Citations

Abstract Abstract 1563 Intro: Optimal treatment for non-follicular low grade B-cell lymphoma (NFLGL) is not well defined. Clinical trial design for these subtypes would be enhanced by further understanding of early presentation and management. A large prospective observational study was used to identify presenting clinical features, describe patterns of care and compare the prognostic utility of International Prognostic Index (IPI) and the Follicular Lymphoma International Prognostic Index (FLIPI). Methods: The University of Iowa/Mayo Clinic SPORE Molecular Epidemiology Resource (MER) is a prospective, longitudinal observational study designed to collect information on patterns of care and outcomes for patients with newly diagnosed lymphoma. Patients seen at the Mayo Clinic, Rochester MN and the University of Iowa within 9 months of their initial diagnosis of lymphoma are offered enrollment. Baseline patient reported data, clinical data and initial management are collected using a standard protocol and a central pathology review is performed. After enrollment, patients are actively followed for events (disease progression, retreatment, and death) and disease related comorbidities. This analysis includes 198 patients diagnosed with extranodal marginal zone (EMZL), 22 with nodal marginal zone (NMZL), 47 with splenic marginal zone (SMZL), 48 with lymphoplasmacytic lymphoma (LPL), as well as 67 patients with unclassifiable low-grade B-cell lymphoma (B-NOS). Results: 382 newly diagnosed NFLGBL patients were enrolled in the MER from 2002–2009. The median age at enrollment was 63 years (range 22–95). 52% were male. The most common types of initial therapy after diagnosis were observation (41 %), alkylator- based chemotherapy +/− rituximab (R) (17%), radiation therapy alone (15%) and R monotherapy (13%). At median follow-up of 60 months (range 1–121), 51 patients were deceased and 155 had an event. The clinical characteristics that comprise the IPI and FLIPI were similar across the subtypes. Approximately half of the cases presented at low risk (55% IPI; 48% FLIPI). A majority had a normal LDH (81%), limited nodal involvement (91% had ≤ 4 groups), normal hemoglobin (71% ≥12 g/dL), good performance status (95% 0–1), and advanced stage (57% stages III-IV). There were notable differences among the NFLGBL subtypes. Patients with SMZL and LPL presented with high risk FLIPI of 3–5 (49% and 46% respectively) and high to high-intermediate IPI of 3–5 (21% and 13%). Abnormal LDH and anemia (< 12 g/dL) were more frequent in patients with SMZL (40%; 56%) and LPL (25%; 62%). EMZL presented with lower stages (70% stage I-II) and NMZL presented with increased nodal involvement (38% >4 sites). SMZL had the highest rates of surgical resection (21%) and EMZL was more frequently treated with radiation therapy (25%). LPL (30%) and NMZL (32%) more commonly received alkylator based chemotherapy +/− R. While both IPI and FLIPI differentiated outcome in these patients, FLIPI had higher c-statistics than IPI for both EFS (0.583 vs 0.568) and OS (0.685 vs 0.661), respectively. Conclusions: This large prospective collection of data on NFLGBL patients presenting to academic medical centers provides a modern picture of presentation and management patterns useful to investigators designing clinical trials. FLIPI may have more prognostic utility than IPI in this group of patients. Disclosures: Ansell: Seattle Genetics, Inc.: Research Funding.

