CALR Type Research Articles

ELC52: a novel megakaryocytic leukemia cell line with a CALR type 1 mutation

ELC52: a novel megakaryocytic leukemia cell line with a CALR type 1 mutation

Real World Data on Safety and Efficacy of Pegylated Interferon (PEG-IFN) in Patients with Myeloproliferative Neoplasms (MPN)

Introduction: Patients with Myeloproliferative neoplasms (MPN) require cytoreduction to normalise the elevated counts to reduce risk of thrombosis. We present real world data from a single centre in the UK on PEG-IFN in patients with MPN. Methods: Real World prospective data collection of patients who were commenced on PEGIFN between Jan 2014 to July 2022. Patient demographics, indications to treat, dose and response rates at quarterly follow up in year 1 and biannually from year 2 onwards, thrombotic events, transformation, discontinuation rate and adverse events were collected and presented here. Starting dose of PEG IFN was 45 mg/2 weeks; it was increased gradually to a maximum of 180 mg/week. Once complete response (CR) according to ELN criteria was achieved dose was reduced to minimum effective dose. Results: This study accrued 212 patients with MPN who commenced PEGIFN from Jan 2014 to July 2022. Median duration of follow up was 60 m (range 12 - 114 m); 92 males, 120 Females; 93 patients were diagnosed to have Polycythaemia Vera PV), 98 Essential Thrombocythemia (ET) and 21 had Myelofibrosis (MF). 154 patients had mutated JAK2, 41 CAL-R (type 1 in 25 and type 2 in 16), 3 MPL and 13 were negative for any mutations. PEG IFN was chosen as first line treatment in 89 patients and at subsequent line after Hydroxycarbamide (intolerant n=, ineffective n= or contraindicated n= due to ulcers) or phlebotomy in 123 patients. Complete Haematological response according to ELN criteria were achieved and sustained in 141 (66%) at a median of 6 m (range: 3 to 60), Partial response in 52 (24%) and no response in 15 (7%) patients. Molecular response was assessed in JAK2 mutated patients (n=153) and shown in figures 1 and 2 with respect to diagnosis and response rate. Complete molecular response was seen in 4 patients at a median of 58 m. Deeper sustained responses were associated with earlier use of PEG-IFN in the course of disease, younger patients as first line as compared to it being used at second or subsequent line (74% Vs 63%) . PEG IFN was discontinued in 36 patients at 6 to 18 m due to being ineffective in 7, intolerant in 18, unrelated causes in 10 and disease progression/transformation in 3 patients (1 AML 2 MF). Thrombotic events whilst on PEG-IFN were seen in 14 patients (11 arterial and 3 venous) unrelated to control of blood counts, 12 were JAK2+ MPN and 10 patients had PV. Adverse events such as hypothyroidism in 8 (3.7%), grade 1-2 hepatitis in 46 (21.6%), grade 3 hepatitis in 4 (1.8%), alopecia in 2, skin rash in 3, worsening of psoriasis in 2 patients were managed with reduction or temporary suspension of PEG IFN and recommencing at a lower dose and frequency. 29 patients had underlying depression and 22 were stable on anti-depressants, 4 patients came off interferon due to panic attacks. 5 patients developed second primary malignancy on PEG IFN. Conclusion: PEG-IFN is a safe and effective cytoreductive agent in all myeloproliferative neoplasms and is an alternative to Hydroxycarbamide, as a second line option in older patients and a first line option in younger patients. It corrects the elevated counts but also modifies the disease course as evident in JAK2 VAF reduction and sustained haematological responses and reduced risk of thrombosis and transformation. In addition, it is least restrictive in terms of quality of life such as family and holiday planning. Figure 1: Waterfall plot: JAK2 allele burden percentage change on Peg-IFN, each bar represents the % change in allele burden for one patient, and ranked Figure 2: Fall in JAK2 VAF with respect to type of Haematological Response

High molecular risk variants, severe thrombocytopenia and large unstained cells count affect the outcome in primary myelofibrosis

Apart from the driver mutations, high molecular risk (HMR) variants and other factors have been reported to influence the prognosis of primary myelofibrosis (PMF). The aim of our study was to investigate the impact of laboratory and molecular characteristics at the time of diagnosis (TOD) on the PMF outcome. The study group consisted of 82 patients recruited from three Polish university centers. Among the driver mutations, only CALR type 1 positively influenced the overall survival (OS). The risk of progression to accelerated or blastic disease phase (AP/BP) did not depend on the driver mutation type, but was closely associated with the presence of HMR variants (p = 0.0062). The risk of death (ROD) was higher in patients with HMR variants (OR[95%CI] = 4.33[1.52;12.34], p = 0.0044) and in patients with a platelet count at the TOD between 50–100 G/L (HR[95%CI] = 2.66[1.11;6.35]) and < 50 G/L (HR[95%CI] = 8.44[2.50;28.44]). Median survival time was 7.8, 2.2 and 1.4 years in patients with large unstained cells (LUC) count of [0.0–0.2], (0.2–0.4] and > 0.4 G/L at the TOD, respectively. We found an unexpected, hitherto undescribed, association between LUC count at the TOD and PMF prognosis. Our analysis led to the following conclusions: in PMF patients at the TOD 1) the presence of HMR variants, especially combined, is associated with an increased risk of progression to the AP and BP, and shorter OS, 2) severe thrombocytopenia confers worse prognosis than the moderate one, 3) LUC count is closely related with the disease phase, and associated with the ROD and OS.

Molecular prognostication in Ph-negative MPNs in 2022.

