ALBERT

Description: BCR-ABL negative myeloproliferative neoplasms (MPNs), such as polycythemia vera (PV), essential thrombocythemia (ET) and myelofibrosis (MF) are chronic myeloid malignancies characterized by overproduction of hematopoietic cells. JAK2 mutations are found in most patients with PV, and in only 50-60% of patients with ET and MF. JAK2 mutation testing has greatly simplified MPN diagnosis, but distinguishing JAK2-wildtype ET from reactive thrombocytosis remains a diagnostic challenge. Mutations in signalling pathways (MPL, LNK) and epigenetic regulators (TET2, DNMT3A, IDH1/2, EXH2, ASXL1) have been found in a minority of MPNs. However genome-wide data are lacking and the pathogenesis of MPNs that do not harbor JAK2 or MPLmutations remains obscure. Methods Exome sequencing was performed in 151 MPN patients on matched tumor and constitutional samples. CALR status was assessed in 3412 samples using Sanger sequencing and analysis of exome/genome sequencing data. Presence of CALR mutations in hematopoietic stem and progenitor cells was assessed by flow sorting and sequencing. Phylogenetic trees were established using hematopoietic colonies. Calreticulin cellular localisation was assessed in patient samples and cell lines expressing CALR variants by flow cytometry and immunofluorescence. Results Exome sequencing identified 1498 somatic mutations with a median of 6.5 mutations in PV and ET, and 13 in MF (MF vs ET, P=0.0002; MF vs PV, P=0.008). JAK2V617F was found in all cases of PV (n=48), 56% of ET (35/62), and 69% of MF (27/39), and MPL mutations in 7 ET and MF cases.  Mutations in epigenetic regulators TET2, DNMT3A, ASXL1, EZH2, and IDH1/2 were identified in 22, 12, 12, 4, 3 patients respectively, and components of the splicing machinery (U2AF1, SF3B1 or SRSF2) were mutated in 9 patients.  Mutations in rare genes reported to be mutated in MPNs were found in four patients (1 CBL; 2 NFE2; 1 SH2B3/LNK). We found novel somatic mutations in CHEK2 (1 PV, 1 ET and 1 MF) which have not been previously reported in MPNs.  The mutation spectrum showed a predominance of C〉T transitions. Pairwise associations between MPN genes demonstrated that ASXL1 and SRSF2 mutations were positively correlated with mutations in epigenetic modifiers. Novel somatic mutations in calreticulin (CALR) were identified by exome sequencing in the majority (26/31) of JAK2 or MPL unmutated patients. CALR and JAK2/MPL mutations were mutually exclusive, and 97% of patients harbored a mutation in 1 of these 3 genes. In an extended follow up screen of 1345 hematological malignancies, 1517 other cancers and 550 controls we found CALR mutations in 71% of ET (80/112), 56% of idiopathic MF (18/32), 86% of post ET-MF (12/14) and 8% of myelodysplasia (10/115), but not in other myeloid, lymphoid or solid cancers. Compared to JAK2-mutated MPNs, those with CALR mutations presented with higher platelet counts (Wilcoxon rank-sum, P=0.0003), lower hemoglobin levels (Student’s t test, P=0.02) and showed a higher incidence of transformation to MF (Fishers exact, P=0.03). All CALR mutations were insertions or deletions affecting exon 9, with 2 common variants L367fs*46 (52 bp deletion) and K385fs*47 (5 bp insertion). Loss of heterozygosity over CALR was seen in a minority of patients. Of 148 CALR mutations identified, there were 19 distinct variants. Remarkably, all generated a +1 basepair frameshift, which results in loss of most of the C-terminal acidic domain of the protein as well as the KDEL Golgi-to-endoplasmic reticulum (ER) retrieval signal, raising the possibility of compromised ER retention. Mutant proteins were readily detected in transfected cell lines and localised to the ER in the same manner as wildtype CALR, without Golgi or cell surface accumulation. These results are consistent with studies reporting KDEL-independent mechanisms of ER retention. Mutation of CALR was detected in highly purified hematopoietic stem/progenitor cells. Clonal analyses demonstrated CALR mutations in the earliest phylogenetic node in 5/5 patients, consistent with it being an initiating mutation in these individuals. Conclusions We describe the mutational landscape of BCR-ABL negative MPNs and demonstrate that somatic mutations in the endoplasmic reticulum chaperone CALR are found in the majority of patients with JAK2-unmutated MPNs. These results reveal a novel biological pathway as a target for tumorigenic mutations and will simplify diagnosis of MPN patients. Disclosures: Bowen: Celgene: Honoraria. Harrison:S Bio: Honoraria, Membership on an entity’s Board of Directors or advisory committees; Shire: Speakers Bureau; Celgene: Honoraria; YM Bioscience: Honoraria, Membership on an entity’s Board of Directors or advisory committees; Sanofi: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau; Novartis: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Gilead: Honoraria, Membership on an entity’s Board of Directors or advisory committees. Vannucchi:Novartis: Honoraria, Membership on an entity’s Board of Directors or advisory committees.

