SRSF2 Mutations Research Articles

The Adverse Effect of Myelodysplasia-Related Mutations in De Novo Acute Myeloid Leukemia Is Associated with Higher Variant Allelic Frequency (VAF): A Proposal for a Numeric Cutoff for Variant Allelic Frequency

Mutations in myelodysplasia-related genes ASXL1, BCOR, EHZH2, RUNX1, SF3B1, SRSF2, STAG2, U2AF1 and ZRSR2 (MRmut) are class-defining alterations in acute myeloid leukemia (AML) in the latest World Health Organization (WHO, with the exception of RUNX1) and International Consensus Classification (ICC) schemes and indicate adverse-risk per European Leukemia Net (ELN) 2022 guidelines, unless occurring in favorable-risk AML. The lower limit of detection (LOD) for most clinical-grade next generation sequencing (NGS) is ~1-2% variant allelic frequency (VAF); however, data on the prognostic significance of MRmut relative to VAF is lacking. No guidelines that provide a numeric cutoff for VAF are available for utilizing these mutations to classify AML. Our aim was to define a clinically meaningful VAF cutoff for MR mutations in de novo AML. We included patients (pts) with de novo, untreated AML with MRmut treated at our institution between 2017 to 2022. We excluded pts with acute promyelocytic leukemia, core binding factor AML, and other ELN adverse-risk categories (adverse karyotype and/or TP53 mutation). NGS at baseline was performed using a panel of 81 genes recurrently mutated in myeloid neoplasms (LOD ~1-2%). We performed a best fit classifier on individual MRmut to determine optimal VAF cutoffs using event-free survival (EFS) and overall survival (OS) as endpoints. VAF for MRmut involving X-linked genes was adjusted for men. Pts (n=145) included 92 (63%) men and 53 (37%) women with a median age of 68 years (range, 58-75). 85 (59%) pts had diploid karyotype AML, 51 (35%) had other intermediate-risk non-diploid karyotype AML, and 9(6%) had insufficient metaphases for analysis. 34 (23%) pts had ELN favorable-risk and 111(77%) had ENL adverse-risk AML. Pts were treated with low-intensity+venetoclax (VEN) (72/50%), low-intensity (26/18%), high-intensity (22/15%), and high-intensity+VEN (12/17%) regimens. Median follow-up was 26.9 months (range, 13.9 - 40.8). 72 (49%) pts had 1 MRmut; the remaining had 2-4 concurrent MRmut. MRmut had the following frequencies and VAFs: ASXL1 (28%; median VAF: 26%, [range 2-48%]); BCOR (18%; median VAF 37% [3-100%]); EHZH2 (9%; median VAF 7% [1-55%]), RUNX1 (32%; median VAF 47% [1-96%]), SF3B1 (9%; median VAF: 38% [1-55%]), SRSF2 (46%; median VAF: 37% [1-76%]), STAG2 (20%; median VAF: 44% [15-98%]), U2AF1 (12%; median VAF: 33% [2-43%]) and ZRSR2 (2%; median VAF: 94% [93-95%]). 34 (23%) pts had ELN favorable-risk AML including 28 (23%) with mutated NPM1 without FLT3-ITD and 6 (4%) with CEBPA bZIP mutations, respectively; in 12/34 pts NPM1 or CEBPA bZIP mutations were subclonal compared with clonal MR mutation(s). A summary of baseline genetic and treatment data is provided in Fig 1A. The overall composite remission rate (CR+CRi) was 88% (64% and 24%, respectively) Median OS was 30.3 months and estimated 12/24 month OS were 77%/60%. The median EFS was 24.6 months and estimated 12/24 month EFS were 65%/51%. Pts with ELN favorable-risk AML with MRmut had longer OS and EFS compared with the adverse-risk group (median OS 34.9 vs 27.5 months, median EFS 34.9 vs 22.9 months) but the difference was not significant (p=0.60 and 0.30, respectively). The VAF cutoff for MRmut associated with EFS and OS, respectively, was: ASXL1: 21%/21%, BCOR 25%/25% , EHZH2 15%/15%, RUNX1 25%/27%, SF3B1 31%/31%, SRSF2 32%/35%, STAG2 40%/21%, U2AF1 44%/44% and ZRSR2 47/47%.There was no significant difference in OS or EFS between pts with 1 MRmut vs those involving ≥2 MR genes. Pts treated with high-intensity, high intensity+ VEN and low intensity+VEN regimens had longer OS (Fig 1B) and EFS compared with pts treated with low intensity regimens without VEN (OS: not reached, 31.7 months, 31.4 months vs 8.9 months, respectively, p<0.001; EFS: not reached, 31.7 months, 29.6 months vs 3.7 months, respectively, p<0.001). Our data suggest that the poor prognostic effect of MRmut in de novo AML is associated with higher VAF and not a binary presence or absence of MRmut. The minimum VAFs associated with worse outcome for each MRmut ranged from 15-47%. Additional analysis to create predictive models is in progress to determine the optimal VAF cutoff when using MRmut to assign AML to the WHO/ICC MR categories and to ELN adverse-risk group. Importantly, our results suggest that pts with MRmut and non-adverse karyotype have significantly better outcomes when treated with high-intensity and/or venetoclax-based treatment regimens. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Differentiation Scoring (DS) Derived from Cellworks Computational Omics Biology Model (CBM) Predicts Response to Hypomethylating Agents (HMA) and Patient Survival in Myelodysplastic Syndrome (MDS)