Abstract The identification of mutations in BRAFV600E and other kinases in systemic histiocytoses changed our understanding of the pathophysiology of these disorders from inflammatory non-malignant conditions to clonal disorders driven by altered MAP kinase signaling. In addition, BRAFV600E mutations have recently been noted in bone marrow (BM) CD34+ cells of patients with Langerhans Cell Histiocytosis (LCH), suggesting that LCH represents a clonal disorder arising from hematopoietic stem/progenitor cells (HSPCs). However, it is unknown if HSPCs from LCH or other histiocytoses patients can functionally give rise to these disorders. Moreover, whether or not patients with histiocytosis have additional hematological disorders related to the presence of HSPC-based mutations is unclear. Here we attempted to understand the spectrum of hematological disorders in patients with histiocytoses and the cell-of-origin of histiocytic neoplasms by functionally analyzing HSPCs from histiocytoses patients. We first analyzed a multicenter cohort of 190 adult histiocytoses patients. This unexpectedly identified a high frequency of patients with a co-existing myeloid malignancy. Of the 190 patients, 9.5% (18/190) were diagnosed with Erdheim-Chester Disease (ECD) and/or LCH concomitantly with a classic MPN (3.7%; 7/190), MPN/MDS overlap (4.7%; 9/190), or MDS (1.1%; 2/190) (Figure). This clinical observation was confirmed by detection of co-existing histiocytoses-associated kinase mutations (including BRAF, MAP2K1, NRAS, or KRAS mutations) with JAK2 or CALR mutations, as well as other mutations recurrently found in myeloid malignancies (such as IDH1/2, ASXL1, and TET2 mutations (Figure)). These data therefore reveal a heretofore-unrecognized clinical overlap of adult-onset systemic histiocytoses and WHO-classified myeloid malignancies while further highlighting the possibility of an aberrant HSPC origin for histiocytic neoplasms. In most cases, the BRAF/MAP2K1/RAS mutation predominated in the histiocytic lesion while the JAK2/CALR mutation predominated in the BM/peripheral blood suggesting likely distinct clones driving each clinical condition. Next, to test the self-renewal and differentiation capacity of HSPCs from histiocytoses patients, CD34+ cells were purified from 8 patients including 6 with ECD or LCH plus a concomitant myeloid neoplasm, and 2 with ECD alone. 0.1-0.8x106 CD34+ cells from each patient were transplanted by intrafemoral injection into sublethally irradiated NOD/SCID IL2Rγ transgenic human GM-CSF, IL-3, and SCF expressing (NSG-SGM3) mice. Human engraftment was monitored by monthly flow cytometric analysis of peripheral blood until mice became moribund. Thereafter, animals were sacrificed and tissues were analyzed using flow cytometry, histology, immunohistochemistry, and sequencing analyses to detect driver mutations identified in the histiocytosis/co-occurring myeloid neoplasm. Successful engraftment of human myeloid cells was verified in grafts generated from 2/8 patients after a mean of 90 days (range: 60-120 days). This included lethal engraftment of KRAS-mutated ECD patient cells at 90 days manifested by infiltration of human hCD45+ cells co-expressing human myeloid and monocyte lineage markers hCD33 and hCD14 in the bone marrow, spleen, liver, lung, and kidney (Figure). Immunostains revealed that tissues were infiltrated by an hCD45+hCD163+hCD68+ population of foamy histiocytes, characteristic of ECD (Figure). Furthermore, genomic analysis of DNA from the engrafted animals BM and spleen revealed the same KRASG12S mutation found in the donor patients ECD lesion. Engraftment of a patient diagnosed with concomitant BRAFV600E-mutant ECD and ASXL1/TET2-mutant CMML was seen at 60 days. In this case, however, only engraftment of human CMML was detected without evidence of the BRAFV600E-mutant ECD component. This study suggests that adult histiocytic neoplasms frequently co-occur with other myeloid neoplasms. Moreover, histiocytosis disease-driver mutations are present in the CD34+ HSPCs, which we show for the first time can initiate disease that resembles human histiocytosis in a patient-derived xenograft. Importantly, however, even though the CD34+ compartment gives rise to both the histiocytic and myeloid neoplasm disease component, each disease is likely initiated by distinct precursors. Figure. Figure. Disclosures No relevant conflicts of interest to declare.