Description: Background Thrombosis is a common and sometimes unpredictable complication of the myeloproliferative neoplasms (MPN). MPN management is often directed by perceived thrombotic risk. Numerous factors are predictive for thrombosis including haematocrit, age and prior thrombotic event. More recently leucocyte count and JAK2V617F allele burden have been described as potentially contributing to this thrombotic risk profile. In addition, both platelet activation status and tissue factor expression have been shown to be elevated in MPN patients compared to controls and postulated to predict for thrombosis. Cytoreduction with hydroxycarbamide has been shown to decrease thrombotic risk in this population. The introduction of JAK inhibitors (JAKi) has had a profound effect upon the therapeutic landscape for MPN, however the potential effect of these drugs upon thrombotic risk is unknown. We postulated that treatment with JAKi may affect key surrogate markers for thrombosis. Materials and Methods Patients were recruited prior to the commencement of JAKi therapy, either with ruxolitinib or SAR302503. Baseline citrated samples were taken pre drug administration and subsequent samples were collected following a minimum of 1 month of JAKi treatment for flow cytometric analysis on a Beckman Coulter Navios instrument. Platelet-neutrophil aggregates were defined as CD15+/CD42b + and CD15+/CD62p+. Platelet-monocyte aggregates were defined as CD14+/CD42b+ and CD14/CD62p+. Platelet activation was defined by expression of CD63 and CD62p. Monocyte tissue factor expression was defined as co-expression of CD14+ and CD142+. Activated neutrophils were defined as CD15/CD63+. Results We evaluated 15 MPN patients (13 myelofibrosis and 2 polycythaemia vera) pre and post JAKi therapy as well as 14 MPN patients not receiving JAKi (10 patients on hydroxycarbamide, 1 on interferon-α and 3 on no treatment). Among the 15 MPN patients receiving JAKi, the median age was 64 years and the median duration of disease was 6 years and 1 month, 9 patients were JAK2V617F positive, 1 was MPLW515L positive, and 3 had a prior history of thrombosis (2 deep venous thromboses, 1 arterial thrombosis). Four patients received SAR302503 and 11 patients received ruxolitinib. At the time of sample collection, 8 patients were receiving aspirin and 1 was receiving warfarin. We found no statistically significant difference in surrogate markers of thrombosis between MPN patients on conventional therapy and MPN patients selected to receive JAKi treatment. When comparing paired samples pre and post JAKi we found a decrease in platelet monocyte aggregates, neutrophil activation and monocyte tissue factor expression following JAKi therapy but these results did not reach statistical significance (see table). Of note, there was a significant increase in monocyte count with treatment (p=0.0078) but no significant change with respect to neutrophil, total leucocyte and platelet count. No thrombotic events occurred during the study period. Conclusions Given the substantial interest in the role of JAKi in MPN, it will be of key importance to evaluate the effects of these agents upon risk of thrombosis, a surrogate biomarker for that could be a demonstrated effect upon laboratory markers. In this study we were unable to detect a statistically significant effect of JAKi upon novel markers for thrombosis although the overall trend was for a decrease in monocyte activation despite an increase in monocyte count. This may be due to a number of factors including small sample size and short interval (1 month) between testing but warrants further investigation to address this important question. Disclosures: Harrison: Novartis: Honoraria; Sanofi : Honoraria.

