute lymphoblastic leukemia, and chronic myelogenous leukemia] and Stratum B (relapsed/refractory chronic lymphocytic leukemia/small cell lymphocytic leukemia; CLL/sCLL). Some Stratum A patients were treated at the MTD to assess clinical activity.

RESULTS

RG7112 was administered to 116 patients (96 patients in Stratum A and 20 patients in Stratum B). All patients experienced at least 1 adverse event, and 3 dose-limiting toxicities were reported. Pharmacokinetic analysis indicated that twice-daily dosing enhanced daily exposure. Antileukemia activity was observed in the 30 patients with AML assessed at the MTD, including 5 patients who met International Working Group (IWG) criteria for response. Exploratory analysis revealed TP53 mutations in 14% of Stratum A patients and in 40% of Stratum B patients. Two patients with TP53 mutations exhibited clinical activity. p53 target genes were induced only in TP53 wild-type leukemic cells. Baseline expression levels of MDM2 correlated positively with clinical response.

CONCLUSIONS

RG7112 demonstrated clinical activity against relapsed/refractory AML and CLL/sCLL. MDM2 inhibition resulted in p53 stabilization and transcriptional activation of p53-target genes. We provide proof-of-concept that MDM2 inhibition restores p53 function and generates clinical responses in hematologic malignancies.

Randomized Phase II Trial Comparing Obinutuzumab (GA101) With Rituximab in Patients With Relapsed CD20+ Indolent B-Cell Non-Hodgkin Lymphoma: Final Analysis of the GAUSS Study

PURPOSE

Obinutuzumab (GA101), a novel glycoengineered type II anti-CD20 monoclonal antibody, demonstrated responses in single-arm studies of patients with relapsed/refractory non-Hodgkin lymphoma. This is the first prospective, randomized study comparing safety and efficacy of obinutuzumab with rituximab in relapsed indolent lymphoma. The primary end point of this study was the overall response rate (ORR) in patients with follicular lymphoma after induction and safety in patients with indolent lymphoma.

PATIENTS AND METHODS

A total of 175 patients with relapsed CD20(+) indolent lymphoma requiring therapy and with previous response to a rituximab-containing regimen were randomly assigned (1:1) to four once-per-week infusions of either obinutuzumab (1,000 mg) or rituximab (375 mg/m(2)). Patients without evidence of disease progression after induction therapy received obinutuzumab or rituximab maintenance therapy every 2 months for up to 2 years.

RESULTS

Among patients with follicular lymphoma (n = 149), ORR seemed higher for obinutuzumab than rituximab (44.6% v 33.3%; P = .08). This observation was also demonstrated by a blinded independent review panel that measured a higher ORR for obinutuzumab (44.6% v 26.7%; P = .01). However, this difference did not translate into an improvement in progression-free survival. No new safety signals were observed for obinutuzumab, and the incidence of adverse events was balanced between arms, with the exception of infusion-related reactions and cough, which were higher in the obinutuzumab arm.

CONCLUSION

Obinutuzumab demonstrated a higher ORR without appreciable differences in safety compared with rituximab. However, the clinical benefit of obinutuzumab in this setting remains unclear and should be evaluated within phase III trials.

Abstract 4308: Serum ferritin as a predictive marker for increase in infection and increased mortality in patients with myelodysplastic syndrome

Background: Myelodysplastic Syndrome (MDS) is a disorder of the bone marrow wherein hematopoietic cells fail to develop and differentiate into their mature forms. High iron stores in the body are known to have a detrimental effect on the overall outcome for the patient, however its exact role in the disease spectrum is currently unknown. We sought out to elucidate the role of Serum Ferritin against two end points - infection and death.

Methods: The patient data was queried from METEOR (Methodist Environment for Translational Enhancement and Outcomes Research), a clinical data warehouse and analytics environment. We obtained baseline demographics, laboratory data, diagnostic workup, treatment plan, infection incidences, ferritin levels and dead/alive status.

