ALBERT

Description: Myelodysplastic syndrome (MDS) and chronic myelomonocytic leukaemia (CMML) are haematological disorders that develop in haematopoietic stem or progenitor cells (HSPCs) and are characterised by ineffective haematopoiesis. 5'-Azacitidine (AZA) is a DNA demethylating agent that is effective in treating MDS and CMML. However, response rates are less than 50% and the basis for poor response is currently unknown. A patient's potential to respond cannot be currently determined until after multiple cycles of AZA treatment and alternative treatment options for poor responders are limited. To address these fundamental questions, we enrolled patients on a compassionate access program prior to the listing of AZA on the pharmaceuticals benefit scheme in Australia. We have collected bone marrow from 18 patients (10 MDS, 8 CMML) at seven different stages of treatment, starting from before treatment until after six cycles of AZA treatment, and isolated high-purity CD34+ HSPCs at each stage. 10 of these patients (5 MDS and 5 CMML) responded completely to AZA while 8 did not achieve complete response. We performed next-generation sequencing (RNA-seq) of these HSPCs to identify the basis of poor response to AZA therapy. Analysis of the RNA-seq data from pre-treatment HSPCs has revealed a striking differential expression of 1148 genes between patients who were subsequently complete (CR) or non-complete responders (non-CR) to AZA therapy (Figure 1A). Using a Fluidigm nanofluidic system, we have validated the differential expression of a subset of these genes between CR and non-CR patients in two independent cohorts, totalling 67 patients, from the U.K. and Sweden. We have additionally confirmed that our gene signature does not simply segregate patients based on disease severity or poor overall survival, but rather uniquely prognosticates best AZA response. Pathway analyses of the differentially expressed genes indicates that the HSPCs of non-CR patients have decreased cell cycle progression and DNA damage pathways, while concomitantly possessing increased signalling through integrin and mTOR/AKT pathways. Using computational methods, we have determined that the expression of 15 genes (within the 1148 gene set) is sufficient to separate CRs from non-CRs across independent cohorts (Figure 1B). We have also developed a predictive AZA response algorithm that utilises the expression of these genes to identify potential complete and non-complete responders to AZA with high specificity and sensitivity (Figure 1C). Furthermore, we have identified statistically significant correlations between recurrent DNA mutations in MDS and our prognostic gene signature (SF3B1 & TET2 with CR, STAG2 and NUP98 with non-CR, p

Description: Key Points First comprehensive and time-resolved characterization of platelet cAMP/PKA signaling upon iloprost treatment. More than 2700 phosphorylation sites quantified between 4 time points and from 3 individual healthy donors.

Description: A woman with lymphoblastic lymphoma was treated with combination chemotherapy. She subsequently became febrile while granulocytopenic and was given unirradiated granulocyte transfusions from normal, unrelated donors. She recovered, but 12 days later noted the onset of progressive skin rash, hepatic dysfunction, diarrhea and pancytopenia and, 22 days after her last granulocyte transfusion, died of gram negative septicemia. Histologic examination of multiple tissues including the skin, liver, and intestinal tract showed changes characteristic of acute graft-versus-hose disease (GVHD). Y-chromatin analysis of the patient's peripheral blood just before death indicated the presence of male cells. HLA typing of lymphocytes and skin fibroblasts from the patient and lymphocytes from the family and granulocyte donors was also consistent with engraftment of cells from one of the male granulocyte donors. This donor most likely was homozygous for one of the patient's halotypes, perhaps facilitating engraftment of his cells and subsequent development of transfusion- induced acute GVHD. Until more precise guidelines can be established, we recommend that all cellular blood products given to patients receiving intensive chemotherapy be irradiated with 1500 rad.

Description: Key Points ERG overexpression in transgenic mice induces a transcriptional leukemia stem cell program characteristic of human AML. PIM1 and RAS are relevant ERG therapeutic targets.