The application of genomic techniques, including cytogenetics and DNA sequencing, to decipher the molecular landscape of patients with myeloproliferative neoplasms (MPNs) has radically modified diagnostic approach and management through improved risk stratification. Three driver mutated genes (JAK2, MPL, CALR) are variably harbored by >80% of patients and associated with clinical characteristics, as well as major disease-related complications and different survival outcomes. Therefore, JAK2 V617F mutation is included in the revised International Prognosis Score of Thrombosis for Essential Thrombocythemia score for prediction of thrombosis in patients with essential thrombocythemia and prefibrotic primary myelofibrosis, while a CALR type 1 mutated genotype constitutes a favorable variable for survival in patients with myelofibrosis (MF). Novel, integrated clinical and cytogenetic/mutation scores (Mutation-Enhanced International Prognostic Score System for Transplantation-Age Patients with Primary Myelofibrosis [MIPSS70/v2], genetically inspired prognostic scoring system [GIPSS], Myelofibrosis Secondary to PV and ET- Prognostic Model [MYSEC-PM]) have been devised that guide selection of stem cell transplantation candidates with MF or help predict the risk associated with the transplant procedure (Myelofibrosis Transplant Scoring System), with greater performance compared with conventional scores based on hematologic and clinical variables only. On the other hand, several clinical needs remain unmet despite the great amount of molecular information available nowadays. These include the prediction of evolution to acute leukemia in a clinically actionable time frame, the identification of patients most likely to derive durable benefits from target agents, in primis JAK inhibitors, and, conversely, the significance of molecular responses that develop in patients receiving interferon or some novel agents. Here, we discuss briefly the significance and the role of genomic analysis for prognostication in patients with MPNs from a clinician's point of view, with the intent to provide how-to-use hints.

Clinical Features and Mutational Landscape of Patients Referred for Suspected Essential Thrombocytosis: A Descriptive Study Using a 'Real-World’ Database

Background: Essential Thrombocythemia (ET) is a myeloproliferative neoplasm characterized by persistent thrombocytosis and often associated with mutations in JAK2, CALR, or MPL. Next Generation Sequencing (NGS) has become widely used in patients with suspected hematologic malignancies but its role in the investigation of unselected patients referred for thrombocytosis remains to be defined. This project describes the characteristics and mutational landscape of patients referred for isolated thrombocytosis with the aim of developing a clinical prediction rule for ET to help guide diagnosis and improve utilization of genomic testing. Methods: All adult patients referred to the Hematology Service at London Health Sciences Centre, Ontario, Canada, between January 1, 2018, and May 31, 2021 were reviewed for thrombocytosis (≥ 450 x 109 cells /L). NGS testing was performed using the Oncomine Myeloid Research Assay (Thermofisher Scientific, MA, USA). Patients were classified into two groups: Clinical ET and secondary thrombocytosis. Clinical ET was defined as any patient meeting the World Health Organization (WHO) 2016 criteria for ET or any patient meeting all criteria but lacking a bone marrow biopsy. Results: 446 consecutive patients were evaluated for thrombocytosis with NGS testing. 102 patients were excluded due to meeting criteria for other WHO defined conditions such as chronic myeloid leukemia, polycythemia vera, other myeloproliferative neoplasms and/or myelodysplastic syndromes. In the remaining, 342 patients, the overall yield of molecular testing was 188 (55.0%). Mutations in JAK2, CALR, MPL were identified in 84.7% of patients with clinical ET (JAK2 in 48.9%, CAL-R type 1 or 2 in 27.6%, and MPL in 8.5%), with triple negative making up the remaining 8.5%. There was no statistically significant difference between CBC parameters, ferritin, ESR, and CRP between clinical ET and secondary thrombocytosis groups. In contrast, clinical factors such as previous history of arterial thrombosis were highly predictive of ET, whilst active malignancy, chronic inflammatory disease and post splenectomy and iron deficiency were all associated with secondary thrombocytosis. Conclusion: Overall yield of molecular testing for this population of patients referred for thrombocytosis was high (55.0%), suggesting appropriate use of NGS testing, but the identification of clinical factors predicting secondary causes might suggest further improvement in utilization. In our cohort, CBC parameters did not readily distinguish between ET and secondary thrombocytosis. Clinical factors such as smoking, active malignancy, chronic inflammatory disease and post splenectomy and iron deficiency are associated with secondary thrombocytosis. These results may help inform development of a clinical prediction rule to assist in determining the pre-test probability of ET in patients referred for thrombocytosis. #co-first authors Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Clinical, Molecular, and Histopathological Correlates in a Series of 24 Consecutive Cases of Suspected Myeloproliferative Neoplasms with a JAK2V617F Variant Allele Frequency ≤1%

Background: JAK2V617F is detected in >95% of polycythemia vera (PV) and 50-60% of essential thrombocythemia (ET) and primary myelofibrosis (PMF). JAK2V617F variant allele frequency (VAF) is associated with different clinical characteristics and outcome. Highly sensitive molecular assays led to detect JAK2V617F mutation also in healthy subjects, associated with a higher risk of coronary heart disease (N Engl J Med. 2017;377(2):111-121) in the context of CHIP. To date, comprehensive data on suspected MPN patients with a JAK2V617F VAF≤1% are lacking. Aim and methods: The aim was to analyze clinical, molecular, and histopathological correlates in a series of suspected MPN patients (pts) with a JAK2V617F VAF≤1% (from 2017 to 2022) at our Center. JAK2V617F VAF was measured in granulocytes by highly sensitive RTQ-PCR. Conventional karyotype and target next-generation sequencing (NGS) analysis were performed (complete data will be presented at the meeting). Bone marrow (BM) biopsies were reviewed by two independent expert pathologists, R.S. and U.G., the latter included as an author in the International Consensus Classification (Blood 2022; 2022015850). Results: 21 males and 3 females (M/F=7:1), with a median age of 58 y (range, 22-81) were included. Median JAK2V617F VAF was 0.2% (0.1-1). In the suspicion of MPN, complete diagnostic work-up was carried out in pts presenting with erythrocytosis (n=15), thrombocytosis (n=4), history of atypical thrombosis (n=3), splenomegaly (n=1) and leukocytosis (n=1), (Fig.1). In pts with erythrocytosis, median (range) Hb and Hct values were 17 g/dL (15.8-18.5) and 51.5% (50.4-54.7), whereas leukocytes (6.6 x 109/L, 5-11) and platelet (258 x 109/L, 172-440) were within normal range. EPO level (10 mUI/mL; 1.8-12.5) was subnormal in 3 pts. Abnormal karyotype was documented in one case (45,X,-Y[7]/46,XY[13]). Additional mutations were documented in 3 pts: HBB T124N, SH2B3 S186I and cKIT D816V. In pts with thrombocytosis, platelet range was 460-1450 x 109/L; Hb, Hct and leucocytes values were normal. MPL W515K and CALR L367Tfs*46 additional mutations were in one and two pts, respectively. Considering pts with atypical thrombosis, one had a history of arterial events while the others experienced cerebral venous sinus and portal vein thrombosis. Thrombophilia screenings were negative. Karyotype was normal in two pts, whereas one had 45,X,-Y[3]/46,XY[20]. Additional CBL p.D460dup was detected in one case. The subjects investigated for splenomegaly/leukocytosis had normal karyotype, no additional mutations. Morphological features consistent with PV were documented in 4 pts (Fig. 2, A-B). In one of these cases, multifocal dense infiltrates of CD117+/CD25+ mast cells were detected, fulfilling the diagnostic criteria for systemic mastocytosis with associated hematological neoplasm. In the other cases, microscopic examination showed age-adjusted normal or focally increased cellularity, regular or mildly expanded erythroid lineage with no/only minor increase in granulocytic lineage and a higher number of megakaryocytes with PV-like features (i.e. polymorphic forms without atypia and no dense cluster formation) (Fig. 1, C-D). Neither reticulin fibrosis nor excess blasts were detected and these pts had a final diagnosis of MPN unclassifiable (MPN-U), with a PV-like morphology. In pts with thrombocytosis histology was consistent with ET in three cases and overt-PMF in one. Among ET, one pts harbored MPLW515K with grade 1 reticulin fibrosis (Fig. 2, E-F), whereas the overt PMF had CALR type 1 additional mutation. BM biopsies of pts presenting with atypical thrombosis, leukocytosis and mild splenomegaly showed non-specific MPN-like features (including focally increased cellularity, mild expansion of erythroid or granulocytic lineages, higher number of megakaryocytes with a TE-like or a PV-like morphology) and were diagnosed as MPN-U. Conclusions: This study highlights the importance of using highly sensitive assays to detect JAK2V617F, as well as the need to search for CALR and MPL mutations, particularly in pts with thrombocytosis. Moreover, in pts presenting with erythrocytosis and JAK2V617F positivity with VAF≤1%, histopathological diagnostic clues to MPN may be subtle as in the early phase of the disease, emphasizing the need to integrate histopathology with clinical and genetic data in order to address patients to proper clinical management. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Clonal haematopoiesis of indeterminate potential and impaired kidney function-A Danish general population study with 11 years follow-up.