Abstract Histiocytic neoplasms are clonal, hematopoietic disorders characterized by an accumulation of abnormal monocyte-derived dendritic cells or macrophages in Langerhans Cell (LCH) and non-Langerhans (non-LCH) histiocytoses, respectively. The discovery of the BRAF V600E mutation in ~50% of patients with LCH and the non-LCH Erdheim-Chester Disease (ECD) provided the first molecular target in these patients and novel insights into the pathogenesis of these disorders. However, recurrent mutations in the majority of the ~50% of BRAF V600E-wild type patients with non-LCH are unknown. Moreover, recurrent mutations outside of the MAP kinase pathway are undefined throughout histiocytic neoplasms. To address these issues, we performed whole exome sequencing (WES) of frozen biopsies from 24 patients with LCH (n=10) or ECD (n=14) paired with peripheral blood mononuclear cells. 13/24 patients also underwent RNA sequencing (RNA-seq). All mutations in activating kinases were validated by droplet-digital PCR, while targeted-capture next-generation sequencing validated all others. Both adult (n=18; n=2 with LCH) and pediatric cases (n=9; n=8 with LCH) were included. Using combined WES/RNA-seq, activating kinase alterations were identified in 100% of patients. In LCH, 60% and 40% had BRAF V600E and MAP2K1 mutations, respectively. In non-LCH 51%, 14%, 14%, and 7% were BRAFV600E, ARAF, MAP2K1, and NRAS mutant (Fig1A). Overall, a mean of 7 non-synonymous mutations per adult patient was identified (range 1-22) compared with 5 mutations per pediatric patient (range 4-9; p =ns). Mutations affecting diverse cellular processes were found to co-exist with kinase mutations including mutations in epigenetic modifiers and the p38/MAPK pathway. In addition to kinase point mutations, RNA-seq identified recurrent, in-frame kinase fusions-a first for these disorders. All identified fusions were validated using FISH and RT-PCR. This includes novel fusions in BRAF (RNF11-BRAF and CLIP2-BRAF), as well as therapeutically important fusions in ALK (2 separate KIF5B-ALK fusions) and NTRK1 (LMNA-NTRK1;Fig1B). Expression of each fusion in Ba/F3 cells conferred cytokine-independent growth. Importantly, the BRAF fusions were found to be sensitive to MEK inhibition but resistant to vemurafenib while the ALK fusions conferred sensitivity to the ALK inhibitors crizotinib or alectinib. We next interrogated a validation cohort of 37 BRAF V600E-wild type, non-LCH, formalin-fixed, paraffin-embedded tissue samples using targeted mutational profiling for MAP2K1, ARAF, NRAS, KRAS, and PIK3CA. This revealed activating mutations in MAP2K1 (32%; n=12), NRAS (16%; n=6), KRAS (11%; n=4), PIK3CA (8%; n=3), and ARAF (3%; n=1). Three of the investigated non-LCH patients with refractory disease and progressive organ dysfunction were treated with targeted therapies based on the discovery of novel kinase alterations described above. Treatment of 2 refractory MAP2K1- mutant, non-LCH patients with MEK inhibitors (trametinib or cobimetinib) resulted in dramatic clinical improvement (Fig1C). Both patients have been maintained on MEK inhibitor single-agent therapy with a sustained clinical response for >100 days. Further evidence of effective targeted inhibition was found in a refractory ECD patient carrying an ARAF S214A mutation. This patient failed to respond to 3 lines of prior therapies and suffered near blindness due to disease infiltration in the retina and optic nerves. Given a recent report of complete response to sorafenib in a lung cancer patient with an ARAF S214C mutation, we initiated sorafenib. Within 12 weeks, there was improvement in the patientÕs eyesight and decreased infiltrative disease, coinciding with >50% decrease in mutant ARAF DNA in plasma cell-free DNA. Whole exome and transcriptome sequencing identified activating kinase mutations or translocations in all patients with the common downstream effect of activating the MAPK pathway. The preliminary, dramatic, clinical efficacy observed with use of MEK and RAF inhibitors in MAP2K1 - and ARAF-mutated, non-LCH patients further supports the central role of targeting the MAPK pathway in these tumors. The discovery of the discussed mutations and fusions in diverse kinases provides critical new insights into the genetic events central to a spectrum of adult and pediatric histiocytic neoplasms. Figure 1. Figure 1. Disclosures Off Label Use: This abstract describes use of MEK inhibitors (both tremetinib and cobimetinib) as well as sorafenib for MEK1 and ARAF mutant histiocytosis. . Stephens:Foundation Medicine, Inc.: Employment, Equity Ownership. Miller:Foundation Medicine, Inc.: Employment, Equity Ownership. Ross:Foundation Medicine Inc.: Employment. Ali:Foundation Medicine Inc.: Employment. Hyman:Chugai Pharma: Consultancy; Biotherapeutics: Consultancy; Atara: Consultancy, Honoraria.