Description: We hypothesized that after allogeneic hematopoietic stem cell transplant (HSCT), GvHD-affected tissues harbor expanded “immunodominant” T-cell clones, and characterization of these clones can be used to develop markers of disease. A multiplex PCR was used to detect T-cell receptor variable beta (VB) chain rearrangements in target tissue. Molecular analysis of the amplified VB CDR3 sequences allowed for identification and quantitation of putative disease-associated “clonotypes” and for the development of clone-specific PCR. We studied 5 HSCT patients for the presence of signature clonotypes in 10 skin biopsies taken during diagnostic GvHD work-up. Size distribution analysis of VB PCR products showed a skewed peak pattern in 9 biopsies; immunodominant clones (per definition frequency ≥30%) were detected in 6/7 biopsies with histologically confirmed GvHD, consistent with the presence of expanded clonotypes and the oligoclonal nature of the tissue-specific alloresponse. Immunodominant clones were also found in 2 of 3 biopsies not diagnostic for GvHD but obtained based on strong clinical suspicion, raising the possibility that they were associated with early evolving GvHD not distinguishable by histology. For example, when serial skin biopsies were analyzed, a GvHD-positive post-transplant d63 biopsy contained an immunodominant clone (frequency 60%), which was also detected in a subsequent biopsy positive for GvHD (frequency 33%). Similar results were seen in another patient, in whom serial biopsies taken on d214 (not diagnostic) and d217 (GvHD-positive) showed an identical immunodominant clone, not present in a d13 GVHD-negative biopsy. This finding suggests that the d214 biopsy might have contained early GvHD that was not detectable morphologically. In a patient who rejected an initial MUD graft (Tx 1) and then received a MUD SCT (Tx 2) from a different, unrelated donor, immunodominant clones were identified in GvHD-positive biopsies following each transplant, that were distinct for each graft. To examine whether immunodominant clonotypes derived from biopsies could be used as markers of disease, clonotypic PCR was developed for an immunodominant biopsy-derived clonotype for each transplant. The Tx 1 clonotype was detected in blood and skin following Tx 1, but not in tissue or blood taken after Tx 2. Specificity and correct size of the clonotypic PCR product were confirmed by both Genescan analysis and sequencing. Clonotypic PCR designed for an immunodominant clonotype from the Tx 2 donor detected the putative allospecific clonotype in serial samples after the second engraftment. Neither clonotype could be found in either donor, indicating that the disease-associated clones expanded to detectable levels following transplant. These results indicate that clonotypic PCR can distinguish distinct GvHD-associated clonotypes from different donors in both blood and tissue following transplant. Monitoring of the relative frequency of disease-associated clones in recipient blood indicated a significant peripheral expansion of disease-associated clones at the time of active GvHD. Our results demonstrate an efficient method for identification of disease-associated clonotypic markers, which can be used to aid diagnosis and monitoring of GvHD.

Description: Objective Viral infections lead to activation of coagulation which enhances inflammatory responses. For instance, influenza A is associated with activation of coagulation and the increased risk for thrombotic events, such as myocardial infarction. Protease-activated receptor 4 (PAR-4) is the main functional receptor on mouse platelets. Here, we investigated the role of tissue factor (TF) and platelets in influenza A infection in mice. Methods We used male LowTF mice, which express 1% of normal TF levels, PAR-4 deficient mice and respective control mice. All mice were infected intranasal with influenza A H1N1/PR8. Changes in body weights and survival were analyzed up to 14 days after infection. In addition, bronchoalveolar lavage (BAL) was collected and analyzed 7 days after virus challenge. Results LowTF mice exhibited increased loss of body weights compared to littermate control mice between day 4 and 6 after infection (P