Description: Introduction Myelodysplastic Syndrome (MDS) is classically a disease of older people, with median age at presentation of 70-75 years. The incidence of MDS is estimated at 5-13/100,000/year, but rises to 〉20/100,000/year in older populations. An increase in diagnosis over the last decades is in part due to improved recognition of MDS, but likely also to an increase in the ageing population. There is very little data on the clinical course, management and outcomes for very old patients (≥85 years of age) with MDS. Patients and Methods: This was a retrospective, multicentre analysis of 84 patients with MDS or Chronic Myelomonocytic Leukemia (CMML) aged ≥85 years at diagnosis from 6 centres in Ireland. Results: We identified 84 patients aged ≥85 years at time of diagnosis of MDS (n= 70) or CMML (n=14), including 47 men (56%) and 37 women (44%). Median age at diagnosis was 87 years (range 85-98). Most patients (93%) were anemic at presentation, including 45/47 men (96%) and 33/37 women (89%). Median hemoglobin (Hb) was 9.5 g/dl (range 5.9 -13.8). Median neutrophil count was 2.4 x109/L (range 0-72). Forty-four patients had thrombocytopenia (median platelet count 144 x 109/L (range 18-624)). Data regarding co-morbidities were available for 75 patients: 69% had hypertension, 36% ischemic heart disease, 39% atrial fibrillation, 31% heart failure, 19% diabetes and 39% renal dysfunction. Ferritin was elevated in 18 (32%) of 57 patients tested. 2006 WHO subgroups were reported for 81 patients: RCMD (32; 40%), CMML (14; 17%), RA (10; 12%), RAEB-1 (10; 12%), RAEB-2 (7; 9%), RARS (2; 3%), t-MDS (2; 3%), Hypoplastic MDS (1; 1%) and 5q- Syndrome (1; 1%). Cytogenetic analysis was performed in 49 patients (58%); results were available for 39 (46%). No patient had molecular studies for MDS-associated mutations or p53 deletions/mutations. Karyotype was normal in 23 patients (59% of those with results available), deletion Y in 5 (13%), Trisomy 8 in 5 (13%), complex in 3 (7.7%), 5q- in 2 (5.2%), and monosomy 7 in 1 (2.5%). Risk stratification by IPSS-R was available for only 37/84 patients, primarily due to lack of cytogenetic testing. Data were available regarding treatment strategies for 81 patients. Thirty-five (43%) received supportive care only. Forty-five patients (57%) were transfused; 29 (34%) became transfusion-dependent during the course of their disease. Of these, only 14 (48%) received erythropoietin (EPO). Of 50 patients with significant anemia likely to cause symptoms (Hb 〈 10g/dl), only 21 (42%) received EPO. Five patients (6%) received azacitidine (1-18 cycles; median 5), 7 (8%) received G-CSF; none received lenalidomide or iron chelation. Median survival for all patients was 17 months (range 0-147), 16 months for men (range 0-70), and 27 months for women (range 1-147). In 35 patients who had IPSS-R data available, median survival was 49 months for Very Good, 30 months for Good and 13 months for Intermediate category patients. For 4 patients in the Poor and Very Poor categories median survival was 1, 5, 7 and 28 months. Median survival for patients with RA was 28 months (n=10), RCMD 25 months (n=29), CMML 13 months (n= 14), RAEB-1 10 months (n=10) and RAEB-2 19 months (n=7). Six patients (including 3 with RAEB-1, 1 with CMML and 1 with t-MDS) developed Acute Myeloid Leukaemia (7%) at a median of 4.5 months from diagnosis. Median survival for these patients was 9.5 months. Of 84 patients, 60 have died. The main causes of death included marrow failure, sepsis, cardiac events, other malignancies and gastrointestinal bleeding. Conclusions Anemia is the commonest presenting feature of MDS in the very old, and may be the sole cytopenia. Unexplained anemia in the very old should trigger suspicion of underlying MDS, especially if associated with a high MCV. In many patients over 85 years cytogenetic analysis is not performed, precluding accurate prognostic evaluation. MDS in these very old patients is not often actively managed with pharmacological intervention or chemotherapy. Up to 50% of transfusion-dependent patients do not receive erythropoeitin. Azacitidine and lenalidomide are infrequently used. Co-morbidities (especially cardiac and renal disorders) are very common. Survival can be prolonged, especially in patients with low-risk disease. With an ageing population, management of very elderly patients with MDS is becoming more challenging and a more proactive approach should be considered. Figure. Figure. Disclosures Quinn: Janssen: Honoraria.

Description: Background The myeloproliferative neoplasms (MPN), in particular myelofibrosis, are associated with elevated levels of inflammatory cytokines and constitutional symptoms. Treatment with JAK inhibitors (JAKi) have lead to marked improvement in symptoms and splenomegaly. Signaling through the JAK pathway is critical for T cell development and differentiation. However the baseline immune signature remains largely undescribed in MPN as does the effect of JAK inhibition on the immune subsets in this disease. Materials and Methods The % and absolute number of CD4+ T cell subsets (TH1, TH2 and TH17 and Foxp3+ T regulatory cells) in peripheral blood (PB) were investigated by flow cytometry. T cells were stimulated and stained intracellularly for IFNg, IL-4, IL-17 & TNFα. Tregs were defined as CD4+ CD25highCD27+FOXp3+. The serum level of 30 cytokines was also measured by Luminex. Patients received either ruxolitinib (n=21) or SAR302503 (n=13) as JAKi. Results We analysed 50 MPN patients (30 Myelofibrosis, 15 Polycythemia Vera, 5 Essential Thrombocythemia) and 14 healthy donors (HD). 34 patients were treated with JAKi and sequential PB samples were obtained at 1, 3, 6 and 12 month intervals (median follow up 6 months). Tregs are significantly lower in MPN patients compared to HD and drop further following treatment (p