Background: Differentiation arrest resulting from aberrant methylation represents a key pathogenic and phenotypic feature of MDS. Hypomethylating agents (HMA) can reverse epigenetic dysregulation, but as single agents fail to control the disease in approximately 50% of patients, many of whom progress to AML and carry a dismal prognosis. We hypothesized that Differentiation Scoring (DS) derived from Cellworks Computational Omics Biology Model (CBM) of each patient's genomic aberrations could serve as a biomarker to predict response to HMA. Methods: We studied 169 MDS patients treated with azacytidine (n = 86) or decitabine (n = 83) whose genomic aberrations and clinical outcomes were available from public databases. Biosimulation of the disease state was computationally derived from pathways that were up- or down-regulated by individual genomic aberrations. DS was defined as the ratio of the quantified impact of key differentiation biomarkers in myeloid malignancies (CEBPA, GATA1, SPI1 and ITGAM) divided by the impact of HOXA9 transcription, a known repressor of differentiation, and normalized on a log2 scale. We also used CBM to determine the change in DS attributable to HMA to define an efficacy score (ES) as a parameter of drug response. A Pearson correlation coefficient was obtained using the two variables. DS in clinical responders (R) and non-responders (NR) was evaluated with the Student t-test. We defined DS > 1.5 as DS-high and < 1.5 as DS-low. Survival data were available for 101 patients and correlated with DS-high (n=49) and DS-low (n=52) groups using a KM-curve. Results: Median age of this cohort was 69 years (range, 20-87 years), including 56 females, 111 males, and 2 of unknown sex. Regarding HMA response, 62 patients were R while 107 were NR. Prior to therapy, 86 patients had DS-high and 83 had DS-low scores. Post-treatment DS were correlated with HMA ES (R = 0.58, p < 2.2e-16), and showed a favorable HMA response for DS-high patients. Biosimulation showed the incremental benefit on DS of HMA was greater for people with DS-high than DS-low scores (44% vs 16%, p = 7.51 e-17). Median DS was higher in R than NR (p=0.00232). Patients with DS-high scores had superior survival compared to those with DS-low scores (log rank p = 0.0016). (Figure 1a) Different genomic aberrations contributed to the DS scores. DS-high patients had more TP53 mutations, 17p del, 8q amp, and 5q del. On the other hand, DS-low patients more often had mutations in ASXL1, SRSF2, RUNX1, DNMT3A, EZH2, NF1, NRAS, CBL, or 7q deletion. (Figure 1b) Loss of TP53 due to mutation or deletion upregulates DNMT1 and silences HOXA9 transcription, leading to DS-high scores. KAT6A (8q) amp also upregulates EZH2 and CpG methylation, while 5q del causes GATA1 transcription, increasing CpG methylation via SALL4 to produce high ß-catenin signaling that led to DS-high scores. By contrast, 7q loss, ASXL1, SRSF2, and EZH2 mutations downregulated EZH2, diminished CpG methylation and unsilenced HOXA9 transcription. As a result, HOXA9 arrested differentiation results in DS-low scores. Additionally, NF1 or NRAS mutations upregulate ERK signaling which inhibits CEBPA, and also caused DS-low scores. Conclusions: Computational biosimulation based on patients’ individual genomic aberrations reveals a spectrum of DS among patients with MDS. DS strongly predicted HMA response. In general, NR had lower DS and survival than DS-high patients. While patients with DS-low scores might have fared even worse without HMA therapy, we propose that DS-low patients should be considered for novel combination therapy at the time of diagnosis given their unsatisfactory outcomes with HMA therapy as a single agent. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Genome-Wide DNA Methylation Profiling in Blastic Plasmacytoid Dendritic Cell Neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive blood cancer and an ongoing therapeutic challenge. In a recent multiomics analysis, we characterized the unique molecular landscape of BPDCN. Beyond an expected classical pDC-derived subtype, we thereby identified a common(c)DC-enriched subtype, which was shown to predominantly arise in elderly patients, whilst harboring fewer mutations and an inferior outcome. The identification of several therapeutically targetable vulnerabilities may pave the way for precision oncology approaches toward this rare cancer. Several genomic alterations in both subtypes were found to be known determinants of the epigenetic regulation of gene expression. However, the epigenetic landscape of BPDCN remains sparsely characterized. We therefore characterized the genome-wide DNA methylation patterns in 54 BPDCN patients on the Illumina MethylationEPIC BeadChip and correlated our findings with WES/RNA-seq data from both previous and new studies. Further, we evaluated our observations according to the newly defined subtypes of BPDCN. Unsupervised clustering of the 420 most variably methylated cytosine guanine dinucleotide (CpG) sites resulted in the segregation of the study cohort into four clusters. These were subsequently annotated genomically and transcriptionally in a clinical context. Cluster two was hereby shown to be of special interest as it was exclusively composed of C2-BPDCN cases with SRSF2 or DNMT3A mutations. Cluster four revealed a strong C1-BPDCN predominance and typical C1 driver mutations including EP300, ARID2 and NF1 (Figure 1). Secondly, differential methylation analysis according to our recently established subtypes of BPDCN revealed a subset of significantly differentially methylated genes between the two clusters. Overall, we observed more methylation among C2 patients with regulation of several oncogenes and tumor suppressor genes such as NOTCH4 and MAP3K13 but a predominant regulation of inflammatory genes including TLR9, IL10RA and IL2RA. Our current observations suggest that genome-wide DNA methylation levels resemble and potentially help shape clinically and genomically distinct subgroups of BPDCN. Synoptic analysis of the methylome in concert with gene-expression profiling data alongside ATAC-Seq of our BPDCN samples is currently under way in order to integratively assess chromatin accessibility and ultimately transcriptional impact. Figure legend Figure 1. Genome-wide DNA methylation profiling in blastic plasmacytoid dendritic cell neoplasm. Unsupervised clustering of the 420 most variably methylated CpG sites resulted in the segregation of the study cohort into four clusters. These were subsequently annotated genomically and transcriptionally in a clinical context. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Outcomes of Myelofibrosis Patients in the Era of Using JAK2 Inhibitor with Allogeneic-HSCT at the University of Southern California