Description: Abstract 2129 Objectives: T cell lineage is an independent high risk factor in acute lymphoblastic leukemia (ALL). T-ALL requires high dose multi-agent chemotherapy, conferring many toxic side effects. T-ALL treatment therefore needs new, targeted agents that preserve or improve current treatment efficacy, yet cause fewer side effects than existing chemotherapeutic regimens. To identify such drugs, we pioneered an in vivo screen using transgenic zebrafish with T cell-specific green fluorescent protein (GFP) expression. We reasoned that immature T cells in 5-day-old zebrafish larvae are developmentally analogous to T-ALL lymphoblasts, and likely rely upon similar signaling pathways. Hence, compounds that specifically eliminate T cells in zebrafish larvae might likewise selectively target T-ALL cells. An added benefit of our in vivo screen is that drugs added to the water housing fish larvae must cross an epithelial barrier, can be metabolized by the liver, and can be renally cleared, characteristics not assessed in in vitro-based screening strategies. In addition, by using early larvae as our subjects, drugs lacking T cell specificity will likely impair normal development and/or survival, which we postulate is a predictor of unwanted toxicities. In these ways, our screen mimicked the scenario encountered in patients. Our use of the transgenic p56lck::EGFP zebrafish line facilitated rapid visual assessment of efficacy of a large number of compounds in 96-well format. Materials and Results: In a proof-of-principle experiment, we identified several known anti-T-ALL drugs, most prominently glucocorticoids, from the “Spectrum” library (MicroSource Discovery Systems, Inc., Gaylordsville, CT) of well-characterized compounds. We then screened 39,200 small molecules from the “ChemBridge DIVERSet” combinatorial chemistry library (ChemBridge Corp., San Diego, CA) for those active against zebrafish larval T cells. Of 20 novel “hits” identified, one compound, dubbed Lenaldekar (“LDK”), met additional prioritization criteria. LDK does not impair the cell cycle of developing zebrafish, is well tolerated and orally bioavailable with favorable pharmacokinetic properties in mice. In addition, pilot studies with LDK indicate it is efficacious in treating T-ALL in juvenile and adult fish from an established transgenic rag2::ER-human cMyc T-ALL model. LDK kills all of several murine T-lymphocytic malignancies, induces apoptosis in all human T-ALL lines tested, and shows some activity in human B-ALL lines. However, glioblastoma, colon carcinoma, melanoma, or immortalized human embryonic kidney cell lines are not affected by LDK, even at high concentration (up to 25μM). Using the recently established “phosflow” technique we measured phosphorylation status of key signaling proteins in permeabilized T- and B-ALL lines. Regardless of PTEN status, PDK1, AKT and mTOR downstream targets p4EBP1 and p70S6kinase were dephosphorylated by LDK treatment, as was the p65 subunit of NFκB on serine 529. Results were corroborated by conventional Western blots. However, phosphorylation of STAT3, STAT5, pERK1-2, and p38 were not affected by LDK. LDK's action is distinguished from other AKT/mTOR inhibitors by its lack of activity against AKT-dependent glioblastoma and melanoma cell lines, and its lack of effect on cell size. Finally, LDK decreased tumor burden of human T-ALL in murine xenografts. Conclusions: In view of its apparent lymphocyte selectivity, we posit that LDK modulates a pathway relatively unique to ALL (and immature lymphoblast) cells. This suggests that LDK can serve as a novel molecular tool for studies of normal and malignant lymphocyte biology. Moreover, with its favorable pharmacokinetics, apparent lack of toxicity, and in vivo efficacy in two vertebrate ALL models, LDK is an attractive molecule for development into a targeted treatment for ALL and perhaps other lymphocytic malignancies. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 4502 Graft-versus-host disease (GVHD) is a major complication and one of the main causes of death after hematopoietic stem cell transplantation (HSCT). The GVHD prophylaxis influences the incidence of GVHD, relapse rate, and patient's survival. GVHD is associated with graft-versus-leukemia effect, which is mediated by donor T lymphocytes and decreases the risk of relapse. Therefore, a reduced post-transplant immunosuppression might have a positive impact on patient's survival. The outcome of different immunosuppressive prophylaxis regimen for adult patients has been studied extensively, whereas the effect on children has yet to be determined. Therefore, we performed a retrospective study analyzing 62 children (median age, 11 years) with acute lymphoblastic leukemia (n=35) or acute myeloid leukemia (n=27) who underwent bone marrow (n=56), peripheral blood stem cell (n=4), or umbilical cord blood (n=2) transplantation in a single center between November 1984 and July 2008. All respective donors were HLA-identical siblings. The patients received an immunosuppressive prophylaxis consisting of cyclosporin A (CSA) plus methotrexate (MTX) (n=43) or cyclosporin A alone (n=19). Patients in the CSA+MTX arm received CSA at a total dose of 10 mg/kg/day on day -1, 5mg/kg/day on days 0 to 4, and 3 mg/kg/day starting on day 5, and in addition MTX at a dosage of 10 mg/m2 on days 1, 3, 6, and 11. The 19 patients in the CSA arm received CSA at a total dose of 3 mg/kg/day starting on day -1. Concerning the patient's gender, age, diagnosis, and state of remission prior to transplantation, the two groups did not differ significantly. Patients who received CSA alone as post-transplant immunosuppression had a significantly reduced cumulative incidence of relapse (5% versus 40%; p=0,002), a significantly increased 5-year event-free survival (84% versus 35%; p=0.001), and a significantly increased 5-year overall survival (84% versus 42%; p=0.004). Interestingly, the incidence of acute GVHD grade II-IV in patients in the CSA arm was equivalent to the CSA+MTX arm (26% versus 19%; p=0.440). In addition, we did not observe a significant difference in the cumulative incidence of chronic GVHD (32% in the CSA arm versus 23% in the CSA+MTX arm; p=0.428). There was also no significant difference in the cumulative incidence of treatment related mortality after 1 year (10% in the CSA arm versus 23% in the CSA+MTX arm; p=0.165). In conclusion, CSA alone for post-transplant immunosuppression allows a stronger graft-versus-leukemia effect and thereby reduces the relapse rate and the number of patients dying of leukemia effectively without increase of acute and chronic GVHD. Post-transplant immunosuppression consisting of CSA alone leads to a superior outcome and should be preferred in children with a HLA-identical sibling as donor. Disclosures: No relevant conflicts of interest to declare.