Abstract Epigenetic silencing of tumor-suppressor genes has potential therapeutic relevance if the diagnostic and prognostic utility of particular DNA methylation patterns could be established. SHP1 is a tumor-suppressor gene that can be downregulated in various neoplasms. The aims of this study are (i) whether SHP1 was lost/ suppressed in diffuse large B cell lymphoma (DLBCL) (ii) Understanding the role of various epigenetic mechanisms including CpG hypermethylation and histone modifications in SHP1 loss, and (iii) whether SHP1 in DLBCL can be re-expressed with epigenetic therapy. We initially analyzed SHP1 mRNA expression in DLBCL (n=9) patient specimens and normal B-cells by QRT-PCR. Decreased expression of SHP1 mRNA was observed in all the DLBCL patient samples as compared to normal B cells. DLBCL tumor samples (n=37) along with normal tonsils (n=10) were stained for SHP1 protein by immunohistochemistry (IHC). SHP1 expression was lost or suppressed in 53% of DLBCL tumors compared to normal controls. These data, when taken together, confirm that SHP1 is strongly expressed in normal B-cells and can be lost or suppressed in DLBCL tumors. We performed epigenetic studies of SHP1 CpG promoter 2 (named CPG1 P2) in 37 DLBCL tumors and 6 DLBCL cell lines by methylation specific (MSP1) PCR and pyrosequencing methods. Surprisingly, SHP1 CpG1 P2 hypermethylation (0/37) was not detected in patient samples or cell lines by both methods. Our data conclusively demonstrate that SHP1 CpG1 P2 hypermethylation is absent in DLBCL tumors. The finding that SHP1 was lost or silenced in many of the clinical samples without finding any CpG1 P2 hypermethylation led us to extend our methylation studies to a novel, more proximal CpG island within P2 (named CpG2) that has not been previously studied in any hematological malignancies. We designed the primers specific for these CpG2 sites and ran the pyrosequencing on the same 37 DLBCL tumors as used above for CpG1 methylation. Using a cut off of >25% (intermediate to high methylation) 57% (21/37) of patient samples were methylated. The Ly3, Ly10, and DHL2 DLBCL cell lines were also hypermethylated at CpG2. To confirm the role of CpG2 methylation in SHP1 expression, we treated the Ly3 and DHL2 cells with the DNA methyltransferase inhibitor, 5-Azacytidine (Aza). We observed increased SHP1 expression compared to untreated control cells in Ly3 and DHL2 cells followed by a progressive demethylation of SHP1 CpG2, as shown by positive U-MSP with increasing amplification intensity. This resulted in a corresponding down-regulation of activated STAT3 in a similar time dependent manner. Treatment of Ly3 and DHL2 cells with 5-Aza for 0-6 days significantly (p=0.0008 for Ly3 and p=0.03 for DHL2) reduced the cell survival (40% decrease at day 6). To further investigate epigenetic control of SHP1 in DLBCL, we proceeded to study whether histone modifications in the SHP1 promoter were involved in the regulation of SHP1 expression. Chromatin immunoprecipitation assays were performed in the Ly3, Raji cell line and normal B cells, by using antibodies to repressing marks on histones. We observed that the SHP1 promoter in the Ly3 and Raji cells was enriched for both H3K9me3 and H3K27me3 repressing marks as compared to normal B cells. To confirm the role of histone modifications in SHP1 expression, we treated Ly3 cells with the histone methyltransferase inhibitor (HMT) DZNEP and the HDAC inhibitor LBH589 (Novartis Pharmaceuticals). DZNEP has been shown to be very specific for histone suppressive marks H3K27me3 that are mediated through EZH2. Treatment with DZNEP partially reverted the H3K27me3 histone marks in the SHP1 promoter followed by increased the SHP1 expression in Ly3 cells. LBH589 treatment was not able to inhibit H3K27me3 marks, but was able to inhibit the CpG2 methylation within the SHP1 promoter 2 alone or in combination with 5- Aza. In conclusion, these data provide a comprehensive characterization of the epigenetic mechanisms leading to SHP1 deregulation in the DLBCL tumors. These findings support the notion that control of SHP1 P2 in DLBCL tumors is associated with both DNA promoter methylation and histone methylation, which explains our results that treatment with 5-Aza, DZNEP and LBH589 could reactivate SHP1 expression and inhibit DLBCL cell survival. Therefore, SHP1 may prove useful diagnostic and prognostic marker and provide a rationale to use epigenetic therapy for patients with DLBCL. Disclosures: No relevant conflicts of interest to declare.