Introduction: In myelofibrosis (MF) patients, the standard of care curative option is with allogeneic-hematopoietic stem cell transplantation (allo-HSCT) but no clear standard of care pre- and post-allo-HSCT management exists. Questions then arise such as whether use of JAK inhibitors pre- or post-transplant lead to better outcomes. In addition, further elucidation of patient characteristics/risks/response are needed due to scarcity of data post-transplant. In this study, we aim to provide further data concerning this field. Methods: This retrospective chart review included patients aged 18 years with MF diagnosed in 2012-2020 and received allo-HSCT at our institution. Primary objectives include over-all survival (OS) and progression-free-survival (PFS) since transplant, stratified by risk, peri-transplant JAK2 inhibitor use and conditioning + associated graft versus host disease prophylaxis (GVHD ppx) use. Secondary objectives include patient/treatment/transplant characteristics, response, survival and GVHD rates. Two-sided p value ≤ 0.05 was significant. RESULTS: 21 screened MF patients received allo-HSCT at our institution, median age 61.1 years (85.7% non-Hispanic and 14.3% Hispanic). 71.4% had primary MF. 9.5% had unfavorable/high risk karyotype/cytogenetics with 38.1% at high risk per Dynamic International Prognostic Scoring System (DIPSS) Plus, and 38.1% high risk, 28.6% very high-risk per Mutation-Enhanced International Prognostic Score System (MIPSS) 70+ v2.0. 52.4% had JAK2 V617F mutation, 28.6% triple negative (lacked JAK2/MPL/CALR mutations) with 23.8% as having any positivity in either ASXL1, EZH2, SRSF2, IDH1/2 and U2AF1 mutations. Pre-transplant, 100% had pancytopenia requiring transfusions. 9.5% had CR/PR, 42.9% had PD and 47.6% had SD. Of note, 57.9% had any peri-transplant JAK2 inhibitor use (defined as use within 3 months pre- and post-transplant) with or without other MF related-treatments. 33.3% underwent MSD, 38.1% MUD and 28.6% underwent HAPLO allo-HSCT. 80% had reduced intensity conditioning (RIC) with an equal distribution of fludarabine-based regimens. In terms of GVHD ppx, 55% received tacrolimus+ methotrexate and 35% had post-transplant cyclophosphamide (PTCY). 30% underwent HAPLO + PTCY. In terms of outcomes and adverse events, pancytopenia improved from 90.5% at d+30 to 57.1% at d+365. Transfusion dependency decreased from 60% from d+90 to 26.7% by d+365. None had leukemic transformation. Clinical improvement rates increased from 33.3% d+30 to 78.6% by d+365. CR/PR rate increased from 5% at d+90 to 28.6% at d+365. 14.3% had relapsed/PD, 37.5% had primary graft failure with 33.3% any deaths post allo-HSCT. 42.9% had any acute GVHD pre-d+100, 42.1% had any chronic GVHD post d+100. Of note, 100% of our population were alive at d+100, and 78.9% alive by d+365. Since transplant, 3y OS was 62.6%, 3y EFS at 59.2% with corresponding worsening of OS/EFS with higher DIPSS (p=0.19-0.33) and a 3y OS (40%) (p=0.29) and EFS (40%) (p=0.41) in patients with very-high risk per MIPSS 70+ v2.0. With peri-transplant JAK2 inhibitor use, 3y OS was 56.8% vs 75% without; 3y EFS was 51.1% vs 75% without (p=0.33-0.51) (Fig.1). For patients who underwent HAPLO+PTCY GVHD ppx, OS and EFS reached at 16 months while patients who underwent non-HAPLO+ any GVHD ppx did not reach their median OS yet and achieved an EFS median of 57 months. 2y OS and EFS was at 50% for those who underwent HAPLO+PTCY vs a 67.1% OS and a 61.9% EFS for those who had non-HAPLO+ any GVHD ppx (p=0.51-0.72) (Fig.2). CONCLUSIONS: Given that most of our patients had high/very high-risk scores, we achieved a good rate of clinical improvement with less transfusion dependency. A good survival rate was also achieved (100% survival at d+100 and 78.9% at 1y). Our 3y OS of 62.6% and 3y EFS of 59.2% is also appreciable even with the rates of GVHD. Our data also further supports that having a higher risk score per DIPSS/MIPSS leads to poorer survival. Interestingly, there may be no difference in OS/EFS with peri-transplant JAK2 inhibitor use. Also, those who underwent HAPLO+PTCY had their median OS/EFS reached first (16 months) with a possible lower survival trend compared to those who underwent MSD/MUD + any GVHD ppx combination treatment. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Pathogenetic Role of RNA Splicing and NRAS Mutation Combination in Chronic Myelomonocytic Leukemia

Chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic neoplasm characterized by monocytosis and recurrent gene mutations including those of SRSF2, ASXL1, TET2, RUNX1 and NRAS. Different mutation combinations may explain the diverse clinicopathologic features in this disease, ranging from those of myelodysplastic syndrome (MDS) to myeloproliferative neoplasm (MPN) phenotype and even transformation to acute myeloid leukemia (AML). A zebrafish program was initiated to understand the pathogenetic roles of mutation combinations in CMML and generate animal models for high throughput drug screening. In this study, we reported our findings based on SRSF2 and NRAS mutation combination. Transgenic zebrafish lines expressing human SRSF2P95H and NRASG12Dmutations (F0), as driven by Runx1 promoter, were generated using Tol2 transgenesis. These lines were out-crossed with wildtype (WT) to generate F1. F1 SRSF2P95Hmutant were then crossed with F1 NRASG12D mutant to generate WT, Tg(Runx1:SRSF2P95H), Tg(Runx1: NRASG12D) and Tg(Runx1:SRSF2P95HNRASG12D). Expression of mutations was confirmed in embryos and adult kidney marrow (KM) by quantitative RT-PCR and DNA sequencing. At 3 months, there was no morphologic changes in peripheral blood (PB) or KM in double or single mutant fish. From 6-12 months, there was progressive weight loss in Tg (Runx1: SRSF2P95H NRASG12D) fish but not single mutant and WT siblings. In the double mutant fish, the PB showed monocytosis and presence of blasts. KM showed increase in cellularity, immature monocytes and blast population but decrease in erythropoiesis. Neutrophils were dysplastic as evident by hypogranularity, abnormal nuclear configuration and features resembling pseudo Pelgar-Huet anomaly as in human MDS. Increased monocytic compartment in KM was confirmed by non-specific esterase (NSE) which was sensitive to fluoride inhibition. Survival of the Tg(Runx1:SRSF2P95HNRASG12D) was significantly shorter than those of single mutant and WT siblings. Both the double mutant and Tg(Runx1:NRASG12D) showed splenomegaly. Of the 49 Tg(Runx1:SRSF2P95HNRASG12D) adult fish examined, 9 developed MDS/AML with 10-19% KM blasts and 18 developed AML with ≥ KM 20% blasts. Zebrafish model of CMML based on co-expression of SRSF2 and NRAS mutations recapitulated the diverse clinical repertoire of this disease, ranging from MDS to MPN and leukemic transformation into AML occurred in some animals. The molecular basis underlying the difference in penetrance might account for the diverse clinicopathologic characteristics in patients and it warrants further investigations.