Description: The IL-1 superfamily member IL-33 is produced in barrier tissues. IL-33 binds to the receptor suppression of tumorigenicity 2 (ST2), expressed on stromal cells, regulatory T cells (Tregs), myeloid derived suppressor cells (MDSCs), and macrophages. IL-33 has both anti-inflammatory and pro-inflammatory properties. It is not known if IL-33 plays a role in acute GvHD, and if so what properties it exerts. By immunohistochemistry staining of gut tissues, IL-33 production by non-hematopoietic cells was increased in mice post-conditioning and in patients during GvHD. To determine whether IL-33 could augment GvHD via a host signaling mechanism, we compared st2-/-to wildtype (wt) hosts and observed decreased GvHD lethality (Figure 1A). Additionally, IL-33-/- versus wt hosts had a marked decrease in GvHD lethality and reduced TNFα production. Conversely, IL-33 administration during the peak inflammatory response worsened GvHD. Previous studies have shown increased levels of the soluble form of ST2 (sST2) are a biomarker for steroid-refractory GvHD (Vander Lugt, NEJM, 2013). We hypothesized that sST2 acted not only as an indicator of tissue injury and biomarker of GvHD but also as an immune modulator during GvHD. In rodents, we found that ST2 was upregulated on alloreactive T cells and sST2 increased as GvHD progressed. St2-/-versus wt donor T cells had a marked reduction in GvHD lethality (Figure 1B) without compromise of graft-vs-leukemia responses. Comparable data was seen in 2 different strain combinations. Alloantigen-induced IL-18 receptor upregulation was significantly lower in the absence of ST2, which was linked to significantly reduced IFNγ production by st2-/- vs wt CD4 and CD8 T cells during GvHD. Similarly, sST2 transgenic hosts and wt recipients given exogenous sST2-Fc fusion protein infusions (Figure 1C) to block ST2/IL-33 interaction each had significantly reduced GVHD lethality, establishing the functional role of ST2 as a decoy receptor modulating GVHD. During the peak of the GvHD inflammatory response, IL-33 signalling of either donor or host cells promoted activation of donor T cells, while the use of exogenous sST2-Fc protein to prevent IL33/ST2 engagement ameliorates disease. Together, these studies point to targeting of the IL-33/ST2 axis as a novel and potent target for GvHD therapy. Disclosures Warncke: Novartis Pharma AG: Employment. Junt:Novartis Pharma AG: Employment.