Abstract Introduction: AL amyloidosis is a very heterogeneous disease. Prognosis is a function of organ tropism, extent of organ damage, and ability of tissues to heal, the last of which relates both to hematologic response and intrinsic toxicity of the light chain. Using mass spectroscopy (MS) technology, we are able to distinguish immunoglobulin light chain variable gene family (IGVL) usage on clinical samples. The goal of this study was to evaluate if IGVL usage impacts patient outcomes in patients with light chain amyloidosis (AL). Methods: IGVL usage was determined by mass spectroscopy (MS) of amyloid in clinical tissue specimens of Mayo Clinic patients. Specimens were from fat pad (n=257), bone marrow (n=172), myocardium (n=113), gastrointestinal (n=58), kidney (n=20), lung (n=15), and nerve (n=5). For those cases for which the IGVL could not be identified--not otherwise specified (NOS)—but constant region could be identified as lambda or kappa, we assume that the amyloid consisted primarily of immunoglobulin light chain gene constant regions or variable genes with somatic mutations making them uninterpretable to our matching algorithms. The medical records from these 700 patients were abstracted for relevant clinical and laboratory data. Results: The baseline characteristics of patients are shown in table 1. Three hundred and thirty-two patients have died with a median follow-up of surviving patients of 38 months. The estimated median survival for the entire population is 59 months. Out of 700 patients, 214 (31%) achieved a CR or a VGPR, 432 (62%) were not evaluable (NE) for hematologic or organ response, and 54 (8%) achieved a PR or did not respond (NR). The distribution of IGVL cases is shown in table 2. Overall survival (OS) for the whole group was not different across different IGVLs on univariate analysis, but when corrected for hematologic response, outcomes differed significantly based on IGVL. Patients could be further assembled into two groups, based on risk for death on univariate analyses: an IGVL high risk, which included KV1, LV1, LV2, LV3, and LV6; and low risk, which included all other cases (Figure). In a multivariate model that included level of hematologic response (CR/VGPR versus PR/NR/NE) and IGVL, IGVL family was independently associated with overall survival (RR=1.5 (95% CI 1.2-1.9, p=0.008). The risk ratio for CR/VGPR was 0.28 (95% CI 0.20-0.38, p<0.0001). This effect persisted when either the Mayo 2006 or the 2012 staging system was included in the multivariate. Conclusion: IGVL usage appears to have prognostic significance in patients who have not achieved VGPR or better to initial chemotherapy. Table 1. Baseline characteristics of patients N= 700 Age 63 (32-94) Male, (%) 447 (64%) Biopsy site Solid organ/Soft tissue 271 (39%) Fat pad 257 (37%) Bone Marrow 172 (25%) Organ involvement Cardiac 432 (62%) Renal 346 (49%) Gastrointestinal 168 (24%) Liver 56 (8%) Nerve 107 (15%) Lung 42 (6%) Soft Tissue 92 (13%) Organs involved 1 321 (46%) 2 228 (33%) ≥3 151 (22%) Laboratory characteristics NTBNP, pg/ml 2547 (11.3-70000) Troponin, ng/ml 0.03 (0.001-0.84) dFLC, mg/dl 26 (0.04-2330) Cardiac Stage 1 59 (18%) 2 125 (38%) 3 144 (44%) Table 2. Variable region family distribution. Light Chain N=700 N (%) KV1 107 (15%) KV2 3 (0.4%) KV3 17 (2%) KV4 25 (4%) KV6 1 (0.1%) LV1 85 (12%) LV2 64 (9%) LV3 118 (17%) LV4 3 (0.4%) LV6 97 (14%) LV8 1 (0.1%) LV9 1 (0.1%) Kappa NOS1 34 (4%) Lambda NOS1 140 (19%) Heavy chain amyloidosis 4 (0.6%) 1 No IGVL family could be identified Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Abstract Peripheral T- and NK-cell lymphomas (PTCLs) are fatal in the majority of patients, and conventional chemotherapy is minimally effective. Targeted inhibition of tyrosine kinases (TKs) might be a useful treatment strategy, but TK overexpression by PTCLs has not been well characterized (except ALK). Recently a novel translocation t(5;9) fusing the ITK and SYK genes was reported in a subset of unspecified-type PTCLs, associated with high SYK gene expression and Syk protein positivity. Syk is a non-receptor TK important in immunoreceptor signal transduction, providing proliferation and survival signals in a variety of hematopoietic cells. Syk is absent or expressed at very low levels in most normal post-thymic T cells, where this signal transduction role is fulfilled by ZAP70. Since Syk TK inhibitors are now in clinical trials for other diseases, we sought to determine the incidence of t(5;9) and Syk overexpression in PTCL. Tissue microarrays were constructed using triplicate cores from paraffin-embedded tissue blocks. Cases were studied using fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC). Additional studies were performed using flow cytometry and Western blot. There were 141 PTCLs, including 35 angioimmunoblastic, 66 unspecified, 21 anaplastic large cell, 2 enteropathy-associated, 5 hepatosplenic, 5 extranodal NK/T, and 7 other. No evidence of t(5;9) was identified by FISH in 86 informative cases. Normal T-cell subsets from peripheral blood, spleen, and lymph node were negative for Syk by IHC, flow cytometry, and Western blot. Syk was positive by immunohistochemistry in 133 of 141 (94%) PTCLs. All 8 Syk negative cases were extranodal, cytotoxic PTCLs. Western blot on frozen tissue correlated with IHC results in paraffin. All 4 Syk-positive cases tested showed phosphorylation of tyrosine residues 525/526, known to be required for Syk activation. We conclude that Syk is overexpressed in most PTCLs, including the vast majority of nodal cases. Syk may substitute for ZAP70 in these tumors and provide ongoing proliferation and survival signaling. The overexpression of Syk and phosphorylation of its Y525/526 residues suggest Syk may be a suitable target for pharmacologic TK inhibition as a treatment option for patients with PTCL.