Cooperative Effects of SRSF2 and STAG2 mutations on Development of Myelodysplastic Syndrome and Its Related Disorders

Cooperative Effects of SRSF2 and STAG2 mutations on Development of Myelodysplastic Syndrome and Its Related Disorders

Effect of Mutation Allele Frequency on the Risk Stratification of Myelodysplastic Syndrome Patients

Introduction Myelodysplastic syndrome (MDS) is a diverse group of clonal myeloid neoplasms. The accumulation of mutations in stem cell compartments is involved in MDS pathogenesis. Mounting evidences demonstrate that the addition of mutation data improves the prognostic stratification in MDS patients. In addition to mutational profiles, the variant allele frequency (VAF) of individual mutations also influence the prognosis in MDS patients. Materials and Methods A total of 698 primary MDS patients were recruited. The diagnoses were based on the 2016 World Health Organization classification. Patients with antecedent chemotherapy/radiotherapy or hematologic malignancies were excluded. TruSight myeloid sequencing panel (Illumina, San Diego, CS, USA) and the HiSeq platform (Illumina, San Diego, CA, USA) were adopted to analyze the gene alterations and mutant allele burdens. Because of the sequencing sensitivity issue, we verified CEBPA mutations and FLT3-ITD via Sanger sequencing. Results Exploration of the correlation between prognosis and VAF of individual genes showed that compared with wild-type genes, high VAF of mutations in 9 genes, including DNMT3A (cutoff value 40%, hazard ratio HR 1.67, p<0.001), TET2 (45%, HR 1.60, p<0.001), ASXL1 (20%, HR 1.48, p<0.001), E.ZH2 (40%, HR 1.45, p=0.037), SETBP1 (15%, HR 1.39, p=0.025), BCOR (80%, HR 1.57, p=0.045), SRSF2 (50%, HR 1.89, p=0.002), ZRSR2 (60%, HR 1.70, p<0.001) and TP53 (25%, HR 2.79, p<0.001) were significantly associated with shorter leukemia-free survival (LFS). With the exception of EZH2, SETBP1, and BCOR mutations, high VAF of all other six mutations were also associated with shorter overall survival (OS). In addition, the patients with SRSF2 and TP53 mutations, even at lower VAF, had poorer prognosis for both LFS and OS compared with those with wild-type genes. For other 7 above-mentioned mutations, only higher VAF conferred poorer outcomes; the patients with lower mutation VAF had outcomes similar to the patients with wild-type genes. In multivariable analysis (Table 1), female sex and receiving allogenic hematopoietic stem cell transplantation (HSCT) were independent favorable factors for both LFS and OS, while older age and higher-risk IPSS-R predicted shorter LFS and OS. Mutant IDH2 and CBL predicted both shorter LFS and OS, while U2AF1 mutation and DNMT3A and ZRSR2 mutations with high VAF were associated poorer OS. The mutation status and VAF levels of TP53 mutations could distinguish patients into three hierarchical groups with different prognoses. The presence of poor-risk mutations as identified in the multivariable Cox analysis could re-stratify the IPSS-R risk groups. Patients with these unfavorable mutations in each IPSS-R risk subgroup had survivals worse than other patients of the same risk but similar to or even worse than those in the next higher-risk subgroup (Figure 1). Considering OS, the incorporation of the molecular data in the IPSS-R could reclassify 8.9% (18/202) of IPSS-R very low/low-risk patients to intermediate-risk subgroup, 17.9% (33/184) of IPSS-R intermediate to high-risk subgroup, and 34.4% (54/157) of IPSS-R high to very high-risk subgroup. Patients harboring U2AF1 mutation had poorer LFS and OS if they were not treated with hypomethylating agents (HMA), but had similar LFS (wild-type vs. mutant-type, 14.3 vs. 15.5 months, p=0.537) and OS (wild-type vs. mutant-type, 22.2 vs. 40.1 months, p=0.450) compared with those with wild-type U2AF1 if they received HMA treatment. Moreover, patients with low TP53 mutant VAF got benefit from HMA treatment considering LFS. Conclusion We provide evidences that VAF is critical for risk stratification in MDS patients and should be considered in novel scoring systems. Our data fostered our understanding of the mutation burden of the diseases and provided future patient-tailored therapeutic avenues. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Prevalence, Clinical and Molecular Features, and Prognostic Value of Tetraploidy/Near-Tetraploidy in Patients with Acute Myeloid Leukemia

In patients with acute myeloid leukemia (AML), more common aneuploid alterations, such as complex- or monosomal karyotype (CK and MK, respectively) have been intensively studied and are known to confer an adverse prognosis. In contrast, little is known about the prognosis of clonal tetraploidy/near-tetraploidy (T/NT), another rare aneuploidy, defined by presence of 92 chromosomes in tetraploid, and 81-103 chromosomes in near-tetraploid cases. Therefore, we aimed to evaluate prevalence, clinical as well as molecular characteristics and prognostic impact of T/NT in a large cohort of AML patients. We retrospectively assessed 4259 AML patients treated within Study Alliance Leukemia (SAL) trials and/or registered in the SAL AML registry and for whom valid cytogenetic data were available from 1996 until 2020 (the cohort was subsequently enriched by 5 T/NT cases from the AML cooperative group (AMLCG) AML registry). T/NT was defined by presence of ≥ 81 chromosomes in ≥ 10% of metaphases in G-banded karyograms and/or ≥ 4% T/NT cells in interphase fluorescence in-situ hybridization (iFISH). Bone marrow mononuclear cell (BMMC) nuclear area was assessed in patients with available bone marrow smears. In 22 patients with available BMMCs were available, panel next generation sequencing (NGS) and/or whole genome sequencing (WGS) was performed. Student's t test and Kaplan-Meier estimation were used for statistical analyses. We identified 35 patients with T/NT (prevalence 0.82%). Median age was 60.1 years, 34.2% were female. Most patients were diagnosed with de-novo AML (77.2%); secondary AML and therapy-related AML was seen in 20.0% and 2.8%, respectively. Median WBC was 2.9 ×109/L, platelet count was 59 ×109/L and hemoglobin was 6.2 mmol/L; median bone marrow blast count was 64%. As per standard of care molecular studies, there was no evidence of biallelic CEBPA or NPM1 mutations, only one patient harbored an FLT3-ITD mutation; a complex karyotype was observed in 22.9%. In 24 patients considered fit/eligible for intensive chemotherapy (IC) the CR rate was 54.2%, allogeneic hematopoietic cell transplantation (HCT) was performed in 34.2% of patients. As compared to AML patients with diploid karyotype, median BMMC nuclear area was increased (209 µm2 vs. 129 µm2, p = .02). NGS/WGS revealed an accumulation of RUNX1 (15 variants in 11/22 patients), TET2 (15 alterations in 7/22 patients) and SRSF2 (7 variants in 7/22 patients) mutations. Moreover, frequent chromosome 14 aberrations, e.g. del(14q) were observed (5/22 patients). In contrast, only two patients harbored FLT3 mutations and no variants in CEBPA or NPM1 were seen; also, CBF fusions and KMT2A rearrangements were absent (Figure 1A). Median overall survival (OS) of the entire cohort was 9.6 months. Of note, when evaluating patients with sole T/NT vs. patients with T/NT and additional adverse aberrations, median OS in T/NT patients without additional adverse alterations was 26.1 months vs. 5.5 months in patients with T/NT and adverse risk (Figure 1B). Thus, T/NT per se do not seem to confer an adverse prognosis. In summary, we report the first comprehensive evaluation of AML patients with T/NT. T/NT was associated with distinct clinical (male predominance, large BMMC nuclear area) and molecular features (mutations in RUNX1, TET2, SRSF2; del(14)). Most importantly, isolated T/NT was not associated with a poor prognosis; accordingly, we suggest assigning AML patients with T/NT without additional adverse-risk alterations to the intermediate-risk category. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Molecular Patterns Identify Distinct Subclasses of Myeloid Neoplasia