Results: We reviewed the records of 2249 patients who were treated with a diagnosis of MDS from January 2006 - June 2014. We matched patients with infection during hospital stay due to any cause (sepsis, febrile neutropenia, colitis, pneumonia, URTI, etc) against their maximum ferritin level. The mean Ferritin in those without infection was 809.82 (95% CI: 575.17 - 1044.48) while the mean Ferritin in those with infection was 2360.09 (95% CI: 1094.69 - 4167.12). We then performed the non-parametric, Wilcoxon-Rank sum (Mann-Whitney U) test between the two variables and concluded that there was a statistically significant relationship between Serum Ferritin and Infection rates (p &lt;0.001). A student t-test with unequal variances was performed which, confirmed the statistical significance (p 0.021).

We matched patients who passed away during hospital stay against their maximum ferritin level. The mean Ferritin in those survived was 872.32 (95% CI: 592.96 - 1151.68) while the mean Ferritin in those died was 2941.78 (95% CI: 1255.05 - 4628.50). We then performed the non-parametric, Wilcoxon-Rank sum (Mann-Whitney U) test between the two variables and concluded that there was a statistically significant relationship between Serum Ferritin and death rates (p &lt;0.001). A student t-test with unequal variances was performed which, confirmed the statistical significance (p 0.018).Lastly, we also performed the non-parametric Kruskal-Wallis test to assess for the significance levels across all the three groups - Ferritin, infection and death. This test confirmed the significance with a p value of 0.0001 for each of the outcomes.

Conclusion: Our data review reveals that increased ferritin is directly related to increased mortality and morbidity. One explanation of this finding could lie in the potential role of Iron as an oxidative agent, which increases free radical damage, impair oxidative phosphorylation and promote mitochondrial dysfunction resulting in cellular death. We conclude that increased ferritin represents a serious threat to the health of the patient and recommend that iron chelation therapy be instituted accordingly.

Note: This abstract was not presented at the meeting.

Citation Format: Anish Konde, Mamta Puppala, Pallavi Srivastava, Stephen T. Wong, Kelty Baker, Lawrence Rice, Swaminathan Padmanabhan Iyer. Serum ferritin as a predictive marker for increase in infection and increased mortality in patients with myelodysplastic syndrome. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4308. doi:10.1158/1538-7445.AM2015-4308

Utility of ¹⁸fluoro-deoxyglucose positron emission tomography for prognosis and response assessments in a phase 2 study of romidepsin in patients with relapsed or refractory peripheral T-cell lymphoma

BACKGROUND

For patients with peripheral T-cell lymphoma (PTCL), the value of (18)fluoro-deoxyglucose positron emission tomography (FDG-PET) scans for assessing prognosis and response to treatment remains unclear. The utility of FDG-PET, in addition to conventional radiology, was examined as a planned exploratory end point in the pivotal phase 2 trial of romidepsin for the treatment of relapsed/refractory PTCL.

PATIENTS AND METHODS

Patients received romidepsin at a dose of 14 mg/m(2) on days 1, 8, and 15 of 28-day cycles. The primary end point was the rate of confirmed/unconfirmed complete response (CR/CRu) as assessed by International Workshop Criteria (IWC) using conventional radiology. For the exploratory PET end point, patients with at least baseline FDG-PET scans were assessed by IWC + PET criteria.

RESULTS

Of 130 patients, 110 had baseline FDG-PET scans, and 105 were PET positive at baseline. The use of IWC + PET criteria increased the objective response rate to 30% compared with 26% by conventional radiology. Durations of response were well differentiated by both conventional radiology response criteria [CR/CRu versus partial response (PR), P = 0.0001] and PET status (negative versus positive, P < 0.0001). Patients who achieved CR/CRu had prolonged progression-free survival (PFS, median 25.9 months) compared with other response groups (P = 0.0007). Patients who achieved PR or stable disease (SD) had similar PFS (median 7.2 and 6.3 months, respectively, P = 0.6427). When grouping PR and SD patients by PET status, patients with PET-negative versus PET-positive disease had a median PFS of 18.2 versus 7.1 months (P = 0.0923).