The myeloproliferative neoplasms are associated with chronic kidney disease but whether clonal haematopoiesis of indeterminate potential (CHIP) is associated with impaired kidney function is unknown. In the Danish General Suburban Population Study (N=19 958) from 2010 to 2013, 645 individuals were positive for JAK2V617F (N=613) or CALR (N=32) mutations. Mutation-positive individuals without haematological malignancy were defined as having CHIP (N=629). We used multiple and inverse probability weighted (IPW)-adjusted linear regression analysis to estimate adjusted mean (95% confidence interval) differences in estimated glomerular filtration rate (eGFR; ml/min/1.73 m2 ) by mutation status, variant allele frequency (VAF%), blood cell counts, and neutrophil-to-lymphocyte ratio (NLR). We performed 11-year longitudinal follow-up of eGFR in all individuals. Compared to CHIP-negative individuals, the mean differences in eGFR were -5.6 (-10.3, -0.8, p=.02) for CALR, -11.9 (-21.4, -2.4, p=0.01) for CALR type 2, and -10.1 (-18.1, -2.2, p =.01) for CALR with VAF ≥ 1%. The IPW-adjusted linear regression analyses showed similar results. NLR was negatively associated with eGFR. Individuals with CALR type 2 had a worse 11-year longitudinal follow-up on eGFR compared to CHIP-negative individuals (p=.004). In conclusion, individuals with CALR mutations, especially CALR type 2, had impaired kidney function compared to CHIP-negative individuals as measured by a lower eGFR at baseline and during 11-year follow-up.

P997: PROTEOMIC ANALYSIS ON PLATELETS OF ESSENTIAL THROMBOCYTHEMIA PATIENTS UNDERSCORES THE ROLE OF MITOCHONDRIA IN JAK2 V617F PLATELET REACTIVITY AND FUNCTION

Background: Essential thrombocythemia (ET) is a heterogeneous disease subdivided into five genetic groups according to WHO, based on the common MPN driver mutations (JAK2 V617F, MPL W515K/L, and CALR Type I&II). Current treatment strategies include anti-platelet (e.g. acetylsalicylic acid (ASA)) or cytoreductive agents (e.g. hydrea (HU)) and target mainly complications related to platelet dysfunction (i.e. hemorrhage/thrombosis). Platelet activation is an energy demanding process fueled mainly by a dynamic equilibrium between mitochondria oxidative phosphorylation and glycolysis1. Importantly, altering the platelet catabolic response to activation has been shown to prevent thrombus formation2. JAK2 V617F platelets have been reported to be more activated than CALR mutated platelets3, as well as JAK2 mutated patients have a greater thrombotic risk in comparison to other ET groups. However, the cause of this phenotype is not completely understood. Aims: In this study we aimed to analyze the proteome of ET platelets and to characterize their functional properties according to the mutational background and treatment regimens. Methods: 22 healthy donors (HD) and 67 ET patients have been included in the study. Most of the patients were treated with low dose aspirin (ASA), anagrelide (ANA) or hydrea (HU) or a combination of these. Specifically, 35 out of the 67 ET platelet samples and 8 out of 22 HD were subjected to label-free quantitation mass spectrometry (LFQ-MS). All HD and ET platelets were also analyzed for surface marker expression, degranulation and aggregation capacity by flow cytometry. Results: Hierarchical clustering of the mass spectrometry data revealed different proteomic profiles between HD and ET mutational groups and specifically between JAK2 V617F and CALR I and CALR Type II treated and/or untreated platelets. In general, HD platelets were more enriched for proteins related to platelet activation, and degranulation as compared to ET platelets and clustered next to JAK2 V617F ASA-treated platelet samples (Figure 1). In particular, the JAK2 V617F ASA-treated platelets presented significant enrichment in platelet activation metabolic and mitochondrial proteins in contrast to the CALR Type I and Type II ET platelets. Of note, no peptides corresponding to the mutant CALR were detected using label-free MS methods. Surface marker expression was variable among ET patients. However, CD49B and CD36 surface markers were the most affected among the JAK2V617F and CALR Type I and II platelets and their levels (mean fluorescence intensity-MFI-) were inversely correlated. With regards to platelet aggregation, JAK2 V617F platelets presented similar or lower levels when compared to HD platelets, in line with their proteomic profiles. Differences in aggregation and degranulation levels were also observed between CALR Type I and Type II platelets specifically in the untreated condition. Image:Summary/Conclusion: ET platelets are functional but they show different capacities to respond upon various stimuli and treatment regimens. JAK2 V61F platelets are more activated than any other ET group according to their proteome profile, which is not fully reflected by the functional assays. Mitochondrial activity arises as an important factor in the control of platelet reactivity and it could be critical in disease management and treatment strategies, specifically for the JAK2 V617F patients.