The diverse molecular pathogenesis of MDS underpins its pathomorphologic and clinical heterogeneity, ultimately converging in a stepwise progression to leukemia. The identification of hallmarks morphological features, hampered by inter-observer variability, limited a precise resolution of pathogenic differences, partially mitigated by the inclusion of cytogenetic abnormalities, the two pillars of MDS classification. The advent of NGS led to the discovery of a multitude of mutations, and their combinations unveiled a tremendous molecular diversity in MDS. Intuitively, molecular patterning has been used in supervised fashion to fit morphologic classification, but this approach ensured only a limited success. Machine learning (ML) analytic methods, as demonstrated in acute myeloid leukemia (AML), provide new opportunities to integrate molecular data and identify functionally convergent patterns manifesting with similar clinical outcomes. Particularly, ML approaches can identify cryptic molecular interactions and pathogenic mechanisms irrespective of their often comparable impact on outcomes. Here, we took advantage of a large, well-annotated multicenter cohort of MDS and secondary AML (sAML) cases (N=3588) to test the hypothesis that related molecular patterns can be analyzed in an unbiased/unsupervised fashion to characterize molecularly-defined configurations. Our aim was not meant to compete with or replace current prognostication tools (including the new molecular prognostic score)2 but rather to illuminate the genetic sub-classification of MDS and related conditions in an operator-independent fashion, according to molecular correlations and mutual functional proximity, irrespective of their impact on clinical outcomes. Molecular signatures driving each cluster were identified and used for genomic subclassification that separated functionally related subtypes in an outcome independent fashion. We then validated the model on 412 patients from two external institutions. Among the 3588 patients included in this cohort, 735 (20%) had sAML, 774 (22%) had higher-risk MDS (HR-MDS), and 2079 (58%) had lower-risk MDS (LR-MDS). Abnormal karyotype was found in 43% of the cases, and 77% had at least one somatic mutation, with 8% harboring >4 mutations. ML analysis identified 14 distinctive molecular clusters (MCs) with unique pathobiological associations, treatment responses, and prognosis (Fig.1A). Normal karyotype (NK) was enriched in MC2, MC4, MC6, MC9, MC10, and MC12 with different distributions of ASXL1, DNMT3A,JAK2, RAS, SF3B1, and TET2 mutations. Complex karyotype and trisomy 8 were enriched in MC13 and MC1, respectively. Remarkably, our ML approach identified functionally relevant genomic clusters (Fig.1A). For instance, MC2, MC6, and MC8 demonstrated distinct genomic signatures: MC2 included cases with NK only (100%) and some DNMT3A (11%), JAK2 (11%), and RAS pathway (10%) mutations; MC6 cases had similar features to MC2 but were also enriched in SRSF2 (49%) and RAS mutations (23%); MC8 was instead characterized by the presence of del5q/-5 (100%), DNMT3A (17%), and TP53 (17%) mutations. MC13 contained cases with complex karyotype (100%) and TP53 (44%) mutations (Fig1.B). We then identified five risk groups to reflect the biological differences between clusters. Our clustering model highlighted the significant survival differences among patients assigned within similar IPSS-R risk groups but displaying heterogeneous molecular configurations. Different response rates to hypomethylating agents (e.g., MC9 and MC13 [OR: 2.2 and 0.6, respectively]) paralleled the biological differences across the clusters. Interestingly, our MCs retained significant survival differences regardless of the bone marrow blast percentage. Our model is available via web-based access resource (https://drmz.shinyapps.io/mds_latent). Despite the complexity and the diversity of molecular alterations in MDS/sAML, by deploying ML we were able to identify and distinguish functional and pathologically related MCs irrespective of the anamnestic clinico-morphological features. In recognition that similar outcomes do not warrant similar molecular features, our model provides genomic signatures for a better understanding of the pathobiological mechanisms of disease, progression to higher stages, and identification of future therapeutic vulnerabilities. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Clinicopathologic spectrum of myeloid neoplasms with concurrent myeloproliferative neoplasm driver mutations and SRSF2 mutations

AbstractMyeloproliferative neoplasms (MPNs) are frequently associated with classic driver mutations involving JAK2, MPL or CALR. SRSF2 is among the most frequently mutated splicing genes in myeloid neoplasms and SRSF2 mutations are known to confer a poor prognosis in patients with MPNs. In this study, we sought to evaluate the clinicopathologic spectrum of myeloid neoplasms harboring concurrent MPN-driver mutations and SRSF2 mutations. The study cohort included 27 patients, 22 (82%) men and five (19%) women, with a median age of 71 years (range, 51–84). These patients presented commonly with organomegaly (n = 15; 56%), monocytosis (n = 13; 48%), morphologic dysplasia (n = 11; 41%), megakaryocytic hyperplasia and/or clustering (n = 10; 37%) and bone marrow fibrosis >MF-1 (17/22; 77%). About one third of patients either initially presented with acute myeloid leukemia (AML) or eventually progressed to AML. Eighteen (68%) patients had a dominant clone with SRSF2 mutation and nine (33%) patients had a dominant clone with a classic MPN-associated driver mutation. Our data suggest that the presence of an SRSF2 mutation preceding the acquisition of a MPN driver mutations is not a disease-defining alteration nor is it restricted to any specific disease entity within the spectrum of myeloid neoplasms. In summary, patients with myeloid neoplasms associated with concurrent SRSF2 and classic MPN driver mutations have clinical and morphologic features close to that of classic MPNs often with frequent dysplasia and monocytosis.

Srsf2P95H/+ co-operates with loss of TET2 to promote myeloid bias and initiate a chronic myelomonocytic leukemia-like disease in mice.