CONCLUSIONS

Routine use of FDG-PET does not obviate conventional staging, but may aid in determining prognosis and refine response assessments for patients with PTCL, particularly for those who do not achieve CR/CRu by conventional staging. The optimal way to incorporate FDG-PET scans for patients with PTCL remains to be determined.

TRIAL REGISTRATION

NCT00426764.

Highly effective combination of LSD1 (KDM1A) antagonist and pan-histone deacetylase inhibitor against human AML cells

The histone demethylase LSD1 (KDM1A) demethylates mono- and di-methylated (Me2) lysine (K) 4 on histone H3. High LSD1 expression blocks differentiation and confers a poor prognosis in AML. Here, treatment with the novel LSD1 antagonist SP2509 attenuated the binding of LSD1 with the co-repressor CoREST, increased the permissive H3K4Me3 mark on the target gene promoters, and increased the levels of p21, p27 and C/EBPα in cultured AML cells. Additionally, SP2509 treatment or LSD1 shRNA inhibited the colony growth of AML cells. SP2509 also induced morphologic features of differentiation in the cultured and primary AML blasts. SP2509 induced more apoptosis of AML cells expressing mutant NPM1 than MLL fusion oncoproteins. Treatment with SP2509 alone significantly improved the survival of immune-depleted mice following tail-vein infusion and engraftment of cultured or primary human AML cells. Co-treatment with pan-HDAC inhibitor (HDI) panobinostat (PS) and SP2509 was synergistically lethal against cultured and primary AML blasts. Compared to each agent alone, co-treatment with SP2509 and PS significantly improved the survival of the mice engrafted with the human AML cells, without exhibiting any toxicity. Collectively, these findings show that the combination of LSD1 antagonist and pan-HDI is a promising therapy warranting further testing against AML.

Romidepsin for the treatment of relapsed/refractory peripheral T-cell lymphoma: pivotal study update demonstrates durable responses

BACKGROUND

Romidepsin is a structurally unique, potent, bicyclic class 1 selective histone deacetylase inhibitor approved by the US Food and Drug Administration for the treatment of patients with cutaneous T-cell lymphoma who have received ≥ 1 prior systemic therapy and patients with peripheral T-cell lymphoma (PTCL) who have received ≥ 1 prior therapy. Approval for PTCL was based on results (n = 130; median follow-up, 13.4 months) from the pivotal study of romidepsin for the treatment of relapsed/refractory PTCL. The objective is to present updated data (median follow-up, 22.3 months) and to characterize patients who achieved long-term responses (≥ 12 months) to romidepsin.

METHODS

Patients with PTCL who relapsed from or were refractory to ≥ 1 prior systemic therapy received romidepsin 14 mg/m2 as a 4-hour intravenous infusion on days 1, 8, and 15 every 28 days for up to 6 cycles; patients with response or stable disease could continue romidepsin beyond 6 cycles. The primary endpoint was rate of confirmed/unconfirmed complete response (CR/CRu) determined by an Independent Review Committee. Secondary endpoints included objective response rate (ORR) and duration of response (DOR). For patients who achieved CR/CRu, baseline characteristics by DOR (≥ 12 vs < 12 months) were examined.

RESULTS

The ORR to romidepsin was 25%, including 15% with CR/CRu. The median DOR for all responders was 28 months (range, < 1-48+) and was not reached for those who achieved CR/CRu. Patients with lack of response or transient response to prior therapy achieved durable responses with romidepsin. Of the 19 patients who achieved CR/CRu, 10 had long-term (≥ 12 months) responses; none of the baseline characteristics examined-including heavy pretreatment, response to prior therapy, or advanced disease-precluded long-term responses to romidepsin. With a median progression-free survival of 29 months, patients who achieved CR/CRu for ≥ 12 months had significantly longer survival vs those with CR/CRu for < 12 months or < CR/CRu. Extended treatment and longer follow-up did not affect the reported safety profile of romidepsin.