Description: Abstract 1568 Introduction Non-Hodgkin lymphoma (NHL) represents 60% of lymphoma diagnoses in children, and NHL subtypes change considerably from childhood to adulthood.[1] Recent studies have implicated age-associated biological differences in certain NHL subtypes.[2] AYAs with cancer fall between pediatric and adult patients clinically and potentially biologically. Although environmental stressors and the psychosocial transition of adolescence likely impacts these outcomes, age-related biological differences need to be better understood. The majority of pediatric NHLs are high-grade tumors, whereas low- and intermediate-grade tumors are more common among adults.[1] Recent studies have found that young adults with NHL have poorer survival compared to children.[2] Although the incidence of AYA lymphoma has increased over the past 20 years, survival has not significantly improved, demanding a better understanding of the epidemiology and biology of lymphoma among this patient population.[3] Methods Cases were identified using the Nebraska Lymphoma Study Group database and chart review. All patients with DLBCL from 1983–2010 were identified (n = 1328), and 36 (2.7%) cases are included in this study of AYA DLBCL (age 13–30 years). The Kaplan-Meier method was used to estimate overall survival (OS) and event-free survival (EFS) distributions, and the log-rank test was used to compare survival distributions between groups. OS is defined as the time from the beginning of therapy to death or last follow-up. EFS is defined as the time from the beginning of therapy to progression, death, or last follow-up. P-values less than 0.05 are considered to be statistically significant. SAS software V 9.2 (SAS Institute Inc., Cary, NC) was used for all data analysis. The study was approved by the Institutional Review Board. Results The median age of the 36 AYA DLBCL patients was 24.2 years (range, 14.5–29.8) with a female to male ratio of 1.8:1, and 53% were primary mediastinal B-cell lymphoma. Patient characteristics are shown in table 1. Of the 36 patients, 18 have died and 18 are alive at last follow-up. Fifteen deaths were due to lymphoma, 1 treatment related, 1 unrelated to disease, and 1 of unknown cause. The 5-year EFS is 52% (95% CI 34–67%, figure 1) and OS is 58% (95% CI 49–72%). The median follow-up of patients alive at last follow-up is 8.8 years (range, 1.8 – 29). OS was not affected by gender (p=0.32), stage (p=0.43), LDH (p=0.11), B symptoms (p=0.98), or size of the largest mass at diagnosis (0.93). Nearly all patients (97%) were treated on adult chemotherapy protocols. Discussion This study presents data on 36 AYA patients with DLBCL. The 5-year EFS was 52% and OS was 58%. Pediatric patients report a 5-year EFS of 87–96% [2, 4] compared to adults which have a 5-year EFS of 44–80%.[4] In contrast to other reports, in this study, gender, elevated LDH, and advanced stage (III-IV) did not impact EFS or OS, although the comparisons may be under-powered due to the small sample size. Although pediatric patients have better outcomes compared to adults, AYA patients have worse EFS than both pediatric and adult DLBCL patients, demanding further understanding of the biology of AYA DLBCL and improved treatment strategies. Disclosures: No relevant conflicts of interest to declare.