Recurrent mutations in RNA splicing proteins and epigenetic regulators contribute to the development of myelodysplastic syndrome (MDS) and related myeloid neoplasms. In chronic myelomonocytic leukemia (CMML), SRSF2 mutations occur in ~50% of patients and TET2 mutations in ~60%. Clonal analysis indicates that either mutation can arise as the founder lesion. Based on human cancer genetics we crossed an inducible Srsf2P95H/+ mutant model with Tet2fl/fl mice to mutate both concomitantly in hematopoietic stem cells. At 20-24 weeks post mutation induction, we observed subtle differences in the Srsf2/Tet2 mutants compared to either single mutant. Under conditions of native hematopoiesis with aging, we see a distinct myeloid bias and monocytosis in the Srsf2/Tet2 mutants. A subset of the compound Srsf2/Tet2 mutants display an increased granulocytic and distinctive monocytic proliferation (myelomonocytic hyperplasia), with increased immature promonocytes and monoblasts and binucleate promonocytes. Exome analysis of progressed disease demonstrated mutations in genes and pathways similar to those reported in human CMML. Upon transplantation, recipients developed leukocytosis, monocytosis, and splenomegaly. We reproduce Srsf2/Tet2 co-operativity in vivo, yielding a disease with core characteristics of CMML, unlike single Srsf2 or Tet2 mutation. This model represents a significant step toward building high fidelity and genetically tractable models of CMML.

IPSS-M has greater survival predictive accuracy compared with IPSS-R in persons ≥ 60 years with myelodysplastic syndromes

There are considerable new data on mutation topography in persons with myelodysplastic syndromes (MDS). These data have been used to update conventional risk models such as the Revised International Prognostic Scoring System (IPSS-R). Whether the molecular IPSS (IPSS-M) which includes these data improves survival prediction accuracy is untested. To answer this question, we compared survival prediction accuracies of the IPSS-R and IPSS-M in 852 consecutive subjects with de novo MDS. Concordance statistics (C-statistics) of the IPSS-R and IPSS-M in the entire cohort were similar, 0.67 (95% Confidence Interval [CI] 0.64, 0.71) and 0.68 (0.64, 0.71). Average numbers of mutations and of IPSS-M related mutations were greater in persons ≥ 60 years (2.0 [Interquartile Range [IQR], 1, 3] vs. 1.6 [0, 2], P = 0.003; 1.6 [0, 2] vs. 1.3 [0, 2], P = 0.006). Subjects ≥ 60 years had a higher incidence of mutations in RUNX1, TP53, TET2, SRSF2, DNMT3A, STAG2, EZH2 and DDX41. In contrast, mutations in U2AF1 were more common in persons < 60 years. Next we tested survival prediction accuracy based on age < or ≥ 60 years. C-statistics of the IPSS-R and IPSS-M in subjects ≥ 60 years were 0.66 (0.61, 0.71) and 0.69 (0.64, 0.73) whereas in subjects < 60 years they were 0.67 (0.61, 0.72) and 0.65 (0.59, 0.71). These data indicate an advantage for the IPSS-M over the IPSS-R in subjects ≥ 60 years but not in those < 60 years probably because of a great frequency of mutations correlated with survival in those ≥ 60 years.

RUNX1 deficiency cooperates with SRSF2 mutation to induce multilineage hematopoietic defects characteristic of MDS

AbstractMyelodysplastic syndromes (MDSs) are a heterogeneous group of hematologic malignancies with a propensity to progress to acute myeloid leukemia. Causal mutations in multiple classes of genes have been identified in patients with MDS with some patients harboring more than 1 mutation. Interestingly, double mutations tend to occur in different classes rather than the same class of genes, as exemplified by frequent cooccurring mutations in the transcription factor RUNX1 and the splicing factor SRSF2. This prototypic double mutant provides an opportunity to understand how their divergent functions in transcription and posttranscriptional regulation may be altered to jointly promote MDS. Here, we report a mouse model in which Runx1 knockout was combined with the Srsf2 P95H mutation to cause multilineage hematopoietic defects. Besides their additive and synergistic effects, we also unexpectedly noted a degree of antagonizing activity of single mutations in specific hematopoietic progenitors. To uncover the mechanism, we further developed a cellular model using human K562 cells and performed parallel gene expression and splicing analyses in both human and murine contexts. Strikingly, although RUNX1 deficiency was responsible for altered transcription in both single and double mutants, it also induced dramatic changes in global splicing, as seen with mutant SRSF2, and only their combination induced missplicing of genes selectively enriched in the DNA damage response and cell cycle checkpoint pathways. Collectively, these data reveal the convergent impact of a prototypic MDS-associated double mutant on RNA processing and suggest that aberrant DNA damage repair and cell cycle regulation critically contribute to MDS development.

MDS-472 STAG2 and SRSF2 Mutations Might Define Prognosis of MDS Patients With Isolated Trisomy 8

Isolated trisomy 8 is a karyotypic abnormality frequently found in hematological neoplasms. It is found in 10% of myelodysplastic syndromes (MDS) with cytogenetic aberrations. It is classified as an intermediate risk subgroup in MDS IPSS-R (Revised International Prognostic Scoring System) because of the heterogeneous clinical course of the patients. The aim of this study was to determine whether mutational profile could be useful to improve the risk reclassification of MDS with isolated trisomy 8. In a cohort of 591 MDS patients, we included 38 patients with isolated trisomy 8 confirmed through karyotype and FISH. We carried out next generation sequencing in bone marrow samples of these patients with an in-house custom panel with more than 100 myeloid-related genes. NGS files were processed with our own pipeline. Statistical analysis was performed with SPSS. A total of 102 somatic mutations were found in our cohort. The most frequently mutated genes were TET2, STAG2, ASXL1 and SRSF2. Interestingly, the mutational profile allows the differentiation of two subtypes of isolated trisomy 8: patients with mutations in either SRSF2 or STAG2 (n=16), and those without mutations in these genes (n=22). Both groups presented similar clinical characteristics. However, patients with STAG2 and/or SRSF2 mutations had a shorter time to progression to AML and lower overall survival than patients without these mutations (p<0.05). Surprisingly, the risk for AML progression and the overall survival of patients with STAG2/SRSF2 alterations was similar to those MDS classified as high risk in IPSS-R (p>0.05). Similarly, patients with trisomy 8 without these mutations did not show significant differences in survival and progression to AML when compared to the group of MDS with low IPSS-R risk (p>0.05). This study demonstrates, for the first time, that mutational profile of MDS with isolated trisomy 8 allows these patients to be reclassified into two groups based on the presence or absence of mutations in STAG2 and/or SRSF2. These alterations are clearly associated with an adverse prognosis. Therefore, we suggest the need to study the mutational profile of these patients in order to reclassify them on the prognostic scale.