CONCLUSIONS

Treatment with romidepsin leads to highly durable responses in a subset of patients with relapsed/refractory PTCL, with responses ongoing as long as 48 months.

Phase I study of MLN8237--investigational Aurora A kinase inhibitor--in relapsed/refractory multiple myeloma, non-Hodgkin lymphoma and chronic lymphocytic leukemia

Purpose Amplification or over-expression of the mitotic Aurora A kinase (AAK) has been reported in several heme-lymphatic malignancies. MLN8237 (alisertib) is a novel inhibitor of AAK that is being developed for the treatment of advanced malignancies. The objectives of this phase I study were to establish the safety, tolerability, and pharmacokinetic profiles of escalating doses of MLN8237 in patients with relapsed or refractory heme-lymphatic malignancies. Methods Sequential cohorts of patients received MLN8237 orally as either a powder-in-capsule (PIC) or enteric-coated tablet (ECT) formulation. Patients received MLN8237 PIC 25–90 mg for 14 or 21 consecutive days plus 14 or 7 days’ rest, respectively, or MLN8237 ECT, at a starting dose of 40 mg/day once-daily (QD) for 14 days plus 14 days’ rest, all in 28-day cycles. Subsequent cohorts received MLN8237 ECT 30–50 mg twice-daily (BID) for 7 days plus 14 days’ rest in 21-day cycles. Results Fifty-eight patients were enrolled (PIC n = 28, ECT n = 30). The most frequent grade ≥3 drug-related toxicities were neutropenia (45 %), thrombocytopenia (28 %), anemia (19 %), and leukopenia (19 %). The maximum tolerated dose on the ECT 7-day schedule was 50 mg BID. The terminal half-life of MLN8237 was approximately 19 h. Six (13 %) patients achieved partial responses and 13 (28 %) stable disease. Conclusion The recommended phase II dose of MLN8237 ECT is 50 mg BID for 7 days in 21-day cycles, which is currently being evaluated as a single agent in phase II/III trials in patients with peripheral T-cell lymphoma.

Cryptococcal meningitis presenting as sinusitis in a renal transplant recipient

Cryptococcal meningitis is a relatively common invasive fungal infection in immunocompromised patients, especially in solid organ transplant recipients. Clinical presentation typically includes fever, headache, photophobia, neck stiffness, and/or altered mental status. Unusual presentations may delay diagnosis. Therapy is challenging in renal transplant patients because of the nephrotoxicity associated with amphotericin B, the recommended treatment. We present a case of cryptococcal meningitis in a renal transplant recipient presenting as acute sinusitis with successful treatment using fluconazole as primary therapy.

Clinical and laboratory studies of the novel cyclin-dependent kinase inhibitor dinaciclib (SCH 727965) in acute leukemias

Purpose

Dinaciclib inhibits cyclin-dependent kinases 1, 2, 5, and 9 with a better therapeutic index than flavopiridol in preclinical studies. This study assessed the activity of dinaciclib in acute leukemia both in the clinic and in vitro.

Methods

Adults with relapsed/refractory acute myeloid leukemia (n = 14) and acute lymphoid leukemia (n = 6) were treated with dinaciclib 50 mg/m² given as a 2-h infusion every 21 days.

Results

Most patients had dramatic but transient reduction in circulating blasts; however, no remissions were achieved on this schedule. The most common toxicities were gastrointestinal, fatigue, transaminitis, and clinical and laboratory manifestations of tumor lysis syndrome, including one patient who died of acute renal failure. Dinaciclib pharmacokinetics showed rapid (2 h) achievement of maximum concentration and a short elimination/distribution phase. Pharmacodynamic studies demonstrated in vivo inhibition of Mcl-1 expression and induction of PARP cleavage in patients’ peripheral blood mononuclear cells 4 h after dinaciclib infusion, but the effects were lost by 24 h and did not correlate with clinical outcome. Correlative in vitro studies showed that prolonged exposures to dinaciclib, at clinically attainable concentrations, result in improved leukemia cell kill.