AbstractObjectiveTo evaluate variability in antenatal sonographic prognostication of congenital diaphragmatic hernia (CDH) within the North American Fetal Therapy Network (NAFTNet).MethodsNAFTNet centre were invited to complete a questionnaire and participate in videoconference calls, during which participants were observed while measuring lung area by ultrasound using the anteroposterior (AP) method, longest method, and trace method. Each center identified 1–2 experienced fetal medicine specialist(s) or medical imaging specialists locally to participate in the study. Practices were compared among NAFTNet centre within and without the fetal endoscopic tracheal occlusion (FETO) consortium.ResultsNineteen participants from 9 FETO center and 30 participants from 17 non‐FETO center completed the survey and 31 participants were interviewed and observed while measuring sonographic lung area. All Centres measured observed‐to‐expected lung‐to‐head ratio (o/e LHR) or LHR for CDH prognostication. Image selection criteria for lung area measurement were consistent, including an axial section of the chest with clear lung borders and a 4‐chamber cardiac view. Lung area measurement methods varied across NAFTNet, with most centre using longest (4/9 FETO vs. 13/29 non‐FETO) or trace (3/9 FETO vs. 11/29 non‐FETO) method. Centres differed in expected reference ranges for o/e LHR determination and whether the lowest, highest or average o/e LHR was utilized.ConclusionVariability in antenatal sonographic prognostication of CDH was identified across NAFTNet, indicating a need for consensus‐based standardization.

Abstract Primary myelofibrosis (PMF) is a clonal hematologic malignancy resulting from the transformation of a pluripotent hematopoietic progenitor cell leading to increased hematopoiesis and overproduction of abnormal blood cells. PMF is characterized by bone marrow (BM) fibrosis, extramedullary hematopoiesis, increased numbers of circulating CD34+ cells, splenomegaly, and a propensity to evolve to AML. Patients also display anemia and thrombocytopenia and harbor abnormal, immature megakaryocytes (Mks) in their BM and spleen. Numerous mutations are associated with PMF including JAK2, CALR, MPL, TET2, CBL, ASXL1, and IDH. The presence of abnormal Mks in the BM of PMF patients is an important characteristic of the disease, as these cells are believed to contribute to the fibrosis.Here, we performed an analysis of Mk differentiation from individuals with PMF compared to healthy individuals as a way to better understand the mechanism leading to their defects. CD34+ cells obtained from PMF and healthy donors were cultivated in presence of thrombopoietin to induce Mks differentiation. Under these conditions, we observed that the proliferative capacity of CD34+ cells from PMF patients was increased as compared to normal CD34+ cells. At the same time, the percentage of mature Mks obtained was reduced. Semi-solid culture conditions confirmed the proliferative advantage of the PMF CD34+ cells. To investigate the mechanism responsible for this phenotype, we performed genome wide expression analysis of sorted Mks from patients versus controls. Nine PMF patients with different mutations (5 JAK2V617F, 1 MPLW515L, 2 CALR and 1 triple negative) and 4 healthy donors were included in the study. Gene Set Enrichment Analysis (GSEA) analysis revealed that the top scoring pathways included the RPS14 signature, ribosome biogenesis, rRNA metabolic process, and rRNA processing. We first studied the RPS14 geneset, which consists of a group of genes that were up-regulated in CD34+ cells after knock-down of RPS14, a component of the small ribosome subunit. Using shRNA against RPS14, we discovered that its knock down leads to a significant reduction in the development of mature Mks from normal CD34+ cells. The microarray data also revealed changes in the expression of several myeloid genes. CEBPa and GFI-1 were over-expressed in PMF Mks, whereas GFI-1b and PF4, which are associated