P1032: REAL-LIFE VALIDATION OF MIPSS70: A RETROSPECTIVE MULTICENTER AND NGS ANALYSIS FROM THE GEMFIN DATABASE

Background: Primary myelofibrosis (PMF) is a myeloproliferative neoplasm characterized by the presence of driver mutations (JAK2, CALR or MPL) in most of the patients. The development of next generation sequencing (NGS) has favored the incorporation of mutational information in novel prognostic scores. However, most of these risk stratification models also include cytogenetic information, which is only available for a fraction of patients with this disease, thus reducing their real-life applicability. Mutation-enhanced international prognostic scoring system for transplant-age patients (MIPSS70) is based on clinical and mutational risk factors and it is useful in the absence of cytogenetic information, but it has not been validated yet in a real-life clinical setting. Aims: To validate MIPSS70 risk stratification model for transplant-age PMF patients from a multicenter database. Methods: From the GEMFIN multicenter database, 668 myelofibrosis patients with enough information to calculate MIPSS70 were selected. As the score is intended for patients aged ≤70 years with PMF, the final analysis was carried out in 218 patients meeting these criteria. Patients who received allogeneic stem cell transplantation were censored on the date of transplantation. Results: Median age was 61 years (range 18-70), 69% of patients were male and median follow-up time was 4.65 years. Regarding the presence of MIPSS70 variables at disease diagnosis, 45% of patients had constitutional symptoms, 43% had hemoglobin <100g/L, 15% leukocytes >25 (x109/L) and 33% platelets <100 (x109/L). Circulating blasts were ≥2% in 30% and most patients presented BM fibrosis grade ≥2 (74%). CALR type 1 mutation was detected only in 12%, while any high-molecular risk (HMR) mutation was present in 31% (8% for ≥2 HMR mutations). In brief, in comparison to MIPSS70 training cohort, the patients in the present series were older and presented a higher proportion of adverse risk factors (Figure 1A). More than half of the patients were classified as high risk according to MIPSS70 (52%), while 35% were intermediate and 13% low risk. The 5-year overall survival (OS) was 44% (median 4.6 years), 77% (median 13 years) and 95% (median not reached) for high, intermediate and low risk patients respectively (p<0.001, Figure 1B). The 5-year leukemia-free survival (LFS) was 42%, 77% and 95% for high, intermediate and low risk groups (p<0.001). Univariate analysis of each MIPSS70 variable on OS was carried out, with statistically significant differences being confirmed for all variables except fibrosis grade and HMR mutations. ASXL1 was mutated in 27%, but it did not impact OS in our patients (HR 0.96, p=0.89). SRSF2 was the only MIPSS70 mutated gene (8%) associated with inferior OS (HR 2.5, p=0.04), while EZH2 and IDH1/2 mutations were only present in 2.5% of patients each. However, the analysis of the complete NGS panel allowed the identification of other genes associated with shorter OS in our series: CBL (HR 3.7, p=0.014), SETBP1 (HR 4.9, p=0.034) and KRAS (HR 4.6, p=0.041), with a tendency for U2AF1 (HR 2.3, p=0.061) and NRAS (HR 3.6, p=0.083). Image:Summary/Conclusion: This study constitutes the first real-life validation of MIPSS70 in a multicenter analysis. The score was able to stratify our cohort in three categories with significant differences in OS and LFS. Of note, mutation on ASXL1 gene was not associated with shorter OS in our patients. By contrast, several other genes with potential prognostic significance were identified. Further cooperative studies are needed in order to unravel PMF mutational landscape and its prognostic implications.

P983: SINGLE CELL ANALYSIS ALLOWS THE EARLY DETECTION OF LEUKEMIC CLONES IN MPN PATIENTS

Background: Myeloproliferative neoplasms (MPNs) are a group of hematopoietic stem cell disorders resulting in the overproduction of myeloid differentiated cells. Primary Myelofibrosis (PMF) is characterized by the worst prognosis and 15-20% of cases develop secondary Acute Myeloid Leukemia (AML). MPNs driver mutations affect JAK2, CALR or MPL genes. Moreover, mutations in epigenetic regulators can exacerbate the disease and alter response to treatment. Our group recently demonstrated through single cell analysis that MPNs progression is due to increased genetic heterogeneity, loss of heterozygosity and parallel AML evolution. Aims: In this work we sought to define the genomic architecture of MPN patients during disease evolution, and gain insight into the chromatin and transcriptional perturbations induced by epigenetic modifiers’ mutations. Methods: In order to describe MPNs clonal hierarchy at the single cell level, we employed Mission Bio Tapestri platform. We analyzed the CD34+ compartment of 3 patients during the chronic phase of the disease and after leukemic transformation through a custom panel comprising 29 genes frequently mutated in myeloid neoplasms. CNV assessment was performed on the same data through Mosaic algorithm. On one patient, single nucleus RNA (snRNA-seq) and ATAC-seq were then conducted through 10x genomics instrument on CD34+ cells from the chronic and blast phase. Data were analyzed through Seurat R package. Results: Genomic analysis was performed on 20.652 single cells coming from 7 samples. The analyzed patients suffered from Essential Thrombocythemia (n=2) or PMF (n=1); 2 patients harbored CALR type 1 driver mutation, while one patient carried JAK2V617F variant. In all patients, the first mutational hit occurred on epigenetic remodeler genes (i.e. TET2, ASXL1). Driver mutations’ allele frequency remained stable during disease progression and did not seem to drive leukemic transformation; in one case, JAK2V617F variant was lost in blast phase. In one patient, single cell analysis revealed the acquisition of 3 mutually exclusive pathogenic variants in RAS pathway (two NRAS mutations and a KRAS mutation). Notably, leukemic driver mutations, affecting genes such as IDH2, TP53 and KRAS, were already traceable at very low allele frequency in the chronic phase of the disease of all patients, despite being undetectable by bulk diagnostic NGS analysis. For all patients, CNV analysis highlighted a higher gene dosage imbalance in the leukemic clones when compared with those in the chronic phase. Preliminary analysis of single cell ATAC+RNAseq data showed that the leukemic sample is enriched in more primitive cell types (e.g. multipotent progenitors). Moreover, genes found to be upregulated and more accessible in blast phase erythroid progenitors and HSC clusters are associated with AML poor prognosis. Summary/Conclusion: Altogether this analysis suggests that MPNs’ first mutational hit frequently occurs in chromatin remodeler genes and affects a large fraction of neoplastic cells, confirming their impact on MPNs pathogenesis. Single cell multiomic analysis suggests that epigenetic alterations contribute to alter CD34+ cells differentiation state and activate the expression of pro-leukemic genes. Moreover, genomic analysis highlighted that clones carrying driver mutations remain stable during time and do not seem to drive leukemic transformation. On the other hand, genetic alterations, such as SNVs and CNVs, driving AML evolution are early identified by single cell analysis despite being undetectable by bulk sequencing.