Conclusions

While dinaciclib given as a 2-h bolus did not exhibit durable clinical activity, pharmacokinetic and pharmacodynamic data support the exploration of prolonged infusion schedules in future trials in patients with acute leukemias.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-013-2249-z) contains supplementary material, which is available to authorized users.

The transcription factor Wilms tumor 1 confers resistance in myeloid leukemia cells against the proapoptotic therapeutic agent TRAIL (tumor necrosis factor α-related apoptosis-inducing ligand) by regulating the antiapoptotic protein Bcl-xL

Tumor necrosis factor α-related apoptosis-inducing ligand (TRAIL) is considered a promising cancer therapeutic agent due to its ability to induce apoptosis in a variety of cancer cells, while sparing normal cells. However, many human tumors including acute myeloid leukemia (AML) are partially or completely resistant to monotherapy with TRAIL, limiting its therapeutic utility. Therefore, identification of factors that contribute to TRAIL resistance may facilitate future development of more effective TRAIL-based cancer therapies. Here, we report a previously unknown role for WT1 in mediating TRAIL resistance in leukemia. Knockdown of WT1 with shRNA rendered TRAIL-resistant myeloid leukemia cells sensitive to TRAIL-induced cell death, and re-expression of shRNA-resistant WT1 restored TRAIL resistance. Notably, TRAIL-mediated apoptosis in WT1-silenced cells was largely due to down-regulation of the antiapoptotic protein Bcl-xL. Moreover, WT1 expression strongly correlated with overexpression of Bcl-xL in AML cell lines and blasts from AML patients. Furthermore, we found that WT1 transactivates Bcl-xL by directly binding to its promoter. We previously showed that WT1 is a novel client protein of heat shock protein 90 (Hsp90). Consistent with this, pharmacological inhibition of Hsp90 resulted in reduced WT1 and Bcl-xL expression leading to increased sensitivity of leukemia cells to TRAIL-mediated apoptosis. Collectively, our results suggest that WT1-dependent Bcl-xL overexpression contributes to TRAIL resistance in myeloid leukemias.

The O-GlcNAc transferase gene resides on the X chromosome and is essential for embryonic stem cell viability and mouse ontogeny

Nuclear and cytoplasmic protein glycosylation is a widespread and reversible posttranslational modification in eukaryotic cells. Intracellular glycosylation by the addition of N-acetylglucosamine (GlcNAc) to serine and threonine is catalyzed by the O-GlcNAc transferase (OGT). This "O-GlcNAcylation" of intracellular proteins can occur on phosphorylation sites, and has been implicated in controlling gene transcription, neurofilament assembly, and the emergence of diabetes and neurologic disease. To study OGT function in vivo, we have used gene-targeting approaches in male embryonic stem cells. We find that OGT mutagenesis requires a strategy that retains an intact OGT gene as accomplished by using Cre-loxP recombination, because a deletion in the OGT gene results in loss of embryonic stem cell viability. A single copy of the OGT gene is present in the male genome and resides on the X chromosome near the centromere in region D in the mouse spanning markers DxMit41 and DxMit95, and in humans at Xq13, a region associated with neurologic disease. OGT RNA expression in mice is comparably high among most cell types, with lower levels in the pancreas. Segregation of OGT alleles in the mouse germ line with ZP3-Cre recombination in oocytes reveals that intact OGT alleles are required for completion of embryogenesis. These studies illustrate the necessity of conditional gene-targeting approaches in the mutagenesis and study of essential sex-linked genes, and indicate that OGT participation in intracellular glycosylation is essential for embryonic stem cell viability and for mouse ontogeny.