with Mk differentiation, were down-regulated. Surprisingly the expression of GATA1, a master regulator of megakaryopoiesis, was not changed. However, consistent with previous report, we discovered that GATA1 protein level was reduced in PMF Mks. GATA1 deficient Mks are impaired in their maturation, so we reasoned that the reduction in GATA1 contributes to the defects in PMF. Indeed, we found that overexpression of GATA1 in PMF CD34+ cells rescued Mk differentiation. To understand how GATA1 protein but not mRNA, is reduced, we knocked down RPS14 in the JAK2 mutant SET2 megakaryoblastic cell line. As predicted, we observed a reduction in GATA1 protein, but not mRNA. By ribosomal profiling, we saw that the shRPS14 led to an abnormal ribosomal profile with a reduction of the 40s peak. Finally, by RT-PCR analysis of the ribosomal and polysomal fractions, we found that GATA1 mRNA was less abundant in the polysomal fraction in cells expressing the shRPS14. This finding is consistent with recent data showing that alterations in ribosomal genes cause a decrease in GATA1 protein in Diamond-Blackfan Anemia. Although we identified the RPS14 gene signature, we did not observe changes in RPS14 expression or in any of the ribosomal subunits. Since our GSEA analysis also identified deficiencies in three ribosomal biogenesis pathways, we looked for genes present in all three signatures. NOP58, a ribonucleoprotein required for ribosome biogenesis, was significantly reduced in all samples of PMF Mks. To link the reduction in NOP58 expression with PMF associated mutations, we expressed MPLW515L or the CALR type II mutant in hematopoietic progenitor cells and detected a reduction in NOP58 expression. Our findings suggest that the activation of JAK/STAT signaling leads to a reduction in NOP58, which contributes to defects in ribosome assembly, decreased GATA1 expression and subsequent impairment in Mk differentiation. This work reveals, for the first time, that defective ribosomes contribute to the pathogenesis of PMF and suggests new avenues for therapeutic intervention. Disclosures Stein: Incyte Corporation: Honoraria, Speakers Bureau; Sanofi Oncology: Honoraria.

Abstract Abstract 3992 Little is known about the rare entities of heavy and light chain amyloidosis (AHL) and heavy chain amyloidosis (AH). In this study, we report the renal and hematologic characteristics, pathology, and outcome of 17 patients with renal AH/AHL including 5 with AH (4 IgG and 1 IgA) and 12 with AHL (7 IgGλ, 3 IgAκ, 1 IgAλ, and 1 IgMλ), and compare them with 202 patients with renal AL amyloidosis (AL) diagnosed during the same time period. All cases were diagnosed by kidney biopsy that showed Congo red-positive deposits. Amyloid typing was done by laser microdissection and mass spectrometry (LMD/MS) (12 patients) or by immunofluorescence (5 patients). All patients with renal AH/AHL were Caucasians, with a M:F ratio of 2.4 and a median age at biopsy of 63 years. Compared with patients with renal AL, those with renal AH/AHL had less frequent concurrent cardiac involvement, higher likelihood of having circulating complete monoclonal Ig, lower sensitivity of fat pad biopsy and bone marrow biopsy for detecting amyloid, higher incidence of hematuria, and better patient survival. The hematologic and renal responses to chemotherapy were comparable to renal AL. In 42% of patients, AH/AHL could not have been diagnosed without LMD/MS. In conclusion, renal AH/AHL is an uncommon but under-recognized form of amyloidosis, and its diagnosis is greatly enhanced by the use of LMD/MS for amyloid typing. The accurate histological diagnosis of renal AH/AHL and distinction from AL may have important clinical and prognostic implications. Table 1. Demographics and hematologic characteristics AH/AHL AL p value No. of patients 17 202 Gender: Male/female 12/5 (71%/29%) 126/76 (62%/38%) 0.61 Age, median (range) 63 (50–77) 62 (36–86) 0.73 Additional organ involvement 8 (47%) 126 (62%) 0.3 Cardiac involvement 