Cerebral Venous Thrombosis and Myeloproliferative Neoplasms: A Three-Center Study of 74 Consecutive Cases

▪BackgroundThe recent association of cerebral venous thrombosis (CVT) with COVID-19 vaccinations (JAMA; 2021; 325, N Engl J Med 2021; 384) motivated the current review of CVT and MPN. Our objectives were, i) provide an estimation of the incidence of CVT in the context of MPN, followed by a description of clinical phenotype and therapeutic strategies, ii) determine long term outlook in terms of recurrent thromboses, hemorrhage, and survival, iii) identify salient features which distinguish MPN associated from COVID vaccine- related CVT.Methods74 consecutive MPN patients with CVT that underwent evaluation at the Mayo Clinic, Rochester MN, USA (n=36), Catholic University, Rome, Italy, (n=23), and University of Florence, Italy (n=15) between 1991 and 2021 were included. The cohort from a previously published multi-center study that included 42 MPN cases with CVT, which were not included in the current study, was used for comparison of observations. Diagnosis of CVT was established with computed tomography or magnetic resonance imaging with venography.Results •Patient characteristics at time of CVTAmong 74 patients with CVT and MPN (median age 44 years, range 15-85; 61% females); disease-specific frequencies were 1.3% (39/2,893), 1.2% (21/1,811) and 0.2% (3/1,888) for essential thrombocythemia (ET), polycythemia vera (PV) and primary myelofibrosis (PMF), respectively.CVT occurred prior to (n=20, 27%, median time to MPN diagnosis 16.5 months), at (n=32, 44%) or after (n=21, 29%, median time to CVT 26 months) MPN diagnosis. 72% of patients presented with headaches, 22% visual changes, 12% nausea/vomiting, 8% neurological deficits, and 6% seizures. Transverse (51%), sagittal (43%) and sigmoid (35%) sinuses were involved with central nervous system hemorrhage in 10 (14%) patients.MPN phenotype included ET (n=39, 53%), PV (n=21, 28%), pre-fibrotic MF (n=6, 8%), MPN-unclassified (n=4, 5%), PMF (n=3, 4%) and post-PV MF (n=1, 1%). Driver mutation testing was performed in 65 patients: 91% harbored JAK2V617F, 3% CALR type 1, 2% MPL, 5% triple negative; moreover, JAK2V617F was mutated in 27/33 (82%) ET patients. An underlying thrombophilia was identified in 19 (31%) cases. No patient had thrombocytopenia. (Table 1). Notably, one patient received the Ad26.COV2.S vaccine, five days prior to presenting with CVT, not associated with thrombosis in other sites, thrombocytopenia or platelet factor 4 antibodies. A history of thrombosis was documented in 10 (14%) patients with three splanchnic venous events. These observations were similar to those noted in our comparative group from a previously published report that included 42 cases; (ET (n=25, 60%), PV (n=11, 26%), PMF (n=5, 12%); median age 51 years, range 16-84; 55% females; 81% JAK2V617F mutated). Prior thrombosis occurred in 8(19%) patients with four splanchnic venous events.Treatment for CVT included systemic anticoagulation alone in 27 (36%) patients or in conjunction with aspirin (n=24, 32%), cytoreductive therapy (n=14, 19%), or both aspirin and cytoreduction (n=9, 12%). 5/21 (24%) patients with CVT post MPN diagnosis, were on anticoagulation at the time of CVT.1.Outcome following CVTAt a median follow-up of 5.1 years (range; 0.1-28.6), recurrent CVT was documented in 3 (4%) patients; incidence rates for other arterial and venous thromboses and hemorrhage were 11% (2 per 100 patient-years), 9% (1.9 per 100 patient-years) and 14% (3 per 100 patient-years), respectively. 3 of 7 (43%) venous thromboses were splanchnic events. Antithrombotic therapy was ongoing in 53% and 80% of patients with thrombotic recurrences and hemorrhage, respectively. A higher incidence of venous thrombosis was noted in the aforementioned previously published cohort (12 (29%) vs 7 (9%), p=0.01); with 5/12 (42%) splanchnic events. Incidence rates for arterial thrombosis and major hemorrhage were similar. Fibrotic and leukemic transformation occurred in 5 (8%) and 1(1%) patient, respectively, with five (7%) deaths unrelated to CVT.ConclusionsThe current study highlights close association of CVT with JAK2V617F, younger age, and female gender. Clinical features distinguishing COVID vaccine-related from MPN-associated CVT include lower likelihood of concomitant non-CVT venous thromboses with the latter; moreover, the absence of thrombocytopenia resulted in a lower rate of intracerebral hemorrhage in MPN cases; as a result, MPN-CVT was not fatal. [Display omitted] DisclosuresVannucchi: AbbVie: Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees.