AML-440 Prognosis of Molecularly-Defined Secondary Acute Myeloid Leukemia Patients

Mutations in ASXL1, BCOR, EZH2, SF3B1, SRSF2, STAG2, U2AF1 and ZRSR2 were proposed as secondary AML (sAML) defining mutations independent from the patients' history. We evaluated the prognostic impact of molecularly-defined sAML (msAML) patients in the context of the European LeukemiaNet (ELN) risk categories. 459 adult newly-diagnosed AML patients (median age 54) with available genetic and follow-up data were included. Patients received standard induction and consolidation chemotherapy or underwent allogeneic hematopoietic cell transplantation (alloHCT). Patients were classified as de-novo AML (dnAML), msAML carrying ≥ 1 sAML-defining mutations, and clinically-defined secondary AML (csAML) based on previous medical history and cytogenetics. 208 (45%) patients had dnAML, 155 (34%) msAML, and 96 (21%) csAML. 62 msAML patients overlapped with csAML. Of msAML patients, 104 (67%) had 1, 39 (25%) 2, and 12 (8%) 3 or more msAML-defining mutations. The most frequently mutated msAML-defining genes were ASXL1 (n=48, 31%) and SRSF2 (n=44, 28%). The likelihood to reach complete remission (CR) was higher for dnAML compared to msAML patients (92% vs 79%, P =.003), but there was no difference between csAML and msAML patients. The median follow-up of all patients was 5.56 years. The transplantation rate in first CR was similar in dnAML, msAML and csAML patients (33%, 37%, 44%, respectively). Overall survival (OS) was significantly worse in msAML compared to dnAML patients (median OS 3.3 years vs not reached, HR = 1.7, 95%CI 1.2-2.2, P<.001), also when ASXL1 mutated patients were excluded (HR = 1.7, 95%CI 1.2-2.4, P<.001). OS was similar in csAML vs dnAML and in msAML vs csAML patients. In the ELN favorable and intermediate risk groups msAML patients (n=19 and n=52) had a significantly worse OS compared to dnAML patients (n=66 and n=80) (HR=3.1 95%CI 1.5-6.3, P=.001 and HR=2, 95%CI 1.2-3.2, P=.008, respectively). OS was similar in the ELN adverse risk group between msAML (n=79) and dnAML patients (n=31). Accordingly, the ELN risk groups did not stratify OS in msAML patients. msAML-defining mutations identify a subgroup of dnAML patients with poor prognosis and reclassify 10% of all patients in our cohort from favorable/intermediate to the adverse risk group.

MPN-352 Clinicopathologic and Molecular Correlates of Organ Damage Across the Spectrum of Advanced Systemic Mastocytosis.

Advanced SM (AdvSM) comprises 3 subtypes: aggressive SM (ASM), SM with an associated hematologic neoplasm (SM-AHN), and mast cell leukemia (MCL). The patterns of organ damage, which have been defined by WHO, IWG, and modified IWG (mIWG) criteria, across the spectrum of AdvSM have not been well characterized. 1) To describe the distribution of organ damage in AdvSM patients (pts) at initial presentation or at the time of trial enrollment; 2) To evaluate clinicopathologic and molecular correlates of organ damage. Observational study of adults with AdvSM. Tertiary referral center. Our cohort included 240 AdvSM pts: 66 from the Stanford MPN registry and 174 from the phase I EXPLORER and phase II PATHFINDER studies of avapritinib in AdvSM. None. Hematologic and non-hematologic organ damage as defined by WHO, IWG, and mIWG criteria. Thirty-seven pts (15%) had ASM, 165 (69%) had SM-AHN, and 38 (16%) had MCL. Pts with MCL had the highest transfusion requirement and the largest liver and spleen volumes by imaging. In multivariate analyses comparing SM-AHN to ASM/MCL, SM-AHN pts had higher absolute neutrophil and monocyte counts and presence of SRSF2, ASXL1, or RUNX1 (S/A/R) mutations. ASM/MCL pts had higher tryptase levels and bone marrow mast cell burden. Compared to midostaurin-naïve pts, those who had received midostaurin had a greater bone marrow mast cell burden (P=0.06) but less frequently met WHO liver (P<0.001) and WHO malabsorption (P<0.001) criteria. Compared to pts with KIT D816V only, pts with ≥1 S/A/R mutations had lower median hemoglobin (P=0.02) and platelet count (P=0.02) and higher direct bilirubin (P=0.02), alkaline phosphatase (P=0.03), and spleen volume (P=0.06). They exhibited more WHO-defined cytopenias (P=0.007) and were more likely to meet WHO hypersplenism criteria (P=0.03). In AdvSM, patterns of organ damage reflect disease subtype, prior therapy, and mutation profile. These data can help inform enrollment of AdvSM pts into clinical trials that currently require ≥1 organ damage findings. Grant Acknowledgments: ASH HONORS Award, NIH grant P30CA124435.

MPN-215 Outcomes of Myelofibrosis Patients Post Allogeneic-HSCT at the University of Southern California, a Retrospective Study.

In myelofibrosis (MF) patients, the standard of care curative (SOC) option is through an allogeneic-hematopoietic stem cell transplantation (allo-HSCT); however, no SOC pre- and post-transplant management exists. To report outcomes of MF patients, post-allo-HSCT at our institution with consideration of patient characteristics, risks, and pre-transplant treatment. A retrospective chart review. Single institution: academic center hospital/county hospital Patients or Other Participants: 18-99YO M/F patients with MF diagnosis by bone-marrow biopsy since 2012-2020 and received allo-HSCT at our institution. Chart review. Primary: OS, PFS since time of transplant, stratified to JAK2 inhibitor use, MF type and associated patient characteristics/risks. Secondary: Patient/treatment characteristics, response/mortality rates. P≤ 0.05 is considered significant. In 18 patients, median age 60.7 years 61.1% White/Non-Hispanic, 16.7% Hispanic with 44.4% high, 55.6% intermediate-1/2 risk by DIPSS, 27.8% high and 33.3% very high risk by MIPSS70+. 66.7% had primary MF. At time of transplant, 11.1% was CR/PR, 38.9% SD, and 50% PD. 38.9% received MSD, 27.8% MUD, and 33.3% received haploidentical stem cells. 76.5% had RIC and 23.5% underwent MAC. 44.4% were +JAK2 V617F, 16.7% had either: ASXL1, EZH2, SRSF2, IDHL1/2, U2AF1. 11.1% had high-risk karyotype/cytogenetics. 61.1% received a JAK2 inhibitor, 72% received non-JAK2 inhibitor treatments pre-transplant. Post-transplant, 78% alive at 1 year. Since transplant, 3-year (3y) OS was 66.7% in primary MF patients, 55.6% in secondary (p=0.75) with similar EFS. 3y-OS in JAK2 V617F+ patients was 83.3% (p=0.13) with similar EFS. 3y-OS of those who received a JAK2 inhibitor pre-transplant was 47.7% (p=0.17) with similar EFS (p=0.16). Those without either ASXL1, EZH2, SRSF2, IDHL1/2, or U2AF1 mutations achieved a higher, 72.2%, 3y-OS (p=0.076) than those with any. High-risk karyotype/cytogenetics 3y-OS was 50% (p=0.43). OS/EFS rates were generally lower with higher DIPSS and MIPSS70+. Given most of our patients were high/very high risks, achieving 3y-OS of 66.7% in primary and 55.6% in secondary MF since the time of transplant is appreciable. Interestingly, even with higher OS/EFS for JAK2V+ patients, the OS/EFS is lower for those who received a JAK2 inhibitor. This could be from the low sample size. Further studies are necessary.