3 (18%) 100 (50%) 0.01* % of plasma cells in bone marrow, median (IQR) 8 (5–15) 6 (5–10) 0.82 ≥30 plasma cells 4 (24%) 11/198 (6%) 0.02* Positive SPEP/SIF for paraprotein 15 (88%) 158/200 (79%) 0.53 Presence of whole monoclonal protein on SPEP 14 (82%) 108/200 (54%) 0.04* Positive UPEP/UIF for paraprotein 13/16 (81%) 158/189 (84%) 0.73 Presence of whole monoclonal protein on UPEP 10/16 (63%) 61/189 (32%) 0.03* Abnormal serum FLC ratio (<0.26 or >1.65) 9/12 (75%) 150/188 (80%) 0.71 Markedly abnormal FLC ratio (< 0.125 or > 8) 5/12 (42%) 100/188 (53%) 0.55 Positive bone marrow for amyloid 6/16 (38%) 135/183 (74%) 0.004* Positive fat pad biopsy for amyloid 2/14 (14%) 105/145 (72%) <0.001* IQR, interquartile range. Table 2. Renal characteristics at kidney biopsy AH/AHL AL p value No. of patients 17 202 24h urine protein in g, median (IQR) 5.1 (3.2–9.0) 6.0 (3.2–10.0) 0.9 Full nephrotic syndrome 9/16 (56%) 132/197 (67%) 0.42 Serum albumin in g/dl, median (IQR) 2.7 (2.2–3.3) 2.5 (1.9–2.9) 0.29 % albuminuria on UPEP, median (IQR) 68 (61–72) 70 (60–76) 0.47 Serum creatinine in mg/dl, median (IQR) 1.4 (1.1–2.1) 1.2 (0.9–1.8) 0.25 Serum creatinine >1.2 mg/dl 10/16 (63%) 92/201 (46%) 0.3 eGFR, median (IQR) 47 (27–67) 58 (36–75) 0.29 Decreased eGFR 10/16 (63%) 103/201 (51%) 0.44 Microscopic hematuria 9/16 (56%) 44/169 (26%) 0.02* IQR, interquartile range. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 443 Background: MYC translocations have been reported to have inferior outcome in aggressive non-Hodgkin lymphomas. Here we present MYC translocation prevalence and outcome from two cohorts of newly diagnosed diffuse large B-cell lymphoma (DLBCL) patients treated in the chemotherapy (C) and immunochemotherapy (IC) eras. Methods: Tissue microarrays were created from 302 newly diagnosed DLBCL patients evaluated at the Mayo Clinic with availabel paraffin tissue. 233 DLBCL patients first diagnosed from March 1986-July 2001 were retrospectively identified based on a diagnosis of DLBCL and treatment with anthracycline-based chemotherapy. 69 DLBCL patients diagnosed from March 2002-October 2005 and treated with immunochemotherapy were prospectively enrolled in the University of Iowa / Mayo Clinic Lymphoma SPORE Molecular Epidemiology Resource. Central pathology review was performed on all samples to confirm the diagnosis of DLBCL. Interphase FISH was performed using a breakapart strategy for MYC and BCL6 gene regions and a dual fusion strategy for t(14;18)(IGH&/BCL2). Results: Chemotherapy (C) era patients were primarily treated with CHOP (88%); immunochemotherapy (IC) era patients were all treated with an R-CHOP based regimen. The median age at diagnosis was 65 years (range, 22-92) for C patients and 65 years (range, 20-82) for IC patients. Median follow-up for C patients was 11.3 years (range, 2.7-21.3) with 145 (62%) deaths; for IC patients, the median follow-up was 5.0 years (range, 2.1-6.4) with 17 deaths (25%). FISH was successful in 195 of 302 patients (65%). MYC translocations were identified in 6 of 141 C patients (4%) and 3 of 54 IC patients (6%). MYC translocations were associated with inferior overall survival in the C patients (p=0.001), the IC patients (p=0.04), and in the combined group (p≤0.001). Median survival of patients with MYC translocations was 19 months and 16 months for C and IC respectively, compared to 112 months (C) and unreached (IC) for DLBCL patients without MYC translocations. 4 of the 9 MYC translocation patients had a double hit (2 with both MYC and BCL2 translocations and 2 with translocations of MYC, BCL2, and BCL6). Associations of MYC and outcome remained significant in all patients after adjusting for treatment and IPI (p<0.05). Conclusions: MYC translocations are present in approximately 5% of DLBCL patients and are associated with poor outcome in patients treated with C or IC. New treatment approaches are needed for DLBCL patients with MYC translocations. Disclosures: No relevant conflicts of interest to declare.