CAMK2G is identified as a novel therapeutic target for myelofibrosis

AbstractAlthough JAK1/2 inhibition is effective in alleviating symptoms of myelofibrosis (MF), it does not result in the eradication of MF clones, which can lead to inhibitor-resistant clones emerging during the treatment. Here, we established induced pluripotent stem cells (iPSCs) derived from MF patient samples (MF-iPSCs) harboring JAK2 V617F, CALR type 1, or CALR type 2 mutations. We demonstrated that these cells faithfully recapitulate the drug sensitivity of the disease. These cells were used for chemical screening, and calcium/calmodulin-dependent protein kinase 2 (CAMK2) was identified as a promising therapeutic target. MF model cells and mice induced by MPL W515L, another type of mutation recurrently detected in MF patients, were used to elucidate the therapeutic potential of CAMK2 inhibition. CAMK2 inhibition was effective against JAK2 inhibitor-sensitive and JAK2 inhibitor-resistant cells. Further research revealed CAMK2 γ subtype was important in MF model cells induced by MPL W515L. We showed that CAMK2G hetero knockout in the primary bone marrow cells expressing MPL W515L decreased colony-forming capacity. CAMK2G inhibition with berbamine, a CAMK2G inhibitor, significantly prolonged survival and reduced disease phenotypes, such as splenomegaly and leukocytosis in a MF mouse model induced by MPL W515L. We investigated the molecular mechanisms underlying the therapeutic effect of CAMK2G inhibition and found that CAMK2G is activated by MPL signaling in MF model cells and is an effector in the MPL-JAK2 signaling pathway in these cells. These results indicate CAMK2G plays an important role in MF, and CAMK2G inhibition may be a novel therapeutic strategy that overcomes resistance to JAK1/2 inhibition.

Clinical and molecular predictors of fibrotic progression in essential thrombocythemia: A multicenter study involving 1607 patients.

The current retrospective study involving a total of 1607 patients was designed to identify clinical and molecular variables that were predictive of inferior myelofibrosis‐free survival (MFS) in WHO‐defined essential thrombocythemia (ET), utilizing three independent patient cohorts: University of Florence, Italy (n = 718); Mayo Clinic, USA (n = 479) and Policlinico Gemelli, Catholic University, Rome, Italy (n = 410). The Florence patient cohort was first examined to identify independent risk factors for MFS, which included age > 60 years (HR 2.5, 95% CI 1.3–4.9), male sex (2.1, 1.2–3.9), palpable splenomegaly (2.1, 1.2–3.9), CALR 1/1‐like or MPL mutation (3.4, 1.9–6.1) and JAK2V617F variant allele frequency > 35% (4.2, 1.6–10.8). Subsequently, an operational molecular risk category was developed and validated in the other two cohorts from Mayo Clinic and Rome: “high molecular risk” category included patients with JAK2V617F VAF >35%, CALR type 1/1‐like or MPL mutations; all other driver mutation profiles were assigned to “low molecular risk” category. The former, compared to the latter molecular risk category, displayed significantly higher risk of fibrotic transformation: Florence cohort with respective fibrotic transformation risk rates of 8% vs. 1.2% at 10 years and 33% vs. 8% at 20 years (p < 0.001; HR 6.1; 95% CI 3.2–11.7); Mayo Cohort, 16% vs. 7% at 10 years and 44% vs. 25% at 20 years (p < 0.001; HR 2.5; 95% CI 1.6–4.1); and Rome cohort 7.8% vs. 4.6% at 10 years and 31.2% vs. 7.1% at 20 years (p = 0.007, HR 2.7; 95% CI 1.3–5.8). The present study provides practically useful risk signals for fibrotic transformation in ET and facilitates identification of patients who require close monitoring and appropriate counseling.

Clinical and Laboratory Features of JAK2 V617F, CALR, and MPL Mutations in Malaysian Patients with Classical Myeloproliferative Neoplasm (MPN).

Mutations of JAK2V617F, CALR, and MPL genes confirm the diagnosis of myeloproliferative neoplasm (MPN). This study aims to determine the genetic profile of JAK2V617F, CALR exon 9 Type 1 (52 bp deletion) and Type 2 (5 bp insertion), and MPL W515 L/K genes among Malaysian patients and correlate these mutations with clinical and hematologic parameters in MPN. Mutations of JAK2V617F, CALR, and MPL were analyzed in 159 Malaysian patients using allele-specific polymerase chain reaction, including 76 polycythemia vera (PV), 41 essential thrombocythemia (ET), and 42 primary myelofibrosis (PMF) mutations, and the demographics of the patients were retrieved. The result showed that 73.6% JAK2V617F, 5.66% CALR, and 27.7% were triple-negative mutations. No MPL W515L/K mutation was detected. In ET and PMF, the predominance type was the CALR Type 1 mutation. In JAK2V617F mutant patients, serum LDH was significantly higher in PMF compared to PV and ET. PV has a higher risk of evolving to post PV myelofibrosis compared to ET. A thrombotic event at initial diagnosis of 40.9% was high compared to global incidence. Only one PMF patient had a CALR mutation that transformed to acute myeloid leukemia. JAK2V617F and CALR mutations play an important role in diagnostics. Hence, every patient suspected of having a myeloproliferative neoplasm should be screened for these mutations.

A Distinct Mutation Profile Might Contribute to the Dismal Outcome of Triple Negative Patients with Primary Myelofibrosis