MDS-406 Prognostic Implication of the Molecular Profiles of Patients With Hypocellular Myelodysplastic Syndrome

Hypocellular myelodysplastic syndrome (hMDS) is a subset of MDS that has not been fully characterized. This study aimed to better identify the clinical characteristics and molecular profile of hMDS and study the prognostic impact of mutations in hMDS. We conducted a retrospective review of patients with newly diagnosed MDS in a single tertiary cancer center registry from 2010 to 2021. Of 1,899 patients with MDS, 176 (10%) patients had hMDS. The median follow-up period was 19.5 months. hMDS patients were more likely to be younger and have therapy-related disease and more thrombocytopenic and neutropenic than normo/hypercellular MDS (non-hMDS). All other clinical characteristics were comparable. The distributions of IPSS-R cytogenetic scores (≥3, or <3) were comparable. hMDS patients had similar overall survival (OS) to non-hMDS (median 28.3 vs. 29.0 months) or AML transformation rates (23% vs. 19%). These findings were maintained after multivariate adjustment. Hypocellularity did not affect survival in either de novo or t-MDS. We further analyzed 1,352 (71%) pts with mutation data available. Patients with hMDS had less frequent ASXL1, RUNX1, TET2, or IDH1 mutations, whereas the frequency of TP53 and RAS pathway mutations were comparable. In de novo MDS, hMDS patients had less frequent RUNX1, SRSF2, or TET2 mutations. In t-MDS, hMDS pts had less frequent TP53 or U2AF1 mutations. The survival of hMDS can be stratified by IPSS-R with some overlaps. In hMDS, mutations in the RAS pathway or TP53 were associated with inferior OS, whereas TET2 mutations correlated with superior OS. Based on the mutation data, patients were stratified into 3 groups: (1) with TET2 mutations, (2) with TP53 or RAS pathway mutations without TET2 mutations, and (3) without TET2/TP53/RAS mutations. The TET2 mutant group showed marginally better mOS (HR 0.50, P=0.081), and the TP53/RAS pathway group showed inferior mOS (HR 2.74, P=.005) compared with the group without TET2/TP53/RAS pathway mutation. Patients with hMDS had similar outcomes to patients with non-hMDS but exhibit distinct molecular profiles; hMDS had less frequent driver mutations commonly seen in non-hMDS. The integration of molecular profiles into risk stratification in hMDS could be a study of interest.

Prospective validation of a biomarker-driven response prediction model to romiplostim in lower-risk myelodysplastic neoplasms – results of the EUROPE trial by EMSCO

The EUROPE phase 2 trial investigated the predictive value of biomarkers on the clinical efficacy of single agent romiplostim (ROM) treatment in patients with lower-risk myelodysplastic neoplasms (LR-MDS) and thrombocytopenia within the ‘European Myelodysplastic Neoplasms Cooperative Group‘ (EMSCO) network. A total of 77 patients with LR-MDS and a median platelet count of 25/nl were included, all patients received ROM at a starting dose of 750 μg by SC injection weekly. Thirty-two patients (42%) achieved a hematologic improvement of platelets (HI-P) with a median duration of 340 days. Neutrophil (HI-N) and erythroid (HI-E) responses were observed in three (4%) and seven (9%) patients, respectively. We could not confirm previous reports that HI-P correlated with baseline endogenous thrombopoietin levels and platelet transfusion history, but SRSF2 mutation status and hemoglobin levels at baseline were significantly linked to HI-P. Sequential analysis of variant allelic frequency of mutations like SRSF2 did not reveal an impact of ROM on clonal evolution in both responders and non-responders. In summary, our study confirms the safety and efficacy of ROM in LR-MDS patients and may allow to better define subgroups of patients with a high likelihood of response.

33714 Palisaded neutrophilic and granulomatous dermatitis in the setting of SRSF2-mutated chronic myelomonocytic leukemia: Case report and review of the literature

Palisaded neutrophilic and granulomatous dermatitis (PNGD) is a rare cutaneous histopathologic reaction pattern associated with several underlying disorders. Few cases of PNGD have been associated with hematologic malignancies, in particular with chronic myelomonocytic leukemia (CMML), a malignant hematopoietic disorder with features of myeloproliferative neoplasm and myelodysplastic syndrome. CMML is characterized by peripheral blood monocytosis and bone marrow dysplasia, and can be supported by an acquired clonal cytogenetic abnormality most commonly in TET2, SRSF2, ASXL1, RUNX1, NRAS, and CBL. We present a patient with a papulosquamous rash on the neck, chest, and shoulders with histomorphological features on the spectrum of PNGD. Subsequent lab workup demonstrated a persistent mild monocytosis, raising concern for CMML. The patient was referred to hematology-oncology for a bone marrow biopsy, which ultimately led to her diagnosis. Cytogenic studies of the bone marrow biopsy demonstrated mutations in SRSF2, IDH2, and ASXL1, which were strongly supportive of this diagnosis. After discussion at a multidisciplinary tumor board, treatment directed at the skin eruption alone was recommended. She was started on prednisone taper and demonstrated marked clinical improvement. PNGD in the context of CMML has been scarcely reported, with only 4 prior reports in the literature. Our patient is the fifth reported case, and the fourth case with confirmed underlying SRSF2 mutation. This is likely a novel and reproducible clinical-histopathologic-molecular subtype of reactive granulomatous disease. The findings in this case strengthen the previously made association between PNGD and SRSF2-mutated CMML, and may help better define a unique recognizable subtype for dermatopathologists.