Background: Recent data indicate that driver mutations are prognostically informative in patients (pts) with primary myelofibrosis (PMF). Patients with CALR type 1/like (Ty1) mutation had better survival (OS) compared with pts with CALR type 2/like (Ty2) and JAK2 V617F/ MPL W515 mutation (Tefferi A, Blood 2014; Guglielmelli P, BCJ. 2015); conversely, pts lacking any driver mutation, i.e. “triple negative”(TN), suffered from the worst survival (Rumi E, Blood 2014; Guglielmelli P, Blood 2017). Furthermore, a high molecular risk category (HMR), pointing to pts harboring at least one of ASXL1, EZH2, IDH1/2 and SRSF2 mutated genes, independently predicted for shortened survival and increased risk of leukemia (Vannucchi A, Leukemia 2013; Guglielmelli P, Leukemia 2014).Aims: To comparatively evaluate the molecular landscape of TN patients in comparison with other driver mutation categories and the possible relationships with the adverse outcome of this pts' group.Methods: The patient cohort included 680 PMF patients, diagnosed according to WHO-2016 criteria, who provided informed consent for the study. Pts were referred by 6 Italian Centers belonging to the AGIMM group. For all patients driver (JAK2, MPL, CALR) and HMR mutation status was obtained by PCR and NGS, respectively. For 201 of these patients (38 Ty1, 20 Ty2, 110 JAK2/MPL and 32 TN), extended NGS sequencing was performed using Ion Torrent platform in Florence (n=133) and a hybrid-capture NGS-CGP assay [FoundationOne heme® assay (He J et al, Blood, 2016)] in Cambridge (n=68). NGS covered a panel of 20 non-driver genes including: all coding sequence of c-KIT, TET2, RUNX1, NRAS, KRAS, DNAMT3A, IKZF1, EZH2, TP53 ; hot spot of IDH1/2 and SRSF2 and selected exons of CBL, IDH2, ASXL1, SF3B1, NFE2, SH2B3, U2AF1 and SETBP1 . The nonparametric Wilcoxon rank-sum test, Kaplan-Meier estimate of survival and log-rank test were used as appropriate.Results: Of the 680 pts included, 419 were JAK2 +(70%), 38 MPL + (5.6%), 82 TN (12.1%) and 140 CALR + (22%; 105 (75%) Ty1 and 35 (25%) Ty2). Overall, 81 pts (11.9%) progressed to AML. Death occurred in 325 pts (47.8%) after a median follow up of 4.8y. Median survival of CALR Ty1 was 17.8y vs 8.6y for CALR Ty2, 7.2y for JAK2/MPL and 2.6y for TN (P<.0001). The corresponding hazard ratio, taking CALR Ty1 as reference, was 1.6 (95%CI,1.0-2.9), 2.2 (95%CI, 1.5-3.1) and 4.9 (95%CI, 3.2-7.5) for CALR Ty2, JAK2/MPL and TN pts, respectively. HMR status was associated with shortened survival (HR 2.4, 95%CI 1.9-3.0; P<.001) as it was having >2 HMR mutations (HR 4.1, 95%CI 3.0-5.6; P<.001). Among the mutated genes of the extended panel, those associated with shortened OS, in addition to the 5 HMR genes, were NRAS (P=.002), TP53 (P=.049), U2AF1 (P=.035) and SETBP1 (<.001). Negative impact on survival was maintained irrespective of underlying driver mutation.TN pts showed enrichment of SRSF2 mutations (28% vs 1% in CALR Ty1, 6% CALR Ty2, 9% JAK2/MPL ; P<.0001) and ASXL1 (37% vs 23% in CALR Ty1, 29% CALR Ty2, 25% JAK2/MPL ; P=0.02). As many as 56% of TN pts were in the HMR category compared with27% in CALR Ty1, 37% CALR Ty2, 36% JAK2/MPL (P=0.02) and >2 HMR mutations were found in 27% of TN pts vs 4% Ty1, 9% Ty2, 9% JAK2/MPL (P<.001). Regarding the additional prognostically meaningful mutations of the extended panel, 69% of TN pts had at least 1 mutated gene compared with 38% Ty1, 39% Ty2, 48% JAK2/MPL (P<.01); furthermore, 2 and more mutated genes were found in 53% of TN pts vs 13% in Ty1, 17% in Ty2, 27% in JAK2/MPL (P=.01). In particular, NRAS mutations were found in 18% of TN pts vs 8% Ty1, 10% Ty2, 2% JAK2/MPL (P=.006). The median OS was significantly reduced in TN pts having at least one of the additional mutations: 1.9y (range 1.8-2.1y) compared with pts lacking those mutations (OS not reached; HR 5.3; 95%CI, 1.5-18.8). The median age of TN pts (67y, 13-91y) was no different from JAK2/MPL (65y; 19-90) and Ty2 (60y, 18-88y), while Ty1 were significantly younger (48y, 16-96); therefore, accumulation of mutations among TN pts in comparison with other driver mutation categories could not be explained by advanced age, except for CALR Ty1.Conclusions: These findings suggest that the worse outcome associated with Triple Negativity in PMF might be explained, at least in part, by an underlying greater mutation complexity. DisclosuresNahas:Foundation Medicine inc: Employment, Other: stockholder. He:Foundation Medicine Inc: Employment, Other: stockholder. Agarwal:Foundation Medicine Inc: Employment, Other: stockholder. Rambaldi:Novartis, Roche/Genentech, Amgen, Italfarmaco: Consultancy; Novartis, Amgen, Celgene, Sanofi: Other: Travel, Accomodations, Expenses. Mughal:Foundation Medicine Inc: Other: stockholder. Passamonti:Novartis Pharmaceuticals Corporation: Consultancy, Honoraria, Speakers Bureau. Vannucchi:Novartis: Honoraria, Speakers Bureau; Shire: Speakers Bureau.

JAK2, CALR, and MPL Mutation Profiles in BCR-ABL Negative Myeloproliferative Neoplasms, a Referral Center Experience in the Middle East.

Background & Objective:JAK2, CALR, and MPL genes play pivotal roles in the pathogenesis of BCR-ABL negative myeloproliferative neoplasms. This study was conducted to evaluate the frequency of JAK2, CALR, and MPL mutations in BCR-ABL negative myeloproliferative neoplasms and their association with demographic data and hematologic parameters in a referral center, in the Middle East. Methods:Seventy-one patients with BCR-ABL negative myeloproliferative neoplasms were evaluated for JAK2 V617F, CALR type 1, CALR type 2, and MPL by allele-specific PCR and conventional PCR from 2018 to 2019.Results:Twenty-three patients were categorized as polycythemia vera, JAK2 V617F was observed in 91.3% of these cases. Thirty-eight patients were classified as essential thrombocythemia of which 52.6% showed JAK2 V617F, 18.4% demonstrated CALR type 1, 7.9% denoted CALR type 2 and there was no mutation reported in 21.1%. Seven patients were recognized as primary myelofibrosis and exhibited JAK2 V617F mutation in 57.1%, CALR type 1 in 14.3 %, CALR type 2 in 14.3% and no mutation in 14.3%. Three patients were diagnosed as MPN, unclassifiable and 33.3% revealed JAK2 V617F mutation, and no mutation was found in 66.6%. The age (59.15±13.10) and neutrophil percent (70.78±10.14) were higher in patients with JAK2 V617 mutation compared to other mutations (P=0.000, and P=0.03). Platelet count was significantly higher in patients with CALR type 1 mutation (1240400± 402053) (P=0.000).Conclusion:JAK2 V617F was associated with patients’ higher age and higher neutrophil count in CBC. CALR mutation had an association with higher platelet count. No MPL mutation was found in this study and it seems that its frequency is lower than what is expected in this region.

Evaluation of the prognostic value of MIPSS70-plus in Chinese patients with primary myelofibrosis

目的评价MIPSS70-plus预后积分系统对中国原发性骨髓纤维化（PMF）患者的预后评估价值。方法回顾性分析113例PMF患者的临床资料，应用Log-rank和COX回归模型进行预后相关因素分析；应用似然比检验比较MIPSS70-plus和动态国际预后积分系统（DIPSS）的预后评估效能。结果113例PMF患者中男71例，女42例，中位年龄55（20～70）岁。依据MIPSS70-plus染色体核型分组标准，染色体核型预后良好组90例（79.6%），预后不良组23例（20.4%）。二代测序基因突变检测结果示，JAK2V617F突变63例（55.8%），CALR外显子9突变20例（17.7%）（其中1型CALR突变15例，2型CALR突变5例），MPLW515突变5例（4.4%），25例（22.1%）未检测到JAK2、MPL和CALR基因突变（三阴性）。高分子风险（HMR）突变检出率依次为ASXL1突变44例（38.9%）、SRSF2突变8例（7.1%）、IDH1/2突变5例（4.4%）、EZH2突变4例（3.5%）；51例患者（45.1%）有1种以上高危基因突变。MIPSS70-plus预后积分低危组、中危组、高危组、极高危组分别为28例（26.7%）、20例（19.0%）、41例（39.0%）、16例（15.3%），2年预期总生存率分别为100%、89.7%（95%CI 76.2%～100.0%）、64.8%（95%CI 47.0%～82.6%）、35.0%（95%CI 10.3%～59.7%）（P<0.001）。MIPSS70-plus的-2log似然比显著低于DIPSS（86.355对95.990，P＝0.001），表明MIPSS70-plus较DIPSS有更准确的预后分组预测效能。结论MIPSS-70plus较DIPSS预后积分系统对中国PMF患者有更好的预后评估效能。

Genetic analysis of BCR-ABL negative chronic myeloproliferative diseases at initial diagnosis and their clinical effects

Purpose: The aim of this study to discuss frequency and clinical significance of JAK2-V617F, Calreticulin (CALR type 1 and type-2) and MPL-W515K/L mutations in patients at initial diagnosis of bcr-abl negative chronic myeloproliferative diseases (CMPD).Materials and Methods: In this study, the demographic characteristics, subtype, risk status and mutation analysis were investigated between July 2017 and March 2019 in patients diagnosed with bcr-abl negative CMPD.Results: JAK2 V617F mutation was detected in sum of 27 patients, 18 of them (85,7%) diagnosed with polycythemia vera (PV) and rest of them (N=9, 56,2%) diagnosed with essential thrombocytosis (ET). Calreticulin mutation was positive in 4 (57,1%) patients, who were also JAK2 V617F negative, diagnosed with ET. CALR-type 1 mutation was detected in three patients and CALR-type 2 was in one. MPL-W515K/L was not detected in any of patients diagnosed with ET. Thrombotic event was accompanied 12,6% of patients with PV and 6,25% patients with ET. Splenomegaly was noted in 14 (37,8%) of patients. Conclusion: Pathogenesis, classification, and risk groups of CMPD have been well characterized with the identification of some genetic mutations in recent years. JAK2 V617F, CALR and MPL are the most common somatic mutations in the pathogenesis of CMPD, which are important in the diagnosis, risk classification and follow-up of the disease and gain importance in personalized medicine.

Abstract 816: Utility and validation of a comprehensive cost-effective targeted DNA panel including FLT3-ITDs, CALR and CEBPA on a next-generation sequencing (NGS) platform for hematological malignancies

Abstract A clinical next generation sequencing (NGS) assay comprises various factors taken into consideration including selection of appropriate markers thereby panel size, nucleic acid input, assessment and interpretation, and workflow. The downstream benefits of the development of such panels therefore involve improvement in prognosis, patients' outcome, and benefit from targeted therapy. Myeloid malignancies such as myeloproliferative neoplasms (MPN), myelodysplastic syndrome (MDS), MDS/MPN, acute myeloid leukemia (AML) are associated with somatic mutations in around 25 to 50 genes. Herein, we describe clinical validation of a DNA based targeted NGS assay utilizing QIAact Myeloid DNA UMI panel in combination with QIAGEN GeneReader NGS system. The assay employs unique molecular index technology (UMI) into a gene specific, primer based target enrichment technology enabling sequencing of specific regions of interest providing an integrated solution by simultaneously assessing many candidate genes for actionable mutations. The QIAact Myeloid DNA UMI panel is a 25 gene panel for markers of known clinical significance, including single nucleotide variants (SNV), and large insertion/deletion mutations. At the lab, 40 individual AML specimens with known mutation profiles were tested. The limit of detection (LOD) was assessed by sequencing Seraseq myeloid mutation DNA mix as positive control. For accuracy, inter-run and intra-run controls were also implemented. All samples were previously characterized by using another 54 gene NGS panel. The samples were prepared using QIAact Myeloid DNA UMI panel kits, sequenced with QIAGEN GeneReader NGS system, and mutations identified using the QIAGEN Clinical Insight (QCI) Analyze software suite, adjusted specifically for variant calling. Variant calling was accurate and reproducible at allele frequencies ≥5%. Limit of detection (LOD) studies also determined that input of 40ng DNA was optimal for high analytical sensitivity. High positive and negative percentage agreement with prior results was observed across all variant categories. The assay was also able to identify 52bp deletion CALR type 1 variant, and CEBPα amplicons mutations which require separate bi-directional Sanger sequencing for identification. Also, the assay was able to identify FLT3 ITDs up to 101bp insertion which are detected by performing PCR separately. Hence, the study presents the data establishing the QIAact Myeloid DNA UMI panel suitable for implementation as a routine clinical NGS test for myeloid malignancies. The optimized chemistry allows high-throughput analytical sensitivity for detection of highly relevant mutations including large Insertion/Deletion (InDel). Citation Format: Meenakshi Ahluwalia, Ashis Mondal, Nikhil Sahajpal, Allan Njau, Kimya Jones, Pankaj Kumar Ahluwalia, Yasmeen Jilani, Ravindra Kolhe. Utility and validation of a comprehensive cost-effective targeted DNA panel including FLT3-ITDs, CALR and CEBPA on a next-generation sequencing (NGS) platform for hematological malignancies [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 816.

Determining Clinical Correleation of CALR Type 1 and CALR Type 2 Gene Mutations In Chronic Myeloproliferative Disease Cases

Determining Clinical Correleation of CALR Type 1 and CALR Type 2 Gene Mutations In Chronic Myeloproliferative Disease Cases